Study Support Kamil Wichterle Ostrava 2015 -...

SELECTED CHEMICAL TECHNOLOGIES

Study Support

Kamil Wichterle

Ostrava 2015

VYSOKÁ ŠKOLA BÁŇSKÁ – TECHNICKÁ UNIVERZITA OSTRAVA

FAKULTA METALURGIE A MATERIÁLOVÉHO INŽENÝRSTVÍ

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Title: SELECTED CHEMICAL TECHNOLOGIES

Code: 617-2011/02

Author: Kamil Wichterle

Edition: first, 2015

Number of pages:

Academic materials for the Economics and Management of Industrial Systems study

programme at the Faculty of Metallurgy and Materials Engineering.

Proofreading has not been performed.

Execution: VŠB - Technical University of Ostrava

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THE CONTENT

THE CONTENT .................................................................................. 2

1 CHEMICAL TECHNOLOGY - INTRODUCTION ................................ 6

1.1 Demand of chemicals .................................................................................................................. 6

1.1.1 Direct use of chemicals ................................................................................................................. 6

1.1.2 Main products of chemical technologies ...................................................................................... 6

1.2 Processes and equipments .......................................................................................................... 8

1.2.1 The balance of chemical reactions ................................................................................................ 8

1.2.2 Equilibrium of the chemical reactions .......................................................................................... 8

1.2.3 Kinetics of the chemical reactions ................................................................................................ 9

1.2.4 Batch and flow reactors ................................................................................................................ 9

1.2.5 The separation of the mixtures ................................................................................................... 10

2 OXIDIZING AGENTS ................................................................... 12

2.1 Air .............................................................................................................................................. 12

2.1.1 The composition of air ................................................................................................................ 12

2.1.2 Use of air ..................................................................................................................................... 12

2.1.3 Air as a chemical material ........................................................................................................... 13

2.1.4 Humidity of air ............................................................................................................................ 13

2.2 Separation of gas mixtures ........................................................................................................ 13

2.2.1 Methods of separation of the gases and vapors ........................................................................ 13

2.2.2 Separation of distillations ........................................................................................................... 13

2.2.3 Liquefying of gases ...................................................................................................................... 13

2.2.4 Separation of absorptions ........................................................................................................... 14

2.2.5 Separation of adsorptions ........................................................................................................... 14

2.2.6 Separation by membranes .......................................................................................................... 14

2.3 Oxygen ....................................................................................................................................... 14

2.3.1 Separation of air by distillation ................................................................................................... 14

2.3.2 Other processes of air separation ............................................................................................... 14

2.4 Other oxidants ........................................................................................................................... 15

3 REDUCING AGENTS ................................................................... 16

3.1 Fuels and their processing ......................................................................................................... 16

3.1.1 Occurrence and use of carbon fuels ........................................................................................... 16

3.1.2 Coal and its processing ............................................................................................................... 16

3.1.3 Crude oil and its processing ........................................................................................................ 17

3.1.4 Natural gas .................................................................................................................................. 17

3.1.5 Non-fossil fuels ........................................................................................................................... 17

3.1.6 Carbonization of non-fossile substances .................................................................................... 17

3.1.7 Bioethanol ................................................................................................................................... 17

3.1.8 Biodiesel ...................................................................................................................................... 17

3.1.9 Biogas .......................................................................................................................................... 17

3.2 Hydrogen ................................................................................................................................... 18

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3.2.1 Use of hydrogen .......................................................................................................................... 18

3.2.2 Overview of production of hydrogen.......................................................................................... 18

3.2.3 Carbonization of coal .................................................................................................................. 18

3.2.4 Blue gas ....................................................................................................................................... 18

3.2.5 Steam reforming ......................................................................................................................... 18

3.3 Electropositive Metals ............................................................................................................... 19

4 SIMULTANEOUS OXIDATION AND REDUCTION ......................... 20

4.1 Electrolysis ................................................................................................................................. 20

4.1.1 Electrolysis of water .................................................................................................................... 20

4.1.2 Electrolysis of sodium chloride melt. Metal sodium ................................................................... 20

4.1.3 Electrolysis of sodium chloride water solution .......................................................................... 20

4.1.4 Electrolytic production of chlorine and sodium hydroxide ......................................................... 21

4.1.5 Diaphragmal and membrane electrolysis of sodium chloride dilution ....................................... 21

4.1.6 Amalgam electrolysis of sodium chloride dilution ...................................................................... 21

4.1.7 Electrolysis leading to sodium hypochlorite, chlorate and perchlorate ..................................... 21

4.1.8 Electrolysis of aluminium ............................................................................................................ 22

5 REACTIVE COMMODITIES ......................................................... 23

5.1 Fixed nitrogen ............................................................................................................................ 23

5.1.1 Nitrogen in the nature ................................................................................................................ 23

5.1.2 Obtaining of nitrogen substances from coal ............................................................................... 23

5.1.3 Combustion of nitrogen .............................................................................................................. 23

5.2 Ammonia ................................................................................................................................... 24

5.2.1 Direct synthesis of ammonia ...................................................................................................... 24

5.2.2 Ammonia reactor ........................................................................................................................ 24

5.2.3 Use of ammonia .......................................................................................................................... 24

5.3 Sulphur and sulphuric materials ................................................................................................ 24

5.3.1 Cycle of sulphur .......................................................................................................................... 24

5.3.2 Sources of sulphur for the industry ............................................................................................ 25

5.3.3 Hydrogen sulphide ...................................................................................................................... 25

5.4 Elementary phosphorUS ............................................................................................................ 25

5.5 Unsaturated hydrocarbons ....................................................................................................... 26

5.5.1 Steam catalytic cracking (ethylen pyrolysis) ............................................................................... 26

5.5.2 Separation of products by cracking ........................................................................................... 27

5.5.3 Acetylene and products from acetylene ..................................................................................... 27

6 ACIDS ....................................................................................... 29

6.1 Sulphuric acid ............................................................................................................................ 29

6.1.1 Contact production ..................................................................................................................... 29

6.1.2 Use .............................................................................................................................................. 29

6.2 Nitric acid ................................................................................................................................... 30

6.2.1 Production of nitric acid .............................................................................................................. 30

6.2.2 Characteristics and use ............................................................................................................... 30

6.2.3 Ammonium nitrate ..................................................................................................................... 30

6.3 Phosphoric acid ......................................................................................................................... 31

6.3.1 Thermic phosphoric acid ............................................................................................................. 31

6.3.2 Extractive phosphoric acid .......................................................................................................... 31

6.3.3 The use of phosphoric acid ......................................................................................................... 31

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6.4 Acid Gases ................................................................................................................................. 31

7 BASIC AGENTS .......................................................................... 33

7.1 Lime ........................................................................................................................................... 33

7.1.1 The use ........................................................................................................................................ 33

7.1.2 Lime production .......................................................................................................................... 33

7.2 Sodium hydroxide ...................................................................................................................... 34

7.2.1 Production through caustification of soda ................................................................................. 34

7.2.2 Production by electrolysis ........................................................................................................... 34

7.2.3 Potassium hydroxide................................................................................................................... 34

7.3 Ammonia ................................................................................................................................... 34

8 BIOTECHNOLOGY...................................................................... 35

8.1 Carbon in living organisms ........................................................................................................ 35

8.1.1 Photosynthesis ............................................................................................................................ 35

8.1.2 Aerobic processes ....................................................................................................................... 35

8.1.3 The anaerobic processes ............................................................................................................. 35

8.2 Biological cleaning of waste water ............................................................................................ 36

9 FURTHER REFERENCES .............................................................. 37

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1 CHEMICAL TECHNOLOGY - INTRODUCTION

Study time

4 hrs

The aim

To introduce typical commodities and final products of chemical technology

To show specific features of chemical industry and its development

To refresh knowledge of chemical equilibrium and kinetics

To point out the methods of chemical reactor control to yield demanded products

To show importance of physical separation for pure products manufacture

1.1 DEMAND OF CHEMICALS

1.1.1 Direct use of chemicals

Direct use of chemicals in households is not common, just to remind a few: salt, sodium, baking soda,

salt acid, gypsum, sometimes even ammonia, boric acid, potash, lye. Gardeners and handymen can

broaden this list even more. The species are known more by commercial names, without considering

them as simple chemicals. If we bypass fuels (natural gas, LPG, gasoline, diesel) and common

solvents (acetone, trichloroethylene), user does not come also across any simpler organic substances.

The chemistry and the chemicals are however involved in a preparation of most important products,

starting with such vital substances as potable water, as well as utility - industrial water and treatment

of waste water, sometimes also the air is treated with chemicals. Food industry also uses the chemical

processes already in the production of sugar and amyl, but also in fermentative and other

biotechnologies, in preparation of tasting and fragrance substances, processing of milk, fats,

production of detergents, during processing and conserving of meat and vegetables. Important group

of very complicated, but usually low-ton chemical processes can be found also in a pharmacy during

production of pharmaceuticals, strengthening substances, drugs and cosmetics. Fine solid, liquid and

gas fuels including fuels, greases, additives go through a difficult chemical processing. A very

demanding chemical process gives us nuclear fuels. Chemical additives can also ease the production

and utility of building materials (mortar, bricks and ceramics, glass, cement, construction plastics).

Typical chemical operations are the production of the chemical pulp and paper and also the

production of polymers – plastics, synthetic fibres, rubbers, cements and glues. The industry of paints,

pigments and binders of paints is also very broad. The textile industry uses chemicals in the

production and treatment of fibres and cloths, a traditional application is in tannery. Agriculture uses

fertilisers, regulators of growth, additives for feedstuff and pesticides (herbicides, fungicides,

insecticides, or rodenticides). Industry of explosives both for army and civil use is also very broad.

The metallurgy of metals (iron, non-iron and special materials for electronics) consists also from

many chemical technologies, from extraction of ores to finalizing of materials.

The parts of the chemical productions, where special final products are produced (usually in

smaller volume) are known as qualified chemistry.

1.1.2 Main products of chemical technologies

Qualified chemistry uses (in large volumes) substances, for which are not usually highly demanded on

the retail market. These are the substances which by their reactivity make chemical processes work;

they are usually labelled as agents. Their production in the pure and concentrated form from

accessible materials is known as basic or heavy chemistry. The process of extraction is usually not

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one-tier, but is usually based on many physical and chemical operations, which are generally called

production technology.

The key inorganic agents are usually strong alkalis (soda, sodium hydroxide, calcic hydroxide),

strong acids (hydrochloric acid), or with an oxidising effect (nitric acid, sulphuric acid), oxidising

agents (chlorine, oxygen, hypochlorite, chlorate, permanganate), reduction agents (hydrogen, carbon,

carbon monoxide, sodium, phosphor, sulphites). We also prepare substances, which contain elements

in a reactive form (for example phosphor, sodium, chlorine and aluminium directly as elements,

nitrogen, which is as an element non-reactive in the form of compounds: ammoniac or nitric acid).

There is also a demand for intermediate products which are well keepable (sulphur instead of

hydrogen sulphide, dichloroethane instead of vinyl chloride). Although the tank and tube

transportations of chemicals are frequent, it is more common that chemical factories prepare agents

directly in the place of their use. Most of the population will never come across, for example sulphuric

acid, nitric acid, sodium hydroxide, hydrogen, ethylene, benzene or chlorine. Although these are the

substances which are produced and are used in an amount of about 50 kg per capita yearly.

Evaluate yearly use of the chemicals and other high-capacity products per capita

(from the data for the Czech Republic for the year 2004): 60 m3 of drinking water, 20 t of aggregate, 5000 kg of

coal, 3000 l of liquid fuels, 1300 kg of cereals, 600 kg of steel, 400 kg of cement, 400 kg of potatoes, 350 kg of

coke, 180 l of beer, 100 kg of plastics, 80 kg of flour, 60 l of milk, 40 kg of paper, 30 kg of detergents, 8 kg of

coating compounds, 4 kg of sugar, etc.

Try to find newer data and fill in further interesting data.

Think about what the products are and what the intermediate products are

Example: how many kg of seed is gathered, how much flour is milled, how much dough is prepared, how much

bread is baked? How many kg are produced in this industry generally? Remember the economical term “added

value”.

Although the general production of the final chemical products is lowered permanently about 5% a

year, in the times, where the motto is lowering of energy and raw material as well as human labour, we

can see, in the recent years a slow decrease of production of the basic chemical substances by a major

lowering of the number of employees and increasing of their qualification.

- Is the production of chemicals demanding?

171 000 workers participated on the production of the basic chemicals in the USA in 2002 – only about 18% of

employees of chemical industry, their salaries ($981 a week) were 30% higher than the average salary in the

chemical industry.

- The evolution of the chemical industry Until the industrial revolution in the 19th century, the production of chemicals was very limited.

Leaching and distillation of natural materials provided substances, which were assumed that can only,

be created with the help of plants and animals by the effect of the life force (“vis vitalis”). Sugar, oils,

amyl, vinegar, spirit, various paints and aromatic substances were separated, and the separation is

present even today, when we divide the organic and inorganic chemistry. Substances which come from

inanimate nature have interesting reaction under the influence of heating. Metals were gained from

ores and pyrites; lime was obtained from limestone and other substances were prepared, which reacted

with the water and other liquid agents.

Industries developed from the technology, such as metallurgy of bronze (2000 B.C.) and iron (1000

B.C.). These technologies depend on the use of charcoal, the same goes with the production of lime.

The latter middle ages brought the production of gun agents, and the production of glass, tannery and

textile agents.

The industry was growing especially in large cities supported by a good transport infrastructure and by

sufficiency of workforce. The chemical industry has however specific demands, it needs, for example,

very much energy, especially for the heating and the cooling and it produces solid, liquid and gas

waste. This is why chemical factories were built in areas near rivers.

The chemical industry obviously subjects to globalisation. Some commodities can be profitably

produced only in high capacity units and it is cheaper to transport them on large distances. Besides

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pipelines and gas conduits there are other product lines (fuels, diesel, and ethylene), liquid ammonia is

also transported via lines and in some areas compressed hydrogen is transported also. Rail and road

tanks exist in a large selection and are adjusted also for the transportation of corrosive, flammable,

explosive and toxic substances. This makes large competitive environment, where large companies

survive very well. Many chemical substances are produced, for example, in China; these substances

are cheaper, because China does not follow standards of safety and hygiene of work which is binding

in Euro-Atlantic area.

1.2 PROCESSES AND EQUIPMENTS

1.2.1 The balance of chemical reactions

We have learnt stoichometric calculations in chemistry according to the chemical equations. In

process engineering we were able to cope with more difficult balance schemes. It is necessary to

solve perfectly these tasks for the chemical technology. Often all material is not changed into the

desired product, this can be caused by the fact that there are simultaneously running reversible reaction

and the result is balanced compound.

There are also running simultaneous and concurrent reactions, and besides the main product

several intermediate products and by-products are created. In these conditions we need to somehow

express where the reaction has happened. We measure this by the changes of some accordingly chosen

substance, so called key component, which is usually the most important or most expensive raw

material. Then we use the term conversion, which is molar fraction, or a percent of the changed key

component. If there are more different products created, we also use yield of chemical reaction,

expressing which part of the key component has changed into the monitored product. Further used

term is selectivity, which is a ratio of the key component changed into the desired product.

- the production creates formaldehyde by oxidation of CH4 + O2 HCHO +H2O. Besides that there is

running an unwanted oxidation of CH4 + 2O2 CO2 + 2H2O. 1000 moles CH4 come into the reactor and out

comes 300 moles of HCHO and 100 moles of CO2. The key component is CH4.

- there remain unreacted 1000-300-100=600 moles of CH4 ,

- conversion is ((1000-600)/1000)*100% = 40%,

- yield of formaldehyde is (300/1000)*100% = 30%,

- selectivity is (300/(300+100))*100% = 75%.

1.2.2 Equilibrium of the chemical reactions

The maximum possible level of changeover is given by the balance of the chemical reaction. Some

reactions can happen practically entirely and these are called irreversible reactions. For balanced

reaction

aA+bB=cC+dD

is defined the balanced constant by compound of final mixture. We use equilibrium constant for the

reactions in liquids by the relation

ba

dc

BA

DCK

][][

][][ ,

in which terms in square brackets are equal by the given way to chosen activities of each reactant and

product. Fairly small mistake can happen in diluted solutions, when instead of activities we use values

of concentration of compounds in the units mol/dm3, while we use one for not perfectly dissolved

solid compounds.

For reactions in gas phase we use a modifiedconstant

b

B

a

A

d

D

c

C

ppp

ppK

Where the values pi are respective partial pressures if the system behaves like ideal gas; otherwise

fugacities, should be applied.

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Neither values K nor Kp can usually be found in databases, but we remember from the physical

chemistry that they are related to a given change of free (Gibbs’) energy ΔG. The reaction happens, if

there is ΔG<0. If there is ΔG>0, reaction happens in the opposite way and by ΔG=0, it is in balance.

In basic chemical databases we can find mostly only values of ΔG298 for combining reaction of

particular clear substances from elements in a standard state for inorganic compounds. For organic

compounds combustion ΔG298 are more common. We can find out from this, by adding values,

multiplied by relevant stoichiometric coefficients for products, and by subtraction of reactants, how

the studied type of reaction would react under normal conditions.

Level of interchange can be influenced by the shifting of equilibrium which happens according to Le

Chatêliere’s principle: "Any change in status quo prompts an opposing reaction in the responding

system”.

- by the increasing of temperature we support endothermic reaction,

- by the increasing of pressure we support the reaction with decreasing of the volume of

mixture,

- we also support the reaction by the increasing of the concentration of some input substance or

by the decreasing of the concentration of the input substance, for this can be also used the

influence of dilution by inert substance

The synthesis of ammonia 3H2 + N2 2NH3 is a reversible reaction with the change of the volume of gases. Its

equilibrium can be shifted by the increasing of pressure. Pressures of 30-100 MPa, are used in practical reality.

1.2.3 Kinetics of the chemical reactions

The rate of proceeding of the chemical reactions towards the equilibrium generally grows with the

concentration of reactants. If the reactants are spent the speed of the reaction falls.

The dependence of the speed of the reactions on the compound can be a direct proportion, but mostly

it is more complex. Catalysts influence majorly the speed of the reaction; however they do not, in any

case, change the equilibrium. However they can suppress the possible influence of unwanted

concurrent and consecutive reactions by the change of the speed of reactions.

The rate of reaction grows exponentially with the temperature; usually during the growth of the

temperature of 10 K, it doubles or triples.

The reversible endothermic reaction

Higher temperature shifts the equilibrium to the products and at the same time increases the speed of their

creation.

An example is the industrial production of hydrogen during the reaction CH4 + H2O 3H2 + CO, which

operates at the temperatures around 1000°C (higher temperature would bring disproportionate demands on the

material and construction of the device).

Reversible exothermic reaction:

Lower temperature shifts the equilibrium to the products and at the same time slows their production. Higher

temperature shifts the equilibrium back and at the same time increases the speed of the creation of products.

Obviously there is a certain optimum of temperature, by which there is created enough of the product with the

acceptable speed.

Examples are the industrial productions of

ammonia 3H2 + N2 2NH3 ,

sulphur trioxide 2SO2 + O2 2SO3 ,

which are unbearably slow at the temperatures below 400° C and which process with low yield at higher

temperatures. Slow reaction demands a large reactor, by low yield there is a high demand for the separation of

the product from the mixture of reaction. Optimal temperature is chosen based on the economical balance of the

according investment and operating costs.

1.2.4 Batch and flow reactors

Classic reactors were mostly for batch. Working process began by the filling of reactants, further

there was a reaction, which was usually supported by the heating or the cooling. After an interception

of the reaction, the products were changed by a physical method. The batch processes are usual in the

work with small volumes of liquids, or grain materials in laboratories or in qualified productions. As

https://en.wikipedia.org/wiki/Status_quo

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soon as the gases are processed, it is switched into semi-continuous reactors; the gas is led into the

batch.

The chemical mass production tries to use continuous reactors, into which there are reactants

constantly led and simultaneously the products are led out. If there is a reliably secured preserving of

all flows, temperatures and pressures, flow reactors do not require any demanding operation and they

are only periodically stopped for a planned control, cleaning and maintenance. An example of a flow

reactor for slower reactions is the continuous stirred tank reactor, in which reactants stay for an

estimated period, which is possible to tell according to “the spatial time”, which is a ratio of the

volume of reactor to the flow. An easier device is the tube reactor, suitable for quick reactions.

Especially some reactions in gases need only a fraction of a second and reaction takes place as

quickly, as we are able to bring it onto the reaction temperature.

1.2.5 The separation of the mixtures

Raw material of the chemical industry, but also the results of the chemical reactions are usually

mixtures, from which we need to separate the desired substances. That is why major part of the

chemical production units are separation devices. We usually use these processes for dividing of the

mixture, in the final phase

- physical principles, like sedimentation, filtration or membrane dividing.

This is usually preceded by the process of the dividing of mixtures into different phases (gas, liquid,

solid particles of demanded size). We use for example:

- helping agents, for example, for solution of solid particles, or absorption of gases in the water,

or in organic liquid, liquid extraction, drying with air, adsorption on the surface of sorbents

etc.

- a proper setting of the temperatures and pressures – for example evaporation and

condensation, distillation, melting, crystallizing .

For good manipulation there is usually needed a mechanical processing of solid materials: sorting,

grinding, crushing, but sometimes also agglomeration and granulation.

The summary of terms

Chemical commodities

Qualified chemicals

Chemical balance, stoichiomettry

Chemical equilibrium, le Chatelieur principle

Chemical kinetics, catalysts

Batch and continouous reactors

Two phase mixtures

Physical separation

Questions

Which are properties of important chemical agents?

How much chemicals is manufactured?

What is chemical equilibrium and how to control it?

What is rate of chemical reaction and how to control it?

What are various kind of chemical reactors good for?

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Used literature

This publication was made based on a very detailed and continuously supplemented text

WICHTERLE K.: Chemická technologie, (Chemical technology) available for free at

http://homen.vsb.cz/~wih15/Technologie/Chem_Tech.pdf

In the English language literature there is a great place for monography

- AUSTIN G.T., BASTA N.: Sre Shreves Chemical Process Industries Handbook, 5. edition, 860

pages, McGraw-Hill 1998, ISBN 007135011X.

Considerable accent on problems of environment is given in a modern book

- HOCKING M.B.: Handbook of Chemical Technology and Pollution Control. 2. edition, 778

pages, Academic Press New York 1998, ISBN 0-12-350810-X. (available for free in electronic

form in Science Direct through server of library of VŠB)

It is possible to use encyclopedia for details, comparatively brief is

- CONSIDINE D.M.: Chemical and Process Technology Encyclopedia, 1184 pages, McGraw-Hill

1974, ISBN 007012423X

http://homen.vsb.cz/~wih15/Technologie/Chem_Tech.pdf

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2 OXIDIZING AGENTS

Study time

3 hrs

The aim

To point out significance of air in chemical technologies

To present techniques of gas mixture separation

To show application of pure oxygen in industry

2.1 AIR

2.1.1 The composition of air

Air is one of the basic chemical materials. The air in nature contains a changeable amount of humidity

(from 0,01% to 10%).

The composition of the rest, so called dry air is very stable in the atmosphere:

% boiling point[K] [oC]

N2 78 77 -196

O2 21 90 -183

Ar 0.9 87 -186

CO2 to 0.04 195 -78

For example O3, SO2, NOX (it means mixtures N2O4, NO and N2O), NH3, H2S, CH4 and other

VOC (volatile organic compounds) and aerosols can also be found in the air.

.

2.1.2 Use of air

Air is very important in the industry as a heat carrying medium (air coolers, air condition) and as a

drying medium (hot air dryers). We can transfer energy on distance (pneumatic machines, for

example nailing machines) or information (pneumatic measuring and regulation) in the form of

compressed air. The air is used as source of oxygen in combustion and oxidising processes without

major adjustments; in these processes is large occurrence of inert nitrogen not a problem.

We need higher temperature in the processes with the combustion of solid, liquid and gas fuels in processes..

- in heating and power plant drums,

- in apparatus of chemical industry,

- in metallurgy of iron and non iron metals,

- in the production of building materials.

Higher temperature is necessary sometimes only for an effective execution of physical processes such as

- drying,

- calcination (production of calcium sulphate).

Sometimes changes of the structure of the heated material occur – air oxygen enters into the products as well

(calcination of metal sulphates).

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The oxidation happens by the use of the air as the material for supplementing of oxygen into the real chemical

productions, for example:

- during the production of sulphuric acid and catalytic oxidation of SO2,

- during the production of nitric acid: combustion of ammonia and oxidation of NO,

- during the production of thermi, phosphoric acid: combustion of P4 ,

- during the production of sulphur by oxidation H2S,

- during biological cleaning of wastewater in aerobic process, etc..

2.1.3 Air as a chemical material

- The air today is practically the only material for the production of each of the technical

gases: oxygen, nitrogen, argon and other rare gases.

The separation of air is not very expensive industrial operation in large production.

Laboratories and small users buy oxygen and nitrogen and each precious gases in pressure

vessels with the pressure of 15 MPa and volumes up to 50 dm3. Major use of oxygen is also during

the creation of high temperature flame, for example for welding and burning of metals, or melting of

glass.

2.1.4 Humidity of air

Voluminal share of water steams in the temperate zone is in the summer up to 0,5%, in polar areas it is

only 0,01%. The adjustment of humidity is necessary in places where we use an air condition, where it

is usually drying – a decreasing of humidity to reach an appropriate comfort. To dispose of the excess

humidity, the temperature is decreased below the temperature of the condensation point, when steams

condensate. If the demands on dryness are high, we use the absorbing of humidity into hygroscopic

substances (for example concentrated sulphuric acid, dehydrated disodium oxosilanediolate (silica

gel), waterless calcium chloride, etc.)

2.2 SEPARATION OF GAS MIXTURES

2.2.1 Methods of separation of the gases and vapors

Gases and steams are unlimitedly mixable, so dividing of their mixtures is usually done by diverting of

a part of the gas into the liquid (or solid) phase, while the compound of created phases usually differs.

Other possibility is to get the gas into the contact with liquid, or with solid phase in which it is

preferentially dissolved, or on which surface some of the components of mixture settle on the surface.

More and more usual is the separation of gases with the help of membranes.

2.2.2 Separation of distillations

Liquefying of the vapor (in primal state under the critical temperature) is possible to reach either by

cooling, or compression. During the separation of steam from the liquid – distillation - we get the

steam enriched for volatile parts and impoverished of the liquid rest. During repeated distilled

separation we can come to purer components. The device for this operation is usually thin, distillation

(rectification) column. Fractional distillation is a process of the separation of multi-component

mixture, where the pipe, with takings of steam in different heights, works as a row of columns built

behind one another.

2.2.3 Liquefying of gases

For the transformation of gases (in primal state above the critical temperature) into the vapors, or

liquid, we always have to cool it below the critical temperature at first. If the critical temperature is

low, there is not an according cooling agent available, and then we must use machine cooling (like in

refrigerator). The isothermal compression is usually used for liquefying of gases and further adiabatic

expansion.

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2.2.4 Separation of absorptions

We can have the effect on the gas mixture also with another liquid phase –solvent. If the solubility of

gases is different enough in this dissolvent, then more soluble component is preferably absorbed into

the liquid. Then absorption happens, with the advantage of higher pressure and lower temperature. In

opposite by desorption we can release any caught component.

2.2.5 Separation of adsorptions

Under specific circumstances, relaxed molecules of some components of gas settle on the surface and

in pores of some grain materials – sorbents; there comes to the adsorption, again with the advantage

of higher pressure at lower temperature. The PSA process (pressure swing adsorption) cyclically

catches and releases some components from the mixture by the change of the pressure.

2.2.6 Separation by membranes

Different mobility of molecules in micropores and nanopores of some materials can be used

for the separation of gases on a similar principal as the filtration. In the present time the development

of effective and trustworthy material of membranes for industrial separations quickly moves forward.

The separation of air is inexpensive bulk industrial operation.

2.3 OXYGEN

Bulk consumers of oxygen, especially steel plants, produce oxygen on the place of use and

nitrogen is usually unused waste. Nitrogen is used by the chemical industry especially for the

synthesis of ammonia. The use of collaterally obtained oxygen is always found. The reduction of the

price of oxygen led into its implementing into the productions in which there had been traditionally

worked with air. This concerns not only classic chemical productions, but also metallurgy of iron and

aerobic fermentations in the biotechnologies.

2.3.1 Separation of air by distillation

Machine cooling is used for liquefying. Nitrogen evaporates from the liquefied air the easiest,

then there is argon and oxygen stays in the liquid the longest. We obtain other rare gases in demanded

purity during careful multistage separation.

The use of Linde column was set for the separation of liquid air, these are two separated pipes

built above each other. Rough separation of mixture happens in lower pressure column. Pressure of 0,5

MPa in the high pressure part is chosen so, to respond to the boiling point of nitrogen -179° C is here

above the boiling point of oxygen by the normal pressure, -183° C. We heat the boiling oxygen during

increased pressure through the wall at the bottom of low pressure upper column by condensed nitrogen

and we do not have to use further cooling, or heating medium. The separation is very good and we get

argon or other rare gases from the centre of the column.

2.3.2 Other processes of air separation

Air can be also separated by the alternating adsorption and desorption PSA (pressure swing

adsorption) on micropore surfaces, “molecular filtration”.

Other possibility is to use the specific difference of throughput of each component through

suitable membranes.

Both methods are used in smaller scale, but they are not suitable for large production with

high demands on the purity of the products.

15

2.4 OTHER OXIDANTS

An important oxidizing agent is chlorine. There is also a great number of liquid and solid

oxidizing agents which are used for laboratory and industrial oxidations. Let us mention oxidizing

acids H2SO4, HNO3 or salts – nitrates, chlorates, chromates, permanganates etc.


Air

Oxygen

Distillation, distillation column

Liquid and solid sorbents, absorption and adsorption

Membrane separation

Questions

What are industrial application of air?

Why air is sometimes unsuitable for oxidation?

How to separate gas mixtures?

How to reach low temperature?

16

3 REDUCING AGENTS

Study time

4 hrs

The aim

To introduce natural reducting agents – fuels and products of their processing

To point out methods of hydrogen manufacture and its significance

To mention metals, which can be used for reductions

3.1 FUELS AND THEIR PROCESSING

3.1.1 Occurrence and use of carbon fuels

Common fuels are carbonaceous substances, which occur in nature as solid fossil fuels (coal from the

oldest anthracite to the youngest lignite). Further are liquid fuels (crude oil and its modifications) and

gas fuels (natural gas). Biomass is one of non-fossil fuels (lignocellulose material of plant origin), in

smaller amount fats and other changed plant and animal products. All kind of organic waste has also

been used as a fuel in the recent years.

Classic use of fuels is simple - obtaining of heat (or light) from fuels by their air oxidation. Further is

the use of fuels as reduction agents, commonly in metallurgy.

Refining of fuels with different goals has also been beneficial besides simple combustion:

- Obtaining of pure fuels (carbon, hydrocarbon, carbon monoxide, hydrogen) with higher

thermal power and easier storability and manipulability,

- Obtaining of purer reduction agents (production of hydrogen, phosphor etc., metallurgy)

- Obtaining of raw material for organic synthesis (coke chemistry and petro chemistry).

3.1.2 Coal and its processing

Coal is not chemically defined substance. The compound and structure of coal is only slightly similar

for each mining basin and there are major differences even among different stratums of one mine.

Main chemical compound of coal is carbon. Further 2-6% of weight H is in all element composition of

coal. Oxygen – from 3% is in anthracite, more found in common coal, and up to 45% in the youngest

coal – lignite. Nitrogen and sulphur are usually around 1%, but sometimes even more.

Most common way of processing of solid fuels is carbonization, which is done by the heating in

absence of the air. Metallurgic coke with high mechanical hardness, suitable for blast-furnaces, is

obtained by carbonising of high quality anthracites at 900-1200°C. Carbonisation is done in a batch

way in the coking chambers, where there is stomped powder coal and then it is heated for several

tens of hours. During that is the coal substance linked into the pore coke and volatile combustible

leaks. Volatile combustible contains released substances: oxygen from the coal changes into CO,

hydrogen is released, both in the form of hydrocarbons, and in an elemental form as gaseous H2. After

condensation of heavier organic substances (tar) and after washing off more volatile aromatic

substances – “crude benzol” and inorganic NH3, H2S and HCN coke gas contains over 50% of H2,

10% CO and 35% hydrocarbons CH4 and C2H6. It was important material for obtaining hydrogen in

the past. Tar and crude benzol are important sources of aromatic hydrocarbons nowadays.

Gasworks were important in the past, here brown coal was carbonized with the goal of obtaining

town-gas for lighting and heating.

17

3.1.3 Crude oil and its processing

Crude oil (British English: petroleum, American English: oil, crude oil) is a liquid substance which

consists mostly from hydrocarbons. Although it was also created from biomass, it contains less oxygen

and nitrogen than coal. It has a different content of sulphur, 0,1-3 % S.

By its separation by atmospheric distillation (during normal pressure) LPG (liquefied petroleum gas)

is obtained as the most volatile part, and we also obtain the base of petrol (American English:

gasoline), diesel oil and black oil. This is then processed by vacuum distillation to gain heavier oils

and asphalt remains as the rest.

Motor fuels are supplemented and refined with products of petrochemical cracking at temperatures of

450-550°C, which breaks larger hydrocarbon molecules of particles of black oil and less interesting

oils into the liquid hydrocarbons. Catalytic reforming at 300-600° C increases share of aromatic,

cyclical and branched hydrocarbons, and the octane and cetane number grow by this.

3.1.4 Natural gas

Main component of natural gas is methane, CH4 typically above 90% and other gas hydrocarbons.

Hydrogen sulphide, separated from earth gas and crude oil is today’s main source of sulphur for the

chemical industry.

3.1.5 Non-fossil fuels

Processing of non-fossil materials and organic waste into fine fuels is more demanding and costly,

but it is taken as exigence. Surplus agriculture in developed countries is a large contributor to this as

well.

3.1.6 Carbonization of non-fossile substances

The basis of production of charcoal is carbonization, after which carbon remains in the form of

charcoal. Special conditions of carbonization can give us, from different biological materials, almost

pure, nanoporous carbon – active coal, usable as adsorption, or catalytic material.

3.1.7 Bioethanol

Ethanol, C2H5OH, which is easily created during alcohol fermentation of sugar, can be obtained also

from other carbohydrates. Alcohol fermentation lasts by itself several weeks and ends when the

concentration of ethanol reaches around 12% and alcohol starts to be a poison also for the yeast. For

the use as the fuel, ethanol has to be separated by distillation from water and the rest of the substrate.

3.1.8 Biodiesel

Many plants store energy in their seeds into lipids. These are esters of glycerine and higher fatty acids

(even number of carbons 16-22, 0-3 dual bind). They are generally labelled as fats or oils.

Reesterification by methanol (substitution of glycerine for methanol) in alkali environment at slightly

increased temperature creates glycerine and fatty acid methyl ester (FAME), which is used as fuel for

diesel engines.

3.1.9 Biogas

Biogas is created by slow metabolism of anaerobic organisms, which have the organic waste

dissolved. There is methane CH4 created in the mixture with CO2 and it is a low heating fuel. By

clearing of CO2 NH3 and H2S we get quality equivalent of natural gas.

18

3.2 HYDROGEN

3.2.1 Use of hydrogen

70% of produced hydrogen is an intermediate product of the synthesis of ammonia, NH3 .

Around 25% of hydrogen is produced in the petrochemical factories and is used on the spot for

hydrogenation and refining.

3.2.2 Overview of production of hydrogen

Coke gas and coal gas contain mostly H2, CO and hydrocarbons. It is possible to condensate

the rest of the components and remaining hydrogen during deep freezing to -200°C. It is used only as a

fuel in the present.

Purer mixture of CO a H2, so called blue gas, prepared by the reduction of water steam on

flaming coke was main source of hydrogen (90%) in European chemical industry until 2nd World war.

In present it is more common to obtain it by steam reforming of hydrocarbons.

Hydrogen is also created in the petrochemical industry as a side product during high

temperature cracking of hydrocarbons.

Production of hydrogen by the electrolysis of water is relatively expensive, potentially it is

considered as a method of use of surplus electricity from irregularly producing recoverable resources.

3.2.3 Carbonization of coal

During coking, this means the heating of coal in absence of air up to about 800°C, hydrogen is

released in the forms of hydrocarbons and in the elementary form as gas H2. Coke gas contains above

50% of H2 after condensation and after washing of NH3, H2S and HCN.

3.2.4 Blue gas

90% of hydrogen was obtained in so called generator before the 2nd World war. There are

these reactions in the cycle in a layer of the coke. Exothermic oxidation happens during the blowing of

layer by air

C + O2 → CO2 ΔH= -393 kJ/mol

and at a higher temperature CO2 reacts with other carbon of molten coke

CO2 + C → 2CO ΔH= +173 kJ/mol

to produce low heat value combustible gas.

After reaching high enough temperature, water steam is introduced and there comes to the

endothermic reaction

C + H2O → H2 + CO ΔH= +131 kJ/mol

by which is the carbon gradually cooled and the cycle returns to the beginning.

In the last step created energetically rich product is called blue gas and it was one of the

classic sources of hydrogen. Blue gas was an important material for the production of hydrogen and it

is an entry to C1 chemistry for synthesis of simple organic substances (light hydrocarbons, methanol

and other alcohols, ketones). It is also an interesting reduction agent for metallurgy.

3.2.5 Steam reforming

Fischer-Tropschov (F-T) synthesis of hydrocarbons from hydrogen and carbon monoxide

by catalytic reaction at temperatures about 200°C is

(2n+1) H2 + n CO ↔ n H2O + H[CH2]nH ΔH ≈ -160n kJ/mol

It is reversible exothermal reaction; direction from right to left at high temperature is the most

used way of production of hydrogen in the present.

In the case of methane it is an endothermic reaction

CH4 + H2O ↔ 3H2 + CO ΔH= +206 kJ/mol

It is made in heated tubes at temperatures of 750-800°C by using catalyser NiO.

Outer heating of the reactor can be avoided by the use of exothermal partial oxidation

CH4 + ½ O2 → 2H2 + CO ΔH= -36 kJ/mol .

19

For obtaining of pure hydrogen, we make firstly so called conversion on ferrous catalyser at

500°C

CO + H2O ↔ H2 + CO2 ΔH= -41 kJ/mol

Created CO2 is then possible to separate from hydrogen perfectly, for example by the PSA

method.

3.3 ELECTROPOSITIVE METALS

While noble metals do not react spontaneously with oxygen, highly electropositive metals can

be oxidized easily. Metals like Na, Ca, Mg, Al, Zn can be used for number of laboratory reductions.

Cheaper metals like Al, Zn are also employed for cementation of less electropositive elements, e.g.

Zn + Cu++ → Zn++ a Cu


Fossil fuels, coal, oil, natural gas

Biomass

Carbonization, coke, volatiles, tar

Hydrogen

Steam reforming

Blue gas

Electropositivity

Questions

Where are fossil fuels used for chemical purposes other than a simple combustion?

How are refined fuels produced from coal and oil?

Which chemical processes employ hydrogen?

20

4 SIMULTANEOUS OXIDATION AND REDUCTION

Study time

2.5 hrs

The aim

To explain principle and quantities characterizing electrolysis.

To show variability of products, according to the electrolyser configuration.

4.1 ELECTROLYSIS

We make oxidation during electrolysis (taking of negative electric charge) and reduction (adding of

negative electric charge) simultaneously for the price of supplied electric energy. Principle of

electrolysis is the fact that moving ions in liquids (in solutions or melts) provide transfer of electric

energy in a way that positive cations move towards the negative cathode and negative anions towards

the positively charged anode. The discharge happens when the voltage between electrodes exceeds a

certain balanced value (it is in units of volts). Electric charge needed for transferring of one mole of

electrons is independent on type of the reaction and is expressed by Faraday constant

F = 96500 C/mol. (C is a symbol for 1 coulomb, which is charge, transferred in 1 second by the electricity of 1 Ampere.)

Reduced substance is created by discharging of cations, oxidised substance is created by the

discharge of cations.

4.1.1 Electrolysis of water

Water is decomposed by electrolysis into a gaseous oxygen and gaseous hydrogen. Because water

itself has small electrical conductivity (distilled – deionised water is practically non-conductor), it

increases its conductibility with a helping electrolyte, for example H2SO4 or KOH.

Electrolyte KOH is chosen the most commonly for production of hydrogen and it is processed in the

pressure of 3 MPa. Consumption of energy is 4-4,5 kWh/Nm3 of hydrogen that means 45-50 kWh/kg.

4.1.2 Electrolysis of sodium chloride melt. Metal sodium

There are ions Na+ and Cl- in the melt of sodium chloride. For a sufficiently fast transfer of the charge

there is put direct flow charge 7-8 V on electrodes. There is a reaction on the cathode

Na+ + e- → Na

Simultaneously with the reaction on anode

Cl- - e- → ½ Cl2 .

Elementary sodium metal is a low ton chemical (World production of Na is about 250 thousand of tons a

year – compare to 80 million tons of NaOH a year. It is not produced in the Czech Republic).

4.1.3 Electrolysis of sodium chloride water solution

The ions Na+ and Cl- are also present in the water dilution of sodium chloride, however there are

also ions H+ (more specifically H3O+) and OH- and of course molecules of water. The fact which

reactions run primarily depends on the material of electrodes, on input voltage and also on

temperature. But chlorine on an anode is created primarily

Cl- - e- → ½ Cl2

The reaction has priority on cathode

2H2O + 2e- → H2 + 2 OH- .

21

Solution NaCl reduces itself of appropriate ions, so chloride ion is gradually replaced by ion OH-, so

often the most important product of this electrolysis is sodium hydroxide NaOH.

Energy for electrolysis:

the reaction (2)(6) gives us during the passing of charge of 1 mole of electrons F=96 500 C 1 mole NaOH (40g)

and half of mole H2 (11 dm3) and half of mole Cl2 (11 dm3). Working voltage for this process is larger than

equilibrium 2,3 V, usually U = 3V (the larger voltage the larger consumption of energy, but better use of device;

there is optimum). Energy needed for preparation of 1 mole NaOH is according to this F.U= 290 000 J = 0,08

kWh. For preparation of 1 kg of NaOH there is needed around 2kWh of electric energy, while we obtain

simultaneously 0,28 m3 of hydrogen (25 g) and chlorine (890 g).

4.1.4 Electrolytic production of chlorine and sodium hydroxide

Both products are interesting chemical commodities and in history there were several periods

when main products were either sodium hydroxide or chlorine. In the present time there is growing

demand for sodium hydroxide and chlorine becomes hardly utilisable side product.

We use two reaction mechanisms during the production; from which the classic belongs to

amalgam electrolysis and more modern to diaphragm electrolysis and the newest membrane, which

will possibly win in the industry in the future. − amalgam process prevails in western Europe (June 2000):55%

− diaphragm process prevails in the USA: 75%

− membrane process prevails in Japan: > 90 %

4.1.5 Diaphragmal and membrane electrolysis of sodium chloride dilution

When we divide spaces of anode and cathode by porous barrier – diaphragm, or membrane,

allowing only the flow of ions Na, and dilution NaCl (salt water) is supplied into the anode space,

created gases (Cl2 a H2) leave independently electrolyser, pure NaOH dilution is taken from the

cathode space. This turns into melt connectively during evaporating of water, and it is left to freeze by

cooling into the form of known pips or lamellas.

4.1.6 Amalgam electrolysis of sodium chloride dilution

A special behaviour is given by cathode from liquid mercury. Hydrogen is not created on this cathode;

it is absorbed into mercury without reacting with water. During reaction

Na+ + e- + Hg → Na-Hg

alloy Na-Hg is created - alloys of metals with mercury were called amalgam. Sodium amalgam is led

as liquid metal from electrolyser into a separate vessel, in which it meets with water. Here the mercury

is not charged as cathode and sodium is released from it by the reaction

Na-Hg + H2O → Hg + NaOH +1/2 H2

Mercury returns and by crystallization we get pure sodium hydroxide

4.1.7 Electrolysis leading to sodium hypochlorite, chlorate and perchlorate

We pay attention during the production of NaOH so that the created chlorine will leave the space of

electrolyser in the form of gas as soon as possible. If we do not use diaphragm and we use mixing,

chlorine gets in contact with hydroxide, and this creates hypochlorite

Cl2 + 2 OH- → ClO- + Cl- +H2O ,

Sodium hypochlorite, NaClO, is strong oxidation agent, releasing elemental oxygen, and it is used

for example for bleaching and disinfection.

If we increase the voltage between electrodes and we increase the temperature to 70°C, we can reach

further oxidation of hypochlorite in electrolyser, turning hypochlorite into chlorate.

3 ClO- → ClO3- + 2 Cl- ,

It is a part of matches and pyrotechnic mixtures as an oxidising agent.

Further electrolysis on platinum anode can lead to sodium perchlorate, NaClO4, which is even more

efficient oxidising agent.

22

4.1.8 Electrolysis of aluminium

Aluminium is important, more as a base of metal materials than as a reducing agent. Raw material for

its production is bauxite, red brown rock, containing only around 60 % of alumina. It is necessary to

isolate pure Al2O3 from it. Aluminium is then created by the cathodic reduction of melt of oxide on

cathode, created by melted Al. Melting point of Al2O3 is decreased to about 800-900°C by adding

cryolite Na3AlF6. Anode is carbon and gradually subsides by oxidation into CO. Production of

aluminium is energetically very demanding, electric voltage is 5,5-7 V, consumption of energy is

around 20 kWh per kg of aluminium, when electric input covers besides electrolysis itself also heating

of batch.


Cathode, anode, charge

Faraday constant

Amalgam electrolysis

Diaphragm electrolysis, membrane electrolysis

Questions

Which products and by-products can be obtained by sodium chloride electrolysis?

What is function of cathode in aluminium manufacture?

23

5 REACTIVE COMMODITIES

Study time

4 hrs

The aim

To present examples of manufacture starting materials for other chemical processes

To elucidate how reactive organic compounds can be obtained from oil and gas

There are also several important commodities (merchantable substances), which are used for

further chemical processes, besides the substances put directly into the chapters of agents. Sometimes

these are elements, sometimes more reactive purer, better storable and transportable compounds. We

will mention fixed nitrogen as ammonia, sulphur, phosphor and unsaturated hydrocarbon in this

chapter.

5.1 FIXED NITROGEN

5.1.1 Nitrogen in the nature

Nitrogen is an element, which is found in the nature, especially in an elementary form as

practically non-reactive N2 in the air. The deficit of nitrogenous compounds in nature can be covered

by some special microorganisms, so called nitrogen bacteria, which are able to take oxygen for their

creation from the air. Nitrates were the only material for chemistry of nitrogen in the past, they were

obtained from the evaporation from suds and later Chilean nitre was imported.

In 1828 the first organic substance was prepared from inorganic material: Wöhler – revolution in the

conception of chemistry –ammonium cyanate – carbamide (by heat in liquid dilution) CNONH4 →

CO(NH2)2

5.1.2 Obtaining of nitrogen substances from coal

Ammonia is released during the production of coke from coal. This is then washed in cold

water, which gives us ammonia water. Ammonia brought the possibilities of synthesis of organic

compounds. These compounds then led to commercially interesting textile colourings, explosives

and pharmaceuticals.

During the absorption into sulphuric acid there was created a dilution by neutralisation

2NH3 + H2SO4 → (NH4)2SO4

of the oldest industrial azotic fertiliser, ammonium sulphate.

5.1.3 Combustion of nitrogen

The creation of compounds happens in reality also by the direct combination of particles of air

N2 + O2 ↔ 2NO , H=+181 kJ /mol G=+173 kJ /mol

during extremely high temperature of electric arc. Reactive nitrogen oxides were industrially prepared

in this way in Norway in hydro power stations, where it was allowed, because of the accessibility of

cheap electricity.

24

5.2 AMMONIA

5.2.1 Direct synthesis of ammonia

Haber and Bosch, in 1913 in Germany, discovered a way for rational mastering of direct synthesis of

ammonia, NH3, from elements

3 H2(g) + N2 (g) ↔ 2 NH3 (g) , H= -92 kJ/mol,

and they opened a new gate for the development of the industry of fixed nitrogen and industrial

production started in 1915. Germany, which had taken until then a third of the production of Chile

saltpetre, became independent on import. The process needs very high pressure, higher temperature

and use of catalysts.

Today’s production of ammonia is around 50-100 kg a year per capita and represents one of the main

pillars of the chemical industry.

5.2.2 Ammonia reactor

The catalyst is porous iron doped by other trace substances.

It would be advantageous to work at higher pressure, lower temperature and with removal of the

product from the mixture from the point of view of balance. The reaction happens very slowly at a

usual temperature, it is hard work with pressures of 50-100 MPa, and temperatures around 400°C and

with recycling of non-reacted synthetic gas.

A reaction is exothermal, created heat is partly used for pre-heating of synthetic gas.

The ammonia is easily kept in a liquid form at low pressure 1,6 MPa, it is easily storable and

transportable in iron containers, including rail tankers.

5.2.3 Use of ammonia

- Characteristics Ammonia is easily liquefiable gas, it has the boiling point of -33°, it is easily diluted in water

and in acids by creation of NH4+ ions. It has a characteristic smell, manifesting itself already in

concentrations of 17 ppm.

- Direct use – The boiling point -33°C urges to use it as a cooling medium into the closed circuits of machine

cooling industrial systems in the chemical and food production facilities, in cooling plants and on

skating rinks.

– Ammonia is used as a reduction agent for liquidation of NOx

– Ammonia has to be perfectly relieved of humidity for nitride of steels.

- Products from ammonia: – 75% of production of ammonia is for preparation of azotic fertilisers, which are nitrates,

ammonia salts of nitric acid, phosphoric, or sulphuric, urea (10%) and ammonia itself

– 5% of nitric acid for other purposes, nitration, leaching of stones, etc.

– 5% of ammonium nitrate as part of explosives

– the urea (besides the fertilisers, also as part of feedstuff and a material for some polymers)

– ammonium salts of qualified chemistry (chloride, carbonate, acid carbonate, phosphates)

– hydrogen cyanide and cyanides (for the leaching of ores, for the production of acrylonitrile,

etc.)

– hydrazine N2H2 (an interesting reduction agent, rocket fuel for manipulation in the space)

– acrylonitrile, caprolactam, hexamethylenediamine (for synthetic fibres)

5.3 SULPHUR AND SULPHURIC MATERIALS

5.3.1 Cycle of sulphur

Suplhur, S is in elementary crystal form (for example nearby volcanoes) in nature only very

scarcely. Sulphides are represented mainly among the minerals, sulphides, which are not as interesting

as a source of sulphur, but they are mainly basic sources of many non-iron metals. Sulphur is a

biogenic element which is present in the creation of cells of organisms (it is a part of some amino

https://en.wikipedia.org/wiki/Hexamethylenediamine

25

acids). Live substance contains only about 0,5% of S, which reflects also into the content of sulphur in

fossil fuels. Sulphur is released in the form of sulphur dioxide, SO2 during burning. Smelly, toxic

hydrogen sulphide H2S, is released by its anaerobic decomposition (rotting) or by pyrolysis without

the access of the air.

5.3.2 Sources of sulphur for the industry

A main part of the material is created by sulphur obtained from desulphurizing processes

(purifying of earth gas, refining of crude oils, coking plants, iron-works, and power plants).

Altogether, two thirds of the world’s consumption of sulphur are nowadays gained in the form of

hydrogen sulphide washed from crude earth gas, or released by the reaction of crude oil with

hydrogen (hydro-desulphurizing).

5.3.3 Hydrogen sulphide

Hydrogen sulphide is an inconsiderable part of earth gas (up to 5%) and can also be found in other

fossil fuels. In the reduction environment of coking plants and gas houses gaseous H2S is released

from fixed sulphur during processing of crude oil and during pyrolysis of coal. It can be destructed by

a diversion into sulphur by partial oxidisation at 300°C on iron oxide catalyst

2H2S(g) +O2(g) →2S(l) + 2H2O(g),

or

2H2S(g) +SO2(g) →3S(l) + 2H2O(g),

A product is liquid sulphur and water steam. This way of obtaining sulphur is called Claus’

process. An advantage is that obtained sulphur can be (in opposite of unfavourable gases H2S or SO2 )

easily stored and transported.

While in cool stage, the H2S can be oxidised in water solution also by oxygen transferred by a

homogeneous catalyst, for example by dilution of vanadate, which is a part of a modern

desulphurizing process of gas fuels. The newest technologies use transfer of oxygen through trivalent

iron, fixed in chelate.

5.4 ELEMENTARY PHOSPHORUS

Practically the only raw material for the production of phosphoric substances is highly

insoluble phosphate, Ca3(PO4)2, which is stabilised by the presence of other ions on practically

insoluble mineral apatite, most commonly fluorapatite Ca5(PO4)3F. Phosphor is produced by the

reduction of apatite by carbon monoxide, during the presence of coke and sand in heating above

1400°C. Relevant reaction is

Ca3(PO4)2 + 5CO → 3CaO + 5CO2 + 2P

however CO2 reacts back with hot coke

CO2 + C → 2CO.

present silica sand, SiO2 makes liquid slag

SiO2 + CaO → CaSiO3

so general reaction works as

Ca3(PO4)2 + 3 SiO2 + 5C → 3 CaSiO3 + 5CO + 2P ∆H=1520 kJ/mol

Phosphorus is released from the reactor at a given temperature in the form of vapour, which, after

cooling, release solid white phosphorus. If the raw material is fluorapatite, then part of the fixed

fluorine changes as CaF2 into the slag, but about a quarter of it reacts with the present sand creating

gaseous SiF4.

If there are present ferrous compounds as polluting part of apatite, liquid metal iron is created by their

reduction, into which there is a major part of phosphor diluted and there is created compound

ferrophosphor, which is released through the bottom of the furnace.

26

The temperature needed for process of the reaction among solid substances, is obtained by the electric

arc. It is typical electro-thermal technology.

This production is more or less expensive, for obtaining of 1 kg of phosphorus it is necessary to use 15

kWh of electric energy and 8 kg of phosphate, 3 kg of silica and 1,2 kg of coke is used. Also arc

furnace itself is a more expensive device. Elementary phosphorus and other products from it are

imported into the Czech Republic (from Russia and Ukraine).

Phosphorus is material for preparation of pure (thermic) phosphoric acid and also for the

chemical specialties of organic chemistry. Elementary phosphorus is self-igniting. It was important

during the production of matches in the past, when there the matches needed only to be rubbed to be

ignited. In the mixture with soap, it created military self-igniting mixture “napalm”, which cleaved

easily on any surface it hit. Organophosphates, derivates of thiophosphoric acid, are active

insecticides (agents killing insects), some are nerve poisons, acting also on higher living beings

(forbidden combat chemical substances “sarin”, “soman”, etc.). Some organophosphorus substances,

however, are very good fire extinguishers.

5.5 UNSATURATED HYDROCARBONS

We get, almost exclusively, little reactive saturated hydrocarbons from the fossil material.

Unsaturated hydrocarbons are more appropriate for most of organic syntheses, especially for the

preparation of polymers. The most important input material was acetylene (ethyne) and recently it is

ethene, C2H4, in technical terminology traditionally called ethylene and other unsaturated

hydrocarbons with three or four carbonaceous molecules. 400 thousand tons/year of ethylene (40 kg

per capita yearly) are produced in the Czech Republic; it is 70 kg per capita yearly in the USA.

5.5.1 Steam catalytic cracking (ethylen pyrolysis)

Cracking is generally a thermal destruction of hydrocarbons at higher temperatures. Cracking of

ethane happens through this reaction

C2H6 ↔ C2H4 + H2 ΔH=125 kJ/mol.

Ethylene is produced mainly, it is the simplest hydrocarbon with double bond: H2C=CH2. It is a gas

(boiling temperature -103,7°C), not present in the nature in major concentrations. The balance of the

endothermic reaction is majorly shifted to the right at higher temperatures, in practical reality; the

common temperatures are at 750°-900°C. Because the number of moles increases, it is more

convenient to have lower pressure; this is obtained by the decreasing of the partial pressure of the

mixture by dilution with the water steam. The present steam also suppresses the creation of coke crust.

This process is then called steam catalytic cracking. A usual catalyser is Cr2O3 built-up on an

aluminium carrier (Al2O3). The reaction is made in tubes, coming through the pyrolytic oven, when

period of delay of the mixture at high temperature is just a fraction of a second (0,1-1s). Then there is

fast cooling, fewer than 650°C to prevent further reactions (for example reaction of water with

hydrocarbons – steam reforming by the creation of hydrogen and carbon monoxide). During the

controlled processing of the reaction, the yield is around 70% and selectivity up to 80%. Yield of reaction represents what part of the reactant is converted.

Selectivity of reaction represents what part of products form the desired product.

Above 50% of ethene and not-reacted ethane comes out of the reactor.

Because ethane and other gaseous hydrocarbons are available only from some sources of earth gas and

crude oil, cracking of higher hydrocarbons is used and in the whole Europe is used, for the

production of olefins, some less useable fraction of crude oil (gaseous oil). The technique of cracking

is the same as by the cracking of ethane, the product is a more wide mixture of unsaturated

hydrocarbons. (More common material for the production of olefins is methane from earth gas in the

USA,).

A little less ethene (28%) is created during the cracking of oils, but more commercially important

olefins are created, such as propene (propylene) (16%) and butadiene (5%). Methane (14%) is also

created and other important group of products is benzene and others (11%). During large production

of ethylene is also important around 1% of hydrogen, which is used for some following

hydrogenations.

27

The problem is solid elementary carbon, pyrolytic coke, which settles on the walls of apparatuses. We

get rid of it in quickly by firing (oxidation), which heats the apparatus on the needed temperature.

Carbon settled on fluidized heat transfers and catalytic particles can be continuously fired in the part of

the fluid bearing. If pyrolysed hydrocarbons are sulphur free, the coke from wall can be cleared also

mechanically, because it can be a quality material, for example for the production of carbon

electrodes.

5.5.2 Separation of products by cracking

The products of the steam cracking are gaseous or liquid at normal temperature. If we want to separate

the lighter gaseous shares by distillation, it is necessary to deeply cool in about 5 levels of isothermal

compression and adiabatic expansion to -150°C, to condensate everything besides hydrogen. Gradual

distillation in many pipes releases methane, then C2 fraction (ethane, ethene, ethyne), next C3 and C4

fraction (propylene, budadiene, etc). Heavier liquid parts can be divided also by a liquid extraction,

this means by the dilution in chosen solvents. Propane and butane are not usually further processed

and they are added into LPG.

5.5.3 Acetylene and products from acetylene

Until ethylene pyrolysis became common (1970) ethyne (acetylene) had been almost exclusive

material of C2 chemistry, which had been obtained by the decomposition of calcium carbide. Calcium

carbide, CaC2 is produced in an electric oven at 2000-2200°C during endothermic reaction of lime

and carbon (coke) CaO + 3C → CaC2 +CO .

This reaction happens during the operation of water at a normal temperature

CaC2 + H2O → CaO + C2H2 .

This process was made also in small amounts in miners’ lamps, where acetylene was used for the

lighting.

Presently we can obtain acetylene for the bulk chemical production by cracking, similarly to ethylene,

with the difference that this happens at much higher temperatures (1500°C). Usually we come from

methane

2 CH4 ↔ CH≡CH +3 H2 ΔH=376 kJ/mol.

The product has to be cooled quickly; the best way is to directly inject water or oil. High temperature

is reached, for example by a mutual input of oxygen and a part of material in reactor burns directly.

Other possibility is to make the reaction electrothermic, directly in the electric arc. The production is

energetically demanding in all cases and so this leads to a higher price of acetylene.

Acetylene is unstable reactive substance; it can dissolve into the elements at higher pressure. It reacts

with Ag and Cu into silver and cuprous acetylides, which are very sensitive explosives. Acetylene – in

the present mainly for welding, is distributed in pressure cylinders, in which is the infusioral earth

soaked with the dilution of acetylene in acetone, as dissous gas (from French dissolved).


Fixed nitrogen

Ammonia

Ammonia reactor

Hydrogen sulphide, sulphur

Claus process

Phosphates, phosphorus

Electro-thermic processes

Unsaturated hydrocarbons

Ethylene pyrolysis

Hydrocarbon cracking

28

Questions

How to fix nitrogen in reactive compounds?

Which pressure and temperature should be used to synthetize ammonia?

How to transform organic sulphur and hydrogen sulphite to elementary sulphur?

Which conditions are necessary to obtain phosphorus?

What are unsaturated hydrocarbons good for?

How to obtain unsaturated hydrocarbons?

29

6 ACIDS

Study time

3 hrs

The aim

To present the most important inorganic acids,

To teach ways of their manufacture

To show industrial employment of acids

6.1 SULPHURIC ACID

H2SO4 is pure, colourless liquid which is much heavier (1,8×) and more viscous (25×) than water.

6.1.1 Contact production

Today’s production of H2SO4 has three main steps:

1. Preparation of SO2

Main way of the preparation of sulphur dioxide in the present is burning of sulphur

S(s) + O2 (g) → SO2(g) ΔH= -296,8 kJ

Sulphur in melted state is injected into the furnace in the form of small drops. Heat which is

produced by burning, is lead out of the furnace, through cooling system of the walls and can be

used for the production of power plant steam. Air is supplied in dry state; when we want to get

disposed of water, we use the contact with produced sulphuric acid.

2. The most difficult part of the production of H2SO4 is the oxidation of SO2.

SO2 + ½ O2 ↔ SO3 ΔH= -98,9 kJ

It is an exothermic equilibrium reaction, so the equilibrium is completely shifted to the left at high

temperature. The reaction on SO3 happens only at lower temperature of 400-600°C and it is slow. In

the present, a very efficient catalyser is used – which is vanadium pentoxide V2O5 laid on the clay.

Layers of catalyser alternate with the cooling parts in the contact tower.

2. Dissolving of SO3 in water

Reaction

SO3(g) + H2O(l) → H2SO4(l) ΔH= -132,5 kJ

is strongly exothermal

6.1.2 Use

It is a basic agent of chemical industry.

- The decomposition of rocks is the largest consumer of 65%. It is the decomposition of

phosphates in the production of mineral fertilisers after the damping of the production of

uranium;

- It is also used as an environment to keep pH low

30

- It is an oxidizing agent – it changes into sulphur dioxide,

2H2SO4 + Cu → CuSO4 + SO2 + 2H2O

6H2SO4 + 2FeTiO3 → Fe2(SO4)3 +2TiOSO4 +SO2 + 6H2O

- It creates complexes, e.g. sulphato complex of uranyl, UO2(SO4)34-,

- It is hygroscopic, it is used during removal of water, e.g. during nitration (the production of

explosives and other azotic organic substances),

- It reacts with organic substances during creation of esters (a group -OSO3H), sulphonic

acids (a group -SO3H), and sulphonated chemicals (group –SO2), which are the key for the

production of many detergents, pharmaceuticals, paints etc.

-

6.2 NITRIC ACID

6.2.1 Production of nitric acid

Present process of the production of diluted HNO3 contains:

1) The preparation of nitrogen oxides happens by the combustion of ammonia on platinum-

rhodium net at the temperatures above 600°C

4NH3 +5O2 → 4NO + 6H2O

The created oxide should be cooled as fast as possible.

2) An absorption of nitrogen oxides into water – we lead the mixture with the air into the

absorption tower through cooling coils. After the reaction during the creation of gaseous

brown NO2

3NO2 + H2O → 2HNO3 + NO ,

oxidises again with the presence of air with NO

2NO + O2 → 2NO2

etc. Diluted HNO3 (up to 65%) flows out of the bottom.

6.2.2 Characteristics and use

HNO3 is a semi-strong acid, which has strong oxidising effects. HNO3 dilutes most metals,

including some of noble metals; it creates nitrates with them, which are all very well dissoluble in

water. Waterless acid, used for example for nitration, fumes with released NOx. Concentrated nitric

acid (65%) is delivered into the distribution, it is easier to store. HNO3 strikes many organic substances

– if there is alcohol, OH – group, present, esters are created with the group –O-NO2 (nitrates), or nitro

substances of yellow colour are created - NO2.

6.2.3 Ammonium nitrate

Major amount of HNO3 (above ¾) is used during the production of ammonium nitrate by the

neutralisation of acid by gaseous ammonia

HNO3 + NH3 NH4NO3 .

Ammonium nitrate is, from major part, used directly as a well dissolvable fertiliser, rich in nitrogen.

During fierce heating NH4NO3 can also dissolve in an explosive way during the release of oxygen and

large volume of other gaseous products:

NH4NO3 N2 + 2H2O(g) + 1/2 O2 H= -118 kJ/mol.

That is why about 15% of produced ammonium nitrate is used as an oxidising part of the industrial

and military explosives.

31

6.3 PHOSPHORIC ACID

There are two industrial processes for the production of H3PO4. We call the acid either

thermic phosphoric acid because of the production through elementary phosphor, or extractive

phosphoric acid, if it is extracted from decomposed phosphates.

6.3.1 Thermic phosphoric acid

Very pure phosphoric acid can be obtained by these two reactions:

4 P + 5 O2 → 2 P2O5 ,

P2O5 + 3 H2O → 2 H3PO4 .

The first reaction in these two is burning of phosphorus, which happens also spontaneously, if

we expose phosphorus to the air. Created oxide (the melting point 24°C, the boiling point 175°C) is in

the form of vapour lead into the cooled water, or into the diluted H3PO4 , where it comes to the second,

also exothermic reaction.

Less than 5% of H3PO4 is produced in this way. The price of the production of thermic

phosphoric acid is mainly influenced by the higher price of elementary phosphorus.

6.3.2 Extractive phosphoric acid

A mixture called superphosphate, is obtained by the effecting of sulphuric acid on

phosphates – the oldest and, in the present not produced, fertiliser which contains water soluble

calcium dihydrogen phosphate in the form of solidified crystal mash.

2 Ca5(PO4)3F + 7 H2SO4 + 3 H2O → 7 CaSO4 + 3 Ca(H2PO4)2. H2O + 2HF

By excess of H2SO4 there comes to a reaction,

Ca5(PO4)3F + 5 H2SO4 + 10 H2O → 5 CaSO4. 2H2O + 3 H3PO4+ HF .

Gaseous hydrogen fluoride leaks from the mixture and we get crude extractive phosphoric

acid by the division of the sediment of gypsum.

The production of purer extractive phosphoric acid by very demanding refining is still cheaper

than the production of thermic acid.

If we are able to properly clear the filter cake of CaSO4. 2H2O (calcium sulphate dihydrate),

it is usable for the production of gypsum for building purposes.

6.3.3 The use of phosphoric acid

We generally understand, under the term of phosphoric acid, trihydrogen phosphoric acid

(formerly orthophosphoric acid), H3PO4. It is strong acid, which does not have oxidising effects.

Hydrogenphosphates a dihydrogenphosphates are created during its neutralisation, they are weaker in

acidity and they keep the value of pH dilutions (buffering ability) in broader borders.

The main use is for the production of phosphorous fertilisers, which are not demanding on

purity, for example for “amofos”

H3PO4 + 3 NH3 → (NH4)3PO4 ,

Purer phosphates are used for water softening, degreasing and passivating of metals, but also

for baking powder for pastry

6.4 ACID GASES

Instead of liquid acids, sometimes gaseous acidic agents can be employed, e.g. HCl, SO2, CO2

NOx, and others.

32


Sulphuric acid

Contact process

Nitric acid

NOx gases

Phosphoric acid

Thermic and extractive processes

Questions

Which is the main raw material for sulphuric acid manufacture?

Which is the main raw material for nitric acid manufacture?

Which is the main raw material for phosphoric acid manufacture?

Which acids are also oxidizing agents?

Do you know some gaseous acidic agents?

33

7 BASIC AGENTS

Study time

1.5 hrs

The aim

To present the mostly applied industrial basic agents.

.

7.1 LIME

7.1.1 The use

Anhydrous lime, which has the chemical basis CaO, and air-slaked lime Ca(OH)2 are the most

commonly and cheaply available alkalic chemicals and let us remind that its use and regeneration was

a very important step of alchemistic production of NaOH by caustification of soda, which had been

used until electrolysis was implemented. It is still done in cycle of the regeneration of white lye in

sulphate pulp mills. Ca(OH)2 is used as an alkalic agent in sugar factories and in many productions of

organic chemistry.

7.1.2 Lime production

Burnt lime is produced by heat decomposition of limestone

CaCO3(s) → CaO(s) + CO2(g)

in furnaces at the temperatures above 900°C. The process is energetically demanding, around 3kg of

CaO on 1 kg of coal is produced during coal heating in a modern kilns, which means the use of heat is

about 4 GJ/t. Classical kilns were shaft furnaces. Later they were sometimes used simultaneously as

the generators of carbon dioxide, for example during production of soda or in sugar factories. Modern

kilns use rotation furnaces, which are slowly rotating, slightly sloped horizontal cylinders, in which

there is lime stone slowly scattered in the environment of hot burnt gas of solid, liquid and gaseous

fuels.

The product of the classical kiln was lump burnt lime, which was converted with slow

sprinkling of water (strongly exothermic process with the danger of splashing of strongly basic

dilution) onto partially soluble paste of slaked lime, suitable for the preparation of mortar, plastering

and painting of walls. There is a reaction during slaking

CaO(s) + H2O(l)→Ca(OH)2(s) ΔH=-66,5 kJ/mol.

By stoichiometric amount of water during sufficient mixing there is industrially prepared

powder slaked lime, which is now distributed under the name of calcium hydroxide. There is lime

mortar by the mixing of slaked lime with sand and water. This, after small loss of water, keeps its

form, however it stays soft. Further there is ripening – lime mortar hardens definitely with acceptance

of CO2

Ca(OH)2 + CO2 - H2O → CaCO3(s).

Nano-crystalline CaCO3, is a cheap white pigment.

34

7.2 SODIUM HYDROXIDE

.

7.2.1 Production through caustification of soda

Older production of sodium hydroxide is based on the reaction

Na+2CO3

2- + Ca2+(OH-)2 → 2 Na+OH- + CaCO3 .

This should move, presumably, more to the left in the dilution, thanks to the separation of insoluble

CaCO3 it moves, however, to the right. The process was called caustificaction. Caustic soda is a

common name for soluble NaOH (opposite to trivial name “ash soda” for carbonate).

7.2.2 Production by electrolysis

NaOH and its most common present production by electrolysis were described in the chapter

4.1. Obtained hydroxide is very pure, but also more expensive chemical agent.

7.2.3 Potassium hydroxide

KOH is usually not produced by the electrolysis, but by the crystallisation from the solution of NaOH

and KCl.

7.3 AMMONIA

The production of ammonia was described in detail in the chapter 5.2. Most of ammonia is used for

the neutralisation of phosphoric and nitric acids for the production of mineral fertilisers, which bring

lacking fixed nitrogen into the soil.


Limestone, lime, slaked lime

Hydroxides

The questions

Which basic chemicals are cheap ones?

How to produce lime?

Which ways can be employed in hydroxide manufacture?

Do you know some basic gases?

35

8 BIOTECHNOLOGY

Study time

2 hrs

The aim

To understand energy storage in nature, and its employment in technology

To understand aerobic and anaerobic microbiological processes

The definition

8.1 CARBON IN LIVING ORGANISMS

8.1.1 Photosynthesis

The key reaction, without which any life on Earth would not be possible, is photosynthesis, catalysed

by green pigment chlorophyll. The summary result is for example the creation of sucrose:

12 CO2 +11 H2O → C12H22O11 + 12 O2 ΔH= +5644 kJ/mol.

Sucrose (beet sugar) is one of glycides (carbohydrates), particularly hexose of the general formula

HO-[ - C6H10O5-]n-H

Larger amount of units are in amyls and with high n it is cellulose (chemical pulp), the most important

building part of the plants and the main material for the production of paper.

Significant is that all of the energy for photosynthesis is taken from the light by the pulp substance of

green plants. The atmosphere containing highly reactive oxygen and organic substance were created

thanks to the photosynthesis. Reverse decomposition of carbohydrates (breathing) is a way in which

the cells of aerobic organisms (using air oxygen) obtain energy for further syntheses. Often reverse

oxidation is not full, especially by the absence of oxygen.

8.1.2 Aerobic processes

Aerobic microorganisms convert nutrient substances into CO2, but also into other, only partially

oxidized organic products. Specialised microorganisms are carefully industrially planted. They

provide, by fermentation in oxygen saturated dilution, for example, acetic acid, citric acid, but also

more complicated compositions such as antibiotics. Tens of other commodities (products for sale) are

produced in the biotechnological way. Of course, new live cellular substance and new spare

substances are created by this.

The most commonly industrially used aerobic process is the activation in sewage clarification plants,

where there is a reverse intention, to have all organic substances present originally in water, ended

either as carbon dioxide or as hygienically harmless live substance of activated sludge, which is

further left to rot out.

8.1.3 The anaerobic processes

Anaerobic microorganisms take all oxygen from the energy storing substances and by slow reaction

during the creation of reduced and oxidised component, for example

C12H22O11 + H2O → 6 CO2 + 6 CH4 ΔH= -300 kJ/mol,

36

which creates the mixture called biogas. This reaction goes along with the decomposition of organic

substances by inaccessibility of air in swamps or in intestines of animals.

Other anaerobic organisms (yeast) produce for example ethanol of the fermentation of spirit during

the obtaining of the energy:

C12H22O11 + H2O → 4 CO2 + 4 C2H5OH ΔH= -176 kJ/mol.

In the presence of oxygen fermentation can change into the aerobic process and the result is then the

creation of aldehydes and vinegar. Omnipresent non-specialised microorganisms perform simple reactions (for example milk fermentation: sauer

kraut, pickles, silage).

Higher organisms, plants and animals, produce, besides glycides, other types of energy storing

substances in larger amounts, such as oils, fats, waxes, proteins. Complex natural substances such

as pharmaceuticals, toning substances, drugs, colourings, essential oils are further separated from

them; many of these are more advantageous to synthesize.

8.2 BIOLOGICAL CLEANING OF WASTE WATER

The most common way of cleaning of the waste city water uses the biological process of

aerobic organisms, so called activation of activated sludge, which, if it is given intensive aeration

oxygen by the artificial, quickly (in tens of minutes) consumes all organic contaminations and changes

them mostly into CO2 and nitrates. Harmless water is then separated by the sedimentation, it is led into

the stream and grown waste sludge, which is usually subjugated to further anaerobic process –

digestion. This is much slower (weeks) and produces biogas which contains CO2, CH4, NH3, H2S.


Photosynthesis

Saccharides, fats, proteins

Aerobic processes

Anaerobic processes

Biogas

Questions

Which chemicals can be produced by biotechnical way

Which biological processes are employed in waste water cleaning

37

9 FURTHER REFERENCES

Used literature

If we want to get detailed information on chemical technologies, there are broad and very detailed

works, available only in larger chemical libraries

- Kirk-Othmer Encyclopedia of Chemical Technology (26 volumes)

- Ullmann's Encyclopedia of Industrial Chemistry (37 volumes)

- McKetta: Encyclopedia of chemical processing and design (69 volumes)

Recently these books have been also issued in the electronic forms on CD ROM.

Essential information, available on the internet, can be found under acronyms:

- BAT (Best Available Techniques)

- BREF (Best available techniques REFerence document)

- IPPC (Integrated Pollution Prevention and Control)

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