Chemical Industry

THIS MODULE IS STILL UNDER CONSTRUCTION

Chemical Industry

Introduction

All chemical content of the previous modules is being applied in daily life. Unbelievable how many chemical things you are using every day, but also every time when you use energy, or what happens in your body after a dinner, it is all chemistry, mostly you are not conscious of that. The economy depends for a great deal on chemistry. This chapter we look at several applications in the chemical industry.

Still most of our energy is made with fossil fuels. But every year more, we simply recieve our energy from the sun, the wind, the sea, and others. Energy will be found in a more physical way, compared to the chemical way of the fossil industry. But still there is a lot of chemistry involved, like substances that absorbe sun radiation, or when it comes to Hydrogen combustion. Every cleaning substance is made in factories through chemical processes. Most nutricients in the supermarkets are treated chemically. And so on.
In the chemical industry all parts of chemical knowledge can be found in the previous modules. Now they find their applications. An extra module about chemical industry may not fail. Only some important industries will be treated.

Content

1. Coal power plant

2. Steelproduction

3. Synthetic material, plastic

4. Natural gas

5. Oil refinery

1. Coal energy plant

A nice description of the coal fuel power station can be fount in wikipedia, Internet: Coal energy plant or coal power station
A short resume is found below:

A coal power station is an thermic electricity plant, based on the burning of coal.
The chemical reaction is simple:

C(s) + O₂(g) CO₂(g)

Obviously all other substances present in the coal, will also be burned. Think of Sulphur and Nitrogen, who can, burning, can produce: NO, NO₂ and SO₂. These oxydes are delevered to the atmosphere and cause acid rain.
Apart from those gaseous oxydes, also a subtile substance is formed, an invisible kind of soot free in the air, very bad for peoples health.
Also large amounts of carbondioxyde are formed, CO₂, not poisenous for people, but heating the earth and creating climate problems.
Coal plants, for that reason, are considered as the most damaging things for environment.

Coal is burned, the delevered heat is used to overheat steam, that makes a turbine turn around. The turbine is connected to a generator that will produce electricity.
A lot of chemistry is involvedd:

The coal must be crushed first, sometimes changed into gas. Crushed of gasious, it reacts with oxygen.
Nitrogen oxydes are 'caught', to prevent them from coming free in the atmosphere. A catalyst is used.
burning ashes, remains of the burning process, are caught and removed.
Sulphur oxides are caught, to prevent them from coming free in the atmosphere.

About the whole process, all the chemical reaction, the substances released to the atmosphere, in spite of instruments, escaping bad substances, the opinions are various. Anyhow, lots of carbondioxyde comes free in the air, climate change as the result. Also important is the origine of the coal, where does it come from? how is life there? What quality has the coal from that region?

Have a look at next picture to know something about the huge machines:

stoomturbine (29K)

Interesting critical note: Coal power plants sometimes are proud to have reduced their outlet of Nitrogen oxydes with 35%. Mind that still 65% is released to the atmosphere. It is a hell of a lot.

Below a number of extra chemically related aspects:

1.
Burning of coal also releases oxydes of Nitrogen, often indicated with NO_x. Nitrogen can have different oxydes:
NO, NO₂, N₂O₃, N₂O₄, N₂O₅ en N₂O
The first two in particular exist as 'nitrous vapors'. The NO₂ color is light brown. NO is colorless and N₂O₄ (mostly also present) has again a light brown color. Inhaling nitrous vapors is suffocating, like Clorine gas. The vapors are strong oxydising agents en bad for health.

2.
Burning coal can also create problems when not enough Oxygen is available.
Normally, carbondioxyde (CO₂), is formed, but in the case of insufficient oxygen, CO, carbonmonoxyde can be formed, odourless and colorless, but dangerous, poisonous. The molecule resembles the molecule of oxygen (O₂). When absorbed in the blood, in the molecules of Hemoglobine, CO does not want to leave anymore. consequence is that the blood had less of no possibility to transport oxygen. You wil go to sleep softly and die unconscious.

2C(s) +O₂(g) 2CO(g)

In the coal plants, electric energy is made using chemical and physical processes.
Always a continuous process is applied. The coal - if needed after crushing, is introduces continuously for heating and burning. So the delivery of electric current can be ruled in a stable way.
This basic material coal needs lots of water, that does not react itself, but is there to be heated in the process.
Unfortunately there are many unpleasant product, like the oxydes of Nitrogen, sulphur and carbon.

The chemical techniciens are looking for safer solutions that also support the economy. All devices that rule the process are controlled by them. The techniciens define and controll the chemical reactions.

2. Steel production / Blast furnaces

As usual, first try wikipedia about the Steel production in blast furnaces.
We use this website, leave some data out or include others:

A blast furnace is an installation wherein iron ore and carbon are mixed and strongly heated. A number of chemical reaction produce at the end liquid iron. The carbon simultaneously is fuel and reductor for the ore.
The liquid iron can be tapped and contains, of course, a certain percentage of carbon.

History
In China kind of blast furnaces already existed in the fifth century before Christ; in the West only since about 1000 AC. The furnace process spread out in Belgium, city of Namen.
In 1491, the blast furnace was introduced in England. The needed fuel was then charcoal.
When charcoal (and wood) began to be scarce, they started using cokes, at the end of the eitheens century. After another century the proces was reinforced by blazing preheated air/oxygen.

The modern blast furnace
The temperature in the furnace can these days be raised that the product, iron, is tapped in liquid state. They produce 8.500 to 12.000 tons of raw iron per day.

hoogoven (112K)

In the top of the furnace, layers of cokes (2 ,5) and layers of ore (1, 6) are loaded.
Down, at the blowing air entrances, hot air (7) of about 1200°C and powdered coal (16) are blazed in, possibly enriched with oxygen.

2C(s) + O₂(g) 2CO(g)

Oxygen from the air will burn the carbon of cokes and the powdered coal; carbonmonoxyde (CO)is produced. This gas with a temperature of about 2200-2400°C will rise through the different layers of cokes and ore.

Fe₂O₃(s) + 3CO(g) 3 CO₂(g) + 2Fe(l) (Reduction of iron ore into iron)

The oxydes of iron are reduced, under these circumstances, into iron, that - at those high temperatures, remains liquid. This liquid raw iron seeps through the layers downstairs and is collected at the bottom of the furnace.

As soon as sufficient liquid iron is collected, the furnace is drilled open and the raw ironcurrent moves (9) via the hole to the exterior. Mixers (11) collect the iron and transport it on train wagons to the steel factory for further treatment.
When all raw iron is tapped, the hole is closed again. The tapping process takes about 90 minutes.

The raw iron ores and their additives contain - apart from the iron oxydes - also impurities such as calcium oxyde (CaO) and silicium oxyde (SiO₂). These substances will form slack (8) to be tapped and treated for the cement industry.

For the production of 1 ton of iron in the furnace, an average of 0,5 ton cokes is neededd + 1,6 ton iron ore with an iron value of 60%.

Blast furnace
IJmuiden (34K)

Below some theoretical remarks:

A keyword in de production of steel is: reduction.
In module 10 about redoxreactions we find that reduction is the opposite of oxidation en that these two always occur simultaneously:
Electrons are transmitted from the reductor to the oxydator
Reduction is in fact: that a substance is forces to take up electrons.
In the furnace process: Iron ore contains Fe³⁺. These ions are forced to accept three electrons per ion and thus to become neutral Iron, Fe.

Fe³⁺ (present in ore) + 3 e^- Fe (first in the liquid, later in the solid iron)

Those electrons are delivered by the reductor CO, that in this proces will change into CO₂. About that more:
" You remember the concept 'oxydation number'?
The oxydation number of Iron(III)ions is +3 because the atom Fe is missing 3 electrons.
The Carbon atom in CO has another oxydation number than it has in CO₂.
In CO one C is connected to one O. The O has the oxydation number of -2. This means that C must have here an oxydation number of +2.
In CO₂ one C atom is connected tot 2 O-atoms (both -2). So the one C-atom has in this case an oxydation number of +4.

Thus the oxydation number of C, during this reaction in the furnace will change from +2 into +4. This is only possible when the C-atom will release two electrons. Only than this atom can become more positive. You see: there is the oxydator, the particle that will release electrons to the reductor Fe³⁺.
Anyway and allways the number of electrons released and taken up must be the same. So the reaction between Iron and CO must obey the relation, the proportion of 2:3
Fe₂O₃(s) reacts with 3CO(g) or: two iron-ions react with three Carbon atoms.

3. Synthetic material, plastic

A lot of information can be found in: wikipedia. Much of the text below is taken from wikipedia.

Synthetic materials are build up of very large molecules (macromolecules). The are produces in large scale in the industry; the basic materials have much smaller molecules. The very small molecules are connected to form 'polymeres'.
att.: Not every synthetic material is a polymere.
But anyway, they are chemical compounds, mostly made in factories through chemical processes. The macromolecules/polymeres made by nature, like starch of proteins, are not considered synthetic.

We distinguish three kinds of plastics:

Elastomeres (elastic material; you can compress it, but it will return to its original form. a kind of synthetic rubber.
Thermoharders these will not become softer on heating, because the macrolulecules are connected via internal cross connections. These molecules are settled in a very strong network. We call them sometimes 'duroplasts'.
It is difficult to make these plastics; the proces is called 'injection molding' or 'injection moulding'. This kind of plastic is difficult to recycle.
Thermoplasts A synthetic material that becomes softer on heating. The macromolecules are not cross connected; they are loose from each other, meaning: there are no cross connections between the macromolecules. There is some freedom of movement of the molecules relative to each other.

Poly-ethene (PE) The polymere poly-ethene is the most popular synthetic substance, the well known plastic. There is an older name (poly-ethylene) still used.
PE is made by connecting lots of ethene molecules in long chains

Production process
Polyethene is made via polymerisation of ethene. Ethene itself is a product in the cracking process of naphta, a light derivate of crude oil. Estimated is dhat 1.2% of all crude oil is used to produce PE.
Polyethene is synthesised in a 'radical' polymerisation of ethene:

polyetheen (17K)

Poisonness and environment
As we can see in the above molecular formula of PE, it only contains carbon and hydrogen atoms. Complete combustion in incinaration of waste only give the non toxic substances carbondioxyde and water. Burning of PE does not create a dangerous situation voor human of nature.
However, there is always the option of incomplete combustion, creating (lots of) the verty poisonous carbon monoxyde. This is always the case in incomplete combustion.
Apart from that, the production of carbondioxyde is also a great disadvantage, being the well known greenhousegas.

Just like other synthetics, PE will not easy be breached down by bacteria, and thus will stay for a very long time in the environment.
When it reaches the water surface and after being transported tot the sea / ocean, after many years it will be part of the 'plastic ocean soup.
We are able to recycle PE easily. It can be melted; it is a so called thermoplast. Unfortunately we do not recycle every kind of PE, for example when people consider the recycling as a non profitable thing.

Classification of PE
Polyethene can be produced in different processes:

High Density PE (HDPE or PE-HD) is made at lower pressure, with the help of a catalyst.
At lower pressure, linear chains appear and that gives the substance a cristalline constitution. The density of HDPE is about 0,95 to 0,97 g/cm³.
The density of LDPE is about 0,91 to 0,94 g/cm³.
The density of LLDPE is about 0,93 g/cm³.
HDPE can sustain a maximum temperature of 90 degrees Celsius.
Low density PE (LDPE or PE-LD) is made at higher pressure, about 200 MPa (= 2000 bar). At high pressure, a polymere is produces with a high degree of side chains and the substance now is not very cristallyne. An exeption is 'linear low density polyethene (LLDPE) with mainly linear chains. LDPE can have a maximum temperature of 70 degrees Celsius.

attention: These names frequently create confusion. HDPE is not produced at high pressure, LDPE is.

5. Crude oil & Petrochemistry

Information: wikipedia

crude oil

The most important components of crude oil are carbonhydrogens with relatively long chains (the quality of the cruede oil depends on that).
The various carbonhydrogens can be separated by means of distillation, but there is a problem:
Most molecules are too big and therefore a big part remains behind as tar and afphalt; and we get too few applicable products.
Look at the traffic: you need a lot of asphalt, but much more petrol and diesel (having much smaller molecules) to drive on that asphalt.
To improve the amount of smaller molecules in crude oil, there is a method of 'cracking':
Strong heating of the crude oil (please no oxygen present!) can break those big molecules in smaller ones.

We are talking about main processes (cracking and then distillation) of the oil refineries.
Specially the cracking process needs very good catalysts.

The final products of the oil refinery, those with the smaller molecules, in there turn, are raw materials for the chemical industry and often build up of the elements Hydrogen and Carbon: the Carbonhydrogens.
You might name them: carbonhydrides.
They are the raw materials for many derivates of the chemical industry, applied for society, as: petrol, plastic, nylon, etc.

A distillation tower:

Destillatietoren (63K)

Fractions with a high boiling point will condense low in the tower where the temperature is very high; fractions with a low boiling point will only condense in the upper regions of the tower. Crude oil will be separated in various components (fractions)with increasing molecular weight. This kind of distillation is sometimes called 'fractionation'.
At the same time impurities in the crude oil are removed. The upcoming products can serve as fuel or as basic raw material for many petrochemical product.

The flowdiagramme of a modern refinery:

flowdiagram-destillatietore (59K)

An oil-refinery is an installation, a plant for the refinery of crude oil into usefull products.

raffinaderij2 (142K)

History
The very basic oil plant was created by the American Samuel Kier in 1855. It was nothing more than a vessel wherein the content was tried to distill in the same way as done by the alcohol industry. We talk about a batch process whereby the energetic yield was neglected. The aim was: production of kerosine, to be used as lamp oil (petroleum). The lighter fractions, as petrol, were considered as damaging and dangerous. The residu was not further fractionated, but sold als fuel (gasoil).
In Europe however there was more attention for efficiency. crude oil was found a lot and easily, but useful fuel was scarce and expensive.
In Galicia, in 1871, for the first time a system was applicated with two vessels upon each other: in the lower one the residu was distilled for a second time and the heavyestfractions (bitumen) were separated en removed. Peruts made another step in the direction of a continuous process and only once in four days the process needed to be restarted, to remove the bitumen in the lower vessel.
In 1875,Fuhst, developped a system composed of a number of vessels, connected in series, with in between a system of overlope pipes. The residu of the one vessel flowed into the next one. Also the coolers were connected in series, in order to use the cooling water as efficient as possible. The fractions have, as they get more heavy, a higher outflow temperature; their boiling points are higher. The aim of all this was to avoid redistillation (rectification). This was needed because the products of the primitive refineries were composed of too many different fractions.
The first complete continuous refinery process started in Bakoe, in 1873, but custom authorities did not trust the case, fearing tax defaulting. in 1880 - 1881 Alfred Nobel built an installation, a plant, consisting of 17 vessels, capable to work continuously. He asked patent for it. This technology was now going to dissimilate in het whole world. Shell was one of the first.

Soon were distinguished nine groups of product:

Refinery gases (propane, butane, pentane)
Petrol (America: gas)
Kerosine or petroleum
lubricants
Grease
Mineral oil
Paraffina
Bitumen
Fuel oil

For a long time, kerosine was the most important product, but a number of invents (such as combustion motor) would change the whole pattern. From 1920 onwards was developped the petrochemistry, and a number of light products (named: naphta) got a useful destination.

Further developments
An important characteristic of the refinery is its flexibility. Meaning: the refinery is capable to refine several kinds of crude oil, even if they are very different, and also to deliver the needed products in the right amounts. The composition of crude oil is well known, and difficult to change; but the refinery must be capable to influence the fractions, through mixing processes.

In this process, cracking is extremely important, with help of catalysts (catalitic cracking) and with Hydrgen (hydrocracking). The heavier hydrocarbons can be cracked into lighter ones. In this way, it is possible, for example, to increase the yield of petrol.
These processes were already developped at the end of the 19th century, but processes of catalytic reforming (with Platinum as catalyst) were introduced only after 1940. This because of the needs during the second world war. Naphta was converted in more complex compounds, such as aromatic compounds and branched chains (isomerisation). This not only produced petrol with a high octane number, but also basic materials for the petrochemical industry.

Side processes in the refinery can be: desulphurisation and hydrogen plants.

Distillation of crude oil
Every component in crude oil has its own boiling point. Therefor the crude oil is heated up to 350-370°C where the oil changes from liquid to gaseous in the distillation tower. The vapours are rising in the distillation tower and simultaneously cooled. The most heavy components have higher boiling points, the lighter ones have lower boiling points. The heavy ones will condensate first, the lighter ones will rise more. At the end different products can be separated at various hights, levels of the tower.

fraction	temperature	C atoms per molecule
gas	<20°C	1-4
light naphta	20-80°C	5-6
heavy naphta	80-175°C	7-10
kerosine	175-260°C	10-14
gasoil	220-350°C	9-25
residue	>350°C	>25

Hydro-treating
Difficult atoms, causing problems during the process like S, N and O can be removed from the fractions through reactions with Hydrogen, whereby bonds as C-S, C-N and C-O are broken.
The aim of hydrotreating is:

protecting catalysts from being poisoned
improvement of properties
protection of the environment

Gasoil in particular contains a lot of sulphur. Without removal of the sulphur, air pollution is the result; SO₂ creates acid rain. Sulphur also must be removed, making the products as Naphta unapplicable for further treatment. Sulphur finds itself in so called thiol-groups. Adding Hydrogen and a catalyst can take the sulphur out of the thiols and change it into hydrogensulphide. The last can be changed into elementary Sulphur of into gypsum, plaster.

Catalytic Reforming
With help of a Pt-catalyst, chains can be branched or changed into cyclic hydrocarbons.

Cracking
Mostly the conversion of heavier into lighter fractions.
The lighter fractions could be gases too. But these gases are converted into petrol, if possible.

Polymerisation

Under influence of a catalyst, two or more olefinemolecules are connected. The result is a mixture of isomers containing only one double bond. Normally they have a higher octane number than homologes of paraffine.

Alkylation

Alkylation is a reaction between olefines and isobutane to create strongly branched alkanes. The meaning of this is the production of petrol with a high octane number. It starts with low molecular alkenes and isobutane.

The Petrochemistry

A lot of information about this topic on: wikipedia

Petrochemistry is involved in the treatment of crude oil and its products obtained through cracking and distilling. The first commercial applacation of a petrochemical product was in 1920, the isopropylalcohol, used for cosmetics.
Important petrochemical installations are owned by SHELL, ExxonMobil and others.

Aromates
Some kinds of crude oil, like the Borneo-oil of BPM, are very richt in aromatic compounds. Those compounds were already playing a role in the coaltarchemistry. Product, for example: coloring substances, medicines, explosives, etc. Later the companies succeeded in producing those products from all kinds of crude oil.
In Reisholz near Düsseldorf a factory was built where they could execute a nitration process with help of sulphuric acid and nitric acid. The product was named mononitrotoluene, a very important basic substance for pigments industry.
The first World War was demanding huge amounts of explosives, like TNT, that needs toluene. In the USA, in the refinery of San Francico, Standard Oil made toluene for TNT-production.

An aromatic compound, aromate, is an organic compound respondig tot the Hückel rule. Such a compound has up and under the molecule a cyclic cloud of delocated p-electrons; the number of delocated p-electrons is 4n + 2. (n = 0, 1, 2, ... ).
An important characteristic of aromatic compounds is the fact that all atoms of the molecule stay in one flat plane.

When in between two atoms not two, but four electrons are shared, so that the chemical bond is a double bond, with a pi-bond, two of those electrons are located between between the atoms, and the two other electrons (p-electrons) in a plane just besides that bond.
In the case of two double bonds, separated by one single bond, the p-electrons of the two double bonds stay in the same plane, these electrons can move freely between the two double bonds. Such systems are called conjugated. and the free moving electrons are 'delocated'.
When in such a delocated system are 4n+2 electrons (2, 6, 10, 14 or ...) and these electrons are delocated in rings, then the molecule has an extra stability. Such a molecule is 'aromatic'.

The simplest aromatic compound is benzene. Naphtalene consists of two 6-rings with 10 electrons. Then you have three 6-rings (anthracene) and fenanthrene. Pyrene is an example of an aromatic moleculee with four 6-rings and 18 p-electrons.

Aromatic compounds with a great number of rings are called polycyclic aromatic hydrocarbons, or PAK's. Most of these compounds have carcinogenic character; they can interact with DNA.