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Benzene is an aromatic hydrocarbon that is produced by the burning of natural products. Its molecular formula is C6H6. Benzene is a component of products extracted from coal and petroleum and is found in gasoline and other fuels. Benzene is a colourless liquid at room temperature and its density is 0.87 g/cm3 at 20oC. It has a relatively low boiling point, a high vapour pressure, highly flammable, can evaporate into the air very quickly and dissolves slightly in water.
It is mainly used in industries to produce other chemicals which are used to make plastics, resins, and nylon and other synthetic fibres. Some examples of the companies are:
Benzene International Pte Ltd
Caldic Belgium N V
Triveni Chemicals is one of the leading industrial chemicals manufacturer and supplier. They deal in both organic and inorganic chemicals. They are engaged in the manufacture and supply of Fluoride, Sulphate, Carbonate, Chloride, Benzene and many more.
Toshi Group is a well known manufacturer and trader of well formulated range of chemicals, lubricating oils, Lubricating oils, thinners, diluents & solvents.
Benzene International Pte Ltd is involved in manufacturing procurement distribution and export of commodities and products. They are mainly focused on Petro-Chemical Division.
Caldic Belgium N V are distributors of various chemicals such as acid, alkyl benzene, benzoic acid, boric acid, caustic soda, castor oil, cellulose gum, ether,
formic acid and many more.
Star Chemicals are the largest manufacturer of acid slurry.
Benzene has many products/by-products, the main products produced from benzene is Styrene or vinyl benzene (53%), Cumene (22%), Cyclohexane (12%), Nitrobenxe (5%), Detergent Alkylate (3%) and Chlorobenzenes and other products (5%), it is also used as an additive in gasoline because it occurs naturally in crude oil and is a by-product of oil refining processes.
From these main products of benzene they are then used to create everyday products, there are three main branches which are:
One of the types of products made is called Expanded Polystyrene (EPS). The chemical makeup of polystyrene is a long chain hydrocarbon with every other carbon connected to a phenyl group. Polystyrene's chemical formula is (C8H8).
Expanded Polystyrene consists of carbon, hydrogen, and oxygen.
The benefits of using this product is its superior product protection and reduced damage and replacement costs. Expanded Polystyrene is lightweight, insulates temperature sensitive products and is water resistant. Expanded Polystyrene foam is also environmentally sound and is recyclable.
Expanded Polystyrene is made from 95% air and 5% plastic (Polystyrene, Ethylene and Benzene).
To manufacture EPS, ethylene and benzene is joined together to form styrene. Styrene is then introduced to "Suspension Polymerization" and then it's given a polymerization initiator. This converts it into polystyrene, after the polymer is formed to the correct specifications the reaction is then stopped which forms polystyrene beads. They are then heated and expanded and left to cool for a day so they can harden.
Benzenes Role: The properties benzene gives the Expanded Polystyrene is:
High melting points
Good electrical properties
Excellent resistance to gamma radiation.
Process of Benzene
One of the processes of benzene is the converting toluene into benzene. This is a "hydrogen-intensive process". Toluene is added with hydrogen and then placed in a catalyst at 600 °C and 60 atmospheric pressure. Under these conditions Toluene then undergoes de-alkylation to benzene and methane:
"C6H5CH3 + H2 â†’ C6H6 + CH4" Formula from ______________________________
This is an irreversible reaction which is used to produce biphenyl.
"2 C6H6 H2 + C6H5-C6H5" Formula from ________________________________
If the original material contains non aromatic parts they are likely to decompose the lower hydrocarbons, this causes more hydrogen to be used.
Health and Safety
Exposure to benzene has serious health effects. Some of the short term consequences of breathing high levels of benzene can result in death, where as low levels can cause drowsiness, headaches and unconsciousness.
Long term exposure to benzene can blood problems. Benzene targets vital organs and can cause DNA strand breaks, it can damage the bone marrow which will cause a decrease in red blood cells, which can cause anaemia.
The United States Environmental Protection Agency states that "a maximum permissible level of benzene in drinking water at 0.005 milligrams per litre and has also a permissible exposure limit of 1 part of benzene parts per million of air in the workplace during an 8-hour workday, 40-hour workweek and a short term exposure limit for airborne benzene is 5 parts per million for 15 minutes."
Benzene is produced in two ways; chemically and naturally occurring from processes such as wild fires and chemical bonding. Benzene is a human carcinogen and the most common type of exposure is by inhalation of air from motor vehicles and cigarettes.
Write a report which explains the alkylation of benzene using the Friedel Crafts reaction
Friedel Crafts reaction is a substitution reaction, catalyzed by aluminium chloride, in which a hydrogen atom is replaced by an alkyl group or an acyl group of an aromatic nucleus.
Haloalkane reacts with benzene with an aluminium halide present. This forms alkyl benzene and hydrogen halide. This reaction is called the Friedel Crafts alkylation of benzene.
With primary halides, the reaction starts with the acid moving to the halogen of the substance. This causes a positive charge to be formed on the halogen carbon, causing it to be more electrophilic. This then causes a benzene ring to lose a proton therefore opening it up.
With secondary and tertiary halides, the free carbonations are usually formed as intermediates.
Benzene is then treated with a chloroalkane with an aluminium chloride acting as a catalyst.
Substituting a methyl group gives methylbenzene
Aluminium chloride AlCl3 is used in this reaction but it is not shown because as it's a catalyst.
The formation of the electrophile
The electrophile is CH3+. It is formed by reaction between the chloromethane and the aluminium chloride catalyst.
Toluene C6H5CH3 is a clear, colourless, flammable liquid with a sweet odour it's know as an aromatic hydrocarbon and is mainly used in industry as a solvent.
Some Industrial uses of toluene include the dealkylation to benzene. Toluene can also be used to open red blood cells in order to extract haemoglobin in biology experiments. Toluene can also be used in combustion engines as an octane booster in fuel.
Industrial uses of Toluene
How it is used
Carpet adhesive solvents
Solvents - Dilution
Solvents - Extraction
Solvents - Paint Stripping
Pesticide Mfg (Insecticides)
Solvents - Insecticide Manufacture
Solvents for Gravure Printing
Solvents - Rubber Manufacture
Wood Stains and Varnishes
Machinery Mfg and Repair
Solvents - Machinery Manufacture and Repair
Solvents - Metal Degreasing
Properties of Benzene
0.8765 g/mL3 at 20oC
Solubility in water
0.8 g/L (25 °C)
0.652 cP at 20 °C
Properties of Toluene
0.8669 g/mL at 25oC
Solubility in water
0.47 g/l (20-25°C)
0.560 cP at 25°C
Write a report which explains an industrial process associated with a petrochemical.
Fractional Distillation of Crude Oil
Fractional distillation is the separation of a compound into parts or fractions. An example of this is separating a chemical compounds by its boiling point by heating it up which causes different fractions of the compound to evaporate in different sections.
Crude oil is the main source of organic chemicals. It was produced over millions of years by the breakdown of plant and animal remains at the high pressures and temperatures deep below the sea. It is called a fossil fuel and is not renewable.
Crude oil is a mixture mostly of alkanes, both unbranched and branched. Crude oils from different sources have different compositions.
To convert crude oil into useful products the mixture has to be separated. The first step is heating it and collecting the fractions that boil over different ranges of temperatures. Each fraction is a mixture of hydrocarbons that have a similar chain length and therefore similar properties. The process is called fractional distillation and it is done in a fractionating tower.
The crude oil is first heated in a furnace so that it vaporises.
The vapours pass into a tower that is cooler at the top than at the bottom.
They pass up the tower via a series of trays containing bubble caps until they arrive at a tray that is sufficiently cool (at a lower temperature than their boiling point). Then they condense to liquid.
The mixture of liquids that condenses on each tray is piped off.
The shorter chain hydrocarbons condense in the trays nearer to the top of the tower, where it is cooler, because they have lower boiling points.
The thick residue that collects at the base of the tower is called tar or bitumen and is used for road surfacing
Industrial distillation performed in large, vertical cylindrical columns called distillation towers, with diameters ranging from 700 millimetres to 6 meters and heights ranging from 6 meters to 60 meters and possibly more.
The distillation towers have outlets placed along the column which allows the withdrawal of different fractions or products which have different boiling points or boiling ranges. The products with the lowest boiling point leave from the top of the distillation tower and the products with the highest boiling point leave from the bottom of the distillation tower.
Fractional distillation is used in oil refineries mainly to separate crude oil into useful products which have different hydrocarbons at different boiling points. The crude oil with higher boiling points has:
More carbon atoms
Higher molecular weights
Difficulty to ignite and to burn
Fractions from Crude Oil
Name of fraction
Boiling range (oC)
Length of carbon chain
Liquefied petroleum gas
Up to 25
Gas oil (diesel)
Central heating fuel
Lubricating oil petrochemicals
Fuel for ships
The amount of each fraction distillation provides from crude oil:
Fractional distillation of crude oil
percent from distillation
Petrol and Naphtha
Fuel oil and bitumen