5 Production Methods of Benzene cyclic hydrocarbon first isolated by Faraday a natural component of crude oil can be produced using different methods Pyrolysis gasoline, coal tar, Catalytic Reforming, Toluene hydrodealkylation, Toluene disproportionation

1. 5 Methods of Industrial
Benzene Production
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2. Benzene History, Chemical Properties
 Benzene is considered as simplest form of arene and
cyclic hydrocarbon. In 1825 benzene was first isolated by
Faraday. Benzene is a natural component of crude oil,
and is one of the most elementary petrochemicals. In
1845, Hoffmann isolated benzene from coal-tar.
 Benzene molecular formula is C6H6 and benzene
structure is having alternative double bonds with
hexagon shape. Hydrogens present in the benzene can be
replaced by some of the other functional groups. As a
result number benzene derivatives will be
generated. Derivatives of benzene are ethylbenzene,
cumene.

3. Benzene structure
 Benzene ring structure was deduced
by Friedrich August Kekule. The carbons present
in benzene ring are arranged in a hexagon, and he
suggested alternating double and single bonds
between them. Each carbon atom has two hydrogens
instead of four hydrogens. To satisfy the tetravalency
of carbon, the benzene ring consisted of alternate
single and double bonds.
 August Kekule in dream saw a snake coil up, and
grabs its own tail then he proposed benzene might be
a ring structure.

4. Benzene preparation methods
 Sodium benzoate is heated with soda-lime (NaOH) and
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when it gets decarboxylated benzene is obtained.
Phenol vapors are passed over heated zinc dust, benzene
is formed.
When ethyne is passed through a red hot copper tube, it
polymerizes to benzene
Benzene is formed on the reduction of benzene
diazonium chloride with sodium stannite
or hypophosphorus acid.
Benzene sulphonic acid on hydrolysis with superheated
steam gives benzene.
C6H5.SO3H + H2O —> C6H6 + H2SO4

5. 5 major processes for production of benzene
 Following are the other major processes for
production of benzene
 Catalytic reforming
 Toluene hydrodealkylation
 Toluene disproportionation
 Pyrolysis gasoline
 Production from coal tar

6. Pyrolysis gasoline
 Pyrolysis gasoline is the by-product of steam cracking
of petroleum by products like paraffin gases, naphthas,
gas oils. Pyrolysis gasoline contains 5 per cent diolefins.
In addition it also contains 60 per cent aromatic
compounds, 50 per cent of benzene. Different techniques
are applied on diolefins to produce benzene, these are
 Distillation of diolefins to olefins
 Saturation of olefins to remove sulfur content
 Execution of solvent extraction and distillation process to
obtain benzene

7. Production from coal tar
 This process improved methods of recovery and
purification that coke-oven benzene has been able to
withstand the competition of petroleum-derived
benzene as well as it has. Production of benzene from
coal tar involves recovering benzene from coal tar.
 Extraction of lowest boiling point fractions
 Applying of caustic soda for the removal of tar acids
 Crude oil distillation
 Crude oil purification through hydrodealkylation

8. Toluene Hydrodealkylation
 Toluene hydrodealkylation reaction takes place is as follows
 Mixing of toluene with aromatics or paraffins
 At specific pressures these mixtures are heated in the
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presence of hydrogen gas
The steam which is formed in previous step then moved to
reactor containing dealkylation catalyst
In this reactor toluene reacts with hydrogen as a
result, benzene and methane products will form
At high pressures benzene is separated from methane
Then methane also removed from reactor
Here in this step benzene can be recovered from
fractionalization column and then be stored.

9. Catalytic Reforming
 Catalytic reforming involves the dehydrogenation of naphthenes to
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aromatics, or the isomerizatoin of alkylnaphthenes and it follows
dehydrogenation process. The feed for this process is naptha.
First the naptha is hydrotreated to remove sulfur contaminant.
Recycled hydrogen is then added, mixed and heated.
Conversion of paraffins to aromatic compounds in catalytic reactors
and in this reactors platinum or rhenium chloride is acts as catalyst.
In further step a stream is formed which is rich in aromatic
compounds.
Then stream is sent to separation section to separate hydrogen and
this hydrogen recycled as basic feedstock.
Liquid portion of stream fed to a stabilizer which separates
hydrocarbons from liquids.
The liquid is then sent to a debutanizer
Benzene, toluene and xylenes are then extracted using glycol and
sulfonate solvents