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DEFINITION
Benzene and Toluene are pure
aromatic hydrocarbon compounds having fixed boiling points, unlike other petroleum
products which are mixtures of hydrocarbon compounds. They are colorless
and flammable
liquids possessing characteristic aromatic odour.
The boiling points of Benzene
and Toluene are 80.1 deg C and 110.6 deg C respectively. Benzene is slightly soluble in
water whereas Toluene is virtually immiscible with water.
MANUFACTURING PROCESS
Benzene and Toluene are
manufactured from stabilized reformat produced in the reformer. The feed to reformer unit
is 60-90 deg C cut Naphtha which is produced in a feed preparation unit. Benzene and
Toluene are extracted from the reformat with the help of Sulfolane Solvent in an
extraction section. The extracted aromatics are separated by fractionation to produce
Benzene and Toluene separately. The Sulfolane solvent is recovered and reused in the
extraction plant.
BENZENE
SPECIFICATION
Benzene marketed meets IS
specifications 534 -1974 for both Benzene grades 1 & 2.
BENZENE END USE
It is primarily used as a
chemical raw material in the synthesis of styrene (Polystyrene plastics and synthetic
rubber), phenol, cyclohexane (nylon), aniline, maleic anhydride (Polyester resins), alkyl
benzenes (detergents), chloro benzenes and other products used in the production of drugs,
dyes, insecticides and plastics.
TOLUENE SPECIFICATIONS
Toluene is marketed meeting IS
537-1967 specification for Toluene, pure Nitration grade.
TOLUENE END USE
Toluene is primarily used in
the manufacture of chemicals, drugs, explosives, food flavouring and sweetening agents,
paints and resins.
IDENTIFICATION
Benzene and toluene being pure
aromatic compounds, can easily be identified by measuring their physical properties like
density, boiling point etc. In addition to this, Benzene can also be identified by
checking its crystallizing point. In fact, the purity of Benzene or Toluene is assessed by
measuring the above physical properties. Apart from the above, Gas chromatographic
analysis is also carried out to exactly identify and determine the purity of Benzene or
Toluene.
COLOUR
Colour is determined by visual
comparison with standard aqueous solution of potassium dichromate or platinum cobalt in a
Nessler's tube.
RELATIVE DENSITY
/SPECIFIC GRAVITY
Being pure Aromatic
Hydrocarbon compounds, Benzene and Toluene have their relative densities / specific
gravities stipulated in their specifications unlike other petroleum products, where
density is never specified. Measurement of density enables to check and keep a uniform
quality of product during manufacture. It also gives a quick check for determining the
contamination.
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