SATHYA P NARAYANAN
SAURABH CHANSOLIYA
SAURAV JAYAN
B130512CH
B130524CH
B130196CH
CONTENTS

 Raw materials
 Chemical reactions
 Properties
 Flow diagram
 Process descriptions
 Engineering problems
 Applications
 Alternate processes for production
RAW MATERIALS

 Petroleum Naphtha is the main raw material
 Coke
 Hydrogen
 Toluene
CHEMICAL REACTIONS

 Xylenes undergo electrophilic substitution reactions
in the same manner as toluene. Upon oxidation
with KMnO4 or K2Cr2O7, Xylenes form
corresponding dicarboxylic acids.

 M-xylene to P-xylene
PROPERTIES

 CHEMICAL PROPERTIES:
 Reactions involving the position of the alkyl substituents:
 These reactions include isomerization, disproportionation and
dealkylation.
 Acids catalyze the interconversion of the three-xylene isomers.
Xylenes isomerize
 to near equilibrium levels in a hydrogen fluoride – boron
trifluoride system with
 low boron trifluoride concentrations. Isomerization at lower
temperatures
 produces more p-xylene and o-xylene.


 PHYSICAL PROPERTIES
 Because of their similar structure, the three xylenes and the
isomeric ethyl
benzene exhibit similar properties. The distillation characteristics
of the C8
aromatic compounds are of considerable importance.
 o-xylene is more readily separated from m-xylene because of a 5°C
difference in boiling point.
 The difference in freezing point between the p-xylene and other C8
aromatic compounds is utilized for p-xylene separation. The
critical compression ratios are 14.2, 13.6, and 9.6 for p-xylene, mxylene and o-xylene respectively.
 The research octane values are 113, 116.4, 117.5 and 107.4 for Ethyl
benzene, pxylene, m-xylene and o-xylene respectively.
FLOW DIAGRAM

Meta Xylene Production

P-Xylene Production

Process Description

 Catalytic Reforming
Catalytic reformate is the major source of xylene,
accounting for approximately 95 percent
of the xylene production capacity feedstocks.1,3
Catalytic reforming involves the catalytic
dehydrogenation of straight-run light naphtha in the
presence of hydrogen (which reduces coke
formation) to yield a mixture of aromatic hydrocarbons
(e.g., benzene, toluene, and the
xylenes.

 P-Xylene is produced by catalytic reforming of
petroleum naphtha as part of the BTX aromatics
(benzene, toluene and the xylene isomers) extracted
from the catalytic reformate. The P-Xylene is then
separated out in a series of distillation, adsorption or
crystallization and reaction processes from the mxylene, o-xylene and ethylbenzene. Its melting point
is the highest among this series of isomers, but
simple crystallization does not allow easy
purification due to the formation of eutectic
mixtures. It is also highly flammable.
Problems

 Atmospheric releases of xylenes are primarily as fugitive
emissions from industrial sources (e.g., petroleum refineries,
chemical plants); as emissions in automotive exhausts; and as a
result of volatilization from their use as a solvent. Due to the
high volatility of xylenes, most environmental releases
partition to the atmosphere.
 Xylenes are moderately mobile in soil, where they may be
adsorbed.
 Xylenes may leach into groundwater, where they can persist
for several years.
 Xylenes are rapidly transformed by photo-oxidation in the
troposphere, and can participate in the formation of groundlevel ozone.
 Xylenes are stable to hydrolysis and oxidation in the aquatic
environment.
Applications

 Terephthalic acid and related derivatives
 p-Xylene is the principal precursor to terephthalic
acid and dimethyl terephthalate, both monomers used in
the production of polyethylene terephthalate (PET) plastic
bottles and polyester clothing. 98% of p-xylene
production, and half of all xylene, is consumed in this
way. o-Xylene is an important precursor to phthalic
anhydride. The demand for isophthalic acid is relatively
modest so m-xylene is rarely sought (and hence the utility
of its conversion to the o- and p-isomers).

 Xylene is used as a solvent. In this application, the mixture of isomers is often
referred to as xylenes or xylol. Solvent xylene often contains a small
percentage of ethylbenzene. Like the individual isomers, the mixture is
colorless, sweet-smelling, and highly flammable. Areas of application include
the printing, rubber, and leather industries. It is a common component of
ink, rubber, and adhesive. In thinning paints and varnishes, it can be
substituted for toluene where slower drying is desired, and thus is used
by conservators of art objects in solubility testing.
Cleaning agent
 Similarly it is a cleaning agent, e.g., for steel, silicon wafers, and integrated
circuits. In dentistry, xylene can be used to dissolve gutta percha, a material
used for endodontics (root canal treatments). In the petroleum industry,
xylene is also a frequent component of paraffin solvents, used when the
tubing becomes clogged with paraffin wax. For similar reasons, it is often the
active ingredient in commercial products for ear wax (cerumen) removal.

 Laboratory uses
 It is used in the laboratory to make baths with dry ice to cool
reaction vessels, and as a solvent to remove synthetic immersion
oil from the microscope objective in light microscopy. In histology,
xylene is the most widely used clearing agent. Xylene is used to
remove paraffin from dried microscope slides prior to staining.
After staining, microscope slides are put in xylene prior to mounting
with a coverslip.
 Precursor to other compounds
 Although conversion to terephthalic acid is the dominant chemical
conversion, xylenes are precursors to other chemical compounds.
For instance chlorination of both methyl groups gives the
corresponding xylene dichlorides (bis(chloromethyl)benzenes)
whilst monobromination yields xylyl bromide, a tear gas-agent used
in World War I.
NEWER ALTERNATIVES FOR
PRODUCTION OF XYLENE

 CRYSTALLISATION TECHNOLOGY
 This process is characterized by the use of adsorption
technology to produce a medium-purity paraxylene
feedstock stream that goes into a low-temperature
crystallization plant to produce crystals. These
crystals are centrifuged and melted to produce high
purity paraxylene.
.

 TOLUENE ALKYLATION
 A relatively new development is the toluene alkylation
process, in which p-xylene is obtained by reacting toluene
and methanol with little benzene by-product. In the pxylene recovery field, adsorptive separation has been the
dominant process worldwide, although crystallization
technology has attracted renewed interest. In addition to
updated configuration and processing schemes, which
result in higher unit efficiency, modern crystallization
plants use more reliable and larger-scale equipment. New
p-xylene crystallization capacity additions have been
made in combination with the paraselective toluene
disproportionation technology

Thank You.