This document studies catalytic alkyl-transfer (transalkylation and disproportionation) reactions of alkylaromatics, with the aim of understanding the principles governing these reactions. Transalkylation involves transferring an alkyl group between aromatic compounds, and is used in the petrochemical industry to produce p-xylene, styrene, and other compounds. Disproportionation and transalkylation of toluene produce xylenes using zeolite catalysts. Unlike disproportionation, transalkylation transfers an alkyl group between different alkylaromatic molecules. Zeolites are crystalline and porous catalysts used for these reactions due to their ion exchange and adsorption properties.

1. Prepared by:
Ayad Idrees Sleman
Supervisor by: Dr. Kanaan R .Ahmad
MAY 2016
2016:AD 2716K 1437H

2. Content Page
The Aim of Study 3
1.Introduction 4
2.Alkylation 5
3-Disproportionation 7
4-Transalkylation 8
5-Zeolite catalysts 10
Reference 11
2Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts

3. • Catalytic alkyl-transfer (transalkylation, disproportionation) reactions,
reaction conditions, and catalysts of alkylaromatics were studied for
the aim of sorting out the principles that governs them.
3Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts

4. • Transalkylation is a chemical reaction involving the transfer of an alkyl group from
one organic compound to another. The reaction is most commonly used for the transfer of
methyl groups between benzene rings and is widely used in the petrochemical industry to
manufacture p-xylene , styrene, and other aromatic compounds. Motivation for using trans
alkylation reactions is based on a difference in production and demand for benzene, toluene,
and xylenes. During the process of xylene production, a number of reactions such as
transalkylation disproportionation, and dealkylation take place. The methyl groups are shifted
from one benzene ring to the other via transalkylation and disproportionation to produce
mixed xylenes.
4Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts

5. Acid catalysts used for alkylation of aromatic hydrocarbons are Brönsted acids
containing acidic protons These include acidic halides such as aluminium chlorides and
boron fluoride, acidic oxides and zeolites protonic acids especially sulfuric acid,
hydrofluoric acid and phosphoric acid, and organic cation exchange resins. Metal halides
usually called Friedel-Crafts catalysts, have been used extensively for aromatic
alkylation in the past, they are highly active and allow the reaction to be carried out in
liquid phase at low temperatures
5Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts

6. 6

7. • Transalyklation as used by the petrochemical industry is often used to
convert toluene into benzene and xylenes. This is achieved through a
disproportionation reaction of toluene in which one toluene molecule
transfers its methyl group to another one. The reaction is not selective,
and the xylene produced can be ortho, meta, or para. There is a higher
demand for para xylene, so it is often separated out, and the reaction is
allowed to produce more para product
7Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts

8. • Unlike disproportionation, in Transalkylation one of the alkyl groups is
transferred from one Alkylaromatic molecule to another aromatic
molecule of a different kind.
• Transalkylation Is transfer of alkyl group from 1,2,4-trimethylbenzene
to toluene to produce xylene
8Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts
CH3
2
toluene
CH3
CH3
xylene
+
CH3
CH3
CH3
1,2,4-trimethylbenzene

9. CH3
Disproportionation & Transalkylation
CH3
CH3
CH3
CH3
CH3
CH3
1,4-xylene
1,3-xylene
1,2-xylene
1.poly(p-xylene) 2.terephtalic
acid
poly(ethylene
terephtalate)_
poly(butylen
terephtalate)
Isophthalic acid
1-Unsaturated
poly ester
2-Alkyd
resins
3-poly amide
resins
4- Diphenyl Isophthalate
polybenzimidozoles
Phthalic
Anhydride
1-Alkyd
resins
2-Unsaturate
d poly ester
3-Poly ester
polyol
Urethanes
9Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts

10. Zeolites are crystalline and porous materials with an open structure that
consist of AlO4 and SiO4 tetrahedral units linked through oxygen atoms.
Owing to their unique properties in ion exchange and
adsorption capacity and catalytic activity, zeolites have been widely used as
adsorbents, molecular sieving agents and catalysts for a variety of different
chemical reactions.
10Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts

11. 1. Tsai, Tseng-Chang "Disproportionation and transalkylation of alkylbenzenes
over zeolite catalysts". Elsevier Science, 1999
2 https://en.wikipedia.org/wiki/Transalkylation
3. A L K Y L – T R A N S F E R ( T R A N S A L K Y L A T I O N ) R E A C T I O N S O
F A L K Y L A R O M A T I C S O N S O L I D A C I D C A T A L Y S T S
4. Stefanidakis, G.; Gwyn, J.E. (1993). "Alkylation". In John J. McKetta. Chemical
Processing Handbook. CRC Press. pp. 80–138. ISBN 0-8247-8701-3
11Disproportionation & Transalkylation Of Alkyl benzenes over Zeolite Catalysts

12. Disproportionation & Transalkylation Of Alkyl benzenes over
Zeolite Catalysts
12