Alkyl- transfer (Transalkylation) reactions of alkylaromatics on solid acid catalysts
Date
2006-11-16T06:10:42Z
Authors
Mokoena, Kgutso
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Abstract
Alkyl-transfer (transalkylation, disproportionation) reactions of alkylaromatics were
studied for the purpose of finding out the principles that governs them. Alkyl-transfer
of simpler alkylaromatics ranging from mono to polyalkyl-benzenes and
alkylnaphthalenes were studied in a fixed bed reactor system on solid acid catalysts
(zeolites) at temperatures up to 400 °C. Results showed that alkyl-transfer reactions
are reversible reactions with disproportionation favoured at lower temperatures while
transalkylation seemed to be dominant at higher temperatures. The outlined
mechanism showed that the catalyst pore sizes and the type of pores as well as the
feed composition of binary mixtures play important roles in the transfer of alkyl
groups between aromatic molecules. In alkyl-transfer reactions, the ease of
conversion depends on the number of alkyl groups on the aromatic ring/s, the chain
length, the type of alkyl substituent/s and the ring conjugation of the aromatic moiety.
Zeolitic catalysts are rapidly deactivated by carbonaceous material deposition during
alkyl-transfer reactions especially at higher temperatures while deactivation through
molecular retention is dominant at lower temperatures. Nevertheless, zeolites can be
regenerated by high temperatures in oxidizing atmospheres. Bulkier alkylaromatics
(those found in coal and petroleum liquids) can be transformed through alkyl-transfer
reactions if a suitable catalyst with the required strength and appropriate pore sizes
can be developed, preferably a tri-dimensional arrangement as shown by the results
of this study. Thus the alkyl-transfer process has promising future applications in
petrochemical and related industries; especially those interested in the transformation
of coal to chemicals.
Description
Student Number : 9502913H -
PhD thesis -
School of Chemistry -
Faculty of Science
Keywords
transalkylation, zeolites, alkylaromatics