ETD Collection

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    Alkyl- transfer (Transalkylation) reactions of alkylaromatics on solid acid catalysts
    (2006-11-16T06:10:42Z) Mokoena, Kgutso
    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.