Trimerization of Isobutene Over Solid Acid Catalysts

Abstract

Oligomerization of isobutene is a very promising reaction not only for the production of isobutene oligomers such as trimers but also for the separation of isobutene from C 4 mixtures. Several solid acid catalysts have been applied for the continuous oligomerization of isobutene in liquid phase. This review analyzes the trimerization of isobutene over various solid acid catalysts such as zeolites, oxides (zirconias and titanias) and acid resins. Trimers selectivity increases with increasing isobutene conversion, irrespective of catalysts such as zeolites and acid resins. Very stable operation with high trimers selectivity is accomplished with WO x /ZrO 2 catalyst having tetragonal zirconia or various zeolite catalysts with high Lewis acid site-to-Brønsted acid site ratio (LA/BA ratio). For a good performance, acid resins should be macroporous and strong acid (sulphonic acid group) with high acid concentration. Inorganic catalysts are superior to acid resins because the deactivated inorganic materials can be regenerated by simple calcination. The WO x /ZrO 2 catalyst may be applied to a commercial process because about several thousand tons of isobutene can be oligomerized per one ton of zirconia catalyst in a catalytic cycle without regeneration. The oligomerization of isobutene may be improved further because the reaction has been started only recently and no research has been done for the optimization of the reaction and catalysts. It is expected to develop a new inorganic catalyst having suitable acidity, LA/BA ratio and phase, etc. by further research. The isobutene trimers, with or without hydrogenation, may be used for various purposes, and the importance of this trimerization reaction will be increased considering the expected surplus of isobutene due to the banned use of methyl-tert-butyl ether.

Formation of Isobutene from 3-Hydroxy-3-Methylbutyrate by Diphosphomevalonate Decarboxylase

“…Isobutene is a product of petroleum refining that is used for the production of butyl rubber, specialty chemicals, and a gasoline additive known as alkylate (15,22,28). Gasoline alkylate is produced by polymerization of a mixture of alkanes and alkenes (such as isobutene) and is usually blended with gasoline at a level of 10 to 15% (22).…”

Alkenes oligomerization with resin catalysts

“…In the case of resins selectivity is partially due to matrix effects [32] and good results are generally found. Unlike other solid acids, resins have low thermal stability which limits the range of operation (usually up to 423 K [23]) and hinders regeneration by calcination (to remove pore blocking organic compounds [36]). Resin catalysts are regenerated by washing with a suitable solvent (e.g.…”

“…Resin catalysts are regenerated by washing with a suitable solvent (e.g. n-butane) but generally, in comparison with the fresh resin, activity is lower and deactivation rate is higher [36,37]. Overall, an easy regeneration process of the aged catalysts is required for long-term efficient performance of resins in commercial applications [38].…”

“…As illustrated in Fig. 5 [36] the low volatile isobutene dimers can be easily hydrogenated to isooctane (2,2,4-trimethylpentane) [2,53] while hydrogenated isobutene trimers can be used as solvents or as diesel additives to increase the cetane number [64,68,69].…”

“…Recently they received more attention due to the advent of special "neo-acids" produced by reacting triisobutene isomers with carbon dioxide [58]. Triisobutenes are also promising materials for the synthesis of special chemicals such as dodecylbenzene, antirusts, lubricants, gas oil additives, and solidifying agents for epoxy resins [36]. As depicted in Fig.…”