Liquid-Phase Isobutane/Butene-Alkylation Using Promoted Lewis-Acidic IL-Catalysts

Abstract

The effect of different promoters on activity and selectivity of Lewis-acidic chloroaluminate ionic liquid catalysts was studied for isobutane/2-butene alkylation. When tert-butyl halides are used as promoters, the active species of the alkylation reaction, which is the tertbutyl cation, is directly generated whereas upon catalysis with Brønsted-acid supported ionic liquids, this species is indirectly provided through a hydride shift between protonated 2-butene and isobutane. Experimental results both from batch and continuously operated liquid phase alkylation reactors indicate, that tert-butyl halides are able to speed up the reaction rate significantly and shift the C 8 -selectivity towards the desired high-octane trimethylpentanes (TMPs). However, secondary reactions like oligomerization and cracking could not be suppressed by the use of this additives and high deactivation rates in continuous opperation were observed. Suggestions are made, how the product composition is effected by the additive and how the promoted IL-catalyst system is deactivated with time on stream.

Enhanced activity and selectivity in n-octane isomerization using a bifunctional SCILL catalyst

“…The promoting effect of chloroalkanes in acidic chloroaluminate ionic liquids observed here was already demonstrated by our group in a previous publication [26] (see also Supporting information for details, Fig. S11) and was first described by the group of Jess for the alkylation of isobutane and 2-butene [27].…”

Ionic Liquids in Catalysis

“…Other important acid catalyzed reactions that have been successfully carried out in form of liquid-ionic liquid biphasic catalysis include oligomerization [36], cracking [37,38] and refinery alkylation reactions [39][40][41]. The latter represent the transformation of short-chain olefins (C 3 -C 5 ) with isobutane to produce high octane fuels.…”

Alkylation in Petroleum Processing

“…The superacid properties of protons in acidic chloroaluminate ionic liquids have been explained by the reaction between dissolved HCl and the acidic species, which releases protons with extremely low solvation and therefore very high reactivity (Wasserscheid and The cations used in ionic liquids for alkylation are typically quaternary ammonium, quaternary phosphonium, or trialkylsulfonium species (Lacroix et al 1998;OlivierBourbigou et al 2002). Many authors, including Aschauer et al (2011), have published results using 1-butyl-3-methyl-imidazolium (BMIM) chloroaluminate ionic liquid. Chevron has numerous patent examples using 1-butyl-pyridinium (BP) chloroaluminate ionic liquids (Elomari et al 2008;Harris et al 2009).…”