Effective and Intrinsic Kinetics of Liquid-Phase Isobutane/2-Butene Alkylation Catalyzed by Chloroaluminate Ionic Liquids

Abstract

The kinetics of the IL-catalyzed reaction of isobutane with 2-butene and the size distribution of the dispersed IL droplets were investigated in a stirred tank reactor. The results were used to calculate the intrinsic reaction rate constant with a model accounting for the interplay of external and internal mass transport and chemical reaction. The intrinsic reaction rate was found to be very high, leading to a low effectiveness factor of the IL catalyst. The used fraction of the IL droplets with a diameter of about 400 μm was very small, and the actual reaction took place only in a thin spherical shell with a thickness of about 5 μm.

Lewis Acidic Ionic Liquids

“…Refinery alkylates for use in high octane fuels had been produced on an industrial scale using either H 2 SO 4 or HF as the acid catalyst [124], with aluminium(III) chloride described as too acidic and thus inducing side reactions, such as cracking [126]. However, Chauvin and co-workers reported the successful use of chloroaluminate ILs as catalysts for isobutane-butene alkylations, which was then expanded upon by Jess et al [108,[127][128][129]. Tuneable acidity of the ionic liquid was found to play a crucial role: high v AlCl3 values led to cracking (like neat AlCl 3 ), whilst low acidity caused polyalkylations [130].…”

Understanding interfacial behaviors of isobutane alkylation with C4 olefin catalyzed by sulfuric acid or ionic liquids

“…Besides the solubility of isobutane, the diffusion of isobutane at the interface in acid/hydrocarbon dispersions is another important factor that affects the quality of alkylate. It is believed that the diffusion of isobutane across the hydrocarbon‐acid interface is the rate‐limiting step for the whole isobutane alkylation . The self‐diffusion coefficients D z of 2‐butene and isobutane at the interface for all systems are calculated using the modified Langevin equation, as shown in Figure .…”

Lewis Acidic Ionic Liquids

“…Refinery alkylates for use in high octane fuels had been produced on an industrial scale using either H 2 SO 4 or HF as the acid catalyst [ 124 ], with aluminium(III) chloride described as too acidic and thus inducing side reactions, such as cracking [ 126 ]. However, Chauvin and co-workers reported the successful use of chloroaluminate ILs as catalysts for isobutane–butene alkylations, which was then expanded upon by Jess et al [ 108 , 127 – 129 ]. Tuneable acidity of the ionic liquid was found to play a crucial role: high χ AlCl3 values led to cracking (like neat AlCl 3 ), whilst low acidity caused polyalkylations [ 130 ].…”