Kinetic Analysis of Isobutane/Butene Alkylation over Ultrastable H−Y Zeolite

Abstract

The alkylation of isobutane with trans-2-butene over ultrastable Y-type zeolites has been studied. It is well-known that this reaction is accompanied by a rapid deactivation of the catalyst. The objective of our study is to elucidate the route to catalyst deactivation so that the means of mitigating this problem can be identified. Using the initial reaction rate data, evidence has been found for a Brönsted acid mechanism. Under liquid-phase conditions, the reaction has been found to be severely diffusion limited. Using a kinetic model that accounts for the effect of diffusion, it was found that alkylation over this catalyst suffers from slow hydride transfer relative to olefin addition. This gives rise to a rapid formation of C12 + carbocations. The formation of these cations has been tied to catalyst deactivation, using a mathematical model for the reaction. On the basis of the insight gained from the experiments and modeling work, optimal reactor and catalyst design issues are examined. It is inferred from the reaction mechanism and confirmed experimentally that alkylation under pulsed flow conditions yields higher trimethylpentane/dimethylhexane ratios and slower rates of deactivation. It is suggested that the cause of the slow rate of hydride transfer is steric hindrance. Strategies for relieving this steric hindrance are proposed.

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

“…For a simplified kinetic analysis, a pseudo first order approach was assumed for the olefin. This assumption is also made in the literature [32][33][34]. For a first order, the rate constant k can be determined by the following equation: Figure 6 and Table 4 show the influence of different amounts of tert-butyl bromide on the rate constant of isobutene/2-butene alkylation.…”

Alkylation of Isobutane by 1-Butene over H-beta Zeolite in CSTR (Part 2) Deactivation Mechanism of Zeolite Catalyst and Optimization of CSTR Conditions

“…The most important reaction step for alkylation is hydride transfer from iso butane to C8 13), 14) and should be faster than multialkylation or oligomerization of 1-butene to avoid the deactivation of catalyst. Therefore, application of a continuously stirred tank reactor (CSTR) is a promising way to suppress deactivation of the catalyst because this system can maintain a lower ratio of 1-butene to cation concentration 15)～17) .…”

Environmental analysis of gasoline blending components through their life cycle

“…The composition of alkylate described by Simpson et al [15] includes 17 chemical species from C 5 to C 9 alkane isomers. Nagpal et al [16] list a typical fluidised catalytic cracker (FCC) naphtha fraction.…”