Development of an Empirical Model for Catalyst Lifetime in Isobutane/Butene Alkylation

Dimensional analysis of the governing equations in liquid-phase, solid-acid-catalyzed alkylation was used to develop an empirical model for the catalyst lifetime in terms of important operating variables. It was found that the dimensionless catalyst lifetime in a continuous stirred tank reactor was a function of four dimensionless groups, incorporating all important kinetic and operating variables. A power-law correlation was found to be adequate in representing the available experimental data. Because the alkylation reactions are highly diffusion-limited, it was shown that only three of the four exponents in the power-law correlation were independent. As such, the fourth exponent was obtained without a need to fit the correlation with its corresponding experimental data. The lifetime was found to be proportional to the concentration of active sites raised to the power of 0.8. Among the various operating variables, the olefin feed concentration most significantly influenced the catalyst lifetime.