Reaction—regeneration cycles in the isomerization of cis-butene and calculation of the reactivation kinetics of a silica—alumina catalyst

Abstract

The reactivation kinetics has been determined (activity vs time of stripping and of combustion) as a function of temperature and time of the reaction step, for a silica—alumina catalyst used in the isomerization of cis-butene to 1-butene and trans-butene. A pronounced hysteresis has been found in the relationship of activity—coke-content in the reaction—regeneration cycles, which shows that the elimination of “volatile” coke in the stripping with an inert (previous to combustion of “non-volatile” coke) means an important recuperation of activity. The experimentation involved the analysis of coke in a thermoanalyser and carrying out reaction-regeneration cycles. The evolution of acidity in the reactivation has been analysed. This analysis shows that the very strong acidic sites are the ones that are initially reactivated. The calculated kinetics of reactivation has been used together with the kinetic equations of the main reaction and of deactivation in the simulation of subsequent cycles of reaction—regeneration. The simultaneous optimization of reaction and regeneration steps, with the aim of maximizing the apparent production rate of 1-butene or trans-butene, has been studied. The results of simulation have been experimentally proven in the automated reaction—regeneration equipment, in which the optimum conditions of both the steps have been used.