Application of Parallel Difference Tests to Resolve the Axial Activation\u2013Deactivation Profile of Copper\u2013Zinc Oxide Catalyst During Hydrogenation of Methyl Acetate

Abstract

The deactivation of a copper–zinc oxide catalyst has been studied in a set of parallel tests which covered a range of space-times with equal flow and variable catalyst quantity, from 1/8th bed to full bed. The activation–deactivation trends over time in different segments of the full catalyst bed have been determined by two alternative parallel difference methods. The relative trends in segmental activity over time were followed by (a) using a pre-determined reaction model, and (b) by referencing the axial conversion profile against the initial profile. The trends estimated by both methods were in broad agreement. The results show that the front segment of the catalyst bed experienced a more rapid process of deactivation than the rest of the catalyst bed. This process is consistent with the known susceptibility of this type of catalyst to deactivation by chlorine and sulfur impurities in the feedstock. The main part of the catalyst bed appeared to undergo a process of activation during the first 150 h, followed by a slow process of deactivation which was more rapid during periods at increased temperature. The slow deactivation is most likely associated with sintering of copper particles. The conversion parallel difference method provides a convenient and rapid tool for segmental analysis of parallel life tests, and is well-suited to resolving the impact of a poison front within a catalyst bed.