Unravelling the deactivation of CuZnO-based catalysts at the industrial scale: a micro to macro scale perspective†

Abstract

Unexpected changes in catalyst performance can have a significant impact on manufacturing plant operations with respect to both economics and sustainability. The useful lifespan of a catalyst is influenced by various factors, including catalyst performance aging (activity and selectivity), or the mechanical damage of catalyst pellets leading to high reactor pressure drops. Deactivation of industrial catalysts often results from thermal (metal sintering, loss of active surface areas, and vaporization), chemical (poisons: inorganic and organic and fouling), and mechanical mechanisms (abrasion, fracture, and dusting). Conducting a proper root-cause analysis can be complex and typically requires multidimensional fundamental scientific approaches. This study illustrates the mechanical degradation of CuZnO catalyst pellets under industrial hydrogenation conditions, leading to an increased pressure drop and reduced catalyst lifetime. Post-mortem analysis at different length scales in combination with the development of accelerating aging tools played a substantial role in the identification of catalyst failure modes for these industrial catalysts. Careful interpretation of the microscopy results enabled the identification of characteristic fingerprints of the failure mechanism. The presence of organic chloride impurities in the feed in combination with a reducing atmosphere accelerated both the sintering of ZnO and deformation of the catalyst pills. This reduced the effective lifespan of the catalyst, as the decrease in particle void fractions led to an increased reactor pressure drop, eventually necessitating the reloading of the reactor with a fresh catalyst. Understanding these mechanisms at both micro and macro scales is crucial for improving the economics and sustainability of commercial operations.