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

Abstract

Unexpected changes in catalyst performance can have 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 drop. Deactivation of industrial catalysts often results from thermal (metal sintering, loss of active surface area, vaporize), chemical (poisons: inorganic and organic, fouling), and mechanical mechanisms (abrasion, fracture, 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 increased pressure drop and reduced catalyst lifetime. Post-mortem analysis at different length scales in combination with development of accelerating aging tools, played a substantial role in the identification of catalyst failure mode 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 fraction led to an increased reactor pressure drop, eventually necessitating the reloading of the reactor with fresh catalyst. Understanding these mechanisms at both micro and macro scales is crucial for improving economics and sustainability of commercial operations.