Affiliation:
1. Inorganic Chemistry and Catalysis group Institute for Sustainable and Circular Chemistry and Debye Institute for Nanomaterials Science Utrecht University Universiteitsweg 99 3584 GC Utrecht The Netherlands
2. Present Address: California Institute of Technology Department of Chemical Engineering 1200 East California Boulevard Pasadena CA 91125 USA
Abstract
AbstractHydrocarbon conversion catalysts suffer from deactivation by deposition or formation of carbon deposits. Carbon deposit formation is thermodynamically favored above 350 °C, even in some hydrogen‐rich environments. We discuss four basic mechanisms: a carbenium‐ion based mechanism taking place on acid sites of zeolites or bifunctional catalysts, a metal‐induced formation of soft coke (i.e., oligomers of small olefins) on bifunctional catalysts, a radical‐mediated mechanism in higher‐temperature processes, and fast‐growing carbon filament formation. Catalysts deactivate because carbon deposits block pores at different length scales, or directly block active sites. Some deactivated catalysts can be re‐used, others can be regenerated or have to be discarded. Catalyst and process design can mitigate the effects of deactivation. New analytical tools allow for the direct observation (in some cases even under in situ or operando conditions) of the 3D‐distribution of coke‐type species as a function of catalyst structure and lifetime.
Funder
Nederlandse Organisatie voor Wetenschappelijk Onderzoek