Elucidation of deactivation mechanisms of zeolites used in petroleum and biomass upgrading processes
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Zeolites have been identified and utilized as excellent heterogeneous catalysts in a variety of processes involving the upgrading of biomass and fossil-fuel feedstocks. However, the deactivation of zeolites has been observed with time on stream in catalytic reactions. Despite the increasing number of literature reports on zeolites in the past years, deactivation of zeolite catalysts is still a major economic concern, and there is a substantial motivation to investigate the deactivation of zeolites, in order to understand the different pathways that contribute to loss in activity, and to suggest efficient and cheap preventive measures. In this thesis, the structural changes, coke formation, sintering of impregnated metals and the associated deactivation behavior of microporous, hierarchical and metal-impregnated zeolites has been investigated. Three different processes, involving the upgrading of bio-oils and petroleum feeds, have been studied. The focus is on the different pathways of zeolite deactivation, taking into account the combined effect of zeolite morphology, process operating conditions and properties of the reaction medium (such as pH, presence of water or chelating agents etc.).