Hydrothermal study of Pt-Sn-based SAPO-34 supported novel catalyst used for selective propane dehydrogenation to propylene

Catalyst's regeneration is unavoidable part during dehydrogenation. The hydrothermal treatment influence on the performance of Pt-Sn-based SAPO-34 supported novel catalyst, used for propane dehydrogenation to propylene is investigated in this study. The catalyst shows excellent stability for mild steaming (nitrogen mixed steam), during four consecutive runs (reaction-regeneration mode). On the other hand, Pt-Sn/ZSM-5 was largely affected on mild steaming due to severe dealumination. In order to get into mechanistic understanding, severe hydrothermal treatment was carried our using pure steam. The substation loss in catalyst activity was noted. Both fresh and severe hydrotreated catalysts were characterized by XRD, XRF, O-2-pulse analysis of coke, NH3-TPD, IR spectrum of adsorbed ammonia, H-2-TPR, HR-TEM and XPS, to explore reasons for change in catalytic properties. The texture/topology is found stable. Changes in surface ensembles occur due to the loss of Sn, Al, formation of SnO species and in particular Pt sintering. This leads Pt active sites (zeolite-SnO-Pt) to inactive sites (zeolite-Pt, zeolite-PtO-Sn, Pt-Sn alloy, etc.) formation and reduced catalyst activity. TEM micrographs and H-2-chemisorption analysis confirms Pt particles agglomeration and/or sintering. About 98% catalyst activity is recovered by re-dispersed Pt using chlorination technique and credit goes to hydrothermally stable support (SAPO-34). (C) 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.