Regeneration of a Spent TS-1 Zeolite Catalyst for Liquid-Phase Epoxidation of Propylene and H₂O₂

This paper carries out a systematic deactivation andregenerationstudy on a spent TS-1 zeolite extrudate catalyst, which was obtainedfrom a scale-up propylene liquid-phase epoxidation test after a 1800h time on stream under simulated industrial conditions. Results showthat the catalyst deactivation is mainly due to blocking of zeoliticframework Ti active sites by heavier oligomers and surface-adsorbedlow-boiling-point substances. These blocking substances are easy tobe thoroughly cleared away by H2O2 washing orhigh-temperature calcination regeneration, and consequently, the catalyst'sactivity can be restored satisfactorily. However, the regeneratedcatalysts show deterioration of durability and reduction of initialPO selectivity, which are closely related to the irreversible hydrolysisof the Ti-O-Si bond of the TS-1 zeolite catalyst byH(2)O(2) solution, increasing surface hydroxyl groupsand acidity. This irreversible hydrolysis can occur during the epoxidationreaction process, and thus future studies will be focused on measuresto cope with this tough challenge.