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

This paper carries out a systematic deactivation and regeneration study on a spent TS-1 zeolite extrudate catalyst, which was obtained from a scale-up propylene liquid-phase epoxidation test after a 1800 h time on stream under simulated industrial conditions. Results show that the catalyst deactivation is mainly due to blocking of zeolitic framework Ti active sites by heavier oligomers and surface-adsorbed low-boiling-point substances. These blocking substances are easy to be thoroughly cleared away by H2O2 washing or high-temperature calcination regeneration, and consequently, the catalyst's activity can be restored satisfactorily. However, the regenerated catalysts show deterioration of durability and reduction of initial PO selectivity, which are closely related to the irreversible hydrolysis of the Ti–O–Si bond of the TS-1 zeolite catalyst by H2O2 solution, increasing surface hydroxyl groups and acidity. This irreversible hydrolysis can occur during the epoxidation reaction process, and thus future studies will be focused on measures to cope with this tough challenge.