Mechanistic insights into Ti/ SiO 2 ‐catalyzed gas‐phase synthesis of glycolide from methyl glycolate

Abstract Gas‐phase catalytic synthesis of glycolide (GL) from methyl glycolate (MG) offers a promising route for sustainable production of polyglycolic acid, yet suffers from unfavorable catalytic performances due to limited mechanistic understandings. Here, a series of Ti/SiO 2 catalysts supported on mesoporous materials with distinct pore structures were synthesized to elucidate the structure–performance–mechanism relationship. Among them, Ti/KIT‐6 exhibited the highest MG conversion and GL yield, attributed to its large pore size, three‐dimensional interconnected mesostructure, and well‐dispersed tetrahedral Ti(IV) species. Comprehensive structure characterizations and mechanistic studies establish a linear correlation for MG conversion rate and GL formation rate with the tetrahedral Ti(IV) content, pointing to Ti(IV) as the intrinsic active sites. Further combining with temperature‐programmed and in situ spectroscopy experiments, a possible reaction mechanism is proposed for MG‐to‐GL on the active site. This study provides mechanistic insights to guide design of Ti‐based catalysts for gas‐phase ester cyclization reactions.