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环氧丙烷(PO)是仅次于聚丙烯和丙烯腈的第三大丙烯衍生物,广泛应用于轻工、医药和纺织等行业。相比于传统的氯醇法和共氧化法,在临氢条件下使用氧气直接氧化丙烯生产PO的工艺具有绿色环保、操作简单、经济性高等优势,是当前国内外PO生产领域的研究热点。本文针对该领域仍存在的催化剂寿命短、活性低等亟待解决的问题,综述了国内外近年来的研究进展,着重介绍催化剂中含钛载体的表面和结构性质、金属颗粒的形貌和电子效应对丙烯直接气相环氧化反应活性、稳定性的影响机制,并评述了催化剂的反应机理及结焦失活机理。此外,还总结了Cs、Ag、Pd、Pt、Ge、表面烷基化、离子液体、氮掺杂等助剂对催化性能的影响,分析了丙烯环氧化反应过程尚存的难题。最后,从载体材料的选择、催化剂性能的改进等方面展望了可能的解决途径和方向。
Propylene oxide (PO) is the third largest propylene derivative after polypropylene and acrylonitrile and is widely used in light industry, pharmaceuticals and textile industries. Compared with the traditional chlorohydrin method and the co-oxidation method, the process of directly producing propylene oxide by oxygen using hydrogen in the presence of hydrogen has the advantages of environmental friendliness, simple operation and high economy, and is currently a hot spot in the field of PO production at home and abroad. In view of the shortcoming of short catalyst life and low activity in this field, this review summarizes the research progress in recent years at home and abroad, focusing on the surface and structural properties of titanium-containing catalysts, the morphology and electronic effects of metal particles On propylene direct gas-phase epoxidation reaction activity and stability mechanism, and reviews the catalyst reaction mechanism and coking inactivation mechanism. In addition, the effects of additives such as Cs, Ag, Pd, Pt, Ge, surface alkylation, ionic liquid and nitrogen doping on the catalytic performance were summarized. And the remaining problems in epoxidation of propylene were analyzed. Finally, the possible solutions and directions are prospected from the aspects of the selection of carrier materials and the improvement of catalyst performance.