生产低硫柴油的加氢催化剂

燃油车辆排放的尾气造成大城市空气的污染 ,生产清洁燃料已引起社会的广泛关注。为迎接生产低硫柴油的挑战 ,炼油厂将不得不改造现有的加氢处理装置或新建装置。了解待精制柴油中的含硫化合物 ,对于选择加工工艺和催化剂十分重要。柴油中的二苯并噻吩和具有取代基的二苯并噻吩是最难脱去的含硫化合物 ,其加氢脱硫存在两种平行途径 ,即直接途径和间接途径。前者为直接从分子中脱去硫原子 ,后者是一个芳香环先加氢 ,然后再脱去硫原子。介绍了国内外已工业应用和正在研发中的几种新型柴油加氢脱硫催化剂。建议炼油厂根据进料的含硫质量分数和装置实际合理选择催化剂 ,在低空速和中压条件下选用Ni-Mo催化或混合使用Co -Mo、Ni-Mo催化剂 ;新建装置应考虑芳烃饱和 ,采用加氢脱硫与加氢脱芳技术 ,实现两段加氢 ,生产低硫低芳烃柴油

Hydrodesulfurization Catalysts for Low Sulfur Diesel Production

Due to the air pollution over large urban areas caused by the emission of automobile fumes, much attention has been focused on the technology for clean-fuel production. To meet the challenge in making diesel with lower sulfur levels, refiners will have to revamp their existing hydrotreating units or build new one. Understanding the reactivity of sulfur-containing compounds is important for the right selection of process technology and catalysts. Dibenzothiophene and alkylated dibenzothiophene in diesel are less reactive than others, from which two possible reaction-pathways for the removal of sulfur could be used. The first is the direct extraction of the sulfur atom from the molecule, and the second is the hydrogenation of one aromatic ring followed by extraction of the sulfur atom. Several new developing catalysts with higher activity, which have been used in commercialization, were introduced. Refiners can upgrade the performance of the existing hydrodesulfurization units by application of high-activity catalysts. At low space velocities and moderately high pressures, Ni-Mo catalysts or combination of Co-Mo and Ni-Mo catalysts are suggested. To build new unit, two-stage process can be followed, base metal catalysts are used in the first stage and nobel metal catalysts in the second.