汽油烃类异构化的研究及应用

催化裂化汽油脱硫降烯烃过程,促进烃类的异构化反应,可以弥补由汽油烯烃饱和组成的辛烷值损失。研究了分子筛结构、表面修饰、金属种类及双功能活性中心距离等,对正庚烷异构化性能的影响。发现异构化选择性主要受两方面因素的影响:一方面是分子筛的孔道特性,包括分子筛的孔口大小、分子筛的内部孔结构等;另一方面是金属和酸性活性中心的配合。异构化反应在分子筛的内外表面同时进行。低温时以外表面反应为主;升高反应温度,内部反应随之发挥重要作用。外表面可能是中孔分子筛裂化反应的中心。当金属和酸性活性中心的比例合适且间距靠近时,异构化中间产物可以很快地加氢,从而减少二次裂化的发生。在此基础上开发的烃类异构化催化剂应用于工业装置,表现了良好的特性。

Study and Application of Hydrocarbon Isomerization

By studying of molecular composition and the thermodynamics equilibrium, it is found that isomerization of hydrocarbon is benefit to offset the octane loss due to olefin saturation during FCC gasoline hydrotreating process. The affect of molecular sieve structure, surface modification and the type of metal on heptane isomerization was studied. The isomer selectivity is affected by two sides' factors. The first one is channel feature of molecular sieve, including pore diameter, pore structure, etc., and the second one is the matching of acid and metal active sites. Isomerization could be performed on the internal and external surface of molecular sieve simultaneously. The external surface is the main active position when reaction is carried out at low temperature. The internal surface becomes major only when the temperature increases. For medium pore molecular sieve, external surface may be the cracking position. When the metal center and acid center maintain suitable ratio and quite less distance, the intermediate products could be hydrogenated very quickly, and reduced the secondary cracking effectively. The developed catalyst depending on such concepts has been used in commercial unit and shows good performance.