Kinetics Of FCC Gasoline Selective Hydrodesulfurization Over Co-Mo/γ-Al₂O₃ Catalyst

As we all know, over 90 percent of sulfur in automotive oil comes from FCC gasoline which will pollute the environment when burned into sulfur oxides. The key to produce clean gasoline is to eliminate sulfur in FCC gasoline. By now, the best way to eliminate the sulfur compounds is hydrodesulfurization and Co-Mo/Al2O3 is the most common catalyst used in this area. The main sulfur compounds in FCC gasoline are thiophene, benzothiophene and their ramifications. Most studies focused on the separate hydrodesulfurization of thiophene or benzothiophene instead of the co-hydrodesulfurization which is necessary to understand the real hydrodesulfurization of FCC gasoline. In the process of hydrodesulfurization, the alkene in FCC will get saturated. It will not only consume more hydrogen but also decrease the octane number. So, it’s necessary to maintain the octane number when increasing the desulfurization efficiency.In this thesis, the kinetics of separate hydrodesulfurization and co-hydrodesulfurization of thiophene and benzothiophene over Co-Mo/γ-Al2O3 was investigated experimentally after excluding the impact of diffusion and the LHHW kinetic equations of the process were established. Besieds, the LHHW kinetic equations of hydrogenation of 1-octene over Co-Mo/γ-Al2O3 were also established.The kinetics of separate hydrodesulfurization and co-hydrodesulfurization was different. The activation energy of separate hydrodesulfurization and co-hydrodesulfurization of benzothiophene was larger than that of thiophene. Besides, the activation energy of co-hydrodesulfurization was larger than that of separate hydrodesulfurization. The kinetics of hydrodesulfurization will get changed caused by different sulfur compounds and this conclusion can be drawed from the different kinetics of separate hydrodesulfurization and co-hydrodesulfurization of thiophene.In addition, the activity and selectivity of hydrodesulfurization of benzothiophene, thiophene and 1-octene were studied systematically. The results showed that H2S will inhibit the hydrodesulfurization of benzothiophene and thiophene. However, it also showed no effect on the activity and selectivity of hydrogenation of 1-octene. These results indicated that the active sites of hydrogenation of sulfur compounds and 1-octene were different. Alkene hydrogenation can only occur on rim surface of the catalyst, and sulfur compounds hydrodesulfurization can occur on both rim and edge surface of the catalyst. In order to increase the selectivity of hydrodesulfurization, the proportion of rim should be reduced which is equal to increase the thickness of catalyst.