Hydrodesulfurization Performance Of Metal Catalysts Supported On Mesoporous Materials

The limit on maximum allowable sulfur content in diesel has beengradually decreased to reduce environmental pollution caused by SO_X.Currently, with environmental legislation becoming more and morerigorously, the maximum sulfur content in diesel is restricted to10ppm inmost of the developed countries. Traditional CoMo-based aluminacatalysts are widely used in industry for the hydrodesulfurization （HDS）of sulfur-containing compounds in diesel. But because of their low HDSactivity, complete removal of highly refractory molecules such asdibenzothiophene（DBT） and especially4,6-substitued dibenzothiophene（4,6-DM-DBT） are inevitable on mild conditions.4,6-DM-DBT can bedesulfurized mainly via hydrogenation（HYD） route owning to the sterichindrance of the methyls at4and6positions. So catalysts possessingwith higher hydrogenation activity is very important. It is well known thatnoble metal has a better hydrogenation activity, but they are sensitive tosulfur. Therefore, Pd, Pt and Pd-Pt can be supported on strong acidiczeolites for improving their sulfur resistance ability and hydrogenationability.It is well known that during the process of steam dealumnization forpreparing Ultra-Stable Y zeolite（USY）, it brings about mesopores. Inchapter2, we proceed with steam dealumnization for Y zeolite graduallyat different temperatures for synthesizing USYs which contain differentmesoporous volume and different acidity strength. XRD, SEM, N2adsorption and so on were performed to characterize the structure of them.Also we prepared Pd supported catalysts for HDS of DBT and4,6-DMDBT at mild conditions. We compare HDS performance of DBTand4,6-DM-DBT over Pd/USY. The kinetics of DBT HDS catalyzed by Pd catalysts were also studied.In chapter3, we prepared mesoporous MgO by pressurizedcarbonization method and they were characterized by XRD, SEM andother instruments. CoMo/MgO catalysts were prepared by the wetimpregnation method. And the HDS reactions of DBT and4,6-DM-DBTwere conducted to evaluate the HDS performance of the prepared catalyst.The hydrodesulfurization activity of DBT over CoMo/MgO was20%higher than that over traditional hydrodesulfurization catalystCoMo/γ-Al₂O₃. The kinetics of DBT HDS catalyzed by CoMo catalystswere also studied.Because there are disadvantages of microporous molecular sievesand mesoporous molecular sieves in the applications ofhydrodesulfurization, in recent years synthesising mesoporous zeolite hasbecome a hot topic. In chapter4, we attempted using soft template tosynthesis mesoporous ETS-10zeolite and was used for the reaction ofDBT hydrodesulfurization.