Hydrothermal Synthesis And Hydrodesulfurization Performance Of Unsupported Sulfided Mo-based Catalyst

These environmental concerns have led to increasingly drastic regulations onsulfur, nitrogen and aromatics content in fuels. Sulfur content in the motor and dieselfuels is continuously reduced by regulations to lower levels. By use of the catalystwith ultra-higher hydrodesulfurization activity when products clean fuel is one of themost economical and most effective way. Hydrodesulphurization （HDS） of petroleumfeed stocks are commercially achieved with MoS₂or WS₂supported on alumina andpromoted by Co or Ni. Because of the support will limit active component capacity,conventional supported catalyst to further enhance its activity is so hard.In the dissertation, unsupported MoS₂hydrodesulfurization catalyst wasprepared by hydrothermal method with ammonium molybdate （（NH₄）6Mo₇O₂4·4H₂O）,（SC（NH₂）2） as precursors. With the foundation, the unsupported Co-Mo-Shydrodesulfurization catalyst was prepared also. The resulting materials werecharacterized by BET, BJH, XRD, SEM,EDS and TEM. The activity of catalysts werestudied by measuring the hydrodesulfurization （HDS） of thiophene.MoS₂hydrodesulfurization catalyst was prepared by hydrothermal method, but thesurface area, pore volume, diameter are poor. The temperature has a great impact forcatalyst preparation, the surface area increased at first and then decreased with therising of temperature. Its activity was not better by measuring the HDS of thiophene.The characteristic of catalyst was improved by adding an appropriate amount of thecationic surfactant （CATB）, the anionic surfactant （SDBS） or nonionic surfactants（PEG）. The results showed that the catalyst particles with the addition of surfactantswere loose, while the catalyst without the addition of surfactant exhibited seriousagglomeration phenomenon. The surface area, pore volume, diameter and the numberof the stacked layer of the catalyst with the addition surfactant was much greater thanthat of the other one. The surface area are high to140m2·g-1. The figure of pore sizedistribution showed it have two most probable pore diameter, the rate of Meso-poroushas prominent increasing. The catalyst with the addition cationic surfactant is the bestone. The catalysts with the addition surfactant showed high activity in the HDS ofthiophene, the conversion of thiophene could reach to98%need5hours at573K and4.0MPa pressure. Furthermore, the catalyst （Mo-S-C） with the addition of cationicsurfactant showed the highest activity among these catalysts, and the conversion of thiophene was high to99.9%. By comparing the conversion, the reactivity order of thecatalysts was: Mo-S-C>Mo-S-S>Mo-S-P>Mo-S-N.In the dissertation, Co-Mo-S catalysts were successfully prepared byhydrothermal method and reflow method. The element of Co cannot significantimpact on physical characteristics but can promote the activity significantly. Thereflow method is better than hydrothermal method. Reflux method are easier tocontrol the product type, Co element can be evenly distributed to the surface and poreof catalyst. The catalysts with the addition Co element showed very high activity inthe HDS of thiophene, the conversion of thiophene could reach to100%just need3hours at573K and4.0MPa pressure. The catalytic activity of catalyst by reflowmethod showed slightly higher than the catalyst by hydrothermal method.