Preparation And Properties Of SBA-15Zeolite-Based Diesel Hydrodesulfurization Catalysts

One source of acid rain is the use of diesel with high sulfur content. To develop catalystsof higher HDS activity and make full use of the traditional existing HDS devices is a keyproject of the HDS research, especially for developing countries like China.Micro-mesoporous molecular sieves are good catalyst suppor because of their uniquestructures and properties, and attract significant interest of the intensive study. However, theinformation of catalytic mechanisms by Micro-mesoporous molecular sieves based HDScatalyst is still insufficient. Due to that, systematic research in the preparation, evaluation andcatalytic mechanisms of Micro-mesoporous molecular sieves based HDS catalyst are needed.Micro-mesoporous molecular sieve SBA-15-supported Ni-Mo and Co-Mo bimetallicHDS catalysts were prepared, and characterized by means of XRD, UV-Vis, TPR, TEM andN2adsorption-desorption. The HDS activities of the prepared catalysts were investigatedusing a representative polyaromatic sulfur-containing model compound, such asdibenzothiophene （DBT） and4,6-dimethyldibenzothiophene. The performace of theprepared catalysts were compared with a commercial deep hydrodesulfurization catalyst.It isshown that the maximum HDS activity was observed at Ni （Co）/Mo atomic ratio of0.50, andthe performents of Ni-Mo catalysts are better than Co-Mo catalysts at the same reactioncondition and higher selectivity of hydrogenation （HYD）. This is the innovation of this paper.The metal oxides MO （V₂O₅, CeO₂,Y₂O₃and Nd₂O₃） were used to modify SBA-15, andthen Ni （Co）-Mo/M-SBA-15with Ni （Co）/Mo atomic ratio of0.50were prepared. Throughthe analysis of the structure and surface properties of catalysts, the relationship wereresearched between modified metal oxide and HDS activity or the selectivity of the product.The results showed that Nd, Y, Ce, V can improve the dispersion of the Ni （Co）-Mo oxideson SBA-15, and strengthen the interaction force between Ni （Co）-Mo active component andsupport. Both DBT conversion rate and selectivity of hydrogenation （HYD） decrease after Nd,Y, and Ce modification while the opposite result after V modification. Weakly acidic metaloxide modified SBA-15improve the HDS activity; on the contrary, weakly alkaline metaloxide may reduce the HDS activity. One of the HDS activity center model-Remote control theory was used to explain the phenomenon above. This is anther innovation of this paper.Ni-Mo catalysts supported on SBA-15containing different of V₂O₅（2wt.%,4wt.%and8wt.%） content were prepared. The results showed that the HDS activity of DBT first increaseand then decrease with increasing V₂O₅content, and catalysts with4wt.%V₂O₅content hadthe maximum HDS activity. High content of modified metal causes active component andcarrier strong interactions while low content of it results the poor dispersion of the activecomponent on the support, both of these may decrease HDS activity. At a temperature of340℃, initial hydrogen pressure of4.0MPa, stirring rate of500rpm, solution volume of40mL and catalyst amount of0.30g, the desulfurization degree of diesel with1900μg·g-1ofsulfur content was90%while that with370μg·g-1of sulfur content was97.2%. The preparedcatalysts had higher activity than commercial HDS catalyst.