制备条件对碳化钼催化剂加氢脱硫性能的影响

Effect of Preparation Conditions on Dibenzothiophene Hydrodesulfurization Performance of Molybdenum Carbide

以MoO3为前驱体,在CH4/H2气氛中程序升温还原碳化反应制备了Mo2C催化剂,用XRD和BET进行了表征.以二苯并噻吩/环己烷溶液为模型反应物,评价了制备条件对碳化钼催化剂加氢脱硫性能的影响.结果表明,在还原碳化温度为675℃,恒温保持150 min的合成条件下可制得高纯度的β-Mo2C催化剂,该催化剂表现出了较高的加氢脱硫活性,用质量分数为0.6%的二苯并噻吩/环己烷溶液为反应物,反应压力3.0 MPa,反应空速8 h-1,反应温度330℃实验条件下的二苯并噻吩加氢脱硫转化率达到了73.29%.随还原碳化温度的升高和恒温保持时间的延长,制备的碳化钼催化剂的比表面积下降,表面积炭增多,引起其二苯并噻吩加氢脱硫活性的下降.适当增大制备过程中还原碳化气体空速,有利于还原碳化反应过程中C、O之间局部规整反应的进行,并对其二苯并噻吩加氢脱硫活性有明显的促进作用.实验确定的还原碳化气体空速以1.8×104h-1为宜.

Molybdenum carbide catalysts, prepared by temperature-programmed reaction （TPR） using CH4/H2 gas mixture to molybdenum oxide, were characterized by XRD and BET techniques. The effect of preparation condi- tions on the catalytic performance of molybdenum carbide for hydrodesulfurization（HDS） has been evaluated using dibenzothiophene（DBT） as the model reactant. The results indicates that the β-Mo2C can be prepared by TPR in CH4/H2 mixture to molybdenum oxide at 675 ℃ for 150 rain, and the DBT conversion over the catalyst reaches to 73.29% using O. 6% DBT as the model reactant under the reaction conditions of 330℃, 3.0 MPa and space velocity 8 h^-1. It is found that raising the carburizing temperature and increasing the carburizing time in preparation of molybdenum carbide decreased the BET surface area and aggrandized the carbon deposited on the catalyst surface, so reduce the DBT HDS activity of the catalysts. It has also been found that the topotactic reaction of C and O was favorable and the DBT HDS activity of Mo2 C was markedly promoted. The suitable carburizing space velocity is 1.8 x 10^4h^-1.