炭负载Co-Mo催化剂的二苯并噻吩加氢脱硫性能研究

Hydrodesulfurization properties of dibenzuothiphene over carbon-supported Co-Mo catalysts

利用X射线衍射及程序升温还原技术 ,对等体积浸渍法制备的Co Mo/AC催化剂进行了表征。采用高压微反装置、以二苯并噻吩为模型化合物 ,在一定的温度和空速下对催化剂进行了加氢脱硫活性评价。X射线衍射表征结果表明 ,柱状活性炭具有良好的担载催化剂活性组分的能力 ,活性组分在载体表面能很好地分散 ,因而只检测到部分活性组分很弱的衍射峰。在 12 0℃和 2 6 0℃条件下处理的催化剂表面物种主要是MoO3 ,没有发现含Co的物种和CoMoO复合氧化物的衍射峰 ;5 0 0℃焙烧处理的催化剂的表面物种主要是MoO2 。程序升温还原表征结果表明 ,Co Mo/AC催化剂表面物种的还原温度低于Co Mo/γ Al2 O3 催化剂。加氢脱硫活性评价结果表明 ,催化剂的还原特性和加氢脱硫活性有一定的对应关系。在Co Mo/AC体系中 ,Co与Mo原子比为 0 .7的催化剂的加氢脱硫活性高于γ Al2 O3 负载的Co Mo催化剂 ;而Co与Mo原子比为 0 .2 ,0 .35和 0 .5的Co Mo/AC催化剂的加氢脱硫活性却低于Co Mo/γ Al2 O3

The X-ray diffraction (XRD) and temperature-programmed reduction (TPR) techniques were used to characterize the Co-Mo/AC catalysts prepared by using pore volume impregnation method. The activity and selectivity of catalysts in hydrodesulfurization (HDS) were evaluated, taking dibenzothiophene (DBT) as the model compound in the high-pressure micro reactor. The XRD results show that the column active carbon has a capacity for carrying the active components of catalysts, and all the active phases are well dispersed on the surface of the activated carbon supporter. The main species on the surface of the Co-Mo/AC catalyst heat-treated at 120 ℃ and 260 ℃ under the protection of nitrogen is MoO_3, whereas, the main species on Co-Mo/AC catalyst calcinated at 500 ℃ is the low-valence MoO_2 . The active phase diffractions of cobalt species and CoMoO have not been detected by the XRD technique during the experiment. The TPR curves reveal that the active species in Co-Mo/AC catalytic system are more easily reduced at lower temperature than those dispersed on γ-Al_2O_3 supporter. The activated carbon supporter favors the dispersion and reduction of active species. The HDS activity evaluation experiments reveal that there is a certain relationship between HDS activity of catalyst and its TPR properties. In the Co-Mo/AC system, the atom ratio of cobalt to molybdenum has a great influence on the HDS activity. The Co-Mo/AC catalyst with atom ratio of 0.7 has higher activity than the commonly used Co-Mo/γ-Al_2O_3 catalyst. However, the Co-Mo/AC catalysts with Co-to-Mo ratios of 0.2, 0.35 and 0.5 have less activity than commercial Co-Mo/γ-Al_2O_3 catalyst.