Ni-Mo-Al_2O_3催化剂覆碳改性对其加氢脱硫性能的影响

Effect of Carbon Modification of Ni-Mo-Al_2O_3 Catalysts on Their Hydrodesulfurization Performance

在催化剂制备的不同阶段引入碳物质,制备3种覆碳改性的NiMo-Al_2O_3加氢脱硫催化剂,采用低温氮静态容量吸附-脱附法、X射线衍射、H_2程序升温还原和高分辨透射电子显微镜对3种催化剂进行表征,并考察催化剂的加氢脱硫性能。结果表明:引入碳物质能够提高催化剂的加氢脱硫活性;采用前覆碳法即在载体上负载活性组分前引入碳前躯物,或采用共浸渍法即将活性组分与碳前躯物共同浸渍到载体上制得的催化剂,都能够增加八面体Mo物种的数量;采用共浸渍法制得催化剂活性组分分散性良好,MoS_2纳米颗粒堆垛层数多,其脱硫率比未覆碳改性催化剂的高6.8%;采用前覆碳法制得催化剂的金属分散性良好,其脱硫率比未覆碳改性催化剂的高5.1%;与未覆碳改性的催化剂相比,采用后覆碳法即在已负载活性组分的Ni-Mo-Al_2O_3催化剂上引入碳前躯物制得催化剂的脱硫率提高程度不大。

Three kinds of carbon modification Ni-Mo-Al_2O_3 hydrodesulfurization catalysts were prepared through incorporating carbon into the catalysts at different stages of catalyst preparation. The catalysts were characterized by BET, XRD, H_2-TPR and HRTEM, and their catalytic performance was tested. The results show that the incorporation of carbon into Ni-Mo-Al_2O_3 is benefit for improving the hydrodesulfurization performance of the catalysts. More octahedral Mo can be formed by pre-carbon coating method in which the carbon is incorporated onto the alumina support before the active component loading or by co-impregation method in which the carbon is added into the catalyst alone with the active components loading. The catalysts prepared by co-impregation method exhibit higher dispersion of active components and more number of stacking layers of MoS_2 nano-particles. Compared with the catalyst without carbon modification, the desulfurization degree of the catalysts is increased by 6.8%. The catalysts prepared by pre-carbon coating method exhibit higher dispersion of active components. Compared with the catalyst without carbon modification, the desulfurization degree of the catalysts is increased by 5.1%. The carbon modification Ni-Mo-Al_2O_3 is also prepared by post-carbon coating method of incorporating carbon into the catalyst after the active component loading, and its hydrodesulfurization catalytic performance is relatively low compared with the catalyst without carbon modification.