负载型氮化物催化剂的性质及加氢精制性能

PROPERTIES AND HYDROTREATING ACTIVITY OF SUPPORTED METAL NITRIDE

采用N_2/H_2程序升温还原法制备了非负载型氮化钼(Mo_2N)和氮化镍钼(Ni_2Mo_3N)催化剂,并以Al_2O_3为载体制备了负载型氮化钼(Mo_2N/Al_2O_3)和氮化镍钼(Ni_2Mo_3 N/Al_2O_3)催化剂。采用XRD、BET、H_2-TPR和NH_3-TPD等方法对制备的氮化物催化剂的性质进行了研究,并分别以含2%(质量分数,下同)噻吩和10%四氢萘的环己烷溶液为含硫、含芳烃的柴油模型化合物,考察了制备的负载型氮化物的加氢脱硫(HDS)及加氢脱芳烃(HDA)性能。结果表明,以金属氧化物为前驱物,采用N_2/H_2程序升温还原法制得的氮化钼为Mo_2N(γ型)、氮化镍钼为Ni_2Mo_3N;经钝化处理后,氮化物表面形成了金属氧化物保护层,其中Mo_2N/Al_2O_3和Ni_2Mo_3N/Al_2O_3表面氧化层的还原温度分别为350和300℃。Mo_2N/Al_2O_3和Ni_2Mo_3N/Al_2O_3催化剂的表面酸性以弱酸为主;二者均表现出较好的HDS性能,但Mo_2N/Al_2O_3的HDA性能很差,而Ni_2Mo_3 N/Al_2O_3的HDA性能较Mo_2N/Al_2O_3有一定程度的提高.说明镍钼共存有利于提高金属组分的分散性及催化剂的加氢饱和性能。

Unsupported molybdenum nitride （Mo2N） and nickel-molybdenum mixed nitride （Ni2Mo3N） catalysts were prepared by the method of temperature program reduction （TPR） with N2/H2 gas mixture as reductant, so were alumina supported molybdenum nitride （Mo2N/Al2O3） and nickel-molybdenum mixed nitride （Ni2Mo3N/Al2O3） catalysts. The properties of these catalysts were characterized by XRD, BET, He TPR and NH3-TPD, etc. Their hydrodesulphurization （HDS） and hydrodearomatization （HDA） performances were examined with 2% （mass fraction） thiophene/cyclohexane and 10% naphthalene/cyclohexane as feedstocks, respectively. Results showed that the molybdenum nitride and nickel-molybdenum mixed nitride prepared with metal oxides as precursor were γ-Mo2N and Ni2 MoaN composite nitrides; when the catalysts were deactivated, a thin film of metal oxides were coved on the surface of the metal nitrides, the reduction temperature of metal oxides on the surface of Mo2N/Al2O3 and Ni2MoaN/ Al2O3 were 350 and 300℃, respectively. The acidity of Mo2N/Al2O3 and Ni2MoaN/Al2O3 was mainly weak acidity. The HDS performance of both MoeN/Al2O3 and Ni2Mo3N/Al2O3 was good, but the HDA performance of Mo2N/Al2O3 was very bad, whereas the HDA performance of Ni2Mo3N/Al2O3 was better in some extent, which illustrated that the co-existing of Ni and Mo benefited for the dispersity of the metal component and the hydrogenation performance of the catalyst.