磷添加方式对NiMo/Al2O3催化剂加氢脱硫性能的影响

Effect of phosphorus adding manners on the performance of NiMo/Al2O3 catalyst in hydrodesulfurization

采用分步浸渍法制备了不同磷添加方式改性的NiMo/Al2O3催化剂,在固定床微反装置上考察了该系列催化剂对焦炉煤气中噻吩加氢脱硫(HDS)性能的影响,采用BET、X射线衍射(XRD)、H2程序升温还原(H2-TPR)、NH3程序升温脱附(NH3-TPD)、C4H4S(H2)程序升温脱附[C4H4S(H2)-TPD]、X射线光电子能谱(XPS)、高清透射电镜(HRTEM)和拉曼(Raman)等分析手段对催化剂进行表征。结果表明,不同磷添加方式制备NiMo/Al2O3催化剂的HDS性能存在较大差异。其中,催化剂PNi-Mo/Al和PMo-Ni/Al表面弱吸附解离活性位增强,对焦炉煤气中噻吩有较好的低温加氢脱硫活性,以含292.5mg/m~3噻吩的模拟焦炉煤气为原料时,PNi-Mo/Al在250℃下对噻吩的脱硫率达61%。对于PNi-Mo/Al和PMo-Ni/Al催化剂,先浸渍P、Ni或者P、Mo时,P优先和载体Al2O3作用,减弱了活性金属组分Ni、Mo与载体间的相互作用,而又防止Ni或者Mo与载体间相互作用过低而聚集,提高了Ni、Mo在载体表面的均匀分散,生成能够促进硫化形成Ⅱ型活性相Ni-Mo-S的NiMoO4物种。NiMoO4和MoO3之间的协同作用提高了催化剂的硫化度,使HDS活性得以提高。

NiMo/Al2O3 catalysts modified by phosphorus addition in different manners were prepared by step impregnation method.The effect of these catalysts on the performance of thiophene hydrodesulfurization(HDS)in coke oven gas was investigated on a fixed bed microreactor.The catalysts were characterized by BET,XRD,H2-TPR,NH3-TPD,C4H4S(H2)-TPD,XPS,HRTEM and Raman.The results showed that the HDS performance of the NiMo/Al2O3 catalysts was greatly different.The weak adsorption dissociation on the activity sites of the catalysts of PNi-Mo/Al and PMo-Ni/Al was enhanced,and the catalysts had better low temperature HDS activity.When the simulated coke oven gas containing 292.5mg/m3 thiophene was used as raw material,the desulfurization rate of thiophene by PNi-Mo/Al at 250℃was more than 61%.For PNi-Mo/Al and PMo-Ni/Al catalysts,the first impregnation of P and Ni or P and Mo made P preferentially interact with Al2O3,and weakened the interactions between Ni or Mo with the support of the active metal component but not too much so that the Ni or Mo could evenly disperse on the surface of the support,and hence NiMoO4 were generated which can promote the formation of typeⅡactive phase Ni-Mo-S by the sulfidation of Ni in the catalyst.The synergistic effect between NiMoO4 and MoO3 increased the sulfidation of the catalyst,resulting in the increased HDS activity.