络合剂添加对CoMo催化剂加氢脱硫选择性的影响

以ZSM-5-Al2O3复合物为载体制备了系列添加络合剂柠檬酸、氮川三乙酸、乙二胺四乙酸和环己二胺四乙酸的CoMo负载型催化剂，考察络合剂对CoMo催化剂加氢脱硫选择性的影响，并采用N2吸附-脱附、X射线衍射、傅里叶变换红外光谱、H2-程序升温还原、NH3-程序升温脱附、高分辨透射电镜、27Al固体高分辨核磁共振及X射线光电子能谱等手段进行表征。结果表明：催化剂制备过程中添加的络合剂优先与Co及载体中的Al络合，该络合作用可降低金属组分的还原温度，提高Mo的硫化度，增加催化剂活性中心数目。将络合剂引入催化剂后，MoS2片晶堆垛层数和MoS2片晶长度均增加，但 MoS2片晶堆垛层数对脱硫的促进作用占据主导地位，致使络合剂改性催化剂的脱硫活性增加幅度大于烯烃饱和活性增加幅度。

EFFECT OF CHELATING AGENT ON HDS SELECTIVITY OF CoMo CATALYST

A series of CoMo/ZSM-5-Al2O3 HDS catalysts was prepared with different chelating agents, such as citric acid, nitrilotriacetic acid, ethylene diamine tetraacetic acid and trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid and characterized by FT-IR, H2-TPR, HRTEM, 27Al NMR and XPS techniques. The effect of the chelating agents on the HDS selectivity was investigated. The results showed that the agents preferentially complexed with Co and Al in the carrier and reduce the reduction temperature of metal components, improve the sulfurization degree of Mo, and increase the number of active center of the catalyst. The use of chelating agent increases the number of stacking layer and the length of MoS2 lamella. The number of stacking layer played a dominant role in promoting desulfurization, resulting in a greater increase in desulfurization activity of the modified catalyst than that in olefin saturation.