二甲基二硫醚对Ni/Al_2O_3催化剂加氢性能的影响

考察了二甲基二硫醚(CH3SSCH3)对Ni/Al2O3催化剂上苯、环己烯和苯乙烯加氢活性的影响,并采用BET、XRD、H2-TPR、XPS、SEM和EA等手段对催化剂进行表征。实验结果表明,在CH3SSCH3存在下,Ni/Al2O3催化剂对苯和环己烯加氢迅速失活,且环己烯加氢对CH3SSCH3的耐硫性要略强于苯加氢,而苯乙烯中共轭烯烃的加氢转化率则维持100%长时间不变。CH3SSCH3的影响顺序为芳环单烯烃共轭烯烃。此外,通过设计实验研究了CH3SSCH3对催化剂的毒化机理,发现CH3SSCH3分子首先吸附在催化剂的表面,并发生氢解生成甲烷随尾气逸出,故CH3SSCH3分子中碳对催化剂的失活影响较小,而留下的硫原子则与镍活性组分发生相互作用,毒化催化剂。

Study of poisoning effect of dimethyl disulfide on Ni/Al2O3 catalyst for hydrogenation

Poisoning effect of dimethyl disulfide (CH₃SSCH₃) on Ni/Al₂O₃ catalysts for hydrogenation of benzene, cyclohexene and styrene was studied. The structures and properties of the catalysts were investigated by means of BET, XRD, H₂-TPR, XPS, SEM and EA. Results indicated that with the existence of CH₃SSCH₃, Ni/Al₂O₃ catalysts quickly deactivated for benzene and cyclohexene hydrogenation, while the activity for styrene hydrogenation remained well. The sulfur tolerance of Ni/Al₂O₃ catalysts for cyclohexene hydrogenation was little better than that of benzene hydrogenation. The conversion of conjugated double bond of styrene can keep 100% for a long time. For hydrogenation reactions, the poisoning effects of CH₃SSCH₃ over Ni/Al₂O₃ were in the order of aromatic nucleus>monoene>conjugated alkene. In addition, poisoning mechanism of CH₃SSCH₃ for Ni/Al₂O₃ catalyst was also discussed. CH₃SSCH₃ molecules were firstly adsorbed on the surface of catalyst and then dissociated to CH₄ under the function of hydrogen and catalyst. It is concluded that the toxicity of carbon in CH₃SSCH₃ for catalysts is neglectful and remaining sulfur is the dominant poisoning factor by the interaction with active component.