摘要
Micro-mesoporous ZK-1 molecular sieves with different Si/Al ratios were used as supports for binary Co-Mo hydrodesulfurization（HDS） catalysts.The CoMo/ZK-1 catalysts were prepared using an over-loading impregnation method,and characterized using N2 physisorption,X-ray diffraction,temperature-programmed NH3 desorption,temperature-programmed reduction（TPR）,ultraviolet-visible diffuse reflectance spectroscopy,and high-resolution transmission electron microscopy（HRTEM）.The results show that the CoMo/ZK-1 catalysts have high surface areas（～700 m^2/g）,large pore volumes,and hierarchical porous structures,which promote the dispersion of Co and Mo oxide phases on the ZK-1 supports.The TPR results show that the interactions between the Co and Mo oxide phases and the ZK-1 support are weaker than those in the CoMo/γ-Al2O3 catalyst.The HRTEM results show that the CoMo/ZK-1 catalysts have better MoS2 dispersion and more active edge sites.The catalysts were tested in HDS of dibenzothiophene.Under mild reaction conditions,the activity of Co and Mo sulfides supported on ZK-1 was higher than those of Co and Mo sulfides supported on ZSM-5,A1KIT-1,and γ-Al2O3.
近年来,柴油发动机产生的废气污染己成为一个严重问题,环境法规对燃油中的硫含量限制越来越严格.因此,开发高效的深度加氢脱硫催化剂成为当今的热门课题之一.在柴油馏分中,由于存在空间位阻作用,二苯并噻吩(DBT)及其烷基取代的衍生物是最难脱除的.传统的加氢脱硫(HDS)催化剂通常是将活性金属担载在γ-Al_2O_3上.近年来,介孔材料如MCM-41,SBA-15,HMS,KIT-1和KIT-6等也被用作加氢脱硫催化剂载体,其大的比表面积有利于活性组分分散,大的规则孔径有利于反应物和产物扩散.其中,KIT-1介孔分子筛具有三维短蠕虫状介孔结构和大的比表面积,其酸性和水热稳定性都高于MCM-41.然而,由于无定形的孔壁使得介孔分子筛的酸性和水热稳定性较差,限制了其在石油化工领域的应用.而介微孔复合分子筛兼具了微孔分子筛酸性强、水热稳定性好和介孔分子筛的孔道优势,因此一经出现就引起了研究者广泛关注.有研究认为,增加载体酸性有利于加氢及促进C-S键氢解反应.载体中的微孔可高效吸附氢分子,降低HDS过程所需的温度和压力,实现温和条件下燃油超深度脱硫.目前,已有研究者将Y-MCM-41,介孔ZSM-5及Beta-KIT-6等多级孔分子筛用作催化剂载体,并进行了加氢脱硫性能研究,取得了良好效果.我们曾利用双模板剂一步晶化法水热合成了介微孔复合分子筛ZK-1.该分子筛既具有与KIT-1相似的短蠕虫状三维介孔孔道,又具有ZSM-5的微孔结构.其介孔孔径为2.7 nm,微孔孔径为0.6 nm.该分子筛具有良好的水热稳定性和较高的酸性.本文在上述研究基础上,以不同硅铝比的ZK-1为载体通过过量浸渍法担载Co,Mo活性组分制备了CoMo/ZK-1(Si/Al=30)和CoMo/ZK-1(Si/Al=40)催化剂,并以相同方法制备了CoMo/γ-Al_2O_3,CoMo/AlKIT-1,CoMo/ZSM-5和CoMo/Mix(等量的ZSM-5和AlKIT-1混合物)催化剂作为对比.催化剂的N_2吸附和NH_3程序升温脱附表
基金
financially supported by the National Natural Science Foundation of China (NNSFC,21206017)~~
