Pd-Mo-K/Al2O3催化剂的结构及合成醇性能

采用ＸＲＤ、ＥＸＡＦＳ技术研究了不同Ｐｄ含量的Ｐｄ－Ｍｏ－Ｋ／Ａｌ２Ｏ３催化剂结构，并关联其合成低碳混合醇性能。结果表明，在氧化态Ｍｏ－Ｋ／Ａｌ２Ｏ３催化剂体系中添加Ｐｄ后，“Ｋ－Ｍｏ”物相晶粒变小，分散度提高，说明钯可能和钾钼物种发生了较强的相互作用。经硫化还原处理后，发生了氧硫交换，钼主要以ＭｏＳ２物种形式存在，其粒度随着Ｐｄ含量的增加而明显减小。尺寸的显著变化可能导致ＭｏＳ２与载体作用形式的

Structure of Pd-Mo-K/Al2O3 Catalysts and Their Activity for Alcohol Synthesis

A series of palladium-modified Mo-K/Al2O3catalyst samples was prepared by varying the palladiumloading between 0 and 1.0% and maintaining molybdenum and potassium contents as con-stants. The structuresof the sampleswere characterized by techniquesof XRD, EXAFS and correlated to the catalytic properties of the samples for alcohol synthesis fromsynthesisgas. It is found that in the oxi-dic palladium-modified samplesastrong interactionof the palladiummodifierwith thesupported K-Mo-O species occurs. This interaction leads to a decrease in the size of the molybdenum species and stabi-lization of the cationic palladium species on the samples during sulfidation. Upon sulfidation, the sulfided molybdenum species in the palladium-free sample mainly present as large patches of MoS2-like slabs with their basal sulfur planes interacting with the support surface. With the modification of palladium to the samples, the supported MoS2-like species become highly dispersed as revealed by the decrease in the average size of thesulfided molybdenumspecies. The interactionof the palladiumspecieswith the molyb-denum component may cause the basal planes of the MoS2-like species to become oriented perpendicular to the support surface due to favorable bonding of the MoS2edge planes to the support through Mo-O-Al bonds. In comparison with the sulfided sample free of palladium, the properties of the palladium-modifiedsamples for alcohol synthesis from synthesis gas are much improved. It most probably results from the synergic interaction of the palladium with the molybdenum species which gives rise to the ap-pearance of the catalytically active sites.