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采用XRD、EXAFS技术研究了不同Pd含量的Pd -Mo-K/Al2 O3 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/Al2 O3 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 与载体作用形式的改变 ,从而影响CO加氢催化反应的性能。在硫化态催化剂中 ,Pd的添加不仅能提高CO加氢合成醇的收率和选择性 ,而且有利于改善产物的分布。基于以上结果 ,认为“K -Mo”作用物种和Pd物种均为合成醇的催化活性组份 ,它们间的相互协同作用使催化剂性能得到显著改善
The structure of Pd-Mo-K / Al 2 O 3 catalysts with different Pd contents were studied by XRD and EXAFS techniques, and the properties of the synthesized low-carbon mixed alcohols were correlated. The results show that after the addition of Pd in the oxidation state Mo-K / Al 2 O 3 catalyst system, the grain size of “K -Mo” phase becomes smaller and the dispersion degree increases, indicating that palladium may have a strong interaction with potassium and molybdenum species. Sulfide reduction treatment, the occurrence of the exchange of oxygen and sulfur, molybdenum mainly exist as MoS2 species, the particle size decreases with the increase of Pd content. Significant changes in size may lead to changes in the form of MoS2 interaction with the support, thereby affecting the catalytic performance of the CO hydrogenation reaction. In the sulfurized catalyst, the addition of Pd can not only improve the yield and selectivity of CO hydrogenation of alcohols, but also help to improve the product distribution. Based on the above results, it is considered that both the “K-Mo” acting species and the Pd species are the catalytically active components of the synthetic alcohol, and the synergistic effect among them causes the catalyst performance to be significantly improved