不同金属助剂对HZSM-5分子筛催化分解甲硫醇性能的影响

Promoter effects on HZSM-5 zeolite catalysts for catalytic decomposition of methyl mercaptan

采用浸渍的方式制备不同系列金属(Cr、La和Na)改性HZSM-5催化剂,并研究其对甲硫醇催化分解活性的影响以及分析相关性能差异的原因。通过XRD、BET、SEM、NH_3-TPD、CO_2-TPD、H2-TPR和XPS等表征手段对催化剂的物化性质进行测定,结果表明:不同系列金属改性HZSM-5对甲硫醇表现出不同的催化活性及影响效果,其中Cr和La改性HZSM-5能明显提高催化剂的催化活性,在500℃下可实现甲硫醇的完全催化转化,这主要归因于Cr的引入提高了催化剂的氧化还原能力,从而促进甲硫醇的催化分解;La的引入增加了催化剂表面的碱性位点,有利于甲硫醇在催化剂表面的吸附和活化。而Na改性HZSM-5表现出较差的催化活性,主要是由于过多Na的添加严重破坏了HZSM-5的骨架结构,从而导致催化剂的催化稳定性能降低。

The metal oxides of Cr,La and Na supported on bare HZSM-5 were prepared by an incipient-wetness impregnation method and used for CH_3 SH catalytic decomposition tests. XRD,BET,SEM,NH_3-TPD,CO_2-TPD,H_2-TPR and XPS measurements were carried out to investigate the effects of these promoters on the structural and physicochemical properties of the supported HZSM-5 zeolite catalysts. It is found that Cr/HZSM-5 and La/HZSM-5 catalysts exhibit greatly improved catalytic activity owing to the improved redox capacity and the increased amounts of basic sites of the Cr and La doped HZSM-5 catalysts. CH_3 SH can be completely converted over Cr and La modified HZSM-5 catalysts at 500℃. For Na modified HZSM-5,the excessive Na,however,may seriously destroy the framework of the catalyst structure and causing the poor catalytic stability of the catalyst.