还原-氧化-还原过程对
Co-ZrO2共沉淀催化剂结构及其费托合成反应性能的影响
Influence of reduction-oxidation-reduction treatment on the structure and catalytic performance of Co-ZrO2 for Fischer-Tropsch synthesis
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摘要: 采用程序升温还原、氮吸附、X射线衍射、Raman、XPS和H2-TPD等方法研究了还原（400℃，氢还原）-氧化（室温，暴露空气中氧化）-还原（250℃或400℃，氢还原）预处理过程对Co-ZrO2共沉淀催化剂结构的影响, 考察了催化剂在不同反应器中的费托反应性能。结果表明, 催化剂还原氧化前后钴物种均以Co3O4形式存在，颗粒直径无明显变化; 还原氧化处理后催化剂表面钴物种含量有所下降, 但 H2-TPD结果显示催化剂经还原-氧化-还原后氢吸附量增加。另外, 还原氧化过程能够降低催化剂表层钴物种的还原温度。反应结果表明，催化剂经还原氧化还原处理后活性明显增加, 甲烷选择性降低。
Abstract: Co-ZrO2 precipitated catalyst is treated by reduction in H2 at 400℃, Oxidation of the reduced catalyst in air at room temperature, and reduction again in H2 at 250℃ or 400℃. The influence of this reduction-oxidation-reduction treatment on the properties of Co-ZrO2 precipitated catalyst was investigated by TPR, N2 physical sorption, H2-TPD, XPS, XRD, and Raman spectra; the performance of treated catalysts in Fischer-Tropsch (F-T) synthesis was considered in both slurry phase and fixed bed reactors. The results showed that cobalt in the catalyst is in the form of Co3O4 with little change in particle sizes after the reduction-oxidation process. The concentration of cobalt on the catalyst surface is reduced a little after the treatment, but the amount of H2 uptake is increased significantly. The reduction-oxidation treatment can lower the reduction temperature of surface cobalt species. As a result, the catalytic activity of Co-ZrO2 for F-T-synthesis is improved and the selectivity to CH4 is depressed by the reduction-oxidation treatment. Furthermore, the catalyst reduced at a relatively high temperature exhibits much better performance in the fixed bed reactor.
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