Influence of pretreatment conditions on the structure and catalytic performance of supported cobalt catalysts derived from metal-organic frameworks
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摘要: 通过金属有机框架材料介导的合成策略制备了负载钴催化剂(Co@C-ZnZrO2和Co/ZnZrO2) 并进行费托合成性能评价,重点研究了金属有机框架材料热解对负载钴催化剂结构和费托合成性能的影响。采用粉末X射线衍射、透射电镜、高分辨率透射电镜、N2吸附-脱附和X射线光电子能谱对负载钴催化剂的晶相和微观结构进行了表征。费托合成性能研究显示,Co/ZnZrO2的CO转化率为18.1%,C5 + 选择性为77.4%,而Co@C-ZnZrO2的CO转化率为8.5%,C5 + 选择性为35.2%。Co/ZnZrO2较高的CO转化率是由于暴露了较多的活性钴位点。而在Co@C-ZnZrO2催化剂上活性Co位点的作用受到碳层的限制,抑制了合成气在Co位点上的吸附和活化。Abstract: Supported cobalt catalysts (Co@C-ZnZrO2 and Co/ZnZrO2) were prepared through a metal-organic frameworks (MOFs)-mediated synthesis strategy. The influence of MOFs pyrolysis on the structure and Fischer-Tropsch synthesis performance of supported cobalt catalysts was investigated. The crystalline phase and microstructure of supported cobalt catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), N2 adsorption-desorption and X-ray photoelectron spectroscopy (XPS). The Co/ZnZrO2 showed the CO conversion of 18.1% and the C5 + selectivity of 77.4%, whereas the Co@C-ZnZrO2 exhibited the CO conversion of 8.5% and the C5 + selectivity of 35.2%. The excellent CO conversion for Co/ZnZrO2 was attributed to the more exposure of active Co sites. Meanwhile, the activity of Co sites on Co@C-ZnZrO2 catalyst was restricted by the carbon layer, suppressing the adsorption and activation of syngas on Co sites.
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Table 1 N2 adsorption-desorption measurement results of the catalysts
Sample SBET /(m2·g−1) vmic /(cm3·g−1) dave /nm ZCZ-MOF 67.2 0.02 8.7 Co@C-ZnZrO2 132.6 0.21 10.4 CoOx/ZnZrO2 28.3 0.11 17.5 -
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