杨儒,胡天斗.负载型非晶态Cu/SiO2催化剂局域结构的研究[J].分子催化编辑部,1998,(4):241-245
负载型非晶态Cu/SiO2催化剂局域结构的研究
Structure Characterization of the Supported Amorphous Cu/SiO 2 Catalysts
  
DOI:
中文关键词:  超细 非晶态 铜 二氧化硅 甲酸甲酯 氢解 催化剂
英文关键词:Ultrafine, Amorphous, Cu/SiO 2, EXAFS,
基金项目:国家自然科学基金
杨儒  胡天斗
[1]中国科学院山西煤炭化学研究所煤转化国家重点实验室 [2]中国科学院高能物理研究所正负电子
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中文摘要:
      采用XPS和EXAFS方法,研究了以sol-gel法制得的超累粉体SiO2为载体,用化学还原沉积法制备的负载型非晶态Cu/SiO2催化剂在甲酸甲酯氢解反应前后的表面结构和局域结构。结果表明,非晶态样品中的铜原子以零价铜的形式存在,但配位数却大幅度地低于铜樯档,意味着铜原子在高比表面超细SiO2载体上处于高分散的非晶状态,表面悬空键显著增多,表面能增大,导致配位键收缩。
英文摘要:
      Studies were made of XPS and the extended X ray absorption fine structure (EXAFS) with the K absorption edge for copper in the supported amorphous Cu/SiO 2 catalysts before and after the methyl formate hydrogenolysis reaction. The XPS results indicate that copper atoms of amorphous Cu/SiO 2 exist in Cu 0 form. The results of EXAFS show that copper atoms of amorphous Cu/SiO 2 with different copper contents have the same shape of Cu K edge as the copper model, but their coordination numbers were significantly lower than that of the latter. When the copper content decreased from 37.96% to 5.79%, their coordination numbers decreased from 4.2 to 2.3, which illustrates further that amorphous copper supported on the ultrafine SiO 2 formed very small amorphous copper grain and highly dispersed on the ultrafine SiO 2 support with high surface area. It leads to the obvious increase of surface Cu-Cu bond and surface energy, and makes the coordination bond to shorten. After F2 sample (copper content 14.66%) was used in methyl formate hydrogenolysis for a given time at different reaction temperatures, EXAFS results illustrate that copper atoms of amorphous Cu/SiO 2 still existed in Cu 0 form. When reaction temperature is higher, the diffusion ability of copper atoms enhanced and the amorphous copper atom of nonsteady state rearranged, gathered and converted gradually into stable crystal form, which was accompanied by the increase of coordination number and the growth of crystal grain.
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