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机构地区:[1]中国科学院兰州化学物理研究所
出 处:《分子催化》1990年第2期156-162,共7页Journal of Molecular Catalysis(China)
摘 要:自从Keller等报导了有关甲烷氧化偶联的开拓性研究以来,有关该反应的催化剂探索研究的报导与日剧增。在众多的催化剂体系中,尽管LiCl有可能通过不同途径损失,但含LiCl的催化剂材料,仍以它的高活性和选择性优势,引起催化界的极大关注。The effect of doping Na2SO4, Na2SO3, Na2S2O3, Na2SiO3, Na3PO4 and Na4P2O7 on LiCl/SiO2 catalyst in oxidative coupling of methane has been studied. The results show that Na2SO4, Na2SO3 and Na2SiO3 improved the activity and selectivity of LiCl/SiO2. Among them Na2SO4 is the best promoter. Detailed study of LiCl/SiO2 catalyst containing Na2SO4 has been carried out using XRD, FTIR,BET, Ion-elect rode and catalytic reaction. Yields of C2 hydrocarbons for the LiCl/SiO2 catalyst displayed a maximum at 30% ( mol ) Na2SO4, beyond which the yield rapidly dropped. In the meantime, some decrease of the corresponding selectivity with the increase of Na2SO4 content was observed. The best reaction temperature for this catalyst was found to be 700℃. Na2SO4. LiCl/ SiO2 was considerably more stable than LiCl/SiO2, and the relative loss of Cl- ion in the catalyst was markedly reduced. Results of XRD analysis showed that LiCl and SiO2 in the LiCl/ SiO2 catalyst form some new compounds, and no crystal line phase of LiCl was observed. In comparing the change of FTIR spectra of LiCl/SiO2 and Na2SO4 LiCl/SiO2 before and after reaction, the characteristic band of LiCl at 1613 cm-1 of the former was much weakened after reaction for a short time,while the corresponding band (at 1607 cm-1 ) of LiCl for the latter was clearly not much changed after reaction. From all the results cited above it can be concluded that Na2SO4 plays an important role in stabilizing the structure of LiCl/SiO2 catalyst and retarding the loss of Cl-1 in the catalyst.
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