固体杂多酸盐催化性能　Ⅰ.钨磷、钨硅杂多酸碱金属盐的合成、表征和催化酯化反应

摘要/Abstract

摘要： 合成了HPW₁₂、HSiW₁₂杂多酸的一系列铯盐:C_sxH_3-xPW₁₂(x=0～3),C_sxH_4-xSiW₁₂(x=0～4).测定了它们的酸强度、pH滴定曲线、NH₃-TPD、IR光谱和比表面积。以乙酸和正丁醇的酯化为探针反应,考察了催化剂的酸催化活性。实验发现,碱金属取代后,PW₁₂系列的多数催化剂的酸强度提高,而SiW₁₂系列的则降低,但对同一系列来说,由NH₃-TPD测得的酸强度和酸量均随取代量增加而减小,pH滴定的结果与此类似,当x=2.5时,两系列催化剂的比表面积均存在一个极值。对乙酸和正丁醇的催化酯化活性只与总酸量有关,与表面积无关,属假液相反应。

关键词: 固体杂多酸盐, 酸性质, 酯化反应

Abstract: A series of Cs^- salts of heteropolyacids(HPW₁₂, HSiW₁₂) were synthesized. The Hammett function H₀ was determined in order to investigate the acid strength. Their acid contents were measured by acid-base titration and NH₃-TPD respectively; both Bronsted and Lewis acidic sites were observed by monitoring the IR spectra of adsorbed pyridine. The specific surface areas were determined by BET-method. The acid catalytic activity of various salts was also investigated using the esterification of HAc and n-butyl alcohol as a test reaction. The results showed that the Hammett functions H₀ of Cs_xPW series were more strong than that of Cs_zSiW series, while the acidic strength and acid contents decreased with the amount of alkali metal. What is more interesting is that the samples in which their Cs contents are x=2.5 have a maximum surface area. It was confirmed that, not the acid contents on the surface but in the bulk are responsible for the catalytic activity. The reaction seems to be a pseudoliquid phase process.

Key words: solid salt of heteropolyacid, acidity, esterification

谢文华, 叶兴凯, 杨向光, 吴越. 固体杂多酸盐催化性能　Ⅰ.钨磷、钨硅杂多酸碱金属盐的合成、表征和催化酯化反应[J]. 应用化学, 1996, 0(2): 37-40.

Xie Wenhua, Ye Xingkai, Yang Xiangguang, Wu Yue. Catalytic Behaviours of Salts of Heteropolyacids Ⅰ. Synthesis, Characterization and Catalytic Activity of Cs-Salts of PW₁₂and SiW₁₂-Heteropolyacids[J]. Chinese Journal of Applied Chemistry, 1996, 0(2): 37-40.

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