Studies on WO3/ZrO2and MoO3/ZrO2Solid Superacid Sytems

Abstract

Abstract: The dispersion and crystal phase changes of tungsten and molybdenum compounds on samples prepared by impregnating ammonium metatungstate and ammonium paramolybdate on amorphous ZrO₂during the calcination have been investigated in detail. It was found that after the calcination at 350℃ tungsten and molybdenum existed in the form of isopolyacidic anions,so that the apparent dispersion thresholds determined by XRD method were much greater than the calculated monolayer dispersion capacities of WO₃and MoO₃on ZrO_2.After calcination at 800 ℃ the Wand Mo dispersed on ZrO₂transformed into the form of WO₃on ZrMo₂O₈,and the experimental apparent dispersion thresholds became approximate to the monolayer dispersion capacities of WO₃and ZrMo₂O₈on ZrO_2.The results of measurements by Hammett indicator and n-pentane isomerization methods showed that Ho of the WO₃/ZrO₂systems reached^-13.8--14.5 and that of the MoO₃/ZrO₂systems^-12.0--12.7,and the samples containing the amounts of WO₃and MoO₃close to their monolayer dispersion capacities and calcined at 800℃ displayed stronger superacidity.

Key words: Solid superacid, WO₃/ZrO₂, MoO₃/ZrO₂, Characterization of acidity

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GAO Zi, CHEN Jian-Min, YAO Yu-Ning, HUA Wei-Ming, MIAO Chang-Xi. Studies on WO₃/ZrO₂and MoO₃/ZrO₂Solid Superacid Sytems[J]. Chem. J. Chinese Universities, 1995, 16(1): 111.

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Studies on WO₃/ZrO₂and MoO₃/ZrO₂Solid Superacid Sytems

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