Microstructure of cesium hydrogen salts of 12-tungstophosphoric acid relevant to novel acid catalysis

被引：263

作者：

Okuhara, T ^{[1
]}

Watanabe, H ^{[1
]}

Nishimura, T ^{[1
]}

Inumaru, K ^{[1
]}

Misono, M ^{[1
]}

机构：

[1] Univ Tokyo, Grad Sch Engn, Dept Appl Chem, Bunkyo Ku, Tokyo 1138656, Japan

来源：

CHEMISTRY OF MATERIALS | 2000年 / 12卷 / 08期

关键词：

D O I：

10.1021/cm9907561

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

A comprehensive interpretation of the microstructure and mechanism of the formation of a versatile solid acid catalyst, Cs2.5H0.5PW12O40, has been attempted by combining the new results obtained with solid-state NMR, XRD, SEM, and Nz porosimetry with the data reported previously. The precipitates of Cs2.5H0.5PW12O40 just formed from aqueous solutions of H3PW12O40 and Cs2CO3 consist of ultrafine crystallites in which the acid form, H3PW12O40, is epitaxially deposited on the surface of Cs3PW12O40 crystallites. Calcination of the precipitates brings about the migration of H+ and Cs+ in the solid to form a nearly uniform solid solution in which protons distribute randomly through the entire bulk, as revealed by XRD and P-31 solid-state NMR. Impregnation of Cs3PW12O40 With the aqueous solution of H3PW12O40 also gives the uniform salt after calcination. Pore-size distribution evaluated by the analysis of Nz desorption isotherm showed that Cs2.5H0.5PW12O40 has mesopores as well as micropores that are interparticle voids of the crystallites. The initial heat of NH3 sorption indicated the presence of very strong acid sites on Cs2.5H0.5PW12O40. High catalytic activity of Cs2.5H0.5PW12O40 reported for solid-liquid reaction systems is thus principally attributed to the strength and number of acid sites and the mesoporous structure appropriate for the rapid diffusion of molecules.

引用

页码：2230 / 2238

页数：9

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