Influence of thermal, hydrothermal, and acid-base treatments on structural stability and surface and catalytic properties of AlPO45-

Choudhary, V. R. ; Akolekar, D. B. ; Singh, A. P. ; Sansare, S. D. (1988) Influence of thermal, hydrothermal, and acid-base treatments on structural stability and surface and catalytic properties of AlPO45- Journal of Catalysis, 111 (2). pp. 254-263. ISSN 0021-9517

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/002195...

Related URL: http://dx.doi.org/10.1016/0021-9517(88)90084-X

Abstract

Effects of thermal treatment (at 813-1433 K), hydrothermal treatment [low-pressure water vapor (35 Torr) at 773 K for 0-168 h, high-pressure steam (16 atm), and water (at autogenous pressure) at 473 K for 12 h], and acid-base (pH 1-12.5) treatment (at 303 K for 20 h) on the structural stability, physical properties (viz., size and morphology of crystals, relative surface concentrations of Al and P, and N2 sorption capacity at 78 K), acidity, and catalytic activity (in the cumene cracking and o-xylene isomerization reactions at 673 K) of AlPO45- have been investigated. Although AIPO5-4 has good thermal stability, calcination at higher temperatures (≥973 K) causes a small decrease in its crystallinity and N2 sorption capacity and a large decrease in its acidity and catalytic activity. The crystallinity, surface properties, acidity, and catalytic properties of AlPO45- are affected significantly by hydrothermal treatment, particularly treatment with high-pressure steam or water at autogenous pressure at 473 K. These treatments lead to a complete collapse of the channel structure. AlPO45- dissolves completely in both HCl and NaOH solutions at concentrations of 0.1 mol cm-3 or greater. The pH of the acid or alkali solutions has a pronounced effect on its structural stability, as well as its surface and catalytic properties and acidity.

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