ISSN:
1572-8943
Keywords:
differential scanning calorimetry
;
heteropoly acids
;
microwave irradiation
;
thermal stability
;
water content
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The thermal stability of heteropoly acids of the Keggin type (H4[SiMo12O40], H3[PMo12O40], H4[SiW12O40] and H3[PW12O40]), being important new catalytic materials, was studied by DSC. Two groups of signals were observed: the low temperature endothermic peak group belongs to the water content, while the high temperature one is exothermic and indicates the thermal decomposition of the acids. The effect of microwave irradiation on the target compounds was also studied. The emphasis, however, was placed on the characterization of the water content of the acids. Several types of water can be classified and DSC curves provide additional information to explain the differences in the catalytic behavior. The study of the effect of heat treatment and the subsequent water absorption of the acids provided additional unique information concerning the pseudoliquid phase in the secondary structure of heteropoly acids.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1010192309961
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