THERMAL-PROPERTIES OF NEW CATALYSTS BASED ON HETEROPOLYANION-DOPED POLYANILINE

Thermal properties of a new family of catalysts, namely, heteropolyani on-doped polyaniline, have been studied by thermogravimetry (TG) and d ifferential thermal analysis (DTA). Two types of samples have been tes ted: bulk-doped and surface-doped polyaniline. It has been found that all systems exhibit good thermal stability in the temperature of their catalytic application (up to 250 degrees C) in both oxidative and ine rt reaction atmospheres. Thermal stability varies significantly with t he dopant used, being the highest for 12-tungstosilicic acid and the l owest for 12-molybdophosphoric acid. Although the latter shows signifi cantly lower thermal stability as compared with all other catalysts st udied, it still can be used in ethyl alcohol conversion, giving predom inantly redox activity products. On the basis of thermogravimetric dat a, Gram-Schmidt chromatograms and FT-IR spectra of volatile products, some preliminary conclusions about the mechanism of degradation have b een formulated. (C) 1997 Elsevier Science S.A.