Heteropolyacid (HPA)-polymer composite films as catalytic materials for heterogeneous reactions

Abstract

In this work, H 3PMo 12O 40-polymer composite film catalysts were prepared by a membrane preparation technique by blending H 3PMo 12O 40 with polymers using a mixed solvent of methanol(M)–chloroform(C) or ethanol(E)–chloroform(C). Polyphenylene oxide (PPO) and polysulfone (PSF) were used as blending polymers because of their excellent thermal and mechanical stability. The composite film catalysts were cut into small pieces, and applied as heterogeneous catalysts to the liquid-phase TBA( tert-butyl alcohol) synthesis and to the vapor-phase ETBE (ethyl tert-butyl ether) synthesis. It was observed that H 3PMo 12O 40 was finely dispersed throughout the polymer supports, and the blending patterns of the composite film catalysts were different depending on the identity of polymer material used. In the liquid-phase TBA synthesis, catalytic activities were in the following order; H 3PMo 12O 40-PPO-MC>H 3PMo 12O 40-PSF-MC>homogeneous H 3PMo 12O 40. Not only high absorption capability of H 3PMo 12O 40-PPO-MC for isobutene but also high stability of H 3PMo 12O 40-PPO-MC during the reaction was responsible for its enhanced catalytic performance. In the vapor-phase ETBE synthesis, catalytic activities were in the following order; H 3PMo 12O 40-PPO-EC>H 3PMo 12O 40-PSF-EC>bulk H 3PMo 12O 40. It was revealed that the residual ethanol in the composite film catalysts played an important role to improve and maintain the catalytic activities of the composite film catalysts.