Physicochemical features of polyaniline supported heteropolyacids

Abstract

Polyaniline with incorporated heteropolyanions was prepared by using a two-step reaction. This method involved synthesis of polyemeraldine base by polymerisation of aniline followed by deprotonation with ammonia. Then polyemeraldine base was protonated with heteropolyacid (HPAs) in a mixture water: ethanol = 1:1. The structure and texture of H 3 PMo 12 O 40 (HPMo) and H 4 PVMo 11 O 40 (HPVMo) supported on polyaniline was studied by XRD, FT-IR, low temperature nitrogen adsorption and scanning electron microscopy (SEM) with EDS analysis. Thermal stability of both HPAs supported on polyaniline was studied by TG and DSC measurements. The thermal decomposition of PANI support started at ca. 400°C, while for PANI-supported HPAs a decrease of decomposition temperature are observed. FT-IR studies showed that HPAs anions preserved their Keggin structure after deposition on polyaniline support. X-ray diffraction and SEM studies confirmed the uniformity of the distribution of active phase in the catalyst samples. The values of specific surface area of both HPAs increased by deposition on polyaniline support. It is found that most of HPMo and HPVMo (active phases) in samples are well dispersed on the support and polyaniline-supported HPA still keeps its Keggin structure. The surface morphology of the PANI-supported samples is almost similar to that of PANI support. A relatively uniform distribution of active phase in the support pores was evidenced by EDS analysis.