Mechanistic study of acidic and basic sites for CO oxidation over nano based Co(2-x)Fe(x)WO(6) catalysts

Abstract

This paper deals with systematic study of (M sup(I) M sup(II) WO(6) (M sup(I) = Co and M sup(II) = Fe) mixed oxide catalysts for carbon monoxide (CO) oxidation. The catalysts were prepared by polymer based citrate sol-gel method and characterized by X-ray diffraction, thermal analysis, infrared spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average particle size calculated using TEM studies were found to be in the range 20-40 rim. DC electrical conductivity showed phase transition from extrinsic to intrinsic behaviour. The ammonia and carbon dioxide adsorption over these catalysts surfaces were used as a probe to confirm the acidic and basic sites. The acidic and basic sites ascertained by temperature programmed desorption (TPD) studies carried out using thermogravimetry and differential scanning calorimetry technique. The presence of acidic and basic sites in equal ratio on the catalyst surface exhibited better CO oxidation activity as compared to unequal number of sites. The equal affinity for CO adsorption over acidic and O-2 on basic sites were found to be essential criteria for catalytic CO oxidation reaction.