The influence of palladium on the catalytic activity for ethanol conversion over heteropoly tungstate catalysts

The dehydration reaction was studied using pure and palladium doped Keggin type heteropoly compounds (H 3 PW 12 O 40 and Cs 2.5 H 0.5 PW 12 O 40 ) in the temperature range from 433 to 573 K. The structure and texture of catalysts were characterized by thermal analysis, FTIR, XRD, BET and SEM–EDS methods. Pd doped samples exhibit a deviation of Pd concentration value from the stoichiometric ones, while parent samples have concentration values similar to the stoichiometric ones. The catalytic activity of the compounds was tested by continuous flow reactor technique at different temperatures. The favorable effect of Pd doped on the catalysts for dehydration reaction to ethylene results from the examination of apparent activation energies E a and reaction rate values. Evidence of a decreasing E a was obtained for ethylene formation in the case of PdCs2.5PW (83.4 kJ/mol) comparatively with pure Cs2.5PW (160.7 kJ/mol). For all reaction temperatures, the reaction rates of ethylene formation are higher for palladium-doped samples than undoped ones.