EFFECTS OF FEED CONCENTRATION AND WATER VAPOR ON CATALYTIC COMBUSTION OF ETHYL ACETATE AND BENZENF IN AIR OVER CR-ZSM-5 CATALYST

Catalytic combustion of ethyl acetate (EAc) and benzene (Bz) over chromium exchanged ZSM-5 {Si/AI=240} is reported. Ati 11 mm i.d. Fixed-bed catalytic reactor, operated at temperatures between 100 °C and 500 °C, and under excess oxygen condition, was used for the catalytic activity measurement. Apparent order of reaction and apparent activation energy were determined by operating the reactor differentially at a gas hourly space velocity (GHSV) of 78,900 If and feed concentrations between 3,500 pptn to 17,700 ppm and 3,700 to 12,400 ppm for ethyl acetate and benzene, respectively. Ethyl acetate was more reaetive than benzene due to highly reactive carbonyl group in the molecule. The combustion process satisfactorily fitted pseudo first-order kinetics with respect to organic concentration and a zero-order dependence on the oxygen concentration. The presence of water vapor (9,000 ppm) in the feed stream was found to weaken the reactivity of these organics which could also be demonstrated with increases in the activation energy from 23.1 kJ/mole to 37,6 kJ/mole for ethyl acetate and from 27,6 kJ/mole to 46,1 kJ/mole for benzene. Water vapor was found to play a positive role in the formation of carbon dioxide yield in ethyl acetate combustion. Deactivation of catalyst by water appeared to be only temporary and the activity reverted back to its Original value once tlie source of water vapor was removed.