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Mixture Effects in the Catalytic Oxidation of VOCs in Air

S. K. GangwalK. RamanathanP. CaffreyM. MulllinsJames J. Spivey

其他書名	Project Summary
出版	U.S. Environmental Protection Agency, Air and Energy Engineering Research Laboratory, 1988
URL	http://books.google.com.hk/books?id=26ygSgAACAAJ&hl=&source=gbs_api

註釋Most volatile organic compound (VOC) releases into the environment are mixtures. However, most fundamental studies of the catalytic deep oxidation of such compounds are usually confined to single components. This study examines the deep oxidation of organic mixtures over a heterogeneous catalyst in an attempt to explain earlier observations concerning the apparent inhibition or enhancement of destruction of some components to establish a scientific basis for the design and operation of catalytic incineration systems for VOC control. To elucidate these effects, the oxidation kinetics of n-hexane, benzene, ethyl acetate, and methyl ethyl ketone in air were examined over a commercial catalyst (0.1% Pt/3% Ni on [gamma]-alumina.) Reaction rates of these components individually were determined at temperatures of 150 to 360°C from differential reactor studies. When these were compared to overall destruction efficiencies from integral reactor studies for both individual compounds and mixtures, the Mars/van Krevelen (MVK) reaction rate model satisfactorily represented the results for some single organic compounds at lower temperatures. By incorporating pore diffusion effects, the MVK model adequately explains the single component data over the entire temperature range for some of the compounds. A multicomponent MVK model incorporating competitive adsorption effects is moderately successful in predicting the observed behavior for a binary mixture of benzene and n-hexane; however, it cannot predict the apparently enhanced reaction rate observed for ethyl acetate at higher temperatures (>200°C). Other reaction pathways available for compounds with carbon-oxygen linkages and/or the advent of catalytically supported homogeneous combustion with free radical precursors may explain this phenomenon. The enhancement of ethyl acetate conversions in humidified air streams suggests that autocatalysis by-product water may be a possible mechanism.