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The objective of this study is to investigate the modes of methane (CH$ removal from simulated compressed natural gas (CNG) fueled vehicle exhaust under net oxidizing, net reducing, and stoichiometric conditions. Model reaction studies were conducted. The results suggest that the oxidation of methane with oxygen contributes to the removal of methane under net oxidizing conditions. In contrast, the oxidation of methane with oxygen as well as nitric oxide contributes to ita removal under net reducing conditions. The steam reforming reaction does not eignificantly contribute to the removal of methane. The methane conversions under net reducing conditiona are higher than those observed under net oxidizing conditions. The study shows that the presence of carbon monoxide in the feed gas lea& to a gradual decrease in the methane conversion with increasing redox ratio, under net oxidizing conditions. A minimum in methane conversion is observed at a redox ratio of 0.8. The higher activity for the methane-oxygen reaction resulting from a lowering in the overall oxidation state of palladium and the contribution of the methane-nitric oxide reaction toward the removal of CH4 appear to account for the higher CHI conversions observed under net reducing conditions. IntroductionNatural gas is an attractive source of fuel for vehicles. The advantagea provided by natural gas include lower fuel cost, longer engine life, lower maintenance, and reduced oil consumption. Methane (CHJ is the major constituent of natural gas. The development of catalysts for oxidizing the unburnt methane in the exhaust stream of natural gas fueled vehiclea is of importance. Several inveatigators have reported studies on noble metal and base metal catalysts

SynopsisThe transport of gases in many glassy polymers can be described satisfactorily by means of a "dual-mode sorption" model. The transport behavior observed with a given gas/polymer system can be characterized by the model parameters, which are obtained from solubility measurements in conjunction with absorption/desorption or permeability measurements. The present study discusses the inverse problem, namely, the prediction of the absorption/desorption behavior of a gas in a glassy polymer from a specified set of dual-mode sorption parameters. Satisfactory agreement is obtained between reported absorption rates of sulfur dioxide in glassy polycarbonate and of water vapor in Kapton@+ and the rates predicted by the dual-mode sorption model. This study also confirms the consistency of the model.