Kinetic Analysis of the Inhibition of CH4 Oxidation by H2O on PdO/Al2O3 and CeO2/PdO/Al2O3 Catalysts
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- 作者：Mina Alyani ; Kevin J. Smith
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2016
- 出版时间：August 3, 2016
- 年：2016
- 卷：55
- 期：30
- 页码：8309-8318
- 全文大小：438K
- 年卷期：0
- ISSN：1520-5045
文摘
Addition of CeO2 to a PdO/Al2O3 catalyst, assessed for the oxidation of CH4 in the presence of 5% H2O at various temperatures, reduces the inhibition effects of H2O. A simplified kinetic analysis that assumes Langmuir adsorption of H2O on the catalyst active sites is used to model both the dynamic response and the steady-state CH4 conversion following H2O addition to the feed gas and to quantify the effect of CeO2 addition. The analysis shows that less H2O is adsorbed on the 2.9Ce/6.5Pd/Al2O3 than the 6.5Pd/Al2O3 catalyst and that the rate of H2O desorption is higher on the Ce-promoted catalyst. Both factors result in reduced inhibition of CH4 conversion by H2O on the 2.9Ce/6.5Pd/Al2O3 catalyst compared to the 6.5Pd/Al2O3 catalyst. The apparent activation energy for CH4 oxidation over the 2.9Ce/6.5Pd/Al2O3 catalyst (61 ± 11 kJ mol–1) is shown to be statistically the same over the 6.5Pd/Al2O3 (56 ± 9 kJ mol–1). Catalyst characterization data show minimal changes in catalyst properties after reaction, and removal of H2O from the reactant feed gas results in partial recovery of the catalyst activity. The data are consistent with H2O adsorption on the catalyst/support that may also inhibit O exchange with Pd-*/PdO site pair (Pd-* is an O-vacancy), the effect of which is reversible.