Low-concentration methane combustion over a Cu/γ-Al2O3 catalyst: effects of water

Abstract

The influence of water on low-concentration methane oxidation over a Cu/γ-Al₂O₃ catalyst was investigated in a fixed bed reactor. This paper studied the effect of water on the activity of methane combustion, using parameters such as water reversible adsorption, regeneration of the activity and surface characteristics of the catalyst. Apparent activation energy was found by experiments, and water surface coverage was calculated using the Langmuir equation. It was found that the activity of methane combustion over a Cu/γ-Al₂O₃ catalyst decreased with time due to water adsorption. The inhibitory effect generated by water weakened as the temperature rose above 550 °C. Reactivity could be refreshed if the catalyst particles were scavenged by N₂. Kinetic experiments showed that, if water was added into the feed, apparent activation energy (E_a) increased noticeably (81.4 kJ mol⁻¹ → 153.0 kJ mol⁻¹) and the reaction order with respect to water was −0.6 to −1. Using the Langmuir equation, it could be concluded that the coverage of water adsorption on catalytic active sites increased noticeably as vapor was introduced into the feed. If the temperature increased, water coverage went down and tended towards 0% above 625 °C.