Methane formation route in the conversion of methanol to hydrocarbons

The influence factors and paths of methane formation during methanol to hydrocarbons (MTH) reaction were studied experimentally and thermodynamically. The fixed-bed reaction results show that the formation of methane was favored by not only high temperature, but also high feed velocity, low pressure, as well as weak acid sites dominated on deactivated catalyst. The thermodynamic analysis results indicate that methane would be formed via the decomposition reactions of methanol and DME, and the hydrogenolysis reactions of methanol and DME. The decomposition reactions are thermal chemistry processes and easily occurred at high temperature. However, they are influenced by catalyst and reaction conditions through DME intermediate. By contrast, the hydrogenolysis reactions belong to catalytic processes. Parallel experiments suggest that, in real MTH reactions, the hydrogenolysis reactions should be mainly enabled by surface active H atom which might come from hydrogen transfer reactions such as aromatization. But H2 will be involved if the catalyst has active components like NiO.

Graphical AbstractThe experimental results and thermodynamic analysis results indicate that both decomposition and hydrogenolysis reactions of methanol and DME pay main responsibility for methane formation. They belong to thermal chemistry process and catalytic process, respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide