Catalytic behaviour of a bifunctional system for the one step synthesis of DME by CO2 hydrogenation

• An integrated one-step process for CO2 hydrogenation to DME is proposed.
• Cu–ZnO–ZrO2 and HZSM-5 were combined in different reactor bed configurations.
• A balanced ratio between metal and acid sites is crucial for high DME production.
• Bifunctional catalysts prepared by physical mixing show superior catalytic activity.

One-step CO2 hydrogenation reaction to dimethyl ether (DME) on a bifunctional system constituted by Cu–ZnO–ZrO2 (ZCZ) methanol synthesis catalyst and HZSM-5 zeolite was studied. The influence of the reactor configuration in terms of combination procedure of the admixed samples on activity, selectivity and DME yield has been evaluated. The results obtained at TR = 513 K, PR = 3.0 MPa and GHSV = 9000 NL gcat−1 h−1 show a superior DME productivity (4.4 mmol kgZCZ−1 s−1) using the bifunctional catalyst prepared by physical mixing. A combined effect of active sites located at metal/oxide(s)–acid interface was claimed as the main factor affecting the CO2 conversion and DME productivity. The strong surface acidity of ZCZ catalyst is not suitable to drive DME synthesis through a consecutive mechanism, while DME formation effectively proceeds on weak and medium acid sites of HZSM-5.

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