The CuO–Fe2O3–ZrO2/HZSM-5 bifunctional catalyst was prepared and used for the direct synthesis of dimethyl ether (DME) from CO2 and H2. The results revealed that doping the CuO–Fe2O3 catalyst with ZrO2 might increase the specific surface area and change the chemical combination state of CuO by decreasing the outer-shell electron density of Cu via an obvious change in the interaction between CuO and Fe2O3. Addition of ZrO2 to the catalyst strongly affects the hydrocarbon selectivity. When using the CuO–Fe2O3–ZrO2/HZSM-5 bifunctional catalyst system, both the conversion of CO2 and the yield of DME were much higher than those obtained using CuO–Fe2O3/HZSM-5 as catalysts. Reactions carried out at 260 °C and 3.0 MPa with a gaseous hourly space velocity of 1500 mL·gcat –1·h–1 using CuO–Fe2O3–ZrO2/HZSM-5 with 1.0 wt % ZrO2 as the hydrogenation catalyst provided a 28.4% conversion of CO2 with 64.5% selectivity for DME.

An intrinsic kinetics model was established for CO 2 hydrogenation to dimethyl ether (DME) with a Cu-Fe-Zr/HZSM-5 catalyst based on H 2 /CO 2 adsorption, simulation, and calculation of methanol synthesis from CO 2 intermediates and experimental data. H 2 /CO 2 -temperature programmed desorption results show a dissociative H 2 adsorption on Cu site; CO 2 was linearly adsorbed on Fe 3 O 4 weak base sites of the catalyst; the adsorbing capacity of H 2 and CO 2 increased after Zr-doping. Density functional theory analysis of methanol synthesis from CO 2 and H 2 revealed a formate pathway. Methanol synthesis was the rate-limiting step (173.72 kJÁmol 21 activation energy) of the overall CO 2 hydrogenation reaction, and formation of H 2 CO is the rate-determining step of methanol synthesis. Relative errors between calculated and experimental data of partial pressures of all components were less than 10%. Therefore, the kinetics model may be an accurate descriptor of intrinsic kinetics of CO 2 hydrogenation to DME.

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