Multifunctionality of Cu–ZnO–ZrO2/H-ZSM5 catalysts for the one-step CO2-to-DME hydrogenation reaction

• Different methods were used to realize a Cu–ZnO–ZrO2/H-ZSM5 multifunctional catalyst.
• The generation of the methanol catalyst was realized in a slurry containing the zeolite.
• The ammonia carbonate coprecipitated catalyst showed the highest DME productivity.
• The CO2-to-DME hydrogenation functionality was related to a multisite reaction path.

A series of Cu–ZnO–ZrO2/H-ZSM5 multifunctional catalysts for the one-step CO2-to-DME hydrogenation reaction was prepared via coprecipitation of methanol catalyst precursors by means of different precipitating agents (i.e., sodium bicarbonate, ammonium carbonate, oxalic acid and urea) in a slurry containing dispersed zeolite particles. The samples were characterized by XRF, XRD, N2 adsorption/desorption isotherms, SEM, N2O-titration, TPR and NH3/CO2 TPD techniques, while the catalytic testing was carried out in a fixed-bed reactor operating at 3.0 MPa, in the TR range 473–513 K and space velocity of 10,000 h−1 (CO2/H2/N2, 3/9/1). The experiments revealed that the preparation methodology significantly affects catalyst properties and hence catalyst activity. The multifunctional catalyst prepared via ammonium carbonate precipitation resulted to be the most active in CO2 conversion, also accomplishing high DME selectivity, with a maximum space-time yield of 0.225 kgDME/kgcat/h. Catalyst characterization disclosed that the strength of basic sites, the ratio between acid and basic sites along with the Cu particle sizes are crucial to achieve maximum catalytic performance, keeping CO selectivity to a minimum value.

Dimethyl ether synthesis can be effectively realized from carbon dioxide by catalytic hydrogenation in presence of Cu–ZnO–ZrO2/H-ZSM5 multifunctional catalysts.Figure optionsDownload as PowerPoint slide