CO2 hydrogenation to methanol over CuZnGa catalysts prepared using microwave-assisted methods

• Methanol synthesis from CO2 over (CuZnGa)MW catalyst prepared using MW-assisted route.
• MW-treatment effective for Cu dispersion and strong basic sites formation.
• Single-step MW-assisted route enhances Cu-support interaction in the presence of Ga2O3.
• One-pot MW-assisted route improves CuZnGa performance in CO2 hydrogenation to CH3OH.

A series of CuZnGa catalysts was synthesized by microwave-assisted method and their performance for CO2 hydrogenation to methanol was measured under a range of reaction conditions (temperatures between 250 °C and 270 °C and pressure up to 4.5 MPa). The influence of the preparation method on the physicochemical properties of catalysts was studied by N2 adsorption, XRD, TPR, XPS, N2O titration and CO2 adsorption followed by temperature programmed desorption and calorimetry. The results indicate that the one-pot microwave-assisted precipitation method used in the preparation of the (CuZnGa)MW catalyst, promoted copper and Ga2O3 dispersion. Moreover, the mean basic site strength of (CuZnGa)MW was higher than that of the other catalysts prepared. All of these factors were found to affect its catalytic performance greatly in terms of CO2 conversion and methanol selectivity. (CuZnGa)MW was highly stable and produced 4.87 mol methanol kgcat−1 h−1 at 250 °C with a selectivity of approximately 50% (P = 4.5 MPa, GHSV = 3000 h−1, CO2/H2 = 1/3). The strong interaction between copper and support prevented metallic copper sintering, affording high stability of catalyst. The promoting effect was related to an intimate association between highly dispersed copper species and strong basic ZnO species in the presence of small particles of Ga2O3.

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