CO2 Conversion to Dimethyl Ether on Cu/ZnO/Al2O3-ZSM-5 Tandem Catalysts in a Double-Bed Reactor : Tuning the ZSM-5 Catalyst Acidity and Porosity

Mohamed, Assem T. and Ahmad, Yahia H. and Anwer, Abdul Hakeem and Soliman, Ahmed and Saad, Mohamed Ali H. and Aroua, Mohamed Kheireddine and Al-Qaradawi, Siham Y. and Benamor, Abdelbaki (2025) CO2 Conversion to Dimethyl Ether on Cu/ZnO/Al2O3-ZSM-5 Tandem Catalysts in a Double-Bed Reactor : Tuning the ZSM-5 Catalyst Acidity and Porosity. Energy and Fuels, 39 (4). pp. 2059-2074. ISSN 0887-0624

Abstract

This research evaluated the effectiveness of thermally and microwave-assisted alkali-treated HZSM-5 zeolites with varying silica/alumina ratios in catalyzing the direct one-step synthesis of dimethyl ether (DME) from CO2. The reactions were carried out in a dual-bed reactor configuration. A primary catalyst, consisting of Cu/ZnO/Al2O3 (CZA) with a formulation of 10 wt % alumina, 30 wt % Zinc, and 60 wt % Copper, was used to convert CO2 to methanol. Subsequently, zeolite or modified zeolite was utilized as a secondary catalyst for the dehydration of methanol to DME. The catalysts were extensively characterized using various advanced analytical techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen physisorption analysis, X-ray diffraction (XRD), ammonia temperature-programmed desorption (NH3-TPD), and hydrogen temperature-programmed reduction (H2-TPR). The CO2 hydrogenation study was carried out at a pressure of 40 bar and a temperature of 250 °C. The results demonstrated that alkali treatment had minimal impact on the crystallinity of the zeolites, but it greatly improved their textural properties. Moreover, the alkali modification enhanced the stability of catalysts and increased their selectivity for DME production.