Multi-walled carbon nanotubes as catalyst promoter for dimethyl ether synthesis from CO2 hydrogenation

The mixed acid of H2SO4/HNO3-pretreated multi-walled carbon nanotubes was employed as supports and ultrasound-assisted co-precipitation method was designed to prepare multi-walled carbon nanotubes supported CuO–ZnO–Al2O3/HZSM-5 catalyst. The catalyst was characterized by means of X-ray diffraction spectrum (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermal analysis (TG) and Brunauer–Emmett–Teller (BET). The catalyst activity for the preparation of dimethyl ether from hydrogenation of CO2 was investigated in a fixed-bed reactor, which showed that multi-walled carbon nanotubes could promote the catalyst activity of CuO–ZnO–Al2O3/HZSM-5. Under the reaction conditions of temperature at 262 °C, pressure at 3.0 MPa, H2/CO2 = 3 (volume ratio) and space velocity (SV) = 1800 mL gcat−1 h−1, the conversion per pass of carbon dioxide was 46.2%, with the dimethyl ether yield and selectivity of 20.9% and 45.2%.