Effect of Chromium Doping on the Catalytic Behavior of Cu/ZrO₂/CNTs-NH₂ for the Synthesis of Methanol from Carbon Dioxide Hydrogenation

Abstract

A series of Cu/ZrO2/CNTs-NH2 catalysts with various chromium dopings were prepared using a coprecipitation method for the synthesis of methanol by the hydrogenation of CO2. The impact of the addition of chromium on the catalytic performance of the Cu/ZrO2/CNTs-NH2 catalyst was investigated in a fixed-bed plug flow reactor. When the chromium loading was set to 1% of the total amount of Cu 2+ and Zr 4+ , the methanol yield increased to a maximum of 7.78% (reaction conditions: 3.0 MPa, 260°C, V(H2):V(CO2):V(N2)=69:23:8 and gaseous hourly space velocity (GHSV)=3600 mL•h-1 •g-1). The catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), temperature-programmed desorption of H2 (H2-TPD), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of CO2 (CO2-TPD), differential thermal analysis (DTA), and scanning electron microscopy (SEM). The results of these analyses indicated that the introduction of chromium reduced the size of the Cu nanoparticles, enhanced the dispersion of the Cu species, inhibited the phase