Promoted stability of Cu/ZnO/Al2O3 catalysts for methanol production from CO2 hydrogenation by La modification

The crystal shape and phase composition of the sample were determined by the Bruker D8-Focus X-ray diffractometer (XRD) manufactured by Bruker GMBH in Germany. Using A Cu Kα ray (λ = 1.5406 A) as the radiation source, the tube voltage and current are 40 kV and 40 mA, respectively, and the scanning speed is 8°∙min-1.X-ray photoelectron spectroscopy (XPS) tests were performed using the ESCALAB 250Xi spectrometer from Thermo Fisher Technologies. AlKα X-ray (hν = 1486.6eV) is used as the light source. The binding energy (BE) of the sample was calibrated using the C1s (284.4 eV) peak of the foreign contaminated carbon as the baseline.The performance of CO2 hydrogenation to methanol was tested in a fixed bed reactor. 0.2 g of 40-60 purpose catalyst was evenly mixed with quartz sand and put into the reaction tube. Prior to the catalytic test, the catalyst was reduced with pure hydrogen at a flow rate of 12.5 mL∙min-1 at 270 °C for 1 h, maintaining a heating rate of 2 oC∙min-1 throughout the reduction process. When the reactor was cooled to room temperature, it was switched to CO2 mixture (CO2:H2:N2 = 24:72:4), and the pressure was raised to 3 MPa. The purity of the gas used in the experiment was 99.99%. Stability tests were performed at 200 °C at an airspeed of 12,000 mL∙g-1·h-1. The exit gas is analyzed by a Beifeng Ruili SP-3420 gas chromatograph (GC) connected to a thermal conductivity detector (TCD) and a flame ionization detector (FID). Non-condensable gases (e.g., N2, CO, CO2) can be detected and analyzed by TDX-01 column and TCD. Liquid products are analyzed using a connected FID assay equipped with a Porapak Q-column.