Microrod networks CuO-ZnO-Al₂O₃ catalyst for methanol synthesis from CO₂: Synthesis, characterization, and performance demonstration

Microrod-shaped CuO-ZnO-Al2O3 (CZA) catalysts are synthesized in a single-step hydrothermal method. Several characterization techniques, such as XRD, SEM, BET, XPS, H-2-TPR, HR-TEM, and CO2-TPD, are used to investigate the physico-chemical properties of the prepared catalysts. A bench-scale high-pressure fixed-bed flow reactor is used to evaluate the performance of the synthesized catalysts. XRD analysis confirmed the presence of monoclinic CuO and hexagonal ZnO phases in the CZA catalysts. A uniform distribution of interconnected microrod-like morphology is observed in the CZA-4 catalyst. The metal dispersion, metal-support interactions, and surface basicity of CZA-4 are significantly improved during the hydrothermal synthesis under the continuous stirring and addition of CTAB, which positively impacts the CO2 conversion (14%) and methanol yield (7%). The CO2 conversion and methanol yield increases in the following order CZA-3 < CZA-1 < CZA-2 < CZA-4. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis confirmed the formate-methoxy pathway for methanol formation.