Effects of magnesium and chromium addition on stability, activity and structure of copper-based methanol synthesis catalysts

Cu/ZnO/Al2O3-based catalysts for methanol synthesis are prepared through coprecipitation by addition of Mg and Cr. Precursors are characterized by XRD and AirTGA. Catalysts, calcined at 450 degrees C, are examined by XRD and BET. Reduction characteristics of the catalysts are analyzed via H-2-TPR and H-2-TGA. Surface acidity of the catalysts is determined by TPAD-TGA. Addition of Mg and Cr causes formation of smaller CuO crystallite size, and increases surface area of catalysts by improving dispersion of CuO. Cr also improves stability of the catalysts against ambient conditions and prolongs their shelf life. The catalyst containing 6.4 mol % Cr has a methanol selectivity of 83.5% and a catalytic activity of 14.2 g methanol production which is the highest among other synthesized catalysts. High Cr loadings (32 mol %) reduce the catalytic activity. Cr containing catalysts continue to produce the highest amounts of methanol as compared with the catalysts without Cr where Cr prevents deactivation and sintering.