Structure and activity of Cu/ZnO catalysts co-modified with aluminium and gallium for methanol synthesis

This contribution describes the modification in the structure and activity of Cu/ZnO catalyst in the methanol synthesis reaction induced by the co-modification with a low amount of Al and Ga (Al + Ga = 3% atom). To elucidate the effect of the co-modification, the catalysts were characterized by means of variety of techniques (XRD, N-2 physisorption, FTIR, TGA, TEM, TPR and N2O chemisorption) and tested in the methanol synthesis reaction carried out in a flow reactor at 250 degrees C and total pressure of 3 MPa using syngas. The combined characterization and activity tests demonstrated that the co-doping with Al and Ga affects the structure and activity of Cu/ZnO catalysts in a different manner depending on the Al/Ga ratio used. The best catalyst co-loaded with Ga and Al in equal amount shows an improvement in the activity for methanol synthesis respect to the activity obtained on catalysts individually loaded with Al and Ga. The difference in the activity of the samples co-loaded with Al and Ga normalized by N2O chemisorption point to a different participation of the copper surfaces in combination with the defect sites of ZnO depending on the Al and Ga loading.