Preparation, characterization and application of Cr2O3/ZnO catalysts for methanol synthesis

Several Cr2O3/ZnO catalysts were prepared via co-precipitation with either K2CO3 or (NH4)2CO3 and subsequently characterized by X-ray diffraction (XRD), N2-BET, and activity for methanol synthesis at 593 K. XRD and BET analyses of samples prepared with (NH4)2CO3 after calcination in dilute O2 from 473 to 973 K revealed that mixed Cr2O3/ZnO materials (for which Cr/Zn<2) have smaller volume-weighted crystallite sizes and higher surface areas than the pure component oxides. These (NH4)2CO3-precipitated catalysts exhibited a maximum specific activity for methanol synthesis near Cr/Zn=0.39; however, the maximum areal rate was observed for ZnO. Ultimately, the specific activities of the (NH4)2CO3-precipitated catalysts could be described well by a simple linear combination of areal rate data for the pure component oxides. The surface areas, specific activities, and areal rates of all K2CO3-precipitated catalysts for which Cr/Zn<2 were lower than those for all corresponding (NH4)2CO3-precipitated catalysts.