Effects of metal promotion on the performance, catalytic activity, selectivity and deactivation rates of Cu/ZnO/Al2O3 catalysts for methanol synthesis

Abstract

Methanol synthesis catalysts of Cu/ZnO/Al2O3 were prepared using co-precipitation method in presence of Cr and Mg promoters. Precursors were characterized by Air-TGA and XRD. After calcination at 350 °C, catalysts were analyzed by BET and XRD. H2-TGA and H2-TPR were used to determine reduction properties of the catalysts. Co-addition of Cr and Mg resulted in the formation of larger surface area and smaller CuO particles by enhancing dispersion of CuO in the catalyst composition. Catalytic activity, selectivity and deactivation rates of synthesized catalysts were tested at 270 °C and 3 MPa for 144 h. Mg or Cr addition to the catalyst formulation reduced the methanol productivity whereas the co-addition of Cr and Mg increased the methanol productivity. At 144 h reaction time, catalysts with Mg:Cr molar ratios of 2:1 and 1:1 had the highest methanol selectivities and methanol weight time yields of 97.7 and 98.3%, and 0.53 and 0.52 gtotal methanol production gcatalyst−1 h−1, respectively. The catalysts without Cr promoter deactivated rapidly. The presence of Cr in the catalyst composition reduced deactivation rates and sintering of the catalysts. Deactivation rates of Mg and Cr co-promoted catalysts followed a cyclic trend and possible regenerative characteristics.