Synthesis of alcohols and alkanes over potassium and vanadium promoted molybdenum carbides

Abstract

Effects of modification of molybdenum carbides (β-Mo2C) catalyst using potassium (K) and vanadium (V) on the production of alcohols (AOHs) and alkanes from the hydrogenation of CO were studied. Both K and V promoters show the effectiveness on the conversion of CO (XCO), alcohol specific production rate (SPRAOH, g/h/g-catal), and alcohol selectivities (SAOH). At the K/Mo weight ratio of 0.52, the contributions of XCO and yield of alcohol (YAOH) are as high as 28.78% (in C%) and 18.14% (in C%), respectively. At the V/Mo weight ratio of 0.049, the XCO and YAOH are 26.17 and 12.01%, respectively. The corresponding XCO and YAOH for the case using β-Mo2C are 21.54% and 6.59%, respectively. The comparison indicates that both K and V are promoters for enhancing the XCO and YAOH, with K exhibiting more vigorous effect. The V–K co-modified β-Mo2C catalyst with V/K/Mo=0.1/1/2 gives XCO of 35.05% and YAOH of 25.41% with selectivity of ethanol (SEtOH) as high as 39.88% (in C%). The results reveal the synergistic enhancement of K and V on the XCO and YAOH, especially on the SEtOH.The presence of water induces the water-gas shift reaction (WGS) of CO which further contributes the formation of reactive radicals, thus enhancing the yields of alcohols. The XCO and YAOH can reach as high as 35.74% and 26.79%. The SEtOH may be retained at satisfactory value of 35.79%. Some ethanols are converted to higher alcohols of propanol and butanol due to the presence of H2O which contains H and O.The deviation of methanol (MeOH) from the linear Anderson–Schulz–Flory (ASF) distribution for the cases using K–Mo2C, V–Mo2C and V–K–Mo2C catalysts indicates that the reaction mechanisms of the chain-propagation of alcohols are different from those using sole β-Mo2C. This may be due to the functions of V or/and K on the mechanisms, such as the insertion and re-adsorption. For the alkanes, the ASF distributions are linear for the un-modified and modified β-Mo2C catalysts, revealing that reaction mechanisms of alkanes are not altered by the K and V added on the catalysts.