Alcohol Synthesis from CO and H₂, and the Related Effects of Addition of Some Metal Salts

Abstract

Methanol and a small amount of ethanol were catalytically produced (in more than 90%selectivity) under an atmospheric pressure of CO-H₂ over Pt, Pd and Cu catalysts supported on the selected metal oxides such as La₂O₃, Y₂O₃, Nd₂O₃ as rare earth oxides and MgO and CaO as alkali metal oxides. The relative rates of methanol formation decreased in the orde r; Pd/La₂O₃ PtiLa₂O₃ Cu/La₂O₃, which was in parallel with the decreasing order of their hydrogenation activities.. The kinetic parameters for methanol and methane formation were obtained in the atmospheric pressure CO-H₂ reactions over Pd/La₂O₃ as V_OH3OH=k1 P_H2 Pco^0.4 exp(-14000/RT) and V_CH4=-k₂P_H2^0.8Poo-^-0.4exp(-29000/RT). The Pd/La₂O₃ catalyst was app lied to the higher pressure syngas conversion and gave higher yields and selectivities for methanol production, in comparison with those over Pd/SiO₂ catalyst.
The specific promoting effects of these basic oxide supports for the methanol synthesis were considered from the kinetic and IR spectroscopic studies to be based on the formation of a formate ion intermediate in the reaction between associatively chemisorbed CO on Pd and Pt and basic sites such as OH^-and O^2-, which might be converted by hydrogen to methanol. The effects of addition of some other metal salts such as MnCl₂, ReCl₅, NbCl₅ and NaOH, which could be incoorporated in the catalytic preparation showed that the Re and Mn salts enhanced the yields of methanol specifically and that the Re addition improved the ethanol selectivities in the oxygenated product in the CO-H₂ reaction catalyzed by Pd/La₂O₃ and Pt/La₂O₈ catalysts.