Alkali-Promoted Copper-Zinc Oxide Catalysts for Low Alcohol Synthesis

Alkali and barium hydroxide promotion of the Cu/ZnO methanol synthesis catalysts has been investigated with the following results: (i) at low temperatures, high H2/CO ratios, water-free and CO2-free synthesis gas, the alkali promote methanol synthesis rates in the order Cs>Rb>K>Na>Li; (ii) the alkali hydroxides are highly dispersed on the catalyst surface; (iii) Ba hydroxide agglomerates and shows little effects; (iv) at temperatures above 280°C and low H2/CO ratios, the synthesis of higher alcohol is promoted by the alkali via a mechanism in which the addition of C1 intermediate on the beta carbon of the growing alcohol chain dominates; and (v) methyl esters are side products of the higher alcohol synthesis. A method is given for a quantitative treatment of X-ray photoelectron spectra for the determination of the surface concentration of the dopant.