Isobutanol and Methanol Synthesis on Copper Catalysts Supported on Modified Magnesium Oxide

Abstract

Alcohols are selectively produced from CO/H2on K–CuMgCeOxcatalysts, but synthesis rates are strongly inhibited by CO2formed during reaction. Reaction pathways involve methanol synthesis on Cu, chain growth to C2+alcohols, and metal–base bifunctional coupling of alcohols to form isobutanol. Ethanol reactions on K–Cu0.5Mg5CeOxshow that Cu catalyzes both alcohol dehydrogenation and aldol condensation reactions. CeO2increases Cu dispersion and MgO surface area and K decreases Cu dispersion, but increases the density of basic sites. Reactions of acetaldehyde and13C-labeled methanol lead to 1-13C-propionaldehyde, a precursor to isobutanol. The density and strength of basic sites were measured using a12CO2/13CO2isotopic jump method that probes the number and chemical properties of basic sites available at typical isobutanol synthesis temperatures. K or CeO2addition to CuMgOxincreases the density and strength of basic sites and the rates of base-catalyzed ethanol condensation reactions leading to acetone andn-butyraldehyde. The presence of CO in the He carrier during temperature-programmed surface reactions of ethanol preadsorbed on Cu0.5Mg5CeOxdecreases the rate of base-catalyzed condensation reactions of preadsorbed ethanol, possibly due to the poisoning of basic and Cu sites by the CO2formed from CO via water–gas shift reactions.