A commercial Zn/Cr spinel methanol synthesis catalyst obtained fromEngelhard was promoted with potassium and tested for methanol and isobutanol synthesis using a syngas feedstream (1:1 H2and CO). An equal molar mixture of methanol and isobutanol would be an ideal feedstock for production of methyl tertiary butyl ether (MTBE) for use as an additive to gasoline to increase the octane number and reduce air pollution. Of the reaction conditions examined, the higher temperature, 440°C, and higher pressure, 1500 psig, result in the highest isobutanol production rate over mostof the catalysts examined. The effect of the K promotor loading also was examined. Increasing the amount of K from 0 to 1 wt% increases the hydrocarbon by-product rate, but the addition of 3 or 5 wt% K decreases the hydrocarbon by-product rate consequently increasing the selectivityto total alcohols. Increasing the K loading above 3 wt%, however,raises the methanol-to-isobutanol mole ratio. The use of the 3 wt% K-containing catalyst results in the lowest methanol-to-isobutanol moleratio of 1.5 which is near the desired value of 1.0 for MTBEsynthesis. An isobutanol production rate of 103 g/kg-cat/hr isattained using a 1 wt% K-promoted Zn/Cr spinel catalyst.Surface-characterization studies were performed on the 3 wt%K-containing catalyst. Ion-scattering spectroscopy data reveal thatthe outermost surface layer of the fresh catalyst consists of C, O,Cr, and Zn. Since the catalysts are reduced prior to testing in thereactor, surface studies also were performed after reducing thecatalyst in 1×10−7Torr of H2for 4 hr at 250°C.The addition of the alkali is necessary for higher alcohol synthesis(HAS), and the pretreatment results in migration of the K promotor tothe outermost surface layer where the catalytic reactions occur.X-ray photoelectron spectroscopy (XPS) data are consistent with theseresults and also reveal that the near-surface regions of thenontreated and H2-treated samples consist primarily of ZnO. The K ispresent as K2Cr2O7or K2CrO4. Although the outermost atomiclayer of the reduced catalyst contains a large amount of K,relatively little is observed in the near-surface region using XPS,indicating that most of the K is located at the surface. Thecatalytically active surface for HAS consists of alkali species lyingon top of a ZnO phase. The chemical state of the Cr species isaltered during reaction. The K2Cr2O7or K2CrO4present on the fresh and reduced catalyst is converted to Cr2O3, Cr(OH)xandCr0with age, but no other phases of Zn other than ZnO areobservable before or after aging. The Zn/Cr spinel is not importantfor activity toward isobutanol production and acts only as ahigh-surface-area support.