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K±Cu y Mg 5 CeO x and Cs±Cu/ZnO/Al 2 O 3 are selective catalysts for the synthesis of alcohols from an H 2 /CO mixture at relatively low pressures and temperatures. CO 2 produced in higher alcohol synthesis and water±gas shift (WGS) reactions reversibly inhibits the formation of methanol and higher alcohols by increasing oxygen coverages on Cu surfaces and by titrating basic sites required for aldol-type chain growth steps. Inhibition effects are weaker on catalysts with high Cu-site densities. On these catalysts, the abundance of Cu sites allows reactants to reach methanol synthesis equilibrium and maintain a suf®cient number of Cu surface atoms for bifunctional condensation steps, even in the presence of CO 2 . The addition of Pd to K±Cu 0.5 Mg 5 CeO x weakens CO 2 inhibition effects, because Pd remains metallic and retains its hydrogenation activity during CO hydrogenation. Basic sites on Mg 5 CeO x are stronger than on ZnO/Al 2 O 3 and they are more ef®ciently covered by CO 2 during alcohol synthesis. K and Cs block acid sites that form dimethylether and hydrocarbons. Alcohol addition studies show that chain growth occurs predominantly by aldol-type addition of methanol-derived C 1 species to ethanol and higher alcohols, following the rules of base-catalyzed aldol condensations. The initial C±C bond formation required for ethanol synthesis, however, proceeds directly from CO, at least on K±Cu y Mg 5 CeO x catalysts. A detailed kinetic analysis shows that chain growth probabilities are very similar on K±Cu y Mg 5 CeO x and Cs±Cu/ZnO/Al 2 O 3 catalysts. The growth probabilities of C 1 chains to ethanol and of iso-C 4 chains to higher alcohols are much lower than for other chain growth steps. # 1998 Elsevier Science B.V.

Liquid and cured epoxy-phenolic lacquers used as can coatings were characterized. Tinplate was used as the base material, which was coated with lacquers of different epoxy to phenolic ratios (EPRs) from a commercial source. Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) were used together to obtain helpful information about the degree of curing and the composition of the lacquers. From FTIR analysis, we were able to infer that the lacquers were composed of a high-molecular-weight diglycidyl ether of bisphenol A type epoxy resin and a resol-type phenolic resin. In addition, from FTIR spectra, we estimated the EPRs of lacquers applied on the tinplate and detected if they had been overcured. The EPRs of the applied lacquers were estimated also from DSC analysis. From TGA, we detected undercuring in the applied lacquers.

The thermal decomposition of Cu-Zn-AI hydroxycarbonate precursors to obtain watergas shift catalysts was studied by employing a variety of experimental techniques. A set of six samples containing 34 wt% of Cu and different AI/Zn ratios were prepared by coprecipitation. Depending on the cation ratio, the ternary precursors contained hydrotalcite, aurichalcite and/or rosasite phases. Malachite and hydrozincite were determined in binary Cu/AI and Cu/Zn samples, respectively. The precipitates decomposed in three endothermic transformations in the temperature ranges 363-453 K, 453-673 K and 673-923 K. In the first step (AW=0-9%), the hydrotalcite-containing samples lost the crystallization water of the hydrotalcite phase. In the middle-temperature transition (AW=18-30%), the samples were completely dehydroxylated and simultaneously eliminated a proportion of the carbonate ions through a two-step dehydroxylation/decarbonation process. The high-temperature transformation (AW=3-7%) corresponded to the final decarbonation of the samples. Mixed oxides with a high dispersion of copper were obtained from hydrotalcite-containing precursors: the higher the amount of hydrotalcite in the precursor, the lower the CuO crystallite size in the resulting mixed oxide.