Upgrading of diols by gas-phase dehydrogenation and dehydration reactions on bifunctional Cu-based oxides

作者：Torresi P A^*; Diez V K; Luggren P J; Di Cosimo J I

来源：Catalysis Science & Technology, 2014, 4(9): 3203-3213.

DOI：10.1039/c4cy00639a

Biomass-derived short-chain polyols can be transformed into valuable oxygenates used as building blocks. The gas phase conversion of a model molecule of 1,3-diols (1,3-butanediol), was studied on bifunctional Cu-Mg, Cu-Al and Cu-Mg-Al mixed oxide catalysts that exhibit surface Cu-0 particles and acid-base properties. A series of ZCuMgAl catalysts (Z = 0.3-61.2 wt.% Cu, Mg/Al = 1.5 molar ratio) was prepared by coprecipitation and thoroughly characterized by several techniques such as BET surface area, TPR-N2O chemisorption, XRD and TPD of CO2. The ZCuMgAl catalysts promote the upgrading of diols by a series of dehydrogenation and/or dehydration reactions proceeding at reaction rates that depend on the copper content (Z). The overall activity increases linearly with the amount of surface Cu-0 species thereby confirming the participation of metallic sites in the rate-limiting steps. Besides, surface Cu-0 sites favor the reaction pathway toward 1,3-butanediol dehydrogenation. Thus, the dehydrogenation/dehydration selectivity ratio increases with Z as a result of the enhanced amount of exposed Cu-0 particles. ZCuMgAl catalysts with Z < 8 wt.% dehydrogenate-dehydrate-hydrogenate the diol at low rates giving mainly C-4 ketones and break the intermediates forming C-1-C-3 oxygenates; catalysts with Z > 8 wt.% have higher activity and yield valuable multifunctional C-4 oxygenates such as hydroxyketones and, to a lesser extent, unsaturated alcohols and ketones. A strongly basic Cu-Mg catalyst promotes the C-C bond cleavage reaction giving short carbon chain oxygenates at low rates; an acidic Cu-Al catalyst converts the diol into C-4 saturated ketones and olefins.

• 出版日期2014