Vapor-phase hydrogenation of ethyl lactate over copper–silica nanocomposites

Silica-supported Cu was studied as a catalyst for hydrogenation of ethyl lactate to produce 1,2-propanediol. The dispersion of Cu on silica was highly influenced by the preparation method, which was a major factor affecting the catalytic activity in the reaction. The conversion of ethyl lactate over the catalyst by precipitation–deposition method was about two times higher than that by sol–gel and wet impregnation methods, although the BET surface area of the catalyst by precipitation–deposition was much lower. Copper loading could be increased up to 80 wt% on silica while maintaining a Cu particle size smaller than 15 nm by the precipitation–deposition method, where the highest specific Cu surface area was obtained. In this nanocomposite, further growth of Cu crystals seemed to be prevented by the inclusion of silica nanoparticles between Cu nanoparticles. Compared with hydrogenation of lactic acid over the conventional lowly loaded silica-supported Cu catalysts, the productivity of 1,2-propanediol from ethyl lactate is enhanced about 10 times under mild reaction conditions.

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► The dispersion of Cu on silica was enhanced greatly by the precipitation–deposition method.
► Cu loading could be increased up to 80 wt% on silica with maintaining Cu particle size smaller than 20 nm.
► The productivity of 1,2-propanediol is enhanced significantly with Cu–silica nanocomposites.