Effect of calcination and metal loading on the characteristics of Co/NaY catalyst for liquid-phase hydrogenation of ethyl lactate to 1,2-propanediol

• Co/NaY was prepared by impregnation of NaY with ethanol-cobalt nitrate solution.
• Co/NaY was applied in the ethyl lactate hydrogenation.
• 100% conversion and 96% selectivity to 1,2-PDO was achieved.
• The structural characteristics were affected by the condition of preparation.
• Conversion of ethyl lactate correlates linearly with number of surface metallic Co.

Co/NaY catalysts prepared by impregnation of NaY with a cobalt nitrate-ethanol solution were used to catalyze liquid-phase hydrogenation of ethyl lactate to 1,2-propanediol (1,2-PDO). To elucidate the effect of calcination conditions and cobalt loading, the catalysts were characterized using XRD, N2 physical adsorption, H2-TPR, XPS, H2-TPD, and TEM. The results show that both high calcination temperature and high amount of Co loading result in relatively large Co3O4 particles. The reduced cobalt catalysts consist of three cobalt species, including metallic Co, cobalt oxides and cobalt species interacting with zeolite (cobalt aluminate/silicate), due to incomplete reduction of cobalt species. The absence of the characteristic peak of metallic Co in the XRD pattern confirms its high dispersion on NaY, in agreement with the TEM results. H2-TPD effectively quantifies the number of surface metallic Co sites, which correlates linearly with the ethyl lactate conversion. This correlation indicates that metallic Co is the active site for ethyl lactate hydrogenation. A complete conversion of ethyl lactate with a selectivity of 96% to 1,2-PDO has been achieved over the 6Co/NaY-673-5 catalyst.

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