Liquid phase hydrogenolysis of ethyl lactate to 1,2-propanediol was performed over silica supporting cobalt catalysts prepared by two different methods:precipitation-gel (PG) technique and deposition-precipitation (DP)procedure. The cobalt species (CoO/cobalt phyliosilicate) present in the corresponding calcined PG and DP catalysts were different as a consequence of the preparation methods,and Co-OH-Co olation and Si-O-Co oxolation molecular mechanisms were employed to elucidate the chemical phenomena during the different preparation procedures. In addition,the texture (BET),reduction behavior (TPR and in-situ XRD),surface dispersion and state of cobalt species (XPS),and catalytic performance differ greatly between the samples. Because of small particle size,high dispersion of cobalt species and facile reducibility,the Co/SiO catalyst prepared by precipitation-gel method presented a much higher activity than the catalyst prepared by deposition-precipitation method. Metallic cobalt is assumed to be the catalytically active site for the hydrogenolysis reaction according to the catalytic results of both cobalt samples reduced at different temperatures and the structure changes after reaction.
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