Cu/C‐catalyzed Hydrogenolysis of Sorbitol to Glycols–On the Influence of Particle Size and Base

Abstract

AbstractHerein, a series of Cu catalysts supported on activated carbon with increasing particle size was tested for the conversion of sorbitol to glycols including 1,2‐propanediol and ethylene glycol in the presence of Ca(OH)2. Activity measurements reveal a distinct correlation between TOF and particle size, which increases until 14 nm (N2O chemisorption based) after which a plateau is reached. However, variation of the particle size has no apparent effect on the selectivity for C3/C3 and C2/C4 cleavage. In contrast, variation of the Ca(OH)2 equivalence has a profound impact on selectivity. The ratio of C3/(C2+C4) products reaches an optimum at 0.45 equiv. of Ca(OH)2. Notably, the time course of the reaction demonstrates that the by‐products lactic acid and glycerol are in‐situ converted to the desired product 1,2‐propanediol, contributing to the unprecedented combined glycol selectivity of 84.5 % at 513 K, 5 MPa H2 and 0.3 equiv. of Ca(OH)2. Furthermore, recycling tests reveal a rapid deactivation which is attributed to aggregation of Cu observed in TEM.