Ag/Al2O3 for glycerol hydrogenolysis to 1,2-propanediol: activity, selectivity and deactivation

Abstract

A series of γ-Al₂O₃ supported silver catalysts (Ag/Al₂O₃) prepared with various Ag loadings and calcination temperatures were used to convert glycerol to 1,2-propanediol. A catalyst with 2 mmol Ag per gram Al₂O₃ and calcined at 400–500 °C presented the highest activity (glycerol conversion 46 mol%) and selectivity (96 mol%) at 220 °C, glycerol/Ag (molar ratio) = 100/2, 1.5 MPa initial H₂ pressure and 10 h. Optimal prereduction, elevated reaction temperature and hydrogen pressure promote the activity, but the selectivity deteriorates at higher reaction temperatures. Excessive water is detrimental to the performance. Catalyst deactivation was observed, mainly due to Ag sintering under reducing environment. The spent catalyst could be calcined to fully recover the activity.