Selective hydrogenolysis of glycerol over copper catalysts both in liquid and vapour phase: Correlation between the copper surface area and the catalyst's activity

Abstract

The hydrogenolysis of glycerol was performed both in liquid and in vapour phase by the use of different copper catalysts. The reactions in liquid phase were carried out using copper catalysts which differ in their copper content (36–89 wt.%) and, thus, in their composition while for the hydrogenolysis of glycerol in the vapour phase a set of different silica supported copper catalysts (Cu/SiO 2, low copper loading) was prepared either by incipient wetness (IW) or by ion exchange technique (IE). Concerning the reactions in the vapour phase complete conversion of glycerol and a selectivity to 1,2-propanediol of 87% was achieved over a Cu/SiO 2_IE catalyst under optimised reaction conditions (255 °C, 15 bar, 300 ml/min H 2). In liquid phase hydrogenation, 1,2-propanediol was nearly the sole product (selectivity = 98%), and conversions up to 52% were obtained according to a space–time–yield of 5.9 g 1,2-propanediol/(g Cu h). N 2O chemisorption was carried out in order to determine the specific copper surface area of the catalysts. For both the reaction in liquid phase and in vapour phase there is a linear relationship between the specific copper surface area and the catalytic activity not only for glycerol hydrogenolysis, but also for glycerol dehydration to acetol and the subsequent hydrogenation of the latter to 1,2-propanediol.