The selective continuous flow synthesis of lower alcohols from polyols – a mechanistic interpretation of the results

In an endeavour to understand the hydrogenolysis pathway of glycerol to lower alcohols over Ni on Al sub(2)O sub(3) and SiO sub(2) catalysts, the role of the intermediates (1,2-propanediol (1,2-PDO), 1,3-propanediol (1,3-PDO), ethylene glycol (EG) and ethanol) was investigated. Under the reaction conditions employed in this study, it was clear that the hydrogenolysis of the C-C and C-O bonds of glycerol takes place to a lesser extent as compared to dehydrogenation and dehydration which are seen as the dominating initial steps. Ethanol was produced in high selectivities (~67%) with 1,2-propanediol as feed and 1-propanol (1-PO, ~80%) was the main product obtained when 1,3-propanediol was used as feed. Ethylene glycol gave methanol and methane as products, whereas ethanol gave methane and CO sub(2) as major products.