Hydrogenolysis of glycerol over a catalytic system based on heteropoly ionic liquid

A series of ionic liquids coupled with Raney Ni were used as dual functional catalysts in the hydrogenolysis reaction of glycerin to prepare propylene glycol. Effects of the ionic liquid structure on catalytic performance was studied. As a result, a solid heteropoly ionic liquid HMIM₃PW₁₂O₄₀ with suitable acid strength was selected and characterized by FT-IR, ¹H-NMR and TG. The composite catalyst HMIM₃PW₁₂O₄₀/Raney Ni could give 83.3% glycerol conversion and 57.3% selectivity for 1,2-propanediol under the optimized conditions: 20 g 40% glycerol solution, 0.2 mmol HMIM₃PW₁₂O₄₀ and 0.3 g Raney Ni dosage, 6 MPa hydrogen pressure (hydrogen to alcohol 2.37:1), 230 ℃, 11 h. What's more, the low cost composite catalyst could be prepared simply and recycled easily with good stability.