Study On The Hydrogenolysis Of Glycerol Catalyzed By Ir-Ionic Liquid And Cu-Cr-O

Petroleum and natural gas are two important non-renewable petrochemicalresources, which constitute the cornerstone of today's fuels and chemical industries.Unfortunately, their declining reserves and the environmental problems caused bytheir use have become two major bottlenecks of sustainable development of thesociety and economy, which have in turn greatly promoted the R&D of the renewablebiomass resources. Glycerol, a major byproduct of biodiesel production, is such akind of very ideal renewable biomass resource. The hydrogenolysis of glycerol for thesynthesis of propylene glycol and ethylene glycol to reuse the growing supply ofglycerol can improve the economic efficiency and therefore has great research value.Therefore, this paper developed Ir-ionic liquid catalyst and the Cu-Cr-O catalysts forsynthesis of propylene glycol by glycerol hydrogenolysis.Two ionic liquids [BMIM]Cl and [(Et)₃NH][HSO₄] were synthesized by one-steptechnique and characterized by IR or ¹H-NMR to confirm their structures. Ir-ionicliquid catalyst was prepared in ionic liquid medium. The SEM image shows Irparticles are stable and well dispered in ionic liquid with an average diameter about100 nm. While catalyzed by Ir(0)-[BMIM]Cl in sulfolane, a maximum conversion ofthe hydrogenolysis of glycerol is as high as 75.3%, and the yield of 1,3-PDO andethylene glycol are 3.0% and 9.7%, respectively.Cu-Cr-O catalysts were prepared by six different methods for hydrogenolysis ofglycerol, and then comprehensively studied the parameters of catalyst preparationmethod, calcination temperature, catalyst pretreatment, glycerol concentration,catalyst dosage, reaction temperature and run-time. Furthermore, the reactionparameters were optimized with the most activity Cu-Cr-O catalyst which synthesizedvia a citric acid complexing method and calcinated at 500℃for 3 hours. It wasfound a maximum glycerol conversion of 47.8% with 59.9% selectivity toward1,2-propylene glycol were obtain after 24 hours at 220℃in 4 MPa hydrogen pressure with the dosage of Cu-Cr-O being 1/30 (w/w) of glycerol, and using 75% (v/v)glycerol-water as substrate. The Cu-Cr-O catalysts were characterized by TEM, XRDand BET before and after the hydrogenolysis process. Results show that the particlesof catalyst maintained a certain degree of stability with the particle size of about 50nm and evenly distributed. The crystalline phases appeared symbiosis of CuCr₂O₄ andCuCrO₂ two-phase by the reduction of hydrogen during the hydrogenolysis processwhich may enhance the activity of Cu-Cr-O catalysts.The supported Cu-Cr-O/SiO₂ catalyst synthesized via sol-gel method for thehydrogenolysis of glycerol was preliminary studied. The pore size of the catalystparticles is found only 14.8 A by BET, which may prevent glycerol from enteringinside the catalyst. As a result, the activity of catalyst couldn't be fully exhibited.