Study On In-situ Hydrogenolysis Of Glycerol Aqueous Solution Over Pt-based Catalysts

With biodiesel becoming a new kind of biomass energy and could replace fossil-based energy, its large scale production cause abundant surplus of glycerol. It is an effective value-added route to convert glycerol into 1,2-propanediol and ethylene glycol by hydrogenolysis pathway. But traditional hydrogenolysis reaction exist a lot of disadvantages, so researchers developed glycerol in-situ hydrogenolysis, which make glycerol aqueous-phase reforming (APR) for hydrogen generation incorporate into the reaction system of glycerol hydrogenolysis to produce 1,2-propanediol. This production strategy is regarded as advantageous in atom economy and energy efficiency, thus being considered as very promising.In this work, catalysts were prepared with Pt as active component, the performance of glycerol in-situ hydrogenolysis reaction were evaluated on various types of supported (Al2O3, AC, SiO2, HT, ZrO2)Pt catalysts. The results showed that the Pt/AC catalyst gives the highest selectivity to 1,2-propanediol. Further, the properties of Pt/AC with different reduction methods (H2, KBH4, N2H4, HCHO, Carbonthermal) were investigated.80.5% of glycerol conversion and 45.1% of 1,2-propanediol selectivity were achieved at 230℃ under 1MPa of N2 with 12h on 2%Pt/AC catalyst reduced by KBH4.Pt-M/AC (M=Fe, Ni, Co, Zn, Cu) series catalysts were prepared and used for glycerol in-situ hydrogenolysis. The activity was show in the order of Pt-Fe/AC>Pt-Ni/AC>Pt-Co/AC > Pt-Zn/AC> Pt-Cu/AC.98.3% of glycerol conversion and 60.5% of 1,2-propanediol selectivity were achieved on Pt-Ni/AC at 220℃ under 1.0MPa of N2 with 8h. After five times of recycling, the selectivity of 1,2-PDO remained unchanged. The results indicated that Pt-Ni/AC catalyst has excellent catalytic stability. XRD, TEM indicated that nanoparticles with an average size of 2-5 nm were uniformly dispersed on the support. The formation of Pt-M phase due to the incorporation of the second metal M in the Pt lattice.With mechanical mixing of mono-component Pt/AC and Ni/AC, the catalyst (denoted as Pt+Ni) was prepared and used in this reaction. It was found that the Pt+Ni catalyst had lower activity compared with co-impregnated Pt-Ni/AC catalyst, but higher than mono-component Pt or Ni catalyst. From HRTEM, SAED and XPS results, it was inferred that synergistic effect between Pt and Ni was the main reason of increasing Pt-Ni/AC activity. The possible reaction mechanism in glycerol in-situ hydrogenolysis was also discussed.