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The use of biomass-based glycerol to produce chemicals with high added value is of great significance for solving the problem of glycerol surplus and thus reducing the production cost of biodiesel. The production of 1,2-propanediol (abbreviated as 1,2-PDO) and 1,3-propanediol (abbreviated as 1,3-PDO) via the hydrogenolysis of glycerol is one of the most representative and highest-potential processes for the comprehensive utilization of biomass-based glycerol. Glycerol hydrogenolysis may include several parallel and serial reactions (involving broken C–O and C–C bonds), and therefore, the catalyst is a key factor in improving the rate of glycerol hydrogenolysis and the selectivities of the target products. Over the past 20 years, glycerol hydrogenolysis has been extensively investigated, and until now, the developments of catalysts for glycerol hydrogenolysis have been active research topics. Non-precious metals, including Cu, Ni, and Co, and some precious metals (Ru, Pd, etc.) have been used as the active components of the catalysts for the hydrogenolysis of glycerol to 1,2-PDO, while precious metals such as Pt, Rh, Ru, Pd, and Ir have been used for the catalytic conversion of glycerol to 1,3-PDO. In this article, we focus on reviewing the research progress of the catalyst systems, including Cu-based catalysts and Pt-, Ru-, and Pd-based catalysts for the hydrogenolysis of glycerol to 1,2-PDO, as well as Pt-WOx-based and Ir-ReOx-based catalysts for the hydrogenolysis of glycerol to 1,3-PDO. The influence of the properties of active components and supports, the effects of promoters and additives, and the interaction and synergic effects between active component metals and supports are also examined. [ABSTRACT FROM AUTHOR]

Abstract: Bimetallic Ru–Re/SiO2 and monometallic Ru/SiO2 catalysts were prepared by impregnation method and their catalytic performances were evaluated in the hydrogenolysis of glycerol to propanediols (1,2-propanediol and 1,3-propanediol) with a batch type reactor (autoclave) under the reaction conditions of 160°C, 8.0MPa and 8h. Ru–Re/SiO2 showed much higher activity in the hydrogenolysis of glycerol than Ru/SiO2, and the pretreatment conditions of the catalyst precursors had great influence on the catalytic performance of both Ru–Re/SiO2 and Ru/SiO2 catalysts. The physicochemical properties of Ru–Re/SiO2 and Ru/SiO2, such as specific surface areas, crystal phases, morphologies/microstructures, surface element states, reduction behaviors and dispersion of Ru metal, were characterized by N2 adsorption/desorption, XRD, Raman, TEM–EDX, XPS, H2-TPR and CO chemisorption. The results of XRD, TEM–EDX and CO chemisorption characterizations showed that Re component had an effect on promoting the dispersion of Ru species on the surface of SiO2, and the measurements of H2-TPR revealed that the co-existence of Re and Ru components on SiO2 changed the respective reduction behavior of Re or Ru alone. High pre-reduction temperatures would decrease the activities of Ru–Re/SiO2 and Ru/SiO2 catalysts, compared with the corresponding calcined catalysts (without pre-reduction), which actually went through an in-situ reduction during the reaction. XPS analysis indicated that Ru species was in Ru0 metal state, while Re species was mostly in Re oxide state in the spent Ru–Re/SiO2 sample. Re component was probably in rhenium oxide state rather than Re0 metal state to take part in the reaction via interaction with Ru0 metal. [Copyright &y& Elsevier]

Several supported Ru–Re bimetallic catalysts (Ru–Re/SiO2, Ru–Re/ZrO2, Ru–Re/TiO2, Ru–Re/H-β, Ru–Re/H–ZSM5) and Ru monometallic catalysts (Ru/SiO2, Ru/ZrO2, Ru/TiO2, Ru/H-β, Ru/H–ZSM5) were prepared and their catalytic performances were evaluated in the hydrogenolysis of glycerol to propanediols (1,2-propanediol and 1,3-propanediol) with a batch type reactor (autoclave) under the reaction conditions of 160 °C, 8.0 MPa and 8 h. Compared with Ru monometallic catalysts, the Ru–Re bimetallic catalysts showed much higher activity in the hydrogenolysis of glycerol, and Re exhibited obvious promoting effect on the performance of the catalysts. The supported Ru monometallic catalysts and Ru–Re bimetallic catalysts were characterized by N2 adsorption/desorption, XRD, TEM-EDX, H2-TPR and CO chemisorption for obtaining some physicochemical properties of the catalysts, such as specific surface areas, crystal phases, morphologies/microstructure, reduction behaviors and dispersion of Ru metal. The results of XRD and CO chemisorption indicate that the addition of Re component could improve the dispersion of Ru species on supports. The measurements of H2-TPR revealed that the coexistence of Re and Ru components on supports changed the respective reduction behavior of Re or Ru alone on the supports, indicating the existence of synergistic effect between Ru and Re species on the bimetallic catalysts. The hydrogenolysis of some products (such as 1,2-propanediol, 1,3-propanediol, 1-propanol and 2-propanol) were also examined over Ru and Ru–Re catalysts for evaluating influence of Re–Re on the reaction routes during glycerol hydrogenolysis. The results showed that over Ru–Re catalysts, glycerol was favorable to be converted to 1,2-propanediol, but not favorable to ethylene glycol, while 1,2-propanediol and 1,3-propanediol were favorable to be converted to 1-propanol. The influence of glycerol concentration in its aqueous solution on the catalytic performance was also evaluated over Ru and Ru–Re catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Ru/Al2O3, Ru/C and Ru/ZrO2 catalysts were applied to the hydrogenolysis of glycerol to propanediol, and the effect of Re as an additive on the catalytic performance of Ru catalysts was examined. The catalyst systems were characterized by N2 adsorption/desorption, XRD, TEM-EDX and XPS. The hydrogenolysis of glycerol was carried out under the conditions of 120–180°C, 4–10MPa hydrogen pressure and 4–8h, and the conversion of glycerol varied from 18.7% to 29.7% over Ru/Al2O3, Ru/C and Ru/ZrO2 catalysts. The reaction results indicate that Re possesses high promoting effect on the catalytic performance of Ru catalysts in glycerol hydrogenolysis. [Copyright &y& Elsevier]

Pd-Re/SBA-15 catalysts with different Pd precursors were prepared by the impregnation method. N 2 adsorption-desorption, XRD, H 2 -TPR, TEM and NH 3 -TPD were used to characterize the physical and chemical properties of the catalysts. Pd-Re catalysts with different precursors showed different activities in the reaction of glycerol hydrogenolysis. 5Pd-5Re/SBA-15 with PdCl 2 as Pd precursor had higher activity than those with Pd(NO 3 ) 2 and Pd(OAc) 2 as precursors. The existence of Cl could affect the particle sizes, reduction behaviors and the acid properties of Pd-Re catalysts. [ABSTRACT FROM AUTHOR]

Highlights: [•] ·Ru catalysts with HZSM5(X) were used during glycerol hydrogenolysis. [•] ·As the acid amount increased, the glycerol conversion and CH4 selectivity increased. [•] ·The acid amount and acid strength of HZSM5(X) affected the C C bond cleavage. [•] ·Loading Ru on HZSM5(X) could modulate the acidity and decrease CH4 selectivity. [ABSTRACT FROM AUTHOR]