Modification of iridium catalyst with rhenium oxide for the hydrogenolysis of glycerol to 1,3-propanediol
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Modification of iridium catalyst with rhenium oxide for the hydrogenolysis of glycerol to 1,3-propanediol
Yasushi Amada1 Shuichi Koso1 Yoshinao Nakagawa1 and Keiichi Tomishige1 1 School of Engineering, Tohoku University, 6-6-07, Aoba Aramaki Aza Aoba-ku, Sendai, 980-8579, Japan
ABSTRACT Rhenium-oxide-modified supported iridium nanoparticles on silica catalyzes direct hydrogenolysis of glycerol to 1,3-propanediol in an aqueous media. The selectivity to 1,3-propanediol at an initial stage reaches 67%. The yield of 1,3-propanediol reaches 38% at 81% conversion of glycerol. The characterization of catalyst shows that oxidized Re clusters are formed on Ir metal particles. The synergy between Ir metal and ReOx clusters enables the catalytic activity.
INTRODUCTION For the realization of sustainable society, production of useful chemicals and fuels from biomass-related materials is absolutely essential. Since biomass-related materials contain higher oxygen than most valuable chemicals, development of catalytic hydrogenolysis for wide range of substrates is greatly desired. Glycerol is the co-product of biodiesel production by transesterification of vegetable oils, and is one of the biomass-related materials that can be regarded as renewable feedstock. Hydrogenolysis of glycerol produces 1,2-propanediol (1,2-PrD), 1,3-propanediol (1,3-PrD), overhydrogenolysis products and degradation products. 1,3-PrD is used as a raw material for the production of polyester and polyurethane resin. 1,3-PrD has been currently produced by fermentation or chemical syntheses via hydration of acrolein or hydroformylation of ethylene oxide. Because of the low productivities of these processes, 1,3-PrD is much more valuable than glycerol and 1,2-PrD. We have reported that the modification of Rh/SiO2 with Re, Mo and W much enhances the activity for hydrogenolysis of glycerol [1]. However, the selectivity to 1,3-PrD is not so high in the case of glycerol hydrogenolysis. In this study, we report that the ReOx-modified iridium 1
nanoparticles catalyzes the selective hydrogenolysis of glycerol into 1,3-PrD in water. The modification effect of Ir with ReOx is much more remarkable than the case of Rh in terms of the initial selectivity to 1,3-PrD (68%) and maximum yield (38%) [2, 3].
EXPERIMENTAL DETAILS An Ir/SiO2 catalyst was prepared by impregnating SiO2 (535 m2/g) with an aqueous solution of H2IrCl 6. The loading amount of Ir was 4 wt%. Ir–ReOx/SiO2 catalysts were prepared by impregnating Ir/SiO2 after the drying procedure with an aqueous solution of NH4ReO4. These catalysts were calcined at 773 K for 3 h. The ratio of Re to Ir was optimized to maximize the selectivity to 1,3-PrD in the glycerol hydrogenolysis and was determined to be Re/Ir = 1 (molar basis). Catalyst pretreatment was performed under 8 MPa H2 pressure, 473 K, 1 h. The standard reaction conditions were catalyst (150 mg, 31 μmol Ir), glycerol (4 g), water (1 g), sulfuric acid (H+/Ir = 1) and H2 (8 MPa) at 393 K. The products were analyzed using gas chromatograph.
RESULTS AND DISC
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