Selective transformation of glucose into propylene glycol on Ru/C catalysts combined with ZnO under low hydrogen pressures

Abstract

a b s t r a c tRecently, biomass resources have garnered significant attention as sustainable and renewable raw materials for the production of chemicals. Propylene glycol (PG) is a valuable chemical product that can be synthesized from biomass. Herein, the selective transformation of glucose into PG was investigated on a carbon-supported 5 wt% Ru catalyst (5%-Ru/C) combined with solid acid-base catalysts under low hydrogen pressures. The reaction conditions, namely the amount of ZnO, temperature, and hydrogen pressure, were also evaluated. At a hydrogen pressure of 0.4 MPa, a full conversion of glucose and 38% yield of PG were obtained using the ZnO + Ru/C system at 453 K for 20 h, while the yield of PG on Ru/C alone was only 9.3% under the same conditions. Studies on the reaction mechanism indicated that the transformation of glucose into PG consisted of the isomerization of glucose to fructose, retro-aldol reaction of fructose to triose (dihydroxyacetone and glyceraldehyde), dehydration of glyceraldehyde to pyruvaldehyde, and successive hydrogenation of pyruvaldehyde to PG via hydroxyacetone. The ZnO catalyst promoted both the isomerization and retro-aldol reaction steps, and the Ru catalyst promoted the hydrogenation steps. The retro-aldol reaction, which included the cleavage of C3 C4 bond in glucose, enabled the selective transformation of glucose into PG under low hydrogen pressures. These findings provide novel insights into the efficient synthesis of PG from glucose, which could be achieved by combining and optimizing the retro-aldol and hydrogenation steps.

Ru-(Mn-M)OX Solid Base Catalysts for the Upgrading of Xylitol to Glycols in Water

“…Yet, previous studies have reported that the combination of Cu and ZnO was active and selective in the hydrogenolysis of alditols to glycols [21,[36][37][38]. The activity of Ru-(Mn-Zr)O X and Ru-(Mn-Ti)O X catalysts was 33 h −1 , i.e., lower than the activity of Ru-(Mn-Al)O X (57 h −1 ).…”

“…This observation suggests that TiO 2 and ZrO 2 were amorphous, unlike in a Cu-ZrO 2 -MgO material obtained after similar thermal treatment [31]. It is worth noting that the pattern of Ru-(Mn-Al)O X recorded with a higher time per step ( Figure A1) exhibited peaks associated with Mn 3 O 4 in the 2θ region of [28][29][30][31][32][33][34][35][36][37][38] • . This phase might also be present in the other Ru-(Mn-M)O X .…”

Bio-Based Solvents and Gasoline Components from Renewable 2,3-Butanediol and 1,2-Propanediol: Synthesis and Characterization

“…The synthetic trees for 1,2-PD derivatives have been made up starting from bioglycerol-derived propylene glycol. Although there are precedents for a one-step 1,2-PD synthesis by a retroaldol glucose conversion [61,62], currently only the glycerol hydrogenolysis process is employed on an industrial scale. Carbohydrate fermentation is supposed to be an appropriate source of the renewable acetone.…”

“…Carbohydrate fermentation is supposed to be an appropriate source of the renewable acetone. The synthesis of TMD is implemented via the direct ketalization of 1,2-PD with acetone, since the feasibility of the one-step 1,2-PD to TMD conversion seems to be rather arguable in essence, Although there are precedents for a one-step 1,2-PD synthesis by a retroaldol glucose conversion [61,62], currently only the glycerol hydrogenolysis process is employed on an industrial scale. Carbohydrate fermentation is supposed to be an appropriate source of the renewable acetone.…”

Solar Fuels by Heterogeneous Photocatalysis: From Understanding Chemical Bases to Process Development

“…It is also known that side pathways yield alkanes from the alkyl chain of alcohols [171], thus lowering hydrogen yield. It is worth noting that these alcohols can be obtained from biomass through chemical [253][254][255] or biochemical [256] processes, while glycerol is an abundant by-product of the biodiesel industry [257]. Other organic compounds have been also used, such as carboxylic acids and aldehydes, since they constitute bio-oil [258] and wastewater [259].…”