Catalytic Conversion of Biomass-Derived Carbohydrates to Methyl Lactate by Acid–Base Bifunctional γ-Al₂O₃

Abstract

We report the catalytic conversion of biomass-derived carbohydrates to methyl lactate using metal oxides. The combination of Lewis acid–base sites on γ-Al2O3 is superior to several amphoteric oxides for the production of methyl lactate from both dihydroxyacetone and glucose in methanol. The successful production of methyl lactate from glucose by γ-Al2O3 is attributed to high densities of both acid and base functionalities that are essential for the promotion of the stepwise reaction, which consists of isomerization, retro-aldol, and dehydration reactions.

Lewis Acid and Base Catalysis of YNbO4 Toward Aqueous‐Phase Conversion of Hexose and Triose Sugars to Lactic Acid in Water

“…Table S1 summarizes representative results for the chemocatalytic conversion of glucose to LA and alkyl lactate . Homogeneous catalysts such as Lewis acidic metal salts that contain Al 3+ , Pb 2+ , and Sn 2+ and a Brønsted base (Ba(OH) 2 ) are selective catalysts for LA production .…”

“…However, Nb 2 O 5 predominantly catalyzes HMF formation from glucose by step‐wise dehydration in water, instead of consecutive isomerization and retro‐aldol reaction that triggers LA production. Despite their moderate activity, some amphoteric oxides, as represented by γ‐Al 2 O 3 , offer Lewis acid‐base pairs that convert glucose to methyl lactate in methanol . Based on these results, we conceived that a niobium‐based complex metal oxide containing strong Nb‐derived Lewis acid sites and lattice oxygen that functions as a conjugated Lewis base would be a stable and active heterogeneous catalyst for direct LA production from glucose.…”

“…Chemocatalytic glucose conversion with metallosilicates [20][21][22][23] and metal oxides [24][25][26] has been extensively investigated as an alternative approach toward the production of LA and its ester derivatives. Scheme 1 shows a proposed reaction pathway for the conversion of glucose to LA over acid or base catalysts.…”

“…[28] Table S1 summarizes representative results for the chemocatalytic conversion of glucose to LA and alkyl lactate. [20][21][22][23][24][25][26][29][30][31][32][33] Homogeneous catalysts such as Lewis acidic metal salts that contain Al 3 + , Pb 2 + , and Sn 2 + and a Brønsted base (Ba(OH) 2 ) are selective catalysts for LA production. [29] Although LA can be selectively formed, even at room temperature, in a strongly basic Ba(OH) 2 solution (the maximum yield of 95.4 %), this process produces barium lactate as obtained in biological fermentation, which is inevitably accompanied by acidification treatment and the formation of salt waste.…”

Catalytic Upgrading of Biomass‐Derived Sugars with Acidic Nanoporous Materials: Structural Role in Carbon‐Chain Length Variation

“…Although significant progress in the conversion of carbohydrates into LA has been achieved over dual Brønsted/Lewis acid porous catalysts, some undesirable side reactions associated with the dehydration of carbohydrates occur in aqueous solution due to the presence of Brønsted acid sites . Thus, a Lewis acid–base bifunctional catalyst (Zn‐Sn‐Beta) was developed with the aim of suppressing side reactions related to carbohydrate dehydration, thereby facilitating the formation of LA .…”