Fig. 2: Synthesis of α-ketoglutaric acid (KGA) from pyruvic and glyoxylic acids.
From: Sustainable synthesis of α-ketoglutaric and methanetriacetic acids from biomass feedstocks
a Evolution of conversions and selectivities for aldol condensation of pyruvic and glyoxylic acids (i.e., the first step of KGA synthesis) with reaction times. C5: 2-hydroxy-4-oxopentanedioic acid; C5-DH: 4-oxopent−2-enedioic acid; C5-GA: by-products derived from further condensation of C5 with glyoxylic acid. Reaction conditions: 2 mmol sodium pyruvate, 2 mmol sodium glyoxylate, 80 °C, 10 mL H2O. b Effect of molar ratios of pyruvic acid to glyoxylic acid on products selectivities in their aldol condensation reaction. Reaction conditions: 2 mmol sodium glyoxylate, 80 °C, 10 mL H2O, at nearly complete glyoxylic acid conversions obtained by varying reaction time. c Evolution of conversions and selectivities for sequential dehydration and hydrogenation reaction of C5 intermediate (i.e., the second step of KGA synthesis) with reaction times. Reaction conditions: 5 mL condensation reaction solution of pyruvic and glyoxylic acids with an initial ratio of 4:1 at nearly complete conversion of glyoxylic acid from the first step, 5 mL H2O, 30.0 mg Pd/TiO2 (2 wt% Pd), 110 °C, 1.0 MPa H2. d Proposed reaction pathways for KGA synthesis via two steps from pyruvic and glyoxylic acids (not including by-products of C5-GA and 2-hydroxypentanedioic acid, for clarity).
