Fig. 3: Synthesis of methanetriacetic acid (MTA) from α-ketoglutaric acid (KGA) and glyoxylic acid.
From: Sustainable synthesis of α-ketoglutaric and methanetriacetic acids from biomass feedstocks
a Evolution of conversions and selectivities for aldol condensation of KGA and glyoxylic acid (i.e., the first step of MTA synthesis) with reaction times. Reaction conditions: 50 °C, 5 mmol sodium α-ketoglutarate, 5 mmol sodium glyoxylate, 10 mL H2O. b Effect of α-ketoglutaric acid (KGA) concentrations on KGA conversions and selectivities for aldol condensation of KGA and glyoxylic acid. Reaction conditions: molar ratio of KGA to glyoxylic acid = 1:1, 50 °C, 3.0 h, 10 mL H2O. c Evolution of conversions and selectivities for hydrodeoxygenation (i.e., the second step of KGA synthesis) of 3-(carboxymethyl)-2-hydroxy-4-oxopentanedioic acid (C7) and 3-(carboxymethyl)-4-oxopent−2-enedioic acid (C7-DH) with reaction times on Pd/TiO2 and MoOx/TiO2. Reaction conditions: 0.5 mL condensation reaction solution of KGA and glyoxylic acid (2.0 mol L−1) at nearly complete conversion of KGA from the first step, 9.5 mL H2O, 3.0 mmol HCl, 0.10 g Pd/TiO2 (2 wt% Pd), 0.10 g MoOx/TiO2 (5 wt% Mo), 200 °C, 2.0 MPa H2. C7-Diol: 3-(carboxymethyl)−2,4-dihydroxypentanedioic acid; C7-ol: 3-(carboxymethyl)−2-hydroxypentanedioic acid. d Proposed reaction pathways of MTA synthesis from KGA and glyoxylic acid.
