Synthesis of Methacrylic Acid by Catalytic Decarboxylation and Dehydration of Carboxylic Acids Using a Solid Base and Subcritical Water

Abstract

Methacrylic acid was synthesized from the biobased substrates citric acid, itaconic acid, and 2-hydroxyisobutyric acid (2-HIBA). Hydrotalcite, a solid base catalyst, was employed to form methacrylic acid (MAA) through decarboxylation of itaconic acid and citric acid. The effect of temperature, catalyst mass, residence time, substrate concentration, and fermentation media, on carboxylic acid conversion and methacrylic acid yield was determined. Optimum MAA yields occurred at a substrate to catalyst mass ratio of 9.6 g-substrate/g-catalyst and 21% for citric acid and 6.4 g/g and 23% for itaconic acid (250 °C, 15 min). Catalyst reusability experiments resulted in higher methacrylic acid yields for both citric and itaconic acid. Methacrylic acid was also formed from 2-hydroxyisobutyric acid in a single-step dehydration reaction. Among these three substrates, the highest yield of methacrylic acid (71.5%) was achieved at 275 °C (1 min) using 2-HIBA and subcritical water. Finally, we tested conversion of these three acids in a simulated residual fermentation broth (0.1 M NaOH, 0.04 M Na 2 SO 4 , 0.04 M Na 2 HPO 4 , 0.06 M glucose, 0.12 wt % albumin) and MAA yields from itaconic acid and citric acid using hydrotalcite increased in the presence of these fermentation "impurities" and decreased slightly from 2-HIBA.

Subgram-Scale Synthesis of Biomass Waste-Derived Fluorescent Carbon Dots in Subcritical Water for Bioimaging, Sensing, and Solid-State Patterning

“…The uses of the SBCW apparatus in various fields such as chemical reaction, extraction, and material processing have been realized in laboratory scale and even in large-scale industrial applications. 28 − 30 However, as far as we are aware, few studies have been focused on the synthesis of FCDs in SBCW apparatuses.…”

Production and Polymerization of Biobased Acrylates and Analogs

“…Pirmoradi and Kastner took a different approach using calcinated hydrotalcite, a cheap solid base catalyst composed of magnesium and aluminum oxides. [ 76,77 ] They achieved modest yields (20–25%) at moderate temperatures (250 °C) in subcritical water, without pH neutralization or expensive catalysts. The multiple uses of the hydrotalcite increased yields, as did the addition of fermentation impurities (up to 30%), which would have resulted from unknown catalyst modifications.…”

“…In the same work they did on IA decarboxylation, Pirmoradi and Kastner exemplified for the first time the dehydration of 2‐HIBA in subcritical water, with a 70% isolated yield, leading them to believe that this route is probably more convenient for producing biobased MAA than the IA pathway, if a suitable green synthesis of 2‐HIBA is available. [ 76 ] Since it has been found that naturally occurring microorganisms produce polyhydroxybutyrate (PHB) via the formation of 3‐hydroxybutyrate (3‐HBA), recent efforts have been dedicated to stop these metabolic pathways to 3‐HBA and to extend them to its 2‐HIBA isomer ( Figure ). Evonik and Genomatica Inc. have been particularly active in this area.…”

A Review of the Biotechnological Production of Methacrylic Acid

“…Both 3-hydroxyisobutyrate (3-HIBA), derived from valine catabolism as discussed above, as well as its isomer 2-hydroxy-isobutyrate (2-HIBA), have been considered as biological end products (Volker and Schindelmann, 1969;Burgard et al, 2009;Rohwerder and Müller, 2010;Dubois et al, 2011;Burk et al, 2012;Marx et al, 2016). The conversion of 3-HIBA to MA has been reported with conversions from 20 to > 90% (Volker and Schindelmann, 1969;Marx et al, 2016) while the dehydration of 2-HIBA has been accomplished at conversion yields of 71.5% (Pirmoradi and Kastner, 2017). As mentioned above, 3-HIBA is a natural intermediate in valine catabolism.…”