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.

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Continuous hydrogenation of aqueous furfural (4.5%) was studied using a monolith form (ACM) of an activated carbon Pd catalyst (∼1.2% Pd). A sequential reaction pathway was observed, with ACM achieving high selectivity and space time yields (STYs) for furfuryl alcohol (∼25%, 60–70 g/L-cat/h, 7–15 1/h liquid hourly space velocity, LHSV), 2-methylfuran (∼25%, 45–50 g/L-cat/h, 7–15 1/h LHSV), and tetrahydrofurfuryl alcohol (∼20–60%, 10–50 g/L-cat/h, <7 1/h LHSV). ACM showed a low loss of activity and metal leaching over the course of the reactions and was not limited by H2 external mass transfer resistance. Acetic acid (1%) did not significantly affect furfural conversion and product yields using ACM, suggesting Pd/ACM’s potential for conversion of crude furfural. Limited metal leaching combined with high metal dispersion and H2 mass transfer rates in the composite carbon catalyst (ACM) provides possible advantages over granular and powdered forms in continuous processing.

Pd-TiO2, Pd-Cu and Pd-Fe activated carbon (AC) supported catalysts were employed for continuous selective hydrogenation of furfural. Effect of reaction parameters on product selectivity and space time yield (STY) was...