Experimental studies for levulinic acid production from whole kernel grain sorghum

Levulinic acid has potential as an important basic chemical material. This study proposed a method of making levulinic acid using abundant and low cost whole kernel sorghum grain as the raw material. Flour made from grinding whole kernel sorghum grains was blended with 2%, 5% and 8% aqueous solutions of sulfuric acid. Mixtures were heated to 160 or 200 °C in a pressurized reactor. A stepwise heating scheme helped improve the yield of levulinic acid. Levulinic acid yield was determined based on sorghum flour content, as opposed to total sorghum mass. Levulinic acid yield increased as reaction temperature increased. Higher sulfuric acid concentration also significantly increased the levulinic acid yield. However, flour loading had an adverse effect on levulinic acid yield. A maximum yield of 32.6% levulinic acid was achieved at 200 °C, 8% sulfuric acid concentration and 10% flour loading. A linear regression model was capable of predicting the levulinic acid yield with respect to effects of reaction temperature, mineral acid concentration and flour loading (R2=0.88).