Cleaner production: levulinic acid from rice husks

Abstract

Residual rice husks were used for the production of levulinic acid. By means of acidic depolymerization, glucose can be produced as an intermediate, in a process in which glucose is dehydrated to 5-hydroxymethylfurfural and subsequently generates levulinic acid. 1.00 g of rice husks was batch hydrolysed with 10.0 mL of 4.5% (v/v) HCl in a pressurized reactor (50–60 bar). The presence of levulinic acid in the hydrolysate, as well as that of 5-hydroxymethylfurfural and other concomitants, was investigated with the aid of LC-MS/MS; levulinic acid and 5-hydroxymethylfurfural were quantified by means of HPLC-DAD. Factorial design was employed to optimize the operational conditions and the highest yield of levulinic acid (59.4%, w/w) was achieved for Soxhlet aqueous extraction pretreated rice husks using 4.5% (v/v) HCl, 170 °C, 56 bar and 60 min. To the best of our knowledge, there have been no previous studies regarding the use of pretreated rice husks to produce levulinic acid by pressurized hydrolysis.