Cleaner production: levulinic acid from rice husks

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 degrees 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. (C) 2013 Elsevier Ltd. All rights reserved.