Novel One-Step Process for the Production of Levulinic Acid from Furfural over Hierarchical Zeolites in a Microwave Reactor

摘要

Here, a novel one-step process is reported for the production of levulinic acid (LA) from furfural over hierarchical zeolites in a microwave reactor. The furfural conversion and product distribution are determined as a function of formalin concentration (C-F) in water, catalyst properties, and heating mode. 20 wt% formalin is found to be the critical concentration, above and below which the 5-hydroxymethylfurfrual and the LA are formed, respectively. The conversion and LA yield over H-zeolite are higher by 2.3 and 17 times, respectively, as compared to those over Na-zeolite. The Bronsted to Lewis acid sites ratio is found to be a crucial catalytic parameter to obtain the best activity and LA yield. Under optimal reaction conditions and with the best catalyst, 42% LA yield is obtained at 90% furfural conversion. The humins formed during the process are characterized using Fourier transformed infrared spectroscopy and thermogravimetric analysis. The humins yield, functionality, and decomposition temperatures are varied with both C-F and catalyst properties. The reaction pathways and intermediates are also postulated. The integration of the developed process/route with the existing C6 routes allows the utilization of the entire carbohydrate content of the lignocellulosic biomass to produce LA, and consequently, the overall process becomes more economical.