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

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.

Automated summary

A novel one-step process for producing levulinic acid from furfural over hierarchical zeolites in a microwave reactor is reported. The conversion and product distribution are influenced by formalin concentration, catalyst properties, and heating mode. A critical formalin concentration of 20 wt% is identified, with higher conversion and yield over H-zeolite compared to Na-zeolite.