Sustainable production and purification of furfural from waste agricultural residue: An insight into integrated biorefinery

Furanic chemicals are the most significant renewable bio-chemicals with furfural being the basic platform chemical that can serve as a viable alternative to replace several petroproducts. Industrial furfural production poses several drawbacks such as poor yields, highly toxic effluents, energy intensive operations and accumulation of low value solid residue that restricts its tremendous potential. In this purview, the present research maneuvered a two-step translation strategy of corncobs, an abundant agricultural residue to furfural in a cost effective as well as environmental benign manner. Initially, the corncob is hydrolyzed using an aqueous low transition temperature mixture (LTTM) that selectively converts xylan in the lignocellulose matrix to xylose without disrupting the remaining biopolymers. The obtained xylose solution is enriched through strategic recycle of the hydrolysate with a cumulative yield of 76% after four cycles which is a potential substrate for subsequent xylose dehydration without any additional catalyst. Interestingly, autocatalysis in the LTTM media could yield 70% of theoretical furfural using nitrogen as a stripping media with 44% lower dilution of the furfural condensate. Furfural is further purified through an ecofriendly extraction technique utilizing hydrophobic deep eutectic solvents (HDES) as an effective extractant with the highest distribution coefficient being 66.2 for 1-tetradecanol and thymol based HDES portraying 98.6% recovery. The proposed furfural production process exhibits 13.8% overall yield with respect to corncob and 30% higher recovery of cellulose in the pretreated residue compared to conventional route which presents a high value integrated biorefinery with environmental compatibility.