Effects of formaldehyde on fermentable sugars production in the low-cost pretreatment of corn stalk based on ionic liquids

Low cost processing of lignocellulosic biomass is of great importance for sustainable chemistry and engineering. Herein, a low cost system composed of 1-butyl-3-methylimidazolium chloride ([C₄C₁im]Cl), HCl and formaldehyde (FA) was developed for the pretreatment of corn stalk at 80 °C. The efficiency of this technology was compared with that in dioxane system or without FA addition. Due to FA stabilization, the extent of acid-hydrolysis of carbohydrate fraction can be significantly decreased while 70% above of lignin was removed with the pretreatment of [C₄C₁im]Cl/HCl/FA system at 80 °C for 2 h. A maximum reducing sugar yield of 93.7% and glucose concentration of 7.0 mg⋅ml⁻¹ were subsequently obtained from enzymatic hydrolysis of the slurry. There were great differences in compositions of small molecule degraded products obtained with FA addition or not. The present [C₄C₁im]Cl based system exhibits great potential of substituting volatile organic solvents (i.e. dioxane) in developing low cost lignocellulosic biomass pretreatment at low temperature. Also, this work would gain insight into understanding on the roles of stabilization methods on the economic improvement of IL based biomass processing.