One-step fabrication of carbonaceous solid acid derived from lignosulfonate for the synthesis of biobased furan derivatives.

An eco-friendly and low-cost lignosulfonate-based acidic carbonaceous catalyst (LS-SOH) was effectively fabricated using the sulfite pulping by-product of sodium lignosulfonate as a precursor by facile one-step simultaneous carbonization and sulfonation, and employed for the synthesis of promising biofuel furan derivatives from biorenewable feedstocks. The catalyst preparation conditions significantly affected the preparation and properties of LS-SOH. A relatively high catalyst preparation yield (40.4%) with strong -SOH density (1.33 mmol g) were achieved when the lignosulfonate was treated in concentrated HSO solution at 120 °C for 6 h. The preparation yield of LS-SOH was nearly twice as much as that of one-step prepared catalyst using alkaline lignin (another technical lignin from pulping) as a precursor. The as-prepared LS-SOH had similar textural characteristics to the frequently-used two-step prepared carbonaceous catalyst involving pyrolysis carbonization and sulfonation. LS-SOH was found to show good catalytic activity for the synthesis of 5-ethoxymethylfurfural (EMF) in ethanol medium, affording around 86%, 57% and 47% yields from 5-hydroxymethylfurfural (HMF), fructose and inulin, respectively. Also, a high HMF yield of 83% could be obtained from fructose when DMSO was replaced as reaction medium. The used LS-SOH was readily recovered by filtration, and remained active in recycle runs.