Lignosulfonate-based macro/mesoporous solid protonic acids for acetalization of glycerol to bio-additives

The enclosed paper introduces a novel, scalable and environmentally benign process for making strongly acidic solid meso/macroporous carbon catalysts from Na-lignosulfonate (IS), a byproduct from sulfite pulping. Ice-templated LS was converted to strongly acidic macro/mesoporous solid protonic acids via mild pyrolysis (350-450 degrees C) and ion/H+ exchanging technique. The synthesized materials Were extensively characterized by FT-IR, Raman, XRD, XPS, TGA, FE-SEM, TEM and N-2-physisorption methods. These LS derived materials exhibited a macro/mesoporous and highly functionalized heteroatom doped (O, S) carbon structure with large amounts of surface -OH, -COOH and -SO3H groups similar to the sulfonated carbon materials. Further, these carbon materials showed excellent potential as solid acid catalysts upon acetalization of glycerol with various bio-based aldehydes and ketones (acetone, methyl levUlinate and furfural), easily outperforming the commercial acid exchange resins (Amberlite (R) IR120 and Amberlyst (R) 70). Most importantly, the optimum LS catalyst exhibiting a large specific surface area demonstrated exceptional potential for continuous solketal production (liquid phase atmospheric pressure operation) maintaining its activity (glycerol conversion >= 91%) and structural features even after 90 h time on stream.