Preparation of polyurethane from lignin and crude glycerol

Abstract

Polyurethane foam (PUF) was prepared by a novel approach, using a renewable polyol derived from only biofuel production by-products, lignin and crude glycerol. This could potentially be a high value bio-refinery application for the two byproducts from cellulosic ethanol and biodiesel production, respectively.Renewable polyols were synthesized by the liquefaction of lignin in crude glycerol.Three different technical lignins were individually employed to preparepolyols viz.: kraft lignin, lignosulfonates and organosolv lignin.Water-blown polyurethane (PU) foam was prepared by reacting the polyols with commercial diphenylmethane-4,4'-diisocyanate (MDI). The PUF had compressive strength which conform to industry requirements for thermal insulation [1]. The PUF had renewable content as high as 44 wt%.A major benefit of these renewable polyols is that PUF could be prepared without the need to add any petroleum derived polyols. Making use of lignin instead of untreated agricultural residues i.e. lignocellulose, enables the production of both biopolyols and cellulosic ethanol.The structural differences of technical lignins clearly have a significant influence on the ensuing PU properties. Biomass pretreatmentmethods and species therefore need to be selected with consideration to their effect on lignin properties if the high lignin content present in many biomass types are to be exploited