Study On Degradation Of Lignin Catalyzed By Solid Base Catalysts And The Synthesis And Modification Of Polyurethane

Though the degradation of lignin in alkaline solution can react, whichwill consume a higher concentration of alkali, products from degradation oflignin need a large amount of acid to neutralize the reaction solution. All ofabove can cause corrosion of equipments and uneconomy greatly. In order toefficiently catalyze degradation reaction of lignin, and for ideal alcohol phenoldegradation products with lower relative molecular mass and polyhydroxy,solid base has used as catalyst to catalyze degradation of lignin.The study adopts the isovolumetric impregnation method to prepare solidbase catalysts MgO/CaO, KOH/γ-Al2O3and KNO3/γ-Al2O3loaded intoγ-Al2O3as a carrier, MgO/SBA-15, KOH/SBA-15and KNO3/SBA-15loadedinto SBA-15mesoporous molecular sieve as a carrier. Phase, valence state andmorphology of catalysts were characterized by X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy(SEM).In this paper, examines catalytic effect of the solid base catalysts underdifferent preparation conditions on the degradation of lignin. The molecular structure and morphology of degradation products of lignin were characterizedby gel permeation chromatography (GPC), nuclear magnetic resonancespectroscopy (1H-NMR), ultraviolet spectroscopy (UV)，Fourier transforminfrared spectroscopy (FTIR) and scanning electron microscopy (SEM).The degradation products (alcohols and phenols with small molecularweight) used to synthez polyurethane by replacing parts of polyether polyols,while a little part wherein residual mixed system as a flame retardant forpolyurethane modification research. Molecule structure, oxygen index,residual carbon rate and morphology of the polyurethane after modificationwere characterized by thermogravimetric (DTG), fourier transform infraredspectroscopy (FTIR), oxygen index (OI), rate of residual carbon, scanningelectron microscopy (SEM) and other methods.The experiment found that under the conditions of loading, calcinationtemperature, calcination time of solid base catalyst optimized, the addingamount of0.10g/g lignin and adding5%phenol，Mw of degradation productswere reduced to below800, HN also generally increased to more than400.Preparation conditions of catalyst can influence the basicity of thecatalysts. Under optimal reaction conditions, the basicity of the catalysts havea direct effect on the catalytic degradation of lignin. With the basicity of thecatalysts increasing, catalytic effect of degradation of lignin is better and better.When beyond a certain limit, catalytic effect presents constant. Additionly, inthe same basicity, catalytic effect of solid base catalysts with SBA-15 mesoporous molecular sieve as a carrier is better than solid base catalysts withγ-Al2O3as a carrier, even CaO/MgO composite catalyst. The reason lies theintroduction of the mesoporous molecular sieve with larger aperture(1.5-10nm) can absorb lignin with macromolecular structure, which increasesthe effective contact area of the reactors, and improves the validity ofdegradation reaction of lignin from kinetic behaviors.After the polyurethane was modified by lignin-based flame retardant,oxygen index and residual carbon rate were both markedly improved. Weightloss temperature raises through the thermal analysis, besides the selfquenching time of modified polyurethane shortened from ignition test.Modification products of polyurethane with excellent flame retardantperformance have been gotten, and industrialization production can berealized shortly.