Study On Hydrogenolysis Of Lignin To Prepare Phenolic Resin Foamed Material

High value utilization of biomass has attracted much attention with the rapid consumption of energy and the aggravation of environmental pollution.Lignin is the only renewable resource with aromatic structure and has great potential in the production of phenolic compounds and fuels.However,because of the irregular natural polymer structure of lignin,the yield of phenolic monomers and liquid products decreased with the occurrence of repolymerization during lignin degradation.If lignin can be efficient degraded by catalysts and the repolymerization reaction can be inhibited,the possibility of lignin to produce the high-additional chemicals will be improved.Catalysts with different properties were prepared by solid-state synthesis using tannin and lignin as carbon sources in this study.The effects of different carbon sources,catalyst proportion and reaction conditions on the hydrogenolysis of lignin were discussed.After that,phenolic resin was prepared by partially replacing phenol with lignin hydrogenolysis products.The resin was used to prepare foamed material and to study its flame retardancy,realizing the high value utilization of biomass resources.A series of Ni-supported mesoporous catalysts were synthesized by ball milling with tannin,organosolv lignin,alkaline lignin and dealkaline lignin as carbon sources and F127 as template compound.The synthesis process had the advantages of low cost,solvent free,rapidity and simplicity,and the nickel salts in the catalyst could be reduced to nickel nanoparticles by ortho-carbon in N₂ atmosphere without further reduction with H₂.Among them,the Ni/MC catalyst prepared by tannin had the larger pore size,smaller particle size and the highest catalytic activity.After catalytic hydrogenolysis of lignin for 6 h under 280?,50ml ethanol and 2 MPa H₂,the hydrogenolysis products yield,solid residue and the maximum yield of phenolic monomers were 83.7 wt.%,3.7 wt.%and 22.4 wt.%,respectively.Moreover,solid residue would be eliminated when the temperature reached 300?.Meanwhile,the molecular weight of the lignin hydrogenolysis products was small?678 g/mol?and its dispersity was low?1.26?.Elemental analysis showed that the O/C ratio decreased while the H/C ratio increased,and the calorific value of the lignin hydrogenolysis products was as high as 30.56 MJ/kg.This indicated that lignin was efficiently depolymerized into phenolic monomers and oligomers,inhibiting the repolymerization reaction.The effects of hydrogenolysis products substitution rates and different kind of lignin substitution for phenol on phenolic resin were compared.The experimental results showed that when 50%hydrogenolysis products substituted for phenol,the resins not only conformed to the national standard in free aldehyde content,free phenol content and solid content,but also had a moderate viscosity and suitable for the preparation of foamed material.The mechanical properties and flame retardancy of phenolic foamed material were optimized after adding lignin.The compressive strength increased from 0.25 MPa to 0.38 MPa,and the limiting oxygen index increased from 36.6%to 39.5%.Simultaneously,the material had uniform pore size and low perforation rate.Lignin based phenolic foamed material was modify with three component composite flame retardant?10%MP,10%expansible graphite and 10%aluminum hydroxide?,the limiting oxygen index was as high as 48.2%,and other properties were better than pure phenolic foamed material.