The Preparation Of Reed Ethanol Lignin-resin Composite Material

With the rapid development of industry and environmental concern about today's society continues to heat up,more and more studies are focusing on the development of sustainable or biodegradable materials.The autocatalytic ethanol pulping cooking process can product acetic acid acting catalyst spontaneously to reduce pharmaceutical pollution,meanwhile ethanol is non-toxic and easy for its recovery,thus it can solve the pollution problems of the conventional pulping drastically.Sugar,formic acid,acetic acid,levulinic acid,furfural and other components separated from ethanol pulping waste liquor after separation and purification can be used as a number of platforms in chemical synthesis with high potential value.The enzymolysis-mild acid hydrolysis method was used to extract lignin and the purification process optimization was carried at the same time.This paper uses three factors and three levels orthogonal experiment to optimize the cellulase enzymolysis process of extracted lignin.The results showed that the order of primary and secondary factors which effects cellulase enzymolysis was: pH value>enzyme dosage> reaction temperature.Combined with conditions experiment,the better technology were that the pH value was 5.5,the enzyme dosage was 10U/g,and the reaction temperature was 40 ?.Under the condition aforementioned,cellulase enzymolysis lignin relative purity was 92.25 %,3 percent higher than extracted lignin.Studies suggested that the order of primary and secondary factors which effects xylanase enzymolysis was: pH value> enzyme dosage> reaction temperature.Taking conditions experiment into consideration,we came to the conclude that the better enzymolysis technology was that the pH value was 5.5,the enzyme dosage was 10U/g,and the reaction temperature was 45 ?.In this condition,xylanase enzymolysis lignin relative purity was up to 96.85%,which was 6% higher than extracted lignin,and the remaining experimental group lignin relative purity also reached around 95%,indicating that the impurities type in reed ethanol extracted lignin was mainly hemicellulose.Analysis about cellulase and xylanase enzymatic hydrolysate was carried out separately by ion chromatography,the better level of enzymatic hydrolysis of cellulase was as follows: pH value was 5.5,the enzyme dosage was 10U/g,and reaction temperature 40 ?.The better level of xylanase enzymolysis levels was as follows: pH value was 5.5,the enzyme dosage was 10U/g,and the reaction temperature was 45 ?.The two enzymatic conditions both consistent with the characterization of the relative purity,confirmed the reasonableness of the experimental design.In a better level of extracted lignin hydrolysis,the extracted lignin were separated two groups,one treated with cellulose and lignin and xylanase separately,the other treated jointly.The results showed that the impurity removal of combined enzymatic hydrolysis lignin was 2% higher than the separate group,relative purity increased by about 1.6%.So for the enzyme purification process of reed ethanol extracted lignin,joint enzymatic hydrolysis was a better choice.Determination of the content of lignin phenolic hydroxyl and carboxyl functional groups by non-electric conductivity titration indicated that in ectracted lignin,phenolic hydroxyl content was 5.06%,which was 3.03% higher than the natural reed lignin.After treated by enzymatic hydrolysis,lignin was dealed with 0.01 mol/L hydrochloric acid in pyridine water mixed solvent for 2h.Mild acid hydrolysis lignin were neutralised by two kinds of alkaline,NaOH and NaHCO₃.Acid precipitation of lignin in subsequent process of system neutralised by NaHCO₃ would occur delamination that means both upper and lower levels was lignin precipitation while the middle layer was clear and transparent.This phenomenon can not be seen in NaOH neutralization system in which the precipitation of lignin were all in the bottom of the solution with a colour of dark brown.This phenomenon provides a new idea for black liquor lignin separation.Acid-precipitated lignin of NaOH neutralization system content of carboxyl and phenolic hydroxyl functional group and is slightly lower than NaHCO₃ neutralization system,but both were lower than extracted lignin.With maleic anhydride as modifier,enzymatic hydrolysis lignin esterification modification was accomplished.To characterize the modification effect of lignin,peak area methods of the infrared quantified method was used.Preferable process proceeds was as follows: modification reaction time was 7h,mass ratio of lignin and maleic anhydride?maleic anhydride?was 1:2,and modified temperature was 60?,under these conditions a higher grafting rate can be obtained.Using MAH-g-PP as the coupling agent,the amount optimization of wood flour in PPWood meal system was carried out,30% wood powder was optimum.In this case,the maximum tensile strength of the composite material was 42.61 MPa,yield strength and fracture strength was also the highest,respectively 42.60 MPa and 27.81 MPa.Flexural strength and impact strength were both lower than pure PP,respectively 0.53 J ??cm²?^-1 and 62.51 MPa.TGA tests showed the purified lignin thermal stability decreased slightly relative to extracted lignin while the acid hydrolysis lignin thermal stability increased a little.TGA test on MAPP-PP wood flour composite showed that maximum weight loss temperature of seven kinds composite were all at 440 ?.Only pure PP material had one loss rate peak,while the rest of the group had two more than pure PP material because of the wood flour and MAPP's adding.Extracted lignin,purified lignin and modified lignin were performed characterization of FT-IR.Results showed that for extracted lignin,the cellulase and xylanase enzymatic hydrolysis will shift-OH stretching vibration peak and carbonyl stretching vibration peak of the non-conjugated offset,the remaining peak position did not change.In addition,the modified lignin-OH stretching vibration occurred a right shift,while 1708 cm^-1 ester peaks was a evidence which confirmed the esterification had really happened.The modified lignin used as the coupling agent was applied to the Wood flour-PP system,through tensile,impact,flexural strength and other indicators,its effects were characterized.The results suggested that the modified lignin can be used as a partial substitute for MAPP,but it was subject to the effective control of the added amount of modified lignin.Comparative study of the thermal stability of the various composites were completed by TGA.The results showed that composites stability of 2.5% modified lignin conbined with 2.5% MAPP as a coupling agent was weaker than the other three groups.When modified lignin was used alone,the thermal properties of the material added with 2.5% or 5% can be comparable with 2.5% MAPP.Scanning electron microscope photos showed a lot of wood flour particles attached to the thrust plane surface of the wood flour-PP material for coupling agent was not added,and the bonding strength was also weak too.With 5% MAPP as coupling agent,when the amount of wood flour was 30% the surface material was preferably combined.A high smoothness surface was found in sample of 2.5% modified lignin combined with 2.5% MAPP used as coupling agent,meanwhile there had some resin coated layers indicating compound coupling agent showed a better coupling effect than modified lignin or MAPP used alone.