Ultrafiltration And Application Of Poplar Auto-catalytic Ethanol Lignin

Plants structure is formed by lignin, cellulose and hemicelluloses. Lignin is the secondlarge crude high-molecular material, hardly less than cellulose in quantity. However, thelignin itself polydispersity，as well as lignin molecules differences in degradation methods andthe degree of degradation in cooking process. Lignin molecular structure and molecularweight distribution is extremely uneven one. Molecular weight distribution from severalhundred to several thousands,. Its performance in different molecular weight will producedifferent effects. This makes it has not yet been fully and effectively utilized. How to makefull use of lignin? Turning waste into treasure, and this has important practical significancefor resource sustainable development.In this paper, poplar auto-catalytic ethanol pulping black liquor was fractionated bymeans of ultrafiltration, and the ultrafiltration operating conditions was discussed. Theoptimum conditions of ultrafiltration are: pressure0.20MPa, temperature60℃, stirring speed600r/min. The structural changes of lignin of different fractions were studied by IR. Result isindicated: lignin of different fractions contains essentially the same types of functional groups,and its content was regularly changed. With the increase in molecular weight of lignin, thecontent of phenolic hydroxyl, non-conjugated carbonyl, methoxyl were decreased.In this paper, Lignin-based retention and drainage aid of different molecular weights wasprepared by using the lignin of different fractions and the acrylamide. By the analysis ofLignin-based retention and drainage aid of different molecular weights IR: grafted productcontain-CONH2graft chain, and grafted chains and lignin molecules mainly ether bondconnectivity; with the increase in molecular weight, the content of-CONH2were reduced.Through tested Lignin-based retention and drainage aid of different molecular weights onretention and drainage effects showed that: for the molecular weight less than10,000fraction,with the increase in molecular weight, the ash and filler retention rate increased, beatingdegree decreased; For the molecular weight greater than10,000fraction, with the increase inmolecular weight, the ash and filler retention rate decreased, beating degree increased. Amongthem, the5000~10000fraction have the best retention and drainage effects, ash and filler retention rate reached17.96%and75.04%, as compared with a blank pattern, higher8.21and44.63percentage points; Beating degree was36°SR, as compared with the blank pattern,beating degree reduced by5degrees.In this paper, used formaldehyde proceeded modification on lignin of different fractionsin order to enhance the reaction activity of modification lignin. The effects of molecularweight of lignin on hydroxymethylation content were studied. The results showed that theincrease in molecular weight, the content of lignin hydroxymethylation decreased. The testcopolymerized lignin with PAE resin under alkaline conditions to prepare lignin-based paperwet strength agent, and studied the effects of molecular weight of lignin on the lignin-basedpaper wet strength agent performance. The results show that the increase in molecular weight,the paper wet tensile index and the wet bursting index gradually decreased.For the molecularweight less than5,000fraction, wet tensile index and the wet bursting index were11.02N m/gand1.29kPa m2/g, wet tensile index of retention rates and wet bursting index retention rateswere34.25%and46.8%, significantly higher than other fractions.Lignin-based sizing agent was synthesized in alkaline conditions taking lignin ofdifferent fractions and epoxy propyl dimethyl dodecyl ammonium chloride as raw materials.The test studied the effects of molecular weight of lignin on the lignin-based sizing agentperformance. The results show that the increase in molecular weight, sizing prformanceweakened. Molecular weight less than5000fraction have the best sizing results, the sizingdegree was42s. The effects of lignin-based sizing agent of different molecular weights on thepaper strength were studied. The results are listed as follows: Adding lignin-based sizingagent of different molecular weights and unclassified Lignin-based sizing agent to thecytoplasm sizing, the breaking length, tear index, burst index and folding resistance werehigher than the base paper without sizing; With the increase in molecular weight of lignin,the breaking length, tear index, burst index and folding resistance were decreased. Formolecular weight less than5000fraction, the breaking length, tear index, burst index andfolding resistance to the highest, compared with the blank pattern, were increased by25.3%,26.3%,15.9%and32.2%.