Liquefaction Of Chitin And Preparation Of Blending Material Based On Liquefied Products

Every year,there are as many as 6 to 8 million tons of marine products such as shrimp and crab shells are produced worldwide.Only a small amount is used for low value-added products such as animal feed,and most of them are discarded directly.It has caused serious environmental problems,at the meantime,it is also a waste of resources.Chitin is one of the main components in shrimp and crab shell waste.Because of its high-nitrogen content,it is favored by domestic and foreign scientific research workers.Since 1990s,liquefaction technology has been considered as one of the effective methods for utilization of biomass waste.In this paper,chitin is used as raw materials,and ethylene glycol and mixtures of PEG400/glycerol are used as solvents,respectively.Sulfuric acid is used as a catalyst to liquefy chitin under different reaction temperatures,liquefaction times and catalyst dosages.The optimal liquefaction conditions were obtained.Besides,at different reaction temperatures,the relationship between the residual rate of chitin liquefaction reaction and the reaction time was investigated.The reaction kinetics model was established to obtain the relationship between the reaction rate and the residue rate.Linear equations are fitted to explain the entire reaction using transitional state theory.The chitin liquefaction product was then blended with polyvinyl alcohol to form a film,and the blend film was characterized by means of infrared spectroscopy,scanning electron microscopy,thermogravimetric analysis,meanwhile,the antibacterial activity of the blending film was valuated.The main contents and innovations in this paper are as follows:The results indicated that a higher temperature,a larger catalyst dosage,or a longer reaction time was associated with a lower residue content.The optimum liquefaction conditions were obtained as:reaction temperature of 165 ℃,catalyst dosage of 1 mmol/g,liquid/solid ratio of 10:1 and reaction time of 120 min.Under these conditions,the residue rate was 51.7%.Analysis of liquefied products demonstrated that deacetylation of chitin was occurred during liquefaction.At different temperatures,the residual rate of chitin liquefaction reaction was decreased with the prolonged reaction time.The relationship between reaction rate and residue rate is obtained by the reaction kinetic model.Kinetic studies revealed that a complex multistage reaction was involved in liquefaction of chitin,having an apparent activation energy Ea=34₅ KJ/mol,a pre-exponential factor A=254.17 S-12,a mean enthalpy of energy△Hr=30.86 KJ/mol,the average activation entropy △Sr=-210 J/mol,and all the reactions were endothermic and their apparent reaction rates were constantly increased with raising temperature.The reaction system changed orderly with the input of external energy.In PEG400/glycerol mixed solvent system,the liquefaction rate of chitin was as high as 81%when the liquefaction temperature was 160 ℃,the liquid to solid ratio was 7:1,the catalyst amount accounted for 7.14%of the mixed solvent,and the reaction time was 90 min.Combined with FTIR,1H NMR and SEC analyses of LBMC,it was turned out that depolymerization and deacetylation reactions during liquefaction process,as well as the Mw and DD’ values of LBMC were determined as 5145 and 38%,respectively.The results of FTIR showed that LBMC was further successfully blended with PVA through some chemical and physical interactions between-OH,-NH2 and-NHAc groups in LBMC and-OH groups in PVA to form high-performance membranes.The optimum blend membrane with higher tensile and heat resistance than pure PVA membrane.In addition,blend membranes exhibited higher weight loss and better water resistance than pure PVA membrane,and the blend of LBMC into PVA could significantly enhance the antibacterial activity of the membrane.