Preparation And Application Of Sodium Carboxymethyl Cellulose With High Substitution Degree By Poplar Fermentation Cellulose Residue

At present,cotton and hemp with high cellulose purity are mostly used to prepare Sodium carboxymethyl cellulose(CMC-Na,the same below)in industry.However,because of the high price of cotton and hemp raw materials,the production cost of CMC-Na must be increased.Poplar is a fast-growing woody plant,and China’s poplar production area is vast and rich in resources.The production of CMC-Na from poplar residue after steam explosion,enzymatic hydrolysis and fermentation not only reduces the production cost and material constraints,but also reuses the poplar residue after ethanol production,increases its added value and helps to improve economic development.In this paper,poplar pulp board cellulose was used as raw material to optimize the preparation process on the basis of multiple alkalization and etherification,so as to explore the best process route for preparing CMC-Na with high degree of substitution.The effects of alkalization time and temperature,dosage of alkalinizer,etherification time and temperature,dosage of etherifying agent,ultrasonic and high-speed shearing AIDS on the degree of substitution of CMC-Na were investigated,and the process route for preparing CMC-Na with high degree of substitution was explored,and then the process was optimized by orthogonal test.Then poplar wood residue after steam explosion,enzymatic hydrolysis and fermentation to produce bioethanol was used as raw material,and the optimum technological conditions for separating cellulose from poplar wood residue are explored.Then the cellulose from poplar wood residue was used as raw material to prepare CMC-Na with high degree of substitution by using the optimized process route of preparing CMC-Na with high degree of substitution,and then the substitution degree,viscosity and Na+content of CMC-Na prepared from the two raw materials were compared.Carboxymethyl cellulose lithium(CMC-Li)was prepared from poplar residue cellulose,poplar pulp board cellulose,refined cotton cellulose,chemical pure CMC-Na by different methods(hereinafter referred to as CMC-Li).The effects of reaction time and temperature on the degree of substitution of CMC-Li at each stage under different methods were explored,so as to determine the optimum preparation method of CMC-Li and the optimum technological route under this method.Finally,the protective effect of CMC-Na solution on vitamin Vc was explored and compared with inorganic salts and other solutions.The main experimental results are as follows:1.Popalar residue after steam explosion,enzymatic hydrolysis,and fermentation to produce bioethanol was put into hot water at 90℃and stirred for 3hour before dried.Dried after refluxed in acidic detergent at 95℃ for 1 hour;then reacted for 2.5 hours at NaOH concentration of 45 g/L,material-liquid ratio of 1:40,reaction temperature of 70℃,and dried after washed;and then stirred for 90 minutes in 10%NaOH solution at 70 ℃(solid-liquid ratio of 1:40),At last,Poplar residue cellulose was obtained by stirred and refluxed in 70℃ 15%H2O2 solution(solid-liquid ratio 1:20)until the powder was pale yellow,filtrated and washed to neutral and then dried.The structure of the samples was determined by infrared spectroscopy and solid state nuclear magnetic resonance.2.Poplar oar board cellulose wasused as raw material,The optimized process route of alkalization and etherificationn is as follows:first alkalinization time is 60 minutes at room temperature,second alkalinization and first etherification reaction time is 30 minutes at 50℃ third alkalization and second etherification reaction time is 90 minutes at 70℃,sodium chloroacetate dosage:NaOH dosage:alkaline cellulose dosage=1.4:1:1;after pretreatment and twice etherification three alkalinization.The degree of substitution of the product was 1.33 and the viscosity was 404.0 mPa·s.In the process of alkalization and etherification,after alkalization at room temperature,high-speed shear dispersion was used for 10 minutes(A grade),after first etherification,ultrasonic treatment was used for 10 minutes(49KHz,power 99%).The degree of substitution of the final product increased from 1.33 to 1.48,but the viscosity decreased from 404.0 mPa.s to 181.9 mPa·s.3.Poplar residue cellulose used as raw material,and the above process was utilized to prepare CMC-Na.The substitution degree and viscosity of CMC-Na,which Prepared bybleached poplar residue cellulose,were 0.77 and 334.8mPa·s.The substitution degree and viscosity ofCMC-Na,which Prepared byunbleachedpoplar residue cellulose,were 0.67 and 286.6 mPa·s.The substitution degree and viscosity of CMC-Na,which prepared by refined cotton and used above process,were 0.59 and 256.5mPa·s.4.Poplar residue cellulose,Poplar oar board cellulose and refined cotton cellulose were used as raw materials respectively,the process route mentioned in 2 was adopted,and sodium chloroacetate and sodium hydroxide were replaced by lithium chloroacetate and lithium hydroxide to prepare poplarCMC-Li.The substitution degree and Li+content of poplar CMC-Li respectively were 0.349,1.65mg/L;0.563,1.86mg/L;0.485 and 1.75mg/L.5.Carboxymethyl cellulose lithium(CMC-Li)was prepared from Chemical PureCMC-Na by acidification and lithium substitution.In acidification stage:absolute ethanol was used as reaction medium,98%concentrated sulfuric acid(mass ratio 1:0.27)was slowly dripped at 70℃,ultrasonic stirred for 2 hours;Lithification stage:absolute ethanol was used as reaction medium,12%lithium hydroxide solution(mass ratio 1:0.22)was slowly dripped at 70℃,ultrasonic treatment and stirred for 2 hours.Then CMC-Li was prepared from CMC-Na prepared from different raw materials.The substitution,viscosity and Li+content of CMC-Li prepared from different raw materials were compared.Finally,the structure of CMC-Li was determined by infrared spectroscopy.6.Different concentrations of CMC-Na,β-CD,PEG(400,600),NaCl,KCl,MgCl2,NaBr and 0.01g/L Vc mixed solutions were allocated.The experimental results show that 1 mol/L NaCl solution has the best protection effect on Vc,followed by 0.2 g/L CMC-Na solution.When the concentration of NaCl solution is 0.2g/L,the protection effect is much worse than that of CMC-Na solution.The amount of dissolved oxygen in the above solutions is correlated with the stability of VcThe species and concentration of ions in inorganic salt solution have an effect on dissolved oxygen,while the relative viscosity of CMC,PEG and β-CD solution has an effect on dissolved oxygen.