Study on Clean Production Process of Furfural and Comprehensive Utilization of Biomass

Author:Sui Guang Hui

Supervisor:wang zi chen

Database:Doctor

Degree Year:2019

Download:23

Pages:149

Size:4921K

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In recent years,biomass resources utilization has attracted more and more attention,not only because biomass has wide sources and various types,but also can replace fossil resources to alleviate environmental problems.Accelerating the comprehensive utilization of straw resources is of great importance for stabilizing agricultural ecological balance,improving energy structure and reducing environmental pressure.Furfural is a biomass-based platform compound with broad application prospects,and it is also the precursor of biofuels.Therefore,it has great practical significance to develop a clean and green technology for furfural production.However,the traditional"one-step"production technology of furfural has low yield,high energy consumption and serious pollution problems.In order to promote the further development of furfural industry,this paper adopts a novel type"two-step"technology to produce furfural,namely hemicellulose hydrolysis,fixed bed catalytic dehydration-cyclization,gas phase neutralization.It was a continuous production process for furfural(chapter 2,chapter 3 and chapter 4).As the platform compound,furfural was used to synthesis phenol-furfural resin,phenol-glucose resin and phenol-xylose resin.This expands the field of furfural applications(chapter 5).For comprehensive utilization of biomass resources,the residue(refers to the residue of the rice husk hydrolysis)was carbonized and separated into carbon and silicon,which were made into capacitive carbon and calcium silicate whiskers(chapter 6).The specific research contents of this paper are as follows:1.Biomass hemicellulose hydrolysis.According to the different content of hemicellulose,corn cob was hydrolyzed once,straw and rice husk were hydrolyzed three times respectively.The optimized hydrolysis conditions were as follows:(1)corn cob hydrolysis were acid concentration 9.0 wt%,solid-liquid ratio 1:5,reaction time 2.0 h,reaction temperature 100℃,and the obtained xylose concentration was9.5 wt%,(2)corn straw were acid concentration 7.0 wt%,solid-liquid ratio 1:8,reaction time 2.5 h,and the obtained xylose concentration was 9.0 wt%,(3)and rice husk were acid concentration of 7.0 wt%,solid-liquid ratio of 1:8,reaction time of 2.0h,and the obtained xyose concentration of was 9.0 wt%.In addition,the kinetic study of corn cob hemicellulose hydrolysis showed that the activation energy of hemicellulose hydrolyzed by acid was 27.90 kJ/mol,and the activation energy of xylose degradation was 5.19 kJ/mol.2.Fixed bed catalytic dehydration-cyclization.This part mainly studied the effect of acid concentration,reaction temperature,xylose concentration,catalyst type and dosage on furfural yield.The order of influence of co-catalyst type on the furfural yield was Na2SO4<MgSO4<no catalyst<FeCl3·6H2O<ZnCl2<MgCl2·6H2O<NaCl,and the highest yield of furfural achieved 74.1%.The results showed that high concentration of H+inhibited the hydrolysis of Lewis acid(strong acid and weak base salt),so it had no significant effect on the yield of furfural.The fixed bed catalytic conditions optimized by orthogonal experiment were acid concentration 2.5 mol/L,reaction temperature 170℃,xylose concentration 10.0 wt%,sodium chloride 70 g.Using xylose liquid,corn cob hydrolysate,corn straw hydrolysate and rice husk hydrolysate as raw materials,the furfural yields achieved 74.3%,73.7%,73.1%and73.1%,respectively.The study of furfural separated by N2 showed that the N2contributes to the escape of furfural steam from the reaction system.3.Furfural steam gas phase neutralization.This process solves the acidity problem of furfural steam,studies the influence of neutralizer type,neutralizer concentration and reaction temperature on the yield and acidity of furfural,and the acid recycling was also studied.The results showed that different metal cationic neutralizer had little effect on the yield of furfural.The effect order of different anionic neutralizer on the yield and acidity of furfural was SO42->Cl->CO32->OH-.For considering the neutralizer cost and acid recycling,this paper chose sodium sulfate as neutralizer.The solution after the neutralization was adjusted the acidity and sodium chloride content,and then was used in the fixed bed catalytic dehydration-cyclization as the catalyst,of which the yield of furfural achieved 72.6%.4.Furfural application.Furfural was applied in synthetic resins as a platform compound.The optimum parameters of phenol-furfural resin were determined by orthogonal experiment,with the molar ratio of phenolic aldehyde 1:1,the alkali content of phenol 28 wt%,alkali concentration 20 wt%,reaction temperature 70℃ and reaction time 2.5 h.Phenol-furfural-glucose resin,phenol-glucose resin and phenol-xylose resin were synthesized by replacing furfural with glucose and xylose.The synthetic resins were characterized and a possible formation mechanism of the resin was proposed.When the resin was used as wood adhesive,the bonding strength of phenol-furfural-glucose adhesive(mfurfural:mglucose=1:1)achieved 0.85 MPa.5.High efficiency utilization of xylose residue.This part chose the residue of rice husk hydrolysis(mainly containing cellulose,lignin and SiO2)as raw material.The residue was treated by carbonization,separation and activation,resulting obtained capacitor carbon.The specific surface area,pore structure and electrochemical properties of the capacitor carbon were characterized.The results showed that C2activated with 15 mL 8.0 wt%NaOH solution had the maximum capacitance of 77.3F/g,the specific surface area of 950 m2/g,the pore volume of 0.72 cm3/g,and the capacitance retention rate of more than 99.0%after 5,000 cycles of constant current charge and discharge.The separated silicon was converted into a calcium silicate whisker by hydrothermal method.The results showed that the calcium silicate whisker broom-like crystal,and had good thermal stability.From the above,this paper provides a novel project for the clean production of furfural.That is a new technological route which is feasible in technology,environmental protection and economy.