Study On The Preparation Of 5-hydroxymenthyfurfural From Corn Stalk-based Cellulose

The synthesis platform compound 5-hydroxymethylfurfural(5-HMF)from lignocellulosic such as corn stalks has been extensively studied owing to its extensive range of sources,economic and environmental protection.However,the complex structure of lignocellulose limits its large-scale industrial application.In order to break the structure of lignocellulose and improve its chemical reaction performance,this paper pretreated corn stalks in a targeted manner,and then prepared 5-HMF through chemical conversion,and discussed the reaction mechanism of the conversion process.First of all,this article explored the effect of NaOH dosage,reaction solid-liquid ratio,reaction time and 1,4-butanediol content in NaOH/1,4-butanediol pretreatment on cellulose recovery,lignin removal rate and recovery rate.Through component analysis,it was concluded that:(1)The removal rate of lignin increased with the increase of the amount of NaOH and the reaction time,first raised and then reduced with the raise of the solid-liquid ratio,and reduced with the raises of the alcohol content.(2)The recovery rate of lignin first increased and then decreased with the increase of the four factors;(3)The recovery rate of cellulose first increased and then decreased with the increase of the amount of NaOH,alcohol content and reaction solid-liquid ratio.As the reaction time increased,it first increased and then decreased.And further analysis and characterization of the degree of polymerization,SEM,XRD and FT-IR confirmed that the surface morphology of the corn stalks became rough after the pretreatment,the cellulose macromolecular chain was broken,the lignin and hemicellulose were removed,and the intermolecular hydrogen bonds of cellulose were broken.Then,using fructose,glucose,microcrystalline cellulose and corn stalk-based cellulose as raw materials,the catalytic performance of the four catalysts of zirconia,phosphotungstic acid,chromium chloride and ruthenium chloride were compared,and the results showed that the best catalyst was ruthenium chloride.By optimizing the reaction conditions,the best reaction conditions were obtained.The best reaction conditions are as follows:reaction solvent was DMSO,220℃,2.5 h,solid-liquid ratio was 1:25,catalyst concentration was 0.125 mol/L.Furthermore,the corn stalk-based cellulose obtained with different pretreatment intensities was used as the raw material,and the above-mentioned optimal reaction conditions were used to prepare 5-HMF.The results showed that the 5-HMF yield and cellulose conversion rate were both higher than those without pretreatment.And both increased with the increase of pretreatment alkali dosage and reaction time,decreased with the increase of alcohol content,and first increased and then decreased with the increase of pretreatment reaction solid-liquid ratio.The significant effects on 5-HMF yield and cellulose conversion rate were:NaOH dosage,1,4-butanediol content>reaction solid-liquid ratio>reaction time.Finally,the reaction mechanism of ruthenium chloride catalyzed by corn stalk-based cellulose was discussed:(1)Ru3+coordinated with the oxygen atom of the C-O-C bond in cellulose to cause acetal hydrolysis to degrade cellulose into glucose;(2)Ru3+is coordinated with the oxygen atom of the glucose hemiacetal part and the nearest-OH to form an alkene glycol intermediate through 1,2-hydrogen transfer;(3)the alkene glycol intermediate is isomerized to fructose;(4)fructose is dehydrated to form 5-HMF.