Corn Bran Hemicellulose Hydrolysis Catalyzed By Solid Acid Catalyst And Comprehensive Utilization

Corn bran is the main by-product of starch by wet grinding method,it accounts for 10%¹4%?dry basis?of corn raw material.Corn bran was main applied to feed industry that caused exceedingly waste and low additional value.Corn bran is called corn fiber as the non-starch content of corn,it is the epidermis part of corn kernel and it is made up by cellulose,hemicellulose,protein,fat,a small amount of ash and other microconstituents.Hemicellulose is the main constituent of corn bran,it is made up by hexose and pentose which include xylose,arabinose,glucose mannose and galactose.These sugars cann't be fermented by distillery yeast,but those can be used to product feeding yeast,furfural and xylitol etc.It has very high added value and wide range of potential applications.For now,inorganic acid?sulfuric acid,hydrochloric acid,oxalic acid,etc?were used to hydrolyze hemicellulose of corn bran.These inorganic acids have inexpensive price and good catalytic effect,but they could caused environmental pollution and could not be reutilized.Solid acid is a new type acid catalyst which was been researched and development in recent years,it is friendly to the invironment and has extensive industrial application prospet.The study of solid acid has very important meaning,it has become one of the hot spots.SO₄^2-/Mx Oy type solid acid has such good features,for example,high acidity,high activities,highly selective,non-corrosive,low pollution,easy separated from product and environmentally-friendly,etc.It was wide range used to various kinds of chemical reactions.It was not reported about SO₄^2-/Mx Oy type solid acid catalyst to catalyze hydrolysis of hemicellulose of corn bran,this acid catalyst greatly overcame disadvantages of other catalysts.This paper studied the preparation of SO₄^2-/Fe₂O₃/?-Al₂O₃ support-type solid acid catalyst which prepared by Fe₂?SO₄?₃ as precursor and ?-Al₂O₃ globules as carrier.Used the catalyst to catalyze the hydrolysis of corn bran hemicellulose,the hydrolysis products?hydrolysate,solid residue?were utilized.A new process route was developed of corn bran comprehensive utilization,it provide ideas and methods for corn bran and even by-products of other agricultural products,it has important realistic significance and research value.1.The main points of study?1?Studies on preparation technology of SO4/Fe₂O₃/?-Al₂O₃ support-type solid acid catalyst and characterization analysis of catalyst.?2?Studies on reaction technology of corn bran hemicellulose hydrolysis catalyzed by SO₄^2-/Fe₂O₃/?-Al₂O₃ support-type solid acid catalyst and reaction kinetics.?3?Studies on reaction technology of furfural made from hydrolysate of corn bran hemicellulose and reaction kinetics.?4?Studies on technology of cellulose'extract by alkali hydrolysis method from solid residue which was obtained from hydrolysis.?5?Studies on technology of preparation MCC from cellulose by acid hydrolysis method and characterization analysis of product.?6?Studies on preparation of blend films which contain MCC from corn bran and characterization of films.2.Results of studies?1?The total sugar content as index,the optimum preparation conditions of SO₄^2-/Fe₂O₃/?-Al₂O₃ solid acid catalyst were abtained : calcination temperature was 500??calcination time was 4h ? the capacity of Fe was 6%,Fe₂?SO₄?₃ solution maceration temperature was 60? ? Fe₂?SO₄?₃ solution maceration time was 3h,H2SO4 solution concentration was 1mol/L.The catalyst were characterized by XRD?XPS et al,the results indicated that,Fe₂O₃ of catalyst existed in ?-Fe₂O₃ form.The Fe₂O₃ particles which had uniform size was highly dispersed on the carrier surface evenly.Calcination was the key step to make the catalyst generate acidity.The XRD?XPS?TG-DTA?SEM-EDS?NH3-TPD?FT-IR characterization results showed that enhance the calcination temperature was advantageous to Fe₂O₃ crystallization,the specific surface area and activity of catalyst declined simultaneously followed the largen of Fe₂O₃ crystal particle.The calcination temperature been enhanced could destruct the framework structure of catalyst,which could make the SO₄^2-drain as sulfur oxides and the amount of acid sites decline,the activity of catalyst declined.The calcination temperature of catalyst would not exceed 500?.?2?Used SO₄^2-/Fe₂O₃/?-Al₂O₃ support-type solid acid as catalyst to catalyze the hydrolysis of corn bran hemicellulose.The single-factor experiments included catalyst amount,hydrolysis temperature,hydrolysis time,solid-liquid ratio,On the basis of single-factor experimental results,used Box-Behnken experimental design method,pentose yield as the index,the optimal synthetic parameters were explored by response surface experiments.Results indicated that the optimal synthetic parameters were catalyst amount 12 m L,hydrolysis temperature 120 ?,hydrolysis time 4 h,solid-liquid ratio 1:10,The pentose yield was 22.45%.Composition and monosaccharide content in the hydrolysate was analyzed by HPLC,the results shows that three main monosaccharides in the hydrolysate:glucose 4.99%,xylose 34.78%,arabinose 55.90%.FT-IR of corn bran and residues shows that the structure of xylose and arabinose had changed,it means that hemicellulose had degraded.The hydrolysis reaction kinetics of corn bran hemicellulose catalyzed by solid acid were studied,k₁ meant the reaction rate constant of hemicellulose hydrolysis and k₂ meant the reaction rate constant of reducing sugar decomposition.By comparison of k₁,k₂ of different temperatures,the conclusions were obtained that k₁,k₂ proportioned to temperatures;The activation energy E1>E2 showed that reducing sugar decomposition was easier happen to hemicellulose hydrolysis.k0 and k0' were pre-exponential factor of reaction rate equation,k0 was higher than k0' for 4 order of magnitudes,it meant that the speed of hemicellulose hydrolysis reaction was faster than the speed of reducing sugar decomposition reaction.?3?The furfural was produced from xylose dehydration catalyzed by HTLW.The single-factor experiments included reaction temperature,reaction time,the initial concentration of xylose,dosage of toluene.On the basis of single-factor experiental results,furfural yield as the index,,the optimum technology parameters were determined used Box-Behnken experimental design method.Results indicated that the optimum technology parameters were reaction temperature188? reaction time 6 h,the initial concentration of xylose 120 g/L,dosage of toluene 25 m L,The furfural yield was 68.72%.The product was analysised and represented by GC-MS,Contrast the GC-MS of product furfural spectrogram and furfural standard spectrogram,the matching degree between them was 77.3%,the results showed that the products was furfural.The reaction kinetics of xylose dehydration to prepare furfural were studied,k₁ meant the reaction rate constant of xylose dehydration and k₂ meant the reaction rate constant of furfural decomposition,by comparison of k₁,k₂ of different temperatures,the conclusions were obtaied that k₁ was proportional to temperatures and inverse proportional to the initial concentration of xylose when reaction temperature been fixed.The activation energy E1 and E2 were all inverse proportional to the initial concentration of xylose;E1>E2 meant that furfural decomposition was easier happen to xylose dehydration.k0 was higher than k0' for many order of magnitudes,it meant that the speed of xylose dehydration reaction was faster than the speed of furfural decomposition reaction.?4?This experiment studied the technology of extract cellulose from hemecellulose hydrolysis residues of corn bran by alkali hydrolysis method.The extraction rate of cellulose as index,We determined the optimum process conditions through the orthogonal experiment based on single factor experiments: sodium hydroxide concentration was 8%,sodium hydroxide hydrolysis temperature was 60?,sodium hydroxide hydrolysis time was 0.5 hour,solid-liquid ratio 1:12.the extraction rate of cellulose reached 83.71%,the content of cellulose was 82.3%.?5?The preparation process of microcrystalline cellulose using cellulose as raw material was studied.The optimum process conditions was hydrolytic temperature 70 ?,hydrolytic time 75min,the ratio of material to solution 1:25,hydrochloric acid concertrationthe 6%.The yield of MCC was 70.68%.The results was accuracy and had practical value.The FT-IR spectrogram displayed that the characteristic absorption peak of cellulose structure of MCC were more stronger than cellulose's;XRD results showed that MCC were?type cellulose,the deffracter intensity of crystalline region enhanced and non-crystalline regin receded.TG results showed that the thermostability of cellulose were better than MCC's.SEM results showed that the structure of MCC were more regularer than cellulose's,MCC had strip populated structure and smooth surface.Above all,cellulose was hydrolyzed catalyzed by hydrochloric acid,its amorphous regin was destroyed and a high polymerization degree MCC product was obtained.?6?MCC/PVA blend film was prepared by tape casting method with PVA as main film forming matter.The crystallinity,tensile properties and thermal properties of the blend film were tested.The result showed that MCC/PVA film had rough surface and larger specific surface area,MCC could compatible with PVA.The tensile properties of blend film were improved,but elongation at bread declined.The tensile strength reached the max value when the mass fraction of MCC was 10%.There existed the hydrogen bond which declined the move ability of PVA molecule between MCC and PVA.Tg and Tm of blend film all moved to higher temperature,the thermal properties were improved and the thermal decomposition temperature increased by addition MCC.MCC/CS blend film was prepared by tape casting method with CS as main film forming matter.The crystallinity,tensile properties and thermal properties of the blend film were tested.The result showed that MCC could compatible with CS,MCC/CS film had rough surface and larger specific surface area,the blend film had good elasticity,flexibility and poor rigidity.The tensile properties of blend film were improved,the tensile strength reached the max value when the mass fraction of MCC was 15%.Tg and Tm of blend film all moved to lower temperature,the thermal properties were improved and the thermal decomposition temperature increased by addition MCC.