Conversion Of Cellulose From Xylose Residue Into Bioethanol And 5-HMF

At present,the problems of environmental pollution and energy crisis are becoming more and more serious.Scientists are eager to find a new kind of green,economical and renewable energy to replace the traditional fossil energy.Biomass energy is a good choice.Through bioreftning or biological transformation,the biomass materials can be degraded to platform chemical and transformed into bioethanol,to meet the needs of life or industrial production.Xylose residue(XR)is one kind of industrial residue in the process of industrial production of commercial xylose by dilute pretreatment from com eob.It is adequate and eurrently considered as a waste byproduct and mainly used for heat generation.In fact,XR is a promising potential lignocellulosic source for bioethanol production.As the most obvious aspects,XR is enriched in cellulose and almost free of hemicellulose,which has been acidic hydrolyzed during xylose production.Meanwhile,the lignin in XR can be more easily removed or altered,because of deploymerization and re-polymerization reaction.In this thesis,we will make full use of XR to product 5-HMF and bioethanol.Firstly,the XR was pretreated by NaOH directly,and the parameters such as the temperature and the amount of NaOH in the reaction process were controlled to explore the most optimal conditions of NaOH pretreatment.Then,the composition of the treated XR was analyzed,and the changes of the surface morphology,crystallinity and crystal shape were observed.At Iast,the treated solids were treated by enzymatic hydrolysis and simultaneous saccharification and fermentation(SSF).The results showed that the largest removal rate of lignin was 72.2%,under the condition of 140oC,15%NaOH(g/gsubstrate).Compared to the untreated sample,the sample which was tread under the optimum treatment condition became rougher and more holes appeared,observed by Scanning electron microscopy(SEM).Though X-ray diffraction(XRD),it was found that the crystallinity of cellulose increased with the increase of treatment conditions,and the change of crystal form(from cellulose ? to cellulose ?)was observed.These changes are beneficial to the adhesion of cellulose and cellulose,and promote the efficiency of enzymatic hydrolysis.Finally,the maximum ethanol yield was 16.3 g/L by SSF(15 FPU/g).This is more than four times as much as the ethanol content of untreated samples treated by SSF.In order to overcome the problems that need high temperature and more chemical reagents in the process of pretreatment XR using NaOH,and further improve the utilization rate of XR,we used NaOH/urea(Urea)system to study the pretreatment of XR.In reaction,the gradient of different parameters of temperature,time and the amount of NaOH and Urea were setted.It have been explored at 21?,8%NaOH and 12%Urea under the condition of pretreatment of 30 min can reach the maximum enzymatic efficiency(98.8%),and it also using scanning electron microscopy(SEM),X-ray diffraction(XRD)and micro-infrared spectrometer(FTIR)instrument to studied the enzymatic reaction mechanism of urea NaOH/Urea system.5-hydroxymethyl furfural(5-HMF)is a very important platform compound,which can produce more refined chemicals,liquid fuels and other industrial products.In order to make more use of cellulose in XR,we use the ionic liquid[EMIM]Cl to dissolve the cellulose in XR,and then add the metal catalyst CrCl2 to catalyze the degradation of HMF.By controlling the amount of catalyst,temperature and reaction time,the optimal catalytic conditions were explored.Under the condition of 1400C,30 ?moL CrCl2,2 h,the maximum productivity of 5-HMF(38.34%)was obtained.Furthermore,the reaetion mechanism of XR eatalyzed by ionic liquids and CrCl2 was further explained.Finally,the recovery and utilization of CrCl2 were discussed in the end of the paper.It is proved that XR degradation to HMF catalyzed by CrC12 is very promising.