| Lignincellulose converse to bioethanol has been developed in some distance for its advantages, but there are still some drawbacks hinder the converse technology, such as the harvest, storage and transportation of raw aterials, the cost of pretreatment technology, the fermentation with high solid content without detocification and so on. These drawbacks made the efficiency of bioethanol conversion very low and difficulty to realize factoric production. Based on this, this research paper carried out studies on how to enhance the bioethanol efficiency from pretreatment and conversion technolygy:1. Based on the advantage raw materials for bioethanol conversion,four energy crops (switch grass, silver grass, giant reed and Pennisetum)compared with corn stalk. The results showed Pennisetum has more advantageds than the other energy crops, such as high cellulose content,low lignin content and high bioethanol conversion efficiency. Besides, the productivy was 60t/hm2/year, which is much higher than the other three energy crops. For these characters, Pennisetum was choosen as the further study substrate for bioethanol conversion. Compared steam explosion pretreatment and dilute sulfuric acid pretreatment deal with two raw materials, the results showed the steam explosion has more advantages for bioethanol conversion.2. Pretreatment is another point to inhance bioethanol production.Using sulfuric acid and bisulfite combined with steam explosion to deal with Pennisetum in order to optimize the pretreatment effect, which we call it steam explosion pretreatment with sulfite to overcome the recalcitrance of lignocelluloses, (SEPSORL). The results of pretreatment showed sulfirc acid hydrolysis hemicellulose effectively and bisulfite hydrolysis lignin effectively. When this two chemical worked together,the hemicellulose and lignin removal for Pennisetum and corn stalk was 71.55% and 78.38%, and lignin removal was 51.56% and 33.97%,respectively. The combined effect of these two chemical for hemicellulose and lignin removal were between they worked sepereately.Bisulte can decrease the inhibitors formation during the sulfuric acid pretreatment for Pennisetum. The fermentation results of 20% solid content and detoxification (Q-SSCombF) after Pennisetum pretreated by SEPSORL can reach up to 43.65% bioethanol conversion. The fermentation result of substrate pretreated by sulfuric acid with steam explosion was only 39.39% bioethanol conversion. Because of the ration between lignin and bidulfite was not the optimal, the bioethanol production need to improve.3. Based on the research of energy cost of pretreatment, this research constructed kinetic model to indicate pretreatment intensity. Combine hydrolysis factor (CHF) has the indicate effect of pretreatment enery cost.CHF was studied on SPORL (Sulfite pretreatment to overcome recalcitrance of lignocellulose) pretreated poplar NE222. When pretreatment carried on different chemical concentration, temperature,time, CHF can indicate xylan remaining (XR) in pretreated substrates.The relationship between CHF and XR wasXR ?0.822e-CHF +0.178e-0.156CHF. CHF can be used in balancing the xylan dissolution and inhibitor formation and reach the high ethanol production during pretreatment and fermentation. When CHF=2, enzyme loading was 15FPU·g-1 glucan,solid content was 20%wt without detoxification, the concentration of glucose can reach up to 41 g·L-1 (about 27ml·kg-1 upretreated wood),which was in high commercial potential.4. In order to predict the effect of SEPSORL pretreatment, construct kinetic model. Depending on the same characters and differences between SEPSORL and SPORL, connected with Clapeyion description of tempwrature and pressure, the combine hydrolysis factor of steam explosion can be difined as:CHFse = e(a-E(B-LnP)/Dh+?CA+?CB)(CA+CB) t. The active energy of Pennisetum xylan dsollution was 89.69kJ/mole. Xylan removal was obove 90%, which was 20% high than unoptimized. The relationship between CHFse and XRse was XRse = 0.78e-CHFse +0.22e-0.282CHFse.Based on Pennisetum, when hemicellulose and lignin was in the same quatity, the optimal retio between sulfuric acid and bisulfite was 1:10 for pretreatment to realize the best enzyme hydrolysis effect. When CHFse?5, the fast dissolution of xylan was finished, XRse???0.22. The relationship between XRse and furfural and HMF were linear (R2>0.9).The relationship between acetic acid concentration and XRse was Conc.(AA) =0.9XRse-0.6. The mechanism of acetic acid, furfural and HMF was different which caused the different relationship between them, linear relationship between them was R2?0.8. Xylan removal was more effective than lignin removal for bioethanol conversion. The relationship between SED and XRse was SED=28+221exp ( -XRse/0.04) . When the enzyme hydrolysis conversion was 70%, inhibitors concentration was in the torlerance of yeast M3013, then it can be deduced the pretreatment intensity was the proper pretreatment intensity for highest bioethanol production in theoretically.5. Inhance the utilization of facility in different abandon factorys contribute to save the cost of ampmify bioethanol conversion. But transportation of the pretreated substrates was a important problem for the low density of biomass. Densification the pretreated substrates were very important for transportation. The effects of bioetnaol conversion of densificated substrates were studied. The results showed when desification temperature was below 110?, water retention value and the cellulose accecebility to cellulase was all the same with the un-densificated substrates. The hornification extent was blow 0.26. The cellulase bounding of poplar NE222 densificated at 110? was decrease from 1.9 to 1.6 mg protein/glucan, but the glucose concentration of enzymatic hydrolysis at 72 hours was almost the same. There was no big difference in fermentation result of 18% solid content densificated substrates and the control.6. During bioethanol conversion, the inhibitor formation by lignin decompose was an obvious drawback for fermentation. Combine converse biomass to aviation fuel and bioethanol can save the pretreatment energy cost for bioethanol production, because lignin was first refinery for aviation fuel converse. When apple wood was first-refinery for aviation fuel conversion, lignin was utilized as possible as it could be. The enzymatic hydrolysis of the left substrates (catalyzedby Ni) can reach up to 88%. Low catalyst concentration (0.4g·L-1 Ni) had no effect for enzymatic hydrolysis, but Ru/C can drawback the efficiency of enzyme hydrolysis to 47%. When fermentation carried with catalyst(Q-SScombF), the catalyst affected yeast fermentation obviously. When ferment without catalyst the effiency of fermentation can reach up to 70%.Combine aviation fuel and bioethanol converse from biomass was feasible. |
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