| The lignocellulose is one of the renewable resources, such as corn stover, which ismade of cellulose, hemicelluose and lignin. In addition, the cellulose can be extensivelyused in the fermentation and chemical industy for fuel alcohol and lactic acids and so on.With the energy and envionmental problems in the world are getting worse and worse,much attention has been focused to develop an alternative and to low cost for new fuel.In China, corn stover is one of the most abundant distributions. Thus, it is an effectiveway to solve energy crisis and envionmental problems. In this process, pretreatment is akey step, which has a deeply influence on subsequent operations, such as fermentation.So developing a reasonable and cheap pretreatment of lignocellulose is necessary forimproving the availability of corn stover.Firstly, the corn stover was selected as the object of study and the pretreatmentprocess of three metal ions was optimized. And then, the material treated at optimalmetal ion conditions were further treated by ionic liquid [BMIM]Cl. According to thecharacteristics and enzymatic hydrolysis of corn stover by metal ion and ionic liquid[BMIM]Cl after metal ion activation, the pyrolysis kinetic research of ferric chloridewas studied. The main works and conclusions are included as follows:First of all, the metal ion pretreatments of corn stover by ferric chloride, zincchloride and aluminum chloride were optimized with uniform design. Characterizationof the treated products, which were recovered from pretreatment techniques, wasinvestigated to determine composition contents and cellulose enzyme of corn stover.Structural characteristics including cellulose crystalline and surface morphology werealso assessed and compared by using X-ray diffraction (XRD), scanning electronmicroscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The optimalpretreatment conditions were as fllows: ferric chloride concentration was0.6mol/l, ratioof liquid to solid was10:1, reaction temperature was170℃and reaction time was15min, zinc chloride concentration was0.6mol/l, ratio of liquid to solid was10:1, reactiontemperature was120℃and reaction time was30min, and aluminum chlorideconcentration was0.3mol/l, ratio of liquid to solid was15:1, reaction temperature was170℃and reaction time was30min. Under the above conditions, the recoveredmaterials from metal ion solution pretreatment of corn stalk were significantly damagedand enhance the level of enzyme hydrolysis. Reducing sugar yield of treated corn stover was increased by131.6%,119.4%and46.6%, respectively. The relative content ofamorphous material decreased, while cellulose increased by72.19%,18.54%and7.95%,respectively. The compact structure of corn stover was significantly ruined.Secondly, the experiment conditions of corn stover treated by ionic liquid[BMIM]Cl after three metal ions process were optimized with the response surfacemethodology. compared with untreated corn stover，the reducing sugar yield canincreased by157.85%,154.14%and150.41%, and the relative content of celluloseincreased by68.11%,63.24%and60.54%, respectively. Structural of corn stover washeavily damaged by ionic liquid [BMIM]Cl after three metal ions solution pretreatment,as characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) andFourier transform infrared spectroscopy (FTIR). The optimal pretreatment conditionswere as fllows: ionic liquid [BMIM]Cl after ferric chloride pretreatment, Substrateconcentration was4.2%, reaction temperature was85℃and reaction time was185min,ionic liquid [BMIM]Cl after zinc chloride pretreatment, Substrate concentration was3.8%, reaction temperature was103℃and reaction time was357min, and ionic liquid[BMIM]Cl after aluminum chloride pretreatment, Substrate concentration was3.6%,reaction temperature was105℃and reaction time was230min.Finally, the ferric chloride solution pretreatment was ultimately selected as anactivation method，ionic liquid [BMIM]Cl was used as a further treatment step.Pyrolysis of corn stover by ferric chloride solution and ionic liquid [BMIM]Cl afterferric chloride solution at the heating rates of10,20,30K/min were investigated. Thereaction kinetic parameters and activation energy E at different experimental conditionswere calculated. The results of pyrolysis indicated that: the pyrolysis process of cornstover includes three steps: losing water and pre-pyrolysis, main pyrolysis andcarbonization. The corn stover of untreated was the most stable among the threesamples. It was confirmed that the thermal progress were related to the progressivechanges of the composition contents of the corn stover.In this paper, three metal ions pretreatment was firstly applied and optimized.Based on which, the mechanism of ferric chloride solution pyrolysis was analyzed inparticular. All these basic researches will have a significant value on application oflignocelluloses. |
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