Study On Alcoholysis Liquefaction Of Woody Biomass

Nowadays, energy security and environmental pollution problems caused by fossil resources become increasingly severe, the use of renewable biomass resources by thermochemical conversion for energy and chemicals attract more and more people’s attention. Biomass thermochemical conversion processes include pyrolysis, liquefaction, gasification, etc. Biomass liquefaction has the potential for industrial applications because of its relatively mild reaction conditions. Traditional liquefaction methods usually use inorganic liquid acid as catalysts. Eventhough inorganic liquid acids exhibits excellent catalytic performance in the liquefaction of biomass, they can easily lead to corrosion of equipment, production safety and environmental pollution problems due to their strong oxidizing, which limits the industrial application of liquefaction technology to a certain degree. Therefore, looking for environmentally friendly and efficient catalyst is a key point in developing the liquefaction technology. In this paper, with acid ionic liquid or phosphotungstic acid as catalyst, fir sawdust as the woody biomass feedstocks, the application of the "green" acid catalyst was investigated in woody biomass alcoholysis liquefaction in order to provide theoretical and practical basis to develop biomass "green" efficient liquefaction technology.On one hand, a series of acid ionic liquids containing HSO4were synthesized by the imidazolium cation functionalization and applied to the fir sawdust liquefaction in1-octanol as catalyst, respectively. Firstly, their catalytic performances were compared with H2SO4in order to elect the ionic liquid which has the best catalytic performance. Secondly,with octanol as solvent, the selected ionic liquid as catalyst, the effects of reaction parameters on liquefaction yield and distribution of liquefaction products were systematically studied by single factor experiments in the liquefaction of fir sawdust. Additionally, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TG), environmental scanning electron microscope (ESEM), elemental analyzer, Gas Chromatography and Mass spectrometer (GC-MS) were used for liquefaction product characterization. The liquefaction experimental results of electing the best catalytic performance ionic liquid showed that the acid ionic liquids exhibited good catalytic performance for the liquefaction of sawdust, and1-(4-sulfobutyl)-3-methylmidazolium hydrosulfate ([Bsmim]HS04) had the best catalytic performance,which was close to the sulfuric acid under the same conditions. The single factor experimental results show the optimal reaction conditions:the amount of fir sawdust10g, average particle diameter of1.265mm, solvent to solid ratio6:1, the reaction temperature150℃, catalyst concentration5wt%, the reaction time60min, and the liquefaction was78.4%. There exists a competitive relationship between wood degradation and intermediate repolymerization during the liquefaction process. Based on the analysis results, liquefaction oil yield is directly related to the level of liquefaction rate. Liquefaction of lignin is harder than that of cellulose and hemicellulose. Hemicellulose, cellulose and Lignin, are orderly decomposed, and then depolymerized and liquefied in the sawdust liquefaction process. The HHV of the biomass oil is more than twice the raw material, which indicates that the bio oil has a good combustion value. Light oil is mainly originated from the degradation of cellulose and hemicellulose, and lignin liquefaction products are rich in heavy oil.1-octanol as the solvent is also a reactant which is beneficial to improving the octane rating of light oil. Light oil is a very complex mixture containing esters, ethers, alkanes, aldehydes, etc.and can be used as biofuels directly.On the other hand, Fir sawdust was liquefied under supercritical condition in a stainless-steel autoclave with phosphotungstic acid as catalyst, and ethanol as solvent. The effects of reaction parameters (catalyst dosage, temperature, time) on the liquefaction yield were investigated, the liquefaction residue and the oil product were characterized by Fourier transform infrared (FT-IR) and Agilent7890A/5975C gas chromatography-mass spectrometry (GC-MS), respectively. The experimental results show that phosphotungstic acid exhibits excellent catalytic performance in liquefaction of fir sawdust in the environment of supercritical ethanol.The liquefaction yield reached95.35%when0.5g phosphotungstic acid was used as catalyst at260℃after30min. The liquefaction residue mainly contains phosphotungstic acid and lignin derivatives. The oil product was mainly composed of the esters, phenols and its derivatives, which can be further upgraded into fuels or chemicals. In the liquefaction process, ethanol can be used not only as the liquefaction solvent, but also as a reactant.