【作者】 赵炜；

【导师】 魏贤勇；

【作者基本信息】 中国矿业大学 ， 化学工艺， 2009， 博士

【摘要】 随着化石资源的日益减少和环境污染的加剧,寻求新的和洁净的可再生资源迫在眉睫。包括农作物秸秆在内的生物质资源因其产量巨大、洁净性和可再生性而备受关注,开发其高效利用的新方法和新技术也成为能源领域和资源领域的前沿课题。本文以稻秆、麦秆、玉米皮和玉米芯4种农作物秸秆为研究对象,以KOH/γ-Al₂O₃、CaO/γ-Al₂O₃和CaO/γ-Al₂O₃/Fe₃O₄为催化剂,以高压釜为反应器,研究了秸秆在亚/超临界醇中的液化。以石油醚为溶剂,比较了索氏萃取、超声波辐射萃取和微波辐射萃取3种方法脱除4种秸秆中蜡份的效果,利用GC/MS分析了蜡份的组成。结果表明,微波辐射是最有效的脱蜡方法。秸秆蜡份中除含有烷烃、醇、醛、酮和酯以外,还含有具有高附加值的化学品甾醇、棕榈酸、反油酸、维他命E和角鲨烯,其中甾醇、反油酸、维他命E和角鲨烯首次在秸秆中检测到。研究了反应温度、反应时间和秸秆/醇比对玉米皮在亚/超临界甲醇中液化的影响,考察了反应温度对稻秆、麦秆和玉米芯在亚/超临界甲醇中以及玉米皮在亚/超临界乙醇中液化的影响,用GC/MS分析了液体产物（LPs）的组成,探讨了LPs组成分布随温度变化的规律。结果表明,玉米皮在甲醇中适宜的液化条件为液化温度、液化时间和秸秆/醇比分别是300 oC、30 min和1:30 g/mL。温度对液化的影响最显著。比较甲醇和乙醇对玉米皮的液化,乙醇作为溶剂液化效果好。在适宜的液化条件下,玉米皮、稻秆、麦秆和玉米芯在甲醇以及玉米皮在乙醇中的转化率分别为87%、75%、85%、94%和87%,LPs收率分别为36%、30%、40%、43%和43%。秸秆在亚/超临界醇中液化产生的LPs的主要组成成分包括短链脂肪酸衍生物、呋喃衍生物、环戊酮衍生物、含有取代基的肉桂酸衍生物、芳醛或酮衍生物、苯酚衍生物、苯衍生物,长链脂肪酸衍生物和甾族化合物。秸秆在亚临界醇中液化时,LPs包括木质素侧链断裂产生的含有取代基的肉桂酸衍生物和2,3-二氢苯并呋喃;在超临界醇中,秸秆中的三大组分纤维素、半纤维素和木质素都发生解聚,且随着温度的升高解聚加剧。木质素解聚产物低温时以肉桂酸酯衍生物为主,高温时以苯酚衍生物为主。制备并表征了催化剂KOH/γ-Al₂O₃、CaO/γ-Al₂O₃和CaO/γ-Al₂O₃/Fe₃O₄,将其用于催化液化麦秆,考察了催化剂对麦秆在超临界乙醇中液化所产生的LPs和固体残渣（SRs）收率的影响。用GC/MS分析了LPs的组成,探讨了催化剂对LPs组成分布的影响。KOH/γ-Al₂O₃、CaO/γ-Al₂O₃和CaO/γ-Al₂O₃/Fe₃O₄催化液化麦秆得到的LPs收率分别为86.1%、57.8%和104.6%,SRs收率分别为14.2%、16.3%和10.9%。3种催化剂催化液化麦秆所得LPs组成主要包括短链脂肪酸乙酯、呋喃衍生物、环戊醛酮、苯酚衍生物、苯衍生物、芳酸衍生物、长链脂肪酸乙酯和甾族化合物。3种催化剂都提高了短链脂肪酸乙酯、环戊醛酮和苯酚衍生物的收率,其中皆以CaO/γ-Al₂O₃/Fe₃O₄的提高幅度最大。KOH/γ-Al₂O₃和CaO/γ-Al₂O₃/Fe₃O₄提高了呋喃衍生物的收率,KOH/γ-Al₂O₃提高了苯衍生物的收率。提出了秸秆在亚/超临界醇中的液化机理。测试了麦秆在超临界乙醇中液化得到的LP的燃料性能,分析了LP的组成。结果表明,LP的主要成分包括短链或环状脂肪酸及其酯、呋喃衍生物、环戊烯衍生物、苯酚衍生物、苯衍生物、芳酮、芳酸及其乙酯、长链脂肪酸乙酯和甾族化合物,经提质其主要指标达到了燃料油的标准。更多还原

【Abstract】 In this study, liquefaction of crop stalks, including rice straw, wheat straw, corn skin and corn core, with methanol and ethanol under sub/supercritical conditions without catalyst or with different catalysts such as KOH/γ-Al₂O₃, CaO/γ-Al₂O₃ and CaO/γ-Al₂O₃/Fe₃O₄ was investigated.Soxhlet, ultrasonic-, and microwave-assisted extractions for dewaxing from rice, wheat, corn skin and corn core stalks with petroleum ether were compared. The compositions of the waxes extracted by different methods were determined by gas chromatography/mass spectrometry （GC/MS） analysis. The results show that microwave-assisted extraction is the most effective method for dewaxing from the stalks. Besides chain alkanes, alcohols, aldehydes, ketones, and esters, a large number of sterides, palmitic acid, （E）-9-octadecenoic acid, vitamin E, and squalene are found, which are more value-added chemicals in the waxes from the four stalks mentioned. Sterols, （E）-9-octadecenoic acid, vitamin E, and squalene in waxes were first detected from crop stalks.The effect of temperature, time and the ratio of stalk to solvent on the liquefaction of corn skin in sub- and supercritical methanol was investigated. And the effect of temperature on the liquefactions of rice, wheat and corn core stalks in sub- and supercritical methanol as well as corn skin stalk in sub- and supercritical ethanol was also researched. The liquid products （LPs） from liquefaction of stalks were analyzed by GC/MS. The change of composition distribution of LPs with temperature was studied. The results show that the optimum conditions of corn skin liquefaction in methanol are that reaction temperature, reaction time and the ratio of stalk to methanol are 300 oC, 30 min and 1: 30 g/mL, respectively. The effect of temperature on liquefaction of stalk is the most notable. The liquefaction has better effect when ethanol was used as solvent comparing methanol as solvent. Under the optimum liquefaction condition, the conversion yields of corn skin, rice, wheat, and corn core in methanol as well as corn skin in ethanol are 87%, 75%, 85%, 94% and 87%,respectively, and LPs yields are 36%, 30%, 40%, 43% and 43%. The main compositions of LPs include shorter chain carboxylic acid derivatives, furan derivatives, cyclopentanone, phenol derivatives, benzene derivatives, cinnamic acid derivatives, longer chain carboxylic esters and sterides. Cinnamic acid derivatives and 2,3-dihydrobenzofuran from the cleavage of lignin branch chain are the dominant compositions of LPs from stalk liquefaction in subcritical alcohol. When stalks are liquefied, three main components of stalks are all depolymerized, and the depolymerization is intensified with the temperature increase. The depolymerization of lignin from stalks forms cinnamic acid derivatives at lower temperature and phenol derivatives at higher temperature. KOH/γ-Al₂O₃, CaO/γ-Al₂O₃ and CaO/γ-Al₂O₃/Fe₃O₄ were prepared and characterized, and used to catalyze wheat straw liquefaction in supercritical ethanol. The effect of catalyst on LP yields was investigated. LPs were analyzed by GC/MS. The change of composition distribution of LPs with temperature was studied. The yields of LPs from wheat straw liquefaction with KOH/γ-Al₂O₃, CaO/γ-Al₂O₃ and CaO/γ-Al₂O₃/Fe₃O₄ reach 86.1%、57.8% and 104.6%, respectively. Shorter chain carboxylic acid ethyl esters, furan derivatives, cyclopentanone, phenol derivatives, benzene derivatives, aromatic acid derivatives, longer chain carboxylic ethyl esters and sterides are main compositions of LPs with the above three catalysts. The three catalysts all enhance the yields of shorter chain carboxylic acid ethyl esters, cyclopentanone and phenol derivatives, and CaO/γ-Al₂O₃/Fe₃O₄ shows a better effect. KOH/γ-Al₂O₃ and CaO/γ-Al₂O₃/Fe₃O₄ improve the yield of furan derivatives, and KOH/γ-Al₂O₃ raises the yield of benzene derivatives.Mechanisms for stalks liquefaction in sub- and supercritical alcohol were proposed. Fuel properties of LP from wheat straw liquefaction in supercritical ethanol were tested. The composition of LP was analyzed by GC/MS. The main compositions of LP are shorter chain carboxylic acid and their ethyl esters, furan derivatives, cyclopentanone, phenol derivatives, benzene derivatives, aromatic ketone, aromatic acid derivatives, longer chain carboxylic ethyl esters and sterides. After upgrading, the main indexes reach the standard of fuel oil.更多还原