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生物油水热条件下的原位加氢提质研究
曾影
学位类型硕士
导师林伟刚 ; 王泽
2016-07
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业化学工程
关键词生物油 苯酚 加氢脱氧 Ru/mcm-41
摘要

随着化石燃料日益短缺以及因长期应用而引起的环境污染、温室效应等问题的日益凸显,可再生能源的开发利用迫在眉睫。生物质能因其二氧化碳“零排放”、可再生、利用方式多元等优点而备受关注。然而其热解所得生物油存在氧含量高、酸性和腐蚀性强、热值低等不利因素,极大限制了生物油的高价值应用,因此针对生物油的脱氧提质研究具有重要意义。其中,生物油在水热环境下的催化加氢是重要的提质方法,但所用氢气原料的高储运危险性是该技术路线的极大弊端。鉴于此,本论文针对以液体供氢试剂替代氢气作为氢源的生物油加氢脱氧方案进行了研究,考查了以苯酚为生物油模型化合物的原位加氢催化脱氧反应体系中,催化剂、供氢试剂、操作条件等影响因素对苯酚转化率及脱氧效率的影响规律和作用机制。主要研究结果如下:针对以甲酸为供氢试剂的苯酚催化加氢脱氧反应体系,筛选考查了多种催化剂载体和活性金属的影响,结果显示,不同金属负载催化剂对苯酚的转化率和脱氧效率的催化活性水平为:Ru/MCM-41 > Pd/SiO2 > Pd/MCM-41 > Pd/CA > Pd/Al2O3 > Pd/HY-zeolite ≈ Pd/ZrO2 ≈ Pd/CW > Pd/HSAPO-34 > Pd/HZSM-5 > Pt/MCM-41。载体的有效比表面积越大,布朗斯特酸量越高,以及活性金属的亲氧性越强,则催化剂表现出的活性越好。进一步针对优选催化剂Ru/MCM-41作用下的反应体系,对催化剂还原温度和活性金属负载量对催化剂性能的影响规律进行了深入研究。结果表明,随还原温度升高和负载量增加,苯酚的转化率和脱氧效率相应增加,但当还原温度达到500oC时,MCM-41载体的孔结构出现明显坍塌,导致催化剂活性反而降低。另一方面,当负载量达到15wt.%时,也会因负载金属原子间团聚重叠而使催化剂性能变差。在所研究的条件范围内,400oC和10wt.%分别为催化剂的最佳还原温度和活性金属负载量。 除甲酸外,另考查了其他四种供氢试剂在苯酚原位加氢脱氧过程中的产氢及加氢反应活性。研究显示,不同供氢试剂的加氢活性水平为:甲酸 ≈ 甲醇 > 乙二酸 ≈ 乙醇 > 乙酸。针对甲酸供氢试剂的研究表明,增加原料中甲酸与苯酚的物料配比有助于苯酚转化率和脱氧效率的提高。进一步通过反应时间对液体产物分布影响规律的研究,提出了甲酸、苯酚催化反应体系中苯酚原位加氢脱氧过程的反应路径,即反应过程中甲酸首先快速脱氢分解产生大量H2和CO2,同时通过平行脱水反应得到少量CO和H2O,所得CO进一步通过水汽变换反应产生更多H2和CO2,所得H2为CO的甲烷化和苯酚的加氢脱氧反应所耗用,并且苯酚的加氢脱氧转化主要通过苯环加氢后的逐步加氢脱氧过程实现,同时伴随少部分的酚羟基直接加氢脱氧反应。

其他摘要

As the application of fossil fuel facing with the severe problems like shortage of deposits, environmental pollution, and the global warming, it is urgent to develop the renewable energy sources. Biomass has attracted much attention due to its “zero” emission in CO2, short regeneration period, and the diversity in utilization. Bio-oil, derived from pyrolysis of biomass, has the undesirable properties of high oxygen content, corrosivity, and low HHV, which limit its high-value application. Therefore, it is significant to upgrade bio-oil into higher-quality bio-fuel. Nowadays, hydrogenation is the most effective way to upgrade bio-oil. However, the high hydrogen consumption in this process causes some problems like high cost and risks in utilization and storage. Therefore, the thesis investigated the in-situ hydrodeoxygenation of bio-oil with liquid hydrogen donor as hydrogen source and phenol as model compounds of bio-oil. The investigation included the effect and mechanism of catalysts, hydrogen donor, and operating conditions on the conversion and deoxygenation of phenol. The main results are as follows:With phenol as model compound and formic acid as hydrogen donor, the effect of support and active metal compound of catalyst on the in-situ HDO of phenol was evaluated firstly. The apparent activities of different supported metal catalysts for the conversion and deoxygenation of phenol follow: Ru/MCM-41 > Pd/SiO2 > Pd/MCM-41 > Pd/CA > Pd/Al2O3 > Pd/HY-zeolite ≈ Pd/ZrO2 ≈ Pd/CW > Pd/HSAPO-34 > Pd/HZSM-5 > Pt/MCM-41. The high effective surface area and acidity of support and the strong affinity of active metal to the oxygen could benefit the activity of catalyst.The further study concerning the best performing catalyst, Ru/MCM-41, focus on the influence of reduction temperature and theoretical loading on the performance of catalyst. Increasing the reduction temperature and theoretical loading improved the conversion and deoxygenation of phenol. When the reduction temperature reached to 500oC, the collapse was observed in the mesopore structure of MCM-41, which thereby resulted in the decreased activity of Ru/MCM-41. A similar reduction in activity of catalyst was found when the theoretical loading of Ru was 15wt.%, as the agglomeration of metal atoms appeared. The optimistic value for the reduction temperature and theoretical loading are 400oC and 10wt.%. Apart from formic acid, other four different hydrogen donors were also used to investigate their capability in dehydrogenation and hydrogenation. The performance of those hydrogen donors can be ranked as: formic acid ≈ methanol > oxalic acid ≈ ethanol > acetic acid. In the case of formic acid, increasing the feed ratio of formic acid to phenol could promote the conversion and deoxygenation of phenol. The reaction pathways of in-situ hydrodeoxygenation of phenol were proposed further, based on the effect of residence time on the liquid product distribution. The reactions at the early reaction time were the rapidly decomposition of formic acid through dehydrogenation, along with a part of the dehydration of formic acid forming CO and H2O. Thereafter, more H2 and CO2 was formed through water-gas shift reaction. The generated H2 was meanwhile consumed in methanation of CO and conversion of phenol through directly hydrodeoxygenation of aromatic ring and subsequent hydrodeoxygenation of phenolic hydroxyl group. 

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/22871
专题研究所(批量导入)
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曾影. 生物油水热条件下的原位加氢提质研究[D]. 北京. 中国科学院研究生院,2016.
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