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Thesis Advisor张锁江 ; 辛加余
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline化学工程
Keyword木质素 离子液体 类均相体系 加氢脱氧

木质素是最重要的生物质组分之一,通过断裂解聚和加氢脱氧除去木质素中的氧,是将木质素转化为基础化学品的重要手段之一。在本研究中,我们在温和条件下,采用离子液体和贵金属纳米颗粒构成的类均相体系实现了C-O键的断裂和加氢脱氧。首先,在离子液体中,原位合成了Pd, Pt, Rh和Ru四种纳米颗粒。选取苯酚和愈创木酚作为木质素单体模型化合物,用于研究木质素单体中的加氢脱氧行为,二苯醚等二聚体作为模型化合物,研究单体之间C-O键断裂行为。结果表明,类均相体系中,单体和二聚体模型化合物可以在130 °C下实现完全转化,并且该催化体系可循环数次而没有明显的活性降低。在类均相体系中,催化剂纳米颗粒的大小顺序为Pd ? Pt > Rh ~ Ru,而催化剂的活性与纳米颗粒大小成反比。其中活性最好的是Pt/[Bmim]PF6体系,该体系能高效转化大部分模型化合物。然而,发现在多次循环后,类均相体系中的纳米颗粒不稳定,发生了团聚现象,使得催化活性降低,因此,我们进一步提出了用纳米反应器来实现木质素模型化合物的转化。采用多孔空心结构的碳壳作为反应器,将贵金属固定在空心碳壳内表面形成NPs@HCS催化剂,使得每个碳小球作为一个独立的纳米反应器。实验中,首先合成了球壳大小均一的NPs@HCS催化剂,再将其应用于木质素模型化合物的转化。结果表明,在相同条件下,离子液体中底物的转化率远高于多数常用加氢溶剂,充分体现了离子液体在加氢反应中溶剂效应的优势。将NPs@HCS催化剂用于苯酚,邻苯二酚,愈创木酚,2,6-二甲氧基苯酚的转化中,探究了-OH和-OCH3取代基对加氢脱氧反应的影响。

Other Abstract

To produce basic chemicals from lignin, depolymerization and removal of oxygen from lignin through C-O cleavage and hydrodeoxygenation (HDO) are crucial steps. In this study, a novel catalyst system, pseudo-homogeneous catalyst system, consisting of uniformly stabilized noble metal nanoparticles (NPs) in ionic liquids (ILs) is developed for the selective reductive cleavage of C-O and HDO. Four types of NPs including Pd, Pt, Rh, Ru were in-suit synthesized and well-distributed in ILs without aggregation. Phenol and guaiacol as lignin monomer model compounds are investigated to get an insight into the possible HDO pathway, meanwhile, dimeric model compounds, such as diphenyl ether, benzyl phenyl ether, are studied for the cleave C-O bonds between aromatic units. These catalytic systems displayed almost 100% conversion for various monomer and dimer lignin model compounds at 130 °C and were recycled several times without lossing activity. The catalytic selectivity of metals for HDO/C-O cleavage normally decreases with the order of Pt > Rh ~ Ru >> Pd that is similar with the order of NPs size Pd >> Pt > Rh ~ Ru. With mean diameter of 5.6 nm, Pt NPs in [Bmim]PF6 is identified as the best catalytic system for the transformation of lignin monomers and dimers model compounds with almost 100 % conversion and maximum 97 % selectivity.Since the instability of the pseudo-homogeneous catalyst system after several times recycling, the hollow carbon spheres (HCS) were synthesized to form NPs@HCS as nano-reactors for stabilizing the noble metal particles. NPs@HCS with uniform diameters were used in conversion of lignin model compounds to investigate the solvent effect and impact of substituent group. The conversion of diphenyl ether in ILs is much higher than most common used solvents in hydrogenation. It is the proof of solvent effect of ILs is in favor of hydrodeoxygenation. The inhibiting effect of substituent group –OH and -OCH3 is proved by employing phenol, catechol, guaiacol and 2,6-Dimethoxyphenol as the substrates. 

Document Type学位论文
Recommended Citation
GB/T 7714
陈露. 木质素模型化合物在离子液体类均相体系中的温和转化[D]. 北京. 中国科学院研究生院,2016.
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