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锌铝复合氧化物负载Ni基催化剂催化β-O-4木质素模型化合物加氢解聚的研究
其他题名化学工程
许晨
学位类型硕士 ; 学位论文 ; 硕士 ; 学位论文
导师木质素模型化合物 ; 解聚 ; 反应路径 ; 锌铝复合氧化物
2017-05
学位授予单位中国科学院大学
学位授予地点北京
学位专业木质素由于其特殊的结构和碳氢比,使得其有望成为生产芳烃、烷烃、环烷烃等生物基燃油和精细化学品的重要可再生原料,而且木质素也是自然界中唯一能够提供可再生芳香类化合物的非化石资源。每年全球造纸和生物乙醇行业的木质素产量大约有5000万吨左右,而只有约5%用于低值商业用途,其余均用作低端燃料,没有得到合理利用,造成巨大的的资源浪费和环境污染。因此,开展木质素的高效解聚转化研究势在必行,对于解决当前的石化资源的匮乏和日益突出的环境问题具有十分重要的意义。 木质素是由苯丙类化合物聚合而成,对羟苯基、愈疮木基、紫丁香基三种单体以乱无章的方式相互连接,但单体之间的连接以醚键链接为主,包括β-O-4、α-O-4、4-O-5等化学键。通过精心设计和改良催化剂,选择合适的催化体系并优化反应条件,有望选择性地活化与断裂木质素分子中特定的化学键,从而高选择性地获得某种或某类特定的目标产物,实现木质素的精准催化解聚和转化。 近年来,镍基催化剂在木质素的催化解聚和酚类模型化合物的加氢精制反应中,表现出较高的催化活性和产物选择性,吸引了越来越多的关注。镍基催化剂通常负载在酸性载体上进行木质素模型化合物的研究。然而,这种双功能催化剂体系存在严重的积炭问题,并且水热稳定性不高。相比之下,采用碱性载体负载金属催化剂,有着优良的抗积碳能力和较高的水热稳定性。此外,固体碱是介孔材料,有利于解聚单体的转移和扩散,表面氧空位有利于消除氧原子,使其具备了适度的催化加氢脱氧活性,显示出较好的应用前景。 因此,本研究以锌铝复合氧化物负载的镍基催化剂催化β-O-4木质素模型化合物加氢解聚为研究对象,考察催化剂载体锌铝比与反应温度对β-O-4木质素模型化合物加氢解聚性能的影响;分析和归纳了β-O-4木质素模型化合物加氢解聚的反应路径;并在此基础之上开展了β-O-4木质素模型化合物加氢解聚动力学研究。
关键词工程硕士
摘要中文
其他摘要Because of the special structure and hydrocarbon ratio, lignin is expected to be Important renewable raw materials which can produce the aromatic hydrocarbon, paraffin, high-grade biofuels and high value-added chemicals. What’s more, lignin is the only able to provide renewable aromatic compounds of fossil resources in nature. The yield of lignin in the field of papermaking and bioethanol production is about 50 million tons, in which only about 5% was used for commercial purposes in the global each year. The rest are being used as fuel in the low-end and didn't get reasonable use which caused great waste of resources and environmental pollution. Therefore, it is imperative to develop efficient depolymerization of lignin to solve the current energy and environmental problems which has the very vital significance. Lignin is a three-dimensional, highly branched, polyphenolic substance containing plenty of hydroxy- and methoxysubstituted phenylpropane units through ether bond linkages containing β-O-4, α-O-4, 4-O-5 bond. Elaborately designing and improving the catalyst, choosing the appropriate catalytic system and optimizing the reaction conditions are expected to can selectively activate and break the certain chemical bond in the lignin. Thus, it can access some or some kind of specific target product to achieve to the accurate transformation of lignin. In recent years, nickel-based catalysts have shown excellent catalytic activity and selectivity for products in depolymerization and hydrogenation reaction of lignin to produce phenolic compounds which have attracted more and more attentions. Most of the nickel-based load on the acid support were studied. It should be noted that this kind of bifunctional catalyst system suffers from remarkable carbon deposition and moderate hydrothermal stability. In contrast, catalysts supported on solid base have long been regarded as robust catalysts and show the resistance to carbon deposition but have moderate HDO catalytic activity. Additionally, solid base substrates are mesoporous materials which are benefit to the transfer and diffusion of depolymerization monomer. The oxygen vacancy on the solid base surface is similar to that on the sulfide type catalyst surface and is advantageous to the removal of oxygen atoms. In the present work, a series of nickel catalysts supported on ZnO-Al2O3 composites with varying Zn/Al atom ratios (Zn/Al = 2, 3, 5, ∞) have been prepared and tested for the hydroprocessing of lignin model compound (2-phenoxy-1-phenylethanone). We have studied the effect of the Zn/Al atom ratio in the support and reaction temperature on the cleavage of β-O-4 linkage ,and we also analyzed and summarized the possible reaction pathways proposed. On this basis, we further explored the kinetics of the β-O-4 lignin model compound depolymerization.
作者部门多相催化转化团队
公开日期2017-06-30
学位类型硕士 ; 学位论文 ; 硕士 ; 学位论文
语种中文
文献类型学位论文
条目标识符http://ir.qibebt.ac.cn/handle/337004/9984
专题多相催化转化团队
作者单位中国科学院大学
推荐引用方式
GB/T 7714
许晨. 锌铝复合氧化物负载Ni基催化剂催化β-O-4木质素模型化合物加氢解聚的研究[D]. 北京. 中国科学院大学,2017.
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