负载型Ni基催化剂高效催化木质素制取芳香族化合物

发布时间：2018-03-26 15:40

本文选题：镍基催化剂　切入点：芳香族化合物　出处：《北京化工大学》2016年硕士论文

【摘要】：芳香族化合物作为经济价值较高的一种化工产品,在各个领域都有着广泛地应用。而今,芳香族化合物多来自于石油化工行业,然而随着石油资源的日益枯竭,利用可再生的木质素资源制备芳香族化合物具有重要的意义。在木质素精制过程中,常用的催化剂有均相催化剂如强碱NaOH,负载型催化剂如Mo,Cu, Pt,Rh,Ni等,然而,这些催化剂的对C-O断裂的选择性比较差,且对芳环加氢能力往往过强,得到多为经济价值比较低的小分子或环烷烃。所以目前由木质素出发制取芳香族化合物的过程中主要面临两方面的问题：其一,C-O键断裂活性和选择性差；其二,芳环极易深度加氢。因此,如何提高木质素C-O键选择性断裂的同时抑制芳环的深度加氢成为该过程面临的最大的挑战。由于Ni基催化剂价格便宜,反应条件温和,我们针对目前负载型Ni基催化剂结构进行了调控,并分别用对-羟基苯基型,愈创木基型,紫丁香基型的木质素模型化合物进行催化评价。本文将通过调控活性中心金属Ni的电子结构和晶粒尺寸以及载体的碱性来提高Ni基催化剂对C-O键断裂的活性以及选择性,抑制对芳环深度加氢反应。本论文研究的内容如下：1.通过在Ni基催化剂中加入不同的金属助剂(Zr、Sm、La)以及调变活性金属与助剂的比例,来调控活性中心的电子结构以及载体的碱性,以对-羟苯基型模型化合物,愈创木基型模型化合物,紫丁香基型模型化合物为底物,活性中心Ni的电子云密度越低,越有利于p位C-O键断裂；载体的碱性越强,越有利于α位C-O键断裂。此外,活性中心Ni的电子云密度越低,更利于对芳环深度加氢的抑制。2.通过调控催化剂前体中的活性金属含量,合成不同晶粒尺寸的Ni基催化剂,以对-羟基苯基型模型化合物为底物,催化剂的粒径越大,活性越高,粒径越小,对芳环深度加氢的抑制作用越强。
[Abstract]:Aromatic compounds as a kind of chemical products with high economic value, in various fields have been widely used. Now, aromatic compounds come from the petrochemical industry, but with the increasing depletion of oil resources, utilization of renewable resources to prepare lignin aromatic compounds has important significance in lignin refining process. In the commonly used catalysts have homogeneous catalysts such as alkali NaOH, catalysts, such as Mo, Cu, Pt, Rh, Ni and so on, however, the cleavage of the C-O selectivity of these catalysts is relatively poor, and the aromatic ring hydrogenation ability is often too strong, get more economic value low compared to small molecules or naphthenic hydrocarbon. There are mainly two aspects of problems so far by lignin preparation of aromatic compounds: the first, C-O bond cleavage activity and selectivity; second, aromatic ring hydrogenation easily. Therefore, how to improve the wood The quality of selective C-O bond breaking and inhibition of aromatic ring hydrogenation has become the biggest challenge facing the process. Because the Ni based catalyst is cheap, mild reaction conditions, we aimed at the structure of Ni based catalyst was regulated, and were p-hydroxyphenylacetate, guaiacyl, catalytic evaluation of purple syringyl type lignin model compound. In this paper, the regulation of the active center of Ni metal electronic structure and grain size as well as the basic carrier to improve Ni based catalysts for C-O bond cleavage activity and selectivity, inhibit the reaction of aromatic ring hydrogenation. The contents of this thesis are as follows: 1. by adding different metal additives in the Ni based catalyst (Zr, Sm, La) and the ratio of variable reactive metals and additives, the electronic structure and carrier to control the activity of alkaline center, to compound p-hydroxyphenyl model Guaiacyl, syringyl type model compounds, model compounds as substrate, electron cloud density of the active site of Ni is lower, more conducive to the P C-O bond cleavage; vector alkaline is stronger, more conducive to the alpha C-O bond breaking. In addition, the electron density of active center of Ni is lower, more conducive to the inhibition of.2. on aromatic ring hydrogenation by active metal content in the body of the catalysts, Ni based catalysts for the synthesis of different grain sizes, with p-hydroxyphenylacetate model compounds as substrate, the catalyst particle size is larger, the higher the activity, the smaller the particle size, the stronger the inhibition effect of aromatic ring depth hydrogenation.

【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36;O625

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