铌基复合氧化物纳米管固体酸的构建及酸性特征研究

发布时间：2018-04-14 07:11

本文选题：H_4Nb_6O_(17)纳米管 + 固体酸　；参考：《安徽理工大学》2017年硕士论文

【摘要】：作为重要的有机化合物,乙酸正丁酯是一重要的精细化工产品,它由乙酸与正丁醇在酸催化作用下通过酯化反应获得。通常用硫酸作为催化剂,虽然催化剂活性高,但存在产品难分离,腐蚀设备,废水污染环境等问题。固体酸可以克服硫酸带来的这些问题,而且拥有表面强酸性、选择性好、无污染等优点,因此固体酸作为催化剂取代液体酸已得到了广泛的研究,且发展潜力巨大。本文通过高温固相法合成K4Nb6O17前驱体,经过质子交换、剥离、溶胶-溶胶复合、酸沉积、焙烧、硫酸浸渍等途径对其进行改性获得铌基复合固体酸材料,采用XRD、HRTEM、N2吸附-脱附、Raman、FT-IR、NH3-TPD等技术对本文所制备样品的理化性质进行表征和分析,并以乙酸正丁醇的酯化反应来评价它们的酸催化活性,通过比较得出酸催化活性最高的固体酸催化剂为SO42--ZrO2@NT-Nb2O5(1:3,0.5)复合材料。研究结果表明:纳米管NT-H4Nb6O17材料是由片层H4Nb6017自卷曲形成,且其具有较大的比表面积182 m2·g-1和孔体积0.46 cm3·g-1,管径均匀且管长较长。使用硫酸浸渍处理使NT-H4Nb6O17材料的比表面积、酸强度和酸量都有所增加,且硫酸浓度越大,增加的越明显。复合材料的形貌与复合物中Zr与Nb的摩尔比有关,当Zr:Nb摩尔比为1:3时,复合材料具有纳米管结构,而Zr:Nb摩尔比为1:2时复合材料呈现片状结构。ZrO2氧化物粒子分散在层板的表面,改变了层板表面的应力,当复合比例增大时,层板不再能自我卷曲形成纳米管。与NT-H4Nb6O17材料相比,复合材料的比表面积和孔体积均减小。硫酸浸渍增加了复合材料的比表面积、酸强度以及酸量,且硫酸浓度越大,增加的越明显。选择一定的酯化反应条件,以乙酸正丁醇的酯化反应来评价NT-H4Nb6017材料及其改性材料的酸催化活性,结果显示SO42--ZrO2@NT-Nb205(1:3,0.5)复合材料呈现较好的酸催化活性。选择乙酸正丁醇的摩尔比、反应温度、反应时间、催化剂用量四种因素作为试验考察因素指标,同时对每个因素取三个水平进行正交设计,考察SO42--ZrO2@Nb2O5(1:3,0.5)复合材料对乙酸正丁醇酯化反应的催化活性。试验结果表明:在最优方案下,酯化率高达90.3%,这主要归功于其纳米管结构、较高的酸量以及较强的酸性。并对SO42--ZrO2@Nb2O5(1:3,0.5)复合材料进行单因素优化试验,从而获得最佳的反应条件。
[Abstract]:As an important organic compound, n-butyl acetate is an important fine chemical product, which is obtained by the esterification of acetic acid and n-butanol in the presence of acid.Sulfuric acid is usually used as catalyst, although the catalyst activity is high, but there are some problems such as product separation, corrosion equipment, wastewater pollution and so on.Solid acid can overcome these problems caused by sulfuric acid, and has the advantages of strong acidity, good selectivity, no pollution and so on. Therefore, solid acid as a catalyst to replace liquid acid has been widely studied and has great potential for development.In this paper, the K4Nb6O17 precursor was synthesized by high temperature solid state method. It was modified by proton exchange, stripping, sol-sol composite, acid deposition, roasting and sulfuric acid impregnation to obtain niobium based composite solid acid material.The physicochemical properties of the samples prepared in this paper were characterized and analyzed by means of XRDX HRTEMN _ 2 adsorption-desorption technique, such as Ramann FT-IRN NH _ 3-TPD, and their acid catalytic activity was evaluated by esterification of n-butanol acetate.By comparison, the solid acid catalyst with the highest acid catalytic activity is SO42-ZrO2NT-Nb2O5 (1: 30.5) composite material.The results show that the nanotube NT-H4Nb6O17 material is formed by the self-crimp of H4Nb6017 lamellar, and it has a large specific surface area of 182 m2 g ~ (-1) and pore volume of 0.46 cm3 g ~ (-1). The diameter of the nanotube is uniform and the length of the tube is longer.The specific surface area, acid strength and acid content of NT-H4Nb6O17 materials were increased by sulfuric acid impregnation, and the higher the sulfuric acid concentration was, the more obvious the increase was.The morphology of the composite is related to the molar ratio of Zr to NB in the composite. When the molar ratio of Zr:Nb is 1:3, the composite has nanotube structure, while the composite exhibits a flake structure. ZrO 2 oxide particles are dispersed on the surface of the laminates when the molar ratio of Zr:Nb is 1:2.The stress on the surface of the laminates is changed. When the composite ratio increases, the laminates can no longer curl themselves to form nanotubes.Compared with NT-H4Nb6O17, the specific surface area and pore volume of the composites are reduced.Sulfuric acid impregnation increased the specific surface area, acid strength and acid content of the composites, and the higher the sulfuric acid concentration, the more obvious the increase.The acid catalytic activity of NT-H4Nb6017 and its modified materials was evaluated by esterification of n-butanol acetate under certain esterification conditions. The results showed that SO42-ZrO2NT-NT-Nb205- 1: 30.5) composite showed better acid catalytic activity.Four factors, the molar ratio of n-butanol acetate, reaction temperature, reaction time and the amount of catalyst, were selected as the index of the experimental investigation, and the orthogonal design was carried out at three levels of each factor.The catalytic activity of so _ 42--ZrO _ 2 @ NB _ 2O _ 5 / 1: 3O _ (0.5) composite for the esterification of n-butanol acetate was investigated.The experimental results show that the esterification rate is as high as 90.3% under the optimal scheme, which is mainly attributed to its nanotube structure, high acid content and strong acidity.The single factor optimization test of so _ 42--ZrO _ 2 @ NB _ 2O _ 5 / 1: 3O _ (0.5) composite was carried out, and the optimum reaction conditions were obtained.
【学位授予单位】：安徽理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ225.24

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