介孔结构铁钴硅酸盐复合材料的可控制备及催化性能研究
发布时间：2018-10-15 17:59
【摘要】：具有核壳结构的纳米复合材料的性质比单组分材料的性质优异,因此在催化、填料、多功能涂层材料以及药物载体、生物医药等诸多方面有着广泛的应用和发展前景。过渡金属催化剂因热稳定性高、原料廉价易求,所以常用于催化硝基苯液相加氢生产苯胺。本论文的研究成果总结如下:1.介孔硅酸铁微球的水热合成及表征。在水热条件下,采用牺牲模板界面反应法,合成了具有中空结构的介孔硅酸铁微球,并对合成过程进行了初步的研究。研究发现:不同的碱性环境会影响产物的形貌和物相组成,非碱性环境下会生成棒状的氧化铁。当反应物硅铁摩尔比为1:2时得到的水热产物为尺寸均一的银耳状花球。随着反应时间的延长,水热产物由核壳微球变为空心微球。因此,可以通过控制反应时间来调整产物的微观结构,合成具有核壳或空心结构的硅酸铁。硅酸铁空心球的比表面积为142.2 m2/g,且具有介孔结构。2.介孔Fe/SiO_2的制备及催化性能研究。将介孔硅酸铁空心微球在氢气气氛下,保持600°C还原3 h,得到介孔Fe/SiO_2催化剂,还原前后微球的尺寸和形貌没有很大变化,仍保持空心结构。将Fe/SiO_2用于硝基苯液相加氢制备苯胺,考察Fe/SiO_2的催化活性,研究表明:提高反应温度有利于硝基苯转化为苯胺,加快催化反应的速度,节省反应时间。当催化温度为100 °C时,时间为5 h时即可达到平衡,硝基苯的转化率为75%,苯胺的选择性是83%;Fe/SiO_2催化剂的催化性能随水热反应时间的延长而提高,在水热反应时间达到24 h时,产物是空心球结构,比表面积更大,催化效果更好。3.Fe-Co/SiO_2的水热-还原合成及催化性能。在180 °C下反应12 h得到了具有介孔结构的海胆状碱式硅酸钴空心微球,在氢气气氛下被完全还原为介孔Co/SiO_2空心微球,还原前后样品的形貌没有较大变化,比表面积分别是382.78 m2/g,158.25 m2/g。将Co/SiO_2用于催化硝基苯液相加氢制备苯胺,表现出较高的催化活性。当铁钴摩尔比为2:1,碱性水热环境下得到了尺寸均一、形貌稳定的铁钴硅酸盐复合微球。研究发现:升高水热反应温度能够加快反应速度,但温度过高会导致中空结构不稳定而发生坍塌。水热产物被氢气还原为介孔Fe-Co/SiO_2中空微球,比表面积较大,有利于物质的传输并发挥催化活性,由于双金属的协同效应,使得铁钴复合催化剂的催化性能比单一金属催化剂的催化性能更好。
[Abstract]:The properties of nanocomposites with core-shell structure are better than that of single-component materials, so they are widely used and developed in catalysis, packing, multifunctional coating materials, drug carriers, biomedicine and so on. Because of its high thermal stability and cheap raw materials, transition metal catalysts are often used to catalyze the liquid phase hydrogenation of nitrobenzene to produce aniline. The research results of this paper are summarized as follows: 1. Hydrothermal synthesis and characterization of mesoporous iron silicate microspheres. Mesoporous ferric silicate microspheres with hollow structure were synthesized by sacrificial template interface reaction under hydrothermal conditions. It is found that the morphology and phase composition of the product will be affected by different alkaline environment, and the rod-like iron oxide will be formed in non-alkaline environment. When the molar ratio of silicon to iron was 1:2, the hydrothermal product was a uniform Tremella flower ball. With the increase of reaction time, the hydrothermal products changed from core-shell microspheres to hollow microspheres. Therefore, the microstructure of the product can be adjusted by controlling the reaction time to synthesize ferric silicate with core-shell or hollow structure. The specific surface area of iron silicate hollow spheres is 142.2 m2 / g and has mesoporous structure. Preparation and catalytic properties of mesoporous Fe/SiO_2. The mesoporous iron silicate hollow microspheres were reduced to 600 掳C for 3 h in hydrogen atmosphere, and the mesoporous Fe/SiO_2 catalyst was obtained. The size and morphology of the mesoporous Fe/SiO_2 microspheres did not change greatly before and after reduction, and the hollow structure was maintained. Fe/SiO_2 was used in liquid phase hydrogenation of nitrobenzene to prepare aniline. The catalytic activity of Fe/SiO_2 was investigated. The results showed that increasing the reaction temperature was beneficial to the conversion of nitrobenzene to aniline, accelerating the rate of catalytic reaction and saving the reaction time. When the catalytic temperature is 100 掳C, the reaction time is 5 h, the conversion rate of nitrobenzene is 75, the selectivity of aniline is 83% Fe / SiO2 catalyst, and the catalytic performance of the catalyst increases with the prolongation of hydrothermal reaction time, and when the hydrothermal reaction time reaches 24 h, the selectivity of aniline increases with the increase of hydrothermal reaction time. The product is hollow sphere structure with larger specific surface area and better catalytic effect. Hydrothermal reduction synthesis and catalytic performance of 3.Fe-Co/SiO_2. The basic cobalt silicate hollow microspheres with mesoporous structure were prepared at 180 掳C for 12 h. The microspheres were completely reduced to mesoporous Co/SiO_2 hollow microspheres in hydrogen atmosphere. The morphology of the samples did not change significantly before and after the reduction, with a specific surface area of 382.78 m2 / g ~ 158.25 m ~ (2 / g), respectively. Co/SiO_2 was used to catalyze the hydrogenation of nitrobenzene to aniline in liquid phase and showed high catalytic activity. When the molar ratio of iron and cobalt is 2: 1, the Fe-Co silicate composite microspheres with uniform size and stable morphology are obtained in alkaline hydrothermal environment. It is found that the reaction rate can be accelerated by increasing the hydrothermal reaction temperature, but the hollow structure will collapse due to the instability of the hollow structure when the temperature is too high. Hydrothermal products were reduced by hydrogen to mesoporous Fe-Co/SiO_2 hollow microspheres with large specific surface area, which was conducive to the transport of materials and played a catalytic activity, due to the synergistic effect of bimetallic materials. The catalytic performance of Fe-Co composite catalyst is better than that of single metal catalyst.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;O643.36
[Abstract]:The properties of nanocomposites with core-shell structure are better than that of single-component materials, so they are widely used and developed in catalysis, packing, multifunctional coating materials, drug carriers, biomedicine and so on. Because of its high thermal stability and cheap raw materials, transition metal catalysts are often used to catalyze the liquid phase hydrogenation of nitrobenzene to produce aniline. The research results of this paper are summarized as follows: 1. Hydrothermal synthesis and characterization of mesoporous iron silicate microspheres. Mesoporous ferric silicate microspheres with hollow structure were synthesized by sacrificial template interface reaction under hydrothermal conditions. It is found that the morphology and phase composition of the product will be affected by different alkaline environment, and the rod-like iron oxide will be formed in non-alkaline environment. When the molar ratio of silicon to iron was 1:2, the hydrothermal product was a uniform Tremella flower ball. With the increase of reaction time, the hydrothermal products changed from core-shell microspheres to hollow microspheres. Therefore, the microstructure of the product can be adjusted by controlling the reaction time to synthesize ferric silicate with core-shell or hollow structure. The specific surface area of iron silicate hollow spheres is 142.2 m2 / g and has mesoporous structure. Preparation and catalytic properties of mesoporous Fe/SiO_2. The mesoporous iron silicate hollow microspheres were reduced to 600 掳C for 3 h in hydrogen atmosphere, and the mesoporous Fe/SiO_2 catalyst was obtained. The size and morphology of the mesoporous Fe/SiO_2 microspheres did not change greatly before and after reduction, and the hollow structure was maintained. Fe/SiO_2 was used in liquid phase hydrogenation of nitrobenzene to prepare aniline. The catalytic activity of Fe/SiO_2 was investigated. The results showed that increasing the reaction temperature was beneficial to the conversion of nitrobenzene to aniline, accelerating the rate of catalytic reaction and saving the reaction time. When the catalytic temperature is 100 掳C, the reaction time is 5 h, the conversion rate of nitrobenzene is 75, the selectivity of aniline is 83% Fe / SiO2 catalyst, and the catalytic performance of the catalyst increases with the prolongation of hydrothermal reaction time, and when the hydrothermal reaction time reaches 24 h, the selectivity of aniline increases with the increase of hydrothermal reaction time. The product is hollow sphere structure with larger specific surface area and better catalytic effect. Hydrothermal reduction synthesis and catalytic performance of 3.Fe-Co/SiO_2. The basic cobalt silicate hollow microspheres with mesoporous structure were prepared at 180 掳C for 12 h. The microspheres were completely reduced to mesoporous Co/SiO_2 hollow microspheres in hydrogen atmosphere. The morphology of the samples did not change significantly before and after the reduction, with a specific surface area of 382.78 m2 / g ~ 158.25 m ~ (2 / g), respectively. Co/SiO_2 was used to catalyze the hydrogenation of nitrobenzene to aniline in liquid phase and showed high catalytic activity. When the molar ratio of iron and cobalt is 2: 1, the Fe-Co silicate composite microspheres with uniform size and stable morphology are obtained in alkaline hydrothermal environment. It is found that the reaction rate can be accelerated by increasing the hydrothermal reaction temperature, but the hollow structure will collapse due to the instability of the hollow structure when the temperature is too high. Hydrothermal products were reduced by hydrogen to mesoporous Fe-Co/SiO_2 hollow microspheres with large specific surface area, which was conducive to the transport of materials and played a catalytic activity, due to the synergistic effect of bimetallic materials. The catalytic performance of Fe-Co composite catalyst is better than that of single metal catalyst.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;O643.36
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相关期刊论文 前10条
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2 秦祖赠;栗西亮;蒋月秀;谢新玲;粟海锋;;硝基苯气-固相催化加氢为苯胺的实验研究[J];实验室研究与探索;2016年03期
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