镍基纳米催化剂的制备及催化合成4-甲氧基环己酮的研究

发布时间：2018-03-25 19:02

本文选题：镍基纳米催化剂　切入点：催化加氢　出处：《河北大学》2017年硕士论文

【摘要】：催化加氢反应具有原子经济性的特点,符合绿色化学化工的发展要求,是目前国内外研究的热点之一。其中,利用酚类化合物加氢制备相应的醇、酮类化合物,可广泛应用于医药、农药、染料等领域。目前,酚类化合物的加氢反应均采用钯等贵金属催化剂,价格昂贵,且有时还存在原料转化率偏低、目标产物选择性偏差等问题。针对这些问题,本文首次采用廉价的镍基纳米催化剂用于4-甲氧基苯酚的加氢反应,研究了不同催化剂结构与活性和稳定性之间的关系,并对4-甲氧基环己酮合成中氧化反应的条件进行了探究。首先,分别采用沉积-沉淀法和浸渍法制备了负载型镍基纳米催化剂Ni/Al_2O_3,并将其应用于4-甲氧基苯酚的加氢反应。考查了两种制备方法及反应条件对催化剂活性和稳定性的影响。通过X射线衍射(XRD)、H2-程序升温还原(H2-TPR)及透射电子显微镜(TEM)等测试手段对催化剂进行了表征,发现利用沉积-沉淀法制备的Ni/Al_2O_3-DP催化剂中的活性粒子分散度高、粒径较小,并且活性粒子与载体之间有较强的相互作用,比浸渍法制备的Ni/Al_2O_3-IMP催化剂具有更好的活性和稳定性。接着,为了进一步提高Ni/Al_2O_3-DP的催化活性和稳定性,我们通过添加改性金属制备了一系列Ni-X/Al_2O_3催化剂,并将其应用于4-甲氧基苯酚的加氢反应。系统研究了改性金属和反应溶剂的极性对催化反应活性的影响,重点探究了催化剂结构与稳定性之间的关系。结果表明Ni-Mg/Al_2O_3催化剂在正己烷中连续使用27次后,其催化活性基本没有下降,显示出了优异的稳定性。最后,为了提高对目标产物4-甲氧基环己酮的总选择性,我们以草酸和钨酸钠制备的配合物为催化剂,以双氧水为氧化剂,对上述加氢反应液进行了进一步的氧化,重点考查了氧化条件对4-甲氧基环己酮总选择性的影响。结果表明在最佳的氧化条件下,4-甲氧基环己酮的总选择性可达到95.3%,上述研究结果对于酮类化合物的绿色合成具有较好的借鉴意义。
[Abstract]:Catalytic hydrogenation has the characteristics of atomic economy and meets the requirements of the development of green chemistry and chemical industry, so it is one of the research hotspots at home and abroad, among which, the corresponding alcohols and ketones are prepared by hydrogenation of phenolic compounds. It can be widely used in medicine, pesticide, dye and so on. At present, the hydrogenation of phenolic compounds all use palladium and other noble metal catalysts, the price is expensive, and sometimes the conversion of raw materials is low. In view of these problems, the cheap nickel-based nanocatalysts were used for the hydrogenation of 4-methoxy phenol for the first time. The relationship between the structure of the catalysts and the activity and stability of the catalysts was studied. The conditions of oxidation reaction in the synthesis of 4-methoxy cyclohexanone were studied. The supported Ni / Al _ 2O _ 3 nano-catalyst Ni / Al _ 2O _ 3 was prepared by deposition-precipitation method and impregnation method, and applied to the hydrogenation reaction of 4-methoxy phenol. The activity and stability of two preparation methods and reaction conditions on the catalyst were investigated. The catalyst was characterized by means of X-ray diffraction (XRD) and temperature programmed reduction (TPR) and transmission electron microscopy (TEM). It was found that the active particles in the Ni/Al_2O_3-DP catalyst prepared by deposition-precipitation method had high dispersion, small particle size, and strong interaction between the active particles and the support. In order to further improve the catalytic activity and stability of Ni/Al_2O_3-DP, we prepared a series of Ni-X/Al_2O_3 catalysts by adding modified metal. The effects of the polarity of modified metal and reaction solvent on the catalytic activity of 4-methoxy phenol were systematically studied. The relationship between the structure of the catalyst and the stability of the catalyst was studied. The results showed that the catalytic activity of Ni-Mg/Al_2O_3 catalyst did not decrease after 27 times of continuous use in n-hexane, showing excellent stability. In order to improve the overall selectivity of the target product 4-methoxycyclohexanone, the hydrogenation solution was further oxidized with oxalic acid and sodium tungstate as catalyst and hydrogen peroxide as oxidant. The effects of oxidation conditions on the total selectivity of 4-methoxycyclohexanone were investigated. The results showed that the total selectivity of 4-methoxycyclohexanone could reach 95.33A under the optimum oxidation conditions. The above results were green to ketones. The synthesis has good reference significance.
【学位授予单位】：河北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ234.21

【参考文献】