固体酸催化环己酮肟液相Beckmann重排

发布时间：2018-11-06 16:49

【摘要】：固体酸催化剂是一种新型的环保催化材料,具有很高的催化活性、良好的选择性、低腐蚀性、易回收循环使用的特点,随着环保意识和绿色化学理念的不断加深,环境友好型的绿色催化工艺技术受到了越来越多的重视。将固体酸催化剂应用于环己酮肟液相Beckmann重排中,不仅可以缓解催化剂的结焦,延长催化剂的寿命,又能实现催化剂与反应液的迅速分离,对开发环境友好的己内酰胺生产工艺具有十分重要的意义。本文制备了四种类型的固体酸催化剂,对其进行了表征分析,催化环己酮肟液相Beckmann重排,并对催化剂的活性中心、重排产物的生成历程进行了探究。本文首先采用沉淀-浸渍法合成了硫酸化氧化锆S-ZrO_2,对其进行了傅里叶红外、热重、吡啶吸附红外和NH3-TPD等表征分析,并将其应用于液相Beckmann重排中。结果表明,由于S-ZrO_2的比表面太小,其对环己酮肟的活性很低,但SO42-与Zr形成的酸性位利于己内酰胺的生成。除环己酮外,体系中主要副产物是环己酮肟的缩聚产物、聚合产物和己内酰胺的缩聚产物,而环己酮肟聚合生成的水会进一步水解环己酮肟生成环己酮。其次,采用MFI结构的沸石分子筛为载体,先向其中掺入杂原子Zr,再用硫酸浸渍,使Zr与SO42-结合形成类似超强酸的结构,制备出硫酸化锆硅分子筛S-ZS,并考察其催化液相Beckmann重排的性能。结果表明,Zr原子的掺入和硫酸功能化都能增加催化剂对环己酮肟的活性,增加对己内酰胺的选择性并减少对环己酮的选择性。S-ZS的强酸中心生成的己内酰胺更难脱附,易进一步反应生成高沸点产物,其催化环己酮肟Beckmann重排反应的副产物种类和体系中水的生成途径与S-ZrO_2相同。进一步采用模板离子交换法和原位合成法制备了两种含铝分子筛TIE-MCM-41和SA20-MCM-41,对两种催化剂进行了表征,对比了两种分子筛催化Beckmann重排的结果,并对结果的差异进行了分析。结果表明,相对于Si-MCM-41,由于两种含铝分子筛的酸总量增加,对环己酮肟的活性都有提高。TIE-MCM-41对己内酰胺的选择性提高的原因是Al的掺入后使得B酸略有增加且硅羟基的酸强度减弱酸量减小所致,SA20-MCM-41对己内酰胺的选择性最高是由于其B酸含量最高且呈弱酸性的邻式硅羟基含量的减少进一步抑制了环己酮的生成。本文最后采用后接枝方法和原位合成方法制备了磺酸功能化的介孔分子筛M-SO3H-P6和M-SO3H-Y,对两种催化剂进行了表征,并对比了两种催化剂对Beckmann重排催化性能上的差异。结果表明,相对于纯硅MCM-41,由于磺酸基团的引入增加了催化剂的强酸中心,两种方法合成的磺酸功能化材料都对环己酮肟的活性都有所提高。原位磺酸功能化MCM-41的B酸含量大于后接枝磺酸功能化MCM-41,并且前者几乎不含表面硅羟基,抑制了环己酮肟的水解,对己内酰胺的选择性更高。
[Abstract]:Solid acid catalyst is a new type of environmental protection catalytic material, with high catalytic activity, good selectivity, low corrosion, easy to recycle and recycling. With the deepening of environmental awareness and green chemical idea, solid acid catalyst is a new type of environmental protection catalyst, which is characterized by its high catalytic activity, good selectivity, low corrosion and easy recycling. More and more attention has been paid to the environmental friendly green catalytic technology. The application of solid acid catalyst in liquid phase Beckmann rearrangement of cyclohexanone oxime can not only alleviate the coking of the catalyst, prolong the life of the catalyst, but also realize the rapid separation of the catalyst from the reaction liquid. It is of great significance to develop environmental friendly caprolactam production process. In this paper, four types of solid acid catalysts were prepared, characterized and analyzed to catalyze the liquid phase Beckmann rearrangement of cyclohexanone oxime. The active sites of the catalysts and the formation process of the rearrangement products were investigated. In this paper, the sulfated zirconia S-ZrO _ 2 was synthesized by precipitation-impregnation method and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), pyridine adsorption infrared (IR) and NH3-TPD, and was applied to the liquid phase Beckmann rearrangement. The results show that the activity of S-ZrO_2 to cyclohexanone oxime is very low due to its small specific surface, but the acidic site formed by SO42- and Zr is favorable to the formation of caprolactam. In addition to cyclohexanone, the main by-products in the system are the condensation products of cyclohexanone oxime, the polymerization products and the condensation products of caprolactam, and the water produced by the polymerization of cyclohexanone oxime will further hydrolyze cyclohexanone oxime to cyclohexanone. Secondly, zeolite molecular sieve with MFI structure was used as carrier, then mixed with heteroatom Zr, and impregnated with sulfuric acid, Zr and SO42- were combined to form superacid-like structure, and S-ZS molecular sieve was prepared. The catalytic properties of Beckmann rearrangement in liquid phase were investigated. The results showed that the addition of Zr atom and the functionalization of sulfuric acid could increase the activity of cyclohexanone oxime, increase the selectivity of caprolactam and decrease the selectivity of cyclohexanone. It was more difficult to desorption caprolactam from the strong acid center of S-ZS. It is easy to react further to form high boiling point products, which catalyze the Beckmann rearrangement of cyclohexanone oxime and the way of water formation in the system is the same as that of S-ZrO_2. Two aluminum-containing molecular sieve TIE-MCM-41 and SA20-MCM-41, were prepared by template ion exchange method and in situ synthesis method. The results of Beckmann rearrangement catalyzed by two molecular sieves were compared. The difference of the results is analyzed. The results showed that compared with Si-MCM-41, the total acid content of the two aluminum-containing molecular sieves increased, The activity of cyclohexanone oxime was improved. The reason for the increase of TIE-MCM-41 selectivity to caprolactam was the slight increase of B acid and the decrease of acid content of silica hydroxyl group due to the addition of Al. The highest selectivity of SA20-MCM-41 to caprolactam is due to the decrease of the hydroxyl content of ortho-silica with the highest B acid content and weak acidity, which further inhibits the formation of cyclohexanone. Finally, M-SO3H-P6 and M-SO3H-Ywere prepared by post-grafting and in-situ synthesis. The two catalysts were characterized. The difference of catalytic performance between the two catalysts for Beckmann rearrangement was also compared. The results showed that compared with pure silicon MCM-41, the activity of cyclohexanone oxime was increased by both the sulfonic acid functional materials synthesized by the two methods because of the addition of sulfonic groups. The B acid content of in situ sulfonic acid functionalized MCM-41 is higher than that of post graft sulfonic acid functionalized MCM-41, and the former has almost no surface silica hydroxyl, which inhibits the hydrolysis of cyclohexanone oxime and has higher selectivity for caprolactam.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ236

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