TAPO-5分子筛催化环己酮氨肟化反应性能的研究

发布时间：2019-05-25 00:01

【摘要】：环己酮肟是尼龙-6纤维和工程塑料产业链的主要组成部分。目前工业上主要采用环己酮-羟胺法生产环己酮肟,该工艺存在制备过程复杂、产率较低、设备易受损、环境污染严重等问题。为提高工业生产的经济与环境效益,研究者一直探索开发新型合成路线。环己酮肟液相氨肟化合成法是新型绿色合成工艺,但反应过程中使用的催化剂TS-1因生产成本高、易失活、难回收等问题限制了该工艺的推广。设计、开发新型高效催化剂体系来替代TS-1,仍是研究者关注的焦点。过渡金属钛原子取代的磷酸铝分子筛(TAPO-5),由于结构规整、组成均匀、同时具有Lewis酸和反应活性中心,成为最有研究前景的催化剂。本文采用水热法进行TAPO-5分子筛的制备,系统考察了钛含量、晶化时间、焙烧气氛等因素对TAPO-5分子筛物化性质及催化性能的影响。采用XRD、XRF、N2物理吸附、DR UV-Vis、Raman、Py-FTIR等方法对分子筛的晶体结构、比表面积、酸性质、分子筛骨架中的钛含量及不同钛物种等物化性质进行表征,考察不同条件下制备的TAPO-5分子筛催化环己酮液相氨肟化性能,并对其催化活性及影响因素进行分析探讨。主要结论有以下方面:(1)Ti作为催化反应的活性中心,TAPO-5分子筛中随着Ti含量的增加,环己酮液相氨肟化反应的收率逐渐增大,但同时分子筛中钛含量的增加造成了结晶度降低,微孔、介孔孔道结构减少;(2)在TAPO-5分子筛中,引入的Ti原子主要有三种存在形式:骨架Ti,非骨架Ti及锐钛矿型TiO2。Py-FTIR的分析表明,非骨架Ti能产生相应的L酸性,在一定程度上有助于催化环己酮氨肟化;(3)使用模板法,在(N_2-H_2)混合气氛中焙烧模板剂,以此对分子筛进行碳改性,并用于催化环己酮氨肟化,结果表明:随焙烧温度的升高,模板剂碳化程度逐渐增加,在氨肟化反应中,反应的选择性也逐渐增大,最高为91.7%。
[Abstract]:Cyclohexanone oxime is the main part of nylon-6 fiber and engineering plastic industry chain. At present, Cyclohexanone oxime is mainly produced by cyclohexanone-hydroxyamine method in industry. There are some problems in this process, such as complex preparation process, low yield, easy damage of equipment, serious environmental pollution and so on. In order to improve the economic and environmental benefits of industrial production, researchers have been exploring and developing a new synthetic route. The liquid phase ammonia oximation synthesis of cyclohexanone oximate is a new green synthesis process, but the catalyst TS-1 used in the reaction process is limited because of its high production cost, easy deactivation and difficult recovery. The design and development of a new type of high efficiency catalyst system to replace TS-1, is still the focus of researchers. Aluminum phosphate molecular sieves (TAPO-5) replaced by transition metal titanium atoms have become the most promising catalyst because of their regular structure and uniform composition, as well as Lewis acid and reactive sites. In this paper, TAPO-5 molecular sieves were prepared by hydrothermal method. The effects of titanium content, crystallization time and calcination atmosphere on the physical and chemical properties and catalytic properties of TAPO-5 molecular sieves were investigated systematically. The crystal structure, specific surface area, acid properties, titanium content in molecular sieves skeleton and physical and chemical properties of different titanium species were characterized by XRD,XRF,N2 physical adsorption and DR UV-Vis,Raman,Py-FTIR. The catalytic performance of TAPO-5 molecular sieves in liquid phase ammoximation of cyclohexanone under different conditions was investigated, and its catalytic activity and influencing factors were analyzed and discussed. The main conclusions are as follows: (1) Ti is used as the active center of catalytic reaction. With the increase of Ti content in TAPO-5 molecular sieves, the yield of liquid phase aminooximation of cyclohexanone increases gradually. At the same time, the increase of titanium content in molecular sieves resulted in the decrease of crystallinity, micropores and mesoporous pore structures. (2) in TAPO-5 molecular sieves, there are three main forms of Ti atoms: skeleton Ti, non-skeleton Ti and anatase TiO2.Py-FTIR analysis show that non-skeleton Ti can produce corresponding L acidity. To a certain extent, it is helpful to catalyze the ammoximation of cyclohexanone. (3) the molecular sieves were modified by using template method and calcined in (N_2-H_2) mixed atmosphere. The results showed that with the increase of calcination temperature, the molecular sieves were modified by carbon and used to catalyze the ammonia oximation of cyclohexanone. The carbonation degree of template increased gradually, and the selectivity of the reaction increased gradually in the ammoximation reaction, the highest was 91.7%.
【学位授予单位】：山西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O621.251

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