原子经济性导向PO生成的钛活性中心的构建及其反应行为研究

发布时间：2018-04-08 14:09

本文选题：原子经济性　切入点：HPPO　出处：《华东师范大学》2017年博士论文

【摘要】：钛硅分子筛(TS)/H2O2体系因其优异的催化性能而受到广泛重视,而如何实现其催化丙烯环氧化高效生成PO是HPPO工艺技术发展的趋势。论文以绿色化学核心思想-原子经济性为指导,针对TS/H2O2体系催化丙烯环氧化生成PO的反应,从提高反应体系中的C原子经济性和O原子经济性角度出发,对反应体系中Ti活性中心的构建及其反应行为进行探究,试图阐明TS/H2O2体系中酸中心本质、高性能Ti活性中心构筑以及影响O有效传递的关键因素,期望形成的科学认识和技术方法将为研发新一代HPPO过程高效生成PO工业技术提供有力的支撑。主要内容包括以下三部分工作。(1)首先,基于建立的HPPO反应体系网络,设计PO与CH3OH和H2O的溶剂解开环反应并结合IR光谱的表征,对TS/H2O2体系中的酸中心类型、酸强度以及影响溶剂解开环反应的因素等进行探究,并提出相应的策略抑制酸中心的影响。结果表明造成HPPO体系中PO溶剂解开环反应的酸中心有四种,且其醇解开环反应活性依次呈现Ti-OOHSi-OH(Ti)Ti4+ ≈ Ti-OH。钛硅分子筛结构中的Si-OH(Ti)基团和TS/H2O2体系中形成的Ti-OOH基团所显示的Br(?)nsted酸是导致PO发生醇解开环反应的主要酸中心。进一步,首次将酸中心类型与相应的醇解产物(1-甲氧基-2丙醇(PPM)和2-甲氧基-1丙醇(SPM))分布进行关联,发现,Br(?)nsted酸中心催化倾向于生成SPM,而显示出Lewis酸中心的Ti4+中心倾向于生成PPM。PPM和SPM的产物分布有助于指导对钛硅分子筛和TS/H2O2体系酸中心的选择性抑制。通过精细的离子交换和添加剂的引入可以选择性地对催化剂和催化体系中的酸中心进行抑制,达到PO的高选择性合成、提高C原子经济性的目的。(2)其次,基于C原子经济性的另一个角度-即提高反应活性,从高性能Ti活性中心的构建出发,成功的定向构建出具有六配位"TiO6"活性中心的TS-1+和开放的四配位Ti(OSi)3OH活性中心的TS-1s催化剂,并对相应的活性中心形成机理以及催化性能进行探讨。通过对TS-1进行TPABr和EA水热处理,成功地合成出具有六配位"TiO6"物种的TS-1+分子筛。过UV-Vis、UV-Raman以及IR等表征结果表明TS-1+中六配位"TiO6"物种是通过骨架四配位"TiO4"物种定向转变而来。而对其形成过程中微观结构变化的跟踪,证明了 "TiO6"物种是通过对Ti周边的Si进行选择性地溶解并同时将溶解的Si迁移至外表面晶化而得到,整个过程中未流失骨架Si和Ti物种。通过对"TiO6"物种形成条件的考察,发现"TiO6"物种形成的关键在于控制Si溶解速率与晶化速率的平衡。进一步的催化性能表明具有"TiO6"物种的TS-1+在烯烃环氧化和环己酮氨肟化反应具有优异的催化氧化性能,并且"TiO6"物种在正己烯环氧化反应的TON约是传统"TiO4"物种的2-3倍,是一个具有潜在工业应用前景的催化剂。通过对TS-1进行小分子胺(EA等)水热处理,成功地合成出具有开放状态的四配位Ti(OSi)3OH活性中心的TS-1s催化剂。通过对其结构的表征及形成过程的跟踪,发现Ti(OSi)3OH活性中心是来源于碱对钛硅分子筛表面闭合的Ti(OSi)4活性中心周边的Si进行选择性地溶解转化而来,且处理过程中未明显溶硅产生介孔。TS-1s在烯烃环氧化以及环己酮氨肟化反应具有优异的催化氧化性能,且进一步的半定量分析表明Ti(OSi)3OH活性中心在不同Ti物种中具有最高的催化性能,不同Ti物种之间催化性能依次呈现出Ti(OSi)3OH"TiO6"Ti(OSi)4。(3)最后,由于TS/H2O2体系催化的本质在于H2O2的活化与传递,因此基于建立的H2O2反应路径,以氧化剂(H2O2和t-BuOOH等)利用率作为O传递的评价指标,对影响Ti-OOH中间体的形成与稳定的Ti活性中心、溶剂、氧化剂、添加剂和反应底物五个因素进行探究。结果表明,对于烯烃环氧化反应,提高O原子经济性的关键在于提高Ti活性中心活化H2O2形成Ti-OOH的能力,并同时通过溶剂和添加剂等的氢键作用对其进行稳定,促进Ti-OOH中的O异裂形式,进而抑制竞争副反应中H2O2或Ti-OOH的无效分解,实现O的高效传递。
[Abstract]:Titanium silicon molecular sieve (TS) /H2O2 system because of its excellent catalytic properties have attracted wide attention, and how to realize the efficient generation of propylene epoxidation catalyzed by PO is HPPO technology development trend. Based on the core idea of green chemistry and atom economy as a guide for generating PO propylene epoxidation catalyzed by TS/H2O2 system. From the point of improving the reaction system C O atom atom economy and economic point of view, construction of the Ti active center in the reaction system and reaction behavior study, attempts to clarify the acid center TS/H2O2 system in essence, the key factors of high performance Ti and O activity center to construct the effective transfer of scientific knowledge and technology method of expectations formation for the development of a new generation of HPPO process for the efficient generation of PO technology to provide strong support. The main contents include the following three parts. (1) first, the establishment of HPPO reaction system based on Network design of PO and CH3OH and H2O of the solvent and ring opening reaction combined with characterization of IR spectra, in the system of TS/H2O2 acid type, acid strength and the influence factors of the reaction solvent and ring opening of inquiry, and puts forward the corresponding strategy effect of inhibiting acid center. The results showed that PO caused by acid solvent and ring opening reaction the HPPO system has four kinds, and the alcoholysis reaction of ring opening activity were presented Ti-OOHSi-OH (Ti) Ti4+ = Ti-OH. titanium silicon molecular sieve structure in Si-OH (Ti) Ti-OOH group and TS/H2O2 group formed in the system shown in Br (?) nsted Acid is the main cause of PO acid sites by ring opening reaction for the first time. Further, the acid type and corresponding alcoholysis products (1- methoxy propanol (-2 PPM) and 2- methoxy propanol (SPM) -1) Distribution Association, found that Br (?) nsted Acid Catalyzed tend to form SPM, which showed that Lewis acid A selective guide to the titanium silicon molecular sieve and TS/H2O2 acid center product distribution center inhibit heart Ti4+ tend to generate PPM.PPM and SPM. Through the introduction of ion exchange and fine additives can inhibit the acid catalyst and catalytic system selectively, high selective synthesis of PO, improve the C atom economy. (2) second, another point of C atom economy -- Based on enhancing the activity, starting from the construction of high performance Ti active center, successfully constructed has six directional coordination "TiO6" activity in the heart of TS-1+ and open the four coordinated Ti (OSi) TS-1s catalyst 3OH active center, and the active center of the corresponding formation mechanism and Catalytic Performance were discussed. Based on the TS-1 TPABr and EA hydrothermal treatment was successfully synthesized with six coordinated TS-1+ molecular sieve TiO6 species. UV-Vis, UV-R Aman and IR characterization results show that TS-1+ in the six coordination "TiO6" species by four coordinate framework "change TiO4" species orientation. And the formation of microstructure changes in the process of tracking the show "TiO6" species is selectively dissolved by Ti and Si at the same time will dissolve around Si migration to the outer surface crystallization by skeleton Si and Ti species without loss in the whole process. Through the investigation on the formation of "TiO6" species, found that the "TiO6" key species in the formation of Si dissolution rate and the crystallization rate control balance. Further catalytic performance showed that the "TiO6" species TS-1+ has excellent catalytic performance in the epoxidation of olefin and ammoximation of cyclohexanone, and "TiO6" species in the epoxidation of n-hexene TON is about 2-3 times of the traditional "TiO4" species, is a potential industrial application prospect through the catalyst. TS-1 small molecular amine (EA) hydrothermal treatment was successfully synthesized with the open state of the four coordinated Ti (OSi) TS-1s 3OH catalyst active center. Through the formation and characterization of its structure, the process of tracking, Ti (OSi) 3OH activity center is derived from alkali on titanium silicon molecular sieve surface closed Ti (OSi) activity center 4 surrounding Si selective dissolution and transformation to process, and no obvious solution silicon mesoporous.TS-1s has excellent catalytic performance in the epoxidation of olefin and ammoximation of cyclohexanone, and further semi quantitative analysis showed that Ti (OSi) 3OH activity the center has the highest catalytic performance in different Ti species, the catalytic performance between different Ti species appeared in order Ti (OSi) 3OH "TiO6" Ti (OSi) 4. (3) finally, due to the nature of TS/H2O2 catalyst system is activated and transfer of H2O2 based on H2O2, so the reaction path established, The oxidant (H2O2 and t-BuOOH) using O transfer rate as the evaluation index, the Ti activity center, influence the formation of Ti-OOH intermediate and stable solvent, oxidant, additive and substrate five factors were explored. Results show that for the epoxidation of olefins, provided the key high atom economy is O increase the activity of Ti activated H2O2 Ti-OOH center formation ability, and at the same time by hydrogen bonding solvents and additives on the stability of Ti-OOH in O, promote heterolytic form, thereby inhibiting invalid decomposition of H2O2 or Ti-OOH in the competition side reaction, efficient delivery of O.

【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36

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