Ammoximation of ketones on titanium silicalite. A study of the reaction byproducts

In the new EniChem process cyclohexanone oxime is directly synthesized by ammoximation of cyclohexanone with ammonia and hydrogen peroxide on titanium silicalite catalyst. The ammoximation reaction is suitable for the synthesis of several oximes by reaction of the corresponding ketones with ammonia and hydrogen peroxide on titanium silicalite. New results on ketones ammoximation and on reaction byproducts are reported. The effect of some reaction parameters on the oxime yield and on byproducts formation is discussed.     

TS-1催化丙酮氨氧化制丙酮肟的本征动力学研究

丙酮肟是一种优良的除氧剂.TS-1催化丙酮氨氧化合成丙酮肟是一种新型绿色工艺.借助高效液相色谱技术,研究了在TS-1分子筛催化下以氨、过氧化氢直接氧化丙酮为丙酮肟的本征反应动力学.在本实验条件下,TS-1催化剂平均粒径为200nm,内扩散可以忽略,当搅拌速度大于580 r·min-1时,外扩散已基本消除,反应进入动力学控制区;反应对于丙酮、过氧化氢和氨的反应级数分别为0.87、0.05和1.0,反应活化能为101.88 kJ·mol-1,反应指前因子为5.20×1013mol-092·L0.92·min-1.这可为TS-1催化-膜分离耦合制备丙酮肟过程开发提供基础数据.     

A novel titanosilicate with MWW structure: Highly effective liquid-phase ammoximation of cyclohexanone

The liquid-phase ammoximation of cyclohexanone with ammonia and hydrogen peroxide was conducted over Ti-MWW. Ti-MWW is capable of giving both cyclohexanone conversion and oxime selectivity >99% under optimum reaction conditions. It is a highly active, selective, and reusable catalyst for the synthesis of cyclohexanone oxime in the presence of water. In comparison to other titanosilicates, Ti-MWW shows much higher catalytic activity, even superior to that of TS-1. The catalytic performance of Ti-MWW depends greatly on the operating conditions of the reaction, especially the method of adding substrates. The reason why the method of adding substrates plays such an important role in the ammoximation of ketones or aldehydes over Ti-MWW was investigated after a detailed evaluation of the reaction mechanism.     

三相体系中TS-1分子筛催化环己酮氨肟化制环己酮肟(英文)

An innovative green process of producing ε-caprolactam was proposed by integrating ammoximation and Beckmann rearrangement effectively. As a first part of the new process, TS-1 molecular sieve-catalyzed synthesis of cyclohexanone oxime from cyclohexanone, ammonia and hydrogen peroxide was carried out in a batch plant. Cyclohexane was used as the solvent in the three-phase reaction system. The influences of essential process parameters on ammoximation were investigated. Under the reaction conditions as catalyst content of 2.5% (by mass); H 2 O 2 /yclohexanone molar ratio of 1.10; NH 3 /cyclohexanone molar ratio of 2.20; reaction temperature of 343 K; reaction time of 5 h, high conversion of cyclohexanone and selectivity to oxime (both>99%) were obtained. Thus, the three-phase ammoximation process showed equal catalytic activity as TS-1 but much more convenient and simpler for the separation of catalyst in comparison to the industrial two-phase system with t-butanol used as solvent.     

Catalytic mechanism and reaction pathway of acetone ammoximation to acetone oxime over TS-1

A series of two-step reactions and several special experiments were designed and carried out to discover the reaction pathway of acetone ammoximation to acetone oxime over titanium silicalites-1 (TS-1) employing 25 wt% ammonia and 30 wt% hydrogen peroxide as the ammoximation agents. The experimental results show that the acetone oxime can form even if there is no direct contact between acetone and TS-1 catalysts, indicating the hydroxylamine route may be the most important catalytic mechanism for the reaction. HPLC, GC/MS and ion chromatography characterization results show that hydrogen peroxide can oxidize acetone oxime to acetone, nitrite and nitrate in the presence of TS-1. In addition, nitrite and nitrate can form in the reaction of H₂O₂ and NH₃ over TS-1. Based on these results, a possible overall reaction pathway of acetone ammoximation over TS-1 has been proposed.     

Ammoximation reaction with titanium doped amorphous silica

The catalytic behavior and the role of the acidic sites and of the activated forms of molecular oxygen in the ammoximation reaction of cyclohexanone to cyclohexanone oxime were investigated on pure and titanium doped amorphous silicas. The samples were prepared by the sol-gel method under acidic and basic conditions. The introduction of low amounts of titanium on silicas, prepared under basic conditions, strongly increased the oxime yield and conversion. The sample containing 0.25% titanium resulted in a very active and selective catalyst. A further increase of the titanium content decreased the catalytic activity and also the catalyst deactivation, because of a decrease of the tars formation rate. The comparison of the catalytic data and the results of FT-IR and EPR analysis confirmed the bifunctional nature of the amorphous silica catalyst. On the first step of the reaction pathway, the imine formation, the paramount parameter is an intrinsic property of pure silica, related to its textural and structural features. The adsorption experiments showed that the silica prepared under basic conditions, the only active in ammoximation, was able to form surface imine on acidic sites. The nature and the role of the oxidizing sites seem more complex. EPR results showed the presence of radical species on titanium modified silica and also, in small amount, on silica itself; however, the oxime formation did not seem to be a property related only to the presence of activated oxygen species anchored to titanium sites. It has been proposed that the formation of oxime is due to a combined effect of the presence of tars and of the activated oxygen species due to the titanium, which are able to oxidize the imine to oxime.     

氨肟化反应中影响双氧水分解因素浅析

本文对环己酮氨肟化反应体系中引发H2O2分解的因素进行了研究,针对各种影响因素提出控制H2O2分解的优化措施。结果表明：在氨肟化反应体系中,NH3过量导致的碱性环境、H2O2过量加入或H2O2浓度过高以及氨肟化反应不完全,是引起H2O2分解的主要原因;反应温度、反应压力等操作条件的变化也可改变H2O2的分解速度;微量的锰、锌、铜、铁、镍等金属离子的存在,也会大大加速H2O2的分解。控制适当的NH3浓度及酮/H2O2摩尔比、反应条件以及降低金属离子含量有利于提高H2O2的有效利用率,这些结果可以为优化氨肟化反应工艺、降低H2O2消耗提供依据。     

钛硅分子筛TS-1合成及催化环己酮氨氧化的研究进展

钛硅分子筛TS- 1催化的环己酮氨氧化反应是一个绿色过程。介绍了TS- 1分子筛的合成、TS- 1分子筛催化的环己酮氨氧化及环己酮氨氧化与过氧化氢生产的集成。指出提高催化剂的性能、降低其生产成本是今后研究的重点 ,绿色氧化剂过氧化氢的生产与氨氧化过程的集成是今后环己酮肟生产的发展方向     

Titanhaltige Molekularsiebe als Katalysatoren für selektive Oxidationsreaktionen mit Wasserstoffperoxid

Titanium Containing Molecular Sieves as Catalysts for Selective Oxidation Reactions with Hydrogen Peroxide Titanium silicalite (TS-1) is known to be a highly-efficient and selective redox molecular sieve that has been found to catalyze a range of synthetically useful oxidation reactions with hydrogen peroxide under mild conditions. Among these reactions which are often influenced also by the shape-selective properties of the Ti-containing molecular sieve are olefin epoxidation, the oxidation of alcohols to carbonyl compounds, aromatic hydroxylations and ammoximation of cyclohexanone to cyclohexanone oxime. A critical review on the present literature on TS-1 catalysts and further Ti-containing molecular sieves is given mainly focused on the questions connected with the identification of the catalytic active titanium species and the mechanism of some of the reactions. Therefore, the procedure of the synthesis of TS-1 as well as the results obtained from the most of the physico-chemical investigations are analyzed. There are no final correlations to realize between the parameters of the synthesis, the results of characterization and the catalytic properties of TS-1.     

绿色化学中的新催化方法

本文简述了绿色化学中几种有前景的新催化方法，包括固体酸取代液体酸的酸催化，晶格氧代替分子氧的氧化，TS－1分子筛H2O2的清洁氧化新工艺及羰化催化的新发展。     

Structural and Physicochemical Features of Titanium Silicalites

The review presents a comparison and discussion of the substantial amount of information about the state and coordination of titanium ions in titanium silicalites. The results from structural characterization of titanium silicalites with spectral, electrochemical, and quantum-chemical methods with emphasis on location of the Ti ions in framework or extraframework positions, their coordination, and the relationship of some spectral features to concrete structures at the atomic level are summarized. The main methods for the determination of some specific characteristics of titanium silicalite samples are considered—presence of metal ion impurities, extraframework titania, acidity, hydrophobicity, diffusion, and other sterical restrictions. Speculations on how these properties influence the catalytic activities and selectivities of the samples are discussed. Some experimental results for interaction of molecules—solvents, water, and hydrogen peroxide—with titanium silicalites are also presented. The review could be used as an appropriate basis for continuation of the discussion on molecular aspects of catalytic activity of titanium silicalites in partial oxidation with hydrogen peroxide.     

丙烯环氧化合成环氧丙烷新技术的研究进展

评述了以分子氧和双氧水为氧源的丙烯环氧化催化剂体系的最新研究进展。其中包括金属Ag催化剂。金属熔盐混合物，钛硅沸石TS-1和过渡金属络合物催化剂体系，根据氧转移机理。金属Ag催化剂和熔盐体系是以分子氧为直接氧源，而TS-1和最近报道的反应相转移含钨催化剂本质上是以过氧化氢为直接氧源。TS-1和反应相转移含钨催化剂和优点是反应条件较温和，生成环氧丙烷的选择性和产率较高。如一种负载成“蛋壳醇作为溶剂），环氧丙烷选择性和产率（以双氧水计）分别可达92%和90%以上。催化剂运转1000h以上性能稳定，今后的一个重要发展方向是开发以分子氧为起始氧源，简单高效的原位双氧水工艺。     

钛硅分子筛催化环己酮氨肟化本征动力学

对钛硅分子筛(TS-1)催化环己酮氨肟化反应进行了研究。根据该反应体系中环己酮可能部分吸附在TS-1分子筛活性中心上与氨发生亚胺机理,未被吸附的环己酮和羟胺中间体发生羟胺机理(双机理),建立了氨肟化反应以及该反应体系中过氧化氢分解的动力学方程,结合实验数据,对参数进行了估算及统计检验,对氨肟化反应和过氧化氢分解的动力学模型的计算值与实验值进行了比较,结果表明该模型能真实反映TS-1分子筛催化环己酮氨肟化的反应规律。同时,对双机理模型中各机理也进行了模拟计算,结果表明,双机理模型中的亚胺和羟胺机理在反应体系中发生的几率跟反应温度有很大关系。另外,过氧化氢分解动力学模型只适用于该反应体系。     

氨肟化反应中双氧水分解的影响因素探讨

在实验装置上对环己酮氨肟化反应体系中引发双氧水分解的因素进行了分析,将实验结果应用于工业化生产。结果表明:在氨肟化反应体系中,氨过量导致的碱性环境、双氧水过量加入或氨肟化反应不完全是双氧水分解的主要原因;反应温度、反应时间等反应条件的变化可改变双氧水的分解速度;微量的铜、铁、铬等金属离子的存在会加速双氧水的分解;适当控制氨浓度、环己酮∶双氧水摩尔比、反应条件及降低金属离子含量有利于提高双氧水的有效利用率;在工业生产装置中,控制反应液中氨质量分数2.0%～2.8%,环己酮∶双氧水摩尔比为1∶(1.05～1.10),反应温度78～81℃,催化剂(相对于环己酮)质量分数小于4%,双氧水利用率提高了3.7%。     

Preparation of aldoxime through direct ammoximation using titanium silicalite-1 catalyst

The liquid phase direct ammoximation of 5-isooctyl salicylaldehyde with ammonia and hydrogen peroxide was studied using titanium silicalite-1 (TS-1) catalyst. The effect of reaction parameters on the yield of the product was studied, which include reaction temperature, reaction time, molar ratio of ammonia to aldehyde as well as hydrogen peroxide to aldehyde. The influence of the amount of catalyst on the reaction results was also investigated. The maximum 5-isooctyl salicylaldoxime yield of 98.76% was achieved under the following optimal reaction conditions:the molar ratio of 5-isooctylaldehyde to hydrogen peroxide and ammonia of 1:1.4:1.6, the reaction temperature of 70℃, the amount of TS-1 of 17.5 g·mol^-1 (5-isooctyl salicylaldehyde), and the feeding time of 2 h. This method has the mild reaction conditions and avoids the shortcomings of traditional methods. Moreover, useless inorganic salts by-products are avoided, and there is no environmental pollution.     

Influence of Pt–Pd/TS-1 Catalyst Preparation on Epoxidation of Olefins with Hydrogen Peroxide

The catalytic performance of the platinum–palladium/titanium silicalite, which was a common catalyst for the direct epoxidation of olefins with hydrogen and oxygen, was tested by epoxidation of allyl chloride with hydrogen peroxide. The epoxidation capacity of the TS-1catalyst was reduced after loading palladium and platinum on it. Ti leaching and crystallinity decrease were observed by XRD and FT-IR. The decomposition of hydrogen peroxide was accelerated by the supported Pd and Pt. These contributed to the loss of epoxidation capacity of TS-1. Ti leaching and crystallinity decrease were probably main causes. We propose that the Ti leaching had the most important influence on the loss of epoxidation capacity     

TS-1催化环己酮氨氧化反应本征动力学模型

由TS-1催化环己酮氨氧化反应机理出发,分析了反应过程的特点及反应规律,根据推测的机理,建立了反应本征动力学模型.结合搅拌釜中测得的动力学数据,对动力学模型进行了参数估值及模型筛选.结果表明,假设反应合乎羟胺机理、双氧水吸附、表面反应为控制步骤时所导出的模型能较好地拟合实验数据,并满足统计检验.根据该动力学模型,通过模拟计算对部分操作条件进行了分析和优化.     

Patterns of phenol oxidation process with an aqueous solution of hydrogen peroxide

This paper presents experimental data on the study of catalytic systems based on titanium silicalite (TS-1) for liquid-phase oxidation of phenol. The influence of the main parameters of the process of liquid phase oxidation of phenol with aqueous solution of hydrogen peroxide on the catalyst; the formed titanium silicalite (initial molar ratio of phenol/hydrogen peroxide, temperature) has been studied based on the basic parameters of the process, including the degree of conversion of hydrogen peroxide, the degree of conversion of phenol, the selectivity of the formation of catechol, hydroquinone and 1,4-benzoquinone, and the ratio of products in the reaction mass.     

微乳条件下环己酮的氨肟化反应

针对钛硅分子筛(TS-1)催化环己酮氨肟化反应在浆态条件下进行时存在的固液分离和溶剂回收等问题,尝试采用微乳化的方法加以解决。以十六烷基三甲基溴化铵(CTAB)/水/氨水/环己酮的水包油(O/W)型微乳液作为反应介质,实现了TS-1催化环己酮的氨肟化反应。通过实验考察了反应温度及助表面活性剂(叔丁醇)的用量对反应选择性及转化率的影响。结果表明,升高反应温度,在环己酮转化率随之提高的同时,环己酮肟的选择性先升高后降低,且在65℃时达到最高;而助表面活性剂(叔丁醇)的用量对环己酮的转化率没有明显影响,却显著影响了反应的选择性。X射线衍射图和傅立叶变换红外谱图显示,所得的环己酮肟结晶度好、纯度高。