磁性钛硅催化剂催化环己酮氨肟化传递-反应研究

磁性钛硅分子筛是具有原子经济特征和磁回收功能新型绿色催化剂。通过研究磁性钛硅分子筛催化环己酮氨肟化制备环己酮肟过程,考察了环己酮、H2O2和NH3·H2O的初始浓度和搅拌雷诺数对氨肟化过程的影响。在消除内扩散和外扩散的条件下,确定了环己酮氨肟化的动力学方程,反应指前因子为5.89×1012(mol-0.87·L0.87)·min-1,反应活化能为101.3kJ·mol-1,环己酮、H2O2和NH3·H2O的反应级数分别为0.65、0.16和1.06,对反应速率计算值和实验值进行了比较,平均相对误差为6.86%。     

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。     

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.     

Epoxidation of allyl alcohol to glycidol using titanium silicalite TS-1: effect of the reaction conditions and catalyst acidity

The epoxidation of allyl alcohol to glycidol using the titanium silicalite TS-1 with hydrogen peroxide as the oxidant is described and discussed in detail. The reaction conditions (alcohol, solvent, temperature) required to obtain 100% selectivity to glycidol are described and this selectivity has been observed at conversions of allyl alcohol of up to 20%. Addition of excess hydrogen peroxide enhances conversion but does not appear to affect selectivity to glycidol deleteriously, whereas addition of hydrogen peroxide over an extended time period is not particularly beneficial. The major side reactions are the oxidation of the alcohol solvent and the ring opening solvolysis of the glycidol that leads to the formation of alkoxy diols. Base treatment of the TS-1 using sodium azide enhances the glycidol selectivity, whereas the incorporation of Brønsted acid sites by addition of aluminium into the framework structure of TS-1 enhances the selectivity to the products of solvolysis ring opening reactions.     

钛硅分子筛失活与再生的研究进展

介绍了在烯烃环氧化、环己酮氨肟化、苯酚羟基化等催化氧化反应中钛硅分子筛失活的研究现状,分析了反应副产物堵孔是催化剂失活的主要原因,同时钛流失或硅溶解也是导致催化剂失活的原因之一。总结了钛硅分子筛目前采用的主要再生方法,简述了不同再生过程对催化剂结构与性能的影响。展望了钛硅分子筛再生研究的发展方向。     

新型催化剂在氨肟化装置的应用

从催化剂的定向氧化性、可再生性、可分离性、催化作用的连续性等几个方面,对石家庄炼化16万t扩容改造核心装置——环己酮氨肟化装置所采用的新型催化剂进行了较为详细的论述,并从不同角度说明催化剂性能对环己酮氨肟化装置的稳定运行起着重要作用。     

Re-investigation of titanium silicalite by X-ray absorption spectroscopy: Are the novel titanium sites real?

EXAFS studies have been carried out on titanium silicalite-1 (TS-1). The titanium atom is coordinated to four oxygen atoms at the distance of 1.80(1) Å. There is no evidence for the presence of 5- and 6-coordinated titanium species or the novel 4-coordinated titanium species involving [TiO _x ] units sharing edges with [SiO₄] units. The EXAFS spectrum of TS-1 appears to be consistent with the model that titanium resides at the tetrahedral sites of the framework.     

Selective oxidation of secondary amines over titanium silicalite molecular sieves,TS-1 and TS-2

Titanium silicalite molecular sieves, TS-1 and TS-2 having MFI and MEL structures, respectively, catalyze the oxidation of secondary amines to the corresponding hydroxylamines using hydrogen peroxide as the oxidant. Higher concentrations of H₂O₂ lead to further oxidation of hydroxylamine to nitrone. Diffuse reflectance spectroscopy shows the formation of a titanium peroxo complex upon addition of hydrogen peroxide to the TS-1 catalyst. The titanium peroxo complex oxidizes the substrate and reforms to a titanyl group.     

Epoxidation of allyl alcohol to glycidol using titanium silicalite TS-1: effect of the method of preparation

The epoxidation of allyl alcohol with hydrogen peroxide catalysed by the microporous titanium silicalite TS-1 has been investigated with respect to the effect of the method of catalyst preparation. Three methods of TS-1 synthesis have been studied using the standard tetrapropyl-ammonium cation as template (i) using tetraethyl orthosilicate, tetraethyl orthotitanate as reagents, (ii) using a fluoride method and (iii) using tetrabutyl orthotitanate as the titanium source. The TS-1 samples were characterised by electron microscopy, X-ray diffraction and infrared spectroscopy. The method of preparation controlled the morphology of the TS-1 crystals and in particular the crystallisation time was found to be an important parameter. Data are presented that correlate the activity for the epoxidation of allyl alcohol with the morphology of TS-1. In addition it is found that the catalytic activity of TS-1 for this reaction is not related to the intensity or presence of the infrared absorption band at ca. 960 cm^–1.     

TS-1分子筛催化苯乙酮氨肟化反应

研究了钛硅分子筛(TS-1)催化苯乙酮氨肟化反应中溶剂、反应温度、助催化剂(氧化铝和乙酸铵)、氨水及H2O2用量对反应的影响. 结果表明,适宜的溶剂为乙醇,最佳反应温度为80℃,助催化剂乙酸铵在溶液中的浓度不低于0.43%(w)时能显著提高苯乙酮氨肟反应的转化率,而Al2O3的作用不明显. 为了获得较高的转化率,物料中NH3/苯乙酮以及H2O2/苯乙酮的摩尔比应分别控制在2.00和1.27以上.     

TS-1催化氯丙烯环氧化反应过程中的溶剂效应

研究了具有不同官能团的溶剂对TS-1催化氯丙烯环氧化反应性能的影响,发现与无溶剂的反应结果相比,含羟基的溶剂和丙酮对反应有明显的促进作用,在含氰基的乙腈溶剂中,环氧化反应效果变差。试验中还发现,溶剂分子的空间结构影响环氧化的反应速率,并且部分溶剂会与氯丙烯发生竞争性氧化,降低H2O2的有效利用率。在甲醇或丙酮溶剂中混入一定比例的乙腈可提高产物的选择性,但对提高催化剂稳定性效果不显著。     

Influence of technological parameters on the epoxidation of 1‐butene‐3‐ol over titanium silicalite TS‐2 catalyst

BACKGROUND: The influence of technological parameters on the epoxidation of 1‐butene‐3‐ol (1B3O) over titanium silicalite TS‐2 catalyst has been investigated. Epoxidations were carried out using 30%(w/w) hydrogen peroxide at atmospheric pressure. The major product from the epoxidation of B3O was 1,2‐epoxybutane‐3‐ol, with many potential applications. RESULTS: The influence of temperature (20–60 °C), 1B3O/H₂O₂ molar ratio (1:1–5:1), methanol concentration (5–90%(w/w)), TS‐2 catalyst concentration (0.1–6.0%(w/w)) and reaction time (0.5–5.0 h) have been studied. CONCLUSION: The epoxidation process is most effective if conducted at a temperature of 20 °C, 1B3O/H₂O₂ molar ratio 1:1, methanol concentration (used as the solvent) 80%(w/w), catalyst concentration 5%(w/w) and reaction time 5 h. Copyright © 2009 Society of Chemical Industry     

Ammoximation of methyl ethyl ketone with H2O2 and ammonia over TS‐1

The ammoximation of methyl ethyl ketone and hydrogen peroxide to form methyl ethyl ketoxime was studied over zeolites (TS‐1) in the temperature range 308–373 K. The reaction was carried out in a batch autoclave at autogenous pressure. The conversion of methyl ethyl ketone and the selectivity to methyl ethyl ketoxime can reach 99% and approximately 100%, respectively, and the by‐products were the small amounts of corresponding methyl ethyl ketazine and trace amounts of unidentified compounds. Important factors were the reaction temperature, solvents and slow addition of hydrogen peroxide. The molar ratio of NH₃ to ketone had no significant effect on the conversion of methyl ethyl ketone, but increase in the ratio of NH₃ to ketone had a beneficial effect on selectivity. Copyright © 2006 Society of Chemical Industry     

钛硅分子筛的改性对环己烷氧化反应的影响

使用不同改性液H_2SO_4-H_2O_2、(NH_4)_2CO_3-H_2O_2、(NH_4)HF_2-H_2O_2和(NH_4)_2CO_3+(NH_4)HF_2-H_2O_2混合溶液对中空钛硅分子筛进行改性。采用XRD、UV-Vis和拉曼光谱进行表征分析,考察改性前后钛硅分子筛在环己烷氧化反应的催化性能。结果表明,改性过程没有破坏钛硅分子筛的MFI拓扑结构,但提高了钛硅分子筛相对结晶度,并脱除了部分锐钛矿相TiO_2;与未改性钛硅分子筛相比,环己醇和环己酮选择性及H_2O_2有效利用率明显提高,以改性液(NH_4)_2CO_3+(NH_4)HF_2-H_2O_2改性钛硅分子筛效果最佳,醇酮选择性提高12.78个百分点,H_2O_2有效利用率提高17.33个百分点;(NH_4)_2CO_3+(NH_4)HF_2-H_2O_2混合溶液改性钛硅分子筛显著降低H_2O_2用量,在己内酰胺生产过程中有很好的应用前景。     

钛硅分子筛催化氧化脱除粗苯中的有机硫化物

采用以钛硅分子筛(TS-1)为催化剂,双氧水为氧化剂,水为溶剂的反应体系,对粗苯中的噻吩有机硫化物的脱除进行了研究。通过单因素试验考察了时间、温度、氧化剂用量、催化剂用量及溶剂用量对反应的影响,确定了各因素对反应的影响大小顺序为:TS-1用量>双氧水用量>反应时间>温度;以噻吩的脱除率为指标,采用正交实验方法,得出最佳的反应条件为:n(噻吩)∶n(双氧水)=4∶1,时间8h,温度75℃,TS-1用量为0.15%(质量分数)。在此条件下,噻吩的脱除率达99.58%。实验表明:该法具有操作简单,反应条件温和(低温常压下即可进行),低成本费用以及高有机硫脱除率的特点。是一条具有较好应用和推广价值的工业有机硫脱除新途径。     

高性能钛硅分子筛可控合成及其催化丙烯气相环氧化研究进展

随着绿色化工发展战略的推进,钛硅分子筛凭借其独特的选择性环氧化能力而引起广泛关注,合理调控钛硅分子筛的结构是提升烯烃环氧化反应效果的关键。本文分别对钛硅分子筛的结构类型、硅钛原子比、表面疏水性、颗粒传质性能的调控方法进行了介绍,系统总结了高活性钛硅分子筛的合成策略,并概述了TS-1钛硅分子筛工业生产技术的进展。以负载金属的钛硅分子筛催化剂为例,着重讨论了基于该催化剂的丙烯直接临氢气相环氧化反应的性能与机理,肯定了催化剂中包括载体钛位点和负载金属位点的双位点在环氧化反应中的重要性,并从金基催化剂的电子性质、空间分布、尺寸效应三个方面总结了高效金属位点的调控策略。此外,基于丙烯气相临氢环氧化当前存在的问题与挑战,进一步提出其潜在的解决方案与未来的发展方向。     

Factors influencing the catalytic activity of titanium silicalites in selective oxidations

Titanium silicalites synthesized via different procedures are tested in the oxidation of phenol, l-octene and n-hexane by aqueous H₂O₂. It is shown that the presence of titanyl groups, on which H₂O₂ is activated by formation of titanium peroxo complexes, is a prerequisite for oxygenation activity. Furthermore, in order to afford high selectivities, titanium silicalites should be free of impurities which cause acid catalyzed side reactions or H₂O₂ decomposition.     

用丙烯双氧水环境友好法制备环氧丙烷的研究

在实验室中研究了丙烯双氧水环境友好法制备环氧丙烷的工艺,双氧水的转化率98．5％,环氧丙烷的选择性为95．1％;催化剂运行1218h后,活性和选择性没有明显下降。建成了1000t／a中试装置,进行了催化剂寿命试验。结果表明：催化剂单程运行寿命〉1400h,双氧水转化率〉95．0％,环氧丙烷选择性〉97．0％,进行了100kt／a环氧丙烷工业放大工艺包设计。     

纳米技术与纳米材料(Ⅸ)--纳米TiO2的液相合成

综述了液相法合成纳米TiO2，比较了各种液相法的优缺点，详细讨论了液相法合成纳米TiO2的研究进展和发展趋势。认为以TiCl4、TiOSO4和H2TiO3为原料时，产品成本较低。低温液相合成纳米TiO2的生产工艺由于省去了高温煅烧工序而最具竞争力。并指出过滤和防团聚是液相法规模化生产纳米TiO2需要重点解决的问题。