Silicalite-1的后处理对其催化环己酮肟气相Beckmann重排反应性能的影响

 研究了silicalite-1分子筛的不同后处理方法对其催化环己酮肟Beckmann重排制己内酰胺性能的影响,这些方法包括水(或氨)蒸气处理以及在碱性、酸性或中性条件下用NH4NO3处理. 结合XRD,FT-IR和 29Si MAS NMR表征结果对silicalite-1催化剂的活性中心进行了探讨. 结果表明,碱性条件下用NH4NO3进行后处理对提高分子筛的催化性能最为有利. 分子筛上无规则排布的末端硅羟基数量的减少,以及具有相互氢键作用的邻式硅羟基的产生是其催化性能提升的主要原因.     

环己酮肟在B2O3/Al2O3-TiO2催化剂上的气相Beckmann重排反应

制备了B2O3/Al2O3-TiO2复合载体催化剂,并考察了其对环己酮肟气相Beckmann重排制己内酰胺反应的催化性能. 结果表明,载体中TiO2的含量、B2O3的负载量、载体的预处理温度及催化剂的焙烧温度等均对催化剂的性能产生明显的影响. 当载体中TiO2含量为60%,B2O3负载量为20%,催化剂经350 ℃焙烧时,环己酮肟的气相Beckmann重排反应的转化率和选择性很高. 用BET,NH3-TPD,XRD和IR等方法对催化剂的织构、表面酸性和晶相等进行了表征,并与催化剂的活性进行了关联,表明催化剂表面中等强度的酸中心浓度与催化剂的选择性具有对应关系.     

Silicalite-1空心球材料制备及其在Beckmann重排反应中催化应用研究

以碳微球作为硬模板、纳米Silicalite-1分子筛作为壳层,采用水热法合成了Silicalite-1空心球材料。采用XRD、SEM、FT-IR、N_2吸附、29Si M AS NM R、TG、XPS等技术对催化剂的物相、形貌和性能等进行表征,发现该空心材料具有较高的结晶度、发达的多级孔道结构和丰富的表面羟基。与传统方法制备的Silicalite-1分子筛催化剂相比,Silicalite-1空心材料在环己酮肟Beckmann重排反应中表现出优异的催化性能,使环己酮肟的转化率达99%、己内酰胺的选择性达94%,同时催化剂保持极佳的稳定性。研究表明,Silicalite-1空心材料中具有的大量巢式硅羟基和末端硅羟基是Beckmann重排反应的主要活性位,且可通过简单焙烧再生实现羟基活性位的完全恢复。     

B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应研究 Ⅲ. 反应条件的影响

 对B2O3／TiO2－ZrO2催化环己酮肟气相Beckmann重排制己内酰胺的反应条件进行了优化研究，系统考察了反应温度、原料空速、载气及其流速和稀释剂等对催化剂催化性能的影响．结果表明，当反应温度为300℃、环己酮肟的重时空速WHSV）为0．33h－1、氮气为载气（流速30ml／min）及乙腈为稀释剂时，B2O3／TiO2－ZrO2催化剂的催化性能最佳，连续反应6h，环己酮肟的转化率为100％，己内酰胺的选择性高达98．6％．     

B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应中的溶剂效应

 采用不同极性的溶剂作为环己酮肟的溶剂,考察了溶剂极性对B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应性能的影响. 结果表明,除乙醇外,随着溶剂极性的增大,己内酰胺的收率逐渐提高. 在所考察的溶剂范围内,当采用极性最强的乙腈为溶剂时,B2O3/TiO2-ZrO2的催化性能最佳,连续反应9 h,环己酮肟的转化率为100%,己内酰胺的选择性高达98.6%. 极性较强的溶剂可显著改善B2O3/TiO2-ZrO2催化性能的原因主要是其有利于反应所生成的己内酰胺从催化剂表面快速脱附,从而可抑制己内酰胺进一步发生聚合及分解等副反应.     

B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应研究Ⅱ.焙烧温度的影响

采用XRD、FT-IR和NH3-TPD等方法，研究了载体预焙烧温度和催化剂活化焙烧温度对B2O3/TIO2-ZRO2催化剂的结构、酸性和催化环己酮肟气相Beckmann重排反应性能的影响。结果表明，在383-773K范围内，载体预烧温度对催化剂性能的影响不大，但经973K高温预焙烧后，由于生成了ZrTiO4晶相，使其与H3BO3的相互作用减弱，从而导致催化剂的酸性和反应性能降低，提高催化剂活化焙烧温度，有利于B2O3与TiO2-ZrO2的相互作用，生成更多的Beckmann重排反应所需的中等强度酸中心，使催化剂的活性和选择性提高；但活化焙烧温度过高，会使催化剂中大量的B2O3晶粒析出，引起酸中心数量和催化活性的明显下降。     

氢键驱动的二苯甲酮肟Beckmann重排反应研究

在充分分析Beckmann重排反应机理的基础上,通过设计合成氨基功能化介孔氧化硅,对之进行酸化,获得质子化氨基功能化介孔氧化硅材料HAF-SBA-15.利用HAF-SBA-15中的质子氢与肟羟基氧上的孤对电子形成配位键及N、H、O间形成的氢键,协同弱化肟羟基与N之间的结合力,加速肟羟基离去及碳正离子的形成,从而促进Beckmann重排反应.以二苯甲酮为底物合成二苯甲酮肟,在HAF-SBA-15催化下进行Beckmann重排反应,结果证明二苯甲酮肟转化率较大、获得的N-苯基苯甲酰胺纯度较高.此外,还探索溶剂类型、反应温度、催化剂用量等因素对二苯甲酮肟Beckmann重排反应的影响,获得最佳反应条件,该反应条件温和,50℃即可发生高效的二苯甲酮肟Beckmann重排反应.     

改性钛锆复合氧化物催化环己酮肟气相Beckmann重 排反应

制备了经SO4^2-,PO4^3-,MoO3,WO3和B2O3改性的钛锆复合氧化物(TiO2-ZrO2)催化剂,并用常压连续流动固定床微型反应器考察了它们对环己酮肟气相Beckmann重排反应制己内酰胺的催化性能。结果表明,在反应温度300℃时,B2O3/TiO2-ZrO2具有较高的己内酰胺选择性(97.0%)和收率(96.7%),且明显高于B2O3/TiO2和B2O3/ZrO2催化剂,用N2吸附和NH3-TPD,CO2-TPD等方法对催化剂的经表面积、孔容、孔分布和表面酸、碱性分别进行了测定,讨论了这些物化性能对催化剂活性、选择性和稳定性的影响。     

钛硅分子筛催化气相环己酮肟贝克曼重排反应

 对比研究了具有MFI结构的TS－1，silicalite－1，Al－ZSM－5和B－ZSM－5分子筛对气相环己酮肟贝克曼重排反应的催化性能．结果显示，TS－1适宜用作重排反应的催化剂，而含骨架B或Al的ZSM－5分子筛的催化性能较差，表明将Ti引入至sili－calite－1有利于改善其对环己酮肟重排反应的催化性能．反应氛围（溶剂、载气和原料添加物）对TS－1催化性能的影响规律说明，弱酸性气体的存在有利于TS－1对环己酮肟的活化与己内酰胺的选择性生成．优化的反应氛围包括以甲醇或乙醇为溶剂，二氧化碳为载气，以及醋酸为原料添加物．     

TiO_2柱层状HTiNbO_5的合成及在环己酮肟气相Beckmann重排反应中的催化性能

钛酸异丙酯(TIP)、CH3COOH和H2O按体积比1∶16∶40混合后得到Ti(Ⅳ)多聚阳离子柱化液,与正癸胺插层钛铌酸盐进行交换反应后制得钛(Ⅳ)多聚阳离子插层钛铌酸盐,其层间距为1.70 nm.在空气气氛中于623 K焙烧处理后,所得产品能保持良好的层柱结构.在空气气氛中于723 K焙烧后所得的TiO2柱层状钛铌酸(TiO2-HTiNbO5),其层间距为0.97 nm,比表面积为89 m2/g.以TiO2-HTiNbO5为载体,用浸渍法制备了一系列B2O3负载量不同的负载型样品B2O3/TiO2-HTiNbO5,考察了它们在环己酮肟气相Beckmann重排反应中的催化性能并测试了它们的红外光谱.B2O3/TiO2-HTiNbO5的催化性能优于TiO2-HTiNbO5.在B2O3负载质量分数为7.31%的催化剂上,环己酮肟转化率接近100%且在4.5 h内无明显改变,己内酰胺选择性接近90%.红外光谱分析结果表明,当B2O3负载量很低时,硼组分高度分散于载体TiO2-HTiNbO5表面,并主要以BO4结构形式存在;当B2O3负载质量分数高于7.31%时,BO3结构形式在数量上占优势.将催化性能与红外光谱结果关联后可知,对于负载型样品B2O3/TiO2-HTiNbO5,表面的BO3和BO4两种结构形式在环己酮肟气相Beckmann重排反应中具有协同促进作用.     

The Catalysis of Vapor-Phase Beckmann Rearrangement for the Production of ε-Caprolactam

Recently, Sumitomo Chemical Co., Ltd. developed the vapor-phase Beckmann rearrangement process for the production of -caprolactam. In the process, cyclohexanone oxime is rearranged into -caprolactam using a zeolite as a catalyst instead of sulfuric acid. EniChem in Italy developed the ammoximation process that involves the direct production of cyclohexanone oxime without producing any ammonium sulfate. Sumitomo Chemical Co., Ltd. has commercialized the combined process of vapor-phase Beckmann rearrangement and ammoximation in 2003.In this paper, the authors focus on some aspects of the vapor-phase Beckmann rearrangement catalysis. A solid catalyst that is mainly composed of a high-silica MFI zeolite (Silicalite-1) has been developed for the vapor-phase Beckmann rearrangement. This catalyst does not possess acidity that can be detected by ammonia TPD. Methanol fed into the reactor with cyclohexanone oxime improves the yield of caprolactam. Methanol reacts with terminal silanols on the zeolite surface and converts them to methoxyl groups. The modification of the catalyst by methanol has an important role for the Beckmann rearrangement reaction.Nest silanols located just inside the pore mouth of the MFI zeolite are supposed to be the active sites of the catalyst. We propose that the coordination between the NOH group of cyclohexanone oxime molecule and the nest silanols through hydrogen bonding is responsible for the reaction. The reaction mechanism of Beckmann rearrangement under vapor-phase conditions is the same as in the liquid phase, namely, the alkyl group in anti-position against the hydroxyl group of the oxime migrates to the nitrogen atom's position.     

Hierarchically structured monolithic silicalite-1 consisting of crystallized nanoparticles and its performance in the Beckmann rearrangement of cyclohexanone oxime

In this study, we present a synthetic pathway for the fabrication of self-supporting zeolite monoliths consisting of crystallized nanoparticles. A resorcinol-formaldehyde-based organic aerogel is used as a template, and silicalite-1 is used as the zeolite example. The silicalite-1 monoliths obtained consist of individual well-defined zeolite nanocrystals with sizes of 30-40 nm. The monoliths exhibit a high mechanical stability and have hierarchical porosity, with micropores within the zeolite particles, a mesopore system formed by the packing of the nanoparticles, and a macropore system on the monolith level. Such monolithic zeolites show high selectivity typically above 80% to epsilon-caprolactam combined with a high rate of reaction of 0.46 g(caprolactame)/(g(catalyst).h) in the Beckmann rearrangement of cyclohexanone oxime.     

钴催化的高效贝克曼重排反应

利用廉价易得的氟硼酸钴水合物, 在温和、 无添加剂的空气条件下, 高效催化酮肟衍生物的贝克曼重排反应, 底物的普适性和官能团的兼容性均较理想, 产物收率最高达97%. 基于该高活性的氟硼酸钴水合物, 实现了10 g级二苯甲酮肟的贝克曼重排反应, 收率为71%. 同时, 也实现了钴催化酮类衍生物和盐酸羟胺的一步法贝克曼重排反应, 产物最高收率为94%, 反应体系中无溶剂及添加剂, 反应体系的原子经济性和底物普适性较好.     

Vapor-phase Beckmann rearrangement of cyclohexanone oxime over B2O3 catalysts supported on TiO2-ZrO2 mixed oxide

A novel catalyst, boria supported on titania-zirconia mixed oxide, exhibits very high catalytic activity and selectivity in vapor-phase Beckmann rearrangement of cyclohexanone oxime to e-caprolactam. It gives 99.7% oxime conversion and 97.0% lactam selectivity at 300°C.     

Pervaporation separation of ethanol/water mixtures with chlorosilane modified silicalite-1/PDMS hybrid membranes

<正>Ultra-fine silicalite-1 particles were modified with four kinds of chlorosilanes(dodecyltrichlorosilane, octyltrichlorosilane,hexadecyltrichlorosilane and octadecyltrichlorosilane) and characterized by FI-IR,TGA,contact angle measurements and BET analysis.It was found that the surface hydrophobicity of silicalite-1 particles was improved significantly as the alkyl group was strongly bonded to the particle surface.Modified silicalite-1 particles were incorporated into PDMS(poly(dimethylsiloxanediol)) membranes,which were applied for the pervaporation separation of ethanol/water mixtures.The effect of surface properties,zeolite loading and operation conditions on pervaporation performance of the membranes was investigated.The separation factor of PDMS membranes filled with modified silicalite-1 increased considerably compared with that filled with unmodified ones,and the total flux decreased with increasing zeolite loading. The solution and diffusion selectivity of hybrid membranes were also measured to explain the pervaporation properties of silicalite-1 filled PDMS membranes.It was found that modification of silicalite-1 with dodecyltrichlorosilane effectively improved the solution and diffusion selectivity of silicalite-1 filled PDMS membranes with high zeolite loading.This may be attributed to the high surface hydrophobicity of modified silicalite-1 and its good integration with PDMS membranes.Both the high separation factor and solution selectivity indicated that modification of silicalite-1 with chlorosilanes was an effective method to improve the selectivity of silicalite-1/PDMS hybrid membranes for ethanol.     

Beckmann rearrangement of 15N-cyclohexanone oxime on zeolites silicalite-1, H-ZSM-5, and H-[B]ZSM-5 studied by solid-state NMR spectroscopy

By means of solid-state 15N NMR spectroscopy, evidence for the formation of nitrilium ions as intermediates of the Beckmann rearrangement of 15N-cyclohexanone oxime to epsilon-caprolactam on silicalite-1, H-ZSM-5, and H-[B]ZSM-5 is reported. The zeolites under study are characterized by different acid strengths (silicalite-1 < H-[B]ZSM-5 < H-ZSM-5). Depending on the nature of catalytically active surface OH groups, reactant and product molecules exist in the nonprotonated or protonated state. In addition, formation of byproducts such as 5-cyano-1-pentene and epsilon-aminocapric acid as a result of dehydration and hydrolysis of the reactant and product molecules, respectively, were observed.     

A Novel Method for Beckmann Rearrangement of Oximes with Silica Sulfuric Acid under Mild Condition

The conversion of ketoxime into corresponding amide, known as the Beckmann rearrangement, is a common method used in organic chemistry and is also a topic of current interest. It accomplishes both the cleavage of carbon-carbon bond and the formation of a carbon-nitrogen bond, and represents a powerful method particularly for manufacture ε-caprolactam in chemical industry. This reaction, however, generally requires high reaction temperature, strong Br?nsted acid and dehydrating media, causing …     

Catalytic Gas‐phase Fluorination of Hexachlorobutadiene to 1,2‐Dichlorotetrafluorocyclobutene over Cr/Zn‐based Catalysts

In this paper, the gas‐phase fluorination of hexachlorobutadiene (HCBD) to synthesize 1,2‐dichlorotetrafluorocyclobutene (DTB) was carried out over a series of Cr/M/Zn catalysts (M = Ni, Co, Cu, In, Al). The influence of prefluorination by different fluorinating agents (HF, 95%HF + 5%Cl₂, 95%HF + 5%O₂, CF₂O, CF₂Cl₂) on catalytic performance of Cr/Co/Zn sample was also investigated. The addition of prompters to the Cr/Zn catalyst improved remarkably its catalytic properties. The Cr/Ni/Zn catalyst exhibited the best catalytic activity (1.318 mmol/h/g) at 390 °C and the Cr/Co/Zn catalyst showed the best DTB selectivity (42.5%) at 350 °C. Compared to that of gaseous HF, the catalytic performance of the Cr/Co/Zn catalyst after treatment by HF + O₂ and CF₂O increased considerably, whereas for HF + Cl₂ and CF₂Cl₂ it showed little effect. In order to identify the different species (Cr─O, Cr─F, CrO _xF _y) present on catalysts’ surface and determine their exact role, these catalysts before and after the reaction were characterized by X‐ray photoelectron spectroscopy. It was found that the concentration of the various species was responsible for the activity and lifetime of catalysts. Moreover, a possible reaction route is proposed based upon the product distribution. The most feasible formation pathway of DTB proceeded via the cyclization of C₄Cl₄F₂ or C₄Cl₃F₃ to yield c‐C₄Cl₄F₂ and c‐C₄Cl₃F₃ followed by further the Cl/F exchange.