Redox solid catalysts for the selective oxidation of cyclohexane in air

The selective oxidation of cyclohexane to cyclohexanol, cyclohexanone and adipic acid using molecular oxygen as the oxidant and at moderate temperatures (403 K) has been investigated over four different cobalt‐containing aluminophosphate (AlPO) molecular sieves. There is a correlation between catalytic activity and the fraction of (framework) Co(II) ions that is first oxidised to Co(III) in air. CoAlPO‐36 (pore aperture 6.5 x 7.5 Å) exhibits significant activity for the oxidation of cyclohexane in contrast to CoAlPO‐18, which, although it has the highest fraction of oxidisable cobalt, does not show any activity chiefly because of its smaller pores.     

Capillary reactor for cyclohexane oxidation with oxygen

Cyclohexane oxidation is the first step in the currently used technology for production of Nylon-6 and Nylon-6,6 which employs a two-stage process. In the first stage 80% selectivity to two main products, cyclohexanol and cyclohexanone (KA oil) is obtained at 4–8% cyclohexane conversion in staged bubble columns or stirred tanks. There have been reports that increased oxygen concentration in the gas phase or pure oxygen is beneficial to cyclohexane oxidation and this was confirmed in our previous study (Jevtic et al., 2009). To fully utilize this advantage here, we present a novel, safer capillary reactor for cyclohexane oxidation with pure oxygen. The discrepancy between the experimental and modeling results was attributed to lower than expected mass transfer achieved in the capillary. With a better design for gas–liquid mixing and contacting this type of a reactor could potentially become attractive for gas–liquid reactions of similar nature.     

微管内环己烷氧化反应研究进展

介绍了微管反应器和微管内环己烷氧化反应的特点;详述了微管内环己烷无催化氧化的反应工艺、微管内气液流动情况、反应机理以及微管内壁负载催化剂的环己烷催化氧化反应工艺;指出无催化及内壁涂覆催化剂的微管内环己烷氧化反应在改善反应的安全性、强化气液传质效果和提高催化性能等方面具有较大优势,微管内壁负载纳米金催化剂的反应器形式在环己烷氧化反应中前景看好。     

碳化硅微反应器用于环己烷氧化反应工艺的研究

利用微反应器的高速混合、高效传热等特点,采用碳化硅微反应器对环己烷氧化反应进行了研究,在不加任何引发剂或催化剂的情况下进行实验(即空白实验)的基础上,主要考察了叔丁基过氧化氢(TBHP)、环己酮、环烷酸钴等引发剂、催化剂、纯氧条件下等对环己烷氧化反应的影响。结果表明:空白实验时,采用较高的温度,如温度在180℃或190℃时,环己烷的转化率低,最高值为0.90%;在其他条件不变的情况下,用纯氧代替空气,由于反应较为剧烈,选择性普遍较低;在温度为180℃,压力为1.4 MPa,环己烷表观流速为15 mL/min,空气表观流速为640 mL/min,环烷酸钴的加入质量分数为0.03%,TBHP的加入质量分数为0.5%时,环己烷氧化反应效果最佳,转化率可以达到4.7%,选择性为89.1%。     

环己烷液相氧化工艺研究进展

介绍了近年来环己烷液相空气均相和非均相催化氧化、光诱导催化氧化、无催化氧化、纯氧氧化等的研究进展 ,并对今后的研究发展方向进行了分析。     

环己烷富氧氧化反应器内液相空间危险性分析

通过冷模实验对环己烷富氧氧化反应器内液相空间危险性进行分析,测试了液相空间气泡危险性。结果表明:环己烷富氧氧化(氧气体积分数大于30.0%)反应时,液相气泡的危险性比空气氧化的危险性大;在空气氧化和富氧氧化(氧气体积分数小于50.4%)工艺条件下,均未观察到气泡经点火后引起反应器体系内压力升高的现象,液相气体内反应均无燃爆危险。     

改性VPO催化剂及其环己烷液相氧化反应性能

采用共沉淀法制备了铋改性钒磷氧催化剂,并用X射线衍射(XRD)、FTIR、SEM等技术对催化剂进行了表征。以环己烷为原料,H2O2为氧化剂,铋改性的钒磷氧化物为催化剂,研究了氧化合成环己醇和环己酮反应,研究了Bi/V比率、P/V比率、溶剂和反应温度等因素对其反应性能的影响。结果表明,Bi/V比率提高时,环己烷转化率,尤其是环己酮的选择性明显提高。P/V比对改性催化剂活性和结构影响较大,P的加入破坏了V2O5的晶型结构,形成大量磷酸盐物种。在Bi/V摩尔比为0.1、P/V摩尔比为0.92、丙酮为溶剂、65℃的反应条件下,反应8h,环己烷转化率为81.4%,环己酮和环己醇的收率分别为58.2%和23.2%。     

Cobalt molybdenum oxide catalysts for selective oxidation of cyclohexane

Oxidation of cyclohexane has been carried out using molecular oxygen over cobalt molybdenum oxide (CoMoO₄) catalysts in solvent free conditions. The catalysts were prepared using citrate method with three different molar ratios of Co:Mo, 1:1, 1:2, and 2:1 along with individual oxides for comparative studies. While all the catalysts showed significant activity and selectivity, CoMoO₄ with 1:1 ratio showed the best performance compared to the others with a conversion of 7.38%, with selectivity to cyclohexanol and cyclohexanone (KA oil) of 94.3%, in 1 h. The performance of the catalyst, has been studied as a function of oxygen pressure, reaction temperature, and catalyst loading. It was observed that the catalyst deactivates during the course of the reaction. The reasons for deactivation and methods for restoring the activity have been studied. A kinetic model is presented that captures the complex kinetics and matches well with the experimental data. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4384–4402, 2016     

环己烷氧化液中的环己醇和环己酮含量的测试

建立了环己烷氧化液中丁基环己基醚、环己醇、环己酮含量测定的气相色谱分析方法,载体用红色硅藻土代替白色硅藻土,改变了固定液配比,优化了分析条件。该方法中的固定液:载体质量比为25:75,柱温150℃,汽化温度180℃,检测温度200℃,氮气流速30 mL/min,其方法的相对标准偏差为0.08%~0.49%,回收率为99.3%~99.5%。     

Comparison of a contactor catalytic membrane reactor with a conventional reactor: example of wet air oxidation

A wet air oxidation reaction was carried out in a gas/liquid catalytic membrane reactor of the contactor type. The oxidation of formic acid was used as a model reaction. The mesoporous top-layer of a ceramic tubular membrane was used as catalyst (Pt) support, and was placed at the interface of the gas (air) and liquid (HCOOH solution) phases.

A similar reaction was carried out in a conventional batch reactor, using a steering rate high enough to avoid gas-diffusion limitations, and exactly identical conditions than for the CMR (amount of catalyst, pressure, etc.). At room temperature, the CMR showed an initial activity three to six times higher than the conventional reactor. This activity increase was attributed to an easier oxygen access to the catalytic sites. Nevertheless, the catalytic membrane gradually deactivated after a few hours of operation. Different deactivation mechanisms are presented.     

光催化环己烷选择氧化合成环己酮/环己醇催化研究进展

环己烷选择性氧化合成环己醇/酮具有重要工业价值,工业上热氧化路线反应温度高、副反应多、转化率低、选择性不高,亟需条件更温和、更环保的替代路线。以太阳光为驱动的光催化环己烷氧化路线可在常温常压下实现环己烷的选择性氧化,受到极大关注。本文综述了近10年来光催化环己烷选择性氧化催化体系、反应机理和反应影响因素的研究情况,对光催化环己烷选择性氧化催化循环中环己烷分子活化、环己酮/醇形成、活性自由基再生的基元过程和催化剂失活机理进行总结和分析;对影响光催化环己烷选择性氧化的反应参数进行深入分析和讨论;指出·OH为主要的活性自由基,环己基过氧化氢是重要的中间产物,环己酮/醇主要通过环己基过氧化氢的光催化分解形成,光辐射条件（光强和波长）、溶剂、催化剂结构和表面性质都是光催化环己烷选择性氧化的重要影响因素。最后指出光催化环己烷选择性氧化规模化应用的关键是进一步提高光催化剂的寿命和稳定性以及设计结构合理、高效利用光能的光催化反应装置。     

Reactions of cyclohexane in a microwave discharge reactor

A study has been made of the reactions of cyclohexane in a continuous-flow microwave discharge reactor. Butene-1 and propylene were the major reaction products; ethylene and hydrogen were produced in smaller amounts. The distribution of reaction products was found to depend on the reactor pressure and flow-rate. The results show that the fragmentation of cyclohexane is not the sole source of butene-1. The insertion of nickel wire into the reactor enhanced the production of ethylene and propylene; yields of butene-1 were diminished. In the presence of nickel the production of ethylene and propylene became independent of pressure. When carbon dioxide was added to the cyclohexane feed the major reaction product was acetylene. The carbon dioxide did not react chemically. The yields of acetylene per unit energy input were found to be fairly high.     

环己烷选择性氧化催化剂的研究进展

由环己烷直接氧化生产环己酮、环己醇等含氧化合物的选择性氧化反应虽早已应用于工业生产中 ,但由于产物产率很低 ,能耗大及污染严重等方面的严重不足 ,一直以来 ,科学家们都在对该反应体系加以改进 ,尤其是对催化剂的改进更成为研究的重点。本文主要阐述了近年来该领域的最新研究与进展     

Gold nanoparticles in mesoporous materials showing catalytic selective oxidation cyclohexane using oxygen

The nano-Au supported mesoporous materials were prepared and characterized by XRD, N₂ adsorption/desorption, UV–vis, XPS, and ICP-AES. The liquid-phase selective oxidation cyclohexane to cyclohexanol and cyclohexanone over nano-Au in mesoporous materials catalyst was carried out in a solvent-free system, in which oxygen was the only oxidant and the reaction conditions are very moderate.     

Supported liquid phase catalysis in selective oxidation

The application of supported liquid-phase catalysis (SLPC) to selective oxidation examples is discussed to provide valuable alternatives to the purely homogeneous or heterogenous processes. Specific examples discussed are the Wacker type ethylene oxidation on heterogenous catalysts and the vinyl acetate production by ethylene acetoxylation. The potential industrial application of SLPC for these oxidations and the possible extensions of this technology to other oxidation processes are also discussed.     

气相色谱法测定环己烷氧化液中一元有机酸含量

应用GC-2010气相色谱仪和热导检测器、FFAP50 m ×0.32 mm ×0.4μm色谱柱,采用程序升温,外标法定量,建立了气相色谱法测定环己烷氧化液中一元有机酸含量的分析方法.结果表明:该方法准确测定了氧化液中甲酸、乙酸、丙酸、丁酸、戊酸、己酸含量.6种一元有机酸的标准曲线相关系数均大于0.98;该方法的相对标...     

Gas hold-up and liquid velocity in a two-dimensional air lift reactor

Gas hold-up and liquid circulation velocity were studied in a two-dimensional air lift reactor. A comparison was made between bubble column and air lift operation.Four different gas spargers were studied, and several different gases: He, CO₂, Ar, air and Freon 114. No influence on the measured variables could be attributed to gas distribution. The nature of the gas had a strong influence in the case of bubble column operation. Helium does not exhibit the maximum in the hold-up which is characteristic of the “transition regime”, and in general gives lower values.In air lift operation, the differences due to the nature of the gases are much smaller, and can be neglected.The liquid recirculation velocity depends on the gas superficial velocity, J_G, raised to the power 0.4. This concurs with published data obtained in large air lift devices. It is concluded that a two-dimensional air lift can be used for research and development, since it present the same basic fluid—dynamic characteristics as large air lift reactors. In addition, the two-dimensional device allows the examination of flow patterns and configuration, which are decisive in design and scale-up of this type of reactor.     

环己烷分子氧选择性氧化固体催化剂研究进展

对环己烷分子氧催化氧化制环己酮固体催化剂的最新进展进行了综述,重点介绍了贵金属催化剂、过渡金属及其氧化物催化剂和分子筛催化剂。指出锆基复合氧化物催化剂和负载在分子筛上的金催化剂具有较高的催化活性和选择性及好的稳定性,具有一定的应用及工业化前景。     

Membrane pilot reactor applied to selective oxidation reactions

The partial oxidation of butane to maleic anhydride was studied in a conventional fixed bed as well as a novel reactor configuration consisting of a porous metallic membrane immersed in a gas–solid fluid bed. The diameter of both reactors was at a commercial scale greater than 30 mm. A range of gas flow rates, temperatures and butane concentrations were tested. Maleic anhydride yield was generally higher in the membrane reactor due to higher butane conversion. Maleic productivity in the fixed bed equalled that observed in the membrane reactor when the gas–solid fluid bed was maintained at a higher temperature of as much as 30 °C. The butane feed rate to the membrane reactor was limited by hot spots. These hot spots were unanticipated and underscore the importance of increasing heat transfer in order to commercialize this technology.     

环己烷在Au-Co/SBA-15上选择性氧化的研究

以沉积-沉淀法制备了Au-Co/SBA-15催化剂,在没有任何有机溶剂或助剂的条件下,研究了以空气为氧化剂的环己烷选择性氧化。当Au-Co/SBA-15催化剂中金的质量百分含量为1.0%,催化反应在423 K 3.0 MPa下进行120 m in时,催化效果最好,此时环己烷的转化率为22.7%,环己酮和环己醇的总选择性为95.2%,酮醇比为2.9,且催化剂重复使用五次后活性基本不变。