负载金作为非均相催化剂催化选择性液相加氢反应的研究进展(英文)

The great potential of gold catalysts for chemical conversions in both industrial and environmental concerns has attracted increasing interest in many fields of research. Gold nanoparticles supported by metal oxides with high surface area have been recognized as highly efficient and effective green heterogeneous catalyst even at room temperature under normal reaction conditions, in gas and liquid phase reactions. In the present review, we dis-cuss the recent development of heterogeneous, supported monometal ic gold catalysts for organic transforma-tions emphasizing mainly liquid phase hydrogenation reactions. Discussions on the catalytic synthesis procedures and the promoting effect of other noble metals are omitted since they are already worked out. Appli-cations of heterogeneous, supported monometal ic catalysts for chemoselective hydrogenations in liquid phase are studied including potential articles during the period 2000–2013.     

Methanol synthesis in a three‐phase catalytic bed under nonwetted condition

To overcome the heat removal problem encountered in methanol synthesis at high syngas concentrations in the gas phase, a three‐phase nonwetted catalytic system was established by introducing an inert liquid medium into a fixed‐bed reactor. To form a repellent interface between the liquid and the catalyst, the catalyst was modified into hydrophobic, while the liquid medium was chosen as a room temperature ionic liquid with hydroxyl groups. The liquid‐solid contact angle was measured to be 115°, and only 20% of the catalyst external surface was wetted by the liquid. Under three‐phase condition, the reaction rate was measured to be 60%–70% of gas‐phase reaction, while it was merely 10%–20% for the fully wetted catalyst. From the resistance analysis on the mass transfer and reaction steps, the overall reaction rate is expected to increase further if the surface could be more wet proofed. © 2016 American Institute of Chemical Engineers AIChE J, 63: 226–237, 2017     

Kinetics studies of ketazine formation: Effect of temperature and catalyst concentration

Formation of methyl ethyl ketazine is a distinct case of homogeneous catalyzed gas–liquid–liquid reactions. Kinetics studies of methyl ethyl ketazine formation has been carried out in a semi‐batch reactor. The effects of temperature and catalyst concentration on the percentage yield of ketazine have been studied extensively. The yield of ketazine is found to increase with increase in temperature and then levels off. Increase in catalyst concentration favours the formation of ketazine. The conversion of peroxide is found to increase with increase in temperature thus indicating that chemical reaction is rate‐limiting step in the system. The desired temperature for carrying out the reaction is found to be 60°C and the required catalyst to peroxide ratio is 2.5. The activation energy for the reaction is 24.5 kJ/mol.     

Investigation of multiphase hydrogenation in a catalyst‐trap microreactor

BACKGROUND: Multiphase hydrogenation plays a critical role in the pharmaceutical industry. A significant portion of the reaction steps in a typical fine chemical synthesis are catalytic hydrogenations, generally limited by resistances to mass and heat transport. To this end, the small‐scale and large surface‐to‐volume ratios of microreactor technology would greatly benefit chemical processing in the pharmaceutical and other industries. A silicon microreactor has been developed to investigate mass transfer in a catalytic hydrogenation reaction. The reactor design is such that solid catalyst is suspended in the reaction channel by an arrangement of catalyst traps. The design supports the use of commercial catalyst and allows control of pressure drop across the bed by engineering the packing density. RESULTS: This paper discusses the design and operation of the reactor in the context of the liquid‐phase hydrogenation of o‐nitroanisole to o‐anisidine. A two‐phase ‘flow map’ is generated across a range of conditions depicting three flow regimes, termed gas‐dominated, liquid‐dominated, and transitional, all with distinctly different mass transfer behavior. Conversion is measured across the flow map and then reconciled against the mass transfer characteristics of the prevailing flow regime. The highest conversion is achieved in the transitional flow regime, where competition between phases induces the most favorable gas–liquid mass transfer. CONCLUSION: The results are used to associate a mass transfer coefficient with each flow regime to quantify differences in performance. This reactor architecture may be useful for catalyst evaluation through rapid screening, or in large numbers as an alternative to macro‐scale production reactors. Copyright © 2008 Society of Chemical Industry     

化学反应体系的多定态特性

化学反应体系的多定态特性是化学反应体系存在的固有特性。近年来,对它的研究已成为化学反应工程研究的热门课题。本文对化学反应体系的多定态特性的研究进展,特别是对化学反应器、催化剂题粒的多定态特性及其理论研究模型和实验研究成果进行了评述,指出了今后研究工作的发展方向。     

MASS TRANSFER WITH CHEMICAL REACTION IN PARTIALLY WETTED FLAT PLATE CATALYST PELLETS: RIVULET FLOW ANALYSIS

Mass transfer with chemical reaction is analyzed in a system formed by a flat plate solid catalyst, partially wetted by a flowing rivulet of a liquid in contact with a stagnant pure gas. The paper solves the fluid dynamic problem of the liquid phase first, and afterwards incorporates the mass transfer and the chemical reaction. The system is assumed to be isothermal and at steady state, with a first order kinetics whose limiting reactant is in the gas phase. This work studies the influence of the gas-liquid surface tension, the liquid reactant flow rate, the liquid viscosity and the angle of inclination of the solid, upon the wetting factor. The model proposed also predicts the effect of these parameters and the Thiele modulus on the overall effectiveness factor and the molar flux of the limiting gaseous reactant at the catalytic solid-liquid interface in a direct way. This approach makes the wetting factor a non-manipulated variable.     

环己酮肟Beckmann重排制己内酰胺的研究进展

环己酮肟Beckmann重排制己内酰胺是重要的工业过程。本文较详细地介绍了不使用浓硫酸催化的反应，主要有气固相反应、固液相反应、离子液体系及超临界水条件下的反应。研究表明：气固相反应中，副产物较多，催化剂易失活，使用寿命短；固液相反应条件温和，且副产物少；离子液体系和超临界水条件下的Beckmann反应中，可避免使用有机溶剂，且反应副产物少。     

An Economical,Green Pathway to Biaryls: Palladium Nanoparticles Catalyzed Ullmann Reaction in Ionic Liquid/ Supercritical Carbon Dioxide System

In this paper, an economical, green pathway involving the palladium nanoparticles (Pd NPs) catalyzed reductive Ullmann reaction of an aryl chloride to afford a biaryl with high conversion and selectivity in an ionic liquid (IL)/supercritical carbon dioxide (ScCO₂) system was developed. The combination of IL and ScCO₂ provides superior advantages in product separation, catalyst recycling and reuse of reaction media over traditional organic solvents. Further investigations showed that the Brønsted‐acidic imidazolium IL {e.g., (1‐butyl‐3‐(sulfobutyl)‐imidazolium) hydrogen sulfate, [bmim(HSO₃C₄)][HSO₄]}, can replace the traditional active hydrogen donor readily with much enhanced product separation efficiency, the use of IL also led to an obvious improved stability of the Pd NPs, which was very helpful for catalyst recycling. Carbon dioxide, a naturally abundant, non‐flammable, relatively non‐toxic, economical and recyclable “greenhouse” gas, was found to significantly promote the selectivity of the Pd NPs‐catalyzed aluminium‐induced reductive Ullmann reaction of aryl chlorides. Investigations showed that the Pd NPs catalyst and IL can be recycled for at least five runs, indicating the economic viability of this process.     

叔丁醇下游产品开发及应用进展

叔丁醇作为重要的精细化工原料,具有广泛的应用价值。主要介绍叔丁醇在汽油添加剂、有机溶剂和有机合成等精细化工领域的产品开发及应用进展,重点综述叔丁醇在有机合成领域的化学合成应用、反应机理研究、催化剂应用、下游产品产能及消费趋势等,指出在工业化应用过程中面临的各种问题并提出当前研究的方向和需要改进的地方。     

Numerical simulation of influence of mass transfer on phase transfer catalytic reaction

Mass transfer with chemical reaction by liquid/liquid phase tranfer catalysis (LLPTC) for an isothermal batch reactor was analyzed. The results for the phase transfer catalyzed reaction system can be generally described by a pseudo first-order hypothesis, whereas the reaction system can be controlled by simultaneous mass transfer of the catalysts between two liquid phases and chemical reaction in the organic phase. The mass transfer limitation is mainly from the mass transfer step of QX from the organic phase to the aqueous phase. The concept of catalyst-effectiveness vs. physically meaningful parameters in a liquid/liquid phase transfer catalyzed reaction is introduced. The catalyst effectiveness is increased as the mass transfer factors increase, the ratio of reaction rate coefficients of aqueous forward reaction to organic increases, and the equilibrium constant in the aqueous solution increases.     

Rapid Hydrogenation of Aromatic Nitro Compounds in Supercritical Carbon Dioxide: Mechanistic Implications via Experimental and Theoretical Investigations

An exceptionally rapid hydrogenation of nitrobenzene to aniline [TOF=252,000 h⁻¹] over palladium containing MCM‐41 (Pd/MCM‐41) with excellent yield of >99% can be achieved in supercritical carbon dioxide at 50 °C and a hydrogen pressure of 2.5 MPa. It has been observed that this promising method preferred a single phase between liquid substrate and carbon dioxide‐hydrogen system. The ascendancy of the supercritical carbon dioxide medium is established in comparison with the conventional organic solvent and solvent‐less conditions. Changes in the reaction parameters such as carbon dioxide and hydrogen pressure, temperature and the reaction time do not affect the selectivity. A combined experimental and theoretical study has elucidated the mechanism under the studied reaction condition because experimental observations revealed a direct conversion of nitrobenzene to aniline. However, density functional theory (DFT) calculation shows that the direct conversion is energetically unfavourable; hence, a stepwise mechanism has been proposed. Theoretical predictions and experimental observations suggested that the rate‐limiting step of nitrobenzene conversion is different from that of the liquid phase hydrogenation. This catalytic process can also be successfully extended to the hydrogenation of other aromatic nitro compounds with different substituents. Easy separation of the liquid product from catalyst and the use of an environmentally friendly solvent make this procedure a viable and an attractive green chemical process.     

铜系低温选择性催化还原脱硝催化剂的研究进展

选择性催化还原（SCR）技术已广泛应用在燃煤电站烟气脱硝技术中,开发低温高活性、高抗中毒性能的催化剂体系已经成为国内外学者的研究重点。Cu系催化剂由于具有良好的脱硝性能及水热稳定性,得到了广泛的研究和关注。本文综述了近年来活性组分Cu负载在TiO₂、Al₂O₃、碳基材料和分子筛等材料上的研究进展;重点分析了Cu系催化剂低温SCR反应机理,主要包括Eley-Rideal （E-R）机理和Langmuir-Hinshelwood （L-H）机理,同时分析了SCR反应的两个必然过程：吸附（NH₃吸附和NO_x吸附）和反应;简要地介绍了Cu系催化剂的抗水抗硫中毒性能研究现状以及反应机理,同时介绍了碱金属中毒、飞灰和催化剂烧结对催化剂失活的影响,结合生命周期分析SCR脱硝系统还原剂氨和尿素对NO排放的影响。在此基础上展望了未来铜系催化剂的研究方向：采用新型方式对催化剂进行改性、进一步采用表征和模拟技术研究催化体系的反应机理、优化锅炉和催化剂设计减轻催化剂失活以及研究适用于其他还原剂条件的高选择性催化剂。     

CFD modeling of slurry bubble column reactors for Fisher-Tropsch synthesis

Industrial bubble column reactors for Fischer-Tropsch (FT) synthesis include complex hydrodynamic, chemical and thermal interaction of three material phases: a population of gas bubbles of different sizes, a liquid phase and solid catalyst particles suspended in the liquid. In this paper, a CFD model of FT reactors has been developed, including variable gas bubble size, effects of the catalyst present in the liquid phase and chemical reactions, with the objective of predicting quantitative reactor performance information useful for design purposes. The model is based on a Eulerian multifluid formulation and includes two phases: liquid-catalyst slurry and syngas bubbles. The bubble size distribution is predicted using a Population Balance (PB) model. Experimentally observed strong influence of the catalyst particles concentration on the bubble size distribution is taken into account by including a catalyst particle induced modification of the turbulent dissipation rate in the liquid. A simple scaling modification to the dissipation rate is proposed to model this influence in the PB model. Additional mass conservation equations are introduced for chemical species associated with the gas and liquid phases. Heterogeneous and homogeneous reaction rates representing simplified FT synthesis are taken from the literature and incorporated in the model.Hydrodynamic effects have been validated against experimental results for laboratory scale bubble columns, including the influence of catalyst particles. Good agreement was observed on bubble size distribution and gas holdup for bubble columns operating in the bubble and churn turbulence regimes. Finally, the complete model including chemical species transport was applied to an industrial scale bubble column. Resulting hydrocarbon production rates were compared to predictions made by previously published one-dimensional semi-empirical models. As confirmed by the comparisons with available data, the modeling methodology proposed in this work represents the physics of FT reactors consistently, since the influence of chemical reactions, catalyst particles, bubble coalescence and breakup on the key bubble-fluid drag force and interfacial area effects are accounted for. However, heat transfer effects have not yet been considered. Inclusion of heat transfer should be the final step in the creation of a comprehensive FT CFD simulation methodology. A significant conclusion from the modeling results is that a highly localized FT reaction rate appears next to the gas injection region when the syngas flow rate is low. As the FT reaction is exothermal, it may lead to a highly concentrated heat release in the liquid. From the design perspective, the introduction of appropriate heat removal devices may be required.     

Experimental study of vaporization effect on steady state and dynamic behavior of catalytic pellets

The impact of the combined evaporation of the liquid phase and reaction on single catalyst pellet performance has been studied experimentally. The exothermic, catalyzed hydrogenation of -methylstyrene (AMS) to cumene has been employed as a model reaction. Steady state and dynamic experiments have been performed in a single catalytic pellet reactor using five catalytic pellets of different porous structures, thermal conductivity, apparent catalytic activity and distribution of catalyst in the pellet. Gas-phase temperature, concentration of AMS in the gas phase and the liquid flow rates have been varied. The measured center and surface temperatures of each pellet reveal the existence of two significantly different steady states in the range of liquid flow rate. The range of the liquid flow rate over which the two steady states were observed, the pellet temperature and the pellet dynamics depend strongly on the amount of AMS vapor in the gas phase and the catalyst properties. The obtained experimental data are helpful to elucidate the mechanism of hot-spot formation and runaway in multiphase fixed-bed reactors.     

催化蒸馏元件的流体力学性能

采用内径为206 mm的有机玻璃塔,在常温常压条件下,以空气和水为介质,对一种新型的反应液渗流式催化蒸馏元件进体力学实验研究,并研究了气相流通截面分率和固体催化剂在元件内装填高度对流体力学参数的影响;利用最小二乘法回归实验数据得到了床层压降、动持液量及泛点气速的预测关联式,各关联式误差均在±4.5%以内,可作为工业设计的参考依据。     

Cyclic mass transport phenomena in a novel reactor for gas–liquid–solid contacting

This study introduces a novel reactor concept, referred to as the Siphon Reactor, for intensified phase contacting of gas–liquid reactants on heterogeneous catalysts. The reactor comprises a fixed catalyst bed in a siphoned reservoir, which is periodically filled and emptied. This serves to alternate liquid–solid and then gas–liquid mass transfer processes. As the duration of each phase can be manipulated, mass transfer can be deliberately harmonized with the reaction. Residence time experiments demonstrate that, in contrast to periodically operated trickle‐bed reactors, the static liquid hold‐up is exchanged frequently and uniformly due to the complete homogeneous liquid wetting. A mathematical model describing the siphon hydrodynamics was developed and experimentally validated. The model was extended to account for a heterogeneously catalyzed gas–liquid reaction and capture the influence of siphon operation on conversion and selectivity of a consecutive reaction. © 2016 American Institute of Chemical Engineers AIChE J, 63: 208–215, 2017     

A highly efficient polymer‐anchored palladium(II) complex catalyst for hydrogenation,Heck cross‐coupling and cyanation reactions

BACKGROUND: Precise architectures of steric and electronic properties of palladium species play a crucial role in designing highly functionalized catalyst systems responsible for target organic transformations. Pd catalysts supported on polymer materials have been employed extensively as catalysts not only for hydrogenation but also for coupling reactions in the production of fine chemicals. RESULTS: A new polymer‐anchored Pd(II) complex has been synthesized and characterized. The catalyst shows high catalytic activity in the hydrogenation of styrene oxide, Heck cross‐coupling and cyanation reactions of aryl halides. The effect of various reaction parameters were investigated to optimize reaction conditions. The catalytic system shows good activity in the hydrogenation of styrene oxide (conversion 98%) with a selectivity to 2‐phenylethanol (93%) which is higher than its homogeneous analogues. The catalyst also exhibits excellent catalytic activity for the Heck cross‐coupling and cyanation reactions of various substituted and non‐substituted aryl halides. CONCLUSIONS: Results demonstrate that the catalyst is robust and stable and can be recovered quantitatively by simple filtration and reused several times without loss of activity. Copyright © 2010 Society of Chemical Industry     

Predicting solvent effects on the 1‐dodecene hydroformylation reaction equilibrium

Solvent effects on the reaction equilibrium of the 1‐dodecene hydroformylation in a decane/N,N‐dimethylformamide solvent system is investigated. The reaction was performed at different decane/N,N‐dimethylformamide ratios and at temperatures between 368 K and 388 K. The equilibrium concentrations of all reactants and products were determined experimentally. The enthalpy and Gibbs energy of this reaction at the ideal‐gas standard state were determined by quantum‐chemical calculations in good agreement with literature data. Moreover, quantum‐chemically calculated standard Gibbs energies of reaction at infinite dilution in liquid decane/DMF‐solvent mixtures allowed a qualitative prediction of the solvent effect on the equilibrium concentrations. Based on the standard Gibbs energy of reaction at the ideal‐gas standard state and on fugacity coefficients calculated using the Perturbed‐Chain Statistical Associating Fluid Theory, the equilibrium concentrations of reactants and products for the 1‐dodecene hydroformylation performed in decane/N,N‐dimethylformamide mixtures of different compositions could be predicted in very good agreement with experimental data. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4576–4585, 2017     

PROPOSAL FOR A NOVEL CHEMICAL HEAT PUMP DRYER

A new chemical heat pump (CHP) system for ecofriendly effective utilization of thermal energy in drying is proposed from the viewpoints of energy saving and environmental impact. CHPs can store thermal energy in the form of chemical energy by an endothermic reaction and release it at various temperature levels for heat demands by exo/endothermic reactions. CHPs have potential for heat recovery and dehumidification in the drying process by heat storage and high/law temperature heat release. In this study, we estimate the potential of the CHP application to drying systems for industrial use. Some combined systems of CHPs and dryers are proposed as chemical heat pump dryers (CHPD). The potential for commercialization of CHPDs is discussed.     

金属基消毒材料对芥子气降解研究进展

芥子气被称为“毒剂之王”，是一类典型的糜烂性化学战剂。催化降解法具有效率高、安全性好等特点，在降解芥子气的同时可防止芥子气降解为其他的剧毒产物，如有毒的砜产物等。催化降解使用的材料主要有次氯酸盐、过氧化氢、酶、金属基催化剂等。其中，金属基催化剂具有温和、高效、高选择的特性，主要通过氧化反应、水解反应、脱卤消去反应催化降解芥子气。该文归纳了金属氧化物、多金属氧酸盐（POMs）、金属有机框架材料（MOFs）等金属基催化剂降解芥子气的催化性能及其降解芥子气的原理；总结了降解芥子气的金属基催化剂材料的制备方法；最后，对金属氧化物、POMs和MOFs材料进行展望，以期对后续的研究提供新的思路。