生物柴油新反应器及其应用

生物柴油是石化柴油的重要补充.用传统的搅拌釜和管式反应器制备生物柴油,存在反应速率慢、转化率低的问题.从提高反应速率和转化率两方面综述了生物柴油新反应器的研究进展.提高反应速率的反应器包括:微波反应器、空化反应器、旋转床反应器、振荡流反应器、高剪切反应器、静态反应器、微反应器和液液膜反应器.提高转化率的反应器包括:反应/分离器、反应蒸馏反应器和膜反应器.比较了它们的优势和缺陷.提出联合使用几种技术,将强化传质与分离技术进行有效整合,使反应器小型化并缩短工艺流程,以建立适应未来的生产效率高的便携式生物柴油厂.     

Chemical Vapor Deposition of CuOx Films by Cul and O2: Role of Cluster Formation on Film Morphology

CuO _x films were deposited on silica substrates by the chemical vapor deposition (CVD) method, using CuI and O₂ as source gases at low pressure in a tubular reactor. The growth mechanism to obtain a dense and uniformly distributed (in the axial direction in a tubular reactor) film was investigated. It was found that the occurrence of homogenous nucleation caused an abrupt increase of deposition rate and made the film porous. Homogeneous nucleation can be prevented by properly selecting reactant concentration, reactor temperature, and reactor diameter. Based on an aerosol diffusion theory from laminar pipe flow, a method of predicting cluster size in this CVD reaction system was proposed. The result showed that the clusters formed by homogeneous nucleation had an average size of about 1 nm in diameter.     

多孔电极臭氧发生器氧化废水中有机物的吸收和反应动力学分析(英文)

A novel electrode design for the in situ generation of ozone in the reaction zone of a tubular reactor is described in this work.The ozone generator uses a porous inner electrode tube in the corona discharge assembly,and the ozone generated around the outer periphery of the porous tube diffuses into the tubular reactor and reacts with the contaminants in the fluid that is being treated.A mathematical model that includes absorption and second order reaction in the film is developed to describe ozonation kinetics of a contaminant dye in the tubular reactor.The model describes the experimental data for dye decolorization,oxidation byproducts,dissolved ozone,and ozone gas concentrations well.Model analysis indicates that the fast dye decolorization reaction occurs partly in the liquid film and partly in the bulk fluid.The model can be used in the selection of appropriate gas-liquid contactors for efficient oxidation of contaminants in effluents.     

氯醇化管式反应器的设计计算方法

根据氯醇化反应的特点，利用气液反应的双膜理论，导出了宏观反应速率式，结合管式反应器的流动模型，提出了一个简便、有效的反应器的设计计算方法     

Electrochemical oxidation of perfluorobutane sulfonate using boron-doped diamond film electrodes

This research investigated oxidation of perfluorobutane sulfonate (PFBS) at a boron-doped diamond (BDD) film anode. PFBS oxidation produced carbon dioxide, sulfate, fluoride, and trace amounts of trifluoroacetic acid (TFA). Rate constants for PFBS oxidation as a function of current density and temperature were measured using a rotating disk electrode (RDE) reactor. Reaction rates in the RDE reactor were zeroth order with respect to PFBS concentration, which is indicative of a reaction limited by the availability of reactive sites. The apparent electron transfer coefficient and apparent activation energy were used to evaluate the rate-limiting step for PFBS oxidation. Density functional simulations were used to calculate the reaction energies and activation barriers for PFBS oxidation by hydroxyl radicals and by direct electron transfer. Simulation results indicated that the experiments were performed at sufficiently high overpotentials that the rate-limiting step was an activationless direct electron transfer reaction.     

Analysis of centrifugal annular reactor with radial flow

A model for centrifugal annular catalytic reactor is presented. The gas flows radially through the annulus while the inner cylinder is rotated to produce the centrifugal effect. A catalytic consecutive reaction takes place at the external surface of the annulus. The reactor is aimed to utilize the fact that heavier substances concentrate on the external walls of rotating reactors more than the lighter ones, so as to improve the conversion and yield of the desired intermediate product in consecutive reactions.The reaction performance is examined for various reaction kinetics, angular velocity and gas flow rate. The gas flow direction (inward or outward) is aIt is shown that for a given reaction and reactor geometry, an optimal angular velocity exists, where the reaction conversion is maximum. It is also sh     

Cluster Size Determination in the Chemical Vapor Deposition of Aluminum Nitride

Aluminum nitride was prepared in a laminar-flow, tubular reactor using an atmospheric pressure chemical vapor deposition (APCVD) method at a reaction temperature ranging from 700° to 1100°C and AlCl₃ and NH₃ concentrations of 0.4 and 8 mol%, respectively. Films grew on the reactor wall and particles formed in the gas phase. The production rates of films and particles were independently determined. A comprehensive model was constructed to estimate the molecular size of the growth species in the APCVD process to simultaneously form films and particles of AIN from AlCl₃, and NH₃. Transport equations of a dominant growth species used in growing films on the reactor wall and particles in the gas phase in a laminar-flow, tubular reactor were formulated and solved. An assumption made in the model was to use the surface reaction rate constant measured for the film surface for the particle surface. Comparing the film and particle growth data measured experimentally with those obtained from model prediction allows us to conclude that the growth species are clusters ranging in size from 0.8 nm at 700°C, equivalent to 8 units of AIN, to 0.5 nm at 1100°C, equivalent to 1 unit of AIN.     

Comparison of mass transfer effects in the heterogeneously catalysed hydrogenation of phenyl acetylene in heptane and an ionic liquid

The selective heterogeneous catalytic reduction of phenyl acetylene to styrene over palladium supported on calcium carbonate is reported in both an ionic liquid and a molecular solvent. By using a rotating disc reactor in conjunction with results from a stirred tank reactor it is possible, for the first time, to disentangle the mass transfer contributions in the ionic liquid system. For both heptane and 1-butyl-3-methyl imidazolium bis{(trifluoromethyl)sulfonyl}imide, the reaction in the rotating disc reactor is dominated by reaction in the entrained film on the disc compared with very limited reaction in the bulk liquid. The lower reaction rate obtained in the ionic liquid compared with the organic solvent is shown to be due to the slow transport of the hydrogen dissolved in the liquid. It is clear from the results presented herein that, although the hydrodynamics of similar reactors used for biological treatment of wastewater are well understood, on using a more viscous fluid and higher rotation speeds necessary for fine chemical catalysis these simple relationships breakdown.     

Studies of deactivation of metals by carbon deposition

Studies of carbon deposition from aliphatic and aromatic hydrocarbons over metal catalysts were carried out over the temperature range 700–1025 K using a microbalance coupled with a tubular reactor. The influence of the nature of the reactor wall on the rate of carbon formation, as well as the effect of hydrogen in preventing deactivation of the catalysts, was investigated. A general reaction scheme is proposed to explain the relationships between the different types of carbon formed on the catalysts.     

Melt polycondensation of poly(ethylene terephthalate) in a rotating disk reactor

A multicompartment model is proposed for a semibatch melt polycondensation of poly(ethylene terephthalate) in a rotating disk polymerization reactor and compared with laboratory experimental data. The reactor is a horizontal cylindrical vessel with a horizontal shaft on which multiple disks are mounted. The reactor is assumed to comprise N equal sized compartments and each compartment consists of a film phase on the rotating disk and a bulk phase in which disks are partially immersed. The effects of disk rotating speed, number of disks, reaction temperature, and pressure were investigated. It was observed that ethylene glycol is predominantly removed from thin polymer layers on the rotating disks and the enhanced interfacial area exerted by ethylene glycol bubbles accounts for about 30–50% of the total available interfacial mass transfer area. Although the rate of polymerization increases as more disks are used, the maximum number of disks in a reactor must be determined properly in order to prevent the formation of thick polymer films that result in a reduced specific interfacial area and reduced polymerization efficiency. At a fixed reaction pressure, the equilibrium conversion is reached but the rate of reaction can be further increased by increasing the reaction temperature. The results of the proposed multicompartment model are also compared with those predicted by a simple one-parameter model. © 1995 John Wiley & Sons, Inc.     

Numerical investigation and experimental validation of the performance of a tubular packed bed reactor for hydrogenation of diene‐based polymers

A process which comprised a tubular reactor (that can be packed with different internal structures) has been modeled and theoretically analyzed for conducting the hydrogenation of nitrile butadiene rubber (NBR). The dynamics of the tubular reactor and the intrinsic hydrogenation kinetics are coupled, and detailed numerical simulations are performed under isothermal and isobaric conditions. The proposed model thus obtained involves coupled, nonlinear, partial differential equations (distributed parameter system). The effect of different reactor design parameters such as Peclet number, carbon–carbon double bond loading, mass transfer to reaction resistance, and solubility of hydrogen with respect to hydrogenation of the NBR has been investigated numerically. The conversions predicted using the proposed model for tubular packed bed reactor are compared with those possible in conventional plug flow reactor and continuous stirred tank reactor models. The optimal parameters and operating conditions for efficient production of hydrogenated NBR are suggested. Finally, the validity of the proposed model is confirmed by comparing the predicted and the experimental degree of hydrogenation obtained in a tubular reactor packed with Intalox saddles. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

HIGH-TEMPERATURE SOLAR CHEMICAL REACTORS FOR HYDROGEN PRODUCTION FROM NATURAL GAS CRACKING

This study deals with the thermal cracking of natural gas for the coproduction of hydrogen and carbon black from concentrated solar energy without CO₂ emission. A laboratory-scale solar reactor (1 kW) was tested and modeled successfully. It consists of a tubular graphite receiver directly absorbing solar radiation, in which a mixture of Ar and CH₄ flows. A temperature increase or a gas flow rate decrease results in chemical conversion increase. Methane conversion higher than 75% was obtained. Reaction occurred near the wall where temperature is maximal and gas velocity is minimal due to the laminar flow profile. The work focused also on the design of a medium-scale tubular solar reactor (10 kW) based on the indirect heating concept. A reactor model including gas hydrodynamics and heat and mass transfers coupled to the chemical reaction was developed in order to predict the reactor performances. Temperature and species concentration profiles and final chemical conversion were quantified. According to the results, temperature was uniform in the tubular reaction zone and the predicted chemical conversion was 65%, neglecting the catalytic effect of carbon particles.     

Microwave assisted flow synthesis: Coupling of electromagnetic and hydrodynamic phenomena

This article describes the results of a modeling study performed to understand the microwave heating process in continuous‐flow reactors. It demonstrates the influence of liquid velocity profiles on temperature and microwave energy dissipation in a microwave integrated milli reactor‐heat exchanger. Horizontal cocurrent flow of a strong microwave absorbing reaction mixture (ethanol + acetic acid, molar ratio 5:1) and a microwave transparent coolant (toluene) was established in a Teflon supported quartz tube (i.d.: 3 × 10^?3 m and o.d.: 4 × 10^?3 m) and shell (i.d.: 7 × 10^?3 m and o.d.: 9 × 10^?3 m), respectively. Modeling showed that the temperature rise of the highly microwave absorbing reaction mixture was up to four times higher in the almost stagnant liquid at the reactor walls than in the bulk liquid. The coolant flow was ineffective in controlling the outlet reaction mixture temperature. However, at high flow rates it limits the overheating of the stagnant liquid film of the reaction mixture at the reactor walls. It was also found that the stagnant layer around a fiber optic temperature probe, when inserted from the direction of the flow, resulted in much higher temperatures than the bulk liquid. This was not the case when the probe was inserted from the opposite direction. The experimental validations of these modeling results proved that the temperature profiles depend more on the reaction mixture velocity profiles than on the microwave energy dissipation/electric field intensity. Thus, in flow synthesis, particularly where a focused microwave field is applied over a small tubular flow reactor, it is very important to understand the large (direct/indirect) influence of reactor internals on the microwave heating process. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3824–3832, 2014     

The effect of nitrogen on the growth,morphology, and crystalline quality of MPACVD diamond films

The influence of varying nitrogen concentrations (5–1000 ppm) on the conventional CH₄/H₂ diamond film deposition process using a microwave plasma disk reactor is investigated. This reactor has important differences, such as reactor volume, power density, gas flow, from the common tubular microwave reactors. The experimental behavior indicates, that similar to the tubular reactors, the addition of small amounts of a nitrogen stabilizes the growth of high quality, {100} faceted films. However, the actual threshold nitrogen concentrations and the variation of these threshold concentrations versus other independent experimental variables differs considerably from tubular reactor performance. This suggests that reactor design has an important influence on the deposition process in the presence of impurities.     

转鼓反应器中油酸氧化裂解制备壬二酸的研究

在转鼓反应器中实现了油酸臭氧氧化裂解制备壬二酸的连续化操作。考察了转鼓转速、液体流量、气体流量对转鼓反应器内气液传质反应速率的影响。在双膜理论的基础上,利用恩田公式来计算气相传质系数、液相传质系数,建立了转鼓反应器中两步反应速率模型,并将模型预测值与实验值进行了比较。实验结果表明:在转鼓反应器中,油酸氧化裂解反应速率分别随转鼓转速和液体流量的增大,先增大后趋于平缓;随着气体通量的增加,转鼓反应器内油酸氧化裂解反应速率先增大然后减小;在转鼓转速为1 699 r/min、液体流量为45 mL/min、气体流量为3 L/min时,在转鼓内油酸氧化裂解可获得最大的气液传质反应速率。模型预测值与实验值比较,两者吻合得较好,验证了模型的可靠性。     

Thermolysis of methane in a solar reactor for mass-production of hydrogen and carbon nano-materials

Solar thermolysis of methane to produce hydrogen and carbon nano-materials in a volumetric reactor/receiver with carbon particles cloud either priory seeded or chemically produced in the reactor, has been developed and tested. The reactor is based on absorbing of the concentrated solar radiation by the carbon particles and maintaining a reaction core at high temperature while the reactor walls are kept at relatively low temperatures, compatible with existing ceramic materials. The main advantage of the volumetric approach lies in its excellent heat transfer effectiveness and scalability to larger scales. As a result of computational fluid dynamics (CFD) analysis a compound reactor was designed and tested. The reactor’s most important characteristics are: high reaction temperature, transparent window protection and directional streaming flow (tornado) without boundary layer separation. Experimentally, high temperatures (up to 1500 °C) in the reaction domain were achieved resulting in complete conversion of methane to hydrogen and solid carbon nano particles. Experiments were operated for periods of about 60 min with steady-state temperatures and reaction products. Organometallic catalysts were mixed together with the methane feed to produce multiwalled carbon nanotubes (MWCNT). In the catalytic experiments lower temperatures were maintained which, although resulted in lower methane conversion, enhanced the MWCNT production.     

HEAT TRANSFER ENHANCEMENT WITH CHEMICAL REACTION-MODEL COMPARISONS

A one dimensional tubular reactor model which incorporates heat transfer enhancement calculations in the presence of homogenous chemical reactions is presented. The model compensates for the distortion in the actual radial temperature profile due to chemical reaction by calculating the temperature profile in the film next to the reactor wall which is then used to correct for the heat transfer coefficient based on the non-reactive case. The relative simplicity and rapidity of the model makes it a viable alternative to the two dimensional model     

Modeling of a continuous rotating disk polycondensation reactor for the synthesis of thermoplastic polyesters

A dynamic multicompartment model is proposed for a continuous flow rotating disk reactor for the finishing stage melt polycondensation of poly(ethylene terephthalate). In the multicompartment reactor model, ethylene glycol is removed from both the bulk melt phase and the film phase formed on the rotating disks. The specific interfacial area for the film phase is estimated using the empirical correlation for polymer film thickness, and the mass transfer coefficient is calculated using the penetration theory. The mass transfer enhancement factor is introduced to account for the increased interfacial area due to ethylene glycol bubbles. The effects of reactor design and operating parameters on molecular weight and ethylene glycol removal have been investigated through model simulations. In particular, a detailed analysis is presented on the ethylene glycol removal rate from the two phases. © 1996 John Wiley & Sons, Inc.     

A COMPREHENSIVE MATHEMATICAL MODEL FOR A MULTIZONE TUBULAR HIGH PRESSURE LDPE REACTOR

In this study a comprehensive mathematical model of high pressure tubular ethylene polymerization reactors is presented. A fairly general reaction mechanism is employed to describe the complex kinetics of ethylene polymerization. To determine the variation of molecular properties along the reactor length the method of moments is applied to the infinite set of species balance equations to transform it into a low order system of differential equations in terms of the leading moments of the number chain length distribution. Detailed algebraic equations are given describing the variation of kinetic rate constants, thermodynamic and transport properties of the reaction mixture with temperature, pressure and composition. A new correlation is derived to describe the change of reaction viscosity with reactor operating conditions. The model permits a realistic calculation of temperature and pressure profiles, monomer and initiator concentrations, molecular properties of LDPE (i.e. M_n, M_m, LCB and SCB) as well as the variation of inside film heat transfer coefficient with respect to the reactor length. Simulation results are presented illustrating the effects of initiator concentration, inlet pressure, chain transfer concentration and wall fouling on the polymer quality and reactor operation. The present model predictions are in good agreement with experimental observations in industrial high pressure tubular LDPE reactors.     

An Ru-based catalytic membrane reactor for dry reforming of methane—its catalytic performance compared with tubular packed bed reactors

The methane reforming with CO₂ seems to be a promising reaction system useful to reduce the greenhouse contribution of both gases into the atmosphere. On this basis, and considering the potentiality of this reaction system, the dry reforming reaction has been carried out in an Ru-based ceramic tubular membrane reactor, in which two Ru depositions have been performed using the co-condensation technique. Experimental results in terms of CH₄ and CO₂ conversion versus temperature during time are presented, as well as product selectivity and carbon deposition. These experiments have also been carried out using a traditional reactor. A comparison with literature data regarding dry reforming reaction is also provided. Experimental evidence points out a good catalyst activity for the methane dry reforming reaction, confirming the potentiality of a catalytic membrane applied to the reaction system.