有机相的加入对气液体系流动及传质特性的影响

以难溶气体的吸收作为研究的基本过程,纯CO2为气体溶质,0.5MK2CO3／0.5MKHCO3为连续相,异戊醇、苯、正己烷分别作为有机相,探索有机相对气液传质的增强作用,实验探求从不同有机相以不同油分率、表观气速对三相传质系数、增强因子等的影响。     

Study of Ethylene Polymerization Under Single Liquid Phase and Vapor‐Liquid Phase Conditions in a Continuous‐Flow Tubular Reactor

The feasibility of using continuous‐flow tubular reactors (CFTR) as an efficient research tool for polymerization reactions is investigated. This is a continuation of the extensive effort that had been made at Dow in recent years to set up and employ an electro‐thermal microreactor (an ohmically‐heated CFTR), which resulted in several internal and external publications and a US Patent. The main focus of this work is to investigate the effect of operating conditions and flow composition, mainly the number of existing phases, on the molecular weight of the polymer. A series of polymerization experiments were performed in single‐phase (liquid) and two‐phase (vapor‐liquid) flow regimes. In single‐phase polymerization, the ethylene concentration falls continuously along the length of the reactor. This will have a significant effect on the kinetics of polymerization, particularly the molecular weight of the produced polymer. A key advantage of operating in the two‐phase region is that an almost constant ethylene concentration is maintained along the length of the reactor. In effect, the vapor phase serves as a reservoir that replenishes the ethylene consumed in the liquid phase by polymerization. The molecular weight data show that this assumption is valid provided that the rate of mass transfer is significantly higher than the rate of the polymerization reaction.     

Liquid‐Liquid Biphasic,Platinum‐Catalyzed Hydrosilylation of Allyl Chloride with Trichlorosilane using an Ionic Liquid Catalyst Phase in a Continuous Loop Reactor

The platinum‐catalyzed hydrosilylation of allyl chloride with trichlorosilane was investigated in an ionic liquid‐organic biphasic reaction mode. After an ionic liquid screening and repetitive batch mode experiments, the process was realized in a continuous mode using a loop reactor concept with integrated continuous separation and recycling of the ionic liquid catalyst phase. The continuous reactor could be operated for 48 h at constant activity and selectivity without addition of platinum indicating that platinum leaching into the product phase was far below 1 ppm. Enhanced selectivity for the product trichloro(3‐chloropropyl)silane (compared to the state‐of‐the art) and the possibility to use simple platinum tetrachloride (PtCl₄) as platinum source are further attractive features of this new ionic liquid‐based process concept.     

Polymerization of vinyl chloride at reduced monomer accessibility. IV. The effect of diffusion control on polymerization rate,molecular weight,and thermal stability

The effect of diffusion control on the polymerization of vinyl chloride has been studied by observing the rate as well as the molecular weight and the thermal stability of the polymer formed. The polymerizations were performed at 97% of saturation pressure in a water-suspended system at 55°C, using emulsion PVC latex as seed and a water-soluble initiator. The monomer was charged as vapor from a storage vessel kept at a lower temperature. Characterization included determination of molecular weight distribution by GPC and viscometry, and thermal dehydrochlorination. The gas–liquid contact was varied by changing the speed of agitation and the design of the stirrer. With a propeller the polymerization rate increased with the agitation up to ca. 1000 rpm, where after it became almost constant. Simultaneously, the molecular weight and the thermal stability increased. This indicates diffusion control, and thus decreased monomer concentration, at low agitation speeds, while the polymerization becomes reaction controlled at higher speeds. By a comparison with earlier data, obtained at different pressures and under reaction control, the actual monomer concentration could be calculated, which allowed an evaluation of the mass transfer constant. The possibilities to encounter problems with diffusion control in commercial polymerization of vinyl chloride is discussed. It is demonstrated that diffusion control is utilized in continuous polymerization of vinyl chloride, which explains the lower thermal stability of such materials.     

液体纯物质导热系数的预测

在估算导热系数的Weber方程和Sato—Riedel法的基础上,根据对液体导热系数影响因素的分析,提出了估算液体导热系数的计算模型。利用该模型计算了34种液体物质（包括27种有机物和7种无机物）100个数据点的导热系数,计算值与试验值的总平均相对偏差为3．00％,计算准确性优于文献方法,方法简单方便,利用被估算液体物质的摩尔质量、临界温度临界压缩因子和正常沸点温度数据,就可以直接预测这些液体在不同温度下的导热系数。     

液相色谱及液质联用技术在环境分析中的应用

高效液相色谱（HPLC）是在经典液相色谱法和气相色谱法的基础上发展起来的新型分离分析技术。20世纪80、90年代后,HPLC技术发展迅速,特别是21世纪初,液相色谱与现代质谱的联机技术有了很大的发展,使HPLC的应用前景更为广阔。在全部已知的有机化合物中近80％的有机化合物属于挥发性低,易受热分解或者大分子化合物,适合于高效液相色谱进行分析。本文主要从HPLC分析方法的特点为切入点,介绍液相色谱及液质联用技术在环境分析中的应用。     

硅胶固载离子液体催化剂的制备及在酯化反应中的应用

为了减少离子液体用量及解决催化剂分离问题,该文采用溶胶-凝胶法制备出一种硅胶固载Brφnsted酸性离子液体催化剂{[Hmim]TsO/silicagelw([Hmim]TsO)=62%},用DRFITS、FTRaman、BET对其进行了表征,结果表明,离子液体已较好地固载于硅胶上,催化剂比表面积为51.15m2/g。将其应用于催化合成醋酸丁酯反应,较佳反应条件为:95℃,n(丁醇)∶n(醋酸)=1.2∶1,离子液体用量为反应物总质量的5.6%,反应时间6h,酯化率可达94%。与单纯离子液体[Hmim]TsO催化效果相比,离子液体质量减少72%,酯化率提高了8.9%,催化剂易分离,循环使用6次后,酯化率仍可达到83.3%。     

基于激光光谱法的尿素水溶液液膜多参数测量

在选择性催化还原（SCR）系统中，对尿素水溶液液膜多个参数（厚度、浓度及温度）进行高精度的定量分析，对减少液膜形成、提高SCR系统的催化反应效率、降低NO_x对环境的污染至关重要。基于比尔-朗伯定律，通过结合1420 nm和1488 nm两个波长的半导体激光器，提出一种恒温度条件下尿素水溶液液膜厚度和浓度同步测量，以及恒浓度条件下尿素水溶液液膜厚度和温度同步测量的新方法。并在此基础上，利用标准具验证了该方法的测量精度。结果表明恒温度条件下，该方法同步测量尿素水溶液液膜厚度和浓度的平均测量误差分别为0.82%和3.93%；恒浓度条件下，同步测量尿素水溶液液膜厚度和温度的平均测量误差分别为0.79%和2.58%。     

Continuous Methanolysis of Palm Oil Using a Liquid–Liquid Film Reactor

A system for the continuous methanolysis of palm oil using a liquid–liquid film reactor (LLFR) was developed and characterized. This reactor is a co-current, constant diameter (0.01 m), custom-made packed column where the mass transfer area between the partially miscible methanol-rich and vegetable oil-rich phases is created in a non-dispersive way, without the intervention of mechanical stirrers or ultrasound devices. An increase in contact area between phases enhances reaction rate while the absence of small, dispersed droplets of one phase into the other diminishes the settling time at the end of the reaction. In this study variations on the concentration of catalyst (sodium hydroxide), flow rate of palm oil and normalized length of the reactor (L/L _max) were explored, keeping constant both the methanol to oil molar ratio and the temperature of the reaction (6:1 and 60 °C). The best experimental results with a reactor of 1.26 m (L/L _max = 1.0) showed a conversion of palm oil of 97.5% and a yield of methyl esters of 92.2% of the theoretical yield, when the mass flow rate and the residence time of the palm oil were 9.0 g min⁻¹ and 5.0 min, respectively. To determine the mean residence time and the degree of axial mixing in the reactor, a residence time distribution (RTD) study was performed using a step-function input. The dispersion model appears to fit well the RTD experimental data.     

Ni-W/SSY催化裂化生物正构烷烃制备航空燃料

以超稳SSY分子筛负载Ni-W制得加氢裂化催化剂,用于加氢裂化生物正构烷烃(C16、C18),得到以煤油和汽油为主的液体生物燃料,可以提高中油组分收率。通过氮气物理吸附,扫描电镜(SEM),X射线光电子能谱(XPS)等分析手段对催化剂进行了表征。在微型固定床连续加氢裂化反应器上,考察了反应条件对单程转化率和煤油/汽油质量比的影响规律。结果表明:255℃、1.0 MPa、质量空速为0.33 h-1、氢油比为4 000:1的反应条件下,单程转化率达到60%以上,煤油与汽油质量比超过2.0。Ni-W/SSY催化剂活性高,可以用于长链烷烃加氢裂化制备煤油组分为主的液体燃料。     

液体有机物导热系数的估算

在计算液体导热系数的Weber方程和Sato关系式的基础上,根据对有机物液体导热系数影响因素的分析研究,提出了估算有机物导热系数的计算模型;利用该模型计算了22个体系74个数据点的有机物液体的导热系数,计算值与实验值的总平均相对偏差3.18%,计算准确性优于文献方法;计算结果表明,利用被估算物质的摩尔质量、临界温度、正...     

Separation and Concentration of Phenylalanine by Emulsion Liquid Membrane in a CSTR Extraction Process

Abstract

The extraction and concentration of phenylalanine by the continuous CSTR emulsion liquid membrane (ELM) separation process has been evaluated. We discussed the influence of operating conditions on the separation and concentration efficiencies of phenylanine. It was found that the extraction rate of phenylalanine increased as the amount of emulsion used and the internal concentration of H⁺ increased. However, the concentration ratio of phenylalanine increased as the emulsion amount and acid concentration increased only up to a certain limit and then declined with further increases of these. The reduction of the concentration ratio is due to the swelling of the emulsion drops. Two effects, swelling owing to osmotic pressure and swelling caused by the entrainment of water due to mechanical agitation, are responsible for the swelling of emulsion drops. A mass transfer model for analyzing the extraction of phenylalanine by liquid surfactant membrane is presented. The model assumes that the extraction and stripping reactions are reversible, and that the reaction equilibrium exists in both the internal and the external interfaces. The scheme for mass transfer is based on a hollow sphere model. The phenomena of osmotic swelling, mechanical entrainment, and breakage are all considered in the mathematical treatment. The effects of operation parameters on the extraction efficiency and concentration ratio are discussed by simulation.     

己内酰胺苯磺酸类离子液体催化甲苯选择性硝化反应的研究

制备了己内酰胺对甲基苯磺酸和苯磺酸离子液体作为催化剂和溶剂,用于催化甲苯与等摩尔67%(m/m)硝酸的硝化反应,并用1H NMR进行了表征。研究了不同的反应温度、时间和离子液体用量及不同的离子液体等因素对甲苯硝化反应的影响。结果表明:该离子液体对甲苯的硝化有较好的对位选择性,产物中邻、对异构体质量比为1.2,较硝硫混酸硝化(邻、对异构体质量比约2.0)显著降低,收率可达37.1%,且可重复使用。     

Liquid phase methanol and dimethyl ether synthesis from syngas

The Liquid Phase Methanol Synthesis (LPMeOH^TM) process has been investigated in our laboratories since 1982The reaction chemistry of liquid phase methanol synthesis over commercial Cu/ZnO/Al₂O₃ catalysts, established for diverse feed gas conditions including H₂-rich, CO-rich, CO₂-rich, and CO-free environments, is predominantly based on the CO₂ hydrogenation reaction and the forward water-gas shift reactionImportant aspects of the liquid phase methanol synthesis investigated in this in-depth study include global kinetic rate expressions, external mass transfer mechanisms and rates, correlation for the overall gas-to-liquid mass transfer rate coefficient, computation of the multicomponent phase equilibrium and prediction of the ultimate and isolated chemical equilibrium compositions, thermal stability analysis of the liquid phase methanol synthesis reactor, investigation of pore diffusion in the methanol catalyst, and elucidation of catalyst deactivation/regenerationThese studies were conducted in a mechanically agitated slurry reactor as well as in a liquid entrained reactorA novel liquid phase process for co-production of dimethyl ether (DME) and methanol has also been developedThe process is based on dual-catalytic synthesis in a single reactor stage, where the methanol synthesis and water gas shift reactions takes place over Cu/ZnO/Al₂O₃ catalysts and the in-situ methanol dehydration reaction takes place over -Al₂O₃ catalystCo-production of DME and methanol can increase the single-stage reactor productivity by as much as 80%. By varying the mass ratios of methanol synthesis catalyst to methanol dehydration catalyst, it is possible to co-produce DME and methanol in any fixed proportion, from 5% DME to 95% DMEAlso, dual catalysts exhibit higher activity, and more importantly these activities are sustained for a longer catalyst on-stream life by alleviating catalyst deactivation.     

A qualitative computational study of mass transfer in upward bubble train flow through square and rectangular mini-channels

In this paper we present a new method for numerical simulation of conjugate mass transfer of a dilute species with resistance in both phases and an arbitrary equilibrium distribution coefficient. The method is based on the volume-of-fluid technique and accounts for the concentration jump at the interface by transforming the discontinuous physical concentration field into a continuous numerical one. The method is validated by several test problems and is used to investigate the mass transfer in upward bubble train flow within square and rectangular channels. Computations are performed for a single flow unit cell and a channel hydraulic diameter of 2 mm. The simulations consider the transfer of a dilute species from the dispersed gas into the continuous liquid phase. Optionally, the mass transfer is accompanied by a first-order homogeneous chemical reaction in the liquid phase or a first-order heterogeneous reaction at the channel walls. The results of this numerical study are qualitative in nature. First, because periodic boundary conditions in axial direction are not only used for the velocity field but also for the concentration field and second, because the species diffusivity in the liquid phase is arbitrarily increased so that the liquid phase Schmidt number is 0.8 and the thickness of the concentration and momentum boundary layer is similar. Two different equilibrium distribution coefficients are considered, one where the mass transfer is from high to low concentration, and one where it is vice versa. The numerical study focuses on the influence of the unit cell length, liquid slug length and channel aspect ratio on mass transfer. It is found that for the exposure times investigated the liquid film between the bubble and the wall is saturated and the mass transfer occurs by the major part through the bubble front and rear so that short unit cells are more efficient for mass transfer. Similar observations are made for the homogeneous reaction and for the heterogeneous reaction when the reaction is slow. In case of a fast heterogeneous reaction and when the main resistance to mass transfer is in the gas phase, it appears that for square channels long unit cells are more efficient, while large aspect ratio rectangular channels are more efficient than square channels, suggesting that for these conditions they might be more appropriate for use in monolithic catalysts.     

Recycling and Activity Recovery of Chloroaluminate Ionic Liquid as Catalyst for Alkylation of Benzene with 1-Dodecene

Performances of 1-butyl-3-methylimidazolium aluminium chloride ([BMIM]Cl-AlCl3) ionic liquid as catalyst for the alkylation of benzene with long chain olefins were investigated in a continuous operation mode. A small pilot plant with continuous mixing-reacting-separating-recycling functions, equipped with a static mixer reactor, a tube packed with metal Al thread and a combined liquid-liquid settling phase separator, was introduced as an alternative. The results showed that the continuous fast mixing and separation of ionic liquid catalyst from reactant mixture could be synchronously accomplished within a wider flow rate ratio range of the recycling reaction mixture to the ionic liquid catalyst. The recycling of chloroaluminate ionic liquid was realized. ICP-AES detection results of Al content in the reactants proves that in-situ Al compensation to the reaction system may be an important choice to prolong the stable running time of moisture-sensitive ionic liquid [BMIM]Cl-AlCl3 when feedstock inevitably contains trace water. It suggests that the activity of chloroaluminate ionic liquid is recovered under the in-situ Al compensation operation.     

New Approach in the Prediction of RDC Liquid‐Liquid Extraction Column Parameters

The liquid‐liquid extraction process is well‐known for its complexity and often entails intensive modeling and computational efforts to simulate its dynamic behavior. This paper presents a new application of the Genetic Algorithm (GA) to predict the modeling parameters of a chemical pilot plant involving a rotating disc liquid‐liquid extraction contactor (RDC). In this process, the droplet behavior of the dispersed phase has a strong influence on the mass transfer performance of the column. The mass transfer mechanism inside the drops of the dispersed phase was modeled by the Handlos‐Baron circulating drop model with consideration of the effect of forward mixing. Using the Genetic Algorithm method and the Numerical Analysis Group (NAG) software, the mass transfer and axial dispersion coefficients in the continuous phase in these columns were optimized. In order to obtain the RDC column parameters, a least‐square function of differences between the simulated and experimental concentration profiles (SSD) and 95 % confidence limit in the plug flow number of the transfer unit prediction were considered. The minus 95 % confidence limit and sum of square deviations for the GA method justified it as a successful method for optimization of the mass transfer and axial dispersion coefficients of liquid‐liquid extraction columns.     

Kinetic Model of Gas‐Liquid‐Liquid Reactive Extraction for Production of Hydrogen Peroxide

The kinetic aspects of the gas‐liquid‐liquid reactive extraction process for the production of hydrogen peroxide were investigated in a batch reactor. It was observed that the gas‐liquid reaction rate is strongly affected by mass transfer of oxygen across the liquid film and the reaction can be simplified to pseudo‐first order. The extraction rate is governed by both reaction and liquid‐liquid mass transfer, and is slightly lower than the reaction rate. In addition, a kinetic model of the reactive extraction process for the production of hydrogen peroxide was developed. Kinetic parameters under different conditions were determined by experiments. The data calculated from the kinetic model match experimental data well under different conditions for hydrogen peroxide production in gas‐liquid‐liquid reactive extraction.     

Thermally Coupled Catalytic Reactor for Steam Reforming of Methane and Liquid Hydrocarbons: Experiment and Mathematical Modeling

An energy-efficient catalytic reactor for producing synthesis gas from methane and liquid hydrocarbons is proposed that is based on the coupling of an endothermic reaction (steam reforming of methane, hexane, or isooctane) and an exothermic reaction (hydrogen oxidation by atmospheric oxygen) in a single cocurrent apparatus. To describe the processes in such an apparatus, a two-dimensional two-temperature mathematical model is developed. It was revealed experimentally and by mathematical modeling that the heat- and mass-transfer coefficients of the gas flow in contact with the catalytically active wall in the exothermic reaction zone considerably affect the thermal conditions in the reactor.     

COMBINED EFFECT OF FREQUENCY OF MIXING AND FREQUENCY OF CHEMICAL REACTION ON THE RATE OF MASS TRANSFER AT A FREE LIQUID INTERFACE

The combined effect of mixing and chemical reaction on mass transfer at a free liquid interface subjected to a quasi-periodic motion is studied, taking as an example the wave motion in a thin liquid film flowing down a vertical wall. The equation of convective-diffusion with first-order reaction is solved in the small penetration approximation by using a method of successive transformations which contracts it to a pure-diffusion type equation. It is found that the amplification factor due to the wave motion diminishes as the reaction rate constant increases, and approaches unity in the limit of very rapid reaction. However, in the case of instantaneous bimolecular reaction, it is found that the amplification factor due to wave motion is not affected by the occurrence of reaction.