伴有瞬时化学反应微溶固体颗粒的气液传质

为研究瞬时化学反应性固体颗粒对气液传质过程的影响,对伴有瞬时反应性固体颗粒/水浆料体系吸收气体过程进行了理论分析。考虑了固体颗粒在气液界面附近的溶解,以及固体颗粒尺寸对传质的影响,将cell模型融入溶质渗透理论,建立了气液二相间传质模型,并对模型进行了解析求解,得到了液相传质系数的解析表达式。结果显示:固含率、固体颗粒尺寸和溶解度对气液传质过程具有重要影响,液相传质系数随固含率和固体颗粒在液相中饱和浓度的增加而增大,随固体颗粒粒径增大而减小。在搅拌式反应器中利用Mg(OH)2/水浆料吸收SO2气体,对传质模型进行了实验验证。模型计算结果与实验值吻合良好。     

High temperature water–gas shift reaction over hollow Ni–Fe–Al oxide nano-composite catalysts prepared by the solution-spray plasma technique

The effect of Fe content in Ni–Fe–Al oxide nano-composites prepared by the solution-spray plasma technique on their catalytic activity for the high temperature water–gas shift reaction was investigated. The composites showed a hollow sphere structure, with highly dispersed Fe–Ni particles supported on the outer surface of the spheres. When the water–gas shift reaction was performed over an Ni–Al oxide composite catalyst without Fe, undesired CO methanation took place predominantly compared to the water–gas shift reaction, and significant amounts of hydrogen were consumed. When appropriate amounts of Fe were added to the Ni–Al oxide composite catalyst during the plasma process, methanation was suppressed remarkably, without serious loss of activity for the water–gas shift reaction. The catalyst was characterized by STEM, XRD and H₂ chemisorption measurements.     

Absorption of carbon monoxide with reversible reaction in cualcl4-toluene-complex solutions

The absorption of CO in CuAlCl₄-toluene-complex solutions was studied in a stirred reactor. The reaction was found to occur in a fast reaction regime. The effect of CO partial pressure, CuAlCl₄-toluene-complex concentration and temperature on the rate of absorption was studied. The results have been interpreted using a theoretical model for mass transfer with reversible chemical reaction and the rate parameters were determined. The equilibrium constants were also determined experimentally. An interesting observation showing a decrease in the rate with an increase in temperature was made for this system. This is explained on the basis of a higher activation energy for the reverse reaction. The activation energies evaluated for the forward and reverse reactions are 32.93 and 97.42 kJ/mol, respectively.     

Effect of surface resistance arising due to surfactant on gas absorption accompanied by a chemical reaction in a foam-bed-reactor

On the basis of an idealized foam bed, a model to predict conversion in a foam-bed-reactor containing surfactant has been developed. The model takes into account the effect of surface resistance, arising due to the presence of a surface active agent, on gas absorption accompanied by a chemical reaction in a foam matrix. To verify the theory, experiments have been carried out in a semi-batch foam-bed-reactor for the absorption of air-carbon dioxide mixture in a foam of sodium hydroxide solution containing finite; concentrations of different surfactants. The surface resistance offered by the molecules of surfactant at the gas-liquid interface reduces the mass transfer rates significantly. The proposed model predicts fairly well the experimentally found depletion values of sodium hydroxide.     

Experimental study on the ozone absorption accompanied by instantaneous chemical reaction

This work deals with gas absorption accompanied by chemical reaction in a liquid phase. Ozone absorption in potassium indigotrisulfonate solution was investigated in a batch bubble column. Enhancement factor for absorption accompanied by instantaneous chemical reaction in the liquid phase was experimentally determined, as a ratio of the volumetric mass transfer coefficient for the absorption accompanied by reaction to that for pure physical absorption. The influence of (a) the initial concentration of the solute from liquid phase and (b) the ozone concentration in gas phase on the enhancement factor were experimentally examined. The absorption accompanied by instantaneous chemical reaction is a diffusion-controlled process, whose rate depends upon the diffusivities of the absorbing gas and the solute in liquid phase. The influence of these diffusivities was found to be more significant for lower values of the enhancement factor. The rate of ozone absorption was followed by the time change of the solution color, using new method based on the computer program SigmaScan Pro 5 (Systat Software, Inc., San Jose, CA, USA). This investigation is a contribution to the prediction of the ozone consumption in wastewater treatment, in cases when ozone instantaneously reacts with substances present in water.     

Experimental study of O2 diffusion coefficient measurement at a planar gas–liquid interface by planar laser‐induced fluorescence with inhibition

A new method for determining the molecular diffusivity of oxygen in liquids is described. The technique was applied through a flat air–liquid interface in a Hele‐Shaw cell (5 × 5 × 0.2 cm³) and was based on planar laser‐induced fluorescence (PLIF) with inhibition. A ruthenium complex (C₇₂H₄₈N₈O₆Ru) was used as the fluorescent dye sensitive to oxygen. A mathematical analysis was developed to determine the molecular diffusivity of oxygen simply by localizing the gas diffusion front. The specificity of this mathematical analysis is that it does not require the properties of the fluids (such as the saturation concentration) to be considered, which is especially relevant for complex media that are sometimes difficult to characterize properly. This technique was applied to three different fluids (viscosities ranging from 1 to 2.4 mPa·s) corresponding to binary diffusion coefficients ranging from 9.5 × 10^?10 to 2 × 10^?9 m²/s. Experimental data were found with an uncertainty of about 5% and were in good agreement with the literature. Particle image velocimetry and numerical simulations were also carried out to determine the optimal gas flow rate (0.01 L/s) to reach purely diffusive transfer, and the corresponding hydrodynamic profiles of the two phases. © 2012 American Institute of Chemical Engineers AIChE J, 59: 325–333, 2013     

W-promoted Co–Mo–K/γ–Al2O3 catalysts for water–gas shift reaction

The effects of incorporating tungsten into the traditional Co–Mo–K/γ–Al₂O₃ catalysts on the catalytic performances for water–gas shift reaction were investigated. Activity tests showed that W-promoted Co–Mo–K/γ–Al₂O₃ catalysts exhibited higher activity than W-free Co–Mo–K/γ–Al₂O₃ catalyst. Raman and H₂-TPR studies indicated that part of the octahedrally coordinated Mo–O species on Co–Mo–K catalysts transformed into tetrahedrally coordinated Mo–O species in the presence of W promoter.     

Mass transfer parameter estimation using optimization technique: Case study in CO2 absorption with chemical reaction

This paper proposes a new approach of applying an optimization technique to simultaneously determine a physical liquid—film mass transfer coefficient (K^o_L) and effective interfacial area (a_v) from a pilot plant data. The mass transfer mechanism of the CO₂-NaOH system was modeled using the two-film theory to represent the behaviors of packed absorbers. The model presents an overall absorption rate (R_v) as a function of K^o_L and a_v. The optimization algorithm used in this study follows a modified Levenberg-Marquardt method with a trust region approach. The R_v predictions from the model are in good agreement with the experimental data, with an average error of 6.5%.     

Analysis of gas absorption accompanied by a zero-order chemical reaction in a liquid-foam film surrounded by limited gas pockets

Gas absorption accompanied by a zero-order chemical reaction in a finite liquid-foam film has been analysed to obtain expressions for the amount of gas absorbed and for fractional absorption in such a film. These equations may be readily incorporated into a single-stage model of a foam-bed reactor to extend it to chemisorption with zero-order kinetics. The equations for physical absorption result naturally from a special case.     

Variation in physical and mechanical properties with coating thickness in epoxy–diamine–aluminum system

The mechanical properties and glass‐transition temperature within different thickness organic coatings made of diglycidyl ether of bisphenol A epoxy resin and 3‐aminomethyl‐3,5,5‐trimethylcyclohexylamine hardener are determined. The coatings are deposited on aluminum alloy (1050) substrates after degreasing. Dynamic mechanical thermal analysis and differential scanning calorimetry experiments are carried out on debonded coatings before and after the material from the opposed surface to the polymer/metal interface is removed by polishing. The results clearly show that the values of the physical and mechanical properties in those coatings depend on their thickness, but there is no gradient of properties within such coatings. Therefore, at a given thickness, those properties are homogeneous within the coating. To gain a better fundamental understanding of this behavior, a qualitative model involving the chemical reactions that take place at the epoxy/metal interface and the related diffusion phenomena is given. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 891–895, 2005     

Stability of polyaniline synthesized by a doping–dedoping–redoping method

Stability, including thermal stability, conductivity stability in air and after thermal treatment (100–200°C), of the polyaniline (PANI) films synthesized by a doping–dedoping–redoping method was investigated. It was found that thermogravimetric analysis (TGA) curves undergo three steps: loss of water or solvent, dedoping and decomposition, and those depend on the counterions. Compared with PANI films doped with camphor sulfonic acid (CSA) in m‐cresol, the thermal stability of the doped PANI films is improved by the new method, and thermal stability in the order of PANI–H₃PO₄ > PANI–p‐TSA > PANI–H₂SO₄ > PANI–HCl, PANI–HClO₄ > PANI–CSA was observed. The conductivity of the doped PANI films at room temperature was reduced after thermal treatment, and it is dependent of the counterions. It was found that the conductivity stability of PANI–p‐TSA and PANI–CSA is the best below 200°C. When the doped PANI films were placed in air, their conductivity decrease slowly with time due to deproton, and also depends on the counterions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 615–621, 1999     

喷射吸收制取超细碳酸钙的传质研究

在喷射塔 (Φ =1 8mm、H =3.3m)中 ,以无内折平垂圆锥形喷杯 (喷嘴直径Φ =5mm) ,研究了气体流速、液体流量对Ca(OH) 2 悬浊液喷射吸收CO2 的气膜传质系数的影响。     

Magnetic Nanoparticle‐Supported Morita–Baylis–Hillman Catalysts

A magnetic nanoparticle‐supported quinuclidine was prepared and evaluated as a recoverable Morita–Baylis–Hillman catalyst. The supported catalyst 2 demonstrated comparable activity with that of DABCO and could be simply recycled with the assistance of an external magnet. The thus recycled catalyst could be reused for 7 times without significant loss of activity.     

Mesoscopic study of cylindrical phases of poly(styrene)-poly(isoprene) copolymer: Order–order phase transitions by temperature control

Phase transitions of cylindrical structures of poly(styrene)–poly(isoprene) copolymer (PS–PI) toward spherical and gyroid structures were explored using DPD simulations and a coarse-grained model. Cylindrical phases were first obtained within a composition interval (“predominance region”) 0.2 < f_PS < 0.26 (volume fraction of poly(styrene)). The predominance region of cylindrical structures was then subject to thermal heating cycles. The thermodynamic instabilities of cylindrical microdomains induce anisotropic composition fluctuations and phase transitions. A transition from the cylindrical phase at low composition limit to a spherical arrangement was observed during the thermal heating process. The cylindrical phase at the intermediate and high composition limit within the predominance region exhibits a transition towards a gyroid arrangement. The phase transition control during thermal heating on the cylindrical phases was governed by small variations in composition. The results are consistent with experimental studies.