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961.
Scott Battersby Mikel C. Duke Shaomin Liu Victor Rudolph Joo C. Diniz da Costa 《Journal of membrane science》2008,316(1-2):46-52
In this work, we investigate the performance of metal (Cobalt) doped silica membranes in a membrane reactor (MR) configuration for the low temperature water gas shift (WGS) reaction. The membranes were hydrostable and showed activated transport even after 2 weeks exposure to steam. High CO conversions resulted in the H2 and CO partial pressures in the reaction chamber moving in opposite directions, thus favouring H2/CO separation to treble (5–15) from 150 to 250 °C. On the other hand, the separation of H2/CO2 remained relatively low (2–4) as the driving force for diffusion or partial pressure of these gases remained equal in the reaction chamber irrespective of the extent of conversion. Below approximately 40% CO conversion, the MR is ineffective as the H2 driving force for permeation was so low that H2/CO selectivity was below unity. Operating under equilibrium limited conversion (space velocities 7500 h−1) conditions, very high conversions in excess of 95% were observed and there were no significant advantages of the MR performance over the packed bed reactor (PBR). However, for higher throughputs (space velocities 38000 and 75000 h−1) conversion is affected by the reaction rate, and relatively enough H2 is removed from the reactor through the membrane. Increasing temperature to 250 °C as a function of the space velocity (75000 h−1) allowed for the CO conversion in the MR to shift up to 12% as compared to the PBR. 相似文献
962.
Kockmann N Gottsponer M Zimmermann B Roberge DM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(25):7470-7477
Microstructured devices offer unique transport capabilities for rapid mixing, enhanced heat and mass transfer and can handle small amounts of dangerous or unstable materials. The integration of reaction kinetics into fluid dynamics and transport phenomena is essential for successful application from process design in laboratory to chemical production. Strategies to implement production campaigns up to tons of pharmaceutical chemicals are discussed, based on Lonza projects. 相似文献
963.
Benoit Boulinguiez Abdelkrim Bouzaza Smail Merabet Dominique Wolbert 《Journal of photochemistry and photobiology. A, Chemistry》2008,200(2-3):254-261
Photocatalytic treatment of polluted air by odorous contaminants – ammonia and butyric acid – is investigated in a plug-flow reactor covered by non-woven fiber textile coated with TiO2. For the first time, the single-component degradation pathway of ammonia by photocatalysis at ambient condition is highlighted. It appears fundamentally different compared to the butyric acid degradation pathway. The ammonia degradation pathway highlights a possible auto-accelerated behavior of the reaction. The chemical degradation kinetics follows the Langmuir–Hinshelwood model, though observed oxidation rates depend upon flow conditions in the reactor. Thus, interpretation of degradation results through a model considering the Langmuir–Hinshelwood approach and mass transfer phenomenon is presented. This model succeeds with a pair of determined kinetic constants and mass transfer coefficients to describe experimental results for different flow rates and for both pollutants, though they present wide dissimilarities in their degradation pathways. 相似文献
964.
《Arabian Journal of Chemistry》2023,16(2):104464
Due to the complexity of the structure–activity relationship of the CuAl2O4 spinel catalyst, optimization of the catalyst structure is a great challenge. In this paper, three different CuAl2O4 spinel catalysts were prepared by the solid-phase method using copper hydroxide, copper nitrate, and copper oxide as the copper source, respectively, to study the difference in the structure of CuAl2O4 spinel catalysts induced by the raw materials and the catalytic behavior for CO hydrogenation. The structure of CuAl2O4 spinel catalyst was characterized by XRD, BET, SEM, TEM, H2-TPR and XPS. The activity of CO hydrogenation over the CuAl2O4 spinel catalyst without pre-reduction was evaluated in the slurry reactor. The results demonstrated that different copper sources had obvious influence on the CuAl2O4 spinel texture properties, surface enrichment degree, as well as decomposition and reduction ability, which further regulated the ratio of Cu+/Cu0 and thus affected the catalytic performance, especially the alcohol distribution. The CuAl2O4 spinel, employing copper hydroxide as the copper source, showed better selectivity of C2+OH, which was assigned to a higher ratio of Cu+/Cu0, along with larger pore size and pore volume. Moreover, the synergistic effect between Cu0 and γ-Al2O3 improved the selectivity of dimethyl ether. 相似文献
965.
采用居里点裂解仪-气相色谱仪(Py-GC)联用的方法研究了4种煤的快速热解特性,分析了挥发分主要气相产物及其析出规律.结果表明,大于等于50%的挥发分在热解初期(t ≤ 2 s)释放,采用箔片装载方式的居里点裂解仪完全热解1 mg煤样需要10 s;挥发分主要气相产物中,各气体组分的生成量(mmol/gcoal)顺序为H2 > CH4 > CO > CO2 > C2(C2H6、C2H4)> C3(C3H8、C3H6);挥发分释放量随热解温度的升高而增加,相同热解条件下,次烟煤挥发分的释放率高于贫煤和无烟煤;H2和CH4的生成量依赖于热解温度,热解温度越高,H2和CH4的生成量越多;CO和CO2的生成量不仅与热解温度相关,而且与煤中的氧含量紧密相关,氧含量越高的煤热解生成的CO和CO2越多;C2和C3气体的生成量相对于其他气体很少,体积占挥发分气相产物的5%. 相似文献
966.
Heat transfer characteristics in three-phase fluidized beds of floating bubble breakers have been studied in a 0.142 m I.D. x 2.0 m high Plexiglas column fitted with an axially mounted cylindrical heater.Effects of the liquid and gas velocities, the particle size, the volume ratio of floating bubble breaker to particles on phase holdup, the vertical bubble length, and the heat transfer coefficient have been determined.In the bubble-coalescing regime, the heat transfer coefficient in three-phase fluidized beds having the volume ratio Vf/Vs of 10–15% produced a maximum increase in heat transfer coefficient of about 20% in comparison to that in the bed without floating bubble breakers. Also, bubble length and gas-phase holdups exhibited their maximum and minimum values at a volume ratio of 10–15%. The heat transfer coefficient in three-phase fluidized beds of floating bubble breakers can be estimated from the surface renewal model with isotropic turbulence theory.Heat transfer coefficients expressed in terms of the Nusselt number have been correlated with the particle Reynolds number and the volume ratio of floating bubble breakers to particles. 相似文献
967.
《Comptes Rendus Chimie》2015,18(10):1030-1035
Three-dimensional numerical analysis for simultaneously developing fluid flow and heat transfer through triangular and sinusoidal channels is simulated in this paper. ANSYS FLUENT 12 was used for simulations. Numerical results were compared with experimental ones for the same channels dimensions. The research was conducted to verify that very short metallic monoliths could be applied to engine pre-turbo catalytic converters. It was shown that short monoliths have high potential to reduce HC/CO emissions due to higher temperatures and flow velocities in front of the turbocharger, resulting in increased heat and mass transfer and reaction kinetics accompanied with reduced flow resistance. 相似文献
968.
基于对球形托卡马克ST聚变堆的研究,提出了ST聚变嬗变堆的设计概念。对堆芯参数作了初步选择,确定了一组适合于嬗变包层的堆芯参数供中子学计算和结构设计参考,给出了在以嬗变次锕系元素(MA)核废物为目标的一维中子学计算结果。 相似文献
969.
In the present work, conductimetry is applied for on-line evaluation of anionic surfactant dynamics during emulsion polymerisation of methyl methacrylate and styrene and for on-line estimation of particle size and number. Reactor and jacket temperatures are used to perform energy balance computations on-line and to provide on-line evaluation of monomer conversion. The parameters of a previously proposed model are re-estimated in order to describe the conductivity signal during methyl methacrylate runs. Some important issues regarding the effects of the surfactant micelles over the conductivity signal are addressed. Finally, the model is inverted and combined with conversion and reactor temperature measurements, providing good predictions of the number of polymer particles in the latex, without needing of on-line measurements of particle size. 相似文献
970.