Microchannel reactors for Fischer-Tropsch synthesis:Experimental investigation and mathematical modeling

The Fischer-Tropsch synthesis is a significant technology for converting coal,natural gas,and biomass into synthetic fuels.In recent years,the use of microchannel reactors for the Fischer-Tropsch synthesis has attracted significant attention.Fischer-Tropsch synthesis experiments were carried out in a microchannel reactor and the influences of reaction conditions on the experimental results were investigated in this study.Based on the experimental data,a dynamic multi-component pseudo-homogeneous variable-volume flow model of microchannel reactors for the Fischer-Tropsch synthesis was built to determine the pressure-,velocity-,conversion-and(component-wise)concentration-distributions in reaction channels.The model takes into account the combined effects of gas volume expansion caused by the frictional pressure drop and gas volume contraction caused by reaction consumption.A novel effective method for calculating the pressure and superficial gas velocity values in microchannel reactors was proposed in the model.Besides that,two sets of experimental data were selected from references to evaluate the validity and accuracy of the model.The reaction performances in the microchannels were analyzed carefully based on the calculated results.

Modelling of Microchannel Reactors for Fischer-Tropsch Synthesis

The Fischer-Tropsch synthesis is an important step in coal liquefaction,natural gas liquefaction,and biomass liquefaction.In recent years,the use of microchannel reactors for Fischer-Tropsch synthesis has received widespread attention.Since thermocouples and other sensors cannot be placed easily in a microchannel reactor,it is very vital to establish a model to provide calculated results highly compatible with the experimental data.This paper mainly introduces the establishment and solution of microchannel reactor models for Fischer-Tropsch synthesis.General mass transfer differential equations,heat transfer differential equations and related parameters(such as reaction rates,dispersion coefficient,and convective heat transfer coefficient)are listed.To solve the models,numerical solutions,such as the CFD simulation methods and the programming methods,are reviewed.It is recommended that a more accurate solution strategy is the combination of CFD simulation and programming methods.

The effect of operating conditions on acylation of 2-methylnaphthalene in a microchannel reactor

Acylation of 2-methylnaphthalene(2-MN) is a very important reaction in organic synthesis,and the effiency of the continuous reactor is more than one of the batch reactor.Considering that the Friedel–Crafts acylation is a rapid exothermic reaction,in this study,we perform the acylation of 2-MN in a stainless steel microchannel flow reactor,which is characterized by high mass and heat transfer rates.The effect of reactant ratio,mixing temperature,reaction temperature,and reaction time on product yield and selectivity were investigated.Under the optimal conditions,2-methyl-6-propionylnaphthalene(2,6-MPN) was obtained in 85.8% yield with 87.5% selectivity.Compared with the conventional batch system,the continuous flow microchannel reactor provides a more efficient method for the synthesis of 2,6-MPN.

CFD and experimental investigations on the micromixing performance of single countercurrent-flow microchannel reactor

Microchannel reactors are widely used in different fields due to their intensive micromixing and, thus, high masstransfer efficiency. In this work, a single countercurrent-flow microchannel reactor(S-CFMCR) at the size of ~1 mm was developed by steel micro-capillary and laser drilling technology. Utilizing the Villermaux/Dushman parallel competing reaction, numerical and experimental studies were carried out to investigate the micromixing performance(expressed as the segregation index XS) of liquids inside S-CFMCR at the low flow velocity regime.The effects of various operating conditions and design parameters of S-CFMCR, e.g., inlet Reynolds number(Re),volumetric flow ratio(R), inlet diameter(d) and outlet length(L), on the quality of micromixing were studied qualitatively. It was found that the micromixing efficiency was enhanced with increasing Re, but weakened with the increase of R. Moreover, d and L also have a significant influence on micromixing. CFD results were in good agreement with experimental data. In addition, the visualization of velocity magnitude, turbulent kinetic energy and concentration distributions of various ions inside S-CFMCR was illustrated as well. Based on the incorporation model, the estimated minimum micromixing time tmof S-CFMCR is ~2 × 10-4s.

Novel Preparation of Magnetic Microcapsules by Using T-Shaped Microchannel Reactor

Traditional preparation of magnetic microcapsules involves cumbersome processes and often results in irregular-shaped products. Due to the stable laminar flow of reaction solution and the moderate reaction conditions, the T-shaped microchannel (T-MC) reactor is supposed to yield microcapsules with regular shape. In this paper, magnetic particles of ferroferric oxide modified by oleic acid (OA-Fe3O4) and dispersed in tetrachloroethylene were used as core material. Polymethyl methacrylate (PMMA) was used as shell material. Magnetic microcapsules were prepared by using a T-MC reactor. Factors that influenced the encapsulated reaction were investigated in details, which included the velocity ratio of aqueous phase to oil phase, the length and the inner diameter of the microchannel. The morphology, composition, and magnetic responsiveness of the magnetic microcapsules were analyzed and characterized by SEM, FTIR, XRD, TGA, and vibrating sample magnetometer (VSM). The results confirmed that magnetic microcapsules prepared by T-MC reactor were regular in shape.

Enhanced oxygen reduction reaction performance of Co@N–C derived from metal-organic frameworks ZIF-67 via a continuous microchannel reactor

Traditional methods of preparing metal-organic frameworks(MOFs)compounds have the disadvantages such as poor dispersion,inefficient and discontinuous process.In this work,microchannel reactor is used to prepare MOFs-derived zeolite-imidazole material via flash nanoprecipitation to form ZIF-67+PEI(FNP),which reduces the MOF synthesis time down to millisecond time interval while keeping the synthesized ZIF-67+PEI(FNP)highly dispersed.The Co@N–C(FNP)catalyst obtained by flash nanoprecipitation and carbonization has a higher Co content and thus more active sites for oxygen reduction reaction than the Co@N–C(DM)catalyst prepared by direct mixing method.Electrochemical tests show that the Co@N–C(FNP)catalyst prepared by this method has excellent oxygen reduction performance,good methanol resistance and high stability.The onset potential and half-wave potential of Co@N–C(FNP)are 0.92 VRHE and 0.83 VRHE,respectively,which are higher than that of Co@N–C(DM)(Eonset=0.90 VRHEand E1/2=0.83VRHE).Moreover,the Zn-air battery assembled with Co@N–C(FNP)as the cathode catalyst has high open circuit voltage,high power density and large specific capacity.The performance of these batteries has been comparable to that of Pt/C assembled batteries.Density functional theory(DFT)calculations confirm that the Co(220)crystal plane present in Co@N–C(FNP)have stronger adsorption energy than that of Co(111)crystal plane in Co@N–C(DM),leading to better electrocatalytic performance of the former.

Different efficiency toward the biomimetic aerobic oxidation of benzyl alcohol in microchannel and bubble column reactors: Hydrodynamic characteristics and gas–liquid mass transfer

The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated(CoTPP: cobalt(II) mesotetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel(MMC) reactor and a bubble column(BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor,and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup(2.9 times higher than that of BC reactor), liquid film mass transfer coefficient(8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area(3.8 times higher than that of BC reactor). Moreover,the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.

Multiphase surfactant-assisted reaction-separation system in a microchannel reactor

The Lewis acid-catalyzed addition of tri-methylsilyl cyanide to p-chlorobenzaldehyde in a micro-channel reactor was investigated.The microchannel was integrated to promote both reaction and separation of the biphase system.FeF3 and Cu(triflate)2 were used as water-stable Lewis acid catalysts.Sodium dodecyl sulfate was incorporated in the organic-aqueous system to enhance the reactivity and to manipulate the multiphaseflow inside the microchannel.It was found that the dynamics and the kinetics of the multiphase reaction were affected by the new micellar system.Parallel multiphaseflow inside the microchannel was obtained,allowing for continuous and acceptable phase separation.Enhanced selectivity was achieved by operating at lower conversion values.

Review of structural design, fabrication, and application of microchannel reactors

Microchannel reactors usually have some microchannels with characteristic sizes(i.e., between 1 and 1000 μm). Small channel size and diversity are usually patterned in a microchannel reactor, and these features increase the surface area-to-volume ratio and driving force for heat and mass transport. Microchannel reactors are widely used in the petrochemistry, aerospace, electronics, information technology, and automotive industries, among others. According to the geometric shape of microchannels, a microchannel reactor can be classified as parallel, curved, micro-pin-fin array, bionic, or 3D network type. This review summarizes the fabrication methods of microchannel reactors, including traditional mechanical processing, chemical etching, electroforming injection molding technology, non-traditional machining, and sintering. It also presents the various applications of microchannel reactors in catalytic reactions, heat transfer, mixing, and other areas. Finally, this review describes the development and application prospects of microchannel reactors.

微通道反应器中炔烃的选择性催化半加氢反应研究进展

炔烃选择性催化半加氢反应与石油化工和精细化工生产密切相关,传统上多采用间歇工艺进行,存在自动化程度不高、反应效率低下以及安全隐患等问题。微通道反应器技术的进步使得以连续工艺进行炔烃选择性催化半加氢反应成为可能,有望从根本上解决间歇工艺所存在的问题。鉴于此,总结微通道反应器的类型以及相同反应器类型下催化剂的类别,对近年来微通道反应器中炔烃选择性催化半加氢反应的研究进展进行综述。微通道反应器包括催化毛细管反应器、填充床反应器、蜂窝反应器、独体反应器等,在炔烃选择性催化半加氢反应中的应用促进了石化领域生产技术与工艺的进步。总之,设备的微型化、过程的集成化是顺应可持续发展与高技术发展的需要,微通道反应器技术作为化工过程强化的一种新技术,在化学、化工、能源、环境等领域将会得到广泛的应用。

微通道反应器内低共熔溶剂/水混合物吸收CO_(2)的传质特性

为了探索低共熔溶剂在CO_(2)吸收过程中的应用前景,通过实验对康宁先进流动反应器内低共熔溶剂/水混合物吸收CO_(2)的传质特性进行了研究,并与目前常用的CO_(2)吸收剂(N-甲基二乙醇胺的质量分数为30%的水溶液)进行了比较和分析。结果表明,当低共熔溶剂/水混合物吸收剂体积流量qV,L不变、气相体积流量qV,G增大时,反应器的吸收负荷、体积传质系数均随之增大;而吸收率在qV,G较低时随qV,G增大而增大,当qV,G较大时,吸收率变化趋于平缓;当qV,G不变、qV,L增大时,吸收负荷、体积传质系数随之减小,但压降随之增大,而吸收率在qV,L较小时随qV,L增大而减小,当qV,L较大时变化趋近平缓。采用气、液相Re数、液相Sc数及增强因子等自变量,建立了体积传质系数关联式和压降关联式,平均绝对偏差分别为4.19%和1.74%,最大绝对偏差分别为13.9%和11.7%。

以吗啉与环氧乙烷为原料的无催化剂连续快速合成吗啉乙醇工艺研究

针对以吗啉和环氧乙烷为原料合成吗啉乙醇的反应路线收率不高、反应时间长、安全性不好和需使用催化剂的问题,在以SIMM-V2微混合器和不锈钢管组成的微通道反应器中,进行了连续快速制备吗啉乙醇的工艺研究,考察了反应温度、停留时间、体系压力、物料配比和流量等因素对产物收率的影响。结果表明:利用该反应器,在无催化剂条件下和更短的反应时间内可获得与釜式反应器相当的收率;产物收率随着反应温度、停留时间、环氧乙烷配比的增加均呈现先升高再降低趋势,且相互之间会有影响;存在一个较宽泛的反应条件操作窗口,即在给定某一个条件时,可以通过调节其他条件获得相同的产物收率。在典型的反应条件下,如温度为150℃、吗啉与环氧乙烷摩尔比为1∶1.08、停留时间为3 min、总流量为1 mL min、体系压力为2.5 MPa时,吗啉转化率可达99.55%,吗啉乙醇的选择性为97.1%,远高于釜式反应的结果。

微通道反应器中碳酸乙烯酯、甲醇及乙醇的反应规律研究

在使用微通道反应器的条件下,以甲醇钠作为催化剂,碳酸乙烯酯、甲醇及乙醇为原料进行酯交换反应,对生成的主产物碳酸二甲酯、碳酸二乙酯及碳酸甲乙酯的合成工艺进行研究。最终得出反应规律为:停留时间为2 min时,反应达到平衡状态;随着物料配比的升高,产物含量随之增加;随着催化剂含量升高,产物含量随之增加,但催化剂含量升高至一定值时,DMC含量减少,直至平衡;随着温度的升高,DMC含量随之增加,但温度的上升对DEC、EMC含量影响不大。

奈韦拉平中间体的制备工艺

以2,6-二氯-4-甲基吡啶为原料,经硝化反应,“一锅法”选择性还原、脱氯步骤即可得2-氯-3-氨基-4-甲基吡啶。分别考察了传统的混酸硝化和微通道反应器硝化反应;“一锅法”选择性还原、脱氯反应采用威尔金森催化剂,该催化剂具有选择性高、稳定性好、可多次重复套用的优点。最佳的硝化反应条件采用微通道反应器、反应温度15℃、停留时间60 s,发烟硝酸和2,6-二氯-4-甲基吡啶物质的量比1.2∶1,收率可达93%;最佳的“一锅法”条件为催化剂添加量1.2%,反应温度90℃,压力1.1 MPa,收率92%。

2,6-二氯-4-三氟甲基苯胺的连续流合成工艺

2,6-二氯-4-三氟甲基苯胺是一种可用于制备染料和农药等的重要中间体,尤其在农药领域应用广泛。以4-三氟甲基苯胺为起始原料,使用G1微通道反应器构建预热、氧氯化、降温工艺连续合成2,6-二氯-4-三氟甲基苯胺。考察了各工段温度、系统压力、物料流速和用量等工艺参数对反应的影响。优化条件下,反应收率可达83.0%,产品含量99.0%。该合成工艺利用微通道反应器良好的传质传热性能不仅保证了工艺体系安全,也提高了生产效率,为工业化技术的更新迭代提供了基础。

微反应器制备过氧化新癸酸异丙苯酯

基于微反应器的发展及其固有的安全特性,探讨了用微通道反应器制备对过氧化新癸酸异丙苯酯工艺。研究了反应温度、物料配比、停留时间等对反应固含量和收率的影响,以及合成的最佳条件。结果表明,最佳反应条件为氢氧化钾∶异丙苯∶新癸酰氯(摩尔比)=1.30∶1.05∶1.00,玻璃模块反应温度50℃,碳化硅模块反应温度60℃,反应停留时间57 s,收率和固含量最佳,含固质量分数为86.14%,收率为92.46%。

气溶胶粒子在微通道中的扩散泳效应数值模拟分析

针对快堆内高比活度气态裂变产物吸附、捕集情况,为分析由此产生的气溶胶粒子扩散、泄漏影响,建立空气-水蒸气两组分混合气体二维水平微通道冷凝相变模型。考虑到冷凝现象引起的水蒸气浓度变化,粒子受到由此引起的附加质量力,也就是扩散泳力的作用,针对扩散泳作用,构建亚微米粒子受扩散泳作用影响的沉降模型以及数值模拟方法。通过Fluent中的UDF功能模块实现粒子受扩散泳力作用下的模拟计算,最终得到可以模拟冷凝状态下气溶胶粒子沉降的计算模型。

微通道条件下4,4′-(六氟亚异丙烯基)二邻二甲苯的合成研究

以具有高传热系数和强耐腐蚀性的碳化硅微通道为反应器,对反应的停留时间、反应温度、物料配比及催化剂用量进行了优化。实验发现,实验温度为150℃,实验压力为3 atm,停留时间为20 min,4,4′-(六氟亚异丙烯基)二邻二甲苯的最优产率为65%,放大生产的产率为62.7%,较好地实现了邻二甲苯的氟烷基化反应。相较于传统的间歇式合成法,微通道连续法合成4,4′-(六氟亚异丙烯基)二邻二甲苯具有物料在线量小、反应时间短、工艺简单及反应压力小安全稳定等优点,具有较好工业化生产前景。

微通道反应器中精细化学品合成危险工艺研究进展

卤化、氧化、重氮化、硝化以及催化加氢是精细化工生产中的重要反应,通常以间歇方式在釜式反应器中进行,存在安全隐患,并且反应效率低。微通道反应器技术的发展为解决上述问题提供了有效途径,因此,发展基于微通道反应器的安全高效合成工艺成为当前精细化工领域的研究热点之一。该文综述了近年来微通道反应器中涉及精细化工产品合成危险工艺的研究进展,并指出了微通道反应器存在的不足和今后研究的方向。