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.

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.

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.

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.

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.

微通道反应器内α-烯烃连续磺化工艺的实验研究

α-烯烃磺酸钠(AOS)是具有良好生物降解性、润湿性、低刺激性的阴离子表面活性剂。利用微通道反应器,分别以1-十四烯(AO)和混合烯烃为原料,SO_(3)为磺化剂,考察了磺化温度、SO_(3)/AO摩尔比、磺化剂质量分数、停留时间等工艺条件对活性物AOS含量的影响规律。结果表明:1-十四烯磺化最佳工艺条件为磺化温度40℃、SO_(3)/AO摩尔比为1.2、SO_(3)质量分数为10%;混合烯烃磺化最佳工艺条件为磺化温度50℃、SO_(3)/AO摩尔比为1.1、SO_(3)质量分数为10%。增大流速有利于强化传质过程、提高产物中活性物AOS含量;延长停留时间会加剧副反应发生、降低产物中活性物含量。微通道反应器内α-烯烃磺化是以传质为主的强放热反应,热量移除及时,反应过程易于控制,可有效提高产品质量,大大增强生产工艺的本质安全性,对于开发煤基α-烯烃下游产品具有实际意义。

萘硝化合成一硝基萘安全工艺研究

针对萘硝化间歇式反应存在反应时间长、收率低和风险高等问题,以萘为原料、浓硝酸为硝化剂、二氯乙烷为溶剂,提出了微通道反应器内合成一硝基萘的连续流工艺。考察了硝酸与萘摩尔比、反应温度、硝酸质量分数、反应停留时间4个因素对微通道连续反应的影响,验证了最佳工艺条件下微通道连续反应转化率和收率的稳定性,并对比分析了间歇式反应与微通道连续流反应的反应严重度。结果表明,硝酸与萘摩尔比为2∶1、反应温度为40℃、硝酸质量分数为85%、停留时间为96 s时微通道连续流反应效果最佳;最佳工艺条件下,微通道连续反应稳定,萘的转化率达到99.1%,一硝基萘的收率达到96.3%;间歇反应、微通道连续反应绝热温升分别为103.25℃和1.5℃,表明微通道连续流的萘一段硝化反应风险更低。

串联式微通道反应器中制备壬醛、9-氧代-壬酸甲酯的反应研究

采用微通道反应器对壬醛(N)、9-氧代-壬酸甲酯(M)进行连续化反应的研究。以油酸甲酯(MO)为原料,搭建模块化微通道反应器,对环氧油酸甲酯(EMO)的制备及EMO裂解制备N/M的反应进行串联,在双氧水体系中,分别以浓硫酸和磷钨酸为催化剂,实现EMO和N/M的连续化生产。考察了温度、催化剂用量、停留时间及水油两相进料比(体积比)对反应的影响。得到最优反应条件:MO环氧化反应温度为70℃,硫酸用量为12%(质量分数),停留时间为10 min,水油进料比为4:1;EMO裂解反应温度为60℃,磷钨酸(PTA)用量为9%(占水相质量分数),停留时间为9 min,水油进料比为4:1。在上述条件下,EMO收率为84.99%,N/M收率为72.89%。与间歇反应相比,其具有停留时间短、反应温度低、目标产物可模块化连续化生产等优点。

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%。

微通道反应器微观混合研究

微通道反应器具有良好的传质传热性能、较高的安全性和可移动性,被广泛应用于快速、强放热、强腐蚀等危险反应过程。为研究微通道反应器对流体混合性能的强化效果,针对Ehrfeld Miprowa微反应器及内构件对其微观混合的影响进行了研究。利用Villermaux/Dushman平行竞争反体系,使用离集指数(X_(S))来定量表征微反应器的微观混合性能,考察了流体入口流速、H^(+)浓度以及内构件等因素对微观混合质量的影响。试验结果表明流体流速越高,微观混合性能越好,内构件能够有效地增强微反应器内的微观混合性能。

微通道反应器合成硫酸乙烯酯的工艺研究

以三氧化硫(SO_(3))、环氧乙烷(EO)为原料,以二氯乙烷为溶剂,利用微通道反应器合成了硫酸乙烯酯粗品,经升华得到硫酸乙烯酯纯品,其结构经^(1)HNMR确证,考察了原料配比n(SO_(3))∶n(EO)、反应温度、停留时间和原料质量分数等对硫酸乙烯酯收率的影响。结果表明,在原料配比n(SO_(3))∶n(EO)为1∶1.0、反应温度为0℃、停留时间为30 s、原料质量分数为10%的最佳条件下,硫酸乙烯酯收率为93.2%。

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。

二氧化碳催化加氢合成燃料的微通道反应器

[目的]CO_(2)催化加氢合成燃料是一种经济可行、可大规模实施的CO_(2)利用技术,能够解决环境和资源短缺的问题,近年来获得了国内外广泛的关注。文章旨在研究开发1种CO_(2)催化加氢合成碳氢燃料的微通道反应器。[方法]通过采用热力学计算-催化剂制备-反应器设计-结构优化-性能测试的设计思路进行分析。[结果]热力学理论分析表明:CO_(2)催化加氢可以形成碳氢燃料;开发了6种铁基催化剂,从而提高碳氢燃料合成的反应速率;基于流体数值模拟,设计并优化了微通道反应器的结构,该反应器具有结构简单紧凑、传热传质能力强等优点。实验结果表明:Zn-Fe催化剂表现出最好的CO_(2)催化加氢合成低碳烯烃性能,CO_(2)转化率和低碳烯烃选择性分别为32%和44%。[结论]设计的微通道反应器具备CO_(2)资源化利用合成碳氢燃料的功能,对我国应对气候变化、双碳目标实现以及碳氢燃料产业发展具有重要的意义。

四氟乙烯单体聚合工艺的优化设计探索

聚四氟乙烯(PTFE)因其优异的综合性能在诸多领域得到广泛应用,但传统的四氟乙烯(TFE)单体聚合工艺仍存在引发效率低、温控困难、产物分子量分布宽以及转化率不理想等问题。针对上述难题,从引发剂优选、聚合温度精准调控、链转移剂设计和过程强化等方面,提出了一系列TFE单体聚合工艺的优化策略。实验结果表明,优化后的微通道聚合工艺使PTFE的数均分子量提升1倍以上且分布更均一,结晶度提高10%以上,单体转化率和引发效率分别达到96%和25%以上,为PTFE的绿色高效制备提供了新思路。

三氯化磷合成穿孔百叶窗翅片微通道反应设备数值模拟研究

针对三氯化磷工艺氯化反应的温度控制问题,通过计算流体力学方法,设计了一种新型的穿孔百叶窗翅片导热结构,并分析了开孔尺寸与排列方式对穿孔百叶窗翅片热工水力特性的影响。结果表明:开孔尺寸与穿孔百叶窗翅片热工水力特性正相关,而孔排列方式的影响较小。具有最大孔尺寸的穿孔百叶窗翅片表现出较好的综合性能,在雷诺数191~476范围内,其综合性能因子较常规百叶窗翅片平均提升4.9%。

微通道反应器合成正溴丁烷工艺研究

利用微通道反应器进行正丁醇溴化制备正溴丁烷工艺研究。考察了物料比、反应温度、氢溴酸浓度、停留时间等单因素对反应的影响,得到了较佳的工艺条件:物料比n(HBr)∶n(正丁醇)=1.2,反应温度为170℃,HBr浓度为48%,停留时间133 s。在此条件下,正丁醇的转化率为98.39%,正溴丁烷选择性为90.16%,产率88.71%。与传统釜式间歇操作方法相比,利用微通道技术大大提高了正溴丁烷生产效率,实现了绿色、安全、高效的连续化正溴丁烷生产。

芴基硼酸酯的连续流合成工艺研究

将科研成果“芴基硼酸酯的连续流合成工艺研究”转化为材料专业的本科综合性实验。实验根据间歇法合成硼酸酯的条件设计了连续流硼化反应的路线,通过控制变量法对停留时间、温度、溶剂等进行了条件优化,确定了连续流合成芴基硼酸酯的最佳工艺条件:溶剂为二甲亚砜、停留时间为58 s,浓度0.2 M、温度为150℃、n(2-溴-9-苯基芴醇)∶n(联硼酸频那醇酯)∶n(碱液)=1∶1.5∶3,产物9-苯基芴醇硼酸酯(FOHBin)的产率为87.4%。