Microcapillary film reactor outperforms single-bore mesocapillary reactors in continuous flow chemical reactions
Microcapillary film reactor outperforms single-bore mesocapillary reactors in continuous flow chemical reactions
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DOI：
10.1016/j.cej.2020.127860
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发表时间：
2021-03
影响因子：
15.1
通讯作者：
Kirandeep K. Gill;R. Gibson;K. H. Yiu;P. Hester;N. Reis
中科院分区：
文献类型：
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作者：
Kirandeep K. Gill;R. Gibson;K. H. Yiu;P. Hester;N. Reis
在连续流动化学中经常使用中流和微流反应器，但在放大过程中，毛细管径D对转化率和反应速率的影响往往被忽视。体积、压降和扩散距离/次数必须达到微妙的平衡，才能充分实现连续化学流反应器的流体力学能力。我们进行了全面的计算流体动力学分析，通过详细的流体跟踪、停留时间分布和连续的化学反应(中和和第四伯恩反应)，充分阐明了分子扩散在试剂分散和化学转化中的作用。据我们所知，我们首次从数值和实验上捕捉和报道了从对流、分离流到塞状流和弥散流的转变，我们认为这与扩散到对流的时间尺度tdiff/tconv之间的无量纲比有关。我们测试了三种管状系统：小孔(I.D.)~1100微米)和大口径(I.D.~2400微米)毛细管反应器和一种新型的具有平均直径的多路(10孔)微毛细管膜反应器(MFR)。在MFR狭窄的微毛细管中，我们观察到与小扩散距离有关的良好的径向扩散，低无因次轴向弥散系数值(DAX/UL)在0.0015±0.0005到0.0033±0.0006之间(在流速0.5时至5.0UL/分钟)，表现出高性能的塞式流动系统所需的所有特征。DAX/uL基本保持与雷诺数无关，而对于单一的，大口径毛细管的Dax/uL值(0.032-0.057)随着雷诺数的增加而线性增加，向非常分散的流动转变。我们建议通过多个平行的微毛细管分离流动，因为在MFR中，与忽略扩散效应的增大D相比，MFR是一种更好的放大连续流动反应的策略。
Meso- and micro-flow reactors are routinely used in continuous flow chemistry, however the role of capillary diameter,D, on conversion and reaction rates is often overlooked during scale-up. Volume, pressured drop and diffusion distances/times must be delicately balanced to fully realize the hydrodynamic capabilities of continuous chemical flow reactors. We carried out a comprehensive Computational Fluid Dynamics analysis experimentally validated with detailed fluid tracing, residence time distributions and continuous chemical reactions (neutralization and 4th Bourne reaction) to fully elucidate the role ofDand molecular diffusion in reagents dispersion and chemical conversion. To our understanding, we captured and reported both numerically and experimentally for the first time the transition from convective, segregated flow to plug flow and dispersed flow, which we propose is linked to a dimensionless ratio between the time scales of diffusion to convection,tdiff/tconv. We tested three tubular systems: a small-bore (i.d. ~1100 µm) and large-bore (i.d. ~2400 µm) capillary reactor and a novel multiplexed (10-bore) Microcapillary Film Reactor (MFR) with mean i.d. 363 ± 32.2 µm. In the MFR’s narrow microcapillaries we observed excellent radial diffusion linked to the small diffusion distance, with low dimensionless axial dispersion coefficient values (Dax/uL) ranging from 0.0015 ± 0.0005 to 0.0033 ± 0.0006 (for flow rates 0.5–5.0 mL/min), exhibiting all the desired features of a high-performance ‘plug’ flow system.Dax/uLremained mostly independent of the Reynolds number, whereas for the single, large bore capillary theDax/uLvalues (0.032–0.057) increased linearly with the Reynolds numbers (19.4–48.5), shifting towards very dispersive flow. We propose splitting flow through multiple parallel microcapillaries as in the MFR is a superior strategy for scaling-up continuous flow reactions compared to increasingD,which neglects diffusive effects.