Abstract:

With the development of precision machining technology, microchemical equipment with characteristic size less than 1mm has been gradually considered and applied in many organic synthesis processes due to its high efficiency of mass and heat transfer and intrinsic safety characteristics. The continuous synthesis of dodecyl benzene sulfonic acid in microchannels is an important basis for the development of efficient, green and safe sulfonation process. In this paper, the interaction effects of temperature, flow rate and SO₃/DDB molar ratio on the sulfonation process of dodecylbenzene in the microreactor were studied by response surface experiment. It was found that the content of active substance was most affected by flow rate, and flow rate in T-shaped micromixer mainly affected impact intensity and residence time of the fluid. Therefore, computational fluid dynamics (CFD) was used to characterize the fluid in a T-shaped micromixer. The mixing state of SO₃ and DDB in a T-shaped mixer at different flow rates was simulated, and the variation rule of the mixing state was fairly consistent with the experimental results. The mixing effect in the mixer was not strong at low flow rate, but with the increase of flow rate, the area of components mixing with each other in the mixer increased obviously. It is believed that the increase of the flow rate increases the inertia force of the fluid in the mixer, and enhances the collision of the fluid in the mixing place, and relatively reduces the surface tension of the fluid in the mixer, and enhances the mixing effect. The mixing state of water and toluene in a T-shaped micromixer at different flow rates with or without solvent was studied. It was found that when the flow rate is 0.12m/s without solvent, the two-phase fluid mixes to a certain extent under the action of interfacial tension, and then flows in the form of Taylor flow. When the flow rate is 0.15—0.17m/s, the mixing phenomenon disappears, and the fluid is directly in the form of Taylor flow. When the flow rate is 0.19—0.21m/s, the mixing part appears again under the influence of the enhanced impact. However, in the presence of solvent, the fluid no longer appears obvious Taylor flow, but flows in the pipe in the form of small droplets whose characteristic size is smaller than the pipe size. When the flow rate is 0.12—0.17m/s, the fluid flows appear irregular. When the flow rate is 0.19—0.21m/s, the fluid is distributed in the radial direction of the pipe from the inside to the outside with the density from the largest to the smallest. It was believed that the introduction of solvent reduces the effect of interfacial tension, which makes the dominant role of inertial force stronger when Re number increases.

Key words: microreactor, continuous sulfonation, surfactants, mass transfer, fluid simulation

摘要：

随着精密加工技术的发展，特征尺寸小于1mm的微化工设备因其高效的传质传热效能及本质安全特性逐渐被应用在许多有机合成工艺中。微通道内连续合成十二烷基苯磺酸是开发高效、绿色、安全的磺化工艺的重要基础。本文通过响应面实验方法，研究温度、流量、SO₃/DDB摩尔比对微反应器内十二烷基苯磺化工艺的交互影响，发现产品活性物质含量受流量影响最大，而T形结构微混合器中流量这一因素主要影响流体碰撞强度和停留时间。因此，利用CFD计算流体力学方法对T形微混合器内流体进行表征。模拟了T形混合器内不同流速下SO₃和DDB的混合状态，发现其混合状态变化规律与实验所得结论基本一致，低流速时混合器内混合效果不强，随着流速的增加，混合器内组分互相混合的区域明显增多。认为是流速的增大使得混合器内流体受到的惯性力增大，且增强了混合处流体的碰撞，相对地使混合器内流体受到表面张力减小，增强了混合效果。研究了有无溶剂条件下不同流速时T形微混合器内水和甲苯两相流体混合状态，发现无溶剂条件下流速为0.12m/s时，两相流体受界面张力作用发生一定程度混合后分离呈泰勒流形式流动；流速为0.15~0.17m/s时，混合现象消失，流体直接呈泰勒流形式；流速为0.19~0.21m/s时，受对撞效果增强影响再次出现混合部分。而有溶剂条件下，流体不再出现明显的泰勒流，而是以特征尺寸小于管道尺寸的小液滴的形式在管道内流动，流速为0.12~0.17m/s时流体呈不规则流动，流速为0.19~0.21m/s时流体以密度从大到小由内而外分布在管道径向方向上。认为是溶剂的引入减小了界面张力的作用，使得Re数升高时，惯性力的主导作用更强。

关键词: 微反应器, 连续磺化, 表面活性剂, 传质, 流体模拟