关键词: 微反应器, 连续磺化, 表面活性剂, 传质, 流体模拟

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