The Mass Transfer Characteristic In Microchannel Reactor And Azo Pigment Synthesis

The azo dyes have an extensive application in industrial production for their full color range, outstanding color fasten and excellent applicability. Human used to manufacture azo dyes through traditional intermittent batch method which faced the problems of high level of energy-consumption, long production period and difference in color strength. On the contrary, micromixer, which has many advantages such as short resident time, efficient heat transfer, continuous production available, no back-mix and hot spot, achieve a satisfactory result in azo dyes synthesis.The micromixers which are made of PMMA was fabricated by CNC-micromilling. The equivalent diameter of them are 300μm,500μm,750μm, 1000μm,1500μm,2000μm. Then, we choose deionized water and black ink to start mixing experiment under the range of Reynolds number between 2 to 200. The mixing situation was captured by high-speed photography technology and then we use image J to analyze the grey level. We also compare the mixing characteristic of different micromixer of which aspect ratios are 5:3、1:1、3:5、 1:2 under the same equivalent diameter of 750μm. The experiment shows the mixing situation was sharply decrease and then increase with the increase of Reynolds number. What is more, the smaller of the equivalent diameter, the larger of the aspect ratio, the easier to get well mixed fluid. When the Reynolds number is more than 58.03 the mixing degree can reach more than 92% with the micromixer which equivalent diameter is 750μm and the aspect ratio is 5:3.Based the chosen design parameter, we manufacture a helical micromixer of copper substrate. The micromixer which size is 135mm×45mm×8mm is consist of mixing part p(equivalent diameter:750μm, aspect ratio:5:3, lenth:1.7m)and heat-transfer part. The heat-transfer part used vortex-generated unite and consist of 80mm×1mm×1.5mm parallel microchannel. During the experiment, the coupling component (1-(4-sulfophenyl)-3-methyl-5-pyrazolone, O.lmol/L) mixes with the diazo components (Aniline,0.1mol/L) at the same rate to synthesis the azo dye. Considered the influence of temperature, pH, velocity, resident time, we select the suitable reaction condition(pH:9.85, temperature:25℃, flow rate:17mL/min) to get the ultimate yield of the product as 96%.This paper discuss a lot about the design of micromixers and the energy consume when we used the microfluidic technology to evaluate whether it is a cost-effective process for mass production, which is means a lot to the prospect of the technology.