A microchemical system, including two micromixers and a delay loop, is specially designed to carry out the chlorohydrination of allyl chloride with chlorine in water. Chlorine is dissolved in water in the first micromixer and then reacts with allyl chloride to produce dichloropropanol in the second micromixer. The reaction can be accomplished in the delay loop with a residence time less than 10 s and the selectivity higher than 98%. A multistage strategy which connects several microchemical units in series has been developed and demonstrated. The dichloropropanol concentration higher than 6 wt % with the selectivity higher than 96% can be successfully reached using this strategy. The results show that low temperature and high pressure could greatly improve the microreaction performance. In contrast to the conventional reaction process, the microreaction process has the advantages for higher yield, higher dichloropropanol concentration, less water waste, and lower energy consumption. Moreover, the new process could make the reaction process employing chlorine more controllable and safe.
Ethyl diazoacetate (EDA) commonly experiences intensive decomposition as well as complex conversion concerning safety and efficiency. In this work, a careful kinetics study on the thermal decomposition of EDA was isothermally conducted in a microtube reactor to establish a mechanism-based kinetic model. The model parameters were well calibrated with experimental data including the yield of dimmers and the conversion of EDA, confirming the rationality of the proposed three-step reaction route. It allows the model to concisely describe the complex species transformations during EDA decomposition, which is unavailable for an apparent kinetic model. Considering an isothermal reaction system and the tolerance of EDA consumption by thermal decomposition, this work could help reveal the requirement on the kinetic characteristics of the desired catalytic reaction in which EDA is involved, as a reference on reaction process modeling and regulation.
Polysulphone (PSF) microcapsules containing 1-octanol were prepared with solvent extraction method for the recovery of caprolactam. One-step and two-step processes were, respectively, applied to prepare microcapsules. In order to get high extractant loading, a loading method with the assistance of ultrasound has been developed. With the two-step preparation process the extractant loss can be avoided. A very high extractant loading ratio of 5.96 g g−1 and the maximum uptake to caprolactam of 65.6 mg g−1 were achieved. Under the action of ultrasound the extractant loading efficiency is greatly intensified. With the one-step process 1-octanol loading ratio is highly limited. Only 1.74 g g−1 loading ratio and 29.9 mg g−1 uptake to caprolactam were realized. Meanwhile the extractant loss in the one-step process is serious. Considering extraction capacity and extractant loss in the preparation process, it is suggested that PSF microcapsules containing 1-octanol should be prepared with the two-step process. To fasten mass transfer rate, microcapsules with relatively smaller size are desired.
Interfacial tension is an important physical property affecting the droplet formation process in microfluidic devices. This work presents the variation of dynamic interfacial tension caused by slow adsorption of surfactant, as well as its influence on the liquid/liquid microdispersion process in a T-shaped microchannel. Using hexane/water−Tween 20 as the working system, it was observed that the droplet size changed with the variation of surfactant concentration when the concentration of Tween 20 was lower than 10 mmol/L, but hardly changed at higher concentrations, which was caused by the unsaturated adsorption and saturated adsorption of surfactant, respectively. The saturated interfacial tension was measured with an interfacial tension meter, and the relationship between the interfacial tension and the droplet diameter was established. Accordingly, the dynamic interfacial tension with unsaturated adsorption of surfactant was determined. The main factors affecting the dynamic interfacial tension were discussed, and a semiempirical equation was established to characterize those effects.
An ion chromatographic method for the simultaneous analysis of organic acids and inorganic anions in Dongjiu (alcoholic drink) was developed. An anion exchange column Shim-pack IC-A1(100 mm x 4.6 mm) was used. In non-suppressed anion exchange chromatography, potassium hydrogen phthalate (KHPh) is used as eluent most widely. However, there are several problems in this eluent for the analysis of Dongjiu (alcoholic drink) sample, such as the influence of a negative peak to the determination of acetic acid, ascorbic acid and lactic acid, the non-resolution of ascorbic acid, and lactic acid, and part overlapping of the peak of acetic acid with water peak. In order to solve these problems, a mixed eluent of 0.50 mmol/L KHPh and 0.25 mmol/L phthalic acid(H2Ph) was used in this work. The main organic acids and inorganic anions in Dongjiu were separated without interference peaks. The detection limits obtained by using the mixed eluent were 0.05-0.13 mg/L, several times lower than those obtained by using single KHPh eluent. This method, being without pretreatment, is simple to operate.
In this study, a strategy based on microfluidic method is developed toward a facile fabrication of phase change material microcapsules with uniform and controllable particle size as well as high encapsulation ratio and thermal stability. N-hexadecane, as a phase change material, was successfully encapsulated by a hybrid shell of poly (methyl methacrylate) and polyurea. The fabrication process includes the following three steps: (1) Formation of oil-in-water droplets with uniform micron size in the microfluidic chip; (2) formation of the first polyurea shell to encapsulate droplets by fast interfacial polymerization when the droplets pass through the coiled transport microchannel; and (3) completion of free radical polymerization of methyl methacrylate inside the microspheres by heating to form the hybrid microcapsule shell. The average size, encapsulation ratio, and phase change enthalpy of microcapsules changed by varying the flow rate of the dispersion phase and raw material composition. The highest melting enthalpy of 222.6 J g-1 and encapsulation ratio of 94.5% of the microcapsule were obtained when the flow rates of the continuous and dispersion fluids were 600 μL min-1 and 24 μL min-1, respectively. It is shown that the phase change material microcapsules were stable after 50 heating/cooling cycles.
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