Precipitation Of Ultrafine Particles In A Novel Tube-in-Tube Microchannel Reactor With High Throughput

Micromixing (i.e., mixing at the molecular scale) is the last stage of turbulent mixing. It is believed to play a very important role in the chemical industry when the time scale of the chemical reaction involved is at the same magnitude or smaller than the time scale of the mixing process. Industrial processes, such as liquid crystal material, biophosphatides, polymer composite film, biodegradable capsule, ultrafine coating powder and nanoparticles are greatly influenced by micromixing. Especially, conversion, selectivity, particle size distribution and molecular weight distribution are significantly influenced by micromixing. So, in order to improve the product properties and acquire the maximal benefit, it is necessary to explore more efficient chemical reactors.Microdevice, as a new technique for preparing ultrafine particles, has its advantages over the traditional techniques such as direct precipitation, microemulsion, sol-gel method. The reaction and mass transfer performances can be evidently improved so that the conversion, selectivity and mass transfer rate are significantly increased. Therefore, the microdevice will be an important aspect in the synthesis of micro/nanoparticles. The main contents and findings are summarized as follows.1. The particle size of barium sulfhate decreased with decreasing the micro-pore size of the tube-in-tube microreactor. The increase of the flow rate and reactant concentration can result in the decrease of particle size. Barium sulfhate nanoparticles with a diameter of37nm could be obtained when the flow rate is set at9L/min, and concentrations of BaCl2and Na2SO4are0.35mol/L and0.1mol/L. There is no obvious influence of effective length of tube on the particle size.2. The particle size, size distribution and the crystalline morphology of calcium carbonate can be controlled in the tube-in-tube microreactor by varying the micro-pore size, flow rate, reactant concentration and effective length of tube. Calcium carbonate particles of smaller than1μm in diameter can be prepared by adjusting experimental parameters.3. Ultrafine amorphous cefuroxime axetil (UACA) was prepared by antisolvent recrystallization in the tube-in-tube microreactor. The optimum solvent-antisolvent system was determined according to the experiment results of various solvent systems. The factors affecting the particle size of UACA, including the concentration of the solution, the volume ratio of solvent to antisolvent and the effective length of tube were investigated. The experimental results indicated that the as-prepared product is amorphous cefuroxime axetil with the particle size less than500nm.