| The gas-liquid phase oxidation reaction is one of the most common chemical reactions. For a large part of the fast gas-liquid phase oxidation reactions with oxygen as oxidizer, it is difficult to obtain the desired chemical conversion and reaction rate because of the limit of mass transfer resistance of oxygen into the liquid phase. There are two ways to solve this problem, one is choosing a stronger oxidizer; the other is to intensify the process of mass transfer of oxygen. In the chemical process development and production process, the stronger oxidizer usually means greater investment. Therefore, the intensification of the mass transfer of oxygen is a great concern to most scientists.In the past 20 years, microchemical technology has attracted wide attention. As a key part of the microchemical technology, microreactors have been widely studied. Compared with traditional gas-liquid contactors, microreactors have the advantages of smaller volume, easier operation, better safety and mass transfer performances, exhibiting great application potential in gas absorption, nanomaterials preparation, gas-liquid-solid three-phase hydrogenation reactions, as well as reaction kinetics studies. In view of this, a high-throughput microporous tube-in-tube microchannel reactor (MTMCR) as a noval gas-liquid reactor is studied and applied to the process of oxidation of ammonium sulfite (inorganic system) and the process of ozonation treatment of phenol solution (organic system) in this thesis. The main contents and findings are summarized as follows:1. The sulfite conversion increased with increasing gas volumetric flowrate, partial pressure of oxygen, pH, temperature and Co2+ concentration or decreasing the sulfate concentration, liquid volumetric flowrate, micropore size and annular channel width.2. The experiment results showed an optimum sulfite concentration (about 1.3 mol/L), and the sulfite oxidation rate reached the peak at the optimum sulfite concentration.3. The activation energy of the oxidation of ammonium sulfite was determined as 6.703 kJ·mol-1. The oxidation rate could be almost two orders of magnitude larger than that obtained in the traditional reactor. According to Arrhenius equation and the experimental data, the Equation associating with the ammonium oxidation rate and temperature, the initial concentration of ammonium and oxygen partial pressure can be expressed as:4. By intensifying the ozone mass transfer in the liquid phase in MTMCR, phenol removal percentage reached more than 99% in a very short contact time.5. PH value is the most significant factor to degradation of phenol. At acidic conditions, ozone directly reacts with phenol molecules, and the reaction rate is slow. When the pH is greater than 9, ozone is first converted to hydroxyl radicals of higher activity under the OH- catalysis in the solution, and then the phenol is oxidized rapidly by the hydroxyl radicals. The most suitable pH value was determined as 11;6. Sizes of the inner tube and outer tube affect the gas-liquid mixing and mass transfer characteristics and consequently the phenol removal rate. For the ozone oxidation of phenol in MTMCR, the removal percentage of phenol decreased with increasing micropore size, annular channel width and initial phenol concentration, and increased with increasing ratio of gas volumetric flowrate to liquid volumetric flowrate and reaction temperature. In the experimental conditions, the optimum gas-liquid ratio was determined as 13;These results show that fast gas-liquid oxidation reactions can be intensified in MTMCR and a higher conversion and reaction rate of these reactions can be obtained in MTMCR. Therefore, MTMCR may find broad applications in gas-liquid reaction processes in the future. |
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