Preparation Of Nano-Silica Powder In The New Microreactor

Nano-silica with its non-toxic, tasteless, porous and lightweight is widely used in the field of chemical industry. In industry, it is generally by direct precipitation of the prepared nano-silica, and this is because using in this way obtained a larger particle size and the wide particle size distribution. Therefore, it can only be used for the low-end products, leading to its application has been a lot of restrictions. The key technical problem of the preparation is the good mixing scales and a high degree of supersaturation. The traditional precipitation mostly used the stirred tank reactor to carry out the direct precipitation. As a result, the degree of supersaturation and mixing scales is too low. Therefore, the development of high-performance mixing equipment becomes the key to solve this problem.In this thesis, the main paper contents are as follows:1. Using "Villermaux/Dushman" system as a chemical reaction probe test system, we have examined the membrane dispersion microreactor at different membrane pore size, different flow rates and different R values. Taking sulfuric acid as the dispersed phase and sodium silicate as the continuous phase, we explore the different membrane pore size and flow rate to impact on the nano-silica powder.2. Taking sulfuric acid as the dispersed phase and sodium silicate as the continuous phase, and using a membrane dispersion microreactor, we successfully prepared nano-silica which can be used for high-grade matting agent. At the same time, we investigated the concentration of reactants, final pH, salt concentration, aging time, drying method and spray drying temperature on the performance of silica powder. As follows, the membrane dispersion microreactor and stirring method were compared. Finally, the use of polyurethane coatings extinction performance were tested and compared with the well-known silica mating agent brand. The results show that the membrane dispersion microreactor is the endpoint pH value of about9.5, the reaction temperature is70℃, aging time is2h and spray drying temperature is100℃to obtain the pore volume up to2.0ml·g-1or more and the primary particle diameter of about10nm nano-silica.3. Finally, the paper conducted a preliminary inquiry by conventional stirring method preparing the silica particles. We have investigated the influence of reaction temperature, surfactant and cosurfactant ratio and the active agent with the oil matches ratio of the silica particles. This laid the foundation for the further use of the embrane dispersion microreactor to prepare silica particle.