The Preparation Of Nano-Sized Transparent Calcium Carbonate White Oil Dispersions In A Rotating Packed Bed Reactor And Its Performance Study

Stable monodisperse inorganic nanoparticles in organic or aqueous phase medium could form transparent nanodispersions. Since they displayed better application performances than nanopowder, transparent nanodispersions recently attract more attentions. Nano-sized calcium carbonate has wide applications. When it is used as oil additive, smaller particle size, better dispersity and stability are required. Presently, powder has been widely investigated. However, the preparation of transparent calcium carbonate nanodispersions is seldom reported. In this master thesis, high gravity in-situ self-assembly combined with phase transfer technology was developed to prepare nano-sized transparent calcium carbonate oil phase dispersions. The possible formation mechanism and application performance were investigated. The main contents were as followed.(1) Nano-sized transparent calcium carbonate white oil dispersions were firstly prepared in a traditional stirring batch reactor by adopting in-situ phase transfer technology. The influences of surfactants, orientated promoter, reaction ending, reaction temperature, addition dosage of water and CO2 flow rate on the solid content, the total base number of nanodispersions, particle size and distribution were investigated. The optimum preparation conditions were obtained as followed:reaction ending point with pH of 8-9 and conductivity of k=0.1 μs/cm, surfactant of 10.61%, Ca(OH)2-CaO ratio of 1.5, orientated promoter of 2.15%, water of 1.3%, reaction temperature of 50℃ and CO2 flow rate of 30 mL/min. The as-prepared nanodispersions appeared transparent brownish red color, which had an average particle size of 10-15 nm, a solid content of 38.88 wt.%, calcium content of 15.52 wt.% and the total base number of 410 mgKOH/g. Further, the possible formation was investigated by polarized optical microscope and FT-IR.(2) Nano-sized calcium carbonate white oil transparent dispersions were further prepared by high gravity in situ phase transfer technology in a rotating packed bed (RPB) reactor. The effects of inner or external recycling RPB, rotating speed (gravity level), gas-liquid flow rate ratio, gas and liquid flow rates on the solid content and the total base number of nanodispersions, particle size and distribution were studied. The optimum parameters were achieved as followed:reaction ending point with pH of 8-9 and conductivity of k=0.1 μs/cm, rotating speed of 1500 rpm (gravity level of 76g), and gas-liquid flow rate ratio of 0.082. The size and distribution of calcium carbonate nanopartilces decreased with the increase of RPB rotating speed. The as-prepared nanodispersions still appeared transparent brownish red color, which had the same solid content and total base number as compared to those in a stirring batch reactor. However, the product obtained in RPB had a smaller average size of 5-10 nm and a narrower size distribution, better transparency and lower viscosity.(3) The application performances of nano-sized calcium carbonate white oil transparent dispersions were studied by preliminary bench test. The results indicated that the nanodispersions could significantly enhance extreme pressure property and anti-rust property of oil. The PB (maximum nonseizure load) value of 70 N was obtained with an increase of 40% as compared to white oil. In addition, the corrosion level was excellent, nearly approaching the international product LU5358.