Determination of crystalization conditions in the production of sodium and potassium tetrafluoroborate compounds

In this study, firstly the production and crystallization conditions of sodium tetrafluoroborate (NaBF4) compound, which is used frequently as catalyst in organic and polymer technology, is determined. For this purpose, nucleation temperatures were found by cooling the saturated solutions of the sodium tetrafluoroborate compound at 30.7, 41.8, 52.3, 61 ° C at a mixing speed of 250 rpm at cooling rates of 3, 5, 6, 7, 8, 9, 10 ° C / h. Thus, metastable region widths were obtained. Within the scope of induction period studies, saturated solutions were cooled to different temperatures in their metastable region with maximum cooling rate at 30.7, 41.8, 52.3, 61 ° C. Using the induction period values measured in these experiments, critical nuclei radius (r), number of molecules for critical nuclei (i), formation energy (∆Gv) and critical energy (∆G*) required for nucleation were obtained in each solution. The activation energy of the reaction between sodium carbonate and fluoroboric acid compounds during the production of sodium tetrafluoroborate was calculated as 12.11 kJ / mol. In this reaction, the reaction degree of fluoroboric acid was found to be 1.4 and the reaction degree of sodium carbonate was found to be 1.25. Sodium tetrafluoroborate MSMPR crystallizer to determine the production conditions by crystallization on the particle size distribution of the crystals; effects of residence time, temperature, mixing speed, flow rate, mixer type, calcium chloride and magnesium chloride impurities, boric acid, sodium carbonate and fluoroboric acid excess were investigated. Steady-state residence time of the solution in the MSMPR crystallizer was found as 160 min for crystal size distribution. In the MSMPR crystallizer system, there is a decrease in the crystal size distribution when the amount of temperature, mixing speed, flow rate, mixer type impeller number, calcium chloride, magnesium chloride, boric acid, sodium carbonate and fluoroboric acid concentrations increase. In the second step of the thesis, the parameters affecting the production yield, crystallization and reaction kinetics of potassium tetrafluoroborate (KBF4) compound used in aluminum alloy were investigated. The effects of mixing speed, mixing time, temperature, impurity concentration of calcium chloride and magnesium chloride, excess boric acid and HBF4/KOH mole ratio on reaction yield and particle size distribution were investigated in potassium tetrafluoroborate production. In the studies carried out, it was determined that temperature increase had a negative effect on the reaction yield. Increased reactant concentrations and increased molar ratio of HBF4/KOH increase the reaction yield. The optimum mixing time in terms of reaction yield is 30min. as determined. Calcium chloride impurity reduces the reaction yield and boric acid addition also reduces the reaction yield. Mixing speed does not have a significant effect on the yield up to 500rpm, while reducing the reaction yield at 700rpm. The concentration of the reactants increases the particle size distribution of the potassium tetrafluoroborate compound, while the calcium chloride, magnesium chloride, impurities and boric acid addition reduce the particle size distribution of the potassium tetrafluoroborate compound. The potassium tetrafluoroborate compound is formed quite rapidly by the reaction between potassium hydroxide and fluoroboric acid. In the production of potassium tetrafluoroborate compound by precipitation crystallization method, activation energy value could not be calculated since an acceptable coefficient could not be obtained between the concentration of the reactants and the reaction rate.