The Thermal Decomposition Of KMnO₄, KClO₃ And Other Inorganic Solids

The thermal decomposition of solid is an important research area of solid chemistry, it has a wide application background. The production process of many inorganic salts includes the decomposition process of the raw materials such as carbonate, basic carbonate, sulfate or inter- mediate products. It is of great important practical significance to the technology reform, saving energy, reducing consumption and increasing efficiency for us to proved thermal decomposition mechanism of the solid, made highly efficient and appropriate catalyst. CaCO₃ is an important industrial raw materials in the production of portland cement, its decomposition temperature has an important effect on the quality and energy consumption in portland cement production. In addition, CaCO₃ decomposition as a simple and typical gas-solid reaction, Studying its reaction dynamics is helpful to reveal this type of reaction and the establishment of a complete principle of physical chemistry. It can make us deepen the understanding on the laws of thermal decomposition by the studying on the thermal decomposition mechanism, especially on catalytic thermal decomposi- tion. This is helpful to seek the efficient catalyst of CaCO₃ thermal decomposition, as soon as possible play its industrial value. Of course, this also contribute to the understanding on the laws of BaSO₄ thermal decomposition, then reform all kinds of barium-salt production process.Considering the difficulty and the higher demands of experiment conditions in studying the decomposition of CaCO₃, BaSO₄, we decide to do some works begin from those inorganic solids which are familiar, similar, easy decomposition. Those are helpful to master the basic theories, research means and improve our research capability, accumulate some research experience and complete the hard task. So that we decide to do the research begin from the thermal decomposi- tion of KMnO₄, KClO₃. At present, the mechanism of potassium chlorate thermal decomposition is still very imperfect. Many scholars conducted extensive research on the mechanism of potassium chlorate thermal decomposition. because of the differenent experimental methods, experimental conditions, the researchers come to different mechanism model. None of these mechanism models can give a reasonable explanation completely accepted by us. Therefore, making a further study on the decomposition mechanism of KClO₃ has significant theoretical value. The main achievements of this dissertation are as follows:1 Introduce the progress of CaCO₃, KClO₃ thermal decomposition and the main research methods about thermal analysis kinetics at present in China and abroad. Meanwhile,the deficiency and the improvement approach were put forward in this dissertation.2 KMnO₄ was heated under a given temperature for long time in Muffle furnace, then we calculated the weight loss rate of KMnO₄. we determine the decomposition temperature of KMnO₄ according to the weight loss rate and found that thermal decomposition temperature of KMnO₄ is 190℃which is related to the crystalled status, not 240℃said in some literature. The mechanism models of KMnO₄ thermal decomposition were also firstly proposed by us.3 The mixture solution of ClO₃- and trifle amount ClO₂-, in whichρ(ClO₃- ) = 34.1 g/L,ρ(ClO₂^-) =208 mg/L, was prepared, and the ClO₂- concentration in the solution was tried to be determined directly by iodometricmethod. The influences of varying the detecting conditions and adding ClO₄^- to the solution on the results were investigated. The procedure,precision, accuracy, and the least detectable ClO₂^- concentration of the method,were obtained. In the analysis process, the pH value of the solution to be detected should be adjusted by 0.5 mol/L HCl.4 The researchers have different views on mechanism model and the thermal decomposi- tion temperature of KClO₃. We found that KClO₃ can decomposed at 330℃if it is heated for a long time under a given temperature. And found that reaction atmosphere, light radiation has effect on the thermal decomposition of KClO₃, light radiation can catalyze the thermal decomposition of KClO₃. We also proposed a new mechanism which can explain some experiments very well.5 By studying on the thermal decomposition for the mixture system of KClO₃ and MnO₂, we think that the decomposition temperature of KClO₃ is 330℃which is the same as analytical reagent.we found it belongs to liquid-solid phase catalysis for MnO₂ catalyzing the thermal decomposition of KClO₃. That is to say that MnO₂ can't catalyze the KClO₃ decomposition when KClO₃ is still in solide states. We also found that particle size of KClO₃, heating rate can effect the thermal decomposition of the mixture system, and pointed out that the most suitable amount of MnO₂ in the mixture system is about 10% -25%.6 By studying on the thermal decomposition of the mixture system of KClO₃ and KMnO₄, we found that the situ MnO₂ has a high catalytic activity obtained from the decomposition products of KMnO₄.