【作者】 毛立可；

【导师】 赵临远；

【作者基本信息】 广西师范大学 ， 无机化学， 2008， 硕士

【摘要】 固体的热分解反应是固体化学的重要研究领域,具有十分广阔的应用背景。很多无机盐产品的生产过程都包含碳酸盐、碱式碳酸盐和硫酸盐等原料或中间产物的煅烧分解工序。探明固体热分解机理,取得高效、适用的催化剂,对于相关产品的生产工艺改革、节能降耗、增加效益等有重要实际意义。CaCO₃是硅酸盐水泥生产中重要的工业原料,它的分解温度对水泥的能耗与质量具有重要的影响。另外,CaCO₃分解反应为一种典型的气固反应,对其反应动力学的研究有助于揭示并建立这一类反应的完整物理化学图景。可以通过对CaCO₃热分解机理尤其是催化热分解机理的研究来加深对固体热分解规律的认识,寻求CaCO₃热分解的高效催化剂并尽快投入应用;同时有助于增加对BaSO₄的热分解规律的认识,推进各种钡盐生产工艺的改革。鉴于CaCO₃、BaSO₄等热分解研究的较大难度和对实验条件较高的要求,我们经过长时间认真思考后,决定从一些较常见的、有相似性的、易分解的无机固体开始（实为进入科研启动阶段）,熟悉有关的基础理论和研究手段,提高研究能力,积累研究经验,明确并创造研究条件,最终很好地展开、完成这一艰难、巨大的研究开发课题。对于无机固体的热分解,KMnO₄和KClO₃的热分解是人们再也熟悉不过的实例。但我们通过大量认真细致的调研,竟然发现有关的反应机理完全不清楚。为此我们选择从研究KMnO₄、KClO₃的热分解入手,在深厚、宽广的理论基础上,设计、完成了一系列巧妙、新颖的实验,取得一些重要发现。主要工作如下:1总结了国内外KClO₃、CaCO₃热分解研究的进展及热分析动力学方法,指出了不足之处,提出了有待解决的问题。2采用马弗炉把KMnO₄在一定温度下长时间加热,测定KMnO₄热分解失重率,根据是否失重确定其分解温度,发现KMnO₄热分解温度与其结晶状况有关,分解温度为190℃,不是文献中所载的240℃。首次提出了KMnO₄热分解机理。3配制ClO₃^-和微量ClO₂^-混合存在的溶液,ρ（ClO₃^-） = 34.1g/L,ρ（ClO2-） = 208mg/L,尝试以碘量法直接测定其中亚氯酸根离子的含量。考察测定条件及向待测溶液中添加ClO₄^-对分析结果的影响,确定了方法的测定程序、精密度、准确度和该方法可以较方便检测的最低ClO₂^-浓度。测定过程的关键之处是使用约0.5mol/L的盐酸来调节待测溶液的pH值。4认真研究了KClO₃热分解行为,发现学者们对KClO₃热分解温度和机理模型有不同看法。我们课题组在各个温度下对KClO₃长时间加热,认为其分解温度为330℃。并发现反应气氛、光辐射都影响KClO₃热分解,其中光辐射可以催化KClO₃热分解。同时提出了一个新的机理模型,该机理模型能够较好地解释一些实验现象。5通过对KClO₃和MnO₂混合体系的热分解研究,认为其分解温度与分析纯KClO₃热分解温度相同,为330℃;MnO₂对KClO₃的催化作用属于液-固催化,即MnO₂催化的是熔融态KClO₃的分解,混合体系在固态时MnO₂不起催化作用。同时发现KClO₃颗粒大小、升温速率都影响混合体系的热分解,并指出催化剂MnO₂最合适用量为10%-25%.6通过对KClO₃和KMnO₄混合体系的热分解研究,发现原位产生的MnO₂对KClO₃热分解有较强的催化作用。更多还原

【Abstract】 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.更多还原