【作者】 樊艳金；

【导师】 吴文伟；

【作者基本信息】 广西大学 ， 应用化学， 2008， 硕士

【摘要】 低热固相反应法具有无须溶剂、选择性强、产率高、能耗低、操作简单等诸多优点，已成为合成无机纳米材料的新途径。本文采用低热固相反应法合成了（NH₄）₂Ti（PO₄）₂、Ce_1-xTi_xP₂O₇及NH₄MnPO₄·H₂O系列新型无机纳米粉体。同时对（NH₄）₂Ti（PO₄）₂催化合成乙酸正丁酯及NH₄MnPO₄·H₂O纳米晶的热分解动力学进行了研究。本研究论文共分为六章：第一章绪论介绍了纳米材料的特性及其合成研究进展。同时，综述了固相反应法制备无机材料的原理及其在合成纳米无机材料中的优点。第二章磷酸钛铵的低热固相合成与表征以Ti（SO₄）₂和（NH₄）₃PO₄·3H₂O为原料，采用低热固相反应法制备（NH₄）₂Ti（PO₄）₂。采用TG／DTA、IR、XRD、UV和TEM对产品及其热解产品进行表征。结果表明：80℃下保温5h得到的是无定型的（NH₄）₂Ti（PO₄）₂粉体，其平均粒径约为40nm；产品经900℃煅烧后，得到结晶良好、空间群为Pa3（205）、平均粒径约为23nm的TiP₂O₇晶体。产品及其热分解产品具有较高的紫外吸收能力。第三章磷酸钛铵催化合成乙酸正丁酯的研究以纳米级磷酸钛铵为催化剂，冰醋酸和正丁醇为原料合成了乙酸正丁酯。通过均匀设计法确定了最佳实验条件，结果表明：当酸醇物质的量比为1．92：1，反应时间为5．1h，催化剂用量为1．4g（质量百分比为7．8％）时，其酯化率可达0．99。该催化剂制备工艺简单，可重复使用，基本无腐蚀和污染，是一种颇具工业应用开发前景的催化剂。第四章Ce_1-xTi_xP₂O₇粉体的低热固相合成及其紫外屏蔽性能研究以Na₄P₂O₇·10H₂O、Ti（SO₄）₂、Ce（SO₄）₂·4H₂O为原料，采用低热固相反应法合成了Ce_1-xTi_xP₂O₇（x=0，0．2，0．5，0．7，0．9，和1．0）。通过XRD、TG／DTA、UV和TEM对产品及其热分解产物进行了表征。结果表明，100℃下得到的产品均为无定型纳米粉体，且具有良好的紫外遮光效果。其中，CeP₂O₇的紫外遮光效果最佳，但无定型的Ce_0．8Ti_0．2P₂O₇较CeP₂O₇能稳定至更高的温度。因此，可通过往CeP₂O₇中掺钛来实现CeP₂O₇无定型态的稳定。这种稳定性的改善使这些无定型的焦磷酸盐不仅能适用于化妆品和涂料，同样也适用于塑胶和薄膜中应用。第五章NH₄MnPO₄·H₂O的低热固相合成与表征以MnSO₄·H₂O和（NH₄）₃PO₄·3H₂O为原料，先在室温下研磨反应混合物进行固相反应，然后将混合物于室温下静置陈化12h，接着用水洗去混合物中的可溶性无机盐，后将沉淀物在60℃烘干，即得NH₄MnPO₄·H₂O纳米晶。采用XRD、TG／DTA、IR、UV和SEM对产品表征。结果表明，所得产品为结晶良好、空间群为Pmnm（59）的正交NH₄MnPO₄·H₂O，其平均粒径约为45nm；将NH₄MnPO₄·H₂O分别在600℃、900℃下煅烧3h则得到空间群为C2／m（12）的单斜（Monclinic）Mn₂P₂O₇。它们的粒径分别约为22nm和61nm。第六章NH₄MnPO₄·H₂O的热分解动力学研究采用热重差热法分析研究了NH₄MnPO₄·H₂O的热分解过程，结果表明：NH₄MnPO₄·H₂O在低于600℃下的热分解分两步进行，第一步为结晶水和氨气的脱附，第二步为MnHPO₄脱水缩合成Mn₂P₂O₇。各分解过程的活化能（E）、频率因子（A）和热分解机理函数分别为：反应（1）E=105．7 kJ／mol，lnA=24．9s^-1，G（a）=（1-a）^-1-1；反应（2）E=113．6 kJ／mol，lnA=14．5s^-1，G（a）=[1／（1-a）^1／3-1]²。更多还原

【Abstract】 Solid-state reaction method at low heat has many advantages, such as few solvent, high selectivity, high output, low energy cost, so it has became a novel synthetic technique for preparing nanometer size inorganic materials. In this paper, nanometer size （NH₄）₂Ti（PO₄）₂, Ce_1-xTi_xP₂O₇ and NH₄MnPO₄·H₂O powders were synthesized via solid-state reaction at low heat. Besides, catalytic performance of （NH₄）₂Ti（PO₄）₂ in the synthesis of butyl acetate and thermal decomposition kinetics of nanometer crystalline NH₄MnPO₄·H₂O were also investigated. The paper consists of six chapters.Chapter one: IntroductionCharacteristic and preparation progress of nanometer materials were introduced. Besides, the principle of preparing nanometer inorganic material via solid-state reaction and its advantage were also summarized.Chapter two: Preparation of （NH₄）₂Ti（PO₄）₂ via solid-state reaction at low heat and characterizationThe （NH₄）₂Ti（PO₄）₂ was obtained via solid-state reaction at low heat when Ti（SO₄）₂ and （NH₄）₃PO₄·3H₂O were used as raw materials. Product and its thermal decomposition products were characterized using TG/DTA, IR, XRD, UV and TEM. The results showed that average particle size of amorphous （NH₄）₂Ti（PO₄）₂ obtained at 80℃for 5h was about 40nm. When （NH₄）₂Ti（PO₄）₂ was calcined at 900℃for 3h, the nanometer crystalline TiP₂O₇ with high crystallization, space group Pa-3（205）, was obtained, and its average particle size was about 23nm. The product and its thermal decomposition products behaved as excellent UV-shielding materials.Chapter three: Study on （NH₄）₂Ti（PO₄）₂ used for catalytic synthesis of butyl acetateThe butyl acetate was synthesized when nanometer size amorphous （NH₄）₂Ti（PO₄）₂ was used as catalyst, and glacial acetic acid and n-butanol were used as raw materials. The optimum conditions were obtained via uniform design method. The results showed that the optimum conditions were as follows: molar ratio of acetic acid to butanol was 1.92:1, reaction time was 5.1h, catalyst dosage was 1.4g （7.8%w/w）, and esterification yield was 0.99 under the optimum conditions. The catalyst can be prepared via simple technique, and used repeatedly, little equipment cauterization and environmental pollution, so this catalyst would have a bright future for industrial application.Chapter four: Preparation of Ce_1-xTi_xP₂O₇ powders via solid-state reaction at low heat and study on their UV absorbency.Ce_1-xTi_xP₂O₇（with x = 0, 0.2, 0.5, 0.7, 0.9, and 1.0） were obtained via solid-state reaction at low heat when Ce（SO₄）₂·4H₂O, Ti（SO₄）₂ and Na₄P₂O₇·10H₂O were used as raw materials. The products and its products calicined were characterized using XRD, TG/DTA, UV and TEM. The results showed that naometer size amorphous Ce_1-xTi_xP₂O₇ obtained at 100℃behaved as an excellent UV-shielding materials respectively. There into, the CeP₂O₇ has the most excellent UV-shielding effect, the amorphous state of Ce_0.8Ti_0.2O₇ can keep at higher temperature than CeP₂O₇. Therefore, the stabilization of the amorphous state of the cerium pyrophosphates was carried out by doping titanium （Ti）. This stabilization is a significant improvement, which enables to apply these amorphous pyrophosphates not only to cosmetics and paints, but also plastics and films.Chapter five: Preparation of NH₄MnPO₄·H₂O via solid-state reaction at low heat and characterizationThe nanometer crystalline NH₄MnPO₄·H₂O was obtained when MnSO₄·H₂O and （NH₄）₃PO₄·3H₂O were fully ground via solid-state reaction at room temperature, then mixture was kept at room temperature for 12h, and washed with water to remove soluble inorganic salts and dried at 60℃. Product was characterized using XRD, TG/DTA, IR, UV and SEM. The results showed that average particle size of nanometer crystalline NH₄MnPO₄·H₂O obtained at 60℃with high crystallization, orthorhombic system, space group Pmnm（59）, was about 45nm. When NH₄MnPO₄·H₂O was calcined at 600℃and 900℃for 3h respectively, the nanometer crystalline Mn₂P₂O₇ with space group C2/m（12）, monclinic system, was obtained, and their average particle sizes were about 22 nm and 61nm respectively.Chapter six: Study on thermal decomposition kinetics of NH₄MnPO₄·H₂OThermal decomposition kinetics of NH₄MnPO₄·H₂O was investigated using thermo-gravimetric-differential thermal analysis （TG-DTA）. The results showed that thermal decomposition of NH₄MnPO₄·H₂O at temperature below 600℃occurs in two well-defined steps. The first step is attributed to the desorption of water and ammonia from NH₄MnPO₄H₂O, and the second step is attributed to dehydration of MnHPO₄ and formation of Mn₂P₂O₇. Activation energy （E）, frequency （A）, and mechanism function of each thermal decomposition reaction step are as follows: E = 105.7 kJ/mol, lnA = 24.9 s^-1, G（a） = （1-a）^-1-1 for reaction（1）; and E = 113.6 kJ/mol, lnA=14.5 s^-1, G（a） = [1/（1-a）^1/3-1]² for reaction（2）.更多还原