4Na₂SO₄·2H₂O₂·NaCl加合物的制备及热分解动力学研究

【作者】 杨杰；

【导师】 刘国际； 雒廷亮；

【作者基本信息】 郑州大学 ， 化学工艺， 2002， 硕士

【摘要】 硫酸钠-过氧化氢-氯化钠加合物是一种新型的精细化工产品，分子式为4Na₂SO₄·2H₂O₂·NaCl，H₂O₂含量9.79％（wt），为笼形结构。H₂O₂分子嵌入在SO₄-O原子形成的笼中，可保护过氧化氢不分解，因此结构较稳定。该产品在水溶液中近中性，作为新型的中性洗涤助剂，较适用于洗涤剂行业和清洗行业，因此其应用范围较过碳酸钠、过硼酸钠、过磷酸钠等广。研究开发以芒硝生产4Na₂SO₄·2H₂O₂·NaCl的合成及工艺条件，探讨其分解规律，不仅为芒硝资源的高效利用，生产高附加值的精细化工产品开辟了一条新途径，而且拓宽了过氧化氢加合物的应用领域。且生产过程无三废排出，适应了环保要求。因此该产品的生产及推广应用有着广阔的市场前景，具有显著的经济效益和社会效益。 本文通过正交实验对其制备过程中的影响因素：双氧水浓度、硫酸钠加入量、氯化钠加入量、反应时间等进行了研究。结果表明：双氧水浓度、氯化钠的加入量和反应时间对产品中过氧化氢含量和产品稳定度影响较为显著。为得到较适宜的反应条件，对氯化钠加入量和反应时间进行了单因素优化。从而得到了最适宜的工艺条件：以25毫升双氧水为基准，反应温度为283K，硫酸钠的加入量为8克，过氧化氢浓度为30％（wt），氯化钠的加入量为8克，反应时间为1小时。以将NaCl加入到含有Na₂SO₄的双氧水中为宜。 利用TG-DTG和DSC对制备的产品4Na₂SO₄·2H₂O₂·NaCl进行了热分析。4Na₂SO₄·2H₂O₂·NaCl的分解温度为： ．二I－ TG．DTG DSC 备注 437．4 462石5 实测值 分解温度（K） 433 453 文献值 本文的测定值与文献值吻合的较好。 由TG－DTG曲线可知，4NtaSO。·ZH。O。·NaCI的热分解是一复杂 过程。其分解可分为两个阶段：407．15～423．95K之间DTG曲线为直线， 4NdeSO4·2H2O2·N＆CI的质量减少缓慢，为分解的第一阶段；423二5 K 时样品的质量迅速减少，436．95 K分解速度最快，到449，SS K样品分解 结束，423．95～449．85 K为样品分解的第h阶段，即特征分解曲线。采用 主曲线法对4NazSO。·2H2O2·NaCI分解机理进行了判别，结果表明，其 分解为Am机理，即分解过程受核形成与核增长控制，机理函数 且 gk)＝［11（1—a”。采用微分法、积分法、最大分解速率法求取了动力 学参数，并利用通用模型——成核扩散模型对参数进行了优化，得到了硫 酸钠－过氧化氢－氯化钠加合物的热分解表观活化能和指前因子。微分法所 求数据不能很好的模拟其分解过程，而积分法和优化法均能够较好地拟 合。积分法和优化法求得的4Na。SO。·ZH。Oz·NaCI热分解的活化能和指 前因子为： 活化能 E＊·mol二 指前因子 A 积分法 4．392X10’6171X10’2；’ 优化法 4．179X10‘1．982X105 。；，、。、、。＋、。。、。。、，，，。。。。。、。｛da＼。、。。。。 最大分解速率法求取的活化能仅与Tm。和I二三；有关，与其它因 ＼＊T）－ 素无关。所得活化能为 Ea＝l．739x 10刁·mol”’，较接近于积分法。 积分法和优化法求得的4Na。SO。·ZH。O。·NaCI热分解动力学方程式： 二 －互＊1－ da＿＿＿。。＿。；．0．328＿、＿．＿’、＿1 二＝6．17lxlo川eXP卜一)（—a）卜Ino 一a)］‘ dT“”T da。＾。＾。 0．503。 二二3．94 xlo”exP(－（1一a）‘’””【In(1一a刀‘”” dT“”T 优化法的结果更接近于中N250。·2氏0。·NaQ的实际分解过程。由 DSC狈矢，4NdiSO4·2H2O2·NSCI的分解热为 18．32KJ．m。l1。 4NazSO／ZH刃广NaCI在402刀gK开始分解，这时的分解并不是SO厂 与 HZOZ之间氢键的断裂，应是与 ＊“成的键破裂。在笼形结构的 4NazSO／ ZH?更多还原

【Abstract】 Sodium sulphate-hydrogen peroxide-sodium chloride adduct (4Na2SO4 2H2O2 NaCl) with 9.79% of H2O2 by mass is a new-type of neutral assistant for synthetic detergents. In the clathrate structure of this adduct, the molecule of H2O2 are incorporated in a cage formed by sulphate-oxygen atoms. There is no uniform coordination for Nah ions in adduct. For 9 Na+ ions in the molecule of the adduct, each of 8 Na+ ions is surrounded in a distorted octahedron formed by 5 oxygen atoms and 1 choride ion and another Na+ ion is surrounded in a tetragonal prism formed by oxygen atoms.An experimental scheme based on orthonomalization method was designed and used to optimize the processing conditions for the adduct of 4Na2SO4 2H2O2 NaCl. The experimental results indicated that a high quality of adduct can be achieved when 8 g Na2SO4 and 8 g NaCl were added and stirred into 25 ml H2O2 solution with 30% H2O2 by mass and the whole solution was then stirred for one hour reaction at a temperature of 283 K. In this case, further analyses showed that the final product has a high stability, the concentration of H2O2 in the product is 9.71% by mass and the crystals in the product have a prismatic structure. The experimental results also indicated that a theoretical value of 9.79% H2O2 in the final product can be achieved if 9.5 g Na2S04 and 2-8 g NaCl were added into 25 ml H2O2 solution with 30% H2O2 by mass. However, the concentration of H2O2 in the final product will decrease below the theoretical value if more than 8 g NaCl was added into the same solution. The experimental results further illustrated that the reaction time will increase if Na2SO4 was first added into the H2O2 solution. Therefore, for anefficiency of the processing system and a high production of the adduct, NaCl should be added into the H2O2 solution before adding Na2SO4Thermal analysis was further carried to determine the decomposition temperature of the prepared adduct of 4Na2SO4 2H202 NaCl using both TG-DTG and DSC techniques. The analysis showed that the decomposition temperatures of the product measured by TG-DTG and DSC were 437.4 K and 462.65 K, respectively. Both measured values agree well with the data from the literatures, which are 433 K and 453 K, respectively.The measured TG-DTG curve further illustrated that the decomposition process of 4Na2SO4 2H202 NaCl is very complex. The decomposition process can be divided into two stages: (1) linear part, which is from 407.5 K to 423.95 K in the DTG curve and (2) characteristic curve part, which is from 423.95 K to 449.85 K. During the first stage, the weight loss of 4Na2SO4 2H2O2 NaCl is slow. However, at a temperature of 423.95 K, the weight of the product decreases significantly and the second decomposition begins. The weight loss rate reaches its maximum value at 436.95 K and the decomposition proceeds until the temperature of the product reaches 449.85 K.The decomposition mechanism of 4Na2SO4 2H2O2 NaCl was investigated using main curve method. The results indicate that the decomposition is controlled by the formation and growth of nuclei. The experimental data was further correlated by the Avrami-Erofe’ev equation to model the kinetic process of the decomposition, which is expressed as:The kinetic parameters in the Avrami-Erofe’ev equation were obtained byusing differential, integral and maximum decomposition rate methods, respectively. The parameters were further optimized by the nuclei formation -diffusion model to determine the apparent activation energy and pre-exponent. The Avrami-Erofe’ev equation with two kinetic parameters calculated by differential method cannot predict the decomposition process of the adduct very well. However, the equations with the parameters calculated by integration and optimization methods can achieve a good prediction. With those methods, the apparent activation energy and pre-exponent are determined as:The activity energy determined by the maximum decomposition rate was 1.739xl05 J-mol-1, which is close to the value achieved by the integration更多还原