失效汽车催化剂中铂族金属浸出工艺优化及浸出动力学研究

发布时间：2018-08-08 12:19

【摘要】：治理汽车尾气最有效的方法是安装以铂族金属为活性组分的汽车尾气净化催化剂,当汽车运行一定时间和里程后汽车尾气净化催化剂就失去了其催化活性,由此产生的废料就成为了铂族金属最重要的二次资源。目前报道的提取工艺中主要有火法,湿法和火-湿联用法3类。这些方法要么存在设备要求高、投资大、生产成本高,要么提取效率低、环境污染严重等缺点,急需开发简单、少污染、铂族金属提取率高的浸出方法。论文在文献数据的基础上,对铂钯铑3种铂族金属在氯离子溶液体系中的稳定形态进行了热力学分析研究,结果表明,当溶液中酸度pH约为-1,将电极电势提高至700mv时,即可将铂溶解浸出,钯只需电极电势为500mv,铑仅需420mv;提高溶液的酸度和配位剂氯离子的浓度均有利于铂族金属的浸出。从理论上证明了采用HCl-H_2SO_4-NaClO_3体系能够实现汽车催化剂中铂钯铑的浸出。通过实验研究了从失效汽车催化剂中回收铂族金属的湿法提取工艺,单因素实验结果表明,铂族金属的浸出率随着浸出温度、浸出液酸度、盐酸硫酸比例的增大而增大,与氧化剂氯酸钠浓度、预处理条件、粒度、搅拌速度等因素关联不大,优选出最优的浸出工艺条件是:初始酸度[H+]=9mol·L-1,盐酸硫酸比例为4㑳1,氧化剂氯酸钠为原料量的5%,浸出温度为105℃,搅拌速率为250rpm,浸出时间90min,液固比5㑳1。在上述工艺条件下连续二次浸出,铂、钯、铑的浸出率分别为90%、96.3%和81.2%。在单因素实验基础上通过正交实验进一步对浸出工艺条件进行优化,利用L9(34)正交表设计三水平四因子正交实验。然后在正交实验结果基础上进行极差分析,得到了影响铂族金属浸出率的因子主次排列顺序。对铂浸出率影响因素依次为,盐酸硫酸比例酸度浸出时间温度;对钯浸出率影响因素依次为,酸度温度盐酸硫酸比例浸出时间;对铑浸出率因素依次为,酸度盐酸硫酸比例温度浸出时间。正交优化得到的最佳工艺条件是:初始酸度[H+]11mol·L-1,浸出温度105℃,盐酸硫酸比例3㑳1,浸出时间90min。在上述工艺条件下连续二次浸出得到铂、钯、铑的浸出率分别为92.27%、96.69%和82.98%。相对单因素优化的工艺条件,铂、铑的浸出率均有所提高;同时通过XRD,SEM等现代表征手段证明,湿法浸出铂族金属浸出率较低的原因是失效汽车催化剂中的载体成分镁质堇青石结构稳定,对铂族金属产生了包裹。基于上述工艺条件的研究,结合液固反应动力学研究的特点对失效汽车催化剂中铂、铑的浸出动力学进行了研究,通过考察液固比、氧化剂氯酸钠用量、温度、初始氢离子浓度、初始氯离子浓度对铂、铑浸出速率的影响,研究了失效汽车催化剂在HCl-H_2SO_4-NaClO_3体系中铂、铑的浸出反应动力学。结果表明,失效汽车催化剂中铂、铑的浸出遵循“未反应核缩减”模型,受化学反应控制;提高反应温度,初始氢离子浓度及初始氯离子浓度均可提高铂、铑的浸出率并加速铂、铑的浸出速率;液固比及氧化剂NaClO_3用量对浸出速率影响不显著;采用阿伦尼乌斯公式求出铂浸出反应活化能为45.34kJ·mol-1,氢离子反应级数为1.712,氯离子反应级数为0.613;铑浸出反应活化能为66.719 kJ·mol-1,高于铂的活化能,难浸出,氢离子反应级数为0.779,氯离子反应级数为0.296。针对低浓度铂钯铑浸出液采用常见的还原剂水合肼及硼氢化钠进行了还原富集的研究。水合肼优选的最佳条件为,水合肼的用量为原料量的8%,原料液的酸度控制在1.2mol·L-1左右,反应温度维持在70℃左右,反应时间为10min。经验证铂、钯、铑的还原率分别为98.41%、99.84%、95.55%;硼氢化钠还原浸出液的最佳条件为,反应温度40℃,原料液中酸度[H+]接近0mol·L-1,加入硼氢化钠为原料量的5%,反应时间10min。在此优化工艺条件下铂、钯、铑的还原率分别为99.47%、99.67%、99.32%,其还原效果优于水合肼,还原富集物中铂族金属品位高,便于后续溶解再造液。
[Abstract]:The most effective way to control automobile exhaust is to install the catalyst for purifying the automobile tail gas with the active component of the platinum group metal. When the car runs for a certain time and mileage, the catalyst of automobile exhaust purification loses its catalytic activity. The resulting waste is the two most important resource of the platinum group metal. The extraction process of the present report is reported. There are 3 main types of fire method, wet method and fire wet connection. These methods either have the disadvantages of high equipment requirements, large investment, high production cost, low extraction efficiency, serious environmental pollution and so on. It is urgent to develop a simple, less polluted and high extraction rate of platinum group metal. On the basis of literature, the platinum palladium rhodium 3 kinds of platinum group metals are on the basis of literature The stable morphology in the chloride solution system is studied by thermodynamic analysis. The results show that when the acidity of pH is about -1 and the electrode potential is increased to 700mV, the platinum is dissolved, the electrode potential is 500mv, the rhodium is only 420mv, and the acidity of the solution and the concentration of the chlorine ion of the coordination agent are beneficial to the leaching of the platinum group metal. The leaching of platinum, palladium and rhodium in automobile catalyst by HCl-H_2SO_4-NaClO_3 system was proved theoretically. The wet extraction process of platinum group metal recovered from the failure vehicle catalyst was studied by experiment. The results of single factor experiment showed that the leaching rate of platinum group metal was with the leaching temperature, the acidity of the leaching solution and the proportion of hydrochloric acid. The optimum extraction conditions are: initial acidity [H+]=9mol L-1, hydrochloric acid sulphuric acid ratio 4? 1, sodium chlorate of oxidizing agent 5%, leaching temperature of 105, stirring rate of 250rpm, leaching time 90min, liquid solid. The leaching rate of platinum, palladium and rhodium was 90%, 90%, 96.3% and 81.2%. respectively compared to 5? 1. under the above conditions. The leaching conditions were optimized by orthogonal experiment on the basis of single factor experiments. The orthogonal experiment was used to design the three level Four Factor orthogonal experiment on the basis of L9 (34) orthogonal table. Then the extreme difference was carried out on the basis of orthogonal experiment. The influencing factors of platinum leaching rate are in turn, the temperature of the acid leaching time of hydrochloric acid is in turn; the factors affecting the palladium leaching rate are in turn, the ratio of acid temperature to hydrochloric acid sulfuric acid leaching time, and the factor of rhodium leaching rate in turn, when the acidity hydrochloric acid sulfuric acid ratio is leached by temperature. The optimum process conditions are: initial acidity [H+]11mol L-1, leaching temperature 105 C, hydrochloric acid sulphuric acid ratio 3? 1, leaching time 90min. under the above conditions for two consecutive leaching of platinum, palladium, rhodium leaching rate is 92.27%, 96.69% and 82.98%. phase optimization process conditions, platinum, rhodium leaching rate are all At the same time, through the modern characterization means such as XRD and SEM, it is proved that the low leaching rate of the platinum group metal by wet leaching is the stable structure of the magnesium cordierite in the failure vehicle catalyst and the package of the platinum group metal. Based on the above technological conditions, the characteristics of the study on the kinetics of the bonding liquid solid reaction to the failure vehicle The leaching kinetics of platinum and rhodium was studied in the catalyst. The leaching kinetics of platinum and rhodium in the HCl-H_2SO_4-NaClO_3 body system was studied by investigating the liquid solid ratio, the dosage of sodium chlorate, the temperature, the initial hydrogen ion concentration, the initial chlorine ion concentration on the platinum and rhodium leaching rate. The leaching of platinum and rhodium in the vehicle catalyst follows the "unreacted nuclear reduction" model and is controlled by chemical reaction. Increasing the reaction temperature, the initial hydrogen ion concentration and the initial chloride concentration can increase the leaching rate of platinum, rhodium, accelerate the leaching rate of platinum, rhodium, and the amount of liquid to solid ratio and the amount of oxidant NaClO_3 have no significant effect on the leaching rate; The activation energy of platinum leaching reaction is 45.34kJ mol-1, hydrogen ion reaction series is 1.712, chlorine ion reaction series is 0.613, rhodium leaching activation energy is 66.719 kJ. Mol-1, higher than platinum activation energy, hard leaching, hydrogen ion reaction series 0.779, and chlorine ion reaction series 0.296. against low concentration platinum palladium rhodium leaching solution. Hydrazine hydrate and sodium borohydride have been reduced and enriched. The optimum condition for hydrazine hydrate is that the amount of hydrazine hydrate is 8% of the raw material, the acidity of the raw material is about 1.2mol L-1, the reaction temperature is about 70 C, the reaction time is 10min. empirical platinum, the reduction rate of palladium and rhodium is 98.41%, 99.84%, 95.55, respectively. %, the optimum condition for the reductive leaching solution of sodium borohydride is that the reaction temperature is 40 C, the acidity [H+] in the raw material is close to 0mol. L-1, the sodium borohydride is added to 5% of the raw material, and the reaction time 10min. is 99.47%, 99.67%, 99.32%, respectively, with the reduction rate of platinum, palladium and rhodium, under the optimized process conditions, and the reduction effect is better than hydrazine, and the platinum group metal in the reductive concentration is reduced. High grade, easy to dissolve reengineering solution.
【学位授予单位】：昆明贵金属研究所
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X734.2;TF83

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