【作者】 陈云；

【导师】 冯其明；

【作者基本信息】 中南大学 ， 再生材料工程， 2006， 博士

【摘要】 世界上每年产生含钒、钼的废铝基催化剂大约有50～70万吨,为制造这些催化剂耗用了大量贵金属、有色金属或其氧化物,催化剂中有用金属的含量并不低于矿石中相应金属的含量,甚至远远高于矿石中金属的含量。因此对废催化剂进行综合回收,具有很大的经济效益和环境效益。废铝基钒钼催化剂是一种以氧化铝为载体,富含钒钼的失效催化剂。就目前来看,国内外对废催化剂中有价金属元素的回收进行过一些研究,但主要是针对一种或两种金属进行回收,对其综合回收的研究较少,废铝基钒钼催化剂的综合回收的难点在于液相中两性金属铝、钒和钼的有效分离。本文系统地评述了废铝基催化剂综合回收的现状,在大量的理论分析、试验研究及前人思路的基础上,通过对铝、钒、钼体系溶液化学、热力学计算、分子动力学模拟及各种测试手段,对碱性体系中铝、钒、钼的溶液化学性质及分离技术进行详细的研究,对废铝基钒钼催化剂综合利用的基础理论及工艺技术进行了研究。研究内容与结果如下:1.铝、钒、钼水溶液化学性质的研究:采用溶液化学计算方法对铝、钒、钼体系进行了计算,从理论上分析了铝钒钼在酸性和碱性溶液中的存在状态和溶解性能,绘制了不同浓度及pH条件下铝、钒、钼水体系的优势组分图,分析了离子浓度和pH值对体系中各离子分布的影响,为水溶液中铝、钒、钼的分离技术的选择提供了基础。测定了钒钼在氢氧化钠及铝酸钠溶液中的溶解度,结果表明在铝酸钠溶液中,钼的溶解度受温度影响不大,而钒在铝酸钠溶液中的溶解度受温度影响很大;20℃时钒在铝酸钠溶液中的溶解度为1g/l左右,80℃时其溶解度可达50g/l。为结晶法分离铝酸钠溶液中的钒提供了理论数据。根据已有的电化学数据,绘制了铝钒钼水体系的电位-pH图,并探讨了不同电位下,体系中不同价态离子间的相互转化。其研究结果为废催化剂钒钼提取工艺条件的选择与控制提供重要的参考依据。采用Material Studio中的Discover模块对铝钒钼水溶液体系进行了分子动力学模拟研究。结果表明:Al（OH）₄^-单体形成的“分子簇”有利于聚合铝酸根分子的形成,Na⁺控制聚合铝酸根分子的稳定存在,从而影响铝酸钠溶液中Al（OH）₃的析出。对三种不同pH值下钒钼水溶液体系进行了分子动力学模拟,模拟结果表明不同pH下,体系中钒钼的存在形式与溶液化学研究结果及已有的光谱学测试结果有很好的对应关系。2.论文对Ca（Ba）-V（Mo）-H₂O体系的浓度对数图及电位—pH图进行了研究,有以下研究结果:Ca-V（Mo）-H₂O体系的浓度对数图研究结果表明,Ca（OH）₂须在一定的pH下才能有效地与溶液中的VO₄^3-或MoO₄^2-反应,随着温度的升高,钒酸钙和钼酸钙的稳定区间增大,溶液体系中残余的VO₄^3-和MoO₄^2-离子浓度降低。Ba-V（Mo）-H₂O体系的浓度对数图研究结果表明,温度升高,钒酸钡和钼酸钡的稳定区间增大,溶液体系中残余的VO₄^3-和MoO₄^2-离子浓度降低。与Ca-V（Mo）-H₂O体系的浓度对数图的对比表明,在V（Mo）-H₂O体系中,氢氧化钡比氢氧化钙具有更好沉淀分离钒和钼的效果,当温度为100℃时,体系中的钒和钼的浓度可分别降至10^-7.3和10^-7.0mol/l。Ca（Ba）-V（Mo）-H₂O体系的电位—pH图的研究结果表明,钒的化合物（钒酸钙和钒酸钡）比钼的化合物（钼酸钙和钼酸钡）有更大的稳定区域。在钒钼共存混合体系中,氢氧化钙和氢氧化钡将有可能优先与钒酸根反应,后与钼酸根反应。3.模拟体系中铝钒钼的化学沉淀分离试验结果表明:在V（Mo）-H₂O体系中,试剂CaO、Ba（OH）₂及CaCl₂对溶液中的钒钼都有很好的沉淀效果。在合适的反应条件下,钒和钼的沉淀率可达98%。在V（Mo）-Al-H₂O体系中,CaO和CaCl₂对钒钼的沉淀效果很差,而Ba（OH）₂对钒钼的沉淀效果很好。热力学计算表明,CaO和CaCl₂对钒钼的沉淀效果变差的原因是由于钙与溶液中的大量的铝酸根离子反应,生成了各种形式的铝酸钙,从而使得效果变差,而Ba（OH）₂不会与溶液中铝酸根离子反应。提出了用Ba（OH）₂从含有钒和钼的铝酸钠溶液中分步分离钒、钼的新技术,在合适的反应条件下钒钼的沉淀率分别可达92%和98%,并使铝酸钠溶液得到净化。热力学计算表明:当温度升高时,Ba（OH）₂与VO₄^3-反应的Gibbs自由能略微升高,而Ba（OH）₂与MoO₄^2-反应的Gibbs自由能△G更低,反应平衡常数增大,有利于反应的进一步进行。从而在热力学解释了Ba（OH）₂分离钒钼的作用机理。4.对废催化剂焙烧预处理后的镍钴渣进行了酸浸动力学研究采用硫酸作为浸出剂对镍钴渣进行了酸浸动力学研究,通过对实验数据进行线性回归,得出了钴的酸浸反应动力学方程式,镍钴渣中钴的硫酸浸出属扩散控制,该浸出反应的活化能为10.0kJ/mol。采用30%（w/w）H₂SO₄,反应温度为80℃,反应时间240min,粒度为-0.098mm+0.074mm,搅拌速度为800rpm,固液比为1:8g/ml（1g固体采用8mL浸出液）的浸出条件下,镍钴的浸出率分别可达99.0%和98.5%。5.在理论研究基础上,开发了一种废铝基催化剂综合回收的新技术:对载体氧化铝为刚玉型氧化铝的废铝基钒钼催化剂（V 0.55%、Mo 1.19%、Al₂O₃70.95%）进行了综合回收,在合适的工艺条件下,全流程氧化铝的回收率可达90.6%,纯度为99.9%;钒、钼的回收率不低于92%,分别制得钒酸钡和钼酸钡化工产品。镍、钴的回收率大于95%,可以制备硫酸镍和硫酸钴等化工产品。更多还原

【Abstract】 About 500,000～700,000 tons of spent catalysts are produced each year in the world,large amounts of precious metal,nonferrous metal or its’ oxides are used to the preparation of catalyst, the metal content of spent catalyst is not lower,even higher than the content of raw ore.Recovery of valuable metals from spent catalyst shows great economic benefit and environmental benefit.Spent Al₂O₃-based catalyst is a kind of catalyst using Al₂O₃ as the carder and vanadium/ molybdenum as active constitutent but can not be regenerated again.To date,some investigations had been conducted to recover valuable metals in spent catalyst,but the main difficulty was the efficient separation of valuable metals in solution.This dissertation had made comments on the status of comprehensive utilization of spent catalyst,carded out a great deal of theoretical analyses and experiments with the reference of literature.By the calculation of solution chemistry of Al-V-Mo system,thermodynamic calculation,molecular dynamic simulation and some testing methods,the solution chemisty of Al-V-Mo system in alkaline solution and the separation technology had been studied detalledly,the basic theory and process engineering for the comprehensive utilization of spent catalyst had been researched systematacially.Main conclusions are obtained as follows:1.Research on the solution chemistry of Al-V-Mo system in aquous solutionAccording to the calculation of solution chemistry,the solubility and existing status of Al,V and Mo in acidic and alkalic solution had been analysed in theory.The concentration logarithmic diagram of Al-V-Mo in aquous solution with different concentration and pH had been plotted,the concentration and pH on the distribution of three elements had been analysed.The concentration logarithmic diagram provides some basic data for the separation of Al,V and Mo.The solubility of V and Mo in NaOH and sodium aluminate solution had been determined, which indicated that temperature had little effect on the solubility of Mo in sodium aluminate solution,but showed great effect on the solubility of V.The solubility of V in sodium aluminate solution is about 1g/l at 20℃but 50g/l at 80℃.The potential-pH equilibrium diagram of three kinds of system had been figured according to the data in literatures,the transformation of different valent state ions had been discussed.The diagrams provided theoretical foundation for the comprehensive utilization of spent catalyst.Material Studio was firstly used to molecular dynamic simulation of Al-V-Mo in aqueous solution.The results indicate that the formation of clustering of aluminates in solution,and the clusters are stabilized by sodium ions.Furthermore,the clusters make a contribution to the formation of polyaluminate.The molecular dynamic simulation results of V and Mo at three kinds of pH are in good accordance with spectroscopy results reported in the literatures.2.The concentration logarithmic diagram and potential-pH diagram of Ca（Ba）-V（Mo）-H₂O was firstly studied,the following are the results:The concentration logarithmic diagram of Ca-V（Mo）-H₂O indicated that the stable region of calcium vanadate and calcium molybdate enlarged,the residual concentration of V and Mo in soulution lowered with the increasing of temperature.The concentration logarithmic diagram of Ba-V（Mo）-H₂O indicated that the stable region of barium vanadate and barium molybdate enlarged,the residual concentration of V and Mo in soulution lowered with the increasing of temperature.In constrast to the diagram of Ca-V（Mo）-H₂O,barium showed better effect on the precipitation of V and Mo than calcium under the same condition,the residual concentration of V and Mo in soulution can be down to 10^-7.3and 10^-7.0mol/l in the system of Ba-V（Mo）-H₂O when temperature is 100℃.The potential-pH diagram of Ca（Ba）-V（Mo）-H₂O indicates that the stable region of calcium vanadate and barium vanadate are larger than that of calcium molybdate and barium molybdate. When vanadium and molybdenum coexist in the solution,calcium and barium will be inclined to react with vanadium firstly.3.The precipitation separation of alumina,vanadium and molybdenum had been conducted in the simulated solution,results are listed in the following:CaO,Ba（OH）₂ and CaCl₂ showed good effect on the precipitation of vanadium and molybdenum in the solution of V（Mo）-H₂O,the precipitation of vanadium and molybdenum can be 98%under suitable reaction conditions.In the solution of V（Mo）-Al-H₂O,the effect of CaO and CaCl₂ on the precipitation of vanadium and molybdenum was bad,however,Ba（OH）₂ still showed good effect on the precipitation of vanadium and molybdenum.Thermodynamic calculation indicated that the bad effect of CaO and CaCl₂ was ascribed to the formation of many kinds of calcium aluminate which was formed by calcium and large amounts of aluminate ion in the solution,but Ba（OH）₂ can not react with aluminate ion in solution.Ba（OH）₂ was firstly brought forward and used to separate vanadium,molybdenum and alumina successively in the sodium alumination solution.Under optimum condition,the precipitation of V and Mo can be 92%and 98%respectively,at the same time sodium aluminate solution was purified.Thermodynamic calculation indicated,with the increasing of temperature,the Gibbs free energy of reaction between Ba（OH）₂ and VO₄^3-slightly rose.However,the Gibbs free energy of reaction between Ba（OH）₂ and MoO₄^2-lowered to a more negative value,equilibrium constant of reaction between Ba（OH）₂ and MoO₄^2-enlarged.Hence,increasing temperature was good to the reaction between Ba（OH）₂ and MoO₄^2-.That is why Ba（OH）₂ can be used to separate vanadium and molybdenum successively in the sodium aluminate solution.4.Research on the kinetics of cobalt leaching from spent catalystKinetics of cobalt leaching from spent catalyst was investigated.A kinetic model was suggested to describe the leaching process of cobalt from spent catalyst,leaching kinetics indicated that diffusion through the product layer is the rate controlling process during the reaction. The activation energy was determined to be about 10.0kJ/mol.Leaching rate of about 98.5%of cobalt and 99.0%of nickel were achieved using -150+200 mesh particle size at a reaction temperature of 80℃for 240min reaction time with 30%（w/w）sulfuric acid concentration and the solid/liquid ratio of 1:8g/ml.5.New technology had been developed to recover valuable metals from one kind of spent catalyst on the basis of theoretical research,the results are listed as follows:With regard to a kind of a-Al₂O₃ based spent catalyst（V 0.55%、Mo 0.48%、Al₂O₃70.95%）, the purity of alumina is 99.9%produced with carbonation decomposition process,the recovery of alumina can reach 90.6%in the whole process,the recovery of vanadium and molybdenum is 94.8%and 92.6%,respectively.更多还原