微波焙烧失效Pd-Rh金属催化剂的强化机理研究

The spent automobile exhaust catalyst has become the important secondary sources of platinum group metals. The Pd-Rh noble metal catalyst is widely used in gasoline vehicle. The spent Pd-Rh automobile exhaust catalyst includes inclusion containing Pd and Rh, and oxide such as PdO and Rh2O3. The present recovery processes of Pd-Rh have many disadvantages including low recovery and tedious process, due to that the inclusion and oxide are insoluble in aqua regia. The project will use the spent catalyst as the raw material, open the inclusion via the selective heating of microwave, and cooperatively transform dissoluble oxide phases. The project will study the change of phase and surface morphology of the inclusion under different microwave power density and reveal the open mechanism of the inclusions via charactering the occurrence behavior of precious metals and the electromagnetic characteristics of high temperature of the spent catalyst and its composition. The appropriate transforming agents will be choose according to theoretical calculation. The transformation rules of the insoluble oxide to soluble phase will clarify under the synergistic action of microwave and transforming agent according to the system microwave baking experiment and comparing with the conventional roasting. The relationship between different leaching agents, leaching conditions and the leaching rate of precious metals will be studied. The migration and distribution of noble metal and impurity elements will be proved. The technical prototype will be established. The aim of the project is to develop clean, low consumption and high efficiency method for the recovery of precious metals. The implementation of the project will reveal the mechanism of microwave strengthening reaction, which has an important exemplary function for the efficient recovery of the inclusion type and insoluble precious metal materials.

失效汽车尾气催化剂已成为铂族金属重要的二次资源，普遍应用于汽油车的Pd-Rh贵金属型催化剂失效后，产生了难溶于王水的含有Pd和Rh的α-Al2O3包裹体、氧化物（PdO与Rh2O3），导致处理工艺存在回收率低或工艺繁冗等缺点。本项目拟以该失效催化剂为原料，提出微波选择性加热打开包裹体、协同转化氧化物难溶相的新思路；通过表征贵金属元素的赋存行为、催化剂及组分的微波高温电磁特性，研究不同功率密度下包裹体物相、形貌的变化，揭示微波解离包裹体机制；通过理论计算选取合适的多种转化剂，开展系统微波焙烧实验，与常规焙烧对比，阐明微波与转化剂协同作用下氧化物难溶相向可溶相转化的规律；研究不同浸出剂、浸出条件与贵金属浸出率的关联关系，探明贵金属以及杂质元素的迁移分布规律，进而建立技术原型，实现贵金属的清洁、低耗、高效回收。项目的实施将揭示微波强化反应机理，对包裹型、难溶贵金属物料的高效回收具有重要示范作用。

针对含钯和铑的汽车废催化剂，项目组采用圆柱法测量了介电性能，表明废催化剂是中等吸波物料。结合成分分析建立了微波焙烧-水浸回收汽车废催化剂中钯和铑的新方法。对比研究发现硫酸氢钠作为浸出剂具有明显的优势。采用单因素和响应曲面法系统研究了保温时间、焙烧温度和物料试剂配比对钯和铑的浸出率的影响。影响因素交互分析表明物料试剂配比和焙烧温度对钯和铑浸出率的影响最大。理论和试验证明在物料试剂配比:1:10, 焙烧温度510℃, 保温时间60 min的最佳条件下钯和铑的浸出率分别为99.33%和95.48%。与常规试验对比表明微波焙烧-水浸法将温度降低了100 ℃，时间缩短了约50 %，试剂量减少20 %，钯和铑的浸出率分别提高了约6 %和3 %。动力学分析表明反应活化能E、频率因子A均随微波功率的变化而变化，且微波功率对化学反应的影响是非线性关系。物相和成分分析表明微波焙烧促进了废催化剂、Al2O3、铂族金属与硫酸氢钠的化学反应，进而打开了废催化剂和Al2O3包裹体形成的包裹体。硫酸氢钠和废催化剂的复合体系的升温曲线和介电特性表明硫酸氢钠提高了体系的微波吸收能力。总之，微波作用有效促进扩散和反应过程的进行，提高了钯和铑的浸出率。项目采用8-氨基喹啉改性聚甲基丙烯酸缩水甘油酯(AQ-PGMA)制备了一种从溶液中回收Pd(II)的新型树脂。该树脂在HCl > 0.4 mol/L体系中对Pd(II)的吸附量高达267.90 mg/g，且具有良好的再生性和选择性。经本项目的实施，已发表论文9篇（其中1篇为接受），申报发明专利3件；项目负责人王仕兴晋升为正高级工程师，参与人郑汝莲晋升为高级工程师。项目执行期间培养硕士研究生3名，参加国内外学术交流7次。