硝酸工厂钯合金捕集网回收铂的分析

Analysis of Platinum Recovery by Palladium Alloy Catchment Gauzes in Nitric Acid Plants

自从 70年代在硝酸工厂引入Pd -Au合金捕集网以回收从催化网上损失的铂以来 ,钯合金捕集和回收铂的机理一直受到研究者和生产者的关注。本文分析了在流动氧气氛和氨氧化反应过程中Pd的表面化学状态 ,表明在 80 0℃以上温度Pd的表面应是 1种多层结构 :光亮的Pd金属表面复盖着一层薄的Pd金属蒸气 ,Pd蒸气上又复盖着一层PdO蒸气。Pd合金捕集网回收铂的机制与Pd的表面状态有关 ,它的高的回收率归因于这种独特的多层结构和Pd对PtO2 的还原能力。任何损害这种表面多层结构或Pd的氧化特性的因素都降低Pt回收率。因此 ,含高浓度贱金属 (如Ni)的Pd合金捕集网不能期望有高的Pt回收率。

Using analyses of the surface chemical species formed on palladium in both conditions of flowing oxygen and the ammonia oxidation reaction,it is confirmed that the surface of palladium,at temperatures above 800℃,is a multilayer structure with the bright palladium metal surface being overed by a thin layer of palladium metal vapour and then by a layer of palladium oxide(PdO)vapour. The mechanism of the platinum recovery is related to the surface state of the palladium, and the high recovery rate by the palladium alloy catchment gauzes is attributted to this unique multilayer structure and to the ability of palladium to reduce platinum oxide. Damage to either the surface multilayer structure or the oxidation characteristics of palladium decrease the platinum recovery rate. Thus,the catchment gauzes made from palladium alloys containing high concentration of based metal solutes,such as nickel,cannot be expected to have such a high platinum recovery rate.