Importance

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Abstract

This invention is a method for the recovery of precious metal selected from the group consisting of platinum and rhodium lost from a platinum-containing catalyst during ammonia oxidation processes at a temperature above 850.degree. C. which comprises bringing said lost precious metal into contact with a foraminate element fabricated from a material consisting essentially of palladium, by itself, or palladium and a minor amount of another metal selected from the group consisting of other platinum group metals, Ni, Au, Mn, Mg, Cr, C, B, Cu and alloys of mixtures thereof characterized by (a) a novel configuration whereby the initial product of the formula: curve to flat ratio (C/F) multiplied by mesh size (N) and wire diameter (d.sub.w), for the element is greater than at least about 0.9 and (b) where, for a given nitrogen throughput, the weight recovery efficiency is a function of the curve to flat ratio (C/F), wire diameter (d.sub.w) and mesh size (N) combination and weight recovery efficiency is improved by increasing the mesh size (N) for a given wire diameter, increasing the wire diameter (d.sub.w) for a given mesh size, and increasing the curve to flat ratio (C/F) to a ratio of above about .pi./2. Preferably, the initial product of the formula is in the range of from about 0.9 to about 10. The element is preferably selected from the group consisting of woven gauze, knitted fabric, fibe and combinations thereof. It is preferred that the element consist essentially of palladium by itself or palladium alloyed with one or more metals selected from the group consisting of nickel, cobalt, platinum, ruthenium, iridium, gold, silver and copper.

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First Claim