Process for the recovery of noble metals

Claim 1

A process for the recovery of a noble metal which has volatilised or become detached in a very finely divided state from the surface of a noble metal catalyst gauze in an exothermic reaction of a gaseous mixture, preferably a mixture of ammonia and air to form nitrous gases, carried out under an excess pressure of at least one atmosphere gauge, said process comprising: providing, downstream of said gauze in the direction of gas flow therefrom, a noble metal absorbing and intercepting bed formed of granular acid-soluble alkaline earth metal oxide material, said bed being in the form of channels filled by said material and separated by open channels extending in the direction of gas flow from said gauze to said bed, said bed having a total external gas incident surface of 1.5 to 20 times the cross-sectional area encompassed by said material filled channels and said open channels taken in a plane transverse to said direction, said bed being maintained at a temperature of from about 600° to 900°C; passing the gaseous reaction mixture, after having passed the noble metal catalyst gauze, in said direction into a portion of said open channels; then directing said gaseous reaction mixture transverse to said direction through said material filled channels, thereby removing noble metal from said gaseous reaction mixture, and into the remainder of said open channels, said material filled channels having a thickness in the direction of gaseous flow therethrough of 20 to 40 mm; and thereafter, when the intercepting action of said material of said bed has been exhausted, recovering the noble metal removed by said bed by dissolving said material in acid.