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Morphological and chemical changes in palladium alloy gauzes used for platinum recovery in high‐pressure ammonia oxidation plants
Author(s) -
Fierro J. L. G.,
Palacios J. M.,
Tomás F.
Publication year - 1989
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740140907
Subject(s) - x ray photoelectron spectroscopy , platinum , palladium , alloy , scanning electron microscope , faceting , materials science , recrystallization (geology) , metallurgy , chemical state , chemistry , analytical chemistry (journal) , catalysis , chemical engineering , crystallography , composite material , geology , environmental chemistry , paleontology , biochemistry , engineering
Scanning electron microscopy (SEM) combined with energy dispersive x‐ray analysis (EDX) and x‐ray photoelectron spectroscopy (XPS) have been used to study platinum recovery by catchment on palladium alloy gauzes placed at the outlet of high‐pressure plants for ammonia oxidation. It has been found that Pt evaporated from the Pt–Rh catalyst gauzes is efficiently recovered by a pack of Pd gauzes situated downstream. During this process important geometrical, morphological and chemical changes take place. In general, the wire diameter increase depends on the gauze position in the pack and also on the initial wire diameter. This diameter increase, due to Pt alloying, is accompanied by deep recrystallization and faceting. Chemical analysis by both EDX and XPS revealed that the Pt/Pd ratios depend markedly on the position in the catchment pack, and also on the orientation with respect to the stream (front or back face). In addition, nodular Rh 2 O 3 particles randomly distributed over the Pd alloy surface have been observed. An explanation for these features is given.