Characterization of structure and combustion behavior of the coke formed on a hydroisomerization catalyst

Catalytic stability of a Pd/H-Mordenite catalyst for C₅/C₆ hydroisomerization was tested in a laboratory reactor for 1000 hours. The content, chemical composition and structure of the coke formed on the catalyst discharged from a pilot reactor working in an accelerated condition was characterized using XRD, EPR, MAS-NMR, FTIR and TPO techniques. The catalyst shows stable catalytic activity and selectivity during 1000 hours. The nature of the coke and its combustion behavior depended upon time on stream and varied with the catalyst bed length. As time on stream increased, coke initially formed on palladium metals and then moved to acidic sites on the support where polyaromatic or pseudographite-like structures were formed through further acid catalyzed reactions.