Influences of zeolite structure on formation and location of coke: A 129Xe and 13C CP-MAS NMR study

Abstract

129Xe and 13C CP-MAS NMR have been used to study coking and deactivation behavior of fouled H-beta, H-mordenite, H-ZSM-5 and H-USY zeolites during ethylbenzene disproportionation reaction. The nature and preferable location of coke are investigated for two different reaction severities, namely at low conversions (5–15 wt%) where only disproportionation reactions are expected to take place and high conversions (25–45 wt%) at which side reactions such as cracking may also occur. At low conversion, cokes are alkyl aromatic in nature and consist of both soft and hard cokes, whereas at high conversion only less volatile polyaromatic hard cokes are present. The preferred location of the carbonaceous residues is found to be strongly dependent on the reaction severity as well as the framework structure of the zeolitic catalysts.