COKE FORMATION THROUGH THE REACTION OF ETHENE OVER HYDROGEN MORDENITE .3. IR AND C-13-NMR STUDIES

IR and high-resolution solid-state 13C-NMR studies provided evidence for successive steps in coke formation upon reaction of ethene over the zeolite hydrogen mordenite. Adsorbed at room temperature, ethene polymerizes to branched and possibly also linear alkanes. Upon heating up to 500 K, the alkanes isomerize and crack. Meanwhile, the 13C-NMR spectra show the formation of carbocations of alkylic, allylic and aromatic nature. Above 500 K, high-temperature coke develops under formation of alkylaromatics and subsequently small polyaromatic and/or polyphenylene molecules. Over dealuminated hydrogen mordenites, ethene also forms paraffinic deposits at low temperatures. Above 500 K, however, a substantial amount of C1-C4 alkanes are formed together with unsaturated species.