13C and 1H Magic-Angle-Spinning NMR Studies of the Conversion of Methanol over Offretite/Erionite Intergrowths

Article abstract of DOI:10.1021/j100180a072

13C and 1H NMR with magic-angle spinning (MAS) has been used to monitor the conversion of methanol to low-molecular-weight hydrocarbons over intergrowths of the zeolites offretite and erionite with varying contents of the two structures.The sample richest in offretite shows the lowest selectivity to light olefins; this is correlated to the ease of formation of long-chain polymeric hydrocarbons within the intracrystalline space of offretite.The presence of such polymers is confirmed by 13C MAS NMR and we attribute it to the uninterrupted one-dimensional pore system.In erionite, where the channel system is constricted at every 15.2 Angstroem, polymers cannot form.It appears that a degree of channel 'tortuosity' is preferable in reactions which produce readily oligomerizable molecules, in order to prevent undesirable side reactions.