Methyl tertiary-butyl ether synthesis on zeolite HBeta investigated by in situ MAS NMR spectroscopy under continuous-flow conditions

In situ MAS NMR spectroscopy was applied to investigate the synthesis of methyl tertiary-butyl ether (MTBE) over zeolite HBeta (n(Si)/n(Al) = 15.8) under continuous-flow conditions. Preliminary catalytic tests with on-line gas chromatographic analysis of the reaction products revealed an activity of zeolite HBeta in the MTBE synthesis comparable with that of Amberlyst-15. By exposing the calcined zeolite, filled into an MAS NMR rotor, to a flow of nitrogen gas loaded with methanol and isobutene, the interaction of these reactant molecules with the zeolite OH groups and the dimerization and oligomerization of isobutene were studied. C-13 MAS NMR spectroscopy performed during the conversion of a methanol/isobutene mixture over zeolite HBeta yielded signals at 77 ppm to 90 ppm due to secondary and tertiary carbon atoms of alkoxy complexes formed at the zeolite framework. (C) 1998 Elsevier Science B.V. All rights reserved.