Application of Inelastic Neutron Scattering to the Methanol-to-Gasoline Reaction Over a ZSM-5 Catalyst

Abstract

Inelastic neutron scattering (INS) is used to investigate a ZSM-5 catalyst that has been exposed to methanol vapour at elevated temperature. In-line mass spectrometric analysis of the catalyst exit stream confirms methanol-to-gasoline chemistry, whilst ex situ INS measurements detect hydrocarbon species formed in/on the catalyst during methanol conversion. These preliminary studies demonstrate the capability of INS to complement infrared spectroscopic characterisation of the hydrocarbon pool present in/on ZSM-5 during the MTG reaction. Graphical Abstract& David Lennon

The Effect of Co-feeding Methyl Acetate on the H-ZSM5 Catalysed Methanol-to-Hydrocarbons Reaction

“…INS has considerable potential for investigating zeolite catalysts as it provides access to the vibrational spectra of used catalysts over a wide frequency range without obstruction from zeolite lattice modes [12]. We have recently reported the use of INS to study HZSM-5 catalysts used in the MTH reaction [13,14] and the role of DME in the MTH reaction chemistry [15].…”

Molecular behaviour of phenol in zeolite Beta catalysts as a function of acid site presence: a quasielastic neutron scattering and molecular dynamics simulation study

“…Techniques based on neutron spectroscopy are of growing significance in the field of heterogeneous catalysis, 22 both in the study of the catalyst itself, 23,24 and investigation of the relevant molecular species upon adsorption. 25,26 Quasielastic neutron scattering (QENS) is particularly effective in the study of microporous catalysts, 27 allowing the measurement of molecular movements taking place over timescales of 2 ps-100 ns depending on the instrument, and thus it may be employed to measure both nanoscale diffusion, [28][29][30] and also local motions such as rotation. [31][32][33][34] Crucially, this technique can be employed on sub-micron crystals, in contrast to other methods, such as PFG-NMR, which have timescales from micro-to milliseconds and hence need crystal sizes in the order of micrometres or larger to be able to measure intracrystalline diffusion.…”

Characterization of Metal‐zeolite Composite Catalysts: Determining the Environment of the Active Phase

“…After measuring the INS spectrum, the authors determine that sp2 and sp3 hybridized C−H species are formed at a reaction temperature at 623 K, while hydrogen bonded methanol/methoxy species are produced at 473 K. Howe et al. have further extended the use of INS to observe the full vibrational spectrum of the “hydrocarbon pool” mechanism, which takes advantage of the wide frequency vibrations (up to 4500 cm −1 ) that are detectable by INS . In this mechanism, shown in Figure , two catalytic cycles operate in parallel: Cycle I ) alkenes are methylated and later cracked; Cycle II ) aromatics are methylated and later dealkylated .…”

“…An advantage of INS over infrared spectroscopy is that the frequency of vibrations do not overlap with the zeolite external framework. Therefore, INS can be applied to all catalysts without any sample preparation or coke removal post‐reaction …”