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

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

Structural analysis of IPC zeolites and related materials using positron annihilation spectroscopy and high-resolution argon adsorption

ETH authors thanks for the grant ETH 33 15-1. PE and JČ acknowledge the financial support from the Czech Science Foundation (P106/12/0189). JPR and JČ gratefully acknowledge the financial support from the European Union Seventh Framework Programme (FP7/ 2007-2013) under grant agreement no. 604307. HRTEM characterization was performed at the Advanced Microscopy Laboratory (LMA) and the research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreement 312483 – ESTEEM2 (Integrated Infrastructure Initiative-I3).The advanced investigation of pore networks in isoreticular zeolites and mesoporous materials related to the IPC family was performed using high-resolution argon adsorption experiments coupled with the development of a state-of-the-art non-local density functional theory approach. The optimization of a kernel for model sorption isotherms for materials possessing the same layer structure, differing only in the interlayer connectivity (e.g. oxygen bridges, single- or double-four-ring building units, mesoscale pillars etc.) revealed remarkable differences in their porous systems. Using high-resolution adsorption data, the bimodal pore size distribution consistent with crystallographic data for IPC-6, IPC-7 and UTL samples is shown for the first time. A dynamic assessment by positron annihilation lifetime spectroscopy (PALS) provided complementary insights, simply distinguishing the enhanced accessibility of the pore network in samples incorporating mesoscale pillars and revealing the presence of a certain fraction of micropores undetected by gas sorption. Nonetheless, subtle differences in the pore size could not be discriminated based on the widely-applied Tao-Eldrup model. The combination of both methods can be useful for the advanced characterization of microporous, mesoporous and hierarchical materials.PostprintPeer reviewe

A comparison of experimental procedures for the application of infrared spectroscopy to probe the surface morphology of an alumina-supported palladium catalyst

Structure/function relationships in heterogeneous catalysis play an important role in catalyst design strategies. The combination of chemisorption of suitable probe molecules alongside application of infrared spectroscopy is an established technique for providing information on the metal crystallite morphology of supported metal catalysts. Following a review of key literature on this topic, a variety of experimental arrangements that may be adopted for this task are examined. Specifically, the adsorption of CO over a 5wt% Pd/Al2O3 catalyst is investigated using transmission and diffuse reflectance sampling options and two research grade spectrometers. Although comparable spectra are obtained on all the platforms examined, differences are noted. In particular, temperature-programmed IR spectroscopy on one platform enables resolution of two features assigned to linear CO bound to the Pd particles. The relevance of this sub-division of terminal sites with respect to selective hydrogenation reactions is briefly considered

The application of inelastic neutron scattering to investigate a hydrogen pre-treatment stage of an iron Fischer-Tropsch catalyst

The effect of a hydrogen pre-treatment step on an iron based Fischer-Tropsch catalyst applied to the CO hydrogenation reaction at 623 and 723 K has been investigated by inelastic neutron scattering (INS). The catalyst cannot support methane production over a 6 h period of reaction at 623 K but it is active at 723 K. The INS spectrum indicates the presence of a predominantly aliphatic hydrocarbonaceous overlayer for the post-reaction 623 K sample, whereas the spectrum for the 723 K sample is assigned to an overlayer comprising partially hydrogenated polycyclic aromatic compounds. The hydrocarbonaceous overlayer associated with the active phase of the catalyst is modified by the hydrogen pre-treatment step. The INS spectra are interpreted with reference to microreactor studies, powder X-ray diffraction, temperature-programmed oxidation and transmission electron microscopy. The hydrogen pre-treatment stage favours the formation of amorphous carbon and is deemed not to convey any advantage with respect to CO hydrogenation activity