A Large Sample Volume Magic Angle Spinning Nuclear Magnetic Resonance Probe for In-Situ Investigations with Constant Flow of Reactants
A large-sample-volume constant-flow magic angle sample spinning (CF-MAS) NMR probe is reported for in-situ studies of the reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions. In our approach, the reactants are introduced into the catalyst bed using a fixed tube at one end of the MAS rotor while a second fixed tube, linked to a vacuum pump, is attached at the other end of the rotor. The pressure difference between both ends of the catalyst bed inside the sample cell space forces the reactants flowing through the catalyst bed, which improves the diffusion of the reactants and products. This design allows the use of a large sample volume for enhanced sensitivity and thus permitting in-situ 13C CF-MAS studies at natural abundance. As an example of application, we show that reactants, products and reaction transition states associated with the 2-butanol dehydration reaction over a mesoporous silicalite supported heteropoly acid catalyst (HPA/meso-silicalite-1) can all be detected in a single 13C CF-MAS NMR spectrum at natural abundance. Coke products can also be detected at natural 13C abundance and under the stopped flow condition. Furthermore, 1H CF-MAS NMR is used to identify the surface functional groups of HPA/meso-silicalite-1 under the condition of in-situ drying . We also show that the reaction dynamics of 2-butanol dehydration using HPA/meso-silicalite-1 as a catalyst can be explored using 1H CF-MAS NMR.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1034228
- Report Number(s):
- PNNL-SA-82533; 32911; 35599; KC0302010; TRN: US201203%%451
- Journal Information:
- Physical Chemistry Chemical Physics, Vol. 14, Issue 7; ISSN 1463-9076
- Country of Publication:
- United States
- Language:
- English
Similar Records
Condensed Phase Deactivation of Solid Brønsted Acids in the Dehydration of Fructose to Hydroxymethylfurfural
Sealed rotors for in situ high temperature high pressure MAS NMR
Related Subjects
ABUNDANCE
CATALYSTS
COKE
DEHYDRATION
DESIGN
DIFFUSION
DRYING
FUNCTIONALS
INORGANIC ACIDS
NUCLEAR MAGNETIC RESONANCE
PROBES
ROTORS
SENSITIVITY
VACUUM PUMPS
In-situ NMR
constant flow
sensitivity enhancement
natural abundance 13C NMR
catalyst reaction
2-butanol dehydration
heteropoly acid
Environmental Molecular Sciences Laboratory