Thomas R. Krawietz

Chloromethoxyl and dichloromethoxyl formation on zeolite ZnY, an in situ NMR and flow reactor study

In situ13C and27Al MAS NMR and flow reactor studies were used to study the decomposition of dichloromethane and chloroform on zeolite ZnY. The initially formed products were framework-bound chloromethoxyl (from dichloromethane) and dichloromethoxyl (from chloroform) species, analogous to the non-halogenated alkoxyls observed in previous investigations. The principal components of the13C chemical shift tensors were: chloromethoxyl,δ11 = 116 ppm,δ22 = 79 ppm andδ33 = 37 ppm; dichloromethoxyl,δ11= 128 ppm,δ22= 91 ppm andδ33 = 65 ppm. Formation of both species occurred at 298 K, and each decomposed at 423 K. This decomposition formed HCl which dealuminated the zeolite (as monitored by27Al MAS NMR) causing deactivation (flow reactor studies). Further evidence for the destruction of the zeolite was the NMR observation of CO formation, implying incorporation of oxygen from zinc hydroxyl or framework sites. Although ZnY is shown to be unsuitable for catalytic chlorocarbon destruction, the observation of chloromethoxyl and dichloromethoxyl species is significant, and the formation of halogenated alkoxyl species should be considered in future investigations of halocarbon chemistry on oxides and molecular sieves.

Characterization of poly(carbon monofluoride) by 19F and 19F to 13C cross polarization MAS NMR spectroscopy

High speed 19F MAS NMR and 13C MAS NMR with 19F to 13C cross polarization allows spectroscopic identification of monofluorinated and geminally difluorinated carbon species in poly(carbon monofluoride).

Two-dimensional correlation of solid state and liquid state NMR using a laser temperature jump

Abstract Solid state NMR spectra and the corresponding liquid state spectra have been interrelated through two-dimensional experiments with a fast temperature jump during the mixing time. This jump must, as a minimum requirement, be shorter than the relevant spin lattice relaxation times, and was implemented using a CO 2 laser heater. As the first demonstration of this experiment we report a 2D 1 H solid-liquid spectrum of camphor. Suggested applications of future 2D temperature jump experiments include studies of reversible chemical reactions, reorientational dynamics, phase behavior, and magnetic and electrical properties.

13C MAS NMR observation of photoproducts in zeolites and their further reaction on acid sites

In situ 13 C MAS NMR characterization following UV irradiation of two FAU zeolites with adsorbed benzaldehyde or acetophenone and toluene allows observation of photoproducts and subsequent acid-catalysed chemistry.

19 F to 1H and 1H to 19F Cross polarization MAS NMR of trifluoroethanol chemisorbed on magnesium oxide

19 F magic angle spinning NMR studies of surfaces are greatly facilitated by 1H to 19F cross polarization and 1H decoupling.