Messung intrakristalliner Diffusions-Reaktions-Profile in Zeolithen mittels IR-Imaging
Zusammenfassung der Projektergebnisse
The aims of the Stuttgart group in the current project were: (i) To synthesize, characterize, and deliver high-quality large-crystal zeolites to the Leipzig group and (ii) to create and exchange the knowledge on selecting a suitable catalytic reaction for diffusion studies to be performed by infrared (IR) and interference ((IF) microscopy at the University of Leipzig. For this purpose, large crystals of one-dimensional (MOR-type), two-dimensional (FER-type) and three-dimensional (MFI-type) zeolites were successfully synthesized and delivered to the Leipzig group for their diffusion studies. The delivered zeolite specimens are presently under investigation and are expected to provide direct experimental evidence of transport phenomena in nanoporous host-guest systems of fundamental relevance, including the observation of intracrystalline diffusion fluxes under the conditions of host anisotropy and multi-component adsorption. A systematic study was devoted on the solvothermal synthesis of large-crystal allsilica, aluminum-containing, and boron-containing ferrierite zeolites. The influence of different alkylamines, viz. propylamine, butylamine, and pentylamine as templates and pyridine as solvent in the solvothermal synthesis was studied in detail. In the case of all-silica and boron-containing ferrierite zeolites, the use of different templates and crystallization times led to the formation of large crystals with hexagonal/octagonal, stretched hexagonal, and rectangular flat morphologies. In contrast, for aluminum-containing ferrierite zeolites, rectangular flat crystals were obtained irrespective of the alkylamine used in the synthesis. 27Al and 11B MAS NMR spectroscopic investigations revealed the successful incorporation of aluminum and boron into the framework of the FER-type structure. Several catalytic reactions, viz. the dehydration of isopropanol, isobutanol, tertbutanol, and propene metathesis were screened for their suitability in a fixed-bed flow reactor at 1 bar. The dehydration of tert-butanol was identified as the best suited reaction for the Leipzig group, as significant conversion was attained at temperatures below 373 K. Thus, we propose that the dehydration of tert-butanol will be used for diffusion investigations by infrared and interference microscopy. In addition, the dehydration of isopropanol could be useful as well, if and when temperatures above 373 K can be applied by the Leipzig group. The synthesis of methyl tertiary butyl ether (MTBE) from methanol and isobutene could be another option provided that the experimental set-up in Leipzig can be adapted to catalytic reactions with two reactants.
Projektbezogene Publikationen (Auswahl)
- In-Depth Study of Mass Transfer in Nanoporous Materials by Micro-Imaging, Chem. Ing. Tech. 2011, 83, 2211-2218
F. Hibbe, J.M. van Baten, R. Krishna, C. Chmelik, J. Weitkamp, J. Kärger
- Micro-Imaging of Transient Guest Profiles in Nanochannels, J. Chem. Phys. 2011, 135, 184201
F. Hibbe, V.R.R. Marthala, C. Chmelik, J. Weitkamp, J. Kärger
- Solvothermal Synthesis and Characterization of Large-Crystal All-Silica, Aluminum-, and Boron-Containing Ferrierite Zeolites, Chem. Mater. 2011, 23, 2521-2528
V.R.R. Marthala, M. Hunger, F. Kettner, H. Krautscheid, C. Chmelik, J. Kärger, J. Weitkamp
