Issue 40, 2009

Para-hydrogen induced polarization in homogeneous phase—an example of how ionic liquids affect homogenization and thus activation of catalysts

Abstract

Para-hydrogen induced polarization (PHIP) is observed in an organic solvent-free homogeneous catalyst/substrate system using ionic liquids. The hydrogenation reactions are performed employing a Rh-catalyst/ionic liquid system without further organic solvents. The PHIP phenomenon is demonstrated for the ethyl acrylate system. Small amounts of ionic liquids (ILs) containing weakly coordinating anions such as [Tf2N] act as homogenizing cosolvents for the catalyst in ethyl acrylate, leading to a dramatic activation of the catalytic process and a high PHIP signal enhancement. The achieved enhancement depends strongly on the viscosity of the ethyl acrylate/IL mixture. Furthermore, by deliberate choice of the IL constituents it was possible to design a model system exhibiting both sufficient catalyst solubility and biphasic liquid–liquid behavior. This shows that in ionic liquids PHIP enhancements followed by a fast quantitative removal of the para-hydrogenated product from the catalyst phase is in principle possible. The possible PHIP enhancement factors will depend strongly on the design of a suitable hydrogenation reactor.

Graphical abstract: Para-hydrogen induced polarization in homogeneous phase—an example of how ionic liquids affect homogenization and thus activation of catalysts

Article information

Article type
Paper
Submitted
24 Apr 2009
Accepted
07 Jul 2009
First published
13 Aug 2009

Phys. Chem. Chem. Phys., 2009,11, 9170-9175

Para-hydrogen induced polarization in homogeneous phase—an example of how ionic liquids affect homogenization and thus activation of catalysts

T. Gutmann, M. Sellin, H. Breitzke, A. Stark and G. Buntkowsky, Phys. Chem. Chem. Phys., 2009, 11, 9170 DOI: 10.1039/B908198D

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