A new in situ chemical reactor for studying heterogeneous catalysis by NMR: The GRASSHopper

A new device/technique, Gas Reactor And Solid Sample Hopper designated GRAS SHopper II, is described as an alternative to magic-angle spinning (MAS) fo r in situ NMR experiments on reacting heterogeneous systems. It is capable of supporting NMR studies of heterogeneous catalysis in the batch mode, in the flow reactor mode and for measurements of chemical kinetics. This new a pproach is based on the technique of magic-angle hopping (MAH). Characteris tics, advantages, limitations and potential areas of application are descri bed. Preliminary results are shown on the formation, subsequent hydrolysis and then regeneration (via dehydration) of (C6H5)(3)C+ carbocations in zeol ite HY cavities, and on the gas-solid polymerization of ethylene on a Cp2Zr Cl2/MAO/SiO2 'supported' catalyst. (C) 1999 Elsevier Science B.V. All right s reserved.