Methyltrioxorhenium heterogenized on commercially available supporting materials as cyclooctene metathesis catalyst

Methyltrioxorhenium (MTO) is immobilized on various commercially available supporting materials by sublimation under vacuum. Up to 15 wt% MTO (10 wt% Re) can be immobilized on the different supporting materials. Metathesis experiments with cis-cyclooctene as substrate are performed aiming at a high yield of low molecular weight metathesis products (dimers, trimers, tetramers), which are interesting for aroma and flavour industries. Up to ca. 60% of these desired products can be obtained. A high rhenium loading leads usually to good catalytic activities of the materials in the cyclooctene metathesis. Prolonged reaction times lead to higher yields of the high molecular weight metathesis products. When the same catalyst material is used repeatedly in several catalytic runs, leaching of the grafted Re compounds plays an increasing role, resulting in a reduction of the catalyst performance. None of the examined commercially available carrier materials, however, presents an ideal means for the heterogenization of MTO to obtain particularly high amounts of the desired low molecular weight metathesis products of cyclooctene.