Decomposition and reducibility of rhodium clay catalyst precursors

Abstract

The decomposition of palygorskite-, silica- and titania-supported rhodium catalyst precursors under helium and hydrogen is studied using thermal analytical methods: thermogravimetry and differential scanning calorimetry (TGDSC). Precursors have been prepared from an organometallic rhodium species, [Rh(nbd)(Me 2CO) x ]ClO 4, and different supports. Supported rhodium (I) and -(III) are reduced under hydrogen at various temperatures from 448 K to 513 K depending on the support, producing active rhodium in a hydrogenation reaction. The reduction temperature observed is discussed from the viewpoint of metal-support interaction and therefore the acidity of the support. Catalytic activity in the gas-phase for 1-hexene hydrogenation was performed by catalysts reduced at two different temperatures; one at that determined by TGDSC, and the other at 673 K. All catalysts prepared present higher activities if they are reduced at their minimum reduction temperatures found by TGDSC than if they are reduced at 673 K.