Complete oxidation of acetone over manganese oxide catalysts supported on alumina- and zirconia-pillared clays

The complete oxidation of acetone has been studied over a series of manganese oxide catalysts supported on the unpillared and the Al- and Zr-pillared forms of two natural clays of the smectite class (a montmorillonite and a saponite). The temperatures required for total combustion of acetone over the several catalysts ranged from 610 to 660 K at the relatively low WMn/Fin ratio of 0.40 gMn min mmolacetone−1 used. A significant influence of the clay supports characteristics on the catalytic performance has been found. According to the general behaviour of the various catalysts throughout the light-off tests, the following order of improving catalytic performance can be established with respect to the pillars composition: Al-pillared clays<unpillared clays<Zr-pillared clays. For a given type of pillar, the performance of the catalyst supported on the montmorillonite was better than that of the saponite-supported one. The stability with time-on-stream was higher for the catalysts supported on the unpillared clays than for the ones supported on the Al- and Zr-pillared clays. These results have been discussed in terms of the catalytic behaviour exhibited by the supports, pure Mn2O3, MnO2, Al2O3 and ZrO2, as well as physical mixtures of ZrO2 with the unpillared clays. The effect on the catalytic performance of the possible competition between the acetone combustion and aldol condensation processes has also been considered.