Abstract

--- - Zeolites containing Rh single sites stabilized by phosphorous were prepared through a one-pot synthesis method and are shown to have superior activity and selectivity for ethylene hydroformylation at low temperature (50 degrees C). Catalytic activity is ascribed to confined Rh2O3 clusters in the zeolite which evolve under reaction conditions into single Rh3+ sites. These Rh3+ sites are effectively stabilized in a Rh-(O)-P structure by using tetraethylphosphonium hydroxide as a template, which generates in situ phosphate species after H2 activation. In contrast to Rh2O3, confined Rh0 clusters appear less active in propanal production and ultimately transform into Rh(I)(CO)2 under similar reaction conditions. As a result, we show that it is possible to reduce the temperature of ethylene hydroformylation with a solid catalyst down to 50 degrees C, with good activity and high selectivity, by controlling the electronic and morphological properties of Rh species and the reaction conditions. - Isolated Rh3+ sites are stabilized inside the MFI zeolite channels with phosphorous which is added during zeolite synthesis in the form of a phosphonium zeolite template. This Rh3+ shows high activity in the low-temperature ethylene hydroformylation.