Efficient oxidation of hydrocarbons over nanocrystalline Ce_1-xSm_xO₂ (x = 0-0.1) synthesized using supercritical water

Selective oxidation of hydrocarbons to more functional oxygenated compounds is a challenging task for industrial research. Here we report the synthesis of highly crystalline Ce_1-xSm_xO₂ (x = 0-0.1) using supercritical water and their excellent catalytic activity for selective oxidation of hydrocarbons (ethyl benzene, n-butylbenzene, biphenyl methane, 1,2,3,4-tetrahydro naphthalene, cyclohexene and cyclopentene) to corresponding ketone through the oxidation of activated proton. Materials characterization results revealed the formation of highly crystalline small cube shaped nanoparticles (∼8-10 nm) with highly exposed (100) facet and exhibiting a surface area of 83-96 m² g^-1. The catalytic study revealed that Ce_0.95Sm_0.05O₂ is highly active towards selective oxidation of stable sp³ hybridized C-H bond of different hydrocarbons. The superior activity is most probably due to its high surface area, high degree of crystallinity with exposed high energy active (100) facet and presence of large amount Ce³⁺. In optimized condition as high as 90% conversion of ethyl benzene with 87% selectivity of acetophenone was observed. Among other different substrates n-butylbenzene and cyclopentene showed 100% selectivity towards corresponding ketone with the conversion of 60% and 73% respectively. The catalyst is re-usable for minimum 5 times without any deactivation of its activity.