Formation of the CaSnO 3 crystalline phase during catalytic aldol condensation of acetone under supercritical conditions

The aldol condensation of acetone was carried out under the conditions of the supercritical state of the reagent (350 °C, 8 MPa; 400 °C, 12 MPa) on catalysts prepared by the thermal treatment of CaSn(OH) 6 at 450 and 750 °C. The X-ray amorphous phase of CaSnO 3 transforms into crystalline calcium stannate as the thermal treatment temperature increases from 450 to 750 °C. At 350 °C and 8.0 MPa, the selectivity of the reaction to mesityl and isomesityl oxides is about 85% (for both samples), but the conversion of acetone is much higher on CaSnO 3 after it has been thermally treated at 750 °C. The reuse of the CaSnO 3 -450 catalyst led to its transformation. The conversion of acetone increases, and the reaction parameters (conversion and selectivity) reach values characteristic of CaSnO 3 -750. The catalyst structures were studied by XRD and scanning and high-resolution transmission electron microscopies.