Аннотация:Catalysts MgSnO3-450 and MgSnO3-750 of different morphologies, synthesized by calciningmagnesium hydroxystannate MgSn(OH)6 at 450 and 750C, respectively, are studied in the aldol–crotonic condensation of acetone under supercritical conditions (400C and a pressure of 12.0 MPa). The structure of the catalysts is characterized via XRD, SEM, TEM, DSC, and BET. The X-ray amorphous MgSnO3-450 sample exhibits high activity (0.42 mol/(h gcat)) and selectivity for isomeric phorones (40%). The MgSnO3-750 catalyst, which has a higher degree of crystallinity, exhibits lower activity (0.33 mol/(h gcat)) and a high selectivity toward isomeric mesityl oxides (up to 70%). A comparison of data on the phase composition of the catalysts and the results on the reaction indicates the phase responsible for the selective condensation of two acetone molecules into mesityl oxide when using MgSnO3-750 catalyst is magnesium orthostannate Mg2SnO4. The formation of a MgSnO3 magnesium metastannate phase in the X-ray amorphous MgSnO3-450 catalyst contributes to the formation of phorones, which are products of the condensation of three acetone molecules. It is found that the structure of the MgSnO3-450 catalyst is rearranged as acetone condenses under supercritical conditions.
