Influence of hydrothermal, microwave and mechanochemical treatment of tin phosphate on porous structure and catalytic properties

Micro-mesoporous tin phosphate is prepared via precipitation under acid medium with subsequent modification using hydrothermal, microwave, and mechanochemical treatments (HTT, MWT, and MChT, respectively). The structure of the initial and modified samples is studied using nitrogen adsorption-desorption, DTA-TG and XRD analysis, FTIR spectroscopy, and SEM. Selected samples are tested as catalysts in aldol condensation of formaldehyde with acetic acid and in photocatalytic degradation of safranin T under visible irradiation. It is established that modification, primarily under hydrothermal conditions, results in the formation of mesoporous or meso-macroporous structure which is more accessible for the reagents molecules and more resistant to sintering and coking at higher temperature. Maximum effect is obtained in the case of modification of wet gel. Catalytic performance of the tested samples in aldol condensation is primarily determined by the parameters of their porous structure. The acquisition of photocatalytic activity is due to the narrowing of the band gap as a result of modification.