Catalytic Transformation of Nitroarenes to Amines over Ba[sub. Perovskites in Water

This work is focused on the application of lanthanide-free perovskite Ba[sub.1−x]Sr[sub.x]TiO[sub.3] (0 < x < 1) in valorization of toxic pollutants as 4-nitrophenol (4-NPh). The series of perovskites were fabricated by facile, one-step solid-state preparation method and characterized via various techniques: elemental analysis (Inductively Coupled Plasma Optical Emission Spectrometry, ICP-OES), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and dielectric properties (impedance spectroscopy, IS). The methods confirmed the assumed composition, structure and high purity of the materials. The results showed that substitution of Ba[sup.2+] by Sr[sup.2+] in the perovskite crystal lattice influenced the dielectric properties of samples and the size of the grains. The absorption and catalytic properties of Ba[sub.(1−x)]Sr[sub.x]TiO[sub.3] (0 < x < 1) series were evaluated in reduction of 4-NPh in water using NaBH[sub.4] as reducing agent. No adsorption of 4-NPh was found for all the materials during 180 min of contact (experiment without reducing agent), and the best catalytic performance was found for the Ba[sub.(1−x)]Sr[sub.x]TiO[sub.3] (x = 0.3) sample. The catalytic transformation of 4-NPh to 4-APh follows a pseudo-first-order model, and the catalysts can be easily regenerated via mild annealing (300 °C).