Solvothermal Synthesis and Catalytic Properties of Nanocrystalline ZnFe2−xAlxO4 (x = 0, 1, 2) Spinels in Aniline Methylation

Abstract

ZnFe2−xAlxO4 (x = 0, 1, 2) spinels were obtained by microwave-assisted solvothermal method using 1,4-butanediol as reaction medium. The results of XRD and HRTEM studies have indicated higher nanocrystallinity of aluminium containing spinels, and N2 adsorption–desorption measurements have revealed their enhanced textural properties, in particular much higher specific surface areas. NH3-TPD method and cyclohexanol test have shown the variation of surface acid–base properties with the changes in the spinel composition. All studied spinels were active in aniline methylation and proved to be selective for N-methylation leading to N-methylaniline and N,N-dimethylaniline. The main advantage of aluminium containing spinels is that N-alkylation with methanol is possible at significantly lower temperature (200–260 °C) when pure zinc ferrite is almost inactive.