The acid-base properties of Zn-B-P/gamma-Al2O3/Al catalysts for the direct acylation of diethylamine with m-toluic acid have been studied using ammonia temperature-programmed desorption, probe adsorption, and IR spectroscopy techniques, the catalysts having been synthesized and tested under conditions of microwave-assisted thermal treatment. A correlation between the activity of the microwave-absorbing catalysts in the target N,N-diethyl-m-toluamide formation reaction and the concentration of acid sites of medium strength on the surface of the samples has been revealed. It has been shown that the main reason behind the higher activity of Zn-B-P/gamma-Al2O3/Al catalysts prepared under conditions of the thermal action of microwave field is the formation of a more developed active surface characterized by a prevalence of medium acid sites.