Selective N-methylation of aniline with dimethyl carbonate over Zn1-xCoxFe2O4 (x = 0, 0.2, 0.5, 0.8 and 1.0) type systems

The alkylation of aniline with dimethyl carbonate (DMC) is reported over Zn1-xCoxFe2O4 (x = 0, 0.2, 0.5, 0.8 and 1.0) type systems prepared via. coprecipitation route. The influence of surface acid-base properties, cation distribution in the spinel lattice and various reaction parameters are discussed. It was observed that systems possessing low x values are highly selective and active for N-alkylation leading to N-methyl aniline as the major product. Since the authors have already reported the alkylation reaction using methanol as the alkylating agent over the same ferrospinel systems, in some cases both data are compared to highlight the merits and demerits of the choice of the two alkylating agents. DMC is acting as a better alkylating agent at comparatively low temperature, where methanol shows only mild activity. However, on the selectivity basis DMC as an alkylating agent could not compete with methanol, since the former executed appreciable amount of N,N-dimethylaniline (NNDMA) even at low temperature where methanol gave nearly 99% NMA selectivity. Cation distribution in the spinel lattice influences its acido-basic properties, and hence, these factors have been considered as helpful to evaluate the activity and stability of the systems. (C) 2000 Elsevier Science B.V. All rights reserved.