Alkylation of aniline with methanol: change in selectivity with acido-basicity of faujasite catalysts

The alkylation of aniline with methanol was carried out at 673 K on X and Y zeolites exchanged with Li, Na, K, Rb and Cs cations. At low time-on-stream the X catalysts are more active than the Y ones but they deactivate more rapidly. The activity and selectivity were shown to be strongly dependent on the acido-basicity. The selectivity may be oriented towards alkylation on the nitrogen or on the aromatic ring. The study made at equal conversion shows that the selectivity is governed by the balance between the basicity of the oxygen atoms of the framework and the Lewis acidity of the cations in the cages. Generally, the more basic zeolites (X and Y exchanged with K, Rb or Cs) favour the production of N-alkylates, mainly N-methylaniline. The zeolites with the more acidic cations, Li and Na, give rise to C-alkylation (para- or ortho-toluidine and small amounts of 2,4 or 2,6 dimethylaniline and N,N-dimethylparatoluidine). The more basic zeolites display a considerable aging.