Catalytic performance of Al-MCM-41 materials in the N-alkylation of aniline

Al-MCM-41 mesoporous molecular sieves with Si/Al ratio ranging from 40 to 15 were synthesized and characterized as previously reported. Materials were tested in the N-methylation of aniline with methanol. The aniline methylation was a pseudo-first-order process with respect to aniline concentration. N-Methylation products [N-methylaniline (NMA) and N,N-dimethylaniline (NNDMA)] were predominant with a 65–80% selectivity to NMA at 573 K. Low reaction temperatures favoured the N-alkylation pathway whereas high temperatures produced higher quantities of C-alkylated products. Aniline conversion and selectivity to NNDMA decreased whereas selectivity to NMA continuously increased with time on stream. Selectivity to NMA remained almost the same, irrespective of the aniline conversion, aluminum content and acidity. On the other hand, the re-used Al-MCM-41 catalysts would be described as amorphous aluminosilicates because of their structural deterioration with the water produced in the reaction as a by-product.

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