Aniline methylation on modified zeolites with acidic, basic and redox properties

Four series of molecular sieve catalysts of-different structural types, ZSM-11, L, Y and MCM-41 have been prepared. Each type of materials was modified to obtain acidic (Hforms),. basic. (Cs-forms impregnated with CsOH) and redox (modified with V2O5) catalysts. The catalysts were characterized by AES, XRD, FTIR Si-29, Al-27, H-1 and Cs-133 MAS NMR, NH3-TPD, CO2-TPD, TPR and nitrogen adsorption. The catalytic activities of the materials in aniline methylation was evaluated in a continuous-flow microreactor system at temperatures of 523 to 723 K, a WHSV of 1.8 h(-1) and a molar aniline/methanol ratio of 1:5. In situ C-13 MAS NMR was applied to study the mechanisms of N- and C-alkylation on acidic, basic and redox catalysts and to determine key parameters responsible for the catalyst activity, selectivity and stability. The best. catalyst. performance was observed on zeolite CsNaY/CsOH, which showed an aniline conversion of 99%, a selectivity to N-methylaniline of 98.7% and a high time-on-stream stability.