Alkylation of Aniline on Acidic Zeolite HY

The role of the A,iV,A-trimethylanilinium ions in the overall reaction was further investigated by SF experiments. After A,A,A-trimethylanilinium ions had been formed on zeolite HY under CF conditions, the reactant flow was stopped and an 

MAS NMR investigation of the progressive reaetion on the working catalyst was performed at various reaction temperatures. 

The reaction mechanism including the formation and decomposition of quaternary cations may be a general pathway in amine alkylation processes on acidic zeolites. Pouilloux et al. (247), for example, synthesized dimethylethylamine from ethylamine and methanol on an acidic catalyst. At the reaction temperature of 503 K, trimethylamine was determined by gas chromatographic analysis, which can be explained by the formation and decomposition of trimethylethylammonium ions, (CIl3)3N CH2CH3. 

Furthermore, investigations of template decomposition in zeolites upon calcination of the as-synthesized materials have received much attention by researchers (248-250). However, the decomposition mechanisms of quaternary ammonium salts, which are commonly used as templates for zeolite synthesis, are still not well understood. Thus, MAS NMR investigations of the decomposition of quaternary ammonium ions in zeolites bear the potential of significantly improving the understanding of these processes (243,251). For this purpose, a general method was developed for the synthesis of 

The signals at 16 and 21 ppm originate from ring-alkylated anilines, that is, ortho- and /lara-toluidine, either in their neutral or in their protonated states. Except for N,N, A-trimethylanilinium ions, all the adsorbates on the working catalyst existed in their adsorption/desorption equilibrium with the desorbed state in the gas phase. 

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