Formation of methylamines by the reaction of ammonia with surface methoxy species on zeolite H-Y and the silicoaluminophosphate H-SAPO-34

In the present work, the amination of surface methoxy species formed by methanol on acidic zeolite H-Y and the silicoaluminophosphate H-SAPO-34 was studied and it was found that these methoxy groups are reactive compounds in amination reactions already at room temperature. The above-mentioned reaction was investigated for different molar ammonia to methoxy ratios (N/C) and at various reaction temperatures by ¹³C MAS NMR spectroscopy. By a subsequent thermal treatment, it was evidenced that the selectivities towards monomethylamine, dimethylamine, and trimethylamine strongly depend on the reaction temperature. Moreover, due to the different pore architectures of the catalysts under study, H-SAPO-34 has the higher selectivity towards mono- and dimethylamine in comparison with zeolite H-Y. This finding may be an indication that the silicoaluminophosphate H-SAPO-34 is a selective amination catalyst with the additional ability to change the contents of monomethylamine, dimethylamine, and trimethylamine by varying the reaction temperature.