N-alkylation of aniline with methanol over magnesium phosphates Original Research Article

Various magnesium orthophosphates were tested as catalysts for the alkylation of aniline with methanol. The solids examined had different structures and acid–base properties dependent on the particular synthetic procedure used. They were characterized as Mg3(PO4)2, Mg2P2O7 and NaMgPO4, mainly. Their textural properties were determined by N2 adsorption and their acid–base properties by cyclohexylamine and phenol adsorption, respectively. The catalysts studied give the N-alkylated products only (i.e. N-methylaniline and N,N-dimethylaniline). The magnesium pyrophosphate exhibits the highest activity of all. At high reaction temperatures (above 773 K), the catalysts are strongly deactivated through coke formation; however, their catalytic activity is stable between 523 and 623 K. At 623 K, magnesium pyrophosphate is about 68% selective for alkylation to N-methylaniline with about 45% conversion. The activity of the solids studied in this reaction is related to their acid–base properties, as is their activity and selectivity in the transformation of 2-hexanol.