Activated carbon as a catalyst for the synthesis of N-alkylimidazoles and imidazolium ionic liquids

An activated carbon Norit RX3 has been treated with acids (sulphuric, nitric and sulphonitric mixture). The modified activated carbons have been characterized by elemental analysis, point of zero charge, N2 adsorption, XPS and FTIR. The solids obtained have been used as acidic heterogeneous catalyst in the reaction between imidazole and haloalkanes. The reaction with 1-bromobutane yields an ionic liquid, N,N-di-n-butyl-imidazolium bromide (1). Reaction with 2-bromobutane and 1-chlorohexane yields the corresponding N-alkyl-imidazoles (2) and (3). Sulphuric acid treated carbon is the most active catalyst.

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► Activated carbon with mineral acid yields an acidic heterogeneous catalyst.
► The acidity of the activated carbons is due to modification of functional groups.
► N-alkylation of imidazole can be catalysed by acids.
► Ionic liquids or N-alkylimidazoles are obtained in this reaction, depending on haloalkane.
► Sulphuric acid treated carbon is the most active catalyst.