Sulfonated phenylamine ionic liquids as efficient phase-separation catalysts for the synthesis of trimethylolpropane triacrylate

Abstract

Novel sulfonated phenylamine ionic liquids were prepared through a simple ring-opening reaction of phenylamine with 1,3-propanesulfonate (PS) and evaluated as catalysts for the esterification of trimethylolpropane and acrylic acid to produce trimethylolpropane acrylate. By adjusting the molar ratio of PS to phenylamine, sulfonated phenylamine (PS_n-PA) with different PS group numbers (n = 1, 2, 3) can be obtained. Among them, PS₃-PA possessed the strongest acidity and presented the best trimethylolpropane conversion (100%) and TMPTA selectivity (85.4%) under mild reaction conditions. The results showed that the catalytic performances of PS_n-PA were closely related to their acidic strength. A possible mechanism for the enhanced catalytic activity in the presence of these novel sulfonated phenylamine ILs had been proposed. Moreover, an obvious phase-separation phenomenon, in which the catalyst completely dissolved in a reaction system, but precipitated at the end of reaction, was observed during the reaction process. This work provided an efficient and simple approach for the design of new ionic liquids with multiple acidic sites. This kind of acidic catalyst with phase separation behavior and high performance has potential to be used in more acid-catalyzed reactions, especially for polycarboxylic acid or polyol systems.