Synthesis of fragrance and flavour grade esters: activities of different ion exchange resins and kinetic studies

Abstract

Esters are very valuable chemicals used in the fragrance, flavour, pharmaceutical, dyestuff and plastic industries. Several synthetic routes exist to make esters, but the carboxylic acid–alcohol reaction is the most common for which homogeneous, polluting and corrosive acids are used as catalysts. Perfumery and flavour grade esters need to be free of inorganic impurities and colouration. The current work has evaluated the activity of ion exchange resin catalysts for the synthesis of methyl salicylate and methyl anthranilate, methyl-4-hydroxy benzoate from the respective carboxylic acid and methanol. The order of catalytic activity was found to be: Amberlyst-36>Indion-130>Amberlyst-15>Dowex-M31>Amberlyst-18. The effects of various parameters with Amberlyst-36 were studied and it was found that the reaction was intrinsically kinetically controlled. It was observed that the catalyst chosen has excellent reusability and was not deactivated. The products were perfumery grade.