Vapour phase methylation of pyridine with methanol over the Zn1 − xMnxFe2O4 (x = 0, 0.25, 0.50, 0.75 and 1) ferrite system

Abstract

Alkylation of pyridine by methanol to methylpyridines has been studied in the vapour phase in a fixed bed reactor, in the temperature range 473–723 K over the Zn_1 − xMn_xFe₂O₄ (x = 0, 0.25, 0.50, 0.75 and 1) ferrospinel system. 2-Picoline and 3-picoline were found to be major products. It was observed that, systems possessing high x values are highly selective for 2-picoline. Reaction parameters were optimized over MnFe₂O₄. A maximum yield of 67.6% of 2-methylpyridine, with a selectivity of 79.5%, and 17.5% of 3-methylpyridine with a selectivity of 20.5%, was obtained over MnFe₂O₄ at a temperature of 673 K, using a methanol to pyridine molar ratio of 5 and weight hour space velocity of 0.2 h⁻¹. Catalyst characterization has been made by XRD, infrared spectroscopy and ammonia desorption methods. A tentative mechanism for production of 2-picoline and 3-picoline, involving dihydropyridine as the intermediate has been proposed.