Direct oxidation of 3-picoline (3-methyl-pyridine) to nicotinic acid with pure HNO3

Abstract

© 2023, The Author(s) under exclusive licence to Associação Brasileira de Engenharia Química.Nicotinic acid (NA) was synthesized by directly oxidizing 3-methylpyridine (3MP) with nitric acid. The reaction was performed in an instrumented PARR reactor. The effect of temperature (165 to 195 °C) and the molar composition of the initial reactive mixture were studied. Molar conversions of 3-methylpyridine ranged from 36 to 90%, with a yield of NA ranging from 31 to 62%. Better selectivities occur at low-time reactions and low conversion rates. At the same time, the HNO3 excess and temperature considerably affect 3MP conversion rate and NA yield rather than selectivity, especially at 180 °C, whereas an invariable selectivity of 80% was observed.