Oxidation of Picoline with Oxygen to Nicotinic Acid against Co²⁺, NHPI, and Phosphonium or Ammonium Bromides

Nicotinic acid (NA) is a heteroaromatic carboxylic acid mainly used as feed, in breakfast cereals, and as a beverage additive. Moreover, it is used as an anti-pellagra drug and as an ingredient in multivitamin supplements. It is manufactured using the Lonza process from 3-ethyl-3-methylpyridyne as a raw material using HNO₃ as the oxidant agent. However, the use of such an oxidant is connected with greenhouse gases, thus making the technology non-ecological. Another industrial process is oxidative ammonolysis of 3-picoline followed by hydrolysis of a reaction intermediate to NA. This paper presents the results of research on the selective oxidation of 3-picoline with oxygen to NA. Bromide organic salts, including ionic liquids, N-hydroxyphtalimide, and cobalt(II) salts, were used as the catalysts. The reaction was carried out with acetic acid (AcOH) as a solvent. The bromide salts imidazolium bromide, quaternary ammonium bromide, and quaternary phosphonium bromide were used. They also fill the role of corrosion inhibitors caused by the acidic and highly oxidative reaction environment.