Sustainable Catalytic Process for the Synthesis of Niacin

Nicotinic acid (niacin) is an important vitamin of the B group, with an annual production close to 40,000 tons. It is used in medicine, food industry, agriculture and in production of cosmetics. Older industrial processes have drawbacks such as a low atomic efficiency and the use of toxic catalysts or stoichiometric oxidants. Several studies were carried out during latest years on new technologies for the synthesis of niacin and nicotinate precursors, such as 3-picoline and pyridine-3-nitrile. This thesis reports about the results of three different research projects; the first was aimed at the study of the one-step production of pyridine-3-nitrile starting from 2-methylglutaronitrile, the second at acetaldehyde/acetonitrile condensation for 3-picoline synthesis, and the third at investigating the reactivity of supported vanadium oxide catalysts for the direct gas-phase oxidation of 3-picoline with air; this process would be more sustainable compared to both older ones and some of those currently used for niacin production. For the first two research projects, a catalysts screening was carried out; however, results were not satisfactory. The third project involved the preparation, characterisation and reactivity testing of different zirconia-supported V2O5 catalysts. The effect of parameters, such as the Vanadium oxide loading and specific surface area, on catalytic performance were studied. Operative conditions such as temperature, contact time and feed composition were optimized. Yields to nicotinic acid close to the best ones reported in the literature were achieved; moreover, catalysts based on V2O5/ZrO2 were found to be remarkably active. Catalysts were characterized by means of XRD and in-situ Raman spectroscopy in the aim of finding correlations between catalytic performances and physic-chemical properties. In some cases, ZrV2O7 formed during the reaction. Vanadyl-pyrophosphate was also tested as the catalyst for 3-picoline oxidation, but its performance was lower compared to that one shown by V2O5/ZrO2.