EFFECT OF SOLVENT COMPOSITION ON THE RATE AND SELECTIVITY OF 2-NITRO-2’-HYDROXY-5’-METHYLAZOBENZENE HYDROGENATION ON PROMOTED NICKEL CATALYSTS

The study of the influence of various factors on the kinetic characteristics and selectivity of liquid-phase catalytic hydrogenation of compounds containing several reactive groups is of theoretical and practical significance. In the presented work, the hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene was studied in order to elucidate the reasons and nature of the dependence of the rate and yield of the target products containing the benzotriazole ring on the composition of the catalytic system. In particular, the influence of the composition of aqueous solutions of 2-propanol with different contents of sodium hydroxide and promoting additives of titanium and molybdenum to the skeletal nickel catalyst was considered. According to the data obtained, the determining influence on the patterns of the process is the composition of the liquid phase, and not the nature of the promoter in the catalyst. The introduction of sodium hydroxide into the solvent leads to a change in the ratio of the rates of parallel stages of hydrogenation of the azo and nitro groups in the starting compounds to a much greater extent than the introduction of a promoter. Accordingly, the overall rate and selectivity of hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene to the corresponding benzotriazole and its N-oxide, as well as to aromatic amines, changes. Based on UV spectroscopy data and quantum chemical calculations, the possibility of forming an associative complex of substituted nitroazobenzene with hydrogen in the adsorption layer of the catalyst is substantiated, the rearrangement of bonds in which can lead to cyclization with the formation of benzotriazole N-oxide. It has been established that to obtain compounds containing a benzotriazole ring with a yield of at least 80%, it is recommended, regardless of the nature of the promoting additive in the catalyst, to maintain the molar ratio nNAB:nNaOH=0.5-1.5 and use aqueous solutions of 2-propanol containing 0.2-0.5 m.p. оf alcohol and 150-300 mol/m3 of sodium hydroxide. For citation: Lefedova O.V., Nemtzeva M.P. Effect of solvent composition on the rate and selectivity of 2-nitro-2’-hydroxy-5’-methylazobenzene hydrogenation on promoted nickel catalysts. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 5. P. 101-111. DOI: 10.6060/ivkkt.20256805.7116.