KINETIC OF HYDROGENATION OF 4-NITRO-2'-HYDROXY-5'-METHYLAZOBENZEN ON SKELETAL NICKEL IN AQUEOUS SOLUTION OF 2-PROPANOL

Abstract

The article is devoted to the kinetics of hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel in an aqueous solution of 2-propanol with the azeotropic composition at various initial concentrations of the starting compound. According to the obtained dependences of hydrogen absorption during the process, the changes in the amounts of the initial 4-nitro-2'-hydroxy-5'-methylazobenzene, the processing of the kinetic curves in linear coordinates of different orders, the data on the material balance of reaction products, the conlusion is drawn that at low concentrations the hydrogen addition is carried out through the nitro and azo groups to the starting 4-nitro-2'-hydroxy-5'-methylazobenzene molecule. An increase in the initial amount of 4-nitro-2'-hydroxy-5'-methylazobenzene introduced into the reactor leads to a marked decrease in the content of 4-amino-2'-hydroxy-5'-methylazobenzene. It was experimentally established that at the low initial concentrations, hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel in aqueous solution of 2-propanol with the azeotropic composition proceeds on the first order and zero one for hydrogen. An increase in the initial concentration of hydrogenated compound above the solubility limit leads to a sharp increase in a value of excessive adsorption of 4-nitro-2'-hydroxy-5'-methylazobenzene, to an increase in diffusion inhibition on hydrogen and to a change in the order for reducing agent. At the initial amounts of 4-nitro-2'-hydroxy-5'-methylazobenzene studied the transformation proceeds in two parallel directions. One of the directions is due to the addition of hydrogen on nitro groups to form 4-amino-2'-hydroxy-5'-methylazobenzene, and the second one on azo groups to form 2-amino-4-cresol and 4-nitroaniline.Forcitation:Hoang Anh, Kalashnikova V.A., Lefedova O.V. Kinetic of hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzen on skeletal nickel in aqueous solution of 2-propanol. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 3. P. 10-15