Features of hydrogenization of 2-chloro-4-nitroaniline on supported palladium and platinum catalysts in 2-propanol and ethyl acetate

The article is devoted to studying the solvent and catalyst nature influence on the 2-chloro4-nitroaniline hydrogenation kinetic regularities on supported palladium and platinum catalysts in an aqueous solution of azeotropic composition and ethyl acetate. It is known that the halogen-substituted nitrobenzenes reduction may be accompanied by a secondary stage of hydrogenolysis. In this regard, the development of objective ideas about the selective control methods of the studied reaction the transformations staging is an extremely important task. The paper discusses the influence of the solvent and catalyst nature on the chlorine substituted amine yield. It should be noted that the form of kinetic curves for hydrogen in hydrogenation in ethyl acetate and 2-propanol indicates a significant influence of the solvent nature and a complex relationship between the catalyst structure and the solvent. It was established that a side-effect process that reduces the selectivity of the reaction with respect to 2-chloro-1,4-phenylenediamine is its dehalogenation. In the case of using ethyl acetate as a solvent, the absence of the 2-chloro-1,4-phenylenediamine dehalogenate product in the hydrogenation during the process, on both palladium and platinum catalysts, is noted. It is established that the hydrogen absorption rate in ethyl acetate on a palladium catalyst is eight times higher than on platinum. This effect may be associated with a smaller contribution of diffusion braking on a palladium catalyst. It is obvious that such effects may be due to the structure of the carriers. Probably, platinum, when applied to a substrate, is distributed on the inner surface of the carrier deep pores, while the distribution of the palladium phase is more likely to correspond to the crust distribution. This assumption also explains the fact of the palladium catalyst higher activity, which is accompanied by dehalogenation high degrees in 2-propanol.