Abstract
This article is devoted to the issues of aromatic hydrogenation reactions on supported palladium catalysts: adsorption on palladium catalysts, models of the Pd surface and the location of adsorption centers, features of hydrogenation of aromatic nitro compounds over palladium catalysts with additives of rare-earth elements.Palladium catalysts for hydrogenation of nitro groups in nitro compounds with different functional groups are described.The article discussed theoretical and experimental aspects of data from literature and patent sources.The experimental results of the authors of this article concerning selective hydrogenation of 4,4'-dinitrostilbene-2,2'disulfonic acid to 4,4'-diaminostilbene-2,2'-disulfonic acid are also shown.Pd-Cu/sibunite was used for selective obtaining 4,4'-diaminostilbene-2,2'-disulfonic acid in water.The formation on the surface of mixed active centers of the type of solid solutions of the Cu3Pd composition with a particle size of 5 nm and massive Pd clusters of 100 nm is established, which cause sufficient uniformity of both the surface and the adsorbed hydrogen.This is probably the reason for the high selectivity of the Pd-Cu/sibunite catalyst in the hydrogenation of 4,4'-dinitrostilbene-2,2'disulfonic acid.A highly selective Pd-Cu / sibunite catalyst has been developed, the optimal conditions for the process (temperature and pressure of hydrogen, solvent) have been determined, which make it possible to obtain the target amine, 4,4'-diaminostilbene-2,2'-disulfonic acid, up to 91-92%.The optimal composition of the catalyst is stable when hydrogenating 7-8-fold portions of 4,4'-dinitrostilbene-2,2'-disulfonic acid.