Study of Catalyst Deactivation in Liquid-Phase Hydrogenation of 3-Nitrostyrene Over Au/Al.sub.2O.sub.3 Catalyst in Flow Reactor

For the first time, we report the results of the study of dynamics of the Au/Al.sub.2O.sub.3 catalyst deactivation during the selective liquid-phase 3-nitrostyrene (3-NS) hydrogenation in a fixed bed flow reactor. It is shown that the formation of carbonaceous deposits is the main reason of catalyst deactivation, while the leaching of gold from the Au/Al.sub.2O.sub.3 catalyst or enlargement of the gold particles has not been detected. The content of the carbon deposits on the spent catalyst at the inlet of the reactor is higher than at the outlet and increases as the initial concentration of 3-NS grows. The character of carbonaceous deposits allocation and analysis of reaction products point out to 3-vinylnitrosobenzene as the main source of the Au/Al.sub.2O.sub.3 catalyst deactivation coinciding with the speculation arising from the kinetic modeling.