Deactivation of nickel catalyst used for hydrogenation of PhH was studied in com. reactor. Samples of the used catalyst were analyzed for Cl ion and S contents, sp. surface, porosity, mech. strength, catalytic activity in the hydrogenation of PhH and for C deposit compn. The model calcn. data and results of exp. detn. did not agree. The reasons for catalyst deactivation were connected with C deposition on the catalyst surface.