Abstract <p>This work presents a study of the kinetic features of liquid-phase hydrogenation of 1-methyl-4-nitrobenzene (4-nitrotoluene) in the presence of a supported nickel catalyst Ni/SiO₂ modified by controlled introduction of sulfide ions. The aim of the study is the determination of the correlation between the degree of deactivation of the active sites of the catalyst and its catalytic activity in the reduction reaction of the nitro group. Six catalysts with different concentrations of nickel are synthesized, the physicochemical properties of which are characterized by energy-dispersive analysis, X-ray diffraction analysis, and low-temperature adsorption of nitrogen. Controlled deactivation is executed by introducing different amounts of a solution of Na₂S into the reaction medium. It is found that a sulfide ion predominantly interacts with surface nickel atoms, decreasing the activity of the catalyst proportionately to the amount of adsorbed ions. It is experimentally determined that, on average, 1.5 sulfur atoms block one atom of surface nickel Ni⁰. It is demonstrated that partial deactivation makes it possible to directionally vary the activity and, potentially, selectivity of the catalyst due to the modification of its surface. The results indicate a possibility of using deactivation as an instrument for fine tuning of catalytic properties in hydrogenization processes.</p>