NOVELTY - The method comprises: producing an oxidation layer on a surface of active sites of a catalytic bed of a catalytic reactor by passivation; opening the reactor; and skimming a part of the catalytic bed. The oxidation layer has a thickness of 0.3-3 nm. The passivation step comprises: introducing, to the catalytic reactor, an inert gas comprising an amount of oxidizing agent of 50-100 ppm; and increasing the amount of oxidizing agent by a factor 4-8 and the flow of inert gas until the oxygen content within the reactor is equal to an oxygen content in the atmosphere.    USE - The method is useful for treating a catalytic reactor, which is useful for methanol synthesis, hydrogenation of carbon dioxide, hydrogenation of carbon monoxide, methanation reaction, reforming methane with steam or carbon dioxide, and reforming an alcohol vapor (all claimed).    ADVANTAGE - The method prevents the deterioration of the portion of the catalyst bed, allows the operators to work safely, and optimizes the design and operating costs of the reactor.    DETAILED DESCRIPTION - The method comprises: producing an oxidation layer on a surface of active sites of a catalytic bed of a catalytic reactor by passivation; opening the reactor; and skimming a part of the catalytic bed. The oxidation layer has a thickness of 0.3-3 nm. The passivation step comprises: introducing, to the catalytic reactor, an inert gas comprising an amount of oxidizing agent of 50-100 ppm; and increasing the amount of oxidizing agent by a factor 4-8 and the flow of inert gas until the oxygen content within the reactor is equal to an oxygen content in the atmosphere. The passivation step is carried out at a temperature of less than 100 degrees C and at a pressure of less than 5 atmospheric pressure. The introducing step leads to oxidation of the surface of metal particles on the catalyst bed. During the passivation step, a monitoring of the temperature of the catalytic bed is effected. During the passivation step, the front heat is observed, and the repetition of the introducing step is performed when the front heat pierces an outlet of the catalytic reactor.