Due to the unwanted effects of volatile organic compounds (HOS) emissions into the environment, great attention is given to the development of effective and economically acceptable procedures for reducing their emissions into the atmosphere. Among the many methods for reducing the volatile organic compounds emissions into the environment such as biofiltration, adsorption, absorption, condensation, etc., catalytic oxidation is particularly distinguished as one of the most promising methods due to the large area of potential application, the ability to fulfill strict environmental criteria as well as the economic viability compared to other technologies.The most commonly used catalytic systems in environmental protection is based on the monolithic performance of the reactor. In the theoretical part of this work is given an insight into the issues relating to the emission of volatile organic compounds and review of procedures to reduce their emissions to the environment with special emphasis on the catalytic oxidation processes and appropriate heterogeneous catalysts. In the experimental part is described a process for preparing a metal monolithic catalyst/reactor with a thin layer of a mixed oxide of manganese, copper and iron (Mn-Cu-Fe/Al-Al2O3), as a potential catalyst for the catalytic oxidation of toluene. Also, the catalytic characteristics of the prepared catalyst were tested and compared with the previously tested Mn-Cu/, Mn-Fe/ and MnOx/Al-Al2O3 catalysts. In the final part of the research, the reactor's work was analyzed and it wes suggested a suitable model for its description. The eligibility of the proposed model was based on the comparison between results obtained using the model and experimental results. It has been found that the monolithic Mn-Cu-Fe/Al-Al2O3 catalyst shows almost the same activity as the previously studied bimetal Mn-Fe/Al-Al2O3 catalyst and slightly lower activity compared to Mn-Cu/ and MnOx/Al-Al2O3 catalysts. Very good overlap was made between experimental results and simulation results according to the assumed model of the reactor.