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The objective of this study is to explore the treatment conditions of austenitic stainless steel, AISI 304, for catalytic devices used in volatile organic compounds (VOCs) combustion. The variables studied were treatment exposure time, temperature and atmosphere. AISI 304 steel surface resulted in different morphologies depending on temperature and atmosphere. The oxide layer was composed of mixed oxides of Cr-Fe and Cr-Mn-Fe, forming octahedral and hexagonal crystals. The addition of manganese with the objective of reaching the ideal Mn/Fe ratio improved notably the catalytic performance.

A MnCu-mixed oxide catalyst supported on a cordierite monolith was synthesized. The catalyst showed very good stability and high homogeneity and presented an excellent catalytic activity in the combustion of ethyl acetate, n-hexane, and its mixture. The total conversion temperature of the mixture was determined by the temperature at which the most difficult molecule was oxidized. IntroductionVolatile organic compounds (VOCs) are an important type of air pollutant which covers a wide range of compounds that differ in their properties and chemistry, but display similar behavior in the atmosphere. These compounds require special attention due to their toxicity, high stability, and persistence in the environment [1][2][3]. Catalytic oxidation is an effective way for reducing the emissions of VOCs [4]. Platinum and palladium supported on alumina or silica are the most commonly used catalysts for total oxidation [5][6][7][8][9]. The high cost of noble metals has increased the interest in their replacement by transition metal oxides, such as those of Cu, Mn, Co, and Fe, which might satisfy the requirements of the treatment process [10]. In previous papers [11,12], MnCu-based catalysts, which were synthesized by the coprecipitation method, were studied. It was found that a low amount of Cu in the mixed catalyst was sufficient to obtain a higher catalytic activity than Mn 2 O 3 . Mn9Cu1 catalyst presented the best performance. The synthesis of bulk or supported catalysts in granular form is a wellknown process. Recently, monolithic supports have been considered as an alternative geometry to conventional granular catalysts [13,14]. The advantages of these supports include very low pressure drop, uniform flow distribution within the monolith matrix, and easier accessibility of catalytic active centers of the monolithic walls by the reacting gases. One of the methods used to deposit the active phase on the monolithic supports is coating with a slurry, commonly called washcoating. The monolith is dipped in a slurry of catalyst particles of a comparable size to that of the macropores of the support [15]. This method involves the previous synthesis of the catalyst.The method used to synthesize the Mn9Cu1 catalyst developed in earlier works [11,12] requires the washing of the precipitate for the removal of residual sodium. This implies that a large amount of water has to be treated for a certain quantity of catalyst. In order to obtain a catalyst with excellent catalytic performance in a larger scale, it is necessary to decrease the synthesis steps as well as to minimize the volumes of reagents and solvents used. Thus, an alternative to washcoating is the impregnation method, where the monolith is dipped in a solution of precursor salts containing the active phase.Industrial exhaust gases are mainly composed of VOC mixtures of different chemical character, such as aromatic hydrocarbons, alkanes, and oxy-derivatives, i.e., alcohols, acetates, and ketones. The catalysts have to be able to treat different kinds of substances toget...

MnO x /AISI 304 austenitic stainless-steel monolithic catalysts were prepared by impregnation with aqueous solutions of manganese nitrate or acetate. The preparation method was satisfactory in terms of reproducibility and adherence of the deposited phase. The use of different precursors led to significantly dissimilar results. With manganese nitrate, the formation of Mn-Cr-O mixed phases on the surface was favored, whereas with manganese acetate, Mn 2 O 3 was the predominant active phase. The Mn-Cr-O mixed phases would be highly dispersed but their catalytic activity was low. The major catalytic behavior was obtained with monoliths impregnated with manganese acetate.

The objective of this work is the generation of a suitable surface, in microchannels of AISI 304 stainless steel for the manufacture of a microreactor, which ensures the anchoring of the active phase. The novelty of the work lies in achieving stabilization layer to work in different environments. The roughness generation was carried out by thermal treatment and passivation via alumina deposition by the impregnation method. The characterization was made with SEM-EDX and confocal microscope images. In a humid atmosphere, the generated surface showed high roughness with the presence of multiple filaments of iron oxide. Dilution of the suspension favoured the stability of the formed film.