Catalyst coating metallic substrate pretreatment

One recently proposed pretreatment is the enameling of the microstructured device before coating with the catalyst [50,51], This enamel layer acts as barrier avoiding corrosion phenomena and the modification of the catalyst composition because of the release of metal from metallic substrate to the catalyst. This protective barrier could result in being especially useful for catalytic process taken place at high temperatures or in aggressive reaction media. 

Ca, and Si) resulted from the hydrolysis of ceramic-glass interphase of the enamel with the reactive stream. In the same paper, the authors compared the catalytic behavior of enameled and oxidized micromonoliths, fabricated in ferritic and austenitic stainless steel substrates and coated with similar amount of the same CuOyCeOj catalyst in such reaction, carried out under ideal (50% H, 1% CO, 1% Oj, Nj balance) and realistic (50% H2,1% CO, 1% O2,10% CO2, 10% H2O, N2 balance) PROX mixtmes, observing different catalytic results and cation diffusion as a function of the stainless steel nature and pretreatment, and the reactive stream and reaction conditions, concluding that the metallic substrates are not spectators playing a decisive role in the catalytic performances shown by the monolithic dispositive (Figures 4.4 and 4.5). 

Several methods for the incorporation of catalysts into microreactors exist, which differ in the phase-contacting principle. The easiest way is to fill in the catalyst and create a packed-bed microreactor. If catalytic bed or catalytic wall microreactors are used, several techniques for catalyst deposition are possible. These techniques are divided into the following parts. For catalysts based on oxide supports, pretreatment of the substrate by anodic or thermal oxidation [93, 94] and chemical treatment is necessary. Subsequently, coating methods based on a Uquid phase such as a suspension, sol-gel [95], hybrid techniques between suspension and sol-gel [96], impregnation and electrochemical deposition methods can be used for catalyst deposition [97], in addition to chemical or physical vapor deposition [98] and flame spray deposition techniques [99]. A further method is the synthesis of zeoUtes on microstructures [100, 101]. Catalysts based on a carbon support can be deposited either on ceramic or on metallic surfaces, whereas carbon supports on metals have been little investigated so far [102]. 

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