Catalyst fabrication

Similar to screen printing, the spray coating method [95] is widely used for catalyst fabrication, especially in labs. The major difference between the two is that the viscosity of the ink for spray coating is much lower than that for screen printing. The application apparatus can be a manual spray gun or an auto-spraying system with programmed X-Y axes, movable robotic arm, an ink reservoir and supply loop, ink atomization, and a spray nozzle with adjustable flux and pressure. The catalyst ink can be coated on the gas diffusion layer or cast directly on the membrane. To prevent distortion and swelling of the membrane, either it is converted into Na+ form or a vacuum table is used to fix the membrane. The catalyst layer is dried in situ or put into an oven to remove the solvent. 

Methanol Crossover Catalyst Performance Catalyst Fabrication Carbon Support Membrane Performance MEA Fabrication Pressurized Operation Methanol Concentration Fluid Flow Heat Transfer... 

Recent work demonstrates the feasibility of a somewhat similar concept as just described, based on a semiconducting Sn02 catalyst, fabricated in the shape of a nanowire, and configured as FETs (Zhang et al., 2004b,... 

Model Catalysts Fabricated by Electron-Beam Lithography... 

The authors are grateful to many colleagues worldwide in the Held of heterogeneous catalysis for exchange of ideas concerning the nanocatalysis approach and model catalyst fabrication. In particular, we are thankful to J. Libuda, H.-J. Freund and coworkers at the Fritz-Haber Institute in Berlin, Germany, who did the reactivity measurements on the EBL nanofabricated Pd/Si02... 

Concluding this section, it seems that research on oxidation catalysts and oxidation reactions provides some push to innovation, through (i) the high level of activity in the synthesis of new structures and development of new approaches to catalyst fabrication, (ii) a better knowledge of the state of catalysts during their use, (iii) the role of surface mobility, spillover and remote control, (iv) the use of additives in the feed and (v) a better understanding of the contribution of homogeneous gas phase reactions. 

In recent years, IFP has developed a non-pyrophoric nickel currently employed in the new plants. This eliminates the need for the in situ catalyst fabrication facility. 

Because the surface electronic processes play a fundamental role in catalytic activities, heterogeneous catalytic activity is determined primarily by the surface morphology and composition of the nanoparticle catalyst. The structure and composition of a few atomic layers below the surface play a secondary role, while the bulk of the catalyst remains a spectator of the catalytic activity. At the same time, cost considerations necessitate the optimization of dispersion and homogeneity of the catalytic sites, particularly when expensive noble metals are involved. Consequently, research towards the improvement of existing catalysts and the design of new ones focuses on two aspects tailoring of the surface structure, and minimizing the mass of the catalytically inert material. Therefore, catalyst fabrication techniques that allow control over those factors are desirable. 

Established in-house catalyst fabrication capability, by which otherwise unavailable catalysts can be S5mthesized, e g., 80 weight percent Pt/C catalyst for the DMFC cathode. 

Figure 9.21 Every atom counts changes in catalytic performance affected by minute variation in cluster precursors used in catalyst fabrication. (Reproduced from Ref [85] with permission of john Wiley and Sons ).

Additional demands are due to the fact that new types of reactors appear as very promising reverse-flow and ultrafast reactors, microreactors, reactors for photocatalysis, and so on. Suitable catalysts not only need new chemical formulations and textures, but also preparation processes adapted to the corresponding shaping techniques. Not all cases can be examined in this chapter. However, much emphasis will be laid on the role of a comprehensive approach in the scientific and chemical engineering research for catalyst fabrication. A few examples will illustrate the discussion. Suggestions may come from other fields of science and technology. 

A FEW WORDS CONCERNING OTHER SCIENTIFIC AVENUES AND THEIR PLACE IN PRACTICAL CATALYST FABRICATION... 

Ji, K., Dai, H., Deng, J., Zhang, H., Zhang, L., and Jiang, H. (2014) Catalytic toluene oxidation over the three-dimensionally ordered macroporous EuFeOs catalysts fabricated by the sucrose-assisted polymethyl methacrylate-templating method. Solid State Set, 27, 36-42. 

Grunes J, Zhu J, Anderson FA, Somorjai GA (2002) Ethylene hydrogenation over platinum nanoparticle array model catalysts fabricated by electron beam lithography determination of active metal surface area. J Phys Chem B 106 11463-11468... 

Many types of bimetallic catalysts have been used to investigate electrocatalytic performance, including single-crystal surfaces [6], sputtered particles [5,7], carbon-supported catalysts fabricated by impregnation reduction, and colloidal nanocrystals (NCs). Bimetallic single crystals are indispensable when investigating facet-specific electrocatalytic properties sputtered bimetallic particles can be used as model catalysts with a clean surface to study the effect of composition on... 

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