Preparation processes, catalytic materials

Figure 5.2 Schematic diagram showing different applications of sol-gel processing for the preparation of catalytic materials ...

Research tools and fundamental understanding New catalyst design for effective integration of bio-, homo- and heterogeneous catalysis New approaches to realize one-pot complex multistep reactions Understanding catalytic processes at the interface in nanocomposites New routes for nano-design of complex catalysis, hybrid catalytic materials and reactive thin films New preparation methods to synthesize tailored catalytic surfaces New theoretical and computational predictive tools for catalysis and catalytic reaction engineering... 

In heterogeneous catalysis by metal, the activity and product-selectivity depend on the nature of metal particles (e.g., their size and morphology). Besides monometallic catalysts, the nanoscale preparation of bimetallic materials with controlled composition is attractive and crucial in industrial applications, since such materials show advanced performance in catalytic processes. Many reports suggest that the variation in the catalyst preparation method can yield highly dispersed metal/ alloy clusters and particles by the surface-mediated reactions [7-11]. The problem associated with conventional catalyst preparation is of reproducibility in the preparative process and activity of the catalyst materials. Moreover, the catalytic performances also depend on the chemical and spatial nature of the support due to the metal-support interaction and geometrical constraint at the interface of support and metal particles [7-9]. 

Moser, W. R., Lennhoff, J. D., Cnossen, J. E., Fraska, K., Schoonover, J. W., and Rozak, J. R., The preparation of advanced catalytic materials by aerosol processing, in Advanced Catalysts and Nanostructured Materials, Novel Preparative Techniques (W. R. Moser, Ed.), p. 535, Academic Press, New York (1996). 

Synthesis and preparation process affects some propenies of ceria-based materials such as formed phase, panicle size, surt ace area, catalytic activities, and OSC etc. Therefore, many studies on synthesis, preparation, and modification have been carried out to develop the ceria-based materials of high catalytic activities, OSC, and thermal durability. In this chapter, conventional processes and recent advances in the synthesis and modification of the ceria-based materials are reviewed with the dependence of these methods on the characteristics of the materials. 

Extenders, Plasticizers, and Process Oils. Materials in this class can be prepared from the extracts obtained when narrow wax distillate cuts are solvent-refined— with furfural, for example— in the production of lubricating oils. These materials must have a low pour-point. Hydro-catalytic treatment over a mordenite-based catalyst removes residual n-paraflBnic wax with consequent reduction in pour-point of the product, which is obtained in good over-all yield. 

Heterogeneous catalysts are defined as solids or mixture of solids that are used to accelerate a chemical reaction without undergoing change themselves. The types of solids used in industry as heterogeneous catalysts include simple oxides, mixed oxides, metal salts, solid acids and bases, metals, and dispersed metals. Catalysts are used in a wide variety of chemical and environmental processes worldwide. The global value of fuels and chemicals produced by catalytic routes is about US 2.4-3 trillion per year. About 20% of all products produced in the United States are derived from a catalytic process of some form. As important as catalysis is to the world economy, the number of various chemicals used as a catalyst as well as the form and shape of the material vary as much as the number of processes that use catalysts. Fig. 1 is a picture of a number of various types of catalysts and illustrates the numerous possibilities of shapes and sizes. Naturally, the preparation processes of such a wide variety of products is also numerous. 

The physical and chemical properties discussed above are influenced by every step of the preparation process as well as the choice of raw materials. In addition, several preparation routes may be available to obtain a catalyst with specific properties. On developing a catalyst for industrial applications, the influence of the preparation procedure on these properties must be taken into consideration as well as economical production of a material. Examples of industrial catalytic processes and the method of manufacture of the catalysts are shown in Table 1. This table illustrates the many different types of catalysts as well as preparation methods used in industry. 

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