Pollution abatement applications

Refractory high surface area oxides are deposited from slurries onto the walls of the channels that make up monoliths in order to provide an adequate surface area to support the active catalytic species. Washcoats such as AI2O3 and TiC>2 are commonly used for pollution abatement applications (auto exhaust, stationary NO abatement, etc.) where the monolith is usually a ceramic. Metal monoliths are finding increasing use however, they represent only a small percentage of the total monoliths used. Optical microscopy enables one to see that the catalyzed washcoat follows the contour of the ceramic surface. Figure 7 shows the AI2O3 washcoat-ceramic interface for a typical auto exhaust catalyst. In this case, no evidence of loss of adhesion between washcoat and ceramic can be seen. 

The majority of adsorbents applied in industry has porous sizes in the nanometer region. In this pore-size territory, adsorption is an important method for the characterization of porous materials. To be precise, gas adsorption provides information concerning the microporous volume, the mes-opore area, the volume and size of the pores, and the energetics of adsorption. Also, gas adsorption is an important unitary operation for the industrial and sustainable energy and pollution abatement applications of nanoporous materials. 

SOME CHEMICAL, SUSTAINABLE ENERGY, AND POLLUTION ABATEMENT APPLICATIONS OF NANOPOROUS ADSORBENTS... 

CHEMICAL AND POLLUTION ABATEMENT APPLICATIONS OF ION EXCHANGE IN ZEOLITES... 

In this chapter, the basic principles of heterogeneous catalysis and surface reactions, and chemical, sustainable energy, and pollution abatement applications of heterogeneous catalysts are described [3-5],... 

The author of this book has been permanently active during his career in the held of materials science, studying diffusion, adsorption, ion exchange, cationic conduction, catalysis and permeation in metals, zeolites, silica, and perovskites. From his experience, the author considers that during the last years, a new held in materials science, that he calls the physical chemistry of materials, which emphasizes the study of materials for chemical, sustainable energy, and pollution abatement applications, has been developed. With regard to this development, the aim of this book is to teach the methods of syntheses and characterization of adsorbents, ion exchangers, cationic conductors, catalysts, and permeable porous and dense materials and their properties and applications. 

Multi-channel ceramic monoliths (Fig. 7.4) are now the primary choice as support structures to carry the active catalytic species for cleaning emissions from various sources of pollution.5 Figure 7.4 shows the shapes used for both automotive and stationary pollution abatement applications. 

Transition metal catalysts, specifically those composed of iron nanoparticles, are widely employed in industrial chemical production and pollution abatement applications [67], Iron also plays a cracial role in many important biological processes. Iron oxides are economical alternatives to more costly catalysts and show activity for the oxidation of methane [68], conversion of carbon monoxide to carbon dioxide [58], and the transformation of various hydrocarbons [69,70]. In addition, iron oxides have good catalytic lifetimes and are resistant to high concentrations of moisture and CO which often poison other catalysts [71]. Li et al. have observed that nanosized iron oxides are highly active for CO oxidation at low tanperatures [58]. Iron is unique and more active than other catalyst and support materials because it is easily reduced and provides a large number of potential active sites because of its highly disordered and defect rich structure [72, 73]. Previous gas-phase smdies of cationic iron clusters have included determination of the thermochemistry and bond energies of iron cluster oxides and iron carbonyl complexes by Armentrout and co-workers [74, 75], and a classification of the dissociation patterns of small iron oxide cluster cations by Schwarz et al. [76]. 

Rajeshwar, K., and J. G. Ibanez, Environmental Electrochemistry Fundamentals and Application in Pollution Abatement, Academic Press, San Diego, CA, 1997. 

Rajeshwar K. Ibanes J. Environmental Electrochemistry. Frmdamentals and Applications in Pollution Abatement. Academic Press, Inc. San Diego, Ca. 1997. 

Monolithic catalysts have found a wide range of applications in the removal of pollutants from air, especially in the automotive industry. Specifically, the demand for large surface to small volume, high conversions achieved for low retention times, and low pressure drop led to the development of monolithic supports. More information on automotive catalytic converters has been given in Chapter 1. Usually, a thin layer of alumina is deposited onto a monolith for keeping the precious metal used for air pollutants abatement dispersed. The oxidations that take place are highly exothermic and the reaction rates achieved are in turn high. Hence, the reactants diffuse only a small distance... 

Although catalysts have been extensively used for the abatement of gas-phase pollutants, their application in water-phase processes for environmental purposes is a relatively novel subject with tremendous potential in the near future. However, catalyst durability and activity in such applications have to be definitely improved (Pirkanniemi and Sillanp, 2002). 

On the other hand, in addition to adsorption properties, nanoporous materials are a group of advanced materials with other excellent properties and applications in many fields, for example, optics, electronics, ionic conduction, ionic exchange, gas separation, membranes, coatings, catalysts, catalyst supports, sensors, pollution abatement, detergency, and biology [1-42],... 

Porous materials are of huge practical significance for applications in industry, energy production, and pollution abatement. In this regard, microporous materials, such as zeolites and related materials,... 

To use adsorption as a unitary operation in industrial, pollution abatement, or energy production applications, in most cases, a reactor where a dynamic adsorption process will take place is packed with a concrete adsorbent. The adsorbents generally used for these applications are active carbons, zeolites and related materials, silica, mesoporous molecular sieves, alumina, titanium dioxide, magnesium oxide, clays, and pillared clays. 

The book explores various examples of these important materials, including perovskites, zeolites, mesoporous molecular sieves, silica, alumina, active carbons, carbon nanotubes, titanium dioxide, magnesium oxide, clays, pillared clays, hydrotalcites, alkali metal titanates, titanium silicates, polymers, and coordination polymers. It shows how the materials are used in adsorption, ion conduction, ion exchange, gas separation, membrane reactors, catalysts, catalysts supports, sensors, pollution abatement, detergency, animal nourishment, agriculture, and sustainable energy applications. 

Monitoring pollutants in a variety of composition ranges in motor vehicle and chemical process exhaust gases is a major area of research in pollution abatement technology. Low-temperature CO oxidation catalysts are needed for zero emission vehicles, CO gas sensors, selective oxidation of CO in H2 rich streams in fuel cell applications,1,2 and in closed-cycle C02 lasers used for remote sensing in space applications.3"5 Effective oxidation of CO during... 

Additional benefits to be realized from the low wet pick-up foam application method include greater line speed (especially where the dryer represents a bottleneck in the pad process to be replaced), lower pollution abatement costs due to reduced volumes of effluent and exhaust gases and reduced water consunption. 

Rajeshwar, K. and Ibanez, J. G. (1997) Environmental Electrochemistry. Fundamentals and Applications in Pollution Abatement. Academic, London. 

Polcaro, A.M., Mascia, M., Palmas, S. and Vacca, A. (2004) Electrochemical degradation of diuron and dichloroaniline at BDD electrode. Electrochim. Acta, 49,649-656 Polcaro, A.M., Vacca, A., Mascia, M. and Palmas, S. (2005) Oxidation at boron doped diamond electrodes An effective method to mineralise triazines. Electrochim. Acta 50,1841-1847 Posada, D., Betancourt, P., Liendo, F. and Brito, J.L. (2006) Catalytic wet air oxidation of aqueous solutions of substituted phenols. Catal. Lett. 106, 81-88 Rajeshwar, K. and Ibanez, J. (1997) Fundamentals and Applications in Pollution Abatement, Academic, New York, NY... 

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