Environmental catalysts system

NOx removal at the 80% level or higher can be achieved in favorable cases, but this can fall to 70%, where there is a possibility of significant fouling or poisoning of the catalyst. Deactivation of these and other environmental catalyst systems has recently been reviewed [40]. Often the SCR system is placed downstream of an oxidation catalyst to permit simultaneous removal of NOx, hydrocarbons, and carbon monoxide. 

Catalytic processes frequently require more than a single chemical function, and these bifunctional or polyfunctional materials innst be prepared in away to assure effective communication among the various constitnents. For example, naphtha reforming requires both an acidic function for isomerization and alkylation and a hydrogenation function for aromati-zation and saturation. The acidic function is often a promoted porous metal oxide (e.g., alumina) with a noble metal (e.g., platinum) deposited on its surface to provide the hydrogenation sites. To avoid separation problems, it is not unusual to attach homogeneous catalysts and even enzymes to solid surfaces for use in flow reactors. Although this technique works well in some environmental catalytic systems, such attachment sometimes modifies the catalytic specifici-... 

Examples of multi-disciplinary innovation can also be found in the field of environmental catalysis such as a newly developed catalyst system for exhaust emission control in lean burn automobiles. Japanese workers [17] have successfully merged the disciplines of catalysis, adsorption and process control to develop a so-called NOx-Storage-Reduction (NSR) lean burn emission control system. This NSR catalyst employs barium oxide as an adsorbent which stores NOx as a nitrate under lean burn conditions. The adsorbent is regenerated in a very short fuel rich cycle during which the released NOx is reduced to nitrogen over a conventional three-way catalyst. A process control system ensures for the correct cycle times and minimizes the effect on motor performance. 

The hydration of C-C triple bonds represents one of the most atom economical and environmentally friendly oxidation reactions [37], Recently, Nolan and co-workers reported the cationic [Au(lPr)][SbF ] system, which was generated in situ from [AuCl(lPr)] and AgSbF. The catalyst system showed remarkable activity in the hydration of a large range of alkynes, at An loadings as low as 10 ppm (typically 50-100 ppm), under acid-free conditions (Table 10.6) [38],... 

The ability to efficiently synthesize enantiomerically enriched materials is of key importance to the pharmaceutical, flavor and fragrance, animal health, agrochemicals, and functional materials industries [1]. An enantiomeric catalytic approach potentially offers a cost-effective and environmentally responsible solution, and the assessment of chiral technologies applied to date shows enantioselective hydrogenation to be one of the most industrially applicable [2]. This is not least due to the ability to systematically modify chiral ligands, within an appropriate catalyst system, to obtain the desired reactivity and selectivity. With respect to this, phosphorus(III)-based ligands have proven to be the most effective. 

Previous investigations of heterogeneous sonochemistry have involved ultrasonic extraction of pollutants from sediments and ultrasound assisted reactions employing solid catalysts. However, more extensive quantitative results are needed concerning sonochemistry in environmentally relevant systems. We report results of a preliminary set of experiments, involving the ultrasonic irradiation of bromobenzene, trichloroacetonitrile, and chloropicrin in the presence of silica solids (15 im and 10 nm). 

In recent years, much effort has been spent on developing both selective and environmentally friendly oxidation methods using either air or oxygen as the ultimate, oxidant. One of the most selective and efficient catalyst systems reported to date is based on the use of stable nitroxyl radicals as catalysts and transition metal salts as co-catalysts (15). The most commonly used co-catalysts are (NH4)2Ce(N03)6 (16), CuBr2-2,2 -bipiridine complex (17), RuCl2(PPh3)3 (18,19), Mn(N03)2-Co(N03)2 and Mn(N03)2-Cu(N03)2 (20). However, from an economic and environmental point of view, these oxidation methods suffer from one common drawback. They depend on substantial amounts of expensive and/or toxic transition metal complexes and some of them require the use of halogenated solvents like dichloromethane, which makes them unsuitable for industrial scale production. 

The search for new environmentally-friendly epoxidation methods using 02 as a sole oxidant has attracted much interest. Although there has been some success with 02 and homogeneous catalyst systems in the liquid phase without the use of reducing reagents, there have been few reports concerning heterogeneous epoxidation of olefins [45, 46]. 

Industrial catalysts are commonly divided into petroleum, chemical, polymerization, and environmental catalyst segments of the market. Companies seek to leverage their expertise in surface chemistry and materials science to develop products and systems that, in turn, improve customers products. 

TEES [Thermochemical Environmental Energy System] A catalytic process for destroying organic wastes in aqueous systems by thermochemical gasification. High temperatures and pressures are used. The catalyst is nickel metal supported on sodium carbonate the products are mostly methane, carbon dioxide, and hydrogen. Developed by Battelle Pacific Northwest Laboratory, Richland, WA, in the late 1980s and now licensed by Onsite Offsite, Inc. 

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