Combustion catalyst

A knowledge of these compounds is important because they often have undesirable attributes, e.g., unpleasant odor, the SO2 formed by combustion, catalyst poisoning. There are a number of refining processes to eliminate sulfur compounds. 

Another potential solution is the use of catalytic combustors, which produce extremely low levels of emissions by the use of combustion catalysts such as platinum. The main disadvantage of catalytic combustors, however, is thek high cost. 

With the increasing emphasis on energy conservation and environmental considerations, additives for fuels that can correct combustion-related problems have aroused considerable interest. Many commercial fuel additives are combinations of organometaHics, dispersants, emulsifiers, and carrier solvents. The organometaHic, often a metal soap, acts as a combustion catalyst, increasing efficiency with reduction of smoke, deposits, and corrosion. 

The temperature rise in the inlet stage is limited by taking advantage of the unique properties of palladium combustion catalysts. Under combustion conditions, palladium can be either in the form of the oxide or the metal. Palladium oxide is a highly active combustion catalyst, whereas palladium metal is much less active. Palladium oxide is formed under oxidizing conditions... 

To combat all these combustion-related problems, a wide variety of combustion catalysts and additives are available in the market. 

Alternatively, combustion catalysts may be formulated to act primarily as furnace area catalysts, in which case they reduce the carbon in fly ash and bottom ash. This, in turn, lowers the degree of fouling in the boiler convection area and the economizer. 

For fluidized bed reactors, special water-soluble, combustion catalyst and slag modifier combination products are available. These products are diluted and typically are fed at rates of from 20 to 60 lb per day for every 10 tons of bed extraction. 

This formulation is proposed as a complete treatment, comprising powdered and crystalline combustion catalysts and slag modifiers. It is designed for pulverized fuel (PF), brown coal, lignite, peat moss, and bark, and for application with cyclone burners, chain grates, underfed, and spreader stokers. 

Liquid, Oil-Soluble Combustion Catalyst and Slag Modifier... 

Fig. 3. FT-IR spectra of the adsorbed species arising from the interaction of (a) rerr-butanol and (b) isobutane over a combustion catalyst (MgCr204) at 423 K, and from rerr-butanol (373 K, c), isobutene (300 K, d) and isobutane (380 K, e) on a selective oxidation catalyst.

The same mechanism proposed for the combustion catalyst Mg-chromite apply also to catalysts that allow significant yields in acetic acid from n-butane, like vanadia-titania, that accordingly also show a medium-high Brpnsied acidity. Being acetate ions intermediates in the combustion way, it is easily rationalized that the production of acetic acid is favored by the addition of steam in the reactant mixture and by adjusting the reaction conditions. 

The catalysts that allow the production of maleic anhydride from n-butane with high selectivity, like (V0)2P207, are characterized by a strong acidity, that, like a strong basicity, favors the decomposition of alkoxides to give the olefin and the diene. The catalysts that allow the production of maleic anhydride, either from n-butane or from butenes and butadiene, necessarily have particular sites that allow the insertion of oxygen atoms in the 1,4-position of butadiene. These sites are definitely absent on combustion catalysts. 

The active layer must provide the required activity, selectivity and thermochemical stability properties. Different active phases can be adopted depending on the operating constraints and the fuel type. In the following we will mainly focus on CH4 (i.e. the main constituent of natural gas) as the reference fuel for GT applications. In this respect, the combustion catalysts that have been most extensively investigated for configurations based on lean combustion concepts are PdO-based systems and metal-substituted hexaaluminates. 

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