Soot combustion capacity

Hirano et al. [13] studied strontium-substituted LaFeOs perovskites for soot combustion, and the activity of these perovskites was reported to be only slightly lower than that of a Pt/Al20s reference catalyst. Taniguchi et al. [14] also reported that some Lai tK Fe03 perovskite catalysts outperform the soot combustion capacity of Pt catalysts in experiments performed with air and with soot-catalyst mixtures prepared in loose contact. 

The improvement in soot combustion capacity of LaBOs catalysts (B = Co,... 

The formation of perovskite structures does not always have a positive effect on the soot combustion activity of mixed oxides, and a few examples of catalyst deactivation due to perovskite structure formation have been reported. The stability of Ba, Isoot combustion, was studied. This catalyst was thermally stable after 30 h at 800 °C, but above 830 °C catalyst deactivation due to BaCe03 perovskite structure formation was observed [46]. Ba/Mn-Ce catalysts were also tested for soot oxidation in the presence of NO,c> concluding that the formation of perovskite-type oxides after the high-temperature calcination caused the loss of NO storage capacity and a small increase in soot oxidation temperature, but did not seem to affect the NO oxidation activity [47]. 

As far as toxicology is concerned, one must distinguish between soot, which is formed by the uncontrolled combustion of coal and oil, and carbon black, which is industrially produced under precisely defined conditions. Commercial carbon blacks are characterized by an atomic ratio H C of <0.1, low ash content, and high adsorption capacity. The soluble organic fraction (extractable materials) is less than 0.5 wt%. 

The heat capacity of the calorimeter is to be determined with duplicate mns on solid benzoic acid, CgHjCOOH. Two runs are then made on each liquid ester. Any run with unsat-isfactoiy featmes in the time-temperature plot or indications of incomplete combustion (soot, etc.) must be rejected. If any pair of mns fails to give reasonably concordant results (agreement within 0.5 percent or better), additional runs on the same substance should be made. 

Ceria-based formulations are among the more active catalysts for soot oxidation either under Og or in a NOyOg atmosphere, which decreases the combustion temperature from above 600°C down to 320-350°C. These results are very important for fulfilling new regulations on pollutant emission control. Among the several physicochemical parameters that influence the overall activity, the redox capacity and the availability of surface active oxygen species are certainly the most important. 

Studies of lignoceUulosic biofuel model compounds have likewise increased significantly in the past decade. Reaction pathways with implications for soot, aldehydic, and emissions from oxygenated and otherwise-functionalized fuels have been examined. Several key intermediates in pyrolytic pathways have been identified, including furanic carbenes, furanylmethyl radicals, dihydrofurans, and unsaturated ketones and aldehydes. Low-temperature combustion reactions available to these compounds are largely unexplored and, where modeled, involve highly functionalized per-oxy radicals with the capacity for novel reactions. As cycHc oxygenated species break down into smaller acyclic species, some potential arises for overlap with extant mechanisms for HC combustion. Composite ab initio and DFT calculations have been proved to be particularly useful in recent computational explorations of these compounds and their reaction pathways. 

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