Behavior of different soot combustion catalysts under NOx/O2. Importance of the catalyst–soot contact

Four different catalysts (Pt/Al2O3, Ce0.8Zr0.2O2, PrO2−x and SrTiCuO3) have been investigated on a laboratory scale to evaluate their potential as diesel soot combustion catalysts under different experimental conditions, which simulate the situation found in a continuous regeneration technology trap (dual-bed configuration of catalyst and soot) or a catalyst-coated filter system (single-bed configuration, both catalyst and soot particles mixed under loose-contact mode). Under dual-bed configuration, the behavior of the catalysts towards soot combustion are very similar, despite the differences observed in the NO2 production profiles. However, under single-bed configuration, there are important differences in the soot combustion activities and in the NO2 slip profiles. The configurations chosen have an enormous impact on CO/(CO + CO2) ratios of combustion products as well. The most active catalyst under NOx + O2 is PrO2−x combining a high contribution of active oxygen-assisted soot combustion as well as high NO2 production activity along the catalytic bed.

Isotopic study of ceria-catalyzed soot oxidation in the presence of NOx

The ceria-catalyzed soot oxidation mechanism has been studied by a pulse technique with labeled O2 in the absence and presence of NO, using ceria–soot mixtures prepared in the loose contact mode. In the absence of soot, the ceria-catalyzed oxidation of NO to NO2 takes place with ceria oxygen and not with gas-phase O2. However, the oxygen exchange process between gas-phase O2 and ceria oxygen (to yield back O2, but with oxygen atoms coming from ceria) prevailed with regard to the ceria-catalyzed oxidation of NO to NO2. Gas-phase O2 did not react directly with soot when pulsed to a soot–ceria loose contact mixture. Instead, ceria oxygen is transferred to soot (this step does not require gas-phase molecular oxygen to be present), and gas-phase O2 fills up the vacancies created on the oxide in a further step. The transfer of oxygen between ceria and soot occurred directly in the absence of NO. However, in the presence of NO, NO2 is expected to be additionally generated by ceria oxygen oxidation, which also reacts with soot. The main reaction products of the ceria-catalyzed soot oxidation reaction with NO/O2 were CO2 and NO. Additionally, evidence of the reduction of NOx to N2 was found.

L’episcopio del Tolmo de Minateda (Albacete, Spagna). Architettura e funzione degli ambienti tra la fine del VI e l’inizio dell’VIII secolo

The episcopal complex of Eio, located at El Tolmo de Minateda, was built between the end of the sixth century and the beginning of the seventh century. It may have been created as a result of a political decision taken by the authority of the Visigothic kingdom (based at Toletum) to control the Byzantine territories of south-east Hispania. With a comprehensive study of the construction phases, and of the decoration and location of spaces, we can recreate and interpret the function of each space in the episcopal palatium or episcopium, and detail the chronological development of the building. After the Arab-Berber conquest of Hispania in the early eight century, the whole complex underwent alterations that converted the religious and monumental public area into a private, residential and artisan Islamic quarter.