Properties of BaAl2O4 in the Simultaneous Removal of Soot and NOx

An Overview on the Catalytic Materials Proposed for the Simultaneous Removal of NOx and Soot

Vehicular pollution has become a major problem in urban areas due to the exponential increase in the number of automobiles. Typical exhaust emissions, which include nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO), soot, and particulate matter (PM), doubtless have important negative effects on the environment and human health, including cardiovascular effects such as cardiac arrhythmias and heart attacks, and respiratory effects such as asthma attacks and bronchitis. The mitigation measures comprise either the use of clean alternative fuels or the use of innovative technologies. Several existing emission control technologies have proven effective at controlling emissions individually, such as selective catalytic reduction (SCR) and lean NOx trap (LNT) to reduce NOx and diesel particulate filter (DPF) specifically for PM abatement. These after-treatment devices are the most profitable means to reduce exhaust emissions to acceptable limits (EURO VI norms) with very little or no impact on the engine performances. Additionally, the relative lack of physical space in which to install emissions-control equipment is a key challenge for cars, especially those of small size. For this reason, to reduce both volume and cost of the after-treatment devices integrated catalytic systems (e.g., a sort of a "single brick") have been proposed, reducing both NOx and PM simultaneously. This review will summarize the currently reported materials for the simultaneous removal of NOx and soot, with particular attention to their nature, properties, and performances.

Synthesis and Characterization of BaAl2O4 Catalyst and its Photocatalytic Activity Towards Degradation of Methylene Blue Dye

Hexagonal BaAl2O4 catalyst has been prepared using a gamma-ray irradiation assisted polyacrylamide gel method. The catalysts synthesized at different calcining temperatures were analyzed to insight into their effects on the structural, crystalline, surface morphology, color, optical, fluorescence and photocatalytic properties of the hexagonal BaAl2O4 catalyst. Increasing the calcining temperature has obvious influences on the crystallinity, color, optical properties and the formation of the hexagonal BaAl2O4 catalyst. The optical energy gap (Eg) value of the hexagonal BaAl2O4 catalyst increases with the increasing of calcining temperature. TEM image of the pure hexagonal BaAl2O4 catalyst shows a morphology of flake structure and aggregation. Raman spectroscopy of the pure hexagonal BaAl2O4 catalyst exhibits four luminescent background peaks at 400, 415, 428 and 445 nm mainly due to the oxygen vacancies (VO), Ba vacancies (VBa) and some color centers exists in the BaAl2O4 sample. A comparison of photocatalytic activity among samples for degradation of methylene blue (MB) dye indicates that the pure hexagonal BaAl2O4 catalyst exhibits highest photocatalytic activity under the irradiation of both visible and ultraviolet light. Based on the fluorescence experiment, electrochemical and active species tests, the high photocatalytic activity of the pure hexagonal BaAl2O4 catalyst to be related to hole (h+) and hydroxyl radical (⋅OH) and also to the defects in the sample.