A novel diesel oxidation catalyst with low SO2 oxidation activity and capable of meeting Euro V emission standards

Synthesis of La1-xSrxCoO3-δ and its catalytic oxidation of NO and its reaction path

The oxidation rate of NO to NO2 is a critical parameter in the removal of NOx within selective catalytic reduction (SCR) systems. LaCoO3-δ is a kind of potential catalyst to enhance the oxidation of NO to NO2, it may offers an economic and stable alternative to noble metal catalysts, particularly at elevated temperatures. This study aimed to enhance the catalytic efficiency of LaCoO3-δ through strontium (Sr) doping. La1-xSrxCoO3-δ (with varying x values of 0.1, 0.2, 0.3, 0.4) was synthesized using a sol-gel method. La1-xSrxCoO3-δ exhibited superior NO oxidation catalytic activity compared to LaCoO3-δ, with the most notable enhancement observed at x = 0.3 (84 % conversion). This improvement can be attributed to the substitution of La3+ with Sr2+, which induces lattice distortion and charge imbalance, thereby creating more oxygen vacancies that enhance the catalytic oxidation capability of La1-xSrxCoO3-δ. However, it's important to note that an excessive amount of Sr can result in the formation of SrCO3 deposits on the surface of La1-xSrxCoO3-δ, thereby diminishing its catalytic oxidation performance. The catalytic oxidation reaction behavior adhered most closely to the O2-adsorbed E-R model, the surface defects in La1-xSrxCoO3-δ playing a pivotal role in the catalytic reaction.

An overview of after-treatment systems for diesel engines

Vehicular pollution has become a major problem in urban areas due to the exponential rise in the number of automobiles. Typical exhaust emissions which include nitrogen oxides (NO_x), hydrocarbons (HC), carbon monoxide (CO), soot, and particulate matter (PM) undoubtedly have an unpleasant effect on the environment. Several pollution control bodies are taking this subject seriously and issuing stringent emission norms which are to be complied strictly. Thus, regulation of these harmful pollutants is the need of the hour. Alternative fuels such as biodiesels and alcohols which are considered as a potentially viable solution for the problem of fossil fuel depletion also tend to require exhaust gas after-treatment in order to comply with the upcoming emission norms. Hence, this paper attempts to give a brief insight on the development and advances of different after-treatment devices like diesel particulate filter (DPF), lean NO_x trap (LNT), diesel oxidation catalyst (DOC), and selective catalytic reduction (SCR).

Promoting effect of vanadium on catalytic activity of Pt/Ce-Zr-O diesel oxidation catalysts

A series of Pt-V/Ce-Zr-O diesel oxidation catalysts was prepared using the impregnation method. The catalytic activity and sulfur resistance of Pt-V/Ce-Zr-O were investigated in the presence of simulated diesel exhaust. The effect of vanadium on the structure and redox properties of the catalysts was also investigated using the Brunauer-Emmett-Teller method, X-ray diffraction, H2 temperature-programmed reduction, CO temperature-programmed desorption, X-ray photoelectron spectroscopy, and Energy Dispersive Spectroscopy. Results showed that the Pt particles were well dispersed on the Ce-Zr-O carrier through the vanadium isolation effect, which significantly improved the oxidation activity toward CO and hydrocarbons. An electron-withdrawing phenomenon occurred from V to Pt, resulting in an increase in the metallic nature of platinum, which was beneficial to hydrocarbon molecular activation.