Enhancement of nitric oxide decomposition efficiency achieved with lanthanum-based perovskite-type catalyst

Direct decompositions of nitric oxide (NO) by La_0.7Ce_0.3SrNiO₄, La_0.4Ba_0.4Ce_0.2SrNiO₄, and Pr_0.4Ba_0.4Ce_0.2SrNiO₄ are experimentally investigated, and the catalysts are tested with different operating parameters to evaluate their activities. Experimental results indicate that the physical and chemical properties of La_0.7Ce_0.3SrNiO₄ are significantly improved by doping with Ba and partial substitution with Pr. NO decomposition efficiencies achieved with La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄ are 32% and 68%, respectively, at 400 °C with He as carrier gas. As the temperature is increased to 600 °C, NO decomposition efficiencies achieved with La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄, respectively, reach 100% with the inlet NO concentration of 1000 ppm while the space velocity is fixed at 8000 hr^?1. Effects of O₂, H₂O_(g), and CO₂ contents and space velocity on NO decomposition are also explored. The results indicate that NO decomposition efficiencies achieved with La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄, respectively, are slightly reduced as space velocity is increased from 8000 to 20,000 hr^?1 at 500 °C. In addition, the activities of both catalysts (La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄) for NO decomposition are slightly reduced in the presence of 5% O₂, 5% CO₂, or 5% H₂O_(g). For durability test, with the space velocity of 8000 hr^?1 and operating temperature of 600 °C, high N₂ yield is maintained throughout the durability test of 60 hr, revealing the long-term stability of Pr_0.4Ba_0.4Ce_0.2SrNiO₄ for NO decomposition. Overall, Pr_0.4Ba_0.4Ce_0.2SrNiO₄ shows good catalytic activity for NO decomposition.

Implications: Nitrous oxide (NO) not only causes adverse environmental effects such as acid rain, photochemical smog, and deterioration of visibility and water quality, but also harms human lungs and respiratory system. Pervoskite-type catalysts, including La_0.7Ce_0.3SrNiO₄, La_0.4Ba_0.4Ce_0.2SrNiO₄, and Pr_0.4Ba_0.4Ce_0.2SrNiO₄, are applied for direct NO decomposition. The results show that NO decomposition can be enhanced as La_0.7Ce_0.3SrNiO₄ is substituted with Ba and/or Pr. At 600 °C, NO decomposition efficiencies achieved with La_0.4Ba_0.4Ce_0.2SrNiO₄ and Pr_0.4Ba_0.4Ce_0.2SrNiO₄ reach 100%, demonstrating high activity and good potential for direct NO decomposition. Effects of O₂, H₂O_(g), and CO₂ contents on catalytic activities are also evaluated and discussed.