Abstract
Sol-gel spread self-combustion is the burning of the complexing agent in dried gel and the oxidant. Meanwhile, high temperature takes place during the combustion process, which is harmful to the pore structure of the catalyst. The nitrate from metal nitrate precursors as an oxidant could participate in the spread of the self-combustion process. Therefore, the influence of nitrate from metal nitrate on the spread self-combustion of an iron–cerium–tungsten citric acid gel and its catalytic performance of NOx reduction were investigated by removing nitrate via the dissolution of washing co-precipitation with citric acid and re-introducing nitric acid into the former solution. It was found that the removal of nitrate contributes to enhancing the NH3–SCR activity of the magnetic mixed oxide catalyst. The NOx reduction efficiency was close to 100% for Fe85Ce10W5–CP–CA at 250 °C while the highest was only 80% for the others. The results of thermal analysis demonstrate that the spread self-combustion process of citric acid dried gel is enhanced by re-introducing nitric acid into the citric acid dissolved solution when compared with the removal of nitrate. In addition, the removal of nitrate helps in the formation of γ-Fe2O3 crystallite in the catalyst, refining the particle size of the catalyst and increasing its pore volume. The removal of nitrate also contributes to the formation of Lewis acid sites and Brønsted acid sites on the surface of the catalyst compared with the re-introduction of nitric acid. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrates that both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms exist over Fe85Ce10W5–CP–CA at 250 °C with E–R as its main mechanism.
Highlights
Nitrogen oxide (NOx ) emitted from coal-fired power plants and automobile engines has a strong negative influence on the environment and human health [1,2,3,4,5,6]
A large amount of heat is released during the spread self-combustion of the citric acid dried gel, and brings about a high temperature that acts on the obtained composite oxide catalyst, which might destroy the physical structure of catalyst, thereby influencing its catalytic performance of NOx reduction even though the duration of high temperature is short
0.5 to 2.0 further decreased its catalytic performance. This demonstrates that the nitrate brought from the precursors of metal nitrate shows an inhibition on the NH3 –SCR activity of the magnetic
Summary
Nitrogen oxide (NOx ) emitted from coal-fired power plants and automobile engines has a strong negative influence on the environment and human health [1,2,3,4,5,6]. Due to the non-toxicity, low cost, environment, and the outstanding redox ability between FeIII and FeII , a series of iron-based mixed oxide catalysts prepared through co-precipitation, sol-gel, and impregnation methods have been developed by many. A novel Fe–Ce–W mixed oxide catalyst synthesized via the citric acid sol-gel spread self-combustion method exhibited high catalytic activity of NOx reduction with high-dispersive γ-Fe2 O3 crystallite formed in it [27]. A large amount of heat is released during the spread self-combustion of the citric acid dried gel, and brings about a high temperature that acts on the obtained composite oxide catalyst, which might destroy the physical structure of catalyst, thereby influencing its catalytic performance of NOx reduction even though the duration of high temperature is short. X-ray diffraction (XRD), N2 -adsorption–desorption, x-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (H2 -TPR), temperature-programmed desorption (NH3 -TPD), and scanning electron microscope (SEM) were eventually used to characterize the physical structural and chemical properties of the catalyst
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
