Abstract
This study explores NO x storage in a Pt/K/Al 2O 3 lean NO x trap (LNT) catalyst using in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) in conjunction with chemisorption. The combination of these techniques allows the quantification of surface species for this catalyst system. A free nitrate ion, NO 3 −, is the primary form of stored NO x on the potassium phase at all temperatures, but there was significant nitrite formation observed below 200 °C during short adsorption times. The NO 2 saturation storage on Pt/K/Al 2O 3 decreases from 6.7 μmol/m 2 at 150 °C to 1.8 μmol/m 2 at 400 °C, and DRIFTS indicates that the equilibrated surface species are identical over this entire temperature range. While the final state of Pt/K/Al 2O 3 is identical at all temperatures, the rates and observed surface species change significantly. After 1 min uptake, NO x adsorption varies from 0.35 μmol/m 2 at 150 °C to a maximum of 3.2 μmol/m 2 at 250 °C, and at 400 °C the adsorption decreases to 1.1 μmol/m 2. This temperature sweep illustrates the limiting regimes associated with NO x adsorption: kinetic limitations at lower temperatures due to the strength of the Pt–O bond and insufficient storage sites at higher temperatures. This study propose three routes for the storage of NO x on Pt/K/Al 2O 3, two of them involving a potassium storage site adjacent to Pt sites, and a third route that involves a form of NO 2 disproportionation on storage sites irrespective of their proximity to Pt.
Sign-in/Register to access full text options 
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.
