Evaluation of Co/SSZ‐13 Zeolite Catalysts Prepared by Solid‐Phase Reaction for NO‐SCR by Methane

Abstract

Co/SSZ‐13 zeolites were prepared by heating the finely dispersed mixture of NH4‐SSZ‐13 and different cobalt salts up to 550 °C. Investigations by thermogravimetry – differential scanning calorimetry – mass spectrometry provided new insight into details of the solid‐state reaction. Formation of Co carrying hydrate melt or volatile species was shown to proceed from chloride, nitrate, or acetylacetonate Co precursor salts upon thermal treatment. This phase change allows the transport of the Co species into the zeolite pores. The reaction of the NH4+ or H+ zeolite cations and the mobile Co precursors generates vapor or gas products, readily leaving the zeolite pores, and cobalt ions in lattice positions suggesting that solid‐state ion‐exchange is the prevailing process. The obtained catalysts are of good activity and N2 selectivity in the CH4/NO‐SCR reaction. The thermal treatment of acetate or formate salts give solid intermediates that are unable to get in contact and react with the cations in the zeolite micropores. These catalysts contain mainly Co‐oxide clusters located on the outer surface of the zeolite crystallites and have poor catalytic performance.

Charge Shielding Effect of Sodium Ions in Improving The Hydrophobicity and Performance of Co/Na‐SSZ‐13 Zeolite for Passive NOx Adsorber

“…[ 39,40 ] The reduction curve of Co‐SSZ‐13 can be fitted to six peaks centered at 284, 359, 515, 690, 850, and 963 °C, which can be assigned to the reduction of Co oxo‐ions (284 °C), Co 3 O 4 (359 °C), Co‐O‐Co (515 °C), isolated Co 2+ located at the CHA cage (690 °C) and D6Rs (850 °C) and cobalt phyllosilicate (963 °C), respectively. [ 19,20,41,42 ] It illustrates that more varieties of Co species are formed via a conventional incipient wetness impregnation method. More importantly, a large amount of cobalt phyllosilicate is generated due to the reaction between Co and Si in SSZ‐13 zeolite, which is also detected by Wang et al.…”

Study on the effect and its mechanism of H2O, O2 and CO2 on NTP combined with CH4-SCR

“…Thus, CH4-SCR is considered as an ideal NOx removal system. In recent years, studies show that in the application of CH4-SCR system, the catalyst activity and NOx removal efficiency are the core of this technology (Charrad et al 2020;Shi et al 2020). Among all kinds of catalysts, the zeolite catalysts have good thermal stability and wide activity temperature window.…”

Study on Effect of O 2 /H 2 O on CH 4 and NO x Removal with NTP

“…Thus, CH4-SCR is considered as an ideal NOx removal system. In recent years, studies show that in the application of CH4-SCR system, the catalyst activity and NOx removal efficiency are the core of this technology [9][10]. Among all kinds of catalysts, the zeolite catalysts have good thermal stability and wide activity temperature window.…”