An Application of Steady‐state Isotopic‐transient Kinetic Analysis (SSITKA) in DeNO_x Process

Abstract

This Minireview presents an overview of the advancement and capabilities of the steady‐state isotopic transient kinetic analysis in the selective catalytic reduction of NOx. Firstly, a brief overview of the method and the kinetic parameters of catalyst‐surface reaction intermediates, including concentration and coverage of surface intermediates, surface residence time and intrinsic turnover frequency (TOF), is provided. Furthermore, the focus is on the application of SSITKA or a unique combination of SSITKA‐DRIFTS for the identification of active and/or inactive (spectators) species in NH3−SCR, H2−SCR and HCs−SCR. Different forms of adsorbed species and their formation rates revealing the main elementary steps on the catalyst's surface involving labeled molecules are discussed. The emphasis is laid on the optimization and design of industrial catalysts.

Copper Single Atom-Triggered Niobia–Ceria Catalyst for Efficient Low-Temperature Reduction of Nitrogen Oxides

“…Several techniques including in situ DRIFTS, steady-state isotopic transient kinetic analysis (SSITKA) SSITKA–DRIFTS, and transient nonisotopic experiments have been reported to be effective for the reaction mechanism study. − While some reactive intermediates might be neglected in an in situ DRIFTS study, , transient SSITKA–DRIFTS and transient nonisotopic experiments are more powerful techniques for the NH 3 -SCR mechanism study . Due to limited resources, only combined in situ DRIFTS and kinetic studies were performed for NH 3 -SCR mechanism study in this work.…”

Experimental Evidence for the Relationship between Al Site Distribution and Catalytic Performance in Methanol-to-Olefins Reaction over ZSM-5 Zeolite

“…The two ZSM-5 catalysts exhibited almost identical catalytic performances in the MTO reaction in terms of conversion and product selectivity, which hindered clearly establishing the structure–performance relationship. Therefore, the impact of the Al distribution on the reaction was experimentally studied via a steady-state isotopic transient kinetic analysis (SSITKA), which has been used in the past to track the transient response of an insertion process of a labeled atom into the target product in several reactions. − To the best of our knowledge, this is the first time that the SSITKA method with a high time resolution has been applied to the MTO reaction, which enabled us to track the transient response in much more detail than what has been accomplished in previous studies. − Using 13 C-labeled methanol as the reactant allowed us to unveil the differences in the propylene formation mechanism, as the insertion of 13 C into the propylene fragments clearly worked differently for the two ZSM-5 samples, thus providing direct experimental evidence of the effect of the Al distribution in the zeolite framework on the MTO catalytic performance of the zeolites.…”

Time‐resolved DRIFT Spectroscopy Study of Carbonaceous Intermediates during the Water Gas Shift Reaction over Au/Ceria Catalyst

“…However, the signals from the actual active species are typically weak and strongly overlapped with the signals of spectator species not engaged in the catalytic surface processes. For selective extraction of information on active species, transient spectroscopic techniques have been developed, such as, pulse-reaction, steady-state isotopic transient kinetic analysis (SSITKA) [25,26] and, more recently, modulation excitation spectroscopy (MES). [27,28] MES operates under quasi-steady-state conditions forced by periodic perturbation of the system by changing an external parameter, e. g. concentration, temperature, irradiation, or pH.…”