Mechanism of the Vanadium Oxide-Catalyzed Selective Reduction of NO by NH₃. A Quantum Chemical Modeling

Abstract

Quantum chemical calculations have been performed using density functional theory to model the mechanism of selective catalytic reduction of NO by NH 3 on vanadium oxide. The reaction is initiated by NH 3 adsorption on a Brønsted site modeled as a dimer cluster model representative of vanadium oxide, containing a terminal VdO adjacent to a V-OH group. The calculations indicate that the adsorbed NH 3 behaves as NH 4 + , which is supported by calculated IR spectra. Subsequently NO reacts with this activated NH 3 to yield NH 2 NO and finally the reaction products N 2 and H 2 O. The present results give support to a dual-site Eley-Rideal-type mechanism involving a Brønsted site and agree with isotopic labeling studies.

Elementary steps of the catalytic NOx reduction with NH3: Cluster studies on reaction paths and energetics at vanadium oxide substrate

“…In contrast to experimental results previous theoretical studies investigating NH 3 adsorption at the perfect V 2 O 5 (010) surface could only verify the presence of one strongly bound NH 4 + species [12][13][14][15][16][17][18][19] . Obviously, important details of the reaction mechanism have not yet been unveiled and essential questions, e.g.…”

“…This includes hydrogen, nitrogen, NO, ammonia, as well as NH x species, x= 1, 2, 4 generated by (de)hydrogenation processes at the surface. Going beyond previous theoretical studies by others [12][13][14][15][16][17][18][19] where only sections of the perfect V 2 O 5 (010) surface have been examined, we considered also models for sections of the reduced surface due to oxygen vacancies. Our theoretical study showed that surface reduction strongly affects the adsorption properties and reduced sites may play an important role for the SCR reaction.…”

Density Functional Theory Calculations of the Oxidative Dehydrogenation of Propane on the (010) Surface of V2O5†

“…36 Since the KohnSham orbitals 21 give the total ground-state electron density of the system, they also provide a measure of both the global and local chemical reactivity of the system. 22,27,[37][38][39][40][41][42] The Fukui functions (FF) and related hardness/softness characteristics constitute the major chemical descriptors of molecular species for open systems, in which the number of electrons is a continuous equilibrium variable. 22 In the frozen core approximation the FF represent the density of the relevant frontier molecular orbital involved in electron receiving (nucleophilic attack) or withdrawing (electrophilic attack) processes.…”

Phase‐Selective CVD of Vanadium Oxide Nanostructures

“…Technologically relevant material properties of vanadium oxide compounds rely on the respective electronic state of the vanadium ion that can appear in different valence configurations leading to various applications such as electrodes in batteries, [1][2][3] thermochromic windows or IR protective shields, [4][5][6][7] catalysts for the oxidation of NO x or hydrocarbons, [8][9][10][11][12] and infrared detectors. [13,14] Vanadium oxide phases have been synthesized as one-, two-or three-dimensional materials by several methods such as sol-gel or other wet chemical techniques, [14][15][16] pulsed laser deposition, [17,18] sputtering or physical vapor deposition.…”