Experimental and Theoretical Study of the Reactions between Small Neutral Iron Oxide Clusters and Carbon Monoxide

Abstract

Reactions of small neutral iron oxide clusters (FeO(1-3) and Fe(2)O(4,5)) with carbon monoxide (CO) are investigated by experiments and first-principle calculations. The iron oxide clusters are generated by reaction of laser-ablation-generated iron plasma with O(2) in a supersonic expansion and are reacted with carbon monoxide in a fast flow reactor. Detection of the neutral clusters is through ionization with vacuum UV laser (118 nm) radiation and time-of-flight mass spectrometry. The FeO(2) and FeO(3) neutral clusters are reactive toward CO, whereas Fe(2)O(4), Fe(2)O(5), and possibly FeO are not reactive. A higher reactivity for FeO(2) [sigma(FeO(2) + CO) > 3 x 10(-17) cm(2)] than for FeO(3) [sigma(FeO(3) + CO) approximately 1 x 10(-17) cm(2)] is observed. Density functional theory (DFT) calculations are carried out to interpret the experimental observations and to generate the reaction mechanisms. The reaction pathways with negative or very small overall barriers are identified for CO oxidation by FeO(2) and FeO(3). The lower reactivity of FeO(3) with respect to FeO(2) may be related to a spin inversion process present in the reaction of FeO(3) with CO. Significant reaction barriers are calculated for the reactions of FeO and Fe(2)O(4-5) with CO. The DFT results are in good agreement with experimental observations. Molecular-level reaction mechanisms for CO oxidation by O(2), facilitated by condensed phase iron oxides as catalysts, are suggested.

One step-synthesis of highly dispersed iron species into silica for propylene epoxidation with dioxygen

“…In our case, propylene epoxidation on the highly dispersed iron species into the silica structure also begins under similar conditions. In addition, recent theoretical and experimental works have determined that the critical step for this reaction is the Fe-O formation of the terminal bond, that requires activation of the O=O bond [71,72]. This observation is in agreement with our computational calculations which postulate the interaction between isolated iron species and O 2, causing an increase in the O-O bond length of almost 7% which may react with the propylene adsorbed on the acidic proton located in its immediate vicinity.…”

Methane Activation by Yttrium‐Doped Vanadium Oxide Cluster Cations: Local Charge Effects

“…The product and residual reactant ions are skimmed into a vacuum system of a time-of-flight mass spectrometer for mass and abundance measurements. The instantaneous total gas pressure in the fast flow reactor is estimated to be around 300 Pa at T = 350 K. [25] The bath gas temperature in the reactor is around 300-400 K considering that the carrier gas can be heated during the process of laser ablation. The details of the experiment can be found in reference [12].The clusters in this study are not mass-selected, and all clusters react with a given reactant with the same partial gas pressure for the same period of time, which leads to a reliable determination of the relative rate constants.…”

CH Activation on Aluminum–Vanadium Bimetallic Oxide Cluster Anions

“…The rate constant k of the reaction in the fast-flow reactor can be estimated by I = I 0 expA C H T U N G T R E N N U N G (Àk1l/u) in which I and I 0 are signal magnitudes of the clusters in the presence and absence of reagent gas, respectively; 1 is the molecular density of reactant gas; [32,97] l is the effective path length of the reactor ( % 60 mm); and u is the cluster beam velocity (%1 km s À1 ). The estimated values of k are listed in Table 1.…”

“…[97] The estimated values of À (x = 1-3). The reaction efficiency (F) for each reaction is quite small.…”