Computational study of benzene-to-phenol oxidation catalyzed by N 2O on iron-exchanged ferrierite

An Fe(II) ion at an α-cation exchange position of ferrierite, (Fe)α, was taken as a model for the active site in nitrous oxide decomposition and in the selective oxidation of phenol with nitrous oxide. The oxygen that is deposited via the decomposition of N2O is commonly referred to as α-oxygen, (O)α. Comparison with the results of cluster model calculations was performed for reaction of benzene-to-phenol oxidation. Periodic calculations predict the same reaction path for benzene oxidation as does the cluster model study. Differences in the adsorption modes for both types of calculations were analyzed and discussed

Two Mechanisms of Chlorocuprate Reactions with Alkyl Radicals: Dramatic Role of Nuclearity

Interaction of copper chlorides with radicals is a key step of single electron transfer reactions and is responsible for high selectivity of copper-catalyzed radical processes. In the present article reactions of binuclear copper­(II) chlorides with methyl radical were studied in the scope of density functional theory. The results of quantum-chemical calculations of potential energy surfaces allow proposing that there are at least two reasons for the lower activity of binuclear complexes Cu₂Cl₆^2– in comparison with CuCl₄^2–. First, the radicals react with binuclear chlorocuprates via an atom transfer mechanism through an activation barrier, in contrast to the barrierless character of such reactions with partition of CuCl₄^2–. Second, only in the systems with binuclear copper chloro complexes may an alternative path of spontaneous formation of chloroorganocuprates be realized. These intermediates may be dormant species in radical reactions

Non-localized charge compensation in zeolites : A periodic DFT study of cationic gallium-oxide clusters in mordenite

Periodic DFT calculations show that stability of binuclear cationic gallium–oxo clusters in high-silica zeolites is mainly controlled by the favorable geometrical environment of the Ga3+ ions, whereas the effect of the direct interaction with the charge-compensating framework anionic sites is less important. Extraframework cyclic Ga2O2+2 cations are shown to be active for light alkane dehydrogenation

Cluster Model DFT Study of the Intermediates of Benzene to Phenol Oxidation by N2O on FeZSM-5 Zeolites Citation for published version (APA): Cluster model DFT study of the intermediates of benzene to phenol oxidation by N 2 O on FeZSM-5 zeolites

An Fe(II) ion at an -cation exchange position of ZSM-5 zeolite (Fe/Z) was taken as a model for the active site in the nitrous oxide decomposition and in the selective oxidation of phenol with nitrous oxide. The oxygen deposited by decomposition of N 2 O is commonly referred to as -oxygen (OFe/Z). Cluster model DFT calculations show that the interaction of the OFe/Z center with benzene resulted easily in arene oxide formation. The results indicate a rather low activation energy for this step. Possible transformations of the adsorbed arene oxide are considered and the experimental evidence for the absence of the kinetic H/D isotope effect in phenol formation is discussed. It is concluded that the rate-limiting step for the in situ oxidation of benzene to phenol is the desorption of the product

Cluster model DFT study of CO adsorption to gallium ions in Ga/HZSM-5

Cluster model DFT calcns. of CO adsorption on various possible forms of gallium in Ga/HZSM-5 zeolites have been performed. CO was found to only weakly interact with Ga+, (GaO)+, and (Ga(OH)2-nHn)+ (n = 1, 2) cationic clusters. The resulting shifts of the CO stretching frequency (.nu.CO) are only very small. On the other hand, CO coordination to small mononuclear and binuclear Ga3+ hydride/hydroxide/oxide species results in pos. shifts in the stretching frequency in the range .nu.CO = 20-40 cm-1. Larger shifts (.nu.CO = 70-90 cm-1) are assocd. with CO coordination to Ga ions at the corners of small three-dimensional Ga-oxide clusters. The exptl. obsd. changes in the IR spectrum of adsorbed CO over Ga/HZSM-5 zeolites upon reductive and oxidative treatments are interpreted with these insights. Possibilities for the formation of such polynuclear oxide species in the zeolite micropore space are discussed. On the basis of recent literature insights, we suggest that large shifts derive from CO coordination to oligomeric Ga cationic complexes stabilized by the neg. zeolite charge