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Issue 18, 2012
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Reaction mechanism of dimethyl carbonate synthesis on Cu/β zeolites: DFT and AIM investigations

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Abstract

The mechanism of dimethyl carbonate (DMC) synthesis on Cu-exchanged zeolite β has been investigated employing density functional theory (DFT) calculations and a double numerical plus polarization (DNP) basis set. The adsorption energy (ΔE) and decomposition activation energy (Ea) for O2 are −1.84 and 1.72 eV, respectively, suggesting that the decomposition of O2 occurs readily under reaction conditions on the Cu site. The formed O atom further reacts with methanol to form surface-bound (CH3O)(OH)–Cu(I)/β, in which CH3O and OH were coadsorbed on the Cu+ of the catalyst; this process proceeds without an activation barrier and with an energy release of 1.23 eV. The (CH3O)(OH)–Cu(I)/β species then reacts with another methanol molecule and carbon monoxide to produce DMC through two different reaction pathways. In path I, insertion of carbon monoxide into the (CH3O)(OH)–Cu(I)/β leads to the formation of monomethyl carbonate species (CH3OCOOH), which then reacts with methanol to produce DMC and H2O. The activation energies for both steps are 0.97 and 0.65 eV, respectively. In path II, (CH3O)(OH)–Cu(I)/β reacts with methanol first to produce a dimethoxide species ((CH3O)(CH3O)–Cu(I)/β), and the formation of DMC is via the insertion of carbon monoxide into the (CH3O)(CH3O)–Cu(I)/β. The activation energies for these elementary reactions are 0.65 and 0.70 eV, respectively. The topological properties of electron density distributions for all the related stationary points involved in this reaction have also been examined using the atoms in molecule (AIM) theory for the illustration of the bond paths and weak interactions of all the stationary points in the reaction path.

Graphical abstract: Reaction mechanism of dimethyl carbonate synthesis on Cu/β zeolites: DFT and AIM investigations

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Publication details

The article was received on 14 Mar 2012, accepted on 01 Jun 2012 and first published on 01 Jun 2012


Article type: Paper
DOI: 10.1039/C2RA20480K
Citation: RSC Adv., 2012,2, 7109-7119
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    Reaction mechanism of dimethyl carbonate synthesis on Cu/β zeolites: DFT and AIM investigations

    Y. Shen, Q. Meng, S. Huang, S. Wang, J. Gong and X. Ma, RSC Adv., 2012, 2, 7109
    DOI: 10.1039/C2RA20480K

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