Abstract
A series of Keggin-type heteropoly compounds (HPC) having different countercations (Co, Fe) and different addenda atoms (W, Mo) were synthesized and characterized by means of Fourier-Transform Infrared Spectrometer (FT-IR) and X-ray powder diffraction (XRD). The catalytic properties of the prepared catalysts for the dimethyl carbonate (DMC) synthesis from CO2 and CH3OH were investigated. The experimental results showed that the catalytic activity is significantly influenced by the type of the countercation and addenda atoms transition metal. Among the catalysts examined, Co1.5PW12O40 is the most active for the DMC synthesis, owing to the synergetic effect between Co and W. Investigating the effect of the support showed that the least acidic one (Al2O3) enhanced the conversion but decreased the DMC selectivity in favor of that of methyl formate (MF), while that of dimethoxy methane remained stable.
Highlights
The limited fossil fuel resources and the problems of global warming caused by an increase of atmospheric carbon dioxide concentrations have stimulated research in the utilization of CO2
The main characteristic features of the Keggin structure are observed at 10801060 cm-1, 990-960 cm-1, 900-870 cm-1, and 810-760 cm-1 assigned to the stretching vibration νas (POa), νas (M-Od), νas (M-Ob-M), and νas (M-Oc-M), respectively (M = W or Mo)
The presence of the primary Keggin structure in the synthesized phases was confirmed by Fourier-Transform Infrared Spectrometer (FT-IR) and X-ray powder diffraction (XRD)
Summary
The limited fossil fuel resources and the problems of global warming caused by an increase of atmospheric carbon dioxide concentrations have stimulated research in the utilization of CO2. Among the chemical compounds that can be obtained by using CO2, dimethyl carbonate (DMC) is considered as one of the most important It can be synthesized by reaction of methanol and CO2. It is worth noting that DMC is an important raw material in organic synthesis and has drawn much attention of researchers It has been paid more and more attention due to its low toxicity and wide applications [17]. It can be used as an environment-friendly intermediate and starting material for organic synthesis via carbonylation and methylation, replacing poisonous phosgene and dimethyl sulfate [18]. It is well known that the acidity and redox properties of 12-heteropoly compounds depend on both the constituent elements of polyanions and countercations
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