Continuous dimethyl carbonate synthesis from CO2 and methanol over BixCe1−xOδ monoliths: Effect of bismuth doping on population of oxygen vacancies, activity, and reaction pathway

• Published in: Nano research 2022-02, Vol.15 (2), p.1366-1374
• Main Authors: Chen, Yongdong, Li, Yue, Chen, Wei, Xu, Wen Wu, Han, Zhong-kang, Waheed, Ammara, Ye, Zhongbin, Li, Gao, Baiker, Alfons
• Format: Article
• Language: English
• Subjects: Activated carbon; Atomic/Molecular Structure and Spectra; Biomedicine; Biotechnology; Bismuth; Carbon dioxide; Catalysts; Ceramic coatings; Ceramic honeycombs; Cerium; Cerium oxides; Chemical synthesis; Chemistry and Materials Science; Condensed Matter Physics; Dehydration; Design parameters; First principles; Fourier transforms; Infrared reflection; Infrared spectroscopy; Lattice vacancies; Materials Science; Methanol; Nanocomposites; Nanotechnology; Oxygen; Research Article; Selectivity
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-021-3669-4

We evaluated bismuth doped cerium oxide catalysts for the continuous synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide in the absence of a dehydrating agent. Bi x Ce 1− x O δ nanocomposites of various compositions ( x = 0.06–0.24) were coated on a ceramic honeycomb and their structural and catalytic properties were examined. The incorporation of Bi species into the CeO 2 lattice facilitated controlling of the surface population of oxygen vacancies, which is shown to play a crucial role in the mechanism of this reaction and is an important parameter for the design of ceria-based catalysts. The DMC production rate of the Bi x Ce 1− x O δ catalysts was found to be strongly enhanced with increasing O v concentration. The concentration of oxygen vacancies exhibited a maximum for Bi 0.12 Ce 0.88 O δ , which afforded the highest DMC production rate. Long-term tests showed stable activity and selectivity of this catalyst over 45 h on-stream at 140 °C and a gas-hourly space velocity of 2,880 mL·g cat −1 ·h −1 . In-situ modulation excitation diffuse reflection Fourier transform infrared spectroscopy and first-principle calculations indicate that the DMC synthesis occurs through reaction of a bidentate carbonate intermediate with the activated methoxy (−OCH 3 ) species. The activation of CO 2 to form the bidentate carbonate intermediate on the oxygen vacancy sites is identified as highest energy barrier in the reaction pathway and thus is likely the rate-determining step.