Highly Dispersed Zn Sites on ZrO2 by Flame Spray Pyrolysis for CO2 Hydrogenation to Methanol

• Published in: Topics in catalysis Vol. 66; no. 19-20; pp. 1492 - 1502
• Main Authors: Fujiwara, Kakeru, Akutsu, Taiki, Nishijima, Masahiko, Tada, Shohei
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.11.2023; Springer Nature B.V
• Subjects: Carbon dioxide; Catalysis; Catalytic activity; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Hydrogenation; Industrial Chemistry/Chemical Engineering; Methanol; Original Paper; Pharmacy; Photoelectrons; Physical Chemistry; Solid solutions; Spray pyrolysis; X ray photoelectron spectroscopy; X-ray diffraction; Zinc oxide; Zirconium dioxide; Flame synthesis; Tetragonal ZrO; Solid solution; Methanol synthesis; Zn substitution
• ISSN: 1022-5528; 1572-9028
• DOI: 10.1007/s11244-023-01803-w

In this study, we synthesized x ZnO–ZrO 2 ( x  = 14–40 at%) by flame spray pyrolysis under a lean-fuel condition. The optimal ZnO content was investigated to obtain a ZnO–ZrO 2 solid solution with high specific surface area for CO 2 -to-methanol hydrogenation. The Zn species in ZnO–ZrO 2 were highly dispersed and hexagonal ZnO was not detected by X-ray diffraction (XRD). After heating the particles in Ar at 400 °C for 3 h, hexagonal ZnO particles were observed at x  = 40 at%, while below x  = 28 at%, the Zn species remained high dispersion state. A fraction of the Zn species was substituted into the bulk of the ZrO 2 particles, as evidenced by the shift of the ZrO 2 (101) peak in the XRD patterns. The elemental mapping of Zn and Zr in 28 at% ZnO–ZrO 2 showed that the Zn species on the surface were uniformly distributed. The presence of partially reduced Zr δ+ state (δ < 4) was confirmed by X-ray photoelectron spectroscopy. The Zr δ+ state in the ZnO–ZrO 2 particles was prominent when ZnO content was below 28 at%. The catalytic activity of 28 at% ZnO–ZrO 2 for CO 2 -to-methanol hydrogenation was higher than that of 40 at% ZnO–ZrO 2 . At 300 °C and 1.0 MPa, the CO 2 conversion and the selectivity to methanol over 28 at% ZnO–ZrO 2 were 9 and 48%, respectively, resulting in the high yield of methanol (4.3%). Graphical abstract