Thermal Behavior, Crystal Structure, and Solid-State Transformation of Orthorhombic Mo-V Oxide under Nitrogen Flow or in Air

Masahiro Sadakane; Katsunori Kodato; Nobuhiro Yasuda; Satoshi Ishikawa; Wataru Ueda

doi:10.1021/acsomega.9b01212

Thermal Behavior, Crystal Structure, and Solid-State Transformation of Orthorhombic Mo-V Oxide under Nitrogen Flow or in Air

ACS Omega. 2019 Aug 6;4(8):13165-13171. doi: 10.1021/acsomega.9b01212. eCollection 2019 Aug 20.

Authors

Masahiro Sadakane¹, Katsunori Kodato², Nobuhiro Yasuda³, Satoshi Ishikawa⁴, Wataru Ueda⁴

Affiliations

¹ Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan.
² Catalysis Research Center, Hokkaido University, N-21, W-10, Sapporo 001-0021, Japan.
³ Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-gun 679-5198, Japan.
⁴ Faculty of Engineering, Kanagawa University, Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Kanagawa, Japan.

Abstract

Orthorhombic Mo-V oxide is one of the most active solid-state catalysts for selective oxidation of alkane, and revealing its detailed structure is important for understanding reaction mechanisms and for the design of better catalysts. We report the single-crystal X-ray structure analysis of orthorhombic Mo-V oxide heated under a N₂ flow; V is present in 6-membered rings with partial occupancy, similar to the structure reported by Trunschke's group for orthorhombic Mo-V oxide heated under an Ar flow (Trunschke, ACS Catal.2017, 7, 3061). Our previous paper (Ishikawa, J. Phys. Chem. C, 2015, 119, 7195) reported that V is not present in the 6-membered rings when orthorhombic Mo-V oxide is calcined in the presence of oxygen. Furthermore, Trunschke's paper reported that V in the 6-membered rings moves to the surface of the crystals under oxidation reaction conditions in the presence of H₂O. Our present results provide additional evidence for V migration in the 6-membered rings during heat treatment. We also report the differences in the thermal behaviors, ultraviolet-visible absorptions, N₂ isotherms, and elemental analysis results of Mo-V oxide heated in air and under a N₂ flow. Furthermore, we report the solid-state transformation of orthorhombic Mo-V oxide to tetragonal Mo-V oxide by controlled heat treatment.