Boosting catalytic oxidation of propane over mixed-phase CoO-Co3O4 nanoparticles: Effect of CoO

Abstract

A series of pure Co3O4 and mixed-phase CoO-Co3O4 nanoparticles were synthesized through a facile citric acid complex strategy. Different from pure Co3O4, the extra CoO is beneficial to the formation of small crystalline size (11.8 nm), large specific surface area (62.8 m2·g−1), and high Co2+/Co3+ and Oads/Olatt ratios. Moreover, the interaction between CoO and Co3O4 diminishes the electron cloud density in the outer layer of O atom, weakens the strength of the CoO bond, and improves the mobility of active oxygen species. At a GHSV of 30,000 ml·g−1·h−1, the mixed-phase CoO-Co3O4 converted propane to 90% only at 235 °C. After 40 h of reaction, CoO was oxidized into smaller Co3O4 particles and maintained a stable catalytic activity. Further research found that the mixed-phase CoO-Co3O4 still has good activity (T90 = 250 °C) even at high GHSV (75,000 ml·g−1·h−1). The outstanding performance of nanoparticles makes it possible to achieve deep purification of VOCs under high GHSV.