Solvent-free selective oxidation of cyclohexane to KA oil in air over CoWO4@W18O49 catalyst

• Published in: Journal of environmental chemical engineering 2023-04, Vol.11 (2), p.109380, Article 109380
• Main Authors: Bhandari, Sonu, Andola, Suresh Chandra, Kothari, Anil Chandra, Khurana, Deepak, Singh, Shivani, Poddar, Mukesh Kumar, Khan, Tuhin Suvra, Sasaki, Takehiko, Prasad, V.V.D.N., Bal, Rajaram
• Format: Article
• Language: English
• Subjects: Cobalt tungstate; EXAFS; Green chemistry; Industrial synthesis; KA oil; Oxygen vacancy; Selective oxidation
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2023.109380

The challenge for researchers in heterogeneous catalysis is to develop robust catalysts while using benign reaction conditions, without producing unwanted by-products and preventing leaching of metal during the processes. We have synthesized nanosized CoWO4@W18O49 catalyst with oxygen vacancy sites for molecular oxygen activation from air, and this catalyst selectively oxidized cyclohexane to KA oil (KA oil referred to ketone-alcohol oil) in solvent-free conditions, where under optimum conditions, ∼24 % cyclohexane conversion with ∼93 % KA oil selectivity was achieved. The catalyst has been synthesized by the co-precipitation method and studied with the help of various analytical tools. DFT studies were also performed to calculate the energy needed for the oxygen vacancy generation over the CoWO4 (111), W18O49 (010) and CoWO4@W18O49 (010) surfaces. The energy required for the removal of oxygen atom at the CoWO4@W18O49 (010) surface was found to be − 15.8 kJ/mol, which is 96.2 kJ/mol and 46.9 kJ/mol lower than the CoWO4 (111) and W18O49 (010) surfaces respectively. The exceptional catalytic activity of CoWO4@W18O49 is an outcome of the combined contribution of the active CoWO4 and W18O49 interfaces, which have redox sites and a lot of vacancies of oxygen that benefit from the effective interaction. [Display omitted] •CoWO4@W18O49 catalyst is prepared by Co-precipitation method for oxidation reaction.•Solvent-free oxidation of cyclohexane to KA Oil with air as oxidant.•Catalyst was stable up to 5 cycles without any significant loss in activity.•Oxygen vacancies of CoWO4@W18O49 can activate O2 present in air.•DFT study calculate the energy required for the generation of oxygen vacancy.