Solvent-free oxidation of ethylbenzene over LDH-hosted Co(II) Schiff base of 2-hydroxy-1-naphthaldehyde and 4-amino benzoic acid

Abstract

Co(II) Schiff base complexes derived by condensation of 4-amino benzoic and 2-hydroxy-1-naphthaldehyde was immobilized into layered double hydroxide, {LDH-[NAPABA-Co(II)]} and characterized by various techniques namely ICP-AES, SEM, TEM, EDX, XRD, FTIR, BET surface area, EPR, TGA, and DRUV–vis. spectroscopy. The structures of the Co(II) Schiff base complex are optimized by DFT calculations. The catalytic activity of the heterogenized Co(II) Schiff base complex for the oxidation of ethylbenzene using tert-butylhydroperoxide is studied under a solvent-free condition. Ethylbenzene upon oxidation gave benzaldehyde, acetophenone, and benzoic acid with 67.4% conversion of ethylbenzene and 99.57% selectivity of acetophenone. The catalyst is recyclable up to six cycles without notable loss of their activity.

Keywords:

• Layered double hydroxide
• heterogeneous catalyst
• Co(II) Schiff base complex
• ethylbenzene oxidation
• tert-butylhydroperoxide

Acknowledgements

Further, the authors are thankful to Head, School of Chemical Sciences, UGC-DAE Consortium of Scientific Research, Devi Ahilya University Indore, STIC Cochin and Central Salt and Marines Chemical Research Institute (CSMCRI), Bhavnagar, Gujarat, for providing various analytical facilities.

Disclosure statement

There are no conflicts to declare.

Additional information

Funding

The authors are thankful to University Grant Commission New Delhi, India, for financial support (UGC-RGNF: F1-17.1/2016-17/RGNF-2015-17-SC-MAD-19994/SAIII/Website)