Preparation of a nanostructured iron chromite spinel in the pure form and its catalytic activity for the selective oxidation of benzene to phenol: experimental and DFT studies

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 24; no. 23; pp. 933 - 9314
• Main Authors: Bhandari, Sonu, Khatun, Rubina, Khan, Tuhin Suvra, Khurana, Deepak, Poddar, Mukesh Kumar, Shukla, Astha, Prasad, V. V. D. N, Bal, Rajaram
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 28.11.2022
• Subjects: Benzene; Catalysts; Catalytic activity; Chromite; Chromium oxides; Ferric oxide; Green chemistry; Hydrocarbons; Hydrogen bonds; Iron; Mathematical analysis; Nanostructure; Oxidation; Phenols; Raman spectroscopy; Recyclability; Selectivity; Spinel; X ray photoelectron spectroscopy
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d2gc02335k

Selective oxidation of benzene to phenol in a single step is a long-standing challenge and has been a subject of potential interest for researchers. In this study, a nanostructured iron chromite spinel in the pure form was prepared, and it was found that this catalyst selectively oxidized benzene to phenol in a single step under mild and environmentally friendly conditions. The material was thoroughly characterized by XRD, Raman spectroscopy, BET, TEM, SEM, TPR, XPS and TGA. Under optimum reaction conditions, 71% benzene conversion with a phenol selectivity of 100% was achieved. The recyclability test was conducted and it was found that there was no significant loss of catalytic activity even after 5 recycles confirming the truly heterogeneous nature of the catalyst. For comparison, pure Cr 2 O 3 and Fe 2 O 3 were also prepared by the same hydrothermal method and characterized, and their catalytic activity results were also tested. DFT calculations showed that sp 2 CH bond activation of benzene over FeCr 2 O 4 (102) and Cr 2 O 3 (102) surfaces required an activation energy of 133.6 kJ mol 1 and 144.2 kJ mol 1 , respectively, matching the experimentally calculated activation barrier of 114 kJ mol 1 and 127.4 kJ mol 1 , obtained from kinetic studies. Selective oxidation of benzene to phenol using H 2 O 2 as oxidant, with efficient and recycling FeCr 2 O 4 nanostructured catalyst.