Efficient and Selective Oxidation of Aromatic Amines to Azoxy Derivatives over Aluminium and Gallium Oxide Catalysts with Nanorod Morphology. Issue 2 (24th October 2019)

• Record Type: Journal Article
• Authors: Singh, Bhawan; Mandelli, Dalmo; Pescarmona, Paolo P.
• Is Part Of: ChemCatChem. Volume 12:Issue 2(2020)
• Page Start: 593
• Page End: 601
• Publication Date: 2019-10-24
• Subjects: Transition-metal-free oxide -- aniline oxidation -- azoxybenzene -- hydrogen peroxide -- nanorods; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201901378
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Aluminium oxide and gallium oxide nanorods were identified as highly efficient heterogeneous catalysts for the selective oxidation of aromatic amines to azoxy compounds using hydrogen peroxide as environmentally friendly oxidant. This is the first report of the selective oxidation of aromatic amines to their azoxy derivatives without using transition metal catalysts. Among the tested transition‐metal‐free oxides, gallium oxide nanorods with small dimensions (9–52 nm length and 3–5 nm width) and fully accessible, high surface area (225 m 2 g −1 ) displayed the best catalytic performance in terms of substrate versatility, activity and azoxybenzene selectivity. Furthermore, the catalyst loading, hydrogen peroxide type (aqueous or anhydrous), and the amount of solvent were tuned to optimise the catalytic performance, which allowed reaching almost full selectivity (98 %) towards azoxybenzene at high aniline conversion (94 %). Reusability tests showed that the gallium oxide nanorod catalyst can be recycled in consecutive runs with complete retention of the original activity and selectivity. Abstract : Selective oxidation : Gallium oxide nanorods with small dimensions (9‐52 nm length and 3–5 nm width) and fully accessible, high surface area (225 m 2 g −1 ) displayed high activity and selectivity as heterogeneous catalyst for the oxidation of aromatic amines to their azoxy derivatives with hydrogen peroxide as environmentally benign oxidant.