Magnetically retrievable nickel hydroxide functionalised AFe2O4 (A = Mn, Ni) spinel nanocatalyst for alcohol oxidation

Abstract

Ultrasmall nickel hydroxide functionalised AFe<inf>2</inf>O<inf>4</inf> (A = Mn, Ni) nanocatalyst was synthesized by traditional co-precipitation method and was examined for oxidation of aromatic alcohols to carbonyls using hydrogen peroxide as terminal oxidant. A very high surface area of 104.55 m2 g?1 was achieved for ferromagnetic MnFe<inf>2</inf>O<inf>4</inf> and 100.50 m2 g?1 for superparamagnetic NiFe<inf>2</inf>O<inf>4</inf>, respectively. Efficient oxidation was observed due to the synergized effect of nickel hydroxide (bronsted base) on Lewis center (Fe) of the nanocatalyst. Catalyst recycling experiments revealed that the ultrasmall nanocatalyst can be easily recovered by external magnet and applied for nearly complete oxidation of alcohols for at least five successive cycles. Furthermore, the nickel hydroxide functionalised ultrasmall nanocatalyst exhibited higher efficiency for benzyl alcohol oxidation compared to Ni(OH)<inf>2</inf>, bare MnFe<inf>2</inf>O<inf>4</inf> and NiFe<inf>2</inf>O<inf>4</inf>. Higher conversion rate was observed for nickel hydroxide functionalised NiFe<inf>2</inf>O<inf>4</inf> compared to MnFe<inf>2</inf>O<inf>4</inf>. Ultrasmall magnetic nickel hydroxide functionalised nanocatalyst showed environmental friendly, greener route for the oxidation of alcohols without significant loss in activity and selectivity within successive runs. © 2015, The Author(s).