Preparation of Fe/activated carbon directly from rice husk pyrolytic carbon and its application in catalytic hydroxylation of phenol

Abstract

Rice husk pyrolytic carbon (PC) was pretreated by NaOH solution at 100 °C for 5 h to remove SiO₂ and then used to prepare Fe/activated carbon catalyst. The treated sample was impregnated with ferric nitrate solution, and then activated under N₂ atmosphere, obtaining Fe/activated carbon catalysts. The samples were characterized by temperature programed decomposition-mass spectra (TPD-MS), Brauner–Emmett–Teller (BET), inductively coupled plasma atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The specific surface area increased with activation temperature until 750 °C. With the increase of iron content, the specific surface area of carbon increased first up to 0.39 mmol g⁻¹ iron loaded and then decreased. Reactive decomposition of ferric nitrate happened at 120–350 °C releasing NO and CO₂. Part of ferric (Fe(III)) species was reduced to ferrous (Fe(II)) species forming Fe₃O₄ at 400–550 °C, and metal Fe at 650–750 °C. The Fe/activated carbon exhibited high activity and selectivity for phenol hydroxylation.