A Facile Route Of Acid Treatment For Enhanced Performance Of Cryptomelane In Catalytic Oxidation Of Airborne Toluene

Abstract

This work emphasized a simple route to enhance the catalytic performance of modified cryptomelane in airborne toluene abatement. Cu-cryptomelane and H-cryptomelane materials were prepared by directly treating the pristine cryptomelane material with copper (II) cations and acetic acid, respectively. Wherein the pristine crytomelane was prepared by reducing potassium permanganate with benzyl alcohol and in the aid of hexadecyltrimethylammonium bromide at 60 °C. X-ray diffraction and scanning electron microscope evidences exhibited cryptomelane slabs with the size of 39.1 ± 1.1 nm, 41.4 ± 1.2 nm, and 76.4 ± 2.9 nm for Cu-cryptomelane, for H-cryptomelane, and for the as-prepared cryptomelane samples, respectively. Besides, Cu-cryptomelane presented a co-existence of orthorhombic Cu(OH)2 nanorods leading to a hydrogen reduction peak centered at 180 °C for converting Cu2+ species into metallic copper. Among the three synthesized materials, H-cryptomelane exhibited much more medium acid sites recorded from NH3-TPD profiles, and the highest value of total H2 consumption (3.43 mmolH2/g) promising positive enhancement of catalytic performance in deep oxidation of airborne toluene. Pristine, Cu-, and H-cryptomelane catalysts converted 60% toluene (T60) at 278 °C, 261°C, and 225 °C, respectively. Moreover, 98% of toluene was deeply oxidized at 300 °C (T98) for H-cryptomelane while the T100 of Cu-cryptomelane was 350 °C. Otherwise, the pristine cryptomelane only showed 88% converted toluene at 350 °C of the reaction temperature, testifying a beneficial treatment of acetic acid for improvement of cryptomelanecatalytic oxidation.

Keywords

• oms-2
• sol-gel method
• toluene removal
• ctab
• h-cryptomelane