Construction of surface oxygen vacancy active sites upon MnOx/AC composite catalysts for efficient coupling adsorption and oxidation of toluene

Abstract

Activated carbon (AC) has been widely used as adsorbent and support of noble metal catalysts for the elimination of VOCs, owing to its high specific surface area and effective regulation of interfacial properties of catalysts via metal-support interaction. Herein, a series of MnOx/AC composite catalysts are prepared by in-situ redox precipitation method using KMnO4 as manganese source, ethylene glycol (EG) as reducing agent and coconut shell-based AC as active carrier. The obtained MnOx/AC catalysts have been fully characterized by XRD, SEM, TEM, N2 adsorption-desorption, FT-IR, XPS, EPR, H2-TPR, TPD-MS and toluene-TPSR-Ms (with and without O2) and their catalytic properties are evaluated for low temperature oxidation of toluene. It is found that the introduction of AC support significantly enhanced the adsorption capacity of toluene upon the MnOx/AC composite catalysts. Amongst, the MnOx/AC-0.3 shows excellent low-temperature catalytic activity (T90 = 193 °C), which can be related to highly efficient synergy of AC and MnOx species in toluene combustion. Especially, the construction of efficient MnOx/AC interfaces with more oxygen vacancy active sites, better lattice oxygen mobility, and stronger molecular oxygen activation ability, makes MnOx/AC-0.3 composite catalyst possess the best coupling adsorption oxidation capacity of toluene, and thus resulting in significant improvement in catalytic performance. Additionally, the obtained MnOx/AC-0.3 catalyst has also exhibited good catalytic stability and water resistance (5 vol%). This work deepens the understanding of the metal-support interaction in MnOx/AC composite catalysts and provides new ideas for the design of environmentally friendly catalysts.