An efficient Co-ZSM-5 catalyst for the abatement of volatile organics in air: effect of the synthesis protocol

Co supported on ZSM-5 (Co-ZSM-5) catalysts was synthesized by wet ion exchange (WIE), impregnation (IM), and in situ hydrothermal (IHT) methods. Their adsorptive catalytic activities for the removal of VOC’s [Benzene, Toluene, Ethylbenzene and Toluene (BTEX)] in air were tested. The physicochemical properties were investigated by XRD, FTIR, SEM, XPS, and low-temperature N₂ adsorption. The results indicate that the catalytic performance of Co-ZSM-5 for VOC’s abatement is effective and the synthesis methods reasonably influence the catalytic activity of Co-ZSM-5. Among three samples prepared by three different methods, the catalyst synthesized by the hydrothermal method possesses the highest adsorptive catalytic activity for BTEX oxidation. The optimized contact time was 60 min. The catalytic activities of the prepared catalysts are varied in the order of IHT > IM > WIE based on the combined removal capacity 59.24 > 34.46 > 23.82 (mg/g). For the Co-ZSM-5 WIE catalysts, the procedure has an evident effect on their catalytic performance. For example, the WIE catalysts prepared with cobalt chloride (II) by ion exchange have a higher acidity and surface area than the catalyst prepared with cobalt chloride (II) by impregnation method but less cobalt content. The excellent performance of IHT catalysts may be endorsed to the better availability of the oxidized form (Co³⁺), due to high content, higher surface area and acidity. Moreover, the Co-ZSM-5 catalyst synthesized by the IHT method shows high stability after being used.