Effect of citric acid-ethylene glycol binders on the washcoat adhesion and activity of monolithic catalysts for the catalytic oxidation of dichloromethane

Supported Pt-Co/HZSM-5 catalyst was considered to have excellent activity and stability in the catalytic combustion of chlorinated VOCs, which face challenges in scale-up application. Herein, we used an organic binder (citric acid-ethylene glycol, denoted as CA-EG) to coat the catalyst slurry on honeycomb cordierite. Citric acid can help to synthesize a stable slurry and preserve the activity of the original catalyst powder compared to traditional binders (Al or Si gel). The structure of the reticular long-chain organics in CA-EG makes it highly adhesive and the CA-EG coating has excellent resistance to mechanical stability. Catalyst characterization shows that the catalysts using CA-EG as the binder had enhanced redox properties, richer surface adsorbed oxygen and a more complete pore structure. This resulted in catalysts with lower T90 and lower by-product yields. The monolithic Pt-Co/HZSM-5 catalyst exhibited excellent activity in the oxidation of dichloromethane (T₅₀ = 246.9 °C and T₉₀ = 334.1 °C), and showed stability for at least 48 h (at 90 % conversion with no noticeable drop). Moreover, the water resistance of the monolithic catalyst was also excellent. This study proved that the CA-EG binder is very suitable for the coating process of zeolite-based catalysts.