A laboratory scale fast feedback characterization loop for optimizing coated catalysts for emission control†

Coating of structured substrates like ceramic honeycombs plays an important role in heterogenous gas-phase catalysis. This work aims at understanding the effects of different coating parameters on the activity of a noble metal-based oxidation catalyst by using a novel fast and non-invasive photo-based channel analysis approach. The impact of the milling intensity, binder amount, catalyst layer thickness and distribution in the ceramic cordierite channels were systematically correlated with the activity profiles for CO, methane and propylene oxidation over a 1.8% Pd/Al₂O₃ catalyst. High milling intensities led to the formation of thinner catalyst layers with smaller particles, which were more evenly distributed throughout all channels and allowed the reactants to penetrate more efficiently. In contrast, the amount of binder added had a negligible influence on the catalyst activity. These findings were validated by X-ray tomography and complemented by SEM-analysis, a diffuse backlight-illumination imaging method, and mercury intrusion porosimetry.