One-step dip-coating of uniform γ-Al2O3 layers on cordierite honeycombs and its environmental applications

Cordierite honeycomb with high loading and uniform coating of γ-Al2O3 was prepared by a facile one-step dip coating strategy. The γ-Al2O3 obtained loading, which was as high as 30%, could be calculated according to the different weight of bare and washcoated cordierite honeycomb. SEM micrographs showed that coarser surface and round channels were formed, demonstrating complete coverage of a γ-Al2O3 layer on cordierite. The coating thickness was 30 µm, corresponding very well to the theoretical value, indicating a homogeneous coating of γ-Al2O3. Besides, no crack was observed on the surface or the corner of the channel wall. The washcoat exhibited excellent adherence with no significant weight loss after 3 h ultrasonic treatment, attributing to the “nail-like” strong interaction between the support and the washcoat. The derived PdCl2-CuCl2 monolith catalyst showed excellent activity and stability for CO oxidation at room temperature in microreactor. The catalyst was also effective in pilot-scale test using the diesel exhaust as feed gas, presenting a great application prospect.