Preparation Of Wire-mesh Honeycomb Washcoat And Catalytic Reduction Of NO_x

After-treatment control technique, especially catalytic convert is an effective method to solve the increasing serious atmospheric pollution from the NO_x emission. Metallic monoliths offer plenty of advantages over ceramic monoliths, such as stronger mechanical, strength, higher ductilitical, higher thermal conductibility, lower pressure drop, and now have become most attractive supports in emissions controls. However, the metallic monoliths could not be applied in practice because of the complex of processing and the low specific surface area. It is necessary to deposit the ceramic oxide washcoat with high surface area over metallic monoliths. Since thermal expansion coefficient of the metallic support is different from the ceramic oxide washcoat, the adhesion of washcoat is poor which leads to the washcoat chap and flake away. The poor coating binding strength between the metallic substrate and the washcoat has attracted more attention by the most researchers.After the wrie-mesh honeycomb was manufactured by making alternatively corrugated and plain wire meshes and the coating technique of theγ-Al₂O₃ based ceramic washcoat on surface of FeCrAl metallic substrate by electrophoretic deposition was investigated in this paper.Partly including thepretreatment condition of the metallic substrate and preparation of slurry.The washcoat quality was measured by SEM, XRD, EDX and BET, ultrasonic vibration and thermal shock test. The main works are as following:The wrie-mesh honeycomb was manufactured by two equipment, The manufacture process of wire-mesh honeycomb was simply, which could reduce the price of wire-mesh honeycomb .Washcoat deposited on metallic wire mesh was prepared usingγ-Al₂O powders by electrophoretic deposition. The preparation parameters of washcoat were investigated, such as the deposited solution, the deposited voltage, the deposited time. Wire meshes were dipped in H₂SO₄ solution for wiping off the dirts and enhancing the cohesion between the wire mesh and washcoat. The ability of thermal resistant and vibration resistant was improved by adding additives and higher calcinations temperature, the washcoat calcine at 900℃for 2h and the phase structure of washcoat doesn't change due to increase temperature. SEM showed that alumina washcoat was even and no chap. XRD revealedγ-Al₂O₃ was main monocrystalline presented in the coating.The selective catalytic reduction of NO_x by C₃H₆ was investigated over Pd/Al₂O₃, Pd/ CeZr/Al₂O₃, Pd/CeZr/TiO₂/Al₂O₃ wire-mesh honeycomb. The results showed that 0.186%-Pd/CeZr/TiO₂/Al₂O₃ wire-mesh honeycomb catalyst exhibited high catalytic activity at low temperature over a broad temperature range. The selective catalytic reduction of NO_x by NH₃ was investigated over V₂O₅-WO₃/TiO₂ wire-mesh honeycomb. The results showed that V(3)-W(7)/TiO₂ catalyst provided with more thermal stability and better performance of removing NO_x.