Development And Application Of Wire-Mesh Honeycomb Catalyst

Wire-mesh honeycomb (WMH) is a category of novel monolithic catalysts supported on structured wire-mesh substrate. As the conduct of WMH is made of mesh, whose pores provide fluids the bypass of radical mixing across the bed diameter, which effect can improve the fluid distribution and mixing state, thus raises transfer efficiency. Aimed at developing a WMH for general applications, this thesis tried to breakthrough the key difficulties in WMH preparation. For purpose of demonstration, the WMH washcoated by Pd/Al₂O₃ was prepared and applied in catalytic combustion of air diluted methane, with its result compared to the ceramic counterpart.The key problem in developing WHM is the fast adhesion of the active catalyst powder with the metallic mesh. To solve this problem, an aluminum/alumina coating was prepared by electrophoretic deposition (EPD) on top of wire-mesh surface. Experiments were carried out to find the optimal conditions in ethanol, butanone and acetone suspension for depositing a uniform Al particulate coating, which are concluded as below: in ethanol suspension, PVP: 0.2 wt.%, AlCl₃: 2.5 mM, Al powder: 1wt.%, electric field intensity: 30 V/cm, deposition time: 10min; in butanone suspension, nitrocellulose: 0.6 wt.%, n-butylamine: 10 vol.%, Al powder: 0.2 wt.%, electrical field intensity: 50 V/cm, deposition time: 30 min, while in acetone suspension, acetone: 50 mL, nitrocellulose: 0.1 g, Al powder: 1 g, teramethyl ammonium hydroxide: 0.3 mg, phosphoric acid: 0.25 mg, electrical field intensity: 25 V/cm, deposition time: 3 min. Acetone suspension is more stable and the adherence of deposited coatings are higher than ethanol and butanone suspension, and the coating thickness is 50μm. Well adherent and porous aluminum/alumina top layers were prepared by thermal and chemical treatment of the deposited coatings in acetone suspension.After EPD, thermal & chemical treatment, and mould processing, the WMH support was prepared, which was 25 mm in diameter, 21 mm in height, 10 g in weight and 37.1 cm²/g in geometric surface area. The WMH catalyst washcoated with Pb/Al₂O₃ (Pb wt.% = 0.33%) was tested in catalytic combustion of air diluted methane. Compared at 600℃, CH4 conversion in WMH is 10.89% higher than the catalyst supported on ceramic substrate and the overall reaction rate constant more than doubled.