摘要:
Wall-flow filters can be reproducibly provided with a catalytically active coating by providing a defined quantity of a coating composition and sucking this coating composition through the openings of the entry passages into the filter body. The coating composition is sucked in by applying a subatmospheric pressure to the openings of the exit passages of the wall-flow filters. A different ratio of the coating quantities on the inner surfaces (pore surfaces) and outer surfaces (geometric surfaces of the passage walls) forms depending on the type of coating composition—suspension of fine-particle solids, colloidal solution or solution of soluble precursors of catalytically active components.
摘要:
A process for the coating of the flow channels of a cylindrical, honeycomb form catalyst carrier with a dispersion coating through filling of the vertically oriented flow channels with a fill quantity of the coating dispersion through the bottom face of the catalyst carrier and subsequent downward emptying and clearance extraction of the flow channels, as well as drying and calcination of the catalyst carrier, by the following steps:a) filling of the flow channels with a fill quantity that is about 10% greater than the empty volume of the flow channels, so that the coating dispersion goes over the upper face of the catalyst carrier after completion of the filling cycle,b) removal of the excess coating dispersion at the top before emptying of the flow channels andc) emptying and clearance extraction of the flow channels through an extraction impulse, which is generated by connection of a vacuum tank with the bottom face of the catalyst carrier,whereby the time between the beginning of the fill cycle and the end of the emptying and clearance extraction amounts to no more than 5 seconds.
摘要:
The accuracy of the coating concentration when applying a catalytically active coating to suitable carrier bodies can be increased if, following raw coating with a relatively wide fluctuation range in the coating concentration, excessive or insufficient coating applied is if appropriate corrected iteratively. Excessive coating suspension applied is removed, for example by subsequent suction, while the coating is still in the wet state, whereas insufficient coating suspension applied is topped up, for example by spraying on additional coating suspension.
摘要:
The thermal shock resistance of monolithic catalysts is improved by pre-coating a ceramic monolithic carrier, before the application of catalytic components, with an organic filling material which can be melted and burned out and which comprises a dispersion of very fine solid particles, by heating the carrier above the melting point of the filling material, then applying the catalytic components and then burning out the filling material.
摘要:
The accuracy of the coating concentration when applying a catalytically active coating to suitable carrier bodies can be increased if, following raw coating with a relatively wide fluctuation range in the coating concentration, excessive or insufficient coating applied is if appropriate corrected iteratively. Excessive coating suspension applied is removed, for example by subsequent suction, while the coating is still in the wet state, whereas insufficient coating suspension applied is topped up, for example by spraying on additional coating suspension.