GB1374064A - Auto exhaust catalyst system - Google Patents

Abstract

1374064 Treating exhaust gas W R GRACE & CO 13 March 1973 [31 May 1972] 12070/73 Heading F1B I.C. engine exhaust system catalytic converter comprises a chamber through which exhaust gas flows and which contains a catalyst system comprising at least two monolithic sections, each section having passages for the flow of substantially parallel and linear streams of exhaust gas therethrough and having a catalyst on the passage surfaces, the sections being mounted one after the other within the chamber and having between each two successive sections means for inducing turbulence in the gas flow between the sections. The convertor comprises a housing 17 containing a monolithic ceramic catalyst support 30, having passages 18 to 22 on which a thin film of the catalyst is deposited. The support is in three sections separated by gaps 23 and 24. The flow of gas through the'passages.is laminar and the gaps 23 and 24 which are 0À5 to 5 cms wide create turbulence which gives better contact of the gas with the succeeding sections. The pre- ferred support material is alpha alumina. Other suitable materials are sillimanite, mullite, magnesium silicates, iron, petalite, spodumene, cordierite or aluminasilicates. In an example, the support which was 3À0 ins long and 4À0 ins diameter was coated by dipping one end into platinum sulphide solution and the other end into palladium nitrate solution, drying at 250‹F and calcining for 3 hours at 1000‹F. The preferred thickness of the coating is 0À0004-0À001 in. The surface area of the film is at least 50 sq m/gm and preferably 100 sq m/gm. The carrier has a surface area less than 10 sq m/gm and may be less than 1 sq m/gm. The monolithic support provides 5-200 sq ins (preferably 10-80 sq ins) of superficial surface area per cu in of engine displacement. Air, which may be heated, can be provided in the proportion of 3%-50% of the exhaust gas volume.