| 摘要 |
1311262 Purifying exhaust ENGELHARD MINERALS & CHEMICALS CORP 18 Jan 1971 2414/71 Heading F1B Catalytic exhaust purifying device, for 1. C. engines of large displacement (e. g. greater than 400 cu, in.) having a relatively low temperature exhaust, comprises a housing having a gas inlet at one end and a gas outlet at the other end, a transverse apertured catalyst support plate intermediate the ends and dividing the housing into inlet and outlet sections, a plurality of ceramic block catalyst section secured to the plate at the apertures therein and kept separate from each other, so that exhaust gases pass from the inlet, through gas flow paths in the catalyst sections to the outlet. The housing comprises an inlet section 8 and an outlet section 9 having flanges 3 and 6 respectively for attachment to the remainder of the exhaust system and flanges 12 and 13 by which they are bolted together and to the catalyst support plate 7. The plate 7 has four apertures, each counter-bored on the side facing the outlet to receive one end of a metal tube which receives a catalyst section 11. The sections are retained by an inwardly projecting flange formed by welding a ring to the free end of the tube. The outer surface of each catalyst section is coated with fibrous aluminium silicate and spaced from the inner surface of the tube by a corrugated, knitted metal mesh, shock-absorbing fabric. The catalyst comprises a skeletal ceramic e. g. alpha-alumina or zircon-mullite, the surfaces of which are coated with an active refractory metal oxide by dipping so that the weight of oxide deposited on the surface is (preferably) 5-30% by weight of that of the structure. Suitable oxides are active or calcined alumina, baryllia, magnesia, thoria or silica. A coating of a low ignition oxidation catalyst is applied over the oxide, e. g. by dipping in an aqueous solution of an inorganic salt of a platinum group metal, precipitating the metal as an oxide and activating by heating to 100-1100‹ C. in a reducing atmosphere. In a modification, the support plate 7 has a single aperture and a single tube which contains four 90 degrees-sector shaped catalyst blocks, the plane faces of the blocks being separated by resilient spacers. A cruciform-shaped gas flow barrier plate is tack-welded to the downstream end of the tube, so that it covers the ends of the gaps between the blocks. |
