Exhaust gases from internal combustion engines are purified by catalytic treatment. The systems have an initial catalyst, preferably in a separate vessel near the engine, and a subsequently-in-line catalyst. Preferably, the catalysts are of the honeycomb-type. The exhaust gases and an excess of oxygen, with or without a supplemental fuel, are passed through the initial catalyst during the start-up of the engine to insure that the exhaust gases are purified more or less as soon as the engine begins operation. In order to reduce the amount of nitrogen oxides in the exhaust gas after start-up, an excess of extraneous fuel is fed to the initial catalyst to reduce nitrogen oxides to nitrogen. The subsequently-in-line catalyst serves to reduce the carbon monoxide and hydrocarbon contents of the exhaust gases.

Process and apparatus

A method of at least periodically removing from a lean gaseous stream a sorbable component such as SOx includes passing the gaseous stream through a trap member having an oxidation catalyst combined with a sorbent material at a temperature within the sorbing temperature range of the sorbent material. The sorbed component is periodically removed by introducing a combustible component into the gaseous stream and oxidizing it on the trap member to thermally desorb the sorbed component. The amount of combustible component introduced is limited to maintain the gaseous stream composition lean, but is sufficient to increase the surface temperature of at least part of the trap member to above the bulk temperature of the gaseous stream. Sorbing and desorbing periods are alternated and a composition and an apparatus to carry out the process is provided.

Method for using a regenerable catalyzed trap

This invention relates to catalyst for use in the control of atmospheric pollution and, in particular, to the purification of exhaust gases from internal combustion engines. Specific catalysts of the present invention comprise: A. ruthenium or an alloy thereof and a metal oxide capable of forming a stable mixed oxide (or "ruthenite") with ruthenium dioxide; B. a compound formed by ruthenium dioxide and a metal oxide capable of forming a stable mixed oxide (or ruthenite) with ruthenium dioxide; and C. a mixed oxide containing ruthenium, the oxide being selected from the group consisting of oxides of the pyrochlore type A 2 B 2 O 7 , the perovskite type ABO 3 , the ilmenite type B 2 O 3 and the spinel type AB 2 O 4 . Particularly good results have been obtained where the platinum/ruthenium ratio is within the range 25- 95 wt.% platinum and 5 - 75 wt.% ruthenium.

Catalyst for purifying automotive exhaust gases

A catalytic trap ( 10, 110 ) effective for conversion of NO x in an exhaust gas stream is inert to high-temperature reaction with basic oxygenated compounds of lithium, sodium or potassium. The catalytic trap may be substantially free of silica components and may include a catalytic trap material ( 20, 120 ) which contains a refractory metal oxide support, e.g., alumina, having dispersed thereon a catalytic component, such as a platinum group metal catalytic component, and a NO x sorbent comprised of one or more of the basic oxygenated compounds. The catalytic trap material is coated onto a suitable carrier member ( 12, 112 ), such as one made from stainless steel, titanium, alumina, titania, zirconia or silica-leached cordierite. A method of treating a NO x -containing gas stream involves maintaining the gas stream in alternating periods of ( 1 ) lean and ( 2 ) rich or stoichiometric conditions and contacting the gas stream with the catalytic trap under conditions in which NO x is adsorbed during periods of lean operation and released and reduced to nitrogen during periods of rich operation.

Catalytic trap with potassium component and method of using the same

A method for reduction of NOx in a lean gaseous stream includes passing the gaseous stream at a temperature within the NOx sorbing temperature range through a catalyzed trap member having an oxidation catalyst intimately combined with a sorbent material. The sorbed NOx is periodically removed by introducing a combustible component into the gaseous stream and oxidizing it on the trap member to thermally desorb the NOx. The amount of combustible component introduced is limited to maintain the gaseous stream bulk composition lean and to avoid increasing the bulk temperature of the gaseous stream to a temperature which is too high for effective lean NOx abatement treatment. A suitable NOx abatement catalyst is used to reduce the desorbed NOx. Sorbing (trapping) and desorbing periods are alternated, usually in response to the temperature of the gaseous stream, and an apparatus to carry out the process is provided.

METHOD AND APPARATUS FOR NOx ABATEMENT IN LEAN GASEOUS STREAMS

FOR USE IN THE TREATMENT OF AUTOMIBILE EXHAUST GASES, A CATALYST COMBINATION HAVING BOTH OXIDATION AND REDUCTION CAPABILITY IS EMPLOYED IN A FIRST CONVERTER, THE CATALYST HAVING A RUTHENIUM CONTAINING SECTION FOLLOWED BY A SECTION CONTAINING ANOTHER NOBLE METAL, E.G., RHODIUM. NITROGEN OXIDES ARE REMOVED WITH LITTLE PRODUCTION OF AMMONIA.

Unland Mark Leroy

Papers

Process for treating automotive exhaust