Abstract: This invention is a catalyst for treating the exhaust gases produced during lean-burn engine operation, the gases comprising nitrogen oxides, carbon monoxide and hydrocarbons. The catalyst comprises a support material comprising gamma-alumina, a layer of about 0.01 to 1.5 wt. % tungsten deposited onto the support followed by a layer of about 1 to 3 wt. % silver, both being individually based on the weight of the support material.

Abstract: The present invention broadly relates to a catalyst system for promoting oxidation-reduction reactions of the exhaust gases produced by an internal combustion engine wherein the catalyst comprises a two-stage system of a first-stage nitric oxide removal (by reduction) catalyst and a second-stage carbon monoxide and hydrocarbon removal (by oxidation) catalyst. The first-stage catalyst comprises between about 0.1 and 3% by weight tungsten carried on a support material comprising mostly .gamma.-alumina. The second-stage catalyst is an oxidation catalyst such as platinum on alumina.

Abstract: A three-way catalyst system for efficiently converting the exhaust gas from a CNG-fueled engine when operated under lean conditions at a redox ratio of 0.02-0.9, the system comprising a first stage catalyst comprising a transition metal-containing zeolite; means for injecting a hydrocarbon into said exhaust gas prior to entry of said exhaust gas into said first stage catalyst, said hydrocarbon having a greater affinity than CH.sub.4 in its ability to react with NO; and a second stage catalyst for treating the effluent from said first stage catalyst and comprising a high surface area alumina impregnated with discontinuous La.sub.2 O.sub.3 and palladium.The invention also comprehends a method of treating exhaust gases from a lean-burn CNG-fueled engine, operating at a redox ratio of 0.02-0.

Abstract: A three-way catalyst system for efficiently converting the exhaust gas from a CNG-fueled engine when operated under lean conditions at a redox ratio of 0.02-0.9, the system comprising a first stage catalyst comprising a transition metal-containing zeolite; means for injecting a hydrocarbon into said exhaust gas prior to entry of said exhaust gas into said first stage catalyst, said hydrocarbon having a greater affinity than CH.sub.4 in its ability to react with NO; and a second stage catalyst for treating the effluent from said first stage catalyst and comprising a high surface area alumina impregnated with discontinuous La.sub.2 O.sub.3 and palladium.The invention also comprehends a method of treating exhaust gases from a lean-burn CNG-fueled engine, operating at a redox ratio of 0.02-0.

Abstract: A catalyst system for attaining high conversions of NO, HC, and CO in a fuel-lean emission flow (i.e., containing SO.sub.2, H.sub.2 O, H.sub.2, and considerable excess oxygen), the system comprising: (a) a first stage reducing catalyst for treating the nitric oxide emissions, the catalyst containing highly acidic gamma alumina (i.e., with a pH.sub.pzc of less than 3); (b) means for injecting gaseous or liquid reductants into the emission stream prior to entering said first stage catalyst, said first stage catalyst temperature being selected to be in the range of 550.degree.-650.degree. C.; and (c) an oxidation catalyst effective for treating the effluent from the first stage catalyst.Another aspect of this invention is a method of treating the exhaust gas from a fuel-lean emission flow from a fossil-fueled internal combustion engine having a redox ratio of 0.02-0.

Abstract: A catalyst system that converts the exhaust gas of a compressed natural gas (CNG) fueled automotive engine when operated at stoichiometry or slightly lean thereof, at highly enhanced rates, and having: (a) a first stage catalyst comprising a transition metal-containing zeolite (Cu-ZSM5), and (b) a second stage catalyst for treating the effluent of the first stage and comprising palladium supported on high surface area gamma alumina. The second stage catalyst has the alumina support impregnated with an intimate mixture, by weight, of 0.5-20% La.sub.2 O.sub.3 and 0.2-30% palladium.A method of treating exhaust gases from a CNG-fueled engine, comprising: (a) operating the engine at stoichiometry or slightly lean (0.85-1.