TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalyst is a metal-oxide based catalyst, a zeolite-type catalyst and/or a precious-metal catalyst.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Device: The combustion process occurs in a turbine engine. The exhaust chamber is a portion of the turbine engine.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The method involves flowing an exhaust stream from a combustion process into an exhaust chamber, where the exhaust stream (where temperature of the exhaust stream is 150-1100degreesC) comprises a nitrogen oxide; injecting a reductant stream comprising a hydrocarbon reductant and water into the exhaust chamber using an injection grid comprising several injection nozzles; mixing the reductant stream with the exhaust stream, downstream of the injection grid and upstream of a catalyst, to produce a substantially homogeneous mixture; contacting the homogeneous mixture of the reductant stream and the exhaust stream with the catalyst; decreasing a concentration of the nitrogen oxide in the homogeneous mixture; and releasing the homogeneous mixture with the decreased concentration of the nitrogen oxide into an atmosphere outside of the exhaust chamber. The method further involves mixing the hydrocarbon reductant and water to form a mixture prior to injecting; and heating the hydrocarbon and/or water prior to injecting.Preferred Components: The amount of water in the reductant stream is 0.01-15 vol.% of the reductant stream. The ratio of the exhaust stream to the reductant stream is 50-10000. The hydrocarbon is hexane, butane, propane, ethane, 2,2,4-trimethyl pentane, octane, propene, ethene, butene, methanol, ethyl alcohol, 1-butanol, 2-butanol, 1-propanol, isopropanol, dimethyl ether, dimethyl carbonate, acetaldehyde, acetone, and/or isobutanol. EXAMPLE - The effects of injected reductant concentration on the catalytic conversion of nitric oxide (NO) were determined. The catalyst was a catalytic gallium oxide and silver oxide mixture disposed onto a gamma-alumina support. The catalyst (6.4 g) were loaded into a quartz reactor, and the reactor was initially heated to 500degreesC in air for 2 hours. Subsequently, a gaseous mixture of nitric oxide (NO) (25 ppm), molecular oxygen (12 vol.%), water (9 vol %), with the balance being nitrogen (N2) was injected into the catalyst-loaded reactor and allowed to cool to 400degreesC for 40 minutes.    In independent experiments, 50 ppm, 75 ppm, and 100 ppm of isopropyl alcohol (IPA) was injected into the reactor to provide carbon to NO ratios of 6:1, 9:1, and 12:1, respectively. After 40 minutes, the outlet concentrations of NO, nitrogen dioxide (NO2), and nitrogen containing hydrocarbons (RONO) were measured. It was found that co-injection of isopropyl alcohol and water reduced the nitric oxide concentration.