Abstract: An exhaust gas treatment process, apparatus, and system for reducing the concentration of NOx, CO and hydrocarbons in a gas stream, such as an exhaust stream (29), via selective catalytic reduction with ammonia is provided. The process, apparatus and system include a catalytic bed (32) having a reducing only catalyst portion (34) and a downstream reducing-plus-oxidizing portion (36). Each portion (34, 36) includes an amount of tungsten. The reducing-plus-oxidizing catalyst portion (36) advantageously includes a greater amount of tungsten than the reducing catalyst portion (36) to markedly limit ammonia salt formation.

Abstract: A process for reducing nitrogen dioxide (NO2) to nitric oxide (NO) in a NO2-containing gaseous stream is provided. The process includes contacting the gaseous stream (12) with a catalyst system (28) comprising a catalyst selected from a platinum group metal. The contacting is done in the presence of carbon monoxide (22) and an organic compound (24), which synergistically improves NO2 reduction efficiency, particularly at low operating temperatures.

Abstract: A multi-stage selective catalytic reduction (SCR) unit (32) provides efficient reduction of NOx and other pollutants from about 50-550° C. in a power plant (19). Hydrogen (24) and ammonia (29) are variably supplied to the SCR unit depending on temperature. An upstream portion (34) of the SCR unit catalyzes NOx+NH3 reactions above about 200° C. A downstream portion (36) catalyzes NOx+H2 reactions below about 260° C., and catalyzes oxidation of NH3, CO, and VOCs with oxygen in the exhaust above about 200° C., efficiently removing NOx and other pollutants over a range of conditions with low slippage of NH3. An ammonia synthesis unit (28) may be connected to the SCR unit to provide NH3 as needed, avoiding transport and storage of ammonia or urea at the site. A carbonaceous gasification plant (18) on site may supply hydrogen and nitrogen to the ammonia synthesis unit, and hydrogen to the SCR unit.

Abstract: An exhaust gas treatment process, apparatus, and system for reducing the concentration of NOx, CO and hydrocarbons in a gas stream, such as an exhaust stream (29), via selective catalytic reduction with ammonia is provided. The process, apparatus and system include a catalytic bed (32) having a reducing only catalyst portion (34) and a downstream reducing-plus-oxidizing portion (36). Each portion (34, 36) includes an amount of tungsten. The reducing-plus-oxidizing catalyst portion (36) advantageously includes a greater amount of tungsten than the reducing catalyst portion (36) to markedly limit ammonia salt formation.

Abstract: A method for oxidizing an amount of CO in a CO-containing gas stream, e.g., a combustion stream from fuel combustion, is provided. The method comprises exposing the CO-containing gas stream to a catalytic coating at reaction conditions, including at least 8 vol. % O2 and a temperature of at least 600° C. At these reaction conditions, the method comprises generating gaseous intermediate oxidizing species at the catalytic coating for oxidation of the carbon monoxide within the CO-containing gas stream as a homogeneous reaction to improve CO removal efficiency.

Abstract: A process and system (18) for reducing NOx in a gas using hydrogen as a reducing agent is provided. The process comprises contacting the gas stream (29) with a catalyst system (38) comprising sulfated zirconia washcoat particles (41), palladium, a pre-sulfated zirconia binder (44), and a promoter (45) comprising at least one of titanium, zinc, or a mixture thereof. The presence of zinc or titanium increases the resistance of the catalyst system to a sulfur and water-containing gas stream.

Abstract: Improved processes for activating a catalyst system used for the reduction of nitrogen oxides are provided. In one embodiment, the catalyst system is activated by passing an activation gas stream having an amount of each of oxygen, water vapor, nitrogen oxides, and hydrogen over the catalyst system and increasing a temperature of the catalyst system to a temperature of at least 180° C. at a heating rate of from 1-20°/min. Use of activation processes described herein leads to a catalyst system with superior NOx reduction capabilities.

Abstract: A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.

Abstract: Improved processes for activating a catalyst system used for the reduction of nitrogen oxides are provided. In one embodiment, the catalyst system is activated by passing an activation gas stream having an amount of each of oxygen, water vapor, nitrogen oxides, and hydrogen over the catalyst system and increasing a temperature of the catalyst system to a temperature of at least 180° C. at a heating rate of from 1-20°/min. Use of activation processes described herein leads to a catalyst system with superior NOx reduction capabilities.

Abstract: A process and system (18) for reducing NOx in a gas using hydrogen as a reducing agent is provided. The process comprises contacting the gas stream (29) with a catalyst system (38) comprising sulfated zirconia washcoat particles (41), palladium, a pre-sulfated zirconia binder (44), and a promoter (45) comprising at least one of titanium, zinc, or a mixture thereof. The presence of zinc or titanium increases the resistance of the catalyst system to a sulfur and water-containing gas stream.

Abstract: A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.

Abstract: A method for oxidizing an amount of CO in a CO-containing gas stream, e.g., a combustion stream from fuel combustion, is provided. The method comprises exposing the CO-containing gas stream to a catalytic coating at reaction conditions, including least 8 vol. % and a temperature of at least 600° C. At these reaction conditions, the method comprises generating gaseous intermediate oxidizing species at the catalytic coating for oxidation of the carbon monoxide within the CO-containing gas stream as a homogeneous reaction to improve CO removal efficiency.

Abstract: A selective catalytic reduction (SCR) process with a palladium catalyst for reducing NOx in a gas, using hydrogen as a reducing agent is provided. The process comprises contacting the gas stream with a catalyst system, the catalyst system comprising (ZrO2)SO4, palladium, and a pre-sulfated zirconia binder. The inclusion of a pre-sulfated zirconia binder substantially increases the durability of a Pd-based SCR catalyst system. A system for implementing the disclosed process is further provided.

Abstract: A selective catalytic reduction process with a palladium catalyst for reducing NOx in a gas, using hydrogen as a reducing agent. A zirconium sulfate (ZrO2)SO4 catalyst support material with about 0.01-2.0 wt. % Pd is applied to a catalytic bed positioned in a flow of exhaust gas at about 70-200° C. The support material may be (ZrO2—SiO2)SO4. H2O and hydrogen may be injected into the exhaust gas upstream of the catalyst to a concentration of about 15-23 vol. % H2O and a molar ratio for H2/NOx in the range of 10-100. A hydrogen-containing fuel may be synthesized in an Integrated Gasification Combined Cycle power plant for combustion in a gas turbine to produce the exhaust gas flow. A portion of the fuel may be diverted for the hydrogen injection.

Abstract: A process for producing a stable high-temperature catalyst for reduction of nitrogen oxides in combustion exhaust gases at operating temperatures from 300° C. to over 700° C. without the need for exhaust dilution. A zeolite material is steam-treated at a temperature and duration sufficient to partially de-aluminize the zeolite to approximately a steady state, but not sufficient to fully collapse its chemical structure. Iron is added to the zeolite material. The zeolite material is calcined at a temperature, humidity, and duration sufficient to stabilize the zeolite material. Examples and specifications for ranges, order, and durations of steaming, calcining, and other steps are provided.

Abstract: A selective catalytic reduction process with a palladium catalyst for reducing NOx in a gas, using hydrogen as a reducing agent. A zirconium sulfate (ZrO2)SO4 catalyst support material with about 0.01-2.0 wt. % Pd is applied to a catalytic bed positioned in a flow of exhaust gas at about 70-200° C. The support material may be (ZrO2—SiO2)SO4. H2O and hydrogen may be injected into the exhaust gas upstream of the catalyst to a concentration of about 15-23 vol. % H2O and a molar ratio for H2/NOx in the range of 10-100. A hydrogen-containing fuel may be synthesized in an Integrated Gasification Combined Cycle power plant for combustion in a gas turbine to produce the exhaust gas flow. A portion of the fuel may be diverted for the hydrogen injection.

Abstract: A selective catalytic reduction (SCR) process with a palladium catalyst for reducing NOx in a gas, using hydrogen as a reducing agent is provided. The process comprises contacting the gas stream with a catalyst system, the catalyst system comprising (ZrO2)SO4, palladium, and a pre-sulfated zirconia binder. The inclusion of a pre-sulfated zirconia binder substantially increases the durability of a Pd-based SCR catalyst system. A system for implementing the disclosed process is further provided.

Abstract: A process for producing a stable high-temperature catalyst for reduction of nitrogen oxides in combustion exhaust gases at operating temperatures from 300° C. to over 700° C. without the need for exhaust dilution. A zeolite material is steam-treated at a temperature and duration sufficient to partially de-aluminize the zeolite to approximately a steady state, but not sufficient to fully collapse its chemical structure. Iron is added to the zeolite material. The zeolite material is calcined at a temperature, humidity, and duration sufficient to stabilize the zeolite material. Examples and specifications for ranges, order, and durations of steaming, calcining, and other steps are provided.

Abstract: A multi-stage selective catalytic reduction (SCR) unit (32) provides efficient reduction of NOx and other pollutants from about 50-550° C. in a power plant (19). Hydrogen (24) and ammonia (29) are variably supplied to the SCR unit depending on temperature. An upstream portion (34) of the SCR unit catalyzes NOx+NH3 reactions above about 200° C. A downstream portion (36) catalyzes NOx+H2 reactions below about 260° C., and catalyzes oxidation of NH3, CO, and VOCs with oxygen in the exhaust above about 200° C., efficiently removing NOx and other pollutants over a range of conditions with low slippage of NH3. An ammonia synthesis unit (28) may be connected to the SCR unit to provide NH3 as needed, avoiding transport and storage of ammonia or urea at the site. A carbonaceous gasification plant (18) on site may supply hydrogen and nitrogen to the ammonia synthesis unit, and hydrogen to the SCR unit.

Abstract: An exhaust gas treatment apparatus (20) for reducing the concentration of NOx, HC and CO in an exhaust gas stream (18) such as produced by a gas turbine engine (12) of a power generating station (10). The treatment apparatus includes a multifunction catalytic element (26) having an upstream reducing-only portion (28) and a downstream reducing-plus-oxidizing portion (30) that is located downstream of an ammonia injection apparatus (24). The selective catalytic reduction (SCR) of NOx is promoted in the upstream portion of the catalytic element by the injection of ammonia in excess of the stoichiometric concentration, with the resulting ammonia slip being oxidized in the downstream portion of the catalytic element. Any additional NOx generated by the oxidation of the ammonia is further reduced in the downstream portion before being passed to the atmosphere (22).