Selective catalytic reduction system and process for treating NOx emissions using a zinc or titanium promoted palladium-zirconium catalyst

1. A process for selective catalytic reduction of nitrogen oxides (NO x ) in a gas stream in the presence of H 2 , the process comprising:

contacting the gas stream with a catalyst system comprising sulfated zirconia washcoat particles, palladium, a pre-sulfated zirconia binder, and a promoter comprising at least one of zinc, titanium, or a mixture thereof.

2. The process according to claim 1 , wherein the promoter further comprises tungsten, and wherein a loading of the tungsten is between 0.5 and 5 wt. % of the catalyst system.

3. The process according to claim 1 , wherein the promoter comprises titanium, and wherein a loading of the titanium is between 0.5 and 10 wt. % of the catalyst system.

4. The process according to claim 3 , wherein the promoter comprises titanium, and wherein a loading of the titanium is between 5 and 7.5 wt. %.

5. The process according to claim 1 , wherein the promoter comprises zinc, and wherein a loading of the zinc is between 0.5 and 12 wt. % of the catalyst system.

6. The process according to claim 5 , wherein the promoter comprises zinc, and wherein a loading of the zinc is between 5 and 10 wt. % of the catalyst system.

7. The process according to claim 1 , wherein the promoter further comprises tungsten, wherein the promoter comprises a mixture of tungsten and zinc, wherein a loading of the zinc is between 0.5 and 12 wt. % of the catalyst system, and wherein a loading of the tungsten is between 0.5 and 5 wt. % of the catalyst system.

8. The process according to claim 1 , wherein the sulfated zirconia washcoat particles comprise at least one of (ZrO 2 )SO 4 or (ZrO 2 —SiO 2 )SO 4 .

9. The process according to claim 8 , wherein the sulfated zirconia washcoat particles comprise (ZrO 2 —SiO 2 )SO 4 , and wherein a mass ratio of SiO 2 to (ZrO 2 +SiO 2 ) in the catalyst system is between 0.05 and 0.90.

10. The process according to claim 1 , wherein a loading of the palladium is from 0.01 to 2% by wt. of the catalyst system.

11. The process according to claim 1 , wherein a catalytic bed comprising the catalyst system is installed in a flow path of an exhaust gas stream of a gas turbine, and wherein the exhaust gas stream includes NO x , H 2 O, O 2 , and SO 2 .

12. The process of claim 11 , wherein H 2 O and hydrogen are injected into the exhaust gas between the gas turbine and the catalytic bed, to a concentration of about 5-25 vol. % H 2 O and a molar ratio for H 2 /NO x in the range of 10 to 100 in the exhaust gas.

13. The process of claim 11 , wherein the exhaust gas is passed over the catalytic bed at a temperature maintained in a range of 100-140° C.

14. The process of claim 11 , wherein the catalytic bed is installed in the flow path of exhaust gas of the gas turbine in an integrated gasification combined cycle (IGCC) power generation plant that synthesizes a hydrogen-containing fuel for the gas turbine, and further comprising:

diverting a portion of the hydrogen-containing fuel to supply the H 2 as a NO x reducing agent for the catalytic bed;

maintaining a water content in the exhaust gas to a concentration of about 15-25 vol. % and maintaining the diverted portion of the hydrogen-containing fuel into the exhaust gas between the gas turbine and the catalytic bed at a molar ratio for H 2 /NO x in the range of 10-100 in the exhaust gas; and

passing the exhaust gas over the catalytic bed at a temperature between 70-250° C. to remove an amount of NO x from the exhaust gas.

15. The process of claim 14 , wherein the water content is maintained to a concentration of about 17-21 vol. %.

16. A system for implementing a process for selective catalytic reduction of nitrogen oxides (NO x ) in an exhaust gas from a gas turbine in an integrated gasification combined cycle power plant, comprising:

a fuel gas synthesizer that produces a fuel gas containing at least 10 vol. % H 2 and at least 10 vol. % nitrogen;

a gas turbine that burns a portion of the fuel gas, producing the exhaust gas;

a catalytic bed installed in a flow path of the exhaust gas, the catalytic bed comprising a catalyst system, the catalyst system comprising sulfated zirconia washcoat particles, palladium, a pre-sulfated zirconia binder, and a promoter comprising at least one of titanium, zinc, or a mixture thereof;

a hydrogen injector that mixes a diverted portion of the fuel gas into the exhaust gas between the gas turbine and the catalytic bed;

an H 2 O injector that mixes H 2 O into the exhaust gas between the gas turbine and the catalytic bed; and

sensors and valves at control points in the system connected to a controller that maintains operational conditions in the exhaust gas at the catalytic bed, wherein the operational conditions comprise a temperature between 70-250° C., a molar ratio for H 2 /NO x in the range of 10-100, and H 2 O at a concentration of about 15-23 vol. %.

17. The system of claim 16 , wherein the promoter comprises titanium, and wherein a loading of the titanium is between 0.5 and 10 wt. % of the catalyst system.

18. The system of claim 16 , wherein the promoter comprises zinc, and wherein a loading of the zinc is between 0.5 and 12 wt. % of the catalyst system.

19. The system of claim 16 , wherein the promoter further comprises tungsten, wherein the promoter comprises a mixture of tungsten and zinc, wherein a loading of the zinc is between 0.5 and 12 wt. % of the catalyst system, and wherein a loading of the tungsten is between 0.5 and 5 wt. % of the catalyst system.

20. The system of claim 16 , wherein the sulfated zirconia washcoat particles comprise at least one of (ZrO 2 )SO 4 or (ZrO 2 —SiO 2 )SO 4 , and wherein a loading of the palladium is from 0.01 to 2% by wt. of the catalyst system.