Co clean-up catalyst, after treatment system and after treatment method

Patent metadata

Field	Value
Publication number	US-2020248603-A1
Application number	US-201916263484-A
Country	US
Kind code	A1
Filing date	Jan 31, 2019
Priority date	Jan 31, 2019
Publication date	Aug 6, 2020
Grant date	—

Abstract

An after treatment method is disclosed. The after treatment method may include: operating an engine at a lean air/fuel ratio; calculating an amount of NH3 stored in an SCR catalyst; calculating an amount of NOx which will flow into the SCR catalyst; determining whether conversion to a rich air/fuel ratio is desired; calculating, when the conversion to the rich air/fuel ratio is desired, a rich duration for which the rich air/fuel ratio is maintained and a target air/fuel ratio; and operating the engine at the target air/fuel ratio for the rich duration.

First claim

1 . A CO clean-up catalyst (CUC) comprising 0.2-1.5 wt % of Pt, 0-0.4 wt % of Pd, 0-0.4 wt % of Rh, 0-5.0 wt % of Ba, 40-90 wt % of CeO2, 9.8-59.8 wt % of Al 2 O3, and 0-20 wt % of an additive based on a total weight of the CUC.

2 . The CUC of claim 1 , wherein the additive comprises at least one of La, Zr, Mg, and Pr.

3 . The CUC of claim 1 , wherein a weight ratio of the additive to the total weight of the CUC is 0-10 wt %.

4 . An after treatment system comprising:
an exhaust pipe through which an exhaust gas flows; a three-way catalyst (TWC) mounted on the exhaust pipe, oxidizing HC and CO contained in the exhaust gas at a lean air/fuel ratio, and generating NH3 using NOx contained in the exhaust gas at a rich air/fuel ratio; a selective catalytic reduction (SCR) catalyst mounted on the exhaust pipe at a downstream of the TWC, storing the NH3 generated in the TWC, and reducing the NOx contained in the exhaust gas using the stored NH3; and a CO clean-up catalyst (CUC) mounted on the exhaust pipe downstream of the SCR catalyst and purifying the CO slipped from the TWC or contained in the exhaust gas at the rich air/fuel ratio.

5 . The after treatment system of claim 4 , further comprising a particulate filter disposed between the TWC and the SCR catalyst,
wherein the particulate filter traps particulate matter in the exhaust gas.

6 . The after treatment system of claim 4 , further comprising an additional TWC or an ammonia production catalyst (APC) disposed between the TWC and the SCR catalyst,
wherein the additional TWC or the APC further generates NH3 using the NOx contained in the exhaust gas at the rich air/fuel ratio.

7 . The after treatment system of claim 6 , wherein the APC includes 0.4-0.9 wt % of Pt, 0.057-0.3 wt % of Pd, 0.03-0.1 wt % of Rh, 5.0-15.0 wt % of Ba, 10-30 wt % of CeO2, 48.7-84.513 wt % of a composite of MgO and Al2O3, and 0-5 wt % of an additive based on a total weight of the APC.

8 . The after treatment system of claim 6 , wherein the APC includes 0.4-0.9 wt % of Pt, 0.057-0.3 wt % of Pd, 0.03-0.1 wt % of Rh, 5.0-15.0 wt % of Ba, 10-25 wt % of CeO2, 48.7-79.513 wt % of a composite of MgO and Al2O3, and 0-10 wt % of an additive based on a total weight of the APC.

9 . The after treatment system of claim 6 , wherein a lean NOx trap (LNT) catalyst is further coated in the TWC or the additional TWC, and
wherein the LNT catalyst absorbs the NOx contained in the exhaust gas at the lean air/fuel ratio, and releases and reduces the absorbed NOx into N2 gas or the NH3 at the rich air/fuel ratio.

10 . The after treatment system of claim 4 , wherein the CUC includes 0.2-1.5 wt % of Pt, 0-0.4 wt % of Pd, 0-0.4 wt % of Rh, 0-5.0 wt % of Ba, 40-90 wt % of CeO2, 9.8-59.8 wt % of Al2O3, and 0-20 wt % of an additive based on a total weight of the CUC.

11 . The after treatment system of claim 10 , wherein the additive comprises at least one of La, Zr, Mg, and Pr.

12 . An after treatment method for controlling an after treatment system equipped with a three-way catalyst (TWC), a selective catalytic reduction (SCR) catalyst, and a CO clean-up catalyst (CUC) on an exhaust pipe through which an exhaust gas flows, the after treatment method comprising:
operating an engine at a lean air/fuel ratio; calculating an amount of NH3 stored in the SCR catalyst; calculating an amount of NOx which will flow into the SCR catalyst; determining whether conversion to a rich air/fuel ratio is desired; calculating, when the conversion to the rich air/fuel ratio is desired, a rich duration for which the rich air/fuel ratio is maintained and a target air/fuel ratio; and operating the engine at the target air/fuel ratio for the rich duration.

13 . The after treatment method of claim 12 , wherein the rich duration is calculated according to the target air/fuel ratio and a temperature of the CUC.

14 . The after treatment method of claim 12 , wherein the rich duration is calculated such that a slip amount of CO accumulated at a downstream of the CUC for the rich duration is smaller than or equal to a predetermined value if the engine is operated at the target air/fuel ratio for the rich duration.

15 . The after treatment method of claim 12 , further comprising a particulate filter disposed between the TWC and the SCR catalyst,
wherein the particulate filter traps particulate matter in the exhaust gas.

16 . The after treatment method of claim 12 , further comprising an additional TWC or an ammonia production catalyst (APC) disposed between the TWC and the SCR catalyst,
wherein the additional TWC or the APC further generates NH3 using the NOx contained in the exhaust gas at the rich air/fuel ratio.

17 . The after treatment method of claim 12 , wherein the CUC includes 0.2-1.5 wt % of Pt, 0-0.4 wt % of Pd, 0-0.4 wt % of Rh, 0-5.0 wt % of Ba, 40-90 wt % of CeO2, 9.8-59.8 wt % of Al2O3, and 0-20 wt % of an additive based on a total weight of the CUC.

18 . The after treatment method of claim 17 , wherein the additive comprises at least one of La, Zr, Mg, and Pr.

Assignees

• Hyundai Motor Co Ltd
• Kia Motors Corp

Inventors

• Joo Nahm Roh
• Kim Chang Hwan
• Jung Changho

Classifications

• F01N3/101

  Three-way catalysts · CPC title

• B01D2255/2065

  Cerium · CPC title

• B01D2255/2042

  Barium · CPC title

• F01N3/2066

  Selective catalytic reduction [SCR] · CPC title

• B01J2523/822

  Rhodium · CPC title