Use of cerium oxide for the preparation of a lean nox trap catalytic composition and a method of treatment of an exhaust gas using the composition

Patent metadata

Field	Value
Publication number	US-2022118427-A1
Application number	US-201917417449-A
Country	US
Kind code	A1
Filing date	Dec 19, 2019
Priority date	Dec 28, 2018
Publication date	Apr 21, 2022
Grant date	—

Abstract

The present invention relates to the use of a resistant cerium oxide for the preparation of Lean NOx Trap catalytic composition. The invention also relates to such catalytic composition and to a method of treatment of an exhaust gas to decrease the NOx content using said catalytic composition.

First claim

1 . A lean NO x trap catalytic composition, the composition comprising cerium oxide exhibiting:
a specific surface area (BET) after ageing at 800° C. for 16 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 , of at least 75 m 2 /g;
or
a specific surface area (BET) after ageing at 700° C. for 16 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 , of at least 97 m 2 /g.

2 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a specific surface area (BET) after ageing at 800° C. for 16 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 , between 75 and 80 m 2 /g.

3 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a specific surface area (BET) after ageing at 700° C. for 16 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 , of at least 98 m 2 /g.

4 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a specific surface area (BET) after ageing at 700° C. for 16 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 , between 97 and 102 m 2 /g.

5 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a specific surface area (BET) after ageing at 900° C. for 16 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 , of at least 39 m 2 /g.

6 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a specific surface area (BET) after ageing at 900° C. for 16 hours, under a gaseous atmosphere containing 10% by volume of O 2 , 10% by volume of H 2 O and the balance of N 2 , of at most 50 m 2 /g.

7 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a specific surface area (BET) after calcination in air at 900° C. for 4 hours of at least 65 m 2 /g.

8 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a specific surface area (BET) after calcination in air at 900° C. for 4 hours, of at most 75 m 2 /g.

9 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a specific surface area (BET) after calcination in air at 900° C. for 24 hours, between 40 and 60 m 2 /g.

10 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a reducibility rate r 900° C. comprised between 20.0% and 25.0% after calcination in air at 900° C. for 4 hours, r 900° C. being defined by:
red 900° C. =V H2 from 50° C. to 900° C. /V theoretical ×100  (Ia)

wherein:
V H2 from 50° C. to 900° C. corresponds to the volume of hydrogen consumed by the cerium oxide between 50° C. and 900° C.;
V theoretical corresponds to the theoretical amount of hydrogen consumed by cerium oxide.

11 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a reducibility rate r 600° C. comprised between 8.0% and 12.0% after calcination in air at 900° C. for 4 hours, r 600° C. being defined by:
red 600° C. =V H2 from 50° C. to 600° C. /V theoretical ×100  (Ib)

wherein:
V H2 from 50° C. to 600° C. corresponds to the volume of hydrogen consumed by the cerium oxide between 50° C. and 600° C.;
V theoretical corresponds to the theoretical amount of hydrogen consumed by cerium oxide.

12 . The lean NO x trap catalytic composition according to claim 1 , wherein the cerium oxide exhibits a reducibility rate r 400° C. comprised between 1.5% and 2.0%, more particularly between 1.5% and 1.8%, after calcination in air at 900° C. for 4 hours, r 400° C. being defined by:
red 400° C. =V H2 from 50° C. to 400° C. /V theoretical ×100  (Ic)

wherein:
V H2 from 50° C. to 400° C. corresponds to the volume of hydrogen consumed by the cerium oxide between 50° C. and 400° C.;
V theoretical corresponds to the theoretical amount of hydrogen consumed by cerium oxide.

13 . The lean NO x trap catalytic composition according to claim 1 , further comprising:
at least one platinum group metal (PGM); at least one inorganic oxide; at least one element (E) in the form of an oxide, an hydroxide and/or a carbonate, the element (E) being selected in the group consisting of the alkaline earth metals, the alkali metals or a combination thereof.

14 . A LNT catalytic composition comprising:
a cerium oxide exhibiting: a reducibility rate r 600° C. between 8.0% and 12.0%; and/or a reducibility rate r 900° C. between 20.0% and 25.0%; and/or a reducibility rate r 400° C. between 1.5% and 2.0%;
these reducibility rates being measured after calcination of the cerium oxide in air at a temperature of 900° C. for 4 hours;
at least one platinum group metal (PGM);
at least one inorganic oxide;
at least one element (E) in the form of an oxide, an hydroxide and/or a carbonate, the element (E) being selected in the group consisting of the alkaline earth metals, the alkali metals or a combination thereof.

15 . The LNT catalytic composition according to claim 13 , wherein element (E) is barium.

16 . The LNT catalytic composition according to claim 13 , wherein the inorganic oxide is selected from the group consisting of alumina optionally stabilized by lanthanum and/or praseodymium; ceria; magnesia; silica; titania; zirconia; tantalum oxide; molybdenum oxide; tungsten oxide; and composite oxides thereof.

17 . A process for treatment of an exhaust gas released by the internal combustion engine of a vehicle to decrease its NO x content, the process comprising contacting the exhaust gas with the LNT catalytic composition of claim 13 .

18 . A process for treatment of an exhaust gas released by the internal combustion engine of a vehicle to decrease its NO x content, the process comprising contacting the exhaust gas with the LNT catalytic composition of claim 14 .

Assignees

• Rhodia Operations

Inventors

• Ohtake Naotaka
• Nishimura Kaoru
• Sasaki Toshihiro
• Okazumi Mitsuhiro

Classifications

• B01D2255/9202

  Linear dimensions · CPC title

• B01D2255/9205

  Porosity · CPC title

• B01J37/082

  Decomposition and pyrolysis · CPC title

• B01D53/9422

  for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR) · CPC title

• B01D2255/2065

  Cerium · CPC title