Development of New Effective Catalytic

Systems for Selective Reduction of NOx by

Hydrocarbons and NH3

Professor Z.R.Ismagilov

Laboratory of Environmental Catalysis,

Boreskov Institute of Catalysis SB RAS,

Novosibirsk, Russia, www.catalysis.ru/envicat/

36th ISTC Japan Workshop

on Advanced Catalysis in Russia/CIS

Moscow

St-Petersburg

OmskNovosibirsk

RUSSIAVolgograd

Boreskov Institute of Catalysis:

From Research on Molecular Level

to Industrial Implementation

Boreskov Institute of Catalysis

Created by G.K.Boreskov at 1958

staff: overall ca.1000, researchers ca. 450

web-page: http://catalysis.ru/

Directors: G.K.Boreskov (1958-1984); K.I.Zamaraev (1984-1995); V.N.Parmon (from 1995)

Analytical (composition of catalysts and catalytic reaction products)

• Differential dissolution

• Chromatography

• Superrapid chromatography

• Mass spectrometry

Adsorptive (specific surface area, pore structure, adsorption heat)

• Porosimetry

• Calorimetry

Kinetic

• Gradientless and integral differential catalytic reactors

• Fast relaxation technique

• Stop flow technique

R&D Capabilities of BIC in Analysis Methods

• X-Ray diffraction (including at small

angles)

• TEM and Scanning Electron

Microscopies

• STM

• EXAFS

• X-Ray spectroscopy

• VUV electron spectroscopy

• UV-VIS electron spectroscopy

• Vibrational spectroscopies

(IR and Raman)

• ESR

• NMR

• ESCA (XPS and UPS),

Auger spectroscopy

• LEED

• HREELS

• Radiochemical and isotope

methods

• Flash photolysis and radiolysis

• X-Ray tomography

• NMR microtomography

R&D Capabilities of BIC in Physical Methods

CAPOC 6Sixth International Congress

on Catalysis and Automotive Pollution Control

Brussels, October 2003

• Lean DeNOx – SCR

• NOx storages

• Diesel Particulates

• Soot- NOx

• TWC - Mechanisms - Kinetics - Modelling

• Ageing – Poisoning – Fuel Alternatives

Category Durability NMOG CO NOx

Basis nonmethane organics

(miles) (g/mile) (g/mile) (g/mile)

______________________________________________________

TLEV 50.000 0.125 3.4 0.4

120.000 0.156 4.2 0.6

LEV 50.00 0.075 3.4 0.05

120.000 0.09 4.2 0.07

ULEV 50.00 0.04 1.7 0.05

120.000 0.055 2.1 0.07

SULEV 120.000 0.010 1.0 0.02

ZEV -0- -0- -0- -0-

California Emission Standards

Exhaust emission limits for passenger car engines (EU)

Diesel exhaust aftertreatment system:

The challenge for NOx and Particulates

NOx-adsorber catalyst system

NOx Adsorber Catalyst

Rich Conditions ( < 1)Regeneration

Lean Conditions ( > 1)NOx-Adsorption

Other Exhaust Components

Nitrogen oxide (NOx)

Clean Exhaust Gas

Schematic showing reactions within the adsorber

catalyst during lean and rich conditions

Dual pore concept for hydrocarbon SCR involving

oxidation in small pores and reduction in large pores

Goals and Objectives of Research at BIC

Metal-substituted zeolites (Cu-ZSM-5) have high catalytic activity in direct

decomposition of NO [1] and selective catalytic reduction of NO (SCR NO) with

hydrocarbons [2], including propane, in presence of oxygen excess (2-3 vol.%)

[1] Iwamoto M., et.al. Chem. Lett. 2 (1989) 213.

[2] Iwamoto M., Hamada H. Catal. Today. 10 (1991) 57; Held W. et.al. SAE 900496 (1990) 13.

The nature of active sites in Cu-ZSM-5 are still a matter of discussion.

• Isolated ions Cu2+ (Cu+)

• Copper dimers with oxygen

bridges, [CuOCu]2+ or [Cu2(-O)2]2+

• Copper-oxide clusters, CuxOy

• Kucherov A.V., Slinkin A.A., et.al., Zeolite 5 (1985) 320.

• Dedecek J., Wichterlova B., J. Phys. Chem. B. 101 (1997)

10233.

• Groothaert M.H., Schoonheydt R.A. et.al., J. Am. Chem.

Soc.125 (2003) 7629.

• Shapiro E.S., Gruner W., et.al., Catal. Lett. 24 (1994) 159.

Task:

1. The study of catalytic properties as function of Cu-ZSM-5 preparation conditions;

2. The study of the electron states of copper ions in the catalysts and their peculiarity

as function of Cu-ZSM-5 preparation conditions;

Synthesis of Cu-ZSM-5. Ion-exchange condition.

•Copper loading (wt.%)

• calculated copper exchange level (%)

Cu/AlEL = 2 х 100 х Cu/Alat

• M.Iwamoto, et. al., Chem. Lett. (1990) 1967

1%Cu-ZSM-5-30-71

• zeolite atomic ratio Si/Al

Zeolite H-ZSM-5

Si/Al=17, 30, 45

Copper concentration in solution0.4 8 mg Cu / ml

Ratio of solution volume to zeolite mass (S/Z) 10, 30, 50

рН solution

рН ~ 10

(ammonia solution)

рН ~ 4

рН ~ 6

Temperature

25оС 60оС 80оС

Copper precursor

Cu(CH3COO)2

Cu(NO3)2

Effect of ion-exchange condition on Cu-exchange level in Cu-ZSM-5

Aqueous copper acetate solution (рН6)

0.0 1.6 3.2 4.8 6.4 8.0 9.60

25

50

75

100

125

Exch

an

ge

le

ve

l, %

Copper concentration in ion-exchange solution, mg/ml

Si/Al-17

Si/Al-30

Si/Al-45

S/Z = 10

0 10 20 30 40 500

50

100

Exch

an

ge

le

ve

l, %

Si/Al ratio

8 mg Cu/ml

4 mg Cu/ml

1.6 mg Cu/ml

S/Z = 10

• The maximum achievable level of Cu

exchange with H-ZSM-5 is equal to 75 -100%.

• Exchange level is determined mainly by

copper concentration in solution and by the

zeolite Si/Al ratio.10 20 30 40 50

0

50

100

8 mg Cu/ml

Exchan

ge level, %

S/Z

Si/Al-17

Si/Al-30

Si/Al-45

0 2 4 6 8 100

50

100

150

200

250

300

Exch

an

ge

le

ve

l, %

Copper concentration in ion-exchange solution, mg/ml

Si/Al-17

Si/Al-30

Si/Al-45S/Z = 10

Ammonia copper acetate solution (рН10)

10 20 30 40 500

50

100

150

200

250

300

Exch

an

ge

le

ve

l, %

8 mg Cu/ml

4 mg Cu/ml

2 mg Cu/ml

Si/Al ratio

S/Z = 10

10 20 30 40 500

50

100

150

200

250

300

Si/Al-17

Si/Al-30

Si/Al-45

Exch

an

ge

le

ve

l, %

S/Z

8 mg Cu/ml

• Ammonia copper acetate solution provides

the higher achievable level of Cu exchange

with H-ZSM-5 (up to 300%).

• Exchange level increase with rising of

copper concentration in solution and the

zeolite Si/Al ratio. Its increase is more

apparent as compared with aqueous solution.

Effect of ion-exchange condition on Cu-exchange level in Cu-ZSM-5

Correlation between Cu-ZSM-5 catalytic activity (NO conversion)

and copper loading and exchange level

at 400oC

300 350 400 450 5000

20

40

60

80

100A

Cu-ZSM-5-30

1.83% Cu

1.45% Cu

1.12% Cu

0.52% Cu

0.36% Cu

X(N

O),

%

Temperature, oC

50 100 150 200 250 300 350

40

80

B

Exchange level, %

X(N

O),

%

Si/Al=17: pH-6 ( ), pH-10 ( )

Si/Al=30: pH-4.6 ( ), pH-6 ( , ), pH-10 ( )

Si/Al=45: pH-6 ( ), pH-10 ( )

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

40

80C

X(N

O),

%

Cu loading, %

DeNOx-C3H8 test condition: 42000 h-1 ; (300 ppm NO, 1500 ppm C3H8, 3.5 vol.%O2, N2)

.

Copper state in calcined catalysts:1.1%Cu-ZSM-5-17-45 (1), 1.2%Cu-ZSM-5-30-71 (2), 1%Cu-ZSM-5-45-88 (3)

ESR: g =2.38, g = 2.08, A = 135 Oe

UV-Vis: (T2g -E g) = 12500-13400 cm-1

isolated Cu2+ ions with dx2-y

2 - state

(similar to [Cu(H2O)6]2+)

3

2

1

DPPH

(A)

A½½

= 135 Oeg½½

= 2.38

A½½

= 135 Oe

g=2.07

g½½

= 2.38

100 Oe

H0

3

2

1

x2

ESR

40-50% Cu are ESR silent after calcination in air at 500oC

• reduction of Cu2+ to Cu+

• associate of Cu2+ ions

• CuO formation

О- radical anions with weak exchange coupling through diamagnetic Cu+ ions in

chains –O-—Cu+-O-—Cu+-O-- (p5d10)

10000 15000 20000 25000 30000 350000.0

0.4

0.8

1.2

HVT 300oC

HVT 150oC Initial

CTB

oxide clusters

d-d transition22900

20850

19400

18200

F(R

)

cm-1

Zeolite

adsorbtion edge

–O2-—Cu2+-O2-—Cu2+-O2--Cu Cu

O

O

OO

OO

[Cu(H2O)6]2+

1.5% Cu-ZSM-5-30-92 (N, 80oC, pH=4)

Copper state in CuZSM-5 after vacuum treatment at 150 and 300оС

(UV-Vis)

Electron states of Cun+ cation in Cu-ZSM-5

Ion exchange,

washing[Cun(OH)y(H2O)x]

(2n-y)+ , n= 1-3[Cu(H2O)6]

2+ ,12500 cm-1

[Cu(NH3)4]2+,14500 cm-1

Calcination

(air, 500oC)

Isolited ions Cu2+ (Oh)[Cu(H2O)6]

2+

12500-13400 cm-1

g1 = 2.38-2.39, A

1 = 130 Oe,

Cu Cu

O

O

OO

OO

30000-32000 cm-1

Chains

Cu-O-Cu-O-Cu-O

(ESR silent)

Dehydrationvacuum, 25-400oC

Isolated ions Cu2+ (distorted Oh)

12000-14500 cm-1

g1 = 2.30-2.33, A

1 =145-154 Oe,

g2 = 2.28, A

2 = 165-170 Oe,

Cu2+-O2--Cu2+-O2--Cu2+

18000-23000 cm-1

g = ge

Cu+-O--Cu+-O--Cu+

g = 2.05, g = 2.02

without HFS

Cu2+-O2- - Cu+-O-

15000-17000 cm-1

22500 cm-1

Cu Cu

O

O

OO

OO

28000-32000 cm-1

• Well-known for Cu-

exchanged zeolites

• Well-known for

Cu-oxide systems

• Assumed based on ESR

and UV-Vis experimental data

Copper state in overexchanged Cu-ZSM-5 (Cu/Al>0.5)

after heat vacuum treatment

isolated Cu2+ ions (12500-13400 cm-1)

adjacent (nearby) isolated Cu2+ ions

binuclear Cu oxo/hydroxo complexes

(???)

linear Cu oxo/hydroxo oligomers

(18000-23000 cm-1)

clustered CuO-like nanoparticles

(30000-32000

cm-1)

• by analogy with proposed for Fe/ZSM-5

A.A.Battiston, J.H.Bitter, F.M.F.de Groot et.al. J.Catal. 213 (2003) 251

• Geometry optimizations and search of a transition state (TS) were performed with

the Gaussian-98 package [1] at the DFT level using the hybrid exchange-correlation

functional B3LYP [2,3].

[1] Frisch, M. J.; Trucks, G. W.; et.al.. Gaussian 98, Revision A.11. Gaussian, Pittsburgh, PA (1998).

[2] Becke, A. D. J Chem. Phys. 1993, 98, 5648.[3] Lee, C; Yang, W; Parr, R. G. Phys. Rev. B. 1988, 37, 785.

• The following basis set partition scheme was employed:

- The LANL2 effective core potential [4] with its valence shell basis set double-

(DZ) provided by the Gaussian-98 package was used for Cu and Al atoms. All

atoms belonging to the (HO)3Al-O-Cu-O-Cu molecular cluster were described

using the DZ basis set (B3LYP/LANL2-DZ calculations).

[4] Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270.

- The charge and spin density distributions on the atoms were calculated using

the Mulliken population analysis. Open shells were calculated using unrestricted

density functional (uB3LYP/LANL2-DZ calculations).

• The excitation energy spectra were calculated for the system (HO)3Al-O2-Cu2-O1-

Cu1 using the same basis LANL2-DZ and optimized geometry. The theoretical spectra

were calculated in the frames of DFT approach taking into account the time-

dependent perturbations (TDDFT) [5,6].

[5] Parr, R. G.; Yang, W. Density-Functional Theory of Atoms and Molecules; Oxford University Press:

New York, 1989.

[6] Runge, E.; Gross, E. K. U. Phys. ReV. Lett. 1984, 52, 997.

Quantum chemical model and calculation details

Cluster (HO)3Al-O-Cu-O-Cu as model of catalytic active site in Cu-ZSM-5 (DFT)

0

0.4

0.8

1.2

8000 12000 16000 20000

0

0.4

0.8

1.2

cm-1

Inte

ns

ity

, a

rbtr

.u.

Lin

ew

idth

:

1.0

00

E+

03

Excitation (cm-1

)

17526

2044516000

13883

12030

8642

H

O

H

OA l

O

C u

O

C u

O

H

rs=0.01

rs=0.57

rs=0.33

rs=0.91

Cu1

Cu2

O1

O2

1.87 A

1.76 A

1.76 A

1.80 A

O3-O5

IVT

17526 cm-1

(0.41)

33 b (Cu1O1Cu2) 43 b (Cu2O2)

20445 cm-1

(0.41)

CTB L-M

35 b (Cu1O1O2) 44 b (Cu1O1)

• Self-reduction - autooxydation:

Cu2+ + O2- (d9p6) Cu+ + O- (d10p5),

Cu2+(OH)22H2O

rCu= 0.9; rO= 0.1

Cu+(OH)2

rCu= 0.36; rO= 0.64

+ 2H2O

―hydration‖ redistribution of spin density of unpaired electron

Experimental data for Cu-ZSM-5

O Cu O

H

H

[Cu+O-]

d10p5

O

H H

2A

2A

O Cu O

H

H

[Cu2+O2-]

d9p6

ESR experimental data at hydration - dehydration of HV-treated CuZSM-5

(C)

g½½

=2.28, A½½

=164, g=2.07

(B)

g½½

=2.33, A½½

=134, g=2.07 DPPH

100 Oe

Ho

g=2.05

g½½

= 2.02

1

g = 2.05, g = 2.02, without HFS,

anisotropy of g-factor,

H is independent of ToC

similar to О- radical anion

2.7%CuZSM-5-17-106 (A, pH-10)

–O-—Cu+-O-—Cu+-O-- (p5d10)

1

(B2) g

½½ = 2.30, A

½½ = 154 Oe

(B1) g

½½ = 2.33, A

½½ = 142 Oe

(C)

(B)

g=2.05

g½½

= 2.02

DPPH

ge

100 Oe

Ho

3

2

1- HVT 400oC

2- 8 torr H2O

3- 17 torr H2O

g = ge, without HFS

dz2 - ground state of Cu2+ ion

–O2-—Cu2+-O2-—Cu2+-O2-- (p6d9)

3.1%CuZSM-5-45-274 (A, pH-10)

+ H2O

- H2O

CTB L M 18000-23000 cm-1

–O2-—Cu2+-O2-—Cu2+-O2--

10000 20000 300000.0

0.2

0.4

0.6

0.8

1.0

Initial(2)

HVT (1)HVT (2)

12

50

0

14

50

0

15

80

0

12

50

0

18

80

0

22

50

0

F(R

)

Wavenumber, cm-1

Initial(1)

(1) - 2.7% Cu-ZSM-5-17-115 (A, pH-10)

(2) - 2.4% Cu-ZSM-5-30-140 (A, pH-10)

10000 15000 20000 25000 30000 350000.0

0.4

0.8

1.2

HVT 300oC

HVT 150oC Initial

CTB

oxide clusters

d-d trans.

22900

20850

19400

18200

F(R

)

cm-1

Zeolite

adsorbtion edge

[Cu(H2O)6]2+

1.5% Cu-ZSM-5-30-92 (N, 80oC, pH-4)

Cu Cu

O

O

OO

OO

IVT Cu2+….Cu+

15000-17000 and 22500 cm-1

–O2-—Cu2+-O2-—Cu2+-O2--–O2-—Cu2+-O-—Cu+-O2--- H2O

+ H2O

UV-Vis experimental data at dehydration - hydration of CuZSM-5

10000 20000 30000 40000 500000

1

2

3

4

31

00

0

22

50

0

1

F(R

)

Wavenumber, cm-1

HVT at 4000C/20 h

80 torr O2

HVT at 400oC/0.2 h

Reduction and reoxidation of copper ions in the chain

structures

(HVT - О2 adsorption at 400oC - HVT)

Т, оС

О2

?

?

!

2.7% Cu-ZSM-5-17-115

• 22500 cm-1 (IVT Cu2+ Cu+)

18000 cm-1 (CTB L M [Cu2+-O2-]n)

• 22500 cm-1 (IVT Cu2+ Cu+) and

31000 cm-1 (CTB L M Sq.Ox.Clus.)

Cu+

(O )-

O2

HVT

…Cu+…(O )

- … Cu+…(O )

- …

O-

O-

Cu+ Cu

2+Cu

2+

O OO

• Сhemical reduction at molecules adsorption: Cu2+ Cu+

Low-temperature NO activation on Cu2+ and Cu+ ions

(isolated ions and copper-oxide chain-like structures)NО?

2.7% Cu-ZSM-5-17-115

10000 20000 30000

0.5

1.0

1.5

22

50

0

18

40

0

F(R

)

Wavenumber, cm-1

HVT at 400oC

0.5 torr

1.5 torr

5 torr

10 torr

12

10

0

14

50

01

38

00

19

40

0

25

80

0

!

NO adsorption (0.5-10 torr) at 25oC

Isolated Cu (1200-14500 cm )

2+

-1

Cu …O… Cu2+ +

(22500 cm )-1

(30000-32000 cm )-1

OO

Cu2+

O

Cu2+

OOO

NO

Cu …O… Cu2+ +

(18400 cm , I)-1

Cu …O… Cu2+ 2+

(25600 cm , III)-1

N

O

N

O-

Cu …O… Cu2+ +

(18400 cm , II)-1

NONO

+ NO 25oC

Low-temperature NO activation on Cu2+ and Cu+ ions

(isolated ions and copper-oxide chain-like structures)

Т, оС

NО

?

?

2.7% Cu-ZSM-5-17-115

10000 20000 30000 40000 50000

1

2

3

35

00

0

13

70

0

18

40

0

F(R

)

Wavenumber, cm-1

HVT at 400oC

20 torr NO/25oC

+150oC/ 0.5 h

+300oC/ 0.5 h

22

50

0

!

NO adsorption (20 torr, at 25oC), heating

Nitrite - nitrate

complex

+ NO 300oC

- N2O 25оС

Cu …O… Cu2+ 2+

(30000-32000 cm , IV)-1

O-

Cu …O… Cu2+ 2+

(25600 cm , III)-1

N

O

N

O-

Low-temperature NO activation on Cu2+ and Cu+ ions

(isolated ions and copper-oxide chain-like structures)

Т, оС

NО

?

?

Nitrite - nitrate

complex

+ NO

300oC

- N2O25оС

+ NO

25oC

Isolated Cu(1200-14500 cm )

2+

-1

Cu …O… Cu2+ +

(22500 cm )-1

(30000-32000 cm )-1

OO

Cu2+

O

Cu2+

OOO

NO

Cu …O… Cu2+ +

(18400 cm , I)-1

Cu …O… Cu2+ 2+

(25600 cm , III)-1

N

O

N

O-

Cu …O… Cu2+ +

(18400 cm , II)-1

NONO

Cu …O… Cu2+ 2+

(30000-32000 cm , IV)-1

O-

The amount of NO chemisorbed on Cu-ZSM-5 samples

depending on Cu loading, Si/Al ratio, рН of solution

(adsorbed at 25oC and 2 torr NO from volume 0.6 litre)

Т, оС

NО

?

?

0 50 100 150 200

0

20

40

60

80

100

NO

, m

km

ol/g

Exchange level, %

pH=6, Si/Al= 17 ( ), 30 ( ), 45 ( )

pH=10, Si/Al= 17 ( ), 30 ( ), 45 ( )

• At the most 20 % of copper are

active in NO chemisorbtion;

• The amount of chemisorbed NO

increase with the growth of the

Cu/Al ratio and reach a maximum

value (7080*10-6 mol NO/g) at

Cu/Al ~ 75-100% independent of

• the Si/Al ratio

• pH of the copper acetate

solution used for the catalyst

synthesis.

• These data are in good agreement

with the growth of the catalytic

activity of Cu-ZSM-5 samples in

deNOx-C3H8

The activity increase may be correlated with the growth in the number of

chain copper oxide structures in the samples

Catalytic properties of Cu-ZSM-5 in SCR NO by propane

Cu/AlEL < 50 %

• low Cu loading

- Cu nitrate (рН 4,

0.0125 - 0.4M)

- Cu acetate (рН 10,

<0.0125 M)

• low Si/Al ratio (17)

Isolated Cu2+ ions

Cu/AlEL 75100%

• рН6 and 10

of Cu acetate

• high Si/Al

ration (30, 45)

Chain copper-oxide structures

Cu/AlEL 150%

• high Cu loading

- рН10, > 0.0125 M

• high Si/Al ration

(30, 45)

Square-plain copper-oxide clusters

20

40

60

80

50 100 150 200 250 300

X(N

O),

%

Exchange level, %

A

50 100 150 200 250 300

0.3

0.6

0.9

WN

O*1

03,

mo

l/g

Cu*m

in

B

Exchange level, %

Si/Al=17: pH-6 and pH-10

Si/Al=30: pH-6 and pH-10

Si/Al=45: pH-6 and pH-10

at 42000 h-1 ; 350oC; (300 ppm NO, 1500 ppm C3H8, 3.5 vol.%O2, N2)

Cu/AlEL 100 %

Si/Al=30 and 45

pH6 and 10 Reexchange

(1 M NH4Cl)

Isolated Cu2+ ions

Chain copper-oxide structures

removed

Square-plain copper-oxide

clusters

remain300 400 500

0

20

40

60

80

100

20

40

60

80

50 100 150 200 250 300

X(N

O),

%

Exchange level, %

350oC

A

Si/Al=45

initial: - pH-6, - pH-10

reexchanged:

50 100 150 200 250 300

0.3

0.6

0.9

WN

O*1

03, m

ol/g

Cu*m

in

B

350oC

Exchange level, %

X(N

O),

%

Temperature, oC

1.92%Cu-ZSM-5-45-168

initial

reexchanged

After removal of copper part from the catalyst:

• the NO conversion decreases, especially at temperatures below 400°C,

• specific activity is close to initial value.

Catalytic properties of Cu-ZSM-5 in SCR NO by propane

1. Series of Cu-ZSM-5 catalysts prepared by variation of ion-

exchange conditions used for their synthesis: pH of impregnation

solution, concentration of precursor and the zeolite Si/Al ratio.

2. Catalysts are characterised in SCR of NO by propane.

3. On the basis of UV-Vis and ESR data the chain-like structures

О2 Cu2+О2 Cu2+О2 stabilised in zeolite channels are proposed. They

are characterised by capability to easy reduction and reoxidation of

copper as well as the ability to stabilise neighbour location of two

copper ions having different valences: Cu2+-Cu+.

3. Quantum chemical approach confirmed ESDR spectra.

4. The low-temperature NO activation reaction scheme has been

proposed based on experimental and spectroscopic data.

4. The experimental SCR activity growth with increase of exchange

level up to 75 - 100% can be correlated with the increase in the

number of chain- like copper-oxide structures.

Conclusions

ACKNOWLEDGEMENT

• Dr. Svetlana Yashnik

• Dr. Lidya Tsikoza

• Dr. Nikolai Vasenin

• Dr. Vladimir Anufrienko

• Dr. Vadim Kuznetsov

• Dr. Vladimir Sazonov

• Dr.Tatyana Larina