[PPT] - Hydrocarbons and NH3 Professor Z.R.Ismagilov Laboratory of PowerPoint Presentation

SLIDE 1

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

n Advanced Catalysis in Russia/CIS

SLIDE 2

Moscow

St-Petersburg Omsk

Novosibirsk

RUSSIA

Volgograd

Boreskov Institute of Catalysis: From Research on Molecular Level to Industrial Implementation

SLIDE 3

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)

SLIDE 4

SLIDE 5

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

SLIDE 6

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

SLIDE 7

CAPOC 6

Sixth International Congress

n 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

SLIDE 8

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

SLIDE 9

Exhaust emission limits for passenger car engines (EU)

SLIDE 10

Diesel exhaust aftertreatment system: The challenge for NOx and Particulates

SLIDE 11

NOx-adsorber catalyst system

SLIDE 12

NOx Adsorber Catalyst

Rich Conditions ( < 1) Regeneration Lean Conditions ( > 1) NOx-Adsorption

Other Exhaust Components Nitrogen oxide (NOx) Clean Exhaust Gas

SLIDE 13

Schematic showing reactions within the adsorber catalyst during lean and rich conditions

SLIDE 14

Dual pore concept for hydrocarbon SCR involving

xidation in small pores and reduction in large pores

SLIDE 15

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;

SLIDE 16

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 solution 0.4  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

SLIDE 17

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

Aqueous copper acetate solution (рН6)

0.0 1.6 3.2 4.8 6.4 8.0 9.6 25 50 75 100 125 Exchange level, % Copper concentration in ion-exchange solution, mg/ml Si/Al-17 Si/Al-30 Si/Al-45

S/Z = 10

10 20 30 40 50 50 100

Exchange level, % Si/Al ratio

8 mg Cu/ml 4 mg Cu/ml 1.6 mg Cu/ml S/Z = 10

The

maximum achievable level

f

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 50 100 8 mg Cu/ml

Exchange level, % S/Z

Si/Al-17 Si/Al-30 Si/Al-45

SLIDE 18

2 4 6 8 10 50 100 150 200 250 300 Exchange level, % Copper concentration in ion-exchange solution, mg/ml Si/Al-17 Si/Al-30 Si/Al-45

S/Z = 10

Ammonia copper acetate solution (рН10)

10 20 30 40 50 50 100 150 200 250 300

Exchange level, %

8 mg Cu/ml 4 mg Cu/ml 2 mg Cu/ml

Si/Al ratio

S/Z = 10

10 20 30 40 50 50 100 150 200 250 300 Si/Al-17 Si/Al-30 Si/Al-45

Exchange level, % 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

f

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

SLIDE 19

Correlation between Cu-ZSM-5 catalytic activity (NO conversion) and copper loading and exchange level at 400oC

300 350 400 450 500 20 40 60 80 100

A

Cu-ZSM-5-30 1.83% Cu 1.45% Cu 1.12% Cu 0.52% Cu 0.36% Cu

X(NO), % Temperature,

C

50 100 150 200 250 300 350 40 80

B

Exchange level, % X(NO), %

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 80 C X(NO), % Cu loading, %

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

SLIDE 20

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 dx

2

y

2 - state

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

3 2 1

DPPH

(A)

A฀ ฀ = 135 Oe g฀ ฀ = 2.38 A฀ ฀ = 135 Oe g=2.07 g฀ ฀ = 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

SLIDE 21

 О- radical anions with weak exchange coupling through diamagnetic Cu+ ions in chains –O-—Cu+-O-—Cu+-O-- (p5d10)

10000 15000 20000 25000 30000 35000 0.0 0.4 0.8 1.2 HVT 300

C

HVT 150

C

Initial CTB

xide clusters

d-d transition

22900 20850 19400 18200 F(R) cm

1

Zeolite adsorbtion edge

–O2-—Cu2+-O2-—Cu2+-O2--

Cu Cu O O O O O O

[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)

SLIDE 22

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 g

1 = 2.38-2.39, A 1 = 130 Oe,

Cu Cu O O O O O O

30000-32000 cm-1

Chains Cu-O-Cu-O-Cu-O

(ESR silent)

Dehydration

vacuum, 25-400oC

Isolated ions Cu2+ (distorted Oh)

12000-14500 cm-1 g

1 = 2.30-2.33, A 1 =145-154 Oe,

g

2 = 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 O O O O

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

SLIDE 23

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

SLIDE 24

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

SLIDE 25

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

0.4 0.8 1.2 8000 12000 16000 20000 0.4 0.8 1.2 cm

1

Intensity, arbtr.u. Linewidth: 1.000E+03

Excitation (cm

1)

17526 20445

16000 13883 12030 8642

H O H O A 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)

SLIDE 26

Self-reduction - autooxydation:

Cu2+ + O2- (d9p6)  Cu+ + O- (d10p5),

Cu2+(OH)22H2O 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

SLIDE 27

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

(C) g฀ ฀ =2.28, A฀ ฀ =164, g=2.07 (B) g฀ ฀ =2.33, A฀ ฀ =134, g=2.07

DPPH 100 Oe Ho

g=2.05

฀ ฀

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

(B

2) g฀ ฀

= 2.30, A฀ ฀ = 154 Oe (B

1) g฀ ฀

= 2.33, A฀ ฀ = 142 Oe

(C) (B)

g=2.05 g฀ ฀ = 2.02

DPPH

ge

100 Oe Ho

3 2

1- HVT 400oC 2- 8 torr H2O 3- 17 torr H2O

g = ge, without HFS

 dz

2 - ground state of Cu2+ ion

–O2-—Cu2+-O2-—Cu2+-O2-- (p6d9)

3.1%CuZSM-5-45-274 (A, pH-10) + H2O

H2O

SLIDE 28

CTB L  M 18000-23000 cm-1 –O2-—Cu2+-O2-—Cu2+-O2--

10000 20000 30000 0.0 0.2 0.4 0.6 0.8 1.0 Initial(2) HVT (1) HVT (2)

12500 14500

15800

12500 18800

22500 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 35000 0.0 0.4 0.8 1.2 HVT 300

C

HVT 150

C

Initial CTB

xide 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 O O O O

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

SLIDE 29

10000 20000 30000 40000 50000 1 2 3 4

31000 22500

1

F(R) Wavenumber, cm

1

HVT at 400

0C/20 h

80 torr O2 HVT at 400

C/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 O O

Сhemical reduction at molecules adsorption: Cu2+  Cu+

SLIDE 30

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

22500 18400 F(R) Wavenumber, cm

1

HVT at 400

C

0.5 torr 1.5 torr 5 torr 10 torr

12100 14500 13800 19400 25800

!

NO adsorption (0.5-10 torr) at 25oC

Isolated Cu (1200-14500 cm )

2+

1

Cu …O… Cu

2+ +

(22500 cm )

1

(30000-32000 cm )

1

O O Cu

2+

O Cu

2+

O O O

NO Cu …O… Cu

2+ +

(18400 cm , I)

1

Cu …O… Cu

2+ 2+

(25600 cm , III)

1

N O N O - Cu …O… Cu

2+ +

(18400 cm , II)

1

NO NO

+ NO

25oC

SLIDE 31

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

35000 13700 18400

F(R) Wavenumber, cm

1

HVT at 400

C

20 torr NO/25

C

+150

C/ 0.5 h

+300

C/ 0.5 h

22500

!

NO adsorption (20 torr, at 25oC), heating Nitrite - nitrate complex

+ NO 300oC

N2O

25оС

Cu …O… Cu

2+ 2+

(30000-32000 cm , IV)

1

O

Cu …O… Cu

2+ 2+

(25600 cm , III)

1

N O N O -

SLIDE 32

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

N2O

25оС

+ NO

25oC

Isolated Cu (1200-14500 cm )

2+

1

Cu …O… Cu

2+ +

(22500 cm )

1

(30000-32000 cm )

1

O O Cu

2+

O Cu

2+

O O O

NO Cu …O… Cu

2+ +

(18400 cm , I)

1

Cu …O… Cu

2+ 2+

(25600 cm , III)

1

N O N O - Cu …O… Cu

2+ +

(18400 cm , II)

1

NO NO

Cu …O… Cu

2+ 2+

(30000-32000 cm , IV)

1

O

SLIDE 33

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

? ?

50 100 150 200 20 40 60 80 100 NO, mkmol/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 (7080*10-6 mol NO/g) at Cu/Al ~ 75-100% independent of

the Si/Al ratio
pH
f

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

SLIDE 34

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  75100%

рН6 and 10
f Cu acetate
high Si/Al

ration (30, 45)

Chain copper-oxide structures Cu/AlEL  150%

high Cu loading
рН10, > 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(NO), %

Exchange level, %

A

50 100 150 200 250 300 0.3 0.6 0.9 WNO*10

3, mol/gCu*min

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)

SLIDE 35

Cu/AlEL  100 % Si/Al=30 and 45 pH6 and 10 Reexchange (1 M NH4Cl) Isolated Cu2+ ions Chain copper-oxide structures

removed

Square-plain copper-oxide clusters

remain

300 400 500 20 40 60 80 100 20 40 60 80 50 100 150 200 250 300 X(NO), %

Exchange level, % 350

C

A

Si/Al=45 initial:

pH-6,
pH-10

reexchanged:

50 100 150 200 250 300 0.3 0.6 0.9 WNO*10

3, mol/gCu*min

B

350

C

Exchange level, %

X(NO), % Temperature,

C

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

SLIDE 36

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

SLIDE 37

ACKNOWLEDGEMENT

Dr. Svetlana Yashnik
Dr. Lidya Tsikoza
Dr. Nikolai Vasenin
Dr. Vladimir Anufrienko
Dr. Vadim Kuznetsov
Dr. Vladimir Sazonov
Dr.Tatyana Larina