Poisoning/Deactivation S

V2

O5/TiO2 SCR Cataly

Xiaoyu Guo, Jacob Beutler, Chase An

Aaron Nackos, John Ashton, Calvin Bart

William Hecker, Larry Baxter

ACERC Conference

Feb 26, 2008

Provo, UT
Outline

• Introduction• Objective and Motivation • Results and Discussion• Conclusions• Acknowledgements
Introduction

• SCR: a high efficient NOx abateme

• A commercial post-combustion • Being used on 1⁄4 of the power g

from coal-fired boilers

• Major problem is catalyst deacti

especially for low-rank coals an
Example of SCR System

• Modified from http://upload.wikimedia.org/wikipedia/en/5/5c/S

Ammonia inlet stream
Introduction

• SCR: selective catalytic reduction

• 4NH3 + 4NO + O2 4N2 + 6H2O

• 4NH3 + 2NO2 + O2 3N2 + 6H2O

• SCR catalyst

• Supported vanadia catalyst: 1%V2O5-

• Currently, in monolith or flat plate str

• SCR kinetics: rNO ≈ k CNO
Deactivation Mechanisms

• Plugging• Fouling/Masking• Poisoning
Channel/Pore Plugging
Fouling/Masking

Calcium sulfate coating on catalyst 
Poisoning

• Catalytic activity linked to 

amount/strength of Brønsted acid sites on catalyst surface (Amiridis, Duevel, Wachs, 1999)

• Chemical poisoning results 

from basicity of metal oxide deposits (Chen et al., 1990)

• Flyash from coal/biomass 

contains carbonates, sulfates, and oxides of Na, 

Ca, 

K, As, and Mg, which 

are basic materials
Coal & Biomass Ash Compositions 

Pittsburg

7.8% As

Imperial W heat Straw

15.4% Ash

Red Oa

1.3% As

Black Thunder

7.2% Ash

BiomassCoal
• Objective

• Examine fresh and exposed commerc

catalysts and determine the deactivat

• Determine the impacts of K, Na, Ca, a

vanadia catalyst properties and activisynthesized catalysts

• Motivation

• Poisoning is a potential mechanism f

deactivation

• SO2 is generally present in boiler flue • Previous studies on non-sulfated cata

Objective and Motivation
Slipstream Reactor

• REI operating slipstream 

reactor at Rockport, IN

• Reactor contains 6 separate 

channels for 5 commercial, one BYU -prepared catalyst

• Samples are returned for 

analysis

Pne

One SCR Inlet Heated Sample Line

Ammonia Injector

SCR Reactor

2.5" out

5.0" out

2.5" out 5.0" out

1/8" wall thickness 2.25 x 2.25 inner dimension 4.75 x 4.75 inner dimension

Top view of slipstream reactor.

(Schematic courtesy of REI)
Fresh and Exposed Catalysts Comp

Fresh 2063 hour

exposure

3800 expo
Catalyst Characterization Syste
Monolith Test Reactor

Flow out

Plate heater 

(x4)

Flow in

Flow Catalyst sample Thermocouple

Monolith Test 

Reactor Schematic

Flow Feed:• 900 • 900 • 2% O• ~10% 

• BalaTemp
Fresh and Exposed Catalysts Perfor

Monolith 1 kinetic data Monolit

1510

5

NO reduction rate constant, 

0

k (cm3/m2•s)

520 540 560 580 600

Temperature (K)

 M1 Fresh fit M1 Fresh M1 2063 fit M1 2063 M1 Biomass fit M1 Biomass M1 3800 fit M1 3800

3025201510

5

NO reduction rate constant, 

0

k (cm3/m2s)

520 540 

 M2 Fresh  M2 2063  M2 Biomass  M2 3800 
BET Results

Sample M1 

BET surface 

area, m

2/g

Average pore 

diameter, nm

BET sur

area, m

Fresh 61.5 16.4 56.6 

2063 53.5 17.5 54.5 3800 55.6 17.7 50.0 

Biomass 48.2 19.9 43.9 
Locations of ESEM Analysis
60

5040302010

0

Weight %

 O Na Mg Al Si P S K Ca Ti V 

Elements

 M1 Fresh M1 Bio M1 2000 M1 3800

Flat

Elemental Composition vs. Exp
Elemental Composition vs. Pos

605040302010

0

Weight %

 O Na Mg Al Si P S K Ca Ti V 

Elements

 M1 Fresh M1 3800 Center M1 3800 Edge M1 3800 Flat M1 3800 Ash
Indications from Slipstream Sam

• Short exposure indicates a slight increa• Pore plugging and Fouling appear to be 

significant initially with poisoning occu

• ESEM results indicate poisons deposit 

outside edge than on the inside or centemonolith catalyst

• ESEM results show sulfate accumulates 

outside surface
In situ FTIR - MS Reactor 
Sulfates Enhance NH

3 Adsorptio

Sulfation increases the amount of Brønstethe vanadia catalysts surface

43210

Absorbance

4000 3500 3000 2500 2000 

Wavenumber

 Sulfated Fresh
Sulfates Enhance NO Reduction Rea

Sulfation enhances NO reduction activity by increE

a remains approximately constant before and aft

353025201510

5

K, cm3/g*s

520 530 540 550 560 

Temperature, K

 24-hour sulfated 1% V

2

O

5/TiO

2

 Lightly sulfated 1% V

2

O

5/TiO

2

 Fresh 1% V

2

O

5/TiO

2

A = 1716400 +/- 468000 Ea = 52566 +/- 1240

A = 300888 +/- 76400 Ea = 45758 +/- 1160

A = 182003 +/- 56700 Ea = 44921 +/- 1430
Ca, Na, and K Effects on NH

3 Ads

0.40.30.20.10.0

Absorbance

1600 1500 1400 1300 12

Wavenumber

 1%V-9%W/T 0.5Ca 1%V- 0.5Na 1%V- 0.5K 1%V-9

NH

3 adsorption 

↓ with 

↑ basicity of metals
K, Na, and Ca Impacts on SCR A

201816141210

8642

k, cm3/g•s 

460 480 500 520 54

Temperature, K

 1V-9W/TiO

2

 0.5 Ca 1V-9W/TiO

2

 0.5Na1V-9W/TiO

2

 0.5k1V-9W/TiO

2
Tungsten Impact on NH

3 Adsorp

1000ppm NH

3 adsorption at 50 

 ̊

C

2.01.51.00.50.0

-0.5

Adsorption

1800 1600 1400 12

Wavenumber, cm-1

 1%V - 9%W / TiO

2

 9%W / TiO

2

 TiO

2
NOx Reduction Activity Compar

201510

50

k, cm

3

/g•s

460 480 500 520 540 

Temperature, K

 1%V-9%W/TiO2 1%V/TiO2 9%W/TiO2
Conclusion

• Major deactivation mechanisms fo

catalysts during low-rank coal com

• Plugging by popcorn ash• Fouling and masking by fly ash• Chemical poisoning is not important

• Impacts of sulfation

• Enhances NOx reduction activity • Increases ammonia adsorption• Influences rate, but not mechanism
Conclusion cont.

• Impact of K, Na, Ca

• Significant poisons• K>Na>Ca, proportional to basicity• Biomass potentially is worse than co

• Impact of Tungsten

• Increase the amount of Brønsted acid • Does not provide activity but assists 

significantly in the NO

x reduction
Current work

• Affect of SO2 flowing in reactant g

• Appears to significantly enhance NOx 

activity in preliminary experiment

• More data is needed to validate effect

• Problems

• Forms sticky ammonium salts when m

in stream

• Must heat all lines and MS above 300

plugging
Acknowledgments

• EPRI• DOE/NETL• REI• University of Utah
Statistical Experimental Des

Runs Composition Factor Runs C

K Na Ca SO

4 K 

1 0 0 0 0 9 02 0.5 0 0 0 10 0.5 3 0 0.5 0 0 11 0 4 0 0 0.5 0 12 0 5 0.5 0.5 0 0 13 0.5 6 0.5 0 0.5 0 14 0.5 7 0 0.5 0.5 0 15 0 8 0.5 0.5 0.5 0 16 0.5 
Statistical Experimental Des

Runs Composition Factor Runs C

K Na Ca SO

4 K 

1 0 0 0 0 9 02 0.5 0 0 0 10 0.5 3 0 0.5 0 0 11 0 4 0 0 0.5 0 12 0 
Empirical rate constant express

⎜⎜⎜⎜⎜⎝⎛

⎟⎟⎠⎞

⎜⎜⎝⎛

−

− ⎟

⎟⎠⎞

⎜⎜⎝⎛

−+

++−−−

=

0

0

0

0

11 12.0 11 27.0

38.017.03.076.016.15.2

exp

TTS

S

TT

S

S

V

Ca

V

Na

V

K

k