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Catalizzatori per la rimozione di inquinantiLidia Castoldi

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Lidia Castoldi

Sorgenti di emissione e rischi connessi

Sorgenti:

fisse (impianti di generazione di potenza, boilers industriali, inceneritori, combustione di biomasse);

mobili (veicoli)

Rischi/danni:

problemi respiratori e cardiaci nell’uomo;

piogge acide;

produzione di ozono nella troposfera;

formazione di polveri sottili

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Lidia Castoldi

Civile6%

Commercio4%

Industria18%

Trasporto32%

Energia elettrica40%

Civile6%

Commercio4%

Industria18%

Trasporto32%


2000

L’evoluzione dell’inquinamento

Civile8%

Commercio5%

Industria25%

Trasporto29%


1980

Calo delle emissioni dell’industria grazie al miglioramento delle tecnologie

Aumento delle emissioni da produzione di energia elettrica a causa del maggiore fabbisogno della stessa

Aumento delle emissioni da trasporto, a causa dell’aumento di diffusione degli automezzi, soprattutto in paesi emergenti

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Lidia Castoldi

sorgenti mobili,non diesel

26%

NOx

altro

processi dicombustione,altro

processi di combustione,industria

processi di combustione,utility

sorgenti mobili,diesel

6%5% 14%

23%26%

PM-10

altroaltri processi industriali

processi di combustione,altro

processi di combustione,industria

processi di combustione,utility

sorgenti mobili,non diesel

sorgenti mobili,diesel

24%17%

16%

10%9%6%

18%

L’evoluzione dell’inquinamento

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Lidia Castoldi

POWER DEMAND

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Lidia Castoldi

Power demand: future trend

Global primary energy demand is expected to increase 53% by 2030, during which time demand for electricity will more than double. 70% of this increase will come from developing nations, led by China and India.

By 2025, fossil fuels are expected to constitute 85% of the world’s primary energy mix

By 2025, the US’s consumption of electricity is projected to be 50% greater than in 2003. To meet this rising demand, while also retiring inefficient older plants, 281,000 megawatts of new power generationcapacity will be needed – the equivalent of almost 950 new power plants of 300 megawatts each.

However, America is not alone in its growing demand for energy. Japan imports 99% of its oil and 97% of its natural gas and has now overtaken Korea to become the world’s largest importer of ethanol. Two decades from now, China, the world’s fastest growing consumer of petroleum, could be importing 10 million barrels of oil per day.

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Lidia Castoldi

Power demand: energy consumption

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Lidia Castoldi

Power demand: electric power generation and energy consumption

OECD (Organisation for Economic Co-operation and Development)

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Lidia Castoldi

Previsioni sulla produzione di turbine a gas e impianti di potenza

Given the current need for new baseload capacity, as well as for power plant capacity additions, we believe that the worldwide demand for the latest technology gas turbine-based power plants will result in modest production of the super-large gas turbine machines, those of 180 MW and larger.

Production of those machines could grow from 48 machines in 2003 to 150-160 machines per year in the period 2011-2014. Those machines can be expected to be procured by China, North Korea, Vietnam, Indonesia, Thailand, Brazil, and the Middle East.

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Lidia Castoldi

Previsioni sulla produzione di turbine a gas e impianti di potenza

Worldwide orders for gas turbine machines for electrical generation of 1 MW and larger grew from about 800 machines in 1986/1987 to 875 in 1998/1999.

The trend continued into 1999/2000, when 1,200 machines were ordered, and 2000/2001, when about 1,540 machines were ordered.

Orders then fell off over the next two years to about 840 and 600 machines, respectively.

Orders in the 2003/2004 period totaled about 700 machines, about equal to Forecast International's projection for the 2004/2005 period.

Of the 7,550 machines projected to be manufactured during the next 10 years, machines of 125 MW and larger should account for more than 30% of unit production and over 70% of value of production.

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Lidia Castoldi

EMISSIONS REGULATION: stationary and mobile sources

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Lidia Castoldi

Limiti di emissione: sorgenti fisse

35Inceneritori (11% O2)

25Turbine a gas (15% O2)

50Centrali termoelettriche a gas naturale (3% O2)

75Centrali termoelettriche ad olio combustibile (3% O2)

100Centrali termoelettriche a carbone (6% O2)

EULimiti di emissione NO X (ppm)

USUSUSUSNOx emission budgets set by EPA require thatUtility Generation Stations must achieve in 22 States100 ppm by 2003 in the Ozone seasons (May-September)

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Lidia Castoldi

NOx and PM emission standardsfor mobile sources

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Lidia Castoldi

NOx Emission Control Technologies

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Lidia Castoldi

Tecniche di riduzione degli NO x

� Tecniche primarie� Water/Steam Injection� Lean Premix Combustion (DLN)� Catalytic Combustion

� Tecniche di post-trattamento:

� SCR (Selective Catalytic Reduction)

�urea- or ammonia- SCR

�HC-SCR

� NSR (Nitrogen Storage Reduction)

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Lidia Castoldi

Ammonia- or urea-SCR:- used in stationary applications- when used in vehicles the catalyst is operated under fast transient conditions

- transient kinetics and dynamic model of the catalytic reactor required

NSR:- less mature technology- associated with a number of complications

Tecniche secondarie di riduzione degli NO x

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Lidia Castoldi

LNT & SCR

We have: NOx NO NO2 ONO- NO3-

We want: N2

We add: H2 (CO, HC) or NH 3

O2 H2O CO2

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Lidia Castoldi

Tecnologia SCR: applicazioni per sorgenti fisse

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NOx Emission Control Technologies

Secondary Methods:Conventional SCR 9 ppmHigh-T SCR 9 ppmLow-T SCR 9 ppmSCONOx 2 ppm

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Common Applications : coal-fired power plantsoil-fired power plantsgas-fired power plantsindustrial boilerscogeneration units

Overall capacity of the utility sector: around 300.000 MWe

Other Applications: waste incineratorscombined NOx-dioxin abatementchemical plants (e.g. HNO3 tail gas, FCC Units)steel industries glass industries cement industries

They account roughly for 10-15% of the total catalyst volume.

Applications of SCR technology

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Lidia Castoldi

ENEL - SCR deNOx reference list

SCR DENOx PLANTS: 13.850 MWe IN OPERATION

POWER PLANT SIZE(MWe)

FUELPRIMARY

ABATEMENTSYSTEM

SCRCONFIGUR.

SCRSTART-UP

MONTALTO DICASTRO 4 x 660 O / G OFA / LNOxB (TEA) HIGH DUST 1996 / 98

TORRE VALDALIGANORD 4 x 660 O / G BOOS HIGH DUST 1997 / 98

BRINDISI SUD 4 x 660 C / O / ORIM NOx PORTS / LNOxB HIGH DUST 1997 / 98

FIUME SANTO 2 x 320 C / O / ORIM OFA HIGH DUST 1997 / 98

FUSINA 2 x 320 C / O OFA HIGH DUST 1997 / 98

TURBIGO 250-320 O / G BOOS / LNOxB (TEA) HIGH DUST 1998

ROSSANO CALABRO 4 x 320 O / G BOOS HIGH DUST 1998 / 99

VADO LIGURE 2 x 320 C / O LNOxB (TEA) /REBURNING HIGH DUST 1998 / 99

TERMINI IMERESE 2 x 320 O / G BOOS HIGH DUST 1999

S. FILIPPO DEL MELA 2 x 320 ORIM / O BOOS SIDE STREAM 2000

LA SPEZIA 1 x 600 C / O NOx PORTS / LNOxB HIGH DUST 2000

SULCIS 1 x 240 C / O LNOxB (TEA) TAIL END 2000

FUEL: C: COAL O: HEAVY FUEL OIL ORIM: ORIMULSION

LNOxB: LOW NOx BURNERS

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Tecnologia SCR: la chimica dellareazione

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Selective Catalytic Reduction of NO x with NH 3

4 NH3 + 4 NO + O2 → 4 N2 + 6 H2O Standard-SCR

6 NO + 4 NH3 → 5 N2 + 6 H2O Slow6 NO2 + 8 NH3 → 7 N2 + 12 H2O NO2-SCRNO + NO2 + 2NH3 → 2 N2 + 3 H2O Fast-SCR

Undesired reactions : unselective reactions, ammonia oxidation reactions, oxidation of SO2

Formation of other pollutants consumption of a reactant

Chemistry of the DeNO x SCR

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Lidia Castoldi

Undesired oxidation of SO 2 to SO 3

SO2 + ½ O2 → SO3

SO3 + H2O → H2SO4

NH3 + SO3 + H2O → (NH4) HSO4

2 NH3 + SO3 + H2O → (NH4)2 SO4

SO3 can react with H2O and NH3 to form ammonium sulphates, which

can deposit onto the catalyst and onto the Air Pre Heater downstream

of the SCR reactor.

Chemistry of the DeNO x SCR

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Lidia Castoldi

Deposition of ammonium sulfates

� The deposition of ammonium sulfates is controlled by thermodynamics.

� Temperature above 250-300°C are typically required for stable catalyst operation and ammonia slips of 1-3 ppm are required in the reactor design

� The conversion of SO2 to SO3over the catalyst must be lower than 1%

0.1

1.0

10

100

1000

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Tecnologia SCR: caratteristiche del catalizzatore e del reattore

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Efficiency for NOx removal versus temperature

A. Noble metals catalystsB. Metal oxides catalystsC. Zeolite catalysts

150 200 250 300 350 400 450 500 55020

30

40

50

60

70

80

90

cat. Ccat. B

cat. A

Con

vers

ione

NO

x (%

)

Temperatura (°C)

DeNOx SCR commercial catalysts

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Lidia Castoldi

Metal based catalysts made of homogeneous mixtures o f

TiO2 (≈ 80% w/w)

V2O5 (< 1-2% w/w)

WO3 (≈ 10% w/w) or MoO3 (≈ 6% w/w)

Silico aluminates

Glass fibers

Employed in form of

DeNOx SCR conventional commercial catalysts (300-400 °C)

honeycomb plates

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Lidia Castoldi

TiO2 (≈ 80% wt%) high surface area and S-resistant carrier

WO3 (≈ 10% wt%) surface acidity andthermal stability

V2O5 (< 1-2% w/w) active phase

Silico aluminates mechanical promoters

Glass fibers mechanical promoters

DeNOx SCR conventional commercial catalysts (300-400 °C)

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Monolithic materials

It is a unitary structure composed of inorganic oxides or metals in the form of a honeycomb with uniform sized and parallel channels that may be square, triangular, hexagonal, round.

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Lidia Castoldi

Monoliths are preferred to pellet shaped catalysts in environmental applications: low pressure drop, excellent attrition resistant, good mechanical properties…

Straight parallel channels Large open frontal area

High external surface/volume ratio

Low pressure dropsLow tendency to plugging

High activity

Thin layer of coated active material Lower intra-phase diffusional resistance

High thermal conductivityMetallic substrate

Monolithic materials

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Lidia Castoldi

Why monoliths in the SCR?

� NO reduction is very fast and is controlled by external and internal diffusion.� SO2 oxidation is very slow and controlled by chemical kinetics.

The SCR activity is increased by increasing the catalyst external surface area (i.e. cell density) whereas the S02 oxidation activity is reduced by decreasing the wall thickness of the catalyst.A good balance between macropores to speed up diffusion of reagents and micropores to provide high specific surface area can lead to optimal catalyst performances (in the limit of the required mechanical specifications).

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Honeycomb type catalysts

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Lidia Castoldi

Honeycomb type catalysts

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Plate type catalysts

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Lidia Castoldi

Geometric data forhoneycomb and plate type catalysts

Honeycomb catalysts Plate-type catalysts

Geometry of the element,

mm x mm x mm

150 x 150 x (500-1300) 500 x (500-600)

Number of cells 15 x (15-40)x 40 -

Channel width, mm 8.5-3 -

Pitch, mm 10-3.7 7-3.8

Wall thickness, mm 1.5-0.6 1.2-0.8

Specific surface area, m2/m3 340-860 280-500

Void fraction, % 64-72 ~ 80

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Lidia Castoldi

Monolith matrix made of cordierite or thin metal foils coated with SCR materials

High T catalysts: zeolite-type (high Si/Al ratio)(up to 600°C)

Low T catalysts: noble metal-based(down to 200°C) high vanadium-content

DeNOx SCR non-conventional commercial catalysts

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Lidia Castoldi

Catalyst optimization has significantly reduced the size and the cost of the SCR reactor and has greatly increased the economics of the SCR process.

Catalyst life of 16.000 – 24.000 h is typically guaranteed by catalyst suppliers but longer catalyst life is observed in practice and expected in reality.

Major causes of catalyst deactivation are sintering for gas-fired units, poisoning by alkaline metals for oil-fired units and pore blocking by calcium sulfates for coal-fired units.

Catalyst optimization

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Configuration of the SCR reactor

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Lidia Castoldi

Effect of non uniform distribution

To ensure high NOx removal efficiency and low ammonia slip during industrial operation a uniform distribution of NOx/NH3 mole ratio, temperature and velocity over the entire cross section of the catalytic converter must be approached.

This is achieved by:- use of guide vanes and of dummy layer before the catalyst layers;- use of cold models at a reduced scale and CFD calculations;- proper design of the ammonia distribution grid;- precise tuning of the ammonia distribution grid during plant start up.

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Lidia Castoldi

ESP

Boiler FGD

DeNOx

Tail end

Boiler DeNOx FGD

ESP High dust

ESP

Boiler DeNOx FGD

Low dust

SCR configurations for boilers applications

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Lidia Castoldi

Inceneritori

� I fumi di combustione, in uscita dal filtro a manica, si trovano a T ~ 200°Ce con conc. SOx ~ 0.

� Il reattore SCR è operato a bassa T per minimizzare i consumi energetici.

240-250°CDry-adsorber

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Lidia Castoldi

Il reattore SCR è integrato nel sistema HRSG.

SCR configurationsfor Gas Turbine applications

HRSG

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Lidia Castoldi

Catalyst deactivation

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Tecnologia SCR: meccanismo dellareazione DeNO x

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Inomata et al.

NH3 adsorbed at a Brønsted V site adjacent to a vanadyl reacts with gas-phase NO (Eley-Rideal mechanism ) to form N2 and H2O and a reduced V species.The reduced V species is then re-oxidized by gaseous oxygen

Mechanism of the DeNO x Reaction

M. Inomata et al, J. Catal. 62 (1980) 140

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V

O

OO O

N

H

HH

V

O

OO O

N

H

HH

..

N O.

V

O

OO O

N

H

H

N O

.

V

O

OO OH.

H

N N

H2OV

O

OO O

NH3

/ O21 4/ H2O1 2

Ramis et al.“amide-nitrosamide” mechanism


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Topsøe et al, J. Catal. 151 (1995) 241

Topsøe et al.

NH3 is adsorbed at a V(5+)-OH Brønsted acid site and is activated by a near-by V(5+)=O group, that is then reduced to V(4+)-OH. Gaseous NO reacts with adsorbed NH3 to form an intermediate which decomposes to N2 and H2O.V(4+)-OH is re-oxidized to V(5+)=O by gas-phase oxygen


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Lidia Castoldi

� Both mechanisms proposed by Inomata and by Topsoe require the participation of dymeric vanadyl species.� Mechanism proposed by Ramis et al. require the participation of isolated vanadyl and is consistent with the linear dependence of the rate constant of NOx reduction on the vanadia content.�Other catalyst components in addition to vanadia (i.e. tungsta and titania) do adsorb ammonia and participate in the reaction as “reservoir” of adsorbed ammonia species.�A key step of the mechanism is represented by the formation of areaction intermediate that decomposes selectively and quantitatively to nitrogen and water.


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Tecnologia NSR: applicazioni per sorgenti fisse

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Condizioniricche

Condizionimagre Ba(NO2)2

Ba(NO3)2

NOx

Ba PtO

Ba(NO2)2

Ba(NO3)2

HC

N2

metalli nobili

ossidazione/riduzione

ossidi di metalli alcalini-terrosiaccumulo

Pt-Ba/γγγγ-Al2O3

Tecnologia NSR

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Lidia Castoldi

Tecnologia SCONOX TM

(Goal Line and Süd Chemie)

Rimozione di NOx (SCONOX TM) nelle Turbine a Gas in USA (unità di

cogenerazione Sunlaw Federal di 32 MW,impianto Wyeth Biopharmadi 5 MW, unità di cogenerazione presso University of California).

Catalyst: Pt-K2CO3/Al2O3

Oxidation/adsorption cycle:CO + ½ O2 → CO2

NO + ½ O2 → NO2

2NO2 + K2CO3 → CO2 + KNO2 + KNO3

Regeneration cycle:KNO2 + KNO3 + 4H2 + CO2 → K2CO3 + 4 H2O(g) + N2

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Lidia Castoldi

Regeneration gas generator

1040°CCH4 + ½ O2 + 1.88 N2 → CO + 2 H2 + 1.88 N2

Cat.

(or steam reforming)

shiftCO + 2H2 + H2O + 1.88 N2 → CO2 + 3H2 + 1.88 N2

Tecnologia SCONOX TM

(Goal Line and Süd Chemie)

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Lidia Castoldi

Layout of SCONOx TM catalyst

Turbine package

Exhaust transition

Open isolation louvres

Closed isolation louvresSconox catalyst blocks

High pressure heatrecovery steam generators

Exhaust stack

Louvres closedduring regeneration

Regenerationgas outlet (2)

Regenerationgas inlet (1)

Low pressure heat recovery steamgenerator

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Lidia Castoldi

SCONOxTM layout detail

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Lidia Castoldi

Typical design arrangement

Several catalyst sections

80% of these are in the oxidation/adsorption cycle ⇒ 15-20 minutes

20% of these are in the regeneration cycle ⇒ 3 - 4 minutes

GHSV = 20.000 h-1 (25ppm → 1ppm) 15.000 h-1 (50ppm → 1ppm)

Temperature = 150°- 370°C

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Lidia Castoldi

The SCOSOx sulphur removal system

CO + ½ O2 → CO2

SO2 + ½ O2 → SO3

SO3 + SORBER → [SO3 + SORBER]

[SO3 + SORBER] + 4H2 → H2S + 3H2O

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Sunlaw’s Federal Plant and NO x emissions rateon a rolling 15 minutes average from the SCONOx TM unit

Applied to Gas Turbines SCONOX has been successfully applied downstream of a 34 MW GT.

<1 vppm @ 15% O2

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Lidia Castoldi

Cost impact factors for selected NO x control technologies (1999)

Turbine output (class) 5 MW 25 MW 150 MW

NOx emission control

technology $/ton ¢/kWh $/ton ¢/kWh $/ton ¢/kWh

DLN (25 ppm) 260 0.075 210 n.d. 122 0.054

Water/Steam injection (42 ppm) 1652 0.410 984 0.240 476 0.152

Catalytic combustion (3 ppm) 957 0.317 692 0.215 371 0.146

Conventional SCR (9 ppm) 6274 0.469 3541 0.204 1938 0.117

High temperature SCR (9 ppm) 7148 0.530 3841 0.221 2359 0.134

Low temperature SCR (9 ppm) 5894 1.060 2202 0.429 n.d. n.d.

SCONOx (2 ppm) 16327 0.847 11554 0.462 6938 0.289

1. The $/ton value is a useful comparative indicator when the inlet and outlet concentrations are the same2. The ¢/KWh value provides electricity cost impact of a particular technology. The comparison is most meaningful for an equivalent ppm outlet concentration3. Both values are based on 8.000 full-load operating hours

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Lidia Castoldi

Comments (based on ¢/KWh values)

1. High-T SCR is slightly more costly than conventional SCR

2. Low-T SCR and SCONOx are 2 times more costly thanconventional SCR

3. Each SCR technology fills a unique niche; cost impact may beof secondary significance

4. SCONOx is the only secondary control technology that doesnot require NH3 injection

5. The cost of catalytic combusor is 2-3 times higher a DLN combustor alone. However, to rich the same NOx levels DLN must be equipped with SCR or SCONOx

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Lidia Castoldi

1. The cost impact is highest when emission control technologies are applied tosmall turbines (5MW)

2. DLN technology and catalytic combustion exhibit lower cost impacts thanpost-combustion tecnologies for both small and large GT

3. Catalytic combustion is very promising in view of low cost impact and NOxlevel.

Comparison of NO x control technologies

0.0

0.2

0.4

0.6

0.8

1.0

1.2

DLN

(9-25ppm)

Catalytic

(3ppm)

W/S Inj

(42ppm)

Conven.

SCR

(9ppm)

SCONOx

(2ppm)

Low-T

SCR

(9ppm)

High-T

SCR

(9ppm)

5 MW 25 MW 150 MW

Cos

t of P

ower

Impa

ct (

cent

s/K

Wh)

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RESEARCH OPPORTUNITIES

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Selective Catalytic Reduction

� Improved catalyst design (higher DeNOx effectiveness factor)

� Higher NOx reduction efficiency

� Study of the SCR process for GT

�Applicazione in inceneritori e turbine a gas a bassa T

� Better understanding of several fundamental issues (e.g. catalyst reactivity, mechanism, kinetics)

SCONOx�Study of the process and of the available commercial catalysts� Develop cheaper and S-resistant catalysts

RESEARCH OPPORTUNITIES

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Applicazioni per sorgenti mobili

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How do we get there?

Improvements in the combustion engine technologies c an help…but they are not sufficient… DPF and deNO x systems are mandatory!

BOSCH, 1st MinNOx conf., 2/2007

DENSO, 2nd MinNOx conf., 6/2008

BMW, 2nd MinNOx conf., 6/2008

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Why diesel engines?

DAIMLER, CAPOC meeting, 4/2009

Make the gasoline engine asefficient as the Diesel engineand the Diesel engine as cleanas the gasoline engine

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NOx & PM control techniques

EMITECIVECO

BMWVOLKSWAGEN

2nd MinNOx conf., 6/2008

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NOx control techniques

BASF

BMW

DENSO

DAIMLER, CAPOC meeting, 4/2009


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LNT or SCR?


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LNT + SCR!

DAIMLER,

BlueTEC I

HONDA,

double layer LNT/SCR

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Lidia Castoldi

LNT & SCR

SCR

4NH3 + 4NO + O2 → 4N2 + 6H2O Standard SCRStandard SCR

2NH3 + NO + NO2 → 2N2 + 3H2O Fast SCRFast SCR

4NH3 + 3 NO2 → 3.5 N2 + 6H2O NONO22 –– SCRSCR

• DOC upstream of the SCR (NO � NO2)

• Continuous process with urea/NH3discontinuous dosage

• Commercial catalysts: V2O5–WO3/TiO2 &Fe- or Cu-zeolites (ZSM5, Beta)

LNT

NOx NOx storagestorage

NOx NOx reductionreduction

• PM component

• Cyclic conditions: long lean phases, short rich phases

• Commercial catalysts: Pt-Ba/Al 2O3 & Pt-Al 2O3/BaO/CeO2/TiO2

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Tecnologia SCR: applicazioni per sorgenti mobili

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SCR: linee di tendenza

Motivazioni forti per:

� sviluppare un modello dinamico del reattore monolitico SCR;

� estendere la finestra di lavoro verso la regione delle basse T (~ 300°C �� ~ 200°C) per esempio con l’uso di catalizzatori a base di zeoliti (scambiate con Fe, C u…).

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Lidia Castoldi

Tecnologia di abbattimento di NOx daesausti di mezzi pesanti Diesel

Reazione della standard SCR4NH3 + 4NO + O2 → 4N2 + 6H2O

Urea-SCR

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Lidia Castoldi

La reazione SCR che coinvolge consumi equimolari di NO e NO2 è nota come “fast”SCR di interesse per applicazioni a bassa T :

2 NH3 + NO + NO2 → 2 N2 + 3 H2O

In questo caso è necessario un catalizzatore di pre-ossidazione per convertire parte di NO a NO2

Urea-SCR: reazione fast-SCR

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Principali caratteristiche:

� disproporzione veloce di NO2 a nitriti e nitrati

2 NO2 ↔ N2O4 (+H2O) ↔ HNO2 + HNO3

� decomposizione dei nitriti in presenza di ammoniaca:

HNO2 + NH3 → [NH4NO2] → N2 + 2 H2O

Fast SCR: meccanismo

C. Ciardelli et al., Chem. Comm., 2004;I. Nova et al., Catal. Today, 2006;E. Tronconi et al., J. Catal., 2006;P. Forzatti et al., MI 2007 A 742 del 12.4.2007

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Lidia Castoldi

0

200

400

600

800

experimental langmuir temkin

time

T=280°C

Con

cent

razi

one

(ppm

)

)1(3

θ−= NHadsads Ckr θαθ ⋅

−−=

°

)1(expRT

Ekr deso

desdes

Dynamic modelling of SCR

NH3 adsorption-desorptionStep changes of NH3 inlet concentration over V2O5-WO3/TiO2 catalyst at T=280°C

Large amounts of ammonia are adsorbed, the adsorption of ammonia is fast and the desorption iscompleted only at high T

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0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

700

800

Time (s)

Theor. Exp.C

once

ntra

tion

(ppm

)

NO adsorption-desorptionStep changes of NO inlet concentration over V2O5-WO3/TiO2 catalyst at T=280°C

NO does not appreciably adsorb on the catalyst surface


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Lidia Castoldi

0 500 1000 1500 2000 2500

0

200

400

600

800

INNH3

N2

NO

NH3

Time (s)

Con

cent

ratio

n (p

pm)

rNO is almost unaffected by changes in the ammonia surface coverage at high coverage

Dynamics of the surface reactionStep changes of the NH3 inlet concentration in flowing He + NO + O2 (1%) at 220°C


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0.0 0.2 0.4 0.6 0.8 1.00.00

0.01

0.02

0.03

0.04

0.05

0.06

r NO /[

CN

O]

θNH3

a “reservoir” of NH3 species (adsorbed onto W and Ti sites) is present and available for the reaction upon desorption followed by readsorption at reactive V sites.

ra (NH3) ≈ rNO >> rd(NH3) => ⇒ assumption of equilibrated adsorption incorrect

SCR Rate equation

0 500 1000 1500 2000 2500

0

200

400

600

800

INNH3

N2

NO

NH3

Time (s)

Con

cent

ratio

n (p

pm)

−−−°=*

* 3exp1expθ

θθ NH

NONO

NONO CRT

Ekr


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Lidia Castoldi

2000 3000 4000 5000 6000

0

200

400

600

800

1000

Exp NH3

Exp N2

Exp NO Calc NH

3

Calc N2

Calc NO

Con

cent

ratio

n, p

pm

β

θθ

θ

2OP

11

exp

⋅

−+

⋅⋅

−

=

°

LHK

CRT

Ek

rNO

NOoNO

NO

Step changes of the NH3 inlet concentration in He + NO + O2 (1%) + H2O (1%) at 200°C

The conversion of NO goesthrough a maximum(reaction rate lower inpresence of excess NH3)

This has been described bya dual site LHHW mechanismthat assumes competitionbetween NO and NH3 foradsorption onto the catalyst


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Lidia Castoldi

0 100 200 300 400 500

0.0

0.2

0.4

0.6

0.8

1.0 ETC

NO

x

Time (s)

Validato presso DC suCatalizzatore SCR full scale(25-43 L) e con gas discarico realiCommercializzato da DC per Heavy Duty Vehicles

D. Chatterjee et al., SAE technical paper 2005;D. Chatterjee et al., SAE technical paper 2006;E. Tronconi et al., Catal. Today, 2006


83

Lidia Castoldi

Tecnologia NSR: applicazioni per sorgenti mobili

84

Lidia Castoldi

“NO x storage-reduction” Catalytic Systems

Pt-Ba/γγγγ-Al2O3

noble metal

oxidation/reduction

alkaline – earth metal

storage

NOx abatement

N. Takahashi et al., Cat. Today, 27 (1996) 63

Rich conditions

Lean conditions Ba(NO2)2

Ba(NO3)2

NOx

Ba PtO

Ba(NO2)2

Ba(NO3)2

HC

N2

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Lidia Castoldi

NOx Storage-Reduction Catalysts or Lean NOx Traps: Pt-Ba/γγγγ-Al 2O3

S. Matsumoto, CATTECH, 4 , 2000, 102-109

“NO x storage-reduction” Catalytic Systems

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Lidia Castoldi

O2 ↔ 2 O*

BaO + O* + 2 NO ↔ Ba (NO2)2

Ba(NO2)2 + 2 O* ↔ Ba(NO3)2

NO + ½ O2 � NO2

BaO + 2 NO2 + O* ↔ Ba(NO3)2

BaO + 3 NO2 ↔ Ba(NO3)2 + NO

Ba(NO3)2 + 5H2 ↔ N2 + 5H2O + BaO Ba(NO3)2 + HC ↔ N2 + BaO (+H2O+ CO2)

� Adsorption of oxygen species associated with Pt sites.

� Nitrites are formed first and then are transformed into nitrates.

� NO is oxidized to NO2 and then NO2 is adsorbed to form nitrates.

� Nitrates are reduced to nitrogen.

“NO x storage-reduction” Catalytic Systems: fundamental chemistry

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Lidia Castoldi

Lean NO x Trap materials

The catalytic material adopted is basically alumina containing primarilybarium (Ba) and platinum (Pt), which are the key players in the storage and reduction of NOx.Among alkali and alkaline earth elements, Ba is the most effective element to store NOx in the LNT catalyst.

Other components include:�cerium oxide (CeO2) is used as tank of oxygen;� lanthanum oxide (La2O3) is used to stabilize the alumina support;� rhodium (Rh), and zirconium oxide (ZrO2), both of which are used to promote the formation of hydrogen which efficiently removes sulphates from the catalyst;� titanium oxide (TiO2), which suppresses the absorption of sulphate.

The alumina is coated on a ceramic support. The coating is made as an ultra-thin layer only about 100 µµµµm (0.1 mm) thick, and is very porous, resulting in a high surface-to-volume ratio. One gram of the catalyst provides more than 100 square meters of surface area.

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Lidia Castoldi

NO NO2

NO3-

NO

NO2-

Porous Supportas g-aluminarP= 100ÅVP = 0.82cm3/gby BET;dC= 70Åby XRD

Alkaline earth metalas bariumdC= 70Å as barium carbonate monocl.dC= 150Å as barium carbonate orthoromb.by XRD

Noble metalas platinum%Pt= 60%by chemisorption

Ba

Pt

Al2O3

Lean NO x Trap materials: Pt-Ba/ γγγγ-Al2O3

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Lidia Castoldi

Lean NO x Trap materials

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Lidia Castoldi

Ceramic monoliths present large pores and low surface area (0,3 m2/g). It is therefore necessary to deposit a carrier + active catalyst onto the channel walls.This catalytic layer is called washcoat

Lean NO x Trap materials: monolithic materials

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Lidia Castoldi

SubstratePrimer

Washcoat

Substrate : provides mechanicals and geometrical characteristics to the catalyst (ceramic or metallic).

Primer : favours the adhesion of the washcoat to the substrate (affinity with both substrate and washcoat).

Washcoat : provides high surface area to support active components (e.g. noble metals).


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Lidia Castoldi

The substrate provides geometric, physical and mechanical characteristics to the catalyst.

Desired properties : • Shaped in a structured form.• Resistant at the reaction temperature• Resistant to thermal shock• Low thermal expansion coefficient• Chemical inertia with respect to active washcoat


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Catalytic Muffler

Standard Cordierite Monoliths

Advanced ConceptMetallicMonoliths


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Ceramic Substrates : Cordierite (2MgO* 5SiO2*2Al2O3), Mullite(3Al2O3*SiO2), Alumina (α-Al2O3), Titania (TiO2), Carbon Silica (SiC).

High thermal shock resistance High mechanical strengthHigh melting point (T<1300°C)Good chemical and mechanical bonding of the washcoat

Sw = washcoat thickness

L = cell spacing

d=cordierite wall thickness


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Lidia Castoldi

The washcoat is a layer ofporous ceramic material(5% to 20% w/w ).

Desired properties:

• adhesion to the support

• uniformity in thickness

• high surface area and appropriate

pore distribution

• affinity with the supported

active elements

• thermal and chemical stability

under reaction conditions


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Lidia Castoldi

Desired properties :

• High Activity at Low temperature

• High thermal stability

• Low Vapour Pressure

• High resistance to poisoning

In the washcoat active elements are contained


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Basic layout of LNT catalytic systems

*Exhaust Gas Recirculation (EGR) introduces exhaust gas into the intake of the engine replacing some of the air. This has the effect of reducing NOx emissions by reducing the in-cylinder gas temperatures: NOx production is very temperature sensitive

*

by Ricardo Inc.

Lidia Castoldi

LNT performances

NOx storage behaviour of LNT catalyst at 673 K in engine bench evaluation and definition of NOx

storage amount. The air–fuel mixture feed was switched to a lean mixture (A/F=23.5) from a rich mixture (A/F=10) for 1 s. After 10 min, the air–fuel mixture was switched to a rich mixture for 1 s, and then to a lean mixture again.

S. Matsumoto, CATTECH, 4 , 2000, 102-109

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LNT performances

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Sulphur poisoning

Relationship between the efficiency of NOx

conversion and the amount of sulphur deposit on the Pt-Ba/Al2O3 catalyst after durability test

S. Matsumoto, CATTECH, 4, 2000, 102-109

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Lidia Castoldi

S poisoning mechanism: hypothesis

γ-Al 2O3

BaSO4

BaOPt

SO2 SO3 Lean phase

γ-Al 2O3

BaOPt

SO2

Rich phaseS S S

Formation of aluminumsulphate Al2(SO4)3 which covers the surface of γ-Al2O3 or plugs the micro pores of γ-Al2O3.

Formation of BaSO4 under lean conditions

Formation of Pt-sulphur compounds (sulphides) under rich conditions

Al 2(SO4)3 γ-Al 2O3

BaOPt

SO2 SO3

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Open problems

S resistance :� deactivation/regeneration � catalyst durability� new materials (TiO2-, Rh-, ZrO2-added catalyst)� new structure (the geometrical structure of the catalyst would also function to minimize the size of the sulfate particles and make them easier to be removed from the catalyst, i.e. square cells vs hexagonal cell)� reduction of sulphur in the fuel

Thermal stability (more stable support)

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Lidia Castoldi

Tecnologia NSR: la fase di adsorbimento

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storage :Transient Response Method

(TRM)

regeneration :

Temperature ProgrammedDesorption (TPD)

Techniques: FT-IR, Transient Response Method (TRM) @ 350°CMolecules: NO, NO2, NO+O2, NO2+O2

0 1 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0 5 0 0 0 6 0 0 0

0

2 0 0

4 0 0

6 0 0

8 0 0

1 0 0 0

3 0 0

3 5 0

4 0 0

4 5 0

5 0 0

5 5 0

6 0 0

conc

entr

atio

n, p

pm

T, °C

time, s

NO, NO2 (+O2)

temperature

GHSV=105 Ncc/gcat·h

Methods @POLIMI

Model catalysts : Pt-Ba/γ-Al2O3, Pt/γ-Al2O3 , Ba/γ-Al2O3 (Pt=1% w/w, Ba=16% w/w)

60-701000.82160Pt-Ba/γγγγ-Al 2O3

Pt dispersion(%)

Pore radius(Å)

Pore volume(cm3/g)

Surface area(m2/g)

Catalyst

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Lidia Castoldi

NO/O2 adsorption on Ba/Al 2O3 @ 350°C

NO

NO in

concentration, ppm

time, s

0

1000

500

0 500 1500 25001000

NO2

2000-500

Non-negligible adsorption of NOx (1.6*10-4 mol/gcat).

NOx storage initially occurs as nitrites (and nitrates).

2000 1800 1600 1400 1200 10000.0

0.2

0.4

Abs

orba

nce

Wavenumbers (cm-1)

ionic nitrates(1410, 1320, 1030 cm-1)

bridged nitrates(1545 cm-1)

20 min

15 min

2000 1800 1600 1400 1200 10000.0

0.2

0.4

Abs

orba

nce

Wavenumbers (cm-1)

ionic nitrites

(1330,1210 cm-1)

10 min

3 min5 min

1 min


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Lidia Castoldi

NO

NO in

concentration, ppm

time, s

0

1000

500

0 500 1500 25001000

NO2

2000-5002000 1800 1600 1400 1200 1000

0.0

0.2

0.4

Abs

orba

nce

Wavenumbers (cm-1)



20 min

15 min

NO/O2 adsorption on Ba/Al 2O3 @ 350°C

Non-negligible adsorption of NOx (1.6*10-4 mol/gcat).

NOx storage initially occurs as nitrites (and nitrates).

Nitrites are transformed into nitrates ad-species.

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Lidia Castoldi

NO

NO2 in

concentration, ppm

time, s

0

1000

500

0 2000 4000 500030001000

NO2

NOx

Extensive NOx adsorption (8.9*10-4 mol/gcat), no NOx dead time.

NO2 adsorption with NO release, detection of nitrates

Disproportionation route:

3 NO3 NO22 + BaO + BaO →→→→→→→→ Ba(NOBa(NO33))22 + NO + NO ↑↑↑↑↑↑↑↑

2 NO2 NO22 + BaO → Ba(NO+ BaO → Ba(NO33--NONO22))NONO22 + Ba(NO+ Ba(NO33--NONO22) → Ba(NO) → Ba(NO33))22 + NO+ NO

time, s

0

0.3

0 500 1000 1500

0.1

2000-500

0.2

0.4NO evolved/NO2 consumed

1800 1600 1400 1200 1000

0.0

0.4

0.8

1.2

Abs

orba

nce

Wavenumbers(cm-1)

3 min

5 min10 min

1 min

bridgingnitrates(1545 cm-1)

ionic nitrates(1410, 1320 cm-1)

1800 1600 1400 1200 1000

0.0

0.4

0.8

1.2

Abs

orba

nce

Wavenumbers(cm-1)

1800 1600 1400 1200 1000

0.0

0.4

0.8

1.2

Abs

orba

nce

Wavenumbers(cm-1)

3 min

5 min10 min

1 min





NO2 adsorption on Ba/Al 2O3 @ 350°C

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Lidia Castoldi

NO2 adsorption via the NO2 disproportionation route.

No NOx dead time.

NO2 decomposition to NO and O2.

Detection of only nitrates ad-species.

NO

NO2 in

time, s

0 2000 4000 600030001000

NO2

NOx

O2

5000

NO2 adsorption on Pt-Ba/Al 2O3 @ 350°C

concentration, ppm

0

1000

500

1800 1600 1400 1200 10000.0

0.2

0.4

0.6

Abs

orba

nce

Wavenumbers (cm-1)

10 sec

10 min

5 min

3 min

1 min

bridging nitrates(1545 cm-1)


1800 1600 1400 1200 10000.0

0.2

0.4

0.6

Abs

orba

nce

Wavenumbers (cm-1)

10 sec

10 min

5 min

3 min

1 min





109

Lidia Castoldi

Presence of dead time for NO and NO2 breakthrough.

Oxidation of NO to NO2.

NOx storage occurs initially as nitrites (and nitrates).

Nitrites are readily transformed into nitrates.

NO

NO in

concentration, ppm

time, s

NO2

NOx

2000 1800 1600 1400 1200 10000.0

0.2

0.4

0.6

0.8

1.0

1.2


bridged nitrates(1545, 1030 cm-1)

10 min

5 min

3 min

1 min

Wavenumbers (cm-1)

1 min

ionic nitrites(1330,1210 cm-1)

NO/O2 adsorption on Pt-Ba/Al 2O3 @ 350°C

0 500 1000 1500 2000 2500 3000

0

200

400

600

800

1000

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Lidia Castoldi

Nova et al., Top.Catal., 30/31 (2004) 181Nova et al., J.Catal., 222 (2004) 377

NOx adsorption mechanism on Pt-Ba/Al 2O3

NO + O2

NO2

Pt

Pt BaO

NONO33--

Al 2O3 Nitrate speciesNitrate species

Pt BaO

NONO22--

Al 2O3 Nitrite speciesNitrite speciesPt + Ba

NO

O2NO2Ba

Literature agreement on:• NO2 disproportionation reaction• storage of nitrite & nitrate ad-species

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Lidia Castoldi

Tecnologia NSR: la fase di riduzione

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Lidia Castoldi

H2/H2O-TRM at different T after NO/O2 adsorption @ 350°C

� N2 selectivity increases with T at the expenses of NH3

NH3 is likely an intermediate in N2 formation

0

500

1000

1500

2000H

2 in

150°C

NH3

H2

200°C

NH3

N2

0 300 600 900

0

500

1000

1500

2000

Time (s)

H2

N2

350°C

0

500

1000

1500

2000

H2

N2

NH3

Con

cent

ratio

n (p

pm)

The reduction of NO x stored on PtBa/Al 2O3

1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 00

2 0

4 0

6 0

8 0

1 0 0

5 0

6 0

7 0

8 0

9 0

1 0 0

N 2 s e le c t iv i ty , %

T e m p e ra tu re [°C ]

N O x re m o v a l e ff ic ie n c y , %

The reduction of stored NOx is complete only at high TBoth N2 and ammonia are observed with N2 preceding NH3 Lietti et al., J.Catal., 257 (2008)

270

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Lidia Castoldi

Ba(NOBa(NO33))22 + 8H+ 8H22 →→ BaO + 2NHBaO + 2NH33 + 5H+ 5H22OO

@ lower T: nitrates are selectively reduced by H 2 to NH 3 :

@ increasing T: NH 3 formation ↓↓↓↓ & N2 formation ↑↑↑↑

Ba(NOBa(NO33))22 + 5H+ 5H22 →→ BaO + NBaO + N22 + 5H+ 5H22OO

@ higher T: nitrates are mostly reduced to N 2, but NH 3 is detected


BUT: nitrates are also reduced by NH 3 to N 2

3Ba(NO3)2 + 10NH3 → 3BaO + 8N2 + 15H2O

Is ammonia an intermediate in N2 formation?

The reduction of NO x stored on PtBa/Al 2O3

114

Lidia Castoldi

100 200 300 400

0

200

400

600

800

0

500

1000

1500

2000

H2

N2

NH3

NO

Con

cent

ratio

n, p

pm

Temperature °C

100 200 300 400

0

400

800

1200

H2

N2

NH3

Con

cent

ratio

n, p

pm

Temperature °C

NH3 reduces stored nitrates selectively to N2, but its reactivity is lower than that of H2

NH3/H2O

H2/H2O

The reduction of NO x stored on PtBa/Al 2O3: H2- & NH3-TPRS experiments

115

Lidia Castoldi

Nitrate reduction with H 2 to nitrogen occurs via a two steps in series proces s:

Step 1) Fast reaction of H2 with nitrates to form NH3:

Step 2) Slower reaction of NH3 with nitrates to form N2:

Step 1 + 2 account for the overall stoichiometry of N 2 formation:


3Ba(NO3Ba(NO33))22 + 10NH+ 10NH33 →→ 3BaO + 8N3BaO + 8N22 + 15H+ 15H22OO

Ba(NOBa(NO33))22 + 5 H+ 5 H22 →→ BaO + NBaO + N22 + 5 H+ 5 H22OO

Nitrates reduction by H 2

Lietti et al., J.Catal., 257 (2008) 270

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Lidia Castoldi

Similar amounts of N2 are obtained by reducing of nitrates with H2 or NH3

150 200 250 300 3500,0

5,0x10-5

1,0x10-4

1,5x10-4

2,0x10-4

2,5x10-4

3,0x10-4

N2

[mol

/gca

t]N

2 formation

Temperature [°C]

reduction with H2

reduction with NH3

Reaction of NHReaction of NH 33 with nitrates with nitrates is rateis rate --determiningdetermining

Nitrates reduction by H 2 & NH3

Step 1) Fast reaction of H2 with nitrates to form NH3:

Step 2) Slower reaction of NH3 with nitrates to form N2 (RDS):


3Ba(NO3Ba(NO33))22 + 10NH+ 10NH33 →→ 3BaO + 8N3BaO + 8N22 + 15H+ 15H22OO

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Lidia Castoldi

Zone I: regenerated trap

Zone II: reaction of H2 with nitrates

Zone III: reaction of ammonia with nitrates

Zone IV: spent trap

0

100

200

300

400

160018002000

H2

N2

NH3

0

100

200

300

400

160018002000

N2

NH3

H2

Time (s)C

once

ntra

tion

(ppm

)

Low-T (150 °C)

High-T (300 °C)

Lietti et al., J.Catal., 257 (2008) 270

The H2 front model for the reduction of the stored NO x

118

Lidia Castoldi

Cumaranatunge et al., J.Catal, 246 (2007) 29

NH3 formation over LNTs

Pihl et al., SAE 2006-01-3441

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Lidia Castoldi

� Funzionamento in continuo

� Sfrutta le reazioni di riduzione selettiva ad N2 tra NOX e NH3

� Necessità di un accurato controllo nella strategia di alimentazione di NH3

� Necessità di avere a bordo Urea (precursore NH3)

DeNOx catalytic systems: SCR

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Lidia Castoldi

� Ossidazione NO/NO2� Accumulo NOX come nitriti/nitrati

� Riduzione dei nitriti/nitrati� Produzione di N2 e NH3

Funzionamento ciclico non stazionario

DeNOx catalytic systems: LNT

121

Lidia Castoldi

Meccanismo di riduzione:

Ba(NO3)2 + 8 H2 →→→→ 2 NH3 + BaO + 5 H2O

3 Ba(NO3)2 + 10 NH3 →→→→ 8 N2 + 3 BaO + 15 H2O

Possibilità di uso combinato e sinergico delle due tecniche

L.CumaranatungeL.CumaranatungeL.CumaranatungeL.Cumaranatunge etetetet al. J. al. J. al. J. al. J. CatalCatalCatalCatal 2007.2007.2007.2007.Lietti Lietti Lietti Lietti etetetet al., J. al., J. al., J. al., J. CatalCatalCatalCatal 2008200820082008

DeNOx catalytic systems: SCR + LNT

122

Lidia Castoldi

Combinati (Bluetec)

� Attualmente installato su autovetture

� Funzionamento ciclico

� Sfrutta l’ammoniaca di slip del letto LNT per la rimozione di NOX via SCR

� Emissione di N2 e H2O come “unici” prodotti finali


123

Lidia Castoldi

NH3 NH3 NH3NOx

NOX

Pt-Ba/ γγγγAl 2O3 LNT

Fe-ZSM-5 SCR

Fase Lean(I)

FLOW

NOx

NOX

N2


Fase Lean(II)

FLOW

NOx NOxNH3 NH3

Fe-ZSM-5 SCR

� Produzione di N 2


Fe-ZSM-5 SCR

Fase Rich(I)

FLOW


Fase Rich(II)

FLOW

NOxNH3

Fe-ZSM-5 SCR

NOx NOx

NH3H2

N2

NOx

H2

NH3

� Slip di NH 3 contenuto


124

Lidia Castoldi

Tecnologia DPF: Diesel Particulate Filter

125

Lidia Castoldi

Diesel Particulate Matter (PM) or soot

126

Lidia Castoldi

Diesel Particulate Filter (DPF)

Wall-flow filters: are made of ceramic monolith and are based on a shallow-bed filtration mechanism;

PSA system: employs a SiC wall-flow monolith, a catalytic pre-oxidiser and Ce-fuel additive;

Continuously regenerating DPF (CRT): employs an oxidation catalyst upstream to convert exhaust NO to NO2 and the NO2 is the primary oxidant for the stored PM.

127

Lidia Castoldi

Wall-flow trap: ceramic monolith

Different types of diesel particulate filters have been developed; the most efficient remove more than 99 % by number of the exhaust-gas particulates

The channels are blocked at alternative ends. To pass through the monolith the exhaust gas is forced to flow through the channel walls, which retain the contained particulate matter in the form of soot and allow gaseous components to exit.

128

Lidia Castoldi

PSA (Peugeot-Citroën Société d’Automobiles) system

129

Lidia Castoldi

Abatement efficiencies:

Particulate:90%

CO: 90%

HC: 90%

NOx: 3%

Continuously regenerating Trap System(CRT by Johnson Matthey)

NO →→→→ NO2Oxydising catalyst CO →→→→ CO2

HC →→→→ CO2 and H 2O

Non-catalytic

Wall-flow trap

NO2 + C →→→→ NO + CO2

130

Lidia Castoldi

CRT working principle

131

Lidia Castoldi

Tecnologia DPNR: Diesel Particulate NOx Removal

132

Lidia Castoldi

Reduce PM and NOx simultaneously and continuously

PM is oxidized by active oxygen released in the NOx storage process and by excess oxygen in exhaust gas, or by active oxygen released in the process of reducing the stored NOx

Conversion efficiency of greater-than-80% in both PM and NOx in the initial stage of operation

Requires fuel with low sulfur content to maintain a high conversion efficiency for a long duration

Diesel Particulate NO x Removal (DPNR) features

133

Lidia Castoldi

D-CAT Concept For Clean Diesel Technology

Clean power diesel engines produces levels of NOx and PM emissions that are respectively around 50% and 80% below Euro-4 standards.

The Clean Power engine uses Toyota’s D-CAT (Diesel Clean Advanced Technology): its heart is the DPNR (Diesel Particulate NOx

Reduction system)

134

Lidia Castoldi

Diesel Particulate NO x Removal (DPNR) concept

�A catalytic wall-flow filter coated with a NSR catalyst is used to accomplish the simultaneous removal of soot and NOx

K. Nakatani et al., SAE paper 2002-01-0957

Enlarged view of exhaust gas flowing substrate wall

NOx storage reduction catalyst

Fine porous ceramic structure

NOx storage reduction catalyst

Exhaust gas flow

Fine porous ceramic structure

Exhaust gas

135

Lidia Castoldi

� Investigations on the De-NOx and De-soot reactivity of DPNR catalysts are still scarce

K. Nakatani et al., SAE Paper SP-1674, 2002-01-0957

Diesel Particulate NO x Removal (DPNR) concept

136

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Installazione del sistema DPNR

137

Lidia Castoldi

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