Zero pollution of automobiles via emissions control by ...Ta_Jen/Zero pollution of... · reductant supply, NSR storage capacity limit …) to treat an exhaust with high NO x concentration.

Zero pollution of automobiles via emissions control

by electro-catalytic honeycomb

presented at Global Congress of Catalysis (GCC-2014) on 2014923 by

Ta-Jen Huang Professor (tjhuangchenthuedutw)

Department of Chemical Engineering National Tsing Hua University

Hsinchu TAIWAN 1

How to achieve zero pollution of automobiles

bull Highest possible combustion temperature harr highest possible fuel efficiency

rarr Complete combustion of all precursors of combustible pollutants rarr Gasoline direct-injection compression ignition (GDCI) engine fueled with light gasoline (light un-branched open-chain hydrocarbons)

rarr Zero pollution of CO amp HCs no PM The remaining issue is high NOx control

bull Removal of high-concentration amp near-zero NOx rarr Removing very high NOx to near-zero bull NOx emission control at engine cold-start rarr No delay on NOx control bull No consumption of reducing agent on NOx control rarr No remain of the reducing agent eg NH3 to cause secondary pollution All these done via electro-catalytic honeycomb (ECH) 2

NOX-soot trade-off during EGR of diesel engine

[A Maiboom et al Energy 33 (2008) 22]

3

Old tech

New tech

Current diesel engines have sacrificed the fuel efficiency to

lower NOx concentration by exhaust gas recirculation

(EGR)

Diesel exhaust causes cancer (WHO 2012612) -- Diesel engine exhaust fumes are a definite cause of lung cancer soot NOx

rarr What should we do Not driving diesel automobiles rarr Deleting EGR

needing diesel particulate filter larr

soot particulate matter (PM)

However those very small particulates which can go through the filter can penetrate deep into the lung [American Lung AssociationCalif]

rarr Increasing fuel efficiency at least by

burning more soot precursor in the engine

rarr reduce soot emission

rarr Deleting EGR saving both health amp fuel

World Health Organization

This presentation

eg SCR (Selective Catalytic Reduction)

Deleting EGR

Deleting EGR darr

rarrIncrease combustion temperature in engine rarr Increased NOx ()

preferred

Electro-catalytic honeycomb (ECH) enables saving health amp fuel

4

The most important lean-burn combustion processes are that of gasoline engine being converted from stoichiometric-burn to lean-burn amp that of diesel engine deleting EGR 30 autorsquos fuel saving larr deNOx by Electro-Catalytic Honeycomb (ECH)

ECH looked the same as TWC (Three-way Catalytic) converter

-- for stoichiometric-burn engine

ECH-deNOx reactor for lean-burn engine

This presentation

ECH-deNOx is simpler than TWC (stoichiometric operation) since ECH-deNOx (best for CI engine) does not need control system for engine operation [CI compression ignition]

Engine exhaust pipe

Electro-catalytic honeycomb (ECH)-deNOx mdash a real-world device for promoted NOx decomposition (PND)

bull Lower emission of greenhouse gases (GHG) needs higher fuel efficiency ie lower fuel (energy) consumption rarr cost down

bull Currently fuel efficiency is inhibited by difficulties in deNOx technologies (SCR reductant supply NSR storage capacity limithellip)

to treat an exhaust with high NOx concentration bull TWC can not treat lean-burn exhaust

bull Higher combustion temperature leads to higher fuel efficiency but also higher NOx concentration in the exhaust This is inevitable since the following reactions occur during combustion using air (N2 + O2 )

Initiation O2 rarr 2O (thermal cracking mdash providing O for combustion) Chain reaction O + N2 rarr NO + N N + O2 rarr NO + O Termination NO + O rarr NO2 bull This deNOx difficulty has been resolved by PND with

ECH NOx decomposition for automotive emission control 5

The ECH works on Promoted NOx Decomposition (PND) ie emf-promoted direct NOx decomposition

NOx (NO+NO2) rarr N2+O2

Electro-Catalytic Honeycomb (ECH) for lean NOx emission control

Typical deNOx characteristics of PND are bull No consumption of reducing agent or else

[purely decomposition] Care free bull Higher O2 concentration results in higher

deNOx rate [due to increased promotion with emf] Simultaneous oxidation of hydrocarbons CO amp Particulate Matter (PM) feasible bull Higher NOx concentration can result in higher

deNOx rate [obeying reaction kinetics] Highly fuel-efficient engines bull Relatively constant deNOx rate at very low

NOx concentration [due to a specific reaction mechanism] Zero NOx emission can be achieved bull No temperature window amp effective deNOx

from ambient temperature no treatment delay amp deNOx at cold weather

bull Presence of H2O amp CO2 beneficial amp SO2 OK no N2O formation

bull No use of precious metal Economical These characteristics are all based on the inventorrsquos published results

ECH [EU patent granted amp other patent applications filed]

10 Electro-catalytic honeycomb (ECH) 11 Anode forming ECH structure 111 amp 112 outer amp inner surface of the anode structure 12 Exhaust flow channel 13 Shell covering the outer surface of the anode structure 20 Electrolyte layer coated on the inner surface of the anode structure 30 Cathode layer facing the exhaust flow channel for exhaust treatment

[as automotive catalytic converter]

promoted NOx decomposition

electrochemical cell (generating emf)

electrochemical cell (generating emf)

promoted NOx decomposition

Electromotive force (emf) is generated when there is a

difference in oxidationreduction potentials of AnodeCathode and increases with potential difference

[electrochemical double-cell] EDC

The EDC consists of two electrochemical cells

7

These are typical characteristic curves for promoted NOx Decomposition

for lean deNOx of combustion processes

Secondary air is beneficial

The ECH works on promoted NOx decomposition (PND)

no treatment delay amp no temperature window

Very high NOx concentration preferred

diesel exhaust diesel exhaust diesel exhaust

[TJ Huang et al Chem Eng J 203 (2012) 193]

[TJ Huang et al Appl Catal B 110 (2011) 164] [TJ Huang et al Appl Catal A 445ndash446 (2012) 153]

Temperature (C)

100 150 200de

NO

x ra

te ( micro

mol

e N

Ox m

in

-1 c

m

-2)

4

5

6

7

deN

Ox

rate

( microm

ole

NO

x min

-1 c

m

-2)

01

02

031800 ppm NOx360 ppm NOx

Publications supporting lean deNOx by promoted NOx decomposition (PND) underlined is the inventor of the ECH bull Ta-Jen Huang CL Chou Electrochem Comm 11 (2009) 477ndash480 bull Ta-Jen Huang CL Chou J Power Sources 193 (2009) 580ndash584 bull Ta-Jen Huang CL Chou J Electrochemical Society 157 (2010) P28ndashP34 bull Ta-Jen Huang CL Chou Chem Eng J 160 (2010) 79ndash84 bull Ta-Jen Huang CL Chou Chem Eng J 162 (2010) 515ndash520 bull Ta-Jen Huang IC Hsiao Chem Eng J 165 (2010) 234ndash239 bull Ta-Jen Huang CY Wu YH Lin Environmental Science Technology 45 (2011) 5683ndash5688 bull Ta-Jen Huang CY Wu and CC Wu Chem Eng J 168 (2011) 672ndash677 bull Ta-Jen Huang CY Wu CC Wu Electrochem Comm 13 (2011) 755ndash758 bull Ta-Jen Huang CY Wu CC Wu Chem Eng J 172 (2011) 665ndash670 bull Ta-Jen Huang CY Wu SH Hsu CC Wu Energy Environmental Science 4 (2011) 4061ndash4067 bull Ta-Jen Huang CH Wang Chem Eng J 173 (2011) 530ndash535 bull Ta-Jen Huang CY Wu SH Hsu CC Wu Appl Catal B Environmental 110 (2011) 164ndash170 bull Ta-Jen Huang CY Wu Chem Eng J 178 (2011) 225ndash231 bull Ta-Jen Huang CH Wang J Electrochemical Society 158 (2011) B1515ndashB1522 bull Ta-Jen Huang SH Hsu CY Wu Environmental Science Technology 46 (2012) 2324ndash2329 bull Ta-Jen Huang CY Wu DY Chiang CC Yu Chem Eng J 203 (2012) 193ndash200 bull Ta-Jen Huang CY Wu DY Chiang CC Yu Appl Catal A Gen 445ndash446 (2012) 153ndash158

8

Power generation with NOx substituting O2

-- NOx decomposition in rich oxygen

-- promoted by both voltage amp oxygen-ion migration

NOx decomposition at (promoted by) open-circuit voltage (electromotive force emf)

Lean-burn combustion processes The feasibility of electro-catalytic honeycomb for lean NOx emission control has been verified by using ECHs (400 cpsi [30 cm2cm3] honeycombs with 430 cm2 amp 627 cm2 treating area) for NOx emission control of a gasoline engine (50 cc single cylinder 4-cycle) operating at lean-burn amp with adding oxygen and NOx into the engine exhaust

9

ECH-deNOx reactor Engine exhaust deNOx

Engine exhaust pipe

deNOx characteristics of emf-promoted decomposition of NOx This presenting new tech

bull Very high NOx concentration preferred Highly fuel-efficient engines amp ECH-deNOx does not need any control on engine operation no control system is needed

bull No consumption of reductant or anything else Care free bull Effective at high O2 concentration the higher the better

Simultaneous oxidation of hydrocarbons CO amp PM feasible

bull No temperature window amp effective deNOx from ambient temp no treatment delay amp deNOx at cold weather

bull ECH similar size to engine (shown next) Very compact size for passenger cars

bull No use of precious metal Economical bull H2O amp CO2 beneficial amp SO2 OK no N2O formation bull Zero pollution (near-zero NOx emission) 10

A rough estimate of honeycomb size for highly efficient passenger car

11

rarr The size of ECH can be similar to that of engine rarr Free very much space when replacing current deNOx system for diesel vehicles

For a passenger car with 2000 cc (cm3) gasoline engine operating at optimum lean-burn the NOx concentration can become 4000 ppm [L Guzzella CH Onder Introduction to

modeling and control of internal combustion engine systems Springer-Verlag Berlin (2010)] For 95 NOx removal the required deNOx rate is 254middot105 μmole NOx min-1 average This requires a 400 cpsi (30 cm2 treating areacm3) ECH honeycomb of 2120 cm3 considering an averaged deNOx rate of 4 μmole NOx min-1 cm-2 (a rough estimate from data shown below)

Shortages in current automotive deNOx technologies

bull Three-way catalytic (TWC) converter (honeycomb) Engine operation must be adjusted to accommodate the exhaust treatment The usage of precious metals Stoichiometric burn mdash low fuel efficiency Treatment delay -- the catalyst is not effective at ambient temperature and thus a heating period is required [for all current deNOx via reduction or storage]

bull Exhaust Gas Recirculation (EGR) To result in low NOx concentration in exhaust at the expense of fuel efficiency

bull Selective Catalytic Reduction (SCR) The consumption of reducing agents eg ammonia in urea-based SCR (costly amp inconvenient refilling) The formation of N2O a strong greenhouse gas

bull NOx Storage and Reduction (NSR) mdash lean-NOx trap The consumption of fuel for NOx treatment Limited storage capacity

bull Electrochemical NOx Reduction with applied voltage (electrical current)

The consumption of electricity with low current efficiency 12

Electrochemical cellLSC ndashGDC cathode CatalystLSC ndashGDC (La06Sr04CoO3 ndashCe09Gd01O195) 14 O2 10 H2O 10 CO2 600oC 13

Principle and proof for emf-promoted decomposition of NO rarr N2 + O2

1000 2000 3000 4000 5000 600005

10152025

3000

3500

4000

4500

5000

cell at OCVcatalyst

N2 f

orm

atio

n ra

te ( microm

ol m

in-1

g-1 )

Inlet NO concentration ( ppm )

OCV open-circuit voltage (solid oxide fuel cell operation without consuming anode fuel

ie reductant) ~ electromotive force (emf )

Over the catalyst in a conventional reactor the formed N species from direct NO decomposition can be easily associated to form N2 however the formed O species is strongly adsorbed and facile desorption of the O species as O2 into the gas phase is very important [Y Teraoka et al J Chem Soc Faraday Trans 94 (1998) 1887]

Electrochemical cell can be solid oxide fuel cell (SOFC) --1st stage of this tech electrochemical-catalytic cell (ECC) electro-catalytic tube (ECT) and EDC in electro-catalytic honeycomb (ECH)

The deNOx rate via emf-promoted decomposition is two orders higher than that over conventional catalyst via direct decomposition

Inlet NOx concentration (ppm)0 500 1000 1500 2000 2500

deN

Ox

rate

( microm

ole

NO

x min

-1 g

-1)

0

500

1000

1500

2000

deN

Ox

rate

( microm

ole

NO

x min

-1 g

-1)

0

4

8

12

16ECHCatalyst

14

Facile desorption of oxygen rarr (weakened chemisorptive bond

strength of the O species) darr

This can only be attributed to the generation of an electromotive force (emf) in the electrochemical cell

H2-temperature-programmed reduction (TPR)

La054Sr036Ag01Co095Cu005O3ndashCe09Gd01O195

(LSACCndashGDC)

Profiles of electro-catalytic tube (cell) with LSACCndashGDC cathode and the conventional reactor with

LSACCndashGDC catalyst powder

O2-temperature-programmed desorption

TPR peak 84 oC larr 187 oC diesel exhaust

Dramatically increased amount of O2 desorbed wcell

Ambient-temperature peak wcell

[TJ Huang et al Appl Catal A 445ndash446 (2012) 153ndash158]

Lean deNOx by emf-promoted decomposition of NOx

15

2NO + [ ][ ] rarr N－[O][O]－N 2nd order N－[O][O]－N rarr N2 + [O][O] [O][O] rarr O2 + [ ][ ]

NO rarr N + O ∆H298 = -216 Kcalmole (exothermic) NO2 rarr N + O2 ∆H298 = -8 Kcalmole

The presence of a voltage weakens the chemisorptive bond strength of the O species [CG Vayenas S Bebelis Catal Today 51 (1999) 581] facile desorption of oxygen

for emf-promoted decomposition of NOx

at high enough NO concentration

2NO rarr N2 + O2

rN2 = k [NO]2

Higher NO concentration is highly preferred (according to kinetic law)

La08Sr02Mn095Cu005O3 (LSMC) cell at 450 oC and 100 ml min-1

16

NOx to N2 rate can be three orders larger than those over conventional oxide catalysts for NO decomposition

eg around 1 micromol N2middotmin-1middotg-1 at 500 oC with 4 NO [T Yamashita A Vannice J Catal 163 (1996) 158]

[TJ Huang et al Appl Catal B 110 (2011) 164]

ECC-deNOx--Effect of NOx concentration Two characteristics

increasing NO conversion bullbullbull with increasing NOx

concentration in the high NOx

concentration region (increasing deNOx rate ndash

according to kinetic law) higher fuel efficiency

amp increasing NO conversion bullbullbull with decreasing NOx

concentration in the low NOx concentration

region (relatively constant deNOx rate) zero NOx emission

relatively constant rate

Increasing deNOx rate

ECC-deNOx-- Effect of O2 concentration

17

LSMCu01 cells with inlet 2536 ppm NOx 450 oC with or without HCs (propylene and propane 318 ppm C3H6 and 93 ppm C3H8)

LSCC cell with inlet 2814 ppm NOx

10 H2O 10 CO2 03ndash14 O2 25 ppm SO2 150 ml min-1 [TJ Huang et al Energy Environ Sci 4 (2011) 4061 amp Appl Catal B 110 (2011) 164]

Hydrocarbons (C3H6) can be completely converted

~ Nernst equation Electromotive force (emf )

emf = [(RT)(4F)]middotln[(pO2Cathode)(pO2Anode)] reducing in anode

NiOndashYSZ NindashYSZ

emf-promoted decomposition of NOx

O2 content in cathode gas

Hydrocarbons (HCs) CO andor particulate matter (PM) in the exhaust can be treated simultaneously

The application fields of ECH Schematics of ECH Light-Duty Vehicles and Trucks bull Gasoline passenger cars amp Motorcycles bull Diesel passenger cars (ECH-deNOx) bull Pickup trucks

10 ECH 11 anode forming the structure of the ECH 111 and 112 outer and inner surface of the anode structure respectively 12 exhaust flow channel 13 shell covering the outer surface 111 20 electrolyte layer coated on the inner surface 112 30 cathode layer facing the exhaust

flow channel for exhaust treatment (EU patent)

Heavy-Duty Highway Engines and Vehicles bull Compression-ignition (CI) engines [GDCI] bull Urban buses bull Trucks (ECH-deNOx) bull Long distance buses bull Recreational vehicles bull Long haul trucks bull Spark-ignition (SI) engines rarr Lean burn Nonroad Engines and Vehicles bull Aircraft bull CI engines (underground mining sea oil platformhellip) bull Locomotives (ECH-deSOx amp deNOx) bull Marine CI engines bull Recreational engines and vehicles Stationary sources bull Power plant boilers (burner) Gas turbines bull Fertilizer plants Cement plants bull Large boilers (ECH-deSOx amp deNOx) bull Medium boilers (in Hospitals Care centershellip) bull Small boilers (Household boilers)

Other Combustion exhausts (ECH-deSOx amp deNOx)

The fields for applications of ECH

EDC

Electrochemical double-cell (EDC)

Electro-catalytic honeycomb (ECH)

EDC for testing

Sealing two electrochemical

cells (disks)

The anode side should be enclosed completely

Concluding Remarks

19

bull Lean deNOx by promoted NOx decomposition (PND) no consumption of reductant (no NH3 slip) or other resource

bull Higher O2 concentration preferred for deNOx simultaneous oxidation of hydrocarbons (HCs) CO amp Particulate Matter (PM) feasible bull Very high NOx concentration preferred for deNOx very high temperature in engine allow deleting EGR

minimize HCs CO amp PM formation in engine bull Relatively constant deNOx rate at very low NOx concentration near-zero NOx emission can be achieved bull No temperature window amp effective deNOx from ambient

temperature no treatment delay

Thus especially with GDCI (light Gasoline Direct-injection Compression Ignition) ECH-deNOx can result in

zero pollution of automobiles to help Creating Healthy Livable Cities