Catalyst Handbook - jmdpf. · PDF fileCatalyst Handbook The right chemistry for Tier 4...

Catalyst HandbookThe right chemistry for Tier 4

CAT_Booklet_FINAL.QXD 14/5/07 15:29 Page 2

© Johnson Matthey plc 2007

Catalytic exhaust aftertreatment is one of the keytechnologies that will enable engines to meet theforthcoming Tier 4 and equivalent standards.The introduction of a new class of component is always challenging, the more so when its function

and control is very different to existing engine systems.

The Mark 1 Volkwagen Golflaunched in the USA in 1974.It was one of the first massproduced cars to be fitted with an autocatalyst.

engine componentA new type of

but not to usCatalysts have been used as a standardcomponent on cars for over 30 years andJohnson Matthey supplied the world’s firstproduction batch in May 1974.Since then, we have suppliedmore than 500 millionautocatalysts, around onethird of all the catalystsever fitted to cars.

New to you,


The timetable for Tier 4 is tight, and the cost of non-compliance is very high. The purposeof this booklet is to describe the catalysttechnologies available and how JohnsonMatthey (JM) can work with you to achieve the required emissions reductions whilemaintaining, and in some cases improving,the other features of diesel engines that are valued by your customers.

con

ten

ts

01 Introduction

03 Catalyst Technologies

09 JM’s Capabilities

17 Tier 4 Regulations

19 About Johnson Matthey


01 © Johnson Matthey plc 2007

Diesel cars were first fitted withcatalysts in the early 1990s, since when tighter regulations andincreasing customer demands havedriven the development of engine andaftertreatment technologies together.

Johnson Matthey catalysts andtechnologies have been inside most of the particulate filter systemsretrofitted to heavy diesel enginesaround the world. JM invented theCRT® diesel particulate filter (DPF)system and more than 100,000 havebeen sold for retrofit applications.We are building on this success withthe introduction of the retrofit SCRT® (CRT® + selective catalytic reduction(SCR)) system for integrated control of all regulated diesel pollutants.

Since 2005, tightening emissionsregulations for truck and bus engines in Japan, Europe and the USA have ledto the introduction of particulate filters,SCR systems and NOx adsorbers on newheavy diesel engines. Johnson Mattheyhas developed leading technology tomeet the requirements in all markets.These types of catalysts are all in seriesproduction at JM.

From on-road to non-roadLeaders in Diesel Catalyst Technology


02© Johnson Matthey plc 2007

Non-road machines represent a verydifferent challenge to on-road vehicles.Indeed, it would be better to say thatNRMM represents many thousands of different applications challenges.

Johnson Matthey has been supplyingand applying retrofit aftertreatmentsystems to non-road machines for more than 15 years. Therefore, we have experience of the variety ofoperating requirements, engine dutycycles and packaging constraints foundin non-road machines. We know thedifferences between a tractor and atracked excavator. And we know theregulations. We are very well placed to understand the requirements oncatalytic systems for Tier 4 compliance.

From on-road to non-road

The non-roadApplications Challenge



An emission control catalyst is usually a catalytic coating applied to a ceramic or metallic substrate.The catalyst has open channels and the gases react as they pass through.Some catalysts are designed to be able to store reagents (e.g. oxygen,ammonia) to enhance performance or even to act as a chemical trap,as in the case of NOx adsorbers.

A particulate filter is a physical trap.The most common type is a ceramicmonolith like a catalyst substrate, butwith channels closed at alternate endsso that the gases must pass throughthe channel walls, leaving the sootbehind. These filters are nearly 100%efficient for solid particles. Partialfilters, designed for a lower efficiency,are also available. A DPF does not alwayscontain a catalyst, but catalysts areused to burn the accumulated particulate.

Catalyst: a substance which when present in small amountsincreases the rate of a chemical reaction or process but which is chemically unchanged by the reaction.

Types of catalysttechnology


When designing a catalyst, we make it active to give highconversions from smaller catalysts and to make the bestuse of precious metal.

We make it selective to ensure that it is active for thedesired reactions and does not produce undesirable by-products.

And we make it durable to meet useful life requirementsand to minimise the durability factors that must be applied to new systems. Designing durability requires an understanding of how the catalyst will be used in itsapplication and the exhaust conditions that it will seethroughout its life. It also requires knowledge of thedeactivation mechanisms, both chemical and physical,of each type of catalyst.

? 04© Johnson Matthey plc 2007

What are the properties ofa good catalyst


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Particulate filters are used to trapParticulate Matter (PM). Catalysts are neededto burn the PM collected in the trap, maintainingthe performance of the system. There are two waysthat catalysts can be used to keep DPFs clean, and theseare often used together.

Nitrogen dioxide (NO2) and oxygen (O2) can both be used tocombust the soot trapped in a filter. NO2 has the advantage that it reacts with soot at the temperatures found in diesel exhaust.The O2 reaction requires higher temperatures, but is much faster.

PM Control


NO2 reacts with soot trapped in a filter, making NO and CO2.This reaction can occur from 200°C, so the temperatures found in diesel exhaust streams are sufficient and no additional energy is required. Some of the NOX emitted by an engine is NO2 and more can be made by an oxidation catalyst designed to oxidise NO to NO2.This system – an oxidation catalyst to make NO2 followed by aparticulate filter which is regenerated by the NO2 – is the CRT® system, a Johnson Matthey invention.

Using the CRT® effect to regenerate a filter has two great advantages:it is continuous (helping to maintain a low and even exhaust backpressure) and it requires no additional energy.

Usi

ng NO2 to regenerate

a particulate filter


Usi

ng O2 to regenerate

a particulate filterParticulate matter collected in a filter can be oxidised very quickly using the oxygen (O2) in the exhaust gases. This reaction requires higher temperatures (>550°C) than are reliably found in most diesel engine applications, so some mechanism is required to raise thetemperature of the exhaust periodically.

An oxidation catalyst placed before the filter is a very efficient way ofdoing this. When the filter needs regenerating, the hydrocarbon contentof the exhaust stream is increased. The catalyst burns the hydrocarbon,producing the heat required. The catalyst can also be designed to makeNO2 during normal operation to provide additional regeneration.The hydrocarbon enrichment can be achieved in-cylinder using electronicfuel systems, or by injecting fuel directly into the exhaust system.



An SCR system reduces NOx to nitrogen (N2) and is capable of more than 90% conversion, depending on conditions. To achieve this reactionin normal, lean (i.e. high oxygen, low hydrocarbon) diesel exhaust,a chemical reductant is needed. In most systems, ammonia (NH3) is used,and this is delivered as an aqueous solution of urea (“AdBlue” in Europe).The urea decomposes in the exhaust stream to form ammonia, whichreacts with the NOx to make nitrogen and water.

An SCR system requires a means of storing the urea and injecting theamount required to reduce the NOx emitted by the engine. Carefulcontrol is needed for transient cycles. The SCR catalysts usually have anoxidation catalyst , often called a slip catalyst, at the end as a guard toensure that no ammonia is emitted.

Converting NOx from the engine to nitrogenrequires a chemical reduction. Diesel exhaust

is an oxidising, not a reducing, environment.There are two main strategies to achieve

NOx reduction.

catalyic reductionSelective

NOx Control


Rh

N2

Pt

NOx COCO + HC + H2

+ CO2

NOx Adsorber Catalyst - rich conditions

PtRh

NO2

CO2NO + 1/2 O2

NOx Adsorber Catalyst - lean conditions


NOx adsorber catalysts or NACs,also known as lean NOx traps (LNTs),operate in two modes. In normal dieselexhaust conditions, they adsorb theNOx from the exhaust gas, storingit chemically. In “rich” exhaustconditions, with little or no oxygen (O2)they release the stored NOx and react it with components of the rich exhaustgas - carbon monoxide (CO),hydrocarbons (HC) and hydrogen (H2) - to make nitrogen.

Like any trap, chemical or physical,NACs have a finite capacity so theengine or some auxiliary system mustcreate rich exhaust conditions atintervals to regenerate the catalyst and this reduces the stored NOx tonitrogen. NACs also store sulphur and this reduces their capacity to trapNOx, so periodic “desulphations”,requiring increased exhausttemperatures, are necessary.

NOx adsorber catalysts


and testingDevelopment

Each new Johnson Matthey catalystformulation is the product of fourdecades of development experienceand a fundamental understanding ofcatalyst properties. Research intonew types of catalysts and catalyticproperties is undertaken at JM’s ownresearch facilities. Teams around theworld develop new formulations tomeet the requirements of differentengines, regulations and applications.

Coatings are developed specificallyto exploit the properties of differentsubstrate types.

Test work starts in the laboratoryusing bottled gases to simulateexhaust gas with precise control of gas mix and temperature.Testing then moves to engines forperformance and durability testing.

Catalyst Technology




Johnson Matthey has its own test cells dedicated to diesel engine testing in Europe, the USA and Japan,many capable of transient operation.These cells are used to test and provecatalysts; for catalyst ageing and forcollaborative development programmesusing customer engines. Our facility inDetroit also performs contract testing(see www.jmtesting.com).

JM develops proprietary catalyst-specificaccelerated ageing procedures for its own and customer testing. These are based on catalyst deactivationmechanisms and are validated againstcatalyst aged in real world operation on vehicles and machines.Te

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JM works to develop newaftertreatment systems and makesthem available for new engines andretrofitting. This work covers not just the catalysts themselves, but theoperating principles of the wholesystem. An example of this is the CRT® (Continuously Regenerating Trap)particulate filter system. JohnsonMatthey developed its operatingprinciple in the late 1980s. It has been used in the majority of retrofitparticulate filter systems suppliedaround the world and has also beenemployed in many OEM applications.

JM’s work in this area has movedbeyond particulate filter systems to include systems for NOx and NO2

control and integrated 4-way systems,which simultaneously reduce emissionsof PM and NOx as well as CO and HC.

and applicationsexpertise

Systems technology

Johnson Matthey won the Royal Academy of Engineering MacRobert Award in 2000 for its CRT® technology, in recognition of anoutstanding innovation of benefit to society



Having worked on retrofit applicationssince the early 1990s, Johnson Mattheyhas direct, hands-on experience in the non-road market. This is basedprimarily on particulate filter systems for construction and materials handlingmachines, but we also have experience ofother systems and of rail and agriculturalapplications. This long experience has given us an understanding of theparticular challenges of non-road mobilemachinery: the variable and sometimesextreme duty cycles, the physicaldemands placed on the exhaust system,the packaging constraints, heat rejection,performance monitoring and control.



Modelling

JM builds computer models of catalyst performance,starting with the measured kinetics of individualreactions over real catalysts. These are built up into models capable of modelling fully transientoperation. Models are important tools in JM’s owncatalyst development work but are also madeavailable to customers for their own systemdevelopment and calibration. This approach is particularly valuable in the non-road market,reducing the work required to check the performanceof whole engine systems over different ratings and machine-specific duty cycles.

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Steady state conversionsPoints: MeasuredLines: Simulated

DOC light-off model validation



Catalytic systems for PM or NOx control almostalways contain more than one component. An SCRsystem will have an oxidation catalyst after the SCRcatalyst and sometimes before. A particulate filterusually has an oxidation catalyst before the filter and a catalytic coating on the filter itself.

Systems to control PM and NOx are more than asimple combination of PM filter and NOx controlsystem. It is best when the two are designed to work together: NO2 from a PM filter can help an SCR system downstream; NOx adsorber desulphationcycles can be used to regenerate particulate filters.

To assist packaging, the components themselves canbe integrated, for example with SCR or NAC coatingson particulate filters.

Integ

ratedsystem

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Production

Johnson Matthey has ten TS16949-certified manufacturing plantsaround the world, with two moreunder construction. JM’s proprietarycoating technology enables veryprecise control over the amount ofwashcoat and precious metal appliedto each part, giving consistent highperformance and efficient use of raw materials. It also allows differentcatalytic coatings to be applied todifferent areas of the substrate,further enhancing performance,efficiency and, in some cases,durability. It also enables more thanone function to be built into a singlecomponent, reducing the complexityand cost of the finished system.

JM is in full series production of dieseloxidation catalysts for active filtersystems, catalysed particulate filtersfor light and heavy duty engines, SCRcatalysts and NOx adsorbers.

Manufacturingtechnology



Most emission control catalysts for mobile applications contain preciousmetals. Johnson Matthey is an acknowledged authority on preciousmetal markets and sole marketing agent for Anglo Platinum Ltd,the world’s largest producer of platinum group metals. JM is able toadvise customers on the methods of sourcing, pricing and managingtheir precious metal requirements in the way that best suits their needs.For further information on the platinum group metals markets,visit www.platinum.matthey.com.

Johnson Matthey is also the world’s largest refiner of secondary platinumgroup metals so, at the end of a machine’s life, we are able to recover theprecious metals from the exhaust catalysts and reuse them.

managementPrecious metal



Power <8kW 8-19kWTier 1 2 4 1 2 4

Year 2000 2005 2008 2000 2005 2008

CO 8.0 8.0 8.0 6.6 6.6 6.6

NMHC

NOx

PM 1.0 0.8 0.4 0.8 0.8 0.4

Power 19-37kW 37-56kWTier 1 2 4 4 1 2 4 4

Year 1999 2004 2008 2013 1998 2004 2008 2013

CO 5.5 5.5 5.5 5.5 - 5.0 5.0 5.0

NMHC -

NOx 9.2

PM 0.8 0.6 0.3 0.03 - 0.4 0.3 0.03

RegulationsUS EPA non-roademissions limits

Eng

ines

<56

kW

10.5 7.5 7.5 9.5 7.5 7.5

9.5 7.5 7.5 4.7 7.5 4.7 4.7

Original Tier 2/3 limit of 0.4g/kWhmay be used if 0.03g/kWh limit isintroduced in 2012.



Power 56-75kWTier 1 2 3 4a 4b

Year 1998 2004 2008 2012 2015

CO - 5.0 5.0 5.0 5.0

NMHC - 7.5 4.7 - 0.19

NOx 9.2 - - 3.4 0.4

PM - 0.4 0.4 0.02 0.02

Power 75-130kWTier 1 2 3 4a 4b

Year 1997 2003 2007 2012 2015

CO - 5.0 5.0 5.0 5.0

NMHC - - 0.19

NOx 9.2 3.4 0.4

PM - 0.3 0.3 0.02 0.02

Power 130-560kW

Power 130-225kW 225-450kW 450-560kWYear 2003 2001 2002

NMHC

NOx

Eng

ines

>56

kW

Tier 4 phase-inManufacturers may certify all theirengines according to the 4a and 4bstandards shown in the table.Alternatively, they may phase in theNOx + HC standard as follows:

• 130-560kW engines PM/CO 100% compliance from 2011; NOx/HC 50% compliance in 2011-3

• 56-130kW engines PM/CO 100% compliance from 2012; NOx/HC 25% compliance in 2012-4

Test cycles and fuelsTier 1-3: test cycle is the NRSC(=ISO8178-C1) fuel sulphur <2000ppm

Tier 4: engines must meet limits overNRSC and NRTC fuel sulphur 7-15ppm;NTE (not to exceed) limits apply

NotesThese tables are intended for general guidance only.For full regulations, refer to the regulatory authorities.Standards for engines >560kW not shown.

6.6 6.4 6.4

6.6 4.0

6.4-6.6 4.0

Tier 1 2 3 4a 4b

Year 1996 2001-3 2006 2011 2014

CO 11.4 3.5 3.5 3.5 5.0

NMHC 1.3 0.19

NOx 9.2 2.0 0.4

PM 0.54 0.2 0.2 0.02 0.02



JohnsonMatthey

Johnson Matthey is a speciality chemicalscompany focused on its core skills in catalysts,precious metals and fine chemicals.

The group's principalactivities are themanufacture of autocatalystsand pollution controlsystems, catalysts andcomponents for fuel cells,pharmaceutical compounds,process catalysts and finechemicals, and the refining,fabrication and marketing of precious metals.

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Johnson Matthey has continued to develop its technology for almost 200 years, demonstrating the company’s ability to maintain worldleadership by adapting constantly to rapidly changing customer needs.Rigorous in its own environmental policies, many of Johnson Matthey’sproducts have a major beneficial impact on the environment andenhance the quality of life for millions around the world.

JM’s Emission Control Technologies business is part of the EnvironmentalTechnologies Division. It is the world leader in the development andmanufacture of emission control catalysts for internal combustionengines. It provides exemplary customer service through a globalnetwork of technology centres, manufacturing plants and sales offices,local to customer needs.


United KingdomJohnson Matthey PlcOrchard RoadRoystonHertfordshireSG8 5HEUK

T (44) 1763 253000F (44) 1763 256015

USAJohnson Matthey380 Lapp RoadMalvernPA 19355USA

T (1) 610-971-3100F (1) 610-971-3116

[email protected]/ect

JapanJohnson Matthey5123-3 KitsuregawaSakura-shiTochigi 329-1412Japan

T (81) 286 86 5781F (81) 286 86 5791


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