Catalyst Book

Catalyst Handbook The right chem istry for Tier 4 A new type of engine component Catalytic exhaust aftertreatm ent is one of the key technologies that w ill enable engines to m eet the forthcom ing Tier 4 and equivalent standards. The introduction of a new class of com ponent is alw ays challenging, the m ore so w hen its function and control is very different to existing engine system s. New to you, but not to us Catalysts have been used as a standard component on cars for over 30 years and Johnson Matthey supplied the world’s first production batch in May 1974. Since then,we have supplied more than 500 million autocatalysts,around one third of all the catalysts ever fitted to cars. The Mark 1 Volkw agen Golf launched in the USA in 1974. It w as one of the first m ass produced cars to be fitted w ith an autocatalyst. © Johnson Matthey plc 2007 contents The timetable for Tier 4 is tight,and the cost of non-compliance is very high. The purpose of this booklet is to describe the catalyst technologies available and how Johnson Matthey (JM) can work with you to achieve the required emissions reductions while maintaining, and in some cases improving, the other features of diesel engines that are valued by your customers. 01 Introduction 03 Catalyst Technologies 09 JM’s Capabilities 17 Tier 4 Regulations 19 About Johnson Matthey From on-road to non-road Leaders in Diesel Catalyst Technology Diesel cars were first fitted w ith catalysts in the early 1990s, since w hen tighter regulations and increasing custom er dem ands have driven the developm ent of engine and aftertreatm ent technologies together. Johnson Matthey catalysts and technologies have been inside m ost of the particulate filter system s retrofitted to heavy diesel engines around the world. JM invented the CRT® diesel particulate filter (DPF) system and m ore than 100,000 have been sold for retrofit applications. We are building on this success w ith the introduction of the retrofit SCRT® (CRT® + selective catalytic reduction (SCR)) system for integrated control of all regulated diesel pollutants. Since 2005, tightening em issions regulations for truck and bus engines in Japan, Europe and the USA have led to the introduction of particulate filters, SCR systems and NOx adsorbers on new heavy diesel engines. Johnson Matthey has developed leading technology to m eet the requirem ents in all m arkets. These t ypes of catalysts are all in series production at JM. 01 © Johnson Matthey plc 2007 The non-road Applications Challenge Non-road m achines represent a very different challenge to on-road vehicles. Indeed, it would be better to say that NRMM represents m any thousands of different applications challenges. Johnson Matthey has been supplying and applying retrofit aftertreatm ent system s to non-road m achines for m ore than 15 years. Therefore, we have experience of the variet y of operating requirem ents, engine dut y cycles and packaging constraints found in non-road m achines. We know the differences between a tractor and a tracked excavator. And we know the regulations. We are very well placed to understand the requirem ents on catalytic system s for Tier 4 com pliance. © Johnson Matthey plc 2007 02 Types of catalyst technology An em ission control catalyst is usually a catalytic coating applied to a ceram ic or m etallic substrate. The catalyst has open channels and the gases react as they pass through. Som e catalysts are designed to be able to store reagents (e.g. oxygen, am m onia) to enhance perform ance or even to act as a chem ical trap, as in the case of NOx adsorbers. A particulate filter is a physical trap. The m ost com m on t ype is a ceram ic m onolith like a catalyst substrate, but w ith channels closed at alternate ends so that the gases m ust pass through the channel w alls, leaving the soot behind. These filters are nearly 100% efficient for solid particles. Partial filters, designed for a lower efficiency, are also available. A DPF does not always contain a catalyst, but catalysts are used to burn the accumulated particulate. Catalyst: a substance which when present in small amounts increases the rate of a chemical reaction or process but which is chemically unchanged by the reaction. 03 © Johnson Matthey plc 2007 When designing a catalyst,we make it active to give high conversions from smaller catalysts and to make the best use of precious metal. We make it selective to ensure that it is active for the desired reactions and does not produce undesirable by-products. And we make it durable to meet useful life requirements and 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 its application and the exhaust conditions that it will see throughout its life. It also requires knowledge of the deactivation mechanisms,both chemical and physical, of each type of catalyst. ? What are the properties of a good catalyst © Johnson Matthey plc 2007 04 PM Control Particulate filters are used to trap Particulate Matter (PM). Catalysts are needed to burn the PM collected in the trap, m aintaining the perform ance of the system . There are two w ays that catalysts can be used to keep DPFs clean, and these are often used together. Soot Com bustion Rate (CO2 Intensit y) Nitrogen dioxide (NO2) and oxygen (O2) can both be used to com bust the soot trapped in a filter. NO2 has the advantage that it reacts w ith soot at the tem peratures found in diesel exhaust. The O2 reaction requires higher tem peratures, but is m uch faster. 0 100 200 300 400 500 o Tem perature C 05 © Johnson Matthey plc 2007 600 700 Using NO2 to regenerate a particulate filter NO2 reacts w ith soot trapped in a filter, m aking NO and CO2. This reaction can occur from 200°C, so the tem peratu res found in diesel exhaust stream s are sufficient and no additional energy is required. Som e of the NOX em itted by an engine is NO2 and m ore can be m ade by an oxidation catalyst designed to oxidise NO to NO2. This system – an oxidation catalyst to m ake NO2 followed by a particulate filter w hich is regenerated by the NO2 – is the CRT® system , a Johnson Matthey invention. Using Using the CRT® effect to regenerate a filter has two great advantages: it is continuous (helping to m aintain a low and even exhaust back pressure) and it requires no additional energy. O2 to regenerate a particulate filter Particulate 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 foun d in most diesel engine applications, so some mechanism is required to raise the temperature of the exhaust periodically. An oxidation catalyst placed before the filter is a very efficient way of doing this. When the filter needs regenerating, the hydrocarbon content of the exhaust stream is increased.The catalyst burns the hydrocarbon, producing the heat required.The catalyst can also be designed to make NO2 during normal operation to provide additional regeneration. The hydrocarbon enrichment can be achieved in-cylinder using electronic fuel systems, or by injecting fuel directly into the exhaust system. © Johnson Matthey plc 2007 06 NOx Control Converting NOx from the engine to nitrogen requires a chem ical reduction. Diesel exhaust is an oxidising, not a reducing, environm ent. There are t wo main strategies to achieve NOx reduction. Selective catalyic reduction An SCR system reduces NOx to nitrogen (N2) and is capable of m ore than 90% conversion, depending on conditions. To achieve this reaction in norm al, lean (i.e. high oxygen, low hydrocarbon) diesel exhaust, a chem ical reductant is needed. In m ost system s, am m onia (NH3) is used, and this is delivered as an aqueous solution of urea (“AdBlue” in Europe). The urea decom poses in the exhaust stream to form am m onia, w hich reacts w ith the NOx to m ake nitrogen and w ater. An SCR system requires a m eans of storing the urea and injecting the am ount required to reduce the NOx em itted by the engine. Careful control is needed for transient cycles. The SCR catalysts usually have an oxidation catalyst , often called a slip catalyst, at the end as a guard to ensure that no am m onia is em itted. 07 © Johnson Matthey plc 2007 NOx adsorber catalysts NOx adsorber catalysts or NACs, also know n as lean NOx traps (LNTs), operate in two m odes. In norm al diesel exhaust conditions, they adsorb the NOx from the exhaust gas, storing it chem ically. In “rich” exhaust conditions, w ith little or no oxygen (O2) they release the stored NOx and react it w ith com ponents of the rich exhaust gas - carbon m onoxide (CO), hydrocarbons (HC) and hydrogen (H2) - to m ake nitrogen. Like any trap, chem ical or physical, NACs have a finite capacit y so the engine or som e auxiliary system m ust create rich exhaust conditions at intervals to regenerate the catalyst and this reduces the stored NOx to nitrogen. NACs also store sulphur and this reduces their capacit y to trap NOx, so periodic “desulphations”, requiring increased exhaust tem peratures, are necessary. NOx Adsorber Catalyst - lean conditions NO + 1/ 2 O2 CO2 NO2 Pt Rh NOx Adsorber Catalyst - rich conditions NOx CO + HC + H2 CO Pt Rh N2 + CO2 © Johnson Matthey plc 2007 08 Development and testing Catalyst Technology Each new Johnson Matthey catalyst form ulation is the product of four decades of developm ent experience and a fundam ental understanding of catalyst properties. Research into new t ypes of catalysts and catalytic properties is undertaken at JM’s ow n research facilities. Team s around the world develop new form ulations to m eet the requirem ents of different engines, regulations and applications. 09 © Johnson Matthey plc 2007 Coatings are developed specifically to exploit the properties of different substrate t ypes. Test work starts in the laboratory using bottled gases to sim ulate exhaust gas w ith precise control of gas m ix and tem perature. Testing then m oves to engines for perform ance and durabilit y testing. and ageing Testing Johnson Matthey has its ow n test cells dedicated to diesel engine testing in Europe, the USA and Japan, m any capable of transient operation. These cells are used to test and prove catalysts; for catalyst ageing and for collaborative developm ent program m es using custom er engines. Our facilit y in Detroit also perform s contract testing (see www.jmtesting.com). JM develops proprietary catalyst-specific accelerated ageing procedures for its own and customer testing.These are based on catalyst deactivation mechanisms and are validated against catalyst aged in real world operation on vehicles and m achines. © Johnson Matthey plc 2007 10 Systems technology and applications expertise JM works to develop new aftertreatm ent system s and m akes them available for new engines and retrofitting. This work covers not just the catalysts them selves, but the operating principles of the w hole system . An exam ple of this is the CRT® (Continuously Regenerating Trap) particulate filter system . Johnson Matthey developed its operating principle in the late 1980s. It has been used in the m ajorit y of retrofit particulate filter system s supplied around the world and has also been em ployed in m any OEM applications. Johnson Matthey won the Royal Academy of Engineering MacRobert Award in 2000 for its CRT® technology, in recognition of an outstanding innovation of benefit to societ y 11 © Johnson Matthey plc 2007 JM’s work in this area has m oved beyond particulate filter system s to include system s for NOx and NO2 control and integrated 4-w ay system s, w hich sim ultaneously reduce em issions of PM and NOx as well as CO and HC. Having worked on retrofit applications since the early 1990s, Johnson Matthey has direct, hands-on experience in the non-road m arket. This is based prim arily on particulate filter system s for construction and m aterials handling m achines, but we also have experience of other system s and of rail and agricultural applications. This long experience has given us an understanding of the particular challenges of non-road m obile m achinery: the variable and som etim es extrem e dut y cycles, the physical dem ands placed on the exhaust system , the packaging constraints, heat rejection, perform ance m onitoring and control. © Johnson Matthey plc 2007 12 1.0 CO THC NO NOx 0.8 0.6 0.4 0.2 Points: Measured Lines: Simulated Steady state conversions 0.0 100 150 200 250 300 350 400 450 500 Inlet Temperature / °C Systems integration DOC light-off m odel validation 13 © Johnson Matthey plc 2007 Modelling JM builds computer models of catalyst performance, starting with the measured kinetics of individual reactions over real catalysts. These are built up into m odels capable of m odelling fully transient operation. Models are im portant tools in JM’s ow n catalyst developm ent work but are also m ade available to custom ers for their ow n system developm ent and calibration. This approach is particularly valuable in the non-road market, reducing the work required to check the performance of whole engine systems over different ratings and m achine-specific dut y cycles. System s to control PM and NOx are m ore than a sim ple com bination of PM filter and NOx control system . It is best w hen the two are designed to work together: NO2 from a PM filter can help an SCR system downstream; NOx adsorber desulphation cycles can be used to regenerate particulate filters. To assist packaging, the com ponents them selves can be integrated, for exam ple w ith SCR or NAC coatings on particulate filters. Integrated systems Catalytic system s for PM or NOx control alm ost alw ays contain m ore than one com ponent. An SCR system w ill have an oxidation catalyst after the SCR catalyst and som etim es before. A particulate filter usually has an oxidation catalyst before the filter and a catalytic coating on the filter itself. © Johnson Matthey plc 2007 14 Manufacturing technology Johnson Matthey has ten TS16949certified manufacturing plants around the world, with two more under construction. JM’s proprietary coating technology enables very precise control over the amount of washcoat and precious metal applied to each part, giving consistent high performance and efficient use of raw materials. It also allows different catalytic coatings to be applied to different areas of the substrate, further enhancing performance, efficiency and, in some cases, durability. It also enables more than one function to be built into a single component, reducing the complexity and cost of the finished system. JM is in full series production of diesel oxidation catalysts for active filter systems, catalysed particulate filters for light and heavy duty engines, SCR catalysts and NOx adsorbers. Production 15 © Johnson Matthey plc 2007 Precious metal management Most em ission control catalysts for m obile applications contain precious m etals. Johnson Matthey is an acknow ledged authorit y on precious m etal m arkets and sole m arketing agent for Anglo Platinum Ltd, the world’s largest producer of platinum group m etals. JM is able to advise custom ers on the m ethods of sourcing, pricing and m anaging their precious m etal requirem ents in the w ay that best suits their needs. For further inform ation on the platinum group m etals m arkets, visit w w w.platinum .m atthey.com . Johnson Matthey is also the world’s largest refiner of secondary platinum group m etals so, at the end of a m achine’s life, we are able to recover the precious m etals from the exhaust catalysts and reuse them . © Johnson Matthey plc 2007 16 Power <8kW 8-19kW Tier 1 2 4 1 2 4 Year 2000 2005 2008 2000 2005 2008 8.0 8.0 8.0 6.6 6.6 6.6 10.5 7.5 7.5 9.5 7.5 7.5 1.0 0.8 0.4 0.8 0.8 0.4 CO NMHC NOx PM Power 19-37kW 37-56kW Tier 1 2 4 4 1 2 4 4 Year 1999 2004 2008 2013 1998 2004 2008 2013 5.5 5.5 5.5 5.5 - 5.0 5.0 5.0 7.5 4.7 4.7 0.4 0.3 0.03 CO NMHC 9.5 7.5 7.5 4.7 NOx PM 9.2 0.8 0.6 0.3 0.03 - Original Tier 2/ 3 lim it of 0.4g/ kWh m ay be used if 0.03g/ kWh lim it is introduced in 2012. 17 © Johnson Matthey plc 2007 Engines <56kW Regulations US EPA non-road emissions limits 56-75kW Tier 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 PM 9.2 - - 3.4 0.4 - 0.4 0.4 0.02 0.02 Power 75-130kW Tier 1 2 3 4a 4b Year 1997 2003 2007 2012 2015 CO - 5.0 5.0 5.0 5.0 NMHC - - 0.19 6.6 4.0 - 0.3 0.3 Tier 1 2 3 4a 4b Year 1996 2001-3 2006 2011 2014 11.4 3.5 3.5 3.5 NOx PM 9.2 Power CO Engines >56kW Power 3.4 0.4 0.02 0.02 130-560kW NMHC 1.3 NOx 9.2 PM 0.54 6.4-6.6 4.0 0.2 0.2 Power 5.0 0.19 2.0 0.4 0.02 0.02 130-225kW Year NMHC 225-450kW 450-560kW 2003 2001 2002 6.6 6.4 6.4 NOx Tier 4 phase-in Manufacturers m ay certify all their engines according to the 4a and 4b standards show n in the table. Alternatively, they m ay phase in the NOx + HC standard as follow s: Test cycles and fuels Tier 1-3: test cycle is the NRSC (=ISO8178-C1) fuel sulphur <2000ppm Tier 4: engines m ust m eet lim its over NRSC and NRTC fuel sulphur 7-15ppm ; NTE (not to exceed) lim its apply • 130-560kW engines PM/ CO 100% com pliance from 2011; NOx/ HC 50% com pliance in 2011-3 • 56-130kW engines PM/ CO 100% com pliance from 2012; NOx/ HC 25% com pliance in 2012-4 Notes These tables are intended for general guidance only. For full regulations, refer to the regulatory authorities. Standards for engines >560kW not show n. © Johnson Matthey plc 2007 18 Johnson Matthey Johnson Matthey is a speciality chemicals company focused on its core skills in catalysts, precious metals and fine chemicals. About The group's principal activities are the manufacture of autocatalysts and pollution control systems,catalysts and components for fuel cells, pharmaceutical compounds, process catalysts and fine chemicals,and the refining, fabrication and marketing of precious metals. 19 © Johnson Matthey plc 2007 Johnson Matthey has continued to develop its technology for alm ost 200 years, dem onstrating the com pany’s abilit y to m aintain world leadership by adapting constantly to rapidly changing custom er needs. Rigorous in its ow n environm ental policies, m any of Johnson Matthey’s products have a m ajor beneficial im pact on the environm ent and enhance the qualit y of life for m illions around the world. JM’s Em ission Control Technologies business is part of the Environm ental Technologies Division. It is the world leader in the developm ent and m anufacture of em ission control catalysts for internal com bustion engines. It provides exem plary custom er service through a global network of technology centres, m anufacturing plants and sales offices, local to custom er needs. © Johnson Matthey plc 2007 20 United Kingdom Johnson Matthey Plc Orchard Road Royston Hertfordshire SG8 5HE UK T (44) 1763 253000 F (44) 1763 256015 [email protected] www.jmcatalysts.com/ect USA Johnson Matthey 380 Lapp Road Malvern PA 19355 USA Japan Johnson Matthey 5123-3 Kitsuregawa Sakura-shi Tochigi 329-1412 Japan T (1) 610-971-3100 F (1) 610-971-3116 T (81) 286 86 5781 F (81) 286 86 5791