Automotive Emissions control

• Health and Environment
• ACTALYS™ performance materials for gasoline three-way catalysis
• ACTALYS™ performance
• EOLYS™, Fuel-borne catalyst
• EOLYS™ advantages
• Regulations - Publications

• Health and environement

In conjunction with the regulatory authorities, the key players in the automotive industry have for many years been focusing their efforts on reconciling the automotive vehicle with its impact on public health.

Although considerable progress has already been made, further progress is still necessary, as the motor vehicle remains one of the principal contributors to urban atmospheric pollution.

Impact of automotive emissions on health and the environment

The pollutants contained in engine exhaust gases constitute a public health hazard.
An ever-growing number of studies have demonstrated the detrimental effects of automobile pollution on public health. The three regulated pollutants emitted by gasoline engines are:

• carbon monoxide (CO),
• unburnt hydrocarbons (HC)
• nitrogen oxides (NOx).

And specifically for diesel engines, particulate matter (PM) which is made-up in the most part of soot. When their atmospheric concentration increases, they provoke and exacerbate respiratory and cardiovascular conditions and may cause eye irritation and headaches. The resulting hospitalizations and associated medical expenses represent a major financial cost. Furthermore, automobile pollution contributes greatly to the greenhouse effect and has a deleterious effect on flora and fauna, and the external fabric of buildings.

Conciliated the car and the environment With more than 20 years' experience as a key raw materials supplier, Rhodia has become a recognized partner in the automotive emissions control industry.

To enable further progress and to offer a cost-effective solution to 'cold-start' emissions, Rhodia launched in 1995 the ACTALYS™ range of high performance products. These materials enhance catalyst performance, extend catalyst durability and are ideally suited to 'close-coupled' applications.

Rhodia also offers the Cycleon® catalytic converter recycling service so that the use of three-way catalyst technology has a double environmental benefit.

• ACTALYS™ performance materials for gasoline three-way catalysis

Gasoline three-way catalysiss

The role of the catalytic converter is to transform the primary pollutants in the exhaust gas - carbon monoxide (CO), unburnt hydrocarbons (HC) and nitrogen oxides (NOx) - into non-toxic compounds: carbon dioxide (CO₂), water (H₂O) and nitrogen (N₂).

The exhaust gas is passed through a honeycomb monolith (metallic or more often ceramic) the interior surface of which is coated with the catalyst formulation comprising three key constituents:

• precious metals (platinum, palladium, rhodium),
• alumina,
• Rhodia's ACTALYS™ rare-earth based materials which enhance catalytic activity.

Thanks to their outstanding properties, ACTALYS™ advanced materials are particularly suited to applications where the converter is close to the engine ('close-coupled'). This configuration enables the catalyst to start functioning (or to 'light-off') very soon after starting the engine. This approach is already enabling compliance with 2005 emissions limits.

Technological challenges

Since the advent of the first generation of catalytic converters, emissions-control and engine technologies have made immense progress. Rhodia has participated in this progress by developing high performance materials.

A technological challenge for the year 2000.

To comply with the emissions regulations proposed for the year 2000 and beyond, a real technological breakthrough has been required to develop systems capable of:

• converting 98 % of engine-out primary emissions;
• a working life exceeding 120,000 miles / 192,000 km;
• compatibility with On-Board Diagnostic (OBD) systems.

An emissions-control system effective within the very first minute

The main challenge is to reduce the time (ca. 3 minutes) required after starting the engine for the catalytic converter to reach its operating temperature of about 300° C. It is during these first few minutes that unburnt hydrocarbons (HC) are released.

The solution to these 'cold-start' emissions studied by the large majority of the washcoaters and automakers, is to move the catalytic converter closer to the engine to take advantage of the higher exhaust gas temperatures. In this position the converter 'lights-off' within seconds of starting the engine.

• ACTALYS™ performance

To adapt the catalytic materials to the extreme temperatures and conditions experienced in the 'close-coupled' position, Rhodia developed ACTALYS™ performance products. These rare-earth based materials make the catalyst more thermally robust and extend its durability.

To maintain catalytic activity even under the most extreme conditions, ACTALYS™ materials exhibit three essential properties:

• Excellent thermal stability: physical characteristics are preserved even after exposure to elevated temperatures (peaks > 1 000° C) there by stabilizing the precious metals by preventing sintering and encapsulation;
• Developed and stable surface area: contact between the exhaust gas and the catalyst is greatly facilitated ( 50m2 /g as opposed to 5m2 /g for standard products);
• High and accessible Oxygen Storage Capacity (OSC): ACTALYS™ materials function like an 'oxygen-sponge' being capable of rapidly absorbing and releasing oxygen according to the catalytic reaction required (reduction or oxydation).

The thermal resistance imparted by ACTALYS™ materials is of particular importance in 'close-coupled' applications.

Rhodia has developed the ACTALYS™ range of materials based upon cerium and cerium/zirconium oxides. Their physico-chemical properties are tailored to satisfy the process and performance requirements of the catalyst manufacturer.

ACTALYS™ advanced materials technology adapted to the automaker's needs

The 'close-coupled' three-way catalyst offers a cost-effective technology for compliance with the ambitious, new emission limits.

• This technology requires no additional equipment or appreciable modification of the existing system. Three-way catalyst technology has been used with great success by automakers for over two decades. As a solution to 'cold-start' emissions, it is favoured over alternatives which are still to be proven in series production such as electrically heated catalysts, 'burners' and physical storage systems.
• ACTALYS™ materials enable the optimization of the rate of precious metal incorporation: the cost of precious metals is subject to market fluctuation and vastly superior to that of ACTALYS™ products.
• The composition and specific properties of ACTALYS™ materials are adapted to different catalyst technologies. They are customized to meet the needs of the catalyst manufacturer and those of the automaker.
• Emissions-control systems using ACTALYS™ are already enabling series production gasoline vehicles to comply with 2005 emission limits.

• EOLYS™, Fuel-borne catalyst

The diesel without particles: the engine of the future

The diesel engine compared to its gasoline counterpart displays improved long-term reliability and greater fuel-efficiency (and thus lower CO₂ emissions). The first series-produced passenger vehicle to achieve 3 liters of fuel per 100 km (80 mpg) is fitted with a diesel engine. The diesel engine is the engine of choice for the foreseeable future if its NOx and particulate matter emissions can be sufficiently reduced.

How does a wall-flow filter function?

This particulate filter is a ceramic monolith the channels of which 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.

The diesel particulate filter: the only solution to ultra-fine particles

Different types of diesel particulate filters have been developed; the most efficient remove more than 99 % by number of the exhaust-gas particulates. Today, filtration is the most effective means of reducing diesel particulate emissions and the only one capable of combating ultra-fine emissions. The challenge with filtration is to 'regenerate' the filter before it is completely blocked by the collected particles. This is achieved by burning the soot that the particles form.

The reduction of particulate emissions offers the possibility of simultaneously reducing engine-out NOx emissions by adjusting engine calibration.

EOLYS™ is suitable for use with all types of filters

Assisted-Regeneration

The soot collected in the filter must be regularly burnt-off to avoid an increase in exhaust gas backpressure and a consequent drop in vehicle performance.

The EOLYS™ fuel-borne catalyst facilitates this regeneration by significantly lowering the light-off temperature of the soot and by moderating the exotherm of the resulting combustion. Control over the combustion process is critically important in maintaining the long-term integrity of the filter.
Under certain driving conditions where the exhaust gas temperature is too low to initiate regeneration, additional energy input is necessary. In this way the filter does not become blocked or damaged by a violent regeneration following an over-accumulation of soot.

• 'EOLYS™ advantages

• Environmentally-friendly Toxicological studies have demonstrated the non-hazardous nature of EOLYS™. No secondary gaseous or particulate emissions occur when used in conjunction with a particulate filter. • Sulfur-tolerant Can be used with all currently available grades of diesel fuel.             • High activity One liter is sufficient for a passenger vehicle to travel 100 000 km (60 000 miles). • Compatible Compatible with the majority of plastics and elastomers used in the manufacture of fuel tanks, fuel pumps and fuel lines. • Engine-friendly No engine-wear or fouling and no drop in performance. • Ease-of-use Handles like lubricating oil.

EOLYS™ an essential component in the diesel post-treatment system

• EOLYS™ reservoir with on-board dosing system
- Minimal packaging constraints (highly concentrated active ingredient)
- Temperature stability

• Exhaust gas
- No secondary gaseous emissions
- No mineral particulate emissions
- Particulate matter emissions reduced far below 2004/5 limit values
           
• Particulate filter
- No adverse EOLYS™ / filter material interaction
- Traps in excess of 99 % of particulates
- EOLYS™ enabled regeneration

• Catalyst
- No negative impact on performance

• Diesel fuel tank
- EOLYS™ is compatible with diesel and diesel additives
- Completely miscible with diesel
- EOLYS™ / diesel mixtures are highly stable

• Fuel lines
- EOLYS™ is compatible with the majority of plastics and elastomers

• Engine
- No increase in wear
- No fouling
- No drop in performance
- No impact on oil consumption

The key role of the system-integrator

The development of a robust and reliable post-treatment system is the task of the automaker or the system-supplier. A number of parameters need to be considered which are application specific:

- Type of vehicle: automobile, pick-up truck, bus, heavy duty truck, off-road vehicle, etc.
- Fuel consumption
- Driveability
- EGR
- Exhaust gas temperature
- Exhaust gas back-pressure
- Packaging constraints
- Frequency of severe driving conditions (urban cycle, delivery rounds, taxis, extreme cold)
- Type of filter
- Assisted-regeneration strategy employed
- The nature and quantity of the engine-out particulates
- EOLYS™ dosage rate

• Regulations - Publications - Statistics

Regulations

EUROPE - Passenger vehicules

EU Emission standards Diesel Cars grams/km

EU Emission standards Gasoline Cars grams/km

EUROPE - Heavy-duty vehicules

Limit values for diesel engines - ESC and ELR tests
Conventional engines with or without oxidation catalysts

(1) Derogation to 2005 for engines having a swept volume of less than 0.75 dm3 per cylinder and a rated power speed of more than 3000 min^-1

Limit values for diesel engines - ETC test

Engines with advanced aftertreament or gaseous fuel

(1) Derogation to 2005 for engines having a swept volume of less than 0.75 dm3 per cylinder and a rated speed of more than 3.000 min^-1
(2) For NG engines only
(3) For diesel engines only

Publications

Three-way catalysis

• Contacts

If you want to have more information, please contact us:
ec-catalysis@eu.rhodia.com