Chemicals are central to vehicle emissions reduction

Catalyst for change

05 September 2008 00:00  [Source: ICB]

Strict controls are being introduced to ensure engines are more efficient, and chemicals are playing a major role

CHEMICAL COMPANIES supplying catalysts and additives to reduce emissions from cars, trucks and other motor vehicles are enjoying strong worldwide demand for their products, which is expected to remain robust for years to come.

Perhaps the only major barrier to continued growth is the development and widespread commercialization of highly energy-efficient engines, which could sharply decrease the role chemistry plays in making fuels cleaner.

The need for chemicals to help cut emissions stems from increasingly strict regulatory controls on fuel content and vehicle performance, with the objective of improving or at least maintaining air quality in cities around the world.

But a much more powerful impetus is also now coming from the urgent necessity to decrease carbon dioxide (CO2) emissions because of the relatively large contribution by transport to global warming.

HIGHER EMISSIONS?

Chemicals can help resolve the difficulties engineering has in reconciling solutions for cutting down air pollutants from fuel with those for reducing CO2 emissions. New engine designs can, for example, decrease emissions of carbon monoxide (CO), hydrocarbons, nitrogen oxides (NOx) or particulates - but can also increase CO2 discharges.

"A lot of good work has been done by the engineers in improving engine design to raise fuel efficiency," says Ian Godwin, corporate communications director at Johnson Matthey, a UK-based leading producer of auto catalysts and their materials. "But as the regulations get tighter and tighter, the engineers and the chemists have to work even closer together because there are no single solutions to the major problems."

The biggest challenge is finding ways to deal with discharges from diesel engines for which there is rising demand worldwide because of their greater energy efficiency and hence potential for cutting CO2 emissions. However, they are also dirtier than gasoline engines because of their capacity to release large amounts of particulate matter and NOx.

With gasoline vehicles, the main pollutants are CO, unburned hydrocarbons and NOx. For almost three decades the most effective technology for removing the three substances from gasoline emissions has been the three-way catalytic converter.

"There does not seem to be any need for a dramatic change in the three-way catalytic technology to comply with new regulations because it works so well," says Olivier Touret, director of the catalysis business unit at French chemical company Rhodia.

"That could change if light vehicle manufacturers decide to raise the air-to-fuel ratio in order to improve fuel consumption and CO2 emissions. But a switch to a lean-burn mode would be costly because it would raise NOx emissions and require a different catalytic converter," Touret adds.

Within the next decade, there are unlikely to be any radical changes in the engineering design of cars on a mass scale because of the time it takes to replace existing models. The European Automobile Manufacturers' Association (ACEA) reckons that over 60% of cars being sold in Europe in 2012 would have already been on the market today. Another 30% would have at present been in advanced stages of development.

TOUGHER STANDARDS

Meanwhile, emission regulations will require big reductions in emissions of particulates and NOx. In the EU, under the Euro 5 standard due to come into force next year, particulate emissions from diesel vehicles will have to be cut by 80% and NOx by 20%, compared with the existing Euro 4 standard.

Under the Euro 6 standard, scheduled to be implemented in 2014, NOx emissions from diesel vehicles will have to drop by another 50%.

The US is bringing in stricter controls on emissions in 2010, while California is aiming to make its regulatory limits even tougher than the federal ones. Japan is also tightening up its rules on emissions. Other Asian countries, including China and India, are imposing clean fuel restrictions, particularly for reducing sulfur content.

In Europe, North America and Japan, limits on CO2 emissions are being introduced in both fuel standards and regulations on the performance of new vehicles.

The EU has drawn up a regulation under which car manufacturers have to cut CO2 emissions from new vehicles from a current average of around 160 grams/km, to 120g/km by 2012.

To comply with tougher regulations and other pressures for cleaner fuels, vehicle makers and owners, together with the fuel producers, are being offered a range of technologies by chemical companies based mainly on catalysts. These include, for diesel vehicles, particulate filters in which soot is trapped and destroyed by oxidation catalysts and selective catalytic reduction (SCR) catalysts, which convert NOx into nitrogen and water.

A variety of additives are also available to be placed in fuels in the refinery, during blending or in the central storage tanks of transport fleets. These boost a fuel's cetane number or octane level, keep fuel delivery systems clean, lower combustion chamber deposits and improve lubricity, all of which helps to decrease fuel consumption and reduce emissions.

Detergents are a key group of additives that ensures the modern engine - with high pressures and temperatures, and high-speed fuel injection technologies - works properly.

"If the fuel injector holes start to foul up, there is a massive loss of power and efficiency," says Brian Watt, planning director at UK-based Innospec Fuel Specialties, a leading global producer of fuel additives. "The only way to keep the holes clean is with detergents. These are constantly changing because of the varying needs of customers due to different engine designs and operating temperatures and pressures."

Detergents - mainly surfactants that keep components within the fuel suspended - stop deposits of carbon forming on surfaces within the engine, including the combustion chambers.

Oxonica, a nanomaterials specialist based in Kidlington, UK, has been successful with a nanoscale catalytic cerium additive, which removes carbon deposits in diesel engines.

The product, which saw sales soar by 49% in the first half of this year, reduces fuel consumption by 510% and emissions of particulates by 15%.

"Our customers who run transport fleets like buses and trucks tend to buy the additive to save money, so it is doing well at the moment because of the high fuel prices," says Mike Attfield, Oxonica's planning director.

Growth in the global fuel additives market, estimated to be worth $2bn (€1.4bn), is linked to the consumption of fuel, which is expanding by 22.5%/year. With demand for diesel, which generally requires a lot of additives, expanding at a faster rate, the overall growth for additives is much higher at around 5-10% in volume terms, according to industry sources.

On the other hand, demand for catalysts is tied to vehicle sales, the vast majority of which are fitted with some sort of catalytic system. But they also tend to have higher unit sales per vehicle. So, while vehicle sales are rising by 44.5%, those of catalysts are going up by 56%.

In the EU, where more than half of cars now have diesel engines and consumption of gasoline is declining, a growing number of vehicles will have to be fitted with both a diesel particulate filter (DPF) and an SCR to eliminate NOx because of the new emissions regulations.

This will cause difficulties because of the need for both the DPF and SCR to be placed close to the engine to take advantage of its heat.

"The car manufacturers also want to avoid piling up of catalytic units, which will create back pressure from the exhaust and result in a loss of fuel efficiency," says Touret.

One option is to place the DPF away from the engine and then use a cerium or iron catalyst added to the fuel to eliminate the soot trapped within it.

"The fuel-borne catalyst [FBC] is more effective at lower temperatures than engineering methods for reducing particulates [those close to the engine]," says Watt. "It is also suitable for driving in cities, where, because of the slow speeds, car engines are operating at low temperatures."

The crucial factors dictating selection of catalytic systems will be cost and how effective they are in reducing both fuel consumption and hence CO2 emissions and in cutting the discharge of pollutants.

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Author: Sean Milmo
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