Until they all go emission-free, cars must keep polluting less and less. Here’s how.

Catalytic converters: Solvay’s innovation recognized by the Solar Impulse Foundation

Since the 1980s, increasingly stringent anti-pollution regulations, especially in the USA and Europe and today in China, have imposed the use of automotive catalytic converters and the continuous improvement of their efficiency. Today, innovation continues, as more and more pollutants need to be filtered out of car exhaust and requirements in terms of durability and thermal resistance keep getting more demanding.

Solvay has been active in this market since the very beginning and remains a global leader to this day. The Group sells its rare earth-based mixed oxide formulations – an off-white powder with the consistency of very fine sand – to catalytic converter manufacturers, who in turn supply the automotive industry.
 

Discover why OPtalys® is a Solar Impulse Efficient Solution

  
Stability and durability for better depollution

The key element here is cerium, a rare earth that is one of the only elements on Earth that acts as a stable oxygen buffer. It absorbs and injects oxygen like a sponge into the car’s exhaust in order to enable the elimination of noxious gases and particles, which happens through chemical reactions with the active ingredients in catalytic converters, precious metals such as platinum, palladium and rhodium. In addition to cerium, other rare earths such as lanthanum, neodymium, yttrium and praseodymium are also used.
 
One of the keys to making the process more efficient is to keep the largest possible exchange surface between the precious metals and the exhaust so that the redox reaction that is catalysis can happen (the oxidation and reduction required to tackle noxious molecules – mainly unburnt hydrocarbons, carbon monoxide and nitrogen oxides). The tricky part is ensuring stability, in other words keeping these reactions going even when temperatures in the converter get very high (1,000°C and more) by avoiding sintering and encapsulation, a chemical collapse that insulates the precious metals, thus interrupting the catalysis.
 
Over the past decade, the emergence of gasoline direct injection (GDI) engines with higher fuel efficiency has put an additional strain on catalytic converters by generating hotter exhaust, while at the same time successive US, European and Chinese regulations (dubbed EURO-4, EURO-5, EURO-6 and issued every few years) impose lower and lower tolerance for pollutant emissions. What’s more, as regulations concerning CO2 emissions keep getting stricter, catalytic converters play a key role in ensuring GDI vehicles can comply with the new standards by improving fuel efficiency.
  

  
Improving performance now and anticipating for later

This ongoing evolution led Solvay’s historic Actalys® product, a market standard since the 1990s, to be complemented in 2010 by OPtalys®, a new and improved formulation with increased thermal resistance and stability, designed for these more demanding requirements.

“Clearly, more stringent regulations are a driver for improvements: we answer to new standards and regulations with our performance increases,” says Thierry Seguelong, Market Manager Catalyst at Solvay’s SpecialChem business unit. “At the same time, we’re constantly anticipating future needs. For instance, right now we’re preparing for EURO-7 standards (probably due in 2025-2027) which will come with lower limits for pollutants and higher durability requirements. We need to innovate constantly.” In the meantime, OPtalys® has also been optimized for hybrid engines and is compatible with current and future biofuels, which tend to generate slightly different types of pollutants.

An enabler for the transition towards emission-free mobility

The overriding objective is to ensure the transition from now until the time when most cars are electric or hydrogen-fueled, about a decade from now. During the remaining years when combustion engines are still mainstream, their emissions need to continue to decrease, and catalysis has an important part to play here.

Recognizing this fact, the Solar Impulse Foundation recently labeled OPtalys® as one of its “1000 Solutions for the Future”. This is the 9th Solvay product to be awarded this label under the foundation created by Swiss pilot and explorer Bertrand Piccard seeing in OPtalys® “an intermediate system towards a world functioning independently of fossil fuels. Even incremental improvements on catalytic converters are of great importance in reducing the emissions of harmful gases from vehicles.”
 

Lastly, there is one more benefit to more efficient catalytic converters: cost reduction. “Thanks to optimized formulations, you need smaller amounts of precious metals for the same performance,” says Thierry. “Catalytic converters that can offer higher stability and durability are an efficient way of lowering the overall price of cleaner cars.”

Rare earth-based formulations are paving the way for more sustainable mobility, one oxide at a time.