Thursday, June 26, 2008 - 2:50 PM
South American AB (Capital Hilton)

Novel Green Chemistries to Extend Automobile Catalytic Converter Useful Life While Reducing Exhaust Gaseous Emissions

Ewa Bardasz, The Lubrizol Corporation, Wickliffe, OH

For the last 50 years, phosphorus in the form of zinc dialkyldithiophosphate (ZDDP) has been the most cost-effective antiwear, antioxidant and anticorrosion component of engine oil. When ZDDP fulfills its function in the engine, the phosphorus can enter the exhaust stream, either by consumption or volatilization (released as a vapor). This phosphorus interacts with and decreases the effectiveness of catalytic converters used by automotive manufacturers to reduce exhaust gas emissions. This phenomenon, called catalyst deactivation, inhibits auto manufacturers' ability to meet United States Environmental Protection Agency requirements for a 120,000-mile or 10-year catalyst system warranty.

In 1994, the United States engine oil industry set a limit for the amount of phosphorus engine oil could contain. The maximum of 0.08wt% phosphorus continues to be the limit today. Although a phosphorus limit was set to protect catalysts, the phosphorus present in the oil still can volatize from the engine and react with the catalyst to cause catalyst deactivation. It is known that some ZDDPs are more prone than others to volatilize and therefore deactivate catalysts.

Concerns about losses in catalyst efficiency forced formulators either to design engine oils with lower concentrations of traditional ZDDP or to develop cost-effective, low-volatility ZDDP technology. In 2004, The Lubrizol Corporation introduced its patent-pending, low-volatility ZDDP technology to provide engine oil formulators with an alternative to designing higher-cost engine oils with lower levels of ZDDP.