Impact of Ultra-Clean Fischer-Tropsch Diesel Fuel on Emissions in a Light Duty Passenger Car Diesel Engine

Sulfur and aromatic compounds in diesel fuel impact the emissions profile of current diesel engines. Fuels that do not contain these components can be made from natural gas using Fischer-Tropsch chemistry. Very little data has been presented comparing the emissions characteristics of current low sulfur diesel to fuels with ultra low levels of sulfur and aromatics in passenger car diesel engines. This study reports on an exhaust emission comparison of currently available conventional diesel fuel to Fischer Tropsch diesel fuel free of aromatics and sulfur comparisons included regulated emissions, air toxics, aldehydes and ketones, particle size distribution, and greenhouse gas emissions. Testing was conducted on a current model diesel passenger car using a chassis dynamometer. Regulated emissions were analyzed according to the Code of Federal Regulations (CFR) Title 40 specifications and requirements of the Environmental Protection Agency (EPA) Federal Test Procedure (FTP). Additional testing was conducted on a chassis dynamometer using the US06, an aggressive driving style cycle, and the Highway Fuel Economy Test (HFET) procedure. Results from these tests show that the Fischer-Tropsch fuels containing no sulfur or aromatics substantially reduce regulated except for oxides of nitrogen (NO_x) and unregulated emissions from a passenger car diesel engine that was not specifically tuned to take advantage of the unique characteristics of this fuel.