PERC requested the Southwest Research Institute to measure the effect of sulfur levels in propane fuel on the performance and durability of Three-Way Catalysts (TWC). This report discusses the work performed during the second part of the project.
Fourier transfer infrared (FTIR) spectroscopy was used to measure engine-out emissions from a Ford 6.8L V10 during a heavy-duty FTP cold start test. The gas concentrations were identified based on the average emissions measured between 30 and 125 seconds of the cold state FTP cycle and corresponding bottled gasses were purchased to support catalyst core testing. A stoichiometric light-off test was performed on the catalysts in the fresh condition. The catalysts were then aged by sulfur exposure to the equivalent of 33,600 miles and retested.
The addition of platinum in the formulation can also significantly improve the sulfur tolerance of the catalyst.
Increasing the precious metal content of the catalyst can result in lower light off temperatures and improved cold start performance. The addition of platinum in the formulation can also significantly improve the sulfur tolerance of the catalyst. A sulfur poisoned catalyst can be recovered using a suitable de-sulfation procedure.