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Accelerated Poisoning of Diesel Oxidation Catalysts by Zinc Dialkyldithiophosphate-Derived Phosphorus
| Content Provider | Semantic Scholar |
|---|---|
| Author | Eaton, Scott J. |
| Copyright Year | 2006 |
| Abstract | The phosphorus poisoning of diesel oxidation catalysts (DOCs) by the lube-oil additive zinc dialkyldithiophosphate (ZDDP) is investigated in the present study. A 517 cc single-cylinder, naturally aspirated direct-injection diesel engine is used to accelerate the phosphorus poisoning of DOCs by artificially increasing the ZDDP consumption to approximately 700 times of that found during normal engine operation. Three methods of accelerating the ZDDP consumption rate are investigated, which have been shown in previous literature to cause phosphorus poisoning. These include the injection of high concentration ZDDP-doped lube-oil blended with diesel fuel though the fuel injector as well as injecting ZDDP-doped lube-oil directly into the intake manifold and exhaust manifold, respectively. Each method is shown to produce a different phosphorus poisoning behavior on automotive catalysts by creating unique poisoning exhaust environments causing different deactivation mechanisms; ZDDP passing through the combustion chamber results in phosphoric acid, ZDDP injected into the exhaust results in whole ZDDP molecules and their molecular fragments. The deactivation resulting from each poisoning method is characterized using both total hydrocarbon (THC) and carbon monoxide (CO) light-off degradation as well as phosphorus adsorption and phosphorus chemistry identified within the DOC. Washcoat surfaces evaluated for lube-oil derived contamination using scanning electron microscopy with energy dispersive spectrometers (SEM-EDS) shows that topography depends on the method of ZDDP introduction. Exhaust manifold injection produces a zinc-phosphate glaze, which masks active sites and inhibits gaseous diffusion to the washcoat surface. Fuel and intake manifold injection methods produce chemically absorbed phosphorus, which poison active sites. THC and CO light-off performance degradation is also found to depend on the method of ZDDP introduction, with an increase in light-off temperature between 40 to 100C. Total phosphorus, zinc, and sulfur accumulation within the DOCs is measured using X-ray fluorescence spectroscopy (XRF) and found to vary with both the ZDDP introduction method and the exhaust temperature during poisoning. Elemental (X-ray) maps and line-scans performed using electron probe microanalysis (EPMA) show |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://trace.tennessee.edu/cgi/viewcontent.cgi?article=2992&context=utk_gradthes |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
