Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – Gas or vapor treating
Reexamination Certificate
1995-10-30
2001-02-13
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Regenerating or rehabilitating catalyst or sorbent
Gas or vapor treating
C502S038000, C423S213500, C060S299000
Reexamination Certificate
active
06187709
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to a method of preconditioning automotive vehicle catalysts containing palladium to lower their light-off temperature during subsequent cold-starting of the automotive vehicle. More particularly, it involves oxidizing the catalyst at elevated temperatures.
BACKGROUND OF THE INVENTION
Future emission regulations expected to be implemented in both in the United States and Europe will require the automotive emission system to work with high efficiency within a very short time after cold-starting of the engine, perhaps within 20 seconds. In the automotive industry, a number of approaches are under investigation to achieve rapid emissions control after cold-starting. One approach involves electrically heating the automotive catalyst during cold starting, another involves the use of hydrocarbon adsorption traps in the exhaust system, and yet another the use of exhaust gas burners to rapidly boost the temperature of the exhaust gas. Highly loaded palladium (Pd) containing three-way catalysts which are close coupled to the engine are still another approach to achieve fast light-off. The term “three-way” refers to catalysts that are able to simultaneously convert hydrocarbons, carbon monoxide and nitrogen oxides present in automotive exhaust gases to more desirable species. This last approach shows promise for use either in conjunction with, or in lieu of, the more complicated technologies noted above. This new generation of highly loaded Pd-containing catalysts demonstrates both improved durability and light-off characteristics when compared to conventional platinum/rhodium three-way catalysts.
We have unexpectedly found a novel method of preconditioning Pd-containing three-way catalysts which significantly lowers their light-off temperature during a subsequent cold-starting, as tested in synthetic gas mixtures resembling engine exhaust gases. When this preconditioning method is applied to non-palladium three-way catalysts like platinum, a similar improvement in light-off temperature is not seen.
DISCLOSURE OF THE INVENTION
The invention is a method for preconditioning a highly loaded palladium-containing three-way automotive vehicle catalyst so as to lower its light-off temperature during subsequent cold-starting of the vehicle's engine. The method comprises the steps of providing the highly loaded palladium-containing three-way automotive catalyst (Pd loading of at least 100g/ft
3
on a catalyst support material) at a location in the exhaust system of the automotive vehicle where the steady-state warmed up operating temperatures of the system are at least 450° C., and subjecting the catalyst, either before or after shutdown of the vehicle's engine, to a flow of an oxidizing gas containing at least 0.85 volume % oxygen for a selected period of time, preferably of at least 15 seconds, while the catalyst is at an elevated temperature of at least 450° C. in order to oxidize the catalyst. Preferably, during cold starting of the engine it is operated in the lean-burn mode (such that the air/fuel ratio is greater than stoichiometric) in order to further reduce the light-off temperature of the preconditioned catalyst.
We have unexpectedly and advantageously found that by pre-oxidizing the catalyst as disclosed the light-off temperature can be lowered significantly when the engine is operated in a stoichiometric A/F ratio during subsequent cold-starting and can be lowered even further when the engine is operated in excess oxygen (lean-burn) during subsequent cold-starting.
REFERENCES:
patent: 3662540 (1972-05-01), Murphey
patent: 3771921 (1973-11-01), Rohde et al.
patent: 3779015 (1973-12-01), Maruoka
patent: 3862540 (1975-01-01), Harvey
patent: 3896616 (1975-07-01), Keith et al.
patent: 3943709 (1976-03-01), Holt
patent: 4099377 (1978-07-01), Yoshimura et al.
patent: 4185604 (1980-01-01), Nagaishi et al.
patent: 4231220 (1980-11-01), Takeda
patent: 4315895 (1982-02-01), Bramer et al.
patent: 4364227 (1982-12-01), Yoshida et al.
patent: 4437306 (1984-03-01), Ikenoya et al.
patent: 4484441 (1984-11-01), Kobayashi et al .
patent: 4893465 (1990-01-01), Farrauto et al.
patent: 4916898 (1990-04-01), Gandhi et al.
patent: 5106588 (1992-04-01), Sims et al.
patent: 5185305 (1993-02-01), Subramanian
patent: 5234881 (1993-08-01), Narula et al.
patent: 5345761 (1994-09-01), King et al.
patent: 57-132548 (1982-08-01), None
patent: 1-227815 (1989-09-01), None
Z. Hu, et al. “Hight Temperature Ultra Stable Close-Coupled Catalysts” SAE Technical Paper Series No. 95024, presented Feb. 27, 1995-Mar. 2, 1995.
Ball, D.J. “Warm-Up and Underfloor Parametric Study”, SAE Technical Paper 932765 (1993), pp. 179-189.
Di Mauro Peter
Ford Global Technologies Inc.
Griffin Steven P.
Melotik Lorraine S.
LandOfFree
Palladium catalyst pre-oxidation to reduce light-off... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Palladium catalyst pre-oxidation to reduce light-off..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Palladium catalyst pre-oxidation to reduce light-off... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2579806