Chemistry: analytical and immunological testing – Testing of catalyst
Reexamination Certificate
2001-03-09
2004-04-27
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Testing of catalyst
C436S155000, C436S159000
Reexamination Certificate
active
06727097
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus useful for evaluation of catalysts. More particularly, the present invention is directed to simulating poisoning and deactivating catalysts with catalyst poison compounds at least one catalyst poison compound selected from the group consisting of a compound comprising phosphorous, a compound comprising zinc compound and a compound comprising phosphorous and zinc.
2. Description of the Related Art
The art discloses that additives such as lubricants used in internal combustion engine oils can contain compounds which contain phosphorous and/or zinc. Such compounds include materials such as zinc dialkyldithiophosphate also referred to as zinc dithiophosphate (ZDTP) and zinc dithiocarbamate (ZDTC). Other disclosed zinc and phosphorous additives to oil include metallic detergents including phosphorares and phosphorous compounds included as extreme pressure agents. Reference is made to U.S. Pat. Nos. 4,674,447 and 5,696,065 and European Application No. 95309415. The phosphorous and zinc are disclosed to lower the function of the motor vehicle exhaust treatment catalyst.
As engine technology and exhaust gas treatment technology has improved engines pass less lubricating oil, including phosphorous and zinc compound to the catalysts and the catalysts have been sufficiently active to treat exhaust gases in accordance with various government regulations. However, as engine performance continues to increase and environmental regulations become more stringent catalysts activity will have to be increased and maintained with longer engine life. As engine life increases there will be a greater build up of compounds, particularly phosphorous and/or zinc compounds passing to the emission treatment catalyst from the engine. It is desirable to have a method to simulate the poisoning of the catalyst poisoning and deactivation in the laboratory for different engine systems run at different conditions to for various reasons including to more rapidly screen new catalysts.
Numerous methods have been used in the past to simulate long term deactivation of a catalyst, using an engine bench test. Most of these methods involve running an engine at very high speed and load conditions cyclically for several hours, often creating a large exotherm in the catalyst bed during certain portions of the test cycle. These adverse conditions deactivate the catalytic converter, and a correlation is drawn between this type of rapid aging cycle and on-road deactivation of the emission control system in general, and catalytic converter, in particular. While such correlations can be developed, they do not always mimic the actual deactivation modes, such as poison accumulation.
References such as U.S. Pat. No. 4,771,029 disclose the ad recognition of catalyst poisoning by materials such as phosphorous. U.S. Pat. No. 4,727,746 discloses a modal mass analysis method for simulating driving conditions for evaluating exhaust gases.
Ueda et al.,
Engine Oil Additive Effects on Deactivation of Monolithic Three
-
Way Catalysts and Oxygen Sensors
, SAE, SP-1043, 1994, discloses that it is widely known that ZDTP results in phosphorous poisoning of three-way emissions catalysts. Catalysts and oxygen sensors were “poisoned” on the engine bench by test oils, varying the quantity of phosphorous and ash. The performance of the catalysts and sensors was evaluated using a FTP test on a chassis dynamometer. It was found that calcium and magnesium helped prevent the phosphorous from adhering to the catalyst.
Joy et al.,
The Influence of Sulfur Species on the Laboratory Performance of Automotive Three Component Control Catalysts
, SAE, 1979, discloses that poisons such as phosphorous and sulfur poison catalysts. Studies were done in the laboratory on the effects of sulfur dioxide.
Baba et al.,
Numerical Simulation of Deactivation Process of Three
-
way Catalytic Converters
, SAE, SP-1533, Mar. 6, 2000, discloses a numerical simulation method to predict the deactivation process of three-way catalytic converters. Based on simulated results of the deactivated state inside the bench aged catalysts, which are noble metal particle size and catalyst activity distributions, thermal responses and light-off behaviors during warm-up tests are predicted.
Natoli et al.,
Three
-
way Catalyst Deactivation by Lubricants During Fast Aging Engine Tests
, Gionale ed Atti della Associazione Technica dell'Automobile, Vol. 48, No. 12, p 685, 1995 discloses that engine lubricants play an important role in poisoning three-way catalytic converters. The objective was to reproduce in the laboratory the aging of the catalysts under accelerated conditions in order to evaluate the influence of additive contained in engine oils.
Ball et al.,
Application of accelerated Rapid Aging Test
(
RAT
)
Schedules with Poison: The Effects of Oil Derived Poisons, Thermal Degradation and catalyst Volume on FTP Emissions
, SAE, SP-1296, 43-53, 1997 discloses dynamometer rapid aging tests incorporate both thermal and oil-derived poison degradation are used to age catalysts for FTP emissions studies. Vehicle aged converters are analyzed to determine the axial aged phosphorous distribution throughout the catalyst. These profiles are compared to dynamometer aged RAT aged catalysts.
Other references of interest include: Carol et al.,
High temperature Deactivation of Three
-
way Catalyst
, SAE, 1989; Pattas et al.,
Computer Aided Assessment of Catalyst Aging Cycles
, SAE, 1995. Beck et al.,
Impact of Oil
-
derived Catalyst Poisons on FTP Performance of LEV Catalyst Systems
, SAE, SP-1296, 1-10, 1997. Jobson et al.,
Deterioration of Three
-
way Automotive Catalysts
, SAE, SP-957, 153-66, 1993; and Williamson et al.,
Effects of Oil Phosphorous on Deactivation of Monolithic Three
-
way Catalysts
, Appl. Catal. (1985), 15(2), 277-92.
SUMMARY OF THE INVENTION
Automotive catalytic converters and filters comprise at least one catalyst composition. Such catalyst compositions are susceptible to poisoning due to lubricant oil—derived phosphorus, zinc, sulfur and other compounds. Catalyst compositions (referred to as “catalysts”) can be coated on to a suitable substrate. The coated catalyst when applied to the substrate in a slurry or liquid form is also referred to as a “washcoat”. The poisons may accumulate on the surface of the washcoat, creating a physical barrier, or they may interact with the catalytic material in the washcoat, resulting in loss of catalytic activity, and/or become a barrier to particulate filters such as foam, screens and wallflow filters. The poison level and type can vary, depending upon the design of the engine and the operating conditions. In the development of the emission control system, it is critical to know the type of poison a exposure and the impact of poison on the emissions control system in general, and the catalytic converter, in particular.
The present invention relates to a method and apparatus that effectively duplicates these poisoning conditions in a laboratory environment. In addition, the invention relates to a method and apparatus that duplicates, on an engine test stand, the equivalent of extended on road-type poison exposure, deposition and catalyst deactivation and/or filter clogging.
It is generally known that lubricant-derived phosphorus, zinc and sulfur can accumulate on the catalyst surface and result in deactivation. This poisoning mechanism is quite complex, and highly dependent upon the operating temperature, the oil consumption of the engine, and the source of the oil consumption. For example, when oil leaks past the piston rings, and washes into the combustion chamber, it goes through the combustion process. This will result in certain types of phosphorus and/or zinc compounds (among other contaminants). Particular compounds may have a certain type of deactivation effect on the catalytic converter, depending upon the operating condition. On the other hand, oil that leaks past the exhaust valve guide and stem, may not go thr
Kumar Sanath V.
Rogalo James
Engelhard Corporation
Negin Richard A.
Soderquist Arlen
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