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Title: A Comprehensive Study of Surface Chemistry for Application to Engine NOx Aftertreatment

Abstract

This work focuses on developing a scientific understanding of the processes associated with NO{sub x} trap operation. NO{sub x} traps are the most advanced technology for achieving future emissions standards with diesel engines. Successful development of NO{sub x} traps will allow widespread use of diesel engines in light-duty vehicles, reducing oil imports by as much as 60%. Diesel engines have a high efficiency and low maintenance that makes them the ideal choice for transportation applications. Use of diesel engines in all light-duty vehicles would reduce oil consumption in the USA by 30% and oil imports by 60%, considerably improving our energy security. For heavy trucks, there is no viable alternative to diesel engines. Only diesel engines can provide the necessary high efficiency and long life. These benefits are offset by high emission of pollutants. Diesel engines have high emissions of NO{sub x} and particulate matter. Over the last 20 years, EPA has been reducing allowable emissions from diesel engines, and NO{sub x} emissions are scheduled to be cut by a factor of 10 over the next 7 years. The target NO{sub x} emissions for year 2010 is 0.20 g/hp-hr. This value is well below 1 g/hp-hr, which has been identifiedmore » by one of the authors (Pitz [1]) as the minimum possible NO{sub x} emissions that can be obtained in a diesel engine with satisfactory combustion and without exhaust aftertreatment. An 80% efficient aftertreatment system is therefore necessary for achieving the 2010 NO{sub x} emissions regulation. Achieving this level of diesel aftertreatment efficiency is a daunting task, and one that will require a strong research effort. Manufacturing diesel after treatment systems with 80% efficiency for model year 2010 is an extremely difficult task. Our advanced analysis tools (computational chemistry linked with fluid mechanics and heat transfer) can be used to analyze and optimize NO{sub x} traps, which are the system of choice for diesel engine aftertreatment. NO{sub x} adsorbing catalysts operate by adsorbing the NO{sub x} in the exhaust stream during regular engine operation. After a period of time (1 minute), the catalyst saturates and has to be regenerated. Regeneration is achieved by injecting a reductant (typically fuel, although hydrogen or ammonia can also be used) into the catalyst. The adsorbed NO{sub x} desorbs under rich conditions, and then reacts with the reductant, producing molecular nitrogen, water and carbon dioxide. The regeneration cycle typically lasts about 2 seconds. After the regeneration cycle, the catalyst is ready for a new adsorption cycle. Intermittent regeneration of the catalytic surfaces is a complex process, and much of the basic science behind this process is not understood. Unsolved scientific problems include the development of chemical kinetic mechanisms for surface chemistry; the analysis of sulfur poisoning of the catalyst surfaces and the phenomenon of thermal aging of the catalyst materials. The adsorption and regeneration processes are dependent on gaseous flow rate, surface chemical kinetics and converter geometry. A comprehensive study of this process is of great importance to achieve the desired system efficiency for NO{sub x} reduction. The possibilities and future market opportunities are enormous. This project supports the DOE mission by improving national security through reduced dependence on foreign oil. This work also provides an opportunity for enhancing our surface chemistry analysis capabilities, which have great applicability to missile reentry, fuel cells, and sensors for chemical warfare agents and explosives detection. In addition to this, we will help the US industry remain competitive and will help clean up the environment.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15009793
Report Number(s):
UCRL-TR-202462
TRN: US200430%%1314
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 19 Feb 2004
Country of Publication:
United States
Language:
English
Subject:
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE; 08 HYDROGEN; 29 ENERGY PLANNING, POLICY AND ECONOMY; 30 DIRECT ENERGY CONVERSION; 33 ADVANCED PROPULSION SYSTEMS; ADSORPTION; AMMONIA; CARBON DIOXIDE; CHEMICAL WARFARE AGENTS; CHEMISTRY; DIESEL ENGINES; ENGINES; EXPLOSIVES; FLOW RATE; FLUID MECHANICS; FUEL CELLS; HEAT TRANSFER; HYDROGEN; NATIONAL SECURITY; NITROGEN; PARTICULATES; POLLUTANTS; SECURITY; US EPA

Citation Formats

Aceves, S M, Piggot, T, Pitz, W, Mundy, C, Kuo, W, and Havstad, M. A Comprehensive Study of Surface Chemistry for Application to Engine NOx Aftertreatment. United States: N. p., 2004. Web. doi:10.2172/15009793.
Aceves, S M, Piggot, T, Pitz, W, Mundy, C, Kuo, W, & Havstad, M. A Comprehensive Study of Surface Chemistry for Application to Engine NOx Aftertreatment. United States. https://doi.org/10.2172/15009793
Aceves, S M, Piggot, T, Pitz, W, Mundy, C, Kuo, W, and Havstad, M. 2004. "A Comprehensive Study of Surface Chemistry for Application to Engine NOx Aftertreatment". United States. https://doi.org/10.2172/15009793. https://www.osti.gov/servlets/purl/15009793.
@article{osti_15009793,
title = {A Comprehensive Study of Surface Chemistry for Application to Engine NOx Aftertreatment},
author = {Aceves, S M and Piggot, T and Pitz, W and Mundy, C and Kuo, W and Havstad, M},
abstractNote = {This work focuses on developing a scientific understanding of the processes associated with NO{sub x} trap operation. NO{sub x} traps are the most advanced technology for achieving future emissions standards with diesel engines. Successful development of NO{sub x} traps will allow widespread use of diesel engines in light-duty vehicles, reducing oil imports by as much as 60%. Diesel engines have a high efficiency and low maintenance that makes them the ideal choice for transportation applications. Use of diesel engines in all light-duty vehicles would reduce oil consumption in the USA by 30% and oil imports by 60%, considerably improving our energy security. For heavy trucks, there is no viable alternative to diesel engines. Only diesel engines can provide the necessary high efficiency and long life. These benefits are offset by high emission of pollutants. Diesel engines have high emissions of NO{sub x} and particulate matter. Over the last 20 years, EPA has been reducing allowable emissions from diesel engines, and NO{sub x} emissions are scheduled to be cut by a factor of 10 over the next 7 years. The target NO{sub x} emissions for year 2010 is 0.20 g/hp-hr. This value is well below 1 g/hp-hr, which has been identified by one of the authors (Pitz [1]) as the minimum possible NO{sub x} emissions that can be obtained in a diesel engine with satisfactory combustion and without exhaust aftertreatment. An 80% efficient aftertreatment system is therefore necessary for achieving the 2010 NO{sub x} emissions regulation. Achieving this level of diesel aftertreatment efficiency is a daunting task, and one that will require a strong research effort. Manufacturing diesel after treatment systems with 80% efficiency for model year 2010 is an extremely difficult task. Our advanced analysis tools (computational chemistry linked with fluid mechanics and heat transfer) can be used to analyze and optimize NO{sub x} traps, which are the system of choice for diesel engine aftertreatment. NO{sub x} adsorbing catalysts operate by adsorbing the NO{sub x} in the exhaust stream during regular engine operation. After a period of time (1 minute), the catalyst saturates and has to be regenerated. Regeneration is achieved by injecting a reductant (typically fuel, although hydrogen or ammonia can also be used) into the catalyst. The adsorbed NO{sub x} desorbs under rich conditions, and then reacts with the reductant, producing molecular nitrogen, water and carbon dioxide. The regeneration cycle typically lasts about 2 seconds. After the regeneration cycle, the catalyst is ready for a new adsorption cycle. Intermittent regeneration of the catalytic surfaces is a complex process, and much of the basic science behind this process is not understood. Unsolved scientific problems include the development of chemical kinetic mechanisms for surface chemistry; the analysis of sulfur poisoning of the catalyst surfaces and the phenomenon of thermal aging of the catalyst materials. The adsorption and regeneration processes are dependent on gaseous flow rate, surface chemical kinetics and converter geometry. A comprehensive study of this process is of great importance to achieve the desired system efficiency for NO{sub x} reduction. The possibilities and future market opportunities are enormous. This project supports the DOE mission by improving national security through reduced dependence on foreign oil. This work also provides an opportunity for enhancing our surface chemistry analysis capabilities, which have great applicability to missile reentry, fuel cells, and sensors for chemical warfare agents and explosives detection. In addition to this, we will help the US industry remain competitive and will help clean up the environment.},
doi = {10.2172/15009793},
url = {https://www.osti.gov/biblio/15009793}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Feb 19 00:00:00 EST 2004},
month = {Thu Feb 19 00:00:00 EST 2004}
}