Mitigation of Sulfur Effects on a Lean NOx Trap Catalyst by Sorbate Reapplication

2007 ◽  
Author(s):  
James E. Parks
Keyword(s):  
Natural Gas ◽  
Catalyst Activity ◽  
Sulfur Poisoning ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Washing Process ◽  
Lean Nox ◽  
The Rich

Lean NOx trap catalysis has demonstrated the ability to reduce NOx emissions from lean natural gas reciprocating engines by >90%. The technology operates in a cyclic fashion where NOx is trapped on the catalyst during lean operation and released and reduced to N2 under rich exhaust conditions; the rich cleansing operation of the cycle is referred to as “regeneration” since the catalyst is reactivated for more NOx trapping. Natural gas combusted over partial oxidation catalysts in the exhaust can be used to obtain the rich exhaust conditions necessary for catalyst regeneration. Thus, the lean NOx trap technology is well suited for lean natural gas engine applications. One potential limitation of the lean NOx trap technology is sulfur poisoning. Sulfur compounds directly bond to the NOx trapping sites of the catalyst and render them ineffective; over time, the sulfur poisoning leads to degradation in overall NOx reduction performance. In order to mitigate the effects of sulfur poisoning, a process has been developed to restore catalyst activity after sulfur poisoning has occurred. The process is an aqueous-based wash process that removes the poisoned sorbate component of the catalyst. A new sorbate component is reapplied after removal of the poisoned sorbate. The process is low cost and does not involve reapplication of precious metal components of the catalyst. Experiments were conducted to investigate the feasibility of the washing process on a lean 8.3-liter natural gas engine on a dynamometer platform. The catalyst was rapidly sulfur poisoned with bottled SO2 gas; then, the catalyst sorbate was washed and reapplied and performance was reevaluated. Results show that the sorbate reapplication process is effective at restoring lost performance due to sulfur poisoning. Specific details relative to the implementation of the process for large stationary natural gas engines will be discussed.

scholarly journals Lean NOx Trap Catalysis for Lean Natural Gas Engine Applications

2007 ◽  
Author(s):  
II, James E Parks ◽  
John Morse Storey ◽  
Timothy J Theiss ◽  
Senthil Ponnusamy ◽  
Harley Douglas Ferguson ◽  
...  
Keyword(s):  
Natural Gas ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Lean Nox

Lean NOx Trap Catalysis for NOx Reduction in Natural Gas Engine Applications

2004 ◽  
Author(s):  
James E. Parks ◽  
H. Douglas Ferguson ◽  
Aaron M. Williams ◽  
John M. E. Storey
Keyword(s):  
Power Generation ◽  
Carbon Monoxide ◽  
Natural Gas ◽  
Nox Reduction ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Reciprocating Engines ◽  
Lean Nox

Reliable power generation and distribution is a critical infrastructure for the public and industry. Large-bore spark-ignited natural gas reciprocating engines are a reliable source of power generation. Lean operation enables efficient operation, and engines can conveniently be placed wherever natural gas resources are located. However, stricter emission regulations may limit the installation and use of more natural gas reciprocating engines if emissions cannot be reduced. Natural gas engine emissions of concern are generally methane, carbon monoxide, and oxides of nitrogen (NOx). Methane and carbon monoxide can be controlled by oxidation catalysts; however NOx emissions are difficult to control in lean exhaust conditions. One method of reducing NOx in lean exhaust conditions is lean NOx trap catalysis. Lean NOx trap technologies (also known as NOx adsorber catalysts, NOx storage and reduction catalysts, etc.) have demonstrated >90% NOx reduction for diesel reciprocating engines and natural gas turbines. In the work presented here, the feasibility of a lean NOx trap catalyst for lean burn natural gas reciprocating engines will be studied. Tests were conducted on a Cummins 8.3-liter engine on a dynamometer. The lean Nox trap catalyst was controlled in a valved exhaust system that utilized natural gas as the catalyst reductant. Oxidation and reformer catalysts were used to enhance utilization of methane for catalyst regeneration. The feasibility of this approach will be discussed based on the observed NOx reduction and associated fuel penalties.

A Temperature-Based Analysis Technique and Distributed Model Lean NOx Trap Catalyst

2006 ◽  
Author(s):  
Shawn Midlam-Mohler ◽  
Yann Guezennec
Keyword(s):  
Chemical Reactions ◽  
Measurement Technique ◽  
Spatial Information ◽  
Sulfur Poisoning ◽  
Distributed Model ◽  
Practical Reasons ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Lean Nox ◽  
The Rich

The management of an automotive Lean NOx Trap (LNT) catalyst requires periodic, brief periods of net rich exhaust to regenerate the catalyst by reducing the stored NOx. During the regeneration event, the fuel rich gas first affects the front of the catalyst then, as reductants are available, reach the downstream sections of the catalyst. In a typical engine test cell, it is not feasible to witness these distributed effects by simultaneously measuring multiple points in a catalyst bed due for a number of practical reasons. This is inconvenient because it is often desired to have a continuous or distributed lump model of the catalyst, which is difficult to calibrate without spatially and temporally resolved measurements. A novel measurement technique is presented which uses internal catalyst temperature measurements to detect the gross chemical reactions occurring in the catalyst during the rich reduction phase. The magnitude of the temperature change is shown to correlate with the mass of NOx and O2 reduced from the catalyst substrate. This information is available at each temperature measurement location, allowing spatial information to be collected non-intrusively. Furthermore, the technique contains temporal information regarding the key reactions. The type of information made available, as well as the convenience of the measurement system, makes the technique useful for a number of applications. The basis of the measurement technique is first presented from a theoretical basis, relating the temperature rise of the substrate to the various gross chemical reactions. Experimental validation of the method is then provided, illustrating the good correlation between the mass of stored NOx and O2 estimated by the method and the mass of stored NOx calculated from traditional gas analyzer measurements during the NOx storage phase. After demonstrating the applicability of the method, several applications are suggested including use of the technique for LNT modeling, LNT regeneration control, and sulfur poisoning detection.

Modelling of a Lean NOx-Trap system with NO/NO2 differentiation and sulfur poisoning

2010 ◽  
Vol 3 (2) ◽  
pp. 414-424 ◽  
Author(s):  
Alexis Manigrasso ◽  
PIerre Darcy ◽  
Patrick Da Costa
Keyword(s):  
Sulfur Poisoning ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Trap System ◽  
Lean Nox

scholarly journals Sulfur Poisoning Effects on Modern Lean NOx Trap Catalysts Components

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 492
Author(s):  
Jesus Emmanuel De Abreu Goes ◽  
Annika Kristoffersson ◽  
Louise Olsson
Keyword(s):  
Flow Reactor ◽  
Sulfur Removal ◽  
Sulfur Poisoning ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
So2 Poisoning ◽  
Lean Nox ◽  
Micro Flow ◽  
Diffuse Reflectance Infrared ◽  
Sulfate Species

In the present work, a series of different materials was investigated in order to enhance the understanding of the role of modern lean NOx trap (LNT) components on the sulfur poisoning and regeneration characteristics. Nine different types of model catalysts were prepared, which mainly consisted of three compounds: (i) Al2O3, (ii) Mg/Al2O3, and (iii) Mg/Ce/Al2O3 mixed with Pt, Pd, and Pt-Pd. A micro flow reactor and a diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) were employed in order to investigate the evolution and stability of the species formed during SO2 poisoning. The results showed that the addition of palladium and magnesium into the LNT formulation can be beneficial for the catalyst desulfation due mainly to the ability to release the sulfur trapped at relatively low temperatures. This was especially evident for Pd/Mg/Al2O3 model catalyst, which demonstrated an efficient LNT desulfation with low H2 consumption. In contrast, the addition of ceria was found to increase the formation of bulk sulfate species during SO2 poisoning, which requires higher temperatures for the sulfur removal. The noble metal nature was also observed to play an important role on the SOx storage and release properties. Monometallic Pd-based catalysts exhibited the formation of surface palladium sulfate species during SO2 exposure, whereas Pt-Pd bimetallic formulations presented higher stability of the sulfur species formed compared to the corresponding Pt- and Pd-monometallic samples.

Natural Gas Partial Oxidation and Reforming for Lean NOx Trap Catalysis Regeneration

2005 ◽  
Author(s):  
James E. Parks ◽  
Jim Tassitano
Keyword(s):  
Natural Gas ◽  
Nox Reduction ◽  
Department Of Energy ◽  
Regeneration Process ◽  
Cyclic Process ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Lean Combustion ◽  
Lean Nox ◽  
Environmental Goals

Program goals for the Advanced Reciprocating Engine Systems (ARES) program of the Department of Energy include efficiency and environmental goals. Lean-burn natural gas engines offer higher efficiency than engines that operate with Stoichiometric air-to-fuel mixtures; however, the excess oxygen in the exhaust of lean engines makes NOx reduction with catalytic aftertreatment difficult. Thus, advancing efficiency via lean combustion results in challenges to meet environmental goals. The lean NOx trap catalyst technology is capable of reducing NOx in lean exhaust and, thereby, enables the potential for lean combustion to meet both efficiency and environmental goals. During lean NOx trap catalysis, NOx in oxygen-rich exhaust is trapped on the catalyst by alkali or alkaline earth-based sorbate materials; then, upon exposure to oxygen-depleted exhaust, the NOx is released and reduced to nitrogen in a process called regeneration. The regeneration process renews the catalyst for more NOx trapping; the cyclic process repeats at periods on the order of a minute. Oxygen depletion during regeneration is accomplished by temporarily operating the catalyst at rich air-to-fuel ratios; traditionally, a variety of methods have been utilized to achieve rich conditions for the catalyst. In this presentation, research of a lean NOx trap on a lean natural gas engine will be presented. Natural gas from the engine supply was used to provide the reductant for the lean NOx trap regeneration process. The natural gas is injected into the exhaust system where oxidation and reforming catalysts partially oxidize and/or reform the natural gas into reductants suitable for lean NOx trap regeneration. Studies of the natural gas oxidation and reforming processes and their relation to NOx reduction performance will be presented.

The Effect of Sulfur on Methane Partial Oxidation and Reforming Processes for Lean NOx Trap Catalysis

2006 ◽  
Author(s):  
James E. Parks ◽  
Senthil Ponnusamy
Keyword(s):  
Partial Oxidation ◽  
Exhaust System ◽  
Catalytic Efficiency ◽  
Methane Partial Oxidation ◽  
Lean Nox Trap ◽  
Nox Trap ◽  
Oxidation Of Methane ◽  
Lean Nox ◽  
The Rich ◽  
Catalyst Poisons

Lean NOx trap catalysts have demonstrated the ability to reduce NOx emissions from lean natural gas reciprocating engines by >90%. The technology operates in a cyclic fashion where NOx is trapped on the catalyst during lean operation and released and reduced to N2 under rich exhaust conditions; the rich cleansing operation of the cycle is referred to as “regeneration” since the catalyst is reactivated for more NOx trapping after NOx purge. Creating the rich exhaust conditions for regeneration can be accomplished by catalytic partial oxidation of methane in the exhaust system. Furthermore, catalytic reforming of partial oxidation exhaust can enable increased quantities of H2 which is an excellent reductant for lean NOx trap regeneration. It is critical to maintain clean and efficient partial oxidation and reforming processes to keep the lean NOx trap functioning properly and to reduce extra fuel consumption from the regeneration process. Although most exhaust constituents do not impede partial oxidation and reforming, some exhaust constituents may negatively affect the catalysts and result in loss of catalytic efficiency. Of particular concern are common catalyst poisons sulfur, zinc, and phosphorous. These poisons form in the exhaust through combustion of fuel and oil, and although they are present at low concentrations, they can accumulate to significant levels over the life of an engine system. In the work presented here, the effects of sulfur on the partial oxidation and reforming catalytic processes were studied to determine any durability limitations on the production of reductants for lean NOx trap catalyst regeneration.

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