Zeolites - Off-Road Engine Emission Treatment and Catalytic Hydrocarbon Cracking
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NOx Conversion Efficiency of Cu-ZSM5 |
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Theoretical model of S6 fragment
of La doped Cu-ZSM5 |
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The traditional catalysts for petrochemical industry include a variety of Zeolites. These zeolites have also been shown to be effective catalysts for Selective Catalytic Reduction of NOx employing urea as a reductant (urea-SCR).
SCR catalyst performance gradually but persistently decreases under operating conditions and several mechanism have been proposed including de-alumination, pore blockage, metal sintering, change of chemical states, acidity change, ammonia storage change, aging, and poisoning by Ca, P, Na, K, and S. A thorough understanding of contribution of each of these pathways to ultimate failure of zeolite catalysts is needed in order to a design a durable catalyst system.
We are exploring these failure mechanisms and synthesizing new zeolites that can withstand harsh reaction environment. We have taken a catalyst by design approach and carried out preliminary theoretical studies to determine the energetically stable structures that can result from cation or skeletal substitution. We are also carrying out theoretical studies of NOx reduction on such modified structure. Experimentally, we are synthesizing new zeolites with such modified structures and testing them for their NOx conversion efficiency as a function of temperature under operating conditions. Furthermore, we are exploring the impact of aging on catalyst performance and structure.
For pertrochemical industry, we are exploring hydrocarbon cracking efficiency of new zeolites that can withstand temperatures higher than 850C. Such zeolites can be expected to undergo multiple regeneration cycles leading to longer cycle life for catalysts.
The financial assistance for this research is provided by DOE-EERE-ITP and C3-International, Oak Ridge, TN and is gratefully acknowledged.
The principal technical contact for this project is Dr. Chaitanya K. Narula, tel. (865) 574-8445, e-mail narulack@ornl.gov.
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