Reaction Mechanism for the Formation of Nitrogen Oxides (NO x ) During Coke Oxidation in Fluidized Catalytic Cracking Units

Handle URI:
http://hdl.handle.net/10754/594116
Title:
Reaction Mechanism for the Formation of Nitrogen Oxides (NO x ) During Coke Oxidation in Fluidized Catalytic Cracking Units
Authors:
Chaparala, Sree Vidya; Raj, Abhijeet; Chung, Suk-Ho ( 0000-0001-8782-312X )
Abstract:
Fluidized catalytic cracking (FCC) units in refineries process heavy feedstock obtained from crude oil distillation. While cracking feed, catalysts get deactivated due to coke deposition. During catalyst regeneration by burning coke in air, nitrogen oxides (NOx) are formed. The increase in nitrogen content in feed over time has resulted in increased NOx emissions. To predict NOx concentration in flue gas, a reliable model for FCC regenerators is needed that requires comprehensive understanding and accurate kinetics for NOx formation. Based on the nitrogen-containing functional groups on coke, model molecules are selected to study reactions between coke-bound nitrogen and O2 to form NO and NO2 using density functional theory. The reaction kinetics for the proposed pathways are evaluated using transition state theory. It is observed that the addition of O2 on coke is favored only when the free radical is present on the carbon atom instead of nitrogen atom. Thus, NOx formation during coke oxidation does not result from the direct attack by O2 on N atoms of coke, but from the transfer of an O atom to N from a neighboring site. The low activation energies required for NO formation indicate that it is more likely to form than NO2 during coke oxidation. The favorable pathways for NOx formation that can be used in FCC models are identified. Copyright © 2015 Taylor & Francis Group, LLC.
KAUST Department:
Clean Combustion Research Center
Citation:
Chaparala SV, Raj A, Chung SH (2015) Reaction Mechanism for the Formation of Nitrogen Oxides (NO x ) During Coke Oxidation in Fluidized Catalytic Cracking Units . Combustion Science and Technology 187: 1683–1704. Available: http://dx.doi.org/10.1080/00102202.2015.1059328.
Publisher:
Informa UK Limited
Journal:
Combustion Science and Technology
Issue Date:
11-Jun-2015
DOI:
10.1080/00102202.2015.1059328
Type:
Article
ISSN:
0010-2202; 1563-521X
Sponsors:
KAUST, King Abdullah University of Science and Technology
Appears in Collections:
Articles; Clean Combustion Research Center

Full metadata record

DC FieldValue Language
dc.contributor.authorChaparala, Sree Vidyaen
dc.contributor.authorRaj, Abhijeeten
dc.contributor.authorChung, Suk-Hoen
dc.date.accessioned2016-01-19T13:21:59Zen
dc.date.available2016-01-19T13:21:59Zen
dc.date.issued2015-06-11en
dc.identifier.citationChaparala SV, Raj A, Chung SH (2015) Reaction Mechanism for the Formation of Nitrogen Oxides (NO x ) During Coke Oxidation in Fluidized Catalytic Cracking Units . Combustion Science and Technology 187: 1683–1704. Available: http://dx.doi.org/10.1080/00102202.2015.1059328.en
dc.identifier.issn0010-2202en
dc.identifier.issn1563-521Xen
dc.identifier.doi10.1080/00102202.2015.1059328en
dc.identifier.urihttp://hdl.handle.net/10754/594116en
dc.description.abstractFluidized catalytic cracking (FCC) units in refineries process heavy feedstock obtained from crude oil distillation. While cracking feed, catalysts get deactivated due to coke deposition. During catalyst regeneration by burning coke in air, nitrogen oxides (NOx) are formed. The increase in nitrogen content in feed over time has resulted in increased NOx emissions. To predict NOx concentration in flue gas, a reliable model for FCC regenerators is needed that requires comprehensive understanding and accurate kinetics for NOx formation. Based on the nitrogen-containing functional groups on coke, model molecules are selected to study reactions between coke-bound nitrogen and O2 to form NO and NO2 using density functional theory. The reaction kinetics for the proposed pathways are evaluated using transition state theory. It is observed that the addition of O2 on coke is favored only when the free radical is present on the carbon atom instead of nitrogen atom. Thus, NOx formation during coke oxidation does not result from the direct attack by O2 on N atoms of coke, but from the transfer of an O atom to N from a neighboring site. The low activation energies required for NO formation indicate that it is more likely to form than NO2 during coke oxidation. The favorable pathways for NOx formation that can be used in FCC models are identified. Copyright © 2015 Taylor & Francis Group, LLC.en
dc.description.sponsorshipKAUST, King Abdullah University of Science and Technologyen
dc.publisherInforma UK Limiteden
dc.subjectCoke oxidationen
dc.subjectDensity functional theoryen
dc.subjectNOxen
dc.subjectReaction kineticsen
dc.titleReaction Mechanism for the Formation of Nitrogen Oxides (NO x ) During Coke Oxidation in Fluidized Catalytic Cracking Unitsen
dc.typeArticleen
dc.contributor.departmentClean Combustion Research Centeren
dc.identifier.journalCombustion Science and Technologyen
dc.contributor.institutionDepartment of Chemical Engineering, Petroleum Institute, P.O. Box 2533, Abu Dhabi, United Arab Emiratesen
kaust.authorChung, Suk-Hoen
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