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Sulfur release from a model Pt/Al2O3 diesel oxidation catalyst: Temperature-programmed and step-response techniques characterization

Paper ID Volume ID Publish Year Pages File Format Full-Text
42013 45907 2010 10 PDF Available
Title
Sulfur release from a model Pt/Al2O3 diesel oxidation catalyst: Temperature-programmed and step-response techniques characterization
Abstract

The S release, or desulfation process, of a model Pt/Al2O3 diesel oxidation catalyst (DOC) was investigated using temperature-programmed techniques and step-response methods. During the temperature-programmed experiments, the sulfur loading, H2 concentration and gas composition, in terms of H2O and/or CO2 presence, were systematically investigated. The results show that desulfation is promoted as the gas environment changes from oxidizing to inert and then to reducing conditions. Compared to CO, H2 is more active in a dry environment, and the presence of H2O further promotes the desulfation while CO2 has no obvious effect. Changing the H2 concentration influences the desulfation products, with higher H2 concentrations generating larger amounts of H2S. The data indicate that the desulfation process can be viewed as a stepwise reduction of sulfates to SO2 and then to H2S. Meanwhile, the sulfur loading also affects the SO2/H2S ratio due to the distribution of the sulfur species, and a relatively medium sulfur loading (equivalent to 3 g/L) yields the largest SO2/H2S ratio. The results of the step-response methods show that the desulfation process has a low kinetic dependence on H2. Furthermore, the apparent reaction order with respect to sulfur is temperature dependent, and decreases with increasing temperature. These results suggest that desulfation is mass-transfer limited by the diffusion of sulfur species to the active Pt sites or hydrogen tot he sulfur sites. The apparent activation energy for desulfation was initially 59.1 kJ/mol, but decreased as more S was released to 39.0 kJ/mol due to mass-transfer limitation.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (97 K)Download as PowerPoint slideResearch highlights▶ S release from Pt/Al2O3 is inhibited by O2. ▶ S release from Pt/Al2O3 has a low, positive dependency on H2.▶ S release from Pt/Al2O3 is surface diffusion controlled at high temperature.

Keywords
Desulfation kinetics; Diesel oxidation catalyst (DOC); Sulfur poisoning; NOx emissions
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Sulfur release from a model Pt/Al2O3 diesel oxidation catalyst: Temperature-programmed and step-response techniques characterization
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 383, Issues 1–2, 31 July 2010, Pages 182–191
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us