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Chemical looping capabilities of olivine, used as a catalyst in indirect biomass gasification

Paper ID Volume ID Publish Year Pages File Format Full-Text
45324 46409 2014 7 PDF Available
Title
Chemical looping capabilities of olivine, used as a catalyst in indirect biomass gasification
Abstract

Indirect biomass gasification systems consist of two reactors: an oxidation reactor and a gasification reactor. A bed-material is used to transfer heat from the oxidation to the gasification reactor. Olivine has been widely studied as a reactive bed-material for this process. The iron in olivine can act as a catalyst for the decomposition of tars, produced during the gasification process. Moreover, iron is capable of transferring oxygen to the gasification reactor. In this study, we elucidate the role of iron in this chemical looping process. Mössbauer spectra show that during oxidation in O2/Ar at 750 °C, iron segregates out of the olivine matrix forming free iron oxide phases. These free iron phases form metallic iron upon subsequent reduction in hydrogen. Thermo gravimetric analysis (TGA) is used to quantify oxygen transport under alternating oxidizing/reducing conditions. TGA results indicate that at least 18% of all the iron, present in olivine, is capable of transferring oxygen on the time scale of minutes. X-ray photoelectron spectroscopy (XPS) combined with depth profiling provides insight in the dynamic behavior of olivine under relevant conditions. Iron enrichment at the surface is observed; oxidized olivine has an iron rich surface layer of 400 nm. The increased iron concentration is particularly pronounced at the outermost surface. Upon subsequent reduction, the iron quickly redistributes in the olivine toward the original, homogeneous distribution. These results show that oxygen transport should be taken into account when olivine is evaluated as a catalyst for indirect biomass gasification. Furthermore, both oxygen transport and catalytic properties are heavily dependent on the iron phases present in the material, which in turn depend on the gas environment.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Dynamic behavior of olivine is studied at relevant conditions. ► Mössbauer spectroscopy showed different iron distributions. ► Thermo gravimetric analysis is presented as a tool to quantify oxygen transport. ► XPS depth profiling provided insight in the dynamic behavior of olivine.

Keywords
Olivine; Biomass gasification; Chemical looping; Oxygen transport; Thermo gravimetric analysis
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Chemical looping capabilities of olivine, used as a catalyst in indirect biomass gasification
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 145, February 2014, Pages 216–222
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