Finding an optimum surface chemistry for [Formula] systems as NOx storage materials

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buir.advisorÖzensoy, Emrah
dc.contributor.authorŞentürk, Göksu Seda
dc.date.accessioned2016-01-08T18:12:51Z
dc.date.available2016-01-08T18:12:51Z
dc.date.issued2010
dc.departmentDepartment of Chemistryen_US
dc.descriptionAnkara : The Department of Chemistry and the Institute of Engineering and Sciences of Bilkent University, 2010.en_US
dc.descriptionThesis (Master's) -- Bilkent University, 2010.en_US
dc.descriptionIncludes bibliographical references.en_US
dc.description.abstractTitania promoted NOx storage materials in the form of BaO/TiO2/Al2O3 were synthesized via two different sol-gel preparation techniques, with varying surface compositions and morphologies [1, 2]. The influence of the TiO2 units on the NOx storage component (8 - 20 wt. % BaO), the nature of the crystallographic phases, thermal stabilities and the dispersion of the surface oxide/nitrate domains were investigated. The structural characterization of the synthesized NOx storage materials were analyzed by means of BET surface area analysis, X-ray diffraction (XRD), ex-situ Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X- ray (EDX) and transmission electron microscopy (TEM). Comparative analysis of the results showed that the TiO2/Al2O3 support material derived by the co-precipitation of the corresponding hydroxides via the sol-gel technique, exhibited distinctively more homogenous distribution of TiO2 domains. The functionality/performance of these materials upon NOx and SOx adsorptions were monitored by temperature programmed desorption (TPD) and insitu Fourier transform infrared (FTIR) spectroscopy. An improved Ba surface dispersion was observed for the BaO/TiO2/Al2O3 materials synthesized via the coprecipitation of alkoxide precursors which was found to originate mostly from the increased fraction of accessible TiO2/TiOx sites on the surface. These TiO2/TiOx sites functioned as strong anchoring sites for surface BaO domains and were tailored to enhance surface dispersion of BaO. The relative stability of the NOx species adsorbed on the BaO/TiO2/Al2O3 system was found to increase in the following order: NO+ /N2O3 on alumina << nitrates on alumina < surface nitrates on BaO < bridged/bidentate nitrates on large/isolated TiO2 clusters < bulk nitrates on BaO on alumina surface and bridged/bidentate nitrates on TiO2 crystallites homogenously distributed on the surface < bulk nitrates on the BaO sites located on the TiO2 domains. The detailed study of the interaction of SOx with BaO/TiO2/Al2O3 ternary oxide materials showed that titania (TiO2) was a promising candidate for improving the sulfur tolerance on these type of surfaces. Adsorption of SOx on both pure Al2O3 and TiO2 showed that Al2O3 formed strongly bound SOx species, that were thermally stable up to T > 1073 K. SOx adsorption directly altered stability of the nitrate species on the Ti/Al (Protocol 1, Protocol 2) samples. SOx uptake properties of the BaO/TiO2/Al2O3 materials were found to be strongly influenced by the morphology of the TiO2/TiOx domains and the BaO loadings (8/20 wt% BaO). Consequently, the presence of titania domains was seen to decrease the SOx desorption temperatures and enhance the sulfur-tolerance of these materials by destabilizing the accumulated sulfate species. SOx exposure on the synthesized materials led to a significant decrease in the NOx adsorption capacities. The results obtained from FT-IR spectra showed that the sulfur deposition on the NOx storage materials promoted by Tien_US
dc.description.degreeM.S.en_US
dc.description.provenanceMade available in DSpace on 2016-01-08T18:12:51Z (GMT). No. of bitstreams: 1 0004034.pdf: 3553193 bytes, checksum: aff370d99caeb6b4abebb8524533724e (MD5)en
dc.description.statementofresponsibilityŞentürk, Göksu Sedaen_US
dc.format.extentxx, 130 leaves, illustrationsen_US
dc.identifier.itemidB122594
dc.identifier.urihttp://hdl.handle.net/11693/15072
dc.language.isoEnglishen_US
dc.publisherBilkent Universityen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectNOx storage materialsen_US
dc.subjectNSRen_US
dc.subjectLEANOXen_US
dc.subjectBaOen_US
dc.subjectAl2O3en_US
dc.subjectTiO2en_US
dc.subjectAnataseen_US
dc.subjectRutileen_US
dc.subjectBaTiO3en_US
dc.subjectSulfur poisoningen_US
dc.subjectDeNOxen_US
dc.subjectNO2en_US
dc.subjectSOxen_US
dc.subjectFTIRen_US
dc.subjectTPDen_US
dc.subject.lccQD181.N1 S45 2010en_US
dc.subject.lcshNitrogen oxides--Absorption and adsorption.en_US
dc.subject.lcshOxidation.en_US
dc.subject.lcshSurface chemistry.en_US
dc.subject.lcshSurfaces (Technology)--Analysis.en_US
dc.titleFinding an optimum surface chemistry for [Formula] systems as NOx storage materialsen_US
dc.typeThesisen_US

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