Development of bimetallic Pd-Zn catalysts for methanol steam reforming: hydrogen production for fuel cells

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dc.contributor.advisorFletcher, Jacken_ZA
dc.contributor.advisorLuchters, Nielsen_ZA
dc.contributor.advisorMalatji, Peteren_ZA
dc.contributor.authorXalabile, Philasandeen_ZA
dc.date.accessioned2017-05-16T08:01:22Z
dc.date.available2017-05-16T08:01:22Z
dc.date.issued2015en_ZA
dc.description.abstractProton exchange membrane fuel cell (PEMFC) has been reported as clean and efficient energy technology from conversion of H₂. However, one of the main challenges remains the storage and transport of hydrogen. The promising alternative is to produce H₂ on site by a reformer using a H₂-dense liquid as a fuel, a technology known as fuel processing. Methanol is an attractive source of H₂ compared to other fuels as it presents several advantages, i.e. it is obtained sulphur-free, has a high H to C ratio and therefore produces a H₂-rich reformate, can be reformed at low temperatures (200 - 300°C) and is a liquid at ambient conditions so that it can be easily handled. Typically, Cu-based catalysts are used for steam reforming of methanol due to their high activity (i.e. H₂ production) and high selectivity towards CO₂. As CO poisons anodic catalyst of PEMFC, high selectivity towards CO₂ is crucial so as to eliminate or at least minimize CO removal load downstream a fuel processor. However, Cubased catalysts are thermally unstable and suffer deactivation due to sintering at high temperatures (> 250°C). Moreover, Cu-based catalysts are pyrophoric and therefore difficult to handle. Recent studies show that PdZn catalysts are very promising as they exhibit comparable activity and selectivity to Cu-based ones. Furthermore, PdZn catalysts are thermally stable in the typically methanol steam reforming temperature range (200 - 300°C). Most literature attributes high CO₂ selectivity of PdZn catalysts to formation of PdZn alloy. It is generally agreed that PdZn alloy is formed when PdZn catalysts are reduced in H₂ at high temperatures (> 250°C). In this work, a Pd/ZnO catalyst aimed at 2.5 wt% Pd was successfully prepared via incipient wetness impregnation and the duplicate preparation of the catalyst was successful. Both impregnation catalysts were confirmed by ICP-OES to contain similar weight Pd loadings i.e. 2.8 and 2.7 wt%, respectively. The actual Pd loading (ICP-OES) was slightly higher than the target loading (2.5 wt%) due to Pd content of Pd salt underestimated during catalyst preparation. Furthermore, crystallite size distribution, i.e. PdO crystallites on ZnO support, was similar (i.e. 6.7 ± 2.4 nm and 6.3 ± 1.9 nm) for both impregnation catalysts.en_ZA
dc.identifier.apacitationXalabile, P. (2015). <i>Development of bimetallic Pd-Zn catalysts for methanol steam reforming: hydrogen production for fuel cells</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Catalysis Research. Retrieved from http://hdl.handle.net/11427/24325en_ZA
dc.identifier.chicagocitationXalabile, Philasande. <i>"Development of bimetallic Pd-Zn catalysts for methanol steam reforming: hydrogen production for fuel cells."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Catalysis Research, 2015. http://hdl.handle.net/11427/24325en_ZA
dc.identifier.citationXalabile, P. 2015. Development of bimetallic Pd-Zn catalysts for methanol steam reforming: hydrogen production for fuel cells. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Xalabile, Philasande AB - Proton exchange membrane fuel cell (PEMFC) has been reported as clean and efficient energy technology from conversion of H₂. However, one of the main challenges remains the storage and transport of hydrogen. The promising alternative is to produce H₂ on site by a reformer using a H₂-dense liquid as a fuel, a technology known as fuel processing. Methanol is an attractive source of H₂ compared to other fuels as it presents several advantages, i.e. it is obtained sulphur-free, has a high H to C ratio and therefore produces a H₂-rich reformate, can be reformed at low temperatures (200 - 300°C) and is a liquid at ambient conditions so that it can be easily handled. Typically, Cu-based catalysts are used for steam reforming of methanol due to their high activity (i.e. H₂ production) and high selectivity towards CO₂. As CO poisons anodic catalyst of PEMFC, high selectivity towards CO₂ is crucial so as to eliminate or at least minimize CO removal load downstream a fuel processor. However, Cubased catalysts are thermally unstable and suffer deactivation due to sintering at high temperatures (> 250°C). Moreover, Cu-based catalysts are pyrophoric and therefore difficult to handle. Recent studies show that PdZn catalysts are very promising as they exhibit comparable activity and selectivity to Cu-based ones. Furthermore, PdZn catalysts are thermally stable in the typically methanol steam reforming temperature range (200 - 300°C). Most literature attributes high CO₂ selectivity of PdZn catalysts to formation of PdZn alloy. It is generally agreed that PdZn alloy is formed when PdZn catalysts are reduced in H₂ at high temperatures (> 250°C). In this work, a Pd/ZnO catalyst aimed at 2.5 wt% Pd was successfully prepared via incipient wetness impregnation and the duplicate preparation of the catalyst was successful. Both impregnation catalysts were confirmed by ICP-OES to contain similar weight Pd loadings i.e. 2.8 and 2.7 wt%, respectively. The actual Pd loading (ICP-OES) was slightly higher than the target loading (2.5 wt%) due to Pd content of Pd salt underestimated during catalyst preparation. Furthermore, crystallite size distribution, i.e. PdO crystallites on ZnO support, was similar (i.e. 6.7 ± 2.4 nm and 6.3 ± 1.9 nm) for both impregnation catalysts. DA - 2015 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2015 T1 - Development of bimetallic Pd-Zn catalysts for methanol steam reforming: hydrogen production for fuel cells TI - Development of bimetallic Pd-Zn catalysts for methanol steam reforming: hydrogen production for fuel cells UR - http://hdl.handle.net/11427/24325 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/24325
dc.identifier.vancouvercitationXalabile P. Development of bimetallic Pd-Zn catalysts for methanol steam reforming: hydrogen production for fuel cells. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Centre for Catalysis Research, 2015 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/24325en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentCentre for Catalysis Researchen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherCatalysis Researchen_ZA
dc.subject.otherChemical Engineeringen_ZA
dc.titleDevelopment of bimetallic Pd-Zn catalysts for methanol steam reforming: hydrogen production for fuel cellsen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMSc (Eng)en_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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