Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging

Structural modifications of Cu/ZnO catalysts for methanol steam reforming (MSR) have been investigated as a function of precipitate aging in the catalyst preparation process. Freshly precipitated Cu,Zn-hydroxycarbonate precursor (HC) and Cu,Zn-hydroxynitrate precursor (HN) were aged in their moth...

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Main Author:	Muhamad, Ernee Noryana
Format:	Thesis
Language:	English English
Published:	2006
Subjects:	Copper catalysts - Structure-activity relationships Catalysts
Online Access:	http://psasir.upm.edu.my/id/eprint/115/1/FS_2006_4a.pdf
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spelling	my-upm-ir.1152013-05-27T06:45:39Z Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging 2006-02 Muhamad, Ernee Noryana Structural modifications of Cu/ZnO catalysts for methanol steam reforming (MSR) have been investigated as a function of precipitate aging in the catalyst preparation process. Freshly precipitated Cu,Zn-hydroxycarbonate precursor (HC) and Cu,Zn-hydroxynitrate precursor (HN) were aged in their mother liquor for 120 min followed by washing, drying, calcination and reduction. The characteristics of the precursors before and after aging were determined by means of TG/MS, XRD, and SEM. Generally, more pronounced aging effect was observed for HC precursor (reference catalyst) while no significant effect of aging was observed for HN precursor. In order to determine the microstructural changes as a function of aging, the bulk structure of the Cu/ZnO catalysts was investigated by in-situ XRD, XAS, 63Cu NMR and HRTEM. The observed increase in the activity of the catalysts prepared by HC aging iv coincides with a decrease in copper crystallite size (i.e. an increase in Cu surface area) and an increase in the microstrain in the copper clusters presumably because of the improved interface between Cu and ZnO in comparison to the HN prepared catalysts. Aging of the HN precursors results in large, separated and less strained Cu and ZnO particle with an inferior catalytic activity compared to aging of the HC precursors. An increase in catalytic activity of HN and HC was observed significantly after temporary addition of oxygen was done to the feed mixture. The higher catalytic activity does not correlate with an increase in copper surface area, microstrain or oxygen in copper cluster (Cu-EXAFS), but due to slight changes of the catalyst in the medium range order of Cu and ZnO in XAS analysis. Furthermore, the HRTEM and 63Cu NMR investigations revealed that the copper particles get more sintered resulting in less interfacial contact of Cu to ZnO as was observed after the O2 pulse. Based on these comparative investigations, a structural model of the active catalyst as a function of aging was proposed for the HN preparative route Copper catalysts - Structure-activity relationships Catalysts 2006-02 Thesis http://psasir.upm.edu.my/id/eprint/115/ http://psasir.upm.edu.my/id/eprint/115/1/FS_2006_4a.pdf application/pdf en public masters Universiti Putra Malaysia Copper catalysts - Structure-activity relationships Catalysts Faculty of Science English
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English English
topic	Copper catalysts - Structure-activity relationships Catalysts
spellingShingle	Copper catalysts - Structure-activity relationships Catalysts Muhamad, Ernee Noryana Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging
description	Structural modifications of Cu/ZnO catalysts for methanol steam reforming (MSR) have been investigated as a function of precipitate aging in the catalyst preparation process. Freshly precipitated Cu,Zn-hydroxycarbonate precursor (HC) and Cu,Zn-hydroxynitrate precursor (HN) were aged in their mother liquor for 120 min followed by washing, drying, calcination and reduction. The characteristics of the precursors before and after aging were determined by means of TG/MS, XRD, and SEM. Generally, more pronounced aging effect was observed for HC precursor (reference catalyst) while no significant effect of aging was observed for HN precursor. In order to determine the microstructural changes as a function of aging, the bulk structure of the Cu/ZnO catalysts was investigated by in-situ XRD, XAS, 63Cu NMR and HRTEM. The observed increase in the activity of the catalysts prepared by HC aging iv coincides with a decrease in copper crystallite size (i.e. an increase in Cu surface area) and an increase in the microstrain in the copper clusters presumably because of the improved interface between Cu and ZnO in comparison to the HN prepared catalysts. Aging of the HN precursors results in large, separated and less strained Cu and ZnO particle with an inferior catalytic activity compared to aging of the HC precursors. An increase in catalytic activity of HN and HC was observed significantly after temporary addition of oxygen was done to the feed mixture. The higher catalytic activity does not correlate with an increase in copper surface area, microstrain or oxygen in copper cluster (Cu-EXAFS), but due to slight changes of the catalyst in the medium range order of Cu and ZnO in XAS analysis. Furthermore, the HRTEM and 63Cu NMR investigations revealed that the copper particles get more sintered resulting in less interfacial contact of Cu to ZnO as was observed after the O2 pulse. Based on these comparative investigations, a structural model of the active catalyst as a function of aging was proposed for the HN preparative route
format	Thesis
qualification_level	Master's degree
author	Muhamad, Ernee Noryana
author_facet	Muhamad, Ernee Noryana
author_sort	Muhamad, Ernee Noryana
title	Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging
title_short	Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging
title_full	Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging
title_fullStr	Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging
title_full_unstemmed	Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging
title_sort	structure-activity correlations of cu/zno catalysts derived from different precursors as a function of aging
granting_institution	Universiti Putra Malaysia
granting_department	Faculty of Science
publishDate	2006
url	http://psasir.upm.edu.my/id/eprint/115/1/FS_2006_4a.pdf
_version_	1747810140518612992

Structure-Activity Correlations of Cu/Zno Catalysts Derived from Different Precursors as a Function of Aging

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