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Pd/Ga2O3 methanol steam reforming catalysts: Part II. Catalytic selectivity

Paper ID Volume ID Publish Year Pages File Format Full-Text
43134 45956 2009 8 PDF Available
Title
Pd/Ga2O3 methanol steam reforming catalysts: Part II. Catalytic selectivity
Abstract

Structure, morphology and composition of two Pd/Ga2O3 methanol steam reforming catalysts were correlated with the associated activity and selectivity changes in the methanol steam reforming reaction and linked to studies on pure Ga2O3 supports. For both systems, that are, a Pd/Ga2O3 thin film model catalyst and a powder-supported Pd catalyst, we identified a temperature range in which the reduction with hydrogen yields a single Pd–Ga bimetallic on a reduced oxide support, which in turn suppresses methanol dehydrogenation and results in a high CO2 selectivity in methanol steam reforming. For the thin film catalyst, this included the Pd5Ga2 bimetallic present after reduction in the temperature range 523–600 K, for the powder-supported catalyst, Pd2Ga, formed after reduction between 523 and 773 K, was found to account for the high CO2 selectivity. In contrast to studies on the corresponding Pd/ZnO catalysts, sintering and metal decoration by reduced GaOx species will additionally have to be considered for discussions about structure–activity correlations in Pd/Ga2O3 thin film model catalysts. Reduction at 673 K causes catalyst deactivation and loss of CO2 selectivity due to encapsulation of catalytically active bimetallic particles by mobile GaOx species and hampers oxidative catalyst regeneration. No such behaviour has been observed for the powder-supported catalyst. This difference in catalytic activity and selectivity between the two catalysts is interpreted in terms of their different (bi-)metallic–oxide contact areas.Formic acid formation has been observed on pure Ga2O3 supports, which yields additional CO by formic acid decarbonylation. For the CO2-selective methanol steam reforming reaction over a Pd–Ga bimetallic particle, formic acid is not a gas phase species, which indicates a preferential decarboxylation pathway of adsorbed formate species at low temperatures.

Graphical abstractActivity and selectivity changes in methanol steam reforming are linked to structure, morphology and composition of different Pd/Ga2O3 methanol steam reforming catalysts and correlated with studies on pure Ga2O3 supports. A temperature range in which the reduction with hydrogen yields a single Pd–Ga bimetallic on a reduced oxide support was identified, which in turn suppresses methanol dehydrogenation and results in a high CO2 selectivity in methanol steam reforming.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Catalysis; CO2 selectivity; Methanol dehydrogenation; CO; Ga2O3; Reduction; Pd–Ga alloys; Formic acid
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Pd/Ga2O3 methanol steam reforming catalysts: Part II. Catalytic selectivity
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 358, Issue 2, 1 May 2009, Pages 203–210
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