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Multivariate curve resolution analysis applied to time-resolved synchrotron X-ray Absorption Spectroscopy monitoring of the activation of copper alumina catalyst

Paper ID Volume ID Publish Year Pages File Format Full-Text
54118 46997 2014 9 PDF Available
Title
Multivariate curve resolution analysis applied to time-resolved synchrotron X-ray Absorption Spectroscopy monitoring of the activation of copper alumina catalyst
Abstract

•Copper catalyst supported on hierarchical porous alumina with macro-mesoporosity.•Fast in situ acquisitions of the copper catalysts using a Quick-XAS monochromator.•Two-step reduction of Cu(II) to Cu(0) involving a Cu(I) species at 250 °C.•MCR-ALS method applied to time-resolved XAS data of mixtures of components.

The pure X-ray Absorption (XAS) spectral constituents and related concentration profiles characterizing the reduction of a copper-based catalyst supported on hierarchically porous alumina were disentangled from a set of time-resolved Quick-XAS using a Multivariate Curve Resolution-methodology. First, the number of components involved in the data set and the range of existence of intermediate species were determined by Principal Component Analysis (PCA). Then, a Multivariate Curve Resolution with Alternating Least Squares fitting of the set of time-resolved Quick-XANES was performed using the constraints of non-negativity of both absorption and concentration and of closure of concentration. Consideration about the strategy of use of the chemometric methods and robustness regarding the reliability of results for time-resolved XAS data is discussed. The intermediate copper species determined by MCR-ALS is at the monovalent oxidation state and characterized by a local order of 2 oxygen atoms at 1.915 Å. Upon isothermal treatment under 60% H2/He at 250 °C for 30 min, the intermediate species appears quite resistant to complete copper reduction. Copper speciation obtained using MCR-ALS method leads to very different results than those obtained using bulk CuO, Cu2O and metallic Cu as constituents, MCR-ALS concentration profile so-determined being fully consistent with the reducibility of the catalyst measured by TPR.

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Keywords
Time-resolved XAS; MCR-ALS; PCA; Copper speciation
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Multivariate curve resolution analysis applied to time-resolved synchrotron X-ray Absorption Spectroscopy monitoring of the activation of copper alumina catalyst
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 229, 15 June 2014, Pages 114–122
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
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Any Questions? feel free to contact us