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Quantitative analysis of infrared spectra of adsorbed species using transmission and diffuse reflectance modes: Case study: Heats of adsorption of CO on TiO2 and CuO/Al2O3

Paper ID Volume ID Publish Year Pages File Format Full-Text
42391 45923 2009 9 PDF Available
Title
Quantitative analysis of infrared spectra of adsorbed species using transmission and diffuse reflectance modes: Case study: Heats of adsorption of CO on TiO2 and CuO/Al2O3
Abstract

IR spectroscopy in transmission and in diffuse reflectance modes is used to characterize the adsorbed CO species formed during the adsorption of CO on (a) a TiO2 solid and (b) a partially reduced CuO/Al2O3 solid. The experiments consist studying the evolution of the intensities of the characteristic IR bands with the adsorption temperature Ta at a constant adsorption pressure Pa. For the two IR analytical procedures, the spectra are used to measure the heats of adsorption of the adsorbed CO species on the two solids according to the AEIR procedure previously described using the IR transmission mode. This allows us to fix the experimental conditions allowing a quantitative analysis of the IR spectra recorded in diffuse reflectance. Mainly, it is shown that the relative reflectance at the position of the characteristic IR bands of the adsorbed CO species must be higher than a critical value during the measurements. According to the amount of adsorbed species, this can be achieved by the dilution of the catalyst with another material that does not contribute to the experimental data. In the present study, it is shown that TiO2 and CuO/Al2O3 can be used without and with dilution respectively. For the Cu/Al2O3 catalyst, the alumina support has been used for the dilution whereas KBr that exhibits acceptable optical properties leads to a significant modification of the heats of adsorption of the adsorbed CO species. This study suggests that heats of adsorption of adsorbed species formed on catalysts of low IR transmission can be determined by the AEIR method using the diffuse reflectance mode. This offers a way to extend the application of quantitative analysis of IR spectra of adsorbed species (i.e. AEIR method) to solid of low IR transmission in particular the industrial catalysts.

Graphical abstractThe heats of adsorption of linearly adsorbed CO species on TiO2 and CuO/Al2O3 are determined from the evolutions of their coverages with the adsorption temperature Ta in isobar conditions using either diffuse reflectance or transmission FTIR spectra.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Quantitative DRIFT; Transmission FTIR; Coverage; Heat of adsorption
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Quantitative analysis of infrared spectra of adsorbed species using transmission and diffuse reflectance modes: Case study: Heats of adsorption of CO on TiO2 and CuO/Al2O3
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 371, Issues 1–2, 15 December 2009, Pages 99–107
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