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Title: Surface structure of crystalline and amorphous chromia catalysts for the selective catalytic reduction of nitric oxide. 2. Diffuse reflectance FTIR study of thermal treatment and oxygen adsorption

Abstract

The activation of crystalline and amorphous chromia surfaces by thermal pretreatment in argon and oxygen adsorption at 473 K has been studied by diffuse reflectance FTIR and Raman spectroscopy. The formation of coordinatively unsaturated chromium sites during thermal activation is monitored by observing the evolution of Cr{double bond}O stretching absorptions both in the fundamental and overtone regions of the FTIR spectrum. On {alpha}-Cr{sub 2}O{sub 3}, labile surface oxygen species are largely removed at 498 K, whereas on the amorphous chromia surface, labile oxygen is more tightly bound. As a consequence, coordinatively unsaturated chromium sites are generated on amorphous chromia to a lesser extent than on {alpha}-Cr{sub 2}O{sub 3}. Upon high-temperature oxygen treatment, O{sub 2} is dissociatively adsorbed. Coordinatively unsaturated sites are occupied by the added oxygen, as manifested by an increase in the number of Cr{double bond}O oscillators. Fine structure in the Cr{double bond}O absorptions of the amorphous chromia is observed for the first time, and is tentatively assigned to various types of surface sites. Raman spectroscopic characterization of the amorphous chromia surface reveals laser-induced dehydration and creation of coordinatively unsaturated surface Cr{double bond}O sites, accompanied by progressive crystallization of the amorphous substrate. Differences between crystalline and amorphous chromia withmore » respect to their SCR activity are correlated with the higher density of labile oxygen species available on the surface of amorphous chromia under SCR reaction conditions (423-473 K).« less

Authors:
;  [1]; ;  [2]
  1. Univ. of Bayreuth (Germany)
  2. Swiss Federal Inst. of Tech., Zuerich (Switzerland)
Publication Date:
OSTI Identifier:
7160306
Resource Type:
Journal Article
Journal Name:
Journal of Catalysis; (United States)
Additional Journal Information:
Journal Volume: 133:2; Journal ID: ISSN 0021-9517
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 01 COAL, LIGNITE, AND PEAT; 36 MATERIALS SCIENCE; CHROMIUM OXIDES; CATALYTIC EFFECTS; MORPHOLOGY; NITRIC OXIDE; SELECTIVE CATALYTIC REDUCTION; ABSORPTION SPECTROSCOPY; ADSORPTION; AMMONIA; AMORPHOUS STATE; ARGON; CATALYSTS; CHEMICAL ACTIVATION; CHEMICAL BONDS; CHEMICAL REACTIONS; COMPARATIVE EVALUATIONS; CRYSTAL STRUCTURE; FOURIER TRANSFORMATION; HEAT TREATMENTS; INFRARED RADIATION; OXYGEN; PH VALUE; RAMAN SPECTROSCOPY; SURFACE PROPERTIES; CHALCOGENIDES; CHROMIUM COMPOUNDS; DENITRIFICATION; ELECTROMAGNETIC RADIATION; ELEMENTS; EVALUATION; FLUIDS; GASES; HYDRIDES; HYDROGEN COMPOUNDS; INTEGRAL TRANSFORMATIONS; LASER SPECTROSCOPY; NITROGEN COMPOUNDS; NITROGEN HYDRIDES; NITROGEN OXIDES; NONMETALS; OXIDES; OXYGEN COMPOUNDS; RADIATIONS; RARE GASES; REDUCTION; SORPTION; SPECTROSCOPY; TRANSFORMATIONS; TRANSITION ELEMENT COMPOUNDS; 540120* - Environment, Atmospheric- Chemicals Monitoring & Transport- (1990-); 010800 - Coal, Lignite, & Peat- Waste Management; 360602 - Other Materials- Structure & Phase Studies

Citation Formats

Schraml-Marth, M, Wokaun, A, Curry-Hyde, H E, and Baiker, A. Surface structure of crystalline and amorphous chromia catalysts for the selective catalytic reduction of nitric oxide. 2. Diffuse reflectance FTIR study of thermal treatment and oxygen adsorption. United States: N. p., 1992. Web. doi:10.1016/0021-9517(92)90250-L.
Schraml-Marth, M, Wokaun, A, Curry-Hyde, H E, & Baiker, A. Surface structure of crystalline and amorphous chromia catalysts for the selective catalytic reduction of nitric oxide. 2. Diffuse reflectance FTIR study of thermal treatment and oxygen adsorption. United States. https://doi.org/10.1016/0021-9517(92)90250-L
Schraml-Marth, M, Wokaun, A, Curry-Hyde, H E, and Baiker, A. Sat . "Surface structure of crystalline and amorphous chromia catalysts for the selective catalytic reduction of nitric oxide. 2. Diffuse reflectance FTIR study of thermal treatment and oxygen adsorption". United States. https://doi.org/10.1016/0021-9517(92)90250-L.
@article{osti_7160306,
title = {Surface structure of crystalline and amorphous chromia catalysts for the selective catalytic reduction of nitric oxide. 2. Diffuse reflectance FTIR study of thermal treatment and oxygen adsorption},
author = {Schraml-Marth, M and Wokaun, A and Curry-Hyde, H E and Baiker, A},
abstractNote = {The activation of crystalline and amorphous chromia surfaces by thermal pretreatment in argon and oxygen adsorption at 473 K has been studied by diffuse reflectance FTIR and Raman spectroscopy. The formation of coordinatively unsaturated chromium sites during thermal activation is monitored by observing the evolution of Cr{double bond}O stretching absorptions both in the fundamental and overtone regions of the FTIR spectrum. On {alpha}-Cr{sub 2}O{sub 3}, labile surface oxygen species are largely removed at 498 K, whereas on the amorphous chromia surface, labile oxygen is more tightly bound. As a consequence, coordinatively unsaturated chromium sites are generated on amorphous chromia to a lesser extent than on {alpha}-Cr{sub 2}O{sub 3}. Upon high-temperature oxygen treatment, O{sub 2} is dissociatively adsorbed. Coordinatively unsaturated sites are occupied by the added oxygen, as manifested by an increase in the number of Cr{double bond}O oscillators. Fine structure in the Cr{double bond}O absorptions of the amorphous chromia is observed for the first time, and is tentatively assigned to various types of surface sites. Raman spectroscopic characterization of the amorphous chromia surface reveals laser-induced dehydration and creation of coordinatively unsaturated surface Cr{double bond}O sites, accompanied by progressive crystallization of the amorphous substrate. Differences between crystalline and amorphous chromia with respect to their SCR activity are correlated with the higher density of labile oxygen species available on the surface of amorphous chromia under SCR reaction conditions (423-473 K).},
doi = {10.1016/0021-9517(92)90250-L},
url = {https://www.osti.gov/biblio/7160306}, journal = {Journal of Catalysis; (United States)},
issn = {0021-9517},
number = ,
volume = 133:2,
place = {United States},
year = {1992},
month = {2}
}