Title
Structural and acidic properties of copper silica catalysts .1. a differential scanning calorimetry and fourier transform-infrared photoacoustic study
Author
Faculty/Department
Faculty of Sciences. Chemistry
Publication type
article
Publication
Amsterdam ,
Subject
Chemistry
Source (journal)
Colloids and surfaces: A: physicochemical and engineering aspects. - Amsterdam
Volume/pages
96(1995) :3 , p. 253-260
ISSN
0927-7757
ISI
A1995QR62100004
Carrier
E
Target language
English (eng)
Abstract
Adsorption of pyridine on copper-silica catalysts is studied by differential scanning calorimetry (DSC) and Fourier transform-infrared/photoacoustic spectroscopy (FT-IR/PA), in the region of mid-frequency vibrations as well as in the region of hydroxyl groups. The adsorption of pyridine on copper-silica catalysts shows three modes of sorption in the 1650-1400 cm(-1) region: physisorption or hydrogen-bonded (HPY), and two sites of Lewis acid sorption (LPY(I) and LPY(II)). The Lewis band at 1609 cm(-1) was very strong compared with the 1450 cm(-1) band since the former band showed a shift to higher wavenumbers whereas the latter showed a shift to lower wavenumbers. A relationship was found between the DSC scans, in the low temperature range (240-140 degrees C), and the 1450-1443 cm(-1) band. On the other hand, the high temperature DSC scans (400-360 degrees C) were correlated with the behaviour of the 1609-1612 cm(-1) band. The volumetric results of pyridine adsorption on 9 and 15 wt.% Cu catalysts show a constant behaviour; however, this constancy was also reflected by carbon monoxide adsorption, demonstrated by a similar behaviour of both 2128 and 2259 cm(-1) bands. This was attributed to the blocking of the small pores of silica earlier at the 9 wt.% Cu loading. A new broad band at 2248-2259 cm(-1), not identified in the ion-exchange catalysts, was obtained and attributed to CO adsorbed on agglomerated copper clusters.
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