Infrared spectroscopy and microcalorimetric investigations of .delta.-.theta. and .kappa. aluminas using basic probe molecules: acetonitrile, pyridine, 2,6-lutidine, and n-butylamine

Abstract

An in situ infrared investigation was conducted using four basic adsorbates to identify the acidic sites present onand aluminas. For two adsorbates, pyridine and 2,6-lutidine, adsorption studies were conducted between 298 and 983 K and at adsorbate pressures from 1.33 Pa (Pascal) to 1.33 kPa. The adsorption of acetonitrile and n-butylamine was conducted at 298 K by using adsorbate pressures from 0.66 to 8.65 kPa. Lewis acid and hydrogen-bonded complexes were identified on both aluminas for three adsorbates: acetonitrile, pyridine, and 2,6-lutidine. Using n-butylamine as the probe molecule, complexes for Bronsted, Lewis, and hydrogen-bonded sites were identified onand aluminas. Results from a calorimetric study of the aforementioned adsorbates and adsorbents are also discussed.

Nature of the Ti−Ba Interactions on the BaO/TiO2/Al2O3 NOx Storage System

“…Observed frequencies are in good agreement with the former results presented in the literature that were obtained by adsorbing pyridine on similar oxide systems. [58][59][60][61] These bands can be assigned 58,62 to the υ 15 , υ 9a , υ 19b , υ 19a , υ 8b , two υ 8a , and υ 3 modes of pyridine. Observed IR bands at ca.…”

Key criteria for the design of polymeric stabilizers for aqueous titanium dioxide dispersions of high solid content

“…The pigment used in this study being alumina-coated titanium dioxide, the hydroxyl groups and the Al cations on the surface are the potential sites of adsorption. Therefore, the adsorption is expected to occur first onto the stronger anchoring sites (Al cations) and then on the less energetically favorable sites (OH groups), as reported elsewhere [20,21]. Nevertheless, the question of the availability of these sites to the copolymer must be addressed, because the Al cations lie beneath the hydroxyl groups [22], which makes the adsorption on them very sensitive to steric effects.…”

Molecular Origin of Solvent Resistance of Polyacrylonitrile

“…Multiple vibrational peaks have been reported before between 2100 and 2245 cm -1 for CN bearing compounds. 12 Upon the injection of water, the binodal surface population of CN groups become uniform and only one CN vibrational band is observed at 2237 cm -1 ( Figure 4B). The CN band in contact with water is red-shifted by 1 and 5 cm -1 with respect to the two original bands at 2238 and 2242 cm -1 , respectively.…”

“…The significance of CN frequency shift has been extensively investigated using acetonitrile 7,[12][13][14][15][16] and to a limited extent for PAN. 6,17,18 Blue and red shifts of the nitrile stretching absorption band are possible for both acetonitrile and PAN.…”

“…6,[9][10][11] The current IR assignments and the shifts in the peak positions with environment for CN are available using a small molecule analogue such as acetonitrile. 7,[12][13][14][15][16] The CN infrared stretching vibration band occurs at 2253 cm -1 in acetonitrile liquid, and the position of this band changes from 2253 to 2257 cm -1 upon interaction with various solvents. 15 Much stronger blue shifts have also been reported when CN groups of acetonitrile interact with δ-Al 2 O 3 surfaces (2300 and 2328 cm -1 ).…”