Study of MgO transformation into MgF2 in the presence of CF2Cl2

Alkaline-earth metal oxide aerogels prepared by sol?gel method followed by autoclave drying are nanocrystalline mesoporous materials with high reactivity. Bulk solid-state reaction of MgO aerogels with CF2Cl2 takes place after a long induction period, during which the active sites are accumulated on...

Full description

Saved in:
Bibliographic Details
Published in:Journal of the Serbian Chemical Society 2017, Vol.82 (5), p.523-538
Main Authors: Vedyagin, Aleksey, Bedilo, Alexander, Mishakov, Ilya, Shuvarakova, Ekaterina
Format: Article
Language:English
Subjects:
acid sites
Aerogels
Autoclaving
Chemisorption
Chlorine
destructive sorption
Electron paramagnetic resonance
Electron spin
Electrons
Fluorine
freon-12
Hafnium
Lewis acid
Magnesium oxide
Sol-gel processes
spin probe
Spin resonance
vanadium
Citations: Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Alkaline-earth metal oxide aerogels prepared by sol?gel method followed by autoclave drying are nanocrystalline mesoporous materials with high reactivity. Bulk solid-state reaction of MgO aerogels with CF2Cl2 takes place after a long induction period, during which the active sites are accumulated on the surface of the nanoparticles. It was found that vanadium addition has a promoting effect on this reaction accelerating the process of the active sites formation. A method for characterization of electron-acceptor sites by electron spin resonance spectroscopy using perylene as the spin probe was developed. A good correlation was observed between the rate of the CF2Cl2 destructive sorption and the concentration of weak electron-acceptor sites. Simplified models of such sites were suggested. The acid sites on the modified MgO surface were supposed to be originated from separation of the charged fragments resulting in the surface polarization. Uncompensated oxygen substitution for chlorine and/or fluorine ions leads to appearance of Lewis acid sites while HCl/HF chemisorption results in Bronsted acid sites formation. nema
ISSN:0352-5139
1820-7421
DOI:10.2298/JSC161020037V