Web Release Date: December 22,
Reactivity of the Thermally Stable Intermediates of the Reduction of SO2 on Carbons and Mechanisms of Insertion of Organic Moieties in the Carbon Matrix
and
ndez
Departamento de Química and Departamento de Engenharia Química e Engenharia de Alimentos,
Universidade Federal de Santa Catarina, 88040-670 Florianópolis, SC, Brazil; Departamento de Física,
Universidade Federal do Paran, 81531-970 Curitiba, PR, Brazil; Department of Chemistry, University
College London, 20 Gordon Street, London, WC1H OAJ United Kingdom; and Department of Physical
Chemistry and Chemical Engineering I, University of A Coruña, Rúa Alejandro de la Sota, 1,
E 15008 A Coruña, Spain
Received: August 29, 2007
Abstract:
The reduction of SO2 on carbons proceeds through reactive intermediates bound to the carbon matrix, which
were postulated to be 1,2-oxathiene 2-oxide (or sultine), and 1,3,2-dioxathiolane that decomposes to produce
an episulfide and CO2. The reactivity of these intermediates was studied in this work through several reactions,
using XPS and NMR spectra to postulate their mechanisms. When modified activated carbon obtained after
reaction with SO2 at 630 
C was heated at 900 C, it was observed that the changes of the XPS spectrum
resulted from the forward reaction of decomposition of the oxidized intermediate with S-transfer to produce
the episulfide and CO2 and the reverse reaction with expulsion of SO2. Strong bases hydrolyzed the
dioxathiolane intermediate and the episulfide. The thiolysis, aminolysis, and reaction of alkyl halides with
modified activated carbon occurred with the insertion of the organic moiety in the carbon matrix. Laser
photolysis at 266 nm in t-butanol showed insertion of t-butoxide on the matrix. Consistent mechanisms for
these reactions were postulated. These results provide additional evidence on the mechanism of reduction of
SO2 on carbons and the chemical nature of the intermediates, offering a new method to modify the physical
and chemical properties of a carbon matrix by functionalization with an organic moiety.
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