Chemisorption of SO2 on graphite surface: A theoretical ab initio and ideal lattice gas model study

Surface‐science studies of some reactions have allowed postulating the mechanisms using a variety of techniques. The surface chemistry of Group IV elements has been particularly studied recently because Si, Ge, and C are semiconductors, and the surface organic chemistry to functionalize these elements has seen immense progress in recent years. In this review article we describe the methodology used to study the mechanism of a solid–gas reaction, the reduction of SO2 on carbons, and the necessary conditions that allowed the measurement of the solid conversion and product distribution when the kinetics was chemically controlled and the reaction had reached the steady state. The reaction was first‐order with respect to SO2 and with respect to carbon and the stoichiometry was determined from the product distribution. The reaction proceeds through two thermally stable reaction intermediates bound to the surface, a six‐membered ring 1,3,2‐dioxathiolane and a five‐membered ring 1,2‐oxathietene 2‐oxide or γ‐sultine, both species being in equilibrium. The reaction was shown to be reversible. The primary product is an episulfide that, after a series of consecutive reactions of atomic sulfur, is able to free sulfur. The reactivity of the intermediates and the episulfide was studied for several reactions and consistent mechanisms were postulated from the X‐ray photoelectron spectroscopy and solid state nuclear magnetic resonance spectra. Aminolysis and the reaction with alkyl halides resulted on the insertion of the alkyl moiety in the episulfide primary product, while the thiolysis and photolytic alcoholysis resulted in the insertion of the alkyl moiety in the oxidized intermediates. Copyright © 2012 John Wiley & Sons, Ltd.

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“…), in agreement with the XPS spectrum where the ratio non‐oxidized : oxidized sulfur was 1.2 (Fig. ) …”

Section: Mechanismsupporting

confidence: 88%

“…A theoretical study of the chemisorption process of SO 2 on the graphite surface showed two possible adsorption sites. The adsorption on the zigzag edge was the most favorable, with energies of −61 to −100 kcal mol –1 .…”

Section: Mechanismmentioning

confidence: 99%

Kinetics and mechanisms in flow systems: reduction of SO₂ on carbons

Humeres

Moreira

2012

J of Physical Organic Chem

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“…Theoretical calculations supported the assumption that the reduction proceeds through 1 and 2 (in equilibrium because at 900 o C ∆G o = 1–2 kcal mol −1 ) inserted mainly on a biradical zigzag edge shown in Scheme . First‐principles calculations on graphene sheets functionalized with episulfide and thiol groups confirm that sulfur‐containing groups present in sulfur–graphite nanocomposites are attached mainly to the edges of graphite …”

Section: Introductionmentioning

confidence: 64%

Reactivity of the intermediates of the reduction of SO2. Functionalization of graphite, graphite oxide and graphene oxide

Humeres

Castro

Smaniotto

et al. 2014

J of Physical Organic Chem

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dGraphite particles (0.505 mm) were oxidized to graphite oxide with KClO3 in a H 2 SO 4 /HNO 3 mixture. Graphite and graphite oxide particles were modified by reaction with SO 2 at 630°C. Thiolysis with sodium dodecane-1-thiolate and aminolysis with dodecane-1-amine of these particles occurred with the insertion of the organic moiety in the carbon matrix. Graphite microparticles (6.20 μm) were oxidized by H 2 SO 4 / KMnO 4 / H 2 O 2 mixture and were exfoliated to graphene oxide sheets (MPGO). MPGO was modified by reaction with SO 2 at 630°C. The modified MPGO was refluxed in DMSO with dodecane-1-thiol, dodecane-1-amine, and hexadecane-1-bromide. The reactions occurred with the insertion of the organic moiety in the carbon matrix, according to the X-ray photoelectron and nuclear magnetic resonance spectra. Mechanisms for the reactions were postulated using the atom inventory technique. Despite the structural differences, graphite, graphite oxide, and graphene oxide present the same selectivity for aminolysis and thiolysis reactions, with respect to the oxidized and non-oxidized intermediates of the reduction of SO 2 , as was found for the activated carbon.

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“…MPGO presented only non-oxidized sulfur before the reaction, and after the thiolysis performed refluxing in DMSO (200°C), the interconversion to oxidized intermediates was observed. [19] Interconversion of the intermediates during thermal treatment is plausible SO 2 because according to the theoretical calculations [5] and experimental results [18] , the primary product episulfide is more stable than the oxidized intermediates, and the energetic barrier, as shown in this work, is only 25.81 kcal mol…”

Section: Selective Insertion Of the Intermediates By Thermal Modificamentioning

confidence: 88%

“…The study of (C + SO 2 ) reaction on different carbons (graphite, charcoal, activated carbon, cokes, and graphene oxide (MPGO)) showed that the reaction proceeds through the same stoichiometry for all carbons (Eqn 1), while the reactivity increases with decreasing crystallinity and increasing oxygen content. [1][2][3][4] SO 2 þ C→ CO 2 þ 1 = 2 S 2 (1) Experimental data obtained from SO 2 reduction on carbons along with theoretical calculations [5] allowed a detailed description of the primary reaction ( Fig. 1), where the diradical zigzag fragment represents the site of insertion of SO 2 in the carbon matrix.…”

Section: Introductionmentioning

confidence: 99%

Interconversion and selective reactivity of sulfur dioxide reduction intermediates inserted on graphene oxide

Smaniotto

Humeres

Debacher

et al. 2016

J of Physical Organic Chem

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Graphene oxide, MPGO, was obtained by oxidation of graphite microparticles by a H 2 SO 4 /KMnO 4 /H 2 O 2 mixture followed by thermal exfoliation. Non-thermal plasma treatment of MPGO under SO 2 atmosphere resulted in the insertion of the oxidized intermediates only. Refluxing this material in CS 2 (46°C) showed sulfur elimination and interconversion of the oxidized into non-oxidized intermediates with an energetic barrier of ΔG ‡ = 25.81 kcal mol À1 without decarboxylation. The episulfide content in modified MPGO increases with respect to the oxidized intermediates when increasing temperature. Modification of MPGO with SO 2 at 630°C presented exclusively the non-oxidized intermediate. These results support the hypothesis that there are two major reactions with different energetic demand in the SO 2 reduction on carbons: desulfurization and decarboxylation. The selectivity of thiolysis and aminolysis towards the intermediates inserted in the MPGO matrix allowed the aminothiolysis of a sample containing both intermediates with the insertion of the amino group on the episulfide site followed by an intramolecular thiolysis with double functionalization of the matrix.

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Chemisorption of SO2 on graphite surface: A theoretical ab initio and ideal lattice gas model study

Cited by 44 publications

References 22 publications

Kinetics and mechanisms in flow systems: reduction of SO₂ on carbons

Kinetics and mechanisms in flow systems: reduction of SO₂ on carbons

Reactivity of the intermediates of the reduction of SO2. Functionalization of graphite, graphite oxide and graphene oxide

Interconversion and selective reactivity of sulfur dioxide reduction intermediates inserted on graphene oxide

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Chemisorption of SO2 on graphite surface: A theoretical ab initio and ideal lattice gas model study

Cited by 44 publications

References 22 publications

Kinetics and mechanisms in flow systems: reduction of SO2 on carbons

Kinetics and mechanisms in flow systems: reduction of SO2 on carbons

Reactivity of the intermediates of the reduction of SO2. Functionalization of graphite, graphite oxide and graphene oxide

Interconversion and selective reactivity of sulfur dioxide reduction intermediates inserted on graphene oxide

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Kinetics and mechanisms in flow systems: reduction of SO₂ on carbons

Kinetics and mechanisms in flow systems: reduction of SO₂ on carbons