Heats of Adsorption of Polar Molecules on Carbon Surfaces. I. Sulfur Dioxide

Beebe, Ralph A.; Dell, R.M.

doi:10.1021/j150530a015

Cited by 37 publications

(7 citation statements)

References 4 publications

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“…The Q st,n values show a decrease from 53.8 ± 4.0 kJ mol −1 at zero surface coverage to 36.0 ± 0.1 kJ mol −1 at 7 mmol g −1 (see Figure 4). In comparison, the enthalpy of SO 2 vaporization is 24.9 kJ mol −1 at 263 K. Previous studies have reported values for the isosteric enthalpies of adsorption of 34−36.5 kJ mol −1 for pitch-based activated carbon fibers, 36 26.5−35 kJ mol −1 for graphites, 37 28−63 kJ mol −1 for heat-treated carbon blacks, 38 63−42 kJ mol −1 for carbon blacks, 39 and 146 kJ mol −1 at low surface coverage for activated carbon. 39 The higher enthalpy of adsorption at low surface coverage was attributed to surface oxygen species in the carbons, which interact with SO 2 .…”

Section: Co 2 Adsorptionmentioning

confidence: 89%

Adsorption of Carbon Dioxide, Water Vapor, Nitrogen, and Sulfur Dioxide on Activated Carbon for Capture from Flue Gases: Competitive Adsorption and Selectivity Aspects

2021

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There is extensive interest in postcombustion flue gas treatment for mitigating CO2 emissions and removal of acid gases. In this study we investigate the adsorption of the main flue gas components (CO2, N2, SO2, and water vapor) on Filtrasorb 400 activated carbon to understand adsorption characteristics of the main components and competitive adsorption effects. The adsorption isotherms of the pure components of flue gas, CO2 (273.15–318.15 K and 0–50 bar), N2 (298.15–313.15 K and 0–150 bar), SO2 (273.15–303.15 K and 0–3.6 bar), and water vapor (293.15–303.15 K and 0–41 mbar), were investigated. The isosteric enthalpies of adsorption were determined to be a function of surface excess. The enthalpies at zero surface coverage have the order SO2 > H2O > CO2 > N2. However, the SO2 isosteric enthalpy decreases with increasing surface excess and is lower than that of water vapor at high surface excess uptake values. The temperature range for CO2 adsorption covers the subcritical to supercritical gas transition. There was no evidence for isosteric enthalpy differences over this temperature range. The adsorption kinetics for SO2 (290.65–303.15 K) and H2O (293.15–303.15 K) adsorption were measured for each isotherm pressure increment. In both cases the adsorption kinetics followed the linear driving force model. The adsorption mechanisms for both SO2 and H2O kinetic trends are discussed in terms of the adsorption mechanisms. The water vapor adsorption kinetics showed a minimum in the region where water molecules form clusters around functional groups, which merge in the pores. The SO2 adsorption kinetics also show a minimum with increasing surface coverage, and this is attributed to dipole–dipole interactions. The activation energies for diffusion of both SO2 and H2O into F400 were very low. Both the N2 and CO2 adsorption kinetics were too fast to be measured accurately by the gravimetric method used in this study. Ideal adsorbed solution theory (IAST) was used to calculate competitive adsorption of SO2/CO2 and CO2/N2 from the isotherms of the pure components. The competitive adsorption of CO2/N2 was investigated by using the integral mass balance (IMB) experimental method, and this was used for validation of the IAST. The results provide an insight into the role of competitive adsorption in the capture of CO2 and SO2 from flue gases by adsorption from both thermodynamic and kinetic perspectives.

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Section: Co 2 Adsorptionmentioning

confidence: 89%

Adsorption of Carbon Dioxide, Water Vapor, Nitrogen, and Sulfur Dioxide on Activated Carbon for Capture from Flue Gases: Competitive Adsorption and Selectivity Aspects

2021

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“…In studying the enthalpy of adsorption of SO 2 on the surface of a graphitized carbon black, Beebe and Dell (63) found that removal of surface oxygen complexes resulted in a sharp decrease in the amount of sulfur dioxide adsorbed at 0 • C. Davini (64) came to a similar conclusion, finding that oxygen-containing surface basic groups enhanced SO 2 chemisorption at 25 • C. Other authors have found contradictory results, however, when the carrier gas used contained O 2 and H 2 O. Using activated carbon fibers, Daley et al (65) found that the presence of oxygen functional groups decreased SO 2 adsorption capacity from a gas mixture containing 5% O 2 , 7% H 2 O, and 2500 ppm SO 2 .…”

Section: Effect Of Somentioning

confidence: 99%

Understanding the effects of sulfur on mercury capture from coal-fired utility flue gases

Morris

Morita

Jia

2010

Journal of Sulfur Chemistry

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Coal combustion continues to be a major source of energy throughout the world and is the leading contributor to anthropogenic mercury emissions. Effective control of these emissions requires a good understanding of how other flue gas constituents such as sulfur dioxide (SO 2 ) and sulfur trioxide (SO 3 ) may interfere in the removal process. Most of the current literature suggests that SO 2 hinders elemental mercury (Hg 0 ) oxidation by scavenging oxidizing species such as chlorine (Cl 2 ) and reduces the overall efficiency of mercury capture, while there is evidence to suggest that SO 2 with oxygen (O 2 ) enhances Hg 0 oxidation by promoting Cl 2 formation below 100 • C. However, studies in which SO 2 was shown to have a positive correlation with Hg 0 oxidation in full-scale utilities indicate that these interactions may be heavily dependent on operating conditions, particularly chlorine content of the coal and temperature. While bench-scale studies explicitly targeting SO 3 are scarce, the general consensus among full-scale coal-fired utilities is that its presence in flue gas has a strong negative correlation with mercury capture efficiency. The exact reason behind this observed correlation is not completely clear, however. While SO 3 is an inevitable product of SO 2 oxidation by O 2 , a reaction that hinders Hg 0 oxidation, it readily reacts with water vapor, forms sulfuric acid (H 2 SO 4 ) at the surface of carbon, and physically blocks active sites of carbon. On the other hand, H 2 SO 4 on carbon surfaces may increase mercury capacity either through the creation of oxidation sites on the carbon surface or through a direct reaction of mercury with the acid. However, neither of these beneficial impacts is expected to be of practical significance for an activated carbon injection system in a real coal-fired utility flue gas.

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“…Direct calorimetry can provide useful information on the states of molecules adsorbed. [10][11][12] Hence, there has been active calorimetric research on micropore filling recently. [13][14][15][16][17][18][19][20][21][22][23][24][25][26] Also, newly developed computer simulation studies need calorimetric data on micropore filling of various kinds of molecules.…”

Section: Introductionmentioning

confidence: 99%

“…Micropore filling has been studied extensively over the last 30 years. − However, the relationship between the mechanism of micropore filling and molecular states upon micropore filling is not sufficiently elucidated. Direct calorimetry can provide useful information on the states of molecules adsorbed. − Hence, there has been active calorimetric research on micropore filling recently. − Also, newly developed computer simulation studies need calorimetric data on micropore filling of various kinds of molecules. − …”

Section: Introductionmentioning

confidence: 99%

Effect of Pore Width on Micropore Filling Mechanism of SO₂ in Carbon Micropores

and

Kaneko

1998

J. Phys. Chem. B

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The mechanism of SO 2 micropore filling in slit-shaped micropores was examined by direct calorimetry and potential calculation, and the effect of the pore width on the SO 2 micropore filling mechanism is discussed. Four kinds of activated carbon fibers of different pore widths have been used, and both granular activated carbon and microporous Boehmite aggregates were used for comparison. The differential energy of SO 2 adsorption (q d ) on ACFs varied with change of the average pore width. An increase of the micropore width leads to a decrease of q d in SO 2 micropore filling by decreasing the enhanced micropore field. Molecular potential calculations gave good agreement with the experimental adsorption energy when the image potential due to the SO 2 dipole moment was considered. The image potential contributes 25-32% to the total molecular potential, indicating its importance in micropore filling of dipolar SO 2 .

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Heats of Adsorption of Polar Molecules on Carbon Surfaces. I. Sulfur Dioxide

Cited by 37 publications

References 4 publications

Adsorption of Carbon Dioxide, Water Vapor, Nitrogen, and Sulfur Dioxide on Activated Carbon for Capture from Flue Gases: Competitive Adsorption and Selectivity Aspects

Adsorption of Carbon Dioxide, Water Vapor, Nitrogen, and Sulfur Dioxide on Activated Carbon for Capture from Flue Gases: Competitive Adsorption and Selectivity Aspects

Understanding the effects of sulfur on mercury capture from coal-fired utility flue gases

Effect of Pore Width on Micropore Filling Mechanism of SO₂ in Carbon Micropores

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Heats of Adsorption of Polar Molecules on Carbon Surfaces. I. Sulfur Dioxide

Cited by 37 publications

References 4 publications

Adsorption of Carbon Dioxide, Water Vapor, Nitrogen, and Sulfur Dioxide on Activated Carbon for Capture from Flue Gases: Competitive Adsorption and Selectivity Aspects

Adsorption of Carbon Dioxide, Water Vapor, Nitrogen, and Sulfur Dioxide on Activated Carbon for Capture from Flue Gases: Competitive Adsorption and Selectivity Aspects

Understanding the effects of sulfur on mercury capture from coal-fired utility flue gases

Effect of Pore Width on Micropore Filling Mechanism of SO2 in Carbon Micropores

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Effect of Pore Width on Micropore Filling Mechanism of SO₂ in Carbon Micropores