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Zhang H.,Kunming University of Science and Technology | Cen W.,University of Sichuan | Cen W.,National Engineering Technology Research Center for Flue Gas Desulfurization | Liu J.,Chengdu University of Information Technology | And 6 more authors.
Applied Surface Science | Year: 2015

Carbon materials have been used for low temperature (20-150 °C) catalytic removal of SO2 from the coal-burned flue gases for a long time, but the mechanism at atomic level is still controversial. Density functional theory was used to investigate the adsorption and oxidation of SO2 on elaborated graphene oxides (GOs) to discover the insights. It is found that the hydroxyl groups on GO surface possess bi-functional effects: both enhancing the adsorption of SO2 through H-bonding interaction and reducing the reaction barrier for its oxidation to SO3. The promotion of oxidation is related to a pre-activation of the surface epoxy group. Based on Bader population, charge difference and electron localization function analysis, a charge transfer channel is proposed to explain the pre-activation. © 2014 Elsevier B.V. All rights reserved. Source


Liu Y.,University of Sichuan | Liu Y.,National Engineering Technology Research Center for Flue Gas Desulfurization | Gong M.,University of Sichuan | Fan W.,University of Sichuan | And 4 more authors.
Recent Innovations in Chemical Engineering | Year: 2014

Surface-modified activated carbon fibers (ACFs) with nitrogen-containing groups were prepared by the heat treatment of ACFs with urea, and characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetry (TG). The removal activity of the samples was also tested at an SO2 concentration of 22800 mg/Nm3. The results showed that the surface-modified ACFs significantly improved the SO2-removal ability compared to the unmodified ones. The amount of C=O and the nitrogen-containing groups on the surface of the N-modified ACFs increased, resulting in improved SO2-removal ability. The sample prepared with a urea concentration of 0.15 g/ml showed the best SO2-removal performance. © 2014 Bentham Science Publishers Source


Qu Y.-F.,University of Sichuan | Guo J.-X.,University of Sichuan | Guo J.-X.,National Engineering Technology Research Center for Flue Gas Desulfurization | Chu Y.-H.,University of Sichuan | And 4 more authors.
Applied Surface Science | Year: 2013

Using Mn(NO3)2 as precursor, a series of Mn-based activated carbon catalysts were prepared by ultrasound-assisted excessive impregnation method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The influences of Mn species and nitric acid pretreatment on the removal role of SO2 were investigated. MnO and Mn3O4 coexist in catalysts calcined at 650 and 800 C and exhibit best SO2 removal ability, whereas Mn2O3 formed in the catalyst calcined at 500 C and shows poor activity. After treatment by nitric acid, the CO of activated carbon support increases and the crystal size of MnO decreases, resulting in the enhancement of the catalytic activity. During reaction process, manganese oxides are gradually transferred into MnO2. And this change directly results in a decrease of activity. But the SO2 removal rate has been maintained in the range of 30-40%, indicating that MnO2 still has a certain SO2 removal ability. © 2013 Elsevier B.V. All rights reserved. Source


Shu S.,University of Sichuan | Guo J.-X.,University of Sichuan | Guo J.-X.,National Engineering Technology Research Center for Flue Gas Desulfurization | Guo J.-X.,Sichuan Prov Environmental Protect Environmental Catalysis And Materials Engineering Technology Center | And 6 more authors.
Applied Surface Science | Year: 2016

A series of Fe-loaded activated carbons treated by HNO3 (Fe/NAC) were prepared by incipient impregnation method with or without ultrasonic assistance and characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy disperse spectroscope (SEM-EDS), transmission electron microscopy (TEM) and N2 adsorption/desorption. The desulfurization activities were evaluated at a fixed bed reactor under a mixed gas simulated from flue gas. The results showed that desulfurization activity from excellent to poor is as follows: Fe/NAC-60 > Fe/NAC-80 > Fe/NAC-30 > Fe/NAC-15 > Fe/NAC-0 > Fe/NAC-100 > NAC. Fe/NAC-60 exhibits the best desulfurization activity and has breakthrough sulfur capacity of 319 mg/g and breakthrough time of 540 min. The introduction of ultrasonic oscillation does not change the form of Fe oxides on activated carbon but can change the dispersion and relative contents of Fe3O4. The types of oxygen-containing functional groups have no obvious change for all samples but the texture properties show some differences when they are oscillated for different times. The fresh Fe/NAC-60 has a surface area of 1045 m2/g and total pore volume of 0.961 cm3/g with micropore volume of 0.437 cm3/g and is larger than Fe/NAC-0 (823 m2/g, 0.733 and 0.342 cm3/g). After desulfurization, surface area and pore volume of all samples decrease significantly, and those of the exhausted Fe/NAC-60 decrease to 233 m2/g and 0.481 cm3/g, indicating that some byproducts deposit on surface to cover pores. Pore size distribution influences SO2 adsorption, and fresh Fe/NAC-60 has more pore widths centralized at about 0.7 nm and 1.0-2.0 nm and corresponds to an excellent desulfurization activity, showing that micropore is conducive to the removal of SO2. © 2015 Elsevier B.V. All rights reserved. Source


Liu Y.-J.,University of Sichuan | Liu Y.-J.,National Engineering Technology Research Center for Flue Gas Desulfurization | Qu Y.-F.,University of Sichuan | Guo J.-X.,University of Sichuan | And 12 more authors.
Energy and Fuels | Year: 2015

Manganese supported on activated carbons treated by HNO3 (Mn/NAC) was prepared using an excessive impregnation method and calcined at 650 °C, and the deactivation and recovery factors of Mn/NAC for desulfurization were investigated. The results showed that fresh catalyst calcined at 650 °C has breakthrough sulfur capacity of 141.8 mg/g and breakthrough time of 300 min and that the catalysts thermally regenerated at different temperatures under N2 atmosphere exhibit different removal capacity of SO2. After the catalysts undergo the first thermal regeneration at 650 °C, the catalysts have breakthrough sulfur capacity of 144.9 mg/g and breakthrough time of 299 min. These values are close to those of the fresh catalysts, suggesting that active sites can be recovered almost completely. In the following cycles, the SO2 removal capacity of the regenerated catalysts gradually decreases, indicating that active sites reduce gradually. The fresh catalyst has 710 m2/g specific surface area and 0.404 cm3/g total pore volume with 0.262 cm3/g micropore volume; after desulfurization, the specific surface area and micropore pore volume of the sample decrease to 612 m2/g and 0.220 cm3/g, respectively. The regenerated catalysts at different temperatures have different texture, but the first regenerated catalysts at 650 °C still has an 800 m2/g specific surface area and 0.448 cm3/g total pore volume with 0.291 cm3/g micropore volume. These values decrease with the increase of the number of regeneration cycles. Both sulfates and manganese oxides such as MnO and Mn3O4 are detected in the regenerated catalysts, and with the increase of the number of regeneration cycles, average crystalline size of MnO increase from 29.8 to 40.3 nm, indicating that sulfates are partially decomposed in N2 atmosphere and reduced by neighboring C atoms. After desulfurization, the relative content of C=O and C-O decrease while that of O=C-O is almost unchanged, indicating that C=O and C-O play a role in the desulfurization reaction. Thermal regeneration can recover C=O and change its relative content, while the unreduced sulfates increase with the increase of the number of regeneration cycles and accumulate in the catalysts, leading to a gradual decrease of SO2 removal capacity. © 2015 American Chemical Society. Source

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