Sichuan Prov Environmental Protect Environmental Catalysis And Materials Engineering Technology Center

Chengdu, China

Sichuan Prov Environmental Protect Environmental Catalysis And Materials Engineering Technology Center

Chengdu, China

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Guo J.-X.,Sichuan University | Guo J.-X.,Sichuan Prov Environmental Protect Environmental Catalysis And Materials Engineering Technology Center | Liu X.-L.,Sichuan University | Luo D.-M.,Sichuan University | And 4 more authors.
Industrial and Engineering Chemistry Research | Year: 2015

Fe supported on activated carbons treated by HNO3 (Fe/NAC) was prepared using the incipient wetness method with ultrasonic-assisted oscillation and calcined at different temperatures. The physical and chemical properties were studied using FTIR, XPS, XRD and H2-TPR, and SO2 removal ability of Fe/NAC was also evaluated at a fixed bed. The results showed that α-Fe2O3 and small Fe3O4 coexist in Fe/NAC-500, while catalysts calcined at 700°C only possess Fe3O4. Fe3O4 with small Fe2SiO4 is observed for Fe/NAC-900, but Fe2SiO4 and Fe0 are detected in Fe/NAC-1000, indicating that the interactions between Fe precursor and activated carbons are very complex, and C atoms may take part in the reduction of iron oxides. The relative content of C-C and C-O decreases first and then increases when calcination temperatures increase from 500 to 1000°C, but that of C=O and O=C-OH has a contrary trend, suggesting that calcination temperatures influence the formation of functional groups. Fe/NAC-900 shows the best activity and has a sulfur capacity of 322 mg/g, which is related closely to O=C-OH and good crystallinity of Fe3O4. Fe3O4 is the main active phase in the SO2 removal process. After desulfurization, O=C-OH, α-Fe2O3, Fe3 O4, and Fe0 disappear, and Fe2 (SO4)3 is observed, leading to the decrease of SO2 removal ability. © 2015 American Chemical Society.


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.


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.


Guo J.,University of Sichuan | Guo J.,National Engineering Research Center for Flue Gas Desulfurization | Guo J.,Sichuan Prov Environmental Protect Environmental Catalysis And Materials Engineering Technology Center | Shi Z.,University of Sichuan | And 9 more authors.
Journal of Alloys and Compounds | Year: 2015

A series of Ce0.35Zr0.65-xNdxO2-x/2 (x = 0.05, 0.10, 0.15, 0.20 and 0.25) were prepared, and the combinational effects of Nd and noble metals on the catalytic activities of monolithic cordierite honeycomb catalysts were elucidated. The results showed that the BET surface area and pore volume of CZN3F reach a maximum, 97 m2/g and 0.19 ml/g, but all aged samples undergo a sharp decline. The CZN2 has more oxygen vacancy and higher oxygen storage capacity (OSC) before and after ageing, but OSC of the samples with high Nd content decreases. All fresh samples have cubic Ce0.40Zr0.60O2 phase with nano-size, but the aged samples with low Nd content still exhibit cubic Ce0.40Zr0.60O2 phase. When Nd content (CZN4A) is 20 mol% after ageing at 1000 °C, small Ce0.60Nd0.40O1.80 is segregated from CeO2-ZrO2 cubic phase; when the doped Nd increases to 25 mol% (CZN5A), the CeO2-ZrO2 cubic phase completely converts into Nd050Zr0.50O1.75 cubic phase with 12.4 nm, accompanying a sharp decline of OSC; and O2 pretreatment can change the reductive behavior and H2 consumption of samples because of oxygen absorbed. Noble metals can influence the reduction of Ce0.35Zr0.65-xNdxO2-x/2. Ce0.35Zr0.65-xNdxO2-x/2 shows important differences in the TPR and H2 consumption and can change the dispersion and sintering of noble metals, resulting in different catalytic activities. The light-off temperature (T50%) of catalysts containing CZN2F (C2F) can be as low as 160 °C for CO, 211 °C for NO and 259 °C for C3H8, indicating that appropriate Nd doping is helpful for the improving catalytic activity. © 2014 Elsevier B.V. All rights reserved.

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