Jiangkun Xie

Capture of gaseous elemental mercury from flue gas using a magnetic and sulfur poisoning resistant sorbent Mn/γ-Fe2O3 at lower temperatures

A series of Mn/γ-Fe(2)O(3) were synthesized to capture elemental mercury from the flue gas. Mn(4+) cations and cation vacancies on the surface played important roles on elemental mercury capture by Mn/γ-Fe(2)O(3). Furthermore, the reaction route of elemental mercury oxidization was dependent on the ratio of Mn(4+) cations to cation vacancies. As a result, the capacities of 15%-Mn/γ-Fe(2)O(3)-250 for elemental mercury capture were generally higher than those of 30%-Mn/γ-Fe(2)O(3)-400. SO(2) mainly reacted with ≡Fe(III)-OH and only a small amount of ≡Mn(4+) reacted with SO(2), so the presence of a high concentration of SO(2) resulted in an insignificant effect on elemental mercury capture by 15%-Mn/γ-Fe(2)O(3)-250 at lower temperatures. The capacities of 15%-Mn/γ-Fe(2)O(3)-250 for elemental mercury capture in the presence of 2.8 g N m(-3) of SO(2) were more than 2.2 mg g(-1) at <200°C. Meanwhile, 15%-Mn/γ-Fe(2)O(3)-250 can be separated from the fly ash using magnetic separation, leaving the fly ash essentially free of sorbent and adsorbed HgO. Therefore, 15% Mn/γ-Fe(2)O(3)-250 may be a promising sorbent for elemental mercury capture.

Novel regenerable sorbent based on Zr–Mn binary metal oxides for flue gas mercury retention and recovery

To capture and recover mercury from coal-fired flue gas, a series of novel regenerable sorbents based on Zr-Mn binary metal oxides were prepared and employed at a relatively low temperature. PXRD, TEM, TPR, XPS, and N2-adsorption methods were employed to characterize the sorbents. The Hg(0) adsorption performance of the sorbents was tested, and the effects of the main operation parameters and the gas components on the adsorption were investigated. Zr significantly improved the sorbents mercury capacity, which was nearly 5mg/g for Zr0.5Mn0.5Oy. Furthermore, the spent sorbent could be regenerated by heating to 350°C, and the highly concentrated elemental mercury released could be facilely recycled. Therefore, a much greener process for mercury capture and recovery could be anticipated based on this regenerable sorbent.

Sn–Mn binary metal oxides as non-carbon sorbent for mercury removal in a wide-temperature window

A series of Sn-Mn binary metal oxides were prepared through co-precipitation method. The sorbents were characterized by powder X-ray diffraction (powder XRD), transmission electronic microscopy (TEM), H2-temperature-programmed reduction (H2-TPR) and NH3-temperature-programmed desorption (NH3-TPD) methods. The capability of the prepared sorbents for mercury adsorption from simulated flue gas was investigated by fixed-bed experiments. Results showed that mercury adsorption on pure SnO2 particles was negligible in the test temperature range, comparatively, mercury capacity on MnOx at low temperature was relative high, but the capacity would decrease significantly when the temperature was elevated. Interestingly, for Sn-Mn binary metal oxide, mercury capacity increased not only at low temperature but also at high temperature. Furthermore, the impact of SO2 on mercury adsorption capability of Sn-Mn binary metal oxides was also investigated and it was noted that the effect at low temperature was different comparing with that of high temperature. The mechanism was investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs). Moreover, a mathematic model was built to calculate mercury desorption activation energy from Sn to Mn binary metal oxides.

Synthesis, characterization and experimental investigation of Cu-BTC as CO2 adsorbent from flue gas

Porous Cu-BTC material was synthesized by the solvothermal method. Powder X-ray diffraction (PXRD) was used to test the phase purity of the synthesized material and investigate its structural stability under the influence of flue gas components. The thermal stability of the material was determined through thermal gravimetric (TG) analysis. Scanning electron microscopy (SEM) was employed to study the microstructure of the material. Cu-BTC was demonstrated not only to have high CO2 adsorption capacity but also good selectivity of CO2 over N2 by means of packed bed tests. The adsorption capacity of Cu-BTC for CO2 was about 69 mL/g at 22 degrees C. The influence of the main flue gas components on the CO2 capacity of the material were discussed as well.

The performance of Ag doped V2O5–TiO2 catalyst on the catalytic oxidation of gaseous elemental mercury

To improve the catalytic oxidation ability for gaseous elemental mercury (Hg0), silver was introduced to V2O5–TiO2 catalysts. The catalysts were prepared by an impregnation method with various additives to obtain well distributed silver nanoparticles on the carrier. It was found that doping silver onto V2O5–TiO2 can significantly improve the catalytic oxidation efficiency of Hg0, and the redox temperature range for Hg0 oxidation was enlarged markedly (150–450 °C). The addition of polyvinylpyrrolidone (PVP) during the preparation of the catalysts can improve the dispersion of silver nanoparticles more effectively, which resulted in a higher Hg0 oxidation efficiency up to 90%. However, the oxidation of Hg0 on the catalyst was slightly inhibited due to the larger silver nanoparticles when the ionic liquid (IL) [bmim][BF4] was used as the additive. The characterization results indicated that V can be induced to a higher oxidation state in the presence of silver nanoparticles, and the transformation trend of TiO2 from the anatase to rutile phase caused by Ag can be minimized in the presence of PVP or ILs. Meanwhile, the mechanisms of the elemental mercury oxidation at various temperature ranges were discussed.

CO2 adsorption performance of ZIF-7 and its endurance in flue gas components

Porous ZIF-7 with the sodalite (SOD) cage structure (ZIF, Zeolitic imidazolate framework) were synthesized by the solvothermal method. Synthesized material was characterized by powder X-ray diffraction (PXRD), thermal gravity (TG), scanning electron microscopy (SEM) and N2 adsorption analysis. ZIF-8 with the SOD structure and a little larger pore window was synthesized in a similar way and was characterized for comparisons. Thermal stability and structural stability of ZIF-7 were tested through PXRD analysis, and the capability of the material for CO2 capture from simulated flue gas was investigated through physical adsorption method. The results showed that CO2 adsorption capacity on ZIF-7 was about 48 mL·g−1 while the capacity on ZIF-8 was about 18 mg·g−1 (at 12°C and 0.98 P/P0 relative pressure). Furthermore, the impact of flue gas components on adsorption capacity of ZIF-7 and the selectivity of CO2 against N2 on ZIF-7 was also investigated in this work.

Design of 3D MnO2/Carbon sphere composite for the catalytic oxidation and adsorption of elemental mercury

Three-dimensional (3D) MnO2/Carbon Sphere (MnO2/CS) composite was synthesized from zero-dimensional carbon spheres and one-dimensional α-MnO2 using hydrothermal method. The hierarchical MnO2/CS composite was applied for the catalytic oxidation and adsorption of elemental mercury (Hg0) from coal-fired flue gas. The characterization results indicated that this composite exhibits a 3D urchin morphology. Carbon spheres act as the core and α-MnO2 nano-rods grew on the surface of carbon spheres. This 3D hierarchical structure benefits the enlargement of surface areas and pore volumes. Hg0 removal experimental results indicated that the MnO2/CS composite has an outstanding Hg0 removal performance due to the higher catalytic oxidation and adsorption performance. MnO2/CS composite had higher than 99% Hg0 removal efficiency even after 600min reaction. In addition, the nano-sized MnO2/CS composite exhibited better SO2 resistance than pure α-MnO2. Moreover, the Hg-TPD results indicated that the adsorbed mercury can release from the surface of MnO2/CS using a thermal decomposition method.

[MoS4]2– Cluster Bridges in Co–Fe Layered Double Hydroxides for Mercury Uptake from S–Hg Mixed Flue Gas

[MoS4]2- clusters were bridged between CoFe layered double hydroxide (LDH) layers using the ion-exchange method. [MoS4]2-/CoFe-LDH showed excellent Hg0 removal performance under low and high concentrations of SO2, highlighting the potential for such material in S-Hg mixed flue gas purification. The maximum mercury capacity was as high as 16.39 mg/g. The structure and physical-chemical properties of [MoS4]2-/CoFe-LDH composites were characterized with FT-IR, XRD, TEM&SEM, XPS, and H2-TPR. [MoS4]2- clusters intercalated into the CoFe-LDH layered sheets; then, we enlarged the layer-to-layer spacing (from 0.622 to 0.880 nm) and enlarged the surface area (from 41.4 m2/g to 112.1 m2/g) of the composite. During the adsorption process, the interlayer [MoS4]2- cluster was the primary active site for mercury uptake. The adsorbed mercury existed as HgS on the material surface. The absence of active oxygen results in a composite with high sulfur resistance. Due to its high efficiency and SO2 resistance, [MoS4]2-/CoFe-LDH is a promising adsorbent for mercury uptake from S-Hg mixed flue gas.