Lina Han

Effect of precursor and preparation method on manganese based activated carbon sorbents for removing H2S from hot coal gas.

Activated carbon (AC) supported manganese oxide sorbents were prepared by the supercritical water impregnation (SCWI) using two different precursor of Mn(NO(3))(2) (SCW(N)) and Mn(Ac)(2)·4H(2)O (SCW(A)). Their capacities of removing H(2)S from coal gas were evaluated and compared to the sorbents prepared by the pore volume impregnation (PVI) method. The structure and composition of different sorbents were characterized by XRD, SEM, TEM, XPS and XANES techniques. It is found that the precursor of active component plays the crucial role and SCW(N) sorbents show much better sulfidation performance than the SCW(A) sorbents. This is because the Mn(3)O(4) active phase of the SCW(N) sorbents are well dispersed on the AC support, while the Mn(2)SiO(4)-like species in the SCW(A) sorbent can be formed and seriously aggregated. The SCW(N) sorbents with 2.80% and 5.60% manganese are favorable for the sulfidation reaction, since the Mn species are better dispersed on the SCW(N) sorbents than those on the PV(N) sorbents and results in the better sulfidation performance of the SCW(N) sorbents. As the Mn content increases to 11.20%, the metal oxide particles on AC supports aggregate seriously, which leads to poorer sulfidation performance of the SCW(N)11.20% sorbents than that of the PV(N)11.20% sorbents.

Pd/activated carbon sorbents for mid-temperature capture of mercury from coal-derived fuel gas

Higher concentrations of Hg can be emitted from coal pyrolysis or gasification than from coal combustion, especially elemental Hg. Highly efficient Hg removal technology from coal-derived fuel gas is thus of great importance. Based on the very excellent Hg removal ability of Pd and the high adsorption abilities of activated carbon (AC) for H₂S and Hg, a series of Pd/AC sorbents was prepared by using pore volume impregnation, and their performance in capturing Hg and H₂S from coal-derived fuel gas was investigated using a laboratory-scale fixed-bed reactor. The effects of loading amount, reaction temperature and reaction atmosphere on Hg removal from coal-derived fuel gas were studied. The sorbents were characterized by N₂ adsorption, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicated that the efficiency of Hg removal increased with the increasing of Pd loading amount, but the effective utilization rate of the active component Pd decreased significantly at the same time. High temperature had a negative influence on the Hg removal. The efficiency of Hg removal in the N₂-H₂S-H₂-CO-Hg atmosphere (simulated coal gas) was higher than that in N₂-H₂S-Hg and N₂-Hg atmospheres, which showed that H₂ and CO, with their reducing capacity, could benefit promote the removal of Hg. The XPS results suggested that there were two different ways of capturing Hg over sorbents in N₂-H₂S-Hg and N₂-Hg atmospheres.

Catalytic properties of Pd modified Cu/SAPO-34 for NO x removal from diesel engine

The Cu/SAPO-34 catalysts with different Cu contents were prepared by in situ hydrothermal synthesis. The selected Cu/SAPO- 34 was modified by impregnating 1 wt% Pd(NO3)3. The morphology and structure of the samples were characterized via XRD and SEM techniques. The effects of Cu contents and the Pd modification on the de-NOx activity of the samples were investigated through the selective catalytic reduction by C3H6 and NH3. The Cu contents do not change the skeleton structure of the SAPO-34 crystalline and the Cu/SAPO-34 catalysts with Cu/Si ratios of 0.05, 0.1, and 0.2 have better de-NOx activity than other catalysts. The addition of Pd can improve the de-NOx activity of the Cu/SAPO-34 catalysts. The maximum of NO conversion of samples with Pd could reach 90%. Besides, the effect of aging treatment for Cu/SAPO-34 catalysts with and without Pd on the de-NOx activity was also investigated. The results indicated that the Cu/SAPO-34 catalysts modified by Pd have better antiaging performance than raw samples.

Effect of CuSAPO-34 catalyst preparation method on NOx removal from diesel vehicle exhausts

CuSAPO-34 samples prepared by hydrothermal synthesis (HS), pore-volume impregnation (PVI), and ion-exchange (IE) methods were characterized using X-ray diffraction, scanning electronic microscopy, atomic absorption spectroscopy, temperature-programmed reduction with hydrogen, X-ray absorption near-edge structure spectroscopy, X-ray photoelectron spectroscopy, and N2 adsorption. The selective catalytic reduction (SCR) ability over CuSAPO-34 for NOx from a simulated diesel exhaust was investigated through C3H6-SCR and NH3-SCR, before and after aging of the CuSAPO-34 catalyst. The results indicated that the sample prepared by IE had significantly better activity compared with those prepared using HS and PVI, especially in C3H6-SCR at temperatures below 300 °C. The activity of CuSAPO-34 in NO SCR was affected by the preparation method as a result of changes in the specific area (ABET), pore-size distribution, and the valence state of the active component. The active component of the catalyst prepared by HS was mainly Cu2+, whereas those of samples prepared by IE and PVI were mainly Cu+. Aging treatment can destroy the structure of the catalyst, decrease its surface area, and reduce the number of active Cu components on the catalyst surface, leading to a visible decrease in catalytic activity. The CuSAPO-34 prepared using the PVI method had the smallest decrease in NO SCR activity after aging, showing that it had better anti-aging properties.

One-step hydrothermal synthesis of Cu-SAPO-34/cordierite and its catalytic performance on NOx removal from diesel vehicles

Abstract Cu-SAPO-34/cordierite catalysts were prepared via one-step hydrothermal synthesis method and their performances to remove NOx from the diesel vehicle exhaust were evaluated. The morphology, structure, Cu content and valence state were characterized by SEM, XRD, ICP and XPS, respectively. The experimental results show the active component Cu of the catalysts via in situ synthesis could significantly improve the selective catalytic reduction (SCR) activities of NOx and the optimal Cu content is in the range of 0.30%-0.40% (mass fraction). No N2O is detected by gas chromatograph (GC) during the evaluation process, which implies that NOx is almost entirely converted to N2 over Cu-SAPO-34/cordierite catalyst. The conversion rate of NOx to N2 by NH3 over catalyst could almost be up to 100% in the temperature range of 300–670 °C with a space velocity of 12000 h−1 and it is still more than 60% at 300–620 °C under 36000 h−1. The catalysts also show the good hydrothermal and chemical stability at the atmosphere with H2O.

In situ synthesized Cu-ZSM-5/cordierite for reduction of NO

Abstract ZSM-5 zeolites were directly synthesized on the surface of honeycomb cordierite substrates by hydrothermal method and certified by XRD and SEM techniques; the adhesion of ZSM-5 coatings was evaluated by ultrasonic vibration. Cu-ZSM-5/cordierite monolithic catalyst was prepared by ion-exchange and impregnation method and applied for the selective catalytic reduction (SCR) of NO by NH3 using a simulated diesel exhaust. The results show that the cordierite surface is almost completely covered by ZSM-5 crystals and the crystallization time greatly impacts the loadings and adhesion of ZSM-5 coatings on substrate, the NOx removal rate over Cu-ZSM-5/cordierite is above 90% in a temperature range of 240–480 °C. Moreover, Cu-ZSM-5/cordierite prepared by different methods shows a wide temperature window (240–540 °C) with high NO removal activities.

A Magnetically Recoverable Fe 3 O 4 –NH 2 –Pd Sorbent for Capture of Mercury from Coal Derived Fuel Gas

A sort of magnetical material named Fe3O4–NH2–Pd was prepared by loading varying amounts of immobilizing Pd on the surface of the magnetic Fe3O4–NH2 microspheres. This magnetical material was used firstly for capturing Hg° from coal derived fuel gas based on its recoverability. The experimental results showed that the loading Pd on the amine-functionalized magnetite nanoparticles can greatly improve the efficiency of removing Hg° at a high temperature range between 200 and 300 °C. The magnetic Fe3O4–NH2–Pd sorbent with 5% Pd loaded exhibited significantly high activity and stability in capturing Hg°, affording over 93% capture efficiency at 200 °C for more than 8 hrs. Compared to the Fe3O4–NH2 sorbent that converted the Hg° as HgS, this Fe3O4–NH2–Pd sorbent can remove the Hg° by forming Pd-Hg amalgam and HgS. In addition, the experimental tests indicated that the as-synthesized Fe3O4–NH2–Pd sorbent still showed stable magnetic properties after two regeneration cycles in removing Hg°, which provided the opportunity for preparing a recyclable sorbent which can be easily separated and recovered for Hg° removal.

Removal Hg from Simulated Coal Fuel Gas over Sulfided Iron-Based Sorbent

Iron oxide sorbent TG-1 used effectively in industy and its sulfided sorbent TG-1-S are selected as the samples for experiments of Hg removal. A fixed packed bed reactor is used under different temperature and ambient atmosphere. The results show that the discarded sulfided iron oxide sorbent can be sequentially used removing mercury from coal gas and it is one of efficient and valuable capturing Hg methods. Sulfur or FeSx in TG-1-S sorbent can react with elemental mercury to form stable mercury sulfide, and this cause much higher removal Hg capacity than fresh iron oxide sorbent TG-1 in N2. The optimum temperature range of removing Hg for TG-1-S sorbent is 100-120oC. CO and H2 in inlet gas have the negligible effect, H2S has promoting action for removal mercury with TG-1-S sorbent. In the simulation of coal gas atmosphere, sulfided iron oxide sorbent TG-1-S has higher removing Hg capacity of 3.9 mg /g Hg capacity and the removal efficiency of 95%.