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• MoCe0.5/AC exhibited high Hg0 removal efficiency at 120 °C. • The adsorption mercury species were identified by Hg-TPD technique. • The mechanism for Hg0 removal was reasonably speculated. • The mechanism on high SO 2 resistance of MoCe0.5/AC was investigated. MoO 3 -CeO 2 /cylindrical activated coke samples (MoCeY/AC) synthesized by an impregnation method were employed to investigate elemental mercury (Hg0) removal at 60–210 °C from simulated flue gas without HCl. MoCe0.5/AC with an optimal Mo/Ce molar ratio of 0.5 exhibited an excellent Hg0 removal efficiency (94.74%) at 120 °C, as well as good stability and prominent resistance to SO 2 and H 2 O. The physicochemical property of the samples and the Hg0 removal mechanism were discussed by ICP-AES, SEM, EDX, BET, XRD, H 2 -TPR, XPS and Hg-TPD. The results of characterizations showed that MoCe0.5/AC possessed the special petal-like outer microstructure, large BET surface area, well-dispersed metal oxides and high reducibility, which was conducive for Hg0 removal. Furthermore, the synergistic effect between Mo6+ and Ce3+ was favorable to the high Hg0 removal performance by providing high valence Ce. According to the Hg-TPD tests, the chemisorption of Hg0 was a major approach for Hg0 removal, while physisorption and catalytic oxidation were just accounted for a tiny fraction. Moreover, the chemisorbed mercury could be validly distinguished into weakly-HgO, strongly-HgO, O α -HgO and HgSO 4 (when SO 2 was added). Compared with raw AC, MoCe0.5/AC could enhance the Hg0 oxidation performance and produce O α -HgO during the Hg0 removal process. In addition, the possible reason for the high SO 2 tolerance of MoCe0.5/AC was examined: (i) the preferential combination between sulfate and MoO 3 could protect CeO 2 for Hg0 removal; (ii) SO 2 could contribute to the formations of weakly-HgO and HgSO 4. Finally, the regenerability of MoCe0.5/AC was also discussed. [ABSTRACT FROM AUTHOR]

A series of Mn x Fe y /AC catalysts synthesized by impregnation method were investigated on the efficient and stable removal of HCHO in the fix-bed reactor. Extensive characterizations, BET, SEM, XRD, H 2 -TPR, XPS and FT-IR, were conducted to study the physicochemical properties, HCHO oxidation and surface reaction of catalysts. The optimal Mn 0.75 Fe 6.02 /AC showed enhanced HCHO removal efficiency of 98.30%, as well as excellent performance for simultaneous removal of HCHO (89.96%) and Hg 0 (77.51%). NO and SO 2 balanced in N 2 would inhibit the removal of HCHO, while the addition of 6% O 2 weakened the negative effect of SO 2 and NO + 6% O 2 facilitated the removal of HCHO. Besides, the slight promotion effect of water vapor was contributed to the regeneration of consumed −OH via the activation of surface oxygen by adsorbed H 2 O. Characterization results indicated that Mn 0.75 Fe 6.02 /AC possessed larger BET surface area, well-developed porosity and better dispersion of active components. Mn 0.75 Fe 6.02 /AC exhibited higher reducibility due to the synergistic effect between MnO x and FeO x , and the interaction between Mn-Fe oxides and AC support. At the same time, the oxygen-containing functional groups (C-O-, COO), abundant active surface oxygen and –OH facilitated both adsorption and oxidation of HCHO. Besides, the formate and carbonate intermediates formed on the surface of Mn 0.75 Fe 6.02 /AC in HCHO removal process, which could be further oxidized into CO 2 and H 2 O. On the basis of above investigations, the mechanism of enhanced HCHO catalytic removal over Mn x Fe y /AC was proposed. [ABSTRACT FROM AUTHOR]

To obtain a suitable catalyst for simultaneous removal of mercury and HCHO from waste flue gas, we prepared and investigated CoOx-CeO 2 loaded on commercial activated coke granules treated with sulfate acid by impregnation method to remove the two toxic gases. The results revealed that the removal efficiencies of Hg 0 and HCHO over Co 8 Ce 3 /ACs catalyst were 69.43% and 71.07% respectively in the presence of N 2 and 6% O 2 at 190 °C. And the presence of Hg 0 had little impact on HCHO removal, but formaldehyde had a certain effect on Hg 0 removal. In addition, the effects of individual flue gas component including O 2 , NO, SO 2 and H 2 O on Hg 0 and HCHO simultaneous removal performance over Co 8 Ce 3 /ACs catalyst were researched. The physicochemical properties of catalysts were characterized using BET, SEM, XRD, XPS, H 2 -TPR and FTIR. By analyzing these characterization results, it was found that the good removal property of the Co 8 Ce 3 /ACs catalyst was connected with good texture property, high dispersion of cobalt species and strong redox ability. Besides, the interaction between Co and Ce oxides phases could enhance the mobility of active oxygen species, which greatly improved the removal efficiencies of Hg0 and HCHO. Combined with the experiment and characterization results, end products of Hg 0 and HCHO are mainly HgO, CO 2 and H 2 O, respectively. So the mechanisms for simultaneous removal of mercury and HCHO were proposed. Of course, the Co 8 Ce 3 /ACs catalyst would be still modified to achieve the goal of practical industrial application. [ABSTRACT FROM AUTHOR]

To achieve novel sorbent-catalysts with low cost and high activity for removing HCHO in flue gas, we prepared and investigated CuO-CeO 2 supported on activated coke granules (CuCe/AC) for decomposition of gaseous formaldehyde (HCHO) from simulated coal combustion flue gas. The results indicated that Cu 3 Ce 8 /AC exhibited remarkable conversion performance and good stability for HCHO removal. The presence of NO and SO 2 exhibited a slight inhibitive effect on HCHO removal in the presence of 6% O 2 . The physicochemical properties of CuCe/AC were also studied by combination of N 2 adsorption/desorption, SEM, XRD, H 2 -TPR, XPS and FT-IR. The excellent conversion property of Cu 3 Ce 8 /AC was related to the high surface area, large pore volume, high dispersion of copper species, good adsorption capacity and great redox ability of metal oxides. Besides, the synergy between Cu and Ce species improved the mobility of activated oxygen species and the content of chemisorption oxygen, which facilitated the conversion of HCHO greatly. FT-IR results suggested that adsorbed HCHO on the samples surface was oxidized into intermediates, which could be further decomposed into H 2 O and CO 2 by the surface active oxygen of Cu 3 Ce 8 /AC. Along with the advantages of Cu 3 Ce 8 /AC, it would be a promising material for the removal of HCHO in real industrial application. [ABSTRACT FROM AUTHOR]

FeO and CeO modified activated coke (AC) synthesized by the equivalent-volume impregnation were employed to remove elemental mercury (Hg) from simulated flue gas at a low temperature. Effects of the mass ratio of FeO and CeO, reaction temperature, and individual flue gas components including O, NO, SO, and HO (g) on Hg removal efficiency of impregnated AC were investigated. The samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with optimal mass percentage of 3 % FeO and 3 % CeO on Fe3Ce3/AC, the Hg removal efficiency could reach an average of 88.29 % at 110 °C. Besides, it was observed that O and NO exhibited a promotional effect on Hg removal, HO (g) exerted a suppressive effect, and SO showed an insignificant inhibition without O to some extent. The analysis of XPS indicated that the main species of mercury on used Fe3Ce3/AC was HgO, which implied that adsorption and catalytic oxidation were both included in Hg removal. Furthermore, the lattice oxygen, chemisorbed oxygen, and/or weakly bonded oxygen species made a contribution to Hg oxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel sorbent regenerated from desulfurized activated coke was used for Hg0 removal. • How thermal treatment and desulfurization affected properties of AC was studied. • The regenerated desulfurized AC possessed more active oxygen species and SO 4 2−. • Hg0 adsorption priority on RAC at 60℃ was as ester ≥ carbonyl ≥ SO 4 2− ≥ physisorption. The desulfurized activated coke was recycled through thermal regeneration to recover Hg0 from coal-fired flue gas. And the thermal treated activated coke was also prepared for comparison. BET, acid-base titration, XPS and O 2 -TPD characterizations were performed to identify the structural and chemical properties. Although possessing decreased BET surface area and enlarged pore diameter after thermal treatment, AC-400 exhibited the enhanced Hg0 removal performance due to the generation of oxygen functional groups, while the treatment at 900 °C resulted in the decomposition of surface active oxygen species. Besides, not only the strengthened promotion on the formation of carbonyl and ester groups, but also the deposition of SO 4 2− during regeneration should be responsible for the superior activity of regenerated desulfurized activated coke (RAC) for Hg0 removal. Besides, O 2 addition could weaken the competition between NO/SO 2 and Hg0, and facilitate the formation of Hg(NO 3) 2 /HgSO 4. In combination with Hg-TPD, the specific surface area was in closely correlation with the physisorption of Hg0 on activated coke, and the chemisorption, as the predominant mechanism, of Hg0 mainly depended on the surface active oxygen species. Moreover, when reacted at 60 °C, the Hg0 adsorption priority on RAC was as follows: ester ≥ carbonyl ≥ SO 4 2− ≥ physisorption, and the carbonyl was the leading active sites for mercury adsorption. [ABSTRACT FROM AUTHOR]

Mn-Ce mixed oxides supported on commercial columnar activated coke (MnCe/AC) were employed to remove elemental mercury (Hg 0 ) at low temperatures (100–250 °C) without the assistance of HCl in flue gas. The samples were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Effects of some factors, including Mn-Ce loading values, active component, reaction temperatures and flue gas components (O 2 , SO 2 , NO, H 2 O), on Hg 0 removal efficiency were investigated. Results indicated that the optimal Mn-Ce loading value and reaction temperature were 6% and 190 °C, respectively. Considerable high Hg 0 removal efficiency (>90%) can be obtained over MnCe6/AC under both N 2 /O 2 atmosphere and simulated flue gas atmosphere at 190 °C. Besides, it was observed that O 2 and NO exerted a promotional effect on Hg 0 removal, H 2 O exhibited a suppressive effect, and SO 2 hindered Hg 0 removal seriously when in the absence of O 2 . Furthermore, the XPS spectra of Hg 4f and Hg-TPD results showed that the captured mercury were existed as Hg 0 and HgO on the MnCe6/AC, and HgO was the major species, which illustrated that adsorption and catalytic oxidation process were included for Hg 0 removal over MnCe6/AC, and catalytic oxidation played the critical role. What's more, both lattice oxygen and chemisorbed oxygen or OH groups on MnCe6/AC contributed to Hg 0 oxidation. MnCe6/AC, which exhibited excellent performance on Hg 0 removal in the absence of HCl, appeared to be promising in industrial application, especially for low-rank coal fired flue gas. [ABSTRACT FROM AUTHOR]

This work addressed the investigation of activated coke (AC) treated by acids. Effects of AC samples, modified by ether different acids (H 2 SO 4 , HNO 3 and HClO 4 ) or HClO 4 of varied concentrations, on Hg 0 removal were studied under simulated flue gas conditions. In addition, effects of reaction temperature and individual flue gas components including O 2 , NO, SO 2 and H 2 O were discussed. In the experiments, Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were applied to explore the surface properties of sorbents and possible mechanism of Hg 0 oxidation. Results showed that AC sample treated by HClO 4 of 4.5 mol/L exhibited maximum promotion of efficiency on Hg 0 removal at 160 °C. NO was proved to be positive in the removal of Hg 0 . And SO 2 displayed varied impact in capturing Hg 0 due to the integrated reactions between SO 2 and modified AC. The addition of O 2 could improve the advancement further to some extent. Besides, the Hg 0 removal capacity had a slight declination when H 2 O was added in gas flow. Based on the analysis of XPS and FTIR, the selected sample absorbed Hg 0 mostly in chemical way. The reaction mechanism, deduced from results of characterization and performance of AC samples, indicated that Hg 0 could firstly be absorbed on sorbent and then react with oxygen-containing (C O) or chlorine-containing groups (C Cl) on the surface of sorbent. And the products were mainly in forms of mercuric chloride (HgCl 2 ) and mercuric oxide (HgO). [ABSTRACT FROM AUTHOR]

Abstract: Gas-phase elemental mercury (Hg0) removal by activated coke impregnated with cerium chloride (AICC) was studied under simulated flue gas conditions. Brunauer–Emmett–Teller (BET), X-ray diffractogram (XRD), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX) and X-ray photoelectron spectroscopy (XPS) analyses were used to characterize the samples. The effects of CeCl3 loading values, reaction temperatures and individual flue gas components including O2, NO, SO2 and H2O (g) on Hg0 removal efficiency of AICC samples were investigated. Results showed that Hg0 removal efficiency of AC was significantly enhanced by CeCl3. The optimal CeCl3 loading value and reaction temperature was around 6% and 170°C, respectively. Additionally, the experiment results of effects of flue gas components on Hg0 removal efficiencies showed that when O2 was present in the flue gas, NO and SO2 were observed to promote Hg0 oxidation. However, in the absence of O2, SO2 showed an insignificant inhibition on Hg0 removal. Furthermore, when H2O was added into the flue gas, the Hg0 removal capacity had a slight declination. The analyses of XRD and XPS showed that Ce x O y and C–Cl were generated on the surface of AICC and those active elements had remarkably positive effects on the Hg0 removal. The reaction mechanism indicated that Hg0 oxidation was achieved through two pathways: one was that Hg0 bond with CeO2 and was converted by the catalytic oxidation of valence variable cerium; the other was that Hg0 reacted with C–Cl on the sample and was oxidized favored by chloride presence. And according to Hg 4f XPS analysis, the mercury on the surface of AICC was mainly in the form of mercuric oxide (HgO) and mercuric chloride (HgCl2). [Copyright &y& Elsevier]

• Mn 6 Cu 5 /AC owned superior activity for toluene removal in simulated flue gas. • The positive synergistic effect between MnO x and CuO x was achieved in Mn 6 Cu 5 /AC. • The effects of O 2 , SO 2 , NO and H 2 O on toluene removal were investigated, respectively. • The mechanism of toluene removal was reasonably speculated on Mn 6 Cu 5 /AC. A series of bimetallic oxides of manganese and copper with different loading of copper loaded on activated coke (Mn x Cu y /AC) were synthesized by ultrasound-assisted equivalent volume impregnation method for toluene oxidation in simulated flue gas at 150–300 °C. The physicochemical properties of samples have been investigated by means of XRD, SEM, BET, XPS, H 2 -TPR and DRIFT. Mn 6 Cu 5 /AC exhibited the enhanced toluene removal efficiency (99.38%) at 270 °C, as well as satisfactory reusability and durability. The excellent activity of Mn 6 Cu 5 /AC was connected with the highly uniform distribution of active components and the larger specific surface area, which confirmed the synergistic interaction between MnO x and CuO x , thus leading to the stronger reducibility and the good oxygen mobility. In addition, SO 2 and NO played a hindering role due to the competitive adsorption of active sites in pure N 2 , whereas the negative effect would be reduced by the introduction of O 2. Besides, the influence of H 2 O on toluene removal was complex. Moreover, the reaction process obtained from DRIFT indicated that toluene can be rapidly adsorbed and activated to form the benzaldehyde and maleic anhydride species on Mn 6 Cu 5 /AC, and finally be further oxidized into CO 2 and H 2 O. Finally, the mechanism of toluene oxidation over Mn 6 Cu 5 /AC was proposed. [ABSTRACT FROM AUTHOR]

• The synergistic effect between MnO x and CrO x on 4%Cr 0.5 Mn 0.5 /AC boosted oxygen vacancies formation and active oxygen evolution. • The interaction relationship between toluene removal and Hg0 removal was elucidated. • Effect of flue gas components was explored to fulfill the industrial application. • A possible mechanism for the simultaneous removal of toluene and Hg0 was proposed by In-situ DRIFTS. In this study, a string of Cr-Mn co-modified activated coke catalysts (XCr y Mn 1-y /AC) were prepared to investigate toluene and Hg0 removal performance. Multifarious characterizations including XRD, TEM, SEM, in situ DRIFTS, BET, XPS and H 2 -TPR showed that 4%Cr 0.5 Mn 0.5 /AC had excellent physicochemical properties and exhibited the best toluene and Hg0 removal efficiency at 200℃. By varying the experimental gas components and conditions, it was found that too large weight hourly space velocity would reduce the removal efficiency of toluene and Hg0. Although O 2 promoted the abatement of toluene and Hg0, the inhibitory role of H 2 O and SO 2 offset the promoting effect of O 2 to some extent. Toluene significantly inhibited Hg0 removal, resulting from that toluene was present at concentrations orders of magnitude greater than mercury's or the catalyst was more prone to adsorb toluene, while Hg0 almost exerted non-existent influence on toluene elimination. The mechanistic analysis showed that the forms of toluene and Hg0 removal included both adsorption and oxidation, where the high-valent metal cations and oxygen vacancy clusters promoted the redox cycle of Cr3+ + Mn3+/Mn4+ ↔ Cr6+ + Mn2+, which facilitated the conversion and replenishment of reactive oxygen species in the oxidation process, and even the CrMn 1.5 O 4 spinel structure could provide a larger catalytic interface, thus enhancing the adsorption/oxidation of toluene and Hg0. Therefore, its excellent physicochemical properties make it a cost-effective potential industrial catalyst with outstanding synergistic toluene and Hg0 removal performance and preeminent resistance to H 2 O and SO 2. [Display omitted] [ABSTRACT FROM AUTHOR]

• The synergistic effect between CoO x and CrO x on 6 %Co 0.5 Cr 0.5 /AC boosted oxygen vacancies formation and active oxygen evolution. • The interaction relationship between methylbenzene removal and Hg0 removal was elucidated. • Effect of flue gas components was explored to fulfill the industrial application. • A possible mechanism for the simultaneous removal of methylbenzene and Hg0 was proposed by In-situ DRIFTS. An array of CoCr oxides co-modified activated cokes pretreated with HNO 3 (XCo y Cr 1-y /ACs) were synthesized and evaluated for simultaneously effective and credible elimination of methylbenzene (MB) and Hg0. BET, SEM, TEM, EDX, XRD, H 2 -TPR, in situ DRIFTS and XPS were adopted for exploring the physicochemical characteristics and reaction mechanisms of aforesaid samples. H 2 -TPR result showed the Cr-doped Co-Cr catalysts excellent reducibility in view of the synergistic effect between CoO x and CrO x. Especially, 6 %Co 0.5 Cr 0.5 /AC obtained outstanding performance and prominent stability for MB and Hg0 removal, and it behaved the optimal performance of MB (96.1 %) and Hg0 (88.3 %) at 240 ℃. It could be explained by that the formation of CoCr 2 O 4 spinel entailed more uniform distribution of active components, abundant lattice defects and even the redox cycle of Cr6++Co2+↔Cr3++Co3+, which spawned adequate Co3+ species and active oxygen species. The interaction between MB removal and Hg0 removal was estimated and the presence of Hg0 barely affected MB removal, whereas the existence of MB manifested a distinctly suppressive influence on Hg0 removal, suggesting that MB removal might prevail over Hg0 removal. Meanwhile, the rivalry between MB and Hg0 progressively shifted from adsorption sites to active oxygen species with time. Moreover, the influences of O 2 , NO, SO 2 and H 2 O on MB and Hg0 simultaneous removal were systematically appraised. Notably, 6 %Co 0.5 Cr 0.5 /AC exerted remarkable resistance to SO 2 and H 2 O. Combined with characterizations and experiments, the pathway for the simultaneous removal of MB and Hg0 via adsorption and catalytic oxidation on 6 %Co 0.5 Cr 0.5 /AC was summarized. This work could deliver references to the design of advanced catalysts for simultaneous removal of MB and Hg0. [ABSTRACT FROM AUTHOR]