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To avoid resource waste and environmental pollution, a chain of ErOx-boosted MnOx-modified biochars derived from rice straw and sewage sludge (EryMn1-y/BACs, where biochars derived from rice straw and sewage sludge were defined as BACs) were manufactured for formaldehyde (HCHO) elimination. The optimal 15%Er0.5Mn0.5/BAC achieved a 97.2% HCHO removal efficiency at 220 °C and exhibited favorable EHCHO and thermal stability in a wide temperature window between 180 and 380 °C. The curbed influences of H2O and SO2 offset the boosting effect of O2 in a certain range. Er–Mn bimetallic-modified BACs offered a superior HCHO removal performance compared with that of BACs boosted using Er or Mn separately, owing to the synergistic effect of ErOx and MnOx conducive to improving the samples' total pore volume and surface area, surface active oxygen species, promoting redox ability, and inhibiting the crystallization of MnOx. Moreover, the support's hierarchical porous structure not only expedited the diffusion and mass transfer of reactants and their products but also elevated the approachability of adsorption and catalytic sites. Notably, these prominent features were partly responsible for the outstanding performance and excellent tolerance to H2O and SO2. Using in situ DRIFTS characterization analysis, it could be inferred that the removal process of HCHO was HCHOad → dioxymethylene (DOM) → formate species → CO2 + H2O, further enhanced with reactive oxygen species. The DFT calculation once again proved the removal process of HCHO and the strengthening effect of Er doping. Furthermore, the optimal catalytic performance of 15%Er0.5Mn0.5/BAC demonstrated its vast potential for practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • CeO 2 -NP catalyst contains amounts of oxygen vacancies and shows outstanding toluene oxidation performance. • CeO 2 -NP combined the advantage of oxygen storage-release capacity and nano-size effect. • The XPS characterization demonstrated that both O α and O β are participated in toluene oxidation. • The ring-opening reaction is an essential rate-controlling step in toluene oxidation. Developing efficient and stable non-noble metal catalysts for the catalytic oxidation of volatile organic compounds (VOCs) has always been key for controlling air pollution. For this, cerium dioxide (CeO 2) is a potential material and its morphology has a significant impact on the catalyst performance. Herein, three types of CeO 2 with different morphologies were prepared using the hard template method and successfully applied to toluene oxidation. The CeO 2 nanoparticles catalyst (CeO 2 -NP) exhibited the highest efficiency, excellent water resistance, long-term stability, and cycle regeneration. Notably, the activation and migration of lattice oxygen can be facilitated by increasing the temperature, and the oxygen vacancies on the surface of the catalyst can further promote the process. In addition, the oxidation behavior of toluene over the CeO 2 -NP catalyst was comprehensively understood by in situ diffuse reflectance infrared Fourier transform spectroscopy (In situ DRIFTS) combined with density functional theory (DFT). It was found that the ring-opening reaction is an essential rate-controlling step. Thus, this study provides a new strategy for exploring mono-metal catalysts with high catalytic performances for the oxidation of VOCs and other pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modulation of the crystal structure of manganese oxides using different C 3 alcohols. • MnO 2 -G exhibits a unique structure with amorphous and microcrystalline coexistence. • The MnO 2 -G presented excellent catalytic activity, stability and water resistance. • The mixed crystalline state induces more defects and enhances the reactivity of lattice oxygen. • The conversion pathway of toluene on MnO 2 -G was revealed by in situ DRIFTS. Amorphous transition metal oxides exhibit considerable potential in the catalytic oxidation of volatile organic compounds (VOCs) owing to their distinctive surface properties. In this study, we achieved the modulation of the crystalline structure of manganese oxides by employing various C 3 alcohols (alcohols with three carbons) with distinct hydroxyl types during the reduction process with potassium permanganate. Subsequently, a series of characterization techniques were employed to assess the catalytic performance of the prepared MnO 2 in the oxidation of toluene. Notably, the MnO 2 -G obtained from glycerol presented excellent catalytic activity (T 90 = 219 °C), stability, and water resistance. The unique amorphous/microcrystalline state of MnO 2 -G exposed more phase boundaries, and the unsaturated coordination structure facilitated the generation of additional defective sites, favoring the adsorption and activation of oxygen. Furthermore, the mixed-crystalline state induced the elevated Mn3+ content on the surface of MnO 2 -G, leading to elongation of the Mn-O bond due to the pronounced Jahn-Teller effect of Mn3+. Consequently, the synergistic effects of the mixed crystalline state contributed to the efficient catalytic oxidation of toluene at relatively low temperatures. Additionally, the conversion pathway of toluene on MnO 2 -G was further revealed by in situ DRIFTS. [ABSTRACT FROM AUTHOR]

A battery of agricultural straw derived biomass activated carbons supported LaOx modified MnOx (LaMn/BACs) was prepared by a facile impregnation method and then tested for simultaneous abatement of NO and Hg0. 15%LaMn/BAC manifested excellent removal efficiency of Hg0 (100%) and NO (86.7%) at 180 °C, which also exhibited splendid resistance to SO2 and H2O. The interaction between Hg0 removal and NO removal was explored; thereinto, Hg0 removal had no influence on NO removal, while NO removal preponderated over Hg0 removal. The inhibitory effect of NH3 was greater than the accelerative effect of NO and O2 on Hg0 removal. The physicochemical characterization of related samples was characterized by SEM, XRD, BET, H2-TPR, NH3-TPD, and XPS. After incorporating suitable LaOx into 15%Mn/BAC, the synergistic effect between LaOx and MnOx contributed to the improvement of BET surface area and total pore volume, the promotion of redox ability, surface active oxygen species, and acid sites, inhibiting the crystallization of MnOx. 15%LaMn/BAC has the best catalytic oxidation activity at low temperature. That might be answerable for superior performance and preferable tolerance to SO2 and H2O. The results indicated that 15%LaMn/BAC was a promising catalyst for simultaneous abatement of Hg0 and NO at low temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoCeO x -2-NP exhibited the highest toluene conversion activity (T 90 = 209 °C). • Appropriate Co-doped CeO 2 significantly enhanced the interfacial synergistic effects. • O α and O β played a crucial role in the efficient catalytic oxidation of toluene. • The cracking of the aromatic ring is an essential step in completely oxidizing toluene. • The toluene oxidation over the CoCeO x -NP catalyst follow both L-H and MvK mechanism. The CoCeO x nanoparticles (CoCeO x -NP) with different Co/Ce molar ratios were successfully prepared and applied to toluene oxidation. Appropriate Co-doped CeO 2 significantly enhanced the interfacial synergistic catalysis to boost toluene oxidation. CoCeO x -2-NP exhibited the highest toluene conversion activity (T 50 = 203 °C, T 90 = 209 °C) and CO 2 selectivity under the high weight hourly space velocity (WHSV). Various characterizations were performed to comprehensively analyze the relationship between the structure and performance of the catalysts. The high O β /O tot , good oxygen mobility, and the synergistic effects between cobalt and cerium showed excellent performance for toluene oxidation at lower temperatures. Besides, the CoCeO x -2-NP catalysts exhibited good stability and reusability, making them potential for practical applications in toluene oxidation. Notably, the XPS, DFT, and in situ DRIFTS further investigated the pathway of toluene oxidation, which lays a foundation for an in-depth understanding of the oxidation behavior of toluene and the subsequent development of efficient catalytic materials. [ABSTRACT FROM AUTHOR]

• 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]

To rationally utilize agricultural wastes and expediently simultaneous control of elemental mercury (Hg 0 ) and NO, a series of CoO x -CeO 2 loaded maize straw derived biomass activated carbon (CoCe/BAC) samples were applied for simultaneous NO and Hg 0 removal. These samples’ physicochemical characteristics were characterized by BET, SEM, XRD, NH 3 -TPD, H 2 -TPR, XPS and FTIR. 15%Co 0.4 Ce 0.6 /BAC yielded prominent Hg 0 removal efficiency (96.8%) and superior NO removal efficiency (84.7%) at 230 °C. The separate or synchronous deactivation effects of 400 ppm SO 2 and 5%H 2 O were detected. The interaction between NO removal and Hg 0 removal was investigated, the results demonstrated that abundant Hg 0 exhibited very slightly inhibitory effect on NO removal, and NH 3 negatively affected Hg 0 removal, whereas NO mildly boosted Hg 0 removal in presence of O 2 . The characterization analyses indicated the excellent performance of 15%Co 0.4 Ce 0.6 /BAC could be ascribed to its better texture properties, lower crystallinity and stronger redox ability. Besides, a synergetic effect appeared between cobalt oxide and cerium oxide, resulting in generating more Ce 3+ and Co 3+ to induce more anionic defects and produce more active oxygen and oxygen vacancies. The removal mechanisms of NO and Hg 0 were systematically investigated, and NO reduction reactions were mainly assigned to the Langmuir-Hinshlwood mechanism while both adsorption and Hg 0 oxidation contributed to Hg 0 removal. Meanwhile, Hg 0 oxidation corresponded to the Mars-Masson mechanism prevailed gradually with the increase of reaction time. [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]

A series of industrial desulfuration activated cokes loaded La 2 O 3 and CeO 2 (LaCe/AC) were employed for simultaneous NO and Hg 0 removal from simulated flue gas. The physicochemical characteristics of samples were characterized by BET, XRD, SEM, NH 3 -TPD, TGA and XPS. 25%LaCe/AC exhibited outstanding NO removal efficiency (91.3%) and superior Hg 0 removal efficiency (94.3%) at 180 °C. The effects of Hg 0 on SCR reaction and SCR atmosphere on Hg 0 oxidation were investigated. The results demonstrated that Hg 0 had negligible impact on NO removal efficiency while NO evidently promoted Hg 0 removal efficiency. Meanwhile, NH 3 had an adverse effect on Hg 0 removal efficiency. The slightly inhibitive effect derived from the existence of H 2 O or SO 2 was also detected. The NO removal mainly followed the Langmuir-Hinshlwood mechanism while the Hg 0 removal mechanism was attributed to the combination of physisorption and chemisorption and catalytic oxidation. Especially, the relative contributions of physisorption and chemisorption and catalytic oxidation were distinguished and calculated by designed mercury conversion and desorption tests, the results indicated chemisorption displayed the predominant role. In addition, the stability test of 27 h was carried out and eventually the sample maintained 84.5% Hg 0 removal efficiency and 89.5% NO removal efficiency, indicating its potentially large-scale industrial application at low temperatures in the foreseeable future. [ABSTRACT FROM AUTHOR]

A series of low-cost Cu-Mn-mixed oxides supported on biochar (CuMn/HBC) synthesized by an impregnation method were applied to study the simultaneous removal of formaldehyde (HCHO) and elemental mercury (Hg0) at 100–300° C from simulated flue gas. The metal loading value, Cu/Mn molar ratio, flue gas components, reaction mechanism, and interrelationship between HCHO removal and Hg0 removal were also investigated. Results suggested that 12%CuMn/HBC showed the highest removal efficiency of HCHO and Hg0 at 175° C corresponding to 89%and 83%, respectively. The addition of NO and SO2 exhibited inhibitive influence on HCHO removal. For the removal of Hg0, NO showed slightly positive influence and SO2 had an inhibitive effect. Meanwhile, O2 had positive impact on the removal of HCHO and Hg0. The samples were characterized by SEM, XRD, BET, XPS, ICP-AES, FTIR, and H2-TPR. The sample characterization illustrated that CuMn/HBC possessed the high pore volume and specific surface area. The chemisorbed oxygen (Oβ) and the lattice oxygen (Oα) which took part in the removal reaction largely existed in CuMn/HBC. What is more, MnO2 and CuO (or Cu2O) were highly dispersed on the CuMn/HBC surface. The strong synergistic effect between Cu-Mn mixed oxides was critical to the removal reaction of HCHO and Hg0 via the redox equilibrium of Mn4+ + Cu+ ↔ Mn3+ + Cu2+. [ABSTRACT FROM AUTHOR]

Developing efficient photothermal catalysts with full spectrum response is one of the frontier topics in photothermal catalytic of VOCs. In this work, La 1- x Fe x MnO 3 (0 ≤ x ≤ 0.2) was synthesized via citrate sol-gel method. Under full spectrum illumination of 1.3 × 104 W/m2, La 0.9 Fe 0.1 MnO 3 exhibited a more superior activity (86.7% toluene conversion and 84.6% CO 2 yield). Through controlled experiments, not only the origin of photothermal activity, but the possible intrinsic drivers (Fe doping and photoactivation) of the enhanced activity were also revealed. Particularly, the mechanistic details of their facilitating reactions were thoroughly studied, where the improved mobility and activation of lattice oxygen played the primary role. Moreover, the co-effect of Fe doping and photoactivation on the resistance to complex gas components (SO 2 , H 2 O) and durability was systematically investigated. Eventually, the plausible pathways and mechanisms of toluene oxidation were proposed. This study provides a new insight into photothermal catalysts with full spectrum response for environmental remediation. [Display omitted] • La 1- x Fe x MnO 3 with full spectrum response showed efficient photothermal performance for toluene. • The origin of photothermal activity was revealed. • Fe doping and photoactivation effects improved the mobility and activation of O latt species. • The co-effect of Fe doping and photoactivation enhanced the resistance and durability. • The plausible pathways and mechanisms of toluene oxidation were proposed. [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]

[Display omitted] • LDHs-based materials are promising catalysts for gaseous VOCs abatement. • The catalytic performance and intensified mechanisms of various LDHs-based catalysts were investigated. • LDHs-based catalysts showed excellent resistance to complex gas components. • It remains challenges between research and practical application of LDHs-based catalysts. • LDHs-based materials are also applied in other VOCs abatement fields with promising performance. Volatile organic compounds (VOCs) have received increasing attention for their severe hazards to the ecological environment and human health. Accordingly, various VOCs abatement technologies have been developed, where the selection of efficient catalysts is particularly critical. In recent years, the research of layered double hydroxides (LDHs)-based materials as novel catalysts has become one of the most attractive topics. With the tunability of LDHs in chemical composition, electronic structure and morphology, as well as their unique structural features and superior physicochemical properties, LDHs-based catalysts show enormous potential for environmental applications. This paper reviews the recent advances of LDHs-based materials for gaseous VOCs abatement, mainly covers two fields: photocatalytic oxidation and thermal catalytic oxidation. Especially, we summarize and compare the catalytic performance and intensified mechanisms of various LDHs-based materials, where the mechanistic details that lead to their varying results in terms of catalytic activity and reaction routes are the main focus of the discussion. Moreover, the effect of different gas components (e.g., SO 2 , H 2 O, CO, NO x) on the performance of LDHs-based materials is examined. Our group also overviews the application of LDHs-based materials for VOCs adsorption, sensing and steam reforming. Finally, we provide an outlook on the current challenges and development strategies from the perspective of practical applications. [ABSTRACT FROM AUTHOR]

Total organic carbon (TOC) and humic acid (HA) are very strong contamination potential components in landfill leachate, which were treated by subcritical water catalytic oxidation technology with a batch reactor. Response surface methodology (RSM) was used to evaluate the effects of temperature (180-260 °C), peroxide coefficient (2-3), pH (4-8), and their interactive effects on TOC and HA removal efficiencies. The results demonstrated that RSM was an effective method for the optimization of experimental parameters in the treatment of landfill leachate. The results indicated that the effects on TOC removal efficiency were in the order temperature > pH > peroxide coefficient and that the order on HA removal efficiency was pH > temperature > peroxide coefficient. The experiments were performed in different heterogeneous (CuO, ZnO) and homogeneous (CuSO·5HO, FeSO·7HO, and Cu(NO)·3HO) catalysts; the optimal parameters within the experimental range were temperature of 260 °C, pH of 4.0, peroxide coefficient of 3.0, and Cu(NO)·3HO of 0.03 M. Under the optimum conditions, the TOC and HA removal efficiency can reach 86.42 and 66.10 %, respectively. Using gas chromatography coupled with mass spectrometry (GC-MS) to analyze the composition of liquid, 89 and 76 kinds of principal organic components were detected in the landfill leachate before and after treatment, respectively. In the raw landfill leachate, there were five kinds of organic matters, which belong to the US Environmental Protection Agency (USEPA) list of priority environmental pollutants. After the treatment, the toxic organics were not detected. In summary, the results suggested that the subcritical catalytic oxidation technology can be used as an effective method for the treatment of landfill leachate. [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]

In order to reduce the costs, the recycle of spent TiO-based SCR-DeNO catalysts were employed as a potential catalytic support material for elemental mercury (Hg) oxidation in simulated coal-fired flue gas. The catalytic mechanism for simultaneous removal of Hg and NO was also investigated. The catalysts were characterized by Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) method. Results indicated that spent TiO-based SCR-DeNO catalyst supported Ce-Mn mixed oxides catalyst (CeMn/SCR) was highly active for Hg oxidation at low temperatures. The CeMn/SCR performed the best catalytic activities, and approximately 92.80 % mercury oxidation efficiency was obtained at 150 °C. The inhibition effect of NH on Hg oxidation was confirmed in that NH consumed the surface oxygen. Moreover, HO inhibited Hg oxidation while SO had a promotional effect with the aid of O. The XPS results illustrated that the surface oxygen was responsible for Hg oxidation and NO conversion. Besides, the Hg oxidation and NO conversion were thought to be aided by synergistic effect between the manganese and cerium oxides. [ABSTRACT FROM AUTHOR]

In order to enhance the catalytic activity for elemental mercury (Hg 0 ) oxidation without the aid of HCl, CeO 2 was added into the support to modify V 2 O 5 –WO 3 /TiO 2 catalysts. The performance of V 2 O 5 –WO 3 /TiO 2 –CeO 2 (VWTiCe) catalysts on Hg 0 oxidation as well as the catalytic mechanism was also studied. The catalysts were characterized by BET, XRD and XPS techniques. The results showed that the performance on Hg 0 oxidation was promoted by the introduction of CeO 2 . NO and SO 2 has a promoting effect on Hg 0 oxidation in the presence of O 2 . Besides, the inhibitive effect of NH 3 on Hg 0 oxidation was confirmed by NH 3 consuming the surface oxygen of catalyst. The addition of CeO 2 improved the ability to resist H 2 O. Results also indicated that the Hg 0 oxidation efficiencies of V 0.80 WTiCe 0.25 catalysts were thought to be aided by synergistic effect between V 2 O 5 and CeO 2 . Hg 0 oxidation over V 0.80 WTiCe 0.25 follows a Mars–Maessen mechanism where lattice oxygen of V 2 O 5 reacts with adjacently absorbed Hg 0 . [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]

Highlights: [•] FeMnO x /TiO2 was developed for effective NO oxidation from simulated flue gas. [•] Effects of loading sequences on FeMnO x /TiO2 were systematically investigated. [•] Possible reaction mechanism over Fe(0.15)–Mn(0.3)/TiO2 was put forward firstly. [Copyright &y& Elsevier]

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]

[Display omitted] • Superior toluene catalytic oxidation activity was achieved by Cu 1 Ce 3 binary oxides. • Details of Cu-Ce synergistic effect on toluene catalytic oxidation were studied. • The oxidation of benzyl alcohol into benzoic acid was the rate-determining step. • The toluene catalytic oxidation over Cu 1 Ce 3 binary oxides involves a MvK mechanism. A series of Cu-Ce binary oxides were synthesized via a facile co-precipitation method for toluene catalytic oxidation. The physicochemical properties of these samples were characterized by BET, XRD, SEM, TEM, H 2 -TPR, O 2 -TPD, and XPS. It reveals that Cu 1 Ce 3 catalyst possesses a higher specific surface area, stronger Cu-Ce synergistic effect, and better low-temperature reducibility than other samples. Moreover, Cu 1 Ce 3 catalyst exhibited superior toluene oxidation activity with 99.10% toluene removal efficiency and 97.28% CO 2 selectivity at 200 °C, as well as satisfactory stability and moisture resistance. Therefore, Cu 1 Ce 3 catalyst indicates a huge potential for practical applications, such as coal-fired flue gas and spray coating industry. The reaction pathways for toluene catalytic oxidation over the Cu 1 Ce 3 catalyst were further illuminated by in-situ DRIFTs. In the main pathway, toluene molecules were firstly in contact with the interface lattice oxygen, then the abstraction of H atoms occurred on the methyl group, and benzyl alcohol is considered as the primary intermediate, during which the rate-determining step is the oxidation of benzyl alcohol. In the secondary pathway, a little proportion of toluene molecules were directly oxidized into benzoic acid by the chemisorbed oxygen species. In subsequent steps, all the intermediates were converted into CO 2 and H 2 O. At last, it is confirmed that the toluene oxidation over Cu 1 Ce 3 catalyst involves a Mars-van-Krevelen mechanism via this study. [ABSTRACT FROM AUTHOR]

• SO 2 had a dual effect on Hg0 removal. • O 2 can offset the adverse effects caused by SO 2 and H 2 O. • 1V-8Ce/AC sorbent exhibited good sulfur resistance and excellent stability. The influences of SO 2 on Hg° removal over the 1V-8Ce/AC sorbent were systematically investigated at low temperatures. The experimental results showed that SO 2 has a dual effect on Hg° removal, that is, SO 2 has both a promoting effect and an inhibiting effect on Hg° removal. The SO 2 transient response experiment indicated that SO 2 could not only react with Hg° to promote the removal of Hg° but also react with the active components and poison the sorbent. O 2 is indispensable for the removal of Hg°, which can offset the adverse effects caused by SO 2 and H 2 O. HCl exhibited an obvious promoting effect on Hg° removal in the presence of SO 2. The 1V-8Ce/AC sorbent exhibited good sulfur resistance and excellent stability (E Hg = 90.04 %) after a 24 h reaction performed under the 1000 ppm SO 2 condition at 150 °C. In addition, the Hg-TPD and XPS methods were used to assist in studying the effect of SO 2 on Hg° removal over the 1V-8Ce/AC sorbent. Finally, the mechanism of Hg° removal in an SO 2 atmosphere was also explored, which showed that Hg° was removed by two possible pathways over the 1V-8Ce/AC sorbent. [ABSTRACT FROM AUTHOR]

• Different Mn (II) precursors' effects of MnO 2 on toluene oxidation were observed. • MnO 2 -Ac showed the best activity, and good stability when 5% H 2 O in exhaust gas. • Specific surface areas, Mn3+/Mn4+ and surface adsorbed oxygen affected the activity. • Reaction pathway of toluene oxidation was presented over MnO 2 -Ac sample. MnO 2 -Ac, MnO 2 -N, MnO 2 -Cl and MnO 2 -S samples were prepared by the redox reaction between potassium permanganate and manganese acetate, manganese nitrate, manganese chloride and manganese sulfate and the effect of Mn (II) precursor on the toluene oxidation was studied. The physicochemical properties of these samples were characterized by XRD, TEM, N 2 asdorption-desorption isotherms, H 2 -TPR and XPS. Results showed that the catalytic activity of the four samples decreased in the order of MnO 2 -Ac > MnO 2 -N > MnO 2 -Cl > MnO 2 -S, which was highly related to the specific surface areas, oxygen vacancy concentration and the content of adsorbed oxygen. MnO 2 -Ac owned potential for practical applications. It showed superior toluene oxidation activity with T 90 of 200 °C, as well as excellent water-resistance and stability during 50 h at 300 °C. The good catalytic activities under high WHSV and high toluene concentration were also observed over MnO 2 -Ac. Moreover, the reaction pathway of toluene oxidation was presented with the aid of In-situ DRIFTS. [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]