Mullite-like SmMn2O5-Derived Composite Oxide-Supported Ni-Based Catalysts for Hydrogen Production by Auto-Thermal Reforming of Acetic Acid

The x%Ni/Sm2O3-MnO (x = 0, 10, 15, 20) catalysts derived from SmMn2O5 mullite were prepared by solution combustion and impregnation method; auto-thermal reforming (ATR) of acetic acid (HAc) for hydrogen production was used to explore the metal-support effect induced by Ni loadings on the catalytic reforming activity and product distribution. The 15%Ni/Sm2O3-MnO catalyst exhibited optimal catalytic performance, which can be due to the appropriate Ni loading inducing a strong metal-support interaction to form a stable Ni/Sm2O3-MnO active center, while side reactions, such as methanation and ketonization, were well suppressed. According to characterizations, Sm2O3-MnO mixed oxides derived from SmMn2O5 mullite were formed with oxygen vacancies; nevertheless, loading of Ni metal further promoted the formation of oxygen vacancies, thus enhancing adsorption and activation of oxygen-containing intermediate species and resulting in higher reactivity with HAc conversion near 100% and hydrogen yield at 2.62 mol-H2/mol-HAc.

Impact of Ce/Zr Ratio in the Nanostructured Ceria and Zirconia Composites on the Selective CO2 Adsorption

High surface-area, mesoporous CeO2, ZrO2, and Ce-Zr composite nanoparticles were developed using the hydrothermal template-assisted synthesis method. Samples were characterized using XRD, N2 physisorption, TEM, XPS, and FT-IR spectroscopic methods. The CO2 adsorption ability of the obtained materials was tested under dynamic and equilibrium conditions. A high CO2 adsorption capacity in CO2/N2 flow or CO2/N2/H2O was determined for all studied adsorbents depending on their composition flow. A higher CO2 adsorption was registered for Ce-Zr composite nanomaterials due to the presence of strong O2- base sites and enriched surface oxygen species. The role of the Ce/Zr ratio is the process of the formation of highly active and selective adsorption sites is discussed. The calculated heat of adsorption revealed the processes of chemisorption and physisorption. Experimental data could be appropriately described by the Yoon-Nelson kinetic model. The composites reused in five adsorption/desorption cycles showed a high stability with a slight decrease in CO2 adsorption capacities in dry flow and in the presence of water vapor.

Effecting pattern study of SO2 on Hg0 removal over α-MnO2 in-situ supported magnetic composite

α-MnO₂ was in-situ supported onto silica coated magnetite nanoparticles (MagS-Mn) to study the adsorption and oxidation of Hg⁰ as well as the effecting patterns of SO₂ and O₂ on Hg⁰ removal. MagS-Mn showed Hg⁰ removal capacity of 1122.6 μg/g at 150 °C with the presence of SO₂. Hg⁰ adsorption and oxidation efficiencies were 2.4% and 90.6%, respectively. Hg⁰ removal capability deteriorated at elevated temperatures. Surface oxygen and manganese chemistry analysis indicated that SO₂ inhibited the Hg⁰ removal through consumption of adsorbed oxygen and reduction of high valence manganese. This inhibiting effect was observed to be counteracted by O₂ at lower temperatures. O₂ tended to compete with SO₂ for active sites and further create additional adsorbed oxygen sites for Hg⁰ surface reaction via surface dissociative adsorption rather than replenish the active sites consumed by SO₂. The high valence manganese was also preserved by O₂ which was essential to Hg⁰ oxidation. The intervention of O₂ in the inhibition of SO₂ on Hg⁰ removal was weakened at temperatures higher than 250 °C. Aa a result, Hg⁰ tends to be catalytic oxidized in the condition of low reaction temperatures and with the presence of O₂ over α-MnO₂ oriented composites.

CeO2–Co3O4 nanocomposite with oxidase-like activity for colorimetric detection of ascorbic acid†

A CeO₂–Co₃O₄ nanocomposite (NC) was prepared and characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The obtained CeO₂–Co₃O₄ NC displayed biomimicking oxidase-like activity, which can catalytically oxidize the 3, 3′, 5, 5′-tetramethylbenzidine (TMB) substrate from colorless to the blue oxidized TMB (ox-TMB) product with a characteristic absorption peak at 652 nm. When ascorbic acid (AA) was present, ox-TMB would be reduced, resulting in a lighter blue and lower absorbance. On the basis of these facts, a simple colorimetric method for detection of AA was established with a linear relationship ranging from 1.0 to 500 μM and a detection limit of 0.25 μM. When this method was used to detect AA in human serum and commercially available vitamin C tablet samples, a good recovery of 92.0% to 109.0% was obtained. Besides, the catalytic oxidation mechanism was investigated, and the possible catalytic mechanism of CeO₂–Co₃O₄ NC can be described as follows. TMB is adsorbed on the CeO₂–Co₃O₄ NC surface and provides lone-pair electrons to the CeO₂–Co₃O₄ NC, leading to an increase in electron density of the CeO₂–Co₃O₄ NC. An increased electron density can improve the electron transfer rate between TMB and the oxygen absorbed on its surface to generate O₂˙⁻ and ˙O₂, which further oxidize TMB.

A CeO₂–Co₃O₄ nanocomposite (NC) was prepared and characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction.

Influence of Oxidative Properties of CexZr1−xO2 Catalyst on Partial Oxidation of Dimethyl Ether

Partial oxidation of dimethyl ether (DME) to hydrogen is an efficient route for hydrogen production for application in SOFC. However, quite a large amount of CO2 as a byproduct has been an important obstacle. In this work, cerium–zirconium solid solution (CexZr1−xO2) was applied to determine how the oxidative properties of the catalyst affect the production of CO2 in the partial oxidation of DME. The results show that the catalyst with more adsorbed oxygen (Oads) rather than the lattice oxygen has stronger oxidizability and gives higher DME conversion as well as higher CO2 yield, due to the overoxidation of CO.

Ultra-high adsorption of Hg0 using impregnated activated carbon by selenium

Activated carbon was one of the main adsorptions utilized in elemental mercury (Hg⁰) removal from coal combustion flue gas. However, the high cost and low physical adsorption efficiency of activated carbon injection (ACI) limited its application. In this study, an ultra-high efficiency (nearly 100%) catalyst sorbent-Se_x/Activated carbon (Se_x/AC) was synthesized and applied to remove Hg⁰ in the simulated flue gas, which exhibited 120 times outstanding adsorption performance versus the conventional activated carbon. The Se_x/AC reached 17.98 mg/g Hg⁰ adsorption capacity at 160 °C under the pure nitrogen atmosphere. Moreover, it maintained an excellent mercury adsorption tolerance, reaching the efficiency of Hg⁰ removal above 85% at the NO and SO₂ conditions in a bench-scale fixed-bed reactor. Characterized by the multiple methods, including BET, XRD, XPS, kinetic and thermodynamic analysis, and the DFT calculation, we demonstrated that the ultrahigh mercury removal performance originated from the activated Se species in Se_x/AC. Chemical adsorption plays a dominant role in Hg⁰ removal: Selenium anchored on the surface of AC would capture Hg⁰ in the flue gas to form an extremely stable substance-HgSe, avoiding subsequent Hg⁰ released. Additionally, the oxygen-containing functional groups in AC and the higher BET areas promote the conversion of Hg⁰ to HgO. This work provided a novel and highly efficient carbon-based sorbent -Se_x/AC to capture the mercury in coal combustion flue gas. Graphical abstract Selenium-modified porous activated carbon and the interface functional group promotes the synergistic effect of physical adsorption and chemical adsorption to promote the adsorption capacity of Hg⁰.

Molten salt synthesis of WS2 and MoS2 nanosheets toward efficient gaseous elemental mercury capture

The development of high-efficient adsorbents for Hg⁰ capture in a broad temperature window remains a big challenge. Transition-metal dichalcogenides (TMDs) present great prospects owing to their two-dimensional layered structures and abundant active sulfur species. Here, tungsten disulfide (WS₂) and molybdenum disulfide (MoS₂) nanosheets are easily synthesized via a molten salt route and employed for Hg⁰ sequestration. With the elevation of the annealing temperature, the Hg⁰ capture ability of WS₂ nanosheet gradually enhances, while MoS₂ nanosheet first increases and then decreases. They both display good mercury removal performances in an enlarged temperature range of 60-260 °C. Acidic flue gas components (i.e., SO₂ and NO) subtly interfere the mercury removal process, indicating the prospective application potentials of WS₂ and MoS₂ nanosheets in thermal plants.

Preparation of Ce x Zr1-x O2 by Different Methods and Its Catalytic Oxidation Activity for Diesel Soot

Novel Ce _x Zr_1-x O₂ (x = 0.67, 0.8, 0.9, 1.0) catalysts were designed and synthesized by solvothermal, calcination, and sol-gel methods and were used to catalyze oxidation of soot from diesel vehicle exhaust. The influence of catalysts synthesized by different methods and Ce/Zr molar ratios on the performance was investigated. These catalysts were characterized by XRD, N₂ adsorption-desorption, FT-IR, TEM, XPS, H₂-temperature programmed reduction (TPR), and O₂-temperature programmed desorption (TPD) techniques. The results indicated that Ce_0.8Zr_0.2O₂ prepared by the calcination method has excellent activity and stability at low temperature. The soot ignition point is 322 °C, and the ratio of soot conversion reaches 90% at 497 °C, which is lower than that from the solvothermal and sol-gel methods. The XRD, Raman, SEM, XPS and H₂-TPR results reveal that the structure and oxygen adsorption properties are crucial to soot oxidation activity, and Zr⁴⁺ is successfully doped into the CeO₂ lattice and forms a homogeneous solid solution. Nanostructured Ce_0.8Zr_0.2O₂ with 110.2 m²/g surface areas is produced. The proportion of chemical oxygen and surface adsorbed oxygen in the catalyst prepared from the calcination method is the highest at 23.18%. The structure may lead to charge imbalance, unsaturated bonds, and oxygen vacancies, thus increasing the adsorption of oxygen on the catalyst surface.

A review on removal of mercury from flue gas utilizing existing air pollutant control devices (APCDs)

Mercury is a highly toxic heavy metal pollutant. It is of great significance to develop cost-effective mercury pollution control technologies of coal-fired flue gas. Among various mercury from flue gas removal methods, the application of existing air pollution control devices (APCDs) to remove mercury from flue gas is one of the most valuable methods because it doesn't need to install additional mercury removal equipment, reducing the cost of mercury removal. This review summarizes the recent progress of mercury from flue gas removal by APCDs (e.g., SCR denitration device, WFGD system and dust removal device). SCR denitration device can achieve partial removal of mercury in flue gas through combined with WFGD system, but easy inactivation and poor sulfur/water/heavy metals resistance of SCR catalyzers are still the main problems. WFGD systems can remove most of Hg²⁺ (80%-95%), but have low treatment ability for Hg⁰. Various oxidants can effectively oxidize Hg⁰ into Hg²⁺. However, traditional oxidants have high prices and secondary pollution due to the formation of by-products. Fabric filters (FFs), electrostatic precipitators (ESPs) and hybrid fabric filters (HFs) can all control the emission of mercury in the flue gas to a certain extent, especially can effectively remove most of Hg^P and part of Hg²⁺, but has low removal capacity for Hg⁰. Compared with ESP, FF has better capture efficiency for Hg²⁺ and Hg⁰, and a combination of ESP and FF, that is HF, can effectively improve the mercury removal capacity.

Impact of gas impurities on the Hg0 oxidation on high iron and calcium coal ash for chemical looping combustion

Coal-based mercury pollution from power plants has received increasing attention. In a previous study, high iron and calcium coal ash (HICCA) was found as a promising oxygen carrier (OC) for chemical looping combustion (CLC). The purpose of this study was to investigate the catalytic effect of HICCA on Hg⁰ removal as well as the impacts of several gas impurities, such as HCl, SO₂, and NO. Experiments on Hg⁰ removal efficiencies for different atmospheres were performed in the fixed-bed reactor at 850 °C. Based upon the characterization of BET, SEM, XRD, XPS, and EDS of reaction products, the reaction mechanisms of different gases with the HICCA samples were established. The mechanisms were further explained using the thermodynamic equilibrium calculations. The experimental results showed that the Hg⁰ removal efficiency using HICCA was 11.60%, while the corresponding value in the presence of 50 ppm HCl was 90.46%. Hg⁰ removal by HICCA involving HCl is mainly attributed to homogeneous reaction between Hg⁰ and HCl as well as the formation of reactive species (Cl, Cl₂, Cl₂O, O, S, and SCl₂) through the reactions of HCl with Fe₂O₃ and CaSO₄ in HICCA. The formation of C-Cl bond is not the main pathway for the promotional effect of HCl on Hg⁰ removal. SO₂ played a negative role in Hg⁰ removal by HICCA. The inhibition of SO₂ may be attributed to its effect on the reduction of Fe₂O₃ and its bonding with C-O, COOH, and C(O)-O-C. NO enhanced Hg⁰ removal by HICCA primarily through the homogeneous reactions of Hg⁰ with N₂O and O. In addition, NO also interacted with HICCA and promoted the heterogeneous oxidation of Hg⁰ by producing more C-O, C=O, and COOH/C(O)-O-C on HICCA surface. This study proved the effectiveness of HICCA on Hg⁰ removal in iG-CLC and revealed the mechanisms of the interaction between HCl/SO₂/NO and M_xO_y/CaSO₄ as well as carbon-oxygen groups.

Simultaneous removal of gaseous CO and elemental mercury over Cu-Co modified activated coke at low temperature

Cu-Co multiple-oxides modified on HNO₃-pretreated activated coke (AC_N) were optimized for the simultaneous removal of gaseous CO and elemental mercury (Hg⁰) at low temperature (< 200 °C). It was found that 2%CuOx-10%CoOx/AC_N catalyst calcined at 400°C resulted in the coexistence of complex oxides including CuO, Cu₂O, Co₃O₄, Co₂O₃ and CoO phases, which might be good for the simultaneous catalytic oxidation of CO by Co-species and removal of Hg⁰ by Cu-species, benefiting from the synergistic catalysis during the electro-interaction between Co and Cu cations (CoO ⇌ Co₃O₄ and Cu₂O ⇌ CuO). The catalysis removal of CO oxidation was obviously depended on the reaction temperature obtaining 94.7% at 200 °C, while no obvious promoting effect on the Hg⁰ removal (68.3%-78.7%). These materials were very substitute for the removal of CO and Hg° from the flue gas with the conditions of 8-20 vol.% O₂ and flue-gas temperature below 200 °C. The removal of Hg° followed the combination processes of adsorption and catalytic oxidation reaction via Langmuir-Hinshelwood mechanism, while the catalysis of CO abided by the Mars-van Krevelen mechanism with lattice oxygen species.

Synthesis and catalytic properties of a novel copper- and manganese-substituted cerium dioxide for benzene remediation

Catalysts based on inexpensive and abundant transition metals are necessary for effective environmental remediation. In this study, a series of CuMn-CeO2 catalysts is synthesized by a simple coprecipitation method. The properties of the as-prepared catalysts are characterized by X-ray diffraction, Brunauer–Emmett–Teller analysis, scanning electron microscopy–energy-dispersive spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The introduction of dopants results in rougher surfaces with greater surface areas and pore volumes as well as more surface defects. Furthermore, the dopant-added catalysts exhibit higher activities for benzene oxidation, as the temperature required for 90% benzene removal with Cu4Mn1-CeO2 (656 K) was 231 K lower than that required with CeO2. The superior performance of the dopant-added CeO2 catalyst is attributed to the generation of defect-rich surfaces due to the isomorphous substitution of Cu and Mn in the crystal lattice of CeO2.

Organic-Inorganic Composite Nanorods as an Excellent Mimicking Peroxidases for Colorimetric Detection and Evaluation of Antioxidant

N,N'-Dicarboxy methyl perylene diimide-coated CeO₂ nanorods (PDI/CeO₂ NR) were synthesized via an ultrasonic-assisted method. PDI/CeO₂ exhibits the superb mimic peroxidase functions confirmed by the catalyzed oxidation of TMB by hydrogen peroxide in less than 60 s along with color transformation from colorless to blue. The catalytic mechanism was confirmed to be an electronic transfer mechanism by fluorescence experiment. Thus, a visual colorimetric sensor was constructed for hydrogen peroxide detection with a low detection limit (LOD = 2.23 μM). Comparing the inhibition effects of l-cysteine (Cys), ascorbic acid (AA) and glutathione (GSH) on the catalytic oxidation of TMB, it can be found that they possessed different types of inhibition on the oxidation of TMB by H₂O₂ using PDI/CeO₂, and AA has better antioxidant effect, followed by Cys and GSH. On the basis of the excellent antioxidant effect of AA, a low-cost colorimetric sensor was also used to detect AA, and a lower LOD value (0.68 μM) was obtained in the linear range of 5.0-30 μM.

Mercury in natural gas streams: A review of materials and processes for abatement and remediation

The role of natural gas in mitigating greenhouse gas emissions and advancing renewable energy resource integration is undoubtedly critical. With the progress of hydrocarbons exploration and production, the target zones become deeper and the possibility of mercury contamination increases. This impacts on the industry from health and safety risks, due to corrosion and contamination of equipment, to catalyst poisoning and toxicity through emissions to the environment. Especially mercury embrittlement, being a significant problem in LNG plants using aluminum cryogenic heat exchangers, has led to catastrophic plant incidents worldwide. The aim of this review is to critically discuss the conventional and alternative materials as well as the processes employed for mercury removal during gas processing. Moreover, comments on studies examining the geological occurrence of mercury species are included, the latest developments regarding the detection, sampling and measurement are presented and updated information with respect to mercury speciation and solubility is displayed. Clean up and passivation techniques as well as disposal methods for mercury-containing waste are also explained. Most importantly, the environmental as well as the health and safety implications are addressed, and areas that require further research are pinpointed.

Catalytic oxidation of Hg0 with O2 induced by synergistic coupling of CeO2 and MoO3

Based on Volcano plotting, the controlled combination of weak and strong bond strengths of a bimetallic catalyst has the potential to maximize the catalytic effect via the formation of intermediate bond strength between the reactant and the two different types of active sites. In this study, a rational design approach was adopted to couple MoO₃ and CeO₂ to maximize the catalytic oxidation of Hg⁰ using oxygen as the oxidizing agent. It is found that CeO₂ displayed a relatively strong bond strength with Hg⁰ while MoO₃ has relatively weak bond strength with Hg⁰; the pre-doping of MoO₃ results in the transformation of CeO₂ from clusters to the form with additional exposed CeO₂ (111) surface; the CeO₂ and MoO₃ show synergistic effect on the formation of Brønsted acid sites. Moreover, the results show that there is an overlap between the Hg⁰ desorption region of MoO₃ and the Hg⁰ adsorption region of CeO₂ (with adjusted optimum bond strength with Hg⁰), which contributes to the catalytic reaction of Hg⁰ by O₂. Therefore, this study reveals that the synergistic effects of the coupling of CeO₂ and MoO₃ induced the reaction between Hg⁰ and O₂, which is otherwise difficult.

A novel catalytic oxidation process for removing elemental mercury by using diperiodatoargentate(III) in the catalysis of trace ruthenium(III)

A series of experiments were conducted at a bench scale reactor to investigate the effects of key influencing factors on the Hg⁰ removal from flue gas using the prepared diperiodatoargentate (III) (DPA) as an oxidant, trace ruthenium(III) as a catalyst, respectively. The experimental results showed that the average Hg⁰ removal efficiency reached to 87.5% under the optimal conditions in which the DPA concentration was 1.03 mmol/L, catalyst concentration was 2.0 μmol/L, reaction temperature was 40 °C and solution pH was 8.5. Meanwhile, it was found from the experiments that the high concentrations of SO₂ and NO could inhibit the Hg⁰ removal due to the competition between Hg⁰ and SO₂/NO, while the lower NO concentration exhibited a slight promotion for Hg⁰ removal. The evolutions of DPA(III) and Ru(III) before and after the reaction were characterized by an ultraviolet visible spectrophotometer (UV-vis), from which, the promotional mechanism of Ru(III) on Hg⁰ removal was analyzed. The spent solution was analyzed by a cold vapor atomic fluorescence spectrometer (CVAFS), which verified that Hg⁰ was oxidized into Hg²⁺ by the catalytic system of DPA(III)-Ru(III), and DPA was converted into Ag⁺.

Vanadium silicate (EVS)-supported silver nanoparticles: A novel catalytic sorbent for elemental mercury removal from flue gas

Vanadium silicate (EVS) is a vanadium-substituted form of titanosilicate that has a high potential for use as a sorbent for mercury removal. In the present study, EVS with supported silver nanoparticles (EVS-Ag100) as the catalytic sorbent was synthesized for elemental mercury (Hg°) capture. The physical and chemical properties of the sorbents were investigated. The raw EVS exhibited a poor Hg° capture capacity (7.7 μg g^-1), because most of the vanadium species in the structure of EVS were V⁴⁺. The loading of the silver could significantly enhance the Hg° capture capacity (63.4 μg g^-1). EVS-Ag100 exhibited a superior Hg° capture performance at temperatures of approximately 150 °C. Silver nanoparticles that formed on the EVS were the active sites. In addition, the vanadium species of EVS-Ag100 exhibited higher Hg° oxidation activity than those in the framework of raw EVS. The XPS results revealed the activation of the vanadium species by the silver nanoparticles. After the capture of Hg° in the presence of O₂, more V⁵⁺ was observed on the surface of EVS-Ag100. Exposure of EVS-Ag100 to a continuous simulated flue gas at 150 °C with a gas hourly space velocity of 220,000 h^-1 led to Hg° removal efficiency of >96% in a 1 h test.

CeO2-Decorated ?-MnO2 Nanotubes: A Highly Efficient and Regenerable Sorbent for Elemental Mercury Removal from Natural Gas

CeO₂ nanoparticle-decorated ?-MnO₂ nanotubes (NTs) were prepared and tested for elemental mercury (Hg⁰) vapor removal in simulated natural gas mixtures at ambient conditions. The composition which had the largest surface area and a relative Ce/Mn atomic weight ratio of around 35% exhibited a maximum Hg⁰ uptake capacity exceeding 20 mg?g^?1 (2 wt %), as determined from measurements of mercury breakthrough which corresponded to 99.5% Hg⁰ removal efficiency over 96 h of exposure. This represents a significant improvement in the activity of pure metal oxides. Most importantly, the composite nanosorbent was repeatedly regenerated at 350 ?C and retained the 0.5% Hg⁰ breakthrough threshold. It was projected to be able to sustain 20 regeneration cycles, with the presence of acid gases, CO₂, and H₂S, not affecting its performance. This result is particularly important, considering that pure CeO₂ manifests rather poor activity for Hg⁰ removal at ambient conditions, and hence, a synergistic effect in the composite nanomaterial was observed. This possibly results from the addition of facile oxygen vacancy formation at ?-MnO₂ NTs and the increased amount of surface-adsorbed oxygen species.

Peroxymonosulfate catalyzed by rGO assisted CoFe2O4 catalyst for removing Hg0 from flue gas in heterogeneous system

The cobalt ferrite-reduced oxidized graphene (CoFe₂O₄/rGO) catalyst was synthesized by hydrothermal method and characterized by Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Brunauere Emmette Teller (BET) and Hysteresis loop. For developing a new method of removing elemental mercury (Hg⁰) from flue gas, the effects of catalyst dosage, PMS concentration, solution pH and reaction temperature on the removal efficiency were investigated experimentally by using peroxymonosulfate (PMS) catalyzed by CoFe₂O₄/rGO at a self-made bubbling reactor. The average removal efficiency of Hg⁰ in a 30-min period reached 95.56%, when CoFe₂O₄/rGO dosage was 0.288 g/L, PMS concentration was 3.5 mmol/L, solution pH was 5.5 and reaction temperature was 55 °C. Meanwhile, based on the free radical quenching experiments, in which, ethyl alcohol and tert butyl alcohol were used as quenchers to prove indirectly the presence of ^•OH and SO₄^•-, the characterizations of catalysts and reaction products, and the existing results from other scholars. The reaction mechanism was proposed.

Co3O4/g-C3N4 Hybrids for Gas-Phase Hg0 Removal at Low Temperature

The Co3O4/g-C3N4 hybrids are constructed via the incipient wetness impregnation method by depositing Co3O4 onto the exterior of g-C3N4, and then employed for Hg0 capture within 60–240 °C. The results show that the Co3O4/g-C3N4 hybrid with a Co3O4 content of 12 wt% performs optimally with the highest Hg0 removal efficiency of ~100% at or above 120 °C. The high performances of the Co3O4/g-C3N4 hybrids are probably attributed to the tight interfacial contact between Co3O4 and g-C3N4, with its improved electron transfer, inferring that cobalt oxide and g-C3N4 display a cooperative effect towards Hg0 removal. NO and SO2 shows a significant suppressive influence on the mercury capture performance, plausibly owing to the competing adsorption and side reactions.

High Catalytic Performance of Mn-Doped Ce-Zr Catalysts for Chlorobenzene Elimination

Mn-Ce-Zr-O catalysts doped with varying Mn content were prepared and assessed for the catalytic combustion of chlorobenzene (CB). Nanosized MCZ-0.67 catalyst with amorphous phase exhibited a high and stable catalytic activity among the studied catalysts, achieving 90% CB conversion at 226 °C and withstanding stability tests, including time-based stability and the successive influence of various operating conditions. Meanwhile, the MCZ-0.67 catalyst used showed good recyclability by calcination in air. Characterization results suggested that Mn doping played a dominant role in improving the catalytic performance, resulting in larger surface area, better redox properties and greater amounts of surface active oxygen. In addition, the introduction of Zr was also indispensable for maintaining the good catalytic performance of catalysts. Finally, trace amounts of polychlorinated by-products during CB oxidation were monitored and the oxidation process was discussed.

Simultaneous removal of NOx and Hg0 from simulated flue gas over CuaCebZrcO3/r-Al2O3 catalysts at low temperatures: performance, characterization, and mechanism

To optimize the simultaneous removal of NO_x and Hg⁰, a series of Cu_aCe_bZr_cO₃/γ-Al₂O₃ catalysts prepared by the impregnation method were explored and their physical and chemical properties were analyzed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), NH₃-temperature-programmed desorption (NH₃-TPD), H₂-temperature-programmed reduction (H₂-TPR), in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFT), and Fourier transform infrared spectroscopy (FT-IR). The results showed that 15% Cu_1.4Ce_0.55Zr_0.25O₃/γ-Al₂O₃ resulted in the highest conversion efficiency for the simultaneous removal of NO_x (93%) and Hg⁰ (85%) at low temperatures (200 to 300 °C). Meanwhile, 15% Cu_1.4Ce_0.55Zr_0.25O₃/γ-Al₂O₃ showed good stability and resistance to SO₂ and H₂O, which is due to its low crystallinity, good textural performance, and strong redox ability. According to the TPD, TPR, and XPS results, the strong acidic character of 15% Cu_1.4Ce_0.55Zr_0.25O₃/γ-Al₂O₃ promoted the removal of NO_x and Hg⁰. The synergistic effect between CuO and CeO₂ in 15% Cu_1.4Ce_0.55Zr_0.25O₃/γ-Al₂O₃ can increase the mobility of chemically adsorbed oxygen and activates lattice oxygen, leading to an excellent performance. The DRIFT results showed that NH₃, NH₄⁺, nitrate, and nitrite participated in the selective catalytic reduction (SCR) reaction. On the basis of our experimental results, Hg⁰ and NO_x removal mechanisms were proposed as Hg (ad) + O* → HgO (ad) and 2NH₃/NH₄⁺ (ad) + NO₂/NO₃^- (ad) + NO→2N₂ + 3H₂O/2H⁺, respectively.

Structural defects in 2D MoS2 nanosheets and their roles in the adsorption of airborne elemental mercury

In this research, ab initio calculations and experimental approach were adopted to reveal the mechanism of Hg⁰ adsorption on MoS₂ nanosheets that contain various types of defects. The ab initio calculation showed that, among different structural defects, S vacancies (Vs) in the MoS₂ nanosheets exhibited outstanding potential to strongly adsorb Hg⁰. The MoS₂ material was then prepared in a controlled manner under conditions, such as temperature, concentration of precursors, etc., that were determined by adopting the new method developed in this study. Characterisation confirmed that the MoS₂ material is of graphene-like layered structure with abundant structural defects. The integrated dynamic and steady state (IDSS) testing demonstrated that the Vs-rich nanosheets showed excellent Hg⁰ adsorption capability. In addition, ab initial calculation on charge density difference, PDOS, and adsorption pathways revealed that the adsorption of Hg⁰ on the Vs-rich MoS₂ surface is non-activated chemisorption.

Elemental Mercury Adsorption by Cupric Chloride-Modified Mesoporous Carbon Aerogel

Mesoporous carbon aerogels (MCA) synthesized via aqueous polymerization of resorcinol and formaldehyde were modified by copper chloride and applied for adsorption removal of elemental mercury (Hg0) at a low temperature. The sorbents were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms, and X-ray photoelectron spectroscopy (XPS) techniques. The results show that CuCl2-modified MCA exhibited good ability for Hg0 adsorption in the 40–160 °C temperature range, with Hg0 removal efficiency all above 95.0%. The Hg0 removal efficiency first increased and then decreased with the elevation of reaction temperature. It performed optimally at 80 °C with the highest Hg0 removal efficiency of 98.7%. XPS results indicate that covalent chlorines (C-Cl groups) play an important role in elemental mercury adsorption process. Hg0 is firstly captured in the form of oxidized mercury (Hg2+) and then reacts with C-Cl groups to form HgCl2.

Density Functional Theory Study on Mechanism of Mercury Removal by CeO2 Modified Activated Carbon

Doping of CeO2 on activated carbon (AC) can promote its performance for mercury abatement in flue gas, while the Hg0 removal mechanism on the AC surface has been rarely reported. In this research, density functional theory (DFT) calculations were implemented to unveil the mechanism of mercury removal on plain AC and CeO2 modified AC (CeO2-AC) sorbents. Calculation results indicate that Hg0, HCl, HgCl and HgCl2 are all chemisorbed on the adsorbent. Strong interaction and charge transfer are shown by partial density of states (PDOS) analysis of the Hg0 adsorption configuration. HCl, HgCl and HgCl2 can be dissociatively adsorbed on the AC model and subsequently generate HgCl or HgCl2 released to the gas phase. The adsorption energies of HgCl and HgCl2 on the CeO2-AC model are relatively high, indicating a great capacity for removing HgCl and HgCl2 in flue gas. DFT calculations suggest that AC sorbents exhibit a certain catalytic effect on mercury oxidation, the doping of CeO2 enhances the catalytic ability of Hg0 oxidation on the AC surface and the reactions follow the Langmuir–Hinshelwood mechanism.

Catalytic Oxidation of Benzyl Alcohol Using Nanosized Cu/Ni Schiff-Base Complexes and Their Metal Oxide Nanoparticles

In this work, nanosized Cu and Ni Schiff-base complexes, namely ahpvCu, ahpnbCu, and ahpvNi, incorporating imine ligands derived from the condensation of 2-amino-3-hydroxypyridine, with either 3-methoxysalicylaldehyde (ahpv) or 4-nitrobenzaldehyde (ahpnb), were synthesized using sonochemical approach. The structure and properties of the new ligands and their complexes with Ni(II) and Cu(II) were determined via infrared (IR), nuclear magnetic resonance (NMR), electronic spectra (UV-Vis), elemental analysis (CHN), thermal gravimetric analysis (TGA), molar conductivity (Λm), and magnetic moment (μeff). The combined results revealed the formation of 1:1 (metal: ligand) complexes for ahpvCu and ahpvNi and 1:2 for ahpnbCu. Additionally, CuO and NiO nanoparticles were prepared by calcination of the respective nanosized Cu/Ni complexes at 500 °C, and characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Significantly, the as-prepared nanosized Schiff-base Cu/Ni complexes and their oxides showed remarkable catalytic activity towards the selective oxidation of benzyl alcohol (BzOH) in aqueous H2O2/ dimethylsulfoxide (DMSO) solution. Thus, catalytic oxidation of BzOH to benzaldehyde (BzH) using both ahpvCu complex and CuO nanoparticles in H2O2/DMSO media at 70 °C for 2 h yielded 94% and 98% BzH, respectively, with 100% selectivity.

Application of Plasma Treatment in Preparation of Soybean Oil Factory Sludge Catalyst and Its Application in Selective Catalytic Oxidation (SCO) Denitration

At present, the most commonly used denitration process is the selective catalytic reduction (SCR) method. However, in the SCR method, the service life of the catalyst is short, and the industrial operation cost is high. The selective catalytic oxidation absorption (SCO) method can be used in a low temperature environment, which greatly reduces energy consumption and cost. The C/N ratio of the sludge produced in the wastewater treatment process of the soybean oil plant used in this paper is 9.64, while the C/N ratio of the sludge produced by an urban sewage treatment plant is 10⁻20. This study shows that the smaller the C/N ratio, the better the denitration efficiency of the catalyst. Therefore, dried oil sludge is used as a catalyst carrier. The influence of different activation times, and LiOH concentrations, on catalyst activity were investigated in this paper. The denitration performance of catalysts prepared by different activation sequences was compared. The catalyst was characterized by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The experimental results showed that: (1) When the concentration of the LiOH solution used for activation is 15%, and the activation time is four hours, the denitration effect of the catalyst is the best; (2) the catalyst prepared by activation before plasma roasting has the best catalytic activity.

Low-temperature co-purification of NOx and Hg0 from simulated flue gas by CexZryMnzO2/r-Al2O3: the performance and its mechanism

In this study, series of Ce_xZr_yMn_zO₂/r-Al₂O₃ catalysts were prepared by impregnation method and explored to co-purification of NO_x and Hg⁰ at low temperature. The physical and chemical properties of the catalysts were investigated by XRD, BET, FTIR, NH₃-TPD, H₂-TPR, and XPS. The experimental results showed that 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ yielded higher conversion on co-purification of NO_x and Hg⁰ than the other prepared catalysts at low temperature, especially at 200-300 °C. 91% and 97% convert rate of NO_x and Hg⁰ were obtained, respectively, when 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ catalyst was used at 250 °C. Moreover, the presence of H₂O slightly decreased the removal of NO_x and Hg⁰ owing to the competitive adsorption of H₂O and Hg⁰. When SO₂ was added, the removal of Hg⁰ first increased slightly and then presented a decrease due to the generation of SO₃ and (NH₄)₂SO₄. The results of NH₃-TPD indicated that the strong acid of 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃ improved its high-temperature activity. XPS and H₂-TPR results showed there were high-valence Mn and Ce species in 10% Ce_0.2Zr_0.3Mn_0.5O₂/r-Al₂O₃, which could effectively promote the removal of NO_x and Hg⁰. Therefore, the mechanisms of Hg⁰ and NO_x removal were proposed as Hg (ad) + [O] → HgO (ad), and 2NH₃/NH₄⁺ (ad) + NO₂ (ad) + NO (g) → 2 N₂ + 3H₂O/2H⁺, respectively. Graphical abstract ᅟ.