Temperature-programmed Desorption Analysis Research Articles

Leveraging Cu/CuFe2O4-Catalyzed Biomass-Derived Furfural Hydrodeoxygenation: A Nanoscale Metal-Organic-Framework Template Is the Prime Key.

Enormous efforts have been initiated in the production of biobased fuels and value-added chemicals via biorefinery owing to the scarcity of fossil resources and huge environmental synchronization. Herein, non-noble metal-based metal/mixed metal oxide supported on carbon employing a metal-organic framework as a sacrificial template is demonstrated for the first time in the selective hydrodeoxygenation (HDO) of biomass-derived furfural (FFR) to 2-methyl furan (MF). The aforementioned catalyst (referred to as Cu/CuFe2O4@C-A) exhibited extraordinary catalytic proficiency (100% selectivity toward MF) compared with the conventional Cu/CuFe2O4@C-B catalyst which was prepared by the wet impregnation method. High-resolution transmission electron microscopy and synchrotron X-ray diffraction studies evidenced the existence of both metal (Cu) and mixed metal oxide (CuFe2O4) phases, in which the metal could help in hydrogenation to alcohol and metal oxide could assist in the hydroxyl group removal step during HDO reaction. The stabilization of encapsulated metal/metal oxide nanoparticles in the carbon matrix, modulation of the electronic structure, and regulation of geometric effects in the Cu/CuFe2O4@C-A are thought to play an important role in its excellent catalytic performance, confirmed by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy investigations. Furthermore, the structure and activity interconnection was confirmed by in situ attenuated total reflection-IR studies, which manifested the strong interfacial interaction between FFR and the Cu/CuFe2O4@C-A catalyst. This finding was further supported by NH3 temperature-programmed desorption analysis, which suggested that the presence of more Lewis/weak acidic sites in this catalyst was beneficial for the hydrogenolysis step in HDO reaction. Additionally, H2 temperature-programmed reduction studies revealed that the adsorption of H2 was stronger on the Cu/CuFe2O4@C-A than that over the conventional Cu/CuFe2O4@C-B catalyst; thus, the former catalyst promoted activation of H2. A detailed kinetic analysis which demonstrated the lower activation energy barrier along with dual active sites attributed for the activation of the two separate reactions in the HDO process on the Cu/CuFe2O4@C-A catalyst. This work has great implication in developing a highly stable catalyst for the selective upgradation of biomass without deactivation of metal sites in extended catalytic cycles and opens the door of opportunity for developing a sustainably viable catalyst in biomass refinery industries.

Atomically Dispersed Manganese on a Carbon-Based Material for the Capture of Gaseous Mercury: Mechanisms and Environmental Applications.

A novel, atomically dispersed carbon-based sorbent was synthesized by anchoring manganese atoms with N atoms for the capture of gaseous elemental Hg (Hg0). Oxygen atoms were also introduced into the synthesis process to adjust the oxidizing ability of the Mn atoms. High-valence Mn (Mn4+) anchored by the O and N atoms (Mn-O/N-C) in the carbon-based materials provided more exposed active sites. The mercury removal efficiency of the composite exceeded 99%. The composite with a Mn loading of 0.9 wt % exhibited high affinity for Hg0, and the capacity for Hg0 adsorption within 275 min at room temperature reached 16.95 mg·g-1. The Mn utilization was ∼56.61%, which is much larger than that of reported Mn-based oxide sorbents. The atomic-level distribution of Mn was well evidenced by aberration-corrected high-angle annular darkfield scanning transmission electron microscopy. Density functional theory calculations were conducted to evaluate the energy for adsorption of Hg0 on Mn-O/N-C. The results indicated that the amount of N and O atoms in the Mn coordination environment determined the Hg0 adsorption energy, and the presence of five optimized Mn adsorption structures in Mn-O/N-C was confirmed by Hg temperature-programmed desorption analysis. These materials may be utilized for mercury removal from disposal sites with high concentrations of mercury, broken mercury-containing lamps, or mercurial thermometers. The strategy of atomic dispersion during synthesis of the materials and adjusting the oxidizing ability in the single-atom strategy may be helpful for the development of environmentally benign functional materials.

Determination of active sites during gasification of biomass char with CO2 using temperature-programmed desorption. Part 2: Influence of ash components

The present work is the second part of a study conducted with the aim to determine the amount of active sites present on the surface of a biomass char participating in the gasification reaction with CO2 using the temperature programmed desorption (TPD) technique. In part 1, the methodology and experimental results during TPD of partially gasified samples of beech wood char (WC1600) using CO2 as gasification agent are presented. This work focusses on the influence of the main inorganic ash components of WC1600 on the CO2 and CO signals obtained during TPD of partially gasified char samples. Furthermore, an activated carbon with ash content lower than 1 wt-% is impregnated with Ca and K and partially gasified followed by a TPD analysis. CO2 and CO signals obtained during TPD result from decomposition of oxygenated surface complexes and decomposition reactions of ash components. During gasification, three different kinds of sites are present on the surface of the char: stable, reactive and catalytically active sites. The latter are a measure of the catalytic influence of inorganic matter during char gasification. From the analysis of the TPD spectra, it can be concluded that gasification of WC1600 is dominated by the catalytic influence exerted by Ca and K. Formation of oxygenated surface complexes on WC1600 is limited, possibly due to the high temperature at which the sample was pyrolyzed (1600 °C). However, a direct correlation between specific conversion rate and the amount of reactive and catalytically active sites is developed from the experimental results, corrected by the contribution of ash decomposition.

Preparation of Carbon-Based Solid Acid Catalysts Using Rice Straw Biomass and Their Application in Hydration of α-Pinene

Carbon-based solid acid catalysts were prepared using rice straw (RS) waste, and the effects of carbonization temperature and sulfonation temperature on the catalytic activity were investigated. The properties of the catalysts were characterized using thermo gravimetric (TG), scanning electron microscope (SEM), Brunauer–Emmet–Teller (BET), Fourier transform infrared spectroscopy (FT-IR), temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS), and their activities were investigated through the hydration of α-pinene. The conversion of α-pinene and the selectivity of α-terpineol reached 67.60% and 57.07% at 80 °C and atmospheric pressure in 24 h, respectively. The high catalytic capacity of the catalyst is attributed to the high acid site density and high porosity of the catalyst. TPD analysis and FT-IR spectroscopy showed that the catalyst produced by low-temperature carbonization at 300 °C followed by low-temperature sulfonation at 80 °C had abundant strong acid sites (0.82 mmol/g), which can effectively inhibit the side reactions of hydrated α-pinene. The total acidity reached 2.87 mmol/g. N2-physisorption analysis clearly indicated that the obtained catalysts were mesopore-predominant materials, and the SBET and VTotal of catalysts reached 420.9 m2/g and 4.048 cm3/g, respectively. Preparation of the catalyst involves low energy consumption, and its cheap raw materials make the whole process simple, economical, and environmentally friendly.

Understanding the chemical structure of carbon edge sites by using deuterium-labeled temperature-programmed desorption technique

A deuterium-labeled temperature-programmed desorption (TPD) technique was developed to accurately characterize functional groups on the surface of carbon-based materials. After the protic hydrogen of the functional groups on activated carbons was substituted by deuterium, TPD analysis revealed the desorption of deuterium compounds (D2O, DHO, D2, DH). The functional groups were estimated from the predicted desorption mechanisms of these deuterium compounds, which can be distinguished according to the functional groups and their surrounding chemical structures. Thus, this technique provides information on not only the type of functional groups but also the extensive chemical structure around them. The phenolic group, ether, and edge hydrogen formed on the activated carbons were separately quantified, and the functional groups were further classified into 12 types by the nearby chemical structures. Comparison with IR spectra indicated that the deuterium-labeled TPD gave qualitatively reasonable results. This technique is useful for obtaining a deeper understanding of the surface chemical structure of carbon-based materials.

Structure and Activity of Ni2P/Desilicated Zeolite β Catalysts for Hydrocracking of Pyrolysis Fuel Oil into Benzene, Toluene, and Xylene

The effects of desilication (DS) of the zeolite β on the hydrocracking of polycyclic aromatics were investigated using the Ni2P/β catalysts. The Ni2P/β catalysts were obtained by the temperature-programmed reduction (TPR) method, and the physical and chemical properties were examined by N2 physisorption, X-ray diffraction (XRD), 27Al magic angle spinning–nuclear magnetic resonance (27Al MAS NMR), extended X-ray absorption fine structure (EXAFS), isopropyl amine (IPA) and NH3 temperature-programmed desorption (TPD), CO uptake, and thermogravimetric analysis (TGA). The catalytic activity was examined at 653 K and 6.0 MPa in a continuous fixed bed reactor for the hydrocracking (HCK) of model compounds of 1-methylnaphthalene (1-MN) and phenanthrene or a real feedstock of pyrolysis fuel oil (PFO). Overall, the Ni2P/DS-β was observed as more active and stable in the hydrocracking of polycyclic aromatics than the Ni2P/β catalyst. In addition, the Ni2P/β suffered from the coke formation, while the Ni2P/DS-β maintained the catalytic stability, particularly in the presence of large polycyclic hydrocarbons in the feed.

Promoting SO2 Resistance of a CeO2(5)-WO3(9)/TiO2 Catalyst for Hg0 Oxidation via Adjusting the Basicity and Acidity Sites Using a CuO Doping Method.

The competition between SO2 and elemental mercury (Hg0) for active sites was an important factor for suppressing the Hg0 oxidation properties of catalysts. There were obvious differences in properties of basicity and acidity between SO2 and Hg0. Raising the SO2 resistance via adjusting the basicity and acidity sites of catalysts was promising for reducing the competition between SO2 and Hg0. This study aimed to form multiple active sites with different basicities via Cu, Fe, Mn, and Sn doping. The results indicated that Cu doping had the best modification performance. Five percent CuO doping could significantly improve the SO2 resistance of CuO(5)-CeO2(5)-WO3(9)/TiO2 and increase the mercury oxidation efficiency (MOE) from 54.7 to 85.5% in the condition (6% O2, 100 ppm NO, 100 ppm NH3, and 100 ppm SO2). CO2 temperature-programmed desorption analysis showed that CuO(5)-CeO2(5)-WO3(9)/TiO2 exhibited weak basic sites (CeO2), medium-strong basic sites (Cu-O-Ce), and strong basic sites (CuO). Therefore, the CuO in the Ce-O-Cu structure was prioritized for the reaction with acid gas SO2 and protected CeO2 from SO2 poisoning. This study prepared a highly SO2-resistant catalyst for Hg0 oxidation. This research and development will be conducive for use in Hg0 oxidation in actual coal-fired flue gases.

Unraveling photoexcited electron transfer pathway of oxygen vacancy-enriched ZnO/Pd hybrid toward visible light-enhanced methane detection at a relatively low temperature

In this work, we present a novel CH4 oxidation photocatalyst based on oxygen vacancy-enriched ZnO nanorods/Pd nanoparticles hybrid (OV ZnO/Pd), which could be incorporated into a high-performance photocatalysis-enhanced CH4 sensor operating under visible light illumination at a relatively low temperature. By introducing visible light illumination, the CH4 response of the sensor based on OV ZnO/Pd was enhanced by 6 times compared to that in the dark. The CH4 sensing performance was found to be directly related to the photocatalytic CH4 oxidation activity of the sensing materials. O2 temperature-programmed desorption analysis and in-situ FT-IR spectroscopy suggested the synergistic effect of oxygen vacancies and Pd nanoparticles on promoting the surface oxygen activation and catalytic CH4 oxidation over the OV ZnO/Pd hybrid. Photoelectrochemical measurements revealed a new photoexcited electron transfer pathway in the hybrid, which involved the direct transfer of hot electrons from Pd nanoparticles to the surface oxygen vacancies on ZnO.

Improving catalytic activity of layered lithium transition metal oxides for oxygen electrode in metal-air batteries

Lithium transition metal oxide has superior performance for oxygen evolution reaction (OER), while its activity for catalyzing oxygen reduction reaction (ORR) is too low to meet the demand of practical applications. Herein, the NCM-based (NCM, LiNi1/3Co1/3Mn1/3O2) composite materials are prepared through the two steps method. The NCM-2 (Mn2O3/LiNi1/3Co1/3Mn1/3O2) hybrid material demonstrates excellent ORR catalytic property and high OER catalytic performance, as well as the superior stability. Besides, with NCM-2 hybrid materials as catalysts of air cathode, the Al-air battery and Zn-air battery both exhibit higher power density. Therefore, based on results of Brunauer-Emmett-Teller and O2 temperature programmed desorption analysis, the improved catalytic performance ascribed to large specific surface area, pore structure and enhanced oxygen adsorption ability. In this work, the catalytic activity of lithium transition metal oxide has been improved, and a new method was provided to synthesize bifunctional catalysts for metal-air batteries.

Unravelling the Promotional Effect of La2O3 in Pt/La‐TiO2 Catalysts for CO2 Hydrogenation

This work reports the preparation of a La2 O3 -modified Pt/TiO2 (Pt/La-TiO2 ) hybrid through an excess-solution impregnation method and its application for CO2 hydrogenation catalysis. The Pt/La-TiO2 catalyst is characterized by XRD, H2 temperature-programmed reduction (TPR), TEM, X-ray photoelectron spectroscopy (XPS), Raman, EPR, and N2 sorption measurements. The Pt/La-TiO2 composite starts to catalyze the CO2 conversion reaction at 220 °C, which is 30 °C lower than the Pt/TiO2 catalyst. The generation of CH4 and CO of Pt/La-TiO2 is 1.6 and 1.4 times greater than that of Pt/TiO2 . The CO2 temperature-programmed desorption (TPD) analysis confirms the strengthened CO2 adsorption on Pt/La-TiO2 . Moreover, the in situ FTIR experiments demonstrate that the enhanced CO2 adsorption of Pt/La-TiO2 facilitates the formation of the active Pt-CO intermediate and subsequently boosts the evolution of CH4 and CO. The cycling tests reveal that Pt/La-TiO2 shows reinforced stability for the CO2 hydrogenation reaction because the La species can prevent Pt nanoparticles (NPs) from sintering. This work may provide some guidance on the development new rare-metal-modified hybrid catalysts for CO2 fixation.

Investigation of Oxidative Desulfurization of Light Naphtha by NiMo/-Al2O3 Catalyst

In this research, we investigated the effects of parameters, including reaction time, reaction temperature, the mass ratio (mcat./mfeed), and volume ratio (VH2O2/Vfeed) on sulfur removal conversion of light naphtha under oxidative desulfurization (ODS) reaction. So to achieve this goal, several active catalysts are prepared while molybdenum (Mo) was used as an active metal. Nickel (Ni) was the promoter. 𝛾-alumina (𝛾-Al2O3) was used as a support and modified by chelate agents such as citric acid (C6H8O7), ethylene diamine tetraacetic acid (EDTA), polyethylene glycol (PEG), Sorbitol, and urea ((NH4)2CO). These catalysts were synthesized by using the wetness impregnation in-situ method. Then they were applied to the ODS process for light naphtha. These catalysts were characterized by N2adsorption-desorption isotherms (BET, BJH), Scanning Electron Microscope (SEM), temperature-programmed desorption (NH3-TPD), and FT-IR analysis. The catalyst that synthesized in the presence of sorbitol, had the best performance. The optimization conditions for this catalyst were m (catalyst)/m (feed)= 0.013, reaction temperature of 35 °C, 50 mL of feed, 0.5 g of catalyst, 1 hour reaction time, and V (H2O2)/VFeed = 0.045. It revealed the maximum performance for ODS reaction of the real feed. Under these circumstances, the sulfur of light naphtha decreased from 160 ppm to 38 ppm during the reaction.

Study of the Effect of Adsorption Temperature on Elemental Mercury Removal Performance of Iron-Based Modified Biochar

An iron-based modified biochar was prepared by the coprecipitation method, including single iron-based modified biochar with FeCl3 and iron-based biochar doped with Cu and Mn from CuSO4 and KMnO4. Combined with the physicochemical properties of sorbents, the effect of flue gas temperature on the mercury adsorption performance of the sorbents was explored within the temperature range of 50–350 °C. The adsorption mechanism was further explored by adsorption kinetics, thermodynamics, and temperature-programmed desorption (TPD) analyses. The results showed that the mercury adsorption capacity of unmodified biochar decreased monotonously with temperature, but the adsorption capacities of Fe/BC, FeCu/BC, and FeMn/BC all enhanced first and then weakened, with 200 °C being the optimum adsorption temperature. FeCu/BC had the strongest adsorption capacity, while Fe/BC had the worst one. C═O and COOH, metal oxides and ions, lattice oxygen, chemisorbed oxygen, and Cl ions were all active sites for oxidative adsorption of Hg0, among which Fe2O3 and CuO or CuFe2O4 exerted a synergistic effect. Excessive temperature caused destruction to the porous structure and deactivation of the active centers, leading to the reduction of physisorption and chemisorption. Mercury adsorption on sorbents needs more activated energy due to the enhancement of chemisorption, and the moderate increase of temperature contributed to the adsorption properties of the sorbents. The Hg0 adsorption on modified biochar was spontaneous and endothermic, and the complexity degree of the adsorption process was promoted. TPD results showed that at 200 °C the removal of Hg0 by modified biochar was mainly strong chemisorption and that HgO was mainly formed.

Visible-light photocatalysis enhanced room-temperature formaldehyde gas sensing by MoS2/rGO hybrids

The development of high-performance gas sensors operating at room temperature based on transition metal dichalcogenide (TMD) remains a challenge. Herein, we demonstrated a novel visible-light photocatalysis-enhanced gas sensor based on MoS2/rGO hybrid, enabling high-performance detection of formaldehyde at room temperature. By introducing visible-light illumination, the sensor response to 10 ppm HCHO was increased by over 8 times, and the response time sharply decreased from 79 s to 17 s. The sensor also had advantages of low detection limit, excellent reversibility and long-term stability. The visible-light induced oxygen activation and formaldehyde oxidation over the MoS2 photocatalysts were investigated by X-ray photoelectron spectrometer (XPS), O2 temperature programmed desorption analysis (O2-TPD) and in-situ Fourier transform infrared spectroscopy (in-situ IR). The enhanced room-temperature HCHO sensing by the MoS2/rGO hybrid was connected with the visible-light photocatalytic activity of MoS2 as well as the efficient charge separation rendered by rGO. As a proof-of-concept, the photocatalytic gas sensing approach described here should be a promising strategy for developing room-temperature-operated, high-performance gas sensors based on TMD and other novel semiconductors.

Synthesis, characterization and evaluations of micro/mesoporous ZSM-5 zeolite using starch as bio template

We report a simple and economical method to synthesis hierarchical ZSM-5 zeolite using a natural polymer, soluble starch, as a mesotemplate. The synthesized samples were characterized with X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, nitrogen sorption, ammonia temperature-programmed desorption and thermogravimetric analysis. The crystallinity and Mordenite Framework Inverted structure of the samples was confirmed by X-ray diffraction and Fourier transform infrared spectroscopy analysis. Scanning electron microscopy and transmission electron microscopy images revealed the presence of mesopores in the synthesized samples. The nitrogen adsorption/desorption results of the hierarchical samples have been found to be in agreement with the scanning electron microscopy and transmission electron microscopy results and support the development of mesoporosity. The acidity of the hierarchical zeolite was studied using ammonia temperature-programmed desorption. The thermogravimetric analysis confirmed the thermal stability of the synthesized samples up to 750 °C. The catalytic activities of the modified and unmodified zeolites were specifically tested for the esterification of acetic acid with benzyl alcohol. The results indicate that the hierarchical ZSM-5 catalyst offers a better catalytic yield (76%) than the unmodified systems.

Ultrasonic-assisted green synthesis of β-amino carbonyl compounds by copper oxide nanoparticles decorated phosphate functionalized graphene oxide via Mannich reaction

Highly efficient and active CuO nanoparticle decorated Phosphate functionalised graphene oxide (PGO-CuO) nanocomposite has been synthesized in a water-isopropanol system and used as an active catalyst for the synthesis of β-amino carbonyl compounds via Mannich reaction by using a greener ultrasonic method. • CuO nanoparticles were decorated on PGO via a simple wet chemical synthetic route. • PGO-CuO catalyst was thoroughly characterized by various analytical techniques. • A greener ultrasonic route was used for synthesis of β-amino carbonyl compounds. • Higher catalytic efficiency was obtained under solventless condition. • The catalyst could be recycled for six times without any effective loss in activity. A facile chemical synthetic route has been demonstrated for the synthesis of copper oxide nanoparticles decorated phosphate functionalized graphene oxide (CuO/PGO). The synthesized nanocatalyst was used as an efficient and active candidate for the synthesis of β-amino carbonyl compounds via a green synthetic ultrasonic route. The structural properties of the samples were investigated by means of a number of sophisticated techniques like X-ray diffraction (XRD), Fourier-transform Infrared (FTIR) spectroscopy, High Resolution Transmission Electron Microscope (HRTEM), N 2 adsorption-desorption measurements, X-ray photoelectron spectroscopy (XPS) analysis, Ammonia temperature programmed desorption analysis (NH 3 -TPD) and Raman spectroscopy. HRTEM analysis confirmed the presence of spherical CuO nanoparticles distributed uniformly throughout the PGO surface. XPS analysis demonstrated the presence of Cu 2+ species and minor reduction of oxygen functional groups on GO. A higher surface area of 162 m 2 /g for CuO/PGO was found from N 2 adsorption-desorption isotherms. Later on, the presence of acidic groups on CuO/PGO that play an essential role in the catalytic activity was examined by NH 3 -TPD and pyridine adsorbed IR analysis. The total acidity on the surface of synthesized nanocatalyst was found to be of 0.59 mmol g −1 which includes both Lewis as well as Brönsted acidic sites. A higher product yield of 95% in a shorter period of time of 15 min was achieved which is superior to many reported catalytic systems. A combined strategy involving greener and easier ultrasonic route and use of an efficient acidic graphene oxide-based catalyst resulted in higher catalytic activity and stability with good recyclability.

Highly Effective Ru/BaCeO3 Catalysts on Supports with Strong Basic Sites for Ammonia Synthesis.

BaCeO3 -a and BaCeO3 -b, with strong basic sites, were synthesized by using a co-precipitation method at different calcination temperatures, and used as supports to evaluate their performance in ammonia synthesis. The ammonia synthesis rate with the 1.25 % Ru/BaCeO3 -a catalyst is 24 mmol g-1 h-1 , which is higher than that of 1.25 % Ru/BaCeO3 -b catalyst (18 mmol g-1 h-1 ) at 3 MPa and 450 °C. Moreover, the performance of the 4 % Cs-1.25 % Ru/BaCeO3 -a catalyst was further improved to 28 mmol g-1 h-1 , and no sign of deactivation was observed after a reaction time of 120 h. The XPS and H2 temperature-programmed reduction analyses indicated that the Ru/BaCeO3 -a catalyst has more oxygen vacancies than the Ru/BaCeO3 -b catalyst. In addition, the average Ru particle size of the Ru/BaCeO3 -a catalyst is closer to 2 nm than the Ru/BaCeO3 -b catalyst, which promotes the generation of B5 -type sites (the active site for N2 dissociation). The CO2 temperature-programmed desorption analysis indicates that BaCeO3 -a has a high basic density, which is beneficial for electron transfer to Ru and further facilitates the dissociation of N≡N bonds.

Synergistic effects of UV activation and surface oxygen vacancies on the room-temperature NO2 gas sensing performance of ZnO nanowires

The room-temperature detection of NO2 by metal oxide nanostructures has been a long-term hot topic. The utilization of UV illumination and introducing surface oxygen vacancies (VO) have been demonstrated as effective strategies for enhancing the NO2 sensing performance of metal oxides. Herein, we demonstrated the synergistic effects of UV activation and surface VO on the room-temperature NO2 sensing performance of ZnO nanowires, which were hydrothermally grown and treated in NaBH4 solution to introduce rich surface VO. The room-temperature NO2 sensors based on VO-rich ZnO nanowires showed significantly higher responses and faster response/recovery rates under UV illumination compared with the VO-deficient untreated sample. In addition, the sensors exhibited excellent reversibility, high selectivity and good stability. The synergistically enhanced NO2 sensing performance of ZnO nanowires could be attributed to their improved optoelectronic properties as well as the UV and VO co-modulated surface chemisorption and reactions of Ox− and NOx− species. O2 temperature programmed desorption analysis (O2-TPD), in-situElectron paramagnetic resonance (EPR) and in-situ Fourier transform infrared spectroscopy (IR) spectroscopy studies suggested that surface VO could act as active centers for the ionized adsorption of oxygen to generate highly-active O- species under UV illumination, which would subsequently promote the formation of NO3- species, leading to the enhanced NO2 adsorption and electron transfer at room temperature.

Emission and Migration Characteristics of Mercury in a 0.3 MWth CFB Boiler with Ammonium Bromide-Modified Rice Husk Char Injection into Flue

The emission and migration characteristics of flue gas mercury in a pilot-scale 0.3 MWth circulating fluidized bed combustion boiler system by injecting the adsorbent of ammonium bromide (NH4Br)-modified rice husk char (NBr-RHC) into the flue duct before a fabric filter (FF) were investigated in this study. Mercury concentration in the flue gas was sampled by the Ontario Hydro Method. Meanwhile, the feeding coal, lime, process water, fly ashes both in the flue gas and FF hopper, bottom ash, gypsum, and wet flue gas desulfurization (WFGD) effluent were also collected during the flue gas mercury sampling. The temperature-programmed desorption (TPD) method was used to identify the mercury species in the sample of fly ashes. The results show that the combination system of the selective catalytic reduction (SCR) + adsorbent injection (AI) + FF + WFGD obtains a total flue gas mercury removal efficiency of 94.62%, which is 13.42% higher than that without the AI of NBr-RHC. A total of 93.83% of mercury exists in byproducts of the solid and liquid, and the amount of mercury collected by FF accounts for 97.28% due to the physisorption and chemisorption of gaseous mercury by NBr-RHC injection. The TPD analysis for mercury compound in the particulate matters from the AI device indicates that HgBr2 formation is the key reason for NBr-RHC having high mercury removal efficiency. Elemental mercury is found to oxidize across the SCR, with 70.23% converted to oxidized mercury. WFGD exhibits a good oxidized mercury absorption rate of 86.67%, but elemental mercury increases from 0.19 to 0.26 μg/m3 due to the oxidized mercury reduction, and more attention should be given on this increase.

Enhanced Bifunctional Catalytic Activity of Manganese Oxide/Perovskite Hierarchical Core-Shell Materials by Adjusting the Interface for Metal-Air Batteries.

LaMnO3 perovskite is one of the most promising catalysts for oxygen reduction reaction (ORR) in metal-air batteries and can be compared to Pt/C. However, the low catalytic activity toward oxygen evolution reaction (OER) limits its practical application in rechargeable metal-air batteries. In this work, the MnO2/La0.7Sr0.3MnO3 hierarchical core-shell composite materials with a special interface structure have been designed via the selective dissolution method. The core of La0.7Sr0.3MnO3 particles is wrapped by the porous and loose MnO2 nanoparticles. The as-prepared MnO2/La0.7Sr0.3MnO3 materials have excellent catalytic activity toward ORR/OER and are used as bifunctional oxygen electrocatalysts for metal-air batteries. Based on results of transmission electron microscopy, X-ray photoelectron spectroscopy, valence-band spectroscopy, and O2 temperature-programmed desorption analysis, we conclude that the bifunctional catalytic activity of the MnO2/La0.7Sr0.3MnO3 materials can be effectively promoted due to the specific interface structure between the La1-xSrxMnO3 core and the MnO2 shell. This can be attributed to three aspects: (a) the electronic conductivity, which is beneficial for providing the faster charge-transfer paths and kinetics at the oxide/solution interface than that of the MnO2 sample; (b) the enhancement of oxygen adsorption capacity due to surface defects (oxygen vacancies) and chemical adsorption, which is helpful to improve the reaction kinetics during the process of oxygen catalysis; and (c) the tuning of oxygen adsorption ability via the moderate Mn-O bond strength, which may be conducive to getting for obtain an enhanced Mn-O bond strength on the surfaces for ORR and a weakened Mn-O bond in the lattice for OER.

Study of Mercury-Removal Performance of Mechanical–Chemical-Brominated Coal-Fired Fly Ash

The mechanical–chemical-modified fly ash (FA-MC) and mechanical–chemical-brominated fly ash (FA-MC-Br) were prepared by omnidirectional planetary ball mill, and impregnated–brominated fly ash (FA-I-Br) was also prepared using the same mass ratio of fly ash/NH4Br as a comparison. The mercury-removal efficiency of raw fly ash (FA), FA-MC, FA-MC-Br, and FA-I-Br was evaluated in a fixed-bed reactor. The physical and chemical properties of the four samples were investigated by the Brunauer–Emmet–Teller, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and mercury temperature-programmed desorption analysis. The results showed that the mercury-removal efficiency of the four samples followed the order of FA-MC-Br > FA-I-Br > FA-MC > FA, the value of which was 67, 30.98, 26.12, and 17.96%, respectively. The mercury-removal performance of the four samples was mainly reflected in the oxidation (>90%), while the adsorption only accounted for a small proportion (<10%). The mechanical–...