Designing CO2-selective polymeric membranes with high permeability and selectivity is industrially attractive for both pre-combustion hydrogen purification and post-combustion carbon capture. In this ...work, composite membranes consisting of crosslinked polymer network, CO2-philic small molecules, and metal organic frameworks (MOFs) were designed for dual-enhanced solubility and diffusivity in CO2/N2 and CO2/H2 separation. The presence of MOF in the matrix increased the fractional free volume (FFV) and provided additional pathways for gas diffusion, while small polyethylene glycol (PEG) molecules favored both high CO2 selectivity and diffusivity via CO2-philic –C-C-O- moieties and larger FFV. Moreover, coupling MOF and PEG magnified the effects through their mutual interactions. As a result, a high CO2 permeability of 2580 Barrer is reached, which is 61 % higher than that obtained from the membrane without MOF (crosslinked polymer with PEGDME molecules), while achieving CO2/N2 selectivity of 40.3 and CO2/H2 selectivity of 14.4. This study may open up possibilities for designing membrane materials with high permeability for carbon capture and other applications.
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•MOF in PEGDME-embedded membranes enhances CO2 solubility and diffusivity.•Size-sieving MOF increases selectivity.•Membranes show versatile applications for CO2/H2 and CO2/N2 separations.•The performance for CO2/N2 separation surpasses 2019 Robeson upper bound.
•The synthesized sorbents removed As(III) and As(V) simultaneously.•The mechanism for As(V) removal was adsorption onto Fe oxides.•The removal mechanism for As(III) was adsorption and partial ...oxidation.
Iron oxide and manganese oxide are well-known sinks and oxidants for As(V) and As(III), respectively. In this study, iron- and manganese-impregnated granular activated carbon (IMIGAC) was synthesized to remove arsenic from aqueous streams. The characterization of IMIGAC shows that Fe–Mn binary oxides are well impregnated into the carbon. The adsorption kinetics and isotherms show that this material effectively removes both As(III) and As(V) without pre-oxidation. The kinetics appear to be pseudo-second-order, and the rate-limiting step is determined to be intra-particle diffusion due to the porous structure of the carbon. The isotherm shows that the adsorption capacities for As(III) and As(V) are 18.4mg/g and 16.0mg/g at 293K, respectively. The negative Gibbs free energy change indicates that the reaction is spontaneous. Speciation analysis shows that As(III) is adsorbed onto IMIGAC and then slowly oxidizes to As(V). Based on the experimental results, we conclude that the synthesized IMIGAC can be used to remove As(III) and As(V) from groundwater to yield potable water.
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•Temperature promoted large PAHs molecules, while drove PAHs volatilization.•Pre-loading FeCl3 or Fe(NO3)3 to biomass suppressed formation of PAHs by 32.9-20.5%.•Most generated PAHs ...distributed in bio-oil (72.7–94.6%) and 1.7–11.1% in biochar.•Fe accumulated more high-weight PAHs in biochar and induced high Toxic Equivalent.•Fe(III) transformed into reductive Fe (Fe0, FeO), reducing PAHs precursors.
The pyrolytic production of Fe-enriched composite biochar is receiving increasing attention. However, understanding of the environmental risk from the polycyclic aromatic hydrocarbons (PAHs) potentially generated during composite biochar production is lacking. This study investigated the formation of PAHs from the pyrolysis of barley straw impregnated with FeCl3 or Fe(NO3)3 at 350 °C, 500 °C, and 650 °C. The total amount of PAHs formation increased with increasing heating temperature. Most of the PAHs were concentrated in bio-oil (72.7–94.6%), with only a small fraction retained in biochar (1.7–11.1%) and in biogas (2.2–16.2%). Preloading FeCl3 or Fe(NO3)3 onto the biomass greatly reduced PAH formation by up to 33% and 21%, respectively, compared to that obtained with biomass alone. The suppressed formation of PAHs was due to the generation of more reductive forms of Fe, such as Fe0 and FeO, in the O2-starved pyrolysis atmosphere, which reduced C2H2 and C6H5OH, two important PAH precursors in hydrogen abstraction acetylene addition reactions. Although Fe loading reduced the amounts of PAHs in biochar, the toxic equivalent value increased because Fe induced more accumulation of high-molecular-weight PAHs in the biochar. This study proved that Fe loading suppresses PAH generation during biomass pyrolysis, which can guide the design of composite biochar production.
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•γ-Al2O3 supported Ni and Ru catalysts are applied in CO2 methanation.•Glycerol-assisted impregnation increases the number of available active sites.•Ni-Ru catalysts with Ru < 1.5 wt% ...achieves enhanced catalytic performance.•Ru promotes CO adsorption and boosts Ni capacity to adsorb H atoms.•Reaction mechanism with formates and carbonyls as intermediates is identified.
Conventional Ni/Al2O3 catalyst, currently used for COx removal in ammonia production, admits room for improvement as catalysts for application in low temperature CO2 methanation, which is the aim of this work. The Incipient Wetness Impregnation (IWI) has been replaced by Glycerol Assisted Impregnation (GAI) method and, afterwards, a secondary metal (Ru) has been co-impregnated forming a bimetallic system. The monometallic as well as bimetallic systems have been characterized by several techniques (TGA, XRD, N2-physisorption, TEM, H2-TPR, H2-TPD, STEM-EDX and operando FTIR) and tested for CO2 methanation reaction in a downflow fixed bed reactor (conditions: P =1 bar, H2: CO2 ratio = 4 and WHSV = 30,000 mL h−1 g−1). GAI method together with a reducing calcination atmosphere (20 %H2/N2) results effective to avoid the formation of large metal particles during the synthesis, especially for Ru/Al2O3 formulation. In fact, the Ru dispersion of the catalyst prepared by GAI (RuAlGAI) is around 5 times higher than that of RuAlIWI catalyst. On the other hand, NiAlGAI presents larger population of reduced particles but bigger in size than NiAlIWI catalyst, which finally provides the former with slightly higher metal surface and superior catalytic performance. By co-impregnating small amounts of Ru (0.5, 1.0 or 1.5 wt%) the Ni surface is considerably increased which, together with Ru synergistic collaboration, results in a methane yield rise from 20 to 44 % at 300 °C. The operando FTIR results show no differences in the reaction pathway with GAI preparation method and incorporation of Ru, but different evolution of reaction intermediates concentration with temperature. The bimetallic Ni-RuAl system presents much higher capacity to adsorb CO and hydrogenate the reaction intermediates (adsorbed formates and carbonyls) by dissociated H2 than its monometallic counterparts.
•The novel washing regeneration methods for AC using CuCl2 solution was proposed and verified.•CuCl2 solution showed excellent performance on eluting Hg-containing compounds on spent AC.•Elution ...process restored the well-developed pore structure and reactive functional groups of AC.•CuCl2-AC showed a higher (above 99%) and more stable Hg removal performance than raw AC.•Hg-containing compounds on spent CuCl2-AC were mainly easy-soluble HgCl2.
Mercury pollution in syngas has received increasing attention. Regeneration of AC can reduce the cost and avoid Hg secondary release effectively. The performance of CuCl2 solution on AC regeneration was studied combining fixed-bed reactor, Hg-TPD, and characterization tests (BET, SEM-EDS, XPS, and FT-IR). Hg adsorption on AC in N2 mainly followed physisorption. There was a synergistic contribution of HCl and H2S on Hg removal, in which HCl promotion was stronger than H2S. The main Hg-containing compounds on AC in HCl were HgCl2 and HgO, in H2S were HgO and HgS. The well-developed pore structure of AC enhanced Hg adsorption while inhibited the elution of Hg-containing compounds. CuCl2 solution exhibited an excellent synergy in the elution of Hg-containing compounds and the impregnation modification of AC, which not only eluted the Hg-containing compounds, restored the well-developed pore structure, and recovered the reactive oxygen-containing functional groups effectively, but also brought in Cu and Cl for promoting Hg removal by generating Hg-Cu and HgCl2 respectively. The best impregnation content of CuCl2 was 10% that exhibited higher (above 99%) and more stable Hg removal efficiency than raw AC, and the dominant Hg-containing compound was easy-soluble HgCl2, proving the practicability of CuCl2 solution on AC regeneration.
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•Synergistic interaction of copper-manganese oxide (CuMnOδ) enhances the catalytic performance of Cy-H oxidative dehydrogenation.•The participation of lattice oxygen indicates the ...significance of oxygen availability and mobility in the ODH reaction.•Feed oxygen content critically influences product distribution.•The study unveils Cyclohexanolate, Enolate, Phenolate, Carboxylate, and Bidentate carbonate species formation.•Cyclohexanolate dehydration yields Cy-ene, while Cy-one results from Enolate species rearrangement.
Oxidative dehydrogenation (ODH) is a promising technique for converting Cyclohexane (Cy-H) to Cyclohexene (Cy-ene). However, this reaction yields undesired byproducts (Benzene and CO2) due to deep-dehydrogenation and over-oxidation. Therefore, controlling reaction parameters, comprehending intermediate species, and optimizing catalyst design are crucial for enhancing selective Cy-ene formation. Copper-manganese oxide catalysts were synthesized via the incipient wetness impregnation technique. A solid solution (CuMnOδ) exhibited superior catalytic activity due to synergistic interaction and active site formation. The study elucidated that copper oxide facilitates the deep-dehydrogenation of Cy-H. While manganese oxide incorporation inhibits CO2 and benzene formation, promoting partial dehydrogenation to Cy-ene. The studies unveiled Cy-H activation via hydrogen abstraction, forming Cyclohexanolate intermediates interacting with surface hydroxyls, yielding Cy-ene via dehydration. Notably, Cy-one formation via Enolate intermediates was also observed. The catalyst 10Cu0.25Mn0.75Oδ/Al2O3 exhibited the highest Cy-ene yield (∼12.1 %), facilitated by the synergistic effect, with a Cy-H conversion (∼15.7 %) at 300 °C.
The limitations of oxide/oxide ceramic matrix composites lie in the need to improve their mechanical properties. It is challenging to reconcile the conflict between matrix densification at high ...temperature and the potential thermal damage to fibers. The concept of using element doping to control the sintering behavior of matrix was initially applied to prepare alumina-based ceramic matrix composites (CMCs). To lower the sintering temperature of the Al2O3 matrix, MnO2 dopant was used as a sintering aid. As a result, the thermal damage to alumina fibers was decreased, and the mechanical properties of the composite were significantly enhanced. The effect of MnO2 content on the bending strength and micro-morphology of the composite was investigated. The composite exhibits optimal mechanical properties with a 0.01 wt% MnO2 doping, and its bending strength is approximately 405 MPa. The investigation aimed to determine the mechanism by which the fluctuation in micro-mechanical properties of the composites with different MnO2 contents. After the thermal aging at 1000℃ for 500 h, the bending strength of the N610/Al2O3-0.01 composite decreases to 297 MPa. The evolution and mechanism of thermal aging damage have been studied.
► MgO is well coated on LiLi0.2Mn0.54Ni0.13Co0.13O2 by melting impregnation method. ► The 2wt.% coated sample exhibits initial capacity of 260.8mAhg−1 at 0.1C. ► Capacity retention of 96.4% is ...obtained at 1C (200mAg−1) after 100 cycles at 25°C. ► 94.3% of capacity is retained after 50 cycles at 1C after 50 cycles at 60°C.
MgO-coated LiLi0.2Mn0.54Ni0.13Co0.13O2 was synthesized via melting impregnation method followed by a solid state reaction. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) show that the MgO layer is well coated on the surface of the layered oxide particles. Although the initial discharge capacity of LiLi0.2Mn0.54Ni0.13Co0.13O2 with proper MgO modification decreases compared to the bare one, the 2wt.% MgO coated cathode exhibits the excellent cycling stability with capacity retention of 96.4% at a current density of 200mAg−1 after 100 cycles at room temperature and 94.3% after 50 cycles at 60°C. Electrochemical impedance spectroscopy (EIS) shows that the thin MgO layer mainly reduces the charge transfer resistance and stabilizes the surface structure of active material during cycling. Melting impregnation method is promising for MgO coating to improving the cycling stability of Li-rich layered oxide cathode for Li-ion batteries.
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