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Keywords = 13X molecular sieve

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8 pages, 1018 KiB  
Communication
Construction of a Symmetrical Bi-Hydroxamate Metal–Organic Framework with Chemical Robustness
by Yue Dong, Chaozhi Xiong, Zhen-Wu Shao and Chong Liu
Symmetry 2025, 17(6), 895; https://doi.org/10.3390/sym17060895 - 6 Jun 2025
Viewed by 393
Abstract
Recently, the emerging class of hydroxamate-based metal–organic frameworks (MOFs) has demonstrated significant structural diversity and chemical robustness, both essential for potential applications. Combining the favorable hard–hard Bi-O interactions and chelating chemistry of hydroxamate groups, a rigid and symmetrical three-dimensional bismuth-hydroxamate metal–organic framework was [...] Read more.
Recently, the emerging class of hydroxamate-based metal–organic frameworks (MOFs) has demonstrated significant structural diversity and chemical robustness, both essential for potential applications. Combining the favorable hard–hard Bi-O interactions and chelating chemistry of hydroxamate groups, a rigid and symmetrical three-dimensional bismuth-hydroxamate metal–organic framework was successfully prepared via solvothermal synthesis and structurally elucidated via X-ray crystallography. The MOF, namely SUM-91 (SUM = Sichuan University Materials), features one-dimensional Bi-oxo secondary building blocks (SBUs), which are bridged by chelating 1,4-benzenedihydroxamate linkers. With the demonstrated permanent porosity and molecular sieving effect (CO2 vs. N2), SUM-91 was also found to be stable under harsh chemical conditions (aqueous solutions with pH = 2–12 and various organic solvents). As the structural robustness of SUM-91 could be attributed to the finetuning of the coordinative sphere of Bi centers, this work shed light on the further development of (ultra-)microporous materials with high stability and selective adsorption properties. Full article
(This article belongs to the Section Chemistry: Symmetry/Asymmetry)
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15 pages, 5488 KiB  
Article
Regulation of the Properties of the Hierarchical Porous Structure of Alumophosphate Molecular Sieves AEL by Reaction Gels Prepared with Different Templates
by Arthur R. Zabirov, Dmitry V. Serebrennikov, Rezeda Z. Kuvatova, Nadezhda A. Filippova, Rufina A. Zilberg, Olga S. Travkina and Marat R. Agliullin
Gels 2025, 11(4), 297; https://doi.org/10.3390/gels11040297 - 17 Apr 2025
Viewed by 409
Abstract
Microporous alumophosphate molecular sieves AlPO4-n are promising materials for use in catalysis, gas adsorption, and gas separation. However, AlPO4-n faces problems such as diffusion limitations that lead to a deterioration in mass transfer. To solve this problem, we studied [...] Read more.
Microporous alumophosphate molecular sieves AlPO4-n are promising materials for use in catalysis, gas adsorption, and gas separation. However, AlPO4-n faces problems such as diffusion limitations that lead to a deterioration in mass transfer. To solve this problem, we studied the crystallization of alumophosphate reaction gels prepared using aluminum isopropoxide and various secondary amines as templates, including diethyl-, di-n-propyl-, diisopropyl-, and di-n-butylamines. Using X-ray diffraction, Ramon spectroscopy, and STEM methods, it has been demonstrated that the reaction gels prepared using DPA, DIPA, and DBA are amorphous xerogels consisting of 5–10 nm nanoparticles. The reaction gel prepared with DEA is a combination of a layered phase and an amorphous aluminophosphate. It has been shown that the use of aluminum iso-propoxide allows the production of AlPO4-11 in the form of 2–4 µm aggregates consisting of primary AlPO4-11 nanocrystals. The template was found to exert a significant effect upon both the characteristics of the porous structure and the size of AlPO-11 nanocrystals. A template is proposed for the synthesis of hierarchical AlPO4-11 with a maximum volume of mesopores. The morphology and crystal size of AlPO4-11 were found to strongly influence its adsorption properties in the adsorption of octane. Full article
(This article belongs to the Special Issue Gel-Related Materials: Challenges and Opportunities)
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17 pages, 4442 KiB  
Article
Controllable Preparation of Low-Cost Coal Gangue-Based SAPO-5 Molecular Sieve and Its Adsorption Performance for Heavy Metal Ions
by Le Kang, Boyang Xu, Pengfei Li, Kai Wang, Jie Chen, Huiling Du, Qianqian Liu, Li Zhang and Xiaoqing Lian
Nanomaterials 2025, 15(5), 366; https://doi.org/10.3390/nano15050366 - 27 Feb 2025
Cited by 13 | Viewed by 999
Abstract
With the advancement of industrial production and urban modernization, pollution from heavy metal ions and the accumulation of solid waste have become critical global environmental challenges. Establishing an effective recycling system for solid waste and removing heavy metals from wastewater is essential. Coal [...] Read more.
With the advancement of industrial production and urban modernization, pollution from heavy metal ions and the accumulation of solid waste have become critical global environmental challenges. Establishing an effective recycling system for solid waste and removing heavy metals from wastewater is essential. Coal gangue was used in this study as the primary material for the synthesis of a fully coal gangue-based phosphorus-silicon-aluminum (SAPO-5) molecular sieve through a hydrothermal process. The SAPO-5 molecular sieve was characterized through several methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface analysis, Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS), to examine its mineral phases, microstructure, pore characteristics, and material structure. Adsorption performance towards wastewater with Cd2+ and Pb2+ ions was investigated. It was found that the adsorption processes of these ions are well described by both the pseudo-second-order model and the Langmuir isotherm. According to the Langmuir model, the coal gangue-based SAPO-5 molecular sieve exhibited maximum adsorption capacities of 93.63 mg·g−1 for Cd2+ and 157.73 mg·g−1 for Pb2+. After five cycles, the SAPO-5 molecular sieve retained strong stability in adsorbing Cd2+ and Pb2+, with residual adsorption capacities of 77.03 mg·g−1 for Cd2+ and 138.21 mg·g−1 for Pb2+. The excellent adsorption performance of the fully solid waste coal gangue-based SAPO-5 molecular sieve is mainly attributed to its mesoporous channel effects, the complexation of -OH functional groups, and electrostatic attraction. Full article
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19 pages, 12409 KiB  
Article
Synthesis and Characterization of Hydroxyapatite Assisted by Microwave-Ultrasound from Eggshells for Use as a Carrier of Forchlorfenuron and In Silico and In Vitro Evaluation
by Benjamín I. Romero-De La Rosa, Silvia P. Paredes-Carrera, Jorge A. Mendoza-Pérez, Dulce E. Nicolás-Álvarez, Vicente Garibay-Febles and Carlos A. Camacho-Olguin
Appl. Sci. 2024, 14(24), 11522; https://doi.org/10.3390/app142411522 - 11 Dec 2024
Cited by 2 | Viewed by 1312
Abstract
This study utilized eggshell biomass as a calcium precursor for synthesizing hydroxyapatite (Hap) through a co-precipitation method assisted by a combined microwave-ultrasound (Mu/Us) crystallization process. Different milling techniques (mortar, high-energy mill, and sieving) were employed to prepare the eggshell biomass and identify the [...] Read more.
This study utilized eggshell biomass as a calcium precursor for synthesizing hydroxyapatite (Hap) through a co-precipitation method assisted by a combined microwave-ultrasound (Mu/Us) crystallization process. Different milling techniques (mortar, high-energy mill, and sieving) were employed to prepare the eggshell biomass and identify the most effective calcium precursor. The precursor derived from high-energy milling, followed by sieving and thermal treatment at 750 °C (designated as Sample Hap-H3 750), was selected due to its higher porosity, enhanced crystallinity, and smaller particle size than other synthesized materials. This sample was subsequently used as a carrier for the plant hormone forchlorfenuron (FCF), forming the composite Hap-FCF. Comprehensive characterization was conducted using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), specific surface area analysis (BET method), zeta potential (ZP), scanning electron microscopy (SEM), and bright-field transmission electron microscopy (BFTEM), ensuring reliable and robust data. The in silico evaluation of the phytohormone FCF with two receptors, gibberellin (GA3Ox2) and auxin (IAA7), produced notable results. Docking and molecular dynamics (MD) simulations demonstrated that the gibberellin receptor was preferentially stimulated, as shown by the higher binding affinity and the receptor’s sustained stability during the MD simulations. These findings underscore the potential applications of this research, emphasizing its significance in materials science and biochemistry. Moreover, the in vitro assessment of Hap-H3 750, Hap-FCF, FCF, and the control (distilled water) on the germination and growth of butterhead lettuce seeds (Lactuca sativa) over 30 days revealed that Hap-H3 750 and Hap-FCF promoted plant growth by 275–330% relative to the control. This effect was attributed to the preferential stimulation of the gibberellin receptors responsible for stem and root elongation. These results suggest that HAP nanoparticles could facilitate the controlled delivery of FCF in the agricultural sector, promising to be an effective nanofertilizer. Full article
(This article belongs to the Section Agricultural Science and Technology)
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13 pages, 1934 KiB  
Article
Ceria-Catalysed Production of Dimethyl Carbonate from Methanol and CO2: Effect of Using a Dehydrating Agent Combined with a Solid Cocatalyst
by Dichao Shi, Svetlana Heyte, Mickaël Capron and Sébastien Paul
Molecules 2024, 29(23), 5663; https://doi.org/10.3390/molecules29235663 - 29 Nov 2024
Viewed by 928
Abstract
The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol over ceria-based catalysts, in the presence of a dehydrating agent shifting the thermodynamical equilibrium of the reaction, has received significant interest recently. In this work, several dehydrating agents, such as molecular [...] Read more.
The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol over ceria-based catalysts, in the presence of a dehydrating agent shifting the thermodynamical equilibrium of the reaction, has received significant interest recently. In this work, several dehydrating agents, such as molecular sieves, 2,2-dimethoxypropane (DMP), dimethoxymethane (DMM) and 1,1,1-trimethoxymethane (TMM), are combined with commercial ceria to compare their influence on the DMC yield obtained under the same set of operating conditions. TMM is found to be the most efficient; however, its conversion is not complete even after 48 h of reaction. Therefore, it is proposed for the very first time, to the best of our knowledge, to add a second solid cocatalyst in the reaction medium to accelerate the TMM hydration reaction without degrading the DMC already formed. Basic oxides and acidic zeolites with different Si/Al ratios are employed to accelerate the hydration of TMM, so as to improve the DMC yield. 13X was identified as the best option to play this role. Finally, three different commercial cerias are tested in the presence of TMM and molecular sieve 13X as the second catalyst. The most efficient combination of ceria, TMM, and molecular sieve 13X is ultimately tested in a 250 mL autoclave to start to scale up the process. A very high DMC production of 199.5 mmol DMC/gcat. is obtained. Full article
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15 pages, 5385 KiB  
Article
The Synergistic Effect of Pore Architect and Reducibility in Ceria-Promoted Ni Molecular Sieve for Methane Dry Reforming
by Norah Alwadai, Abdulaziz A. M. Abahussain, Vijay Kumar Shrivastava, Salma A. Al-Zahrani, Anis H. Fakeeha, Naif Alarifi, Mohammed O. Bayazed, Khaled M. Banabdwin, Rawesh Kumar and Ahmed Al-Fatesh
Catalysts 2024, 14(12), 852; https://doi.org/10.3390/catal14120852 - 24 Nov 2024
Cited by 2 | Viewed by 1147
Abstract
Methane and carbon dioxide, the primary contributors to global warming, are now at critical levels, threatening the extinction of numerous organisms on our planet. In this regard, dry reforming of methane reactions have gained considerable attention because of the conversion capacity of CH [...] Read more.
Methane and carbon dioxide, the primary contributors to global warming, are now at critical levels, threatening the extinction of numerous organisms on our planet. In this regard, dry reforming of methane reactions have gained considerable attention because of the conversion capacity of CH4 and CO2 into synthetic/energy-important syngas (H2 and CO). Herein, a molecular sieve (CBV3024E; SiO2/Al2O3 = 30) with ZSM-8-type pore architect, is utilized as the support for the active site of Ni and Ce promoters. Catalysts are characterized by surface area and porosity, X-ray diffraction study, Raman and infrared spectroscopy, thermogravimetry analysis, and temperature-programmed reduction/desorption techniques. A total of 2 wt.% ceria is added over 5Ni/CBV3024E to induce the optimum connectivity of aluminum in the silicate framework. NiO residing in these porous cages are mostly under “prominent interaction with support” which is reduced easily into metallic Ni as the active sites for DRM reactions. The active sites over 5Ni2Ce/CBV3024E remain stable during the DRM reaction and achieve ~58% H2 yield after 300 min TOS at 42,000 mL/(gcat.h) GHSV and ~70% H2 yield after 20 h at 26,000 mL/(gcat.h) GHSV. The high activity after a longer time stream justifies using CBV3024E molecular sieves as the support and ceria as the promoter for Ni-based catalyst towards the DRM reaction. Full article
(This article belongs to the Special Issue Advances in Catalytic Dry Reforming of Methane)
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15 pages, 3081 KiB  
Article
Direct Synthesis of Dimethyl Carbonate from Methanol and CO2 over ZrO2 Catalysts Combined with a Dehydrating Agent and a Cocatalyst
by Dichao Shi, Svetlana Heyte, Mickaël Capron and Sébastien Paul
Catalysts 2024, 14(10), 657; https://doi.org/10.3390/catal14100657 - 24 Sep 2024
Cited by 2 | Viewed by 1948
Abstract
Zirconia nanocrystals as catalysts for the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide have received significant interest recently. In this paper, three zirconia-based catalysts presenting different monoclinic and tetragonal phase contents are prepared and characterized by X-ray diffraction (XRD), [...] Read more.
Zirconia nanocrystals as catalysts for the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide have received significant interest recently. In this paper, three zirconia-based catalysts presenting different monoclinic and tetragonal phase contents are prepared and characterized by X-ray diffraction (XRD), N2 adsorption–desorption, transmission electron microscopy (TEM), and temperature-programmed desorption of NH3 and CO2 (NH3-TPD and CO2-TPD). The catalytic performances of these solids are evaluated in terms of DMC production. This production is low when using the bare zirconias, but it is significantly increased in the presence of 1,1,1-trimethoxymethane (TMM) playing the role of a dehydrating agent, which shifts the thermodynamic equilibrium. Moreover, the production of DMC is further improved by adding a second solid catalyst (cocatalyst), the molecular sieve 13X, to accelerate the hydration of TMM. Hence, the molecular sieve 13X plays a dual role by trapping water molecules formed by the reaction of DMC synthesis and providing strong acidic sites catalyzing TMM hydrolysis. To the best of our knowledge, the combination of two solid catalysts in the reaction medium to accelerate the water elimination to obtain higher DMC production from CO2 and methanol has never been reported. Full article
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12 pages, 2658 KiB  
Article
Research on Modification of Oxygen-Producing Adsorbents for High-Altitude and Low-Pressure Environments
by Ye Li, Huiqing Yue, Quanli Zhang, Dumin Yan, Ziyi Li, Zhiwei Liu, Yingshu Liu, Yongyan Wang, Shifeng Wang and Xiong Yang
Inorganics 2024, 12(9), 250; https://doi.org/10.3390/inorganics12090250 - 14 Sep 2024
Viewed by 1372
Abstract
In oxygen production on plateaus, pressure swing adsorption (PSA) oxygen production is currently the most commonly used oxygen production method. In plateau regions, low pressure leads to a decrease in adsorbent nitrogen–oxygen separation performance, which affects the performance of PSA oxygen production, so [...] Read more.
In oxygen production on plateaus, pressure swing adsorption (PSA) oxygen production is currently the most commonly used oxygen production method. In plateau regions, low pressure leads to a decrease in adsorbent nitrogen–oxygen separation performance, which affects the performance of PSA oxygen production, so it is particularly important to enhance adsorbent nitrogen–oxygen separation performance. In this paper, Li-LSX (lithium low-silicon aluminum X zeolite molecular sieve) adsorbents were modified using the liquid phase ion exchange method, and five kinds of modified adsorbents were obtained, namely AgLi-LSX, CaLi-LSX, ZnLi-LSX, CuLi-LSX, and FeLi-LSX, respectively. The influences of different metal ions and modification time lengths on the adsorbent nitrogen adsorption and nitrogen–oxygen separation coefficients were analyzed. Through theoretical calculations, the nitrogen and oxygen adsorption and separation performances of the modified adsorbents at different altitudes and low adsorption pressures were investigated. It is shown that the nitrogen adsorption capacity of the AgLi-LSX-1 adsorbent obtained from the modification experiment reaches 27.92 mL/g, which is 3.24 mL/g higher than that of Li-LSX; the nitrogen–oxygen separation coefficients of S1 and S2 are 19.24 and 7.54 higher, respectively; and the nitrogen–oxygen separation coefficients of S4 are 20.85 and 7.54 higher than those of Li-LSX, respectively. With the increase in altitude from 50 m to 5000 m, the nitrogen–oxygen separation coefficient of the AgLi-LSX-1 adsorbent increased rapidly from 20.85 to 57, and its nitrogen–oxygen separation coefficient S4 exceeded that of the Li-LSX adsorbent to reach 47.61 at an altitude of 4000 m. Therefore, the modified adsorbent AgLi-LSX-1 in this paper can enhance the performance of the PSA oxygen process for oxygen production in plateau applications. Full article
(This article belongs to the Special Issue Inorganic Composites for Gas Separation)
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26 pages, 8737 KiB  
Article
Ni-Based Molecular Sieves Nanomaterials for Dry Methane Reforming: Role of Porous Structure and Active Sites Distribution on Hydrogen Production
by Ahmed S. Al-Fatesh, Ahmed A. Ibrahim, Anis H. Fakeeha, Ahmed I. Osman, Yousef M. Alanazi, Fahad Saleh Almubaddel and Ahmed E. Abasaeed
Nanomaterials 2024, 14(15), 1320; https://doi.org/10.3390/nano14151320 - 5 Aug 2024
Cited by 4 | Viewed by 2289
Abstract
Global warming, driven by greenhouse gases like CH4 and CO2, necessitates efficient catalytic conversion to syngas. Herein, Ni containing different molecular sieve nanomaterials are investigated for dry reforming of methane (DRM). The reduced catalysts are characterized by surface area porosity, [...] Read more.
Global warming, driven by greenhouse gases like CH4 and CO2, necessitates efficient catalytic conversion to syngas. Herein, Ni containing different molecular sieve nanomaterials are investigated for dry reforming of methane (DRM). The reduced catalysts are characterized by surface area porosity, X-ray diffraction, Raman infrared spectroscopy, CO2 temperature-programmed desorption techniques, and transmission electron microscopy. The active sites over each molecular sieve remain stable under oxidizing gas CO2 during DRM. The reduced 5Ni/CBV10A catalyst, characterized by the lowest silica–alumina ratio, smallest surface area and pore volume, and narrow 8-ring connecting channels, generated the maximum number of active sites on its outer surface. In contrast, the reduced-5Ni/CBV3024E catalyst, with the highest silica–alumina ratio, more than double the surface area and pore volume, 12-ring sinusoidal porous channels, and smallest Ni crystallite, produced the highest H2 output (44%) after 300 min of operation at 700 °C, with a CH4:CO2 = 1:1, P = 1 atom, gas hour space velocity (GHSV) = 42 L gcat−1 h−1. This performance was achieved despite having 25% fewer initial active sites, suggesting that a larger fraction of these sites is stabilized within the pore channels, leading to sustained catalytic activity. Using central composite design and response surface methodology, we successfully optimized the process conditions for the 5Ni/CBV3024E catalyst. The optimized conditions yielded a desirable H2 to CO ratio of 1.00, with a H2 yield of 91.92% and a CO yield of 89.16%, indicating high efficiency in gas production. The experimental results closely aligned with the predicted values, demonstrating the effectiveness of the optimization approach. Full article
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12 pages, 2529 KiB  
Article
Enhanced Ni(II) Removal from Wastewater Using Novel Molecular Sieve-Based Composites
by Zengjie Li, Yalin Lei, Li Dong, Li Yu and Cong Yin
Materials 2024, 17(13), 3211; https://doi.org/10.3390/ma17133211 - 1 Jul 2024
Cited by 2 | Viewed by 1438
Abstract
This study focuses on the efficient removal of Ni(II) from spent lithium-ion batteries (LIBs) to support environmental conservation and sustainable resource management. A composite material, known as molecular sieve (MS)-based metal–organic framework (MOF) composites (MMCs), consisting of a synthesized MS matrix with integrated [...] Read more.
This study focuses on the efficient removal of Ni(II) from spent lithium-ion batteries (LIBs) to support environmental conservation and sustainable resource management. A composite material, known as molecular sieve (MS)-based metal–organic framework (MOF) composites (MMCs), consisting of a synthesized MS matrix with integrated MOFs, was developed for the adsorption of Ni(II). The structural and performance characteristics of the MMCs were evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and N2 adsorption–desorption isotherms (BET). Batch adsorption experiments were conducted to assess the Ni(II) adsorption performance of the MMCs. The results revealed that, under conditions of pH 8 and a temperature of 298 K, the MMCs achieved near-equilibrium Ni(II) adsorption within 6 h, with a maximum theoretical adsorption capacity of 204.1 mg/g. Further analysis of the adsorption data confirmed that the adsorption process followed a pseudo-second-order kinetic model and Langmuir isotherm model, indicating a spontaneous, endothermic chemical adsorption mechanism. Importantly, the MMCs exhibited superior Ni(II) adsorption compared to the MS. This study provides valuable insights into the effective recovery and recycling of Ni(II) from spent LIBs, emphasizing its significance for environmental sustainability and resource circularity. Full article
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15 pages, 1935 KiB  
Article
Carbon Molecular Sieve Membrane Reactors for Ammonia Cracking
by Valentina Cechetto, Gaetano Anello, Arash Rahimalimamaghani and Fausto Gallucci
Processes 2024, 12(6), 1168; https://doi.org/10.3390/pr12061168 - 6 Jun 2024
Cited by 7 | Viewed by 2757
Abstract
The utilization of ammonia for hydrogen storage relies on the implementation of efficient decomposition techniques, and the membrane reactor, which allows simultaneous ammonia decomposition and hydrogen recovery, can be regarded as a promising technology. While Pd-based membranes show the highest performance for hydrogen [...] Read more.
The utilization of ammonia for hydrogen storage relies on the implementation of efficient decomposition techniques, and the membrane reactor, which allows simultaneous ammonia decomposition and hydrogen recovery, can be regarded as a promising technology. While Pd-based membranes show the highest performance for hydrogen separation, their applicability for NH3-sensitive applications, such as proton exchange membrane (PEM) fuel cells, demands relatively thick, and therefore expensive, membranes to meet the purity targets for hydrogen. To address this challenge, this study proposes a solution involving the utilization of a downstream hydrogen purification unit to remove residual ammonia, thereby enabling the use of less selective, therefore more cost-effective, membranes. Specifically, a carbon molecular sieve membrane was prepared on a tubular porous alumina support and tested for ammonia decomposition in a membrane reaction setup. Operating at 5 bar and temperatures ranging from 450 to 500 °C, NH3 conversion rates exceeding 90% were achieved, with conversion approaching thermodynamic equilibrium at temperatures above 475 °C. Simultaneously, the carbon membrane facilitated the recovery of hydrogen from ammonia, yielding recoveries of 8.2–9.8%. While the hydrogen produced at the permeate side of the reactor failed to meet the purity requirements for PEM fuel cell applications, the implementation of a downstream hydrogen purification unit comprising a fixed bed of zeolite 13X enabled the production of fuel cell-grade hydrogen. Despite performance far from being comparable with the ones achieved in the literature with Pd-based membranes, this study underscores the viability of carbon membranes for fuel cell-grade hydrogen production, showcasing their competitiveness in the field. Full article
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24 pages, 66960 KiB  
Article
Morphostructural, Chemical and Genetic Features of Native Gold in Brown Coals from the Yerkovetsky Deposit, Far East Russia
by Veronika I. Rozhdestvina and Galina A. Palyanova
Minerals 2024, 14(5), 503; https://doi.org/10.3390/min14050503 - 10 May 2024
Viewed by 1556
Abstract
We studied the morphostructural features and chemical composition of micron and submicron particles of native gold from brown coals and overcoal sediments of the Yerkovetsky deposit (Zeya-Bureya sedimentary basin, Far East Russia). The samples of coal and host rocks in the form of [...] Read more.
We studied the morphostructural features and chemical composition of micron and submicron particles of native gold from brown coals and overcoal sediments of the Yerkovetsky deposit (Zeya-Bureya sedimentary basin, Far East Russia). The samples of coal and host rocks in the form of thin sections, as well as coal particles and grains of native gold obtained during the process of dispersion and the fractionation of loose and crushed samples divided according to size and density, were analyzed using scanning electron microscopy in combination with X-ray microanalysis, involving various visualization modes. It was revealed that native gold is syngenetic with the mineralization of brown coals, and microphases dispersed in the minerals of overcoal loose and sandy-clay sediments were the source of native gold. In coal, gold is accumulated at the stages of formation (alluvial and eolian, including terrigenous and ionogenic subtypes) and the diagenesis of coal deposits (ground-infiltration subtype). A significant part of the mineralization process of coals and the formation of microparticles of native gold was contributed to by the descending water infiltration of polycomponent colloid solutions. During the dehydration of hydroxysiliconized iron-based hydrogels, mineral phases have an unstable composition and floccular structure and contain submicron gold particles. The coatings of all gold microparticles have identical origin and composition. Coal beds that border host rocks are an open system with a constant inflow of the substance, which leads to the gradual formation of polycomponent aggregated particles in micro cavities. Part of the gold in coals occurs as sulfur-bearing complexes dissolved in pore water. The key factor in the migration and deposition of gold in coals is the inorganic substances involved in the processes of coal mineralization. Organic substances play a more passive role and have medium-forming, fractionating (colloid, molecular, and ionic sieves), and accumulation functions. Full article
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13 pages, 2860 KiB  
Article
Hydrogen Sulfide Adsorption from Natural Gas Using Silver-Modified 13X Molecular Sieve
by Mirzokhid Abdirakhimov, Mohsen H. Al-Rashed and Janusz Wójcik
Materials 2024, 17(1), 165; https://doi.org/10.3390/ma17010165 - 28 Dec 2023
Cited by 2 | Viewed by 2534
Abstract
The removal of hydrogen sulfide from natural gas and other gases such as biogas, refinery gases, and coal gas is required because it is toxic and corrosive, even in traces. Zeolites are widely used in the removal of H2S from the [...] Read more.
The removal of hydrogen sulfide from natural gas and other gases such as biogas, refinery gases, and coal gas is required because it is toxic and corrosive, even in traces. Zeolites are widely used in the removal of H2S from the abovementioned gases. In this work, we prepared an Ag-exchanged 13X molecular sieve by using different concentrations of AgNO3 to increase its adsorption properties. XRD, SEM, and BET techniques were used to characterize samples. To determine the adsorption properties of each of the samples, a laboratory setup with a fixed-bed adsorber was utilized. The adsorption capacity of modified 13X increased when the molar concentration of AgNO3 increased from 0.02 M to 0.05 M. However, the breakthrough time was attained quicker at a high molar concentration of 0.1 M AgNO3, indicating a low adsorption capacity. When compared to unmodified 13X, the adsorption capacity of AgII-13X increased by about 50 times. The results of this study suggest that the silver-modified 13X molecular sieve is highly effective at extracting H2S from natural gas. Full article
(This article belongs to the Special Issue Environmentally Friendly Adsorption Materials)
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13 pages, 2444 KiB  
Article
Study on Green Controllable Preparation of Coal Gangue-Based 13-X Molecular Sieves and Its CO2 Capture Application
by Dawei Yi, Huiling Du, Yefei Li, Yimin Gao, Sifan Liu, Boyang Xu, Haoqi Huang and Le Kang
Coatings 2023, 13(11), 1886; https://doi.org/10.3390/coatings13111886 - 2 Nov 2023
Cited by 8 | Viewed by 2183
Abstract
Carbon dioxide emissions are the primary and most direct contributor to global warming, posing a significant hazard to both the environment and human health. In response to this challenge, there has been a growing interest in the development of effective carbon capture technologies. [...] Read more.
Carbon dioxide emissions are the primary and most direct contributor to global warming, posing a significant hazard to both the environment and human health. In response to this challenge, there has been a growing interest in the development of effective carbon capture technologies. This study involved the synthesis of 13-X molecular sieve porous materials using solid waste coal gangue as a source of silicon and aluminum. The synthesis process involved the controlled utilization of an “alkali fusion-hydrothermal” reaction system. The resulting materials were characterized for their structure, morphology, and crystal composition using X-ray diffraction and field emission scanning electron microscopy. These 13-X molecular sieve materials were employed as adsorbents to capture carbon dioxide gas, and their adsorption performance was investigated. The findings indicated that the 13-X molecular sieve materials possess uniform pores and complete crystalline morphologies, and they exhibited an adsorption capacity of 1.82 mmol/g for carbon dioxide at 0 °C. Consequently, this study not only converted solid waste gangue into high-value products but also demonstrated effective atmospheric carbon dioxide capture, suggesting that gangue-based 13-X molecular sieves may serve as a potential candidate for carbon capture. Full article
(This article belongs to the Special Issue Recent Progress in Surface and Interface Properties of Nanostructures)
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15 pages, 3075 KiB  
Article
Determination of β2-Agonist Residues in Meat Samples by Gas Chromatography-Mass Spectrometry with N-Doped Carbon Dots in Molecular Sieves
by Shanshan Zhu, Binglin Mou, Liao Zheng, Luhong Wen, Ning Gan and Lin Zheng
Separations 2023, 10(8), 429; https://doi.org/10.3390/separations10080429 - 28 Jul 2023
Cited by 1 | Viewed by 1743
Abstract
A simple, effective, and highly sensitive analytical approach was created and applied in this study for the accurate measurement of three β2-agonist residues (clenbuterol, salbutamol, and ractopamine) in meat samples. In the course of the experiment, new adsorbent molecular sieves (ZMS)@nitrogen-doped [...] Read more.
A simple, effective, and highly sensitive analytical approach was created and applied in this study for the accurate measurement of three β2-agonist residues (clenbuterol, salbutamol, and ractopamine) in meat samples. In the course of the experiment, new adsorbent molecular sieves (ZMS)@nitrogen-doped carbon quantum dots (N-CQDs) composite materials were synthesized with the aid of hydrothermal synthesis. The composite adsorbent materials were prepared and characterized through scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, fluorescence, and zeta potential. Four determinants affecting the extraction and elution’s efficiency, such as the amount of adsorbent, the extraction time, desorption time, and the amount of extraction salt, were substantially optimized. The analytes were quantified by gas chromatography–mass spectrometry. Final results of the methodological validation reflected that the ZMS@N-CQDs composite materials were able to adsorb three β2-agonist residues well and had good reproducibility. In the meantime, all analytes indicated good linearity with coefficient of determination R2 ≥ 0.9908. The limit of detection was 0.7–2.0 ng·g−1, the limit of quantification varied from 2.4 to 5.0 ng·g−1, the precision was lower than 11.9%, and the spiked recoveries were in the range of 79.5–97.8%. To sum up, the proposed approach was quite effective, reliable, and convenient for the simultaneous analysis of multiple β2-agonist residues. Consequently, this kind of approach was successfully applied for the analysis of such compounds in meat samples. Full article
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