Mesopore Distribution Research Articles

Pore structure and controlling factors of dolomite-bearing high-salinity shale reservoir in Qianjiang Formation, Jianghan Basin, China

High-salinity shale is a unique and promising shale-oil reservoir in continental basins. We have collected representative samples from different lithologies from wells in the Qianjiang Depression to test the pore structure and basic character from prospective high-salinity oil-bearing shales. We conducted field emission scanning electron microscopy and X-ray diffraction analyses to study the high-salinity shale pore morphology and composition, respectively. We used mercury injection capillary pressure to understand the high-salinity shale macropore distribution, and we used low-pressure nitrogen (N2) adsorption to study the mesopore distribution. The results show that the high-salinity shale-oil reservoir mainly is composed of carbonate (dolomite and calcite), clay, and saline minerals (anhydrite, glauberite, and halite). Many intergranular pores were developed in the high-salinity shale. The mesopores and macropores both were developed well in argillaceous dolomite. The average pore volume of macropores is 0.0588 ml/g, which accounts for approximately 59% of the total pore volume. Therefore, in the high-salinity shale-oil reservoirs that we tested, macropores were more important than other pores. The symbiosis of dolomite and calcite improved the porosity of the high-salinity shale-oil reservoir, and the salt minerals increased the pore complexity.

A functionalized bio-based material with abundant mesopores and catechol groups for efficient removal of boron

Pursuing a low-cost yet sustainable material with a high performance of removing boron is necessary for replacement of the synthetic adsorbents, but remains challengeable. Herein, we fabricated an mesopore-dominated bio-based material (LS-CPAM-TA) with abundant catechol groups by the electrostatic-interaction-driven self-assembly of lignosulfonate (LS), tannic acid (TA) and cationic polyacrylamide (CPAM) for efficient removal of boron. LS-CPAM-TA presented a mesopore area of 53.9 m2/g with a mesoporous distribution of 2–25 nm, as well as a mesopore/micropore volume ratio of 129.7. Such a mesopore-rich feature not only promoted the exposure of catechol groups in TA, which served as the adsorption sites, but also contributed to enhance the fast mass transport of boron. Consequently, a maximum adsorption capacity of 119.05 mg/g was observed for LS-CPAM-TA, surpassing some reported adsorbents. Even for the low concentration boron, LS-CPAM-TA also displayd the high adsorption efficiency. Moreover, LS-CPAM-TA followed the Langmuir isotherm adsorption model, and presented the excellent regeneration performance due to its robust self-assembled structure driven by the electrostatic interaction among LS, CPAM and TA. This work would provide guidelines for target design of bio-based materials with tunable porous structure and versatile adsorption or catalytic sites for various applications.

Evaluation of efficiency and capacity of thermal, chemical and ultrasonic regeneration of tetracycline exhausted activated carbon

ABSTRACT Emerging pollutants have received increasing attention because of their potential environmental risks. As conventional treatment processes are not able to completely remove emerging pollutants, such as drugs, for example, the adsorption process is considered a complementary treatment. However, after some time of use, the adsorbent solids used in this type of process become saturated and there may be a higher demand for replacement of these materials, resulting in a large amount of solid waste. In this context, the objective of this study was to evaluate regeneration techniques of adsorbent solid depleted with emerging tetracycline pollutant. For this, tests were performed using three regenerative methods – thermal, chemical and ultrasonic, where through them were analyzed the influence of temperature, type of solvent and sonification time, respectively. Virgin, saturated and regenerated solids were characterized by their physical structure, micro and mesopore distribution and scanning electron microscopy. For all techniques employed, the regeneration efficiency reached values ⁣⁣above 85%. Thermal treatments at 200°C, 100% methanol solution, 100% deionized water with 60 °C heating and ultrasonic treatment at 5 and 20 minutes were chosen as the most viable methods for the study of adsorption/desorption cycles. Compared to the others, the heat treatment at 200°C remained with consistent results until the sixth cycle, presenting a regenerative capacity of 90%. Therefore, it has been selected as the most suitable regenerative agent, ensuring that CAG can be regenerated and used repeatedly in the treatment of tetracycline contaminated waters.

Hierarchical Porous Graphene-Iron Carbide Hybrid Derived From Functionalized Graphene-Based Metal-Organic Gel as Efficient Electrochemical Dopamine Sensor.

A metal–organic gel (MOG) similar in constitution to MIL-100 (Fe) but containing a lower connectivity ligand (5-aminoisophthalate) was integrated with an isophthalate functionalized graphene (IG). The IG acted as a structure-directing templating agent, which also induced conductivity of the material. The MOG@IG was pyrolyzed at 600°C to obtain MGH-600, a hybrid of Fe/Fe3C/FeOx enveloped by graphene. MGH-600 shows a hierarchical pore structure, with micropores of 1.1 nm and a mesopore distribution between 2 and 6 nm, and Brunauer–Emmett–Teller surface area amounts to 216 m2/g. Furthermore, the MGH-600 composite displays magnetic properties, with bulk saturation magnetization value of 130 emu/g at room temperature. The material coated on glassy carbon electrode can distinguish between molecules with the same oxidation potential, such as dopamine in presence of ascorbic acid and revealed a satisfactory limit of detection and limit of quantification (4.39 × 10−7 and 1.33 × 10−6 M, respectively) for the neurotransmitter dopamine.

Diffusion in hierarchical silica monoliths: impact of pore size and probe molecule

The silica monoliths were prepared by a combination of sol-gel synthesis, pore templating, and a process of phase separation. The as-prepared monoliths are characterized by meso- and macroporosity. The pore size significantly differs for each sample depending on the preparation conditions. The transport properties of the monoliths were investigated using benzene, isopropanol, hexane, and methane as probing molecules. The effective diffusion coefficients in the monoliths were estimated based on the second Fick’s law of diffusion. The obtained diffusivities are quite similar for different samples, demonstrating that the diffusion occurs mainly in the macropores of the monolith. The values of the diffusion coefficients were found to fall outside the Knudsen prediction. In addition, it was investigated that the benzene and hexane transport in the monolith sample with a bimodal mesopores distribution does not follow the Fick’s diffusion law. To describe the mass transfer of the benzene and hexane in this sample the time-fractional diffusion equation was utilized on a phenomenological basis. Several scenarios concerning the role of the relatively small mesopores in the hydrocarbons diffusion are discussed.

Preparation of an N-doped mesoporous carbon sphere and sheet composite as a high-performance supercapacitor

Carbon-based materials with multidimensional structures generally exhibit improved properties compared with single-morphology carbon materials for various applications including catalysis, adsorption, and energy storage. Here, an N-doped mesoporous carbon sphere and sheet composite is prepared by a co-assembly strategy using an ionic liquid ([C18Mim]Br) as the structure-directing agent, ethylenediamine as the catalyst, tetraethyl orthosilicate as the pore-forming agent, and resorcinol formaldehyde resin as the carbon precursor. [C18Mim]Br and ethylenediamine not only induce formation of the unique structure but also lead to in situ nitrogen doping on the N-doped mesoporous carbon skeleton. The obtained N-doped mesoporous carbon shows a unique composite structure of thin sheets embedded with carbon spheres, having high a specific surface area and uniform mesopore distribution. When used as an electrode material, the N-doped mesoporous carbon shows a good specific capacity of 273 F g−1 at a current density of 0.5 A g−1 and a good rate capability (82.1% of the capacitance is retained at a high current density of 10 A g−1). Moreover, the N-doped mesoporous carbon exhibited ideal stability behavior (91.6% capacitive retention after 10,000 cycles), indicating a promising role as an electrode material for excellent performance supercapacitors.

Prediction by Convolutional Neural Networks of CO2 /N2 Selectivity in Porous Carbons from N2 Adsorption Isotherm at 77 K.

Porous carbons are an important class of porous materials with many applications, including gas separation. An N2 adsorption isotherm at 77 K is the most widely used approach to characterize porosity. Conventionally, textual properties such as surface area and pore volumes are derived from the N2 adsorption isotherm at 77 K by fitting it to adsorption theory and then correlating it to gas separation performance (uptake and selectivity). Here the N2 isotherm at 77 K was used directly as input (representing feature descriptors for the porosity) to train convolutional neural networks to predict gas separation performance (using CO2 /N2 as a test case) for porous carbons. The porosity space for porous carbons was explored for higher CO2 /N2 selectivity. Porous carbons with a bimodal pore-size distribution of well-separated mesopores (3-7 nm) and micropores (<2 nm) were found to be most promising. This work will be useful in guiding experimental research of porous carbons with the desired porosity for gas separation and other applications.

The Analysis of the distribution of available mesopores in cellulosic pulp, using Inverse Size Exclusion Chromatography-ISEC

The Analysis of the distribution of available mesopores in cellulosic pulp, using Inverse Size Exclusion. Chromatography-ISEC The aim of the presented research was to determine available mesopores in cellulose masses obtained by industrial methods. Cellulose masses obtained from fast-growing poplar species (Populus sp.) can be used in the production of biofuels of the second generation. One of the factors influencing the effectiveness of hydrolysis is the availability of pores in the material for acids and enzymes used during this process. For this purpose the reverse spatial exclusion chromatography (ISEC) with the use of dextran standards and selected sugars was applied to verify the distribution of available mesopores in cellulose masses. The analysis showed the material with the highest share of available pores, the selection of which will allow to increase the efficiency and profitability of biofuel production from lignocellulosic materials.

Utilization of waste engine oil for carbon nanotube aerogel production using floating catalyst chemical vapor deposition

The floating catalyst chemical vapor deposition (FCCVD) approach has been successfully employed in offering a continuous single-step process to the synthesis of carbon nanotubes aerogel (CNT aerogel) in terms of the industrial scale. Industrial applications require selecting a carbon source that is abundant, cost-effective and environment-friendly. Thus, waste engine oil (WEO) is preferably employed as a carbon source involving the production of CNT aerogel. In this research study, the catalytic decomposition of the WEO was employed to synthesize CNT aerogel. First, fractional distillation of WEO was achieved resulted in five (5) fractions. As per analysis is performed via GC-MS, low molecular weight hydrocarbons could be efficiently separated, which is required for catalyst dissolving. As per CNS analysis, each fraction was found to contain >69% carbon, <0.1% sulfur and <0.3% nitrogen. The FCCVD method was employed to synthesize CNT aerogel via a WEO fraction 1 mixed along with ferrocene catalyst at a temperature of 1150 °C. It was found that the product’s MWCNTs were associated with 86.74% purity and 496% carbon deposition yield. The aerogel was found to possess a mesopore distribution of 142.9 m2 g−1 as its specific surface area, 39.079 nm as average pore diameter and 1.3964 cm3 g−1 as total pore volume. The CNTs tend to assemble randomly as well as get entangled to form a 3-D structure.

Kreiranje mezopora u zeolitu ZSM-5 alkalnim tretmanom - uticaj koncentracije NaOH, temperature i trajanja tretmana

The work presented in this paper was dedicated to the investigation of the influence of the alkaline treatment parameters on the formation of mesopores in zeolite ZSM-5, SiO2/Al2O3=50. Concentration of NaOH, temperature and tretment duration were varied. The obtained samples were characterized using low temperature nitrogen adsorption, X ray diffraction and solid state 27Al MAS NMR spectroscopy. Formation of mesopores was found to be a process sensitive to changes of treatment parameters, which can lead to creation of hierarchical zeolites with different mesopore surfaces and distributions of pore size diameters. Also, treatment duration was found to have a lesser influence on the process, compared to other two investigated parameters. Mesopore introduction resulted in partial crystallinity reduction, in all modified samples. No significant buildup of extraframework Al was detected.

Nanocellulose-assisted synthesis of ultrafine Co nanoparticles-loaded bimodal micro-mesoporous N-rich carbon as bifunctional oxygen electrode for Zn-air batteries

Transition-metal-nitrogen-carbon (M-N/C, M = Co, Fe, etc.)-based materials have been spotlighted as favorable bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Minimizing the size of the transition metal nanoparticles and creating highly porous structures are deemed imperative in maximizing the utilization of active sites of M-N/C materials. However, agglomeration of metallic particles into a bulk phase and shrinkage of the porous structures have always been inevitable during the annealing treatment process, severely impairing the overall efficacy of these catalysts. In this study, cellulose nanocrystals (CNC) were introduced for carrying well-dispersed Co nanoparticles (9 nm), while also enriching a special bimodal distribution of micropores and mesopores. Benefiting from the homogeneous and ample active sites exposed in the conductive N-implanted porous carbon scaffold, the elaborately derived CoA@CNC-700 electrocatalyst displays extraordinary catalytic activity with respect to ORR and OER in alkaline electrolyte. Impressively, such bifunctional catalyst can endow the rechargeable Zn-air batteries with a larger power density (187 mW cm−2), a superior specific capacity (782 mA h g−1), and prolonged charge-discharge cycles in comparison with the commercial Pt/C + RuO2 mixed catalysts, which highlights its great potential for practical applications.

Utilization of municipal solid waste incineration fly ash to produce autoclaved and modified wall blocks

Municipal solid waste incineration fly ash (MSWI) as hazardous solid wastes, its growing generation has become a great burden to the society and thus its proper management is greatly necessary. In this work, MSWI and fly ash (FA) were used as raw materials to prepare solid wastes-based autoclaved wall blocks (SW-AWBs). To further improve the durability of SW-AWBs, three admixtures (NaCl, NaNO3 and NaOH) were separately incorporated and their effects on drying shrinkage, frost resistance, water absorption and thermal conductivity of SW-AWBs were intensively studied. XRD, BET and SEM were combined to comprehensively investigate the microscopic mechanism. The experimental results indicate that as drying for 40 d and 140 d, the drying shrinkage of SW-AWBs with NaCl decreases by 69.5% and 14.4%, respectively. Conversely, NaNO3 and NaOH both increase the drying shrinkage, which is unfavourable to durability of SW-AWBs. In terms of frost resistance, NaCl significantly reduces the loss of mass and strength, because Cl− promotes the synthesis of Al-substituted tobermorite that refines the pore structure of the system. The pore structure of SW-AWBs mixing with NaNO3 and NaOH are similar, mainly consisting of a single distribution of mesopores, therefore the water absorption is relatively large and frost resistance is poor. As for thermal conductivity, NaCl is more beneficial to the heat preservation of SW-AWBs relative to NaNO3 and NaOH. This paper provides a good reference to effectively reuse MSWI and further improve the durability of SW-AWBs prepared by MSWI and FA.

Hierarchical porous carbon monolith derived from lignin for high areal capacitance supercapacitors

Abstract Hierarchical porous carbon with high areal energy density in supercapacitor has attracted extensive attention with increasing demand for compact and portable devices. Lignin based porous carbon monolith was fabricated via dual templates (P123 and silica nanoparticles) and carbonization procedure, where hierarchical porous structure with tuneable mesopore sizes and distributions could be modulated via incorporation of silica nanoparticles with size of 200 nm, 100 nm, and 7 nm, respectively. Due to higher surface area and optimized porous structure which facilitate fast ion diffusion, carbon monolith fabricated from silica nanoparticle of 7 nm exhibited superior electrochemical performance, which reached a high areal capacitance of 2.7 F cm−2 and excellent volumetric capacitance of 104.5 F cm−3 with mass loading of 13.6 mg cm−2 in 6 M KOH aqueous solution. Moreover, the symmetric cell assembled with this carbon electrode gave rise to a large amount of energy (131 μWh cm−2) at high power densities (1368 μW cm−2) and excellent cycle stability of 92.9% after 10 000 cycles, facilitating implementation of lignin-derived materials in commercial energy storage products.

Physicochemical Properties of Potassium-Promoted Fe-Containing Catalysts for the Hydrogenation of CO over Magnesium Aluminum Spinels: IR Spectroscopy

The effect the structural properties of a support, magnesium aluminum spinel, with different structural characteristics has on the physicochemical properties of Fe–K-containing catalysts for the hydrogenation of CO is studied. It is shown that hematite is the main phase in Fe-containing catalysts. A highly disperse distribution of iron oxide on the surface of the substrate is observed in case of a bimodal distribution of meso-pores. It is shown via IR spectroscopy that Fe2+ cations and metallic iron are the main sites of adsorption. The introduction of potassium reduces the surface concentration of clusters (including Fe2+) in different coordination environments. A rise in the contribution from the subcarbonyl forms of adsorption to the spectrum of the absorption bands and a drop in the amount of oxidized iron on the surfaces of metallic iron particles are observed.

Hierarchically assembled porous TiO2 nanoparticles with enhanced photocatalytic activity towards Rhodamine-B degradation

Despite tremendous advances in the development of photocatalysts for waste water treatment, the harmful chemicals used in the synthesis reaching the water bodies add up new environmental issues. In this work, hierarchically assembled porous TiO2 nanoparticles (TiO2 NPs) were prepared by an acid-free eco-friendly hydrothermal approach via condensation of alkoxide precursor (titanium (IV) tert-butoxide). Fine tuning of textural properties was facilitated by change in the hydrothermal treatment time. The structure, morphology and the physicochemical properties of the synthesized samples were characterized by XRD, TGA, N2 adsorption-desorption, FE-SEM, and FE-TEM analysis. N2 adsorption-desorption displays a unique double-slit model isotherms for all the samples. The BJH mesopore distribution curves exhibit intense peak at 6.9 nm and slightly broad peak at 46.1 nm in all the samples with further broad peaks in the range of 80–95 nm. The results showed that the photocatalytic activity is highly depend on the textural properties especially pore diameter. The activity and pore diameter were found to follow the trend: TiO2-12 h > TiO2-48 h > TiO2-24 h > TiO2-6 h whereas the surface area and crystallite size follows the trend: TiO2-48 h > TiO2-12 h > TiO2-24 h > TiO2-6 h. Overall, a simple strategy is presented and could be extended to produce various metal oxides for photocatalytic degradation of various other pollutants and microorganisms.

Experimental study on salt–metal organic framework composites for water absorption

In this article, MIL-101(Cr) powder material was successfully prepared by hydrothermal synthesis and combined with different mass fractions of CaCl2 by immersion method to obtain MIL-101(Cr)/CaCl2 composite materials. The physical properties of the adsorbent were determined by X-ray powder diffraction, N2 adsorption/desorption isotherm, TGA and FTIR. The water vapor adsorption performance of MOFs was tested by a gravimetric instrument to analyze the underlying mechanism. Results indicated that the specific surface area, total pore volume, and pore size distribution of micropores and mesopores of MIL-101(Cr)/CaCl2 composites decreased with increasing CaCl2 content. When P/P0 = 0.9, the water vapor equilibrium adsorption capacities of MIL-101(Cr), MIL-101(Cr)/CaCl2-10%, MIL-101(Cr)/CaCl2-20%, and MIL-101(Cr)/CaCl2-30% were 1.05, 0.88, 1.13, and 1.35 g/g, respectively. MIL-101(Cr)/CaCl2-30% agglomerated after water absorption, so MIL-101(Cr)/CaCl2-20% was selected as the final experimental material. The water vapor adsorption heat of MIL-101(Cr)/CaCl2-20% was 42–58 kJ/mol, which is close to the evaporation enthalpy of water (44 kJ/mol at 25 °C). The analysis of the adsorption kinetics showed the relatively uniform adsorption rate of MIL-101(Cr)/CaCl2-20%. Overall, MIL-101(Cr)/CaCl2-20% exhibited superior water vapor adsorption performance and have great potential for application to adsorption heat pumps.

Designing of Hollow ZSM-5 with Controlled Mesopore Sizes To Boost Gasoline Production from Syngas

Hollow mesoporous ZSM-5 zeolite is synthesized through a method of alkaline treatment with the TPAOH/NaOH mixed solution. The amount and pore size distribution of mesopores in the shell of hollow z...

Fabrication of Activated Porous Carbon Using Polymer Decomposition for Electrical Double-Layer Capacitors

Because of their excellent stability and highly specific surface area, carbon based materials have received attention as electrode materials of electrical double-layer capacitors(EDLCs). Biomass based carbon materials have been studied for electrode materials of EDLCs; these materials have low capacitance and high-rate performance. We fabricated tofu based porous activated carbon by polymer dissolution reaction and KOH activation. The activated porous carbon(APC-15), which has an optimum condition of 15 wt%, has a high specific surface area(1,296.1 m2 g−1), an increased average pore diameter(2.3194 nm), and a high mesopore distribution(32.4 %), as well as increased surface functional groups. In addition, APC has a high specific capacitance(195 F g−1) at low current density of 0.1 A g−1 and excellent specific capacitance(164 F g−1) at high current density of 2.0 A g−1. Due to the increased specific surface area, volume ratio of mesopores, and surface functional groups, the specific capacitance and high-rate performance increased. Consequently, the tofu based activated porous carbon can be proposed as an electrode material for high-performance EDLCs.

Evaluating the internal structure of monodispersed mesoporous silica spheres by small-angle X-ray scattering

Although the spherical morphology and mesoporous structure of monodispersed mesoporous silica spheres (MMSS) have been extensively investigated by scanning electron microscopy and transmission electron microscopy, the statistical distribution of mesopores from the surface to the center of a particle, average density of the spheres, and volume fraction of silica have not been investigated. Herein, small-angle X-ray scattering (SAXS) was performed on aqueous dispersions of MMSS with diverse sphere diameter, mesopore radius, and nanoparticle inclusion. The SAXS spectra fitted by a spherical model showed that the mesopores were homogeneously distributed in each particle. The mass density of the MMSS was obtained from the zero scattering intensity, and the volume fraction of silica was calculated considering the absorbed water in the pores. While the sphere diameter and mesopore radius had little influence, nanoparticle inclusion induced an increase in the volume fraction of silica.

Tunable Surface Area, Porosity, and Function in Conjugated Microporous Polymers.

Simple inorganic salts are used to tune N‐containing conjugated microporous polymers (CMPs) synthesized by Buchwald–Hartwig (BH) cross‐coupling reactions. Poly(triphenylamine), PTPA, initially shows a broad distribution of micropores, mesopores, and macropores. However, the addition of inorganic salts affects all porous network properties significantly: the pore size distribution is narrowed to the microporous range only, mimicking COFs and MOFs; the BET surface area is radically improved from 58 m2 g−1 to 1152 m2 g−1; and variations of the anion and cation sizes are used to fine‐tune the surface area of PTPA, with the surface area showing a gradual decrease with an increase in the ionic radius of salts. The effect of the salt on the physical properties of the polymer is attributed to adjusting and optimizing the Hansen solubility parameters (HSPs) of solvents for the growing polymer, and named the Beijing–Xi'an Jiaotong (BXJ) method.