Mesopore Volume Research Articles

Cu/TiO2 adsorbents modified by air plasma for adsorption–oxidation of H2S

In this study, non-thermal plasma (NTP) was employed to modify the Cu/TiO2 adsorbent to efficiently purify H2S in low-temperature and micro-oxygen environments. The effects of Cu loading amounts and atmospheres of NTP treatment on the adsorption-oxidation performance of the adsorbents were investigated. The NTP modification successfully boosted the H2S removal capacity to varying degrees, and the optimized adsorbent treated by air plasma (Cu/TiO2-Air) attained the best H2S breakthrough capacity of 113.29 mg H2S/gadsorbent, which was almost 5 times higher than that of the adsorbent without NTP modification. Further studies demonstrated that the superior performance of Cu/TiO2-Air was attributed to increased mesoporous volume, more exposure of active sites (CuO) and functional groups (amino groups and hydroxyl groups), enhanced Ti-O-Cu interaction, and the favorable ratio of active oxygen species. Additionally, the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicated the main reason for the deactivation was the consumption of the active components (CuO) and the agglomeration of reaction products (CuS and SO42−) occupying the active sites on the surface and the inner pores of the adsorbents.

Core-shell ZnO/BiOBr p-n heterojunction with excellent photocatalytic performance in degradation of tetracycline hydrochloride

Core-shell ZnO/BiOBr heterojunction was prepared by a simple hydrothermal-ionic liquid method. Hollow ZnO microspheres were firstly synthesized by hydrothermal method. Then BiOBr nanosheets were evenly wrapped on the ZnO microspheres through an ionic-liquid method. The prepared dahlia-like core-shell ZnO/BiOBr microspheres had a much larger BET surface area and mesopore volume than that of ZnO. Its visible-light absorption and charge carrier's separation were greatly enhanced due to the synergistic effect of the core-shell nanostructure and formation of ZnO/BiOBr heterojunction. It had an excellent photocatalytic performance in the degradation of tetracycline hydrochloride (TC): 86.76 % TC was degraded after irradiation for 90 min., which was 1.38 times of the pure ZnO and 1.35 times of the BiOBr, respectively.

Influence of supercritical CO2 on fracture network evolution with nanopore structure linkage in high-rank anthracite matrix

It is essential to understand the permeability evolution of coal reservoirs under the interaction of supercritical CO2 (SC-CO2) in order to be successful in both CO2 geological storage and extraction of coalbed methane. However, the influence of nanopore structure characteristics on the permeability evolution of coal exposed to SC-CO2 has not been elucidated. To this end, the quantitative analysis of the pores in high-rank coal was conducted through low-temperature N2 adsorption, low-temperature CO2 adsorption, and Nuclear Magnetic Resonance (NMR). The analysis revealed that micropores and mesopores are the major contributors to the specific surface area and pore volume of the nanopores, respectively. After SC-CO2 interaction, the pore size and pore number of the coal increased significantly, with small pores changing to large ones, mainly due to the dissolution of SC-CO2 with the contribution of gas pressure being negligible. The proportion of micropore and mesopore decreases while that of macropore increases after SC-CO2 treatment, especially SC-CO2 causes macropores to be continuous and increased the connectivity of fractures. The relationship between nanopore structure characteristics and the deformation of the fracture network under SC-CO2 interaction was studied. The results showed that the specific surface area (SSA) of the micropore and the volume fractal dimension (DLN2) of the mesopore were related to the change of fracture porosity, while the surface fractal dimension (DLN1) of the micropore, the specific surface area (SSA) and pore volume of mesopore were related to the change of fracture complexity. This indicated that the evolution of the fracture network under SC-CO2 interaction is related to the nanopore structure characteristics. A mechanical model was established based on the close correlation between nanopore structures characteristics in the matrix and the evolution of fracture networks under SC-CO2 interaction. This mechanical model elucidates the impact of nanopore alteration resulting from mineral dissolution induced by SC-CO2 on the evolution of fracture networks. This research provides a clearer understanding of the evolution in reservoir permeability during CO2 geological sequestration, offering valuable reference for safety assessments.

Electrospun polyethylenimine (PEI)-derived nitrogen enriched carbon nanofiber for supercapacitors with artificial neural network modeling

This paper presents the utilization of polyethylenimine (PEI) polymer to obtain freestanding, binder-free, and nitrogen- enriched carbon nanofibers (NCNFs) by electrospinning which is an easy and fast method. The PEI polymer played a significant role as a poring agent for the adjustment of surface area and as the heteroatom doping to increase conductivity. NCNFs-10 electrode exhibited a specific capacitance of 200 F/g at 1 A/g with a good retention of 84.25 % at 10 A/g in three electrode system. The assembled supercapacitor had a specific energy of 5.57 Wh/kg at 125 W/kg with a good cycling performance of 80.5 % after 10,000 cycles. Furthermore, an artificial neural network (ANN) method was utilized to understand the relationship between the CNF's structure and supercapacitor performance by modeling the specific capacitance. The input factors were specific surface area (SBET), nitrogen doping (N% at), graphitization degree (ID/IG), internal resistance (Rs), pore size (Vpor), micropore volume (Vmic), the average diameter (Dave), and mesopore volume (Vmeso). Results showed that the first three remarkable variables are SBET, N (%at), and ID/IG.

Synergistic sono-adsorption and adsorption-enhanced sonochemical degradation of dyes in water by additive manufactured PVDF-based materials

The present study proposes the first mechanistic model accounting for the most meaningful physico-chemical phenomena taking place in liquid phase adsorption processes under ultrasound. Initially, this study was aimed at developing an easy-to-make and easy-to-recover piezocatalyst for the degradation of RhB in water by combining the high piezocatalytical performance of BaTiO3 with a compatible piezoelectric support such as PVDF, manufactured by a customised additive manufacturing – direct ink writing system with in-situ poling. However, initial results showed that the resulting PVDF-BaTiO3 composite slabs performed worse than BaTiO3 piezocatalysts on their own, and that poling did not have any effect on their performance (82% RhB removal after 2 h when using either poled or unpoled PVDF-BaTiO3 composite slabs compared to 92% RhB removal after 2 h in presence of BaTiO3 piezocatalysts). Further investigation with pure PVDF materials demonstrated that, instead of piezocatalysis, synergistic ultrasound-assisted adsorption and sonochemical degradation were taking place, enabling the removal of >95% of the dye within 40 min of ultrasound treatment in the presence of 4 g L–1 of additive manufactured PVDF slabs. The results of this study and their evaluation with the mechanistic model proposed for liquid phase adsorption under ultrasound suggest that the adsorption of RhB on additive manufactured PVDF slabs was enhanced by the structure, higher specific surface ratio and higher volume of mesopores achieved through the 3D-printing process, as well as the minimisation of film resistance to mass transport due to ultrasound. Moreover, adsorption on additive manufactured PVDF enhanced the sonochemical degradation of the dye due to its high concentration in the adsorbed phase. This study demonstrates that adsorption processes, especially in the presence of PVDF materials, may be significantly more important in piezocatalysis than what has been reported to date, to the point that the synergistic combination of sono-adsorption and sonochemical degradation in presence of additive-manufactured PVDF slabs may be enough to achieve high removal rates of dyes in water.

Ultrasonic-pretreated hydrothermal synthesis of less dense zeolite CHA from the transformation of zeolite T

Because of containing the same double 6-ring (D6R) building unit, the pure zeolite CHA with lower framework density (FDSi = 15.1 T/1000 Å3) has been transformed from zeolite T with higher framework density (FDSi = 16.1 T/1000 Å3) through ultrasonic-pretreated hydrothermal synthesis in MOH (KOH and NaOH) solution without adding organic template or seed crystals. Ultrasonic pretreatment facilitates the transformation rate and generates high-quality zeolite CHA. The ultrasound condition should be precisely controlled because that CHA phase is metastable, which is inclined to transform to other more stable phase. The ultrasonic conditions at 313 K and 333 K have been investigated in detail. In KOH solution, the ultrasonic treatment at 313 K can effectively restrain the generation of MER phase, however, it is hard to avoid the existence of MER phase when ultrasound temperature is 333 K. In NaOH solution, the samples with ultrasonic treatment of 313 K show the small particles size of about 1 μm, and the GIS framework topology starts to grow with the ultrasonic treatment of 333 K. The products prepared with the appropriate ultrasonic pretreatment represents smaller particles size, larger mesopore volume and higher CO2 adsorption capacity than the sample without the ultrasonic pretreatment. The structural evolution of interzeolite transformation has been explored by XRD, FT-IR and SEM observations. With the assistance of ultrasound, the parent zeolite T can quickly decompose into intermediate phase and then regenerate into CHA phase.

Tailoring Lignin‐Derived Porous Carbon Toward High‐Energy Lithium‐Ion Capacitor Through Varying Sp2‐ and Sp3‐Hybridized Bonding

AbstractLignin‐derived porous carbon (LPC) shows great potential as electrode material for supercapacitors. However, precise control over the pore structure during the conventional carbonization–activation process remains challenging. Here, a molecular‐level strategy to tailor the pore structure through tuning inter‐/intra‐molecular bonding of lignin in a pre‐carbonization process is shown. Based on operando pyrolysis analysis, a molecular evolution model is proposed to elucidate the relationship between pre‐carbonization and the resulting porosity of LPC. Lignin undergoes a condensation process with an increase of sp2‐hybridized carbon bonding during pre‐carbonization, causing the extension of polycyclic aromatic structure and leading to an increased mesopore volume in the final porous carbon. The variation in the content ratio of sp2‐ and sp3‐hybridized carbon bonding provides insights into the spatial structure evolution of pre‐carbonized lignin, which correlates well with changes in the porous structure of LPC. The LPCs show ultrahigh specific surface area up to 3219 m2 g−1 and tailored meso‐/micropore distribution. The lithium‐ion capacitor full‐cell tests demonstrate the great potential of LPCs in energy storage applications with superior energy density and power density. This work provides a feasible strategy to precisely design the microstructure of LPC, offering promising prospects for energy storage technologies.

Robocasting of ordered mesoporous silica‐based monoliths: Rheological, textural, and mechanical characterization

AbstractHierarchically porous, high‐surface‐area silica materials are excellent candidates for multiple applications like catalysis and environmental remediation. Shaping these materials with additive manufacturing (AM) techniques, like robocasting, could enable their use with the benefit of on‐demand, customized shaping and maximizing performance. Herein, ordered mesoporous silica COK‐12 slurries were robocasted into monoliths, containing different ratios of uncalcined COK‐12 and sodium bentonite (0–25 wt.%). The rheology of the mixed slurries is characterized by lower flow indexes (0.69 vs. 0.32) and higher yield stresses (96 vs. 259 Pa) compared to pure COK‐12 ones. Monoliths were printed in woodpile structures and calcined at 600°C. Micro‐CT measurements showed a linear shrinkage of 25% after calcination. Mechanical characterization showed increased uniaxial strength (0.20 ± 0.07 to 1.0 ± 0.3 MPa) with increasing binder/solids ratio from 13 to 25%. The amorphous, mesoporous structure of COK‐12 was retained. The structures exhibited open porosities of 52 ± 4% and showed higher specific mesopore volumes, and increased average mesopore size (6 vs. 8 nm) compared to COK‐12. Small‐angle x‐ray scattering analysis revealed an increased lattice parameter (10.3 vs. 11.0 nm) and reduced wall thickness (3.1 nm vs. 4.1 nm) of the COK‐12 in the monoliths. These properties indicate suitability for their application as porous supports and adsorbents.

Desilicated ZSM‐5 Catalysts: Properties and Ethanol to Aromatics (ETA) Performance

AbstractHerein, desilication in increasingly harsh conditions was used to introduce mesopores into two different industrial ZSM‐5 catalysts (Si/Al ratio 11 or 29). For desilicated samples, increasing BET surface areas, mesopore volumes, and Si(OH) densities were noted. Brønsted acid site (BAS) densities increased upon desilication, as formerly inaccessible BAS in blocked pores became available, while the strength of the BAS was maintained upon desilication. Using KOH instead of NaOH as desilication agent can increase the mesopore volume generated per mass loss. The correlations between desilication strength and properties were largely determined by the parent Si/Al ratio. In general the introduced mesopores increased lifetimes in the ETA conversion, while additional Si(OH) groups introduced by desilication reduce the lifetime again. The lifetime is thus determined by a complex interplay of BAS density, improved reactant transport by introduced mesopores and Si(OH) density. There were no additional aromatics formed in desilicated samples during the conversion of ethanol and the samples were, in terms of aromatic yield, outperformed by a microporous parent. However, as result of longer lifetimes less ethanol was lost due to coke formation. It is concluded that desilication should be combined with other post‐modifications to increase aromatic production and lifetime.

Influences of Evolution of Pore Structures in Tectonic Coal under Acidization on Methane Desorption.

Experiments on corrosion reactions of pulverized coal with monomeric and polymeric (mixed) acid solutions reveal that monomeric acids are listed in a descending order as HF, HCl, and CH3COOH according to their corrosion effects on tectonic coal collected in Faer Coal Mine (Liupanshui City, Guizhou Province, China). In addition, the optimal mixing ratio of mixed acids is 6% HCl + 6% HF + 3% CH3COOH + 2% KCl. The mineral grains filled in pores in coal samples treated with mixed acid solutions are dissolved, so the porosity increases. The volumes of transition pores and mesopores are obviously affected by acidization, and some transition pores are transformed into mesopores and macropores to form dissolved pores. At the same time, inkbottle-shaped pores reduce, while slit pores or open pores increase. The coal samples after acidization show a higher aromatization degree and an increased relative content of oxygen-containing functional groups, with a generally lower hydroxyl content, so the methane (CH4) adsorption capacity of coal declines, which promotes CH4 desorption. The control effect of pore structures after acidization reactions on CH4 desorption was revealed from perspectives of the diffusion coefficient (Kn), adsorption volume (ω), average pore-throat ratio (PT), and average sinuosity (τav). That is, CH4 molecules in tectonic coal after acidization turn from Knudsen diffusion to transitional diffusion, the adsorption volume of CH4 molecules shrinks, the average pore-throat ratio decreases, and the average sinuosity reduces, which promotes CH4 desorption from tectonic coal.

Multi-Scale Fractal Characteristics of the Pore System in Low-Permeability Conglomerates from the Junggar Basin

The pore structure and its complexity play a critical role in fluid migration and recovery efficiency. Multiple pore types, broad pore size distribution (PSD), and extremely irregular pore morphology hinder the comprehensive investigation of pore systems and their complexity in low-permeability conglomerates. In this study, the multi-scale pore system and fractal characteristics of the Permian Lower Wuerhe Formation and Triassic Baikouquan Formation conglomerates from the Junggar Basin were investigated, combining physical property analysis, casting thin sections, scanning electron microscopy, and Nuclear magnetic resonance (NMR). The results show that the pore system of conglomerates consists of residual intergranular pores (RIPs), dissolution pores (DPs), clay-related pores (CRPs), and microfractures. Three types of PSD were identified according to the shape of the T2 spectrum. Based on the fractal characteristics derived from NMR data, pore systems in conglomerates were divided into macropores (mainly RIPs and DPs), mesopores (mainly CRPs), and micropores (reflect adsorption spaces). The fractal dimension of macropores (D3) increases with the increase of clay mineral content and the decrease of contents of quartz and feldspar. Moreover, the volume of macropores decreases with the increase of clay mineral content and the decrease of contents of quartz and feldspar. In addition, the fractal dimensions and volumes of mesopores and micropores have no obvious relationship with mineral composition. D3 and macropore volume control the physical properties and fluid mobility of conglomerates. T2,gm shows a strong negative correlation with D3 and macropore volume. Meanwhile, the high value of D3 would reduce the volume of macropores. These results demonstrate that D3 is a good indicator to reveal the quality of pore structure in low-permeability conglomerates.

Effects of Chemical Activation Conditions on Hierarchical Porous Carbon via Oxytetracycline Adsorption

This study investigated the characteristics and oxytetracycline (OTC) adsorption of hierarchical porous carbons (HPCs) synthesized under different activation conditions using biomass wheat flour (WF) and NaHCO3 as an activator. It was found that the characteristics of the HPCs, such as specific surface area, total and mesopore volume, defects, and crystallinity, were highly dependent on the activation temperature, the dose of the activator, and activation time. In particular, the adsorption mechanisms and adsorption capacity were dominantly governed by the degree of defects in graphitic structures and mesoporosity, which are largely determined by the dose of the activator and the activation temperature. The best OTC adsorption was achieved with the HPC of the most abundant mesopores, which was prepared at 900 °C, a WF:NaHCO3 mass ratio of 1:1, and a duration of 2 h (HPC900_R1.0_2H). Based on the results of the experiments concerning adsorption kinetics, equilibrium adsorption, and the effects of pH, OTC adsorption onto HPC900_R1.0_2H was monolayer in type, homogeneous, governed by the combination of diffusion and chemisorption, and largely attributed to π–π electron–donor–acceptor interactions and electrostatic interactions. The thermodynamic parameters suggest that it is spontaneous and endothermic. These findings provide valuable information about the design and synthesis of HPCs from biomass, which exhibit optimized properties for the adsorption of refractory organic pollutants.

Effect of Pretreatment on the Nitrogen Doped Activated Carbon Materials Activity towards Oxygen Reduction Reaction.

Nitrogen-doped activated carbons with controlled micro- and mesoporosity were obtained from wood and wastes via chemical processing using pre-treatment (pyrolysis at 500 °C and hydrothermally carbonization at 250 °C) and evaluated as oxygen reduction catalysts for further application in fuel cells. The elemental and chemical composition, structure and porosity, and types of nitrogen bonds of obtained catalyst materials were studied. The catalytic activity was evaluated in an alkaline medium using the rotating disk electrode method. It was shown that an increase in the volume of mesopores in the porous structure of a carbon catalyst promotes the diffusion of reagents and the reactions proceed more efficiently. The competitiveness of the obtained carbon materials compared to Pt/C for the reaction of catalytic oxygen reduction is shown.

Hydrocarbon Potential and Reservoir Characteristics of Lacustrine Shale: A Case of Lower Jurassic in the Western Qaidam Basin, NW China

The Lower Jurassic lacustrine shale is well developed in the western Qaidam Basin and characterized by significant thickness and continuous distribution. Previous investigations have indicated its substantial potential as a shale gas resource. Based on experiments of organic carbon content, vitrinite reflectance, rock-eval pyrolysis, X-ray diffraction, and low-temperature nitrogen adsorption, the hydrocarbon potential and reservoir characteristics of Lower Jurassic lacustrine shale in the western Qaidam Basin were systematically analyzed. The results show that the total organic carbon (TOC) content ranges from 1.71% to 4.49%, with an average of 2.98%. The kerogen belongs to type II–III. The vitrinite reflectance (Ro) ranges from 1.05% to 1.95%, with an average of 1.62%, indicating that the kerogen has reached the high thermal maturity stage (gas window). The maximum pyrolysis peak temperature (Tmax) ranges from 408 °C to 580 °C, with an average of 498.38 °C, further supporting the high thermal maturity of the kerogen. The content of brittle minerals, including quartz, feldspar, pyrite, and carbonate, ranges from 21% to 44% (averaging 32.54%), which is comparable to shale minerals found in American Ohio shale. The pore structure of the shale is predominantly characterized by open parallel plate slit pores and inclined slit pores. The pore diameter distribution curve can be divided into two types, including unimodal distribution and bimodal distribution. Micropores and mesopores contribute significantly to the specific surface area, and mesopores account for the highest proportion of pore volume. The thermal evolution degree has a direct impact on pore development of shale reservoirs. The micropore, mesopore, macropore, and total pore volumes of lacustrine shale in the study area show a negative correlation with TOC content, indicating that the organic matter within the shale is probably still in the first pyrolysis stage. However, no significant correlation is observed between pore volume and clay mineral content or between pore volume and brittle mineral content due to the complex interplay of several geological factors. These findings contribute to a better understanding of the lacustrine shale gas resource potential and can guide future exploration and exploitation efforts. In addition, the systematic analysis of reservoir characteristics serves as a foundation for the introduction and exploration of new shale fracturing technologies, which is of great significance for reducing the consumption of water resources and mitigating potential geo-disasters.

Green synthesis of shaped nano-ZSM-5 toward more efficient methanol-to-hydrocarbon conversion

Commonly, in the synthesis of zeolites, calcination is necessary prior to ion exchange to remove organic templates. Herein, shaped nano-ZSM-5 was successfully prepared with the assistance of template-free nano-aggregate seed without the calcination step before ion exchange. This synthesis method dramatically increased mesopores volume compared with the one calcined prior to ion exchange. Besides, employing nano-aggregate as seed gave the synthesized ZSM-5 a markedly smaller particle size and higher yield than the one prepared with conventional silicate-1 as seed, and simultaneously accelerated the crystallization process by providing more nuclei. A possible formation mechanism of the shaped nano-ZSM-5 zeolites was proposed. The shaped nano-ZSM-5 possessed the smallest crystal size, largest mesopore volume, most acid sites and strongest acid strength, which endowed it highest catalytic activity and longest lifetime in methanol to hydrocarbons reaction. This work could attract more attention on the application of nanoscale ZSM-5 catalyst to industry.

Engineered cellulose-based porous carbon adsorbents for superior gas adsorption and selective separation of CH4/H2 and CH4/N2

Adsorption and separation of methane from turquoise hydrogen and coalbed methane is becoming an important method for using unconventional natural gas. Adsorbent performance determines this technique. In this regard, the cellulose-based (Cell-PC) adsorbents were engineered by a facile process with a one-pot calcination method without solvent and an activating reagent-free like KOH with an economical and green approach for CH4/H2 and CH4/N2 separation. The series of adsorbents were synthesized, such as Cell-100, U-Cell-111, O-Cell-111, O-Cell-112, O-Cell-113, and O-Cell-113-a, from cellulose with urea/oxalic acid and sodium hydrogen carbonate, which helps to create pore structure. All adsorbents were characterized by several techniques, including XRD, SEM, XPS, and BET. All Cell-PC adsorbents were used to systematically investigate adsorption studies for CH4, N2, and H2. The O-Cell-113-a adsorbent demonstrated a superior CH4 uptake capacity of 52.75 cm3/g at 273 K and 37.92 cm3/g at 298 K under 100 kPa. It was attributed to the synergistic role of high surface area, mesopore volume, micropore volume, morphology, and surface functional group. However, the O-Cell-113-a showed lower adsorption for N2 and was unable to adsorb H2 at 298 K, indicating the adsorbent has selective adsorption properties for CH4. Furthermore, the ideal adsorbed solution theory (IAST) model was used to calculate the selectivity of CH4/N2, which was found to be around 13.78 at 273 K and 12.64 at 298 K, which is higher than most previously reported porous carbon. The isosteric heat of adsorption of O-Cell-113-a adsorbent was further calculated for CH4 and N2.

Adsorption of yttrium by the sodium-modified titanium dioxide: Kinetic, equilibrium studies and investigation of Na-TiO2 radiation resistance

The adsorption of yttrium cations from an aqueous solution of YCl3 by sodium-modified titanium dioxide (Na-TiO2) was investigated. The Na-TiO2 was obtained by impregnating Na+ cations into the surface layer of TiO2 nanoparticles. The synthesis of nanoparticle TiO2 was performed by a liquid-phase sol–gel method, using the aqua complex of [Ti(OH2)6]3+‧3Cl− as a precursor. Nanoheterostructured Na-TiO2 is an anatase modification of TiO2. The amount of incorporated sodium cations on the TiO2 surface is about 6%. The surface area of Na-TiO2 is 239 m2‧g−1; the volume of mesopores is 0.098 cm3‧g−1; that of micropores is 0.054 cm3‧g−1. Yttrium ion adsorption was investigated under batch conditions. Complexometric titration and mas-spectrometric analysis determined the initial and equilibrium concentration of yttrium. The radiation resistance of Na-TiO2 to the influence of beta irradiation was investigated as well. For this purpose, the radiation of β−-particles of the 90Sr-90Y source “Sirius” was used. The flux of β− – particles was 2.1 ‧ 108 electrons/sm2‧s; the maximal energy of incident electrons was 2.28 MeV. It was shown that the investigated adsorbent has a high adsorption capacity toward yttrium cations. The maximum adsorption is about 259 mg/g. The adsorption kinetic is fit well with the kinetic model based on the pseudo-second-order equation. The equilibrium adsorption of yttrium cations is described by Freundlich's theory with high reliability. The adsorbent is resistant to the influence of β− – irradiation. This is manifested in the invariance of its adsorption capacity toward yttrium cations after irradiation. Na-TiO2 is a promising material for the adsorption of yttrium and Rare Earth elements and can be used as the basis for the 90Y isotopic generator.

Activated three-dimensionally ordered micromesoporous carbons for CO2 capture

Three-dimensionally ordered micromesoporous carbon (3DOmm) has been studied recently as a potential sorbent for CO2 capture at higher pressures. However, the as-synthesized material usually has a low microporous fraction, which could significantly limit CO2 uptake. Herein, we showed that microporosity in 3DOmm carbon can be increased by physical activation, substantially improving its CO2 capture performance in the wide pressure range. The highly porous activated 3DOmm carbons, having amorphous structure, were prepared with ordered spherical mesopores of diameter 22.7–24.7 nm and ultramicropores in the walls of diameter 0.41–0.55 nm. Physical activation was performed by exposing the post-synthesized 3DOmm carbon to high temperatures of 973–1173 K under a CO2 flow for 30 min. The activation procedure did not show any visible destruction of the ordered mesoporous structure in the 3DOmm carbon. However, it had a significant impact on micropore and mesopore volumes and the specific surface area, which in turn affected the CO2 adsorption capacity of the carbons. Accordingly, after activation at 973 K, the micropore volume of 0.23 cm3/g, the mesopore volume of 3.70 cm3/g and the specific surface area of 1058 m2/g in the 3DOmm carbon increased to 0.27 cm3/g, 3.94 cm3/g and 1462 m2/g, respectively. Further increase in activation temperature led to decreasing pore values due to widening and shrinking of the thin carbon walls in the 3DOmm carbon. The 3DOmm carbon activated at 973 K had the highest micropore and mesopore volumes and the highest CO2 adsorption performance over the whole pressure range (3.19 mmol/g at 273 K and 100 kPa; 11.18 mmol/g at 298 K and 2 MPa and 0.38 mmol/g under flue 15% CO2/85% N2 gas conditions at 298 K). All 3DOmm carbons showed fast kinetics, high selectivity for CO2 over N2 (33.2–51.5), the excellent regenerative ability and isosteric heats (18.9–29.2 kJ/mol), indicating physical adsorption.

Highly mesoporous activated carbon fibers using high density polyethylene precursor with a multi-step stabilization technique for automobile carbon canister

In this study, activated carbon fibers (ACFs) for automobile carbon canisters were produced using high-density polyethylene (HDPE) fibers treated with a multistep stabilization process as the precursor. The stabilization of the HDPE fibers involved the following sequential steps: (1) electron beam irradiation, (2) mild sulfonation, and (3) dry oxidation. The stabilized fibers were carbonized at 900℃ in a nitrogen atmosphere. The carbonized fibers were activated at 900℃ in a water–vapor atmosphere from 30-60 min. The textural properties of the activated carbon fibers were determined using N2/77 K adsorption–desorption isotherms. The specific surface area ranged from 1090 to 1980 m2/g, and the total pore volume ranged from 0.56 to 1.11 cm3/g. The specific surface area, micropore volume, and mesopore volume increased with increasing activation time. The fractions of micropores and mesopores were similar across all conditions, whereas the yield decreased gradually until 50 min, and then exhibited a sharp decline at 60 min. The butane working capacity increased as much as 56.24% as the increase in activation time. This can be attributed to the increase in butane activity owing to the increase in micropore volume, along with a decrease in butane resistivity caused by the increase in mesopore volume at a specific diameter.

Hierarchical SAPO-34 Catalysts as Host for Cu Active Sites.

Cu-containing hierarchical SAPO-34 catalysts were synthesized by the bottom-up method using different mesoporogen templates: CTAB encapsulated within ordered mesoporous silica nanoparticles (MSNs) and sucrose. A high fraction of the Cu centers exchanged in the hierarchical SAPO-34 architecture with high mesopore surface area and volume was achieved when CTAB was embedded within ordered mesoporous silica nanoparticles. Physicochemical characterization was performed by using structural and spectroscopic techniques to elucidate the properties of hierarchical SAPO-34 before and after Cu introduction. The speciation of the Cu sites, investigated by DR UV-Vis, and the results of the catalytic tests indicated that the synergy between the textural properties of the hierarchical SAPO-34 framework, the high Cu loading, and the coordination and localization of the Cu sites in the hierarchical architecture is the key point to obtaining good preliminary results in the NO selective catalytic reduction with hydrocarbons (HC-SCR).