Fraction Of Micropores Research Articles

Aging damage characteristics of acid‐etched sandstone samples

AbstractTo investigate the erosive damage effect of the acidic solution on sandstone, experiments were conducted to examine the macro‐ and micro‐characteristics of sandstone samples under different acid etching times. Microscopic morphology changes, pore structure characteristics, mineral composition changes, and mechanical response characteristics were obtained before and after acid etching. Finally, a comprehensive evaluation index for acid etching damage was proposed. The results show that: (1) Acidic solution will erode the sandstone skeleton and cause the sandstone to collapse. The etched surface appears “flocculent” and yellow sediment is produced. (2) The pores in sandstone samples are mainly micro‐ and mesopores, and the total porosity increases exponentially with the duration of acid etching. The volume fraction of micropores can reach up to 81.5%. (3) The acid etching process of sandstone samples includes physical diffusion and chemical dissolution, which can be divided into four stages and three regions from the outside to the inside. After acid etching, the uniaxial compression failure mode of the sample changes from shear to mixed shear‐tensile failure. (4) The comprehensive evaluation index based on three failure modes generated during the loading process shows good consistency with the overall changes of characteristics parameters such as elastic modulus, peak stress, and peak strain. The research findings of this paper can provide theoretical support for the assessment of rock mass stability and disaster prevention in acidic environments.

In English

Fullerenes are interesting objects of research in view of their promising use as a nano-sized additive to coatings, films, adsorbents, as well as active components in medicine, pharmacy, cosmetology. This paper considers the possibility of modifying commercial adsorbents - silica gel and cation-exchanger based on activated carbon with available and inexpensive linear carbon radicals. Behentrimonium chloride (C22H45(CH3)3N+Cl-) and cetyl alcohol (C16H33OН) were chosen as the latter. The obtained adsorbents were compared with a commercial sample of silica gel modified with a linear hydrocarbon radical –C18Н37. The adsorbents were described by the methods of IR spectroscopy, thermogravimetry, the main characteristics of the porous structure were determined by the method of low-temperature adsorption-desorption of nitrogen. Modification of adsorbents based on silica gel leads to a decrease in the specific surface area to 202.4 and 236.5 m2/g and the total pore volume to 0.32 and 0.39 cm3/g, which is almost 2 half source material. Increasing the fraction of micropores contributes to better separation rates of large molecules. Treatment of cation-exchanger based on activated carbon by cation modifier leads to a significant decrease in the specific surface area, as well as to an increase in the size of pores with the predominant formation of mesopores. It is shown that the modification of silica gel is carried out both through silanol and siloxane groups, in contrast to the commercial sample of silica gel. The approximate number of modifier groups on the surface of the original SiO2 matrix was estimated, which is one modifier group ~ per 11 SiO2 molecules. To study the behavior of adsorption of C60, C70 fullerenes and their mixtures on adsorbents, column experiments were carried out with changes in the geometrical parameters of the column and the initial concentrations of the solutions. The results showed that the modified silica gels are potential adsorbents for the separation of a mixture of fullerenes with a ratio of 65/25. Silica gel modified with cetyl alcohol C16H33OH showed the best separation efficiency. By the help of an adsorbent, it is possible to separate C60 - 90.52 % from a less concentrated solution and 87.26 % from a more concentrated solution. To increase the purity of the product, it is necessary to pass the solution through the sorbent 2–3 times. The competitive capability of the proposed modified silica gels, together with economic efficiency, ease of modification, and the possibility of fullerene separation characterize the proposed adsorbents as potential materials for practical application. Due to the significantly lower cost and simpler manufacturing methods, the proposed adsorbents can be used for separation at a large scale.

Excellent gas separation performance of hybrid carbon molecular sieve membrane derived from polyimide/10X zeolite for hydrogen purification

Membrane-based gas separation is attracting more and more attention in hydrogen purification and CO2 separation. One critical challenging remaining for large-scale production is fabricating a high-performance membrane with both inexpensive and excellent separation performance. In this work, a novel hybrid-carbon molecular sieve (CMS) membranes were reported for hydrogen purification by pyrolysis of commercial polyimide precursor (PMDA-ODA) with incorporation of modified 10X zeolite. The addition of modified 10X zeolite provided additional gas transport channels to the CMS mixed matrix membrane (MMM), and contained a significant fraction of micropores within the 0.6–0.8 nm range, which greatly enhance hydrogen adsorption capacity. Interestingly, despite this, the selectivity for H2/N2 and H2/CH4 also increases with higher zeolite content. This unexpected phenomenon may be attributed to the partial blocking of zeolite pores by CMS strand, which narrows the 10X pore size to a dimension smaller than CH4 and N2, enabling differentiation between H2 and CH4 gas pairs. Therefore, the permeability and selectivity of H2 was significantly enhanced. The CMS/10X-7.5 (with 7.5 wt % 10X zeolite) exhibited an advanced H2 permeability (1709 Barrer) and high gas selectivity of 551 for H2/CH4 and 105 for H2/N2, respectively, which is higher than other samples and exceed the 2015 trade-off lines. Furthermore, the CMS/10X-7.5 delivered excellent stability after 20 cycles. Therefore, this hybrid CMS/10X-7.5 obtained by carbonization of zeolite-doped polymer precursors has great potential for larger industrial applications.

New approaches for regulation of structure and adsorption properties of biochar based on freshwater sediments (sapropels)

Biochar based on sapropel have been synthesized and the effect of chemical modification on their textural characteristics, acid-base and adsorption properties has been studied. It was found that preliminary treatment of raw sapropel with a weakly concentrated solution of alkali increases the fraction of micropores: from 0.006 cm3 g−1 (for BС-N) to 0.021 cm3 g−1 (for КОН-BC), and additional treatment with hydrofluoric acid leads to an increase in the fraction of micropores up 0.047 cm3 g−1 (for КОН-BC-HF) and also of specific surface area up to 211 m2 g−1 at a considerable decrease in the fraction of mineral part due to leaching of silicon-containing phases. The proposed chemical modification makes it possible not only to change the ratio of mineral and carbon parts and the pore space, but also to vary the surface properties of biochar: рНPZC, concentration and features of oxygen-containing groups. It is shown that the total content of acidic groups increases in the series BС-N (0.3290 mmol g−1) < КОН-BC (0.5567 mmol g−1) < КОН-BC-HF (1.3046 mmol g−1). Simultaneously the type of treatment affects the nature of oxygen-containing groups: the maximum amount of phenolic groups (0.4845 mmol g−1) in sample КОН-BC, the surface acidity of КОН-BC-HF is contented by the presence of a considerable amount of carboxyl groups (0.9198 mmol g−1). The analysis of the data obtained shows that the total content of acidic groups increases in the series The adsorption of Cu(II) ions from an aqueous solution on the synthesized samples of biochar was studied for the first time. Biochar obtained using the sapropel pretreated with alkali showed the maximum adsorption capacity toward copper ions of 27.9 mg g−1. Conceptual model identifying the mechanisms of adsorption copper (II) ions on biosorbent from sapropels was shown. The experimentally obtained isotherms were approximated using the Freundlich and Langmuir models. It was found that the adsorption of copper on the tested samples can be described quite adequately by the Langmuir monomolecular adsorption model (R2 ≥0.98).

Tuning the ultra-microporosity in hierarchical porous carbons derived from amorphous cellulose towards a sustainable solution for hydrogen storage

Activated carbons exhibit a high grade of porosity, which together with structural stability, regenerability and cyclability makes them capable of achieving excellent hydrogen adsorption capacity. A further advantage comes from the ease of production and the use of recyclable and biocompatible materials. A simple way to produce activated carbons from amorphous cellulose involves procedures in which a pyrolysis process is combined with physical activation in CO2.We used this approach by optimizing the production process tuning the activation times. The aim is to evaluate the influence of this process parameter on the formation of the specific surface area, the pore volume and fraction of micropores with a typical size <2 nm. The influence of these structural parameters on the hydrogen adsorption properties was then evaluated. The textural and adsorption characteristics were investigated using a commercial volumetric apparatus (ASAP 2460, Micromeritics) at −196 °C and pressures between 0 and 1 bar, while the morphological properties were investigated using scanning electron microscopy.The results show that the nanostructured samples are characterized by a very high degree of ultra-microporosity (<0.7 nm) with an average pore size between 0.5 and 0.6 nm and a high specific surface area, reaching maximum values around 1500 m2/g and micropore volume up to 0.58 cc/g. These morphological characteristics strongly influence the hydrogen adsorption properties, where the molecules adsorbed reach values very close to the coverage of ideal monolayer. The synthesized activated carbon samples show a higher hydrogen adsorption capacity than similar commercial materials tested under the same thermodynamic conditions.

Effects of activation temperature and time on porosity features of activated carbons derived from lemon peel and preliminary hydrogen adsorption tests

Lemon peels, a common biomass waste, have an interesting composition in terms of cellulose and mineral salts that makes them good precursors for activated carbon production processes. From a circular economy perspective, this work highlights the possibility of turning a waste material into a new resource. The resulting nanostructures show interesting performance in terms of specific surface area and total pore volume, with excellent grade of microporosity, that make them suitable for various applications ranging from supercapacitors, sensors, gases separation and storage, etc. The last, and in particular hydrogen storage, represents the most interesting one. In this study the development of activated carbon through pyrolysis method, consisting of carbonization in inert ambient and subsequent physical activation in oxidizing atmosphere is reported. Influence of synthesis parameters on the porosity formation was investigated with the aim of textural properties optimization. All produced samples were initially characterized both morphologically and crystallographycally. Then, textural and adsorption properties were evaluated through volumetric apparatus. The experimental results show improvement of both textural and adsorption properties as function of synthesis parameters, developing adsorbent materials with high fraction of micropores (≃84 %), specific surface area (≃500 m2/g) and hydrogen uptake of 0.93 wt% at 77 K and 1 bar.

RAFT Polymerisation and Hypercrosslinking Improve Crosslink Homogeneity and Surface Area of Styrene Based PolyHIPEs.

The influence of a polymerisation mechanism (reversible addition-fragmentation chain transfer; RAFT vs. free radical polymerisation; FRP) on the porous structure of highly porous poly(styrene-co-divinylbenzene) polymers was investigated. The highly porous polymers were synthesised via high internal phase emulsion templating (polymerizing the continuous phase of a high internal phase emulsion), utilising either FRP or RAFT processes. Furthermore, residual vinyl groups in the polymer chains were used for the subsequent crosslinking (hypercrosslinking) applying di-tert-butyl peroxide as the source of radicals. A significant difference in the specific surface area of polymers prepared by FRP (between 20 and 35 m2/g) and samples prepared by RAFT polymerisation (between 60 and 150 m2/g) was found. Based on the results from gas adsorption and solid state NMR, it could be concluded that the RAFT polymerisation affects the homogeneous distribution of the crosslinks in the highly crosslinked styrene-co-divinylbenzene polymer network. During the initial crosslinking, RAFT polymerisation leads to the increase in mesopores with diameters between 2 and 20 nm, resulting in good accessibility of polymer chains during the hypercrosslinking reaction, which is reflected in increased microporosity. The fraction of micropores created during the hypercrosslinking of polymers prepared via RAFT is around 10% of the total pore volume, which is up to 10 times more than for polymers prepared by FRP. Specific surface area, mesopore surface area, and total pore volume after hypercrosslinking reach almost the same values, regardless of the initial crosslinking. The degree of hypercrosslinking was confirmed by determination of the remaining double bonds by solid-state NMR analysis.

NH2-Modified UiO-66: Structural Characteristics and Functional Properties.

The development of new functional materials based on metal-organic frameworks (MOFs) for adsorption and catalytic applications is one of the promising trends of modern materials science. The Zr-based MOFs, specifically UiO-66, are considered as the supports for metallic catalysts for the 5-hydroxymethylfurfural platform molecule reduction into valuable products. The present work focused on the effect of NH2 modification of UiO-66 on its structure and functional properties. The samples were prepared by a solvothermal method. The structure of the obtained materials was studied by X-ray diffraction, IR spectroscopy, UV-visible spectroscopy, and low-temperature nitrogen adsorption. Basic properties were investigated by HCl and CH3COOH adsorption, and electrokinetic properties were studied by electrophoretic light scattering. UiO-66-NH2 samples with different contents of aminoterephthalate linkers were successfully prepared. A gradual decrease in the specific surface area and the fraction of micropores with a diameter of ~0.9 nm was observed with an increase in the aminoterephthalate content. A proportional increase in the total number of basic sites in UiO-66-NH2 samples was established with an increase in the aminoterephthalate content up to 75%. At the same time, a noticeable decrease in the total number of basic sites and an increase in their strength with higher aminoterephthalate content was observed.

Research on the mechanical properties and microstructure of fly ash-based geopolymers modified by molybdenum tailings

The environmental and economic problems caused by the accumulation of molybdenum tailings (MT) have become increasingly prominent. Therefore, a cost-effective method is urgently needed to realize the resource utilization of MT. In this paper, the mechanism of action of MT on fly ash-based geopolymers were systematically researched. The effects of MT on the macro-properties of fly ash-based geopolymers were researched in terms of fluidity, setting time, drying shrinkage and mechanical strength. The reaction mechanism of fly ash-based geopolymers modified by MT were analyzed from the perspective of microstructure and micromorphology by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric (TG) and nitrogen adsorption/desorption (NAD) methods. The results show that the addition of MT could effectively improve the fluidity of fly ash-based geopolymer paste, appropriately delay its setting time and increase its drying shrinkage; When the content of MT was 20%, the bending strength of fly ash-based geopolymers were significantly improved, and the flexural strength at 3, 7 and 28 days were increased by 79.2%, 47.4% and 19% respectively. The SEM, FTIR and TG results confirmed that the main product was glassy sodium calcium aluminum silicate hydrate (N(C)-A-S-H) gel, which was used as a binder to connect residual raw material particles and form hardened geopolymer materials. The XRD results show that the addition of MT would not lead to the formation of new crystal phases in the fly ash-based geopolymers, and when the addition of MT was 20%, the diffraction peak intensity of the crystal phase structure of the fly ash-based geopolymers basically were not changed obviously. The NAD results show that the addition of 20% MT could significantly improve the pore structure of fly ash-based polymers, increased the volume fraction of micropores, and reduced the volume fraction of macropores. The SEM/EDS results show that the MT could be dissolved in alkali activator to form nanorods to fill the pore structure of fly ash-based geopolymers, thus reducing the cracks and defects of fly ash-based geopolymers and improving the compactness of the microstructure.

Prediction of structural properties of activated carbons derived from lignocellulosic biomass components using mixture design of experiments

There is significant interest in using biomass to produce activated carbons for applications such as environmental remediation, energy storage, and construction. To date, the research has primarily focused on exploring the potential of individual biomass sources. There is little research on how interactions between the fundamental components of lignocellulosic biomass affect activated carbons' structural properties, and, therefore, their suitability for various applications. This investigation sought to address this knowledge gap by exploring how the relative compositions of cellulose nanofibers, cellulose nanocrystals, and lignin affected the final properties of activated carbons produced through a two-step KOH activation process. A simplex-lattice mixture design was used to understand how the composition affected activated carbon yield, specific surface area, and micropore fraction. Mixture regression models showed that the specific surface area was highest when the activated carbon was composed of 16.7% cellulose nanofibers, 16.7% cellulose nanocrystals, and 66.7% lignin by mass. In addition, the micropore fraction was largest at 76.3% while also maintaining a high surface area, with a precursor mixture of 50% cellulose nanocrystals and 50% lignin by mass. The results of this investigation provide a foundation for future efforts to be able to predict, and tune, activated carbon properties based on biomass composition.

Impact of Pore Structure on Electrochemical Reduction of Carbon Dioxide in Iron- and Nitrogen-Doped Carbon Materials: Solid–Liquid Interface Versus Solid–Gas–Liquid Triple-Phase Boundary

The effect of porosity on the interface microenvironment and catalytic performance of carbon dioxide reduction reaction (CO2RR) is still unclear for iron- and nitrogen-doped carbon-based (Fe/N/C) materials, and previous studies mainly focus on aqueous electrode test conditions rather than a practical working environment. Herein, several Fe/N/C-based catalysts with very different pore structures were prepared and compared to understand how the surface area and micropores affect the CO2RR between aqueous electrode test and practical working conditions with a solid–gas–liquid triple-phase boundary. The apparent current density correlates positively to the surface area in both test conditions. The onset current density where hydrogen evolution reaction starts is irrelevant to the micropore fraction in the aqueous electrode test but correlates negatively to the micropore fraction in a practical working condition. The inconsistency is attributed to different reaction interfaces in both cases, resulting in different interface microenvironments in different pore size ranges. This work helps in designing porous electrocatalysts for CO2RR or beyond.

A Comparative Study on the Microstructure and Petrophysical Properties of Undeformed and Naturally Deformed Shales

Structural deformation is one of the main impacts responsible for understanding the hydrocarbon accumulation mechanism. Predicting its function in gas storage and migration in a microscopic scale is thus a significant issue in predicting reservoir quality. The purpose of this article is to make a comparative study on the microstructure and petrophysical properties of undeformed and naturally deformed shales developed in the Southeast Sichuan Basin. The results show that (1) organic pores, ranging from 10 to 200 nm, are more developed in undeformed shale, whereas carbonate solvopores, clay-hosted pores, and microfractures are dominant in deformed shale. (2) Undeformed shales have Dubinin–Radushkevich (DR) CO2 adsorbed contents ranging between 0.009 and 0.018 g, DR CO2 micropore surface areas of 3.90–15.59 m2/g, and Dubinin–Astakhov (DA) CO2 micropore volumes of 0.002 and 0.035 cc/g. Naturally deformed shales have larger DR CO2 adsorbed contents, DR CO2 micropore surface areas, and DA CO2 micropore volumes, typically in the ranges of 0.019–0.031 g, 13.15–20.97 m2/g, and 0.006–0.012 cc/g, respectively. (3) Undeformed shales have N2 adsorbed contents ranging between 1.94 and 6.03 cc/g, Brunauer–Emmett–Teller (BET) N2 mesopore and macropore surface areas of 0.55–7.35 m2/g, and Barrett–Joyner–Halenda (BJH) N2 mesopore and macropore volumes of 0.002 and 0.006 cc/g. Naturally deformed shales have larger N2 adsorbed contents, BET N2 mesopore and macropore surface areas, and BJH N2 mesopore and macropore volumes, typically in the ranges of 5.72–14.45 cc/g, 7.47–17.64 m2/g, and 0.005–0.015 cc/g, respectively. (4) All samples have a unimodal micropore size distribution with a distinct peak associated with a 1.5 nm micropore fraction and have a multimodal mesopore and macropore size distribution. Naturally deformed shales show more homogeneous pore size distribution curves with morphological consistency than undeformed shales, indicating that structural deformation can significantly influence pore structural heterogeneity. (5) Deformed shales exhibit higher porosity and permeability compared to the undeformed samples due to the open pore-fracture network associated with the inorganic pores and microfractures. Average porosity and permeability in deformed shales can be 1.8 and 15 times higher than those in the undeformed shales. We conclude that the microstructural heterogeneity from strong to weak and the changes of a relatively single organic pore-dominated pore system to complex pores and microfractures dominated the pore-fracture system within shales due to structural deformation being the key cause of the quantitatively and qualitatively studied microstructure and petrophysical property differences.

Adsorption of cesium and strontium on mesoporous silicas.

Studies are underway on the adsorption reactions of metal ions in confined spaces at the solid-water interface, but it is unclear how the effects of confinement differ for different types of ions. We investigated the effect of the pore size on the adsorption of two cations with different valence, Cs+ and Sr2+, on mesoporous silicas with different pore size distributions. The amount of Sr2+ adsorbed per unit surface area did not differ significantly among the silicas, whereas that of Cs+ was particularly high for silicas with a larger fraction of micropores. The results of X-ray absorption fine structure analysis showed that both ions form outer-sphere complexes with the mesoporous silicas. The results of adsorption experiments were analyzed by fitting using a surface complexation model with the cylindrical Poisson-Boltzmann equation and optimized capacitance of the Stern layer for different pore sizes, and we found that the intrinsic equilibrium constant for the adsorption of Sr2+ is constant regardless of the pore size, whereas that of Cs+ increases as the pore size decreases. The decrease in the relative permittivity of water inside pores with a decrease of the pore size can be interpreted to cause a change in the hydration energy of Cs+ in the second coordination sphere upon adsorption. The reasons for the different confinement effects on the adsorption reactions of Cs+ and Sr2+ were discussed based on the distance of the adsorbed ions from the surface and the chaotropic and kosmotropic nature of Cs+ and Sr2+, respectively.

Hydrosilylation of Alkynes Under Continuous Flow Using Polyurethane‐Based Monolithic Supports with Tailored Mesoporosity

AbstractNon‐porous polyurethane‐based monoliths are prepared under solvent‐induced phase separation conditions. They possess low specific surface areas of 0.15 m2 g−1, pore volumes of 1 µL g−1, and a non‐permanent, solvent‐induced microporosity with pore dimensions ≤1 nm. Mesoporosity can be introduced by varying the monomers and solvents. A tuning of the average solubility parameter of the solvent mixture by increasing the macroporogen content results in a decrease in the volume fraction of micropores from 70% to 40% and an increase in the volume fraction of pores in the range of 1.7–9.6 nm from 22% to 41% with only minor changes in the volume fraction of larger mesopores in the range of 9.6–50 nm. The polymeric monoliths are functionalized with quaternary ammonium groups, which allowed for the immobilization of an ionic liquid that contained the ionic Rh‐catalyst [1‐(pyrid‐2‐yl)‐3‐mesityl)‐imidazol‐2‐ylidene))(η4‐1,5‐cyclooctadiene)Rh(I) tetrafluoroborate]. The supported catalyst is used in the hydrosilylation of 1‐alkynes with dimethylphenylsilane under continuous flow using methyl‐tert‐butyl ether as second liquid transport phase. E/Z‐selectivity in hydrosilylation is compared to the one of the analogous biphasic reactions. The strong increase in Z‐selectivity is attributed to a confinement effect provided by the small mesopores.

Effect of nitrogen on micro-pores in DD33 single crystal superalloy during solidification and homogenization

The DD33 superalloy with ultra-low nitrogen (N) content was prepared by vacuum induced melting, and the effect of N on micro-pores in the DD33 single crystal nickel-base superalloy during solidification and homogenization was investigated by in-situ X-ray computed tomography (XCT). Results indicate that the volume fraction of micro-pores, including shrinkage pores and gas pores, increases from 0.08% to 0.11% with increasing N content from 5 ppm to 45 ppm during solidification. Correspondingly, the level of micro-pores in the sample with high N content is higher than that in the sample with low N content during homogenization at 1,330 °C for different time periods. However, the evolution behaviors of gas pores is different from that of shrinkage pores during solidification and homogenization. The number of gas pores is obviously larger in the high N sample during solidification, while the number of shrinkage pores and gas pores is almost the same in both samples after 1 h homogenization. Quantitative results show that the annihilation of micro-pores is associated with bubble diffusion, while the growth behavior of micro-pores during further exposure is dominated by Kirkendall-Frenkel effect.

Effect of seepage conditions on the microstructural evolution of loess across north-west China

SummaryLoess features metastable microstructure and is deemed susceptible to chemical contaminant permeation. However, studies on the loess permeability evolution under water and chemical environments are remarkably limited. In this study, the response of the loess to the water and sodium sulfate seepages was analyzed using the temporal relationship of cations concentration, X-ray diffraction and fluorescence (XRD and XRF), mercury intrusion porosimetry (MIP), and scanning electron microscope (SEM) tests. The permeability evolution characteristics were identified, and its underlying mechanisms were revealed from aspects of the diffuse double layer (DDL) theory and physiochemical actions. The discharge of Mg2+ and precipitation of calcium carbonate, referred also to as the dedolomitization, degraded the macro permeability when subjected to the water seepage test. The salt-induced swelling, induced by the intrusion of Na+ into the DDL, caused an increase in the micropore fraction under the sodium sulfate seepage test, thereby increasing the macro permeability.

Towards functionalized graphene/polymer monolithic structures for selective CO2 capture

A design of efficient adsorbent for CO 2 selective capture without secondary pollution and by low carbon footprint strategies is crucial towards the decreasing of CO 2 atmospheric concentration. To answer to this demand, in this work we present a versatile and robust technique for production of functionalized 3D porous graphene/polymer monolithic structures based on aqueous self-assembly process, in which the graphene functionalization occurred simultaneously throughout spontaneous addition of functionalized waterborne polymer particles. It was shown that the composite monoliths are truly products-by-process, as their final characteristic can be designed during the synthesis by varying the reaction parameters. The addition of polymer particles to the graphene skeleton was an excellent tool to control the textural properties, resulting in enlarged fraction of micropores, because the polymer particles act as spacers between rGO platelets. The higher microporosity certainly affected positively the performance, especially the selectivity of CO 2 adsorption over that of N 2 , offering alternative technology for post-production CO 2 capture. • Graphene-based polymer porous composites were synthesized under mild conditions. • Functionalized polymer particles were straightforwardly incorporated. • Chemical and textural characteristics were related to CO 2 adsorption and selectivity. • Materials with high-capacity selective CO 2 capture are promising for practical use.

Qualitative assessment of improved oil recovery and wettability alteration by low salinity water injection for heterogeneous carbonates

This study aims to evaluate the qualitative potential for low salinity water injection (LSWI) to alter the wettability and increase oil production in heterogeneous oil-wet coquina cores (one of the facies of Pre-Salt reservoirs) in relevant conditions of brine salinity, temperature, and initial wettability. We also aimed to verify the impact of micro-porosity fraction on oil recovery. Finally, we verified whether the presence of micro-dispersion in the oil phase upon contact with low salinity would have a positive correlation with improved oil recovery due to low salinity water injection.To achieve these objectives, we performed zeta-potential experiments to evaluate the charges at the oil-brine and brine-rock interfaces that affect rock wetting state and contact tests to test for the presence of micro-dispersions in the oil phase and potential for LSWI. A series of spontaneous imbibition and coreflood experiments were performed to calculate the Amott index and evaluate wettability of coquinas in core-scale as a function of brine salinity. Tertiary and secondary low salinity waterfloods were carried out to investigate whether a diluted desulfated seawater would increase oil production in coquina cores. The effect of predominance of macro-, meso-, and micro-porosity on secondary low salinity waterflood was also evaluated. Our results have shown that heterogeneity had a greater impact on recovery factor compared to brine salinity. Oil recovery for low salinity brine for a core with predominance of macro-pores was smaller than for cores with higher fraction of micro-pores flooded with FW and DSW. Low-salinity oil recovery was also smaller than high-salinity was for core with microporosity but with presence of dead-end pores. Secondary injection of low-salinity using the same core with large fraction of micro-porosity showed that it accelerated oil production compared to high-salinity brine. We have also observed that LSWI resulted in increased oil recovery in coquinas both in tertiary mode (average 10%) compared to FW/DSW and secondary mode using the same core (18% compared to FW) due to wettability alteration. This result was supported by spontaneous imbibition as well as zeta-potential results. The contact test between crude oil and low salinity brine resulted in a micro-dispersion ratio of 11.7, showing that a positive oil is likely to result in improved oil recovery due to low salinity injection. Despite the increased oil recovery seen during the tests, the results showed that oil production in tertiary mode was significantly delayed (after 4 PV), likely due to adverse oil/water viscosity ratio and water dispersion due to mixing between low- and high-salinity brines. We observed that for the shorter more oil-wet core significant oil production was measured during bump flow with both high-salinity and low-salinity brines, due to capillary end effects. This could mean that residual oil saturation was not achieved during high-salinity water injection and an overestimation of recovery factor due to low-salinity was seen.

Correlation of EDLC Capacitance with Physical Properties of Polyethylene Terephthalate Added Pitch-Based Activated Carbon.

The electric double-layer capacitor (EDLC) has attracted attention by using activated carbon (AC) as an active electrode material with a high power density and high cost-efficiency in industrial applications. The EDLC has been actively developed over the past decade to improve the power density and capacitance. Extensive studies on EDLCs have been conducted to investigate the relation of EDLC capacitance to the physical properties of AC, such as the specific surface area, pore type and size, and electrical conductivity. In this study, EDLC was fabricated with AC, and its capacitance was evaluated with the physical properties of AC. The AC was prepared using petroleum-based pitch synthesized using pyrolysis fuel oil (PFO) with polyethylene terephthalate (PET). The AC based on PFO and PET (PPAC) exhibited high specific surface area and low micropore fraction compared to the PFO-based AC without PET addition (PAC). Furthermore, the reduction of the EDLC capacitance of PPAC was smaller than that of PAC, as the scan rate was increased from 5 to 100 mV s−1. It was determined that the minor reduction of capacitance with an increase in the scan rate resulted from the development of 4 nm-sized mesopores in PPAC. In addition, a comprehensive correlation of EDLC capacitance with various physical properties of ACs, such as specific surface area, pore characteristics, and electrical conductivity, was established. Finally, the optimal properties of AC were thereupon derived to improve the EDLC capacitance.

Effect of the carbon mesoporous structure on the transport properties of confined lithium chloride aqueous solutions

Accurate determination of fluid dynamics in confined carbons with pore size distribution (PSD) ranging from micro to mesopores is a fundamental aspect for many relevant applications, such as lithium battery electrodes, supercapacitors, or fuel cells. Here we present a synthesis route that enables the preparation of carbons with tailored PSD, which are characterized by nitrogen adsorption methods and nuclear magnetic resonance (NMR). The combination of micro and mesopores is determined straightforwardly by the determination of confined water self-diffusion coefficients and longitudinal relaxation times. Employing 2D-NMR experiments pore interconnectivity was characterized, determining exchange rates for water between micropores, mesopores, and bulk solution. Furthermore, their functionality was tested in simple ion release experiments of a solution of LiCl carried out both by conductivity and NMR experiments. We found that the lithium release rate can be set by tailoring the connectivity between micro and mesopores. For samples with mesopores larger than 5 nm and a small content of micropores, ion mobility is mainly restricted by the material's porosity. On the other hand, tortuosity analysis reveals that carbon wall-ion interaction is the main factor of the sluggish diffusion in materials with a large fraction of micropores well connected to the mesopore network.