Specific Surface Area Of Mesopores Research Articles

Experimental Study on the Improvement of Char Physicochemical Properties and Reactivity by Activation Process in CFB.

Solid carbon can be transformed into activated char with higher reactivity through the activation process in a circulating fluidized bed (CFB) to improve the Boudouard reaction. A new technology for reducing CO2, the activated-reduction technology, was proposed. In order to investigate the influence of relevant parameters (carbon dioxide addition, oxygen concentration, and O2/C) of the activation process on the physicochemical properties and reactivity of activated char, the experiments were carried out on a bench-scale CFB. The relationship between the parameters and the reactivity of activated char is explored. The result shows that compared with the raw coal, the pore structure of activated char is developed, the number of active sites increases, the degree of graphitization decreases, and higher reactivity is possessed. For the activation process, less of the O2/C and moderate oxygen concentration promote the increase in activated char reactivity, which is conducive to the reduction of CO2. The results of the correlation discussion show that the reactivity is difficult to be characterized by a single simple parameter. The reactive specific surface area (RSSA) obtained by multiplying the mesoporous specific surface area and I D3+D4/I all has a good effect on describing the reactivity.

The Response Characteristics of Pore Volume and Specific Surface Area of Different Phases of Carbon Dioxide Injection into Anthracite Coal Pores

After the coal sample reacts with CO2, the porosity and pore volume change. Compared with dry raw coal sample, the porosity of coal after CO2 adsorption is increased. With the increase of CO2 injection pressure, the porosity of coal will gradually increase, especially when CO2 enters the supercritical phase. In terms of pore capacity of coal samples, CO2 adsorption time, CO2 adsorption pressure and CO2-H2O treatment do not show obvious regularity in the changes of pore capacity of coal samples, but in general, the increase of CO2 adsorption pressure and CO2-H2O treatment have a positive effect on the increase of pore capacity of coal samples, especially ScCO2-H2O. The mesoporous pore capacity increased by 137.1%. In terms of macro pore volume of coal sample, the change of macro pore volume after CO2 adsorption is more regular. Extending CO2 adsorption time, increasing CO2 adsorption pressure and CO2-H2O treatment all have positive effects on the increase of macro pore volume of coal sample. Under 8MPaScCO2-H2O, macro pore volume reaches a maximum of 0.016462ml/g. The increase also reached 130.4 percent. On the mesoporous specific surface area of coal sample, increasing CO2 adsorption pressure, prolongating CO2 adsorption time and CO2-H2O treatment can increase the mesoporous specific surface area of the sample. The mesoporous specific surface area of the sample at 8 MPa ScCO2-H2O is 0.631 m2/g, which reaches the maximum in this experiment, with an increase of 334.27%.

Electrospinning prepared nickel-based carbon fibers with enhanced adsorption capacity for adsorption desulfurization of fuels

Enhanced adsorption capacity of adsorbents with excellent regeneration properties always remained the focus of researchers in the adsorptive desulfurization (ADS) technology. In this paper, we report an electrospinning method to prepare nickel-based carbon fibers (NCF), and their adsorption desulfurization performance was compared with those of nickel-based carbon particles (NCP) obtained via traditional solid-state grinding method. The results demonstrated that compared with NCP, NCF contained more abundant mesoporous specific surface area and mesopore volume, well-distributed active metal sites, which would be beneficial to their enhanced adsorption desulfurization performance. As a result, the adsorption capacity of NCF was as high as 13.13 mg S/g in the ADS of thiophene, and its regeneration performance was also far better than that of NCP. In addition, the adsorption process of thiophene was briefly analyzed from the perspective of kinetics, which demonstrated that the adsorption of thiophene in NCF and NCP were both in accordance with the pseudo-second-order kinetic model.

Catalytic regeneration of amine-based absorbents for CO2 capture: The effect of acidic sites and accessibility

The high regeneration energy consumption is the bottleneck problem for the large-scale application of organic amine absorption method. Catalytic regeneration has received a lot of attention because it can be done at low temperatures using solid acid catalysts. Although the catalytic activity of the catalysts presently reported is exceptional, the exorbitant cost renders this technology unsuitable for industrial implementation.The present work uses a composite metal oxide solid acid catalysts for the catalytic regeneration of a CO2-rich 5 M MEA solution at 90 °C. The findings indicate that the inclusion of SO42-/ZrTiOx catalyst resulted in a 99% increase in CO2 desorption rate, a 43% improvement in cyclic capacity, and a 29.09% reduction in relative heat duty when compared to the blank experiment. The catalyst underwent characterization through BET, NH3-TPD, and Py-IR techniques, revealing that its superior catalytic performance can be attributed to its substantial mesoporous specific surface area and significant concentration of acid sites. The catalytic effect and catalytic mechanism of SO42-/ZrTiOx were confirmed using 13C NMR spectroscopy. The stability of the SO42-/ZrTiOx catalyst during regeneration was investigated in five cycles and the cause of catalyst deactivation was investigated by FT-IR. The results show that the SO42-/ZrTiOx catalyst has high catalytic activity and low cost, and has potential for large-scale industrial applications.

RATIONAL CONDITIONS OF PRODUCING THE ACTIVATED CARBON WITH WELL-DEVELOPED NANOPOROUS STRUCTURE FOR THE TREATMENT OF NATURAL AND WASTE WATERS

Rational conditions for the activation of coal of a high stage of metamorphism (anthracite) have been determined, which allow the development of a nanoporous structure. Obtained activate carbon with nanoporous structure can be use for the treatment of natural and waste waters have been carried out. The structurally sorptive characteristics and granulometric size composition of obtained samples were determined. It was established that in order to obtain a sorbent with specified properties, it is necessary to introduce oxygen into the reacting mixture at the second stage of anthracite activation and control the activation time. The activation in the first stage was carried out with steam at a temperature of 750–800 °C, and in the second stage – with steam in the presence of air oxygen at 280–300 °C. The rational content of oxygen in the activating mixture is in the range of 2.7–4.4 %, while the specific surface area of activated carbon increases, which corresponds to nano-sized pores and, accordingly, the volume of the adsorption space of coal. The process led to the development of mesoporosity ~ 0.2–0.3 cm3/g, after which the microporous sample of activated carbon was impregnated with a surfactant solution. Thus, the rational conditions of activation are the duration of the process of 1.5 hours in the presence of 4.4 % oxygen in the activating mixture. It is shown that the largest values of the total specific surface area and the specific surface area of mesopores are achieved when using ionic surfactants with alkyl chain length n = 10–16 as modifiers. In particular, the use of sodium dodecyl sulfate СН3(СН2)11SO3Na as a modifier allows to obtain the largest value of the total surface Stot 1030 m2/g and the surface of mesopores Smе 334 m2/g. It was established that the activation of modified samples of activated carbon leads to a decrease in the size of granules.The content of fractions with a size of 1.0–2.0 mm and 0.5–1.0 mm is 80–85 %, which are rational for use for water purification from organic compounds.

Enhancement of catalytic and anti-carbon deposition performance of SAPO-34/ZSM-5/quartz films in MTA reaction by Si/Al ratio regulation

In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics (MTA) technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrothermal crystallization. The Si/Al ratio of SAPO-34 film was used as the only variable to study this material. The composite zeolite material with 0.6 Si/Al ratio of SAPO-34 has the largest mesoporous specific surface area and the most suitable acid distribution. The catalytic performance for the MTA process showed that 0.6-SAPO-34/ZSM-5/quartz film has as high as 50.3% BTX selectivity and 670 min lifetime. The MTA reaction is carried out through the path we designed to effectively avoid the hydrocarbon pool circulation of ZSM-5 zeolite, so as to improve the aromatics selectivity and inhibit the occurrence of deep side reactions to a great extent. The coke deposition behavior was monitored by TG and GC-MS, it is found that with the increase of Si/Al ratio, the active intermediates changed from low-substituted methylbenzene to high-substituted methylbenzene, which led to the rapid deactivation of the catalyst. This work provides a possibility to employ the synergy effect of composite zeolite film synthesizing anti-carbon deposition catalyst in MTA reaction.

Physicochemical properties, combustion kinetics and thermodynamics of oxidized lignite

Lignite oxidizes easily during storage and transportation. Furthermore, the surface characteristics of lignite change during oxidation, affecting its thermal conversion process. Herein, the surface functional groups and pore structures of lignite oxidized at temperatures below 190 °C were investigated. Moreover, the kinetics and thermodynamics of the combustion of lignite were analyzed using thermogravimetric analysis. The relationship between the surface structure and combustion performance of oxidized lignite was established, and the effect of oxidation on the characteristics of the combustion process was evaluated. The results revealed that the value of CH3/CH2 increased considerably upon increasing oxidation temperature from 70 to 150 °C. The number of –OH groups decreased with increasing in oxidation temperature, whereas the number of CO groups decreased gradually, then increased significantly, and lastly decreased with increasing oxidation temperature. The mesoporous structure of lignite was severely damaged during oxidation, the specific surface area and pore volume of oxidized lignite were lower than those of raw coal, and the average pore diameter of oxidized lignite was significantly higher than that of raw lignite. The poor combustion performance of oxidized lignite was attributed to its low mesopore specific surface area and low pore volume. The activation energy (Ea) of lignite during combustion was calculated to be 35.29 kJ/mol using the Ginstling-Broushtein equation, and the Ea of oxidized lignite ranged between 40.53 and 45.93 kJ/mol. These results indicate that a large amount of energy was required to burn oxidized lignite. Therefore, the oxidation of lignite should be avoided during the storage process to damage the pore structure, thus affecting the combustion performance; the pore structure of oxidized lignite can be adjusted to enhance its combustion performance. This will effectively improve the utilization efficiency and economic value of lignite.

Effects of Liquid CO2 Phase Transition Fracturing on Methane Adsorption of Coal

Liquid CO2 phase transition fracturing (LCPTF) is a kind of novel waterless fracturing technology for enhancing the coalbed methane (CBM) recovery. Relevant current studies are focused on exploring the transformed effect of LCPTF on the nanopore structure in coal. However, its influence on gas adsorption capacity has been rarely reported. This study addresses coal induced with LCPTF. The structure alterations of mesopores (2–50 nm) and macropores (>50 nm) and their effects on the gas adsorption capacity are evaluated with comprehensive measurements of a mercury intrusion porosimetry, low-temperature N2 adsorption, and isothermal adsorption. The results indicate that LCPTF has an enlarged effect on macropores, resulting in an increase in pore size and volume and a reduction of the pore specific surface area. The pore-enlarged-transformed effects of LCPTF cause an increase in pore size and a reduction of the pore volume and pore specific surface area of mesopores. The variations of the pore structure after LCPTF cause a reduction of the adsorption constant a and the increase in the adsorption constant b, indicating LCPTF’s reductive effect on adsorption capacity as well as its enhanced effect on desorption capacity. A novel effect evaluation method of LCPTF for improving CBM recoverability is proposed based on the variations of gas saturation and critical desorption pressure. This study examines, from the perspective of adsorption and desorption, the mechanism of LCPTF for enhancing CBM recovery, which provides theoretical guidance for LCPTF’s technical improvement and optimization of field application so as to secure a more reliable and efficient CBM recovery.

Bifunctional Pt/Hβ catalyzed alkylation and hydrodeoxygenation of phenol and cyclohexanol in one-pot to synthesize high-density fuels

Synthesis of fuels from lignin bio-oil feedstock significantly alleviates energy crises and environmental pollution. Phenol is the simplest model compound for lignin bio-oil feedstocks, and the synthesis of fuel precursors from phenol through alkylation has received increasing attention. Here we report a one-pot strategy for preparing polycyclic alkane high-density fuels from phenol and cyclohexanol over bifunctional Pt/Hβ catalyst by combining alkylation with following hydrodeoxygenation (HDO). The activity of different zeolites for catalyzing the alkylation of phenol and cyclohexanol was explored. It was found that the larger pore size of alkali treated Hβ would not limit the production of polycyclic compounds, and good acid content in a particular mesoporous specific surface area can speed up the reaction rate. The one-pot reaction conditions were then optimized. When the alkali treatment concentration is 0.2 mol/L, the metal loading is 0.2 wt%, and the molar ratio of phenol and cyclohexanol is 1:1, the highest conversion of phenol can reach more than 83 %. The selectivity of alkylphenol can reach more than 97 %, and the yield of bicyclic and tricyclic rings in the final product after HDO can reach 83.42 %. The bifunctional catalyst can also realize the coupling of other acid-catalyzed carbon growth reactions and metal-catalyzed HDO reactions, which allows the direct synthesis of fuel from lignin oil or other biomass compounds.

Effects of pore structure changes on the CH4 adsorption capacity of coal during CO2-ECBM

The effects of supercritical CO2 (scCO2) on pores in coal play a critical role in determining the CH4 adsorption and desorption characteristics and CO2 capacity of coal seams during CO2 geological storage-enhanced coalbed methane recovery (CO2-ECBM). To investigate the effects of pore structure changes caused by scCO2 on the CH4 adsorption capacity of coals, six coal samples with different ranks are exposed to scCO2 and water for 240 h at 62.5 °C and 15 MPa using a scCO2 geochemical reactor. Then, gravimetric isothermal adsorption tests, mercury intrusion porosimetry, N2 adsorption tests, and CO2 adsorption tests are performed to determine the CH4 adsorption capacity, pore volume, and pore specific surface area (SSA) of the coal samples with and without scCO2-H2O treatment. Finally, the influences of scCO2 on the pore structure and the effects of pore structure changes on the CH4 adsorption capacity of the coal samples are analyzed. The results show that the CH4 adsorption capacity of coal and its changes after scCO2-H2O treatment are strongly affected by density effects and pore selection effects. The CH4 adsorption capacity of coal is determined by the micropore volume and SSA; however, their changes only affect the CH4 adsorption capacity in the micropore filling stage when the pressure is <5 MPa with weak effects on the total CH4 adsorption capacity, which is related to their weak changes after scCO2-H2O treatment compared with macropores and mesopores. The changes in CH4 adsorption capacity mainly depend on the changes in macropore and mesopore SSAs after scCO2-H2O treatment; scCO2 mainly changes the CH4 adsorption capacity in the transitional stage, when the pressure is 5–10 MPa, and the monolayer and multilayer adsorption stage, when the pressure is >10 MPa. Meanwhile, the effect of pore structure changes on the CH4 adsorption capacity of coal with different ranks is complex. The CH4 adsorption capacity of subbituminous coal and medium-volatile bituminous coal increases after scCO2-H2O treatment due to the increases in macropore SSA, that of high-volatile bituminous coal slightly decreases, and that of semianthracite coal and anthracite coal slightly increases because of the changes in mesopore SSA after scCO2-H2O treatment. However, the CH4 adsorption capacity of low-volatile bituminous coal increases, which is the result of changes in the SSA of the mesopores and macropores due to slight changes in the micropore volume and SSA.

Effect of hydrothermal carbonization on woody biomass: From structure to reactivity

Hydrothermal carbonization (HTC) pretreatment is an effective method to upgrade the low quality biomass properties. In this work, the pinewood (PIW) and poplar wood (POW) were selected to study the effect of HTC (180–240 °C) on woody biomass structure and reactivity. The results showed that the slight and moderate HTC can make the cellulose structure more ordered, while the severe HTC leaded to the decomposition of cellulose structure. The mesoporous specific surface area and pore volume increased with the HTC temperature, and the pore structure of PIW was more developed than that of POW. The slight HTC had little effect on cellulose structure and the diffusion effect played the dominant role. The severe HTC increased the relative content of lignin and the pyrolysis followed the high order reaction model. The model-free method was used to determine the relationship between T-β-X, and the specific temperature THTC/Traw was calculated. The THTC/Traw value of PIW and POW located in the range of 0.938–1.340 and 0.924–1.422, indicating the HTC pretreatment had great effect on POW pyrolysis reactivity.

Hierarchical ZSM-5 zeolite obtained by designed organosiloxane: synthesis, characterization, and catalytic applications

A new strategy was implemented to synthesize hierarchical ZSM-5 zeolite, which uses self-made organosilanized double-terminal amino polyetheramine (ODAP) as a soft template to generate mesopores. The influence of the additional amount of ODAP on the textural properties and morphologies of the hierarchical ZSM-5 zeolite was investigated. The obtained hierarchical ZSM-5 zeolite was characterized by X-ray diffraction, N2 physical adsorption, SEM, temperature-programmed desorption of NH3, and other methods. The analysis of the experimental results shows that the maximum total BET specific surface area and mesoporous specific surface area of the optimized hierarchical ZSM-5 zeolite reached 609 and 278 m2/g, respectively. Because the synthesized hierarchical ZSM-5 zeolite has a large mesoporous specific surface area and abundant surface acidity, in terms of reactant conversion and product selectivity, compared with microporous zeolite, it exhibits excellent catalytic performance in the thiophene alkylation desulfurization reaction. This synthesis strategy can be extended to the preparation of zeolites with different framework structures, which is of great significance.

Fractal characteristics of pulverized high volatile bituminous coals with different particle size using gas adsorption

To better understand the effect of particle size on fractal characteristics of pores in coal, three high volatile bituminous coals with mean maximum vitrinite reflectance of 0.82–0.90% collected from the Naryksko-Ostashinskaya coalbed methane field in Kuznetskiy Basin in Russia were crushed and sieved to five progressivelydecreasing particle size fractions: 1.0–0.5 mm, 0.50–0.25 mm, 0.250–0.125 mm, 0.125–0.063 mm and 0.063–0.032 mm. For all particle size fractions, particle size distribution measurement, proximate analysis, maceral analysis and low-pressure N2 adsorption and CO2 adsorption analyses were conducted. Fractal dimensions D1 (pore surface roughness) and D2 (pore structural irregularity) were determined from relative pressure intervals of 0–0.45 and 0.45–1 of N2 adsorption isotherm with the application of the fractal Frenkel-Halsey-Hill theory, respectively. The results demonstrate significant differences in fractal dimensions in different particle size fractions. As particle size of coal samples decreases, D1 decreases, while D2 increases. Some constricted mesopores are transformed into non-constricted mesopores during crushing. The non-constricted mesopores increasingly concentrate in smaller pore sizes, which results in smoother pore surface (decreasing D1) and more heterogeneous pore structure (increasing D2). Mesopores with pore width between 2 nm and 5 nm are the key to fractal dimensions. Individual mesopore structure parameters closely associated with particle size have universal correlations with fractal dimensions. The increasing mesopore specific surface area and volume and decreasing average mesopore width lead to a decrease in D1 and an increase in D2, which further confirms the effect of particle size on fractal dimensions.

Biochars intended for water filtration: A comparative study with activated carbons of their physicochemical properties and removal efficiency towards neutral and anionic organic pollutants

Seven biochars (BCs) obtained from pyrolysis or gasification of different vegetal feedstocks were thoroughly characterized in comparison with three commercial activated carbons (ACs) routinely used in drinking water treatment plants. BCs and ACs characterization included the determinations of ash, iodine and methylene blue adsorption indexes, and the release of metals and polycyclic aromatic hydrocarbons, which were performed according to international standards applied for adsorption media to be used in drinking waters. Total specific surface area, micropore and mesopore specific surface area, pH of the point of zero charge, and the release of polychlorinated biphenyls were also determined in all chars. Principal component analysis and cluster analysis were performed in order to summarize the complex set of information deriving from the aforementioned characterizations, highlighting the BC most similar (BC6 from high temperature gasification of woody biomass) and most different (BC7 from low-temperature pyrolysis of corn cob) from ACs. These BCs were studied for their adsorption in ultrapure water towards diiodoacetic acid (an emergent disinfection by-product), benzene, and 1.2-dichlorobenzene, in comparison with ACs, and results obtained were fitted by linearized Freundlich equation. Overall, BC6 showed higher sorption performances compared to BC7, even though both BCs were less performing sorbents than ACs. However, the sorption properties of BCs were maintained also in real water samples collected from drinking water treatment plants.

In Ukrainian

As an alternative to means for lowering total cholesterol and low-density lipoprotein (LDL) cholesterol, the paper considers the possibility of using carbon adsorbents. From a medical point of view, the removal of cholesterol with enterosorbents is extremely effective. By binding cholesterol, sorbents reduce the risk of cardiovascular disease. The paper searches for new raw material sources and attempts to create enterosorbents with a high capability to adsorb cholesterol. The aim of the work was to develop adsorbents from spent coffee residue with a large proportion of mesopores, to determine the parameters of the porous structure and to study their adsorption capacity against cholesterol. Samples of activated carbon with a large proportion of mesopores (399 and 465 m2/g) were obtained by the traditional method of carbonization-activation of spent coffee grounds and pre-treated hexane to remove fatty acids. The sorption of cholesterol from alcohol solutions has been studied by spectrophotometric method and its effectiveness for the prevention and treatment of atherosclerosis was proved. It has been shown that a sample of activated carbon from spent coffee residue pre-treated with hexane (maximum value reaches 7.5 mg/g) has the best sorption capacity. The intermediate position is occupied by the sample obtained without pre-treatment with solvent (maximum value reaches 6.3 mg/g). Natural Brand carbon has the weakest sorption characteristics (maximum capacity reaches 5.3 mg/g). It can be stated that the adsorption of cholesterol increases with the growth of the specific surface area of mesopores. The parameters of adsorption processes were calculated using the obtained sorption isotherms. Adsorption isotherms were calculated using the Langmuir and Freundlich equations. It is shown that the values of the maximum adsorption calculated by the Langmuir equation have a good agreement with the experimental data.

Are activated carbon pore structure parameters linearly positively related to its mass-specific capacitance?

Despite considerable achievements in the use of porous carbon in electrochemical double-layer capacitor or electrode of supercapacitor over the past few years, understanding the relationship between pore structure parameters and electrochemical performance has long been highly desirable. Herein, apricot shell lignin (ASL) was used to prepare activated carbon, after which the galvanostatic charge–discharge (GCD) test was performed. Meanwhile, the pore structure parameters of AAC were determined by the nitrogen adsorption–desorption test. The results confirmed that the AAC pore structure parameters were consistent with the inherent law of activation. Besides, in the low current density ranging from 0.50 A/g to 10.00 A/g, the micropore surface area density of AAC rather than other pore structure parameters (e.g., mesoporosity, micropore specific surface area, mesopore specific surface area) was linearly positively related to its mass-specific capacitance. Additionally, the average of linear fit coefficients between micropore surface area density and mass-specific capacitance was 0.92. Consequently, when using a three-electrode configuration with a 6 M KOH electrolyte, the micropore surface area density of activated carbon can be employed as a universal predictor of mass-specific capacitance in a low current density range 0.50–10.00 A/g.

Surface oxidation of petroleum pitch to improve mesopore ratio and specific surface area of activated carbon

In this study, surface oxidation of petroleum pitch was performed to enhance the thermal stability, specific surface area, and mesopore ratio of activated carbon. The oxygen uptake of the pitch by surface oxidation has a strong influence on the formation of the specific surface area and pore size of activated carbon. It was confirmed that the oxygen uptake from the surface to the inner side of the surface oxidized pitch was the highest at the temperature of 330 °C (IP330-AC), with a mesopore ratio of 63.35% and specific surface area of 1811 m2 g−1. The oxygen content of the surface oxidized pitch increased proportionately with the mesopore ratio in activated carbon. The specific surface area and mesopore ratio of IP330-AC were respectively 163% and 487% higher than those of petroleum-based commercial activated carbon (A-BAC), and 102% and 491% higher than those of coconut-based commercial activated carbon (P60).

Sorption of Phenolic Acids on Powdered Carbon Prepared by Complex Processing of Spent Coffee Grounds

Activated carbons are prepared by conventional two-stage carbonization–activation processing and complex processing of spent coffee grounds. The latter method includes preliminary solvent extraction of organic compounds. The samples prepared by conventional and complex processing methods have a high BET (Brunauer–Emmett–Teller) surface area (SBET = 864 and 1089 m2/g, respectively), specific surface area of mesopores (400 and 464 m2/g), and total pore volume VΣ (0.68 and 0.87 mL/g). It is shown that the complex processing produces activated carbons with a specific surface area 27% higher, compared to the conventional method. We propose that this sorption material can be used in purification of pharmaceutical production effluents. The capacity of the carbons to adsorb phenolic acids, in particular, salicylic and sulfosalicylic acids, which represent pharmaceutical microimpurities, is studied. The equilibrium concentrations of salicylic and sulfosalicylic acids are determined spectrophotometrically at λ = 296 and 294 nm, respectively, using a UV-2450 instrument (Shimadzu, Japan). The carbon produced by complex processing exhibits the most effective sorption properties (18 mg/g). The carbon prepared by conventional method displays intermediate characteristics (13.3 mg/g), and a reference Natural Brand adsorbent derived from lignocellulose material has the lowest characteristics (11.4 mg/g). The same pattern is observed for adsorption of sulfosalicylic acid, with the saturation adsorption being lower for sulfosalicylic than salicylic acid. We can state that substances with good solubility in water exhibit poorer physical adsorption than those with limited solubility. Processing the experimental data within the Langmuir and Freundlich adsorption models suggests that adsorption of the phenolic acids on the highly porous sorbents follows the Langmuir model, i.e., adsorption occurs at active sites where a dynamic equilibrium is established between adsorption and desorption processes.

Factors affecting shale microscopic pore structure variation during interaction with supercritical CO2

Substantial physiochemical changes occur during the interaction between supercritical carbon dioxide (ScCO2) and shale. It is important to clarify the variation and controlling factors of the microscopic pore structure (MPS). Six samples collected from Longmaxi Formation with various material compositions were treated with ScCO2. X-ray diffraction (XRD), scanning electron microscope (SEM), gas adsorption, and the maximum adsorption quantity (MAQ) model were employed to determine parameters before and after ScCO2 treatment. XRD data document feldspar, carbonate, and clay decrease after ScCO2 treatment. Specifically, the dissolution of clay and carbonate increases the micropore volume and mesopore specific surface area (meso-SSA), respectively. From gas adsorption results, two types based on the difference in total organic content (TOC) are identified, i.e. an accelerating improvement (samples with a TOC less than 3.00 %) and a moderating improvement (samples with a TOC greater than 3.00 %). Data from gas adsorption also support increased MPS parameters with pressure, indicating the variation can be classified into three discernible phases, i.e. a negligible variation at low-pressure, a swift increase at medium-pressure, and a sharp increase at high-pressure. Temperature, however, has a limited improvement on the MPS. These findings are likely to impact the MPS variation in the process of CO2-enhanced shale gas recovery (CO2-EGR).

Growth of carbon nanofibers by the catalytic decomposition of methane over Ni-Cu/Al2O3 catalyst

This paper shows that the catalytic decomposition of methane over Ni-Cu/Al2O3 catalyst at pressures of up to 5 bar leads to formation of carbon nanofibers of bamboo-like morphology with a “fish bone” structure with bridges inside the channel. When increasing the pressure, the change of textural characteristics of carbon nanofibers occurs. The surface area of carbon nanofibers increases from 130 to 166 m2/g, the volume of micropores grows from 0.005 to 0.014 cm3/g, the specific surface area of mesopores ranges from 117 to 137 m2/g at the pressure increase from 1 to 5 bar.