Nitrogen Adsorption Method Research Articles

Thermogravimetry of bentonite "navbahor" in nanocatalytic extraction technology and investigation of the convective ehfef drying process

This study presents the results of a study of the process of thermography and convective drying of the retention substance bentonite used in the production of nanocatalysts based on Zol-gel technology. The study of the drying process using the energy of the convex-EHFEF EMF (extremely high-frequency electromagnetic field) in the preparation of a nanocatalystsfrom the retaining substance of bentonite is illuminated by the derivatogram of bentonite from the Navbahor deposit determined by the thermographic method. The determination of the porous structure and the comparable surface surface of the catalysts was carried out in an automatic gas adsorption analyzer using the Brunauer, Emmet, and Wyres (bet) method.The size and pore size of the catalysts were determined from data on desorption and adsorption isotherms, respectively, at a relative pressure R/R0=0.99 in accordance with the BJH (Barette-Joyner-Halend) model. Based on the purpose of the work, the study of the drying process in the technology of obtaining a nan catalyst and the acceleration of its process and technology with its introduction into EHFEF (extremely high frequency electromagnetic field) EMC, was achieved to improve the quality of the porosity of catalysts. In particular, the analysis of the results obtained on the experimental scheme of the grooved-convex drying device, textural descriptions of bentonite of the Navbahor deposit, determined on the basis of standard techniques, porosity of the sample by the method of temperature nitrogen adsorption is presented.

EFFECT OF ANODIZING VOLTAGE ON THE PHOTOCATALYTIC ACTIVITY OF FILMS FORMED BY TITANIUM DIOXIDE NANOTUBES

The influence of the anodizing voltage during synthesis on the specific surface area and on the photocatalytic activity of the TiO2 nanotube was studied. Films formed by titanium dioxide nanotubes were obtained on the surface of titanium foil by electrochemical anodizing. It has been found that an increase in the anodizing voltage from 20 V to 60 V leads to an increase in the inner and outer diameters of nanotubes, an increase in the growth rate and the interpore distance of nanotubes. The photocatalytic activity of the samples was evaluated by measuring the magnitude of the photoinduced current. The film produced at low voltage generated a current 3.5 times higher than the film produced at high voltage, and the degradation of the dye in the presence of the films was 75 and 38%, respectively, over the same period of time. An increase in the photocatalytic activity of the films is mainly associated with an increase in the specific surface area of the nanotubes. Thus, the values of the specific surface area of TiO2 nanotubes were determined by the method of low-temperature nitrogen adsorption. It has been established that with an increase in the anodizing voltage, the specific surface area of the films decreases.

Bioethanol to Hydrogen Membrane Surface Characteristics Change Study

The problem of the gradual transformation of the modern economy towards greater production and consumption of ‘green’ energy requires a significant revision of existing technologies. One of the possible ways to develop green energy is the use of hydrogen as the most environmentally friendly fuel. Hydrogen can be obtained both by electrolysis, using solar energy, and using biorenewable raw materials, which can be used as ethanol, biogas, peat, agricultural waste. At the same time, for regions with a low level of illumination, the production of hydrogen by electrolysis of water using electricity generated by solar panels is inaccessible, and therefore the processing of biorenewable raw materials can take a leading position. Bioethanol is a large-capacity product with a proven production technology that widely uses waste from agriculture and wood processing. Ethanol can be used as a feedstock for hydrogen generation by means of catalytic pyrolysis or catalytic steam reforming. Membrane-catalytic steam reforming of ethanol with the production of hydrogen makes it possible to obtain hydrogen without the use of an additional purification step, however, the efficiency and stability of the membrane becomes the determining parameter that ensures the efficiency of the entire process. The degradation of inorganic membranes during catalytic steam reforming is closely related to the change in porosity as a result of hydrolysis of the membrane surface. In this connection, the study of the physicochemical properties of membranes during operation can make a significant contribution to the development of stable catalytic membranes for hydrogen production. The article presents the results of studying the physicochemical properties of an inorganic membrane for ethanol steam reforming by the method of low-temperature nitrogen adsorption. The Langmuir, Brunauer-Emmett-Taylor, t-plot and Barrett-Joyner-Halenda models were used to estimate the surface change. An increase in the surface area of mesopores during the operation of the membrane was determined.

Hydrolytic Oxidation of Cellobiose Using Catalysts Containing Noble Metals

Studies of the processes of the hydrolytic oxidation of disaccharides are the first step towards the development of technologies for the direct conversion of plant polysaccharides, primarily cellulose, into aldonic and aldaric acids, which are widely used in chemical synthesis and various industries. In this study, heterogeneous catalysts based on a porous matrix of hypercrosslinked polystyrene (HPS) and noble metals (Pt, Au, Ru, and Pd) were proposed for the hydrolytic oxidation of cellobiose to gluconic and glucaric acids. The catalysts were characterized using low-temperature nitrogen adsorption, hydrogen chemisorption, electron microscopy, and other methods. In particular, it was shown that the Pt-containing catalyst contained, on average, six times more active centers on the surface, which made it more promising for use in this reaction. At a temperature of 145 °C, an O2 pressure of 5 bars, and a substrate/catalyst weight ratio of 4/1, the yields of gluconic and glucaric acids reached 21.6 and 63.4%, respectively. Based on the data obtained, the mathematical model of the cellobiose hydrolytic oxidation kinetics in the presence of 3% Pt/HPS MN270 was developed, and the parameter estimation was carried out. The formal description of the kinetics of cellobiose hydrolytic oxidation was obtained.

Hard Carbon Reprising Porous Morphology Derived from Coconut Sheath for Sodium-Ion Battery

Seeking effective energy technology has become a herculean task in today’s world. Sodium-ion batteries play a vital role in the present energy tech market due to their entrancing electrochemical properties and this work is a breakthrough for developing sodium-ion batteries. As per recent reports, the preparation of anode materials seems to be very tedious in the realm of sodium-ion batteries. To remedy these issues, this work enlightens the preparation of hard carbon (HC) derived from coconut sheath (CS) by a pyrolysis process with different activating agents (KOH, NaOH, ZnCl2) and employed as an anode material for Sodium-ion batteries (SIBs). The prepared anode material was characterized for its thermal, structural, functional, morphological, and electrochemical properties. Additionally, the surface area and pore diameter of the as-prepared anode material was studied by nitrogen adsorption and desorption isotherm methods. The coconut sheath-derived hard carbon (CSHC) anode material delivered an initial charge capacity of 141 mAh g−1, 153 mAh g−1, and 162 mAh g−1 at a 1 C rate with a coulombic efficiency over 98.8%, 99.3%, and 99.5%, even after 100 cycles, respectively.

The Use of Diethoxydimethylsilane as the Basis of a Hybrid Organosilicon Material for the Production of Biosensitive Membranes for Sensory Devices.

Biomembranes based on an organosilica sol–gel matrix were used to immobilize bacteria Paracoccus yeei VKM B-3302 as part of a biochemical oxygen demand (BOD) biosensor. Diethoxydimethylsilane (DEDMS) and tetraethoxysilane (TEOS) were used as precursors to create the matrix in a 1:1 volume ratio. The use of scanning electron microscopy (SEM) and the low-temperature nitrogen adsorption method (BET) showed that the sol–gel matrix forms a capsule around microorganisms that does not prevent the exchange of substrates and waste products of bacteria to the cells. The use of DEDMS as part of the matrix made it possible to increase the sensitivity coefficient of the biosensor for determining BOD by two orders of magnitude compared to a biosensor based on methyltriethoxysilane (MTES). Additionally, the long-term stability of the bioreceptor increased to 68 days. The use of such a matrix neutralized the effect of heavy metal ions on the microorganisms’ catalytic activity in the biosensor. The developed biosensor was used to analyze water samples from water sources in the Tula region (Russia).

Fine characterization of pore structure of acidified anthracite based on liquid intrusion method and Micro-CT

Acidification erosion can seriously affect the pore structure characteristics of anthracite. In this paper, the low-temperature nitrogen adsorption method, mercury intrusion method, and Micro-CT scanning are used to analyze the pore structure of coal samples. The microscopic morphology and spatial distribution of coal pores are characterized by fractal dimension calculation and three-dimensional reconstruction. The results show that HCl has the highest removal efficiency of minerals in the Yuwu coal sample, which reduces the mass of coal samples by about 4%. HNO3 increases the proportion of micropore volume by 4.93%. HCl increases the proportion of mesoporous pore volume by 11.4%. Through the 3D reconstruction of coal, it is found that the mineral content in coal decreased by 48.14% after HCl dissolution, and the maximum diameter of mineral particles decreased from 173.588 μm to 57.449 μm. The spatial distribution of minerals is uneven, and the mineral content of coal samples decreases significantly along the direction of strong fluidity. At the same time, HCl increases the pore connectivity of coal samples, the pore roar increases by 56.72%, the isolated pores decrease, and the peak frequency of pore coordination number increases by 4 units, which greatly improves the transport capacity of fluid in coal matrix.

Preparation and electrochemical application of porous carbon materials derived from extraction residue of Ganoderma lucidum

As a valuable biomass resource, a large number of Chinese medicine residue have not been effectively utilized and are often treated as garbage, which not only causes environmental pollution, but also leads to the waste of resources. Ganoderma lucidum is a common raw material of Chinese herbal medicine, its natural mycelium and tube structure is conducive to the formation the porous structure of carbon materials. In this paper, porous carbon materials with high specific surface area and high pore volume were prepared by high temperature carbonization in nitrogen atmosphere using Ganoderma lucidum residue as a raw material and KOH as an alkali activator. The morphology and pore structure of the prepared carbon materials were analyzed and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction, Raman spectroscopy and nitrogen adsorption method. When the mass ratio of carbon to alkali was 1:4 and the temperature was 800 °C, ultra-high specific surface area microporous carbon materials were obtained with specific surface area of 3425 m3 g−1 and total pore volume of 1.74 cm3 g−1. The prepared porous carbon material was assembled into hydrogen peroxide electrode and cholesteric oxide modified electrode, which showed good catalytic performance.

Insights into the Nanoscale Microstructure Diversity of Different Rank Coals

The gas flow pattern of the coal seam is closely related to the pore structure of the coal. In order to better understand the pore distribution in different coal samples, the pore distribution and fractal dimension characteristics of five coal samples with different degrees of metamorphism were investigated and analyzed by using the low-temperature nitrogen adsorption method and CO2 adsorption methods based on the fractal theory. The results showed that the higher the degree of metamorphism, the better the pore development, and the fractal dimension of micropores and mesopores varied with the degree of metamorphism. The pore variability between the outburst and non-outburst coals is mainly in the stage of micropores, with the outburst coal having a larger pore volume and specific surface area and a more complex microstructure. The pore formation and distribution patterns of different coal samples under the combined influence of geological and coalification effects are discussed.

Ecofriendly Composite as a Promising Material for Highly-Performance Uranium Recovery from Different Solutions.

The development of new materials based on biopolymers (as renewable resources) is substantial for environmental challenges in the heavy metal and radionuclide ions removal contaminations. Functionalization of chitosan with sulfonic groups was achieved for improving the uranium sorption, not only from slightly acidic leachate, but also for the underground water. The prepared hydrogel based on chitosan was characterized by series of analysis tools for structure elucidation as FTIR spectroscopy, textural properties using nitrogen adsorption method, pHPZC (by pH-drift method), thermogravimetric analysis (TGA), SEM, and SEM-EDX analyses. The sorption was performed toward uranium (VI) ions for adjustment of sorption performances. The optimum sorption was performed at pH 4 (prior to the precipitation pH). The total sorption was achieved within 25 min (relatively fast kinetics) and was fitted by pseudo-first order rate equation (PFORE) and resistance to intraparticle diffusion equation (RIDE). The maximum sorption capacity was around 1.5 mmol U g−1. The sorption isotherms were fitted by Langmuir and Sips equations. Desorption was achieved using 0.3 M HCl solution and the complete desorption was performed in around 15 min of contact. The sorption desorption cycles are relatively stable during 5 cycles with limit decreasing in sorption and desorption properties (around 3 ± 0.2% and 99.8 ± 0.1%, respectively). The sorbent was used for removal of U from acid leachate solution in mining area. The sorbent showed a highly performance for U(VI) removal, which was considered as a tool material for radionuclides removing from aquatic medium.

Study on the difference of pore structure of anthracite under different particle sizes using low-temperature nitrogen adsorption method.

The low-temperature nitrogen adsorption test was used to study anthracite from Jiulishan coal mine with different particle size ranges of 60-80 mesh, 150-200 mesh, and > 200 mesh. The adsorption isotherm, adsorption capacity, pore volume, pore specific surface area, and average pore diameter of coal samples were analyzed by BET and DFT models in order to study the influence of particle size on the pore structure of anthracite and determine the optimal range of particle size for low-temperature nitrogen adsorption test. The results indicate that the particle size plays a significant effect on the pore structure of anthracite and the adsorption capacity of soft coal is less affected by particle size, while hard coal is substantially affected by particle size. The adsorption capacity of hard coal with particle size of > 200 mesh is increased by 7 times when compared with the particle size of 60-80 mesh, indicating that the gas molecular mobility hindrance decline and pore connectivity improves with the decrease of particle size. The average pore diameter of hard coal decreases continuously from 3.1424 to 2.854nm, while that of soft coal expands from 2.8947 to 3.2515nm and then to 3.0362nm with the decrease of particle size. The effects of particle size on the pore surface area of soft and hard coal are concentrated within the < 10nm pore aperture. Effect of particle size on hard coal pore volume is mainly focused in the pore size < 10nm, whereas that of soft coal is primarily concentrated in the pore with aperture ranges of 2-100nm. When the particle sizes varies from 60-80 mesh to 150-200 mesh, the collapse of large pore of hard coal appears better than that of closed pore. When the particle size of hard coal reaches > 200 mesh, the collapse of closed pores and the damage to small pores are stronger than the collapse of large pores. The fractal dimensions with relative pressure of 0-0.20 and 0.20-0.995 are defined as D1 and D2, respectively, and when the fractal dimension D1 increases, the surface roughness and structural complexity of coal samples increase with the decrease of anthracite particle size, while the fractal dimension D2 shows the opposite trend, which indicates that anthracite of smaller particle size possess higher adsorption capacity. Therefore, 150-200 mesh is recommended as the preferred anthracite particle size in low-temperature nitrogen adsorption test.

Mechanism on Cr(VI) removal from aqueous solution by camphor branch biochar

Removal of Cr(VI) from aqueous solution by biochar obtained from landscaping waste of camphor branch was investigated in order to find new material in producing carbon-based sorbent. Cr(VI) removal efficiency experiments revealed that the optimum pyrolysis temperature of camphor branch was 350 °C (CBB350) and an initial solution pH at 2.0 was favorable for Cr(VI) removal. The characteristics and mechanism of CBB350 on Cr(VI) removal were studied via Brunauer - Emmett - Teller nitrogen adsorption method, the scanning electron microscope equipped with energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometer and kinetic analysis. The results suggested that Elovich equation was best fitted the complex reaction process with fitting correlation coefficient above 0.94, which prompted that the chemical reaction was the control step, the concentration of Cr(VI) decreased sharply at the beginning of the reaction and the removal rate was accelerated in high temperature. The removal mechanism was supposed that the vast bulk of Cr(VI) was reduced to Cr (III) through electrostatic interaction or form new stable inorganic ions and hexa-coordinate complexes chemically adsorbed on the surface of camphor branch biochar, a fraction of Cr(VI) was reduced to Cr (III) species retained or discharged in the solution and the rest Cr(VI) was directly adsorbed on the adsorbent.

Pore Characteristics and Fractal Dimension Analysis of Tectonic Coal and Primary-Structure Coal: A Case Study of Sanjia Coal Mine in Northern Guizhou.

Understanding the pore heterogeneity of tectonic coal and primary-structure coal is of great significance for predicting and preventing tectonic coal. This study adopts the low-temperature nitrogen adsorption method, mercury injection experiment, and other methods, combined with fractal theory, to quantitatively analyze the pore distribution of coal samples inside and outside the outburst cavities of the Sanjia coal mine. The experiments have shown that the contents of aliphatic functional groups and hydrogen in tectonic coal are higher than those of aromatic structural functional groups. Raw coal has more straight chains than side chains, whereas aliphatic hydrocarbon mostly has short chains, and the branching degree is high. Soft and primary-structure coals have similar elemental content and tectonic effects endow the coal with better connectivity. The pores are filled with particles and flakes, and the surfaces of tectonic coal have more pores and fissures on them. According to the experimental curve, the pores are divided into five types. The pore size of primary-structure coal is mainly type II pores, and the pore size distribution of tectonic coal is relatively wide, with the majority being class I and class II pores. The specific surface area of tectonic coal is 60.7% more than that of primary-structure coal. The box fractal dimension of coal decreases with the increase in scanning electron microscopy (SEM) magnification. The minimum fractal dimension of tectonic coal is 2.49, which is 7.8% lower than the peak of 2.70. It can be seen from the fractal dimension that the fractal dimensions of pore types II, III, and IV are rougher.

Effects of chemical solvents on coal pore structural and fractal characteristics: An experimental investigation

Chemical solvent treatment is one of the most effective means to improve pore structure of low-permeability coal and increase production of coalbed methane. Low-temperature liquid nitrogen adsorption method, X-ray diffraction (XRD) mineral analysis and fractal theory were adopted to study variations in coal pore structural parameters and fractal characteristics affected by hydrochloric acid (HCl), tetrahydrofuran (THF) and carbon disulfide (CS2). Liquid nitrogen adsorption results of coal samples were analyzed using density functional theory (DFT), Brunauer-Emmett-Teller (BET) equation and Barrett-Johner-Halenda (BJH) model. Meanwhile, changes in fractal dimensions of pore surface (D1) and pore structure (D2) were calculated based on Frenkel-Halsey-Hill (FHH) model. Relationship between pore volume, average pore diameter, specific surface area and two fractal dimensions were established. Results show that: (1) Hysteresis lines exist in all isothermal adsorption-desorption processes of coal. Pores of raw coal are mainly semi-open pores with poor connectivity. The types of pores do not change significantly after THF and CS2 treatment, while the number of pores rise. In contrast, affected by HCl treatment, ink-bottle pores and open pores increase and pore fracture network connectivity becomes better. (2) Pore sizes of treated coal mainly distribute in range of 0–10 nm. After HCl treatment, many closed pores are opened, with growth in proportion of micropores. Meanwhile, specific surface area (SSA) of pores increases by 55.21% and 31.36%, respectively. THF extraction results in an increase in pore volume and SSA. After CS2 extraction, dissolution of organic material increases pore size and further improve volume of transition pores and mesopores. (3) HCl treatment causes decrease in D1 value of pores. However, in organic-solvent-treatment cases, solvent residues retain on coal pores, resulting in growth in D1 value and pore surface becoming rougher. Proportion of total pore volume of transition pores and mesopores of acidized coal decreases and D2 value rises. Pore distribution is more uneven. Relevant results could provide theoretical references for revealing mechanism of chemical solvents effects on gas flow in coal.

Characterisation of Novel Nitrogen Doped Reduced Graphene Oxide

The utilisation of fuel cells in everyday life is of critical importance for the introduction of clean energy and departure from carbon-based economy. The oxygen reduction reaction (ORR) rate on the cathode is the key factor for effective polymer electrolyte membrane fuel cells. Therefore, novel cathode catalysts have to be designed to reduce the ORR over voltage. One of the most efficient ways to increase the ORR rate is to use nitrogen doping of carbon materials.1 Such materials are also promising for applications in supercapacitors and other energy storage devices.2 In this work, experimental results based on a nitrogen-doped reduced graphene oxide are presented. The nitrogen-doped reduced graphene oxide has been produced by Sea Further SARL using a biological micro-organisms and non-toxic chemicals.3 The material has been characterised by several physical methods: particle size distribution analysis, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, gas adsorption method, and electrical conductivity measurements. X-ray diffraction data reveal the presence of peaks characteristic to reduced graphene oxide. The specific surface area of the bulk material is around 2.4 m2 g− 1 based on the nitrogen adsorption method. The bulk sample, in powder form, exhibited considerable specific conductance under pressure.Additionally, electrochemical measurements have been conducted in 0.1 M HClO₄ and 0.1 M KOH solutions. The electrochemical stability, capacitive behaviour, and ORR activity of nitrogen-doped reduced graphene oxide have been determined using cyclic voltammetry, rotating disc electrode and electrochemical impedance spectroscopy methods. The material under discussion has a good electrochemical stability within the investigated potential region in both media. The measurement data show that the ORR kinetics in alkaline media is much faster than in acidic media. Surprisingly, this material has a high gravimetric capacitance. Therefore, nitrogen-doped reduced graphene oxide has high potential for energy storage devices and is promising co-catalyst material in fuel cell. Acknowledgements This work was supported by the EU through the European Regional Development Fund under project TK 141 “Advanced materials and high-technology devices for energy recuperation systems” (grant number 2014 2020.4.01.15 0011); and by the Estonian Research Council (grant number PUT PRG 676). References N. Daems, X. Sheng, I.F.J. Vankelecom, and P.P. Pescarmona, J. Mater. Chem. A, 2, 4085 (2014).N.A. Elessawy, J.E. Nady, W. Wazeer, and A.B. Kashyout, Sci. Rep., 9, 1129 (2019).V. Iakimov, International Patent Application No. WO2021/059152, WIPO, April 1st 2021.

Laminar structure differences and heterogeneities in reservoirs in continental organic-rich shales: The Cretaceous Nenjiang Formation in the Songliao Basin

Shale has a unique laminar structure that is currently the focus of considerable interest and a great deal of research in the academic community and industry. Studies have focused primarily on the differences among laminar combinations, whereas only a few have investigated the structure of individual lamina. In this study, we use typical organic-rich shale from the Cretaceous Nenjiang Formation in the Songliao Basin as an example and analyze each individual lamina of the shale on a millimeter scale. We have investigated heterogeneities among the different laminae by using X-ray fluorescence analysis, rock slicing, laser scanning confocal microscopy, field emission scanning electron microscopy, total organic carbon (TOC), rock pyrolysis, X-ray diffraction mineral analysis, electronic computer tomography (nano-CT), nitrogen adsorption, and other experimental methods. Four laminar units — composed of clay minerals, feldspar-quartz, and calcite — are distinguished based on their different levels of Ca, K, and Fe. We designate these units as UA, UB, UC, and UD (from the top to bottom in the formation). The palaeoenvironment, organic geochemical parameters, and mineral compositions of the different laminar structures are “two-stage” in character. From UD to UA, TOC values indicate a slightly decreasing trend, whereas the calcite content indicates a substantial increase, which is related to gradual reduction in the paleodepth, increasing aridity of the climate, increase of salinity, and decrease of reducibility during the sedimentary period. Different laminae correspond to different pore structures. The pore types in units UC and UD are mainly clay mineral-related pores and pyrite intergranular pores. In contrast, calcite dissolution pores are common in units UA and UB. Nitrogen adsorption and nano-CT data indicate that the pore development degree and pore size of organic matter in units UC and UD are better than those of units UA and UB. The porosity of UD is 2.6 times higher than that of UA. Laminae have an important influence on shale quality. The traditional approach to shale evaluation takes laminar combinations in shale strata as the research unit. Switching the focus to the heterogeneity of individual lamina could help in the selection of “sweet spots” and identification of optimal locations for shale oil exploration and development.

Effect of silica source on zeolite MFI crystallization in fluoride media and its physicochemical and catalytic properties

A series of MFI zeolites were synthesized in fluoride media from fumed silica hydrogel, fumed silica and TEOS to elucidate the influence of silica source on the physicochemical and catalytic properties of MFI zeolites. The materials obtained were characterized by nitrogen adsorption, XRD, SEM, TPD and 27Al NMR MAS methods and evaluated in MTO and hexane/3-methyl pentane cracking catalytic reactions. It has been demonstrated that crystallization proceeds via solution-mediated mechanism independently on silica source. However, the nature of silica source substantially affects the crystallization rate, the crystal size, the dynamics of Al incorporation into the MFI framework and Al distribution in the zeolite crystals. The application of fumed silica hydrogel and fumed silica with high polymerization degree yields crystals with an Al-enriched core and a siliceous shell. These materials demonstrate faster deactivation in the MTO reaction and higher selectivity to ethylene as compared to the MFI obtained from TEOS with a uniform Al distribution in the crystals. The effect observed is attributed to a longer diffusion path length of the reagent to active sites located mainly in the crystal core and the reaction products outside from the crystal core, resulting in a higher contribution of secondary reactions.

An investigation of pore structure of blended coal coke produced by pyrolysis of three kinds of coal

ABSTRACT Blended coal combustion technology is being adopted by more and more power plants as a clean coal combustion technology, while the combustion of coal coke accounts for more than 85% of the total combustion process of pulverized coal. In order to investigate the effects of different factors on the pore structure and fractal properties of the blended coal coke, a low-temperature nitrogen adsorption method and scanning electron microscopy are used to study the coal coke consisting of three types of coal after pyrolysis. The adsorption isotherm analysis indicates that the pore structure in blended coal coke consisted mainly of semi-open pores with semi-cates. Petroleum coke can severely inhibit microporosity when the content of petroleum coke in the blended coal sample exceeds 10%. The microporosity distribution of blended coal coke with different blending ratios is more concentrated than that of mesopores. In addition, it is found that the trend of D1 is consistent with the trend of the ratio of the microporous specific surface area to the total specific surface area in the blended coal coke. Bituminous coal will make the blended coal coke have a complex structure and petroleum coke will make it have a smooth surface.

Study on Pore Structure of Shale Reservoir by Low Temperature Nitrogen Adsorption Method

Shale gas is one of the most actively explored unconventional sources of natural gas. There are several types of pores in the shale reservoir, and their structural characteristics are complex. Evaluating the characteristics of the shale pore structure is the basis for understanding the shale reservoir performance and the oil and gas migration mechanism. In this paper, the micro- and nanopores of shale samples from the Yanchang Formation, Hunan basin, are studied by applying the low-temperature nitrogen adsorption method. Several pore structure parameters such as the specific surface area, the pore volume, and the pore size distribution of the analyzed samples are calculated. The predominant characteristics of nanopores that influence hydrocarbon accumulation and control the development of pores are discussed. The results indicate that the shale reservoir rocks from the study area are mainly mesoporous with an average pore size distribution between 2 and 50 nm. A small number of micropores (less than 2 nm) and macropores (more than 50 nm) are also present in the pore network. The development of micropores and mesopores in the shale samples is associated with organic matter content, while the development of macropores is linked to clay minerals content. Total organic carbon (TOC) content is the key element to control the nanopore volume and the specific surface area of the reservoir rocks from the study area. At the same time, the organic matter-enriched pore network also provides extensive space for the accumulation of shale gas.

The use of microwave irradiation for preparation and fast-acting regeneration of magnetic biochars

The application of microwave irradiation for rapid synthesis of magnetic biochar from agricultural waste with the subsequent modification of carbon matrix by magnetic nanoparticles was performed. The magnetic biochar was characterized by 57Fe Mössbauer spectroscopy, X-ray diffraction, a low-temperature nitrogen adsorption method, and electron microscopy. Except of magnetic properties, modification of biochar brings surface texture increase (SBET = 21.1 m2/g for char precursor versus 139.1 m2/g for magnetic biochar), and therefore better adsorption properties. The magnetic biochar was tested as an adsorbent of As5+ oxyanion and methylene blue (MB) to study the sorption mechanism and regeneration process. Magnetic biochar is the excellent adsorbent of arsenic (Qm = 24.9 mg/g; pH = 3.8). In the regeneration procedure, fast-acting microwave irradiation (10 s) significantly increases the value of the As5+ desorption rate constant as well as the initial desorption rate. The adsorption of MB on the magnetic biochar (Qm = 55.0 mg/g; pH = 10.2) was realized to study microwave-induced thermal regeneration. After short microwave treatment (30 s), a degradation of MB was observed (no absorption in the UV/VIS spectrum), whereas six degradation products were detected (HPLC/ESI-MS) and proposed formulas were revealed. Longer irradiation (60 s) caused total degradation of MB.