Micropore Surface Area Research Articles

Pore structure evolution of lacustrine shales containing Type I organic matter from the Upper Cretaceous Qingshankou Formation, Songliao Basin, China: A study of artificial samples from hydrous pyrolysis experiments

To characterize the pore evolution of lacustrine shales containing Type I organic matter, we performed hydrous pyrolysis experiments on a lacustrine shale sample to make it reach various maturities. The samples with various maturities were then extracted using dichloromethane. Total organic carbon content, Rock-Eval pyrolysis, and low-pressure gas (CO2 and N2) adsorption analyses were performed on the samples before and after extraction. The results showed that the volumes and surface areas of micropores (<2 nm) of the extracted samples were much higher than those of the artificial samples, but the parameters of mesopores (2–50 nm) of the extracted samples were close to the samples before extraction, indicating that liquid hydrocarbons are mainly stored in micropores. There were no any obvious correlations between pore volumes and mineral contents for the extracted samples, suggesting maturity is the dominant control of pore structure. The pore evolution of the extracted samples is similar to that of the artificial samples. During maturation, micropore volumes initially decreased over the interval 0.71%–0.97% EASY%Ro before increasing at EASY%Ro values exceeding 1.08%. The changes in micropore volume of the extracted samples may be related to the formation and cracking of insoluble organic matter. During this process, mesopore volumes kept increasing, which is mainly aroused by kerogen decomposition or carbon loss. Our results could improve the understanding of pore evolution of lacustrine shales and provide some implications for shale oil storage.

Hydroisomerization of n-hexadecane over Hβ molecular sieve loading palladium bifunctional catalyst: effect of SiO2/Al2O3 molar ratios

Hβ molecular sieves with different SiO2/Al2O3 ratios (Hβ(x))and Hβ(x) loading Pd(0.5 wt%) bifunctional catalysts(Pd/Hβ(x)) were prepared by hydrothermal synthesis and incipient wetness impregnation, respectively. The structure, morphology, pore and acid properties of Hβ(x) and Pd dispersion of Pd/Hβ (x) were characterized using XRD, SEM, N2 physical adsorption, NH3-TPD and H2 chemical absorption. Hβ (x) samples were highly crystalline microporous materials. With the increase of SiO2/Al2O3 ratios, BET surface area, micro-pore surface area and volume of Hβ (x) gradually decreased, and the external surface area and mesoporous volume gradually increased, and the number and acid strength of weak acid sites for Hβ(x) and Pd dispersion for Pd/Hβ(x) decreased. It was known from hydroisomerization perforamce of n-C16H34 that Pd/Hβ(40) catalysts showed the highest conversion of of 96.9% at 230°C. The select ivity of iso-C16H34 reached the highest value at the n-C16H34 conversion of 45~50%. Pd/Hβ(40) cata lysts exhib ited the highest iso-C16H34 selectivity of 84.4%, much more multi-branched iso-C16H34 and C4+C5 cracking components. The decrease of SiO2/Al2O3 molar ratios can increase the number of acid sites and dispersion of Pd/Hβ(x) bifunctional catalysts, thus not only aggravating the secondary heterogeneous reaction, but also accelerating the serious secondary cracking reaction.

Structural Differences of Spontaneous Combustion Prone Inertinite-Rich Chinese Lignite Coals: Insights from XRD, Solid-State13C NMR, LDIMS, and HRTEM

China has a considerable lignite deposit in the Xinjiang province, but surface and underground coal seam fires pose a threat to the resources, environment, economy, and health. As the chemical and physical structure impacts coal fire propensity and behavior, two raw Xinjiang lignites were examined from the Shaerhu (SEH) and Piliqing (PLQ) Collieries. The SEH lignite is more prone to spontaneous combustion (from regional observations). These coals were of the same geological age and were both inertinite-rich 69.8 and 95.6% for SEH and PLQ, respectively (by the point counting approach). The more spontaneous combustion prone lignite had a significantly higher micropore contribution and surface area (92.4% and 195.6 m2/g), while both coals had similar micro- and mesopore size distribution ranges. Despite being classified as lignite by the mean vitrinite random reflectance (Rr, 0.30 and 0.26%) the inertinite contribution displaces some of the structural properties to be similar to the vitrinite-rich, high-vola...

Coal seam porosity and fracture heterogeneity of marcolithotypes in the Fanzhuang Block, southern Qinshui Basin, China

Marcolithotypes play a significant role in coal seam porosity and fracture heterogeneity. The optical microscopy, CO2 and N2 adsorption, and X-ray CT were used for reconstructing the pore-fracture system of different marcolithotypes. The results show that the microfractures are well developed in the bright coal with the characteristics of high fracture density, good connectivity, and strongest fractal dimension, corresponding to the highest permeability and the best seepage capacity. The adsorption capacity measured with N2, CO2, and CH4 indicates that the specific surface area of micropores (<2 nm) increases linearly from the bright to the dull coal, and the bright coal is favorable for gas adsorption by providing more available surface sites. The difference in physical properties of various macrolithotypes causes different logging response characteristics, including the compensated density (DEN), the gamma ray (GR), and the acoustic time (AC). Based on that, the index (N = AC/(GR × DEN)) was put forward to forecast the distribution of coal macrolithotypes quantitatively (N ≤ 1.3, Partings; 1.3 < N ≤ 3, Dull coal; 3 < N ≤ 5, Semi-dull coal; 5 < N ≤ 8, Semi-bright coal; N > 8, Bright coal), and its accuracy was verified by coal cores from different areas, i.e. Fanzhuang, Zhengzhuang, and Hancheng blocks.

Effects of different biochar amendments on carbon loss and leachate characterization from an agricultural soil

Selection of an appropriate biochar as a soil amendment requires a thorough investigation of the effects on soil ecosystems and adjacent water systems via leaching. Different biochar characteristics influence retention or leaching of different soil and biochar components. A lab lysimeter study was conducted to investigate carbon (C) balance and leachate quality with biochar additions. Biochar made from wood pellets (WP) and sewage sludge (SS) produced at 400 °C (WP400 and SS400) and 700 °C (WP700 and SS700), respectively, were applied to silt loam soil at an application rate of 4%. Fluorescence excitation-emission spectrophotometry (EEMs) was utilized to understand the compositional changes in leachate dissolved organic carbon (DOC). Our results show that DOC contributed the largest portion of C leaching loss. The WP treatments increased DOC mass loss, but did not significantly change leachate DOC quality. SS400, in comparison, increased mass loss of DOC and SS700 decreased it probably due to its higher adsorptive capacity to DOC. Unlike WP treatments, SS treatments significantly changed leachate DOC quality. Chemical oxygen demand (COD) was reduced with SS400 and SS700 biochar additions, which is assumed to be related to SS biochar's high oxygen-containing surface functional groups. Reduction in total nitrogen (TN) leaching by WP700 and SS700 treatments might be related to the higher micropore surface area. Over all, our findings imply that changes in the different components of the leachate from biochar-amended soil are related to different biochar properties, such as labile matter content, total surface area, micropore volume and cation exchange capacity.

Waste bones derived nitrogen–doped carbon with high micropore ratio towards supercapacitor applications

Fabrication of high–performance electrodes from waste biomass has attracted increasing attention among the energy storage and conversion field. In this work, we have synthesized nitrogen–doped activated carbon by a simultaneous pyrolysis/activation method from waste bones. It is found that the specific surface area and pore structure of as–synthesized carbon depends on the carbonization temperature (500–800 °C), and the highest specific surface area is 1522 m2 g−1. The electrochemical properties of Pork bone, Blackfish bone, Eel bone based activated carbon (PBAC, BFAC, EBAC) mainly depend on their micro–/mesoporosity. Three samples PBAC–600, BFAC–600 and EBAC–600, which have higher ratio of micropore surface area and nitrogen content, exhibit enhanced specific capacitance of 263, 302 and 264F g−1 in 6 M KOH electrolyte. Furthermore, the assembled symmetric supercapacitors of PBAC–600 can deliver energy density as high as 7.0 and 26.2 Wh Kg−1 in the aqueous and ionic liquid electrolyte, respectively. Such excellent performance can be attributed to the microporous structure, reasonable pore size distribution and nitrogen self–doping of the activated carbon. This research indicates that waste bones have great potential for mass fabrication of the activated carbon electrodes for energy storage applications.

Influence of solvents on pore structure and methane adsorption capacity of lacustrine shales: An example from a Chang 7 shale sample in the Ordos Basin, China

The dissolution of soluble organic matter by solvents can increase the porosity and pore connectivity of shale, which is conducive to the exploitation of shale gas. To explore the influence of solvents on the pore structure and methane adsorption capacity of extracted shale, a sample of the Chang 7 shales from the Ordos Basin, China is extracted using acetone, tetrahydrofuran (THF), carbon disulfide (CS2), and benzene, respectively. Low pressure gas (CO2 and N2) adsorptions and methane adsorption experiments were carried out on the studied sample before and after extraction. The results indicate that the extraction yields of THF, CS2, benzene and acetone were 0.84%, 0.63%, 0.34%, and 0.31%, respectively, which is jointly influenced by the molecular dynamics diameter, aromaticity, boiling point, and polarity. The extraction yield of acetone (0.31%) is the lowest, which may be attributed to its low boiling point. The extraction yield of CS2 is about 2 times higher than acetone. It may be related to that the CS2 can destroy ionic crosslinks in organic matter, improving the extraction yield significantly. The highest extraction yield (0.84%) of THF is consistent with its aromatic structure, high boiling point, and strong polarity. The extraction yield (0.34%) of benzene is relatively low among the used solvents, which may be aroused by its larger dynamic diameter and weak polarity. Interestingly, the size ranges of pores that increased after extraction are strongly controlled by solvents. Acetone is easier to enter the micropores due to its smaller dynamics diameter. Therefore, the organic matters in micropores were more easily dissolved in acetone, which results in the significant increases in micropore volume and surface area. Comparably, mesopore volume and surface area increased greatly after CS2 extraction. One possibility is that CS2 mainly dissolved the organic matters in mesopores. Another possibility is that a part of micropores were enlarged to mesopores by extraction. The macropore volumes of the sample extracted by benzene and THF obviously increased due to their larger dynamics diameters. The methane adsorption capacity of the extracted sample is stronger than the raw sample. The type of adsorption isotherm was not changed. The acetone extracted sample has the highest methane adsorption capacity, followed by THF, CS2, and benzene, which is positively related with their micropore surface areas.

Silica-alumina composite as an effective adsorbent for the removal of metformin from water

The anti-diabetic agent metformin (MF) is one of the most prescribed pharmaceutical compound worldwide. It is not completely metabolized after administration where 52% is excreted in urine. Accordingly, it highly contributes in generating wastewater containing MF. This pollutant is not effectively removed by the conventional wastewater treatment methods. Therefore, an effective advanced treatment technique should be implemented for the removal of MF from wastewater. In this study, silica-alumina (SA) is used as an environmentally-safe and effective adsorbent for removing MF from aqueous solution by adsorption. Adsorption experiments were employed studying the effect of pH, contact time, and MF initial concentration to investigate both the removal efficiency of MF and the interaction mechanism. A set of characterization techniques, such as SEM, BET, FTIR, TPD-MS, and zeta potential were performed before and after adsorption experiments to confirm the role of structural morphology, surface area, porosity, surface acidity and charge in adsorption. The characterization analysis showed that SA has BET surface area of 470 m2/g. From the total BET surface area, the microporous surface area was around 31% (147 m2/g), while the rest corresponds to the mesoporous surface area (323 m2/g). The batch adsorption results showed that high concentrations of MF were efficiently removed from water samples with a maximum uptake of 46 mg/L at optimal pH 9.0 (optimal pH). The mechanism responsible for adsorption was observed to be carried out via an electrostatic interaction between a negatively charged SA and a positively charged MF. TGA/DT analysis was conducted to assess the reusability of the spent SA by thermal regeneration at 673 K. The adsorbent was completely regenerated and maintained a 95% removal after 3 cycles without impacting the surface characteristics.

Efficient carbon-based catalyst derived from natural cattail fiber for hydrogen evolution reaction

Metal-free electrocatalysts for hydrogen evolution reaction (HER) are very important for efficient supply of sustainable and clean fuel. Herein, metal-free N-doped porous carbon fibers (NPCF) is reported by carbonization, activation and nitrogen-doping of natural cattails. The carbon fibers possess high specific surface area (765 m2 g−1) and lots of micropores. Excellent catalytic performances of NPCF are illustrated for HER from electrolysis of water in acidic media. An onset overpotential of 70 mV with a low Tafel slope of 135 mV·dec−1 was observed for NPCF electrode. The electrocatalytic properties of NPCF are much better than those of commercial graphite powder, carbon nanotubes and super-P. NPCF also shows promising electrochemical durability with only 3% recession of current density after 20 h continuous operations. The high catalytic activities of NPCF are attributed to the relatively high specific surface area, abundant micropores, strong electrical conductivity, the high stability of biomass-derived carbon matrix and suitable N content. The preparation and high activities for HER of NPCF offer a novel idea for the promising preparation of metal-free carbon materials derived from earth-abundant biomass for more efficient and cleaner bulk chemical production.

Postsynthetic Modification of a Network Polymer of Intrinsic Microporosity and Its Hydrogen Adsorption Properties

An intrinsically microporous high surface area (772 m2 g–1) hexaazatrinaphthylene-based network polymer has been synthesized. Additionally, the material was postmodified via the introduction of palladium ions to determine the effect of metalation on the properties of the assembly. Both the unmodified as-synthesized and metal-modified polymers were characterized using elemental analysis, Fourier transform infrared spectroscopy, solid-state 13C cross-polarization-magic-angle spinning NMR spectroscopy, Brunauer–Emmett–Teller surface area analysis, X-ray photoelectron spectroscopy, X-ray diffraction analysis (XRD), small-angle X-ray scattering, and thermogravimetric analysis techniques. The hydrogen uptake capacities of these materials were determined for a wide range of pressures up to 2000 bar. The palladium functionalization changed the intermolecular chain distances in the polymer, enhanced the microporosity, and increased the hydrogen uptake at ambient temperature.

Development of dispersive solid-phase extraction with polyphenylene conjugated microporous polymers for sensitive determination of phenoxycarboxylic acids in environmental water samples.

High-performance capturing polar phenoxycarboxylic acids herbicides (PCAs) from water samples remains a great challenge because PCAs form salt easily and dissolve. Polyphenylene-based conjugated microporous polymers (PP-CMPs), a fascinating type of polymers, bear π-conjugation over 3D polyphenylene scaffolds, inherent micropore, and large surface area, which are essential for capturing trace PCAs in complex samples. This work developed a novel approach to quantify trace PCAs using PP-CMPs as an efficient dispersive solid-phase extraction (d-SPE) adsorbent. The developed method based on PP-CMPs achieved high sensitivity with limits of detection of 0.55-3.84 ng L-1, satisfactory correlation coefficients (≥ 0.9912), good linearity (50-10,000 ng L-1), and good precisions (2.0-9.0%). Moreover, this method was used for simultaneous monitoring of the amounts of five PCAs in environmental water samples with satisfactory spiked recoveries (86.9-101.3%). All these fact demonstrated that this new d-SPE technique based on PP-CMPs exhibited a promising potential for highly sensitive analysis of trace PCAs in complex samples.

Removal of chromium (VI) from water by porous carbon derived from corn straw: Influencing factors, regeneration and mechanism.

Porous carbon is one of the most widely used materials to remove Cr(VI) from polluted water. Here we reported one efficient porous carbon material prepared from corn straw. The results of Fourier transform infrared spectroscopy (FTIR), Energy dispersion spectrum (EDS), and X-ray photoelectron spectroscopy (XPS) indicated that the porous carbon surface had functional groups such as COOH, OH and COC, etc, which could be acted as active sites during the adsorption process. Brunauer-Emmett-Teller (BET) results showed that the surface area and total pore volume of the adsorbent were 2131.181 m2/g and 1.128 cm3/g, respectively. The percentages of micropore surface area and micropore volume achieved 91.93% and 80.43%, respectively. The maximum adsorption capacity of Cr(VI) was 175.44 mg/g at 25 °C with the well-developed microporous structure and abundant oxygen-containing functional groups of porous carbon. The adsorption process was well described by the pseudo-second order model and Langmuir adsorption isotherm model. It was mainly based on chemical adsorption of a single molecular layer, accompanied by ion exchange reaction, Cr(VI) reduction, and complexation, etc. The adsorbent exhibited excellent removal performance of Cr(VI) in the co-existing ions wastewater and electroplating wastewater, and could remain high removal performance for four adsorption-desorption cycles.

The influence of crystallite size on the structural stability of Cu/SAPO-34 catalysts

A series of Cu/SAPO-34 catalysts of identical chemical compositions but different crystallite sizes (1–13 μm) was prepared by “one-pot” method. The fresh and low-temperature hydrothermally treated (LHT) catalysts were characterized by a comprehensive set of techniques, including XRF, SEM, EDS, XRD, NMR, BET, XPS, pyridine-FTIR, NH3 and diethylamine TPD, EPR as well as H2-TPR. The reaction rates for NH3-SCR were measured under differential conditions and correlated with their physical and chemical properties. All fresh catalysts, regardless of crystallite size, showed the same bulk properties, such as chemical composition, crystallinity, acidity and copper species. After a hydrothermal treatment (96 h at 70 °C with 80% humidity), loss of micropore surface area, micro volume, relative crystallinities, acidity and isolated Cu2+ species was observed on all catalysts, and the extent of decrease was proportional to the average crystallite size. NH3-SCR reaction rate suffered a similar decrease with increasing crystallite size. Surface analyses by SEM-ESD, XPS and diethylamine-TPD showed an obvious surface enrichment of Si (and Brønsted acidity) on all fresh catalysts, and the degree of enrichment is also proportional to crystallite size. This surface enrichment of Si-O-Al linkages is thought to be the root cause for the structural vulnerability found on larger crystallite catalysts under LHT conditions. This understanding is entirely consistent with the observation found on the H/SAPO-34 reference materials of the same sizes, where the structural destruction is even more severe after the LHT. A mechanism for structural disintegration for larger Cu/SAPO-34 crystals was proposed, and the genesis of the Si gradient was discussed in the context of crystallization kinetics.

AC-Filtering Supercapacitors Based on Edge Oriented Vertical Graphene and Cross-Linked Carbon Nanofiber

There is strong interest in developing high-frequency (HF) supercapacitors or electrochemical capacitors (ECs), which can work at the hundreds to kilo hertz range for line-frequency alternating current (AC) filtering in the substitution of bulky aluminum electrolytic capacitors, with broad applications in the power and electronic fields. Although great progress has been achieved in the studies of electrode materials for ECs, most of them are not suitable to work in this high frequency range because of the slow electrochemical processes involved. Edge-oriented vertical graphene (VG) networks on 3D scaffolds have a unique structure that offers straightforward pore configuration, reasonable surface area, and high electronic conductivity, thus allowing the fabrication of HF-ECs. Comparatively, highly conductive freestanding cross-linked carbon nanofibers (CCNFs), derived from bacterial cellulose in a rapid plasma pyrolysis process, can also provide a large surface area but free of rate-limiting micropores, and are another good candidate for HF-ECs. In this mini review, advances in these fields are summarized, with emphasis on our recent contributions in the study of these materials and their electrochemical properties including preliminary demonstrations of HF-ECs for AC line filtering and pulse power storage applications.

Microwave steam activation, an innovative pyrolysis approach to convert waste palm shell into highly microporous activated carbon

Microwave-steam activation (MSA), an innovative pyrolysis approach combining the use of microwave heating and steam activation, was investigated for its potential production of high grade activated carbon (AC) from waste palm shell (WPS) for methylene blue removal. MSA was performed via pyrolytic carbonization of WPS to produce biochar as the first step followed by steam activation of the biochar using microwave heating to form AC. Optimum yield and adsorption efficiency of methylene blue were obtained using response surface methodology involving several key process parameters. The resulting AC was characterized for its porous characteristics, surface morphology, proximate analysis and elemental compositions. MSA provided a high activation temperature above 500 °C with short process time of 15 min and rapid heating rate (≤150 °C/min). The results from optimization showed that one gram of AC produced from steam activation under 10 min of microwave heating at 550 °C can remove up to 38.5 mg of methylene blue. The AC showed a high and uniform surface porosity consisting high fixed carbon (73 wt%), micropore and BET surface area of 763.1 and 570.8 m2/g respectively, hence suggesting the great potential of MSA as a promising approach to produce high grade adsorbent for dye removal.

Improving Supercapacitance of Electrospun Carbon Nanofibers through Increasing Micropores and Microporous Surface Area

AbstractPrevious papers about electrospun carbon nanofibers do not provide systemic understandings about how in situ activation agents affect the porous structure of carbon nanofibers. In this study, poly(vinylpyrrolidone), poly(methyl methacrylate), and high‐amylose starch (HAS) are used as activation agent to separately prepare porous carbon nanofibers from electrospun polyacrylonitrile nanofibers, and the effects of the polymer activation agents on the porous structure and supercapacitive properties of the resulting carbon nanofibers are examined. The studies indicate that melting point and decomposition temperature are two important parameters deciding the pore size profile. The one with high melting point and low decomposition temperature, such as HAS, allows to form micropore‐dominant porous structure with large specific surface area. The HAS‐activated carbon nanofibers have a micropore specific surface area as high as ≈809 m2 g−1, total pore volume of ≈0.42 cm3 g−1, and micropore content as high as ≈59%. The corresponding electrodes have a capacitance of 282 F g−1 at the current density of 1.0 A g−1 with excellent cycling durability. These novel understandings may be useful for the development of effective carbon nanofibers for high‐performance supercapacitor and other applications.

Preparation of Pore-Size Controllable Activated Carbon from Rice Husk Using Dual Activating Agent and Its Application in Supercapacitor

Activated carbons prepared from rice husk by chemical activation with dual activation agents, KOH and NaOH, have been studied and characterized by BET, SEM, EDX, FTIR, Boehm titration, Raman, and TGA. It was found that the KOH/NaOH impregnation ratio plays an important role on textural properties of AC. At the same amount of total alkali hydroxide, the KOH/NaOH ratio higher than 1.33 resulted in larger specific surface area (2990∼3043 m2·g−1), microporous surface area (2747∼2831 m2·g−1), and higher micropore volume (1.4250∼1.4316 cm3·g−1). The as-prepared samples exist in the form of spherical-shaped particles with the size ranging from 20 to 60 nm and contain numerous surface functional groups. The as-prepared activated carbons were then assessed as an electrode material of supercapacitor operating in the 0.5 M K2SO4 electrolyte in potential windows of −1.0∼0.0 V. The highest capacitance obtained was 205 F·g−1 at the scan rate of 2 mV·s−1 and 225 F·g−1 at a current density of 0.2 A·g−1. At the scan rate as high as 50 mV·s−1, all the as-prepared activated carbons in this study have the specific capacitance greater than 100 F·g−1.

Ultrahigh adsorption of tetracycline on willow branche-derived porous carbons with tunable pore structure: Isotherm, kinetics, thermodynamic and new mechanism study

Abstract The problem of tetracycline (TC) antibiotic pollution in aquatic environment has attracted wide attention and research. It is still meaningful to develop high-efficiency separation materials and investigate their adsorption behavior and mechanism. In this research, porous carbons were prepared using the renewable willow branches as carbon source, via pre-carbonization and alkali activation. The activation temperature and alkali usage played important roles in the pore structure, which was mainly microporous. The WBAC-850-4 obtained at 850 °C and alkali/biochar ratio of 4:1 exhibited the largest specific surface area (3342 m2/g) and total pore volume (1.912 cm3/g), displaying the ultrahigh TC adsorption capacity of 1300 mg/g at 298 K. which was higher than that of the reported TC-adsorbents. WBAC-850-4 kept high adsorption ability with a minor impact in the broad pH range of 3.0–8.0. Thermodynamic analysis implied the physisorption dominated the spontaneous adsorption process. The structure-activity relationship between the TC adsorption capacity and porosity properties was established for the first time. Notably, the adsorption capacity of TC had a positive linear correlation with specific surface area, total pore volume, micropore surface area and micropore pore volume, and the correlation coefficient were higher than 0.97. It was first revealed that micropore filling was the main mechanism for porous carbons to bind TC, which meaningfully provided new insight for designing advanced TC-adsorbents in future.

In English

There are many methods for synthesis of tin dioxide SnO 2 , namely sol-gel, precipitation. However, these methods do not allow to regulate the physical-chemical properties in wide limits in the synthesis stage. The most commonly obtained samples are predominantly microporous as a rule. On the other hand, the meso-macroporous structure is required for the effective use of tin dioxide in sorption processes. The mechanochemical and microwave treatments can be used for eliminating mentioned above disadvantages. Therefore, the purpose of this work was to study the influence of the mechanochemical and microwave treatments on the physical-chemical and sorption properties of SnO 2 prepared by heterogeneous precipitation. SnO 2 gels and xerogels have been obtained by heterogeneous precipitation. The mechanochemical treatment was carried out in air and water at 300 rpm for 0.5 h in the form of dried xerogel as well as wet gel using a planetary ball mill Pulverisette-7. Initial wet gel was subjected to microwave treatment for 1 h using a high-pressure reactor «NANO 2000». We used XRD and DTA-TG analysis, FTIR spectroscopy, adsorption-desorption of nitrogen for characterization of initial and modified samples. The initial sample corresponds to the composition tin oxohydroxide with gross formula Sn 3 O 4 (OH) 4 . For the modified samples a partial removal of the structural OH groups occurs. The initial sample is characterized by high values of specific surface area and high content of micropores. The specific surface area, total volume of pores, mesoporous size are increased as a result of the mechanochemical and microwave treatments. Formation of the secondary porosity that presented by meso- and macropores is peculiarity of xerogel milling in water. The cation exchange capacity under the most optimal conditions for the sorption of U(VI) ions (pH = 5–6, no background, cationic forms of uranium) for the initial sample was 0.82 mEq/g UO 2 2+ . The mechanochemical and microwave treatments result in drastic increase in sorption capacity of tin oxohydroxide in relation to U(VI) ions. The greatest effect was observed for sample milled in the form of wet gel, the sorption capacity А of which increases almost in three times while distribution coefficient K d increases almost 70 times. In case of sorption on the background of 0.1 M NaHCO 3 (pH 8, model of block water of the Chernobyl Nuclear Power Plant), the sorption capacity of sample after mechanochemical treatment of gel increases by 43 % compared to initial sample from 0.31 to 0.43 mEq/g UO 2 2+ . Thus, modified samples can remove both cationic and anionic forms of U(VI) ions in the solution. At the same time, for sorption of Cs(I) and Sr(II) ions, it has been found, that in both cases the mechanochemical and microwave treatments negatively affect to their removal in comparison with initial sample.

PECULIARITIES OF SMALL STRAINED ALICYCLE COMPOUNDS FORMATION IN CATALYTIC TRANSFORMATION OF METHANOL OVER ZEOLITE H-ZSM-5

The article presents the results of strained hydrocarbons formation study during the catalytic transformation of methanol into hydrocarbons on zeolite H-ZSM-5. The formation of the following strained cyclic compounds was determined: 1,1-dimethylcyclopropane, 1,2-dimethyl-cyclopropane, 1,1,2-trimethylcyclopropane, 1,2,3-trimethylcyclopropane, 1,1,2,2-tetramethylcyclo-propane, 1,1,2 , 3-tetramethylcyclopropane. The non-stationary character of strained cyclic hydrocarbons formation with a pronounced hydrocarbons formation rate maximum and subsequent deactivation of the catalyst was found. The temperature effect on strained hydrocarbons yield was evaluated. Thus, with an increase in the process reaction temperature up to 400 °C, a maximum of strained hydrocarbons accumulation rate was achieved as 8-8.5 g(Hyd)/(kg(Cat)·h) on 350 h of reaction, and a further increase in the reaction temperature leads to a decrease in the strained hydrocarbons accumulation rate. The effect of the methanol feed rate on the strained hydrocarbons formation rate was also studied. An increase in the methanol feed rate from 0.02 ml/min to 0.16 ml/min results in increase in the strained hydrocarbons formation rate up to 37 g (Hyd)/(kg(Cat)·h). The article presents results of H-ZSM-5 physicochemical study used by ammonia chemisorption, nitrogen phisisorption, X-ray photoelectron spectroscopy. Physicochemical studies of catalyst samples after the methanol transformation process to form strained hydrocarbons showed a twofold decrease in the number of acid sites from 1.2 mmol(NH3)/g (sample) to 0.3 mmol (NH3)/g(sample) and a significant decrease in surface area of micropores from 294 m2/g for the initial sample to 16 m2/g for the sample after the reaction. The X-ray diffraction spectroscopy method showed that the composition of the catalysts H-ZSM-5 surface includes carbon, oxygen, silicon and aluminum. Carbon concentration was found to be 4.3 at.% on the surface of the initial catalyst. While the carbon concentration increases up to 14.1 at.% during the reaction. Also oxygen content on the catalysts surface decreases from 59.9 to 53.4 at%, silica concentration decreases from 35.5 to 32.1 at.%. The following indicates the formation of a carbon surface layer over the catalysts.