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•Novel macroporous cryogels containing nanostructured iron oxide were synthesized.•Iron oxide was uniformly dispersed in the cryogel matrix.•The cryogels have high mechanical ...stability and low flow-through resistance for solutes through the matrix.•The arsenic adsorption capacity of the cryogels was high.•The cryogels have potential as effective nano-based adsorption devices for water treatment.
Novel macroporous iron oxide nanocomposite cryogels were synthesized and assessed as arsenite (As(III)) adsorbents. The two-step synthesis method, by which a porous nanonetwork of iron oxide is firstly formed, allowed a homogeneous dispersion of the iron oxide in the cryogel reaction mixture, regardless of the nature of the co-polymer forming the cryogel structure. The cryogels showed excellent mechanical properties, especially the acrylamide-based cryogel. This gel showed the highest As(III) adsorption capacity, with the maximum value estimated at 118 mg/g using the Langmuir model. The immobilization of the nanostructured iron oxide gel into the cryogel matrix resulted in slower adsorption kinetics, however the cryogels offer the advantage of a stable three-dimensional structure that impedes the release of the iron oxide nanoparticles into the treated effluent. A preliminary toxicity evaluation of the cryogels did not indicate any apparent inhibition of human hepatic cells activity, which together with their mechanical stability and high adsorption capacity for As(III) make them excellent materials for the development of nanoparticle based adsorption devices for drinking water treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The development of effective catalytic systems for the synthesis of carbon nanomaterials by catalytic pyrolysis is a relevant direction for modern science. In this work, the peculiarities of the ...microdispersed alloy Ni
0.89
Cu
0.11
synthesis by mechanochemical alloying of metal powders in a planetary mill were investigated. The evolution of morphology and phase composition of Ni–Cu composite depending on the diameter of the milling balls and the activation time was studied using X-ray diffraction and particle size analyses, and scanning electron microscopy. The conditions corresponding to the formation of a single-phase Ni–Cu solid solution were determined and a scheme for the appearance of microdispersed alloy particles during the activation process was proposed. The prepared samples of the Ni–Cu composite were tested as catalyst precursors in the ethylene decomposition at 550 °C accompanied with the formation of carbon filaments. An extreme character of the carbon yield dependence on the activation time was found. The maximum carbon yield of 68–78 g/g
cat
after 15 min of reaction was achieved on the sample activated for 5–7 min and possessing slab morphology. The complete disintegration of the microdispersed Ni–Cu alloy was observed after ~ 1 min of a contact with the reaction medium. The resulting active particles were shown to catalyze the growth of carbon filaments. According to EDX data, the average content of copper in the composition of the active particles was estimated to be equal to its initial concentration in the alloy (~ 12 at.%).
The effect of thermal pretreatment on the porous structure and adsorption properties of asphalt-based carbons activated with potassium hydroxide was investigated by FTIR, Raman spectroscopy, TEM, N
2
...and CO
2
adsorption. Two series of the activated carbons were prepared by a one-stage method using KOH as the activating agent and a two-stage method including pretreatment of asphalt at 450 °C. A cross-effect of the KOH/asphalt ratio and pretreatment conditions on the characteristics of the porous structure of the activated carbons was revealed. The pretreatment of asphalt before activation is demonstrated to be a necessary stage for the effective control of the carbon porous structure by variation the KOH/asphalt ratio from 2 to 4. The porous carbon derived from petroleum asphalt exhibited the high CO
2
adsorption capacity of 3.8 mmol/g at 25 °C and 1 atm and good selectivity for CO
2
over N
2
, indicating possible applications in CO
2
capture technology.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The controllable synthesis of carbon nanofibers (CNF) and composites based on CNF (Metals/CNF) is of particular interest. In the present work, the samples of CNF were produced via ethylene ...decomposition over Co-Pt (0–100 at.% Pt) microdispersed alloys prepared by a reductive thermolysis of multicomponent precursors. XRD analysis showed that the crystal structure of alloys in the composition range of 5–35 at.% Pt corresponds to a fcc lattice based on cobalt (Fm-3m), while the CoPt (50 at.% Pt) and CoPt3 (75 at.% Pt) samples are intermetallics with the structure P4/mmm and Pm-3m, respectively. The microstructure of the alloys is represented by agglomerates of polycrystalline particles (50–150 nm) interconnected by the filaments. The impact of Pt content in the Co1−xPtx samples on their activity in CNF production was revealed. The interaction of alloys with ethylene is accompanied by the generation of active particles on which the growth of nanofibers occurs. Plane Co showed low productivity (~5.5 g/gcat), while Pt itself exhibited no activity at all. The addition of 15–25 at.% Pt to cobalt catalyst leads to an increase in activity by 3–5 times. The maximum yield of CNF reached 40 g/gcat for Co0.75Pt0.25 sample. The local composition of the active alloyed particles and the structural features of CNF were explored.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Structural features of bimetallic Pd−Zn catalysts supported on Sibunit carbon material were studied by EXAFS, TEM, XRD and XPS methods, depending on the heat treatment conditions in hydrogen. It was ...found that supported particles of PdZn intermetallic compound of tetragonal structure are formed in all samples. An increase in the duration of catalyst reduction in H2 at 500 °C from 1 to 20 hours leads to an increase in the amount of PdZn intermetallic particles (dav=2–3 nm), which is confirmed by the increasing of the Pd−Zn coordination number from 2.4 to 4.3 and by the decreasing of the surface Pd0/PdZn ratio from 0.63 to 0.18. The observed changes in the nature and structure of active sites provide an increase in the ethylene selectivity of Pd−Zn/C catalysts in liquid‐phase acetylene hydrogenation.
Liquid‐Phase Acetylene Hydrogenation: The duration of reductive treatment of bimetallic Pd−Zn/C catalysts in hydrogen is a reliable tool for controlling the formation of bimetallic sites in Pd−Zn‐samples supported on carbon material. Increasing the time of H2‐treatment from 1 to 20 hours leads to an increase in the ethylene selectivity of liquid‐phase acetylene hydrogenation.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Porous carbon–carbon composite materials (PCCCM) were synthesized by the alkaline dehydrochlorination of polyvinyl chloride solutions in dimethyl sulfoxide containing the modifying additives of a ...nanostructured component (NC): graphite oxide (GO), reduced graphite oxide (RGO) or nanoglobular carbon (NGC), with subsequent two-step thermal treatment of the obtained polyvinylene–NC composites (carbonization at 400 °C and carbon dioxide activation at 900 °C). The focus of the study was on the analysis and digital processing of transmission electron microscopy images to study local areas of carbon composite materials, as well as to determine the distances between graphene layers. TEM and low-temperature nitrogen adsorption studies revealed that the structure of the synthesized PCCCM can be considered as a porous carbon matrix in which either carbon nanoglobules (in the case of NGC) or carbon particles with the “crumpled sheet” morphology (in the case of GO or RGO used as the modifying additives) are distributed. Depending on the features of the introduced 5–7 wt.% nanostructured component, the fraction of mesopores was shown to vary from 11% to 46%, and SBET—from 791 to 1115 m2 g−1. The synthesis of PCCNC using graphite oxide and reduced graphite oxide as the modifying additives can be considered as a method for synthesizing a porous carbon material with the hierarchical structure containing both the micro- and meso/macropores. Such materials are widely applied and can serve as adsorbents, catalyst supports, elements of power storage systems, etc.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Changes in the structural and textural properties of NiAl-layered double hydroxides (LDHs) (with 2–4 molar ratios of metals) and state of nickel that occur in different steps of the synthesis of ...nickel catalysts were studied using XRD, thermal analysis, TPR, low-temperature nitrogen adsorption, XANES, EXAFS, and electron microscopy methods. Relations between nickel content, catalyst reduction conditions, state of nickel, and its catalytic properties were revealed. It was shown that the use of NiAl LDH as the catalyst precursor even at a high content of active metal allows for the obtaining of the dispersed particles of supported nickel that are active in the aqueous-phase hydrogenation of furfural. The catalyst activity and conversion of furfural were found to increase with elevation of the catalyst reduction temperature and the corresponding growth of the fraction of reduced nickel. However, a lower reduction temperature (500 °C) makes it possible to form smaller nickel particles with the size of 4–6 nm, and a high Ni content (Ni:Al = 4) can be used to obtain the active Ni@NiAlOx catalyst. Under mild reaction conditions (90 °C, 2.0 MPa), the furfural conversion reached 93%, and furfuryl alcohol was formed with the selectivity of 70%. Under more severe reaction conditions (150 °C, 3.0 MPa), complete conversion of furfural was achieved, and cyclopentanol and tetrahydrofurfuryl alcohol were the main hydrogenation products.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Novel bimetallic Pd-Co catalysts supported on the carbon material Sibunit were synthesized by an incipient wetness impregnation method and used for ethylene production by selective acetylene ...hydrogenation. It has been established that an increase in the Pd:Co molar ratio from 1:0 to 1:2 in 0.5%Pd-Co/C catalysts, treated in hydrogen at 500 °C, leads to an increase in the ethylene selectivity from 60 to 67% (T = 45 °C). The selectivity does not change with a further increase in the modifier concentration. The catalysts were investigated by TPR-H2, XRD, TEM HR, EDS, and XPS methods. It was shown that palladium and cobalt in the 0.5%Pd-Co/C samples form Pd(1−x)Cox phases of solid solutions with different compositions depending on the Pd:Co ratio. The cobalt concentration in the Pd-Co particles increases with an increase in the Pd:Co ratio up to 1:2 and then remains at a constant level. In addition, monometallic Co particles were present in the samples with the Pd:Co ratio higher then 1:2. The optimal combination of catalytic properties (the ethylene yield is 62–63%) is typical for catalysts with a Pd:Co molar ratio of 1:2–1:4. which is mainly due to the presence of bimetallic particles containing ~41–43% by at. of cobalt.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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•Pd-Ga/Al2O3 catalysts are promising in liquid-phase acetylene hydrogenation process.•Co-deposition of Pd(NO3)2 and Ga(NO3)3 prevents the γ-Ga2O3-Al2O3 phase formation.•Ga changes the ...electronic state of Pd at Pd:Ga = 1:0.5 and C2H4 selectivity is 66%.•Selectivity of C2H4 increases to 70% at Pd:Ga = 1:2 due to the Pd2Ga phase formation.•The catalyst treated in H2 at 500 °C has the highest ethylene selectivity of 75%.
The structural properties of Pd-Ga/γ-Al2O3 samples prepared from joint Pd(NO3)2 and Ga(NO3)3 solution and their catalytic properties in liquid-phase acetylene hydrogenation have been studied. Using temperature programmed reduction (TPR-H2), transmission electron microscopy (TEM), diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO (CO-DRIFTS) and X-ray photoelectron spectroscopy (XPS) it was found that an increase in the ethylene selectivity to ∼ 66–70% is explained by the modification of the electronic properties of palladium by gallium at a Ga:Pd molar ratio of 0.5 and by the formation of bimetallic Pd2Ga particles in the case of Ga:Pd = 2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Pd/C catalysts were doped with zinc, gallium and silver.•The catalysts were studied in the liquid-phase hydrogenation of acetylene to ethylene.•The Pd-Zn/C, Pd-Ga/C and Pd-Ag/C ...catalysts exhibit better activity and selectivity.•In the case of doped catalysts, an increased number of active sites were found.
The present work is devoted to the study of doping effects of zinc, gallium and silver on the structure of active sites and catalytic properties of carbon-supported 0.5 wt% Pd catalysts in the liquid-phase selective hydrogenation of acetylene to ethylene. Carbonaceous graphite-like material Sibunit was used as a support. The reaction was performed in a medium of N-methyl-2-pyrrolidone at 55 °C. It was shown that the bimetallic Pd-Zn/C, Pd-Ga/C and Pd-Ag/C catalysts exhibit better activity and selectivity towards target product if compare with the monometallic Pd/C catalyst. The ethylene yield increases in a row as follows: Pd/C (19%) < Pd-Ag/C (34%) < Pd-Ga/C (42%) < Pd-Zn/C (53%). Using X-ray absorption spectroscopy and transmission electron microscopy it was found that an improvement of the selectivity is stipulated by the formation of bimetallic PdZn, PdxGay and PdAg nanophases. In the case of Pd-Zn/C and Pd-Ag/C systems, an increased distance between neighboring Pd atoms (2.82–2.89 Å) in relation with monometallic Pd/C, where this distance is 2.72 Å, was observed. The higher activity of modified bimetallic systems is connected with increased number of active sites due to enhanced dispersity of supported palladium doped with second metal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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