Influence Of Synthesis Conditions Research Articles

Optimizing the synthesis of Ag/γ‐Al2O3 for selective reduction of NOx with C3H6: Experiments and modelling

AbstractAg/γ‐Al2O3 is an effective catalyst for the selective reduction of NOx (SCR) using propylene as a reducing agent. The catalyst performance is greatly influenced by the synthesis procedure. Various methods for synthesis of Ag/γ‐Al2O3 are analyzed, and their performance is examined via packed bed reactor experiments in this work. An optimal one‐pot synthesis method, single‐step sol–gel (SSG) synthesis, is explored systematically. The SSG‐synthesized catalyst shows better performance than those prepared via wet impregnation. The influence of synthesis conditions, specifically pH, on the textural and morphological properties of the SSG‐synthesized Ag/γ‐Al2O3, and therefore the activity for hydrocarbon‐based SCR in a packed‐bed reactor, are analyzed using experiments and simulations. The optimized catalyst demonstrates excellent performance (90% NOx conversion) for NOx reduction under nominal operating conditions with a wide activity temperature window (300–600°C). The catalyst shows good time‐on‐stream performance and is effective at higher inlet oxygen concentrations and space velocities. A global kinetic model, which uses synthesis‐pH‐dependent parameters, is proposed, and its ability to predict the activities of these catalysts is validated.

ДИЗАЙН НАНОЧАСТИЦ ОКСИДОВ ПЕРЕХОДНЫХ МЕТАЛЛОВ С КОНТРОЛИРУЕМОЙ РАЗМЕРНОСТЬЮ

The paper presents generalized experimental data on the influence of synthesis conditions on the structural features of MeO transition metal oxide nanoparticles in a polymer matrix synthesized by chemical condensation. The synthesis process includes the interaction of aqueous solutions of metal salts of varying concentrations with alkalis in the presence of an aqueous solution of the natural polysaccharide arabinogalactan. Controlled growth of oxide nanoparticles was achieved by encapsulation of emerging NPs in a polysaccharide matrix. The structural properties of the obtained samples were analyzed using X-ray diffraction, IR and UV spectroscopy, and TEM and SEM electron microscopy.

Broadband near-infrared luminescence properties of Sc2(MoO4)3:Cr3+ molybdates

The structural and spectroscopic properties of Sc2(MoO4)3 molybdate containing various concentrations of Cr3+ ions were investigated in a temperature range of 80–300 K. The samples were prepared using hydrothermal as well as solid-state reaction methods. The influence of synthesis conditions and the molybdenum source on the structural properties was studied by X-ray diffraction (XRD), IR (infrared), and Raman methods. The optical properties of Sc2(MoO4)3 samples doped with 0.1, 0.5, 1.0, and 2.0 % of Cr3+ ions were investigated. The broadband near-infrared (NIR) luminescence spectra generated from the 4T2 and 2E levels of Cr3+ ions may be attractive for NIR light-emitting diode (LED) applications. Emission decay profiles and the crystal field parameters of Cr3+ ions are discussed. In particular, the mechanism of photoluminescence generation and the thermal quenching path are described in detail.

Influence of synthesis conditions on the physicochemical and electrocatalytic properties of non-stoichiometric Ba2Sr2La2Ti4O12 perovskites

Present work studies the influence of the pretreatment milling media (deionized water (BLTOS-H) and isopropanol (BLTOS-i)) on the surface characteristics, structure, chemical composition and catalytic activity of non-stoichiometric Ba2Sr2La2Ti4O12 perovskites. The IR spectroscopy and XRD analyses shows a difference in the structure and phase composition of the two materials. X-ray photoelectron spectroscopy detects a Ba2+- and La3+-enriched and Sr2+-depleted surface. The BLTOS-i sample appears to exhibit higher specific surface area (SSA) and pore volume in comparison to BLTOS-H. The electrochemical tests showed that BLTOS-H sample have similar behavior to platinum at current densi-ties up to 10 mA cm-2, while BLTOS-i presented highest electrochemical performance among all tested samples over the entire current range.

Ga-Pt supported catalytically active liquid metal solutions (SCALMS) prepared by ultrasonication - influence of synthesis conditions on n-heptane dehydrogenation performance.

Supported catalytically active liquid metal solution (SCALMS) materials represent a recently developed class of heterogeneous catalysts, where the catalytic reaction takes place at the highly dynamic interface of supported liquid alloys. Ga nuggets were dispersed into nano-droplets in propan-2-ol using ultrasonication followed by the addition of Pt in a galvanic displacement reaction - either directly into the Ga/propan-2-ol dispersion (in situ) or consecutively onto the supported Ga droplets (ex situ). The in situ galvanic displacement reaction between Ga and Pt was studied in three different reaction media, namely propan-2-ol, water, and 20 vol% water containing propan-2-ol. TEM investigations reveal that the Ga-Pt reaction in propan-2-ol resulted in the formation of Pt aggregates on top of Ga nano-droplets. In the water/propan-2-ol mixture, the desired incorporation of Pt into the Ga matrix was achieved. The ex situ prepared Ga-Pt SCALMS were tested in n-heptane dehydrogenation. Ga-Pt SCALMS synthesized in pure alcoholic solution showed equal dehydrogenation and cracking activity. Ga-Pt SCALMS prepared in pure water, in contrast, showed mainly cracking activity due to oxidation of Ga droplets. The Ga-Pt SCALMS material prepared in water/propan-2-ol resulted in high activity, n-heptene selectivity of 63%, and only low cracking tendency. This can be attributed to the supported liquid Ga-Pt alloy where Pt atoms are present in the liquid Ga matrix at the highly dynamic catalytic interface.

Influence of Synthesis Conditions on the Structural, Optical, and Electrophysical Properties of TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O Nanocomposites

Nanocomposites based on anodic titanium oxide nanotubes with copper oxide nanoparticles were formed and their structural, optical, and electrophysical properties were studied. Defects in the structure of the samples were identified by electron paramagnetic resonance and it was shown that, as a result of copper oxide deposition, CuO nanoparticles were formed on the surface of nanotubes. It was found that the conductivity of the structure decreases by several orders of magnitude with an increase in the number of deposition cycles. It was shown that this effect could be associated with the formation of TiO2/CuO heterojunctions on the nanotube surface. It was shown for the first time that an increase in the content of copper oxide in TiO2/CuxO nanocomposites was accompanied by a decrease in conductivity and an increase in the number of defects. Keywords: titanium oxide, nanotubes, nanocomposites, copper oxide nanoparticles, defects, conductivity.

The influence of synthesis conditions, oligosaccharide additive and functional silane on the structure and composition of sol–gel silicas

The influence of synthesis conditions, oligosaccharide additive and functional silane on the structure and composition of sol–gel silicas

Green Synthesis of Nano-Zero Valence Iron with Green Tea and It's Implication in Lead Removal.

The nano-zero valence iron (nZVI) via green synthesis for heavy metal remediation has attracted many attentions due to its low-cost, environmental-safety, relative reproductivity, and high stability. However, influence of synthesis conditions on the physiochemical properties of nZVI via green tea extracts and the responding suspensibility, which is required for high reactivity, has not been fully elucidated. In this study, we investigated the zeta potentials, sedimentation and lead (Pb2+) removal capacity of various nZVIs synthesized using green tea extracts. The results showed that the tea extracts extracted at 80oC presented an excellent activity, which contributed to the outstanding suspensibility and reaction activity of nZVI synthesized in a volume ratio of 1:1 (tea extraction versus Fe2+ solution). Thus, the optimized nZVI was successfully prepared with a Pb2+ removal capacity (377.3mg/g), which was seven times stronger than 50.31mg/g of traditional chemical synthesized nZVI.

PHYSICO-CHEMICAL PROPERTIES OF MAGNETITES IN NANOCOMPOSITES ON THE TEXTILE BASES

The article is devoted to investigation of the physico-chemical properties of magnetites in nanocomposites on the textile bases. It studies of the structure and phase composition of nanocomposite materials on the polyamide and viscose textile bases. It is shown that magnetite particles synthesized in textile material with average sizes of 9.4 nm in viscose textile material and 9.7 nm in polyamide textile material. The influence of synthesis conditions on the size of magnetite nanocrystallites in textile material is established.

Influence of Synthesis Conditions on Physicochemical and Photocatalytic Properties of Ag Containing Nanomaterials

Silver (Ag) containing nanomaterials were successfully prepared by varying synthesis conditions to understand the influence of preparation conditions on the physicochemical and photocatalytic properties of these materials. Different analytical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), Diffuse reflectance UV-vis spectra (DR UV-vis), X-ray photoelectron spectroscopy (XPS) measurements, and N2-physisorption were used to investigate the physicochemical properties of synthesized Ag containing nanomaterials. The samples (Ag-1 and Ag-2) prepared using AgNO3, NaHCO3, and polyvinylpyrrolidone (PVP) template exhibited pure Ag metal nanorods and nanoparticles; the morphology of Ag metal is influenced by the hydrothermal treatment. The Ag-3 sample prepared without PVP template and calcined at 250 °C showed the presence of a pure Ag2O phase. However, the same sample dried at 50 °C (Ag-4) showed the presence of a pure Ag2CO3 phase. Interestingly, subjecting the sample to hydrothermal treatment (Ag-5) has not resulted in any change in crystal structure, but particle size was increased. All the synthesized Ag containing nanomaterials were used as photocatalysts for p-nitrophenol (p-NP) degradation under visible light irradiation. The Ag-4 sample (pure Ag2CO3 with small crystallite size) exhibited high photocatalytic activity (86% efficiency at pH 10, p-NP concentration of 16 mg L−1, 120 min and catalyst mass of 100 mg) compared to the other synthesized Ag containing nanomaterials. The high photocatalytic activity of the Ag-4 sample is possibly due to the presence of a pure Ag2CO3 crystal structure with nanorod morphology with a low band gap energy of 1.96 eV and relative high surface area.

The influence of synthesis conditions on the visible-light triggered photocatalytic activity of g-C3N4/TiO2 composites used in AOPs

Different synthesis temperatures (450–550 °C) were applied to synthesize g-C3N4 with the highest visible-light triggered photocatalytic activity. The best performing g-C3N4 photocatalyst was synthesized at 550 °C due to the created favourable structure that expressed the lowest band gap and charge carrier recombination rate. To further improve the photocatalytic activity of g-C3N4, different g-C3N4/TiO2 (gCN/TNP) composites with varying weight concentrations of g-C3N4 and TiO2 were prepared. Charge carrier separation was enabled due to the injection of photogenerated electrons from the g-C3N4 conduction band (CB) to the TiO2 CB, where they reacted with water-dissolved oxygen to form reactive oxygen species. The best performing composite was 0.50gCN/TNP 2 h with 50 wt% of g-C3N4 and 2 h calcination at 350 °C. The improved photocatalytic activity is due to an appropriate ratio between the shielding effect of TiO2, higher contact area and the consecutive improvement of the charge carrier separation, which is the key determining factor.

Influence of Synthesis Conditions on Gadolinium-Substituted Tricalcium Phosphate Ceramics and Its Physicochemical, Biological, and Antibacterial Properties.

Gadolinium-containing calcium phosphates are promising contrast agents for various bioimaging modalities. Gadolinium-substituted tricalcium phosphate (TCP) powders with 0.51 wt% of gadolinium (0.01Gd-TCP) and 5.06 wt% of (0.1Gd-TCP) were synthesized by two methods: precipitation from aqueous solutions of salts (1) (Gd-TCP-pc) and mechano-chemical activation (2) (Gd-TCP-ma). The phase composition of the product depends on the synthesis method. The product of synthesis (1) was composed of β-TCP (main phase, 96%), apatite/chlorapatite (2%), and calcium pyrophosphate (2%), after heat treatment at 900 °C. The product of synthesis (2) was represented by β-TCP (main phase, 73%), apatite/chlorapatite (20%), and calcium pyrophosphate (7%), after heat treatment at 900 °C. The substitution of Ca2+ ions by Gd3+ in both β-TCP (main phase) and apatite (admixture) phases was proved by the electron paramagnetic resonance technique. The thermal stability and specific surface area of the Gd-TCP powders synthesized by two methods were significantly different. The method of synthesis also influenced the size and morphology of the prepared Gd-TCP powders. In the case of synthesis route (1), powders with particle sizes of tens of nanometers were obtained, while in the case of synthesis (2), the particle size was hundreds of nanometers, as revealed by transmission electron microscopy. The Gd-TCP ceramics microstructure investigated by scanning electron microscopy was different depending on the synthesis route. In the case of (1), ceramics with grains of 1–50 μm, pore sizes of 1–10 µm, and a bending strength of about 30 MPa were obtained; in the case of (2), the ceramics grain size was 0.4–1.4 μm, the pore size was 2 µm, and a bending strength of about 39 MPa was prepared. The antimicrobial activity of powders was tested for four bacteria (S. aureus, E. coli, S. typhimurium, and E. faecalis) and one fungus (C. albicans), and there was roughly 30% of inhibition of the micro-organism’s growth. The metabolic activity of the NCTC L929 cell and viability of the human dental pulp stem cell study demonstrated the absence of toxic effects for all the prepared ceramic materials doped with Gd ions, with no difference for the synthesis route.

Utilization of modified polymeric composite supported crown ether for selective sorption and separation of various beta emitting radionuclides in simulated waste

Theoretically, crown ethers are expected to contribute to the formation of a host–guest composition with a polymer backbone and improve its disadvantages. Based on this hypothesis, preparation of the modified multi-functional polymeric composite was carried out by mini emulsion –irradiation of Poly Sodium styrene sulphonate (Acrylonitrile-Di amino benzo 18-crown-6) PSS (AN-DAB18C6) in the presence of N, N'-methylenediacrylamide (DAM) as a crosslinker and sodium styrene sulphonate as a-surfactant and high-share ultrasonic. The main role of the prepared adsorbent is to modify both the inert crown ether-based and shared monomer into more reactive forms. The influences of synthesis conditions, particularly filler concentration and radiation dose, were examined. The chemical modification reaction was carried out using hydroxylamine hydrochloride to get the amidoxime function group (AO) within the modification of the acrylonitrile (AN) system. The characterization of the composites by SEM, FTIR, and DLS confirmed that the modified polymeric composites exhibit good transformation. The sorption of La3+, Gd3+, Y3+ and Sr2+ ions in aqueous solution on PSS (AN-DAB18C6) and PSS (AO-DAB18C6) composite sorbents was investigated by the batch method. The results showed the higher selectivity of the PSS (AO-DAB18C6) composite towards La3+ and Y3+ions more than that of Gd3+ and Sr2+ions with the maximum sorption capacity of 63, 52, 25, and 24 mg/g, respectively. The experimental data fitted well to pseudo-second-order, elovich kinetic modeling and also fitted well to the Langmuir isotherms.

Фотолюминесценция сульфида цинка, легированного ионами Mn-=SUP=-2+-=/SUP=- и Eu-=SUP=-3+-=/SUP=- в среде додекана

Photoluminescence (PL) of zinc sulfide powder synthesized and doped with Mn2+ and Eu3+ ions by the method of emerging reagents in a dodecane medium was investigated. In the absorption and excitation spectra of the PL samples ZnS and ZnS:Mn2+(Eu3+), bands corresponding to the transitions of electrons from the valence band to the conduction band and to the levels of structural defects of ZnS, as well as bands of transition of 4f – electrons of Eu3+ ions from the ground 7F0 to excited electronic states were recorded. A wide band associated with recombination processes at the energy levels of defects on the surface of ZnS particles is observed in the PL spectra. Narrow bands of PL are attributed to 5D0→7Fj and 4T1→6A1 electronic transitions in Eu3+ and Mn2+ ions. They are associated with the intra-zone glow centers formed by these ions in the ZnS structure. Energy transfer from ZnS defect levels to excited energy levels of Eu3+ ions was registered. Assumptions are made about the mutual influence of ZnS and alloying ions, as well as about the influence of synthesis conditions on the spectral properties of substances.

Photoluminescence of zinc sulfide doped with Mn-=SUP=-2+-=/SUP=- and Eu-=SUP=-3+-=/SUP=- ions in dodecane medium

Photoluminescence (PL) of zinc sulfide powder synthesized and doped with Mn2+ and Eu3+ ions by the method of emerging reagents in a dodecane medium was investigated. In the absorption and excitation spectra of the PL samples ZnS and ZnS : Mn2+(Eu3+), bands corresponding to the transitions of electrons from the valence band to the conduction band and to the levels of structural defects of ZnS, as well as bands of transition of 4f-electrons of Eu3+ ions from the ground 7F0 to excited electronic states were recorded. A wide band associated with recombination processes at the energy levels of defects on the surface of ZnS particles is observed in the PL spectra. Narrow bands of PL are attributed to 5D0->7Fj and 4T1->6A1 electronic transitions in Eu3+ and Mn2+ ions. They are associated with the intra-zone glow centers formed by these ions in the ZnS structure. Energy transfer from ZnS defect levels to excited energy levels of Eu3+ ions was registered. Assumptions are made about the mutual influence of ZnS and alloying ions, as well as about the influence of synthesis conditions on the spectral properties of substances. Keywords: non-aqueous synthesis, dodecane, zinc sulfide, alloying, manganese (II) ions, europium (III) ions, photoluminescence.

Immobilizing metallocene by solid polymethylaluminoxane “sMAO” for slurry-phase ethylene-1-hexene copolymerization

In the field of olefin catalytic polymerization, metallocene catalysts show higher activity than traditional Ziegler-Natta catalysts. In this study, benzoic acid catalyzed the controlled hydrolysis of trimethylaluminum (TMA) to methylaluminoxane (MAO). After pyrolysis, an insoluble form of solid polymethylaluminoxane (sMAO) was synthesized. The influence of synthesis conditions on the particle size and morphy was systematically explored. The synthetic sMAO is used as a carrier to support the metallocene catalyst, and the catalyst is applied to the ethylene/1-hexene copolymerization. The experimental results show that the activity can be as high as 12149.8 gPEꞏ(gcat)-1 when the slurry reaction is catalyzed in a 5L kettle.

Influence of synthesis conditions on structural and spectroscopic properties of the K2SrP2O7 pyrophosphate doped with the Eu3+ and Eu2+ ions

This study is focused on the synthesis condition influence related to structural and spectroscopic properties of the potassium strontium pyrophosphate (K2SrP2O7) co-doped with Eu3+ and Eu2+ ions. The experimental parameters of the urea assisted combustion synthesis were optimized by temperature and time of calcination as well as reduction atmosphere composition. The obtained materials were structurally characterized using the X-Ray Powder Diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Spectroscopic properties were determined by emission spectra, excitation spectra, luminescence kinetics and luminescence temperature quenching measurements. It was found that increasing concentration of Eu3+ ions caused an increase of spectroscopic factors, which correspond to the relative integrated luminescence intensities of 5D0–7FJ transitions as well as structural defects. Moreover, the successful Eu2+ ion incorporation was proven by optical spectroscopic measurements, which showed the allowed f-d transitions.

Influence of synthesis conditions on molecular weight as well as mechanical and thermal properties of poly(hexamethylene 2,5-furanate)

Poly(hexamethylene 2,5-furanate) (PHF) was obtained by melt polycondensation. The process was carried out at temperatures of 230, 235 and 240 ° C. It has been shown that the selection of the optimal parameters of the synthesis process leads to the obtaining of biomaterials of high molecular weight, and thus better mechanical and thermal properties. The relationship between the molecular weight and the mobility of polymer chains, and consequently the temperature of phase changes and mechanical properties, was determined.

Influence of synthesis conditions on the preparation of mononuclear Dy(III) compounds based on β-diketone ligands: Synthesis, structure, magnetic behavior and theoretical analysis

Two mononuclear Dy(III) compounds, [Dy(fbta)3(HCOOH)2] (1) and [Dy(fbta)4]∙C5H6N (2) (fbta ​= ​3-(4-Fluorobenzoyl)-1,1,1-trifluoroacetone), were synthesized based on different pH control reagents including HCOOH and C5H5N. Dy(III) ions in compounds 1 and 2 belong to square antiprism (D4d) configurations with DyO8 coordination environments. Two coordinated carboxyl oxygen atoms of two different HCOOH molecules in 1 are replaced by two coordinated oxygen atoms of one β-diketone anion ligand in 2. One protonated C5H6N guest as a monovalent cation is found to reside in 2, resulting in charge balance. The different synthetic conditions have an important in determining the final structures and magnetic behaviors in 1 and 2. Compound 1 displays SMM behavior under zero dc field, while compound 2 shows neither peak nor frequency dependence at zero dc field. The efficient ON/OFF switching of SMM behavior was interpreted by the theoretical calculations of quantum tunneling of magnetization (QTM) time.

Correction to: Influence of Synthesis Conditions on Clinoptilolitic Zeolite Crystallization

Correction to: Influence of Synthesis Conditions on Clinoptilolitic Zeolite Crystallization