scholarly journals Synthesis of Nanomaterials in a Coaxial Flame

2020 ◽  
Vol 22 (3) ◽  
pp. 177
Author(s):  
B.Т. Lesbayev
Keyword(s):  
Soot Formation ◽  
Experimental Studies ◽  
Oxygen Mixture ◽  
Stoichiometric Ratio ◽  
Optimum Temperature ◽  
Synthesis Conditions ◽  
Low Pressures ◽  
Oxygen Ratio ◽  
Synthesis Of Nanomaterials ◽  
Oxygen Flame

The paper presents the results of experimental studies of the synthesis of fullerenes C60 in a coaxial flame of benzene and acetylene at low pressures; of the synthesis of graphene in a coaxial flame of ethanol and propane, benzene, and acetylene; of the soot formation process in the coaxial flame of propane and ethanol. It has been established that the optimum temperature of a coaxial flame for the formation of fullerenes C60 is 970‒1000 °C with the carbon to oxygen ratio in the internal benzene-oxygen flame C/O ≈ 0.9 ÷ 1. The C/O ratio in an external acetylene-oxygen flame was maintained at a stoichiometric ratio. It was found that the preliminary (before feeding into the burner) treatment of the benzene-oxygen mixture using ultraviolet (UV) radiation with a wavelength of 254 nm promotes an increase in the yield of fullerenes. The synthesis conditions were optimized for: 5‒10 layers graphene in a coaxial flame of acetylene and ethanol; graphene containing more than 10 layers in a coaxial flame of propane and ethanol; one and two-layer graphene in a coaxial flame of ethanol and benzene. The possibility of a significant reduction of the formation of soot particles in the diffusion flame of propane by organizing its coaxial combustion with ethanol is shown.

scholarly journals Melting Point of Carbon Particles behind the Gas Detonation Front

2022 ◽  
Vol 16 (2) ◽  
pp. 59-70
Author(s):  
E. S. Prokhorov
Keyword(s):  
Melting Point ◽  
Detonation Front ◽  
Molar Fraction ◽  
Experimental Studies ◽  
Oxygen Mixture ◽  
Detonation Products ◽  
Gas Detonation ◽  
Nanoscale Particles ◽  
Carbon Particles ◽  
Carbon Condensate

A mathematical model of gas detonation of fuel-enriched mixtures of hydrocarbons with oxygen has been formulated, which makes it possible to numerically study the equilibrium flows of detonation products in the presence of free carbon condensation. Reference data for graphite were used to describe the thermodynamic properties of carbon condensate. The calculations are compared with the known results of experimental studies in which, when detonating an acetylene-oxygen mixture in a pipe closed at one end, it is possible to obtain nanoscale particles from a carbon material with special properties. It is assumed that the melting point of such a material is lower than that of graphite and is about 3100 K. Only with such an adjustment of the melting temperature, the best agreement (with an accuracy of about 3 %) was obtained between the calculated and experimental dependence of the detonation front velocity on the molar fraction of acetylene in the mixture.

Ammonia recovery from high strength agro industry effluents

2002 ◽  
Vol 45 (12) ◽  
pp. 189-196 ◽  
Author(s):  
M. Altinbas ◽  
I. Ozturk ◽  
A.F. Aydin
Keyword(s):  
Experimental Studies ◽  
Ammonium Phosphate ◽  
High Strength ◽  
Stoichiometric Ratio ◽  
Ammonia Content ◽  
Magnesium Ammonium Phosphate ◽  
Fenton’S Oxidation ◽  
Ammonia Recovery ◽  
Fenton's Oxidation ◽  
Opium Alkaloid

The aim of the study was to investigate ammonia recovery from high strength agro industry effluents involving significant amounts of ammonia, by applying magnesium ammonium phosphate (MAP) precipitation technology. Two types of industrial effluents have been tested in the study. The first plant was an opium alkaloid processing industry and the second one was a baker`s yeast industry. High chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and unacceptable dark brown color characterized effluents from both industries. Effluents from the biologically treated opium alkaloid and baker's yeast industries were both applied at the stoichiometric ratio (Mg:NH4:PO4 =1:1:1) and above the stoichiometric ratio (Mg:NH4:PO4 =1.1:1:1.1) to MAP precipitation. NH4 removals of 61-80% were achieved at the pH of 9.2 at the stoichiometric ratio, whereas 83% NH4 removal was obtained at the pH of 9.2 above the stoichiometric ratio. Experimental studies performed on both anaerobically and/or aerobically treated baker`s yeast and opium alkaloid industry effluents have clearly indicated that MAP precipitation was an appropriate treatment option for NH4 removal or struvite recovery from high ammonia content agro industry effluents. Additional ammonia recovery studies were conducted on ozonated and Fenton's oxidation applied effluents and these have also indicated that the amounts of struvite and the quality of MAP precipitate was increased significantly. In this framework, MAP sludge recovered from combined biological and Fenton's oxidation treatment effluents were considered as a more valuable slow release fertilizer for agricultural use.

scholarly journals Influence of different temperature regimes at torrefaction of chicken litter on yield and properties of products

2019 ◽  
Vol 114 ◽  
pp. 06007
Author(s):  
Olga Larina ◽  
Yana Pudova
Keyword(s):  
Chemical Composition ◽  
Thermogravimetric Analysis ◽  
Liquid Fraction ◽  
Experimental Studies ◽  
Calorific Value ◽  
Solid Residue ◽  
Optimum Temperature ◽  
Volume Yield ◽  
Temperature Regimes ◽  
Chicken Litter

The purpose of the research is study the influence of the torrefaction process on the fuel properties of the chicken litter. Experimental studies on lab-scale system at five temperature regimes of torrefaction (220, 240, 260, 280, and 300 °C) with a holding time determined using thermogravimetric analysis were conducted. The products of the torrefaction are solid residue, non-condensable gases, and tar. For the feedstock and torrefied material the elemental composition, the lower calorific value, hygroscopicity limit and bulk density are determined. For liquid fraction the analysis of the chemical composition is carried out. The properties of non-condensable gases as chemical composition and calorific value - are investigated. Mass yields of the solid residue and tar, and specific volume yield of the non-condensable gases are presented. The conclusion about the optimum temperature regime for torrefaction of chicken litter based on the results of experimental studies is made.

scholarly journals Influence of Varying Functionalization on the Peroxidase Activity of Nickel(II)–Pyridine Macrocycle Catalysts: Mechanistic Insights from Density Functional Theory

Computation ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 52
Author(s):  
Jerwin Jay E. Taping ◽  
Junie B. Billones ◽  
Voltaire G. Organo
Keyword(s):  
Density Functional Theory ◽  
Proton Transfer ◽  
Density Functional ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Catalytic Performance ◽  
Stoichiometric Ratio ◽  
Functional Theory ◽  
Pendant Arm ◽  
Spin Singlet

Nickel(II) complexes of mono-functionalized pyridine-tetraazamacrocycles (PyMACs) are a new class of catalysts that possess promising activity similar to biological peroxidases. Experimental studies with ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), substrate) and H2O2 (oxidant) proposed that hydrogen-bonding and proton-transfer reactions facilitated by their pendant arm were responsible for their catalytic activity. In this work, density functional theory calculations were performed to unravel the influence of pendant arm functionalization on the catalytic performance of Ni(II)–PyMACs. Generated frontier orbitals suggested that Ni(II)–PyMACs activate H2O2 by satisfying two requirements: (1) the deprotonation of H2O2 to form the highly nucleophilic HOO−, and (2) the generation of low-spin, singlet state Ni(II)–PyMACs to allow the binding of HOO−. COSMO solvation-based energies revealed that the O–O Ni(II)–hydroperoxo bond, regardless of pendant arm type, ruptures favorably via heterolysis to produce high-spin (S = 1) [(L)Ni3+–O·]2+ and HO−. Aqueous solvation was found crucial in the stabilization of charged species, thereby favoring the heterolytic process over homolytic. The redox reaction of [(L)Ni3+–O·]2+ with ABTS obeyed a 1:2 stoichiometric ratio, followed by proton transfer to produce the final intermediate. The regeneration of Ni(II)–PyMACs at the final step involved the liberation of HO−, which was highly favorable when protons were readily available or when the pKa of the pendant arm was low.

Effects of Synthesis Conditions on the Crystalline Phases and Photocatalytic Activities of Silver Vanadates via Hydrothermal Method

2009 ◽  
Vol 1171 ◽  
Author(s):  
Chao-Ming Huang ◽  
Guan T. Pan ◽  
Lung C. Chen ◽  
C.K. Thomas Yang ◽  
Wen S. Chang
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Surface Area ◽  
Synthesis Method ◽  
Stoichiometric Ratio ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
Synthesis Conditions ◽  
Vis Spectroscopy ◽  
Visible Light Driven

AbstractVisible-light-driven Ag3VO4 photocatalysts were successfully synthesized using low-temperature hydrothermal synthesis method. Under various hydrothermal conditions, the structures of silver vanadates were tuned by manipulating the hydrothermal time and the ratio of silver to vanadium. X-ray diffraction (XRD) results reveal that the powders prepared in a stoichiometric ratio consisted of pure α-Ag3VO4 or mixed phases of Ag4V2O7 and α-Ag3VO4. With increasing the Ag-to-V mole ratio to 6:1, the resulting samples were identified as pure monoclinic structure α-Ag3VO4. UV-vis spectroscopy indicated that silver vanadate particles had strong visible light absorption with associated band gaps in the range of 2.2-2.5 eV. The sample synthesized in the excess silver exhibited higher photocatalytic activity than that synthesized in a stoichiometric ratio. The powder synthesized at silver-rich at 140℃ for 4 h (SHT4) exhibited the highest photocatalytic activity among all samples. The reactivity of SHT4 (surface area, 3.52 m2 g-1) on the decomposition of gaseous benzene was about 16 times higher than that of P25 (surface area, 49.04 m2 g-1) under visible light irradiation. A well developed crystallinity of Ag3VO4 of SHT 4 was considered to enhance the photocatalytic efficiency.

The photolysis of ozone by ultraviolet radiation III. The photolysis of dry ozone/oxygen mixtures at low pressures in a flow system

1970 ◽  
Vol 316 (1526) ◽  
pp. 431-439 ◽  
Keyword(s):  
Quantum Yield ◽  
Atomic Oxygen ◽  
Flow System ◽  
Reaction Scheme ◽  
Oxygen Mixture ◽  
Quantum Yields ◽  
Ozone Decomposition ◽  
Partial Pressures ◽  
Low Pressures ◽  
Hypothetical Reaction

The photolysis at λ = 254 nm of dry ozone + oxygen mixtures (90, 50 and 10% O 3 ) has been studied for partial pressures of ozone between 5 x 10 -2 and 2 Torr. A flow technique was employed, and the extent of ozone decomposition was followed absorptiometrically. Over the pressure range investigated, the quantum yield was virtually independent of ozone pressure for any ozone + oxygen mixture, and increasing dilution of the mixture from 90 to 10% ozone only slightly reduced the observed quantum yield. All quantum yields were near 4. The results are interpreted in terms of the formation of singlet molecular and atomic oxygen in the primary photochemical step; kinetic analysis of a hypothetical reaction scheme predicts quantum yields consistent with those observed.

scholarly journals REGULARITIES OF BAYERITE-STRUCTURED ALUMINIUM HYDROXIDE FORMATION DURING PRECIPITATION

2021 ◽  
Vol 58 ◽  
pp. 11-16
Author(s):  
Ivan I. Torlopov ◽  
Keyword(s):  
High Purity ◽  
Aluminium Hydroxide ◽  
Aqueous Ammonia ◽  
Experimental Studies ◽  
Synthesis Temperature ◽  
Published Data ◽  
Particle Sizes ◽  
Large Particle Size ◽  
Preparation Technology ◽  
Synthesis Conditions

Based on published data and experimental studies of formation regularities of aluminium hydroxide, a reproducible technique for synthesis of bayerite-structured aluminium hydroxide by precipitation was developed as a part of the creation of preparation technology of chromia-alumina dehydrogenation catalyst. A possibility of synthesis of high purity bayerite (above 90 wt.%) with different particle sizes depending on synthesis conditions was shown. A correlation between dispersion of the sediments and synthesis temperature was shown, the optimal precipitation temperature – which allows obtaining bayerite with a sufficiently large particle size and high purity – was found. Based on the experiments, a fundamental difference between technologies and products of precipitation by sodium hydroxide and aqueous ammonia was shown. The influence of duration of precipitation stages on the properties of sediments is analyzed from the standpoint of theory of relative supersaturation

scholarly journals Influence of the drying regime on the quality indicators of dry mare’s milk

2021 ◽  
Vol 937 (2) ◽  
pp. 022099
Author(s):  
S Yu Smolentsev ◽  
L M Sufyanova ◽  
A S Makarov ◽  
N Yu Garafutdinova ◽  
O I Shorkina ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Quality Indicators ◽  
Experimental Studies ◽  
Quality Parameters ◽  
Optimum Temperature ◽  
Optimal Temperature ◽  
Drying Process ◽  
Milk Pasteurization ◽  
Drying Regime ◽  
Selection Of

Abstract The data on the influence of the temperature regime of the spray drying process on the quality parameters of dry mare’s milk are given. The results of experimental studies on the selection of the optimal drying mode for maximum preservation of the quality indicators of the final product are presented. It was revealed that the optimum temperature during the drying process of mare’s milk is the temperature at the entrance to the dryer t = 180°C, at the exit t = 70-80°C. The study of qualitative indicators with this drying mode showed that the particle size (more than 68%) was 117-140 microns, the solubility index was 0.18 ml of insoluble sediment in 50 ml of reconstituted mare’s milk, the moisture in dry mare’s milk was 3.8% (at t = 180°C), which met all the requirements of the standard. In addition, it was found that the correct heat treatment of mare’s milk before drying also affects the quality indicators of the dry product. The most optimal temperature for milk pasteurization is a temperature of no more than 60°C.

NUMERICAL MODELING OF DETONATION INITIATION IN MULTIFOCAL SYSTEMS USING UNSTRUCTURED COMPUTATIONAL MESHES

2020 ◽  
Author(s):  
A. I. Lopato ◽  
◽  
P. S. Utkin ◽  
Keyword(s):  
Numerical Modeling ◽  
Approximation Order ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Detonation Initiation ◽  
Oxygen Mixture ◽  
Two Dimensional ◽  
2D Euler Equations ◽  
End Wall ◽  
Low Pressures

The paper is devoted to the numerical modeling of detonation initiation in the “multifocused” system - the flat channel with the profiled end-wall. Mathematical model is based on two-dimensional (2D) Euler equations supplemented by the model of one-stage chemical kinetics for detonation of hydrogen-oxygen mixture at low pressures. The specific feature of the numerical algorithm of the second-approximation order is the use of fully unstructured computational meshes with the triangular cells. The mechanism of detonation initiation by the incident shock wave (SW) with the Mach number 2.58 in case of one elliptical reflector is described.

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