Composition Of Reaction Products Research Articles

ReaxFF molecular dynamics simulations of the initial pyrolysis mechanism of unsaturated triglyceride

To understand the impact of C = C double bonds in acyl chains of unsaturated triglycerides on the reaction mechanism and product composition in their initial pyrolysis process, ReaxFF molecular dynamics simulations were carried out using a molecular model, trilinolenin, at temperatures of 2000, 2250, and 2500 K. Analyses indicated that the observed pyrolysis mechanisms of unsaturated triglyceride are nearly identical to the saturated triglyceride, and the pyrolysis products also include alkanes, alkenes, alkadienes, aromatics, oxygenated species, CO₂, and H₂. The formation of intermediates and products is a sequential process. Three C--O bonds in trilinolenin molecule are usually successive dissociated first, leading to the formation of unsaturated C₃H₅· radical and straight-chain C₁₈H₂₉O₂· (RCOO·) radicals. Following that, the deoxygenated alkenyl chain is produced through decarboxylation of RCOO · radicals with consequent release of CO₂. The resulting hydrocarbon radicals undergo a variety of disproportionation, isomerization, and hydrogen-transfer reactions, yielding straight and branched-chain hydrocarbons. It was found that the scission of C--O bond and decarboxylation should preferentially occur before the cleavage of the C--C bond β to the C = C bond in the initial decomposition process of unsaturated trilinolenin. In addition, the formation of cyclic hydrocarbons could proceed through intramolecular cyclization mechanisms, including non-radical electrocyclic, biradical cyclization and cyclization of alkenyl radical, which are inconsistent with previously proposed bimolecular Diels-Alder addition mechanisms. More rapid pyrolysis of trilinolenin would occur at higher temperatures without significantly affecting the apparent reaction mechanisms of trilinolenin pyrolysis in the considered temperature range. Aromatic ring structures are observed to be stable after formation and do not decay within the 500 ps simulation period.

Enzymatic Production of Cocoa Butter Equivalents High in 1‐Palmitoyl‐2‐oleoyl‐3‐stearin in Continuous Packed Bed Reactors

AbstractThis study aimed to optimize the lipase‐catalyzed transesterification of high oleic sunflower oil (A) with a mixture of ethyl palmitate and ethyl stearate (B) to produce cocoa butter equivalents with a weight ratio of 1‐palmitoyl‐2‐oleoyl‐3‐stearoyl‐rac‐glycerol (POS) to total symmetric monounsaturated triacylglycerols (SMUT) that is similar to that of cocoa butter by response surface methodology. The reaction was performed in a continuous packed bed reactor, using 0.45 g of Lipozyme RM IM as the biocatalyst. The effects of temperature (Te), residence time (RT), substrate molar ratio (SR, B/A), and water content (WC) of the substrates on the composition of reaction products were elucidated using the models established. Optimal reaction conditions for maximizing total SMUT and POS contents while minimizing the levels of diacylglycerol formation and acyl migration were: Te, 60 °C; RT, 28.5 min; SR, 8.5; WC, 300 mg/kg. The contents of total SMUT, POS, and diacylglycerol in the reaction products and the content of palmitoyl and stearoyl residues at the sn‐2 position of triacylglycerols in the products were 52.0, 25.1, 9.4, and 4.8 %, respectively, under these conditions. Successful scale‐up of the reaction was achieved under the optimal conditions, using 5 g of the lipase. A silver‐ion high performance liquid chromatography analysis showed that the products obtained by the larger scale reaction contained 49.1 % total SMUT and 6.1 % of their positional isomers.

Coupling of resorcinols in retorted kukersite semi-coke

Coupling products of three major phenols appearing in the waste streams of shale oil production from kukersite oil shale were isolated and analysed using high-resolution mass spectrometry (HRMS). The pattern of water-soluble phenols in retorted kukersite semi-coke leachate changes quickly during weathering. The amount of phenols decreases, but the rate of disappearance is dissimilar for different constituents. Oxidation experiments with three major phenols (resorcinol, 5-methyl resorcinol, and 2,5-dimethylresorcinol) and their mixtures in pairs were performed in a reaction medium similar to semi-coke leachate. Reaction products were detected using silica gel thin layer chromatography (TLC) and isolated for further analysis by silica gel dry-column chromatography. The composition of primary reaction products was confirmed by nuclear magnetic resonance (NMR) spectroscopy. The primary coupling products of the studied resorcinols included the corresponding dimeric monoand diquinones. Further coupling brought about the formation of water-insoluble products, which is the reason for the disappearance of resorcinols from the leachate.

Experimental Investigation on Biogas Reforming for Syngas Production over an Alumina based Nickel Catalyst

Biogas is a green sustainable source of energy. Biogas mainly consists of combustible methane and non combustible carbon dioxide. Dry reforming reaction is of particular interest in the context of biogas as both main components of biogas (methane and carbon dioxide) are consumed to produce hydrogen rich syngas. Design and development of a fixed bed type reactor was carried out for reforming of biogas. The chemical equilibrium model was used for predicting the dry reforming reaction product composition followed by experimentation. In prediction of the product gas two ratios for biogas CH4: CO2=1:1 and CH4: CO2=1.5:1 were considered in the temperature range of 300 to 1000°C with the pressure at atmospheric. The catalyst γ -Al2O3 with 10% Ni was used for the dry reforming reaction. Experimentations were conducted with different Gas Hourly Space Velocity, temperature and biogas composition. Encouraging simulated and experimental results were obtained with the yield of almost 49% volume of H2 and 45% volume of CO with very low levels of CO2. Product syngas can be used in the engine for complete combustion and to fulfill the stringent emission norms. Syngas can be used as fuel in the fuel cell application for the remote integrated power generation system.

Magnetic characterization of synthetic titanomagnetites: Quantifying the recording fidelity of ideal synthetic analogs

A series of four synthetic basalts comprising titanomagnetite (Fe3‐xTixO4) grains of varied size and titanium content have been produced by a glass‐ceramic method. Complementary characterization techniques of X‐ray diffractometry, secondary electron microscopy, and transmission electron microscopy (TEM) demonstrate the reaction product composition consisted of mainly Fe3‐xTixO4, pyroxene hedenbergite, fayalite, and SiO2. The samples exhibit bimodal distributions of larger (<2 µm) and smaller Fe3‐xTixO4 particles (<50 nm in diameter), the latter found inside pyroxene crystals, as well as the sporadic occurance of dendritic Fe3‐xTixO4 structures. Magnetic measurements show their bulk characteristics fall into two groups: Ti‐rich titanomagnetite samples with varying Ti content; and near‐stoichiometric magnetite. The TEM technique of off‐axis electron holography allowed for visualization of the magnetic behavior of the synthetic Fe3‐xTixO4 grains. Energy dispersive X‐ray analysis and off‐axis electron holography confirmed the small Fe3‐xTixO4 grains (<50 nm) confined within glassy pyroxene regions to be Fe‐rich and single domain, carrying strong magnetic signals, compared to the relatively magnetically weak larger Fe3‐xTixO4 grains (x ∼ 0.6). The large grains in the pure magnetite sample are shown to be pseudo‐single domain in nature. The quenching process involved in synthesis is considered similar to that of pillow basalts found at mid‐ocean ridges and hence the reaction products are thought ideal in terms of characterization and understanding, for the purpose of studying natural systems.

Self-Propagating High-Temperature Synthesis of Silicon Carbide and Silicon Nitride Nanopowders Composition using Sodium Azide and Halides

<p>Regularities of self-propagating high-temperature synthesis (SHS) or combustion synthesis (CS) by using “silicon – sodium azide – ammonium hexafluorosilicate – carbon – aluminum” powder mixture in the nitrogen atmosphere were investigated. The thermodynamic analysis of the combustion synthesis was performed. Experimental investigation of the combustion process: the measurement of linear rates of the combustion front propagation and the maximum combustion temperatures was conducted in a laboratory reactor with working volume 4.5 liters. The influence of the components ratio in the initial mixture on the combustion temperature, combustion rate and composition of reaction product was studied. The phase composition of the product synthesized was determined with an X-ray diffractometer. It was disclosed that the SHS product consists of the composition (mixture) of silicon carbide nanopowder with silicon nitride whiskers and a final halide. Investigation of surface topography and morphology of the product particles was carried out with a scanning electron microscope. Optimal mixture for the synthesis of nanoscale composition based on silicon carbide was determined: “14Si+6NaN<sub>3</sub>+(NH<sub>4</sub>)<sub>2</sub>SiF<sub>6</sub>+15C+Al”. In this case, the SHS product consists of four phases: silicon carbide (β-SiC) – 48.57 wt.%, α-silicon nitride (<em>α</em>-Si<sub>3</sub>N<sub>4</sub>) – 27.04 wt.%, β-silicon nitride (β-Si<sub>3</sub>N<sub>4</sub>) – 5.83 wt.%, and sodium hexafluoroaluminate (Na<sub>3</sub>AlF<sub>6</sub>) – 18.56 wt.%. The average particle size of the composition was in the range of 70–130 nm. It was shown that the composition of the silicon carbide with silicon nitride and the final halide Na<sub>3</sub>AlF<sub>6</sub> playing a role a flux can be used as a modifier of castable aluminum alloys and as a reinforcing phase of aluminomatrix composites.</p>

Synthesis of Al4SiC4 powders from kaolin grog, aluminum and carbon black by carbothermal reaction

In this paper, the synthesis of Al4SiC4 used as natural oxide materials by carbothermal reduction was investigated in order to explore the synthesis route with low costs. The samples were calcined by using kaolin grog, aluminum and carbon black as raw materials with the selected proportion at the temperature from 1500 to 1800 ° C for 2 hours under flow argon atmosphere. The phase composition of reaction products were determined by X-ray diffraction. The microstructure and elemental composition of different phases were observed and identified by scanning electron microscopy and energy dispersive spectroscopy. The mechanism of reaction processing was discussed. The results show that Al4SiC4 powders composed of hexagonal plate-like particulates with various sizes and the thickness of less than 20 μm are obtained when the temperature reaches 1800 °C.

Conversion of Methane to Hydrogen in a Reversible Flow Reactor in the Process of Filtration Combustion of Fuel Mixtures Enriched with Oxygen

This paper considers the process of partial oxidation of methane to syngas in a reversible flow reactor in the process of filtration combustion of fuel mixtures enriched with oxygen in an inert porous medium. Experimental studies have been made of the influence of the volume concentration of oxygen in the initial fuel mixture on the basic parameters of the conversion process — the maximum temperature in the combustion wave and the composition of reaction products. Investigations have been carried out for fuel mixtures having different calorific values under the same filtration conditions. It has been shown that the addition of oxygen to the initial methane–air mixture permits increasing considerably the efficiency of the conversion process.

Thermo-chemical characterization of a Al nanoparticle and NiO nanowire composite modified by Cu powder

Thermo-chemical properties of the Al nanoparticle and NiO nanowire composites modified by the micro-sized copper additive were investigated experimentally. Their onset temperatures of ignition and energy release data per mass were characterized using differential thermal analysis measurements. These microstructures and chemical compositions of reaction products were analyzed using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The fuel-rich Al/NiO/Cu composites produced two types of metallic spheres. Copper spheres were formed from melting and solidification of the copper additive, while AlNi composite spheres were identified by the energy dispersive X-ray spectroscopy and X-ray diffraction analyses. It was found that the amount of the copper additive did not significantly influence the onset temperature of thermite peaks, but caused a dramatic change in energy release. The aforementioned ignition and energetic properties were compared with these from the Al nanoparticle and CuO nanowire composites.

Methane-to-hydrogen conversion in a reversible flow filtration combustion reactor at a high pressure

The noncatalytic process of partial oxidation of methane to syngas in a reversible flow filtration combustion reactor at high pressures has been considered. The influence of the operating pressure in the reactor on the main parameters of the conversion process — the maximum temperature in the combustion wave and the composition of reaction products — has been investigated experimentally. Investigations were carried out for fuel mixtures of different calorific powers at pressures of up to 6.0 bars. It has been shown that at a fixed value of the specific mass flow of the fuel mixture the efficiency of the process of methane-to-syngas conversion decreases with increasing pressure in the reactor.

Specific features of phase transfer catalytic glycosylation of aromatic hydroxy acids

The catalytic phase transfer reactions of per acetylated alpha-D-glucosaminyl chloride with isomeric hydroxybenzoic, 1-hydroxy-2-naphthoic acids in solid potassium carbonate--acetonitrile were studied. It was found that the composition and yields of reaction products are determined by the nature of the source ofcarboxylic acids, lipophilic phase transfer catalyst, temperature. For the first time found that the O-beta-glycosyl esters of ortho-hydroxyaromatic acids in the presence of potassium carbonate can anomerizovatsya in 1,2-cis derivatives. The structure of the synthesized compounds proved 1H NMR spectroscopy. In in vivo experiments it was established that glycosyl esters of salicylic acid and per acetylated 2-carboxy phenylglucosaminide exhibit analgesic activity similar to aspirin.

Plasma-Chemical Synthesis of Oxide Powders Using Transformer-Coupled Discharge

An experimental investigation of transformer-coupled discharge in an Ar-O2 mixture with the addition of SiCl4, TiCl4 and ZrCl4 has been carried out under the atmospheric pressure of plasma-forming gases. Discharge power and discharge heat losses have been determined, and the dispersion and phase composition of reaction products (oxide powders) has been analyzed with SEM and X-ray diffraction analysis. Investigations reveal the formation of ultrafine oxide powders in the case of vaporized chloride (SiCl4 and TiCl4) injecting into the transformer coupled discharge. In the case of fine powder (ZrCl4) injection, full oxidation was not observed and reaction products consisted of a mixture of ZrO2 and ZrOCl2. A conclusion has been made regarding the perspectives of using transformer-coupled discharge to produce ultrafine oxide powders.

Electrically induced chloride ion transport in alkali activated slag concretes and the influence of microstructure

Abstract Chloride ion transport in alkali silicate powder and liquid activated slag concretes, and the influence of the material microstructure are discussed. Increasing the Na2O-to-slag ratio (n) results in a reduction in the rapid chloride permeability (RCP) and non-steady state migration (NSSM) coefficients (Dnssm) of solid sodium silicate activated slag concretes. Increasing the SiO2-to-Na2O ratio (Ms) of the activator beneficially influences the transport parameters of liquid sodium silicate activated concretes. The chloride transport parameters are related to the reaction product microstructure and composition evaluated using mercury intrusion porosimetry (MIP) and Fourier Transform Infrared (FTIR) spectroscopy respectively. A reduction in the critical pore sizes reduces the transport coefficients to a larger extent than porosity reduction, which is responsible for the better performance of solid sodium silicate activated concretes. The total chloride concentration determined from the charge passed and the ionic transference numbers is used to predict an apparent non-steady state transport coefficient.

KRATTA, a versatile triple telescope array for charged reaction products

A new detection system KRATTA, Kraków Triple Telescope Array, is presented. This versatile, low threshold, broad energy range system has been built to measure the energy, emission angle, and isotopic composition of light charged reaction products. It consists of 38 independent modules which can be arranged in an arbitrary configuration. A single module, covering actively about 4.5msr of the solid angle at the optimal distance of 40cm from the target, consists of three identical, 500μm thick, large area photodiodes, used also for direct detection, and of two CsI(1500ppm Tl) crystals of 2.5 and 12.5cm length, respectively. All the signals are digitally processed. The lower identification threshold, due to the thickness of the first photodiode, has been reduced to about 2.5MeV for protons (∼65μm of Si equivalent) by applying a pulse shape analysis. The pulse shape analysis allowed also to decompose the complex signals from the middle photodiode into their ionization and scintillation components and to obtain a satisfactory isotopic resolution with a single readout channel. The upper energy limit for protons is about 260MeV. The whole setup is easily portable. It performed very well during the ASY-EOS experiment, conducted in May 2011 at GSI. The structure and performance of the array are described using the results of Au+Au collisions at 400MeV/nucleon obtained in this experiment.

Steam gasification of plant biomass using molten carbonate salts

This paper explores the use of molten alkali-carbonate salts as a reaction and heat transfer medium for steam gasification of plant biomass with the objectives of enhanced heat transfer, faster kinetics, and increased thermal capacitance compared to gasification in an inert gas. The intended application is a solar process in which concentrated solar radiation is the sole source of heat to drive the endothermic production of synthesis gas. The benefits of gasification in a molten ternary blend of lithium, potassium, and sodium carbonate salts is demonstrated for cellulose, switchgrass, a blend of perennial plants, and corn stover through measurements of reaction rate and product composition in an electrically heated reactor. The feedstocks are gasified with steam at 1200 K in argon and in the molten salt. The use of molten salt increases the total useful syngas production by up to 25%, and increases the reactivity index by as much as 490%. Secondary products, in the form of condensable tar, are reduced by 77%.

Catalytic hydrothermal gasification of algae for hydrogen production: Composition of reaction products and potential for nutrient recycling

Chlorella vulgaris, Spirulina platensis and Saccharina latissima were processed under supercritical water gasification conditions at 500°C, 36MPa in an Inconel batch reactor for 30min in the presence/absence of NaOH and/or Ni–Al2O3. Hydrogen gas yields were more than two times higher in the presence of NaOH than in its absence and tar yields were reduced by up to 71%. Saccharina, a carbohydrate-rich macro-alga, gave the highest hydrogen gas yields of 15.1mol/kg. The tars from all three algae contained aromatic compounds, including phenols, alkyl benzenes and polycyclic aromatic hydrocarbons as well as heterocyclic nitrogen compounds. Tars from Chlorella and Spirulina contained high yields of pyridines, pyrroles, indoles and pyrimidines. Up to 97% TOC removal were achieved in the process waters from the gasification of the algae. Analyses for specific nutrients in the process waters indicated that the process waters from Saccharina could potentially be used for microalgae cultivation.

Reactivity of a phosphonate layer grafted onto a surface of dispersed hydroxyapatite

The reactivity of a grafted layer contained on the surface of hydroxyapatite modified with diethyl butylphosphonate is studied. Modified hydroxyapatite is shown to interact with nucleophilic agents. The composition of reaction products depends on the nature of the latter.

Synthesis of Ultrafine Cr<sub>3</sub>C<sub>2</sub> Powders by Carbothermal Reduction of Precursors

Ultrafine Cr3C2 powders with globular-like particle of ~0.3-0.8 μm were synthesized by a new precursor method, namely carbothermal reduction of complex chromium oxide-carbon mixture, which was made initially from salt solution containing chromium and carbon elements by air drying and subsequent calcining at 400 °C for 1 h. Phase composition of reaction products was discussed by X-ray diffraction (XRD), and microstructure of the calcined powders and final products was studied by scanning electron microscopy (SEM). The results show that the synthesizing temperature of Cr3C2 powders was reduced greatly by the new precursor method. Thus, the preparation of ultrafine Cr3C2 powders is at only 1000 °C for 2 h. The lowering of synthesizing temperature is mainly due to the homogeneous chemical composition of the complex oxide-carbon mixture. There is a coarsening tendency of Cr3C2 powders with the increase of reaction temperature and time.

Influence of vacuum pressure on the vacuum pyrolysis of plant oil asphalt to pyrolytic biodiesel

Plant oil asphalt (POA) is a waste by-product in the biodiesel and fatty acid industry, especially in China. A novel vacuum pyrolysis method was developed obtaining diesel-like pyrolytic biodiesel from POA. This study was aimed at qualitatively analyzing components of POA and probing the influence of vacuum pressure on reaction selectivity, product composition and properties in POA vacuum pyrolysis. The POA was characterized by FT-IR, TGA, positive ion ESI FT-ICR MS, while the pyrolytic oil and pyrolytic biodiesel were analyzed by GC/MS. Pyrolytic biodiesel was tested for its properties such as density, viscosity, flash point, acid value, and cetane number according to the ASTM standard methods. At 400°C, the pyrolytic biodiesel obtained at vacuum pressure range of 20–60kPa achieved the ASTM standards of diesel fuel. An overall pathway of POA pyrolysis was proposed combining general pyrolysis changes and experimental data. The proposed POA components and their pyrolysis pathway reported are useful for the further study of POA utilization.

Alkaline solution/binder ratio as a determining factor in the alkaline activation of aluminosilicates

This study investigates the effect of the alkaline solution/binder (S/B) ratio on the composition and nanostructure of the reaction products generated in the alkaline activation of aluminosilicates. The experiments used two mixtures of fly ash and dehydroxylated white clay and for each of these, varying proportions of the solution components. The alkali activator was an 8M NaOH solution (with and without sodium silicate) used at three S/B ratios: 0.50, 0.75 and 1.25. The 29Si, 27Al MAS NMR and XRD characterisation of the reaction products reveal that for ratios nearest the value delivering suitable paste workability, the reaction-product composition and structure depend primarily on the nature and composition of the starting materials and the alkaline activator used. However, when an excess alkaline activator is present in the system, the reaction products tend to exhibit SiO2/Al2O3 ratios of approximately 1, irrespective of the composition of the starting binder or the alkaline activator.