Amount Of Reaction Research Articles

Chemical interactions between 1,2,4-trimethylbenzene and n-decane in doped counterflow gaseous diffusion flames

The chemical interaction of the two-components of a jet fuel surrogate, n-decane and 1,2,4-trimethylbenzene (TMB), was studied by adding several hundreds ppm of each chemical to two counterflow diffusion flames, one using methane and the other ethylene as baseline fuels. The objective was to look into evidence of synergistic effects due to the interaction of these reference fuels, that are representative of normal alkanes and aromatics, respectively, making up the bulk of practical fuels. The dopants were added in the same proportions as in the Aachen surrogate of jet fuel. The flames presented two distinct environments: the permanently blue methane flame and the incipiently sooting ethylene flame provide well defined temperature–time histories and chemical environments, with the one based on ethylene being relatively more oxygen-deficient. Profiles of critical pyrolysis products and of some stable soot precursors were determined from GC/MS analysis of gas samples extracted from the flames and compared with results from the OPPDIFF model using a lumped chemical mechanism. Mechanistically relevant synergies among the two fuel components are highlighted considering the production rate of aromatics in both flames when adding the two components either simultaneously or separately. The principal observation is that the combined addition of the two components causes an overproduction of methane in the ethylene flame, a decrease in the concentration of acetylene in the methane flame and an acceleration of the aromatic destruction/growth pathways. The model for the most part fails to capture the principal evidence of synergistic effects. Most of the other quantified species reveal no synergy, their concentration being the sum of the contributions of each component used individually, partly because of the small amounts of reactants that were added to the flames.

Synthesis and electrochemical performances of novel hierarchical flower-like nickel sulfide with tunable number of composed nanoplates

Novel hierarchical flower-like nickel sulfide assembled by nanoplates has been successfully synthesized via a template-free and one-step solvothermal method. The number of composed nanoplates can be tuned by adjusting the additive amounts of reactants. As comparative electrochemical performances are performed on, the sample with more nanoplates shows a higher specific capacitance and promising cycling stability. After 3000 cycles, a high specific capacitance of 778.8 F g−1 still maintains when the current density is 4 A g−1. These satisfactory electrochemical behaviours can be attributed to the hierarchical flower-like architecture, which supply more reactive sites for charge/discharge processes.

Electrochemical Characterization of Li1.07V0.83Fe0.1O2 ANODE Material for Li-ION Batteries

INTRODUCTION Recently a novel compounds based on layered LiV1-yMyO2 (M = Li, Fe, Cr) were found to be promising anode materials for Li-ion technology [1-3], as they exhibit long low-voltage plateau vs. metallic lithium, and higher volumetric capacity than commonly used graphite-based anode materials.This work presents synthesis and evaluation of electrochemical properties of Li1.07V0.83Fe0.1O2, in particular open circuit voltage (OCV) and XRD analysis at different discharge (lithium content) stages. EXPERIMENTAL Li1.07V0.83Fe0.1O2 was synthesized using a high-temperature solid-state reaction method with Li2CO3, V2O3 and Fe2O3 taken as substrates. Stoichiometric amounts of reactants were milled in a high efficiency mill. Obtained powder was pressed into pellets and sintered in two steps: 1) at 800 °C for 10 h in Ar and 2) at 1050 °C for 12 h in 5 vol.% of H2 in Ar, followed by quenching. Structural studies were performed in 10-110° range with CuKα radiation using Panalytical Empyrean diffractometer, followed by Rietveld refinement of identified structures.Electrical conductivity was measured using 4-probe AC technique in -60°C to 70°C temperature range.Electrochemical studies were done in Li/Li+/ Li1.07V0.83Fe0.1O2 cells constructed using CR2032-type containers. 1M solution of LiPF6in EC/DEC (in 1:1 ratio) was used as the electrolyte. For the positive electrode powder of active material was used (mass ≈ 50mg). OCV values were assumed as voltages of batteries after discharging to designated compositions followed by at least 24 h of relaxation. RESULTS AND DISCUSSION XRD analysis shown that the material is single phase and exhibits layered R-3m α-NaFeO2 type structure.Electrical conductivity values are almost two order of magnitude higher than for materials with no iron substitution.Discharge characteristics upon load shown step-like character, distinctly different than in Li1.07V0.93O2with shorter and right-shifted low voltage plateau. ACKNOWLEDGMENT This work was supported by NCN grant no. NCN 2011/02/A/ST5/00447. REFERENCES [1] A. R. Armstrong, C. Lyness, P. M. Panchmatia, M. S. Islam, P. G. Bruce, Nature Mater. 10(2011) 223-229[2] W.-T. Kim, Y. U. Jeong, H. C. Choi, Y. J. Lee, Y. J. Kim, J. H. Song, J. Power Sources 221(2013) 366-371.[3] X. Ma, G. Hautier, A. Jain, R. Doe, G. Ceder, J. Electrochem. Soc., 160 (2013) A279-A284.

How Mechanical and Chemical Features Affect the Green Synthesis of 1H-Pyrazoles in a Ball Mill

This work investigated the chemical and mechanical factors that affect cyclocondensation reactions in a ball mill. Chemical characteristics such as the use or non-use of a catalyst, amount of catalyst and reactants, and product formation, as well as the yield and mechanical factors such as rotation frequency and the number, diameter, and material of the milling balls were evaluated. It was found that a rotation frequency of 450 rpm is efficient for energy transfer to the reactants because the conversion is higher at this rotation. The reaction was highly dependent on the time (3 min) and amount of p-TSA (p-toluenesulfonic acid) utilized as catalyst (10 mol %). Five steel balls of 10 mm were considered to be the ideal number for the efficient mixing of the particles. For this work, the ideal conditions determined were used for the green synthesis of a series of 1H-pyrazoles.

Determination of acetylsalicylic acid in commercial tablets by SERS using silver nanoparticle-coated filter paper

In this work, filter paper was used as a low cost substrate for silver nanoparticles in order to perform the detection and quantification of acetylsalicylic acid by SERS in a commercial tablet. The reaction conditions were 150mM of ammonium hydroxide, 50mM of silver nitrate, 500mM of glucose, 12min of the reaction time, 45°C temperature, pretreatment with ammonium hydroxide and quantitative filter paper (1–2μm). The average size of silver nanoparticles deposited on the paper substrate was 180nm. Adsorption time of acetylsalicylic acid on the surface of the silver-coated filter paper was studied and an adsorption time of 80min was used to build the analytical curve. It was possible to obtain a calibration curve with good precision with a coefficient of determination of 0.933. The method proposed in this work was capable to quantify acetylsalicylic acid in commercial tablets, at low concentration levels, with relative error of 2.06% compared to the HPLC. The preparation of filter paper coated with silver nanoparticles using Tollen’s reagent presents several advantages such as low cost of synthesis, support and reagents; minimum amount of residuals, which are easily treated, despite the SERS spectroscopy presenting fast analysis, with low sample preparation and low amount of reactants as in HPLC analysis.

Energy-Efficient Novel Heterogeneous Gaseous T-Junction Microreactor Design Utilizing Inlet Flow Pulsation

The objective of the study is to investigate the effects of inlet flow pulsation on the mixing and reaction performance of a heterogeneous gaseous T-junction microreactor numerically. The idea is to have a novel modular microreactor design comprised of two microreactors (A and B), arranged in parallel, and a valve to control the flow direction. Flow pulsation can then be implemented to alternately supply reactant to microreactor A and microreactor B. Hence, by feeding the same amount of reactant and thus same pumping power/parasitic loads, the new design is able to run two microreactors and could achieve almost the same level of performance as that of a steady flow microreactor with an expense of one microreactor. The study was carried out for a case of mixing and heterogeneous catalytic reaction of methane (gaseous fuel) oxidation at the microreactor surface coated with a platinum catalyst. A detailed parametric study was performed to include the effect of frequency, amplitude, phase difference, and diff...

Determination of enzymatic reaction enthalpy by simultaneous calorimetry and spectrophotometry

A synchronized calorimetric and spectrophotometric method for measuring enzymatic reaction enthalpy was described. The spectrophotometric method was used to determine the amounts of reactant or product changes during the reaction, and calorimetry was used to determine the thermal changes associated with the reaction. Both methods used a same reaction system to simultaneously measure the progress of reaction. By the synchronized calorimetric–spectrophotometric determination, enthalpy values were obtained as 92.17 ± 3.06 kJ mol−1 by the initial velocity calculation method and 100.9 ± 1.81 kJ mol−1 by the steady-state calculation method for a catalase-catalyzed hydrogen peroxide reaction at 298.15 K and pH 7.0. When comparing with the theoretical values, the results showed that the synchronized method with the steady-state method was in alignment and demonstrated greater stability.

Preparation of ultrafine and nanosized MoSi2 particles by self-propagating high-temperature synthesis with a reduction step

We have developed technological principles of the preparation of ultrafine and nanosized MoSi2 particles by self-propagating high-temperature synthesis (SHS) with a reduction step. The effect of synthesis conditions (starting-mixture composition, relative amounts of reactants, and the presence and amount of an inert diluent) on the composition, structure, and particle size of the powders has been studied. The results demonstrate that inert additives reduce the adiabatic temperature. The crystallite size of MoSi2 decreases with increasing additive concentration. The MoSi2 powders obtained by SHS with a reduction step have the form of agglomerates consisting of spherical particles ranging widely in size: from large (several microns) to ultrafine and nanosized. The composition of the powders was checked by chemical analysis, microstructural examination, and X-ray diffraction.

Effects of hydrothermal conditions on the morphology and phase composition of synthesized TiO2 nanostructures

We investigate the effects of synthetic parameters on the morphologies during hydrothermal process and the crystal structural transitions from intermediate titanate to final TiO2 products by transmission electron microscopy (TEM) and X-ray diffraction (XRD). It reveals that hydrothermal duration, temperature and reactant amount play important roles in controlling the morphologies and crystal structures of titanate products. Anatase nanotubes, anatase nanorafts, TiO2–B nanoribbons, and anatse/TiO2–B nanoribbons were synthesized by modifying these synthetic parameters. We found that the crystal structures of intermediate titanate products influence on the transitions from titanate to TiO2. Our results show that anatase and TiO2–B derive from the orthorhombic and monoclinic titanate, respectively. We suggest that the crystallographic relationships between the intermediate products (hydrogen titanate) and the final TiO2 products play important roles in heat treatment.

Synthesis of novel chiral 1,4-dihydropyridinyl Schiff-base ligands, with characterization and evaluation of calcium channel blocker activity

Treatment of 2-formyl-1,4-dihydropyridines with primary diamines gave rise to different products depending on the molar ratio of reactants. In the case of stoichiometric amounts of substrate and reactant, only tricyclic cis-diastereoisomer was obtained in yields ranging from 53 % up to 54 %. In addition, reaction of the above carboxaldehyde with primary diamines in a molar ratio of 2/1 resulted in the formation of bis-iminoderivatives in high yields of 80–97 %. All these compounds were examined as ligands for synthesis of complexes with metal salts. Ultimately, the selected compounds, in enantiopure and racemic form, were tested for their effect on both basal and agonist (or vanadate)-induced 45Ca2+ influx.

Activation of Molecular Oxygen and the Nature of the Active Oxygen Species for CO Oxidation on Oxide Supported Au Catalysts

Although highly dispersed Au catalysts with Au nanoparticles (NPs) of a few nanometers in diameter are well-known for their high catalytic activity for several oxidation and reduction reactions already at rather low temperatures for almost 30 years, central aspects of the reaction mechanism are still unresolved. While most studies focused on the active site, the active Au species, and the effect of the support material, the most crucial step during oxidation reactions, the activation of molecular oxygen and the nature of the resulting active oxygen species (Oact), received more attention just recently. This is topic of this Account, which focuses on the formation, location, and nature of the Oact species present on metal oxide supported Au catalysts under typical reaction conditions, at room temperature and above. It is mainly based on quantitative temporal analysis of products (TAP) reactor measurements, which different from most spectroscopic techniques are able to detect and quantify these species even at the extremely low concentrations present under realistic reaction conditions. Different types of pulse experiments were performed, during which the highly dispersed, realistic powder catalysts are exposed to very low amounts of reactants, CO and/or O2, in order to form and reactively remove Oact species and gain information on their formation, nature, and the active site for Oact formation. Our investigations have shown that the active oxygen species for CO oxidation on Au/TiO2 for reaction at 80 °C and higher is a highly stable atomic species, which at 80 °C is formed only at the perimeter of the Au-oxide interface and whose reactive removal by CO is activated, but not its formation. From these findings, it is concluded that surface lattice oxygen represents the Oact species for the CO oxidation. Accordingly, the CO oxidation proceeds via a Au-assisted Mars-van Krevelen mechanism, during which surface lattice oxygen close to the Au NPs is removed by reaction with CO, resulting in a partially reduced TiO2 surface, which is subsequently reoxidized by O2. We demonstrate that this is the dominant reaction pathway for Au catalysts based on reducible metal oxides in general, at typical reaction temperatures, while for less active Au catalysts based on nonreducible metal oxides, this reaction pathway is not possible and the remaining activity must arise from another pathway, most probably a Au-only mechanism. At lower reaction temperature, reactive removal of Oact becomes increasingly inhibited, leading to a change in the dominant reaction pathway.

Heterogeneous Fenton Catalyst for the Efficient Removal of Azo Dyes in Water

Heterogeneous Fenton/photo Fenton type processes using a Fe-exchanged zeolite of Y-type have been applied for the degradation of a model textile synthetic water based on Black B azodye. Research work has been directed to compare process efficiency and to establish their advantages over corresponding homogenous Fenton type processes. By optimizing the amount of reactants and process conditions, a complete decolorization of the effluent and a reduction greater than 80 per cent in the total organic carbon content is achieved. The influence of solar radiation on the heterogeneous process has been also studied. Homogeneous and heterogeneous Fenton processes yielded similar decolorization and mineralization, but the concentration of Fe ions in the bulk after the treatment was not significant in the latter case. Moreover, the catalyst support can be reused in successive cycles without significant loss of effectiveness. The use of solar radiation as a source of energy for operating the process accelerates the decomposition of azodye, making the process economical and environmentally sustainable.

Multistep Flow Procedure for the Waste-Minimized Preparation of N-Boc-²-Amino Ketones

A clean and efficient protocol for the synthesis of a wide variety of N-Boc-s-amino ketones 3a-g has been defined using flow approach. The multistep procedure is based on the s-azidation of unsaturated ketones, consecutive reduction of the azido group, and concomitant amino group protection, and furnishes the desired products in good yields and very low E-factors ranging from 3.1 to 5.6. In batch conditions and by water as reaction medium, poorer yields and complicated reaction mixtures are obtained. Adoption of the flow approach, which combines transformations performed in solvent-free conditions and in EtOAc, has been essential in order to avoid side reactions, poisoning of the reduction catalyst, and use of minimal amount of reactants.

Synthesis of symmetrical and unsymmetrical subphthalocyanine dimers containing a hydroquinone bridge

Three novel hydroquinone-based symmetrically and unsymmetrically substituted subphthalocyanine (SubPc) dimers have been synthesized through the axial substitution of the macrocycle. The mono SubPc hydroquinone derivative (Hq-SubPc) first prepared acts as a nucleophile which replaces the chlorine atom of the second SubPc molecule to form the dimer. The dimers were obtained by reacting hydroquinone and the respective SubPcs in a 1:1 molar ratio in toluene at 180 °C in a pressure vessel. This new approach allowed stoichiometric quantities of reactants to be utilized. All dimers were characterized by 1 H NMR, 13 C NMR, UV-vis, fluorescence and mass spectral analysis.

Re-evaluation of Infiltration-driven Regional Metamorphism in Northern New England: New Transport Models with Solid Solution and Cross-layer Equilibration of Fluid Composition

The spatial distribution of reactants and products of infiltration-driven decarbonation reactions can be a record of the geometry and amount of reactive fluid flow during regional metamorphism. In the past, these distributions have been interpreted assuming (1) minerals are fixed in composition and (2) single layers are chemically isolated. Because neither assumption is normally valid, new transport models were developed that specifically predict the spatial distribution of reactants and products of the well-studied biotite-forming reaction in marls from northern New England. The models consider (1) isothermal and isobaric (iso-P–T) flow, (2) horizontal flow in the direction of increasing T (up-T flow), and (3) vertical, upward flow in the direction of decreasing P and T (down-P–T flow). All models assume a medium composed of many thin layers that differ in the amounts and compositions of mineral solid solutions prior to reaction, that fluid flow is parallel to layering, and that fluid composition is homogenized across layering over a distance much greater than layer thickness. All models reproduce (1) the amounts of mineral reactants and products at outcrops in Maine and Vermont where there are extensive data, and (2) regional-scale observations of mineral reactants only at low grades and a region several kilometers wide at higher grade where mineral reactants and products coexist. Models of up-T flow and down-P–T flow are preferred because they additionally predict spatially widespread complete reaction at the highest grades. Results show that when reactants and products are solid solutions, down-P–T flow predicted by simple hydrodynamic models of regional metamorphic fluid flow is fully consistent with observed widespread spatial distributions of mineral reactants and products in metamorphic terrains. Results further demonstrate that layer-scale variations in reaction progress are better explained in terms of layer-by-layer variations in initial mineral abundances and compositions coupled with homogenization of fluid composition across layers than by channelized fluid flow focused into layers with elevated reaction progress. All models predict minimum time-integrated fluid fluxes of ∼103 mol fluid cm−2 rock, ∼1–2 orders of magnitude less than what has been estimated assuming minerals are fixed in composition.

Optimization of SERS scattering by Ag-NPs-coated filter paper for quantification of nicotinamide in a cosmetic formulation

Supported silver nanoparticles on filter paper were synthesized using Tollens' reagent. Experimental designs were performed to obtain the highest SERS enhancement factor by study of the influence of the parameters: filter paper pretreatment, type of filter paper, reactants concentration, reaction time and temperature. To this end, fractional factorial and central composite designs were used in order to optimize the synthesis for quantification of nicotinamide in the presence of excipients in a commercial sample of cosmetic. The values achieved for the optimal condition were 150 mM of ammonium hydroxide, 50 mM of silver nitrate, 500 mM of glucose, 8 min for the reaction time, 45 °C temperature, pretreatment with ammonium hydroxide and quantitative filter paper (1-2 µm). Despite the variation of SERS intensity, it was possible to use an adapted method of internal standard to obtain a calibration curve with good precision. The coefficient of determination of the linear fit was 0.97. The method proposed in this work was capable of quantifying nicotinamide on a commercial cosmetic gel, at low concentration levels, with a relative error of 1.06% compared to the HPLC. SERS spectroscopy presents faster analyses than HPLC, also complex sample preparation and large amount of reactants are not necessary.

Pore diffusion model to predict the kinetics of heterogeneous catalytic esterification of acetic acid and methanol

A novel pore diffusion model in combination with a homogeneous reaction in the bulk solution is proposed to model the kinetic behavior of conversion of acetic acid during its esterification with methanol using ion exchange resin catalyst. The model parameters are determined based on the experimental data of a batch reactor with reactant quantities in stoichiometric ratio. Experimental kinetic data of conversion of acetic acid is obtained for various ranges of parameters such as catalyst loading in g/cc of reactant mixture volume, temperature in the range of 323.15–353.15K, average diameter of catalyst particle varied from 425μm to 925μm and RPM of magnetic stirrer. A multi time scale model is adopted in updating the conversion of acetic acid in the bulk liquid where the measurement is carried out. Since the homogeneous part of catalytic esterification is slow reaction, a large time step is used for updating bulk concentration or conversion, whereas a small time step is used to find the concentration distribution and inward flux of acetic acid inside the catalyst particle in a quasi steady state mode. This multi time scale approach leads to utilizing only the initial time kinetics of reaction for predicting two reaction constants namely kf1, the forward reaction rate constant for homogeneous reaction in bulk solution and kf2, the forward reaction rate constant for reaction inside the catalyst particle. The equilibrium conversion data provides the reaction equilibrium constant. The model predicts the overall kinetics of heterogeneous esterification reaction accurately.

New Efficient Ligand-Free, Copper Nanoparticle Catalyzed Coupling Reactions of Aryl Halides with Diethyl Malonate to Produce α-Arylation of Malonates

Recently synthesized copper nanoparticles (Cu NP) were used to catalyze coupling of aryl halides with diethyl malonates to produce α-aryl malonates. Synthetic conditions, including solvents, relative amounts of reactants, catalyst, and temperature, etc. have been varied to obtain optimum conditions for such reactions using Cu NP. Unlike well-known cases, the present protocol developed here, with Cu NP, leads to synthesis of a wide variety of products under not very extreme conditions.

Synthesis and Thermoelectric Properties of Compositional-Modulated Lead Telluride–Bismuth Telluride Nanowire Heterostructures

We demonstrate the rational solution-phase synthesis of compositional modulated telluride nanowire heterostructures containing lead telluride (PbTe) and bismuth telluride (Bi2Te3). By tuning the ratio between PbTe and Bi2Te3 through adjusting the amount of critical reactants and precursors during the synthesis, the influence of composition on the thermoelectric properties of the nanowire heterostructures has been investigated in hot pressed nanocomposite pellets. Measurements of the thermoelectric properties show strongly reduced thermal conductivity that leads to an enhanced thermoelectric figure of merit (ZT) of 1.2 at 620 K.

Modelling and simulation of an existing MSWI flue gas two-stage dry treatment

Power generation from municipal solid waste incineration (MSWI) is in widespread use as a technology for solid waste treatment and energy recovery. One of the main environmental issues posed by MSWI plants is the continuous emission of pollutants into the atmosphere. Among flue gas components, acid gases are of particular concern due to their high potential impact on the environment. The two-stage dry treatment is among the Best Available Technologies for an enhanced removal efficiency of acid gases. In the first stage the removal process is based on the reaction of acid gases with solid calcium hydroxide (slaked lime), while in the second stage removal is obtained by reaction with sodium bicarbonate. In the present study, design and process data from an existing Municipal Solid Waste Incinerator, where a flue gas two-stage treatment is adopted, were used to test a previously developed operational model. The model was implemented in a simulation software to describe both design and process conditions, taking also into account the recycle rate of solid products and unreacted calcium hydroxide in the first stage. Simulations were carried out with the aim of optimizing both reactant feed rates and amounts of solid wastes formed in the acid gas removal process.