Study on trifluoromethanesulfonic acid-promoted synthesis of daidzein: Process optimization and reaction mechanism

Daidzein has been widely used in pharmaceuticals,nutraceuticals,cosmetics,feed additives,etc.Its preparation process and related reaction mechanism need to be further investigated.A cost-effective process for synthesizing daidzein was developed in this work.In this article,a two-step synthesis of daidzein(Friedel–Crafts acylation and[5+1]cyclization)was developed via the employment of trifluoromethanesulfonic acid(TfOH)as an effective promoting reagent.The effect of reaction conditions such as solvent,the amount of TfOH,reaction temperature,and reactant ratio on the conversion rate and the yield of the reaction,respectively,was systematically investigated,and daidzein was obtained in 74.0%isolated yield under optimal conditions.Due to the facilitating effect of TfOH,the Friedel–Crafts acylation was completed within 10 min at 90℃ and the[5+1]cyclization was completed within 180 min at 25℃.In addition,a possible reaction mechanism for this process was proposed.The results of the study may provide useful guidance for industrial production of daidzein on a large scale.

The reaction mechanism and interfacial crystallization of Al nanoparticle-embedded Ni under shock loading

The shock-induced reaction mechanism and characteristics of Ni/Al system,considering an Al nanoparticle-embedded Ni single crystal,are investigated through molecular dynamics simulation.For the shock melting of Al nanoparticle,interfacial crystallization and dissolution are the main characteristics.The reaction degree of Al particle first increases linearly and then logarithmically with time driven by rapid mechanical mixing and following dissolution.The reaction rate increases with the decrease of particle diameter,however,the reaction is seriously hindered by interfacial crystallization when the diameter is lower than 9 nm in our simulations.Meanwhile,we found a negative exponential growth in the fraction of crystallized Al atoms,and the crystallinity of B2-NiAl(up to 20%)is positively correlated with the specific surface area of Al particle.This can be attributed to the formation mechanism of B2-NiAl by structural evolution of finite mixing layer near the collapsed interface.For shock melting of both Al particle and Ni matrix,the liquid-liquid phase inter-diffusion is the main reaction mechanism that can be enhanced by the formation of internal jet.In addition,the enhanced diffusion is manifested in the logarithmic growth law of mean square displacement,which results in an almost constant reaction rate similar to the mechanical mixing process.

Study of the reaction mechanism for preparing powdered activated coke with SO_(2)adsorption capability via one-step rapid activation method under flue gas atmosphere

In this study,the impact of different reaction times on the preparation of powdered activated carbon(PAC)using a one-step rapid activation method under flue gas atmosphere is investigated,and the underlying reaction mechanism is summarized.Results indicate that the reaction process of this method can be divided into three stages:stage I is the rapid release of volatiles and the rapid consumption of O_(2),primarily occurring within a reaction time range of 0-0.5 s;stage II is mainly the continuous release and diffusion of volatiles,which is the carbonization and activation coupling reaction stage,and the carbonization process is the main in this stage.This stage mainly occurs at the reaction time range of 0.5 -2.0 s when SL-coal is used as material,and that is 0.5-3.0 s when JJ-coal is used as material;stage III is mainly the activation stage,during which activated components diffuse to both the surface and interior of particles.This stage mainly involves the reaction stage of CO_(2)and H2O(g)activation,and it mainly occurs at the reaction time range of 2.0-4.0 s when SL-coal is used as material,and that is 3.0-4.0 s when JJ-coal is used as material.Besides,the main function of the first two stages is to provide more diffusion channels and contact surfaces/activation sites for the diffusion and activation of the activated components in the third stage.Mastering the reaction mechanism would serve as a crucial reference and foundation for designing the structure,size of the reactor,and optimal positioning of the activator nozzle in PAC preparation.

Promotional roles of ZrO_2 and WO_3 in V_2O_5-WO_3/TiO_2-ZrO_2 catalysts for NO_x reduction by NH_3:Catalytic performance,morphology,and reaction mechanism

V2O5/TiO2-ZrO2 catalysts containing various amounts of WO3 were synthesized.The catalyst morphologies,catalytic performances,and reaction mechanisms in the selective catalytic reduction of NOx by NH3 were investigated using in situ diffuse-reflectance infrared Fourier-transform spectroscopy,temperature-programmed reduction（TPR）,X-ray diffraction,and the Brunauer-Emmett-Teller（BET） method.The BET surface area of the triple oxides increased with increasing ZrO2 doping but gradually decreased with increasing WO3 loading.Addition of sufficient WO3 helped to stabilize the pore structure and the combination of WO3 and ZrO2 improved dispersion of all the metal oxides.The mechanisms of reactions using V2O5-9%WO3/TiO2-ZrO2 and V2O5-9%WO3/TiO2were compared by using either a single or mixed gas feed and various pretreatments.The results suggest that both reactions followed the Eley-Ridel mechanism;however,the dominant acid sites,which depended on the addition of WO3 or ZrO2,determined the pathways for NOx reduction,and involved[NH4^＋-NO-Bronsted acid site]^＊ and[NH2-NO-Lewis acid site]^＊ intermediates,respectively.NH3-TPR and H2-TPR showed that the metal oxides in the catalysts were not reduced by NH3 and O2did not reoxidize the catalyst surfaces but participated in the formation of H2O and NO2.

Reaction mechanisms of low-grade molybdenum concentrate during calcification roasting process

The effects of Ca-based additives on roasting properties of low-grade molybdenum concentrate were studied. The resultsshow that calcium-based additives can react with molybdenum concentrate to form CaSO4 and CaMoO4. The initial oxidationtemperature of MoS2 is 450℃, while the formation of CaMoO4 and CaSO4 occurs above 500℃. The whole calcification reactionsare nearly completed between 600 and 650℃. However, raising the temperature further helps for the formation of CaMoO4 but isdisadvantageous to sulfur fixing rate and molybdenum retention rate. Calcification efficiency of Ca-based additives follows theorder： Ca（OH）2〉CaO〉CaCO3. With increasing the dosage of Ca（OH）2, the molybdenum retention rate and sulfur-fixing rate rise, butexcessive dosages would consume more acid during leaching process. The appropriate mass ratio of Ca（OH）2 to molybdenumconcentrate is 1：1. When roasted at 650 ℃ for 90 min, the molybdenum retention rate and the sulfur-fixing rate of low-grademolybdenum concentrate reach 100% and 92.92%, respectively, and the dissolution rate of molybdenum achieves 99.12% withcalcines being leached by sulphuric acid.

Reaction mechanism of preparation of titanium by electro-deoxidation in molten salt

The electro-deoxidation of TiO2 was investigated in molten CaCl2.Back electromotive force measurements,constant voltage electrolytic experiments,contrast experiments of different cathodes,and cyclic voltammograms were carried out for solving the puzzle of reduction mechanism.The results showed that the reduction process proceeded step by step.TiO2 was first reduced to Ti3O5 or Ti2O3,and then further reduced to Ti3O,Ti2O,TiO and Ti.In addition,direct electrochemical reduction of titanium dioxide was the primary cathodic reaction;meanwhile,some calciothermic reduction reactions also happened at the cathode.Cyclic voltammograms of solid titanium dioxide and molybdenum wire in molten salts with different compositions were also studied.

The pivotal effects of oxygen vacancy on Bi_2MoO_6:Promoted visible light photocatalytic activity and reaction mechanism

Bi2MoO6,a typical Bi-based photocatalyst,has received increasing interests and been widely applied in various fields.However,the visible light photocatalytic activity of Bi2MoO6 is still restricted by some obstacles,such as limited photo-response and low charge separation efficiency.In this work,we developed a facile method to introduce artificial oxygen vacancy into Bi2MoO6 microspheres,which could effectively address these problems and realize highly efficient visible light photocatalysis.The experimental and theoretical methods were combined to explore the effects of oxygen vacancy on the electronic structure,photocatalytic activity and the reaction mechanism toward NO removal.The results showed that the addition of NaBH4 during catalyst preparation induced the formation of oxygen vacancy in Bi2MoO6,which plays a significant role in extending the visible light absorption of Bi2MoO6.The visible light photocatalytic activity of Bi2MoO6 with oxygen vacancy was obviously enhanced with a NO removal ratio of 43.5%,in contrast to that of 25.0%with the pristine Bi2MoO6.This can be attributed to the oxygen vacancy that creates a defect energy level in the band gap of Bi2MoO6,thus facilitating the charge separation and transfer processes.Hence,more reactive radicals were generated and participated in the photocatalytic NO oxidation reaction.The in situ FT-IR was used to dynamically monitor the photocatalytic NO oxidation process.The reaction intermediates were observed and the adsorption-reaction mechanism was proposed.It was found that the reaction mechanism was unchanged by introducing the oxygen vacancy in Bi2MoO6.This work could provide new insights into the understanding of the oxygen vacancy in photocatalysis and gas-phase photocatalytic reaction mechanism.

Reaction Mechanism,Synthesis and Characterization of Urea-glyoxal(UG) Resin

The reaction mechanism of glyoxal （G） with urea （U） under weak acid condition was theoretically investigated at PW91/DNP/COSMO of quantum chemistry using density functional theory （DFT） method. The results show that the addition reaction of G with U under the conditions mainly involves the reactions of U with protonated glyoxal （p-G）, protonated 2,2-dihy- droxyacetaldehyde （p-G 1） and protonated bis-hemdiol （p-G2） to form two important carbocation reactive intermediates of C-p-UG and C-p-UG1, and two important hydroxyl compounds of UG and UG1. These compounds play important roles in the formation of UG resin. According to the result of quantum chemical calculation, UG resin was synthesized successfully under weak acid conditions. The UG resin was characterized by matrix assisted laser desorption ionization time of flight mass spectrometry （MALDI-TOF-MS）, ultraviolet and visible spectroscopy （UV-vis）, Fourier transform infrared spectroscopy （FT1R） and nuclear magnetic resonance spectroscopy （13CNMR and 1HNMR）. These instrumental analytical results agree with each other and further confirm the addition reaction pathway of glyoxal with urea proposed by quantum chemical calculation.

Theoretical Studies on Reaction Mechanisms of HNCS with NH(X^3Σ)

The reaction mechanisms of HNCS with NH（X^3∑ ） were theoretically investigated. The minimum energy paths （MEP） of the reaction were calculated by using the density functional theory（DFT） at the B3LYP/6-311 ＋ ＋ G^＊＊ level. The equilibrium structural parameters, the harmonic vibrational frequencies, the total energies, and the zeropoint energies（ZPE） of all the species were calculated. The single-point energies along the MEP were further refined at the QCISD（T）/6-311 ＋ ＋ G^＊ ＊ level. It was found that the mechanisms of the HNCS ＋ NH（X^3∑） reaction involve two channels producing the HNC ＋ HNS and the N2H2 ＋ CS products. Channel 1 plays a dominant role and the HNC ＋ HNS are the main preduets. The reaction is exothermie.

Study on Reaction Mechanism for Cracking FCC Gasoline on Acid Catalyst

This article is based on the experimental data on reaction of FCC naphtha in the presence of acid catalysts. The data published in the literature were reprocessed and compared with experimental data and the relationship of hydrogen and methane contained in the dry gas with the conversion rate was identified.The similarity between the route for cracking of olefin enriched FCC gasoline and the route for reaction of individual hydrocarbons was deduced, while the route for formation of ethylene in dry gas was also proposed to identify the relationship between the reaction path for formation of ethylene and the conversion rate.

SrTiO3/BiOI heterostructure: Interfacial charge separation, enhanced photocatalytic activity, and reaction mechanism

Heterostructured photocatalysts provide an effective way to achieve enhanced photocatalytic performances through efficient charge separation.Although both wide-and narrow-band-gap photocatalysts have been widely investigated,the charge separation and transfer mechanism at the contacting interface of the two has not been fully revealed.Here,a novel SrTiO3/BiOI(STB)heterostructured photocatalyst was successfully fabricated by using a facile method.The heterostructure in the photocatalyst extends the photoabsorption to the visible light range,and thus,high photocatalytic NO removal performance can be achieved under visible light irradiation.A combination of experimental and theoretical evidences indicated that the photogenerated electrons from the BiOI semiconductor can directly transfer to the SrTiO3 surface through a preformed electron delivery channel.Enhanced electron transfer was expected between the SrTiO3 and BiOI surfaces under light irradiation,and leads to efficient ROS generation and thus a high NO conversion rate.Moreover,in situ diffused reflectance infrared Fourier transform spectroscopy revealed that STB can better inhibit the accumulation of the toxic intermediate NO2 and catalyze the NO oxidation more effectively.This work presents a new insight into the mechanism of the interfacial charge separation in heterostructures and provides a simple strategy to promote the photocatalytic technology for efficient and safe air purification.

In situ reaction mechanism of MgAlON in Al–Al2O3–MgO composites at 1700°C under flowing N2

The Al–AlO–MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M, M, and M, respectively, were prepared at 1700°C for 5 h under a flowing Natmosphere using the reaction sintering method. After sintering, the Al–AlO–MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen Mwas composed of MgO and MgAlO. Compared with specimen M, specimens Mand Mpossessed MgAlON, and its production increased with increasing aluminum addition. Under an Natmosphere, MgO, AlO, and Al in the matrix of specimens Mand Mreacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al–AlO–MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an Natmosphere, the partial pressure of oxygen is quite low; thus, when the Al–AlO–MgO composites were soaked at 580°C for an extended period, aluminum metal was transformed into AlN. With increasing temperature, AlOdiffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with AlOto form MgAlO. When the temperature was greater than(1640 ± 10)°C, AlN diffused into AlOand formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and Mg AlOat high temperatures because of their similar spinel structures.

Reaction mechanism of roasting Zn_2SiO_4 using NaOH

The reaction kinetics of roasting zinc silicate using NaOH was investigated.The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows:molar ratio of NaOH to Zn2SiO4 of 16:1,reaction temperature of 550°C,and reaction time of 2.5 h.In order to ascertain the phases transformation and reaction processes of zinc oxide and silica,the XRD phase analysis was used to analyze the phases of these specimens roasted at different temperatures.The final phases of the specimen roasted at 600°C were Na2ZnO2,Na4SiO4,Na2ZnSiO4 and NaOH.The reaction kinetic equation of roasting was determined by the shrinking unreacted core model.Aiming to investigate the reaction mechanism,two control models of reaction rate were applied:chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the diffusion through the product layer model described the reaction process well.The apparent activation energy of the roasting was 19.77 kJ/mol.

Study on the Reaction Mechanism of Naphthalene with Oxalyl Chloride

The reaction of naphthalene with oxalyl chloride in the presence of anhydrous AlCl3 was investigated. The homolog of dinaphthyl methanone can be obtained mainly from this reaction. Naphthalene conversion does not have evident correlation with the amount of AlCl3. The results show that the reaction proceeds via carbon cation electrophilic substitution reaction-free radical substitution reaction pathway.

Microemulsion synthesis of ZnMn2O4/Mn3O4 sub-microrods for Li-ion batteries and their conversion reaction mechanism

The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.

Preparing low-oxygen Ti-6Al-4V alloy powder through direct reduction of oxides and its synergistic reaction mechanism

Ti-6Al-4V alloy powder was prepared through a two-step reduction of a mixture of TiO_(2),V_(2)O_(5) and Al_(2)O_(3) in this study.The oxide mixture was first reduced by Mg in MgCl_(2) at 750℃ in argon,where oxygen was reduced to 2.47 wt%from 40.02 wt%.The oxygen content in the final powder was eventually reduced to an extremely low level(0.055 wt%)using calcium at 900℃ in argon,and the final powder had the composition of 90.12 wt%Ti,5.57 wt%Al,and 3.87 wt%V,which meets the standard specification of Ti-6Al-4V(ASTM F1108-09).Between the two reductions,a heat treatment step was designed to help controlling the specific surface area and particle size.The effect of the heat treatment temperature on the morphology,and composition uniformity of the powder was investigated in detail.Heat treatment above 1300℃ attributed to a dense powder with a controlled specific surface area.Thermodynamic modeling and experimental results indicated that onlyα-Ti enriched with Al andβ-Ti enriched with V exist in the final powder,and other possible phases including Al-Mg and Al-V were excluded.This study also offers a triple-step thermochemical process for producing high-purity Ti-based alloy powder.

Reaction mechanism and kinetics of pressurized pyrolysis of Chinese oil shale in the presence of water

A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.

Preparation of Polystyrenylphosphonous Acid of Low Polymerization Degree and Influence of Initiators upon the Free Radical Reaction Mechanism

The polystyrenylphosphonous acid (PSPA) of low polymerization degree was prepared with one step reaction. The reaction mechanism was changed with different initiators. For the reaction with AIBN or BPO as the initiator, there are 2 or 3 series of radical reaction chains and 5 or 9 series of polystyrenyl products. The main products are PSPA without or with the fragment of the initiator H[CH(C6H5)-CH2]n-PO2H2 and C6H5CO2-[CH2CH (C6H5)]n-PO2H2 respectively.

Porous core–shell CoMn_2O_4 microspheres as anode of lithium ion battery with excellent performances and their conversion reaction mechanism investigated by XAFS

Porous core-shell CoMn204 microspheres of ca. 3-5μm in diameter were synthesized and served as an-ode of lithium ion battery. Results demonstrate that the as-synthesized CoMn204 materials exhibit excel-lent electrochemical properties. The CoMn204 anode can deliver a large capacity of 1070 mAh g-1 in thefirst discharge, a reversible capacity of 500 mAh g^-1 after 100 cycles with a coulombic efficiency of 98.5% at a charge-discharge current density of 200 mA g^-l, and a specific capacity of 385 mAh g^-1 at a muchhigher charge-discharge current density of 1600mA g^-1. Synchrotron X-ray absorption fine structure（XAFS） techniques were applied to investigate the conversion reaction mechanism of the CoMn204 anode.The X-ray absorption near edge structure （XANES） spectra revealed that, in the first discharge-charge cy-cle, Co and Mn in CoMn204 were reduced to metallic Co and Mn when the electrode was discharged to0.01 V, while they were oxidized respectively to CoO and MnO when the electrode was charged to 3.0V.Experiments of both XANE5 and extended X-ray absorption fine structure （EXAFS） revealed that neithervalence evolution nor phase transition of the porous core-shell CoMn204 microspheres could happen inthe discharge plateau from 0.8 to 0.6V, which demonstrates the formation of solid electrolyte interface（SEI） on the anode.

Theoretical Study of the AlCl Disproportionation Reaction Mechanism on the Al(100) Surface

The surface disproportionation reaction mechanism of aluminum subchloride on the aluminum （100） surfaces has been investigated by the plane-wave density functional theory （DFT）. Three kinds of possible reaction mechanism of AlCl disproportionation reaction on the aluminum （100） surfaces have been taken into account. The structures of reactants and products have been optimized, transition states have been confirmed and activation energies have been calculated. The adsorption energy of reactants and desorption energy of products have been determined. All of these have been employed to confirm the reaction mechanism and the rate determining step ofAlCl disproportionation reaction on the aluminum （100） surfaces.