Growth kinetics of titanium carbide coating by molten salt synthesis process on graphite sheet surface

The synthesis of carbide coatings on graphite substrates using molten salt synthesis(MSS),has garnered significant interest due to its cost-effective nature.This study investigates the reaction process and growth kinetics involved in MSS,shedding light on key aspects of the process.The involvement of Ti powder through liquid-phase mass transfer is revealed,where the diffusion distance and quantity of Ti powder play a crucial role in determining the reaction rate by influencing the C content gradient on both sides of the carbide.Furthermore,the growth kinetics of the carbide coating are predominantly governed by the diffusion behavior of C within the carbide layer,rather than the chemical reaction rate.To analyze the kinetics,the thickness of the carbide layer is measured with respect to heat treatment time and temperature,unveiling a parabolic relationship within the temperature range of 700-1300℃.The estimated activation energy for the reaction is determined to be 179283 J·mol^(-1).These findings offer valuable insights into the synthesis of carbide coatings via MSS,facilitating their optimization and enhancing our understanding of their growth mechanisms and properties for various applications.

Continuous synthesis of N,N-dicyanoethylaniline in microreactors:Reaction kinetics and process intensification

Cyanoethylation of phenylamine is one of the important steps for the production of dicyanoethyl-based disperse dyes.However,the exothermic nature of this reaction and the inherent instability of intermittent dynamic operation pose challenges in achieving both high safety and reaction efficiency.In this study,a continuous cyanoethylation of phenylamine for synthesizing N,N-dicyanoethylaniline in a microreactor system has been developed.By optimizing the reaction conditions,the reaction time was significantly reduced from over 2 h in batch operation to approximately 14 min in the microreactor,while high conversion and selectivity were maintained.Based on the reaction network constructed,the reaction kinetics was established,and the kinetic parameters were then determined.These findings provide valuable insights into a controllable cyanoethylation reaction,which would be helpful for the design of efficient processes and optimization of reactors.

Synthesis of NaY zeolite from a submolten depolymerized perlite:Alkalinity effect and crystallization kinetics

NaY zeolites are synthesized using submolten salt depolymerized natural perlite mineral as the main silica and alumina sources in a 0.94 L stirred crystallizer.Effects of alkalinity ranging from 0.38 to 0.55(n(Na_(2)O)/n(SiO_(2)))on the relative crystallinity,textural properties and crystallization kinetics were investigated.The results show that alkalinity exerts a nonmonotonic influence on the relative crystallinity and textural properties,which exhibit a maximum at the alkalinity of 0.43.The nucleation kinetics are studied by fitting the experimental data of relative crystallinity with the Gualtieri model.It is shown that the nucleation rate constant increases with increasing alkalinity,while the duration period of nucleation decreases with increasing alkalinity.For n(Na_(2)O)/n(SiO_(2))ratios ranging from 0.38 to 0.55,the as-synthesized NaY zeolites exhibit narrower crystal size distributions with the increase in alkalinity.The growth rates determined from the variations of average crystal size with time are 51.09,157.50,46.17 and 24.75 nm·h^(-1),respectively.It is found that the larger average crystal sizes at the alkalinity of 0.38 and 0.43 are attributed to the dominant role of crystal growth over nucleation.Furthermore,the combined action of prominent crystal growth and the longer duration periods of nucleation at the alkalinity of 0.38 and 0.43 results in broader crystal size distributions.The findings demonstrate that control of the properties of NaY zeolite and the crystallization kinetics can be achieved by conducting the crystallization process in an appropriate range of alkalinity of the reaction mixture.

Insights into kinetics and reaction mechanism of acid-catalyzed transesterification synthesis of diethyl oxalate

The catalytic performance of different acidic catalysts for diethyl oxalate synthesis from the one-step transesterification of dimethyl oxalate and ethanol was evaluated.The effects of different factors(e.g.,acidity,electron accepting capacity,cations type and crystalline water)on the catalytic activity of acidic catalysts were investigated respectively.It was proposed and confirmed that the transesterification reaction catalyzed by a Lewis acid(FeCl3)and a Bronsted acid(H2SO4)follows a first-order kinetic reaction process.In addition,the Lewis acid-catalyzed transesterification processes with different ester structures were used to further explore and understand the speculated reaction mechanism.This work enriches the theoretical understanding of acid-catalyzed transesterification reactions and is of great significance for the development of highly active catalysts for diethyl oxalate synthesis,diminishing the industrial production cost of diethyl oxalate,and developing downstream bulk or high-value-added industrial products.

Investigation on the Factors Influencing the Synthesis of Butyl Polyglycosides and Its Synthesis Kinetics

[ Objective ] The paper was to study the factors influencing the synthesis of butyl polyglycosides and its synthesis kineties. [ Method ] In the synthesis process of alkyl polyglycosides by transglyeosidation method, p-toluenesulfonie acid and stearie acid were used as composite catalyst, intermediate product butyl polyglycosides was prepared via reactive distillation technology. [ Result ] The suitable preparation conditian of butyl polyglyeasides was as follows： catalyst usage, 1.2 g（ p-toluenesulfoni ：stearie acid = 6：1 ） ; reaction temperature, 110 ℃ ; the ratio of butanol and glucose, 8： 1. The results showed that the larger the molar ratio of butanol and glucose was,the more the butyl monoside content was, and the less the polymerizatian degree of butyl glyeasides was. The catalyst usage and reaction temperature had little influence on the component of butyl polyglyeesides. With the increase of catalyst usage or reaction temperature,the reaction time was shortened dramatically. The kinetic equation for the synthesis of butyl glueeside was finally obtained as follows： -dCA/dt =0.163 7exp（ -1. 968×10^3/RT）CA -0.003 49 exp （ -2.727×10^3/RT） Ce. [ Conclusionl The suitable condition for the preparation of butyl polyglyeasides and its synthesis kinetic equation obtained in the study could provide theoretical basis for the synthesis of long-chain alkyl polyglyeasides.

Navigating the pathways:TAR-DNA-binding-protein-43 aggregation,axonal transport,and local synthesis in amyotrophic lateral sclerosis pathology

Neurons are highly polarized cells with axons reaching over a meter long in adult humans.To survive and maintain their proper function,neurons depend on specific mechanisms that regulate spatiotemporal signaling and metabolic events,which need to be carried out at the right place,time,and intensity.Such mechanisms include axonal transport,local synthesis,and liquid-liquid phase separations.Alterations and malfunctions in these processes are correlated to neurodegenerative diseases such as amyotrophic lateral sclerosis(ALS).

Apparent Kinetics for Electrosynthesis Process of Chromic Acid

A new green technique for producing chromic acid via an electrosynthesis method was studied.The kinetic experiments were carried out on the direct electrosynthesis reaction of chromic acid from sodium dichromate in a self-made electrosynthesis reactor with a multiple-unit metal oxides combination anode,a stainless steel cathode,and a reinforcing combination Nafion 324 cation exchange membrane.The apparent kinetic data were experimentally measured at different reaction time under different reaction conditions by relating many essential cell processes and their interaction,as well as their synergistic effect to the whole electrochemical synthesis process.The results show that the electrosynthesis reaction process follows a quasi-first-order reaction kinetic characteristic.The apparent kinetic model of the electrosynthesis reaction was established,and kinetic parameters were calculated.

Intrinsic Kinetics of Dimethyl Ether Synthesis from Syngas

The intrinsic kinetics of dimethyl ether (DME) synthesis from syngas over amethanol synthesis catalyst mixed with methanol dehydration catalyst has been investigated in atubular integral reactor at 3-7 MPa and 220-260℃. The three reactions including methanol synthesisfrom CO and H_2, CO_2 and H_2, and methanol dehydration were chosen as the independent reactions.The L-H kinetic model was presented for dimethyl ether synthesis and the parameters of the modelwere obtained by using simplex method combined with genetic algorithm. The model is reliableaccording to statistical analysis and residual error analysis. The synergy effect of the reactionsover the bifunctional catalyst was compared with the effect for methanol synthesis catalyst underthe same conditions based on the model. The effects of syngas containing Na on the reactions werealso simulated.

Kinetics of synthesis of Li_4Ti_5O_(12) through solid-solid reaction

Sohd-solid reaction under low heat or low temperature is an approach to synthesize various kinds of materials that were widely used in electrochemistry field. In this paper a theoretical treatment has been presented for analyzing the mechanism of sohd-solid reaction and deriving a series of formulae to describe the variation and rate of reactions. This new model has been used in the manufacturing of spinel Li4Ti5O12. The results show that this new model works very well and will play a useful role for guiding the manufacturing of electrochemical materials.

Kinetics of the water-gas shift reaction in Fischer-Tropsch synthesis over a nano-structured iron catalyst

Based on formate and direct oxidation mechanisms,three Langmuir-Hinshelwood-Hougen-Watson （LHHW） kinetic models of the water-gasshift （WGS） reaction over a nano-structured iron catalyst under Fischer-Tropsch synthesis （FTS） reaction conditions were derived and compared with those over the conventional catalyst.The conventional and nanostructured Fe/Cu/La/Si catalysts were prepared by co-precipitation of Fe and Cu nitrates in aqueous media and water-oil micro-emulsion,respectively.The WGS kinetic data were measured by experiments over a wide range of reaction conditions and comparisons were also made for various rate equations.WGS rate expressions based on the formate mechanism with the assumption that the formation of formate is rate determining step were found to be the best.

One-step hydrothermal synthesis of S-defect-controlled ZnIn_(2)S_(4) microflowers with improved kinetics process of charge-carriers for photocatalytic H_(2) evolution

Engineering lattice defects in two-dimensional(2 D) sulfide semiconductors has been accepted as an effective strategy to enhance the efficiency of the solar-to-fuels conversion.Although many researches have proven the lattice defect-mediated photocatalytic activity of ZnIn_(2)S_(4),the artificial control of Sdefects for optimizing the charge-carrier kinetics process in ZnIn_(2)S_(4) has long been a challenging task.Herein,we report a facile one-step method to modulate the lattice S-content of ZnIn_(2)S_(4) microflowers(MFs) only through adjusting the used amount of S-precursor in the hydrothermal solution that contains the metal precursors with a fixed Zn/In stoichiometric ratio at 1:2.We also demonstrated that the Svacancies at the In facets were the main type of lattice defects in the formed ZnIn_(2)S_(4) MFs,which could enhance both the separation and migration processes of the photoinduced charge-carriers due to the existence of discrete defect energy-levels(DELs) and the reduced effective mass of electrons,as evidenced by the first-principles calculations and the electron spectra analyses.The ZnIn_(2)S_(4) MFs with the optimal content of S-vacancy obtained by a hydrothermal treatment of the precursors with the Zn/In/S stoichiometric ratio of 1:2:8 possessed the long-lived photoinduced electron(~94.64 ns) for contributing to the photo-physical and-chemical processes.Thus,upon visible light irradiation,the H_(2)-evolution rate of this sample reached ~2.40 mmol h^(-1) g^(-1) with an apparent quantum efficiency of ~0.16% at 420 nm even though only using 5 mg of photocatalysts without any cocatalysts.

Kinetics studies of nano-structured iron catalyst in Fischer-Tropsch synthesis

Kinetic parameters of nano-structured iron catalyst in Fischer-Tropsch synthesis （FTS） were studied in a wide range of synthesis gas conversions and compared with conventional catalyst.The conventional Fe/Cu/La catalyst was prepared by co-precipitation of Fe and Cu nitrates in aqueous media and Fe/Cu/La nanostructure catalyst was prepared by co-precipitation in a water-in-oil micro-emulsion.Nano-structured iron catalyst shows higher FTS activity.Kinetic results indicated that in FTS rate expression,the rate constant （k） increased and adsorption parameter （b） decreased by decreasing the catalyst particle size from conventional to nano-structured.Since increasing in the rate constant and decreasing in the adsorption parameter affected the FTS rate in parallel direction,the particle size of catalyst showed complicated effects on kinetic parameters of FTS reaction.

Synthesis and Kinetics of Hydrogenated Rosin Dodecyl Ester as an Environmentally Friendly Plasticizer

The plasticizer is an important polymer material additive.Non-toxic and environmentally friendly plasticizers are developed recently in order to decrease fossil fuel reserves,serious environmental pollution and the toxicity of phthalate esters.In this study,a new,efficient and environmentally friendly plasticizer of hydrogenated rosin dodecyl ester was prepared by an esterification reaction of hydrogenated rosin and dodecanol.The influences of different reaction conditions(including different catalysts,the catalyst concentration,the ratio of the reactants,reaction temperature,and reaction time)on the esterification yield are examined and discussed.Hydrogenated rosin dodecyl ester with 71.8%yield was synthesized under the optimized reaction conditions(1:0.8 molar ratio of rosin to dodecanol,1 mol%tetrabutyl titanate concentration,and 210℃for 6 h).The esterification reaction is a second-order reaction,and kinetic calculations showed that the activation energy is 39.77 KJ·mol^(−1).The structure of the hydrogenated rosin dodecyl ester was confirmed by FT-IR spectroscopy and^(13)C NMR spectrum.Besides,the thermal stability of target product(hydrogenated rosin dodecyl ester)was also tested by thermal gravimetric analysis(TGA),which showed a good thermal stability.

Isothermal Kinetics Modelling of the Fischer-Tropsch Synthesis over the Spray-Dried Fe-Cu-K Catalyst

The isothermal kinetics of the Fischer-Tropsch synthesis （FTS） over Fe-Cu-K spray-dried catalyst was studied in a spinning basket reactor. The experiments were carried out at a constant temperature of 523 K, n（H2）/n（CO） feed ratios of 0.8 2.0, reactor pressures of 1.1 2.5 MPa, and space velocity of 0.556× 10^-3 Nm^3/kgcat·s. Kinetic model for hydrocarbon formation was derived on the basis of simplified carbide mechanism to reduce the number of parameters. Two individual rate constants for methane and ethene were considered. Furthermore, the model was modified empirically by non-intrinsic effect, such as physisorption and fictitious olefin pressures that were taken into account, and the influences of secondary reaction of α-olefins on product distribution. The simulation results showed that the experimental phenomena of FTS and the deviations from ASF distribution, such as the relatively high yield of methane and low yield of ethene observed experimentally could be depicted basically.

Synthesis and kinetics of 2,5-dicyanofuran in the presence of hydroxylamine ionic liquid salts

2,5-Dicyanofuran(DCF)is an important biomass-derived platform compound primarily used to prepare bio-based adiponitrile,which is the key precursor for the synthesis of nylon 66 and 1,6-hexanediisocyanate(HDI).In this study,one-pot,green and safe synthesis of DCF from 2,5-diformylfuran(DFF)and hydroxylamine ionic liquid salts was proposed.Eco-friendly hydroxylamine ionic liquid salts were used as the nitrogen source.Ionic liquid exhibited three-fold function of cosolvent,catalysis and phase separation.The conversion of DFF and yield of DCF reached 100%under the following optimum reaction conditions:temperature of 120℃ for 70 min,volume ratio of paraxylene:[HSO_(3)-b-Py]
HSO4 of 2:1,and molar ratio of DFF:(NH_(2)OH)_(2)
[HSO_(3)-b-Py]
HSO4 of 1:1.5.The reaction mechanism for the synthesis of DCF was proposed,and the kinetic model was established.The reaction order with respect to DFF and intermediate product 2,5-diformylfuran dioxime(DFFD)was 1.06 and 0.16,and the reaction activation energy was 64.07 kJ·mol^(-1) and 59.37 kJ·mol^(-1) respectively.After the reaction,the ionic liquid was easy to separate,recover and recycle.

Green synthesis of bentonite-supported iron nanoparticles as a heterogeneous Fenton-like catalyst:Kinetics of decolorization of reactive blue 238 dye

This study aimed to synthesize green tea nano zero-valent iron(GT-NZVI)and bentonite-supported green tea nano zero-valent iron(BGT-NZVI)nanoparticles using green tea extracts in an environmentally sustainable way.Bentonite was used as a support material because it disperses and stabilizes GT-NZVI,and it helps to reduce the cost,increase the adsorption capacity of GT-NZVI,and decrease the optimum amount of GT-NZVI used in Fenton-like oxidation.A scanning electron microscope,an atomic force microscope,and a Fourier transform infrared spectroscope were used to characterize GT-NZVI and B-GT-NZVI,while the zeta potential was measured to evaluate the stability of iron nanoparticles.The decolorization kinetics of reactive blue 238(RB 238)dye in the aqueous phase in the Fenton-like oxidation process were investigated as well.The effects of various experimental conditions such as reaction time,dosages of catalysts,concentration of H2O2,temperature,addition of inorganic salts,and other parameters were investigated.The results show that the oxidative degradation efficiencies of RB 238 dye catalyzed by GT-NZVI and B-GT-NZVI were 93.5%and 96.2%,respectively,at the optimum reaction conditions as follows:c(H2O2)¼5 mmol/L,r(GT-NZVI)¼0.5 g/L or r(B-GT-NZVI)¼0.5 g/L,c(RB 238 dye)¼0.05 mmol/L,and pH¼2.5 at 180 min.The best catalytic performance was exhibited when B-GT-NZVI was used.Three kinetic models were employed,and the second-order model was found to be the best model representing the experimental kinetic data of RB 238 dye.The value of activation energy decreased from 38.22 kJ/mol for GT-NZVI to 14.13 kJ/mol for B-GT-NZVI.This indicates that the effect of B-GT-NZVI in decreasing the energy barrier is more pronounced than that of the GT-NZVI catalyst,leading to improved Fenton-like oxidation processes.©2020 Hohai University.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Kinetics and product distribution studies on ruthenium-promoted cobalt/alumina Fischer-Tropsch synthesis catalyst

Hydrocarbon production rates and distributions on ruthenium promoted alumina supported cobalt Fischer-Tropsch synthesis （FTS） catalyst were studied by the concept of two superimposed Anderson-Schulz-Flory （ASF） distributions.The results indicated that the characterizing growth probabilities α1 and α2 were strongly dependent on reaction conditions.By increasing the H2 /CO partial pressure ratios and reaction temperatures,deviation from normal ASF distribution decreases and the double-α-ASF distribution changes into a straight line.Based on the concept of double-α-ASF distribution,a useful rate equation for the production of hydrocarbons under industrial reaction conditions is obtained.

FACILE HYDROTHERMAL SYNTHESIS AND GROWTH KINETICS OF Fe-BASED MAGNETIC NANOPARTICLES

The facile hydrothennal method was used to synthesize Fe3O4 nanoparticles with an average diameter of 1 1nm. The pure body-centered cubic （bcc）-Fe nanoparticles were prepared by reduction of Fe3O4 nanoparticles powder in H2 atmosphere. The structure, morphology and magnetic＇properties of the products were characterized by X-ray powder diffraction （XRD）, transmission electron microscopy （TEM）, thermogravimetric analysis-differential scanning calorimetry （TGA-DSC） and vibrating sample magnetometer （VSM）. The results showed that the as-prepared Fe3O4 nanoparticles had a relatively homogeneous size. The particle diameters became bigger with the increase of reaction time. The growth kinetics of the Fe3O4 nanoparticles was also briefly discussed. The products exhibited superparamagnetic properties at room temperature and the specific saturation magnetization was dependent on the particle sizes.

Reaction kinetics for synthesis of sec-butyl alcohol catalyzed by acid-functionalized ionic liquid

The acid-functionalized ionic liquid([HSO3Pmim]HSO4) was synthesized by a two-step method. Nuclear magnetic resonance(NMR) and Fourier transform infrared spectroscopy(FT-IR) show that the synthesis method is feasible and high purity of ionic liquid can be obtained. Using [HSO3Pmim]HSO4as the catalyst, we studied the reaction kinetics of synthesizing sec-butyl alcohol from sec-butyl acetate and methanol by transesterification in a high-pressure batch reactor. The effects of temperature, initial molar ratio of methanol to ester, and catalyst concentration on the conversion of sec-butyl acetate were studied. Based on its possible reaction mechanism, a homogeneous kinetic model was established. The results show that the reaction heat ΔH is 10.94 × 103J·mol-1, so the reaction is an endothermic reaction. The activation energies Ea+and Ea-are 60.38 × 103 and 49.44 × 103J·mol-1,respectively.

Kinetics of Synthesis of YAG Nanocrystals by Ultrasound and Ultrasound-Microwave-Assisted Methods

The Y3Al5O12 （YAG） nanocrystals were synthesized by ultrasound-assisted and ultrasound- microwave-assisted alkoxide hydrolysis precipitation methods. The structures and morphology of the YAG were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The synthesis kinetics of two kinds of YAG nanocrystals was investigated using differential thermal analysis and thermo gravimetric analysis （DTA-TG） at different heating rates in argon gas. The results show that two kinds of YAG precursors have one obvious endothermic peak at 315-600 K. The apparent activation energy of two kinds of YAG precursors was calculated using the Doyle-Ozawa and Kissinger methods, the coefficients of reaction order, frequency factor and kinetic equations were also determined. The average apparent activation energy for the YAG precursor prepared by ultrasound-microwave assisted was calculated to be 80.76 kJ.mol-1 higher than the YAG precursor prepared by ultrasound-assisted synthesis （56.56 kJ.mol-1）.