Kinetics of the Thermal Decomposition of Magnesium Salicylate Powder in Air

IntroductionThe chelate complexes of salicylic acid with rareearth and alkali earth ions have attracted considerableattention because of their special antibacterial proper-ties[1—3].The study of the thermal degradation of metalsalicylates is of major int…     

Synthesis of Diethyl Oxalate by a Coupling—Regeneration Reaction of Carbon Monoxide

This article describes a process for the synthesis of diethyl oxalate by a copling reaction of carbon monoxide,catalyzed by palladium in the presence of ethyl nitrite ,The kinetics and mechanism of the coupling and regeneration reaction are also discussed ,This paper presents the results of a scale-up test of the catalyst and the process based on an a priori computer simulation.     

Characterization of the Microstructure Changes of Polypropylene Induced by Pan—milling

1 INTRUDUCTION Mechanochemistry is an interdisciplinary science based on chemistry and mechanics, related to the changes of structure, properties of matters and the preparation of new materials induced by external mechanical actions, such as attrition, milling, grinding, pulverization, impact etc. Mechanochemical process, such as high-energy ball milling and mechanical alloying, has become a popular method to make nanocrystalline materials and find their wide applications to numerous clas…     

Kinetics and Mechanism of Dechlorination of o-Chlorophenol by Nanoscale Pd／Fe

IntroductionTherehasbeenagrowinginterestintheuseofzero valentironforthetreatmentofchlorinatedor ganiccompounds(COCs)inwaterandgroundwater .Thestudieshavebeenfocusedonsuchcompoundsascarbontetrachloride ,trichloroethene ,pesticidesandtherelatedcompounds[1— 7] .Whenironisincontactwithalessreductivemetalsuchaspalladiumwhosecomplexhasbeenusedtohydrogenatenitroben zene[8] ,themetalcouplecanformgalvaniccells .ThisledtothediscoveryofaPd/Febimetalliccomplexofwhichpalladiumservesasacatalystandironasa…     

Kinetic of Adsorption of Urea Nitrogen onto Chitosan Coated Dialdehyde Cellulose under Catalysis of Immobilized Urease

The adsorption of urea nitrogen onto chitosan coated dialdehyde cellulose (CDAC) under catalysis of immobilized urease in gelatin membrane (IE) was studied in batch system. The pseudo first-order and second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model.     

Kinetics of Oxidative Dehydrogenation of Propance over a VMgO Catalyst

The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550oC over a VMgO catalyst. Vanadium-magnesium-oxides are among the most selective and active catalysts for the dehydrogenation of propane to propylene. Selectivity to propylene up to about 60% was obtained at 10% conversion, but the selectivity decreased with increasing conversion. No oxygenates were detected, the only by-products were CO and CO2. The reaction rate of propane was found to be first order in propane and close to zero order in oxygen, which is in agreement with a Mars van Krevelen mechanism with the activation of the hydrocarbon as the rate determining step. The activation energy of the conversion of propane was found to be 122±6 kJ/mol.     

A New Formulation of the Lindemann Mechanism of Unimolecular Reactions

A new formulation of the Lindemann mechanism of unimolecular reactions in gaseous phase is presented, without the use of steady state hypothesis. It is hereby shown that the nature of applicability of steady state hypothesis in the regime of high reactant gas pressure is different from that in the regime of low gas pressure. In the former case it is an equilibrium approximation, while in the latter case it is a highly reactive intermediate approximation in no connection with a steady state. Furthermore for the latter case it is shown that in the classical formulation of Lindemann mecbRnism the use of steady state hypothesis is an ad hoc assumption. A highly reactive intermediate in the sense that its concentration is very small during the whole course of reaction is a necessary condition for the applicability of very reactive intermediate approximation. When the two distinctive nature of the applicability of steady state hypothesis is mlxed-up, wrong or useless conclusion may be arrived at. The only possible case of realizing a true steady state in a complex reaction is pointed out.     

The reaction of Tanshinones with Amines

The reaction of cryptotanshinone and tanshinone IIA with several biogenic amine metabolites involved in the pathogenic pathways of HE were investigated and eight 1,2,3,4-tetrahydrophenanthrene derivatives,2-6 and 8-10,were obtained.The probable mechanism on reaction was discussed.     

Kinetic simulation of oxidative coupling of methane over perovskite catalyst by genetic algorithm： Mechanistic aspects

The reaction kinetics of oxidative coupling of methane catalyzed by perovskite was studied in a fixed bed flow reactor. At atmospheric pressure, the reactions were carried out at 725, 750 and 775 ℃, inlet methane to oxygen ratios of 2 to 4.5 and gas hourly space velocity (GHSV) of 100 min-1. Correlation of the kinetic data has been performed with the proposed mechanisms. The selected equations have been regressed with experimental data accompanied by genetic algorithm (GA) in order to obtain optimized parameters. After investigation the Langmuir-Hinshelwood mechanism was selected as the best mechanism, and Arrhenius and adsorption parameters of this model were obtained by linear regression. In this research the Marquardt algorithm was also used and its results were compared with those of genetic algorithm. It should be noted that the Marquardt algorithm is sensitive to the selection of initial values and there is possibility to trap in a local minimum.     

Kinetics of the Action of Na2SeO3 on Bacillus subtilis Growth as Studied by Microcalorimetry

Microcalorimetric bioassay for acute cellular toxicity is based on metabolic heat production from cultured cells.The biological response to toxicants is the inhibition of the heat production rate in cells,and toxicity is expressed as the concentration of toxicant that is 50% effective in this inhibition(IC50).In this paper,the effect of Na2SeO3 on Bacillus subtilis growth was investigated at 37℃ by microcalorimetry.The relationship between growth rate constants(k) and concentration of Na2SeO3(c) shows a logarithmic normal distribution,and IC50 is 20.3μg/mL.All these thermokinetic information is readily obtained by an LKB 2277-204 heat conduction microcalorimeter.Microcalorimetry is a quantitative,inexpensive,and versatile method for toxicology research.     

Kinetics of Photocatalytic Degradation of Formic Acid over Silica Composite Films Based on Polyoxometalates

The composite films, XW11O39^n-/SiO2,(X refers to Si,Ge or P,respectively) were prepared by tetraethoxysilane (TEOS) hydrolysis sol-gel method via spin-coating technique. Formation of the composite films is due to strong chemical reaction of organic silanol group with the surface oxygen atoms of XW11O39^n-, resulted in the saturation of the surface of the lacunary polyoxometalates (POMs). Therefore,the coordination structural model of the films was proposed. As for the films, retention of the primary Keggin structure was confirmed by UV-vis, FT-IR spectra and MAS NMR. The surface morphology of the films was characterized by SEM, indicating that the film surface is relatively uniform, and the layer thickness is in the range of 250-350nm. Aqueous formic acid (FA) (0-20mmol/L) was degraded into CO2 and H2O by irradiating the films in the near-UV area. The results show that all the films have photocatalytic activities and the degradation reaction follows Langmuir-Hinshelwood first order kinetics.     

Kinetics of the First Order Autocatalytic Decomposition Reaction of Nitrocellulose （13.86% N）

The kinetics of the first order autocatalytic decomposition reaction of nitrocellulose (NC, 13.86% N) was studied by using DSC. The results show that the DSC curve for the initial 50% of conversion degree of NC can be de scribed by the first order autocatalytic equation dy/dt =-10^16.3 exp (-181860/RT)y-10^16.7ex(-173050/RT)y(1-y) and that for the latter 50% conversion degree of NC described by the reaction equations dy/dt=-10^16.4exp(-154820/RT)y (n=1) and dy/dt=-10^16.9 exp(-155270/RT) y^2.80(n≠1).     

Non-isothermal Kinetics of the First-stage Decomposition Reaction of Cobalt Oxalate Dihydrate

Solid state kinetics has been extensively studied by means of thermal analysis methods. The aim of the study is to determine the mechanism function f(α), the activation energy E and the pre-exponential factor A. In recent years there have been many methods ofprocessing thermal analysis kinetic data. In the present work,     

Kinetics of Phosphatase of Regenerating Liver-3 （PRL-3） Inhibition by Small-molecular Inhibitors

Introduction Proteintyrosinephosphatases(PTPs)playakey roleinsignaltransductionpathways,whichregulatethe growth,differentiationandmalignanttransformationof cells[1].PhosphataseofRegeneratingLiver3(PRL3)belongstoarecentlydiscoveredfamilyofproteinphos phata…     

Microkinetics of H2S Removal by Zinc Oxide in the Presence of Moist Gas Atmosphere

The microkinetics os H2S removeal by ZnO desulfurization in H2O-CO2-N2,H2O-CO-N2 and H2O-O2-N2 gas mixtures was studied by thermogravimetric andlysis.Experiments were carried out with 100-120 mesh ZnO powder at temperatures from 473K to 563K.The results show that the kinetic behaviors of desulfurization could all be described by an improved shrinking-core model.The activation energies of the reaction and the diffusion in different gas atmospheres were estimated.     

Fischer-Tropsch Reaction Kinetics of Cobalt Catalyst in Supercritical Phase

Fischer-Tropsch synthesis under supercritical phase condition was examined in a continuous and a high-pressure fixed bed reactor by employing a cobalt catalyst (Co-R.Ru/γ-Al2O3). An integral reactor model involving Fischer-Tropsch reaction kinetics in the supercritical fluid n-hexane was used to describe the overall performance. On the basis of Langmuir-Hinshelwood-Hougen-Watson (LHHW) model, the reaction rate constants were obtained for the rate equations of CO conversion to CH4 formation under supercritical conditions.     

Intrinsic Kinetics of Dimethyl Ether Synthesis from Syngas

The intrinsic kinetics of dimethyl ether (DME) synthesis from syngas over a methanol synthesis catalyst mixed with methanol dehydration catalyst has been investigated in a tubular integral reactor at 3-7MPa and 220-260℃. The three reactions including methanol synthesis from CO and H2, CO2 and H2, 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 model were obtained by using simplex method combined with genetic algorithm. The model is reliable according to statistical analysis and residual error analysis. The synergy effect of the reactions over the bifunctional catalyst was compared with the effect for methanol synthesis catalyst under the same conditions based on the model. The effects of syngas containing N2 on the reactions were also simulated.     

A New Kinetic Method of Processing TA Data

A new method of investigating the kinetic parameters and mechanism functions of a solid phase reaction is presented. This method is to analyze the data based on the use of these data at the same temperature and the same degree of conversion on a series of TA curves with different heating rates, so that the kinetic triplet--the activation energy E, the pre-exponential factor A and the analytical form of the function of conversionf(α) can be obtained. The main advantage of this method is that the values of E and f(α) are obtained respectively, and the determination of f(α) is not under the influence of the value of E and the calculation of the value of E is not influenced by thef(α) either.     

Kinetics of the Esterification Reaction Catalyzed by Lipase in W／O Microemulsions of Alkyl Polyglucoside

A novel kinetic mechanism of esterification reaction of 1-hexanoic acid with 1-butanol,catalyzed by lipase, was studied in water-in-oil microemulsions. The microemulsions were formed by alkyl polyglucoside C10G1.54/1-butanol/cyclohexane/phosphate buffer solution. The restult shows that when the ratio of mol concentration of 1-butanol to 1-hexanoic acid is about 3.0,the initial rate V0 get the maximum values. This phenomenon was explained by the modified fishlike phase diagrams.     

Kinetics and Mechanism of Oxidation of Lactic Acid by Dihydroxyditelluratoargentate（Ⅲ）in Alkaline Medium

The kinetics of the oxidation of lactic acid(Lac) by dihydroxyditelluratoargentate(Ⅲ）[abbreviated as DDA of Ag(Ⅲ）]anions was studied in an aqueous alkaline medium by conventional spectrophotometry in a temperature range of 25-40℃.The order of the redox reaction of lactic acid and DDA was found to be first-order.The rates increased with the increase in [OH^-]and decreased with the increase in [tellurate].No free radical was detected.In the view of this the dihydroxymonotelluratoargentate(Ⅲ）species(DMA) is assumed to be the active species.A plausible mechanism involving a two-electron transfer is proposed,and the rate equation derived from the mechanism can be used to explain all the experimenttal results.The activation parameters(25℃）and the rate constants of the rate-determining step along with the preequilibrium constants at different temperatures were evaluated.