Study on the catalytic degradation of sodium lignosulfonate to aromatic aldehydes over nano-CuO:Process optimization and reaction kinetics

As one of the few renewable aromatic resources,the research of depolymerization of lignin into highvalue chemicals has attracted extensive attention in recent years.Catalytic wet aerobic oxidation(CWAO)is an effective technology to convert lignin like sodium lignosulfonate(SL),a lignin derivative,into aromatic aldehydes such as vanillin and syringaldehyde.However,how to improve the yield of aromatic aldehyde and conversion efficiency is still a challenge,and many operating conditions that significantly affect the yield of these aromatic compounds have rarely been investigated systematically.In this work,we adopted the stirred tank reactor(STR)for the CWAO process with nano-CuO as catalyst to achieve the conversion of SL into vanillin and syringaldehyde.The effect of operating conditions including reaction time,oxygen partial pressure,reaction temperature,SL concentration,rotational speed,catalyst amount,and NaOH concentration on the yield of single phenolic compound was systematically investigated.The results revealed that all these operating conditions exhibit a significant effect on the aromatic aldehyde yield.Therefore,they should be regulated in an optimal value to obtain high yield of these aldehydes.More importantly,the reaction kinetics of the lignin oxidation was explored.This work could provide basic data for the optimization and design of industrial operation of lignin oxidation.

Copper Indium Sulfide Enables Li-CO_(2)Batteries with Boosted Reaction Kinetics and Cycling Stability

High energy density Li-CO_(2)batteries have attracted much attention owing to the"two birds with one stone"feature in fixing greenhouse gas CO_(2)and providing renewable energy.However,poor reversibility of the discharge product Li_(2)CO_(3)is one of the main problems that limit its application,resulting in poor cycling stability and severe polarization.Herein,copper indium sulfide(CIS),a semiconducting non-precious metal sulfide,is fabricated as cathode catalysts for high-performance Li-CO_(2)batteries.Combined with the synergistic effect of bimetallic valence bonding and coordinated electron transfer,Li-CO_(2)batteries using CIS cathodes exhibit high full specific discharge capacity,excellent rate capability and cycle stability,namely it delivers a high specific full discharge capacity of 8878μAh cm^(-2),runs steadily from 10 to 100μA cm^(-2),and performs a stable long-term cycling behavior(>1050 h)under a high energy efficiency of 84%and a low charge voltage of approximately 3.4 V at 20μA cm^(-2)within 100μAh cm^(-2).In addition,a flexible Li-CO_(2)pouch cell is constructed to reveal the potential of employing CIS to fabricate flexible high energy storage devices in practical applications.This work shows a promising development pathway toward next-generation sustainable energy storage devices.

Thermal Behavior,Nonisothermal Decomposition Reaction Kinetics of Mixed Ester Double-base Gun Propellants

The thermal decomposition behavior and nonisothermal reaction kinetics of the double-base gun propellants containing the mixed ester of triethyleneglycol dinitrate（TEGDN） and nitroglycerin（NG） were investigated by thermogravimetry（TG） and differential thermogravimetry（DTG）, and differential scanning calorimetry（DSC） under the high-pressure dynamic ambience. The results show that the thermal decomposition processes of the mixed nitric ester gun propellants have two mass-loss stages. Nitric ester evaporates and decomposes in the first stage, and nitrocellulose and centralite II（C2） decompose in the second stage. The mass loss, the DTG peak points, and the terminated temperatures of the two stages are changeable with the difference of the mass ratio of TEGDN to NG. There is only one obvious exothermic peak in the DSC curves under the different pressures. With the increase in the furnace pressure, the peak temperature decreases, and the decomposition heat increases. With the increase in the content of TEGDN, the decomposition heat decreases at 0.1 MPa and rises at high pressure. The variety of mass ratio of TEGDN to NG makes few effect on the exothermic peak temperatures in the DSC curves at different pressures. The kinetic equation of the main exothermal decomposition reaction of the gun propellant TG0601 was determined as： dα/dt=1021.59（1-α）3e-2.60×104/T. The reaction mechanism of the process can be classified as chemical reaction. The critical temperatures of the thermal explosion（Tbe and Tbp） obtained from the onset temperature（Te） and the peak temperature（Tp） are 456.46 and 473.40 K, respectively. ΔS≠, ΔH≠, and ΔG≠ of the decomposition reaction are 163.57 J·mol^-1·K^-1, 209.54 kJ·mol^-1, and 133.55 kJ·mol^-1, respectively.

Empirical correction of kinetic model for polymer thermal reaction process based on first order reaction kinetics

Based on the theory of first-order reaction kinetics,a thermal reaction kinetic model in integral form has been derive.To make the model more applicable,the effects of time and the conversion degree on the reaction rate parameters were considered.Two types of undetermined functions were used to compensate for the intrinsic variation of the reaction rate,and two types of correction methods are provided.The model was explained and verified using published experimental data of different polymer thermal reaction systems,and its effectiveness and wide adaptability were confirmed.For the given kinetic model,only one parameter needs to be determined.The proposed empirical model is expected to be used in the numerical simulation of polymer thermal reaction process.

Decomposition reaction kinetics of Baotou RE concentrate with concentrated sulfuric acid at low temperature

Baotou RE concentrate was decomposed with concentrated sulfuric acid by controlling the roasting temperature below 500℃.Thermogravimetry-differential thermal analysis（TG-DTA） and chemical analytical methods were used to study the thermal decomposition process and the thermal decomposition effect.The Freeman-Carroll method was applied to analyze the TG-DTA curves.The activation energy, reaction order, and reaction frequency factor at different stages were calculated.The Satava method was used to deduce the reaction mechanism and the relative reaction rate during the thermal decomposition process.

EFFECTIVE SOLUTION METHOD OF CHEMICAL REACTION KINETICS WITH DIFFUSE

The time integration method with four-order accuracy, self-starting and implicit for the diffuse chemical reaction kinetics equation or the transient instantaneous temperature filed equation was presented. The examples show that both accuracy and stability are better than Runge-Kutta method with four-order. The coefficients of the equation are stored with sparse matrix pattern, so an algorithm is presented which combines a compact storage scheme with reduced computation cost. The computation of the competitive and consecutive reaction in the rotating packed bed, taken as examples, shows that the method is effective.

Reaction Kinetics for Heterogeneous Oxidation of Mn(III) ～Toluene

The reaction kinetics of the heterogeneous oxidation of toluene with Mn 3+ was studied by considering the effects of disproportionation of Mn 3+ in reaction system, a 'parallel' modulus was set up. And then the concentration of Mn 3+ in disproportionation and the concentration of benzaldehyde in oxidation were respectively determined in turn, the rate constant, order and pseudo activation energy of the heterogeneous oxidation were obtained by mathematical deduction and the kinetic equation was concluded. In addition, the reaction mechanism was analyzed. It shows that the results are completely consistent with modulus.

Achieving high-performance sodium metal anodes: From structural design to reaction kinetic improvement

Sodium metal is one of the ideal anodes for high-performance rechargeable batteries because of its high specific capacity(~1166 mAh·g^(-1)),low reduction potential(-2.71 V compared to standard hydrogen electrodes),and low cost.However,the unstable solid electrolyte interphase,uncontrolled dendrite growth,and inevitable volume expansion hinder the practical application of sodium metal anodes.At present,many strategies have been developed to achieve stable sodium metal anodes.Here,we systematically summarize the latest strategies adopted in interface engineering,current collector design,and the emerging methods to improve the reaction kinetics of sodium deposition processes.First,the strategies of constructing protective layers are reviewed,including inorganic,organic,and mixed protective layers through electrolyte additives or pretreatments.Then,the classification of metal-based,carbon-based,and composite porous frames is discussed,including their function in reducing local deposition current density and the effect of introducing sodiophilic sites.Third,the recent progress of alloys,nanoparticles,and single atoms in improving Na deposition kinetics is systematically reviewed.Finally,the future research direction and the prospect of high-performance sodium metal batteries are proposed.

Fe-Ni-F electrocatalyst for enhancing reaction kinetics of water oxidation

Highly active and low-cost oxygen evolution reaction(OER)catalytic electrodes are extremely essential for exploration of green hydrogen via water splitting.Herein,an advanced Fe-Ni-F electrocatalyst is fabricated by a facile annealing strategy using ammonium fluoride,of which the structure feature is unveiled by XRD,FESEM,TEM,EDS,BET,and XPS measurements.The as-prepared Fe-Ni-F addresses a low overpotential of 277 mV and a small Tafel slope of 49 mV dec^(-1)at a current density of 10 mA cm^(-2),significantly outperforming other control samples as well as the state-of-the-art RuO_(2).The advanced nature of our Fe-Ni-F catalyst could also be further evidenced from the robust stability in KOH alkaline solution,showing as 5.41%degradation after 24 h continuous working.Upon analysis,it suggests that the decent catalytic activity should be attributed to the formed bimetallic(oxy)hydroxides because of the introduction of fluoride and the synergistic effect of iron and nickel towards oxygen generation.This work represents the potential of Fe-and/or Ni-based fluoride as efficient catalyst for low-energy consumption oxygen generation.

Mitigated reaction kinetics between lithium metal anodes and electrolytes by alloying lithium metal with low-content magnesium

Lithium(Li)metal is regarded as a promising anode candidate for high-energy-density rechargeable batteries.Nevertheless,Li metal is highly reactive against electrolytes,leading to rapid decay of active Li metal reservoir.Here,alloying Li metal with low-content magnesium(Mg)is proposed to mitigate the reaction kinetics between Li metal anodes and electrolytes.Mg atoms enter the lattice of Li atoms,forming solid solution due to the low amount(5 wt%)of Mg.Mg atoms mainly concentrate near the surface of Mg-alloyed Li metal anodes.The reactivity of Mg-alloyed Li metal is mitigated kinetically,which results from the electron transfer from Li to Mg atoms due to the electronegativity difference.Based on quantitative experimental analysis,the consumption rate of active Li and electrolytes is decreased by using Mgalloyed Li metal anodes,which increases the cycle life of Li metal batteries under demanding conditions.Further,a pouch cell(1.25 Ah)with Mg-alloyed Li metal anodes delivers an energy density of 340 Wh kg^(-1)and a cycle life of 100 cycles.This work inspires the strategy of modifying Li metal anodes to kinetically mitigate the side reactions with electrolytes.

Insight into pyrolysis of hydrophobic silica aerogels:Kinetics,reaction mechanism and effect on the aerogels

Silica aerogels have promising applications in thermal insulation,but their flammability and reaction mechanisms have rarely been investigated.The pyrolysis kinetics and thermodynamics of hydrophobic silica aerogels under N_(2) environment were studied.The kinetic and thermodynamic parameters were obtained by three model-free methods.Based on the calculated kinetic parameters,the pyrolysis mechanism of silica aerogels was discussed by the master plots method.The results indicate that the reactions of the whole pyrolysis phase can be characterized by a random nuclear model.In addition,FTIR test results show that the volatile products of silica aerogel pyrolysis are mainly hydrocarbons generated by the decomposition of hydrophobic groups(methyl groups)on the surface.Finally,the effects of pyrolysis on the properties of silica aerogels Finally,the effects of pyrolysis on the properties of silica aerogels were investigated based on the analysis results of SEM,specific surface area,pore size distribution,X-ray diffraction,XPS and infrared spectroscopy.

Kinetics of the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation

In this study,high-gravity intensified heterogeneous catalytic ozonation is utilized for treatment of phenol-containing wastewater,and the kinetics of the direct reaction between ozone and phenol in the presence of excess tertiary butanol(TBA)is investigated.It is revealed that the direct reaction between ozone and phenol in the rotating packed bed(RPB)follows the pseudo-first-order kinetics with a reaction rate constant higher than that in the conventional bubbling reactor(BR).Under different conditions of temperature,initial pH,high-gravity factor,and gaseous ozone concentration,the apparent reaction rate constant varies in the range of 0.0160–0.115 min-1.An empirical power-exponential model is established to characterize the effects of these parameters on the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation.

Effect of montmorillonite on kinetics of polyurethane preparation reaction

The prepolymerization and curing reaction kinetics of polyurethane/montmorillonite have been studied with end group analysis and FTIR respectively. It was found that the prepolymerization and curing reaction followed the 2nd-order kinetics. But the activation energy of prepolymerization increased from 42.7 kJ/mol to 56.5 kJ/rnol after the montmorillonite was added in the reaction system, and activation energy of curing reaction decreased from 64.4 kJ/mol to 17.5 kJ/mol. 2007 Bing Liao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Sulfite as the substrate of C-sulfonate metabolism ofα,β-unsaturated carbonyl containing andrographolide:analysis of sulfite in rats'intestinal tract and the reaction kinetics of andrographolide with sulfite

One-sixth of the currently known natural products containα,β-unsaturated carbonyl groups.Our previous studies reported a rare C-sulfonate metabolic pathway.Sulfonate groups were linked to theβ-carbon ofα,β-unsaturated carbonyl-based natural compounds through this pathway.However,the mechanism of this type of metabolism is still not fully understood,especially whether it is formed through enzyme-mediated biotransformation or direct sulfite addition.In this work,the enzyme-mediated and non-enzymatic pathways were studied.First,the sulfite content in rat intestine was determined by LC-MS/MS.The results showed that the amount of sulfite in rat intestinal contents was from 41.5 to 383μg·g^(-1),whereas the amount of sulfite in rat feed was lower than the lower limit of quantitation(20μg·g^(-1)).Second,the reaction kinetics of sulfite-andrographolide reactions in phosphate buffer solutions(pH 6-8)was studied.The half-lives of andrographolide ranged from minutes to hours.This was suggested that the C-sulfonate reaction of andrographolide was very fast.Third,the C-sulfonate metabolites of andrographolide were both detected when andrographolide and L-cysteine-S-conjugate andrographolide were incubated with the rat small intestine contents or sulfite,indicating that the sulfite amount in rat intestine contents was high enough to react with andrographolide,which assisted a significant portion of andrographolide metabolism.Finally,the comparison of andrographolide metabolite profiles among liver homogenate(with NADPH),liver S9(with NADPH),small intestine contents homogenate(with no NADPH),and sulfite solution incubations showed that the C-sulfonate metabolites were predominantly generated in the intestinal tract by non-enzymatic pathway.In summary,sulfite can serve as a substrate for C-sulfonate metabolism,and these results identified non-enzymatically nucleophilic addition as the potential mechanism for C-sulfonate metabolism of compounds containingα,β-unsaturated carbonyl moiety.

Kinetics and mechanism of titanium hydride powder and aluminum melt reaction

Based on the measurement of the released hydrogen gas pressure （PH2）, the reaction kinetics between TiH2 powder and pure aluminum melt was studied at various temperatures. After cooling the samples, the interface of TiH2 powder and aluminum melt was studied. The results show that the-time curves have three regions; in the first and second regions, the rate of reaction conforms zero and one order, respectively; in the third region, the hydrogen gas pressure remains constant and the rate of reaction reaches zero. The main factors that control the rate of reaction in the first and second regions are the penetration of hydrogen atoms in the titanium lattice and the chemical reaction between molten aluminum and titanium, respectively. According to the main factors that control the rate of reaction, three temperature ranges are considered for the reaction mechanism： （a） 700-750°C, （b） 750-800°C, and （c） 800-1000°C. In the first temperature range, the reaction is mostly under the control of chemical reaction; at the temperature range of 750 to 800°C, the reaction is controlled by the diffusion and chemical reaction; at the third temperature range （800-1000°C）, the dominant controlling mechanism is diffusion.

Mechanism and Kinetics Analysis of NO/SO_2/N_2/O_2 Dissociation Reactions in Non-Thermal Plasma

The kinetics mechanism of the dissociation reactions in a NO/SO2/N2/O2 system was investigated in consideration of energetic electrons＇ impacts on a non-thermal plasma. A model was derived from the Boltzmann equation and molecule collision theory to predict the dissociation reaction rate coefficients. Upon comparison with available literature, the model was confirmed to be acceptably accurate in general. Several reaction rate coefficients of the NO/SO2/N2/O2 dissociation system were derived according to the Arrhenius formula. The activation energies of each plasma reaction were calculated by quantum chemistry methods. The relation between the dissociation reaction rate coefficient and electron temperature was established to describe the importance of each reaction and to predict relevant processes of gaseous chemical reactions. The sensitivity of the mechanism of NO/SO2/N2/O2 dissociation reaction in a non-thermal plasma was also analysed.

Kinetic Laws of Heating Initiated Reactions for Materials in Aerospace Applications

Cure and decomposition reaction kinetics of typical organic materials in aerospace applications are introduced.From the data of dynamic differential scanning calorimetry(DSC)experiments,and based on changes of the peak temperatures(T_(p))with different heating rates(β),a linear equation,T_(p)=T_(1)+△Tlnβ,has been obtained more reasonably.The above equation can be used to explain some laws of higher or lower of apparent activation energies(E_(a)),by which the apparent activation energy(E_(a))is nearly equal to RT^(2)_(1)/△T.A number of kinetic investigations of typical thermosetting resins and energetic materials in aerospace applications were chosen to validate the above equations.

Investigation of the kinetic mechanism of the demanganization reaction between carbon-saturated liquid iron and CaF2–CaO–SiO2-based slags

The demanganization reaction kinetics of carbon-saturated liquid iron with an eight-component slag consisting of CaO–SiO2–MgO–FeO–MnO–Al2O3–TiO2–CaF2 was investigated at 1553, 1623, and 1673 K in this study. The rate-controlling step（RCS） for the demanganization reaction with regard to the hot metal pretreatment conditions was studied via kinetics analysis based on the fundamental equation of heterogeneous reaction kinetics. From the temperature dependence of the mass transfer coefficient of a transition-metal oxide（MnO）, the apparent activation energy of the demanganization reaction was estimated to be 189.46 kJ·mol^–1 in the current study, which indicated that the mass transfer of MnO in the molten slag controlled the overall rate of the demanganization reaction. The calculated apparent activation energy was slightly lower than the values reported in the literature for mass transfer in a slag phase. This difference was attributed to an increase in the ＂specific reaction interface＂（SRI） value, either as a result of turbulence at the reaction interface or a decrease of the absolute amount of slag phase during sampling, and to the addition of calcium fluoride to the slag.

pH Overpotential for Unveiling the pH Gradient Effect of H^(+)/OH^(−)Transport in Electrode Reaction Kinetics

The pH gradient caused by H^(+)/OH^(−)transport on an electrode surface is the key factor determining reaction performance,but its detailed impact on the electrode reaction kinetics has yet to be clarified.Here,the pH gradient effect was determined by developing electrode reaction equations,considering the overpotential assigned to the pH gradient called pH overpotential.The pH gradient effect was revealed to involve two aspects:(1)the Nernst pH overpotential,accounting for the common Nernst relationship with pH,and(2)the pH-dependent function of the electron-transfer coefficient(α_(pH)).Both parts were verified experimentally using oxygen reduction reaction and hydrogen evolution reaction,obviously,with differentα_(pH) functions.Detailedα_(pH) function effect was clarified based on numerical calculations of the electrode reaction equations.We found that the effect could be assessed suitably by an apparent constant(α_(app))and a nonlinear fitting method proposed forα_(app) value estimation.The results of this study provide the kinetic fundamentals of electrode reactions involving H^(+)/OH^(−)and contribute to the understanding and assessment of their performance with the H^(+)/OH^(−)transport effect.

Reaction condition optimization and kinetic investigation of roasting zinc oxide ore using (NH_4)_2SO_4

An orthogonal test was used to optimize the reaction conditions of roasting zinc oxide ore using（NH_4）_2SO_4. The optimized reaction conditions are defined as an（NH_4）_2SO_4/zinc molar ratio of 1.4：1, a roasting temperature of 440°C, and a thermostatic time of 60 min. The molar ratio of（NH_4）_2SO_4/zinc is the most predominant factor and the roasting temperature is the second significant factor that governs the zinc extraction. Thermogravimetric-differential thermal analysis was used for（NH_4）_2SO_4 and zinc mixed in a molar ratio of 1.4：1 at the heating rates of 5, 10, 15, and 20 K·min-1. Two strong endothermic peaks indicate that the complex chemical reactions occur at approximately 290°C and 400°C. XRD analysis was employed to examine the transformations of mineral phases during roasting process. Kinetic parameters, including reaction apparent activation energy, reaction order, and frequency factor, were calculated by the Doyle-Ozawa and Kissinger methods. Corresponding to the two endothermic peaks, the kinetic equations were obtained.