Steady-state kinetics and osillation phenomena for complete oxidation of benzene over Pt/Al_2O_3 catalyst

The steady-state kinetics for complete oxidation of benzene over has been investigated by the external recycling reactor. The kinetics equation was described by the L-H model of adsorption of benzene and oxygen with the inhibition of carbon dioxide. The parameters of the kinetics model were estimated by the method of orthogonal design. The heats of adsorption of benzene, oxygen and carbon dioxide were determined by the method of gas-adsorption chromatography. The details of oscillations of complete oxidation of benzene were investigated.

Steady-state kinetics of <i>Roystonea regia</i>palm tree peroxidase

Royal palm tree peroxidase (RPTP) has been isolated to homogeneity from leaves of Roystonea regia palm trees. The enzyme purification steps included homogenization, (NH4)SO4 precipitation, extraction of palm leaf colored compounds and consecutive chromatography on Phenyl-Sepharose, TSK-Gel DEAE-5PW and Superdex-200. The novel peroxidase was characterized as having a molecular weight of 48.2 ± 3.0 kDa and an isoelectric point pI 5.4 ± 0.1. The enzyme forms dimers in solution with approximate molecular weight of 92 ± 2 kDa. Here we investigated the steady-state kinetic mechanism of the H2O2-supported oxidation of different organic substrates by RPTP. The results of the analysis of the initial rates vs. H2O2 and reducing substrate concentrations were seen to be consistent with a substrate-inhibited Ping-Pong Bi-Bi reaction mechanism. The phenomenological approach used expresses the peroxidase Ping-Pong mechanism in the form of the Michaelis-Menten equation and affords an interpretation of the effects in terms of the kinetic parameters KmH2O2, KmAH2, kcat, KSIH2O2, KSIAH2 and of the microscopic rate constants k1 and k3 of the shared three-step peroxidase catalytic cycle. Furthermore, the concentration and time-dependences and the mechanism of the suicide inactivation of RPTP by hydrogen peroxide were studied kinetically with guaiacol as co-substrate. The turnover number (r) of H2O2 required to complete the inactivation of the enzyme was 2154 ± 100 and the apparent rate constants of catalysis 185 s–1 and 18 s–1.

Improving hydrogen storage thermodynamics and kinetics of Ce-Mg-Ni-based alloy by mechanical milling with TiF_(3)

Mg-based hydrides are too stable and the kinetics of hydrogen absorption and desorption is not satisfactory.An efficient way to improve these shortcomings is to employ reactive ball milling to synthesize the nanocomposite materials of Mg and additives.In this experiment,TiF_(3)was selected as an additive,and the mechanical milling method was employed to prepare the experimental alloys.The alloys used in this experiment were the as-cast Ce_(5)Mg_(85)Ni_(10),as-milled Ce_(5)Mg_(85)Ni_(10)and Ce_(5)Mg_(85)Ni_(10)+3 wt.%TiF3.The phase transformation,structural evolution,isothermal and non-isothermal hydrogenation and dehydrogenation performances of the alloys were inspected by XRD,SEM,TEM,Sievert apparatus,DSC and TGA.It revealed that nanocrystalline appeared in the as-milled samples.Compared with the as-cast alloy,ball milling made the particle dimension and grain size decrease dramatically and the defect density increase significantly.The addition of TiF_(3)made the surface of ball milling alloy particles markedly coarser and more irregular.Ball milling and adding TiF_(3)distinctly improved the activation and kinetics of the alloys.Moreover,ball milling along with TiF_(3)can decrease the onset dehydrogenation temperature of Mg-based hydrides and slightly ameliorate their thermodynamics.

All‑Covalent Organic Framework Nanofilms Assembled Lithium‑Ion Capacitor to Solve the Imbalanced Charge Storage Kinetics

Free-standing covalent organic framework(COFs)nanofilms exhibit a remarkable ability to rapidly intercalate/de-intercalate Li^(+) in lithium-ion batteries,while simultaneously exposing affluent active sites in supercapacitors.The development of these nanofilms offers a promising solution to address the persistent challenge of imbalanced charge storage kinetics between battery-type anode and capacitor-type cathode in lithium-ion capacitors(LICs).Herein,for the first time,custom-made COFBTMB-TP and COFTAPB-BPY nanofilms are synthesized as the anode and cathode,respectively,for an all-COF nanofilm-structured LIC.The COFBTMB-TP nanofilm with strong electronegative–CF3 groups enables tuning the partial electron cloud density for Li^(+) migration to ensure the rapid anode kinetic process.The thickness-regulated cathodic COFTAPB-BPY nanofilm can fit the anodic COF nanofilm in the capacity.Due to the aligned 1D channel,2D aromatic skeleton and accessible active sites of COF nanofilms,the whole COFTAPB-BPY//COFBTMB-TP LIC demonstrates a high energy density of 318 mWh cm^(−3) at a high-power density of 6 W cm^(−3),excellent rate capability,good cycle stability with the capacity retention rate of 77%after 5000-cycle.The COFTAPB-BPY//COFBTMB-TP LIC represents a new benchmark for currently reported film-type LICs and even film-type supercapacitors.After being comprehensively explored via ex situ XPS,7Li solid-state NMR analyses,and DFT calculation,it is found that the COFBTMB-TP nanofilm facilitates the reversible conversion of semi-ionic to ionic C–F bonds during lithium storage.COFBTMB-TP exhibits a strong interaction with Li^(+) due to the C–F,C=O,and C–N bonds,facilitating Li^(+) desolation and absorption from the electrolyte.This work addresses the challenge of imbalanced charge storage kinetics and capacity between the anode and cathode and also pave the way for future miniaturized and wearable LIC devices.

Description of martensitic transformation kinetics in Fe-C-X(X = Ni,Cr,Mn,Si) system by a modified model

Controlling the content of athermal martensite and retained austenite is important to improving the mechanical properties of high-strength steels,but a mechanism for the accurate description of martensitic transformation during the cooling process must be addressed.At present,frequently used semi-empirical kinetics models suffer from huge errors at the beginning of transformation,and most of them fail to exhibit the sigmoidal shape characteristic of transformation curves.To describe the martensitic transformation process accurately,based on the Magee model,we introduced the changes in the nucleation activation energy of martensite with temperature,which led to the varying nucleation rates of this model during martensitic transformation.According to the calculation results,the relative error of the modified model for the martensitic transformation kinetics curves of Fe-C-X(X = Ni,Cr,Mn,Si) alloys reached 9.5% compared with those measured via the thermal expansion method.The relative error was approximately reduced by two-thirds compared with that of the Magee model.The incorporation of nucleation activation energy into the kinetics model contributes to the improvement of its precision.

Geochemical modeling to aid experimental design for multiple isotope tracer studies of coupled dissolution and precipitation reaction kinetics

It is a challenge to make thorough but efficient experimental designs for the coupled mineral dissolution and precipitation studies in a multi-mineral system, because it is difficult to speculate the best experimental duration, optimal sampling schedule, effects of different experimental conditions, and how to maximize the experimental outputs prior to the actual experiments. Geochemical modeling is an efficient and effective tool to assist the experimental design by virtually running all scenarios of interest for the studied system and predicting the experimental outcomes. Here we demonstrated an example of geochemical modeling assisted experimental design of coupled labradorite dissolution and calcite and clayey mineral precipitation using multiple isotope tracers. In this study, labradorite(plagioclase) was chosen as the reactant because it is both a major component and one of the most reactive minerals in basalt. Following our isotope doping studies of single minerals in the last ten years, initial solutions in the simulations were doped withmultiple isotopes(e.g., Ca and Si). Geochemical modeling results show that the use of isotope tracers gives us orders of magnitude more sensitivity than the conventional method based on concentrations and allows us to decouple dissolution and precipitation reactions at near-equilibrium condition. The simulations suggest that the precise unidirectional dissolution rates can inform us which rate laws plagioclase dissolution has followed. Calcite precipitation occurred at near-equilibrium and the multiple isotope tracer experiments would provide near-equilibrium precipitation rates, which was a challenge for the conventional concentration-based experiments. In addition, whether the precipitation of clayey phases is the rate-limiting step in some multi-mineral systems will be revealed. Overall, the modeling results of multimineral reaction kinetics will improve the understanding of the coupled dissolution–precipitation in the multi-mineral systems and the quality of geochemical modeling prediction of CO_(2) removal and storage efficacy in the basalt systems.

“Buckets effect”in the kinetics of electrocatalytic reactions

In this study,we systematically investigated the effect of proton concentration on the kinetics of the oxygen reduction reaction(ORR)on Pt(111)in acidic solutions.Experimental results demonstrate a rectangular hyperbolic relationship,i.e.,the ORR current excluding the effect of other variables increases with proton concentration and then tends to a constant value.We consider that this is caused by the limitation of ORR kinetics by the trace oxygen concentration in the solution,which determines the upper limit of ORR kinetics.A model of effective concentration is further proposed for rectangular hyperbolic relationships:when the reactant concentration is high enough to reach a critical saturation concentration,the effective reactant concentration will become a constant value.This could be due to the limited concentration of a certain reactant for reactions involving more than one reactant or the limited number of active sites available on the catalyst.Our study provides new insights into the kinetics of electrocatalytic reactions,and it is important for the proper evaluation of catalyst activity and the study of structureperformance relationships.

Catalytic Reaction Kinetics of Propylene Dimerization to 4-Methyl-1-Pentene Using Cu-K/K_(2)CO_(3) Solid Base Catalyst

The catalysis technology of propylene dimerization to form 4-methyl-1-pentene(4MP1)using a Cu-K/K_(2)CO_(3) solid base catalyst is a well-known heterogeneous catalytic reaction.In this study,the intrinsic kinetics of propylene dimerization were studied in a fixed-bed continuous reactor.Internal and external diffusion during the dimerization reaction experiments were eliminated by adjusting the flow rate of the carrier gas and the particle size of the catalyst support.Then,the concentration changes of each substance at the outlet of the catalyst bed under different residence times were investigated.Moreover,the suitable reaction kinetics equations was derived using the Langmuir Hinshelwood-Hougen-Watson kinetic model.Finally,the activation energy for each reaction involved in the dimerization reaction was calculated.The activation energies of 4MP1,branched by-products,and 1-hexene were 115.0,150.8,and 177.4 kJ/mol,respectively.The effect of process conditions on propylene dimerization with solid base catalysts was studied through kinetic model simulation.By comparing the theoretical values obtained from the simulation with the experimental results,the applicability and accuracy of the kinetic model were verified.

Atomic Ni directional-substitution on ZnIn_(2)S_(4) nanosheet to achieve the equilibrium of elevated redox capacity and efficient carrier-kinetics performance in photocatalysis

It is a challenge to coordinate carrier-kinetics performance and the redox capacity of photogenerated charges synchronously at the atomic level for boosting photocatalytic activity.Herein,the atomic Ni was introduced into the lattice of hexagonal ZnIn_(2)S_(4) nanosheets(Ni/ZnIn_(2)S_(4))via directionalsubstituting Zn atom with the facile hydrothermal method.The electronic structure calculations indicate that the introduction of Ni atom effectively extracts more electrons and acts as active site for subsequent reduction reaction.Besides the optimized light absorption range,the elevation of Efand ECBendows Ni/ZnIn_(2)S_(4) photocatalyst with the increased electron concentration and the enhanced reduction ability for surface reaction.Moreover,ultrafast transient absorption spectroscopy,as well as a series of electrochemical tests,demonstrates that Ni/ZnIn_(2)S_(4) possesses 2.15 times longer lifetime of the excited charge carriers and an order of magnitude increase for carrier mobility and separation efficiency compared with pristine ZnIn_(2)S_(4).These efficient kinetics performances of charge carriers and enhanced redox capacity synergistically boost photocatalytic activity,in which a 3-times higher conversion efficiency of nitrobenzene reduction was achieved upon Ni/ZnIn_(2)S_(4).Our study not only provides in-depth insights into the effect of atomic directional-substitution on the kinetic behavior of photogenerated charges,but also opens an avenue to the synchronous optimization of redox capacity and carrier-kinetics performance for efficient solar energy conversion.

Dual-single-atoms of Pt-Co boost sulfur redox kinetics for ultrafast Li-S batteries

Applications of lithium-sulfur(Li-S)batteries are still limited by the sluggish conversion kinetics from polysulfide to Li_(2)S.Although various single-atom catalysts are available for improving the conversion kinetics,the sulfur redox kinetics for Li-S batteries is still not ultrafast.Herein,in this work,a catalyst with dual-single-atom Pt-Co embedded in N-doped carbon nanotubes(Pt&Co@NCNT)was proposed by the atomic layer deposition method to suppress the shuttle effect and synergistically improve the interconversion kinetics from polysulfides to Li_(2)S.The X-ray absorption near edge curves indicated the reversible conversion of Li_(2)Sx on the S/Pt&Co@NCNT electrode.Meanwhile,density functional theory demonstrated that the Pt&Co@NCNT promoted the free energy of the phase transition of sulfur species and reduced the oxidative decomposition energy of Li_(2)S.As a result,the batteries assembled with S/Pt&Co@NCNT electrodes exhibited a high capacity retention of 80%at 100 cycles at a current density of 1.3 mA cm^(−2)(S loading:2.5 mg cm^(−2)).More importantly,an excellent rate performance was achieved with a high capacity of 822.1 mAh g^(−1) at a high current density of 12.7 mA cm^(−2).This work opens a new direction to boost the sulfur redox kinetics for ultrafast Li-S batteries.

Improved hydrogen storage kinetics of MgH_(2) using TiFe_(0.92)Mn_(0.04)Co_(0.04) with in-situ generated α-Fe as catalyst

While TiFe alloy has recently attracted attention as the efficient catalyst to enhance de/hydrogenation rates of Mg/MgH_(2),the difficulty of its activation characteristics has hindered further improvement of reaction kinetics.Herein,we report that the TiFe_(0.92)Mn_(0.04)Co_(0.04) catalyst can overcome the abovementioned challenges.The synthesized MgH_(2)-30 wt% TiFe_(0.92)Mn_(0.04)Co_(0.04) can release 4.5 wt%of hydrogen in 16 min at 250℃,three times as fast as MgH_(2).The activation energy of dehydrogenation was as low as 84.6 kJ mol^(-1),which is 46.8%reduced from pure MgH_(2).No clear degradation of reaction rates and hydrogen storage capacity was observed for at least 30 cycles.Structural studies reveal that TiFe_(0.92)Mn_(0.04)Co_(0.04) partially decomposes to in-situ generatedα-Fe particles dispersed on TiFe_(0.92)Mn_(0.04)Co_(0.04).The presence ofα-Fe reduces the formation of an oxide layer on TiFe_(0.92)Mn_(0.04)Co_(0.04),enabling the activation processes.At the same time,the hydrogen incorporation capabilities of TiFe_(0.92)Mn_(0.04)Co_(0.04) can provide more hydrogen diffusion paths,which promote hydrogen dissociation and diffusion.These discoveries demonstrate the advanced nature and importance of combining the in-situ generatedα-Fe with TiFe_(0.92)Mn_(0.04)Co_(0.04).It provides a new strategy for designing highly efficient and stable catalysts for Mg-based hydrogen storage materials.

Tungsten oxide/nitrogen-doped carbon nanotubes composite catalysts for enhanced redox kinetics in lithium-sulfur batteries

The sluggish redox kinetics of polysulfides in lithium-sulfur(Li-S)batteries are a significant obstacle to their widespread adoption as energy storage devices.However,recent studies have shown that tungsten oxide(WO_(3))can facilitate the conversion kinetics of polysulfides in Li-S batteries.Herein,we fabricated host materials for sulfur using nitrogen-doped carbon nanotubes(N-CNTs)and WO_(3).We used low-cost components and simple procedures to overcome the poor electrical conductivity that is a disadvantage of metal oxides.The composites of WO_(3) and N-CNTs(WO_(3)/N-CNTs)create a stable framework structure,fast ion diffusion channels,and a 3D electron transport network during electrochemical reaction processes.As a result,the WO_(3)/N-CNT-Li2S6 cathode demonstrates high initial capacity(1162 mA·h·g^(-1) at 0.5℃),excellent rate performance(618 mA·h·g^(-1) at 5.5℃),and a low capacity decay rate(0.093%up to 600 cycles at 2℃).This work presents a novel approach for preparing tungsten oxide/carbon composite catalysts that facilitate the redox kinetics of polysulfide conversion.

Recent progress in thermodynamic and kinetics modification of magnesium hydride hydrogen storage materials

Hydrogen energy has emerged as a pivotal solution to address the global energy crisis and pave the way for a cleaner,low-carbon,secure,and efficient modern energy system.A key imperative in the utilization of hydrogen energy lies in the development of high-performance hydrogen storage materials.Magnesium-based hydrogen storage materials exhibit remarkable advantages,including high hydrogen storage density,cost-effectiveness,and abundant magnesium resources,making them highly promising for the hydrogen energy sector.Nonetheless,practical applications of magnesium hydride for hydrogen storage face significant challenges,primarily due to their slow kinetics and stable thermodynamic properties.Herein,we briefly summarize the thermodynamic and kinetic properties of MgH2,encompassing strategies such as alloying,nanoscaling,catalyst doping,and composite system construction to enhance its hydrogen storage performance.Notably,nanoscaling and catalyst doping have emerged as more effective modification strategies.The discussion focuses on the thermodynamic changes induced by nanoscaling and the kinetic enhancements resulting from catalyst doping.Particular emphasis lies in the synergistic improvement strategy of incorporating nanocatalysts with confinement materials,and we revisit typical works on the multi-strategy optimization of MgH2.In conclusion,we conduct an analysis of outstanding challenges and issues,followed by presenting future research and development prospects for MgH2 as hydrogen storage materials.

A Review on Engineering Transition Metal Compound Catalysts to Accelerate the Redox Kinetics of Sulfur Cathodes for Lithium–Sulfur Batteries

Engineering transition metal compounds(TMCs)catalysts with excellent adsorption-catalytic ability has been one of the most effec-tive strategies to accelerate the redox kinetics of sulfur cathodes.Herein,this review focuses on engineering TMCs catalysts by cation doping/anion doping/dual doping,bimetallic/bi-anionic TMCs,and TMCs-based heterostructure composites.It is obvious that introducing cations/anions to TMCs or constructing heterostructure can boost adsorption-catalytic capacity by regulating the electronic structure including energy band,d/p-band center,electron filling,and valence state.Moreover,the elec-tronic structure of doped/dual-ionic TMCs are adjusted by inducing ions with different electronegativity,electron filling,and ion radius,resulting in electron redistribution,bonds reconstruction,induced vacancies due to the electronic interaction and changed crystal structure such as lat-tice spacing and lattice distortion.Different from the aforementioned two strategies,heterostructures are constructed by two types of TMCs with different Fermi energy levels,which causes built-in electric field and electrons transfer through the interface,and induces electron redistribution and arranged local atoms to regulate the electronic structure.Additionally,the lacking studies of the three strategies to comprehensively regulate electronic structure for improving catalytic performance are pointed out.It is believed that this review can guide the design of advanced TMCs catalysts for boosting redox of lithium sulfur batteries.

Thermal Decomposition of Olive-Solid Waste by TGA: Characterization and Devolatilization Kinetics under Nitrogen and Oxygen Atmospheres

Despite the fact that a few countries in the Mediterranean and the Middle East have limited crude oil reserves, they have abundant biomass feedstocks. For instance, Jordan relies heavily on the importation of natural gas and crude oil for its energy needs;but, by applying thermochemical conversion techniques, leftover olive oil can be used to replace these energy sources. Understanding the chemical, physical, and thermal characteristics of raw materials is essential to obtaining the most out of these conversion processes. Thermogravimetric analysis was used in this study to examine the thermal behavior of olive-solid residue (kernel) at three different heating rates (5, 20 and 40 C/min) in nitrogen and oxygen atmospheres. The initial degradation temperature, the residual weight at 500 and 700˚C and the thermal degradation rate during the devolatilization stage (below 400˚C) were all determined. It was found that in N2 and O2 atmospheres, both the initial degradation temperature and the degradation rate increase with increasing heating rates. As heating rates increase in the N2 atmosphere, the residual weight at 500 or 700˚C decreases slightly, but at low heating rates compared to high heating rates in the O2 atmosphere, it decreases significantly. This suggests that a longer lignin oxidation process is better than a shorter one. Coats and Redfern approach was used to identify the mechanism and activation energy for the devolatilization stage of pyrolysis and oxidation reactions. The process mechanism analysis revealed that the model of first-order and second-order reactions may adequately describe the mechanism of heat degradation of the devolatilization step of olive-solid waste for pyrolysis and oxidation processes, respectively.

Optimization of Methylene Blue Dye Adsorption onto Coconut Husk Cellulose Using Response Surface Methodology: Adsorption Kinetics, Isotherms and Reusability Studies

In this study, coconut husk cellulose was employed as a cost-effective and environmentally friendly adsorbent to eliminate methylene blue (MB) dye from aqueous solutions. The successful development of response surface methodology paired with a central composite design (RSM-CCD) enabled the optimization and modelling of the adsorption process. The study investigated the individual and combined effects of three variables (pH, contact time, and initial MB dye concentration) on the adsorption of MB dye onto coconut husk cellulose. The developed RSM-CCD model exhibited a remarkable degree of precision in predicting the removal efficiency of MB dye within the specified experimental parameters. This was demonstrated by the strong regression parameters, with an R2 value of 99.79% and an adjusted R2 value of 99.6%. The study depicted that the optimal parameters for attaining a 98.8827% removal of MB dye using coconut husk cellulose were as follows: an initial MB dye concentration of 30 mg∙L−1, contact time of 120 minutes, and pH 7 at a fixed adsorbent dose of 0.5 g. The Freundlich isotherm model provided the most satisfactory description of the equilibrium adsorption isotherms, suggesting that MB dye adsorption onto coconut husk cellulose occurs on a heterogeneous surface. The experimental results demonstrated a strong agreement with the pseudo-second-order kinetics model, indicating that the number of active sites present on the cellulose adsorbent predominantly influences the adsorption process of MB dye. Additionally, the adsorbent made from coconut husk cellulose exhibited the potential to be reused, as it retained its efficiency for a maximum of three cycles of adsorption of MB dye. The results of this study show that coconut husk cellulose has the potential to be an effective and sustainable adsorbent for removing MB dye from aqueous solutions.

Dissolution mechanism and kinetics ofβ(Mg_(17)Al_(12))phases in AZ91 magnesium alloy

In this study,the phase transformations,crystallization kinetics and dissolution mechanism ofβphase(Mg_(17)Al_(12))in magnesium alloy AZ91 were investigated by optical microscopy,X-ray diffraction,differential scanning calorimetry and differential dilatometry.The results indicate that this AZ91 alloy undergoes a phase transformation during aging,a discontinuous precipitation of theβphase(Mg_(17)Al_(12))at 150℃at the grain boundaries and another continuous at 350℃within the grains.The activation energy of the dissolution reaction of theβphase(Mg_(17)Al_(12))under non-isothermal conditions is 116.781 kJ/mol,while it is 129.7383 kJ/mol under isothermal conditions.The Avrami coefficient,n,relevant for the dissolution kinetics of theβphase(Mg_(17)Al_(12))is 1.152 and 1.211 in the non-isothermal and isothermal conditions respectively.The numerical coefficients m and Avrami n are 0.993 and 1.152.

Comparative investigations of ternary thermite Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3) from pyrolytic,kinetics and combustion behaviors

To develop new energy enhancement energetic materials with great combustion performance and thermal stability,two kinds of ternary thermite,Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3),were prepared and analyzed via mechanical ball milling.The samples were characterized by SEM,XRD,TG-DSC,constant volume and constant pressure combustion experiments.The first exothermic peaks of Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3) appear at 579°C and 564.5°C,respectively.The corresponding activation energies are similar.The corresponding mechanism functions are set as G(a) = [-ln(1-a)]^(3/4) and G(a) =[-ln(1-a)]2/3,respectively,which belong to the Avrami-Erofeev equation.Al/Fe_(2)O_(3)/CuO has better thermal safety.For small dose samples,its critical temperature of thermal explosion is 121.05°C higher than that of Al/Fe_(2)O_(3)/Bi_(2)O_(3).During combustion,the flame of Al/Fe_(2)O_(3)/CuO is spherical,and the main products are FeAl_(2)O_(4) and Cu.The flame of Al/Fe_(2)O_(3)/Bi_(2)O_(3)is jet-like,and the main products are Al_(2)O_(3),Bi and Fe.Al/Fe_(2)O_(3)/Bi_(2)O_(3)has better ignition and gas production performance.Its average ignition energy is 4.2 J lower than that of Al/Fe_(2)O_(3)/CuO.Its average step-up rate is 28.29 MPa/s,which is much higher than 6.84 MPa/s of Al/Fe_(2)O_(3)/CuO.This paper provides a reference for studying the thermal safety and combustion performance of ternary thermite.

Combustion performance of pulverized coal and corresponding kinetics study after adding the additives of Fe_(2)O_(3) and CaO

Combustion performance of pulverized coal(PC)in blast furnace(BF)process is regarded as a criteria parameter to assess the prop-er injection dosage of PC.In this paper,effects of two kinds of additives,Fe_(2)O_(3) and CaO,on PC combustion were studied using the thermo-gravimetric method.The results demonstrate that both the Fe_(2)O_(3) and CaO can promote combustion performance index of PC including igni-tion index(C_(i)),burnout index(D_(b)),as well as comprehensive combustibility index(S_(n)).The S_(n) increases from 1.37×10^(−6) to 2.16×10^(−6)%2·min^(−2)·℃^(−3) as the Fe_(2)O_(3) proportion increases from 0 to 5.0wt%.Additionally,the combustion kinetics of PC was clarified using the Coats-Redfern method.The results show that the activation energy(E)of PC combustion decreases after adding the above additives.For instance,the E decreases from 56.54 to 35.75 kJ/mol when the Fe_(2)O_(3) proportion increases from 0 to 5.0wt%,which supports the improved combustion per-formance.Moreover,it is uneconomic to utilize pure Fe_(2)O_(3) and CaO in production.Based on economy analysis,we selected the iron-bearing dust(IBD)which contains much Fe_(2)O_(3) and CaO component to investigate,and got the same effects.Therefore,the IBD is a potential option for catalytic PC combustion in BF process.

In situ observation of the dissolution kinetics of Al_(2)O_(3) particles in CaO–Al_(2)O_(3)–SiO_(2) slags using laser confocal scanning microscopy

The dissolution kinetics of Al_(2)O_(3) in CaO-Al_(2)O_(3) SiOslags was studied using a high-temperature confocal scanning laser microscope at 1773 to 1873 K.The results show that the controlling step during the Al_(2)O_(3) dissolution was the diffusionin molten slag.It was found that the dissolution curves of Al_(2)O_(3) particles were hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al_(2)O_(3) ratio of slag.A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al_(2)O_(3) in slag.Diffusion coefficients of Al_(2)O_(3) in slag were calculated as 2.8×10to 4.1×10m~2/s at the temperature of 1773-1873 K.The dissolution rate of Al_(2)O_(3) increased with higher temperature,CaO/Al_(2)O_(3),and particle size.A new model was shown to be v_(Al_(2)O_(3))=0.16×r_(0)^(1.58)×x^(3.52)×(T-T_(mp))^(1.11)to predict the dissolution rate and the total dissolution time of Al_(2)O_(3) inclusions with various sizes,where vAl_(2)O_(3) is the dissolution rate of Al_(2)O_(3) in volume,μm^(3)/s;x is the value of CaO/Al_(2)O_(3) mass ratio;R_(0) is the initial radius of Al_(2)O_(3),μm;T is the temperature,K;T_(mp) is the melting point of slag,K.