Characteristics Of Chemical Reactions Research Articles

Thermal-chemical reaction characteristics of Ni/Al2O3 catalytic porous material filled solar reactor for dry reforming of methane process

In solar thermochemical systems, the interaction between heat transport characteristics and chemical reaction characteristics has significant impacts on the system energy conversion and storage efficiency. For the purpose of investigating the thermochemical performance of a catalytic porous material filled solar reactor under multi-field coupling, this study established a numerical model by combining the computational fluid dynamics (CFD) method with dry reforming of methane (DRM) reaction kinetics. The Wu model is adopted to predict the momentum dissipation resulted from the non-Darcy flow in the porous zone, and the DRM reaction kinetics including four side reactions are programmed into the Fluent software via user-defined functions. The numerical results indicate that the reaction temperature presents a linear relationship with the incident peak heat flux, and a quadratic relationship with the inlet flow rate. From the perspectives of feedstock conversion efficiency, syngas yield and carbon deposition degree, the optimal operating conditions are determined to achieve the highest profit. Within the current operating parameters, increasing the heat flux of incident radiation contributes to improving the CO2 conversion and CO yield, but has the disadvantage of aggravating the carbon deposition in the front of the porous ceramic, while appropriately increasing the inlet flow rate can effectively alleviate this contradiction. Additionally, choosing a CH4/CO2-feed ratio over 2.0 cannot help improve the conversion rate and syngas yield, but will greatly increase the amount of carbon deposition.

Metabolism and in vitro drug–drug interaction assessment of viloxazine

Viloxazine is currently being developed as a treatment for attention deficit/hyperactivity disorder (ADHD). The aim of these studies is to update the understanding of the rat and human metabolism and the in vitro drug–drug interaction profile of viloxazine to a degree where it meets current regulatory standards for such investigations. In vivo absorption-distribution-metabolism-excretion (ADME) studies demonstrated that in humans 5-hydroxylation followed by glucuronidation is the major metabolic route. This route was also seen as a minor route in rats where the major route is O-deethylation with subsequent sulfation. In humans, the 5-hydoxylation pathway is mediated by CYP2D6. An estimate for the fraction of the metabolism via this pathway suggests a PM/EM difference of <2-fold, making it highly unlikely that this will be an issue of clinical significance. Viloxazine forms a unique N-carbamoyl glucuronide in humans. The chemical reactivity characteristics of this metabolite are similar to stable glucuronide conjugates and dissimilar from acyl glucuronides; therefore, it is regarded as a stable Phase II conjugate. In vitro drug–drug interaction (DDI) testing indicates that viloxazine is not a significant inhibitor or inducer of CYPs and transporters with the exception of CYP1A2.

Теоретическое исследование силового поля дифтораминотринитрометана в координатах Xδ0

Actual problem of modern chemists-researchers is studying the properties of molecules of compounds. The latest achievements in the field of computer engineering and quantum chemistry make it possible to research various physicochemical parameters of studying compounds using theoretical calculations. Calculation methods can greatly simplify the task, as they are safer and more economical than experiment. It is noted that methane derivatives are also currently of interest for research in connection with their widespread use. This paper is devoted to the study of the force fields of molecule of (difluoro-amino)trinitromethane using quantum chemical calculations. The Becke-Lee-Yang-Parr method of density functional theory (DFT) B3LYP with a hybrid potential of 6-311++G(3df, 3pd) was chosen as the main approximation for the work performed, since when using it, the best quality of the result is noted. Also, in the present work, as an alternative to chemical (natural) coordinates, new coordinates Xδ0 were chosen, which allows one to take into account torsional vibrations. The calculations presented in this work were performed using the Gaussian and GaussView programs, designed to calculate a large number of properties and characteristics of chemical reactions. In this paper, using the proposed approach, the geometry of the molecule of (difluoroamino)tri-notromethane has been optimized, the geometric parameters of these compound were considered, in particular, the valence angles, dihedral angles, and long bonds were calculated, corresponding to the minimum energy of this molecule. For the first time, generalized force coefficients for F2NC(NO2)3 were calculated, and the "stiffness" of the chemical compounds of the molecule under study was evaluated. The frequencies of normal vibrations (wave numbers) for the studied compound in the harmonic approximation were calculated and analyzed. A comparison of the obtained wave numbers with experimental data is given. The results obtained indicate a satisfactory agreement between theory and experiment. A general view of the vibrational spectrum of (difluoroamino)trinotromethane obtained as a result of quantum chemical calculations is presented. The conclusion is drawn about the possibilities of applying the B3LYP 6-311++G(3df, 3pd) approach for calculating the frequencies of normal vibrations and force coefficients.

Теоретическое исследование силового поля тринитрохлорметана в координатах Xδ0

At present, nitro compounds are widely used in industry and medicine. This necessitates a more thorough study of their specific properties and the construction of theoretical models for their prediction. A special role in this process is given to IR and Raman spectroscopy. However, model calculations are needed to interpret vibrational spectra. This work is devoted to quantum-chemical studies of the force field of the ClC(NO2)3 molecule and the solution of the direct spectral problem for the selected object. The Becke-Lee-Yang-Parr B3LYP method with a hybrid potential of 6-311++G(3df, 3pd), as the most promising, was used as the main approach for the study. In addition, in this paper, as an alternative to chemical (natural) coordinates, new coordinates Xδ0 were chosen, it lets talk about the correctness of the calculations. The calculations presented in this article were implemented using Gaussian and GaussView computer programs designed to calculate a number of molecular properties and characteristics of chemical reactions. Using the chosen method, in this work, the geometry of the trinitrochloromethane molecule was optimized, the geometric parameters of the compound under study were examined, in particular, were calculated the values of valence angles, dihedral angles, and bond lengths characteristic of the equilibrium configuration of the compound under study. For the first time, generalized force coefficients were obtained for the ClC(NO2)3 molecule in the Xδ0 coordinates, which were proposed by L.S. Mayants and G.B. Shaltuper, as universal coordinates in which it is possible to correctly solve the spectral problem. An assessment of the "rigidity" of the chemical bonds of the test compound was carried out. The wave numbers (frequencies of normal vibrations) for the studied molecule in the harmonic approximation are calculated and analyzed. A comparison of the obtained wave numbers with experimental data is given. The results obtained demonstrate a satisfactory agreement between theory and experiment. A general view of the vibrational spectrum of trinitrochloromethane obtained by calculation is presented.

Electrolysis of O2-Containing Low Concentration CO2 in Solid Oxide Electrolysis Cells with La-Based Hexaaluminate Cathode for Syngas Production

Excessive emission of CO2, the primary greenhouse gas, has been widely believed to be the main contributor to global warming. Recently, direct-air-capture (DAC) of CO2 is emerging as a promising technique to mitigate the greenhouse problem. In this work, a new technology is developed where the CO2/air mixture captured by DAC1 is directly converted into high value-added syngas using solid oxide electrolysis cells (SOECs)2. In this new system, H2O and O2-containing CO2 (CO2/air mixture) are co-electrolyzed for syngas production in the cathode of SOECs, and in the anode, methane is partially oxidized into syngas to decrease the overpotential and electricity consumption.The cathode materials of SOECs need to keep stable under the condition of strong reduction and high humidity. meanwhile CO2 directly captured from ambient air is mixed with oxygen in the cathode, which poses a challenge to prevent the oxidation of cathode materials. Hexaaluminate3 (AAl12O19-δ or AAl12O17-δ), as a kind of composite metal oxides, is considered as one of the most promising high-temperature catalytic materials due to its unique layered crystal structure. Besides, Al3+ in its structure can be partially or completely substituted by transition metal ions, and the valence state and proportion of its elements and content of oxygen vacancy can be adjusted in a large range. Therefore, hexaaluminate catalysts with high catalytic activity can be designed by means of chemical tailoring according to the characteristics of chemical reactions and requirements for catalysts.In this work, La-hexaaluminate is employed as the cathode material for co-electrolyzing H2O and CO2/air mixture to produce syngas. A series of characterization methods are used to evaluate the basic physical properties of hexaaluminate, including phase structure, oxygen vacancy concentration, thermal stability, thermal expansion coefficient and chemical compatibility with electrolyte materials. Moreover, the stability of electrolytic cell in various operating conditions was investigated, the morphology of cathode and anode materials before and after the operation of the electrolytic cell were compared. The reason of performance attenuation of the electrolytic cell was preliminarily analyzed. The new scheme developed in the present work, provides a way for the effective utilization of O2-containing low concentration CO2 captured by DAC, which is not only useful for alleviating the greenhouse effect, but also gains extra fuels with the help of renewable energy.

An improved Darcian analysis for chemically reacted Maxwell liquid toward convectively heated moving surface with magnetohydrodynamics

Heat transportation analysis subjected to porous medium consideration has increased because of industrial and engineering utilization. Typical examples comprise crude oil production, porous insulation, groundwater pollution, grain storage, mastic transport modeling, nuclear waste discarding and numerous other. The above-mentioned effectiveness of porous medium motivates us to model rate-type Maxwell material under hydromagnetic aspects. We utilized improved Darcian (Darcy–Forchheimer) expression for formulation. Consideration of improved Darcian expression modifies velocity expression through square velocity term. In addition, we accounted Robin’s condition and chemical reaction characteristics. Boundary-layer theory is employed for simplification of mathematical expressions. Dimensionless problems are treated analytically through homotopy scheme. Their significant attributes are further explored in detail. We noticed an increment in solutal and thermal fields when Biot numbers (thermal and solutal) are enhanced.

Exact Invariants of Chemical Reactions with Participation of Two Reagents

Autonomous (temporal) invariants of nonlinear chemical reactions between two reagents are determined. For dynamic models of such reactions, analytical solutions exist that allow exact invariants to be found. Such invariants are ratios that connect non-equilibrium values of reagent concentrations, measured in two experiments with different initial conditions (dual experiments). These ratios remain strictly constant throughout the reaction. The relations obtained in this paper were applied to the study of the nonstationary properties of one-, two-, and three-stage nonlinear reactions proceeding in a closed system with the kinetic law of mass action. The invariant curves found for these reactions are compared with the curves of change in the concentrations of reagents over the entire transition process. It is shown that the dependences of the invariants on time remain strictly constant (have zero order), while the reagent concentrations undergo exponential changes during the transition process. The results obtained expand the understanding of the characteristics of nonlinear chemical reactions and can be used to solve inverse problems of unsteady chemical kinetics and modeling chemical reactors of ideal mixing under isothermal conditions.

Combustion Behavior and Mechanism of Ti14 Titanium Alloy.

The combustion behavior and mechanism of Ti14 titanium alloy are studied by promoted ignition combustion tests at different oxygen pressures in this paper. The burning velocity increases at higher oxygen pressures and also increases with longer burning times instead of a constant at the same pressure. The Cu atoms are found enriched in two zones—i.e., the heat affected zone and melting zone during the combustion process—which can prevent the diffusion process of oxygen atoms. The different combustion behavior of Ti14 and Ti-Cr-V alloys is basically controlled by the characteristics of phase structures and chemical reactions.

Analysis of chemical looping reaction characteristics and mechanism of bituminous coal

Analysis of chemical looping reaction characteristics and mechanism of bituminous coal

Association kinetics and equilibrium in solutions of cross-associating chains that contain inactive spacers

Thermodynamic and kinetic characteristics of chemical reactions in soft matter are affected by volume exclusion caused by an inert component (crowder). In previous molecular dynamics simulations we examined the crowding effect on the association equilibrium in solutions of cross-associating macromolecules that contain, as part of the chains, inactive monomers acting as crowders. Here, we extend our studies to association kinetics. For a number of mixtures where one or both chain species contain inert spacers, a simple mean field approximation describes quite well the composition dependence of the association equilibrium in a wide concentration range. Two main factors determine this dependence: the local distribution of the stickers (the relative excess of one kind of stickers in vicinity of the other) and the local steric effects. The kinetic characteristics of dissociation/association show somewhat similar pattern: the bonded pairs dissociate and recombine slower in solutions with higher content of inactive monomer units. However, the dissociation and recombination dynamics also depends on the reactants’ diffusion and its interplay with effects of chain connectivity and chemical structure. Particularly, when one of the associating components does not carry inert spacers, the recombination accelerates because it makes easier for the sticker from the other chain species to find a new partner for bond formation near its previous partner. These local effects and variations in the subdiffusive behavior of chain molecules are important to take into account for advancing the theory of reversible association in macromolecular systems.

Penetration Behavior of High-Density Reactive Material Liner Shaped Charge.

The traditional polytetrafluoroethylene (PTFE)/Al reactive material liner shaped charge generally produces insufficient penetration depth, although it enlarges the penetration hole diameter by chemical energy release inside the penetration crater. As such, a novel high-density reactive material liner based on the PTFE matrix was fabricated, and the corresponding penetration performance was investigated. Firstly, the PTFE/W/Cu/Pb high-density reactive material liner was fabricated via a cold pressing/sintering process. Then, jet formation and penetration behaviors at different standoffs were studied by pulse X-ray and static experiments, respectively. The X-ray results showed that the PTFE/W/Cu/Pb high-density reactive material liner forms an excellent reactive jet penetrator, and the static experimental results demonstrated that the penetration depth of this high-density reactive jet increased firstly and then decreased by increasing the standoff. When the standoff was 1.5 CD (charge diameter), the penetration depth of this reactive jet reached 2.82 CD, which was significantly higher than that of the traditional PTFE/Al reactive jet. Moreover, compared with the conventional metal copper jet penetrating steel plates, the entrance hole diameter caused by this high-density reactive jet improved 29.2% at the same standoff. Lastly, the chemical reaction characteristics of PTFE/W/Cu/Pb reactive materials were analyzed, and a semi-empirical penetration model of the high-density reactive jet was established based on the quasi-steady ideal incompressible fluid dynamics theory.

Nonlinear process monitoring using kernel dictionary learning with application to aluminum electrolysis process

In practice, because of complex mechanism processes, such as heating process, volume heterogeneity, and various chemical reaction characteristics, there is a nonlinear relationship among variables in industrial systems. The nonlinearity brings some difficulties to process monitoring. In order to ensure that the process monitoring system can work normally in nonlinear production processes, the nonlinear relationship between variables ought to be considered. In this work, a new fault detection and isolation method based on kernel dictionary learning is presented. In detail, the linearly inseparable data is mapped to a high-dimensional space. Then, a new nonlinear dictionary learning method based on kernel method was proposed to learn the dictionary. After obtaining the dictionary, the control limit can be calculated from the training data according to the kernel density estimation (KDE) method. When new data arrive, they can be represented by the well-learned dictionary, and the kernel reconstruction error can be used as a classifier for process monitoring. As for the fault data, the iterative reconstruction based method is proposed for fault isolation. In order to evaluate the effectiveness of the proposed process monitoring method, some extensive experiments on a numerical simulation, the continuous stirred tank heater (CSTH) process, and a real industrial aluminum electrolysis process are conducted. The proposed method is compared with several state-of-the-art process monitoring methods and the experimental results show that the proposed method can provide satisfactory monitoring results, especially for some small faults, thus it is suitable for process monitoring of nonlinear industrial processes.

Effects of mixing sequence on mechanical properties of graphene oxide and warm mix additive composite modified asphalt binder

In this work, the effects of mixing sequence of graphene oxide (GO) and warm mix additives on the mechanical properties of the composite modified asphalt binder (CMAB) were evaluated. The warm mix additives included Sasobit® and waste cooking oil (WCO). The experimental results indicated that the combination of GO and Sasobit® can greatly improve the high-temperature performance of asphalt, and the blending of GO and WCO can significantly enhance the fatigue and low-temperature properties of the asphalt. Statistical analysis results suggested that different GO and Sasobit® mixing sequences have significant influence on the workability, mechanical properties, and chemical reaction characteristics of the CMABs, while the influence of different GO and WCO mixing sequences on these properties of asphalt is not significant. In conclusion, GO is suggested to be added first to achieve the better performance of the nano-modified asphalt binder.

Characteristics of chemical reaction and convective boundary conditions in Powell-Eyring nanofluid flow along a radiative Riga plate

A typical base fluid such as water, oil or glycol is poor conductor of heat due to deficient thermo-physical properties. This deficiency is normally addressed by saturation of thermally strong conductive metallic nanoparticles such as Fe, Ti, Hg, Cu, Au into the base fluid resulting a stronger thermal conductivity, electric conductivity, heat and mass flux of the so formulated nanofluid. Nanoparticles having a diameter size less than 100 nano-meter are preferred in this formulation because these nano-sized particles stay suspended into the base fluid for a longer time-period. This communication aims to investigate the salient features of a nanofluid flow along a radiative Riga plate using Powell-Eyring model and convective boundary conditions. The flow model involves the effect of first order chemical reaction as well as the Brownian motion diffusion and Thermophoresis effects. Governing PDEs are transformed into ODEs using suitable transformations. HAM is applied for convergent series solutions to the boundary value problem. Impact of various parameters including Brownian motion, Thermophoresis, modified Hartman number, Lewis and Prandtl number on flow profiles is analyzed graphically. Parameters of physical interest like Skin-friction, Nusselt and Sherwood numbers are illustrated through numerical data. Effect of modified Hartman number is significant on flow profiles due to involvement of Riga plate. An efficiency is achieved in fluid flow and heat-mass flux through suspension of nanoparticles in base fluid.

On a new approach to assessing the energy characteristics of substances

Within the unified model of chemical bonding and methods of quantitative assessment of components of mixed chemical interaction between the elements in compounds, developed by the authors, a new approach was developed to assess the structural and energy characteristics of substances and fuels. It comprises establishing a correlation between the difference of bonds’ chemical components of reactants and end products. Changes in the chemical bond components affect such characteristics of chemical reactions as the heat of formation of the reaction products, their redox properties, whether reaction is endoor exothermic, as well as the heat of fuel combustion reactions. This approach is an additional reserve for improving the methods for assessing the energy characteristics of fuels and increasing the efficiency of energy production technologies.

Molecular dynamics simulations of shock loading of nearly fully dense granular Ni-Al composites.

We used molecular dynamics simulations to study the shock propagation, inhomogeneous deformation, and initiation of the chemical reaction characteristics of nearly fully dense reactive Ni-Al composites. For shocks with piston velocities Up ≤ 2.0 km s-1, particle velocity dispersion was observed at the shock front, which increased on increasing the shock strength. Plastic deformation mainly occurred at the grain boundaries or grain junction during the shock rise and was accompanied by the generation of a potential hot spot in the region where severe plasticity happens. The composite exhibited higher strength and lower reactivity than the mixtures with certain porosity. In addition, the shock-induced premature melting of Al led to the expansion of particle velocity dispersion from the wavefront to the shocked zone and the formation of a heterogeneous velocity field for stronger shocks beyond critical Up (2.5 km s-1). The velocity heterogeneity in the shocked region led to localized shear, strong erosion of Ni, and occurrence of ultrafast chemical reactions. Therefore, the shock-induced premature melting of Al led to the mechanochemical effect and played a role in the shock-induced chemical reaction in the reactive metal system.

Research on characteristics and effects of combustion performance by amplified ignition energy in CVCC system

This study was conducted to analyze the flame characteristics, which is generated through the combustion process according to air/propane mixture ratio and initial pressure as well as increasing the area of flame kernel generation by connecting high capacity capacitor to a standard ignition device. The experiment method involved constant volume combustion chamber system featuring a standard ignition device connected to amplified ignition device and the flame kernel and flame propagation were observed through the spark generated between the electrodes of spark plug. Also, ANSYS Fluent program was used to suggest interpretive results in order to analyze the characteristics of chemical reaction generated within the flame. Experiment conditions included initial pressure being configured at 2, 3, and 4 bar along with air/propane mixture ratio configured at excess air factor (λ) = 1.0, 1.2, and 1.4. Experimental results showed that amplified ignition increased the flame kernel generation compared to standard ignition and was able to decrease the rate of loss for flame propagation speed compared to that of standard ignition as initial pressure and excess air factor increased. In conclusion, the amplified flame can reduce flame instability by increasing the reaction zone rather than the standard flame even if the initial pressure increases. In addition, it is considered that the thermal expansion on the flame front can be increased by the amplification of ignition energy.

Application of cell agglomeration algorithm coupled with dynamic adaptive chemistry for transient engine simulation of diesel fuel

Comprehensively understanding the characteristics of chemical reactions that occur during the combustion process is necessary to improve the design of modern internal combustion engine. However, huge computational cost limits the application of detailed chemical mechanism for practical combustion technologies. Therefore, the objective of this study is to improve the computational efficiency of the chemical reaction in practical engine simulations based on cell agglomeration (CA). In this study, in situ adaptive tabulation (ISAT), dynamic adaptive chemistry (DAC), and CA algorithms are implemented into the KIVA code. CA coupled with DAC and ISAT methods are carried out to validate the optimal acceleration method for practical engine simulation. The results show that CA can significantly reduce the cost of chemistry calculations by effectively reducing the number of CFD cells in which the chemistry calculation need to be performed during HCCI engine and diesel engine simulations. A maximum speed-up factor of 261-fold can be achieved using a 171-species mechanism. The error tolerance can affect the computational accuracy, particularly while using larger chemical mechanism. For non-premixed combustion, the selected coordinates in the reduced-space species composition can further affect the computational accuracy. Overall, the CA-DAC method can achieve the best computational efficiency without lowering the computational accuracy.

Chemical Reaction Characteristics of Sugarcane-Waste-Fiber-Ash (SWFA), Blended Cement - A Study of the Chemical Shrinkage and Heat of Hydration

Chemical Reaction Characteristics of Sugarcane-Waste-Fiber-Ash (SWFA), Blended Cement - A Study of the Chemical Shrinkage and Heat of Hydration

Chemical reaction characteristics, structural transformation and electrochemical performances of new cathode LiVPO4F/C synthesized by a novel one-step method for lithium ion batteries.

A new cathode LiVPO4F/C with a high working voltage of around 4.2 V was synthesized by a novel one-step method. The color of the solution turns green, which implies that V2O5 is successfully reduced to V3+. The reaction thermodynamics indicates that LiVPO4F/C is formed when the sintering temperature is higher than 650 °C, while the accompanying impurity phase Li3V2(PO4)3/C is also generated. The reaction kinetics proves that the reaction is third order and the activated energy is 208.9 kJ mol−1. X-ray photoelectron spectra imply that the components of LiVPO4F/C prepared at 800 °C (LVPF800) are in their appropriate valence. LVPF800 is composed of micron secondary particles aggregating from nano subglobose. The structural transformation shows that the V : P : F ratio in LVPF800 is close to 1 : 1 : 1. The reason behind generation of impurity Li3V2(PO4)3 at a high temperature of 850 °C is demonstrated directly, which is mainly due to the volatilization of VF3. The electrochemical performances of the cathode are related to the crystallite content of LiVPO4F/C and Li3V2(PO4)3/C. The specific capacities at 0.2 and 5C of LVPF800 are as high as 139.3 and 116.5 mA h g−1. Electrochemical analysis reveals that LVPF800 possesses an excellent reversibility in the extraction and insertion process and minimum charge transfer resistance.