Effect Of Side Reactions Research Articles

Experimental Validation of Side Reaction on Capacity Fade of Vanadium Redox Flow Battery

The all-vanadium redox flow battery (VRFB) is widely regarded as the most effective solution for mitigating the intermittent nature of renewable energy sources and simultaneously achieving “carbon neutrality goals.” Nevertheless, the battery’s overall performance is adversely affected by capacity loss resulting from side reactions, hence constraining its viability for usage in large-scale energy storage systems. This study proposes a novel approach that aims to minimize side reactions and mitigate capacity fade by employing an appropriate charge cut-off voltage mechanism. The experiment centers around the examination of performance indicators, including battery charge/discharge capabilities, internal resistance, capacity retention rate, and efficiency, for analytical purposes. The findings indicate that by setting the charge cut-off reference voltage at 1.65 V, the battery’s capacity can be sustained at 61.76% after 60 cycles. When the charge cut-off voltage is raised by increments of 0.1 V and 0.15 V, the corresponding reductions in battery capacity amount to 1.74% and 5.16% respectively. The aforementioned findings emphasize the significance of considering the effect of side reactions on battery capacity and implement that mechanism can significantly enhance the battery’s overall performance.

Design and Optimization of Hybrid Reactive-Extractive Distillation for Ternary Azeotropic Separation: A Case Considering the Effect of Side Reactions

Design and Optimization of Hybrid Reactive-Extractive Distillation for Ternary Azeotropic Separation: A Case Considering the Effect of Side Reactions

Operating windows for early evaluation of the applicability of advanced reactive distillation technologies

Advanced reactive distillation technologies (ARDT) are often overlooked during process synthesis due to their complexity. This work proposes the use of operating windows with additional features to identify suitable operating limits for ARDT. Data needed to construct the operating windows are thermodynamic properties, kinetic parameters, constraints of materials and experimental methods, and heuristics. In addition, two new concepts are proposed to represent complex features: representative components and a sliding window. Results include the identification of suitable operating limits for ARDT to help assess their feasibility early in process design. The proposed approach is demonstrated by case studies. Methyl acetate production can be carried out at low pressures (0.5–3.6 atm), while lactic acid purification requires vacuum conditions (0.3–0.8 atm) to avoid thermal degradation. Tert-amyl methyl ether production was evaluated in two scenarios where the effect of side reactions is evidenced in a reduction of the reaction window due temperature limits to favour the main reaction over side reaction. This study is the first to evaluate advanced reactive distillation technologies using a graphical representation in an operating window to aid process synthesis, where the results provide key selection insights.

Adsorption and dissociation of Cl2 on CuO(111) surface with first-principles study

The first principle calculation based on density functional theory (DFT) was used to discuss the adsorption and dissociation behaviors of Cl2 on the perfect and oxygen-deficient surfaces of CuO(111) in this paper. The adsorption behavior and reaction mechanism of Cl2 directly adsorbed on two CuO(111) surfaces were analyzed by calculating the adsorption structure, energy of adsorption, charge density difference, the electron localization function and density of states (DOS) of the system. The calculations suggest that the most advantageous site for Cl2 adsorption on the perfect CuO(111) surface is the bridge site between two Cusub atoms. However, on the oxygen-deficient CuO(111) surface, two Cl atoms dissociated from the Cl2 molecule and bound to the Cu site after optimization. The calculations indicate that the existence of oxygen vacancy is highly chemically reactive when it comes to the dissociation of Cl2, which can increase the activity of CuO significantly. Our calculations of the adsorption and dissociation of Cl2 on the CuO(111) surface can offer some microscopic information for the side products of CuO and Cl2 produced by the thermolysis of copper oxychloride and the effect of side reaction on yield.

Capacity and Coulombic Efficiency Measurements Underestimate the Rate of SEI Growth in Silicon Anodes

Capacity measurements and related quantities are the first layer of information acquired during testing of Li-ion cells. It is generally considered that elevated values of coulombic efficiency and capacity retention are absolute indicators of the existence of a stable solid electrolyte interphase (SEI). Here, we challenge this notion by analyzing how the effect of side reactions on cell capacity depends on the choice of electrodes. More specifically, we demonstrate that the extent of measurable capacity fade due to SEI growth is modulated by the shape of the voltage profile of the cathode and anode at the end of charge and discharge half-cycles. This shape-dependency creates a mismatch between SEI growth and cell capacity loss, which is relatively small for graphite anodes but sizable for silicon-containing electrodes. We illustrate this point by showing that, at the same coulombic efficiency and capacity retention, cells containing silicon-based materials could actually exhibit rates of SEI growth that are as much as ≥ 40% higher than graphite cells. The main implication of this behavior is that, for certain systems, capacity measurements may be an unreliable source of information about the extent of reactions at the SEI, allowing other consequences of these side reactions (such as electrolyte depletion) to proceed unchecked while the cell appears to be stable.

The effects of side interactions on the neutronic analysis of HCCR breeding blanket

Helium Cooled Ceramic Reflector (HCCR) is a candidate as Multi-Module Segmentation Breeding Blanket used the Korean DEMO Reactor (K-DEMO). Neutronic analyses of the breeding blanket are substantial due to the prominent role of neutrons in tritium breeding, energy deposition, and radiation damages. This work aims to consider the effects of side reactions with low cross-sections on the neutronic study to make the simulation results more accurate. The neutronic analysis of the HCCR blanket has been performed using the MCNPX.2.6.0 3D Monte Carlo code and ENDF/B-VII nuclear data library. The effects of side reactions have been considered on Tritium Breeding Ratio (TBR) and Neutron Multiplication Factor (NMF) computations. The 9Be(n,T)7Li is a side reaction to tritium breeding, and the 7Li(n,2n) and W(n,2n) reactions with low cross-section cause neutron multiplication. Furthermore, the deposited energy by alpha particles has been investigated. Finally, the reaction rate of the photonuclear response has been examined using MCNPX.

Three-dimensional transient model of zinc-nickel single flow battery considering side reactions

Based on a comprehensive description of the conservation of momentum, mass and charge, as well as the global dynamics involving ion and proton reactions, a three-dimensional transient model for zincnickel single flow battery considering side reactions of hydrogen evolution and oxygen evolution was established. The accuracy of the model is verified by experiments. The effects of current density, electrolyte flow rate, initial ion concentration, temperature and electrode porosity on the side reactions of hydrogen evolution and oxygen evolution were investigated. The effects of side reactions on the activation polarization and concentration polarization of the battery were studied by comparing the two cases of whether side reactions were considered or not. The results show that the reaction rate of hydrogen evolution and oxygen evolution can be effectively reduced by reducing the applied current density, ambient temperature or increasing the flow rate of electrolyte. Increasing the initial concentration of hydroxyl ions inhibited the occurrence of hydrogen evolution side reaction, but also promoted the occurrence of oxygen evolution side reaction. As the porosity of the positive electrode increases, the reaction rate of the side reaction of oxygen evolution and the oxygen concentration in the positive electrode area gradually decrease. In the later stage of charging, when the shielding effect of oxygen bubbles on the positive reaction interface is not considered, compared with the case without considering the side reactions, the positive electrode activation polarization is larger when considering the side reaction.

Effects of side reactions on the kinetics of nanoporous gold formation revealed by real-time X-ray scattering during electrolytic dealloying

Simultaneous SAXS/WAXS studies elucidate passive surface film growth during formation of nanoporous gold by electrolytic dealloying in HClO4, but not in HNO3. This passive surface film hampers dealloying kinetics and slows ligament growth/coarsening.

Optimization of CO2 Capture Process Using Dry Sodium-Based Sorbents

Sodium carbonate (Na2CO3) supported by gamma-alumina (g-Al2O3) is one of the best sorbents for CO2 capture in economic terms because of its low raw material cost and excellent performance in low-temperature operation. The fundamental goal of this study is to optimize the operating conditions of CO2 adsorption by Na2CO3/Al2O3 sorbent in a fixed bed reactor. The sorbent characterization was studied using BET, SEM, XRF, and XRD analyses, and the sorbent structure was compared before and after the carbonation reaction. Moreover, the effects of side reactions on the adsorption process were investigated. The Response Surface Methodology (RSM) was used with Box-Behnken Design (BBD) to design the experiments. The optimum conditions are introduced at the point where initial CO2 capture capacity and deactivation rate constants are as high and as low as possible, respectively. The optimum values of the variables corresponding to the temperature of 50°C, vapor pretreatment time of 9 min, and H2O/CO2 mole ratio of 1. The amounts of initial CO2 capture capacity and deactivation rate constant in the optimum conditions were obtained to be 39.238 mgCO2/gsorbent and 0.416 min-1, respectively.

Comparative Measurements of Side-Reaction Currents of Li[Li1/3Ti5/3]O4 and Li[Li0.1Al0.1Mn1.8]O4 Electrodes in Lithium-Ion Cells and Symmetric Cells

Lithium-ion batteries using Li[Li1/3Ti5/3]O4 and Li[Li0.1Al0.1Mn1.8]O4 (LTO/LAMO) are very attractive for long-life and high-power applications. Capacity fading of the batteries mainly results from the deviation in the state of charges (SOCs) of LTO and LAMO electrodes caused by the difference in the side reaction currents of the electrodes. In this study, “real” and “intrinsic” side reaction currents are measured in LTO/LAMO cells and symmetric cells of LTO/LTO and LAMO/LAMO, respectively. An observed significant difference in the side reaction currents is affected by the coupled electrode. The real side reaction currents for both electrodes are a few times larger than the intrinsic side reaction currents at any temperature, which can be explained by taking into account the influence of oxidation (or reduction) products generated at the positive (or negative) electrode on the negative (or positive) electrode. A mechanism of the side reaction inside the cell is proposed to explain the above phenomenon. The mechanism indicates the importance for understanding the “secondary” effects of side reactions, which are influenced by decomposition products on the other electrode, in addition to “primary” effects of side reactions such as the formation of solid electrolyte interphase.

Preparation of Ti–Ni–Fe phase by levitation and its structural characterisation

This paper presents results concerning the electromagnetic levitation of solid metal samples. It describes the levitation system and some coils designed to melt 10 g metal samples under controlled atmosphere, as well as melting the process. The main advantage of the method is the absence of any type of crucible and owing to this, the effect of side reaction can be avoided, resulting from the influence of the active metal on the walls of the ceramic crucible in the physicochemical investigations. In many cases, the side reaction makes the correct interpretation of the experimental results sometimes difficult and/or impossible. In order to describe the crystallisation process and the change in the microstructure of the samples obtained during electromagnetic melting at the intermetallic Fe–Ni–Ti phase, a scanning electron microscopy analysis and an X-ray diffraction analysis were used.

Side Reactions in Controlling the Quality, Yield, and Stability of High Quality Colloidal Nanocrystals

Effects of side reactions during the formation of high quality colloidal nanocrystals were studied using ZnO as a model system. In this case, an irreversible side reaction, formation of esters, was identified to accompany formation of ZnO nanocrystals through the chemical reaction between zinc stearate and an excess amount of alcohols in hydrocarbon solvents at elevated temperatures. This irreversible side reaction made the resulting nanocrystals stable and with nearly unity yield regardless of their size, shape, and size/shape distribution. Ostwald ripening and intraparticle ripening were stopped due to the extremely low solubility/stability of the possible monomers because all free ligands in the solution were consumed by the side reaction. However, focusing on size distribution and 1D growth that are needed for the growth of high quality nanocrystals could still occur for high yield reactions. Upon the addition of a small amount of stearic acid or phosphonic acid, immediate partial dissolution of ZnO nanocrystals took place. Although the excess alcohol could not react with the resulting zinc phosphonic acid salt, it could force the newly formed zinc stearate gradually but completely back onto the existing nanocrystals. The results in this report indicate that side reactions are extremely important for the formation of high quality nanocrystals by affecting their quality, yield, and stability under growth conditions. Due to their lack of information in the literature and obvious practical advantages, studies of side reactions accompanying formation of nanocrystals are important for both fundamental science related to crystallization and industrial production of high quality nanocrystals.

Analysis of Network Structure of UV-Cured Acrylates by1H NMR Relaxation,13C NMR Spectroscopy, and Dynamic Mechanical Experiments

The network structure of UV-cured acrylates was analyzed by dynamic mechanical experiments, 1H T2 NMR relaxation, and 13C NMR spectroscopy. Photocured mixtures of difunctional (poly(ethylene glycol) diacrylate) and monofunctional (2-ethylhexyl acrylate) were studied. The mean cross-link density and fraction of dangling chains were varied in these networks by changing the content of monofunctional acrylate. Examining networks by 13C NMR spectroscopy, we observed that the conversion is high, and the contribution or the effect of side reactions that generate extra cross-links is negligible. The spatial distribution of cross-links is very heterogeneous in the cured samples; i.e., polyacrylate ziplike network junctions are interconnected by polyether chains. An increase in the content of monofunctional monomer causes a significant decrease in the cross-link density because the monofunctional monomer acts as a chain extender. NMR T2 relaxation method shows good correlation with mechanical tests with respect to molar mass between cross-links, Mc. Obtained values of Mc are significantly smaller compared to molar mass of diacrylate. As anticipated, it is apparent that classical rubber elasticity theories are not applicable for characterization of this type of networks containing ziplike network junctions.

The catalytic oxidative coupling of methane: II. Axial gas sample probing in a bubbling Fluidised‐Bed reactor and the effect of side reactions

AbstractThe atmospheric pressure catalytic oxidative coupling of methane was studied in detail by axial gas concentration probing experiments in a 60 mm OD bubbling fluidised‐bed reactor system. Experimental data demonstrated a very fast reaction which occurred within the vicinity of the distributor (normally in the first 5 mm of bed height) under normal reaction conditions of 850°C and 83 vol%/17 vol% CH4/O2 feed. The data also showed that hydrocarbon selectivity was deleteriously affected by side reactions which were also promoted by the catalysts even though they were good catalysts for the oxidative coupling reaction. If this reduction in hydrocarbon selectivity is inevitable then there will be optimum operating conditions for each catalyst in the bubbling fluidised bed reactor.

Spatially resolved concentration measurements during cathodic alloy deposition in microstructures

Local concentration distributions within microstructures, alloy composition, the effects of side reactions and the influence of convection on electrodeposition in microstructures were measured. Since technically relevant microstructures have complex geometries, experiments involving locally resolved measurements using freely positionable microelectrodes are necessary. The SLCP method is based upon chronoamperometry and was used for simultaneous measurement of absolute concentration values of copper and nickel. In this way concentration profiles were measured as c( xy), c( x) and c( z). In a trench microstructure, concentration distribution was investigated as a function of the aspect ratio in unstirred solution and under convectional influence. In direct comparison to the conditions in the unstirred electrolyte, a notable intrusion of the flow is observed at aspect ratios ≤ 1. At a higher aspect ratio the concentration distribution is uniform. With higher aspect ratios ( eg 1.5) the effects of side reactions on the metal deposition increase. During CuNi alloy deposition the formation of nickel oxide and nickel hydroxide layers can be detected.

Sensitive determination of nitrite by means of a Landolt-type reaction in fluorescent aggregates of a binaphthyl-based amphiphile

The iodine quenching effect on the fluorescence of a binaphthyl-based amphiphile, C8BNC6N, was used for monitoring the Landolt-type reaction between nitrite, iodide, and thiosulfate. Due to the possibility of iodine detection in the 10−8–10−7M range, and to the effective concentration of anionic reagents on the surface of cationic aggregates, the indicator reaction can be monitored using reagents at concentration levels as low as 10−7M. To optimize the analytical system, the effect of pH and reagent concentrations on the rate of indicator reaction were studied. The influence of the matrix of water samples and effect of side-reactions increasing the value of a blank test were examined. A procedure for nitrite determination in water was developed, using the diazo reaction for selective nitrite removal to provide a reference solution, which avoided possible effects of the matrix components. The usefulness of this method was tested by determining trace amounts of nitrite in water samples. The procedure allows determination of nitrite down to 5 ng/ml (detection limit about 2ng/ml) with r.s.d. of 10% in the 20–250 ng/ml range.

Theoretical and experimental studies of the effect of side reactions in copper deposition from dilute solutions on packed-bed electrodes

This paper analyses the effect of side reactions, such as the reduction of oxygen or Fe(III), on copper deposition from dilute acid sulfate solutions. Fundamental studies with a rotating disc electrode were performed to determine the potential regions where the reactions take place and also to calculate kinetic parameters under the conditions of the experiments. Applied studies carried out in a through-flow electrochemical reactor with a packed bed cathode formed by a stack of nets are reported. The experimental data are compared with theoretical results, according to the continuous model, to corroborate its reliability for the case of simultaneous electrochemical reactions. It was found that the agreement between the mathematical treatment and the experimental data is similar to the case of a single reaction in the electrode. Taking into account the side reactions, criteria for the selection of bed thickness parallel to the current flow are discussed.

Computer simulation of urethane formation

AbstractComputer model calculations have been used to simulate the reaction of polyoxypropylene triol with hexamethylene diisocyanate. Various molecular weight distributions and degrees of polymerisation are used in the calculation. The effect of side reactions is investigated and compared with experiment. Good agreement for both cyclisation and gel points is found for bulk and concentrated solutions. The model can be used to simulate random polycondensation reactions with a reliability approaching that of experiments, and it gives crucial results that cannot be obtained in any other way.

Some problems in the crystallization by precipitation as investigated in the system ZnC 2O 4 · 2 H 2O/H 2O

Some problems of the crystallization by precipitation in the system ZnC 2O 4 · 2 H 2O/H 2O has been studied using a combination of makrokinetic and microkinetic methods. The crystallization of this system is characterized by a clearly expressed induction period during which heterogeneous nucleation occurs at low sueprsaturations ( S = 5, pH=2) whereas homogeneous nucleation proceeds at high supersaturations. On the basis of the evolution of the distribution function of the crystals with respect to their dimensions during the process, empirical equations were deduced for the dependence of the growth rate on supersaturation and crystal size. The beginning of recrystallization of the product and the effects of side reactions (nucleation on the walls of the crystallization vessel, agglomeration and crystal breakage) on the kinetics of the total crystallization process were determined.

The effect of side reactions on the molecular weight characteristics of polyamidoacids

In conformity with a proposed mechanism of formation of polyamidoacids the set of kinetic equations is solved by the Runze-Kutt method. The dependence of M w , M n and M w / M n on time is calculated. It is shown that even a small quantity of water lowers M w and M n considerably and increase M w / M n , but a small excess of the dianhydride or diamine enables M w and M n to be increased and M w / M n to be decreased. M w shows greater sensitivity to side reactions than M n . If hydrolysis of amide linkages by water present in the system or released by imidization occurs, or if they undergo scission, the curves of the time dependence of M w , M n and M w / M n pass through a maximum, and after passing through the maximum the M n / M n curve approaches the value of two as t → ∞.