Reaction Equilibrium Research Articles

Absorption of SO2 by deep eutectic solvents composed of EmimCl and dihydric alcohols: Thermodynamic and absorption mechanism studies

As a class of green absorbents, deep eutectic solvents (DESs) show excellent application potential in the field of SO2 separation. In this work, three DESs composed of 1-ethyl-3-methylimidazolium chloride (EmimCl) and polyethylene glycol 200 (PEG 200) or tetraethylene glycol (TeEG) in a specific molar ratio are used for SO2 absorption. TeEG-EmimCl (1:2) exhibits the best SO2 adsorption capacity with up to 13.25 mol·kg−1 and good ideal selectivity of 29.9 for SO2 to CO2 at 298.2 K and 1.0 bar. To study the absorption behavior of SO2, the thermodynamic parameters of SO2 absorption, including equilibrium constant (K0), enthalpy change (ΔHm), entropy change (ΔSm), and Gibbs free energy change (ΔGm), are calculated by combining the solubility data with Henry’s law and reaction equilibrium equation (RETM). Further SO2 absorption mechanism by FTIR and NMR spectroscopy suggested that there is mainly physical interaction between SO2 and DESs, making the TeEG-EmimCl (1:2) with excellent regeneration cycle performance. These DESs reported in the current work can be used as the attractive absorbents for SO2 absorption due to their excellent absorption performance and good reversibility.

Mathematical modeling the methanol production process for direct CO2 hydrogenation over a gallium (Ga3Ni5) catalyst

Carbon capture and utilization as a raw material for methanol production is a good option for addressing environmental, energy and global warming problems. However, commercial methanol synthesis processes have poor performance due to high water production during the process, oxidation and inactivation of the catalyst, and low CO2 conversion. To overcome these barriers, in this study, an efficient process consisting of Ga3Ni5 catalyst for direct CO2 hydrogenation is modeled. Synthesis equations and reaction rate constants, adsorption equilibrium constants and reaction equilibrium constants were used to model the methanol production process in the vicinity of the Ga3Ni5 catalyst using MATLAB software. In the new process, in order to increase safety and control process costs, the process pressure was reduced from 76.98 bar to 2 bar, on the other hand, the water produced as the poisoning agent of Cu/ZnO/Al2O3 catalyst is significantly ineffective in this configuration. The results show that Ga3Ni5 catalyst increases the conversion rate of carbon dioxide to methanol by about 13.75% compared to Cu/ZnO/Al2O3 catalyst. The proposed catalyst is an active and stable catalyst for methanol production that can compete with the traditional synthesis process.

Effect of tubulin self-association on GTP hydrolysis and nucleotide exchange reactions

We investigated how the self-association of isolated tubulin dimers affects the rate of GTP hydrolysis and the equilibrium of nucleotide exchange. Both reactions are relevant for microtubule (MT) dynamics. We used HPLC to determine the concentrations of GDP and GTP and thereby the GTPase activity of SEC-eluted tubulin dimers in assembly buffer solution, free of glycerol and tubulin aggregates. When GTP hydrolysis was negligible, the nucleotide exchange mechanism was studied by determining the concentrations of tubulin-free and tubulin-bound GTP and GDP. We observed no GTP hydrolysis below the critical conditions for MT assembly (either below the critical tubulin concentration and/or at low temperature), despite the assembly of tubulin 1D curved oligomers and single-rings, showing that their assembly did not involve GTP hydrolysis. Under conditions enabling spontaneous slow MT assembly, a slow pseudo-first-order GTP hydrolysis kinetics was detected, limited by the rate of MT assembly. Cryo-TEM images showed that GTP-tubulin 1D oligomers were curved also at 36 °C. Nucleotide exchange depended on the total tubulin concentration and the molar ratio between tubulin-free GDP and GTP. We used a thermodynamic model of isodesmic tubulin self-association, terminated by the formation of tubulin single-rings to determine the molar fractions of dimers with exposed and buried nucleotide exchangeable sites (E-sites). Our analysis shows that the GDP to GTP exchange reaction equilibrium constant was an order-of-magnitude larger for tubulin dimers with exposed E-sites than for assembled dimers with buried E-sites. This conclusion may have implications on the dynamics at the tip of the MT plus end.

Designing White Space for Chemistry Education With the Inspiration of Chinese Artistry

White space is an artistry concept widely used in Chinese painting and calligraphy. It conveys useful information for the readers while retaining certain imagination space for them. Inspired by this artistry, we probe into the white space designing in chemistry education and scientific training in colleges/universities. A few examples are illustrated for the utilization of white spaces in scientific knowledge teaching with detailed discussions. These include half-life time of dynamic studies, mathematical derivation of chemical calculations, equilibrium of chemical reactions and phases of thermodynamics, as well as data processing in scientific studies & developments. Designing white space in lectures/presentations aims to rhythmize the teaching process and to prevent fatigue from both the lecturer and students by cutting off lengthy talking. Moreover, leaving suitable white space in the teaching content may arouse the curiosity of students, stimulate the desire for their exploration, and therefore enrich their learning experiences. We herein propose the designing of appropriate white space in college chemistry education with pernitent examples to promote further discussions on this issue.

Insights into the evolution of Cr(VI) species in long-term hexavalent chromium contaminated soil

Compare to the content of Cr(VI), the distribution of specific Cr(VI) species in soil is rarely paid attention to, which may lead to an inaccurate environmental risk assessment of Cr(VI) contaminated soil or inability to meet stringent requirement for soil remediation. Herein, to reveal the primary mechanisms and factors controlling the evolution of Cr(VI) species in soil, the distribution of Cr(VI) and Cr(III) species in soils with different particle sizes and textures was systematically investigated by using a modified sequential extraction procedure and spectroscopy characterizations (e.g., SEM-EDS mapping). The results show that a significant proportion of Cr(VI) can be captured by minerals containing exchangeable calcium ions and metal oxide hydrates in the soil, forming a relatively stable adsorbed Cr(VI). Also, a small fraction of Cr(VI) can precipitate as calcium chromate with free calcium ion which is the most stable Cr(VI) species in the soil. The majority of Cr(VI) discharged into soil tends to be reduced by ferrous ions or minerals containing ferrous ions with a product of Fe(III)-Cr(III) coprecipitate. Therefore, the speciation of Cr in the soil is closely correlated to Fe and Ca. After the equilibrium of adsorption, precipitation, and reduction reactions of Cr(VI), the rest of Cr(VI) retains as the form of its original water-soluble state in soil. The evolution of Cr(VI) species and the content of specific Cr species in soil are mainly determined by the contents of iron, exchangeable calcium ions and metal oxide hydrates, which effect the Cr(VI) reduction, precipitation and adsorption, respectively.

Electrochemically mediated amine regeneration and proton concentration modulation processes for flue gas CO2 capture: Comparison and artificial intelligence-based optimization

Among different carbon capture and sequestration (CCS) systems, ones that are based on the electrochemical processes are at the center of attention. Developing a CCS system with a high energy efficiency can facilitate their applications. In this study, two electrochemical CO2 capture systems are optimized and compared from energy consumption perspective. The considered systems are electrochemically mediated amine regeneration (EMAR) and electrochemically proton concentration modulation (EPCM). Both systems are modeled using reactions equilibrium constants and species activity methods and then, based on the presented chemical model, their heat and electricity loads are calculated. The chemical and electrochemical models are validated by comparing the species concentrations and electrochemical cell’s potential with those of previous works. Also, a comprehensive parametric study is presented based on the design parameters, where the performances of the two systems are also compared. Additionally, the energy performances of the systems are modeled using artificial neural network (ANN) to the optimization intention. The obtained ANNs, as a multi-objective optimization function considering heat and electricity loads as objectives, are introduced to the genetic algorithm. Applying the genetic algorithm, both objectives are minimized simultaneously and illustrated in a Pareto front diagram. The results show that the EMAR system at different optimum states always exhibits lower heat and electricity loads than the EPCM system. In trade-off mode, consumption of electricity and heat load for the EMAR system are 38.8 kJ/mol CO2 and 79.2 kJ/mol CO2, respectively, while those of the EPCM system are respectively 45.58 kJ/mol CO2 and 200.3 kJ/mol CO2.

Thermodynamic analysis of reaction pathways and equilibrium yields for catalytic pyrolysis of naphtha

Thermodynamic analysis of reaction pathways and equilibrium yields for catalytic pyrolysis of naphtha

Non thermal plasma assisted water-gas shift reactions under mild conditions: state of the art and a future perspective

The water gas shift (WGS) reaction is important for many industrial processes such as ammonia synthesis, oil refining and fuel cells. WGS reaction is exothermic and limited by kinetics and chemical equilibrium, and under conventional thermocatalytic conditions, the desired thermodynamic equilibrium conversion and sufficiently fast kinetics can rarely be achieved simultaneously. To address such limitations, non-thermal plasma (NTP) processes have been recently proposed to enhance the kinetics at low temperatures (via gas phase activation), and realising favourable thermodynamic conversion. Here, a critical review of the relevant state-of-the-art regarding NTP-assisted WGS reactions (including both catalytic and non-catalytic systems) is presented. In addition, it also evaluates the concept of reaction-separation integration using novel membrane reactors to improve WGS reaction by shifting reaction equilibrium to favour hydrogen production. Finally, the prospect regarding future research avenues in advancing the NTP-assisted WGS processes is shared.

Characterization of electrode charges and forces in an electrohydrodynamic thruster

Corona discharge generates an electrohydrodynamic (EHD) flow and a reactive thrust between electrodes in the air. Although the theory for this thrust between two electrodes has been thoroughly developed, the mechanism responsible for the reactive forces acting on the electrode surfaces is not well understood. Here, we numerically and experimentally investigate these forces and the charges that generate them. The results show that the emitter and collector surface charges deviate from the equality of capacitive charges as the discharge initiates. As the applied voltage increases, the emitter surface charge maintains its initial onset value, while the collector surface charge and the volume charge between the electrodes linearly increase. In the same manner, the emitter and collector surface forces deviate from the equilibrium of action and reaction as the discharge initiates. As the circuit current increases, the emitter surface force maintains its initial onset value, while the collector surface force and the thrust linearly increase. In particular, we demonstrate an unconventional thrust-measuring method by installing a windshield in the rear of the thruster. The force exerted on the windshield is equal to a good approximation of the pure EHD thrust. Also, the difference between this force and the thrust measured without the windshield can be taken as the approximate drag force acting on the electrodes.

Remodeling of the osteoimmune microenvironment after biomaterials implantation in murine tibia: Single-cell transcriptome analysis.

Osseointegration seems to be a foreign body reaction equilibrium due to the complicated interactions between the immune and skeletal systems. The heterogeneity of the osteoimmune microenvironment in the osseointegration of implant materials remains elusive. Here, a single-cell study involving 40043 cells is conducted, and a total of 10 distinct cell clusters are identified from five different groups. A preliminary description of the osteoimmune microenvironment revealed the diverse cellular heterogeneity and dynamic changes modulated by implant properties. The increased immature neutrophils, Ly6C + CCR2hi monocytes, and S100a8hi macrophages induce an aggressive inflammatory response and eventually lead to the formation of fibrous capsule around the stainless steel implant. The enrichment of mature neutrophils, FcgR1hi and differentiated immunomodulatory macrophages around the titanium implant indicates favorable osseointegration under moderate immune response. Neutrophil-depletion mice are conducted to explore the role of neutrophils in osseointegration. Neutrophils may improve bone formation by enhancing the recruitment of BMSCs via the CXCL12/CXCR3 signal axis. These findings contribute to a better knowledge of osteoimmunology and are valuable for the design and modification of ‘osteoimmune-smart’ biomaterials in the bone regeneration field.

Three-component 1,1,3,3-tetramethylguanidine based CO2-binding organic liquids: Statistical solvent design and thermodynamic modeling of CO2 solubility by LJ-Global TPT2 EoS

In this study, three-component CO2-binding organic liquids (CO2BOLs) are introduced for high pressure CO2 absorption. The non-aqueous, green solvents consist of a superbase (1,1,3,3-tetramethylguanidine (TMG)), a tertiary alkanolamine (Dimethylethanolamine (DMEA), Diethylethanolamine (DEEA) and N-methyldiethanolamine (MDEA)) and an alcohol (MeOH, n-BuOH, sec‑BuOH, tert‑BuOH and 1-HexOH). The best combination of solvent components was determined to be the TMG/DMEA/n-BuOH BOL (molar ration:1/1/1) based on both CO2 loading (αeq= 0.431 mol CO2/mol solvent) and absorption rate (αR= 0.225 mol CO2/mol solvent within 20 min) by implementing screening experiments. The mixture design approach was applied for the design of experiments, modeling and investigating the effect of components’ proportion on αeq and αR at the constant temperature of 35.0 °C and initial CO2 pressure of 25.0 bar. The highest αeq (0.573 mol CO2/mol BOL) and αR (0.362 mol CO2/mol solvent) were obtained using TMG/n-butanol (1/1) and DMEA BOLs, respectively. The CO2 solubility data in the two-component BOLs: TMG/n-BuOH, TMG/DMEA and DMEA/n-BuOH as well as the three-component TMG/DMEA/n-BuOH BOL were gathered at 25.0, 35.0 and 45.0 °C and the pressures up to 35.0 bar using equimolar solvent mixtures. The LJ-Global TPT2 EoS was used in the simultaneous VLE and chemical equilibrium calculation algorithm for the thermodynamic modeling of CO2 solubility in the BOLs. The AAD% in the modeling of TMG/n-BuOH, TMG/DMEA, DMEA/n-BuOH and TMG/DMEA/n-BuOH BOLs were calculated to be 11.5%, 12.4%, 10.5 and 12.9%, respectively. The enthalpies of CO2 absorption in BOLs and the speciation of the system components were predicted from reaction equilibrium constants and using LJ-Global TPT2 EoS.

Maximizing the selectivity to triacetin in glycerol acetylation through a plastic waste-derived carbon catalyst development and selection of a reaction unit

Carbon catalysts derived from poly(ethylene terephthalate), PET, enriched with surface acidic sites were prepared and used in glycerol acetylation to increase the glycerol conversion and formation of higher acetins, i.e., diacetins and triacetin (DA and TA, respectively). Two approaches of carbon functionalization were applied – treatment with concentrated sulfuric acid or modification with benzenediazonium sulfonate (BDS) generated in-situ. The as-prepared carbons were characterized applying different techniques (e.g., elemental analysis, potentiometric titration, TG method, or XPS studies), and used as catalysts in glycerol esterification with acetic acid under different conditions. Using the synthesized carbons in the process carried out in a classical reaction mode (i.e., batch and reflux conditions, no water removal) enabled us to significantly increase the reaction rate and yields of the produced di- and triacetins compared to the reaction without a catalyst. The most active sample showed a high content of sulfonic groups and gave about 95 % conversion of glycerol and 55 and 20 % selectivity to DA and TA, respectively, just within 1 h of the process at 110 °C. Moreover, the used catalyst caused a significant increase in the TA yield when the reaction was performed with the addition of toluene compared to the toluene-free process. This was related to the continuous removal of water from the reactor and shifting the reaction equilibrium toward the higher esters as well as due to the perfectly-tailored properties of the obtained carbon sample.

(Invited) Ligand Exchange at Chalcogenide and Perovskite Nanocrystal Surfaces Examined Via Isothermal Titration Calorimetry

I will describe our group’s efforts to quantify ligand association and exchange reactions on semiconductor nanocrystal (NC) surfaces via isothermal titration calorimetry (ITC). ITC provides a direct thermal measurement of reaction progress. As shown in earlier work by our group and others examining ligand exchange on chalcogenide and pnictide quantum dots, ITC is able to access the enthalpy change of reaction, equivalency, and effective equilibrium constants, including in cases that are challenging to resolve by NMR alone. Here, we will describe the extension of this approach to ligand exchange reactions on halide perovskite NCs, and to ligand exchange on chalcogenide NCs in aqueous solution. Such advances are needed to contribute a quantitative description of NC surface chemistry toward applications such as advanced optoelectronic devices, bioimaging probes, and photocatalysis.

A Practical Field Test and Simulation Procedure for Prediction of Scaling in Geothermal Wells Containing Noncondensable Gases

Scaling in a hydrothermal type of geothermal well reduces or interrupts the production of geothermal energy. Calcite is one of the most common scales in geothermal wells. The reason for its formation in geothermal production wells is clear. The flowing up of geothermal water causes a change in the pressure and temperature, which results in the escape of CO2 gas from the geothermal water, causing a rise in pH and the supersaturation of CaCO3 in the solution. To predict scaling in a new geothermal well, conditional data for geothermal well simulations are required. It is important to determine what field data are needed and how to obtain them. It is necessary to deal with some parameters that are hard to measure and that have not been described in detail in the existing literature. In this study, a two-phase flow model and a chemical reaction equilibrium model are integrated to simulate the scaling process in production wells. Based on the simulation, a comprehensive and practical approach, including a novel noncondensable gas content measurement method, is applied to predict the depth of the first gas bubble using simple field test data and does not require reservoir permeability and earth conductivity. The result shows good agreement with the location of scaling detected in the field.

Comparison of open- and closed-loop operating strategies for exhaust gas scrubbing in marine applications: Modeling and sea-trial data

A model of a hybrid marine engine exhaust gas scrubber is constructed using sea-trial data and a chemical process simulator. The model can describe the performance of the scrubber under both open-loop and closed-loop operation. Predictions for solubility and reaction equilibria are validated using published data. The model results are consistent with the sea-trial data. Sensitivity analyses are conducted to determine the effect of various operating parameters on the scrubbing performance for both open-loop and closed-loop operation.

High-Luminescence and Submillimeter-Scale MoS2 Monolayer Growth Using Combinational Phase Precursors via Chemical Vapor Deposition

We successfully synthesize high-luminescence and submillimeter-scale monolayers of molybdenum disulfide (MoS2) employing a combinational phase precursor via a chemical vapor deposition (CVD) approach. First, sodium nitrate catalyst is demonstrated to assist the reaction equilibrium of a solid precursor CVD process, leading to an increased density and size of MoS2 monolayer flakes (∼120 μm). However, the monolayers’ photoluminescence intensity is significantly reduced due to the presence of excess residues. A suspension solution-based precursor is also tested using the optimized temperature, pressure, and catalyst from the solid precursor case, and it is found to also give a high density of uniform triangles with an average size of ∼80 μm. Finally, combining both precursor phases (combinational phase precursor) yields the largest monolayer flakes with an average size of ∼200 μm and the highest luminescence, with photoluminescence intensities being 1 order of magnitude higher than that of a standard mechanical exfoliated monolayer.

Reactive extraction of gallic acid using tri-n-octylamine in a biocompatible mixture of diluents

The present study is an approach to develop a biocompatible extraction system using tri-n-octylamine (TOA), with a modifier, 1-decanol and inert diluent, n-dodecane for the recovery of gallic acid (GA) from aqueous solution. The effects of GA concentration, modifier volume ratio, solvent polarity and pH of aqueous solution on reactive extraction of GA, are examined. With optimized extraction system of 20% TOA with 40% 1-decanol and 40% n-dodecane, further investigations are carried out for the determination of reaction stoichiometry ( m = 1.53 – 2.02), equilibrium constants (K E = 20.30 – 83.23) and thermodynamics (∆H o = -94,385.86 J.mol –1 , ∆S o = -267.51 J.mol –1 .K –1 and ∆G o = -14,627.83 to -6602.54 J.mol –1 .K –1 ) in the range of GA concentrations (0.00294 kmol.m –3 – 0.04703 kmol.m –3 ) at different temperature (298.15 K – 328.15 K) using a bio-inspired, population based genetic algorithm, differential evolution (DE). At the temperature 298.15 K, maximum distribution of GA in organic phase is found as 81%.

Yükseköğretim Kurumları Sınavında Yer Alan Kimya Sorularının 2018 Yılı Kimya Dersi Öğretim Programı Kazanımlarına Göre Analizi

Bu çalışmada, 2019-2021 yıllarında TYT (Temel Yeterlilik Testi) ve AYT (Alan Yeterlilik Testi) sınavlarında yer alan kimya testi soruları 2018 yılı Ortaöğretim Kimya Dersi Öğretim Programı’nın kazanımları açısından analiz edilmiş ve sınavların kapsam geçerliliğinin konu boyutu açısından değerlendirmesi yapılmıştır. Çalışma kapsamında 21 tanesi TYT ve 39 tanesi AYT olmak üzere toplam 60 soru analiz edilmiştir. Çalışma sonunda TYT kimya testi sorularının büyük oranda 9 ve 10. sınıf kazanımlarından hazırlandığı görülürken, AYT kimya testi sorularının ağırlıklı olarak 11 ve 12. sınıf kazanımlarından hazırlandığı belirlenmiştir. TYT-2019 kimya testi sorularının 2018 yılı Kimya Dersi Öğretim Programı toplam kazanımlarının %11,8’ini, TYT-2020 ve TYT-2021 kimya testi sorularının sırasıyla programın tüm kazanımlarının %13,4’ünü ve %8,7’sini kapsadığı tespit edilmiştir. AYT-2019, AYT-2020 ve AYT-2021 kimya testi sorularının sırasıyla 2018 yılı Kimya Dersi Öğretim Programı toplam kazanımlarının %22,0; %18,1 ve %17,3’ünden hazırlandığı belirlenmiştir. Ayrıca “Doğa ve Kimya”, “Enerji Kaynakları ve Bilimsel Gelişmeler” ünitelerinin kazanımlarından 2019-2021 yılları arasındaki YKS sınavlarının tamamında kimya testlerinde hiçbir soruya yer verilmediği gözlemlenmiştir. AYT-2019 ve AYT-2020 sınavlarının kimya testlerinde en fazla sayıda kazanıma yönelik soru hazırlanan ünitenin “Kimyasal Tepkimelerde Denge” olduğu belirlenmiştir.

Performance of geopolymer concrete activated by sodium silicate and silica fume activator

This study examined the properties (strength, workability and crack) of geopolymer concrete activated by sodium silicate and silica fume activator. Sodium silicate and sodium hydroxide (NaOH) are commonly activators used to make geological polymer composite. However, they will cause the decline of the performance of geopolymer concrete when it is prone to polymerization in the surrounding of alkaline. Silica fume can improve the workability and strength of geopolymer concrete. The Pearson correlation coefficient and experiment is used to study the performance of geopolymer concrete with sodium silicate and silica fume activator. The influence of two kinds of activators on the slump of geopolymers with different mix ratios was analyzed by Pearson correlation coefficient. The relative coefficient of mineral powder decreased from 0.785 to 0.409. The absolute relative coefficient of calcined magnesite decreased from 0.829 to 0.156. The correlation between slag, calcined magnesite and slump changed from significant to insignificant. The analysis shows that the slump of geopolymers with silica fume activator are less affected by mineral powder and calcined magnesite than that of sodium silicate activator. Geopolymer concrete have more stable performance with silica fume activator. The geopolymer concrete excited by silica fume activator compared with the sodium silicate activator, the cracks and internal porosities on the surface of the specimens are less. The compressive strength and crack of geopolymer concrete excited by silica fume activator reached 43.36 MPa and 0.095 mm, respectively, at 20 ℃ ± 2 ℃ and more than 95% humidity. It shows good early strength and less cracks. The experimental mix proportions are optimized to conduct the complex the equilibrium of physical and chemical reactions and to reinforce the mechanical property of geopolymer concrete with silicate fume activator.

Dynamic Liquid-Liquid Interface: Applying a Spinning Interfacial Microreactor to Actively Converge Biphasic Reactants for the Enhanced Interfacial Reaction.

A liquid-liquid interfacial reaction combines reactants with large polarity disparity to achieve greener and more efficient chemistry that is otherwise challenging in traditional single-phase systems. However, current interfacial approaches suffer from the need for a large amount of solvent/reactant/emulsifier and poor reaction performance arising from intrinsic thermodynamic constraints. Herein, we achieve an efficient interfacial reaction by creating a magnetic-responsive, microscale liquid-liquid interface and exploit its dynamic spinning motion to generate vortex-like hydrodynamic flows that rapidly converge biphasic reactants to the point-of-reaction. Notably, the spinning of this functional interface at 800 rpm boosts the reaction efficiency and its apparent equilibrium constant by > 500-fold and 105-fold, respectively, higher than conventional methods that utilize bulk and/or non-dynamic liquid interfaces, even with external mechanical stirring. By driving reaction equilibrium toward favorable product formation, our unique design offers enormous opportunities to realize efficient multiphasic reactions crucial for diverse applications in chemical synthesis, environmental remediation, and even molecular recycling.