Chemical Thermodynamics and Thermal Analysis最新文献

In this work, thermal conductivity (TC), viscosity, and rheological properties of an ethylene glycol (EG) based single-walled carbon nanotube (SWCNT) nanofluid (NF) have been computed using equilibrium molecular dynamics (EMD) simulation. In SWCNT, for the interaction between carbon atoms, Tersoff potential is used. Results indicate that TC and viscosity increase in nonlinear fashion with volume fraction. However, with temperature, TC increases but viscosity decreases. Increased interaction between CNT and liquid atoms of EG, and the high heat conductance ability of SWCNT nanoparticles enhance the effective conductivity and viscosity of NFs. Longer CNTs provide more efficient heat transfer pathways and more interactions between CNT & base fluid molecules, which contribute to enhanced TC and viscosity of NFs. Weakening of intermolecular forces within the NF with increasing temperature decreases viscosity. To validate the results, radial distribution function (RDF) and stress autocorrelation function (SACF) have been estimated. Mean square displacement (MSD) investigation demonstrates that the diffusion of liquid atoms (or molecules) serves as the fundamental mechanism for heat conduction in nanofluid. The results have been compared with experimental findings for analogous dispersive medium. Broadly, an attempt has been made to explore how interactions between the base fluid and nanoparticles (NPs) can enhance the thermal and rheological efficiencies of nanofluids.

The potential usage of activated carbon from plantain peel (Musa paradisiaca) (TPPC) and unactivated carbon from plantain peel (UPPC) for the removal of Hexachlorocyclohexanes (HCHs) from water systems was investigated. The TPPC and UPPC were characterized using Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Adsorption experiments were conducted as a function of adsorbent weight (2 – 10 g), temperature (30 -50 °C), and solution pH (2 - 9) under an adsorbent packed column. The Optimum removal efficiency of 98.23 % was achieved in the column studies under the following conditions: pH = 5, the dosage of adsorbent = 5 g/100 mL, temperature = 30 °C. The batch adsorption process was employed to evaluate the kinetics, equilibrium, and thermodynamics of the adsorption processes. The equilibrium study showed that Langmuir among other isotherm models applied performed better in fitting the data. Additionally, the kinetic data was best described by the pseudo-second-order model (R² > 0.97), indicating a chemisorption mechanism. Furthermore, the thermodynamic calculations of the adsorption process suggest that HCH adsorption was exothermic (ΔH = -110.87) and spontaneous (-ΔG).

In the initial two publications in this series we established predictive additive Atom Sum thermochemical quantities for inorganic solids for each of the chemical elements. With the chemical elements being a finite set, these data cover the whole of the domain of inorganic solids so far as reference data is currently available.

We here introduce a dataset augmented in hydrates, and divide our analysis between the hydrates and anhydrates. The Atom Sum terms are better directed independently to these disparate inorganic groups thus providing improved estimates of the corresponding predicted thermochemical quantities. In this paper we provide both updated formation reaction entropies and previously unpublished Gibbs energies.

The objective of the study is to synthesize economical and facile ethylenediamine (ED) based protic ionic liquids (PILs) containing various carboxylate anions for CO₂ capture for post-combustion method. The PILs were synthesized using a straightforward process, and the behavior of their CO₂ absorption was investigated in relation to the alkyl chain of odd and even chain anions. The PILs were characterized using ¹H NMR, ¹³C NMR, and HRMS techniques. The study results indicate that ED-ILs with longer alkyl chains are better at absorbing CO₂. Among all the PILs, [ED][Hep] exhibited the highest absorption capacity except [ED][But], absorbing 0.26 CO₂/mol of IL at 298K and 0.1 MPa. The thermophysical properties, including density, sound speed, viscosity, and refractive index of neat ED-based PILs, were tested at different temperatures and 0.1 MPa. Furthermore, the derived parameters such as expansion coefficient (α), molecular volume (V), isentropic compressibility (βs), lattice potential energy (U_POT), standard entropy (S⁰), Intermolecular free length (L_f) and free volume (Vm) were determined using experimental parameters. It was shown that these characteristics were directly related to the PILs ability to absorb CO₂. Overall, the investigation demonstrated that [ED][But] offers a great potential for utilization as a CO₂ absorption solvent because of its high absorption capacity and special qualities as a PIL.

The paper presents a semi-empirical approach to determining densities of chlorinated brines in the 0–4 molal concentration range and 293.15–323.15 K temperature range. This model incorporates continuous density functions for chlorinated salts and temperature, offering enhanced accuracy and reduced errors in density estimations for complex brine systems, including ternary systems. The model provides precise density estimations for applications like seawater and salt flats by considering ion activities and specific concentration ranges. Comparative analysis shows the model's superior performance with error adjustments consistently below 0.2 %. The continuous variable temperature model proves more effective than discrete approaches, contributing to more accurate density predictions.

Vapor pressure (P) data of pure substances in gas/solid-liquid equilibrium is important for scientific research and practical applications. Due to the large temperature range going from melting point to critical point, it is an impossible task to determine the P of a pure substance at each temperature point. Up to now, there is no general equation that can accurately describe the relation between temperature (T) and P for all pure substances. Utilizing Boltzmann distribution, we presented a general expression, ln P = a + bT + cln(T) + d(1/T), for the P of pure substances, that is, the P-T dependence is nearly exponential over the entire range of liquid and solid existence. Furthermore, on the base of above equation, we established a corrected general equation to express the liquid vapor pressure within temperature in going from melting point to critical point.

$\ln P=a+bT+c{T}^{T/T_b}+d\left(\ln \left(T\right)\right)+f{\left(\ln \left(T\right)\right)}^{T/T_b}+g\left(1/T\right)$

The results show that the corrected equation has the advantages of universality, simplicity, and high calculation accuracy for the vapor pressure involving liquid simple substances, liquid inorganic and liquid organic compounds.

Zeolites have wide application in industry, agriculture, medicine for ion exchange, for catalysis, and even for drug delivery so that it is important to understand their stability and synthesis. Although the standard thermochemical quantities (formula volume, enthalpies, entropies, and heat capacities) of zeolites are quite widely reported, there have been no general predictive procedures for the potentially vast numbers of possible examples of zeolites.

We here consider some simple additive schemes for prediction of such properties. These demonstrate that zeolites behave in broad outline as standard ionic solids with dominant coulombic interactions. The Atom Sum method provides the necessary data for first thermochemical prediction with no need for inclusion of special group contributions.

Protonation and deprotonation reactions play an important role in the biological processes. Such processes are fully thermodynamic and occur in complex media where functional groups are surrounded by other chemicals such as molecules, ions, water, etc. In this paper, the compound of interest is the methylprolithospermate (MPL) molecule, which was recently isolated from salvia yunnanensis CH Wright. The intended functional groups for deprotonation are -OH and -COOH. These are the potential groups depicted at four sites located in MPL. Three thermodynamic cycles were required for the estimation of MPL's pKa by the means of DFT at the levels of B3LYP and PW6B95 with the dual basis set 6–311++G(d,p)//6–31+G(d). Cycle 1 is the direct pKa calculation, Cycle 2 is also the direct pKa calculation with proton hydration, and Cycle 3, the proton exchange process with hydroxyl anion hydration. In these cycles, water molecules as, reagents as well as products, were held as monomers in one hand (monomer cycle approaches), and cluster on the other hand (cluster cycle approaches). The isodesmic scheme was used as benchmark method for pKa calculation and yielded: pKa₁ = 3.6 ± 0.3, pKa₂ = 6.6 ± 0.2, pKa₃ = 9.3 ± 0.2, and pKa₄ = 14.4. The inclusion of binding energies of MPL anions in the pKa calculation has improved the results. The best cycles depend on the level of waters and the level of acidity. The more the number of waters clustered to MPL anions, the more the deviation of pKa values.

It has been shown that an improved prediction of the thermodynamic quantity for the hard homonuclear diatomics can be performed with an interpolation scheme that relates the thermodynamic property of the hard sphere to that of tangent hard spheres at the same density. Using the analytic expressions based on the solution of an integral equation an excess Helmholtz free energy per particle and chemical potential for hard homonuclear diatomic fluid have been computed. Calculations are carried out for hard homonuclear diatomics with reduced internuclear separations of 0.1 to 1 at reduced densities of 0.2 to 0.9. Our findings for the excess Helmholtz free energy from the Percus–Yevickand Martynov–Sarkisov approximations presents good agreement with available accurate data, having maximum deviations of 15% from it over the separation and density ranges of the calculations. The excess chemical potential from the Martynov–Sarkisov approximation shows better agreement with accurate available data than those from the Percus–Yevick approximation. For the excess chemical potential, a maximum deviation of 9.5% over the range of the calculations has been shown up for the Percus–Yevick approximation.

In order to gain understanding on the utilization of biogas fuel derived from water hyacinth (WH) biomass and render it appealing as a sustainable gaseous fuel, the study reports on its various thermophysical, combustion and thermodynamic parameters. The parameters include, specific enthalpy, internal energy, low heating value, Wobbe number index, changes in Enthalpy, Entropy and Gibbs free energy. The experimental procedure was performed at temperature range of 29±3 °C for 61 days in a BlueSens laboratory-scale anaerobic digestion equipment. It comprised of three fermenter bottles designated as F1, F2 and F3. F1 served as the control and the rest served as the test fermenter bottles. The digestion of water hyacinth and fruit waste sludge (WH+FWS) recorded the highest biogas volumes of 19,798.79 ml in fermenter F2 and 19,168.55 ml in fermenter F3 with methane contents of 53.46 % and 51.85 %, respectively. In comparison, the biogas produced exclusively from the water hyacinth (WH) biomass yielded 12,014.49 ml in F2 and 11,384.25 ml in F3, with methane contents of 46.41 % and 43.31 %, respectively. The best biogas fuel was produced from the digestion of (WH+FWS) in fermenter F2 with an internal energy and enthalpy values of 258.6 KJ/kg. K and 344.9 KJ/kg. K, respectively. A low heating value and Wobbe number of 17.51 MJ/m³ and 17.78 MJ/m³ were determined respectively. The biogas production was simulated using the Gompertz modified kinetic equation in MATLAB and an average specific rate (K_exp) of 371.49 ml/gVS.day was obtained. The rate constant (K_exp) was applied in the linearized form of the Erying-Polanyi equation to determine the changes in Enthalpy Entropy, and Gibbs free energy as -2510.66 J, -304.78 J and 94,219 J, respectively which indicated that, the anaerobic digestion process in this study was only thermodynamically feasible at low temperatures.