Si2N2O标准生成吉布斯自由能的测定

用两种方法测量了Si2N2O的标准生成吉布斯自由能ΔfGθSi2N2O:其一是在0.1 MPa氮气压力条件下,在1 073～1 869 K范围内,利用Y2O3稳定ZrO2固体电解质,以Cr和Cr2O3为参比电极,用极化法测试;其二是在1 673和1 773 K下通过Ni-NiO平衡控制氧分压法测试。结果表明,两者吻合很好,其表达式可写为:ΔfGθSi2N2O=-960.627+0.292T±6.2(kJ·mol-1),其中1 073 K≤T≤1 869 K。     

一种计算分子筛标准Gibbs生成自由能的新方法

引 言 自Mobil公司于20世纪60年代成功合成高硅分子筛β[1]及ZSM-5[2]以来,分子筛的合成及其应用便成为催化领域研究的热点.然而,对于分子筛的合成及其改性研究基本上都是凭着研究者的经验,而缺乏理论的有效指导.研究表明,分子筛的热力学性质(如生成焓、生成自由能等)对于分子筛的合成及其性能(如热稳定性等)的预测具有重要的指导意义.但由于分子筛的结构非常复杂,测定分子筛的热力学性质十分困难,到目前为止,只有少数分子筛的某些热力学参数已用实验测定[3].为此,人们一直在探索用各种方法直接计算或预测分子筛的热力学参数.     

Brick by brick computation of the gibbs free energy of reaction in solution using quantum chemistry and COSMO‐RS

The computational modeling of reactions is simple in theory but can be quite tricky in practice. This article aims at the purpose of providing an assistance to a proper way of describing reactions theoretically and provides rough guidelines to the computational methods involved. Reactions in liquid phase chemical equilibrium can be described theoretically in terms of the Gibbs free energy of reaction. This property can be divided into a sum of three disjunct terms, namely the gas phase reaction energy, the finite temperature contribution to the Gibbs free energy, and the Gibbs free energy of solvation. The three contributions to the Gibbs free energy of reaction can be computed separately, using different theoretico‐chemical calculation methods. While some of these terms can be obtained reliably by computationally cheap methods, for others a high level of theory is required to obtain predictions of quantitative quality. To propose workflows which can strike the balance between accuracy and computational cost, a number of benchmarks assessing the precision of different levels of theory is given. As an illustrative example, the low‐temperature hydrogenation reaction of acetaldehyde to ethanol in solvent toluene is shown. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3944–3954, 2017     

A new method of estimating standard enthalpies of formation of zeolites

A new method to calculate the standard enthalpies () of formation of zeolites is founded based on the assumption that the standard enthalpy of formation of zeolite is equal to the sum of the standard enthalpies of all oxide components and the reaction standard enthalpy change between the exchangeable ion oxide and alumina. The results show that the deviation of of zeolite calculated by this method is less than 0.7% compared with the experimental value of . The standard enthalpy of formation of hypothetical [SiO₂] unit in zeolite is suggested to estimate the thermodynamic stability of zeolite. It is found that the presence of crystal water in zeolite is in favor of increasing the thermodynamic stability of zeolite.     

Application of the functional renormalization group method to classical free energy models

A simple functional renormalization group method is presented to correct the behavior of classical free energy models near the critical point. This approach is applied to the Soave–Redlich–Kwong equation of state to illustrate its ability to better reproduce the phase behavior of simple fluids and to understand the influence of its parameters on the shape of the vapor‐liquid phase diagram. The method is then extended to account for the correlations induced by intramolecular bonds. It is then applied to a first‐order thermodynamic perturbation theory for chain fluids to examine fluids composed of linearly bonded Lennard‐Jones atoms. Unlike previous approaches for applying renormalization group corrections to chain fluids, this is able to accurately reproduce the critical point without predicting an overly flat liquid‐vapor coexistence region. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2985–2992, 2015     

Rapid prediction of solvation free energy and vapor pressure of liquid and solid from molecular dynamics simulation

We show that the solvation free energy and vapor pressure, important thermodynamic properties of pure substances in liquid or solid states, can be obtained from short, about 20 ps, molecular dynamics simulations. The method combines the determination of free energy of a chemical in vacuum using the normal‐mode analysis (NMA, energy minimization), and in the condensed phase using the two‐phase thermodynamic (2PT) model. We have examined the calculation results for common liquids and solids, including water, alcohol, acid, aromatics, and alkanes. The results, referred to as 2PT‐NMA, is comparable to those calculated from thermodynamic integration (TI) for liquids, and is readily applicable to solids, where simple TI is not applicable. Furthermore, the free energy from 2PT‐NMA converges (20 ps) much faster than that from TI (1 ns). The new method could be a very useful tool for fast screening of condensed phase pressure from the trajectory of MD simulations. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2298–2306, 2015     

Density,refractive index,excess molar volumes and deviations in molar refraction at 298.15 K for binary and ternary mixtures of DIPE (OR TAME) + 1‐methanol (or 1‐propanol) + trihexyltetra‐decylphosphonium bis (2,4,4‐trimethylpentyl) phosphinate

The excess molar volumes (V^E) and the deviations in molar refraction (ΔR) at 298.15 K were determined for the binary systems {diisopropyl ether (DIPE) + 1‐propanol}, {Tert‐amyl methyl ether (TAME) + methanol}, {DIPE + trihexyltetradecylphosphonium bis(2,4,4‐trimethylpentyl)phosphinate ([P_666,14][TMPP])}, {TAME + [P_666,14][TMPP]}, {methanol + [P_666,14][TMPP]} and {1‐propanol + [P_666,14][TMPP]} using a digital vibrating‐tube densimeter and a precision digital refractometer. The V^E and ΔR were correlated with the Redlich–Kister equation for binary systems. In addition, the ternary V^E and ΔR data at 298.15 K were predicted for the ternary systems {DIPE + 1‐propanol + [P_666,14][TMPP]} and {TAME + methanol + [P_666,14][TMPP]} by using the binary contribution model of Radojkovi? with correlated sub‐binary Redlich–Kister parameters. © 2011 Canadian Society for Chemical Engineering     

高温固硫矿物3CaO·3A12O3·CaSO4的热力学数据的计算与验证

Calcium sulfoaluminate,3CaO·3Al2O3·CaSO4,has been widely recognized in the realms of high-temperature combustion and cement chemistry.However,the lack of relevant thermodynamic data limits the progress of its research and development.Through comparative calculations using several different approaches,we obtain the thermochemical properties of 3CaO·3Al2O3·CaSO4 in this work,such as its standard formation enthalpy,Gibbs free en- ergy of formation,entropy,and molar heat capacity.With these fundamental data,thermodynamic calculations become possible for reactions involving this mineral.It is found that some reactions proposed in literature to generate this mineral may not proceed thermodynamically.     

Characterization of cellulose surface free energy

The thin-layer wicking technique was used to determine the surface free energy components and the surface character of three celluloses (Sigmaccll 101, Sigmacell 20, and Avicel 101), using an appropriate form of the Washburn equation. For this purpose, the penetration rates of probe liquids into thin porous layers of the celluloses deposited onto horizontal glass plates were measured. It was found that the wicking was a reproducible process and that the thin-layer wicking technique could be used for the determination of the celluloses' surface free energy components. The size of the cellulose particles was characterized with the Galai CIS-100 system and their crystallinity was measured by X-ray diffraction. The three celluloses have high apolar (y^LWS = 50-56 mJ/m²) and electron donor (γs = 42-45 mJ/m²) components, while the electron acceptor component (γS⁺ ) is practically zero. The free energy interactions of cellulose/water/cellulose calculated from the components are positive, regardless of the cellulose crystallinity. This would mean that the cellulose surfaces have a hydrophilic character. However, the work of spreading of water has a small negative value (3-9 mJ/m²), indicating that the surfaces are slightly hydrophobic. It is believed that the work of spreading characterizes better the hydrophobicity of the surface than the free energy of particle/water/particle interaction, because in the latter case, no electrostatic repulsion is taken into account in the calculations.     

Anisotropy free energy contribution of the ferroelectric domain dynamics in PMN-PT and PIN-PMN-PT relaxor ferroelectrics

A direct correlation between the materials property behavior with its associated ferroelectric domain mechanisms and the anisotropic component of the Landau free energy is established for binary PMN-PT (generation I) and ternary PIN-PMN-PT (generation II) relaxor ferroelectric single crystal material systems. In addition to their trade-off in material properties, the observed ferroelectric domain dynamic and the determined free energy anisotropies, especially as approaching phase transition, provide direct insights into the materials field-dependent behavior between the binary and ternary ferroelectric systems. Domain configuration features such as lamellar structures in binary PMN-PT and concentric oval-like structures in ternary PIN-PMN-PT result in different material responses to external stimuli. Compared to binary PMN-PT, the concentric oval-like domain structures of ternary PIN-PMN-PT result in a 20°C higher temperature range of field-dependent linear behavior, 40% increase in coercive electric field $E_C,$ higher elastic stiffness during ferroelectric domain switching, and lower electromechanical energy losses. Separation of the isotropic and anisotropic components in the Landau free energy reveals a higher anisotropic free energy contribution from the ternary system, especially at temperature for practical applications. The high anisotropic free energy found in the ternary PIN-PMN-PT system implies that the concentric oval-like domain structure contributes to reduced electromechanical energy losses and enhanced stability under external applied fields.     

Solid surface free energy components determination by the thin-layer wicking technique

A thin-layer wicking technique [1] and van Oss et al.'s [2] approach to interfacial free energy interactions were tested to determine the solid surface free energy components: apolar Lifshitz-van der Waals, y^l,w _y; and polar, electron donor, γ^- _y, and electron acceptor, γ⁺ _y. For this purpose, the penetration rates of n-alkanes, diiodomethane, water, formamide, toluene and chloroform were measured. For these studies, silica, used for thin-layer chromatography, and α-Al₂O₃ were used as the model solids. It was found that both are strongly polar, electron donor solids with weak electron acceptor interactions. It is concluded that van Oss, Good et al.'S [2] approach to the interfacial free energy interactions and the thin-layer wicking technique are very useful for cxplaining many interfacial phenomena taking place in the dispersed systems. However, more experimental work using different systems is needed.     

Calculation of the reforming of oil gas by minimizing the gibbs free energy

The Gibbs free energy minimization method is used to calculate the equilibrium of a system with chemical transformations. The advantages of this method over a conventional method for calculating the equilibrium using a set of hypothetical chemical reactions are discussed. The results of calculating the equilibrium compositions in steam, oxygen, and carbon dioxide reforming of oil gas are presented.     

On the relation between activity coefficients and excess gibbs energy functions

The relation between activity coefficients and excess Gibbs energy functions for mixtures of electrolytes and nonelectrolytes is examined under a general framework. It is shown that the use of molality, instead of mole fraction, as a composition variable leads to unusual expressions for the activity coefficients of both solvents and solutes. Explicit expressions for activity coefficients in binary and multicomponent mixtures are derived and the importance of selecting proper standard states is highlighted.     

The role of the surface free energy in the selection of a suitable excipient in the course of a wet-granulation method

Pellets containing metronidazole were produced in a centrifugal granulator, with hydroxypropylcellulose (Klucel LF®) as binding agent, and corn starch, microcrystalline cellulose (Vivapur 101®) and lactose as excipients. The wettability of the pharmaceutical powders was assessed by means of contact angle measurements, and the dispersive and polar surface energies were determined. The spreading coefficients, the work of adhesion and the work of cohesion were calculated and correlated with the pellet properties (friability, bulk and tapped density, and porosity). The aim was to investigate the role of the surface free energy of one- and two-component powder compositions in pellet production. The interactions between the particles were found to be connected with the measured pellet parameters. It was concluded that, in the course of the growth of the pellets, the particle sizes of the pharmaceutical powders and the interactions between them are important. If the work of cohesion of the binder is lower than the work of cohesion of the substrate and the work of adhesion, then the optimal amount of the binding agent is that which coats the particles uniformly in minimal quantity and in continuous layer.     

高温固硫矿物3CaO·3A1_2O_3·CaSO_4的热力学数据的计算与验证(英文)

Calcium sulfoaluminate,3CaO·3Al2O3·CaSO4,has been widely recognized in the realms of high-temperature combustion and cement chemistry.However,the lack of relevant thermodynamic data limits the progress of its research and development.Through comparative calculations using several different approaches,we obtain the thermochemical properties of 3CaO·3Al2O3·CaSO4 in this work,such as its standard formation enthalpy,Gibbs free en- ergy of formation,entropy,and molar heat capacity.With these fundamental data,the...     

Surface free energy analysis of poly(vinyl alcohol) films having various molecular parameters

The molecular parameters of poly(vinyl alcohol) have enormous effects on its physical and chemical properties. Therefore, the surface characteristics of poly(vinyl alcohol) films are also determined by the molecular parameters. In this study, the dependence of the surface free energy on the molecular weight, degree of saponification, and stereoregularity of poly(vinyl alcohol) films has been evaluated with contact‐angle measurements. The surface free energy of poly(vinyl alcohol) films increases with decreases in the syndiotactic dyad content, molecular weight, and degree of saponification. The polar component of the surface energy is not affected by the deviation of the molecular weight and degree of saponification very much. However, it decreases with increases in the syndiotactic dyad content and ranges from 11.64 to 4.35 dyn/cm. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Surface free energy of synthetic chalcocite from zeta potential and contact angle techniques

—The zeta potentials of synthetic chalcocite wetted with n-alkanes were determined in doubly-distilled water. Then the relationship between the coverage of the chalcocite surface with n-heptane or n-hexanol and the zeta potential in water was found. Using an empirical relation, the film pressure of n-heptane and n-hexane was determined. Next the dispersive and polar components of the surface free energy were calculated. The value of the dispersive component was also determined by contact angle measurements. The values obtained were 81.0 and 22.7 mJ/m², for the dispersive and the polar components of the surface free energy, respectively.