OPTIMIZATION OF DRUG SOLUBILITY USING ASPEN PLUS: ACETYLSALICYLIC ACID (ASPIRIN) SOLUBILITY – A SECOND CASE STUDY

Objective: The objective of the study is to optimize the solubility of a drug or a drug-like molecule using Aspen Plus simulation platform. Aspirin (solute) was taken as the second case study. The following solvents were used in our dry (virtual) laboratory experiment: Water, acetone, ethanol, and ethylene-glycol-mono-propyl-ether (PROPGLYC). Methods: A simplified process flow sheet made of a single mixing tank where it has five feed streams, representing the solute, the water, and the set of three organic solvents, and one product stream where aspirin is either solubilized (liquid solution) or remains as solid crystal. Minimization of the molar Gibbs free energy of mixing, ΔGmix, was used as an objective function from an optimization point of view. The Non-random Two-liquid property method was used to analyze the solution properties. Results: Using the molar Gibbs free energy of mixing, ΔGmix, as a criterion of solution thermodynamic stability, it was found that the most stable solution is the quinary mixture made of 24.42% aspirin, 10.22% water, 21.08% acetone, 19.51% ethanol, and 24.77 mole % PROPGLYC. Conclusions: Exploiting Aspen Plus can be extended to handle the solubility of a new drug-like molecule once it is defined within its molecular editor with a little knowledge such as density and/or melting point.

Estimation of Excess Properties of Binary Liquids Systems of Tetrahydrofurfuryl Alcohol with Short-Chain Carboxylic Acids at 298.15 K

At the temperature 298.15 K, some physical properties such as: refractive indices (nD), viscosities (η) and densities (ρ) were studied in four liquid-liquid mixtures: carboxylic acids (HCOOH, CH3COOH, CH3CH2COOH and CH3CH2CH2COOH) with tetrahydrofurfuryl alcohol (THFA) with the identified configuration set. These empirical data were utilized to estimate the excess molar volumes (Vm E), refractive index perversions (ΔR), viscosity deviations (ηE) and excess molar Gibbs free energy (ΔG*E). Values of Vm E, ηE , ΔG*E and ΔR were plotted versus mole fraction of tetrahydrofurfuryl alcohol. In all cases, the values of Vm E, ηE , ΔG*E and ΔR that obtained in this study were found to be negative at 298.15 K. The excess parameters were applied in the Redlich-Kister equation by utilizing multi-parameter coefficients that concluded binary coefficients and in respect to the standard deviation. The difference of these characteristics with the formation of binary liquid systems indicates the absence of bipolar bond, variation in the shape and size of component molecules, hydrogen bonding and dipolar interaction among unlike molecules.

Excess Molar Quantities of Binary Mixture of Dipropyl amine with Aliphatic Alcohols at 298.15 K

Refractive indices (nD), viscosities (η) and densities (ρ) were deliberated for the binary mixtures created by dipropyl amine with 1-octanol, 1-heptanol, 1-hexanol, 1-pentanol and tert-pentyl alcohol at temperature 298.15 K over the perfect installation extent. The function of Redlich-Kister were used to calculate and renovated of the refractive index deviations (∆nD), viscosity deviations (ηE), excess molar Gibbs free energy (∆G*E) and excess molar volumes (VmE) The standard errors and coefficients were respected by this function. The values of ∆nD, ηE, VmE and ∆G*E were plotted against mole fraction of dipropyl amine. In all cases the obtained ηE, ∆G*E, VmE and ∆nD values were negative at 298.15K. Effect of carbon atoms number in the chain of alcohol and hydroxyl groups' position on molecular interactions in these mixtures has also been discussed.

On the reduced Redlich-Kister excess properties for 1,2-dimethoxyethane with propylene carbonate binary mixtures at temperatures (from 298.15 to 318.15) K.

Values of excess properties in 1,2-dimethoxyethane + propylene carbonate binary liquid mixtures at different temperatures from experimental density and viscosity values presented in earlier work, were used to test the applicability of the correlative reduced Redlich-Kister functions and the Belda equation, and to reveal eventual specific interaction hidden by the classical treatment of direct excess Redlich-Kister functions. Their correlation ability at different temperatures, and the use of different numbers of parameters, is discussed for the case of limited experimental data. The relative Redlich-Kister functions are important to reduce the effect of temperature and, consequently, to reveal the effects of different types of interactions. Values of limiting excess partial molar volume at infinite dilution deduced from different methods were discussed. Also, the activation parameters and partial molar Gibbs free energy of activation of viscous flow against compositions were investigated. Correlation between the two Arrhenius parameters of viscosity shows the existence of main different behaviors separated by a stabilized structure in a short range of mole fraction in 1,2-dimethoxyethane (0.45 to 0.83). In this context, the correlation Belda equation has also been applied to the present system for thermodynamic properties in order to reveal eventual solute-solvent interaction at high dilution.

Mechanistic Modeling of Oil Recovery Caused by Low-Salinity-Water Injection in Oil Reservoirs

Summary Low-salinity-water injection (LSWI) is an emerging way to improve waterflood performance at low cost under certain conditions. The effect of LSWI on the oil recovery from carbonate formations has been well-documented in the laboratory and to a limited extent in the field. In this study, a mechanistic geochemical model is proposed that addresses the effect on oil recovery of different geochemical reactions resulting from LSWI. The proposed model was used to history match recently published corefloods by use of the UTCHEM (2000) mechanistic reservoir simulator. Moreover, other sets of corefloods were chosen to validate the proposed LSWI mechanistic model. The geochemical model in the UTCHEM simulator was modified to calculate the molar Gibbs free energy of the brine. In the proposed LSWI mechanistic model, the relative permeability curves, including the residual oil saturation (ROS), are functions of the molar Gibbs free energy. Coreflood experiments were simulated and history matched by use of the proposed model. The proposed LSWI mechanistic model was further extended to include weakly oil-wet to mixed-wet carbonate rocks. The mechanistic model captures the effects on oil recovery of both wettability alteration and/or dissolution/fines migration through changes in the molar Gibbs free energy. This model can now be used for oil-recovery predictions and optimization of LSWI field applications.

A Thermodynamic Analysis on the Effect of Salinity on Interlayer Space of Na-Montmorillonite

ABSTRACTBentonite is used as one of the materials for engineered barrier systems in a radioactive waste repository. Since the major clay mineral constituent of bentonite is montmorillonite, its physico-chemical properties are important. Basal spacing of water-saturated Na-montmorillonite is reported to decrease with increasing Na-montmorillonite density. This paper presents a thermodynamic model to calculate change in the interlayer space of Na-montmorillonite based on the relative partial molar Gibbs free energy (dG) of interlayer water as contacted with a solution of an arbitrary salinity (NaCl concentration). Directly change in montmorillonite density (ρdm) against salinity was calculated by the thermodynamic model. The dG of interlayer water as contacted with a solution of an arbitrary salinity can be calculated by dG = dGH2O+ dGS (dGH2O: relative partial molar Gibbs free energy of interlayer water, dGS: that of water in a solution of an arbitrary salinity). The author previously reported an empirical correlation of dGH2O vs. water content for Na-montmorillonite. The dependence of ρdm on salinity was calculated by replacing dGH2O in the empirical correlation with dG. ρdm increased with salinity. Concretely, initially the ρdm-values of 0.5 and 1.0 Mg/m3 increased to 1.05 and 1.16 Mg/m3 under 0.5 m-NaCl, respectively. Interlayer space vs. salinity was estimated based on the measured results of basal spacing vs. ρdm by XRD and the average density of montmorillonite vs. salinity calculated by this model.

Processes on the Thermodynamic Properties of Lithium Borates

In this paper, the thermodynamic properties including the standard molar enthalpies of formation, the standard molar entropies of formation and the standard molar Gibbs free energy of formation of hydrated lithium borates and the water vapor pressures, the osmotic coefficients, the enthalpy of dilution, the molar heat capacity of aqueous lithium borate solution systems were summarized and the new trend in the future was also pointed out.

Thermodynamics of micellization of hexadecyltrimethylammonium bromide in propylene glycol-water mixture: A conductivity study

Micellization of hexadecyltrimethylammonium bromide (syn. cetyltrimethylammonium bromide, CTAB) in propylene glycol-water (30% v/v) binary mixture, as well as the thermodynamic properties of the resulting micelles, were investigated by electrical conductivity measurements. The conductivity data were used to determine both the critical micellar concentration (CMC) and the micellar ionization degree (?) of CTin the temperature range 298.2-310.2 K. The equilibrium model of micelle formation was applied in order to obtain the thermodynamic parameters (the standard molar Gibbs free energy, ?Gm0, enthalpy, ?Hm0 and entropy, ?Sm0) of the micellization process. The values of DGm0 and DHm0 were found to be negative at all investigated temperatures, while the values of ?Sm0 were positive and became more positive as temperature increased. A linear dependence between ?Sm0 and ?Hm0, i.e. an enthalpy-entropy compensation effect, was observed.