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The Use of Denuders for Semivolatile Characterization Studies in Outdoor Chambers
Published in Douglas A. Lane, Gas and Particle Phase Measurements of Atmospheric Organic Compounds, 2020
Richard Kamens, Zhihua Fan, Myosoen Jang, Jay Odum, Jianxin Hu, Dana Coe, Jianbo Zhang, Shufen Chen, Keri Leach
Activity coefficients will vary with the liquid composition of the particulate matter. Because the true partitioning equilibrium constant of organic compounds in each medium includes an activity coefficient term, the linearity between log Kp and log Po(L) above in Equation (8) can be best estimated by first correcting Kp for the activity coefficient term. To do this it is necessary to calculate the activity coefficient for a given semivolatile organic in a given organic liquid mixture. The most promising method employs a concept called the group contribution method. In it simplest form, this technique uses molecular structural information to calculate thermodynamic quantities such as molar volumes, boiling points, Henry’s law values, and water-octanol partitioning coefficients. In the case of activity coefficients, compounds are structurally subdivided into functional groups, and assignments associated with these functional groups are used to calculate cohesive energies or interaction parameters which in turn are used to calculate the activity coefficient of the compound [21–25].
Ethyl trifluoroacetate formation as a means to recover trifluoroacetic acid from dilute aqueous mixture: reaction, separation and purification
Published in Journal of the Chinese Institute of Engineers, 2023
Reshma R. Devale, Amit Katariya, Yogesh S. Mahajan
kf is the forward rate constant, expressed in Arrhenius form. kf0 is the pre-exponential factor, and Ef as the activation energy. KM is equilibrium constant, and is autocatalysis constant. Objective function is the sum of squares of error (SSE). Ordinary differential equations (ODEs) representing batch reactor model (Equations 3,4) were implemented in MATLAB®. Using initial values of reactant concentrations and guess values of kinetic constants, the ODEs were solved with the help of ‘ode15s’ routine of MATLAB®. Simulated TFA concentrations were compared with the experimental data and SSE between these values was calculated (Equation 5). Nc is the number of components, Nexp is the number of experiments, and NTime is the number of time points. Kinetic constants were varied so as to minimize SSE. ‘Fminsearch’ code of MATLAB® was used for finding optimum values of parameters. Table 2 provides values of constants in the rate expression. ‘UNIQUAC’ parameters were estimated using group contribution method (‘UNIFAC’) of ASPEN PLUS and are given in Table 3. Figures 4(a-c) show comparison between experimental data and model prediction. Figure 4(d) shows that a good fit was obtained (parity plot, R2 = 0.9822). Equations 3–5 pertain to rates and SSE:
Design and optimization of an acetic acid recovery system via extraction–distillation using an isopropyl acetate + isopropanol mixed solvent
Published in Chemical Engineering Communications, 2020
Peng Fang, Chao Yu, Zuoxiang Zeng, Weilan Xue
For HAc recovery, IPA-01 containing a certain amount of IPA-02 was used as an extractant to remove water from its aqueous solution. The nonrandom two-liquid (NRTL) model was widely used to predict liquid activity coefficients (Renon et al., 1968). In this study, this model was selected as a thermodynamic model for the design of the whole process, which was conducted by Aspen Plus V9.0. All the NRTL parameters of this system are shown in Table 1, in which the parameters of water–HAc, HAc–IPA-01, HAc–IPA-02 were estimated by the UNIFAC group-contribution method (Fredenslund et al. 1975). The Hayden–O'Connell second virial coefficients are used to predict the vapor phase of systems (Hayden et al., 1975).
Selection of eco-efficient downstream separation configuration for isopropanol–butanol–ethanol purification process
Published in Chemical Engineering Communications, 2023
Ilayda N. Oksal, Devrim B. Kaymak
The simulations are carried out using Aspen Plus (V10.0). All distillation columns are represented with rigorous RadFrac module, while extractor and decanter are represented by Extract and Decanter modules, respectively. The internals of the columns are represented as equilibrium trays. NRTL is selected as the thermodynamic model of simulations for both process configurations. The NRTL binary interaction parameters (BIP), which do not exist in Aspen Plus, are estimated with UNIFAC group contribution method. Supporting Information Table S2 includes the BIP values estimated with UNIFAC group contribution method.