Strategy for the Management of Thermodynamic Data with Application to Practical Cases of Systems Formed by Esters and Alkanes through Experimental Information, Checking-Modeling, and Simulation

In this work, a methodology is established to manage and use, in a more rigorous way, the experimental information that reflects the thermodynamic–mathematical behavior of dissolutions. The management of experimental information is carried out with an application on binaries of esters and alkanes which is useful in any other case. Specifically, for this work a new real database (of several properties under different conditions) is generated for eight binaries formed by four alkanoates, with a carbon number number ≥ 4, and two alkanes C₆ and C₈. A sequence of operations is proposed, ranging from experimentation to simulation, with two highly relevant intermediate stages, modeling↔verification of the quality of data, whose impact on the simulation is evaluated. The experimental contribution of some properties <i>v</i>^E, <i>c</i>_P^E, <i>h</i>^E, <i>g</i>^E, gives rise to two very important operations, such as the combined modeling of the properties, taking into account the thermodynamic formalism, and the verification of the vapor–liquid equilibrium (VLE) data. For the latter process, the methodology designed in a previous work (J. Chem. Thermodyn. 2017, 105, 385) is put into practice, as well as a new method, rigorous under a thermodynamic–mathematical point of view, in which the modeling of properties is considered. The binomial <i>model-consistency test</i> is generated as a strategic stage to define the quality of the data. To achieve an accurate modeling in the multifunctional correlation that is proposed, two procedures are adopted: (a), step-by-step (SSO), according to the inverse order of the derivation of the Gibbs function, and another (b), by multiobjective optimization (MOO). The parametrization obtained by the latter is implemented in the commercial software of Aspen-Plus to design a rectification operation to purify the compounds of one of the studied systems, comparing the results with those that the simulator emits with the information estimated by UNIFAC

Description of the Behavior of Dichloroalkanes-Containing Solutions with Three [bXmpy][BF₄] Isomers, Using the Experimental Information of Thermodynamic Properties, ¹H NMR Spectral and the COSMO-RS-Methodology

This work studies the binaries of 1-butyl-<i>X</i>-methylpyridinium tetrafluoroborate [b<i>X</i>mpy]­[BF₄] (<i>X</i> = 2, 3, and 4) with four 1,ω-dichloroalkanes, ω = 1–4, using the results obtained for the mixing properties <i>h</i>^E and <i>v</i>^E at two temperatures. The three isomers of the ionic liquid (IL) are weakly miscible with the 1,ω-dichloroalkanes when ω ≥ 5 and moderately soluble for ω = 4. The <i>v</i>^Es of all the binaries present contractive effects, <i>v</i>^E < 0, which are more pronounced with increasing temperature; the variation in <i>v</i>^E with ω is positive, although this changes after ω = 4 due to problems of immiscibility. The energetic effects of the mixing process are exothermic in the solutions with the shorter dichloroalkanes, ω = 1 and 2, and this effect increases slightly with temperature. However, mildly exothermic effects are found in the binaries with larger halides, where (<i>dh</i>^E/<i>dT</i>) > 0. The experimental data are correlated with a suitable equation. The study is completed with ¹H NMR measurements of both the pure compounds and some of the solutions, which showed minor diamagnetic shifts with increasing IL compositions, related to the anisotropy of the pyridine ring. The variation in <i>h</i>^E with ω for a same IL, due to an increase in the contact surfaces, is related to the reduction in polarity which, in turn, depends on the smaller chemical shifts of the pure dihalide compounds. The COSMO-RS method determines the energetic effects of the mixing process and predicts an exothermic contribution for the electrostatic Misfit-interaction which is quantitatively very similar for the three IL isomers. The differences proposed by the model are mainly reflected in the van der Waals interactions, which are exothermic and clearly influenced by the position of the methylene group in the IL. The contribution made by hydrogen bonds is negligible

Highly Specific and Wide Range NO₂ Sensor with Color Readout

We present a simple and inexpensive method to implement a Griess-Saltzman-type reaction that combines the advantages of the liquid phase method (high specificity and fast response time) with the benefits of a solid implementation (easy to handle). We demonstrate that the measurements can be carried out using conventional RGB sensors; circumventing all the limitations around the measurement of the samples with spectrometers. We also present a method to optimize the measurement protocol and target a specific range of NO₂ concentrations. We demonstrate that it is possible to measure the concentration of NO₂ from 50 ppb to 300 ppm with high specificity and without modifying the Griess-Saltzman reagent