Tailoring Synthetic Pelargonic Acid Esters for Bio-Based Lubricant Applications: Exploring the Relationship between Structure and Properties.

Pelargonic acid (PA) is commercially obtained by oxidative cleavage of fatty acid double bonds. Its esters are interesting compounds used to create bio-based products. An industrially relevant application of these compounds is in the field of solvent manufacturing and formulation of green lubricating oils. The physical-chemical and rheological properties of these esters are influenced by the structural features of the alcohol used as starting materials, such as chain length, number of unsaturation, and degree of branching. This work provides an in-depth study of the existing structure-properties relations for fatty acid alkyl esters obtained from PA and different alcohols [i.e., 2-ethylhexanol (EtHex), ethylene glycol, 1,3-propanediol, 1,4-butanediol, trimethylolpropane, and pentaerythritol]. The aim is to evaluate the use of the synthesized product for the formulation of bio-based lubricants. The chosen alcohols are frequently employed in the preparation of bio-based lubricants. In addition, most of them, such as EtHex and diols, can be derived from biomass sources, contributing to the sustainability of the obtained products. For comparison purposes, some of these alcohols were also used for the synthesis of the corresponding oleic acid esters, which were chosen as a benchmark due to their common use in the synthesis of bio-based lubricants. The influence of the structural factors on the viscosity, pour point (PP), and oxidation stability of the synthesized esters was highlighted by comparing the obtained results. Pelargonates showed lower viscosities and higher PPs than that of the oleates, but they present high stabilities to the oxidation due to the absence of unsaturation.

Ibuprofen Adsorption on Activated Carbon: Thermodynamic and Kinetic Investigation via the Adsorption Dynamic Intraparticle Model (ADIM).

The adsorption efficiency of commercial activated carbon toward ibuprofen (IBU) was investigated and described using the adsorption dynamic intraparticle model (ADIM). Although the adsorption capacity of activated carbon has been widely studied, the kinetic models used in the literature are simplified, treating adsorption kinetics with pseudo-kinetic approaches. In this paper, a realistic model is proposed, quantitatively describing the influence of the main operation parameters on the adsorption kinetics and thermodynamics. The thermodynamic data were interpreted successfully with the Freundlich isotherm, deriving an endothermic adsorption mechanism. The system was found to be dominated by the intraparticle diffusion regime, and the collected data allowed the determination of the surface activation energy (ES = 60 ± 7 kJ/mol) and the fluid-solid apparent activation energy (EA = 6 ± 1 kJ/mol). The obtained parameters will be used to design adsorption columns, allowing the scale-up of the process.

Upgrading Sustainable Polyurethane Foam Based on Greener Polyols: Succinic-Based Polyol and Mannich-Based Polyol.

It is well known that the traditional synthetic polymers, such as Polyurethane foams, require raw materials that are not fully sustainable and are based on oil-feedstocks. For this reason, renewable resources such as biomass, polysaccharides and proteins are still recognized as one of the most promising approaches for substituting oil-based raw materials (mainly polyols). However, polyurethanes from renewable sources exhibit poor physical and functional performances. For this reason, the best technological solution is the production of polyurethane materials obtained through a partial replacement of the oil-based polyurethane precursors. This approach enables a good balance between the need to improve the sustainability of the polymer and the need to achieve suitable performances, to fulfill the technological requirements for specific applications. In this paper, a succinic-based polyol sample (obtained from biomass source) was synthesized, characterized and blended with cardanol-based polyol (Mannich-based polyol) to produce sustainable rigid polyurethane foams in which the oil-based polyol is totally replaced. A suitable amount of catalysts and surfactant, water as blowing reagent and poly-methylene diphenyl di-isocyanate as isocyanate source were used for the polyurethane synthesis. The resulting foams were characterized by means of infrared spectroscopy (FTIR) to control the cross-linking reactions, scanning electron microscopy (SEM) to evaluate the morphological structure and thermal gravimetric analysis (TGA) and thermal conductivity to evaluate thermal degradation behavior and thermal insulation properties.

A predictive model for the diffusion of a highly non-ideal ternary system.

Diffusion plays a central part in many unit operations. The Maxwell-Stefan model is the dominant model for both gaseous and liquid diffusion. However, it was developed from the kinetic theory of gases, raising the question of whether it can be extended to non-ideal liquid systems. The dynamic fluctuation model is an alternative model based on the Cussler theory and predicts a smaller thermodynamic influence relative to the linear influence of the Maxwell-Stefan model due to dynamic concentration fluctuations. Since the dynamic fluctuation model, which uses the scaling factor α, had improved performance relative to the Maxwell-Stefan model for a wide range of binary systems, it is postulated that this improved performance should also be observed for a ternary system. In this work, the dynamic molecular fluctuation model was extended to a highly non-ideal ternary system, using the same scaling factor α, through matrix manipulation. Using self-diffusion data measured by NMR, mutual diffusion predictions of the developed model and the Maxwell-Stefan model were compared to experimental mutual diffusion data of the partially miscible system ethanol/toluene/n-decane. It is demonstrated that the dynamic fluctuation model gives improved predictions relative to the Maxwell-Stefan approach, consistent with previous observations on binary systems, showing that the reduced thermodynamic influence of the dynamic fluctuation model is an improvement. In addition, we show that the use of local mole fractions, to account for molecular association, in both the dynamic fluctuation and Maxwell-Stefan models, results in improved diffusion predictions for the ternary system. The results confirm that the dynamic fluctuation model improves predictions of mutual diffusion in liquid mixtures, suggesting a non-linear correction to the thermodynamic correction factor. The results also suggest that that the key assumptions in the Maxwell-Stefan model and its derivation, rooted in the kinetic theory of gases, are not entirely accurate for highly non-ideal liquid systems. The optimum α for the ternary system studied here is approximately 0.45, similarly to the optimum α of 0.40 to 0.80 for a range of binary systems previously studied, suggesting that the use of the α scaling factor, which is grounded in scaling laws theory, is of general validity.

On the Importance of Choosing the Best Minimization Algorithm for the Determination of Ternary Diffusion Coefficients by the Taylor Dispersion Method.

Taylor dispersion method is a common technique for the determination of diffusion coefficients in the case of multicomponent systems. One of the main problems related to the parameter estimation analysis of the collected results is the choice of the best minimization algorithm that allows finding the real minimum of the objective function. Usually, researchers use the Levenberg-Marquardt algorithm, averaging the parameters obtained by different estimation analyses. In this paper, some nonlinear minimization algorithms included in MATLAB R2016a have been tested, and the results are compared in terms of best fit on the experimental data collected for sodium dodecyl sulfate (SDS) + sodium octanoate (SOC) + water system.