Brazilian Journal of Chemical Engineering最新文献

This paper presents a methodology to compute the location of heat exchangers in the chemical process plant based on a fixed-topology heat exchanger network. The location of the heat exchangers is computed by minimising the pipe length required to transport the heat-integrated streams from the supply process equipment to the target process equipment. The pipe length is estimated as the sum of the rectangular distances between the coordinates of the process equipment connected along the pipe, using a mixed-integer linear model, and provides a lower bound for the pipe length required by the exchanger network. Layout constraints can be added to the model, such as minimum distances between equipment and zones of the plant where heat exchangers are restricted to being placed. It is also possible to restrict heat exchangers to being near specific equipment, such as heat-integrated reboilers located beside their distillation columns. The proposed methodology is applied to a number of heat integrated processes, with varying degrees in number of streams and heat exchangers.

Microdroplet formation has been widely used in 3D printing, additive manufacturing, chemical synthesis and other fields. Comprehensive understanding for the microdroplet formation is necessary for process optimization of the above-mentioned fields. In this paper, the Giesekus (GK) model is used to simulate the formation of viscoelastic droplet in T-type microchannels based on OpenFOAM. The effects of liquid phase elasticity, viscosity and channel wall wettability on the formation of viscoelastic droplet were investigated by changing the relaxation time of the dispersed phase, polymer viscosity and wall contact angle. The pressure characteristics, droplet final lengths and detachment time were compared under different operating conditions. The simulation results describe the effect of fluid parameters on droplet formation in the form of pressure, which is used to supplement the shortcomings of existing experiments in stress. The results show that the elasticity hinders droplet breakup during the stretching stage. As the polymer viscosity increases, there is a significant increase in the elasticity of the droplet, which prevents the droplet filaments from stretching and breaking, resulting in a slower frequency of droplet formation. Moreover, the influence of wall contact angle and fluid flow rate on the formation of viscoelastic droplets in T-shaped microchannel is also observed. It is found that the wall contact angle also has an impact on the final droplet length, which cannot be ignored.

Magnesium (Mg) production via electrolysis can offer an efficient and sustainable alternative to conventional metallothermic processes. However, electrolytic systems contain impurities like manganese (Mn) that significantly influence efficiency and product quality. This study investigates the local structure of Mn²⁺ and the intricate electrochemical behavior of Mn(II) within MgCl₂-NaCl-KCl melts, aiming to explore its impacts on electrode kinetics. Deep Potential Molecular Dynamics (DPMD) method is applied for structure introduction, and a strange chloride layer around Mn²⁺ is observed. Furthermore, cyclic voltammetry, chronopotentiometry, and other techniques are employed for study using tungsten electrodes with introduced MnCl₂. Results reveal the quasi-reversible reduction of Mn(II) on tungsten. The diffusion coefficients (D) of Mn(II) at different temperatures are summarized, and an activation energy of 30.60 kJ·mol^-1 for diffusion is found. Mn electrodeposition follows instantaneous nucleation. While limited in scope, these findings provide important insights into Mn(II) interactions that could inform efforts to optimize Mg electrolysis. Further research on Mn(II) effects on melt structure is still needed to understand electrolytic systems comprehensively. This work significantly furthers the fundamental comprehension of Mn(II) electrochemistry within industrial Mg production.

In this study, a sodalite-type zeolite (SOD) was synthesized through the alkaline fusion of kaolin and crystallized under ambient pressure conditions, without the need for autoclaves and high temperatures. The influence of the ratio between fused kaolin and water (g/mL) during crystallization was evaluated. The ratio of fused kaolin with NaOH to water at 1:10 g/mL resulted in the synthesis of zeolite with higher relative crystallinity (70.99%), which was affected by the concomitant formation of thermonatrite phase. Additionally, the zeolite showed a Si/Al ratio of 0.95 and Na/Al ratio of 1.00, and the aluminum atoms exhibited a configuration of perfect tetrahedra. Due to the absence of octahedral aluminum in the zeolitic structure and the charge-balancing cations being Na⁺ ions, the zeolite presented itself as a basic solid.

This research focuses explicitly on the solubility of azlocillin and nimodipine in mixed binary solvents. This is relevant for pharmaceutical companies involved in developing and formulating these drugs. At a constant pressure of 101.2 kPa and temperatures ranging from 283.15 K to 323.15 K, the mole fraction equilibrium solubility of nimodipine and azlocillin in binary solvents (ethanol + ethyl acetate) was determined experimentally by gravimetric method. The results demonstrated that azlocillin and nimodipine solubility improved with higher ethanol mole fractions in mixed solvent systems. Among the three thermodynamic models, the experimental solubility data was best explained by the van't Hoff-Jouyban-Acree (V-J-A) model, followed by the Jouyban-Acree (J-A) model. The greatest RAD and RMSD values occur when two variables are compared to one another (RMSD) were 4.96 × 10⁻² and 10.62 × 10⁻⁴ for azlocillin and 1.463 × 10⁻² and 2.393 × 10⁻⁴ for nimodipine, respectively. The preferential solvation parameter ({delta x}_{1,drug}) is more significant than zero for nimodipine and azlocillin in the respective ranges of 0.60 < x_E < 1 and 0.60 − 0.65 < x_E < 1. This indicates that these two studied drug compounds prefer solvated by ethanol over ethyl acetate under these conditions. These results offer valuable perspectives for researchers in the pharmaceutical sciences, especially regarding the comprehension of drug compound solubility and solvation behavior in mixed solvent systems.

Coffee industry generates large amounts of organic waste such as spent coffee grounds (SCG) and green coffee beans press cake (PC). The extraction of oil and phenolic compounds from PC was evaluated by: 1) Soxhlet extraction system using ethanol and hexane as solvent; 2) Extraction in a fixed bed at 400 bar and 60 °C using as solvent supercritical CO₂ (scCO₂), ethanol or a mixture scCO₂/ethanol 90:10 w/w; and 3) sequential extraction in a fixed bed at 400 bar and 60 °C using scCO₂ followed by pressurized liquid extraction with ethanol, followed by water. PC showed a residual oil content around 6%, which was extracted with pure scCO₂ and with hexane. Multi-stage extractions provide a statistically equal total extraction yield (p ≤ 0.05) to that obtained in a single step with ethanol, which was around 21%. However, ethanolic extract in one step presented about 96 mg CAE/g extract and the ethanolic and aqueous extracts obtained in the sequential stages showed 159 mg CAE/g and 146 mg CAE/g, respectively. The residue from the mechanical extraction of green coffee oil has an important oil content and the amount of phenolic compounds is greater than that from SCG.

Photocatalysts are promising materials for removing organic dyes from the environment. TiO₂ is one of the most extensively studied photocatalysts; however, its application in the photocatalytic industry has yet to be realized. We contend that fundamental research and the quest for synergy are essential in this field. One approach to enhancing the efficiency of TiO₂ is deposition onto porous inert substrates. In this work, we introduce a novel approach by applying TiO₂ onto the surfaces of porous nanosized Al₂O₃ and ZrO₂. Employing two soft chemistry methods — the glycol-citrate route for creating a porous and inert substrate and the peroxide route for depositing a TiO₂ layer — we have created a technology that allows us to vary the TiO₂ concentration on the inert matrix. The developed composite photocatalysts demonstrate competitive efficacy in disintegrating the model dye methylene blue. The most effective photocatalyst was Al₂O₃@TiO₂ (0.26 wt.%) at 1200 °C. This material degrades approximately 98.2% of the methylene blue in 5 h, while nanosized TiO₂ degrades only 33.5% of the dye under the same conditions. The photocatalytic activity of the material is affected by the concentration of TiO₂ in the material due to the dilution of the peroxide solution. Notably, a decrease in the TiO₂ concentration enhances the photocatalytic activity of the composite. We assumed that titanium dioxide was distributed in thinner layers at lower concentrations, which increased the area of effective contact and photocatalytic activity. The most efficient aluminum and zirconium oxides decorated with titanium dioxide had surface areas of 12.7 and 16.9 m²/g, respectively, while Al₂O₃ and ZrO₂ had surface areas of 31.7 and 34.3 m²/g, respectively. Therefore, the decrease in methylene blue concentration was caused by photocatalysis but not by the sorption mechanism. The decomposition of methylene blue in all the samples is consistent with a pseudo-second-order photocatalysis model. The findings of this work lie in the precise application of TiO₂ onto the surfaces of inert matrices, which is valuable for developing photocatalytic materials.

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