Brazilian Journal of Chemical Engineering最新文献

Metal–organic frameworks (MOFs) are porous materials composed of metal ions, clusters and organic ligands. Due to their outstanding chemical, thermal, and solvent stability, as well as numerous unsaturated metal sites, they have proven to be useful catalysts. In this study, MOFs were synthesized using hydrothermal methods with terephthalic acid and Ca, Mg, Al, and Cr nitrates. Subsequently, they were functionalized with diethylamine. The formation of MOF-Al and MOF-Cr structures was confirmed through characterization via XRD, FT-IR, and CHN analyses. However, the synthesis did not yield MOF structures with Ca and Mg as metal ions; instead, phthalates of Ca and Mg were obtained. SEM images revealed the particle size and morphology of the particles, which ranged between 0.2 and 1 μm. TGA/DTA curves revealed that the functionalized MOFs were the most thermally stable. Textural analysis by N₂ adsorption/desorption showed that MOF-Cr and MOF-Cr-NH₂ had high BET area values of 1,769.67 and 998.22 m²g⁻¹, respectively. MOFs were employed as catalysts in Knoevenagel condensation reactions to synthesize (E)-ethyl 2-cyano-3-phenylacrylate and (E)-methyl 2-cyano-3-phenylacrylate, indicating their potential for reactions requiring acidic or basic sites.

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.

Graphical Abstract

Nanoparticles are useful for immobilization due to their size and physical properties. The present study aimed to synthesize herbal silver nanoparticles (SNPs) to immobilize the lipase from Candida rugosa covalently on the nanoparticles as well as to examine the biochemical parameters of the immobilized enzyme. SNPs were synthesized using Cydonia oblonga leaf extract and were characterized. Lipase enzyme was immobilized on synthesized SNPs and the immobilization efficiency was calculated. The biochemical properties of immobilized and free enzymes, including the temperature effect and pH on enzymatic activity, thermal stability, storage stability, and reusability of the immobilized enzyme were specified. Electron microscopy, DLS measurements, and Raman spectroscopy confirmed the 50 nm SNPs and the immobilization of lipase enzyme on them. The efficiency of lipase enzyme immobilization on nanoparticles was estimated to be 48%. The free enzymes and immobilized enzymes had the highest activity at 37°C and 55°C, respectively. Also, the optimal pH was 7 for the free enzyme and 6 for the immobilized enzyme. A comparison of thermal and storage stability of free and immobilized enzymes suggested that immobilized enzymes had more stability and resistance than free enzymes as they also could be reused up to 12 times. The kinetic parameters of the immobilized enzyme compared to the free enzyme indicated a slight decrease in the maximum rate of the enzyme. Immobilized enzymes can be used in industries and are also very crucial for commercial use as they are cost-effective.

Production xylanases at low cost and their storage stability are of utmost importance for the animal feed industry. This work aimed to produce fungal xylanases by solid-state cultivation and to immobilize the enzymes in agricultural residues by spray-drying. The enzymes were obtained by cultivating Myceliophthora thermophila I-1D3b in sugarcane bagasse and wheat bran at 45 °C and 75% moisture content (w.b.) and the titres were as high as 864 U per gram of dry solids. The physical–chemical activity of the enzyme showed to be of interest for the animal feed industry, as the optimal activity was obtained at pH 5.0 and the optimal temperature at 70 °C. The enzymes were spray-dried using soybean meal, wheat bran, and corn bran as carriers, and the most suitable carrier was soybean meal in terms of residual enzyme activity after drying. The operational conditions for soybean meal were optimized, with the outlet temperature, the liquid flow rate, and the total solid content as variables, and only the total solid content was significant. The highest residual enzyme activity was 130.9% after optimization. Experiments for storage of the dry powders of soybean meal showed that the loss of activity was under 30% for storage times up to 45 days. The results here presented are promising for the reduction of costs of xylanases used as feed enzymes and for their preservation for long periods as a dry powder.