Theoretical Foundations of Chemical Engineering最新文献

In this study, sulfide removal was carried out in the Electrocoagulation process under controlled and uncontrolled pH conditions. Under optimum conditions, electrocoagulation took place in less than 40 minutes at uncontrolled pH and less than 30 minutes at controlled pH to reduce the sulfite concentration of the effluent below 0.5 mg/L. The reaction rate constant and iron-sulfide molar ratio for sulfide removal were 14.09 × 10^–2 min^–1 and 0.97 mol/mol, respectively; under uncontrolled pH conditions, they were 22.88 × 10^–2 and 0.97 mol/mol at controlled pH. The mg sulfide removed per g Fe was calculated as 654.0 mg S^2–/g Fe at uncontrolled pH and 508.46 mg S^2–/g Fe at controlled pH. The operating costs for uncontrolled and controlled pH conditions were also calculated as 2.063 $/m³ (0.747 $/kg S) and 0.842 $/m³ (0.628 $/kg S), respectively. Controlled pH conditions were important in sulfide removal by the Electrocoagulation process.

The CeCuO_x composite catalysts for the catalytic conversion of dimethyl formamide were prepared and catalyzed by the sol-gel method with a controlled amount of Cu. The physical and chemical properties and catalytic performance of the CeCuO_x composite catalysts were characterized by X-ray diffraction analysis, N₂ adsorption-desorption, scanning electron microscopy, X-ray photoelectron spectroscopy, and H₂-programmed step-up reduction. The results indicate that the doping of Cu increases the particle size of the CeO_x support and enhances the relative content of Ce³⁺ species on the CeO_x surface. The Cu/Ce ratio significantly influences the activity, product selectivity, and stability of the composite catalyst. Among them, Cu₈₀Ce₂₀ exhibits the best overall performance in the catalytic reaction of dimethylformamide.

The solubility and metastable zone width (MZW) are crucial to design and control of crystallization process. In this work, lysozyme solubility in different pH (4.0–6.0) aqueous solution at temperature ranging from 268.15 to 308.15 K were determined. The solubility and supersolubility of lysozyme with two ionic liquids (ILs) (1-butyl-3-methylimidazolium chloride ([C₄mim]Cl) and 1,3-dimethylimidazolium iodine ([dmim]I)) were measured in aqueous solution at temperature ranging from 283.15 to 298.15 K at pH 5.0, and the MZW was calculated. The results demonstrate that lysozyme solubility increases with raising pH within 4.0 to 6.0. In the presence of ILs, the solubility increases with increasing [C₄mim]Cl concentrations, but decreases with increasing [dmim]I concentrations. The ILs addition concentrations were confirmed to exert obvious effect on MZW of lysozyme crystallization. Compared with no ILs added, the addition of ILs [C₄mim]Cl and [dmim]I expands significantly the MZW, and the MZW increases with increasing ILs concentrations. At constant ILs concentrations, the MZW increases with decreasing saturation temperature. These findings could provide significant insights into the development of crystallization strategy and the control of crystallization process for lysozyme.

Hydrophilic deep eutectic solvents are actively positioned as efficient extractants for removing heterocyclic compounds from light hydrocarbon fractions. Of particular interest is the subclass of natural deep eutectic solvents (NaDESs), since they contain substances of exclusively natural origin. However, these processes have not been systematically studied to date in extraction equipment. To study the process of countercurrent extraction of pyridine, quinoline, and indole from a model solution of light hydrocarbon fractions using commercial equipment, a series of NaDESs based on citric and malic acids, xylitol, and water was used for the first time in this work. The high extraction capacity of these NaDES was demonstrated in laboratory experiments, and the extraction mechanism was determined. A detailed study of the efficiency of extraction of heterocycles with varying process conditions allowed us to move on to studying the process using extractors of the mixer–settler type. From the model solution of light hydrocarbon fractions, pyridine, quinoline, and indole were removed to concentrations <1 ppm by countercurrent extraction using a cascade of six mixer–settlers.

The effect of boric acid amino ester, which was obtained from triethanolamine, boric acid, and triethylene glycol, on the conditions of vapor–liquid equilibrium in the ethyl acetate–ethanol and ethyl acetate–isopropanol azeotropic binary mixtures and the ethyl acetate–ethanol–water ternary mixture was studied both by experimental methods of open evaporation with a Świętosławski ebulliometer, and by modeling using the UNIFAC method. Parameters of the interaction of the CCOO group (in ethyl acetate) with the boron group B were determined, which are absent in the literature. A process for separating the ethyl acetate–ethanol–water azeotropic mixture by extractive distillation was proposed.

In this study, multi-objective optimization of reactive dividing wall column is presented. Production of methyl acetate from acetic acid and methanol is taken as case study. Machine learning approach is introduced in this work by means of artificial neural network and genetic algorithm. Required data generation, input and output variable fixation to model neural network is done from the sensitivity analysis. Based on the dataset, neural network model is trained by Lavenberg–Marquardt algorithm and predict purity and TAC of column with high accuracy. Further parametric constrained optimization of systems has been done using multi-objective genetic algorithm and set of pareto optimal solution is generated. Based on gray relational analysis, best optimal point found out. After optimization the system gives significant reduction on TAC and enhancement in purity. Results shows reactive dividing wall column reduces total annual cost around 17.77%. All the results in present work is validated with exiting literature and also cross validated with ASPEN plus.

It was proved that polymer–bitumen binders undergo a structural transformation after the addition of synthetic waxes. UV spectroscopy study showed that wax macromolecules and compounds of the dispersed oil system enter into chemical interactions, which was detected by the disappearance of the absorption band at 260 nm in the UV spectrum of the wax–bitumen blend. This suggested the formation of crosslinked reinforcing spatial structures, which explain the observed improvement in the performance properties of the polymer–bitumen binder after the addition of synthetic waxes: an increase in the softening temperature and brittleness temperature, a decrease in penetration, and an increase in their dynamic viscosity. It was determined that the transformation of the physicochemical characteristics of the polymer–bitumen binder after the addition of wax depends on its chemical nature. Waxes with an aliphatic branched polyethylene structure (Plastobit 430F, Plastowax 200TD, Plastowax 725T, Honeywell Titan 7686) more strongly change the physicochemical characteristics of the polymer–bitumen binder in comparison with waxes of the ProPolymer MA123 and ProPolymer MA-SK-02 brands, which are maleic anhydride–grafted linear polyethylene.

Curing process of siloxane polymer was studied by determining rate of heat released during Dynamic DSC analysis. Utilizing thermokinetics software were calculated model-free methods such as Kissinger, Flynn–Wall–Ozawa, Friedman and also model-fitting methods such as Coats Redfern. To improve accuracy, Khavam Flanagan’s combined method was utilized and the third-order Avrami model was determined. Simulation of the curing process was done using OpenFOAM open-source software based on the finite volume method. Simulation results were validated using DSC Isothermal data. The results of the simulated sample were in good agreement with the experimental data. The curing time was investigated in cylindrical, spherical, and cubic shapes. The longest curing time was assigned to sphere geometry and the least to rectangular cubes with equal length and width. To achieve the optimal curing method, the influence of various parameters on the curing process of polysiloxane, including oven temperature, mold geometry, boundary conditions (effect of curing in a fan oven) and geometry dimensions, resin density, and thermal conductivity coefficient were investigated.

The ultrasound-assisted extraction was carried out to separate the total cardiac glycoside from the milk of Calotropis gigantea, and the extraction factors was optimized by response surface method using the Box–Behnken design (BBD) on total cardiac glycoside extraction was determined and optimized. A quadratic polynomial parameter mathematical model was established. Under the optimized conditions of ethanol concentration = 40% (vol), liquid-material ratio = 40 : 1, ultrasound power = 420 W and ultrasonic time = 30 min, the total cardiac glycoside yield is 12.75%, which is very close to the predicted value of 12.48%. The model predicts the experimental data well and has a high determination coefficient (R² = 0.992). The variables that have a greater influence on the extraction yield were selected as ultrasonic power, ultrasonic time, ethanol concentration and liquid-material ratio, respectively.

The work considers the results of experimental and numerical study on the hydrodynamic characteristics of a jet vortex reactor, MicroReactor with Intensively Swirled Flows MRISF-1, for which one of the application fields is the synthesis of oxide materials (e.g., perovskite-like material for solar panels). The energy-dissipation rate and micromixing quality are studied (by the iodide–iodate method) for various methods of supplying MRISF-1 and T-shaped millireactors with solutions. Numerical modeling reveals the volumes with the highest energy-dissipation rate. The quality of micromixing in the MRISF-1 is shown to be much higher than in the T-shaped millireactor, due to, among other things, the fact that the zone with the highest energy-dissipation rate is localized near the neck of the MRISF-1.