Band 19, Heft 10

Nanoreactors are a type of chemical reactor that is used mostly in nanotechnology and nanobiotechnology. These unique reactors are critical to the operation of a nano foundry, which is essentially a foundry that produces goods on a nanoscale. Active sites, such as transitional metal species, can also be added to nanoreactors. In this situation, the NR’s limited area might impact reaction rate and mechanism by increasing the contacts between reactants and active sites and changing the concentration of the reactant at the active site. Immobilization of chiral active centers inside porous materials has received a lot of interest in this context, and there have been a lot of publications proving the benefits of nano space confinement in chemical processes. The specific mechanism in which enantioselectivities are strengthened has been clarified using molecular dynamics simulations. Nanoreactors are nanometer-sized chambers with the potential to improve chemical conversions by shielding catalysts from external effects and encapsulating reactors and catalysts in a tiny space for an extended period of time. Natural and synthetic nanoreactors are the two types of nanoreactors that can be found in general. The first group has a more selective function while also having a more complicated structure, whereas the second group has more variation and a simpler structure. Synthetic nanoreactors have so far been made with a variety of molecules and large types of molecules. The space inside the nanoreactors is a good environment for the production of various nanostructures, in addition to a wide range of chemical reactions. When chemical reactions are carried out in confined spaces with nanometer dimensions and micrometer volumes, the kinetics and the entire process path are altered. Nanoreactors are restricted areas used to execute specialized chemical processes. In the cells of living organisms, numerous simultaneous reactions are based on the same concept. As a result, various biological and chemical structures with nanoreactor characteristics are used in this strategy.

The axial cyclone separator has simple structure, operates to reducing dust concentration in grain storehouses, and features low production cost, and convenient installation. Aiming to obtain the separation characteristics of an axial flow guide separator, the particle wall collision and the performance of multi-tubes were simulated with Fluent. The renormalization group (RNG) k  −  ε model was used to study the turbulent modeling and the user define function (UDF) was used to calculate the particle-wall collision. The simulation and experimental results were compared to verify the computation model. The results showed that the basic feature of the flow pattern remains stable and the separation efficiency of 800 kg/m 3 particles is higher than 2650 kg/m 3 particles when the inlet velocity increases from 2 to 5 m/s. When the inlet velocity was 5 m/s, the normal velocity restitution ratio had a significant effect on the efficiency, the separation efficiency of 167  μm particles changed from 76.74 to 97.93% and a smaller normal velocity restitution ratio had a higher the efficiency. In comparison, the efficiency remained unchanged when changing the tangential velocity restitution ratio. Furthermore, the effects of three target wall materials on the separation efficiency were investigated. And the simulated efficiency the of 296 μm particle of 2024 aluminum, 410 stainless steel and Ga1–4V titanium were 82.15, 79.52 and 77.53% respectively. Besides, effects of tube diameter on performances of cyclone separator were discussed and high intense collisions between particles and walls may occur in a small diameter of cyclone tube, causing deteriorated separation performance. Moreover, with the addition of the dust chamber, the efficiency of cyclone used in combination is slightly improved since the vortex in the exhaust pipe has been finely changed.

An integrated kinetic model representing catalytic cracking of eugenol in a fixed bed reactor is developed. Eugenol, a major component of clove oil can act as the most potential bio additive fuel for improving the diesel quality thereby reducing the exhaust emission of the engine. The proposed integrated model includes four lump kinetic model which is plugged with catalyst deactivation model. The reactor design parameters are also included in the integrated model. The effectiveness of the proposed integrated model is compared with the conventional kinetic models and the results are presented. The proposed integrated model is validated against the real time data obtained by conducting an experiment in a real time setup with MoS 2 (Ni 2 P) Al-SBA-15(10) as the catalyst. The advantages of the proposed integrated model are highlighted.

The development of a low-temperature water and sulfur-resistant catalyst with high efficiency of NO removal and element mercury Hg(0) oxidation performance is one of the main directions for the synergistic removal of multiple pollutants from flue gas. The transition metal Mn is used to modify the V-W/Ti catalyst to prepare a modified Mn-SCR catalyst. The effects of Mn loading and complex flue gas components (SO 2 , H 2 O and HCl) on the modified catalysts activity were investigated on a small fixed-bed experimental bench, respectively. As the Mn loading increases, the acid sites on the catalyst surface are significantly enhanced, the window of NO removal temperature is significantly widened, and the Hg(0) oxidation performance is nearly 100%. The optimal loading amount of Mn is 0.2(Mn/Ti, mol). When the Mn loading exceeds 0.2, the particles on the catalyst surface sinter, and the specific surface area decreases. However, little difference is observed in catalyst activity. When SO 2 and H 2 O are present in the flue gas, dual-action catalyst activity can be significantly suppressed, but the effect of H 2 O on catalyst activity is greater than that of SO 2 . With the increase of the HCl concentration from 0 ppm to 50 ppm, the oxidation efficiency of Hg(0) and the removal efficiency of NO increased slightly.

As a kind of fast and efficient mixing equipment, micromixer has been applied to chemical reaction detection. Its application can not only save experimental samples but also reduce the experimental time. In micromixers, Tesla structure is widely used due to its simple structure and special flow mechanism. In this paper, CFD and response surface method are used to analyze and verify the flow field of the configuration of adding diamond obstacles in the Tesla mixer. The results show that the order of layout parameter weight from large to small is obstacle size > vertical offset > horizontal offset. And the Desirability was 0.806, the optimal diamond obstacle size is 46.35 μm and the optimal lateral offset is 18.78 μm. In addition, a constant value OF 20 μm is predicted as the optimal vertical offset of the micromixer. Compared with the Tesla-type micromixer without obstacles, the diamond-shaped barrier Tesla-type micromixer designed in this paper has higher mixing rate and lower pressure drop under the same conditions, which can be applied to chemical reactors, and can also help to improve the accuracy of chemical reaction. It can be demonstrated that the presented optimal design method of obstacles layout in Tesla mixer is a simple and effective technology to improve the liquid mixing in microfluidic devices, and it has a broad application prospect in chemical engineering.

Loofa sponge is a naturally-grown and decomposable material providing high specific surface area and high porosity for potential application as an environmentally-friendly catalyst carrier. In this work, cellular samples of various loofa types cut from different fiber network regions of the fruits were studied in detail using non-invasive imaging techniques. Digital microscopy was applied to characterize the cellular fiber network, which revealed a honeycomb structure in the core region and a sandwich structure in the wall region. Furthermore, reconstructed three-dimensional (3D) morphological images of the loofa samples obtained via micro-tomography (micro-CT) were utilized to extract the geometrical properties cell size, window diameter and strut thickness as well as porosity and volume-specific surface area. The reconstructed loofa samples revealed porosities of about 92% and specific surface areas up to 2057 m 2 /m 3 . In addition, the geometrical properties of manufactured solid foams (ceramic and polyurethane) were also determined via micro-CT and compared with loofa sponge. Finally, the different characteristic cell dimensions were employed to predict the porosity and specific surface area with available geometrical correlations. Deviations between correlation and measurement data (±16%) can be attributed to the peculiarity of the loofa cellular fiber network, which is somewhat different from the tetradecahedral-shaped geometry commonly used as the basis for most of the available correlations.

Residence time distribution (RTD) experiments provide very important information about the performance of reactors. In the present work, RTD experiments were performed with varying recycle and recirculation rates to see their effect on mean residence time (MRT), flow bypassing and stagnant volume in the reactor. A computer program was developed to solve the model equations using fourth-order Runge–Kutta method. A low bypass flow (<5%) was observed from the experimental RTD curves obtained at different operating conditions. A change in the MRT from 1.2 to 1.8 h was observed at different recycle and recirculation rates. At maximum recycle and maximum recirculation, in the study ranges, a 37% stagnant volume (with exchange) was predicted. In the absence of recycle and recirculation, a 53% stagnant volume (with exchange) was predicted corresponding to the best fit of the experimental RTD data.

The performance of a fuel cell depends on multiple factors, one of the most important being the preparation of the membrane electrode assembly (MEA). In the present work, MEAs constituted by gas diffuser electrodes (GDE) were pressed with carbon supported platinum catalysts. As solid electrolyte, a commercial polymeric membrane from Nafion was used, which was pressed at two GDE with loads of 5 and 1.5 mg/cm 2 of catalyst at different temperatures and pressures for a fixed period of time. The assembly was characterized electrochemically using linear sweep voltammetry and electrochemical impedance spectroscopy at three different potentials. Also, the behavior when reversing the supply of hydrogen and oxygen to the GDE was studied. The results of the study showed a great dependence of the charge transfer resistance with the temperature, being secondary the dependence with the pressure in the range of temperature and pressure analyzed. Likewise, changes were observed in the open circuit potential after varying the temperature, pressure and catalyst load, hence affecting its maximum power and efficiency at that point.

Iron removal is an important step in zinc hydrometallurgy, and hematite process not only can effectively remove iron, but also is environmentally friendly and has certain economic benefits, so it has great application potential in zinc hydrometallurgy. The oxidative hydrolysis of Fe(Ⅱ) was studied by the change of ions in solution with different initial ferrous ion concentration. Meanwhile, the oxidation rates of Fe(Ⅱ) at different initial Zn(Ⅱ) concentrations were also studied. The results show that temperature has an important influence on the oxidative hydrolysis of Fe(Ⅱ). Increasing the temperature can inhibit the formation of complex and make more Fe(Ⅱ) precipitate directly in the form of hematite, which is not limited by the hydrolysis rate of Fe(Ⅲ). The oxidation reaction of Fe(Ⅱ) approximately conforms to the second order reaction rate. Zinc sulfate can promote the oxidation of Fe(Ⅱ). When the initial Zn(Ⅱ) concentration was 20, 40, 60 and 80 g/L, the oxidation kinetic constants of Fe(Ⅱ) were 2.433, 4.492, 10.106 and 14.857 L·mol −1 ·min −1 , respectively.

Designing and optimizing a bioreactor can be an especially challenging process. Computational modelling is an effective tool to investigate the effects of various operating parameters on bioreactor performance and identify the optimum ones. In this work, a computational fluid dynamics-population balance model (CFD-PBM) was developed to elucidate the effect of different geometrical and operating parameters on the hydrodynamics and mass transfer coefficient of a batch stirred tank bioreactor. The validated model was projected to predict the effect of different parameters including the gas flow rate, the impeller off-bottom clearance, the number of agitator blades, and rotational speed of the impeller on the velocity profiles, air volume fraction, bubble size distribution, and the local gas mass transfer coefficient ( K l a ) in the bioreactor. Air bubble breakup and coalescence phenomena were considered in all simulations. Factorial experimental design approach was employed to statistically investigate the impacts of the aforementioned operating and geometrical parameters on K l a and bubble size distribution in the bioreactor in order to determine the most significant parameters. This can give an essential insight into the most impactful factors when it comes to designing and scaling up a bioreactor.