In photocatalytic microreactors the catalyst layer is obtained by integration of nanostructure films of semiconductors. One of these nanostructures that have a good photocatalytic activity is ZnO nanowires. The photocatalytic degradation of methylene blue in a continuous flow microreactor with ZnO nanowires deposited film is simulated. A finite element model is developed using COMSOL Multiphysics version 5.3 software to simulate the microreactor performance. The kinetic law of the photocatalytic reaction is assumed to be Langmuir–Hinshelwood. The kinetic constants kLHa and K are determined 1.43×10-7 mol/m2s and 7.5 m3/mol, respectively. The percent of average absolute deviation of the model in predicting the methylene blue outlet concentration obtained about 0.12% mol/m3. The model showed a very good agreement with the published experimental data. The effect of microreactor depth, methylene blue inlet concentration and flow rate on the methylene blue degradation is also investigated. The simulation results showed that the microreactor with shorter depth and lower values of inlet concentration and flow rate has higher efficiency. Thiele modulus and Damköhler number are both estimated lower than 1. It indicates that the photocatalytic reactions occur without internal and bulk mass transfer limitations.

In the pharmaceutical industry, drug synthesis is usually carried out by batch method. However, in recent years, continuous methods, specifically microfluidics and microreactors, have attracted a great deal of attention due to advantages such as better mass and heat transfer, safety, selectivity, yield, and surface-to-volume ratio. Thus, in this review, different microreactor properties such as flow regime pattern, operating pressure, selectivity, safety, reaction phase, operating and control, materials, and cost are addressed and discussed. In addition, microreactor applications in the synthesis of chemicals and drugs, polymerization, nanoparticle synthesis, photochemical, biodiesel production, and catalytic microreactors are presented in detail. Furthermore, a comparison of the flow process of a pharmaceutical industry's microreactor and a batch reactor used for different APIs, intermediates, and lead compounds is presented. The results revealed that 50% of such reactions would show more promising results when carried out in a microreactor system, while only 44% of examined cases preferred such systems. Ultimately, these authors believe that the current review is very suitable for newcomers in pharmaceutical industry material production research who might be attracted to this new technology due to the elementary and basic microfluidics concepts discussed in the present manuscript.

A three-dimensional (3D) simulation of four photocatalytic microreactors is performed using mass and momentum balance equations. The simulated results are validated with the available experimental data for the photocatalytic removal of methylene blue (MB) in two microcapillaries as well as dimethylformamide (DMF) and salicylic acid (SA) in two microchannels. In the surface layers of the microreactor, a photo removal reaction takes place, and the kinetic rates are described by the Langmuir-Hinshelwood (L-H) model. The Damköhler number for these microreactors is less than one, which indicates that the mass transfer rate is limited by the reaction rate. The numerical study and kinetic constants determination are carried out by using computational fluid dynamic techniques. The 3D modelpredictionsare ingood agreementwith the availableexperimental data sets. The results of the parametric study show that by increasing the microreactor length from 50 to 90mm, the removal efficiency improves from 76% to 93%. Moreover, the removal rate is increased by about 40% by reducing the microchannel depth from 500 to 100 .

In recent years, the removal of carbon dioxide as the most important greenhouse gas has been noticed. In this study, the performance of potash-glycerol hybrid solvent in the process of carbon dioxide absorption was investigated using a microreactor. Experiments have been done under different conditions include: flow of inlet solvent (4-8 ml/min), potassium hydroxide concentration (0.3- 0.7 M) and glycerol concentration (0-30 wt.%) at constant temperature of 40 °C, and the percentage of carbon dioxide absorption and the overall volumetric mass transfer coefficient based on gas phase (KGav) have been considered as response. According to the results, with increasing glycerol concentration as physical solvent from 0 to 30 wt. %, the absorption efficiency increases from 59.13 to 66.1%. Also, by increasing glycerol concentration despite increased fluid viscosity, the overall volumetric mass transfer coefficient increases from 55.50 to 66.53 kmol/m3.hr.kPa. Comparison of the reported values for KGav in this study with the values published for monoethanolamine in the packed tower shows that the overall volumetric mass transfer coefficient in the microreactor is about 60 times larger, indicating better microreactor mass transfer performance.

e"> The ultrasound-assisted (UA) soybean oil methanolysis using KOH as a catalyst was studied at different reaction conditions in a microreactor. Box–Behnken experimental design, with three variables, was performed and the effects of three reaction variables, i.e., reaction temperature, catalyst concentration and the methanol-to-oil molar ratio on fatty acid methyl ester (FAME) yield were evaluated by method of analysis of variance (ANOVA) and multiple regression. A quadratic polynomial model was obtained to predict the methyl ester yield. A yield of 97.1% for methyl ester was obtained at the deduced optimal conditions: reaction temperature of 47°C, KOH catalyst concentration of 1.29 (w/w%) and methanol-to-oil molar ratio of 6:1. Validation experiments confirmed the validity of the predicted model.At the optimal operation condition for the ultrasonic process, ahigher yield of methyl esters was obtained in comparison with thatof the non-ultrasonic layout. The results show that UAtransesterification in microreactor minimizes the reaction time andtemperature, alcohol-to-oil molar ratio as well as energyconsumption.

In this study, after separating oil and grease from gasfield produced water, removal of organic pollutants has been investigated to reduce its chemical oxygen demand (COD) from 9500 mg/L to the limits of agriculture irrigation. Since the initial electrical conductivity of the wastewater was too high (6300 µS/cm), evaporation process was used to decrease its dissolved solids content. As results of evaporation, electrical conductivity and COD have been reduced to 1100 µS/cm and 750 mg/L respectively. Afterwards, photoelectrocatalysis as an advanced oxidation process was applied to treat distilled wastewater from evaporation step because of COD content of less than 1000 mg/L. In the photoelectrocatalytic method, “boron carbon nitrite nanomaterial” was used as photocatalyst in a coil type microreactor with surface-to-volume ratio of about 3000 m2/m3, which it causes in rapid oxidation of organics. After fabricating the microreactor, the effect of different parameters on COD removal has been investigated. It has been found out that optimum conditions to remove of 80% COD are accordance with pH = 3, potential difference 20 V and electrical conductivity of 2500 µS/cm, so that COD is reached about 150 mg/L which is suitable for agricultural irrigation.

Nowadays, with the development of microtechnology in chemical synthesis, the application of appropriate systems for the separation and purification of synthesized chemicals is of importance. In this study, the continuous performance of the bromine-lithium exchange reaction and the separation of the resulting organic and aqueous phases of the reaction products in a hybrid microfluidic device, fabricated by laser engraving and thermal bonding, were investigated. The microfluidic device consists of a microreactor and a microscale capillary separator, where after conducting the exchange reaction in the microreactor and injecting water in the main channel of the separator, two existing phases were separated from each other by the capillary channels embedded in the separator. The results of the reaction conductance in the continuous microsystem showed a yield of 73% and conversion of more than 90%. It was found that employing the microsystem increased the efficiency and selectivity of the reaction compared to a batch system.

The methanol steam reforming in a microreactor is simulated using Purnama’s reactions kinetic model. The simulation results were validated against published experimental data in terms of methanol conversion and product composition. A new concept for making the microreactor package more compact is evaluated by simulation. This idea consists of thermal and mass integration of the process, i.e., the required heat of methanol vaporization and methanol steam reforming be supplied by the heat of catalytic heat of combustion of a portion of methanol in an adjacent micro reactor to the reforming section of the package. The simulation results showed that by using this method, it is possible to obtain a product with a hydrogen purity of more than 60% and CO content of less than 2%. The effects of reactor temperature and residence time on the performance of the presented package was investigated and it was shown that the methanol conversion increases with increasing each of these parameters. Also, it was shown that adding small amount of water to the methanol feed stock leads to significant reduction in CO content of the product.

One of the newest technologies in small nuclear power plants is using heat pipe cooled microreactors. In these power plants, several heat pipes transfer the heat produced in the microreactor core to the working fluid inside the main heat exchanger. In this paper the thermodynamic simulation of the Brayton gas cycle is conducted for a nuclear power plant equipped with a heat pipe cooled microreactor with a thermal power of 5 MW using the THERMOFLEX code. The considered working fluid in the Brayton cycle in this case is the supercritical carbon dioxide, and this cycle includes the main heat exchanger, turbine, main compressor, recompression compressor, pre-cooler and high and low-temperature recuperators. The results of the thermodynamic analysis of the studied cycle showed an efficiency of 36.508 % for the considered power plant. Besides that, as the pressure ratio of the main compressor increases up to 3.15, the efficiency of the power plant increases. Whereas, at higher pressure ratios, efficiency decreases. Also, the main compressor power in the cycle was obtained as 2030.1 kW. In addition, when the re-compression compressor is designed with a mass fraction of 23%, the cycle will achieve its highest efficiency. Besides that, the turbine expansion power and shaft power were calculated as 5091 kW and 5040 kW, respectively.

The aim of this study is the numerical investigation of liquid-liquid extraction inside a spiral T-microreactor integrated with ultrasonic waves. The influence of low-frequency ultrasound (20.3, 42.3, and 61.61 kHz) and high-frequency one (1.7 MHz) on extraction efficiency is evaluated by CFD modeling. The organic-aqueous phase flow patterns inside the microreactor are graphically analyzed. The organic phase is regarded as a dispersed phase and the aqueous phase as a continuous fluid using the two-phase VOF. In addition, the SIMPLE algorithm is used for pressure and velocity coupling. The results obtained from the CFD simulation of aqueous-organic phase flow patterns are compared with the experimental results. The application of both types of ultrasounds showed a higher extraction efficiency compared to the condition of not applying it. The decreasing trend for extraction efficiency and ultrasound effect was observed for increasing flow rate. The extraction efficiency is less affected by increasing the power of low-frequency ultrasound up to the range of 600 mV, after which a sharp increase is observed up to 840 mV. In addition, in the range above 600 mV, the increase in extraction efficiency can be attributed to the formation of emulsion, which leads to a higher surface per unit volume and higher extraction efficiency. The results indicated that for low-frequency ultrasound, 20.3 kHz resulted in higher extraction efficiency rather than the other one. Comparing the extraction efficiency for applying high (1.7 MHz) and low-frequency ultrasound (20.3, 42.3, and 61.61 kHz) showed that 1.7 MHz has a considerable positive effect on its increase. Indeed, 1.7 MHz ultrasound resulted in the highest extraction efficiency compared to low frequencies, due to the ability of high-frequency ultrasound to induce micro-jets and micro-streams into the microreactor.