Continuous synthesis of N,N-dicyanoethylaniline in microreactors:Reaction kinetics and process intensification

Cyanoethylation of phenylamine is one of the important steps for the production of dicyanoethyl-based disperse dyes.However,the exothermic nature of this reaction and the inherent instability of intermittent dynamic operation pose challenges in achieving both high safety and reaction efficiency.In this study,a continuous cyanoethylation of phenylamine for synthesizing N,N-dicyanoethylaniline in a microreactor system has been developed.By optimizing the reaction conditions,the reaction time was significantly reduced from over 2 h in batch operation to approximately 14 min in the microreactor,while high conversion and selectivity were maintained.Based on the reaction network constructed,the reaction kinetics was established,and the kinetic parameters were then determined.These findings provide valuable insights into a controllable cyanoethylation reaction,which would be helpful for the design of efficient processes and optimization of reactors.

Assessing mixing uniformity in microreactors via in-line spectroscopy

Mixing behavior is critical for enhancing the selectivity of fast chemical reactions in microreactors.A high Reynolds number(Re)improves the mixing rate and selectivity of the reactions,but some exceptions of increasing side product yield with the higher Re have been reported.This study investigated the mixing uniformity in microreactors with in-line UV-vis spectroscopy to clarify the relationship between reaction selectivity and chaotic mixing with the higher Re.A colorization experiment of thymolphthalein in an acidic solution was conducted with an excess acid amount to the base to indicate a non-uniformly mixed region.Non-uniformity significantly increased with Re.At the same time,the degree of mixing,which was measured by a usual decolorization experiment,showed that the mixing rate increased with Re.The in-line analysis of the Villermaux-Dushman reaction during the mixing clarified that side product yield significantly increased with Re at around 300 and then decreased at around 1100.These results suggest the compensation effect between the mixing uniformity and mixing rate on the selectivity of the mixing-sensitive reactions.Faster mixing,characterized by a larger Re,can disturb mixing uniformity and,in some cases,decrease reaction selectivity.

Kinetics measurement of ethylene-carbonate synthesis via a fast transesterification by microreactors

High-purity ethylene carbonate(EC)is widely used as battery electrolyte,polycarbonate monomer,organic intermediate,and so on.An economical and sustainable route to synthesize high-purity ethylene carbonate(EC)via the transesterification of dimethyl carbonate(DMC)with ethylene glycol(EG)is provided in this work.However,this reaction is so fast that the reaction kinetics,which is essential for the industrial design,is hard to get by the traditional measuring method.In this work,an easy-to-assemble microreactor was used to precisely determine the reaction kinetics for the fast transesterification of DMC with EG using sodium methoxide as catalyst.The effects of flow rate,microreactor diameter,catalyst concentration,reaction temperature,and reactant molar ratio were investigated.An activity-based pseudohomogeneous kinetic model,which considered the non-ideal properties of reaction system,was established to describe the transesterification of DMC with EG.Detailed kinetics data were collected in the first 5 min.Using these data,the parameters of the kinetic model were correlated with the maximum average error of 11.19%.Using this kinetic model,the kinetic data at different catalyst concentrations and reactant molar ratios were predicted with the maximum average error of 13.68%,suggesting its satisfactory prediction performance.

Dynamic behavior of outburst two-phase flow in a coal mine T-shaped roadway:The formation of impact airflow and its disaster-causing effect

The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents.An outburst test in a T-shaped roadway was conducted using a self-developed large-scale outburst dynamic disaster test system.We investigated the release characteristics of main energy sources in coal seam,and obtained the dynamic characteristics of outburst two-phase flow in a roadway.Additionally,we established a formation model for outburst impact flow and a model for its flow in a bifurcated structure.The results indicate that the outburst process exhibits pulse characteristics,and the rapid destruction process of coal seam and the blocking state of gas flow are the main causes of the pulse phenomenon.The outburst energy is released in stages,and the elastic potential energy is released in the vertical direction before the horizontal direction.In a straight roadway,the impact force oscillates along the roadway.With an increase in the solid–gas ratio,the two-phase flow impact force gradually increases,and the disaster range extends from the middle of the roadway to the coal seam.In the area near the coal seam,the disaster caused by the two-phase flow impact is characterized by intermittent recovery.In a bifurcated roadway,the effect of impact airflow on impact dynamic disaster is much higher than that of two-phase flow,and the impact force tends to weaken with increasing solid-gas ratio.The impact force is asymmetrically distributed;it is higher on the left of the bifurcated roadway.With an increase in the solid-gas ratio,the static pressure rapidly decreases,and the bifurcated structure accelerates the attenuation of static pressure.Moreover,secondary acceleration is observed when the shock wave moves along the T-shaped roadway,indicating that the bifurcated structure increases the shock wave velocity.

Enhancement of liquid-liquid micromixing performance in curved capillary microreactor by generation of Dean vortices

Micromixing efficiency is an important parameter for evaluating the multiphase mass transfer performance and reaction efficiency of microreactors.In this work,the novel curved capillary reactor with different shapes was designed to generate Dean flow,which was used to enhance the liquid-liquid micromixing performance.The Villermaux-Dushman probe reaction was employed to characterize the micromixing performance in different curved capillary microreactors.The effects of experiment parameters such as liquid flow rate,inner diameter,tube length,and curve diameter on micromixing performance were systematically investigated.Under the optimal conditions,the minimum value of the segmentation factor XS was 0.008.It was worth noting that at the low Reynolds number(Re<30),the change of curved shape on the capillary microreactor can significantly improve the micromixing performance with XS reduced by 37.5%.Further,the correlations of segment index XS with dimensionless factor such as Reynolds number or Dean number were developed,which can be used to predict the liquid-liquid micromixing performance in capillary microreactors.

Influences of fillet radius and draft angle on local loading process of titanium alloy T-shaped components

In order to study influences of geometric parameters on the T-shaped components local loading process, a new mathematical model considering the fillet radius and draft angle was established by using the slab method. The results obtained by the mathematical model agree with the data form experiment and numerical simulation, and the results are closer to the experimental and simulation results. The influence of draft angle may be neglected under the forming conditions used. The influence of fillet radius is notable, especially in the case that the ratio of fillet radius to rib width is less than 0.75.

Gas–liquid flow mass transfer in a T-shape microreactor stimulated with 1.7 MHz ultrasound waves

This paper describes the application of ultrasound waves on hydrodynamics and mass transfer characteristics in the gas–liquid flow in a T-shape microreactor with a diameter of 800 μm. A 1.7 MHz piezoelectric transducer(PZT) was employed to induce the vibration in this microreactor. Liquid side volumetric mass transfer coefficients were measured by physical and chemical methods of CO_2 absorption into water and Na OH solution. The approach of absorption of CO_2 into a 1 mol·L^(-1) Na OH solution was used for analysis of interfacial areas. With the help of a photography system, the fluid flow patterns inside the microreactor were analyzed. The effects of superficial liquid velocity, initial concentration of Na OH, superficial CO_2 gas velocity and length of microreactor on the mass transfer rate were investigated. The comparison between sonicated and plain microreactors(microreactor with and without ultrasound) shows that the ultrasound wave irradiation has a significant effect on kLa and interfacial area at various operational conditions. For the microreactor length of 12 cm, ultrasound waves improved kLa and interfacial area about 21% and 22%, respectively. From this study, it can be concluded that ultrasound wave irradiation in microreactor has a great effect on the mass transfer rate. This study suggests a new enhancement technique to establish high interfacial area and kLa in microreactors.

Performance of a Self-Aligned InP/GaInAs SHBT with a Novel T-Shaped Emitter

A self-aligned InP/GalnAs single heterojunction bipolar transistor（HBT） is investigated using a novel T-shaped emitter. A U-shaped emitter layout,selective wet etching,laterally etched undercut, and an air-bridge are applied in this process. The device, which has a 2μm×12μm U-shaped emitter area,demonstrates a common-emitter DC current gain of 170,an offset voltage of 0.2V,a knee voltage of 0.5V, and an open-base breakdown voltage of over 2V. The HBT exhibits good microwave performance with a current gain cutoff frequency of 85GHz and a maximum oscillation frequency of 72GHz, These results indicate that these InP/InGaAs SHBTs are suitable for low-voltage,low-power,and high-frequency applications.

Improved design of special boundary elements for T-shaped reinforced concrete walls

This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements ofT-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.

Gas-liquid-liquid slug flow and mass transfer in hydrophilic and hydrophobic microreactors

Gas-liquid-liquid three-phase slug flow was generated in both hydrophilic and hydrophobic microreactors with double T-junctions.The bubble-droplet relative movement and the local mass transfer within the continuous slug and the dispersed droplet were investigated.It was found that bubbles moved faster than droplets under low capillary number(Ca),while droplets moved faster upon the increase of Ca due to the increased inertia.For the first time,we observed that the increased viscosity of droplets fastened the droplet movement.The mass transfer in the continuous slug was dominated by convection,leading to nearly constant global mass transfer coefficient(k_(L)a);while that in the dispersed droplet was dominated by diffusion,resulting in k_(L) decreasing along the channel.Such features are analogical to the corresponding gas-liquid or liquid-liquid two-phase slug flow,but the formation of bubble-droplet clusters caused by relative movement lowered the absolute mass transfer coefficient.These results provide insights for the precise manipulation of gas-liquid-liquid slug flow in microreactors towards process optimization.

Numerical investigation of flow pattern and components of three-dimensional velocity around a submerged T-shaped spur dike in a 90° bend

Spur dike is one of the river training structures. This work presented a numerical simulation of flow field and three-dimensional velocity around a T-shaped spur dike located in bend using SSIIM model. The main objective of this work is to investigate the three-dimensional velocities and streamlines at transverse and longitudinal sections and plan views around the T-shaped spur dike in different submergence ratios(0, 5%, 15%, 25% and 50%). It is concluded that by increasing the submergence ratio from 5% to 50%, the maximum of scour is reduced; the maximum of longitudinal velocity increases by 7.7% and occurs at the water surface in spur dike axis. Near the bed, the maximum of vertical velocity occurs at the end of spur wing. By analyzing the streamlines at transverse sections, the followings were deduced for different submergence ratios: different dimensions and different positions of vortices around the spur dike.

Static and dynamic responses of a microcantilever with a T-shaped tip mass to an electrostatic actuation

In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is modeled as an Euler-Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton’s method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differential equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of inertia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the resonance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the resonance frequency compared to the configuration in which the electrode plate is directly attached to it.

Analytical Modeling of Fluid Sloshing in A 2D Rectangular Container with A Bottom-Mounted T-Shaped Baffle

An analytical procedure is presented to evaluate the fluid sloshing characteristics in a two-dimensional(2D)rectangular container with a bottom-mounted T-shaped baffle.The fluid region is divided into several sub-domains with hypothetical interfaces and the velocities and pressures of the fluid on adjacent interfaces should be identical.The separation of variables in conjunction with the superposition principle is employed to formulate the velocity potential of each sub-domain.The Fourier series expansion is used to derive the eigenvalue equation by substituting the velocity potential solutions into the free surface conditions and the continuity conditions on adjacent interfaces.Under the horizontal base excitation,the total velocity potential of fluid is decomposed of the impulsive and perturbed velocity potentials.The orthogonality of the sloshing modes is demonstrated by implementing Gauss formula.The dynamic response equation is established by incorporating the total velocity potential solution into the surface wave equation.Excellent agreements are achieved between the present results and those from the reported literature and finite element code.Numerical results are exhibited to reveal the effect of the baffle parameters and excitation frequency on sloshing characteristics and responses of liquid.

An efficient microreactor with continuous serially connected micromixers for the synthesis of superparamagnetic magnetite nanoparticles

A new microreactor with continuous serially connected micromixers(CSCM)was tailored for the coprecipitation process to synthesize Fe_(3)O_(4) nanoparticles.Numerical simulation reveals that the two types of CSCM microchannels(V-typed and U-typed)proposed in this work exhibited markedly better mixing performances than the Zigzag and capillary microchannels due to the promotion of Dean vortices.Complete mixing was achieved in the V-typed microchannel in 2.7 s at an inlet Reynolds number of 27.Fe_(3)O_(4) nanoparticles synthesized in a planar glass microreactor with the V-typed microchannel,possessing an average size of 9.3 nm and exhibiting superparamagnetism,had obviously better dispersity and uniformity and higher crystallinity than those obtained in the capillary microreactor.The new CSCM microreactor developed in this work can act as a potent device to intensify the synthesis of similar inorganic nanoparticles via multistep chemical precipitation processes.

Stresses due to an adhesion crack in T-shaped junction of two orthotropic plates

The general solution of stresses is derived for a T-shaped junction of two thin plates with an adhesion crack. The plates are orthotropic. A shear force is applied on the crack surface. The analysis is based on the supposition that the stresses in each plate can be approximated by a plane stress condition. The results obtained are verified by numerical calculation of FEM.

High-efficiency and safe synthesis of tonalid via two Friedel-Crafts reactions in continuous-flow microreactors

Tonalid,an important fragrance ingredient with widespread applicatio n,was synthesized via two FriedelCrafts reactions,which were catalyzed by AlCl_(3).The traditional tonalid production was conducted in batch stirring tank reactors,suffering from low production capacity and the safety hazard of temperature runaway.To solve these problems,the continuous-flow technologies were developed for the highefficiency and intrinsically safe synthesis of tonalid in microreactors.Catalyst AlCl_(3)was neatly homogenized in proper solvents by forming complex with reactant,which was a necessary step for the continuous synthesis in microreactors.Several reaction conditions,including reactant molar ratio,catalyst concentration,temperature,and microchannel hydrodynamic diameter,were investigated for the two Friedel-Crafts reactions in micro reactors.At optimized conditions,the yields of the two Friedel-Crafts reactions were 44.15%and 97.55%,respectively.In comparison with the batch reactors,the reaction times of these two reactions could both be reduced by nearly two thirds in microreactors at the similar yield.

SYNTHESIS OF LIQUID CRYSTALLINE COPOLYESTERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNIT AND CROWN ETHER CYCLE

A novel series of liquid crystalline copolyesters with T-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4′-(α,ω-hexanedioyloxy)dibenzoyl dichloride(M_1),2-(4′-ethoxyphenyl)hydroquinone(M_2)and cis-4,4′-bis(4- hydroxyphenylazo)dibenzo-18-crown-6(M_3).The molecular weights of copolyesters are not high,and the intrinsic viscosity [η]of copolyesters ranges from 0.29-0.43.The monomers ...

Vertical polarization-induced doping InN/InGaN heterojunction tunnel FET with hetero T-shaped gate

A novel vertical InN/InGaN heterojunction tunnel FET with hetero T-shaped gate as well as polarization-doped source and drain region(InN-Hetero-TG-TFET)is proposed and investigated by Silvaco-Atlas simulations for the first time.Compared with the conventional physical doping TFET devices,the proposed device can realize the P-type source and N-type drain region by means of the polarization effect near the top InN/InGaN and bottom InGaN/InN heterojunctions respectively,which could provide an effective solution of random dopant fluctuation(RDF)and the related problems about the high thermal budget and expensive annealing techniques due to ion-implantation physical doping.Besides,due to the hetero T-shaped gate,the improvement of the on-state performance can be achieved in the proposed device.The simulations of the device proposed here in this work show ION of 4.45×10^(-5)A/μm,ION/IOFF ratio of 10^(13),and SS_(avg)of 7.5 mV/dec in InN-Hetero-TG-TFET,which are better than the counterparts of the device with a homo T-shaped gate(InN-Homo-TG-TFET)and our reported lateral polarization-induced InN-based TFET(PI-InN-TFET).These results can provide useful reference for further developing the TFETs without physical doping process in low power electronics applications.

Kondo-Fano Effect in T-shaped Double Quantum Dots Coupled to Ferromagnetic Leads

Using an equation-of-motion technique, we theoretically study the Kondo-Fano effect in the T-shaped double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. We calculate the density of states in this system by solving Green function. Our results reveal that the density of states show some noticeable characteristics not only depending upon the interdot coupling tab, the energy level eal of the side coupled quantum dot QDb, and the relative angle θ of magnetic moment M, but also the asymmetry parameter a in ferromagnetic leads and so on. All these parameters greatly influence the density of states of the eentral quantum dot QDa. This system is a possible candidate for spin valve transistors and may have potential applications in the spintronies.

SYNTHESIS AND CHARACTERIZATION OF LIQUID CRYSTAL POLYMERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNITS (Ⅱ)

A series of liquid crystalline polymers with T-shaped two-dimensional mesogenic unitswere synthesized via low temperature solution polycondensation of 2-(4'-alkoxy-phenyl)hydroquinone with various diacyl dichlorides. The polymers were found to be nematic andshown thermotropic liquid crystalline behaviors through observations using DSC, polarizedmicroscopy and X-ray diffraction. The melting temperature T_m and the isotropizationtemperature T_i of the polymers change regularly with varying of the monomer structures.