Meso-scale Reactors Research Articles

3D-printed cartridge system for in-flow photo-oxygenation of 7-aminothienopyridinones

A 3D-printed polypropylene (PP) continuous-photoflow cell based on a modular cartridge system was developed for the photo-oxygenation of 7-aminothieno[3,2-c]pyridin-4(5H)-ones, using ambient air as the sole co-reactant. This strategy takes advantage of the versatility of 3D-printing to construct cost-effective meso-scale reactors. In addition to scalability, a short residence time (tR 2 min) in 100-W blue LED light that minimizes the formation of dark, insoluble decomposition products is a tangible benefit of this technology.

Experimental study on the effect of external thermal pattern on the dynamics of methane-oxygen and methane-oxygen[sbnd]carbon dioxide premixed flames in non-adiabatic meso-scale reactors

In the current study, the effect of external thermal pattern on the dynamics and characteristics of methane-oxygen and methane-oxygen-carbon dioxide premixed flames in non-adiabatic meso-scale cylindrical reactors is investigated experimentally. In this regard, two different external thermal patterns were imposed on the outer surface of the reactors. The results showed that imposing method/direction and also temperature level of the external thermal pattern have impressive effect on flame dynamics and chemiluminescence in the non-adiabatic meso-scale reactors. Also, it was shown that increasing the temperature level of the external thermal pattern could significantly extend the flame stability and its presence range in the meso-scale reactors, especially for the vitiated mixtures (methane-oxygen-carbon dioxide). Moreover, the results demonstrated that decreasing the inner diameter of a meso-scale reactor, which was subjected to an external thermal pattern, could increase the flame controllability and its presence range in the non-adiabatic meso-scale reactors.

Numerical Study of Methane–Oxygen Premixed Flame Characteristics in Non-adiabatic Cylindrical Meso-Scale Reactors with the Backward-Facing Step

In the present study, the effects of reactor diameter, inlet velocity, velocity profile, equivalence ratio (Phi, Ф), and outer wall convective and radiative heat transfer coefficients on flame characteristics in cylindrical non-adiabatic meso-scale reactors with the backward-facing step were investigated numerically. The results showed that these parameters could strongly affect the mole fraction of radical species within the flame zone. Also, it was shown that as compared to the reactor with 3 mm inner diameter, increasing the inlet velocity in the reactor with 5 mm inner diameter may lead to the opposite effect on the flame location. In addition, it was observed that the velocity profile could sensibly affect the flame location, temperature, and the species mole fractions in the meso-scale reactors. Moreover, it was demonstrated that the effect of equivalence ratio on the flame characteristics was more crucial for the reactors with smaller diameters. Furthermore, it was maintained that the outer wall convective and radiative heat transfer coefficients could cause the flame instability in the meso-scale reactors because of decreasing the mole fraction of important species such as O, H, and OH in the vicinity of the reactor inner wall.

Experimental study on the effects of mixture flow rate, equivalence ratio, oxygen enhancement, and geometrical parameters on propane-air premixed flame dynamics in non-adiabatic meso-scale reactors

In the present study, the effects of reactive mixture flow rate, adding oxygen to propane-air mixture, geometrical parameters, and equivalence ratio on propane-air/oxygen premixed flame dynamics in non-adiabatic meso-scale reactors were experimentally investigated. During the experiments, seven flame regimes of blow-off, blow-out, asymmetric stationary, stationary-repetitive extinction and re-ignition (RERI), forced/self-RERI, RERI-flash-back, and flash-back were observed. The results showed that increasing the reactive mixture flow rate could generally promote variety of the flame regimes and also improve flame stability in the non-adiabatic meso-scale reactors, especially in 40% and 80% oxygen-enhanced cases. Also, the results demonstrated that increasing the reactor inner diameter and equivalence ratio generally extended propane-air- oxygen flame stability and its presence range in the non-adiabatic meso-scale reactors. Moreover, it was shown that increasing the reactor length and also increasing the added oxygen to propane-air mixture more than 40% promoted flame instability and consequently restricted propane-air-oxygen flame presence range in the non-adiabatic meso-scale reactors. Also, it was shown that variations in the mixture flow rate, the reactor length and inner diameter, equivalence ratio, and oxygen concentration in propane-air mixture could significantly influence the flame average propagation speed, acoustic, and chemiluminescence in the non-adiabatic meso-scale reactors.

An experimental study of methane–oxygen–carbon dioxide premixed flame dynamics in non-adiabatic cylinderical meso-scale reactors with the backward facing step

In the present study, we experimentally evaluated the effects of geometrical parameters, Reynolds number, dilution percent, and equivalence ratio on methane–oxygen–carbon dioxide flame dynamics in non-adiabatic cylindrical meso-scale reactors with the backward facing step. Five flame regimes of blow-out, marginal, stationary (asymmetric and spinning), RERI, and flashback were observed during the tests. The results showed that adding carbon dioxide to methane–oxygen mixture could extend RERI flame regimes in the meso-scale reactors. Moreover, it was shown that the presence of RERI flame regime could lead to more uniform temperature distribution on the outer surface of the lengthy meso-scale reactors as compared to the stationary flame regimes. Also, it was demonstrated that increasing the average flow speed in the meso-scale reactors decreased the average frequency of RERI flame regimes.

Experimental study of the effects of geometrical parameters, Reynolds number, and equivalence ratio on methane–oxygen premixed flame dynamics in non-adiabatic cylinderical meso-scale reactors with the backward facing step

In this study, we experimentally investigated the effects of geometrical parameters (such as the reactor length (L) and the inner diameter (DR)), the step height (rin−rR), the Reynolds number (Re), and the equivalence ratio (φ)) of the inlet mixture on the behavior of the rich fuel methane–oxygen flames in non-adiabatic cylindrical meso-scale reactors with the backward facing step. During the experiments, seven different flame regimes were observed. These flame regimes were the blow-out, marginal, stationary (stable), RERI, stationary (stable)-flashback, RERI-flashback, and flashback, respectively. Also, the results showed that the length and diameter of reactors could strongly affect flame dynamics, especially the borders among the observed flame regimes in the meso-scale reactors. As a result, it was demonstrated that the reactor length and diameter obviously influenced the traveling speed and frequency of RERI flame regime. Also, it was shown that decreasing the step height from 1.4mm to 0.4mm suppressed RERI flame regime in the meso-scale reactors. Moreover, in the certain ranges of the equivalence ratio, increasing the Reynolds number decreased the flame presence range in the meso-scale reactors. Finally, it was concluded that RERI flame regime is a prevalent operational regime for applications in which an almost uniform temperature pattern on the outer surface of lengthy meso-scale reactors is required. However, it was shown that this privilege was not valid as compared to the temperature distribution patterns caused by the stationary flame regimes in the small length reactors.

Modeling mesoscale reactors for the production of fine chemicals

Flow based synthesis at the mesoscale level allows precise control over process conditions (such as temperature and mixing), and offers advantages such as reduced processing times, higher reproducibility, and enhanced selectivity compared to batch reactors. Precise heat and mass transfer control allows for safer operations when using toxic or explosive materials or for highly exothermic reactions. We present a simple transient one-dimensional (1-d) dispersion model to analyze mesoscale reactors. The conversions predicted by the 1-d dispersion model matched well with conversions predicted by a two-dimensional (2-d) colaminar model. A computational fluid dynamics simulation (CFD) of a 120° Y-junction leads to a lower conversion at higher Damköhler numbers. Estimation of the kinetic parameters for the reaction between sodium azide and 2-phenylethylbromide demonstrated excellent agreement between the 1-d dispersion model and rates generated using a standard batch experiment.

Flame dynamics in catalytic and non-catalytic mesoscale microreactors

The dynamics of fuel-lean (equivalence ratio φ = 0.5) premixed hydrogen/air flames are investigated numerically in a 2-mm-height planar channel with platinum-coated walls, as a function of the inlet velocity and catalytic reactivity. An elliptic 2-D transient code is used, with elementary heterogeneous (catalytic) and homogeneous (gas-phase) chemical reaction schemes and detailed transport. The channel wall temperature is prescribed and the inlet properties are uniform. The catalytic reactivity is controlled by varying the model parameter A s, which denotes the ratio of the catalytically active area to the geometrical channel surface area. It is shown that the rich flame dynamics of the non-catalytic case ( A s = 0), which include non-stationary repetitive ignition/extinction and oscillating flames, can be suppressed by suitable selection of the catalytic reactivity. The repetitive/ignition extinction flames are eliminated at A s = 0.003 and the oscillating ones for A s > 0.01, while for higher values of A s only stationary “closed symmetric” and “asymmetric” flames are obtained. The results suggest that the application of a predetermined catalyst loading on the channel walls is a feasible method to eliminate unsteady combustion modes in practical mesoscale reactors.

Confined Space Synthesis of ZSM-5 Nanozeolite in Self-assembly Supersolubilizing Reversed Micelles

The self-assembly method for ZSM-5 nanozeolite syntheses was demonstrated in terms of proposed confined space synthesis. The supersolubilizing reversed micelles formed in neutral oil were confirmed to play a key role of mesoreactors for the confined space ZSM-5 synthesis. The results observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques revealed that both the rates of nucleation and growth and the crystal morphologies in size and shape were controlled well in supersolubilizing reversed micelles and that the approach provided superfine nanozeolite with the crystal sizes and shapes similar to the supersolubilizing reversed micelles. The N2 adsorption results of a typical sample showed that the mesopores and macropores existing in synthesized products were derived from interparticle spaces and the textural mesoporosities were different from those in well-known ordered mesoporous materials. Furthermore, the adsorption/desorption behaviors correlated considerably well with the crystal sizes for all the samples. In addition, the heterogeneous nucleation and growth of nanosized crystals were suggested for understanding of the confined space synthesis in mesoscale reactors.

Mesoscale organization of Cu 7S 4 nanowires: Formation of novel sheath-like nanotube array

Highly ordered and uniform array of Cu 7S 4 sheath-like nanotubes has been successfully prepared via a sacrificial template approach. These nanotubes have diameter of 250–600 nm and length of several micrometers with close tips. The wall of the nanotube is actually woven out of many well-distributed Cu 7S 4 nanowires with the diameter of 20–30 nm and the wall thickness of the nanotube is estimated to be about 60–70 nm. This novel hierarchical sheath-like nanotube array may find applications as mesoscale reactors or as other nanodevices.

Just Because It's Small Doesn't Mean It's Well Mixed: Ensuring Good Mixing in Mesoscale Reactors

The advent of high throughput experimentation (HTE) for molecular discovery and rapid screening of new catalyst formulations has led to interest in the mixing characteristics of small stirred vessels at scales below those previously studied. In this paper, particle image velocimetry (PIV) is used to obtain macromixing characteristics for single phase fluids of two different viscosities (μ = 0.001 and 0.433 Pa s) and for two-phase air−water mixtures in a 45 mm diameter vessel using a 6 blade up-pumping pitched-blade turbine. Eccentric agitation is examined as a means of improving the mixing performance since the vessels are used without baffles, and the global circulation of the fluid was comparable with that of a conventional baffled configuration for single-phase mixing at a constant power input per unit mass (0.168−5.5 W kg-1). For high viscosity fluids, the characteristic flow patterns resembled those for a radial device. For two-phase mixing at gassing rates of 0.25 and 0.5 vvm, two sparger configurat...