Segmented Flow Tubular Reactor Research Articles

Helically coiled segmented flow tubular reactor for the hydroformylation of long-chain olefins in a thermomorphic multiphase system

To intensify new or existing chemical processes, novel reactor designs have to be developed. For a homogeneously catalyzed multiphase model reaction, the hydroformylation of 1-dodecene, Kaiser et al. [13] theoretically derived a promising tandem reactor system applying a model-based rector synthesis and dimensioning approach. The reactor tandem, consisting of a helically coiled tubular reactor (HCTR) followed by a continuously stirred tank reactor (CSTR), was constructed and firstly operated within this work. For the validation of the reactor design methodology, a comprehensive hydrodynamic study focusing on the HCTR was performed. Different complementary techniques were used to investigate the geometry influences on mixing and the gas-liquid mass transfer, and liquid phase mixing in smaller model geometries. Since the same Reynolds-number and flow regime in the model geometries and the HCTR were ensured, the transfer of the results between these geometries was possible. The outcome confirms, that the geometrical parameter only minor influence the excellent mixing properties of coiled tubes and the helix geometry has enhanced gas-liquid mass transfer rates. In a next step, the HCTR + CSTR-tandem was operated with closed catalyst recycle and optimized reaction parameters. Thereby, full conversion of 1-dodecene and a selectivity of up to 0.70 to the linear aldehyde, tridecanal, were achieved. These values match the predictions of the numerical calculations and are higher than published results for this process. The outcomes of this study confirm the assumptions made by Kaiser et al. [13] during the reactor dimensioning and validate the reactor network design approach.

Continuous Synthesis of Gold Nanoparticles Using the Segmented Flow Tubular Reactor (SFTR)

Mots-clefs: Continuous synthesis ; Gold nanoparticles ; Narrow PSD ; SFTR Reference EPFL-ARTICLE-223147doi:10.2533/chimia.2016.457Afficher la publication dans Web of Science Notice creee le 2016-11-21, modifiee le 2017-01-25

Continuous synthesis of nanostructured silica based materials in a gas–liquid segmented flow tubular reactor

Synthesizing core–shell particles SiO2@mSiO2, mSiO2and Au@SiO2in a continuous tubular segmented reactor.

Continuous Polyol Synthesis of Metal and Metal Oxide Nanoparticles Using a Segmented Flow Tubular Reactor (SFTR).

Over the last years a new type of tubular plug flow reactor, the segmented flow tubular reactor (SFTR), has proven its versatility and robustness through the water-based synthesis of precipitates as varied as CaCO3, BaTiO3, Mn(1−x)NixC2O4·2H2O, YBa oxalates, copper oxalate, ZnS, ZnO, iron oxides, and TiO2 produced with a high powder quality (phase composition, particle size, and shape) and high reproducibility. The SFTR has been developed to overcome the classical problems of powder production scale-up from batch processes, which are mainly linked with mass and heat transfer. Recently, the SFTR concept has been further developed and applied for the synthesis of metals, metal oxides, and salts in form of nano- or micro-particles in organic solvents. This has been done by increasing the working temperature and modifying the particle carrying solvent. In this paper we summarize the experimental results for four materials prepared according to the polyol synthesis route combined with the SFTR. CeO2, Ni, Ag, and Ca3(PO4)2 nanoparticles (NPs) can be obtained with a production rate of about 1–10 g per h. The production was carried out for several hours with constant product quality. These findings further corroborate the reliability and versatility of the SFTR for high throughput powder production.

Continuous Production of Tailored Silver Nanoparticles by Polyol Synthesis and Reaction Yield Measured by X-ray Absorption Spectroscopy: Toward a Growth Mechanism

Two complementary topics are discussed: (i) the continuous production of silver nanoparticles (AgNPs) and (ii) the measurement of reaction yield by X-ray absorption near-edge spectroscopy (XANES). The continuous polyol synthesis of AgNPs in grams amount and in the size range of 7-104 nm was carried out in the segmented flow tubular reactor (SFTR). Particle size was tailored by controlling the synthesis parameters such as temperature, reactant concentrations, and polyvinylpyrrolidone (PVP) molecular weight. The continuous production was tested for 4 h, and the product has shown constant particle size distribution over the whole production time. Reliable continuous production of 2.3 g h(-1) of similar to 100 nm AgNPs can be achieved with a lab-scale SFTR. The produced particles were fully characterized with respect to size, size distribution, and chemical purity. To better understand the growth mechanism, synchrotron-radiation high-resolution X-ray diffraction, and X-ray absorption spectroscopy data were collected directly on the AgNPs suspension. In particular, from}CANES experiments, the conversion yield of Ag+ to Ag-0 was measured. The results are consistent with a two-step process where PVP controls the particle nucleation while growth is ensured by thermally induced ethylene glycol oxidation.

Continuous synthesis of nickel nanopowders: Characterization, process optimization, and catalytic properties

The preparation of nanoparticles with tailored properties and in quantities in the order of 10–100g prepared with laboratory-scale equipment is a target of great interest. In this study, Ni nanoparticles with different sizes, surface morphologies, magnetic, and catalytic properties were obtained from NiCl2, N2H4, NaOH, and ethylene glycol as solvent by tuning the synthesis parameters. Preliminary syntheses were done in batch reactors and then the continuous synthesis carried out in the Segmented Flow Tubular Reactor (SFTR). For the first time a SFTR system was applied to a non-aqueous system. By combining SEM, HRTEM, XRD, TGA, XPS, FTIR, specific surface area, SQUID, and catalytic tests, the complete structural, morphological, and functional characterization of the produced nanoparticles were performed. The continuous production of 2.1gh−1 of Ni nanoparticles was carried out up to 6h without product properties deterioration. The results allow estimating a production >300gd−1 in an ad-hoc low-cost single-tube SFTR system. Catalytic tests of CO methanation showed good activity at 769K with stable methane yield of 83%. The results presented in this study demonstrate that reliable and reproducible synthesis of relatively high amounts of metal nanoparticles with lab-scale equipment can be achieved. This approach opens new opportunities for reliable and controlled preparation of advanced materials in quantities suitable for a full functional characterization.

Precipitation of Nanosized and Nanostructured Powders: Process Intensification and Scale‐Out Using a Segmented Flow Tubular Reactor (SFTR)

AbstractThe successful scale‐out and process intensification using a segmented flow tubular reactor (SFTR) for ultrafine CaCO3, BaTiO3, and nanosized ZnO from optimized minibatch (20 mL) conditions is presented. The capacity of the SFTR in process intensification was demonstrated by producing ∼ 5 kg batches of BaTiO3 powders with excellent batch‐to‐batch reproducibility. The SFTR scale‐out or numbering‐up capacity was demonstrated for a nanostructured CaCO3 in 500 g batches by scaling‐out from one to six segmented flow tubular reactors run in parallel (scale‐out/‐up ratio of 5000 compared to lab batch experiments). The SFTR was then used to demonstrate its potential for nanosized ZnO powders producing 50 g lots of these nanopowders in a continuous process, a scale‐out/‐up ratio of 250 compared to lab batch experiments without any loss of powder quality. The SFTR allows a precise control of precipitation conditions, leading to an excellent reproducibility in powder characteristics, and shows great promise as a simple production process of powders and advanced nanomaterials with highly controlled properties.

Comparison of two innovative precipitation systems for ZnO and Al-doped ZnO nanoparticle synthesis

This study presents a comparative approach to investigate the potentials of two innovative methods for the synthesis of ZnO and Al-doped ZnO. The first method is a precipitation system working in mild hydrothermal conditions (90?C) using a tubular reactor (Segmented Flow Tubular Reactor, SFTR). The second method is a microwave-assisted hydrothermal process working at 250?C - 38 atmospheres. Nanocrystalline ZnO with a high specific surface area (49-68 m2/g) was obtained with both systems. Smaller equiaxed particles (50-70 nm) were obtained with the SFTR, with an excellent homogeneity in size and morphology, which was attributed to an excellent control of the process parameters (mixing, temperature, volume of reaction). A higher luminescence signal was measured on these samples. The microwave method leads to particles with a higher crystallinity due to the temperature of the reaction. A significant effect of the aluminum was observed, which reduces the crystal growth to produce equiaxed morphologies. This effect was enhanced by adding poly(acrylic) acid (PAA).

Novel Liquid‐Flow Splitting Unit Specifically Made for Numbering‐Up of Liquid/Liquid Chemical Microprocessing

AbstractA liquid‐flow splitting unit for dividing one main liquid stream into six substreams was developed without the need for active flow regulation. The tool has six fluid connectors that allow the numbering‐up of a respective number of microprocess devices for liquid or liquid/liquid processes. One such liquid/liquid process for which the current tool design and tests in particular have been conceived, is the forced precipitation of precious inorganic powders by the segmented flow tubular reactor (SFTR) technique. Such investigations were performed with six micromixers of impinging‐jet or interdigital separation layer type attached to the liquid‐flow splitting unit. Fluid equipartition is achieved via the action of the microdevices as flow resistors, thereby increasing the pressure drop of the system. Liquid splitting was carried out in a cylindrical liquid tank with one inlet and six outlet holes that also served for pulsation dampening. By CFD simulations the impact of two important geometric parameters of this tank, namely, the height at a given diameter and the position of the inlet hole, on the fluid splitting was studied. In addition, the influence of the injection direction with respect to the normal of the tank was analyzed. It turned out that in the presence of flow resistors (typically generating a pressure drop at about 60 mbar) this impact is negligible, i.e., principally, a large flexibility on design and operation is provided. Without these resistors, the before‐mentioned parameters in turn have a large impact that is discussed in detail. Experiments with a liquid‐flow splitting unit and six coupled impinging‐jet micromixers using water as liquid proved a reasonable fluid distribution with a standard and maximum deviation of the substream flow rates of 4 and 11 %, respectively. These deviations are mainly caused by different pressure drops (Δp) of the individual impinging‐jet mixers as a result of tolerances in the microfabrication method, die sinking μEDM manufacture. Already small differences in the microstructured outlet hole diameters (d = 300 μm) of the impinging‐jet mixer have a large influence due to the d–4 ∼ Δp dependence. Additionally, attaching specially adapted interdigital separation layer micromixers to the liquid‐flow splitting unit, a minimum/maximum (standard) deviation of the water distribution below 5 (2) % could be achieved. To obtain this improved result, it was necessary to optimize the choice of material, the design of the microstructure inside the mixer, and the fabrication process.

High-quality nickel manganese oxalate powders synthesized in a new segmented flow tubular reactor

High-quality nickel manganese oxalates have been prepared using an innovative approach for the production of homogeneous powders, the continuous Segmented Flow Tubular Reactor (SFTR). This new reactor is mainly composed of a mixer, a segmenter, a tubular section and a decanter. Mixed Ni–Mn oxalates are synthesized in the SFTR. The powders present controlled morphology, narrow particle size distribution, high purity and desired stoichiometry. Their characteristics are compared to those of powders obtained in a batch reactor. These oxalates are precursors for nickel manganites, used as negative temperature coefficient thermistor (NTC) ceramics.

Development of a Continuous Segmented Flow Tubular Reactor and the “Scale‐out” Concept – In Search of Perfect Powders

AbstractThe synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity and scale‐up problems encountered when using batch reactors. Supersaturation is created by mixing the co‐reactants in a micromixer inducing precipitation; the suspension is then segmented into identical micro‐volumes by a non‐miscible fluid and sent through a tube. These micro‐volumes are more homogeneous when compared to large batch reactors leading to narrower size distributions, better particle morphology, polymorph selectivity and stoichiometry. All these features have been demonstrated on single tube SFTR for different chemical systems. To increase productivity for commercial application the SFTR is being “scaled‐out” by multiplying the number of tubes running in parallel instead of scaling‐up by increasing their size. The versatility of the multi‐tube unit will allow changes in type of precipitate with a minimum of new investment as new chemistry can be researched, developed and optimised in a single tube SFTR and then transferred to the multi‐tube unit for powder production.

Synthesis of Barium Titanate Powders by Low-Temperature Aqueous Synthesis Using a New Segmented Flow Tubular Reactor

Reference LTP-CONF-2002-009View record in Web of Science Record created on 2005-01-12, modified on 2017-05-10

High Quality Powder Precipitation Using a Continuous Segmented Flow Tubular Reactor and the “Scale-Out” Concept

High Quality Powder Precipitation Using a Continuous Segmented Flow Tubular Reactor and the “Scale-Out” Concept

Calcium carbonate precipitation using new segmented flow tubular reactor

AbstractA new segmented flow tubular reactor for the continuous production of powders was used to synthesize calcium carbonate by precipitation. This new reactor uses a nonmiscible phase (air in most cases) to create individual microvolumes of the reacting mixture or suspension ensuring that a plug‐flow regime is maintained. In a microvolume, poor micromixing can be avoided and the homogeneity in reaction conditions is increased better than in larger volumes, leading to a better control of powder characteristics. Calcium carbonate with controlled characteristics could be precipitated continuously using this new segmented flow tubular reactor. Pure calcite could be obtained in the tubular reactor by segmenting a Ca2+ solution with a reactive CO2/NH3 gas mixture. This synthesis process is very promising for industrial production since the scale‐up should easily be achieved by multiplying the number of tubes working in parallel.