Continuous Flow Reaction System Research Articles

Hydrothermal synthesis of Eu3+ doped yttria nanoparticles using a supercritical flow reaction system

Highly crystalline Eu3+ doped yttria nanoparticle was synthesized by hydrothermal reaction in supercritical water using a continuous flow reaction system (FHT). The reactants of Y(NO3)3/Eu(NO3)3 mixed solution and KOH solution were used as starting materials and that was heated quickly up to 350–450°C under the pressure of 30MPa for 0.1–15s as reaction time. The XRD results revealed that the crystal phase of as-prepared particles was YOOH and converted into cubic-phase Y2O3 after annealing above 550°C. Primarily particle size of the YOOH was as small as less than 50nm, keeping after annealing at 800°C. Effects of reaction time, annealing temperature and Eu doping amount on photoluminescence were examined. The as-prepared particles exhibited red emission without annealing at high temperatures whereas photoluminescent intensity at 612nm was increased with an increase in the annealing temperature. Photoluminescent intensity was increased with an increase in the Eu doping amount until 4mol% and saturated at 8mol%. The photoluminescent property was compared with reference samples via conventional co-precipitation (CP) and batchwise hydrothermal (BHT) methods. The photoluminescent intensity for annealed samples increased in the order: FHT<BHT<CP owing to the increased particle size.

Paper-immobilized enzyme as a green microstructured catalyst

The facile and direct introduction of methacryloxy groups into cellulose paper was carried out using a silane coupling technique, leading to the improvement of hydrophobicity and both dry and wet physical strengths of the paper. Immobilization of lipase enzymes onto the methacrylate-modified paper was then accomplished, possibly due to hydrophobic interaction. The as-prepared immobilized lipase on methacrylate-modified paper possessed paper-specific practical utility. During a batch process for the nonaqueous transesterification between 1-phenylethanol and vinyl acetate to produce 1-phenylethylacetate, the paper-immobilized lipase showed high catalytic activity, selectivity and reusability, suggesting that the methacryloxy groups introduced into the cellulose paper played a key role in the hyperactivation of lipases. In addition, a higher productivity of 1-phenylethylacetate was achieved in a continuous flow reaction system than in the batch system, indicating that the interconnected porous microstructure of the paper provided favorable flow paths for the reactant solution. Thus, the paper-immobilized enzyme is expected to offer a green catalytic material for the effective production of useful chemicals.

Supercritical Hydrothermal Synthesis and In situ Organic Modification of Indium Tin Oxide Nanoparticles Using Continuous-Flow Reaction System

ITO nanoparticles were synthesized hydrothermally and surface modified in supercritical water using a continuous flow reaction system. The organic modification of the nanoparticles converted the surface from hydrophilic to hydrophobic, making the modified nanoparticles easily dispersible in organic solvent. The addition of a surface modifier into the reaction system impacted the crystal growth and particle size as well as dispersion. The particle size was 18 nm. Highly crystalline cubic ITO with a narrow particle size distribution was obtained. The advantages of short reaction time and the use of a continuous reaction system make this method suitable for industrial scale synthesis.

ChemInform Abstract: Efficient Synthesis of Unsymmetric Diarylalkynes from Decarboxylative Coupling in a Continuous Flow Reaction System.

AbstractOnly trace amounts of symmetrical diarylalkynes are obtained in some cases as by‐ products.

Efficient synthesis of unsymmetric diarylalkynes from decarboxylative coupling in a continuous flow reaction system

Unsymmetric diaryl alkynes were synthesized from the palladium-catalyzed decarboxylative coupling of aryl halides and propiolic acid using a continuous flow reaction system. This flow chemistry system continuously gave the desired products in moderate to good yields, and produced less byproduct than was formed in the batch reaction.

A Continuous-Flow System for Asymmetric Hydrogenation Using Supported Chiral Catalysts

Abstract Highly active immobilized hydrogenation catalytic systems were used in the H-Cube™ hydrogenation reactor. “In situ” produced [Rh(COD)((S)-MonoPhos)2]BF4 complex was immobilized on commercially available Al2O3 and mesoporous Al2O3 by means of phosphotungstic acid (PTA), respectively. The optimum reaction conditions were determined and studied at different temperature, pressure, and flow rate values. Furthermore, the effect of the substrate concentration, microstructure of the support, and the stability of the complex were investigated. A continuous-flow reaction system using a stationary-phase catalyst for the asymmetric hydrogenation of methyl acetamidoacrylate was developed and run continuously for 12 h with >99% conversion and 96–97% enantioselectivity.

Recent Progress in the Preparation of Organoboron Reagents via Direct Borylations

Recent progress in the preparation of organoboron reagents for cross-coupling reactions is described. Organoboron reagents are versatile synthons in Suzuki-Miyaura coupling. A common method for the synthesis of organoboron reagents is the borylation of aryl or vinyl magnesium (or lithium) intermediates that are produced from aryl or vinyl halides. In addition to these traditional methods, the direct borylation of aromatic and heteroaromatic compounds has also been recently reported as a more atom-economical method. We describe our new homogeneous and heterogeneous catalysts for aromatic C-H borylation. Regarding the heterogeneous catalyst, the recovered catalyst could be reused without a loss of activity. We developed this heterogeneous batch reaction system into a continuous-flow reaction system using a column field with our heterogeneous catalyst.

Conversion of methanol over H-ZSM-22: The reaction mechanism and deactivation

Conversion of methanol to olefins (MTO) over H-ZSM-22 was carried out in the pulse and the continuous-flow reaction systems. 13C labeling technique was used to reveal the reaction mechanism. The materials retained in the deactivated catalyst were detected by GC–MS after dissolving the catalyst framework and then extracting the organic species. The adsorption of these materials in ZSM-22 channels was computationally modeled. The results showed that the olefin methylation-cracking mechanism is the main route for the conversion of methanol over H-ZSM-22. It was suggested that the blockage of the zeolite pore openings by the coke species might be the reason of the relatively rapid deactivation of H-ZSM-22, instead of the prohibition of the formation of large transition-state intermediates involved in hydrocarbon pool mechanism.

Highly Active Heterogeneous Palladium Nanoparticle Catalysts for Homogeneous Electrophilic Reactions in Solution and the Utilization of a Continuous Flow Reactor

A highly active heterogeneous Pd-nanoparticle catalyst for the intramolecular addition of phenols to alkynes was developed and employed in a continuous flow reaction system. Running the reaction in flow mode revealed reaction kinetics, such as the activation energy and catalyst deactivation, and provides many potential practical advantages.

Hydrothermal synthesis of organic hybrid BaTiO 3 nanoparticles using a supercritical continuous flow reaction system

Barium titanate (BaTiO 3: BT) nanoparticles were synthesized by the hydrothermal method in the presence of dispersants using a continuous supercritical flow reaction system. The reactants of TiO 2 sol/Ba(NO 3) 2 mixed solution and KOH solution were used as starting materials and that was heated quickly up to 400 °C under the pressure of 30 MPa for 8 ms as reaction time. The dispersant solution such as polyacrylic acid (PAA) and polyoxyethylene(20) sorbitan monooleate (Tween 80) was injected in the cooling process after the reaction. The crystal phase of the obtained particles was identified as perovskite cubic BaTiO 3 by X-ray diffractometry (XRD) and Raman spectroscopy. Raman spectra and thermogravimetric data revealed that PAA and Tween 80 fabricated hybrid BT nanoparicles. Primarily particle size of the BaTiO 3 nanoparticle was determined by means of BET surface area, as small as less than 10 nm irrespective of dispersants. In contrast, dispersed particle size in solution measured by dynamic light scattering (DLS) technique decreased from 282 nm to less than 100 nm depending on the dispersant. Aggregation of BaTiO 3 nanoparticles might be depressed in the presence of dispersants, especially PAA is the most effective among the dispersants examined.

Hydrothermal synthesis of BaTiO3 nanoparticles using a supercritical continuous flow reaction system

Abstract Highly crystalline BaTiO 3 nanoparticle was synthesized rapidly by hydrothermal reaction in supercritical water using a continuous flow reactor. The reactants of TiO 2 sol (or TiCl 4 )/Ba(NO 3 ) 2 mixed solution and KOH solution were used as starting materials and that was heated quickly up to 400 °C under the pressure of 30 MPa for 8 ms as reaction time. The XRD results revealed that the crystal phase of the obtained particles was cubic BaTiO 3 , indicating that the hydrothermal reaction in supercritical water was successfully proceeded under present reaction conditions. Primarily particle size of the BaTiO 3 nanoparticle was determined by means of BET surface area, as small as less than 10 nm with decreasing the reaction pH. In contrast, dispersed particle size in solution measured by DLS (dynamic light scattering) technique decreased from 260 to 90 nm with increasing the reactants concentration. Aggregation of BaTiO 3 nanoparticles might be depressed in the presence of coexisting nitrate anions.

Development of a Continuous‐Flow System for Asymmetric Hydrogenation Using Self‐Supported Chiral Catalysts

Well-designed, self-assembled, metal-organic frameworks were constructed by simple mixing of multitopic MonoPhos-based ligands (3; MonoPhos=chiral, monodentate phosphoramidites based on the 1,1'-bi-2-naphthol platform) and [Rh(cod)(2)]BF(4) (cod=cycloocta-1,5-diene). This self-supporting strategy allowed for simple and efficient catalyst immobilization without the use of extra added support, giving well-characterized, insoluble (in toluene) polymeric materials (4). The resulting self-supported catalysts (4) showed outstanding catalytic performance for the asymmetric hydrogenation of a number of alpha-dehydroamino acids (5) and 2-aryl enamides (7) with enantiomeric excess (ee) ranges of 94-98 % and 90-98 %, respectively. The linker moiety in 4 influenced the reactivity significantly, albeit with slight impact on the enantioselectivity. Acquisition of reaction profiles under steady-state conditions showed 4 h and 4 i to have the highest reactivity (turnover frequency (TOF)=95 and 97 h(-1) at 2 atm, respectively), whereas appropriate substrate/catalyst matching was needed for optimum chiral induction. The former was recycled 10 times without loss in ee (95-96 %), although a drop in TOF of approximately 20 % per cycle was observed. The estimation of effective catalytic sites in self-supported catalyst 4 e was also carried out by isolation and hydrogenation of catalyst-substrate complex, showing about 37 % of the Rh(I) centers in the self-supported catalyst 4 e are accessible to substrate 5 c in the catalysis. A continuous flow reaction system using an activated C/4 h mixture as stationary-phase catalyst for the asymmetric hydrogenation of 5 b was developed and run continuously for a total of 144 h with >99 % conversion and 96-97 % enantioselectivity. The total Rh leaching in the product solution is 1.7 % of that in original catalyst 4 h.

Steady-state bioluminescence of bacterial luciferase using electrochemical regeneration of flavin substrate and its application to inhibitory analysis

The model system for the biological reaction using a bacterial luciferase (BL) was developed and applied to the inhibitory analysis of the hydrophobic molecules for enzymatic reactions. The homemade flow electrochemical luminescence cell was embedded in the BL reaction system to regenerate the reduced form of the flavin mononucleotide, which is one of the substrates of the BL luminescence reaction, and to measure the luminescence intensity. The constant intensity of the continuous BL luminescence was observed using the continuous-flow BL reaction system. The proposed system was successfully applied to the inhibitory reaction of dodecaneamide on the BL luminescence reaction.

Production of acetic acid by hydrothermal two-step process of vegetable wastes for use as a road deicer

This study aimed to produce acetic acid from vegetable wastes by a new hydrothermal two-step process. A continuous flow reaction system with a maximum treatment capacity of 2 kg/h of dry biomass developed by us was used. Five kinds of vegetables of carrots, white radish, chinese cabbage, cabbage and potato were selected as the representation of vegetable wastes. First, batch experiments with the selected vegetables were performed under the condition of 300°C, 1 min for the first step, and 300°C, 1 min and 70% oxygen supply for the second step, which is the optimum condition for producing acetic acid in the case of using starch as test material. The highest yields of acetic acid from five vegetables were almost the same as those obtained from starch. Subsequently, similar the highest yield of acetic acid and experimental conditions from vegetables were also obtained successfully using the continuous flow reaction system. These results should be useful for developing an industrial scale process.

Rapid synthesis of γ-Al 2O 3 nanoparticles in supercritical water by continuous hydrothermal flow reaction system

Highly crystalline γ-alumina (γ-Al 2O 3) nanoparticle was synthesized hydrothermally in supercritical water by using a continuous flow reaction system from the starting reagent of Al(NO 3) 3·9H 2O. The study was performed under supercritical conditions of water; temperature ranging from 400 to 500 °C, pressures from 25 to 35 MPa and the reaction time was as short as 63 ms to 3 s. Products were characterized by XRD pattern, BET surface areas, transmission electron microscopy (TEM), and dynamic light scattering (DLS). XRD results revealed that γ-Al 2O 3 particles were obtained at 410 °C or higher through the dehydroxylation reaction in supercritical water, while γ-AlOOH phase was predominant at 400 °C. Primary particle size of γ-Al 2O 3 was about 4 nm and did not depend on the reaction temperature and time. Furthermore, DLS results revealed that the secondary particle size of γ-Al 2O 3 dispersed in water increased with increasing reaction temperature and time probably due to particle aggregation. It is noteworthy that secondary particle sizes of γ-Al 2O 3 dispersed in aqueous solution decreased as the Al(NO 3) 3·9H 2O concentration was increased, since particle aggregation was depressed by high zeta potential with lowering the pH.

Rapid synthesis of BaTiO 3 nanoparticles in supercritical water by continuous hydrothermal flow reaction system

Highly crystalline BaTiO 3 nanoparticle was synthesized rapidly by hydrothermal reaction in supercritical water using a continuous flow reactor. The reactant solution of 0.05 M TiO 2 sol and 0.06 M Ba(OH) 2 was used as starting materials and that was heated quickly up to 400 °C under the pressure of 30 MPa with in as short as 2 s to 7 ms reaction time. The X-ray diffraction (XRD) results revealed that the crystal phases of the obtained particles were only BaTiO 3, indicating that the hydrothermal reaction in supercritical water was successfully proceeded under present reaction conditions. Particle size of the BaTiO 3 nanoparticle was determined by means of BET surface area, as small as less than10 nm with reducing the reaction time from 2 s to 7 ms. Furthermore, high-resolution transmission electron microscopy (TEM) image of BaTiO 3 nanoparticles showed highly crystalline nature of BaTiO 3, even if the time for crystallization of BaTiO 3 was extremely reduced. The formation of highly crystalline BaTiO 3 nanoparticles by the short reaction period is thought to be strongly attributed to the properties of supercritical water. Especially, lower dielectric constant property of supercritical water expected to accelerate the hydrothermal reaction of BaTiO 3, and allowed the synthesizing of BaTiO 3 nanoparticles only in 7 ms.

Spurring Radical Reactions of Organic Halides with Tin Hydride and TTMSS Using Microreactors

Tributyltin hydride-mediated radical reactions of organic halides were successfully carried out in a continuous flow system using a microreactor. The reactions proceeded within a very short period of time, coupled with quickly decomposing radical initiators such as V-65 and V-70. The continuous flow reaction system was applied to gram scale synthesis of a key intermediate for furofuran lignans.

Effect of additives on the chemical vapour generation of bismuthane by tetrahydroborate(III) derivatization

The effect of mM concentrations of K(3)[Fe(CN)(6)], Fe(III), Mo(VI), KSCN and KMnO(4) on the generation of BiH(3) by the reaction of 0.2-10 microg ml(-1) Bi(III) with 0.2 M tetrahydroborate(III) at 1 M acidity (HCl or HNO(3)) was investigated. Chemical vapour generation (CVG) of BiH(3) was investigated by atomic absorption spectrometry using a continuous flow reaction system (CF-CVG-AAS) and different mixing sequences and reagent reaction times. Gas chromatography-mass spectrometry (GC-MS) was employed in batch generation experiments with NaBD(4). In the absence of additives, the formation of Bi(0) at high concentrations of Bi(III) caused rollover of calibration curves and limited the linear range to less than 1 microg ml(-1) Bi(III). In the presence of additives, the formation of Bi(0) was not observed and the linear range was increased to 5 microg ml(-1) of Bi(III) while rollover was completely removed. GC-MS experiments indicated that the presence of additives did not affect the direct transfer of H from boron to bismuth. Experiments with CF-CVG-AAS and different mixing sequences and reagent reaction times suggest that additives act by preventing the formation of Bi(0) through the formation of reaction intermediates which evolve towards the formation of BiH(3) at elevated Bi(III)/NaBH(4) ratios.

A New Hydrothermal Process for Producing Acetic Acid from Biomass Waste

Calcium/magnesium acetate (CMA) is known as a low corrosive and environmentally friendly deicer, but is too expensive in comparison to conventional salt deicers. CMA's high cost is mostly attributed to the acetic acid required to produce CMA. This study aimed to develop a hydrothermal reaction system to produce acetic acid from biomass waste. Based on the results obtained using a batch reactor, a continuous flow reaction system with a maximum treatment capacity of 2 kg h −1 of dry biomass was constructed. Results showed that the highest yield of acetic acid and the conditions for obtaining the highest yield of acetic acid in this continuous flow reaction system were almost the same as those obtained in batch experiments not only for usual wet oxidation but also for the new two-step reaction. Results obtained so far indicate that the continuous flow reaction system developed in this study has the expected fundamental performance to produce acetic acid for both usual wet oxidation and the two-step reaction.

A continuous flow reaction system for producing acetic acid by wet oxidation of biomass waste

A continuous flow reaction system designed for producing acetic acid by wet oxidation (WO) of biomass with the maximum treatment capacity of 1 kg/h of dry biomass was developed. Experimental runs with rice hulls and starch were conducted at reaction temperatures between 300–320°C, for time of 2 and 3 min, with oxygen supplies between 70 and 100%, and at pressures between 10 and 30 MPa. The influence of each of these parameters was evaluated.