Magnetic actuation of microparticles for mass transfer enhancement

The motion of magnetic microparticles (250μm diameter) in a circular microfluidic reactor with a diameter of 10 mm under time dependent magnetic field has been studied using CFD code COMSOL. The effect of actuation protocol on the local and average particle velocity has been investigated. The local Sh numbers were obtained as a function of angular particle position in the range of Re numbers between 0.05 and 10 while the particle velocity was changed over two orders of magnitude. Under time dependent magnetic field, the thickness of the boundary layer continuously changes which results in an increased mass transfer towards the particle surface under periodic particle velocity conditions as compared to steady state velocity conditions. A good agreement between numerical and experimental data has been observed

Computational fluid dynamics simulation of blast furnace shaft

Computational fluid dynamics simulation is a tool to better understand the behavior of the gas-solid flow and in-furnace performance of blast furnace. This thesis consists of four parts. First, development and use of a mathematical model to predict the burden distribution which has a great effect on gas distribution and furnace efficiency. Second, simulate the blast furnace shaft process considering chemical reactions, heat exchanges, and gas-solid flow dynamics. Third, validate the burden distribution model and shaft simulation model using plant measurement. Fourth, to conduct parametric study of the major operational parameters i.e. effect of PCI rate, natural gas injection, bosh gas temperature, moisture add, oxygen enrichment, chimney size, and furnace geometry. Simulation is conducted using plant data and a good agreement is observed comparing with plant measurement. The parametric study showed that it is possible to improve the furnace performance by oxygen enrichment, adding moisture. It is also possible to decrease the coke rate by charging more PCI and increasing natural gas injection. Chimney size and furnace geometry can also affect a lot on the gas distribution and pressure drop. The burden distribution model and shaft CFD model can be used as a combination tool to predict the internal condition of a blast furnace

Mn(III)-Initiated Facile Oxygenation of Heterocyclic 1,3-Dicarbonyl Compounds

The Mn(III)-initiated aerobic oxidation of heterocyclic 1,3-dicarbonyl compounds, such as 4-alkyl-1,2-diphenylpyrazolidine-3,5-diones, 1,3-dialkylpyrrolidine-2,4-diones, 3-alkyl-1,5-dimethylbarbituric acids, and 3-butyl-4-hydroxy-2-quinolinone gave excellent to good yields of the corresponding hydroperoxides, which were gradually degraded by exposure to the metal initiator after the reaction to afford the corresponding alcohols. The synthesis of 30 heterocyclic 1,3-dicarbonyl compounds, the corresponding hydroperoxides and the 10 alcohols, their characterization, and the limitations of the procedure are described. In addition, the mechanism of the hydroperoxidation and the redox decomposition of the hydroperoxides are discussed

Sicherer Umgang mit gefährlichen Chemikalien im Durchfluss

Die Durchflusschemie hat sich im Laufe des letzten Jahrzehnts zu einem hervorragenden Werkzeugkasten für anspruchsvolle chemische Umwandlungen entwickelt. Hochexotherme und kinetisch schnelle Reaktionen sind selbst im kleinen Maßstab schwierig zu handhaben, während jede Hochskalierung erhebliche Risiken birgt, wenn herkömmliche Reaktoren in Betracht gezogen werden. Die Durchflusschemie ermöglicht eine exquisite Kontrolle über Mischsequenzen, Reaktionszeit und Abschreckung, die letztendlich den Weg für die Feinabstimmung der chemischen Reaktivität in ,Raum und Zeit‘ ebnet. Dieses Kapitel beschreibt die jüngsten Fortschritte der Durchflusschemie bei der Kontrolle und sogar Entdeckung neuer Reaktivitäten von hochgefährlichen chemischen Arten und instabilen Zwischenprodukten. Dieses Kapitel fasst faszinierende aktuelle Beispiele zusammen, die die Kraft der Durchflusschemie demonstrieren, um allgemein bekannte kryogene Reaktionen bei oder nahe Raumtemperatur, sicheres Handling und In-situ-Produktion von gefährlichen oder giftigen Reagenzien für chemische Umwandlungen durchzuführen, die in herkömmlichen Reaktoren allgemein als unsicher gelten

Microreactors for Gold Nanoparticles Synthesis: From Faraday to Flow

The seminal work of Michael Faraday in 1850s transmuted the “Alchemy of gold” into a fascinating scientific endeavor over the millennia, particularly in the past half century. Gold nanoparticles (GNPs) arguably hold the central position of nanosciences due to their intriguing size-and-shape dependent physicochemical properties, non-toxicity, and ease of functionalization and potential for wide range of applications. The core chemistry involved in the syntheses is essentially not very different from what Michael Faraday resorted to: transforming ions into metallic gold using mild reducing agents. However, the process of such reduction and outcome (shapes and sizes) are intricately dependent on basic operational parameters such as sequence of addition and efficiency of mixing of the reagents. Hence, irreproducibility in synthesis and maintaining batch-to-batch quality are major obstacles in this seemingly straightforward process, which poses challenges in scaling-up. Microreactors, by the virtue of excellent control over reagent mixing in space and time within narrow channel networks, opened a new horizon of possibilities to tackle such problems to produce GNPs in more reliable, reproducible and scalable ways. In this review, we will delineate the state-of-the-art of GNPs synthesis using microreactors and will discuss in length how such “flask-to-chip” paradigm shift may revolutionize the very concept of nanosyntheses

Radical carbonylations using a continuous microflow system

Radical-based carbonylation reactions of alkyl halides were conducted in a microflow reactor under pressurized carbon monoxide gas. Good to excellent yields of carbonylated products were obtained via radical formylation, carbonylative cyclization and three-component coupling reactions, using tributyltin hydride or TTMSS as a radical mediator

Mn(III)-initiated facile oxygenation of heterocyclic 1,3-dicarbonyl compounds

The Mn(III)-initiated aerobic oxidation of heterocyclic 1,3-dicarbonylcompounds, such as 4-alkyl-1,2-diphenylpyrazolidine-3,5-diones, 1,3-dialkylpyrrolidine-2,4-diones, 3-alkyl-1,5-dimethylbarbituric acids, and 3-butyl-4-hydroxy-2-quinolinonegave excellent to good yields of the corresponding hydroperoxides, which were graduallydegraded by exposure to the metal initiator after the reaction to afford the correspondingalcohols. The synthesis of 30 heterocyclic 1,3-dicarbonyl compounds, the correspondinghydroperoxides and the 10 alcohols, their characterization, and the limitations of theprocedure are described. In addition, the mechanism of the hydroperoxidation and theredox decomposition of the hydroperoxides are discussed