Batch Microreactors Research Articles

A heterogeneous catalytic process to mitigate the acidity of bio-oils caused by the presence of volatile organic acids

The removal of the acidity produced by the presence of volatile organic acids in bio-oils, such as acetic acid, assisted by heterogeneous catalysts was investigated. For this purpose, CaO and alumina-supported catalysts were prepared, and silver nanoparticles were used as promoter. The prepared catalysts, both fresh and post-reaction, were characterized by several techniques: N2 physisorption (BET), SEM-EDS, TEM, XRD, and TPR. All catalysts were tested in the elimination of acetic acid, employing two different reaction systems: batch microreactors and a pressurized batch reactor. An appreciable CH3COOH elimination of ~60%–70% was obtained at low temperature (150–200 °C) using the CaO-Al2O3 system. The addition of silver improved the removal percentage. Silver-supported catalysts were also tested in a pressure-controlled system, achieving an excellent percentage of acetic acid removed (~97.5%). Silver would promote the incipient reactions of catalytic ketonization and aldol condensation.

Asymmetric α-hydroxylation of β-dicarbonyl compounds by C-2′ modified cinchonine-derived phase-transfer catalysts in batch and flow microreactors

The asymmetric α-hydroxylation of β-dicarbonyl compounds was catalyzed by C-2′-modified cinchonine-derived phase-transfer catalysts. Excellent yields (up to 95%) and good enantioselectivities (up to 89% ee) were obtained. The reaction was carried out in a flow microreactor and similar results were obtained (up to 93% yield, 84% ee), the residence time was shortened from 24 h in batch to 2 h.

Determining the flow-related cap deformation of Taylor droplets at low Ca numbers using ensemble-averaged high-speed images

Droplets of microscopic Taylor flows can act as stirred batch microreactors, while the continuous phase compartments supply good mixing and mass transfer to the channel walls. The design of reliable reactors, however, requires a priori information about droplet formation frequency and droplet length, which is difficult to obtain. Here, we report about a new method to reliably describe the droplet deformation, which could act as a flow indicator. The flow-related interface shape deformation of liquid–liquid Taylor flows in square micro channels for $$Re < 5$$ and $$Ca < 0.02$$ is quantified by experimental studies and ensemble image averaging. We deduce an easy-to-access droplet cap deformation model, which allows reducing the complex interface curvature information to an ellipse and provide correlation functions to link this deformation ratio to the flow conditions quantitatively. In addition, we introduce an experimental approach using a ternary liquid–liquid material system that allows adjusting $$Re$$ and $$Ca$$ numbers independently without surfactant addition by changing the mass fraction of two liquids forming the continuous phase. In combination, we suggest an image processing method to overcome the optical issues arising from the poor image contrast of Taylor droplets with low differences of refractive index to the bulk material. The presented approach opens the possibility to benchmark numerical studies of the interface deformation and paves the way for improved flow modeling, e.g., pressure drop or relative velocity of Taylor droplets, since the flow-induced curvature could serve as an indicator of the forces acting on the droplet front and rear.

ChemInform Abstract: Visible‐Light Photoredox Catalysis: Direct Synthesis of Fused β‐Carbolines Through an Oxidation/[3 + 2] Cycloaddition/Oxidative Aromatization Reaction Cascade in Batch and Flow Microreactors.

Fused β-carbolines were synthesized via a visible light photoredox catalyzed oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade in batch and flow microreactors. Several structurally diverse heterocyclic scaffolds were obtained in good yields by coupling of tetrahydro-β-carbolines with a variety of dipolarophiles under photoredox multiple C–C bond forming events. The photoredox coupling of tetrahydro-β-carboline with 1,4-benzoquinone was significantly faster in continuous flow microreactors and the desired products were obtained in higher yields compared to batch reactors.

Synergetic hydrothermal co-liquefaction of crude glycerol and aspen wood

Crude glycerol-assisted hydrothermal co-liquefaction of aspen wood was studied in batch micro-reactors. An experimental matrix of 14 experiments was defined to investigate the effects of three different process parameters on the yields of biocrude and char, and on biocrude quality. Co-processing aspen wood and neat glycerol led to a significant reduction in the char yield, and glycerol is hypothesized to act as a radical scavenger, alleviating re-polymerization of especially lignin-derived fragments. In the temperature range of 380–420°C, it was found that biocrude and char yield, and biocrude quality were all invariant to the reaction temperature. By increasing the crude glycerol to aspen wood mass ratio from 0:1 to 3:1, char yield was decreased from 18.3% (only aspen wood) to 3.4%. Furthermore, the biocrude quality in terms of the effective hydrogen-to-carbon ratio (H/Ceff) was significantly affected by the crude glycerol to aspen wood ratio. At a crude glycerol to aspen wood ratio of 3:1 the H/Ceff was 1.6 compared to 0.96 in the case of only aspen wood. The chemical composition of the biocrude was observed to be directly influenced by the two main feedstock constituents, which allows straightforward composition prediction of the biocrude, and hence enables controllability of the biocrude properties by feedstock mixing.

Shrunk to femtolitre: Tuning high-throughput monodisperse water-in-oil droplet arrays for ultra-small micro-reactors

We report a facile, low-cost, and high-yielding microfluidic technology for in situ generating and arraying water-in-oil droplets by shrinking them to the order of femtolitres (fLs) as scalable batch micro-reactors. Instead of generating ultra-small droplets by the direct atomization, which requires dedicate control and high energy input, we shrink droplets to stable smaller ones by utilizing the controlled water diffusion in oil. This “shrunk to fL” method is combined with a three-dimensional microwell design to create high-density addressable droplet arrays. As the result, scalable, high-throughput, and well-aligned W/O arrays with excellent long-term stability and predicable droplet sizes have been achieved.

Some recent advances in the design and the use of miniaturized droplet-based continuous process: Applications in chemistry and high-pressure microflows

This mini-review focuses on two different miniaturizing approaches: the first one describes the generation and use of droplets flowing within a millifluidic tool as individual batch microreactors. The second one reports the use of high pressure microflows in chemistry. Millifluidics is an inexpensive, versatile and easy to use approach which is upscaled from microfluidics. It enables one to produce hierarchically organized multiple emulsions or particles with a good control over sizes and shapes, as well as to provide a convenient data acquisition platform dedicated to slow or rather fast chemical reactions, i.e., from hours to a few minutes. High-pressure resistant devices were recently fabricated and used to generate stable droplets from pressurized fluids such as supercritical fluid-liquid systems. We believe that supercritical microfluidics is a promising tool to develop sustainable processes in chemistry.

Fluid inclusions as micro-samplers in batch experiments: A study of the system C-O-H-S-cement for the potential geological storage of industrial acid gas

Disposal in deep geological reservoirs is one potential solution for the storage of anthropogenic greenhouse gases and acid gases produced by the petroleum industry. Well cement durability during acid gas injection can be simulated in the laboratory and includes the study of toxic fluids (H 2S + CO 2) at high pressures (> 100 bar) and temperatures (> 100 °C). In order to reduce human risk, the experiments were carried out in microreactors (< 3 cm 3). As fluid sampling during experiment is impossible, we propose a method of fluid capture by fluid inclusion synthesis in quartz: natural pre-existing fluid inclusions were emptied by heat-induced decrepitation and used as fluid microsamplers in batch microreactors. Experimental fluids were trapped at 200 °C and 500 bar by sealing the opened inclusions in microcracks. At the end of the experimental runs, quartz sections were collected and the fluid compositions determined by Raman spectroscopy at room and experimental P-T conditions. The number of fluid phases under experimental run conditions was checked indirectly by microthermometry. Variations of PVTX properties of the analysed inclusions are due to the combined effects of heterogeneous trapping and kinetics of well cement reactivity.

Batch microreactor studies of lignin and lignin model compound depolymerization by bases in alcohol solvents

The depolymerization of Kraft- and organosolv-derived lignins by KOH in supercritical methanol or ethanol was studied in rapidly heated batch microreactors. High conversions were realized, with only 7% ether insoluble material remaining after treating organosolv lignin in KOH/ethanol at 290°C. The conversion was rapid, reaching the maximum value within 10–15 min. Further studies with KOH, NaOH, CsOH, LiOH, Ca(OH) 2, and Na 2CO 3 indicate that strong bases give superior conversion, and that combinations of bases can give both positive and negative synergistic effects. An excess of base relative to lignin monomer units was required for maximum conversion. Model compound studies confirm the dominant depolymerization route is the solvolysis of ether linkages. Ethanol solvent is also partially converted to acetic acid, higher alcohols, and other products in addition to alkylating phenolic rings. The formation of acidic products may account for the excess base requirement.

Pyrolysis of Polycyclic Perhydroarenes. 2. 1-n-Undecylperhydronaphthalene

1-n-Undecylperhydronaphthalene (UPN), a prototypical long-chain n-alkylperhydroarene, was pyrolyzed both neat and in benzene in batch microreactors at temperatures between 375 and 475 °C. The global reaction order for UPN disappearance was 1.00 ± 0.08, so UPN pyrolysis followed first-order kinetics. The Arrhenius parameters for the first-order rate constant were A (s -1 ) = 10 10.9 ± 2.6 and E = 46.5 ± 8.4 kcal/mol. All of the reported uncertainties are the 95% confidence intervals. An empirical structure-reactivity correlation in the literature, which was developed for the pyrolysis of saturated cyclic compounds with short n-alkyl chains, did not accurately predict the pyrolysis kinetics of UPN and other long-chain n-alkylperhydroarenes. UPN neat pyrolysis generated numerous primary products, and the primary products with the highest initial selectivities were octahydronaphthalene plus n-undecane, methyleneperhydronaphthalene plus n-decane, and trans-decalin plus 1-undecene. These three product pairs accounted for about 40% of the primary product spectrum from UPN. The remaining 60% was apportioned in roughly equal selectivities among 18 other primary product pairs that consisted of either an n-alkane plus an alkenylperhydronaphthalene or a 1-alkene plus an n-alkylperhydronaphthalene. Secondary reactions included dehydrogenation of decalin and octahydronaphthalene, to form tetralin and eventually naphthalene, and thermal cracking of paraffins, olefins, and other primary products. This product spectrum is consistent with a free radical chain reaction mechanism for UPN neat pyrolysis.

Pathways, Kinetics, and Mechanisms for 2-Dodecyl-9,10-dihydrophenanthrene Pyrolysis

We pyrolyzed 2-dodecyl-9,10-dihydrophenanthrene (DDPh) in batch microreactors. The reaction conditions included neat pyrolyses between 375−450 °C for times of 15−240 min and also pyrolyses in benzene at 400 °C and 90 min but at different initial DDPh concentrations ranging from 0.0095 to 0.238 mol/L. The disappearance of DDPh followed first-order kinetics, and the global first-order rate constant had Arrhenius parameters of (log10 A (s-1) = 13.6 ± 2.8 and E (kcal/mol) = 54.5 ± 9.1, where the uncertainties are the 95% confidence intervals. The decomposition of DDPh can be described by a reaction network that possesses four parallel primary pathways. The major primary path, which involves dehydrogenation, leads to 2-dodecylphenanthrene. The other three primary paths involve C−C bond cleavage, and they lead to 2-methyl-9,10-dihydrophenanthrene plus undecene, to 2-vinyl-9,10-dihydrophenanthrene plus decane, and to numerous minor products. Important secondary and tertiary reactions include the rapid reduction ...

Hydrogenation-dehydrogenation of pyrenes catalysed by sulphided cobalt-molybdate at coal liquefaction conditions

The hydrogenation and dehydrogenation kinetics of pyrene and hydropyrenes were studied in batch microreactors, both with and without catalyst, as a function of time, temperature, pressure and catalyst concentration. Under catalytic conditions at 648 K and 7.2 MPa, 4,5-dihydropyrene and pyrene reached equilibrium in 3 min with a molar ratio of 0.41. The heat of the hydrogenation reaction was —10 ± 1 kcal mol−1 compared with -12 kcal mol−1 for the hydrogenation of phenanthrene to 9,10-dihydrophenanthrene. The hydrogenation and dehydrogenation rates were negligible without catalyst. At 648 K with catalyst, 70% of the hydropyrenes reverted to pyrene in 5 min under nitrogen. The rapid pyrene—4.5-dihydropyrene equilibration implies that the equilibrium constant may be of more importance than the hydrogenation rate constant for predicting the amount of hydrogen available for donation by pyrene-like components in coal liquefaction solvents.