Continuous Synthesis Research Articles

Fabrication of shaping catalyst SO42−/SnO2-RC for high efficient and continuous synthesis of trimethylolpropane oleate in fixed bed reactor

Fabrication of shaping catalyst SO42−/SnO2-RC for high efficient and continuous synthesis of trimethylolpropane oleate in fixed bed reactor

Flow chemical laboratory practice for undergraduate students: synthesis of paracetamol

Generally, chemical engineering students get well acquainted with the batch synthesis of various active pharmaceutical ingredients, however, only tiny focus is provided to undergraduates on the topic of flow chemistry. In this paper, we report that students participating in the chemical engineering BSc course at the Budapest University of Technology and Economics were encouraged to perform the flow synthesis of paracetamol, a common pain painkiller. Two different synthetic routes for the continuous production of paracetamol were investigated and compared the batch and flow methods. Thus, these experiments allowed the students to discover flow chemistry for themselves under supervision: how to set up a flow system, how to carry out a reaction continuously, and to experience the advantages of flow chemistry over batch synthesis. In addition, students also got familiar with in-line Fourier transform infrared spectroscopy, as one of the reactions was monitored in real-time.Graphical The educational manuscript covers the field of continuous flow synthesis of paracetamol supplemented with in-line Fourier transform infrared spectroscopy, which was developed for undergraduate students in the chemical engineering BSc course at the Budapest University of Technology and Economics

Continuous synthesis of ε-caprolactone in a microreactor and kinetics insights into its side reactions

Continuous synthesis of ε-caprolactone in a microreactor and kinetics insights into its side reactions

Kinetic & thermodynamic studies of green fuel additive solketal from crude glycerol over metakaolin clay catalyst

Biodiesel synthesis produces about 10 % glycerol as a byproduct, prompting environmental concerns. The utilization of crude glycerol into valuable products requires an Eco-friendly technique. This study depicts glycerol acetalization using acetone and novel catalyst acid-treated metakaolin clay. Raw kaolin clay was calcined at 600 °C and treated with acid at 102 °C for 3 h. Afterward, acid activated clay was filtrate and dried in oven to remove moisture content. The catalyst prepared with a 5 M solution of sulfuric acid exhibited the highest surface area of 82.33 m2. g−1 and gave the highest yield (80 %) of Solketal with 73 % of glycerol conversion under optimum conditions. The ketalization reaction of Solketal synthesis was studied in terms of thermodynamics and kinetics. A Langmuir-Hinshelwood rate expression based on two-parameter kinetic law was used in this study. From the kinetic studies, activation energies (EA) of forward and backward reactions were found to be K1 = 39.23 kJ. mol−1 and K2 = 35.70 kJ. mol−1 respectively. Furthermore, reaction was exothermic having an enthalpy of ΔHo = −18.86 kJ. mol−1 and the entropy ΔSo = −0.1 kJ. mol−1 calculated from this process. Solketal derived from sustainable sources such as bio-glycerol and biomass-based acetone, has a wide range of uses as fuel additives and medicines industry. This research marks a significant advancement in the development of a continuous synthesis technique for Solketal and its recovery from glycerol-acetone mixtures.

Continuous Flow Synthesis of Nitrosoarenes via Photochemical Rearrangement of Aryl Imines.

Nitrosoarenes are versatile organic building blocks; however, their intrinsic instability and limited synthetic accessibility have so far restricted their widespread use. Herein, we present a new continuous flow route toward these entities that is based on a direct photochemical rearrangement process using o-nitrophenylimines as starting materials. Due to the underlying redox mechanism, a new amide group accompanies the formation of the nitroso group. Crucial to the success of this approach is the use of trifluoroethanol as a solvent and high-power light-emitting diodes (365 nm) as light sources that provide uniform irradiation and high efficiency of the resulting continuous flow method. The process is fast and robust, with high functional group tolerance and high throughput. The formation of the nitroso moiety is supported by full spectroscopic analysis, including X-ray crystallography. The scalability of this flow approach allows access to gram quantities of nitroso species for which we highlight a small set of derivatization reactions underlining their synthetic utility.

Continuous synthesis of boron-doped carbon nitride supported silver nanoparticles in an ultrasound-assisted coiled flow inverter microreactor

Continuous synthesis of boron-doped carbon nitride supported silver nanoparticles in an ultrasound-assisted coiled flow inverter microreactor

Continuous Flow Synthesis of Yttria‐Stabilized‐Zirconia Nanocrystals in Supercritical Solvothermal Conditions

AbstractThe synthesis of yttria‐stabilized zirconia nanoparticles with a fine control on the chemical composition and the distribution of yttrium cations is of major interest to master the mechanical, optical or ionic conduction properties of the final material. However, a fine control of this chemical homogeneity within the particles, especially above 5 mol.% of yttria (Y2O3), is challenging with conventional synthesis routes. In the present study, for the first time the interest of using supercritical sol–gel like synthesis is demonstrated for the continuous production in a single step of high quality zirconia (ZrO2) nanocrystals of 7 nm stabilized with Y2O3 without post‐treatment. Three compositions are investigated, i.e., 1.5, 3, and 8 mol.% of Y2O3 and in‐depth physico‐ chemical characterizations such as X‐ray diffraction, total X‐ray scattering, High‐resolution electron microscopy, Raman and X‐ray photoelectron spectroscopy are performed to asses and thus prove the successful synthesis of these different compositions while keeping a good chemical homogeneity. This enables to confirm that this original process leads to a unique and fine structural control for such small yttria‐doped zirconia nanocrystals.

Scaling Up 3D-Printed Porous Reactors for the Continuous Synthesis of 2,5-Diformylfuran

Scaling Up 3D-Printed Porous Reactors for the Continuous Synthesis of 2,5-Diformylfuran

Development and Scale-Up of a Fully Continuous Flow Synthesis of 2-Hydroxypyridine-N-oxide

Development and Scale-Up of a Fully Continuous Flow Synthesis of 2-Hydroxypyridine-<i>N</i>-oxide

Two photons are better than one: continuous flow synthesis of ꞵ-lactones through a doubly photochemically-activated Paternò-Büchi reaction

AbstractIn this paper we report a [2 + 2] cycloaddition reaction between ketenes and benzils, characterized by an unusual double photochemical activation triggered by visible light. Employment of a flow system and optimization of reaction conditions through Design of Experiments resulted in moderate to good yields of the corresponding β-lactones. A thorough computational analysis allowed to elucidate the mechanism of the reaction and justify the observed diastereoselectivity. The reaction was also successfully tested with mixed benzils, showing complete regioselectivity. Graphical abstract

Continuous gas-phase synthesis of iron nanoparticles at ambient conditions with controllable size and polydispersity

HypothesisBy altering aerosol growth dynamics with unipolar charges, one can obtain aerosols with narrow particles size distributions, a highly desirable feature in applications of functional nanoparticles. ExperimentsUnlike liquid colloid systems, aerosol particles in the free molecular regime undergo coarsening due to Brownian coagulation and will eventually attain a self-preserving size distribution with a typical geometric standard deviation of 1.46 - 1.48. We developed a novel continuous one-step aerosol synthesis reactor that produces iron nanoparticles from ferrocene at ambient conditions, which confines the site of precursor breakdown and particle formation in the downstream vicinity of a positive corona discharge. FindingsWe demonstrated that the particle size could be controlled within 3 - 10 nm with a suppressed geometric standard deviation (1.15 - 1.35). The as-produced iron nanoparticles were successfully used as catalyst for the growth of single-walled carbon nanotubes with a narrow diameter range. With a transient aerosol dynamics model, we showed that a fraction (as small as 0.1%) of unipolar-charged particles could have a significant impact on the aerosol growth dynamics, which eventually results in a narrower particle size distribution with smaller size and higher number concentrations.

Combined continuous nanoparticle synthesis with chromatographic size classification

In this paper, we report a combination of the continuous flow synthesis of gold nanoparticles (AuNPs) with subsequent purification and narrowing of the particle size distribution (PSD) by size-exclusion chromatography (SEC) by adapting the flow rates of synthesis and classification. First, we show scalability of chromatographic classification with respect to column dimension and the absence of irreversible nanoparticle adhesion on the column material. Two different syntheses lead to a large and widely distributed and a small and narrowly distributed AuNP dispersion, which are classified by a semipreparative column. The PSDs of individual fractions are characterized by analytical SEC. The broadly distributed AuNP dispersion was classified into three fractions with distinct PSDs. For the narrowly distributed AuNPs, the separation is almost independent of the mobile phase flow rate: coarse and fine fractions with almost identical PSDs and separation efficiency curves are observed irrespective of the flow rate. Even NP samples with narrow PSDs can be classified into multiple fractions with tailored PSDs while simultaneously removing dissolved impurities from the dispersion. With our study, we demonstrate the potential of a direct combination of continuous NP synthesis with chromatographic classification for the optimization of final PSDs and the simultaneous purification of nanoparticulate dispersions.

Continuous Anhydrous Synthesis of Oxymethylene Dimethyl Ethers by Reaction of Dimethyl Ether with Molecular Formaldehyde.

A novel gaseous synthesis route to oxymethylene dimethyl ethers (OMEn, n = 3-5) starting from CO2 and green H2 by using molecular formaldehyde (FA) and dimethyl ether (DME) is presented. The anhydrous reaction runs in a pressure free, gaseous, and continuous reaction setup. Hetero-geneous cata-lysts including zeolites and ion exchange resins (IER) are investigated, if they catalyze this reaction. While IER is almost inactive, zeolites with a 3D pore structure and an acidity exceeding ρm,H+(NH3,ads) = 250 µmol·gcat.-1 proved to be catalytically active. DME conversions of up to 2.76 mol-% are observed. The observed product gas stream compositions confirm thermo-dynamic considerations with back reactions / OMEn decomposition occurring as part of the equilibria under the investigated reaction conditions (90…180 °C). However, feed gas ratio variations (FA:DME = 1:2 to 1:9.5) highlighted the possibility to shift the product selectivity in favor of OMEn and suppress FA disproportionation to methyl formate. FA trimerization to trioxane is almost completely suppressed by running the reaction at 120 °C. The results presented here provide an important and unprecedented contribution to understand the complex reaction network in the OMEn synthesis reaction necessary to establish an energy efficient sustainable OMEn production process.

Continuous Synthesis of Carbamates from CO2 and Amines.

We present a novel approach for the continuous preparation of carbamates. The simple yet fast synthetic route relies on directly utilizing carbon dioxide and, in contrast with the literature-known methods, only employs 1,8-diazabicyclo[5.4.0]undec-7-ene as an additive. The applicable amines' diversity offers considerable flexibility to the synthetic protocol. Additionally, the continuous method's applicability significantly decreases the reaction time typically required for CO2-based carbamate synthesis and allows for straightforward and precise gas introduction. The mild reaction conditions and omission of the need for column chromatography render the process less time-demanding and environmentally more benign, providing the desired compounds in yields of 45 to 92%. Moreover, the modified procedure can potentially be applied in the selective synthesis of oxazolidinones from aziridines.

Microfluidic Vaterite Synthesis: Approaching the Nanoscale Particles

The challenge of continuous CaCO3 particle synthesis is addressed using microfluidic technology. A custom microfluidic chip was used to synthesize CaCO3 nanoparticles in vaterite form. Our focus revolved around exploring one-phase and two-phase synthesis methods tailored for the crystallization of these nanoparticles. The combination of scanning electron microscopy, X-ray diffraction, dynamic light scattering, and small-angle scattering allowed for an evaluation of the synthesis efficiency, including the particle size distribution, morphology, and polymorph composition. The results demonstrated the superior performance of the two-phase system when precipitation occurred inside emulsion microreactors, providing improved size control compared with the one-phase approach. We also discussed insights into particle size changes during the transition from one-phase to two-phase synthesis. The ability to obtain CaCO3 nanoparticles in the desired polymorph form (∼50 nm in size, 86–99% vaterite phase) with the possibility of scaling up the synthesis will open up opportunities for various industrial applications of the developed two-phase microfluidic method.

Microfluidics-enabled intelligent manufacturing of metal halide perovskite nanocrystals

Large-scale and controllable fabrication is an indispensable step for the industrialization and commercialization of halide perovskite nanocrystals, which are new-generation semiconductor materials for optoelectronic applications. Microfluidics, which provides continuous and precise synthesis, has been considered as a promising technique to fulfill this aspect. The research studies over the past decades have witnessed the advancement of microfluidics as a powerful tool in the fabrication of halide perovskite nanocrystals. In this Perspective, the state-of-the-art research based on microfluidics is introduced initially, including the synthesis of functional structures and materials, devices, as well as the interdisciplinary interactions between microfluidics and artificial intelligence and machine learning, etc. We then detail the issues and challenges in hindering progress in the above areas. Finally, we provide future directions and trends for the technology to achieve its full potential. This Perspective is expected to benefit the collective efforts between the field of nanomaterials and microfluidics in advanced manufacturing.

Continuous Two-Step Synthesis of PS@HMEM Core–Shell Nanoparticles via Emulsion Polymerization in Microreactors

Continuous Two-Step Synthesis of PS@HMEM Core–Shell Nanoparticles via Emulsion Polymerization in Microreactors

Continuous Synthesis of Spherical Polyelectrolyte Brushes by Photo-Emulsion Polymerization in a Microreactor.

Nanosized spherical polyelectrolyte brushes (SPBs) are ideal candidates for the preparation of nanometal catalysts, protein separation, and medical diagnostics. Until now, SPBs have been synthesized by photo-emulsion polymerization in a batch reactor, which remains challenging to scale up. This paper reports a successful continuous preparation of SPBs by photo-emulsion polymerization in a self-made microreactor. The effects of residence time, monomer concentration, and feed ratios on the conversion of monomers and SPB structures are systematically investigated by dynamic lighting scattering and transmission electron microscopy. Poly(acrylic acid) (PAA) SPBs obtained in a microreactor exhibiting a narrow size distribution with a short reaction time are very effective in inhibiting the calcium carbonate scale and are comparable to those produced in a batch reactor. This work confirms the feasibility of continuous preparation and scaled-up production of SPBs.

Scalable fabrication of amine-functionalized microgel composite membranes and their gas permeation characteristics

Post-combustion carbon dioxide (CO2) separation from exhaust gases is a bridge technology to reduce the emissions of traditional combustion processes. Primary amine-functionalized building blocks enhance the CO2 selectivity of membranes via a facilitated transport mechanism. Microgels are polymer-based colloids that can be functionalized with amine groups. However, to serve as a successful membrane building block, high aminesloading, and a scalable fabrication route are necessary. Here, we report the continuous synthesis of amine-functionalized microgels and apply them as a dense selectivity layer to form thin-film composite membranes (TFC). The synthesis process was successfully scaled up from batch to laminar flow reactor, producing microgels containing up to 50 mol% amine incorporation. Amine incorporation influences microgel water uptake important for their gas separation properties. Porous polyacrylonitrile (PAN) membranes containing a spray-coated microgel layer are tested using a mixture of CO2 and N2, with or without humidity in the feed stream. Both CO2 permeance and selectivity increase with the amine content in the microgels and the moisture in the feed stream. At 95% relative humidity, the CO2 permeance improved from 38 to 100 GPU when the amine incorporation rose from zero to 48% of 2-aminoethyl methacrylate (AEMA). The continuous synthesis allows large-scale fabrication of these microgels for applications such as membrane functionalization. Furthermore, the developed microgel-functionalized gas separation membranes are promising for CO2 removal applications from high-humidity streams, such as flue gas.

Modeling and Simulation of N‐(3‐Aminio‐4 methylphenyl)benzamide Synthesis in a Microreactor

AbstractN‐(3‐Amino‐4‐methylphenyl)benzamide is an intermediate product for the production of several medicines. Microreactor technology is a new concept for the continuous synthesis of chemicals. The computational fluid dynamics method was used to simulate the flow synthesis of N‐(3‐amino‐4‐methylphenyl)benzamide. There was good agreement between experimental data and modeling outputs. The effect of operating parameters such as temperature and residence time on system performance was investigated. The results revealed that an increase in temperature from 30 to 70 °C led to the enhancement of N‐(3‐amino‐4‐methylphenyl)benzamide production from about 42 to 76 % at a residence time of 420 s. It was found that the residence time and temperature have the largest influence on N‐(3‐amino‐4‐methylphenyl)benzamide production. Byproduct production was also increased by increasing the temperature and residence time.