Showing papers in "Reaction Chemistry and Engineering in 2016"
TL;DR: In this article, the authors report the development of a convenient numbering-up strategy for the scale-up of gas-liquid photocatalytic reactions in which the gas is consumed.
Abstract: Visible-light photocatalysis is a mild activation method for small molecules and enables a wide variety of transformations relevant for organic synthetic chemistry. However, one of the limitations of photocatalysis and photochemistry in general is the limited scalability due to the absorption of light (Lambert–Beer law). Here, we report the development of a convenient numbering-up strategy for the scale-up of gas–liquid photocatalytic reactions in which the gas is consumed. Only commercially available constituents were used and the system can be rapidly assembled by any practitioner of flow chemistry. The modular design allows us to systematically scale the photochemistry within 2n parallel reactors (herein, n = 0, 1, 2, 3). The flow distribution in the absence of reactions was excellent, showing a standard deviation less than 5%. Next, we used the numbered-up photomicroreactor assembly to enable the scale-up of the photocatalytic aerobic oxidation of thiols to disulfides. The flow distribution was again very good with a standard deviation lower than 10%. The yield of the target disulfide in the numbered-up assemblies was comparable to the results obtained in a single device demonstrating the feasibility of our approach.
155 citations
TL;DR: The safety aspects of these reactions are discussed, followed by an overview of (continuous flow) reactors suitable for aerobic oxidation reactions that can be applied on scale, with particular focus on the scale-up strategy.
Abstract: Molecular oxygen is without doubt the greenest oxidant for redox reactions, yet aerobic oxidation is one of the most challenging to perform with good chemoselectivity, particularly on an industrial scale. This collaborative review (between teams of chemists and chemical engineers) describes the current scientific and operational hurdles that prevent the utilisation of aerobic oxidation reactions for the production of speciality chemicals and active pharmaceutical ingredients (APIs). The safety aspects of these reactions are discussed, followed by an overview of (continuous flow) reactors suitable for aerobic oxidation reactions that can be applied on scale. Some examples of how these reactions are currently performed in the industrial laboratory (in batch and in flow) are presented, with particular focus on the scale-up strategy. Last but not least, further challenges and future perspectives are presented in the concluding remarks.
125 citations
TL;DR: An automated, droplet-flow microfluidic system explores and optimizes Pd-catalyzed Suzuki–Miyaura cross-coupling reactions.
Abstract: An automated, droplet-flow microfluidic system explores and optimizes Pd-catalyzed Suzuki–Miyaura cross-coupling reactions. A smart optimal DoE-based algorithm is implemented to increase the turnover number and yield of the catalytic system considering both discrete variables—palladacycle and ligand—and continuous variables—temperature, time, and loading—simultaneously. The use of feedback allows for experiments to be run with catalysts and under conditions more likely to produce an optimum; consequently complex reaction optimizations are completed within 96 experiments. Response surfaces predicting reaction performance near the optima are generated and validated. From the screening results, shared attributes of successful precatalysts are identified, leading to improved understanding of the influence of ligand selection upon transmetalation and oxidative addition in the reaction mechanism. Dialkylbiarylphosphine, trialkylphosphine, and bidentate ligands are assessed.
121 citations
TL;DR: In this review the recent progress in the field of self-optimizing reactor systems for continuous flow chemistry is presented, with particular focus on the implementation of monitoring tools and realization of computer-controlled reaction optimizations without human interaction.
Abstract: In this review the recent progress in the field of self-optimizing reactor systems for continuous flow chemistry is presented. Particular focus is directed to the implementation of monitoring tools and realization of computer-controlled reaction optimizations without human interaction.
110 citations
TL;DR: In this article, an automated continuous reactor for the synthesis of organic compounds, which uses online mass spectrometry (MS) for reaction monitoring and product quantification, is presented, and the amidation of methyl nicotinate with aqueous MeNH2 was optimised using design of experiments and a self-optimisation algorithm approach to produce >93% yield.
Abstract: An automated continuous reactor for the synthesis of organic compounds, which uses online mass spectrometry (MS) for reaction monitoring and product quantification, is presented. Quantitative and rapid MS monitoring was developed and calibrated using HPLC. The amidation of methyl nicotinate with aqueous MeNH2 was optimised using design of experiments and a self-optimisation algorithm approach to produce >93% yield.
99 citations
TL;DR: In this paper, reversible deactivation radical polymerization (RDRP) techniques have gained significant interest in this respect within the past one to two years, and the underlying principles of the advantage of carrying polymerization out under photoflow conditions are elucidated.
Abstract: Precision polymer design in continuous photoflow reactors is a young, yet rapidly growing research field. By switching from batch to flow processing, polymerizations can be carried out with unmatched efficiency under mild reaction conditions, while concommitantly providing conditions for simple scale up of reactions. Specifically the reversible deactivation radical polymerization (RDRP) techniques have gained significant interest in this respect within the past one to two years. The different photoRDRP methods are herein compared and the underlying principles of the advantage of carrying polymerization out under photoflow conditions are elucidated. Further, the yet unexplored potential of these techniques is identified and discussed towards future development.
86 citations
TL;DR: In this paper, a self-optimizing flow reactors combine online analysis with evolutionary feedback algorithms to rapidly achieve optimum conditions for the final bond-forming step in the synthesis of an irreversible epidermal growth factor receptor kinase inhibitor developed by AstraZeneca.
Abstract: Self-optimising flow reactors combine online analysis with evolutionary feedback algorithms to rapidly achieve optimum conditions. This technique has been applied to the final bond-forming step in the synthesis of AZD9291, an irreversible epidermal growth factor receptor kinase inhibitor developed by AstraZeneca. A four parameter optimisation of a telescoped amide coupling followed by an elimination reaction was achieved using at-line high performance liquid chromatography. Optimisations were initially carried out on a model compound (2,4-dimethoxyaniline) and the data used to track the formation of various impurities and ultimately propose a mechanism for their formation. Our protocol could then be applied to the optimisation of the 2-step telescoped reaction to synthesise AZD9291 in 89% yield.
84 citations
TL;DR: In this paper, the authors investigated the reaction pathway of catalytic hydrogenation of the LOHC compound dibenzyltoluene (H0-DBT) and found that the reaction proceeds with a very high preference for the SSM order at temperatures between 120 °C and 200 °C.
Abstract: The catalytic hydrogenation of the LOHC compound dibenzyltoluene (H0-DBT) was investigated by 1H NMR spectroscopy in order to elucidate the reaction pathway of its charging process with hydrogen in the context of future hydrogen storage applications. Five different reaction pathways during H0-DBT hydrogenation were considered including middle-ring preference (middle-side-side, MSS), side-middle-side order of hydrogenation (SMS), side-ring preference (SSM), simultaneous hydrogenation of all three rings without intermediate formation and statistical hydrogenation without any ring preference. Detailed analysis of the 1H NMR spectra of the H0-DBT hydrogenation over time revealed that the reaction proceeds with a very high preference for the SSM order at temperatures between 120 °C and 200 °C and 50 bar in the presence of a Ru/Al2O3-catalyst. HPLC analysis supported this interpretation by confirming an accumulation of H12-DBT species prior to full hydrogenation to H18-DBT with middle ring hydrogenation as the final step.
78 citations
TL;DR: In this article, the authors combine microfluidics and FT-IR spectroscopy towards spatially resolved information on chemical processes, and show that the results show promising results.
Abstract: Correction for ‘Combining microfluidics and FT-IR spectroscopy: towards spatially resolved information on chemical processes' by Adeline Perro et al., React. Chem. Eng., 2016, DOI: 10.1039/c6re00127k.
74 citations
TL;DR: In this paper, the benefits of coupling spray-drying and continuous flow for continuous synthesis of metal-organic frameworks (MOFs) assembled from high-nuclearity secondary building units (SBUs) are reported.
Abstract: Metal–organic frameworks (MOFs) are among the most attractive porous materials currently available. However, one of the challenges precluding their industrial exploitation is the lack of methods for their continuous production. In this context, great advances have been enabled by recently discovered, novel continuous-fabrication methods such as mechanosynthesis, electrochemistry, continuous-flow synthesis and spray-drying. Herein we report the benefits of coupling two of these processes—spray-drying and continuous flow—for continuous synthesis of MOFs assembled from high-nuclearity secondary building units (SBUs). Using the resulting spray-drying continuous flow-assisted synthesis, we have prepared numerous members of diverse MOF families, including the UiO-66, Fe–BTC/MIL-100 and [Ni8(OH)4(H2O)2(L)6]n (where L = 1H-pyrazole-4-carboxylic acid) series. Interestingly, all of these MOFs were automatically obtained as compact microspherical superstructures (beads). We anticipate that our strategy could be easily employed for synthesizing and shaping multivariate (MTV) MOFs.
69 citations
TL;DR: In this article, continuous flow reactors have been proposed as a scalable method for scaling their solvothermal synthesis, with the largest range of materials accessible, in high yield, and with control over crystal form.
Abstract: Metal–organic frameworks have emerged as one of the most diverse new families of materials in the past few years. Their hybrid structures, combinations of inorganic and organic moieties, give a wide range of complex architectures with resultant properties that are suitable for numerous important fields, including porosity for molecular sieving and sensing, heterogeneous catalysis, drug delivery, and energy storage. If applications of these materials are to be realised then scalable synthesis is required, taking laboratory batch reactions towards industrial production. Continuous flow reactors offer the most versatile method for scaling their solvothermal synthesis, with the largest range of materials accessible, in high yield, and with control over crystal form.
TL;DR: This review outlines the benefits of reaction engineering in this development process, with particular emphasis of reaction kinetics, and says future research needs to focus on rapid methods to collect data at sufficient accuracy that it can be used for the effective design of new biocatalytic processes.
Abstract: Biocatalysis is a growing area of synthetic and process chemistry with the ability to deliver not only improved processes for the synthesis of existing compounds, but also new routes to new compounds. In order to assess the many options and strategies available to an engineer developing a new biocatalytic process, it is essential to carry out a systematic evaluation to progress rapidly and ensure decisions are made on firm foundations. In this way, directed development can be carried out and the chances of implementation of a commercially successful process can be much improved. In this review we outline the benefits of reaction engineering in this development process, with particular emphasis of reaction kinetics. Future research needs to focus on rapid methods to collect such data at sufficient accuracy that it can be used for the effective design of new biocatalytic processes.
TL;DR: In this paper, the authors present a new miniature continuous stirred-tank reactor (CSTR) cascade to handle solid-forming reactions in flow, and demonstrate the ability of the reactor cascade to transport solid particles continuously for hours without significant signs of clogging.
Abstract: Continuous handling of solids creates challenges for realizing continuous production of pharmaceuticals and fine chemicals. We present a new miniature continuous stirred-tank reactor (CSTR) cascade to handle solid-forming reactions in flow. Single-phase residence time distribution (RTD) measurements of the CSTR cascade reveal nearly ideal CSTR mixing behavior of the individual units. Consistency of experimental and predicted conversions of a Diels–Alder reaction further confirms the CSTR performance. Two solid-forming reactions, (i) glyoxal reacting with cyclohexylamine to form N,N′-dicyclohexylethylenediimine, (ii) sulfonylation of 2-octanol with methanesulfonyl chloride, demonstrate the ability of the reactor cascade to transport solid particles continuously for hours without significant signs of clogging.
TL;DR: A review of the research progress in reactor engineering of controlled radical polymerization (CRP) can be found in this paper, where the authors discuss the current status and future development of CRP systems.
Abstract: Controlled radical polymerization (CRP) represents an important advancement in polymer chemistry. It allows synthesis of polymers with well-controlled chain microstructures. Reactor engineering is essential in bringing lab-scale chemistry to industrial realization. This paper reviews the research progress in reactor engineering of CRP, namely, atom transfer radical polymerization (ATRP), reversible addition–fragmentation chain transfer radical polymerization (RAFT), and nitroxide-mediated or stable free radical polymerization (NMP or SFRP). Research activities in semi-batch reactors, tubular reactors, and continuous stirred-tank reactors (CSTR) of both homogeneous (bulk and solution) and heterogeneous (emulsion, mini-emulsion, heterogeneous catalyst, etc.) CRP systems are summarized. Typical examples are selected and discussed in detail. Perspectives on the current status and future development are also provided.
TL;DR: In this article, a single reactor platform is devised to conduct both batch and flow reactions, either singly or in concert, using open source technologies to automate, control and monitor individual processes.
Abstract: Synthesis chemistry need not be limited to either only batch or only flow; rather, in the future we expect that it will consist of an amalgamation of the best and most appropriate methods. We have therefore devised a single reactor platform to conduct both batch and flow reactions, either singly or in concert, using open source technologies to automate, control and monitor individual processes. We illustrate this concept with the multistep synthesis of 5-methyl-4-propylthiophene-2-carboxylic acid to showcase the utility of this approach in a telescoped manner. Automated downstream processing techniques, consisting of continuous extraction and solvent switching steps, were also included, further freeing the chemist from routine laboratory tasks.
TL;DR: In this paper, a photo-spectrometer is used for real-time analysis of photochemical reactions in a continuous fashion, based on the photo-Favorskii rearrangement reaction of α-chloropropiophenone precursor.
Abstract: A new enabling technology for performing photochemical reactions in a continuous fashion is presented. This photo-reactor is compatible with existing flow systems and can be furthermore linked to a photo-spectrometer in order to allow for real time analysis of photochemical reactions. In this communication we wish to report the profiling of this system and its application to the continuous synthesis of ibuprofen based on a photo-Favorskii rearrangement reaction of a readily available α-chloropropiophenone precursor.
TL;DR: In this paper, procedures and conditions that need to be fulfilled to be able to carry out appropriate in situ and operando diffuse reflectance FT-IR (DRIFTS) analyses are discussed.
Abstract: This paper discusses procedures and conditions that need to be fulfilled to be able to carry out appropriate in situ and operando diffuse reflectance FT-IR (DRIFTS) analyses. Spectrum handling and precise control of experimental parameters have a significant importance, even when only qualitative information is sought. In many cases, quantitative data can be obtained, such as surface species concentrations and heats of adsorption. Transient kinetics can help characterize spectator species and potential reaction intermediates. Direct information on the state of the catalyst surface can also be obtained, for instance regarding the alloying state of multimetallic catalysts.
TL;DR: In this article, a simple continuous flow setup for the generation and use of elemental chlorine for organic synthesis has been developed, based on the reaction of HCl with NaOCl, generating NaCl and H2O as the only side products.
Abstract: A simple continuous flow setup for the generation and use of elemental chlorine for organic synthesis has been developed. The chlorine generator is based on the reaction of HCl with NaOCl, generating NaCl and H2O as the only side products. As a proof-of-concept, the reactor has been applied for a variety of chlorinations and oxidations of organic compounds.
TL;DR: In this paper, the authors theoretically and experimentally investigate the growth kinetics in colloidal nanocrystal synthesis using a novel microfluidic reactor integrating independent modules for nucleation and growth.
Abstract: The processes occurring during nanocrystal nucleation and growth are currently not well understood Herein, we theoretically and experimentally investigate the growth kinetics in colloidal nanocrystal synthesis Using a novel microfluidic reactor integrating independent modules for nucleation and growth, we demonstrate the controlled, direct synthesis of high quality nanocrystals in high yield For CdSe nanocrystals, we find that size tuning solely by variation of the reaction time and temperature does not yield product populations of optimal size dispersion or yield Instead, we present an improved method for the synthesis of bespoke nanocrystals that relies on the controlled addition of precise amounts of additional precursor subsequent to nucleation and fine tuning of the reaction time and temperature in the second stage Real-time spectroscopic monitoring of the produced crystals in conjunction with kinetic simulations confirms the close correspondence between the model and the experiment and elegantly quantifies the effects of temperature, concentration, additives and surfactants on conversion, growth and diffusion rates within the model framework We show that the conversion of the precursor to a monomer follows a first order rate law and that the growth rate has a stronger temperature dependence than the conversion rate Moreover, the surfactant concentration retards the reaction by inhibiting diffusion to the growing crystals whilst maintaining a uniform conversion rate Finally, we demonstrate that diphenylphosphine, a common additive in CdSe synthesis, enhances the reaction rate by accelerating precursor conversion
TL;DR: In this paper, a multistep continuous flow setup for the four-step conversion of anilines into pyrazole products is presented, which incorporates the use of amine-redox chemistry through diazotization and a metal-free vitamin C mediated reduction.
Abstract: A versatile multistep continuous flow setup is reported for the four-step conversion of anilines into pyrazole products. The synthesis machine incorporates the use of amine-redox chemistry through diazotization and a metal-free vitamin C mediated reduction. The machine can be used for the synthesis of an array of analogues or the scale up of an individual target.
TL;DR: In this paper, it was shown that in the temperature range of 370 °C to 765 °C of the heat source, a constant high sugar yield of ∼70% (C-basis) can be obtained from the fast pyrolysis of Avicel cellulose while producing hardly any gas and solid residue (<1% above 450 °C).
Abstract: Biomass derived sugars are expected to play an important role as platform chemicals. Herein, we have shown that in the temperature range of 370 °C to 765 °C of the heat source a constant high sugar yield of ∼70% (C-basis) can be obtained from the fast pyrolysis of Avicel cellulose while producing hardly any gas (<1%) and solid residue (<1% above 450 °C). This opens the opportunity to combine the advantages of thermochemical processes, such as high conversion rates and products not being heavily diluted with water, with an increased value of the product slate. In this paper, firstly the screen-heater used to study the very early stages of cellulose pyrolysis is introduced and characterized. Secondly, yield data as a function of process and pyrolysis conditions are presented and interpreted, also using mathematical models, with respect to chemistry, heat transfer, mass transfer and their interplay. It has been shown that next to heat transfer and the residence time in the vapor phase also the escape rate of products from the reacting particle (mass transfer) is a key process determining the overall mass loss rate and/or the product distribution.
TL;DR: In this article, a flow process for direct amination of a pharmaceutically relevant substrate using a Pd-NHC based catalyst was demonstrated in a lab-scale mini-plant and in a pilot-scale plant.
Abstract: A flow process for direct amination of a pharmaceutically relevant substrate using a Pd-NHC based catalyst was demonstrated in a lab-scale mini-plant and in a pilot-scale plant. The lab-scale mini-plant was used to determine catalyst stability under recycling conditions. Results in the mini-plant have shown the maximum space–time yield between the three types of reactor systems: a batch reactor, a mini-plant and a pilot plant. A comprehensive life-cycle assessment study of the synthesis of organometallic catalysts and their impact on the overall LCA of flow vs. batch syntheses was developed. Combined with a simplified economic analysis, the LCA study confirmed the benefits of switching to flow.
TL;DR: In this article, an automated system was used to screen steady-state conditions for offline analysis by gas chromatography to fit a reaction rate model, leading to more rapid determination of the reaction activation energy of the lower temperature regimes.
Abstract: Temperature, pressure, gas stoichiometry, and residence time were varied to control the yield and product distribution of the palladium-catalyzed aminocarbonylation of aromatic bromides in both a silicon microreactor and a packed-bed tubular reactor. Automation of the system set points and product sampling enabled facile and repeatable reaction analysis with minimal operator supervision. It was observed that the reaction was divided into two temperature regimes. An automated system was used to screen steady-state conditions for offline analysis by gas chromatography to fit a reaction rate model. Additionally, a transient temperature ramp method utilizing online infrared analysis was used, leading to more rapid determination of the reaction activation energy of the lower temperature regimes. The entire reaction spanning both regimes was modeled in good agreement with the experimental data.
TL;DR: In this paper, a microstructured falling film reactor was applied to the dye-sensitized photochemical conversion of 1,5-dihydroxynaphthalene to juglone.
Abstract: A microstructured falling film reactor was applied to the dye-sensitized photochemical conversion of 1,5-dihydroxynaphthalene to juglone. This continuous-flow microreactor enables the efficient contacting of a gas and a liquid phase in combination with external irradiation by high-power LED arrays offering various wavelengths. Two sensitizers were used for the photochemical in situ generation of singlet oxygen as key step in the synthesis of the natural product juglone. The photochemical process was investigated according LED wavelength, LED power, oxygen partial pressure, reactor architecture, substrate concentration and flow rate, and optimized to a conversion of X = 97% with 99% selectivity. Based on the experimental results process parameters like quantum efficiency, productivity and space time yield were calculated and used for the evaluation of the photochemically catalyzed synthesis of juglone in continuous-flow mode.
TL;DR: In this article, the development of the technical iron zeolite-based catalysts and the environmental and economic assessment of the process by life cycle analysis are addressed in view of a prospective industrial application.
Abstract: The gas-phase oxidation of glycerol over MFI-type iron zeolite catalysts comprises an attractive technology to prepare dihydroxyacetone with a high productivity, in contrast with the currently practiced biocatalytic system. Herein, we address two crucial aspects in view of a prospective industrial application, i.e., the development of the technical iron zeolite-based catalysts and the environmental and economic assessment of the process by life cycle analysis. Regarding the first task, we show that iron silicalite with the desired structural, acidic and catalytic properties can be prepared by hydrothermal synthesis at the kg-scale and using reagents meeting industrial safety, ecological and cost criteria. The design of suitable mm-sized bodies encompassed the use of shaping methods which minimise the introduction of additional acidity as well as iron clustering and migration from the zeolite to the binder phase. In this respect, silica outperforms kaolin as the binder, pelletisation and polyether-assisted extrusion are superior to water-based extrusion and the calcination and steam activation of the as-crystallised zeolite are preferably done after the forming step. The optimal technical catalyst displays equivalent activity, selectivity and stability to lab-scale pure iron silicalite powder in a 72 h test. From a life cycle perspective, all environmental indicators are drastically improved and the operating cost is halved using a chemocatalytic zeolite-based process for the preparation of high-purity dihydroxyacetone compared to the conventional enzymatic route. This is justified by the high atom economy of the transformation which reduces waste and by the minimisation of the energy input via heat integration and the use of less energy-intensive separation units to purify the substantially more concentrated outlet stream. Since the purity demand for the dihydroxyacetone feedstock to produce lactic acid is lower than that required in the cosmetic and polymer industries, a potential glycerol oxidation process for the former application has an even greater advantage in terms of greenness and cost.
TL;DR: A new reduction methodology to simplify the state-to-state kinetic model for carbon dioxide dissociation in non-thermal microwave plasma and its predictions regarding the concentrations of the heavy species in the afterglow zone are in good agreement with those of the detailed model from which the former was derived.
Abstract: Plasma reactor technologies have the potential to enable storage of green renewable electricity into fuels and chemicals. One of the major challenges for the implementation of these technologies is the energy efficiency. Empirical enhancement of plasma reactors' performance has proven to be insufficient in this regard. Numerical models are therefore becoming essential to get insight into the process for optimization purposes. The chemistry in non-thermal plasmas is the most challenging and complex part of the model due to the large number of species and reactions involved. The most recent reaction kinetics model for carbon dioxide (CO2) dissociation in non-thermal microwave plasma considers more than one hundred species and thousands of reactions. To enable the implementation of this model into multidimensional simulations, a new reduction methodology to simplify the state-to-state kinetic model is presented. It is based on four key elements: 1) all the asymmetric vibrational levels are lumped within a single group or fictitious species, , 2) this group follows a non-equilibrium Treanor distribution, 3) an algebraic approximation is used to compute the vibrational temperature from the translational temperature based on the Landau–Teller formula and 4) weighted algebraic expressions are applied, instead of complex differential equations, to calculate the rates of the most influencing reactions; this decreases substantially the calculation time. Using this new approach, the dissociation and vibrational kinetics are captured in a reduced set of 44 reactions among 13 species. The predictions of the reduced kinetic model regarding the concentrations of the heavy species in the afterglow zone are in good agreement with those of the detailed model from which the former was derived. The methodology may also be applied to other state-to-state kinetic models in which interactions of vibrational levels have the largest share in the global set of reactions.
TL;DR: In this article, photo-chlorination of C-H bonds was investigated by using a photo microreactor and gaseous chlorine in situ generated from HCl and NaOCl.
Abstract: Photo-chlorination of C–H bonds was investigated by using a photo microreactor and gaseous chlorine in situ generated from HCl and NaOCl. Under photoirradiation using a black light (15 W, 352 nm), chlorination of hydrocarbons proceeded smoothly within 1 min residence time to give chlorinated products in good yields.
TL;DR: In this article, a sustainable one-pot procedure for the transformation of carbohydrates into DFF was reported, where boric acid is mainly involved in depolymerization, isomerization and dehydration.
Abstract: 2,5-Diformylfuran (DFF) and 5-hydroxymethylfurfural (HMF) are interesting platform compounds in the chemical industry. A sustainable one-pot procedure is reported for the transformation of carbohydrates into DFF. Mono-, di- and polysaccharides as well as crude biomass (straw and bran) have been transformed. Depolymerisation, glucose isomerisation to fructose, fructose dehydration and finally oxidation of HMF to DFF are involved. The optimised catalytic system contains boric acid in DMSO for HMF synthesis. Addition of sodium bromide and formic acid to the reaction mixture leads to the formation of DFF. Boric acid is mainly involved in depolymerization, isomerisation and dehydration. Large amounts of boric acid lead to the degradation of HMF. NaBr and water are involved in the selective oxidation of HMF. Formic acid is involved in the dehydration step and it accelerates the oxidation of HMF.
TL;DR: In this article, a GaN quantum dot (QD) is prepared in a one-step continuous process using anhydrous solvents at supercritical conditions (and temperatures below 450 °C).
Abstract: GaN quantum dots (QDs) are prepared in a one-step continuous process using anhydrous solvents at supercritical conditions (and temperatures below 450 °C) in short residence times, typically less than 25 s. The as-prepared QDs exhibit a strong luminescence in the ultraviolet (λmax ~ 350 nm) in agreement with the synthesis of quantum-confined GaN nanoparticles.
TL;DR: In this article, three low-cost standard lab chemicals, formic acid, mesyl chloride and triethylamine, were used for instant carbon monoxide (CO) generation at room temperature.
Abstract: Three low-cost standard lab chemicals, formic acid, mesyl chloride and triethylamine, were used for instant carbon monoxide (CO) generation at room temperature. Subsequently this gas was implemented in palladium-catalysed aminocarbonylation chemistry. Moreover, 13C-enriched formic acid was used as one of the most economical CO precursors for 13C-carbonyl labelling.