Process Intensification of Continuous-Flow Imine Hydrogenation in Catalyst-Coated Tube Reactors

Expósito, A.J.; Bai, Yang; Tchabanenko, Kirill; Rebrov, Evgeny V.; Cherkasov, Nikolay

doi:10.1021/acs.iecr.8b06058

Cited by 15 publications

(15 citation statements)

References 72 publications

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“…The coating of microreactors, as above, or tubular reactors [43,44] is a common strategy to promote heterogeneous reactions without feeding the solid continuously into the reactor. However, this requires considerable preparation and analysis time to immobilize the catalyst.…”

Section: Trends In Chemistrymentioning

confidence: 99%

Flow Photochemistry: Shine Some Light on Those Tubes!

Sambiagio

Noël

2020

Trends in Chemistry

313

223

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Continuous-flow chemistry has recently attracted significant interest from chemists in both academia and industry working in different disciplines and from different backgrounds. Flow methods are now being used in reaction discovery/methodology, in scale-up and production, and for rapid screening and optimization. Photochemical processes are currently an important research field in the scientific community and the recent exploitation of flow methods for these methodologies has made clear the advantages of flow chemistry and its importance in modern chemistry and technology worldwide. This review highlights the most important features of continuous-flow technology applied to photochemical processes and provides a general perspective on this rapidly evolving research field. Microflow Technology and Photochemistry: A Perfect MatchThe use of light to promote chemical reactions has been exploited since the 18th century, but only recently a resurgence has been observed in synthetic organic chemistry, in particular due to the development of visible-light photoredox catalysis [1-5]. All transformations involving light (e.g., Figure 1A-D) must consider, besides classical chemical parameters (i.e., reaction conditions), the photophysical aspects of the sensitizer (see Glossary)/photocatalyst (when used), and the reactor design. The latter, although often neglected by chemists, is a critical aspect for the outcome of the studied chemical transformation. This includes, for example, the size, shape, and material of the reaction vessel, the characteristics and positioning of the light source(s), and heat-transfer properties, particularly when high-intensity lamps are used [6,7]. The engineering and technological aspects of photochemical processes are often at the basis of the irreproducibility and non-scalability of such transformations.According to the Beer-Lambert law, light transmittance decreases exponentially with the distance from the light source ( Figure 1F). For a standard batch reactor (diameter at least in the centimeter range), light intensity decreases considerably from the flask walls to the middle of the reaction mixture, resulting in slow reactions and nonhomogeneous irradiation of the reaction mixture. Performing photochemical reactions in microchannels (ID < 1 mm) allows a higher and more homogeneous photon flux, resulting in shorter reaction times and consequently less side-product formation due to over-irradiation, often observed in batch [8,9]. Another advantage of microflow chemistry, correlated with the large surface:volume ratio, is improved heat and mass transfer, with the possibility to perform mass-transfer-limited multiphasic reactions efficiently [10]. Reactive chemicals and intermediates can be handled more safely in flow than in batch, as no accumulation of dangerous components occurs within the confined reactor volume due to the continuous nature of the process. Together, these result in often faster, safer, and higher-yielding reactions, with the possibility to perform reactions under condition...

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Section: Trends In Chemistrymentioning

confidence: 99%

Flow Photochemistry: Shine Some Light on Those Tubes!

Sambiagio

Noël

2020

Trends in Chemistry

313

223

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“…Several methodologies have been developed to obtain secondary amines via N-alkylation of primary amines with alkyl halides 6 or alcohols, [6][7][8][9] Buchwald-Hartwig reaction, 10,11 and reductive amination of carbonyl compounds. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Among all these transformations, reductive amination over heterogeneous metal catalysts is a promising method due to the use of inexpensive and environmentally benign molecular hydrogen as a reducing agent. [15][16][17][18][19][20][21][22][23][24][25][26] This process involves reversible condensation of primary amine with aldehyde or ketone to form imine and the hydrogenation of imine into the secondary amine.…”

Section: Introductionmentioning

confidence: 99%

“…When the reaction is carried out in one step, the initial carbonyl compound is partially hydrogenated to alcohol on the catalyst surface, which decreases the yield of the target product. [24][25][26] However, this drawback can be overcome by two-stage synthesis with imine formation on the first stage in the absence of the catalyst.…”

Section: Introductionmentioning

confidence: 99%

“…Potential benefits of continuous flow synthesis over traditional batch protocols include excellent interfacial mass and energy transfer properties, suppression of by-product formation through a better control over reaction parameters, simplified scaling, lower operational costs, and improved process safety. [27][28][29][30] In general, the continuous reductive amination is realized in the presence of noble metal-based catalysts, such as Pd(OH) 2 /C, 19,31,32 Pd/C, 19,24,25,31,32 Pt/C, 19,24,32 and gold nanoparticles immobilized into a mesoporous silica. 13 The replacement of these elements with inexpensive and abundant alternatives is highly desirable.…”

Section: Introductionmentioning

confidence: 99%

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Cu‐Al mixed oxide derived from layered double hydroxide as an efficient catalyst for continuous‐flow reductive amination of aromatic aldehydes

Nuzhdin

Bukhtiyarova

2020

J of Chemical Tech & Biotech

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BACKGROUND: Secondary amines are important intermediates in the manufacture of pharmaceuticals and other valuable chemicals. Hence, there is a continuing interest in cost-effective and environmentally friendly methods for producing these compounds. Reductive amination of aldehydes or ketones with primary amines over heterogeneous metal catalysts is an attractive approach due to the use of inexpensive and environmentally benign molecular hydrogen as a reducing agent. RESULTS: Various secondary amines were obtained by two-step reductive amination of benzaldehyde derivatives and furfural with primary amines. The condensation of aromatic aldehydes with amines at room temperature in low water methanol gives imines, which are then hydrogenated in a flow reactor over CuAlO x catalyst derived from layered double hydroxide. This process does not require isolation and purification of intermediate imines and can be utilized to obtain several secondary amines in good to excellent yield. The time-dependent study showed that CuAlO x catalyst demonstrates excellent stability in imine hydrogenation. CONCLUSION: An environmentally friendly procedure has been developed for the synthesis of secondary amines through a reductive amination of aromatic aldehydes with primary amines over Cu-based catalyst. This procedure presents a novel way for the sustainable production of secondary amines.

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“…For instance, Jia et al described the development of the ruthenium-catalyzed hydrogenation method for the reduction of imine intermediates to obtain amine monomers [37]. Exposito et al recently developed the imine Pd-catalyzed hydrogenation using the industrial continuous-flow process, thanks to a Pd/C support, which was stable over multiple reaction–regeneration cycles [38].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Pluri-Functional Amine Hardeners from Bio-Based Aromatic Aldehydes for Epoxy Amine Thermosets

Mora

Tayouo²,

Boutevin

et al. 2019

Molecules

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Most of the current amine hardeners are petro-sourced and only a few studies have focused on the research of bio-based substitutes. Hence, in an eco-friendly context, our team proposed the design of bio-based amine monomers with aromatic structures. This work described the use of the reductive amination with imine intermediate in order to obtain bio-based pluri-functional amines exhibiting low viscosity. The effect of the nature of initial aldehyde reactant on the hardener properties was studied, as well as the reaction conditions. Then, these pluri-functional amines were added to petro-sourced (diglycidyl ether of bisphenol A, DGEBA) or bio-based (diglycidyl ether of vanillin alcohol, DGEVA) epoxy monomers to form thermosets by step growth polymerization. Due to their low viscosity, the epoxy-amine mixtures were easily homogenized and cured more rapidly compared to the use of more viscous hardeners (<0.6 Pa s at 22 °C). After curing, the thermo-mechanical properties of the epoxy thermosets were determined and compared. The isophthalatetetramine (IPTA) hardener, with a higher number of amine active H, led to thermosets with higher thermo-mechanical properties (glass transition temperatures (Tg and Tα) were around 95 °C for DGEBA-based thermosets against 60 °C for DGEVA-based thermosets) than materials from benzylamine (BDA) or furfurylamine (FDA) that contained less active hydrogens (Tg and Tα around 77 °C for DGEBA-based thermosets and Tg and Tα around 45 °C for DGEVA-based thermosets). By comparing to industrial hardener references, IPTA possesses six active hydrogens which obtain high cross-linked systems, similar to industrial references, and longer molecular length due to the presence of two alkyl chains, leading respectively to high mechanical strength with lower Tg.

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Process Intensification of Continuous-Flow Imine Hydrogenation in Catalyst-Coated Tube Reactors

Abstract: Please refer to published version for the most recent bibliographic citation information. If a published version is known of, the repository item page linked to above, will contain details on accessing it.

Cited by 15 publications

References 72 publications

Flow Photochemistry: Shine Some Light on Those Tubes!

Flow Photochemistry: Shine Some Light on Those Tubes!

Cu‐Al mixed oxide derived from layered double hydroxide as an efficient catalyst for continuous‐flow reductive amination of aromatic aldehydes

Synthesis of Pluri-Functional Amine Hardeners from Bio-Based Aromatic Aldehydes for Epoxy Amine Thermosets

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