Green and Sustainable Chemical Synthesis Using Flow Microreactors

Abstract

Several features that allow flow microreactors contribute to green and sustainable chemical synthesis are presented: (1) For extremely fast reactions, kinetics often cannot be used because of the lack of homogeneity of the reaction environment when they are conducted in batch macroreactors. Better controllability, by virtue of fast mixing based on short diffusion paths in microreactors, however, leads to a higher selectivity of the products, based on kinetics considerations. Therefore, less waste is produced. (2) Reactions involving highly unstable intermediates usually require very low temperatures when they are conducted in macrobatch reactors. By virtue of short residence times, flow microreactors enable performing such reactions at ambient temperatures, avoiding cryogenic conditions and minimizing the energy required for cooling. (3) By virtue of the precise residence time control, flow microreactors allow to avoid the use of auxiliary substances such as protecting groups, enabling highly atom- and step-economical straightforward syntheses. The development of several test plants based on microreaction technology has proved that flow microreactor synthesis can be applied to the green and sustainable production of chemical substances on industrial scales. (4) Microreactor technology enables on-demand and on-site synthesis, which leads to less energy for transportation and easy recycling of substances.

9.03 Organic Synthesis in Small Scale Continuous Flow: Flow Chemistry

“…The excellent thermal conductivity and high surface-to-volume ratio of microreactors are especially useful in studying extremely fast and exothermic reactions, and for the control of highly reactive, short-lived reactive intermediates. 30 Yoshida et al 31 have demonstrated such control by performing the enantioselective carbolithiations of conjugated enynes 2 with a chiral organolithium species 1, followed by the addition of the unstable intermediates 3 to various electrophiles, obtaining enantioenriched chiral allenes 4. Their microfluidic system consisted of three T-shaped micromixers (M1, M2, and M3) and three microtube reactors (R1, R2, and R3) ( Figure 8).…”

“…30 One such example is the Li-Br exchange reaction of p-dibromobenzene with n-BuLi. By carefully controlling residence times of each step using micromixers, sequential addition of lithiation and electrophiles was achieved ( Figure 33).…”

Integrated Micro‐Flow Synthesis Based on Photochemical Wolff Rearrangement

“…[10][11][12][13][14][15][16][17][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] (1) Precise control of short reaction times (<1 sec) can be achieved.…”

An integrated microfluidic chip enabling control and spatially resolved monitoring of temperature in micro flow reactors

“…Such miniaturized platforms are also very attractive as more sustainable and safe research and development platforms especially when working with hazardous or highly reactive compounds. Due to the minimal resource consumption and enhanced reaction rates of diffusionlimited processes [30][31][32][33], such microdevices are promising tools for fast optimization and investigation of chemical syntheses [34][35][36][37][38], such as catalyst screening.…”