Experimental methods in chemical engineering: Micro‐reactors

Abstract

Whereas the bulk chemical industry has historically sought economic advantage through economies of scale, a paradigm shift has researchers developing systems on smaller scales. Nano-cages and nano-actuators increase selectivity and robustness at the molecular scale. In parallel, micro-contactors with sub-millimetre lateral dimensions are decreasing boundary layers that restrict heat and mass transfer and thus meet the objectives of process intensification with great increases in productivity with a smaller footprint. These contactors continue to serve chemical engineers and chemists to synthesize fine chemicals and characterize catalysts; however, they have now been adopted for sensors in biological and biochemical systems. A bibliometric analysis of articles indexed in the Web of Science in 2016 and 2017 identified five major clusters of research: catalysis and bulk chemicals; nanoparticles; organic synthesis and flow chemistry; systems and micro-fluidics applied to biochemistry; and micro-channel reactors and mass transfer. In the early 1990s, less than 100 articles a year mentioned micro-reactors, while over 943 articles mentioned it in 2017. Here, we introduce micro-reactors and their role in the continuous synthesis of fine chemicals across the various scales to commercialization.

Experimental methods in chemical engineering: Residence time distribution—RTD

“…Pharmaceutical applications belong mostly to the blue cluster including drug delivery, cancer, in vivo, in vitro, tissue distribution, and skeletal muscle. Continuous flow chemistry has been applying RTD to monitor and optimize the contact time and design micro‐mixers …”

Process intensification connects scales and disciplines towards sustainability

“…Macchi et al [ 36 ] recently reviewed microreactor design, technical features, challenges, and points of technological uncertainty within the scope of continuous synthesis of fine chemicals and pharmaceuticals, ranging from laboratory applications to commercial scale. They observe that despite the fact that the pharmaceutical industry is increasingly applying flow chemistry technologies to the synthesis of their products, the commercial application of intensified/miniaturized continuous flow technologies remain limited mostly due to lack of information and technology.…”

“…In the literature there are several examples of reviews dedicated to PI that are technology specific. Examples include static mixers, [15][16][17] cavitational reactors, [18] flow reactors, [19][20][21][22][23][24] membrane gas separation and reactors, [25][26][27] intensified separations, [28,29] microengineered reactors, [30][31][32][33][34][35][36][37] microwave-assisted chemistry, [22,38,39] and low frequency ultrasound processes, [40][41][42] to cite a few. There are, however, fewer reviews on PI as an innovative approach to chemical engineering design in general, each focusing on different aspects of it.…”

Issue Highlights

“…We propose a toolbox concept to select reactor types in order to optimize reactive conditions and then scale up, with relative confidence, through the clinical phases of pharmaceuticals. Research in the field is concentrated into five clusters: catalysis and kinetics; nano‐particles; systems and microfluidics; chemistry and organic synthesis; and mass transfer and micro‐channels …”