Microreactors in Organic Chemistry and Catalysis, Second Edition (2013)

Ivana Dencic and Volker Hessel

9.1. Introduction

In traditional chemical engineering and organic synthesis, there is a large variety of reactors that can be utilized for gas–liquid and gas–liquid–solid reactions. This includes mechanically agitated tanks, slurry reactors, bubble, packed and spray columns, falling film, loop and trickle bed reactors and the less widespread static mixer, venturi, and spinning disk reactors [1, 2]. Microreaction technology is a new continuous processing concept with different types of reactors based on microengineered structures [3–25]. These extend the performance of conventional reactors especially in terms of enhanced mass and heat transfer, for example, to be used for fast, exothermic reactions, and safe operation under extreme processing conditions and with hazardous reagents. The hydrodynamics of gas–liquid microreactors are often characterized by uniform flow patterns such as the Taylor flow (see below and respective reviews [4, 26–28] and relevant scientific papers [29–40]). Some gas–liquid microreactors are just miniaturized analogs of their macroscale counterparts, for example, the falling film microreactor, whereas others offer entirely new multiphase contacting concepts, for example, the Taylor-flow or mesh microreactors.

In the following, some major contacting principles will be given first accompanied by realized reactor examples. Then, the application of the microreactors for gas–liquid and gas–liquid–solid reactions in the field of organic chemistry is presented and will cover the major part of this chapter. Information on hydrodynamics, mass transfer, kinetics, modeling, and other applications have been given elsewhere (see e.g., Refs [4, 26–28] and original citations given therein) and do not fall under the umbrella of this book.