Intensified reactors for gas-liquid-liquid multiphase catalysis: From chemistry to engineering

Biphasic liquid-liquid and particularly gas-liquid-liquid (GLL) environments are used in many chemical transformations performed by homogeneous catalysts where they have proven very effective for catalyst recycling, greatly improving the economy of using costly organometallic catalyst complexes such as for hydroformylation. Reacting GLL systems suffer from mass transfer limitations, for which intensified contacting is necessary to enhance the reaction rate. To tackle this issue, process intensified reactors have been designed and developed throughout the years to create large interfacial areas and high mass transfer coefficients. Apart from the classic continuously stirred tank reactor, setups like static mixer reactors, ejector loop reactors, and microreactors are promising alternatives that have gained momentum throughout the last years. This critical review covers the basic aspects of GLL mass transfer and a discussion on a number of reactions in this type of environment. More extensively, the current state of the art of contacting equipment for intensified GLL operation is described, including aspects of reactor design and correlations for different operating conditions.