A solvent-free alternative for green liquid-liquid biphasic oxidations

Abstract

The work contained within this thesis presents a multidisciplinary method for the integrated reaction and separation of a liquid-liquid biphasic system. The area of multiphase liquid reactions is traditionally addressed through use of a solvent system to achieved mutual dissolution. However, the removal of such solvents in downstream processing often entails a high energy cost. This research investigated the potential to perform these reactions, specifically between oil and aqueous phases, without a solvent, thereby negating the downstream removal cost. The method presented in this thesis proposes the rate limiting step of the liquid-liquid reaction be determined, specifically the relationship between interfacial surface area and rate of reaction. The use of high shear homogenisation, microfluidic and capillary based droplet creation methods enabled a range (3.9 – 9.6x10-4 m2.g-1) of oil-aqueous interfacial areas to be formulated. The rate limiting step of a model reaction, the epoxidation of sunflower seed oil with an aqueous solution of hydrogen peroxide, sodium tungstate and a carboxylic acid, was dependent on the interfacial surface area, but only when less than 0.25 m2.g-1. At oil-aqueous areas in excess of this the reaction system was rate limited by the aqueous phase formation of active catalyst species, a peroxotungstate. The design and construction of a continuous membrane reactor based on the rate of reaction information was carried out. By operating under conditions such that an interfacial surface area in excess of 0.25 m2g-1 was maintained, the biphasic system was successfully reacted on large scale (5 L), and critically the inherent immiscibility of the oil-aqueous system allowed for the facile downstream separation of phases. Therefore this research presents an approach to achieve the non-mass transfer limited reaction and downstream separation of a liquid-liquid biphasic system without the use of solvents.

Date of Award	4 Jun 2014
Original language	English
Awarding Institution	University of Bath
Supervisor	Laura Torrente Murciano (Supervisor) & Janet Scott (Supervisor)