(311b) Development, Control and Modelling of a Scalable Continuous Manufacturing Process for Multiphase Oxidations

In the production of pharmaceuticals and fine chemicals, most reactions are conducted homogeneously in one phase, and typically require additional operations (known as 'work up') to separate the product from byproducts and any remaining starting materials and catalysts at the end of the reaction. Work up/separation procedures can be complicated and time-consuming, and can constitute 40-70% of the costs of chemical processes. They also consume additional resources (energy, materials, solvent, etc.), which is detrimental to the environment [1].

Herein we discuss the design and development of a new type of fully integrated continuous process for multiphase oxidations at scale. Inorganic oxidants are generated electrochemically in an aqueous phase from non-hazardous inorganic salts [2]. The aqueous oxidant solution is subsequently dispensed to mix with reactants in an organic solvent forming a liquid/liquid reactive flow. An unstable emulsion is generated from the reactive flow using either a surface membrane module or a high shear mixer in a recirculation loop. The unstable emulsion is fed forward in to a continuously pulsed flow system as a way of overcoming mass transport limitations by enhancing liquid/liquid interactions [3] and maintaining the emulsion in a kinetically dispersed state. After an appropriate residence time the emulsion is eluted into a coalescence column allowing for a facile separation of the two phases. The aqueous phase is retained and recycled back to the electrochemical cell whereas the organic phase is collected for product analysis, simplifying the workup procedure.

The experimental mini-plant is supported by a predictive multiphase model that has been developed to incorporate different time constants (residence time, droplet formation and coalescence rates as well as intrinsic reaction rates) in order to identify appropriate operating regimes for any given oxidation process.

 

References

[1] Adler, S., et al., Vision 2020: 2000 Separations Roadmap. 2000, American Institute of Chemical Engineers: New York. 1-99.

[2] Zhu, J., K.K. Hii, and K. Hellgardt, Toward a Green Generation of Oxidant on Demand: Practical Electrosynthesis of Ammonium Persulfate. ACS Sustainable Chem. Eng., 2016. 4(4), 2027-2036.

[3] Holdich, R.G., et al., Continuous Membrane Emulsification with Pulsed (Oscillatory) Flow. Ind. Eng. Chem. Res., 2013. 52(1), 507-515.

 

Acknowledgements

The work is supported by EPSRC grants EP/L012278/1 and EP/L011697/1.