Perperi, Evangelia; (2004) A novel continuous homogeneous catalytic process for flourous biphasic systems. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Homogeneous catalysts can provide very high activity and selectivity towards industrial desirable products at relatively mild conditions, but their commercialisation has been so far hampered by the problem of their separation from reaction mixture and solvent and hence the difficulties associated with their recycling. To overcome this problem a new concept of fluorous biphasic homogeneous catalysis has been developed to facilitate the separation and recycling of the catalyst. In these systems the catalyst is dissolved in a fluorous solvent. Under ambient conditions the fluorous phase is immiscible with the organic one containing the reaction components, facilitating catalyst separation and recycling. At reaction conditions only one phase is formed allowing excellent contact between substrate and catalyst and eliminating mass transfer limitation. This is a generic technology with high potential for industrialisation that is applicable to a wide variety of homogeneous catalytic systems. In this work a continuous reaction system is developed, which includes a chemical reactor that is connected via a heat exchanger with a gravity settler, where from the catalyst phase is continuously recycled to the reactor. The work is focused on the hydroformylation of higher alkenes, a reaction system of great industrial importance. The liquid - liquid equilibrium of the fluorous solvent - organic phase was studied. A proof of concept separation study in a continuous system was also carried out demonstrating the efficiency of the separation of the two phases. Finally, reaction studies were carried out in the presence of a fluorous modified rhodium catalyst. Conversion levels up to 70% were observed, with linear to branched product ratios being around 12, while the fluorous catalyst was successfully recycled to the reactor. Efficient stirring was essential for high conversions for minimising alkene isomerisation. Leaching of the ligand, rhodium and the fluorous solvent into the organic product phase was significant.

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