(454d) Ozonolysis in Liquid CO2 As a Platform for Processing of Distributed Feedstocks

Given its high oxidation potential, there has been extensive interest in the use of ozone as an oxidant in the synthesis of various chemicals. Surging interest in making chemicals from biomass feedstocks has generated renewed interest in ozone as an oxidant. The ability to produce ozone on site is well aligned with the distributed biorefinery concept and eliminates problems associated with biomass transport and storage. However, wider application of ozone in industrial processes has been tempered by safety concerns often associated with ozonolysis.

We demonstrate a continuous reactor for performing safe ozonolysis of fatty acid methyl esters (FAMEs) using liquid CO₂ as solvent. The rapid nature of the reaction allows the use of small-volume reactors to completely convert the FAMEs, forming secondary ozonides as the primary products. The short residence times also help maximize the yields of the secondary ozonides by minimizing over-oxidation and the formation of oligomeric products. The liquid CO₂ medium promotes safe reactor operation by providing an essential fraction of overall reactor cooling and by diluting the vapor phase organics. We also demonstrate a continuous stirred reactor for the safe thermal decomposition of the secondary ozonides to their corresponding acids and aldehydes. Using a lumped kinetic model for the thermal decomposition of the ozonolysis products, we estimate activation energy values of 108.6±0.6 kJ mol^-1 for the decomposition of secondary ozonides and 122±3 kJ mol^-1 for the decomposition of the undesired oligomeric species.

The extension of this concept for valorizing lignin and stranded gas sources (such as natural gas liquids) will also be discussed.