Organic synthesis with continuous flow water film pulsed plasma discharge

Abstract

Plasma discharges generated by moderate frequency, low energy pulses in a flowing carrier gas with liquid water have been shown capable of producing hydrogen peroxide at moderately high energy yields. The leading hypothesis for the success of this production method is that free elections produced by the plasma in the gas phase dissociate vaporized water molecules into hydroxyl radicals and hydrogen. The hydroxyl radicals rapidly react to form hydrogen peroxide, which is sequestered into the liquid phase. Many reactor designs have been explored with various gas-liquid contact schemes in order to enhance the overall efficiency of this process. Recently, a continuously flowing, liquid film, pulsed plasma reactor has been developed in our laboratory which has a number of significant benefits over the previously explored configurations. Using this novel reactor configuration in conjunction with inspiration and techniques developed from work with pure water, the main objective of our current research is to explore the synthesis of organic compounds with soft oxidation by hydroxyl radicle attack. To do so, small amounts of organic solvent are vaporized into the plasma where they undergo electron attack and oxidation by hydroxyl radicals formed from water to generate more useful chemical species. Results with n-hexane and cyclohexane show that alcohol, aldehyde, and ketone products can be successfully generated. A significant amount of hydrogen peroxide is also generated in conjunction with the oxygenated products. It has also been found that selectivity of the reaction products is affected by variation of the water flow rate, organic to water ratio, and choice of parent compound. In this presentation we will report on recent experiments in our laboratory which utilize this continuously flowing water film reactor for the chemical synthesis of organic compounds and will focus on how the choice of organic parent compound can affect the distribution and selectivity of reaction products.