While many organic compounds are commonly synthesized using high temperature, high pressure, and/or catalytic processes, the application of low temperature electric discharge plasma processes to perform organic synthesis has the potential to improve energy efficiency and to affect chemical selectivity and yield through spatial and temporal control of the plasma. In order to introduce functionality into hydrocarbons, for example OH groups, this project deals with reactions initiated in low temperature plasma exposed to small droplets of organic liquids. This work will advance our understanding of organic gas-liquid reactions in electrical discharge plasma where the liquid droplets are exposed to the plasma environment under ambient temperature and pressure conditions such that they are not evaporated. The research involves the synthesis of a wide range of organic compounds starting with saturated and unsaturated hydrocarbon liquids that are sprayed into the reactor as small droplets. The pure organic droplets will flow into the low temperature and low power plasma where vapor and interfacial reactions occur. In the case of saturated hydrocarbons, hydroxylation reactions to form alcohols will be investigated with emphasis on hydrocarbons with 6 to 10 carbons. Hydroxyl radicals will be formed from small amounts of water and or hydrogen peroxide vapors added to the flowing gas stream. In the case of unsaturated hydrocarbons hydrogenation reactions will be investigated with hydrogen mixed in an argon carrier. Unsaturated hydrocarbons with 6 to 10 carbons as well as selected oils will be studied. In both cases selectivity and yields will be analyzed as functions of the various reactor properties including gas and liquid flow rates and composition, pulsed input power and frequency, and electrode geometry. The general working hypothesis that will be tested and analyzed is that reaction selectivity and yield for plasma reactions of organic compounds from organic liquid droplets can be controlled through variation of plasma and reactor operating conditions. It is anticipated that the reaction products that are soluble in the organic liquid phase will be favored through a mechanism found previously for hydrogen peroxide generation from liquid water droplets whereby liquid soluble products preferentially accumulate in the liquid phase where they are protected from plasma degradation in the surrounding gas. In general, the project seeks to develop a new way to introduce functionality into organic compounds in the liquid phase through spatial and temporal control of the plasma.
This project will develop fundamental knowledge on how plasma in gas-liquid environments leads to the formation of various synthetic organic compounds. Understanding of how such reactions occur is important for the design and operation of chemical reactors that can be used in practical applications to make many useful compounds. For example various alcohols can be made from hydrocarbons in such systems, and this work will have impact on a range of other applications of plasma processes used in material and chemical synthesis and fuels processing. This work is expected to lead to significant advances in our understanding and further development of plasma chemistry with potential impact on the production of valuable organic compounds efficiently from various liquid hydrocarbon sources.
