Johannes Claußnitzer, M.Sc.
Oxidative desulfurization of liquid gasoline with homogeneous Polyoxometalate catalysts
Distribution coefficients of organic Sulphur compounds
between a water and an isooctane phase
Crude oil is a complex mixture of different hydrocarbons, which were formed during the decomposition process of organic material. For that reason crude oil can contain considerable amounts of Sulphur (depending on the geographical origin) in the form of organic Sulphur compounds. During the combustion process (e.g in a car), those Sulphur compounds are converted to SOx and are emitted to the environment, causing harm to both human health and environment. The actual Sulphur level allowed in gasoline within the EU is 10ppmw. Thus Ultra-Deep-Desulfurization is required by removing the organic Sulphur compounds selectively. This is industrially done by Hydrodesulphurization (HDS). At a typical H2-pressure of 30 bar and temperatures from 580 to 640 K, especially alkylated Dibenzothiophene cannot be removed properly, thus leading to even higher pressures and temperatures. Since those process conditions as well as the high hydrogen recycle stream are undesired, alternative desulfurization techniques are of big interest.
Oxidative Desulfurization seems to be a promising alternative, since the above mentioned disadvantages are avoided. With this new concept, organic Sulphur compounds are oxidatively cleaved, extracting the products immediately from the organic phase. As catalyst water soluble Polyoxometalates are used. The organic matrix is well mixed with the aqueous POM-catalyst solution, facilitating the reaction. Under oxygen rich condition the Polyoxometalate is reoxidised. Advantages are the mild reaction conditions as well as the direct extraction of reaction products (mainly sulfate) from the organic phase.
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