Organosulfur compounds hydrodesulfurization

Although desulfurization is a process, which has been in use in the oil industry for many years, renewed research has recently been started, aimed at improving the efficiency of the process. Envii onmental pressure and legislation to further reduce Sulfur levels in the various fuels has forced process development to place an increased emphasis on hydrodesulfurization (HDS). For a clear comprehension of the process kinetics involved in HDS, a detailed analyses of all the organosulfur compounds clarifying the desulfurization chemistry is a prerequisite. The reactivities of the Sulfur-containing structures present in middle distillates decrease sharply in the sequence thiols sulfides thiophenes benzothiophenes dibenzothio-phenes (32). However, in addition, within the various families the reactivities of the Substituted species are different. 

During the early 1990s IGT collaborated with EBC to develop the BDS process. The combined results from the two companies produced a series of patents describing the process for desulfurization of fossil fuels [237-240], Compared with the patent described in the earlier paragraph [235], these later patents propose a more realistic approach to desulfurization. The basis of these patents is the fact that some of the organosulfur compounds in petroleum are not desulfurized during hydrodesulfurization (HDS), but may be susceptible to BDS. 

Whitehurst, Isoda, and Mochida write about catalytic hydrodesulfurization of fossil fuels, one of the important applications of catalysis for environmental protection. They focus on the relatively unreactive substituted di-benzothiophenes, the most difficult to convert organosulfur compounds, which now must be removed if fuels are to meet the stringent emerging standards for sulfur content. On the basis of an in-depth examination of the reaction networks, kinetics, and mechanisms of hydrodesulfurization of these compounds, the authors draw conclusions that are important for catalyst and process design. 

In addition, several metal-coordinated thials have been described in studies pertaining to hydrodesulfurization (HDS) reactions. This catalytic process is used to remove sulfur from organosulfur compounds present in fossil fuel feedstocks by reaction with hydrogen and a transition metal (Rh, Ir) and possesses both commercial and environmental importance393,394. 

The removal of sulfur from organosulfur compounds is an important catalytic reaction during petroleum refining [198, 199]. A test reaction for this process is the hydrodesulfurization of thiophene to butenes. Describe the process [209]. The removal of nitrogen from organonitrogen compounds is equally important. Describe the process [210]. 

Two approaches for desulfurization, namely, hydrodesulfurization (HDS) and sulfur removal by adsorption, are used with the former being the most mature technology. HDS is a catalytic hydrogenation process that removes sulfur from fossil fuels. In this process, tiie organosulfur compound such as ethanethiol (C2H5SH), a sulfur compound present in some petroleum products, is converted to H2S and sulfur-free organic compounds ethane (C2Hg) by reaction with H2 in the presence of a catalyst as shown below ... 

Deep desulfurization of diesel fuels is particularly challenging due to the difficulty of reduce aromatic sulfur compounds, particularly 4,6-dialkyldibenzothiophenes, using conventional hydrodesulfurization processes (HDS). The HDS process is normally only effective for removing organosulfur compounds of aliphatic and alicyclic types. The aromatic sulfur molecules including thiophenes, dibenzothiophenes (DBT), and their alkylated derivatives are very difficult to convert to H2S through HDS. 

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