Conversion of hydrogen sulfide into hydrogen and sulfur

H₂S removal from natural gas or from gases produced by the petroleum industry typically involves air oxidation of H_S into elemental sulfur and water. The rate of the anthraquinone reduction and sulfur formation reaction in the first stage of the Hysulf^SM process was studied. Details of the 2-tert-butylanthraquinone (TBAQ) to H₂TBAQ reaction mechanism were studied using cyclic voltammetry and an electrochemical cell. When the H₂S concentration was maintained constant through out the test, the rate was dependant only on the TBAQ concentration and a plot typical of a first order reaction was obtained. Computational analysis and reaction data suggested that the initial step of the reaction requires the anthraquinone diradical and the formation of an HS^- species. The formation of these species is necessary to provide a good match between the TBAQ LUMO and HS^- HOMO energy levels. Solvent polarity was not the primary factor that affected the TBAQ conversion. The ability of the solvent to complex with the H₂S and/or the TBAQ to alter their respective HOMO and LUMO energy levels might be a requirement. Tertiary amides, e.g., N-methyl-2-pyrrolidinone or N,N-dimethylacetamide, are better solvents for TBAQ reduction than secondary amides, cyclic ethers, alcohols, or lactones. This is an abstract of a paper presented at the ACS Fuel Chemistry Meeting (Washington, DC Fall 2005).