Chemical mechanisms in hydrogen sulfide decomposition to hydrogen and sulfur

Abstract

Hydrogen sulfide (H2S) conversion into hydrogen (H2) and sulfur was previously investigated using oxidation/reduction chemistry. First, H2S was reacted with 2-t-butylanthraquinone (TBAQ) in a process solvent to form the hydroquinone (HTBAQH) and atomic sulfur. Sulfur was then polymerized into its ring form (S8) for recovery from the process solvent. These first two reactions were aided by a sulfur complexing agent (SCA). Then, HTBAQH was dehydrogenated using a heterogeneous catalyst. In the current work, computational chemistry using semi empirical methods was used to determine the detailed chemical steps occurring through S8 formation. It was found that the process solvent stabilizes the diradical form of TBAQ and the SCA splits H2S into an ion pair. These two mechanisms assisted in the transfer of two electrons and two protons from H2S to TBAQ to form HTBAQH and atomic sulfur. The sulfur atom was computationally shown to be a diradical stabilized by one or two molecules of the complexing agent. Also, sulfur polymerization was computationally shown to be diradical in nature with the growing polymer chain being terminated by one or two SCA.