SBIR-STTR Award

This proposal is concerned with the economic removal of hydrogen sulfide, a toxic material, from sour natural gas and petroleum products.The current status of H2S processing is reviewed. The chemistry of sulfur and sulfide in aqueous solutions and preliminary work already carried out in the continuous electrolysis of H2S to yield hydrogen and sulfur are briefly discussed. The estimated economic gains in H2S removal treatments by the co-production of hydrogen are described, and the economics of thermal and electrochemical processes for H2S removal are compared.Research is proposed, that will lead to the development of a viable and efficient process for the production of hydrogen and sulfur by the electrolysis of H2S in aqueous solutions. The research proposed involves electrode kinetic studies, photoelectrochemical splitting of H2S, laboratory scale electrolysis, and the development-of a bench scale demonstration unit for the production of S and H2 from gas mixtures with H2S.

In the Phase I of the present work on the purification of H2S poisoned natural gas streams, a discovery was made: the difficulty earlier associated with application of the electrolytic method to H2S removal (formation of a non-conducting sulfur film on the anode) is not present in 5 molar NAOH solutions at temperatures over 600 C. The discovery opens the way to the continuous electrolytic removal of H2S, with by-products H2 and S. The Phase II work will have a main goal of design, construction, and operation of a flow cell for electrolysis at the pilot plant level. Flow patterns through the cell will be calculated and observed. Nickel sponge electrodes will be developed. Research is planned in the development of cathodes which are not poisoned by the sulfur ions, flow-through anodes, the construction of porous electrodes with a range of porosity, pore size distribution, tortuosity, specific area and thickness, identification of ions in solution and kinetics of sulfur formation from alkaline solutions. Techniques to be applied involve electrolysis, modeling, cyclic voltammetry, pressure pulse and temperature pulse methods, in-situ techniques (e.g., FTIR), ellipsometry and UV-Vis spectroscopy and ion-chromatography and -Raman spectroscopy to follow the formation of polysulfide ions and their decomposition to sulfur. The proposal contains a comparison of construction and operating costs of a comparable Claus plant with one involving the present process. It now seems certain that the process will give rise to purification of gas streams containing H2S with substantial profits. During the year, the incoming new data will be used to update these cost estimates at monthly intervals. These cost estimates will be developed for the plants at the lkW level.