Sorbents for Desulfurization of Refinery Off-Gases

Many refinery off-gases are sent to flare, which contributes to energy loses and greenhouse gas emissions. Instead, these off-gases could be converted into valuable chemicals such as hydrogen. However, the production of hydrogen uses a nickel-based steam reforming catalyst, which would be poisoned by the large concentrations of sulfur contained in refinery off-gases. Traditionally, the sulfur has been removed by a two-step process: hydrodesulfurization (HDS) and subsequent removal of H2S with an expendable metal oxide absorbent. However, the one-time use of expendable metal oxide sorbents is not practical, because the high sulfur levels in refinery off-gases require high quantities of the expensive sorbent (in contrast to the two-step process for natural gas feedstocks, where the sulfur level does not exceed 5-10 ppmv). This project will develop a regenerable physical adsorbent to desulfurize refinery off-gases. The sorbent will operate at near ambient temperatures (20-60oC) while reducing the sulfur content of the gas stream to less than ppmv levels (with reduction to ppb levels, if needed), thereby protecting the catalyst used in the downstream conversion process. The sorbent will be regenerated by applying a mild temperature swing. Because the sorbent can effectively remove not only H2S but also organic sulfur compounds, the need for the very expensive HDS process will be eliminated. Commercial Applications and other Benefits as described by the awardee: The sorbent technology should provide US refiners with a cost-effective way to remove sulfur from refinery off-gases. The sorbent also can be applied to desulfurize any light hydrocarbon stream that is used as a feedstock for catalytic chemical conversion or as a feed for a fuel cell.