Some hydrocarbons, such as crude oil and jet fuel, contain significant amounts of mercaptans which may have an impact on the value of these hydrocarbon streams. As a result, such hydrocarbon streams are usually sold at a discount in the market or have to be upgraded to meet product spec. Thus, reducing the mercaptan content could substantially improve both the marketability and the value of such hydrocarbons.
Various additives have been employed for the removal of sulfur compounds from hydrocarbon streams (“sweetening” process). Conventional methods in the prior art for removing mercaptans from hydrocarbons typically involve “sweetening,” wherein mercaptans are oxidized to form disulfides. Light mercaptans (C1-C4) may be removed in an aqueous wash in this process but removal of heavy mercaptans (C4+) is less effective due to the poor water solubility of heavy mercaptans. Disulfides which are derived from heavy mercaptans may decompose back to mercaptans at high temperatures, for example, during the distillation process. U.S. Pat. No. 7,914,669 discloses a process to reduce sulfur from liquid hydrocarbon with an agent select from hypochlorites, cyanurates and alkali metal and alkaline earth metal hydroxide.
After treatment with an oxidant such as hypochlorite as disclosed in the prior art, the treated crude product may not be suitable for downstream processing with a high inorganic content in the treated crude. Additionally, transportation of fresh bulk chlorine to distant sites for crude treatment (as well as the removal of waste chlorine after treatment) is a major safety concern since the transport of chlorine gas under high pressure can be very hazardous. The transportation of commercial hypochlorite, which is predominantly water, is very expensive due to stringent regulations to prevent accidental releases.
There is still a need for an improved and effective process for the removal of sulfur containing compounds such as mercaptans from crudes. There is further a need for an integrated system for the removal of mercaptans with minimal chlorite to waste treatment.