Patent EA-005298-B1 (EA)
Title: Process for removing low amounts of organic sulfur from hydrocarbon fuels
Inventor: RAPPAS ALKIS S
IPC: C10G19/02
Filed: 2001-08-03
Abstract: 1. A process for removing sulfur compounds from hydrocarbon fuels, comprising the steps of: contacting the sulfur containing fuel with an aqueous oxidizing solution comprising hydrogen peroxide and formic acid in a mole ratio of at least about 11:1 formic acid to hydrogen peroxide and having less than about 25 wt % water, in an amount such that the hydrogen peroxide present is greater than about two times the stoichiometric amount required to convert the sulfur compounds present to corresponding sulfones, at a temperature of from about 50 degree C to about 130 degree C to form a hydrocarbon fuel phase from which sulfur has been removed and an aqueous phase containing oxidized sulfur extracted from the hydrocarbon fuel phase; separating the aqueous phase containing the extracted sulfur compounds from the hydrocarbon fuel phase; and recovering the hydrocarbon phase containing the fuel having reduced sulfur content. 2. The process of claim 1 wherein the mole ratio of formic acid to hydrogen peroxide is from about 20:1 to about 60:1. 3. The process of claim 1 also including the steps of: flashing the aqueous phase to separate the formic acid and water from the oxidized sulfur compounds; distilling the aqueous phase to remove water from the acid; and recovering the acid. 4. The process of claim 3 also including the step of recycling the recovered acid as part of the acid to use in the aqueous oxidizer solution. 5. The process of claim 1 wherein the formic acid is present in the oxidizing solution in an amount of from about 75 wt % to about 92 wt %, and the hydrogen peroxide is present in an amount of from about 0.5 wt % to about 4 wt %. 6. The process of claim 1 wherein the oxidation step occurs in less than about 15 minutes contact time. 7. The process of claim 1 wherein the amount of the oxidizing solution added is sufficient to provide a stoichiometric excess of from about 2 to about 4 times the amount required to oxidize the sulfur present. 8. The process of claim 7 wherein the stoichiometric excess is from about 3.0 to about 3.3 times the amount required to oxidize the sulfur present in the hydrocarbon fuel. 9. The process of claim 1 including the further step of: treating the recovered hydrocarbon phase with a sufficient quantity of calcium oxide to neutralize any residual acid therein; and separating the neutralized fuel from the calcium oxide. 10. An oxidizer/extractor composition for oxidizing organic sulfur compounds, and during such oxidation, extracting the oxidized organic sulfur compounds from hydrocarbon fuels having less than about 1500 ppm<-1> sulfur calculated as the benzothiophene, which comprises: from about 0.5 % to about 3.5 % hydrogen peroxide; from about 75 wt % to about 92 wt % formic acid; and water in an amount not to exceed about 25 wt %. 11. The composition of claim 10 wherein the composition comprises from about 2 wt % to about 3 wt % hydrogen peroxide, from about 79 wt % to about 89 wt % formic acid, and from about 8 wt % to about 20 wt % water wherein the molar ratio of the formic acid to the peroxide is from about 20:1 to about 60:1. 12. A process for removing sulfur compounds from diesel fuel comprising the steps of: contacting the diesel fuel at a temperature of from about 90 degree C to about 105 degree C for a period of time up to about 15 minutes with an oxidizing solution comprising: from about 79 wt % to about 89wt % formic acid, from about 2 wt % to about 3 wt % hydrogen peroxide, and from about 8 wt % to about 14 wt % water: in an amount such that the molar ratio of formic acid to hydrogen peroxide is from about 20:1 to about 60:1, wherein the amount of oxidizing solution added is such that there is a stoichiometric excess of hydrogen peroxide necessary to oxidize the sulfur present in the diesel fuel in an amount of from about 2.5 to about 3.5 times the amount needed to oxidize the sulfur in the fuel; extracting, during the oxidizing step, the oxidized sulfur compounds from the diesel fuel into the aqueous oxidizing solution to form a hydrocarbon phase and an aqueous phase; separating the aqueous phase containing the extracted sulfur compounds from the hydrocarbon fuel phase; neutralizing any residual acid in the fuel; recovering the neutralized diesel fuel containing less than about 25 ppm sulfur; and recovering the formic acid from the aqueous phase. 13. The process of claim 12 wherein the formic acid is recovered by the additional steps of: flashing the aqueous phase to separate the formic acid and water from the oxidized sulfur compounds as an overhead stream; distilling the overhead stream to remove water from the formic acid; and recycling the formic acid for reuse in the oxidizing solution. 14. The process of claim 13 wherein a gasoil is added to the separated aqueous phase prior to flashing the aqueous phase to separate the water and formic acid from the solvent and oxidized sulfur compounds. 15. The process of claim 12 wherein the diesel contains up to about 500 ppm<-1> sulfur by weight. 16. A process for removing sulfur compounds from a hydrocarbon fuel containing benzothiophenes, dibenzothiophenes, and alkyl-substituted benzothiophenes and dibenzothiophenes comprising the steps of: contacting, at a temperature of from about 50 degree C to about 130 degree C, the sulfur containing fuel with an aqueous oxidizing solution comprising hydrogen peroxide and formic acid in a mole ratio of at least about 11:1, formic acid to hydrogen peroxide, and having less than about 25 wt % water, in an amount such that the hydrogen peroxide present in greater than about 2 times the stoichiometric amount required to convert the sulfur compounds present to corresponding sulfones whereby a hydrocarbon fuel phase is formed which contains oxidized alkyl-substituted benzothiophenes and dibenzothiophenes, as sulfones, and an aqueous phase containing substantially all the oxidized benzothiophenes and dibenzothiophenes; separating the aqueous phase containing the extracted, oxidized benzothiophene and dibenzothiophene sulfur compounds from the hydrocarbon phase containing oxidized alkyl substituted benzothiophenes and dibenzothiophenes; flashing the hydrocarbon phase to remove remaining formic acid and water from the hydrocarbon phase; neutralizing and dewatering the hydrocarbon phase; passing the hydrocarbon phase through a bed of an alumina adsorbent to adsorb the oxidized alkyl-substituted benzothiophenes and dibenzothiophenes from the fuel; and recovering the fuel having substantially lowered sulfur content from the oxidized sulfur compound. 17. The process of claim 16 wherein the drying and neutralization is accomplished by adding calcium oxide to the hydrocarbon phase fuel; and filtering the fuel to remove the solids from the fuel. 18. The process of claim 16 including the additional steps of: cooling the hydrocarbon phase between the flashing step and the neutralizing and dewatering step; and adding the calcium oxide to the hydrocarbon stream prior to introduction into a post treatment vessel serving as a solids liquids separator. 19. The process of claim 16 wherein the sulfur is present in an amount up to about 7000 ppm<-1> by weight sulfur.