Process for removing low amounts of organic sulfur from hydrocarbon fuels

A process for removing sulfur compounds from diesel fuel comprising the steps of:

• contacting the diesel fuel at a temperature of from about 90° C. to about 105° C. for a period of time up to about 15 minutes with an oxidizing solution comprising:
• from about 79 wt % to about 89 wt % 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.

A process for removing sulfur compounds from diesel fuel comprising the steps of:

• contacting the diesel fuel at a temperature of from about 90° C. to about 105° C. for a period of time up to about 15 minutes with an oxidizing solution comprising:
• from about 79 wt. % to about 89 wt % 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;
• adding a gasoil to the separated aqueous phase;
• and,
• recovering the formic acid from the aqueous phase;
• 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.

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° C. to about 130° 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.

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° C. to about 130° 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;
• recovering the hydrocarbon phase containing the fuel having reduced sulfur content;
• adding a gasoil to the separated aqueous phase;
• 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.