Catalytic gasoline desulfurization method having also an olefin selective removal function

Abstract

The present invention provides a catalytic gasoline desulfurization method having also an olefin selective removal function, which comprises: when a catalytic gasoline is pre-hydrotreated, cutting into a light fraction, a middle fraction and a heavy fraction; performing liquid-liquid extraction desulfurization treatment on the middle fraction to produce a sulfur-poor oil and a rich solvent containing sulfur-rich oil; the light fraction back-extracting the rich solvent, using C5 olefin therein to replace a macromolecular acyclic olefin in the sulfur-rich oil, so as to gather together C5 iso-olefins, cycloolefins, aromatic hydrocarbons and sulfides in the sulfur-rich oil; performing hydrogenation, olefin-reduction and desulfurization treatment on the heavy fraction together with the sulfur-rich oil removed from the back-extracted rich solvent to saturate the olefin therein; and finally, preparing together with the sulfur-poor oil to produce a full range gasoline. The sulfur-content of the catalytic gasoline produced by the method of the present invention can be reduced to 10 ppm or less, the olefin content of the catalytic gasoline can be reduced to 22%, the olefin is saturated by up to 8 percentage, and the RON loss of the full range gasoline is 1.5 or less, so that while reducing the olefin content of the catalytic gasoline, it ensures the less octane number loss, thereby satisfying the olefin-reduction requirements upgraded in the gasoline National VI Standard for ethanol-gasoline supply area enterprises.

Claims

1. A catalytic gasoline desulfurization method that is also capable of selective removal of an olefin, comprising: 1) pre-hydrotreating a catalytic gasoline, and then cutting the catalytic gasoline into a light fraction having a sulfur content of less than 10 ppm and mainly containing C5 fractions, a middle fraction mainly containing C6-C9 fractions, and a heavy fraction; 2) performing a liquid-liquid extraction desulfurization treatment on the middle fraction obtained in the step 1) using a desulfurization solvent to produce a sulfur-poor oil with a sulfur content of less than 10 ppm and a sulfur-rich oil, wherein the sulfur-rich oil is also called a rich solvent and contains macromolecular acyclic olefins, aromatic hydrocarbons, and sulfides dissolved in the desulfurization solvent; 3) performing a back-extraction of the rich solvent obtained in the step 2) using part of or all the light fraction obtained in the step 1) to obtain a back-extracted rich solvent containing C5 iso-olefins, cycloolefins, aromatic hydrocarbon, and sulfides; and 4) separating a second sulfur-rich oil from the back-extracted rich solvent in the step 3), then performing hydrogenation, olefin-reduction and desulfurization treatment on the heavy fraction obtained in step 1) together with the second sulfur-rich oil to make olefin contained in the heavy fraction and the second sulfur-rich oil be as saturated as possible to obtain a product having a sulfur content of less than 10 ppm; and preparing a full range gasoline with the product together with the remainder of the light fraction obtained in the step 1) and the sulfur-poor oil obtained in the step 2).

2. The method according to claim 1 wherein, the pre-hydrotreating described in the step 1) is a liquid phase hydrogenation using a cobalt molybdenum catalyst at an operating pressure of 1.0-3.0 MPa, a temperature of 100-200 C., and a hydrogen-oil ratio of 3-10, and a space velocity of 1-3 h.sup.1.

3. The method according to claim 1, wherein said light fraction is obtained at a cutting point of 30-50 C., and said middle fraction is obtained at a cutting point of 130-160 C.

4. The method according to claim 1, wherein the liquid-liquid extraction desulfurization treatment on the middle fraction by using the desulfurization solvent in the step 2) is performed in an extracting desulfurization tower; said middle fraction is fed from a middle of the extracting desulfurization tower, said desulfurization solvent is injected from a top of the extracting desulfurization tower; a temperature at the top of the extracting desulfurization tower is controlled to 85-150 C., a temperature at a bottom of the extracting desulfurization tower is controlled to 70-120 C., a pressure (absolute pressure) at the top of the extracting desulfurization tower is controlled to 0.2-0.7 MPa, a feed ratio of the desulfurization solvent to the middle fraction is controlled to 1.0-5.0, said middle fraction is in multi-stage-countercurrent contact with the desulfurization solvent in an upper part of the tower, and the sulfur-poor oil having a sulfur-content of less than 10 ppm obtained at the top of the extracting desulfurization tower is washed with water for recovering the desulfurization solvent and then sent to a gasoline pool as a blending component.

5. The method according to claim 4, wherein the back-extraction in the step 3) is carried out in said extracting desulfurization tower, said light fraction is fed from a lower part of the extracting desulfurization tower, and a feed ratio of the light fraction to the middle fraction is controlled to 0.1-0.5.

6. The method according to claim 4, wherein separating the second sulfur-rich oil from the rich solvent in the step 4) is carried out in a deoiling tower, a pressure at a top of the deoiling tower is controlled to 0.015 to 0.07 MPa, a temperature at a bottom of the deoiling tower is controlled to 130-175 C.; and after vacuuming distillation and stripping distillation, the second sulfur-rich oil is distilled from the top of the deoiling tower and sent to a hydrogenation apparatus for desulfurizing and reducing olefin, and the desulfurization solvent is extracted from the bottom of the deoiling tower and then returned into the extracting desulfurization tower from the top thereof for recycling.

7. The method according to claim 1, wherein the hydrogenation, olefin-reduction, and desulfurization treatment in the step 4) is performed with a catalyst at a temperature of 240-320 C., a pressure of 1.0-3.0 MPa, a volume ratio of hydrogen to the sulfur-rich oil of 200-500, and a space velocity of 1-4 h.sup.1, the catalyst includes an active component and a carrier, the active component includes at least one selected from the group consisting of nickel, molybdenum, tungsten, and an ion thereof, and the carrier includes an activated alumina.

8. A catalytic gasoline desulfurization method, comprising: (1) pre-hydrotreating a catalytic gasoline via a liquid phase hydrogenation using cobalt molybdenum as an active catalyst at an operating pressure of 1.0-3.0 MPa, a temperature of 100-200 C., a hydrogen-oil volume ratio of 3-10, and a space velocity of 1-3 h.sup.1 to obtain a pre-hydrotreated catalytic gasoline; (2) passing the pre-hydrotreated catalytic gasoline into a fractionation tower, which is a light-fraction-cutting-tower, for cutting the pre-hydrotreated catalytic gasoline into a light gasoline and a residue fraction at a cutting point of 40 C., wherein the light gasoline mainly contains C5 fractions, the light gasoline is discharged from a top of the light fraction cutting tower, while the residual fraction is discharged from a bottom of the light fraction cutting tower; (3) entering the residue fraction into a middle-fraction-cutting tower for cutting the residue fraction into a middle gasoline and a heavy gasoline at a cutting point of 150 C., wherein the middle gasoline mainly contains C6-C9 fractions, the middle gasoline is discharged from a top of the middle-fraction-cutting tower, and the heavy gasoline is discharged from a bottom of the middle-fraction-cutting tower; (4) entering the middle gasoline into a middle part of an extracting desulfurization tower, and entering all or a part of the light gasoline discharged from the top of the light-fraction-cutting-tower in the step (2) into a lower part of the extracting desulfurization tower, and injecting a desulfurization solvent from a top of the extracting desulfurization tower, wherein the extracting desulfurization tower has a temperature of 85-150 C. at the top thereof, a temperature of 70-120 C. at a bottom thereof, a pressure of 0.2-0.7 MPa at the top thereof, a feed ratio of the desulfurization solvent to the middle gasoline is controlled to 1.0-5.0, a feed ratio of the light gasoline to the middle gasoline is controlled to 0.1-0.5, the middle gasoline after being desulfurized is discharged from the top of the extracting desulfurization tower, washed with water for recycling the desulfurization solvent to obtain a desulfurized middle gasoline, and the desulfurized middle gasoline then enters a gasoline pool as a blending component; (5) entering the desulfurization solvent containing small molecular iso-olefins, cycloolefins, aromatic hydrocarbons and sulfides into a deoiling tower from the bottom of the extracting desulfurization tower, wherein the deoiling tower has a pressure of 0.015-0.07 MPa at a top thereof and a temperature of 130-175 C. at a bottom thereof, the desulfurization solvent is purified by vacuuming distillation and stripping distillation, a sulfur-rich oil is distilled off from a location at the top of the extracting desulfurization tower, and an extracted and deoiled desulfurization solvent at the bottom of the deoiling tower is returned into the top of the extracting desulfurization tower for recycling; (6) entering the sulfur-rich oil distilled from the deoiling tower in the step (5) and the heavy gasoline discharged from the bottom of the middle-fraction-cutting tower in the step (3) into an hydrogenation apparatus for performing hydrogenation to saturate an olefin contained therein to to obtain a desulfurized and olefin-reduced fraction having a sulfur content of 10 ppm or less; (7) obtaining a full range gasoline having a sulfur-content of less than 10 ppm and an olefin content of less than 22 vol % with the desulfurized and olefin-reduced fraction together with the light gasoline in the step (2) and the desulfurized middle gasoline.

9. The method according to claim 1, wherein the back-extraction replaces a macromolecular acyclic olefin in the sulfur-rich oil with a C5 olefin in the light fraction.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 is the process flow chart of the preferred embodiment of the present invention.

DETAILED EMBODIMENTS

(2) In order to further illustrate the technical solution of the present invention, the following description is made by the way of giving examples, but the scope of the present invention is not limited to the illustrated examples.

Example 1

(3) A catalytic gasoline desulfurization method having also an olefin selective removal function, the process flow of which is shown as the FIG. 1, specifically comprises the following steps:

(4) (1) Performing the pre-hydrotreatment on the catalytic gasoline: the diene is hydroconverted, and at the same time, the small molecular sulfur is converted to the macromolecule sulfur, so that the sulfur in the light gasoline enters the heavier fraction.

(5) (2) The pre-hydrotreated catalytic gasoline in the step (1) enters the light fraction cutting tower, the light gasoline mainly composed of the C5 fraction is cut at a cutting point of 40 C., the light gasoline is discharged from the top of the light fraction cutting tower, and the residual fraction is discharged from the bottom of the light fraction cutting tower and enters the middle fraction cutting tower.

(6) (3) The middle gasoline mainly composed of C6-C9 fractions is cut at a cutting point of 150 C. in the middle fraction cutting tower, the middle gasoline is discharged from the top of the middle fraction cutting tower, and the heavy gasoline is discharged from the bottom of the middle fraction cutting tower.

(7) (4) The middle gasoline discharged from the top of the middle fraction cutting tower in the step (3) enters the middle part of the extracting desulfurization tower, all the light gasoline discharged from the top of the light fraction cutting tower in the step (2) enters the lower part of the extracting desulfurization tower; and the desulfurization solvent is injected from the top of the extracting desulfurization tower.

(8) The operation conditions of the extracting desulfurization tower are that: the temperature at the top of the tower is 110-120 C., the temperature at the bottom of the tower is 85-95 C.; the pressure (absolute pressure) at the top of the tower is 0.5-0.6 MPa; and the feed ratio of the desulfurization solvent to the middle gasoline is controlled to be 3.0.

(9) The middle gasoline after being desulfurized is sent out from the top of the extracting desulfurization tower, washed with water for recycling the solvent, and then sent to the gasoline pool as a blending component; and the desulfurization solvent concentrated with small molecular iso-olefins, cycloolefins, aromatic hydrocarbons and sulfides is sent into the deoiling tower from the bottom of the extracting desulfurization tower.

(10) (5) In the deoiling tower, the pressure (absolute pressure) at the top of the tower is controlled to be 0.015-0.02 MPa, and the temperature at the bottom of the tower is controlled to be 130-135 C.; the desulfurization solvent is purified by vacuuming distillation and stripping distillation; the sulfur-rich oil is distilled off at the top of the deoiling tower; and the extracted and deoiled desulfurization solvent at the bottom of the deoiling tower is returned into the top of the extracting desulfurization tower described in the step (4) for recycling use.

(11) (6) The sulfur-rich oil distilled from the deoiling tower in the step (5) together with the heavy gasoline discharged from the bottom of the middle fraction cutting tower in the step (3) are sent to the hydrogenation apparatus for performing the highly active hydrogenation, in order to make the olefin therein be saturated, and to remove the sulfur to 10 ppm or less, then obtain the desulfurized and olefin-reduced fraction.

(12) (7) The full range gasoline with a sulfur-content of less than 10 ppm and an olefin content of less than 22% is prepared and obtained by the desulfurized and olefin-reduced fraction obtained in the hydrogenation apparatus in the step (6) together with the middle gasoline obtained at the top of the extracting desulfurization tower in the step (4).

Example 2

(13) A method for desulfurizing catalytic gasoline with a function of selectively removing olefins, the process flow of which is shown as the FIG. 1, specifically comprises the following steps:

(14) (1) Performing the pre-hydrotreatment on the catalytic gasoline: the diene is hydroconverted, and at the same time, the small molecular sulfur is converted to the macromolecule sulfur, so that the sulfur in the light gasoline enters the heavier fraction.

(15) (2) The pre-hydrotreated catalytic gasoline in the step (1) enters the light fraction cutting tower, the light gasoline mainly composed of the C5 fraction is cut at a cutting point of 50 C., the light gasoline is discharged from the top of the light fraction cutting tower, and the residual fraction is discharged from the bottom of the light fraction cutting tower and enters the middle fraction cutting tower.

(16) (3) The middle gasoline mainly composed of C6-C9 fractions is cut at a cutting point of 160 C. in the middle fraction cutting tower, the middle gasoline is discharged from the top of the middle fraction cutting tower, and the heavy gasoline is discharged from the bottom of the middle fraction cutting tower.

(17) (4) The middle gasoline discharged from the top of the middle fraction cutting tower in the step (3) enters the middle part of the extracting desulfurization tower, 80% of the light gasoline discharged from the top of the light fraction cutting tower in the step (2) enters the lower part of the extracting desulfurization tower; and the desulfurization solvent is injected from the top of the extracting desulfurization tower.

(18) The operation conditions of the extracting desulfurization tower are that: the temperature at the top of the tower is 145-150 C., the temperature at the bottom of the tower is 100-120 C.; the pressure (absolute pressure) at the top of the tower is 0.5-0.7 MPa; the feed ratio of the desulfurization solvent to the middle gasoline is controlled to be 3.0; and the feed ratio of the light gasoline to the middle gasoline is controlled to be 0.3.

(19) The middle gasoline after being desulfurized is sent out from the top of the extracting desulfurization tower, washed with water for recycling the solvent, and then sent to the gasoline pool as a blending component; and the desulfurization solvent concentrated with small molecular iso-olefins, cycloolefins, aromatic hydrocarbons and sulfides is sent into the deoiling tower from the bottom of the extracting desulfurization tower.

(20) (5) In the deoiling tower, the pressure (absolute pressure) at the top of the tower is controlled to be 0.045-0.05 MPa, and the temperature at the bottom of the tower is controlled to be 170-135 C.; the desulfurization solvent is purified by vacuuming distillation and stripping distillation; the sulfur-rich oil is distilled off at the top of the deoiling tower; and the extracted and deoiled desulfurization solvent at the bottom of the deoiling tower is returned into the top of the extracting desulfurization tower described in the step (4) for recycling use.

(21) (6) The sulfur-rich oil distilled from the deoiling tower in the step (5) together with the heavy gasoline discharged from the bottom of the middle fraction cutting tower in the step (3) are sent to the hydrogenation apparatus for performing the highly active hydrogenation, in order to make the olefin therein be saturated, and to remove the sulfur to 10 ppm or less, and obtain the desulfurized and olefin-reduced fraction.

(22) (7) The full range gasoline with a sulfur-content of less than 10 ppm and an olefin content of less than 22% is prepared and obtained by the desulfurized and olefin-reduced fraction obtained in the hydrogenation apparatus in the step (6) together with the light gasoline obtained at the top of the light fraction cutting tower in the step (2) and the middle gasoline obtained at the top of the extracting desulfurization tower in the step (4).

Example 3

(23) A method for desulfurizing catalytic gasoline with a function of selectively removing olefins, the process flow of which is shown as the FIG. 1, specifically comprises the following steps:

(24) (1) Performing the pre-hydrotreatment on the catalytic gasoline: the diene is hydroconverted, and at the same time, the small molecular sulfur is converted to the macromolecule sulfur, so that the sulfur in the light gasoline enters the heavier fraction.

(25) (2) The pre-hydrotreated catalytic gasoline in the step (1) enters the light fraction cutting tower, the light gasoline mainly composed of the C5 fraction is cut at a cutting point of 30 C., the light gasoline is discharged from the top of the light fraction cutting tower, and the residual fraction is discharged from the bottom of the light fraction cutting tower and enters the middle fraction cutting tower.

(26) (3) The middle gasoline mainly composed of C6-C8 fractions is cut at a cutting point of 130 C. in the middle fraction cutting tower, the middle gasoline is discharged from the top of the middle fraction cutting tower, and the heavy gasoline is discharged from the bottom of the middle fraction cutting tower.

(27) (4) The middle gasoline discharged from the top of the middle fraction cutting tower in the step (3) enters the middle part of the extracting desulfurization tower, the light gasoline discharged from the top of the light fraction cutting tower in the step (2) enters the lower part of the extracting desulfurization tower; and the desulfurization solvent is injected from the top of the extracting desulfurization tower.

(28) The operation conditions of the extracting desulfurization tower are that: the temperature at the top of the tower is 130-135 C., the temperature at the bottom of the tower is 90-100 C.; the pressure (absolute pressure) at the top of the tower is 0.4-0.6 MPa; and the feed ratio of the desulfurization solvent to the middle gasoline is controlled to be 5.0.

(29) The middle gasoline after being desulfurized is sent out from the top of the extracting desulfurization tower, washed with water for recycling the solvent, and then sent to the gasoline pool as a blending component; and the desulfurization solvent concentrated with small molecular iso-olefins, cycloolefins, aromatic hydrocarbons and sulfides is sent into the deoiling tower from the bottom of the extracting desulfurization tower.

(30) (5) In the deoiling tower, the pressure (absolute pressure) at the top of the tower is controlled to be 0.06-0.07 MPa, and the temperature at the bottom of the tower is controlled to be 150-165 C.; the desulfurization solvent is purified by vacuuming distillation and stripping distillation; the sulfur-rich oil is distilled off at the top of the deoiling tower; and the extracted and deoiled desulfurization solvent at the bottom of the deoiling tower is returned into the top of the extracting desulfurization tower described in the step (4) for recycling use.

(31) (6) The sulfur-rich oil distilled from the deoiling tower in the step (5) together with the heavy gasoline discharged from the bottom of the middle fraction cutting tower in the step (3) are sent to the hydrogenation apparatus for performing the highly active hydrogenation, in order to make the olefin therein be saturated, and to remove the sulfur to 10 ppm or less, and obtain the desulfurized and olefin-reduced fraction.

(32) (7) The full range gasoline with a sulfur-content of less than 10 ppm and an olefin content of less than 22% is prepared and obtained by the desulfurized and olefin-reduced fraction obtained in the hydrogenation apparatus in the step (6) together with the light gasoline obtained at the top of the light fraction cutting tower in the step (2) and the middle gasoline obtained at the top of the extracting desulfurization tower in the step (4).