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 having also an olefin selective removal function comprising the following steps: 1) Pre-hydrotreating a catalytic gasoline, and cutting it into a light fraction having a sulfur content of less than 10 ppm and mainly composed of a C5 fraction, a middle fraction mainly composed of a C6-C9 fraction, and a heavy fraction. 2) Performing 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 in which macromolecular acyclic olefins, aromatic hydrocarbons and sulfides dissolved in the desulfurization solvent; 3) Back-extracting the rich solvent obtained in the step 2) using part of or all the light fraction obtained in the step 1), that is, using C5 olefin in the light fraction to replace a macromolecular acyclic olefin in the sulfur-rich oil, so as to dissolve the C5 iso-olefins, cycloolefins, aromatic hydrocarbon and sulfides in the rich solvent together; and; 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 4) Separating the 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 sulfur-rich oil so as to reduce the sulfur-content to less than 10 ppm and to make the olefin be saturated as more as possible; and finally, preparing together with the reminder of the light fraction obtained in the step 1) and the sulfur-poor oil obtained in the step 2) to produce a full range gasoline.

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

3. The method according to claim 1 wherein, the cutting stated in the step 1) is cutting said light fraction at a cutting point of 30-50 C., and cutting said middle fraction 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 stated in the step 2) is performed in a extracting desulfurization tower; said middle fraction is fed from the middle of the extracting desulfurization tower, said desulfurization solvent is injected from the top of the extracting desulfurization tower; the temperature at the top of the extracting desulfurization tower is controlled to be 85-150 C., the temperature at the bottom of the extracting desulfurization tower is controlled to be 70-120 C., the pressure (absolute pressure) at the top of the extracting desulfurization tower is controlled to be 0.2-0.7 MPa, the feed ratio of the desulfurization solvent to the middle fraction is controlled to be 1.0-5.0, said middle fraction is in multi-stage countercurrent contact with the desulfurization solvent in the upper part of the tower, and the sulfur-poor oil with a sulfur-content of less than 10 ppm obtained at the top of the extracting desulfurization tower is washed with water for recovering the solvent and then sent to the gasoline pool as a blending component for a reserve.

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

6. The method according to claim 1 wherein, separating the sulfur-rich oil from the rich solvent as stated in the step 4) is carried out in a deoiling tower, the pressure (absolute pressure) at the top of the deoiling tower is controlled to be 0.015 to 0.07 MPa, the temperature at the bottom of the deoiling tower is controlled to be 130-175 C.; after vacuuming distillation and stripping distillation, the separated 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 after being deoiled is extracted from the bottom of the deoiling tower and then return into the top of said extracting desulfurization tower for recycling use.

7. The method according to claim 1 wherein, the hydrogenation, olefin-reduction and desulfurization treatment stated in the step 4) adopts the catalyst using the metal of nickel, molybdenum and tungsten and/or ions thereof as an active component and activated alumina as a carrier, and the operation conditions are controlled at temperature of 240-320 C., pressure of 1.0-3.0 MPa, a hydrogen-oil ratio of 200-500 and a space velocity of 1-4 h.sup.1.

8. The method according to claim 1 comprising the following continuous processes: (1) Pre-hydrotreating the catalytic gasoline: it adopts the liquid phase hydrogenation using cobalt molybdenum as an active catalyst, the operating pressure is 1.0-3.0 MPa, the temperature is 100-200 C., the hydrogen-oil ratio is 3-10, and the space velocity is 1-3 h.sup.1. (2) The pre-hydrotreated catalytic gasoline in the step (1) enters a fractionation tower for cutting the light gasoline, which is named 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, while the residual fraction is discharged from the bottom of the light fraction cutting tower and enters another fractionation tower for cutting the middle gasoline, which is named middle fraction cutting tower; (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; (4) The middle gasoline discharged from the top of the middle fraction cutting tower in the step (3) enters the middle part of a extracting desulfurization tower, all or part 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. The operation conditions of the extracting desulfurization tower are that: the temperature at the top of the tower is 85-150 C., the temperature at the bottom of the tower is 70-120 C.; the pressure (absolute pressure) at the top of the tower is 0.2-0.7 MPa; the feed ratio of the desulfurization solvent to the middle gasoline is controlled to be 1.0-5.0; and the feed ratio of the light gasoline to the middle gasoline is controlled to be 0.1-0.5. 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 a deoiling tower from the bottom of the extracting desulfurization tower. (5) In the deoiling tower, the pressure (absolute pressure) at the top of the tower is controlled to be 0.015-0.07 MPa, and the temperature at the bottom of the tower is controlled to be 130-175 C.; the desulfurization solvent is purified by vacuuming distillation and stripping distillation; the sulfur-rich oil is distilled off at the top of the 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. (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. (7) The full range gasoline with a sulfur-content of less than 10 ppm and a 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).

Description

DESCRIPTION OF THE FIGURES

[0034] FIG. 1 is the process flow chart of the preferred embodiment of the present invention.

DETAILED EMBODIMENTS

[0035] 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

[0036] 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:

[0037] (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.

[0038] (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.

[0039] (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.

[0040] (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.

[0041] 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.

[0042] 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.

[0043] (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.

[0044] (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.

[0045] (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

[0046] 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:

[0047] (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.

[0048] (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.

[0049] (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.

[0050] (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.

[0051] 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.

[0052] 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.

[0053] (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.

[0054] (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.

[0055] (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

[0056] 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:

[0057] (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.

[0058] (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.

[0059] (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.

[0060] (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.

[0061] 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.

[0062] 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.

[0063] (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.

[0064] (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.

[0065] (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).