Method for upgrading fluid catalytic cracking gasoline

Abstract

A method for upgrading fluid catalytic cracking gasoline includes the following steps: cutting fluid catalytic cracking gasoline into light, medium, and heavy gasoline fractions; subjecting the medium gasoline fraction to an aromatization/hydroisomerization reaction in the presence of a catalyst to obtain a desulfurized medium gasoline fraction; and blending the light gasoline fraction, the desulfurized medium gasoline fraction and the heavy gasoline fraction to obtain upgraded gasoline; where, a cutting temperature of the light and the medium gasoline fractions is 35-60 C., and a cutting temperature of the medium and the heavy gasoline fractions is 70-160 C. The method according to the present invention not only can realize deep desulfurization of fluid catalytic cracking gasoline, but also can improve octane number significantly.

Claims

1. A method for upgrading fluid catalytic cracking gasoline, consisting of steps of: cutting fluid catalytic cracking gasoline into light, medium, and heavy gasoline fractions, wherein the medium gasoline fraction having a boiling range of 40-160 C. accounts for 40% of the fluid catalytic cracking gasoline, which has the lowest octane number, and has an RON below 80; subjecting the medium gasoline fraction to an aromatization-hydroisomerization reaction in the presence of a catalyst to obtain a desulfurized medium gasoline fraction; and blending the light gasoline fraction, the desulfurized medium gasoline fraction and the heavy gasoline fraction to obtain upgraded gasoline; wherein, a cutting temperature of the light and the medium gasoline fractions is 35-60 C., and a cutting temperature of the medium and the heavy gasoline fractions is 70-160 C.; wherein the catalyst used for the aromatization-hydroisomerization reaction is obtained by using a zeolite and metallic oxide as a composite carrier to load an active metal component, wherein the active metal is gallium; wherein the zeolite is an LTL type zeolite, and the metallic oxide is aluminum oxide.

2. The method for upgrading fluid catalytic cracking gasoline according to claim 1, wherein, in the catalyst used for the aromatization-hydroisomerization reaction, a weight ratio of the zeolite to the metallic oxide is 1:(0.2-0.5), and the active metal has a loading capacity of 0.5-3% on the composite carrier.

3. The method for upgrading fluid catalytic cracking gasoline according to claim 1, wherein a reaction temperature of the aromatization-hydroisomerization reaction is 260-400 C., a reaction pressure is 0.8-2.0 MPa, a volume ratio of hydrogen to oil is 200-800:1, and a weight hourly space velocity is 1.0-6.0 h.sup.1.

4. The method for upgrading fluid catalytic cracking gasoline according to claim 1, wherein, before cutting the fluid catalytic cracking gasoline into the light, the medium and the heavy gasoline fractions, the fluid catalytic cracking gasoline is subjected to sweetening treatment firstly.

5. A method for upgrading fluid catalytic cracking gasoline, consisting of steps of: cutting fluid catalytic cracking gasoline into light, medium, and heavy gasoline fractions, wherein the medium gasoline fraction having a boiling range of 40-160 C. accounts for 40% of the fluid catalytic cracking gasoline, which has the lowest octane number, and has an RON below 80; subjecting the medium gasoline fraction to desulfurization firstly to obtain a first desulfurized medium gasoline fraction, then subjecting the first desulfurized medium gasoline fraction to an aromatization-hydroisomerization reaction in the presence of a catalyst to obtain a second desulfurized medium gasoline fraction; and blending the light gasoline fraction, the second desulfurized medium gasoline fraction and the heavy gasoline fraction to obtain upgraded gasoline; wherein, a cutting temperature of the light and the medium gasoline fractions is 35-60 C., and a cutting temperature of the medium and the heavy gasoline fractions is 70-160 C.; wherein the catalyst used for the aromatization-hydroisomerization reaction is obtained by using a zeolite and metallic oxide as a composite carrier to load an active metal component, wherein the active metal is gallium; wherein the zeolite is an LTL type zeolite, and the metallic oxide is aluminum oxide.

6. The method for upgrading fluid catalytic cracking gasoline according to claim 5, wherein the desulfurization of the medium gasoline fraction is solvent extraction desulfurization, and the solvent extraction desulfurization comprises the following steps: introducing the medium gasoline fraction from a middle lower part of an extraction tower and a solvent from a top of the extraction tower, injecting C5 paraffin from a backflow device at a bottom of the extraction tower, controlling a temperature at the top of the extraction tower between 55-100 C., a temperature at the bottom of the extraction tower between 40-80 C., and a pressure at the top of the extraction tower between 0.2-0.7 MPa, controlling a feed ratio of the solvent to the medium gasoline fraction between 1.0-5.0, and controlling a feed ratio of the C5 paraffin to the medium gasoline fraction between 0.1-0.5.

7. The method for upgrading fluid catalytic cracking gasoline according to claim 6, wherein the solvent is selected from one or more of diethylene glycol, triethylene glycol, tetraethylene glycol, dimethyl sulfoxide, sulfolane, N-formyl-morpholine, N-methyl pyrrolidone, polyethylene glycol and propylene carbonate.

8. The method for upgrading fluid catalytic cracking gasoline according to claim 5, wherein the desulfurization of the medium gasoline fraction is adsorption desulfurization, and the adsorption desulfurization is performed by using a desulfurization adsorbent, wherein the desulfurization adsorbent is obtained by using a zeolite and an active carbon that have been respectively subjected to alkali treatment as a composite carrier to load an active metal component, wherein the active metal is selected from one or more elements of groups IA, VIII, IB, IIB and VIB of a periodic table.

9. The method for upgrading fluid catalytic cracking gasoline according to claim 8, wherein, in the composite carrier of the desulfurization adsorbent, a weight ratio of the zeolite to the active carbon is (20-80): (80-20).

10. The method for upgrading fluid catalytic cracking gasoline according to claim 8, wherein the zeolite in the composite carrier of the desulfurization adsorbent is an X type, a Y type or a ZSM-5 type zeolite.

11. The method for upgrading fluid catalytic cracking gasoline according to claim 8, wherein the active metal in the desulfurization adsorbent is selected from at least two of Ni, Fe, Ag, Co, Mo, Zn and K.

12. The method for upgrading fluid catalytic cracking gasoline according to claim 8, wherein the active metal in the desulfurization adsorbent has a loading capacity of 2-30% on the composite carrier.

13. The method for upgrading fluid catalytic cracking gasoline according to claim 8, wherein the adsorption desulfurization is carried out by using a fixed bed at an atmospheric pressure, and a temperature for the adsorption desulfurization is controlled between 20-100 C., a flow rate of the medium gasoline fraction is 0.3-1 mL/min.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a process flow chart of a method for upgrading fluid catalytic cracking gasoline according to Example 1 of the present invention;

(2) FIG. 2 is a process flow chart of a method for upgrading fluid catalytic cracking gasoline according to Example 3 of the present invention;

(3) FIG. 3 is absorption-desorption isotherms of a ZSM-5 type zeolite before and after alkali treatment according to Example 5;

(4) FIG. 4 is a curve of pore diameter distribution of a ZSM-5 type zeolite before and after alkali treatment according to Example 5;

(5) FIG. 5 is a process flow chart of a method for upgrading fluid catalytic cracking gasoline according to Example 5 of the present invention;

(6) FIG. 6 is a process flow chart of a method for upgrading fluid catalytic cracking gasoline according to Example 6 of the present invention;

(7) FIG. 7 is a process flow chart of a method for upgrading fluid catalytic cracking gasoline according to Example 7 of the present invention;

(8) FIG. 8 is a process flow chart of a method for upgrading fluid catalytic cracking gasoline according to Example 8 of the present invention.

DETAILED DESCRIPTION

(9) In order to make objectives, technical solutions, and advantages of the present invention clearer, technical solutions in examples of the present invention will be described hereinafter clearly and completely with reference to accompanying drawings in examples of the present invention. Obviously, the described examples are only a part of examples of the present invention, rather than all examples of the present invention. All other examples obtained by persons of ordinary skill in the art based on examples of the present invention without any creative effort shall fall into the protection scope of the present invention.

Example 1

1. Prepare a Catalyst

(10) An HZSM-5 zeolite is blended evenly with aluminum oxide at a weight ratio of 70:30 to prepare a composite carrier, where a weight ratio of the zeolite to aluminum oxide is 1:0.4.

(11) The composite carrier prepared above is subjected to incipient wetness impregnation with an aqueous solution of Ga.sub.2 (SO.sub.4).sub.3.16H.sub.2O to obtain an impregnated material; after washing the impregnated material with deionized water, drying it for 20 hours at a temperature of 120 C.; after a dried material is cooled to room temperature, the temperature is elevated to 400 C. at a speed of 6 C./min firstly, and then elevated to 550 C. at a speed of 3 C./min, at this temperature the dried material is calcinated for 4 hours, thereby preparing a catalyst, and Ga has a loading capacity of about 1.8% on the composite carrier.

2. Gasoline Upgrading

(12) Fluid catalytic cracking gasoline produced from Daqing atmospheric residue by catalytic cracking is taken as a feedstock (reference may be made to Table 1 for its composition and property), and reference may be made to FIG. 1 for a process flow of a method for increasing octane number of the fluid catalytic cracking gasoline, which specifically includes:

(13) Step 11, cutting the fluid catalytic cracking gasoline into light, medium and heavy gasoline fractions according to a boiling range from low to high, where a boiling range of the medium gasoline fraction is controlled between 40-160 C.

(14) Step 12, after the above prepared catalyst is placed into a fixed bed reactor, introducing the medium gasoline fraction into the fixed bed reactor, and carrying out an aromatization/hydroisomerization reaction for 200 hours in the fixed bed reactor successively in a condition where a reaction temperature is 380 C., a reaction pressure is 1.5 MPa, a weight hourly space velocity is 5.0 h.sup.1, and a volume ratio of hydrogen to oil is 500:1.

(15) Step 13, drawing out the resultant of the above step, and then blending the same with the light gasoline fraction and the heavy gasoline fraction, thereby obtaining upgraded gasoline, and reference may be made to Table 1 for its composition and property. It can be seen from results of Table 1 that, octane number of the upgraded gasoline is increased significantly.

Example 2

1. Prepare a Catalyst

(16) An MCM-41 zeolite is blended with aluminum oxide at a weight ratio of 80:20 to prepare a composite carrier, where a weight ratio of the zeolite to aluminum oxide is 1:0.25.

(17) The composite carrier prepared above is subjected to incipient wetness impregnation with a ZnSO.sub.4 solution to obtain an impregnated material; after washing the impregnated material with deionized water, drying it for 24 hours at a temperature of 110 C.; after the dried material is cooled to room temperature, the temperature is elevated to 400 C. at a speed of 6 C./min firstly, and then elevated to 450 C. at a speed of 3 C./min, at this temperature the dried material is calcinated for 6 hours, thereby preparing a catalyst, and Zn has a loading capacity of about 0.5% on the composite carrier.

2. Gasoline Upgrading

(18) Fluid catalytic cracking gasoline in Example 1 is taken as a feedstock, and a method for increasing octane number of the fluid catalytic cracking gasoline is:

(19) Cutting the fluid catalytic cracking gasoline into light, medium and heavy gasoline fractions according to a boiling range from low to high, where a boiling range of the medium gasoline fraction is controlled between 40-160 C.

(20) Introducing the medium gasoline fraction into a fixed bed reactor filled with the above prepared catalyst, and carrying out an aromatization/hydroisomerization reaction for 200 hours in the fixed bed reactor successively in a condition where a reaction temperature is 260, a reaction pressure is 0.8 MPa, a weight hourly space velocity is 1 h.sup.1, and a volume ratio of hydrogen to oil is 200:1.

(21) Drawing out the resultant of the above step, and then blending the same with the light gasoline fraction and the heavy gasoline fraction, thereby obtaining upgraded gasoline, and reference may be made to Table 1 for its composition and property. It can be seen from results of Table 1 that, octane number of the upgraded gasoline is increased significantly.

(22) TABLE-US-00001 TABLE 1 Composition and Property of Gasoline Upgraded Upgraded Gasoline gasoline in gasoline in Item feedstock Example 1 Example 2 Density (20 C.), g/cm.sup.3 0.7012 0.7102 0.7123 Group Paraffin 35.0 45.3 40.5 composition, Olefins 48.2 23.3 24.5 m % Naphthene 6.3 9.9 8.2 Aromatics 10.5 21.5 26.8 Octane RON 90.2 93.5 94.2 number MON 80.9 84.1 84.5

Example 3

(23) Fluid catalytic cracking gasoline from Jinan is taken as a feedstock (reference may be made to Table 2 for its composition and property), and reference may be made to FIG. 2 for a process flow of a method for increasing octane number of the fluid catalytic cracking gasoline, which specifically includes:

(24) Step 21, cutting the fluid catalytic cracking gasoline into light, medium and heavy gasoline fractions according to a boiling range from low to high, where a boiling range of the medium gasoline fraction is controlled between 40-150 C.

(25) Step 22, introducing the medium gasoline fraction from a middle lower part of an extraction tower and tetraethylene-glycol from a top of the extraction tower, and meanwhile injecting n-pentane to a backflow device at the bottom of the extraction tower, controlling a temperature at the top of the extraction tower at 80 C., a temperature at the bottom of the extraction tower at 60 C., and a pressure (absolute pressure) at the top of the extraction tower at 0.5 MPa, controlling a weight ratio of tetraethylene-glycol to the medium gasoline fraction at 3.0, and controlling a weight ratio of n-pentane to the medium gasoline fraction at 0.3.

(26) During the extraction, the medium gasoline fraction is in contact with tetraethylene-glycol at an upper section of the extraction tower via a multi-stage countercurrent, while n-pentane is in full contact with tetraethylene-glycol at a lower section of the extraction tower, where desulfurized medium gasoline fraction is carried by tetraethylene-glycol and distilled out of the top of the tower, and after washing the desulfurized medium gasoline fraction with water to remove tetraethylene-glycol, the desulfurized medium gasoline fraction is obtained;

(27) The medium gasoline fraction that continues going downwards along with tetraethylene-glycol is in full contact with N-pentane at the lower section of the extraction tower, and is discharged out of the tower at the bottom along with n-pentane; n-pentane therein is returned to the backflow device of the extraction tower, and water therein is returned to the step of washing the desulfurized medium gasoline fraction with water to remove the solvent as washing water, and tetraethylene-glycol therein is returned to the top of the extraction tower, residual sulfur-rich oil content is collected.

(28) Step 23, introducing the desulfurized medium gasoline fraction into a fixed bed reactor filled with the catalyst prepared in Example 1, and carrying out an aromatization/hydroisomerization reaction for 200 hours in the fixed bed reactor successively in a condition where a reaction temperature is 300 C., a reaction pressure is 1 MPa, a weight hourly space velocity is 2.5 h.sup.1, and a volume ratio of hydrogen to oil is 350:1.

(29) Step 24, drawing out the resultant of the above step, and then blending the same with the light gasoline fraction, the residual sulfur-rich oil content and the heavy gasoline fraction, thereby obtaining upgraded gasoline, and reference may be made to Table 2 for its composition and property. It can be seen from results of Table 2 that, octane number of the upgraded gasoline is increased significantly.

Example 4

1. Prepare a Catalyst

(30) A ZSM-5 zeolite is blended with aluminum oxide at a weight ratio of 83:17 to prepare a composite carrier, where a weight ratio of the zeolite to aluminum oxide is 1:0.2.

(31) The composite carrier prepared above is subjected to incipient wetness impregnation with an aqueous solution of Ga.sub.2 (SO.sub.4).sub.3.16H.sub.2O to obtain an impregnated material; after washing the impregnated material with deionized water, drying it for 18 hours at a temperature of 120 C.; after the dried material is cooled to room temperature, the temperature is elevated to 400 C. at a speed of 6 C./min firstly, and then elevated to 640 C. at a speed of 3 C./min, at this temperature the dried material is calcinated for 5 hours, thereby preparing a catalyst, and Ga has a loading capacity of about 3% on the composite carrier.

2. Gasoline Upgrading

(32) Fluid catalytic cracking gasoline in Example 3 is taken as a feedstock, and a method for increasing octane number of the fluid catalytic cracking gasoline includes:

(33) Cutting the fluid catalytic cracking gasoline into light, medium and heavy gasoline fractions according to a boiling range from low to high, where a boiling range of the medium gasoline fraction is controlled between 50-130 C.

(34) Introducing the medium gasoline fraction from a middle lower part of an extraction tower and sulfolane from a top of the extraction tower, and meanwhile injecting isopentane to a backflow device at the bottom of the extraction tower, controlling a temperature at the top of the extraction tower at 60 C., a temperature at the bottom of the extraction tower at 40 C., and a pressure (absolute pressure) at the top of the extraction tower at 0.2 MPa, controlling a weight ratio of sulfolane to the medium gasoline fraction at 1.0, and controlling a weight ratio of isopentane to the medium gasoline fraction at 0.1, collecting desulfurized medium gasoline fraction and residual sulfur-rich oil content.

(35) Introducing the desulfurized medium gasoline fraction into a fixed bed reactor filled with the catalyst prepared above, and carrying out an aromatization/hydroisomerization reaction for 200 hours in the fixed bed reactor successively in a condition where a reaction temperature is 400 C., a reaction pressure is 2 MPa, a weight hourly space velocity is 6 h.sup.1, and a volume ratio of hydrogen to oil is 800:1.

(36) Drawing out the resultant of the above step, and then blending the same with the light gasoline fraction, the residual sulfur-rich oil content and the heavy gasoline fraction, thereby obtaining upgraded gasoline, and reference may be made to Table 2 for its composition and property. It can be seen from results of Table 2 that, octane number of the upgraded gasoline is increased significantly.

(37) TABLE-US-00002 TABLE 2 Composition and Property of Gasoline Upgraded Upgraded Gasoline gasoline in gasoline in Item feedstock Example 3 Example 4 Density (20 C.), g/cm.sup.3 0.7562 0.7780 0.7685 Group Paraffin 25.6 33.6 28.8 composition, Olefins 30.9 13.8 21.6 m % Naphthene 8.9 14.2 13.6 Aromatics 34.6 38.4 36.0 Octane RON 89.2 93.7 92.0 number MON 80.1 84.5 81.6

Example 5

1. Prepare a Desulfurization Adsorbent

(38) 1) Prepare a Zeolite and an Active Carbon Subjected to Alkali Treatment

(39) After elevating temperatures of two parts 500 mL of NaOH solutions at a concentration of 0.3 mol/L to about 70 C. by a water bath, adding 25 g of ZSM-5 type zeolite and 25 g of active carbon therein respectively to obtain a blending, after stirring the blending for about 200 minutes, immediately lowering a temperature of the blending to a normal atmospheric temperature by an ice bath, filtering the blending and collecting a filter cake, washing the filter cake with deionized water several times till a pH value of the filtrate is about 7, placing the filter cake obtained into an oven at a temperature of 110 C. to be dried for 4 h, and thus a ZSM-5 type zeolite subjected to alkali treatment and an active carbon subjected to alkali treatment are prepared respectively;

(40) In addition, an ASAP2000 type automatically physical adsorption instrument is used to measure specific surface areas and pore diameter distributions of the ZSM-5 type zeolite and the active carbon, and results are as shown in Table 3.

(41) Table 3 Specific Surface Areas and Pore Diameters of ZSM-5 Type Zeolite and Active

(42) TABLE-US-00003 Carbon Total Medium specific Total pore Average surface area pore volume pore S.sub.BET/ volume V/ V.sub.meso/ diameter d/ Carrier (m.sup.2 .Math. g.sup.1) (cm.sup.3 .Math. g.sup.1) (cm.sup.3 .Math. g.sup.1) (nm) ZSM-5 zeolite 380 0.212 0.041 2.241 before alkali treatment ZSM-5 zeolite 427 0.430 0.300 4.031 after alkali treatment Active carbon 1190 0.701 0.326 2.321 before alkali treatment Active carbon 1254 0.742 0.358 2.427 after alkali treatment

(43) It can be seen from FIG. 3 that: the ZSM-5 zeolite before alkali treatment exhibits an I-type isotherm which is particular to micropore properties, the desorption isotherm thereof is almost overlapped with the adsorption isotherm; whereas the ZSM-5 zeolite after alkali treatment exhibits an IV-type isotherm with obvious characteristics, which presents a continuous adsorption state till a saturation pressure within the entire measured pressure range, and which conducts desorption slowly with decrease in the pressure during the desorption firstly, when the pressure reaches a certain value, the desorption amount surges suddenly to form a relatively steep curve, and then the desorption isotherm is overlapped with the adsorption isotherm with a continuous decrease in the pressure, thus it indicates that a great number of mesopores (medium pores) are generated in the ZSM-5 zeolite after alkali treatment.

(44) It can be seen from FIG. 4 that, the ZSM-5 zeolite before alkali treatment is mainly contains micropores, there is a wide distribution before 2 nm, there is a small peak at a position of 3.5 nm, and there are basically no pores after 4 nm, an average pore diameter calculated through a t-plot method is about 2.3 nm; there is still a distribution of a part of micropores before 2 nm for the ZSM-5 zeolite after alkali treatment, and there is a strong peak at a position of about 3.8 nm, the peak is almost about 11 times the height of the ZSM-5 zeolite before alkali treatment, and there is also a relative wide distribution of pores after 4 nm.

(45) Meanwhile, a result of Table 3 shows that: a medium pore volume and an average pore diameter of the ZSM-5 type zeolite after being subjected to alkali treatment are increased significantly, which indicates that a large number of micropores are converted into medium pores, thereby forming a structure of a composite pore of a mesopore and a micropore; the total specific surface area, the total pore volume, the medium pore volume and the average pore diameter of the active carbon after being subjected to alkali treatment are all increased.

(46) 2) Prepare a First Composite Carrier

(47) The ZSM-5 type zeolite subjected to alkali treatment and the active carbon subjected to alkali treatment are placed in a mortar and grounded into powders after being blended at a weight ratio of 40:60, then the powders are placed in an oven at a temperature of 120 C. to be dried for 6 h, thereby a first composite carrier is prepared.

(48) 3) Prepare a Desulfurization Adsorbent

(49) The first composite carrier prepared above is subjected to incipient wetness impregnation with a K.sub.2SO.sub.4 solution firstly to obtain a first impregnated material, after washing, drying and calcinating the first impregnated material, the first impregnated material is subjected to incipient wetness impregnation with NiSO.sub.4 to obtain a second impregnated material, after drying and calcinating the second impregnated material, a desulfurization adsorbent is prepared;

(50) The washing, the drying and the calcinating described above are specifically: after washing the impregnated material with deionized water, drying it for 20 hours at a temperature of 120 C., after the dried material is cooled to room temperature, elevating the temperature to 400 C. at a speed of 6 C./min firstly, and then elevating the temperature to 550 C. at a speed of 3 C./min, at this temperature the dried material is calcinated for 4 hours.

(51) In the desulfurization adsorbent prepared above, K has a loading capacity of about 5% on the first composite carrier, Ni has a loading capacity of about 10% on the first composite carrier; moreover, K and Ni which are loaded on the first composite carrier have a weight ratio of 0.5:1. Upon detection, a sulfur capacity of the desulfurization adsorbent is 0.514, and its lifespan lasts for 8-9 h.

(52) In the present invention, the sulfur capacity refers to total sulfur content (by gram) removed when 1 g of desulfurization adsorbent reduces the total sulfur content in the gasoline feedstock below 10 ppmw, for instance, when the sulfur capacity is 0.514, it indicates that the total sulfur content removed when 1 g of desulfurization adsorbent reduces the total sulfur content in the gasoline feedstock below 10 ppmw is 0.514 g.

2. Prepare a Selective Hydrodesulfurization Catalyst

(53) A ZSM-5 type zeolite is subjected to incipient wetness impregnation with a CoSO.sub.4 solution firstly to obtain a first impregnated material, after washing, drying and calcinating the first impregnated material, the first impregnated material is subjected to incipient wetness impregnation with an aqueous solution of (NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O to obtain a second impregnated material, after washing, drying and calcinating the second impregnated material, a selective hydrodesulfurization catalyst is prepared, where, reference may be made to step 1 for a specific operation of the washing, the drying and the calcinating.

(54) A total specific surface area of the selective hydrodesulfurization catalyst prepared above is about 356 m.sup.2/g, a total pore volume is about 0.315 cm.sup.3.Math.g.sup.1, Co has a loading capacity of about 4% on the carrier, Mo has a loading capacity of about 10% on the carrier; moreover, Co and Mo which are loaded on the carrier have a weight ratio of 0.4:1.

3. Prepare a Catalyst for an Aromatization/Hydroisomerization Reaction

(55) An HZSM-5 zeolite is blended with aluminum oxide at a weight ratio of 70:30 to prepare a second composite carrier, where a weight ratio of the zeolite to aluminum oxide is 1:0.4.

(56) The second composite carrier prepared above is subjected to incipient wetness impregnation with an aqueous solution of Ga.sub.t (SO.sub.4).sub.3.16H.sub.2O to obtain a impregnated material; upon washing, drying and calcinating the impregnated material, a catalyst for an aromatization/hydroisomerization reaction is prepared; reference may be made to step 1 for a specific operation of the washing, the drying and the calcinating, and Ga has a loading capacity of about 1.8% on the second composite carrier.

4. Gasoline Upgrading

(57) Fluid catalytic cracking gasoline produced from Daqing atmospheric residue by catalytic cracking is taken as a feedstock (reference may be made to Table 4 for its composition), and reference may be made to FIG. 5 for a process flow of manufacturing of upgraded gasoline based on such gasoline feedstock.

(58) Firstly, cutting the gasoline feedstock into light, medium and heavy gasoline fractions, where a cutting temperature of the light and the medium gasoline fractions is 60 C., and a cutting temperature of the medium and the heavy gasoline fractions is 100 C.

(59) Contacting the light gasoline fraction with an alkali solution for sweetening treatment in an extraction system, where the alkali used is a 20 wt % NaOH solution, a volume ratio of the light gasoline fraction to the NaOH solution is 5:1, an operating temperature is 30 C., sweetened light gasoline fraction and extracted oil are collected, and the extracted oil is incorporated into the heavy gasoline fraction to proceed with a next step.

(60) Filling the desulfurization adsorbent prepared above into a fixed bed reactor, at a temperature of 30 C. and normal atmospheric pressure, subjecting the medium gasoline fraction to adsorption desulfurization at a flow rate of 0.5 mL/min to obtain a first desulfurized medium gasoline fraction; moreover, after the adsorption desulfurization, sweeping the desulfurization adsorbent that has been subjected to the adsorption desulfurization with steam at a temperature of 150 C. for 3 h for washing, collecting a sulfur-rich component, incorporating the sulfur-rich component into the heavy gasoline fraction to proceed with a next step. Moreover, sweeping the washed desulfurization adsorbent with nitrogen at a temperature of 300 C. for 30 min for drying, and sweeping the dried desulfurization adsorbent with nitrogen at a room temperature (30 C.) for 30 min for cooling, so that the desulfurization adsorbent is regenerated, a sulfur capacity of the desulfurization adsorbent after being regenerated three times is 0.473, and its lifespan lasts for about 7 h.

(61) After the above catalyst prepared for the aromatization/hydroisomerization reaction is placed into a fixed bed reactor, introducing the first desulfurized medium gasoline fraction into the fixed bed reactor, and carrying out an aromatization/hydroisomerization reaction for 200 hours in the fixed bed reactor successively in a condition where a reaction temperature is 380 C., a reaction pressure is 1.5 MPa, a weight hourly space velocity is 5.0 h.sup.1, and a volume ratio of hydrogen to oil is 500:1, thereby obtaining a second desulfurized medium gasoline fraction.

(62) Filling the selective hydrodesulfurization catalyst prepared above into a fixed bed reactor, subjecting the heavy gasoline fraction incorporated with the extracted oil and the sulfur-rich component to selective hydrodesulfurization in a condition where a reaction temperature is 260 C., a reaction pressure is 1.8 MPa, a liquid hourly space velocity is 3.0 h.sup.1, and a volume ratio of hydrogen to oil is 500:1, thereby obtaining a desulfurized heavy gasoline fraction. The desulfurized heavy gasoline fraction is blended with the sweetened light gasoline fraction and the second desulfurized medium gasoline fraction to prepare upgraded gasoline, reference may be made to Table 4 for its composition.

Example 6

1. Prepare a Selective Hydrodesulfurization Catalyst

(63) A selective hydrodesulfurization catalyst is prepared according to the method described in Example 5, the difference lies in that, a loading capacity of Co on the carrier is controlled at about 6%, a loading capacity of Mo on the carrier is controlled at about 10%, and Co and Mo which are loaded on the carrier have a weight ratio of 0.6:1.

2. Prepare a Catalyst for an Aromatization/Hydroisomerization Reaction

(64) An MCM-41 zeolite is blended with aluminum oxide at a weight ratio of 80:20 to prepare a second composite carrier, where a weight ratio of the zeolite to aluminum oxide is 1:0.25.

(65) The second composite carrier prepared above is subjected to incipient wetness impregnation with a ZnSO.sub.4 solution to obtain an impregnated material; after washing the impregnated material with deionized water, drying it for 24 hours at a temperature of 110 C.; after cooling down the dried material to room temperature, the temperature is elevated to 400 C. at a speed of 6 C./min firstly, and then elevated to 450 C. at a speed of 3 C./min, at this temperature the dried material is calcinated for 6 hours, thereby preparing a catalyst, and Zn has a loading capacity of about 0.5% on the second composite carrier.

3. Gasoline Upgrading

(66) Fluid catalytic cracking gasoline from Daqing is taken as a feedstock (reference may be made to Table 4 for its composition), and reference may be made to FIG. 6 for a process flow of manufacturing of upgraded gasoline based on such gasoline feedstock.

(67) Firstly, cutting the gasoline feedstock into light, medium and heavy gasoline fractions, where a cutting temperature of the light and the medium gasoline fractions is 50 C., and a cutting temperature of the medium and the heavy gasoline fractions is 90 C.

(68) Contacting the light gasoline fraction with an alkali solution for sweetening treatment in an extraction system, where the alkali used is a 10 wt % NaOH solution, a volume ratio of the light gasoline fraction to the NaOH solution is 5:1, an operating temperature is 45 C., sweetened light gasoline fraction and extracted oil are collected, and the extracted oil is incorporated into the heavy gasoline fraction to proceed with a next step.

(69) Introducing the medium gasoline fraction from a middle lower part of an extraction tower and tetraethylene-glycol from a top of the extraction tower, and meanwhile injecting n-pentane to a backflow device at the bottom of the extraction tower, controlling a temperature at the top of the extraction tower at 80 C., a temperature at the bottom of the extraction tower at 60 C., and a pressure (absolute pressure) at the top of the extraction tower at 0.5 MPa, controlling a weight ratio of tetraethylene-glycol to the medium gasoline fraction at 3.0, and controlling a weight ratio of n-pentane to the medium gasoline fraction at 0.3.

(70) During the extraction, the medium gasoline fraction is in contact with tetraethylene-glycol at an upper section of the extraction tower via a multi-stage countercurrent, while n-pentane is in full contact with tetraethylene-glycol at a lower section of the extraction tower, where desulfurized medium gasoline fraction is carried by tetraethylene-glycol and distilled out of the top of the tower, and after washing the desulfurized medium gasoline fraction with water to remove tetraethylene-glycol, the first desulfurized medium gasoline fraction is obtained;

(71) The medium gasoline fraction that continues going downwards along with tetraethylene-glycol is in full contact with n-pentane at the lower section of the extraction tower, and is discharged out of the tower at the bottom along with n-pentane; n-pentane therein is returned to the backflow device of the extraction tower, and water therein is returned to the step of washing the desulfurized medium gasoline fraction with water to remove the solvent as washing water, and tetraethylene-glycol therein is returned to the top of the extraction tower, sulfur-rich oil content is collected and is incorporated into the heavy gasoline fraction to proceed with a next step.

(72) Introducing the first desulfurized medium gasoline fraction into a fixed bed reactor filled with the catalyst prepared for the aromatization/hydroisomerization reaction, and carrying out an aromatization/hydroisomerization reaction for 200 hours in the fixed bed reactor successively in a condition where a reaction temperature is 260 C., a reaction pressure is 0.8 MPa, a weight hourly space velocity is 1 h.sup.1, and a volume ratio of hydrogen to oil is 200:1, thereby obtaining the second desulfurized medium gasoline fraction.

(73) Filling the selective hydrodesulfurization catalyst prepared above into a fixed bed reactor, subjecting the heavy gasoline fraction incorporated with the extracted oil and the sulfur-rich component to selective hydrodesulfurization in a condition where a reaction temperature is 300 C., a reaction pressure is 1.5 MPa, a liquid hourly space velocity is 4.0 h.sup.1, and a volume ratio of hydrogen to oil is 600:1, thereby obtaining a desulfurized heavy gasoline fraction. The desulfurized heavy gasoline fraction is blended with the sweetened light gasoline fraction and the second desulfurized medium gasoline fraction to prepare upgraded gasoline, reference may be made to Table 4 for its composition.

(74) TABLE-US-00004 TABLE 4 Composition of Gasoline before and after Upgrading Upgraded Upgraded Gasoline gasoline in gasoline in Item feedstock Example 5 Example 6 Density (20 C.), g/cm.sup.3 0.7012 0.7252 0.7236 Sulfur content, ppmw 282 8.0 8.0 Group Paraffin 35.0 43.2 43.3 composition, Olefins 48.2 20.8 17.6 m % Naphthene 6.3 12.7 12.5 Aromatics 10.5 23.3 26.6 Octane RON 90.2 91.8 92.5 number MON 80.9 82.5 83.0

(75) It can be seen from Table 4 that:

(76) The method for upgrading gasoline as described in Example 5 and Example 6 of the present invention not only can reduce sulfur content in the gasoline feedstock below 10 ppm, but also can control olefins content below 24%, and octane number is increased significantly.

Example 7

1. Prepare a Desulfurization Adsorbent

(77) 1) Prepare a Zeolite and an Active Carbon Subjected to Alkali Treatment

(78) After elevating temperatures of two 500 mL of NaOH solutions at a concentration of 0.2 mol/L to about 80 C. by a water bath, adding 25 g of Y type zeolite and 25 g of active carbon therein respectively, immediately lowering a temperature of the blending to a normal atmospheric temperature by an ice bath after stirring for about 120 minutes, filtering the blending and collecting a filter cake, washing the filter cake with deionized water several times till a pH value of the filtrate is about 7, placing the filter cake obtained into an oven at a temperature of 120 C. to be dried for 3 h, and thus a Y type zeolite subjected to alkali treatment and an active carbon subjected to alkali treatment are prepared, respectively; specific surface areas and pore diameter distributions of the Y type zeolite and the active carbon are shown in Table 5.

(79) TABLE-US-00005 TABLE 5 Specific Surface Areas and Pore Diameters of Y type zeolite and Active Carbon Total Medium specific Total pore Average surface area pore volume pore S.sub.BET/ volume V/ V.sub.meso/ diameter d/ Carrier (m.sup.2 .Math. g.sup.1) (cm.sup.3 .Math. g.sup.1) (cm.sup.3 .Math. g.sup.1) (nm) Y type zeolite 706 0.390 0.053 2.001 before alkali treatment Y type zeolite 713 0.462 0.118 2.139 after alkali treatment Active carbon 1190 0.701 0.326 2.321 before alkali treatment Active carbon 1233 0.729 0.355 2.346 after alkali treatment

(80) 2) Prepare a First Composite Carrier

(81) The Y type zeolite subjected to alkali treatment and the active carbon subjected to alkali treatment are placed in a mortar and grounded into powders after being blended at a weight ratio of 20:80, then the powders are placed in an oven at a temperature of 110 C. to be dried for 6 h, thereby preparing a first composite carrier.

(82) 3) Prepare a Desulfurization Adsorbent

(83) The first composite carrier prepared above is subjected to incipient wetness impregnation with a ZnSO.sub.4 solution firstly to obtain a first impregnated material, after washing, drying and calcinating the first impregnated material, the first impregnated material is subjected to incipient wetness impregnation with a Fe.sub.2(SO.sub.4).sub.3 solution to obtain a second impregnated material, after drying and calcinating the second impregnated material, a desulfurization adsorbent is prepared;

(84) The washing, the drying and the calcinating described above are specifically: after washing the impregnated material with deionized water, drying it for 24 hours at a temperature of 110 C., after the dried material is cooled to room temperature, elevating the temperature to 400 C. at a speed of 6 C./min firstly, and then elevating the temperature to 450 C. at a speed of 3 C./min, at this temperature the dried material is calcinated for 6 hours.

(85) In the desulfurization adsorbent prepared above, Zn has a loading capacity of about 10% on the first composite carrier, Fe has a loading capacity of about 10% on the first composite carrier; moreover, Zn and Fe which are loaded on the first composite carrier have a weight ratio of 1:1. Upon detection, a sulfur capacity of the desulfurization adsorbent is 0.481, and its lifespan lasts for 7-8 h.

2. Prepare a Selective Hydrodesulfurization Catalyst

(86) A selective hydrodesulfurization catalyst is prepared according to the method described in Example 5, the difference lies in that, a loading capacity of Co on the carrier is controlled at about 2%, a loading capacity of Mo on the carrier is controlled at about 8%, and Co and Mo which are loaded on the carrier have a weight ratio of 0.25:1.

3. Gasoline Upgrading

(87) Fluid catalytic cracking gasoline from Jinan is taken as a feedstock (reference may be made to Table 6 for its composition), and reference may be made to FIG. 7 for a process flow of desulfurization of the gasoline feedstock.

(88) Firstly, a mercaptan conversion method (an alkali-free sweetening process) is used to subject the gasoline feedstock to sweetening treatment, where an operating pressure of the reactor may be controlled at about 0.5 MPa, a reaction temperature is controlled at about 40 C., a feeding space velocity is 1.0 h.sup.1 and a volume ratio of an air flow rate to a feeding rate is about 0.5, thereby obtaining sweetened gasoline.

(89) The sweetened gasoline is cut into light, medium and heavy gasoline fractions, where a cutting temperature of the light and the medium gasoline fractions is 60 C., and a cutting temperature of the medium and the heavy gasoline fractions is 100 C.

(90) Filling the desulfurization adsorbent prepared above into a fixed bed reactor, at a temperature of 30 C. and normal atmospheric pressure, subjecting the medium gasoline fraction to adsorption desulfurization at a flow rate of 0.3 mL/min to obtain a first desulfurized medium gasoline fraction; moreover, after the adsorption desulfurization, sweeping the desulfurization adsorbent that has been subjected to the adsorption desulfurization with steam at a temperature of 180 C. for 1 h for washing, collecting a sulfur-rich component, incorporating the sulfur-rich component into the heavy gasoline fraction to proceed with a next step. Moreover, sweeping the washed desulfurization adsorbent with nitrogen at a temperature of 400 C. for 10 min for drying, and sweeping the dried desulfurization adsorbent with nitrogen at a room temperature (10 C.) for 10 min for cooling, so that the desulfurization adsorbent is regenerated, a sulfur capacity of the desulfurization adsorbent after being regenerated three times is 0.481, and its lifespan lasts for about 7 h.

(91) Introducing the first desulfurized medium gasoline fraction into a fixed bed reactor filled with the catalyst for the aromatization/hydroisomerization reaction as prepared in Example 5, and carrying out an aromatization/hydroisomerization reaction for 200 hours in the fixed bed reactor successively in a condition where a reaction temperature is 300 C., a reaction pressure is 1 MPa, a weight hourly space velocity is 2.5 h.sup.1, and a volume ratio of hydrogen to oil is 350:1, thereby obtaining second desulfurized medium gasoline fraction.

(92) Filling the selective hydrodesulfurization catalyst prepared above into a fixed bed reactor, subjecting the heavy gasoline fraction incorporated with the sulfur-rich component to selective hydrodesulfurization in a condition where a reaction temperature is 300 C., a reaction pressure is 1.5 MPa, a liquid hourly space velocity is 4.0 h.sup.1, and a volume ratio of hydrogen to oil is 600, thereby obtaining a desulfurized heavy gasoline fraction.

(93) The desulfurized heavy gasoline fraction is blended with the light gasoline fraction and the second desulfurized medium gasoline fraction to prepare upgraded gasoline, reference may be made to Table 6 for its composition.

Example 8

1. Prepare a Catalyst for an Aromatization/Hydroisomerization Reaction

(94) A ZSM-5 zeolite is blended with aluminum oxide at a weight ratio of 83:17 to prepare a composite carrier, where a weight ratio of the zeolite to aluminum oxide is 1:0.2.

(95) The composite carrier prepared above is subjected to incipient wetness impregnation with an aqueous solution of Ga.sub.t (SO.sub.4).sub.316.H.sub.2O to obtain a impregnated material; after washing the impregnated material with deionized water, drying it for 18 hours at a temperature of 120 C.; after cooling down the dried material to room temperature, the temperature is elevated to 400 C. at a speed of 6 C./min firstly, and then elevated to 640 C. at a speed of 3 C./min, at this temperature the dried material is calcinated for 5 hours, thereby preparing a catalyst, and Ga has a loading capacity of about 3% on the composite carrier.

2. Gasoline Upgrading

(96) Fluid catalytic cracking gasoline from Jinan is taken as a feedstock (reference may be made to Table 6 for its composition), and reference may be made to FIG. 8 for a process flow of upgrading of the gasoline feedstock.

(97) Firstly, a mercaptan conversion method (an alkali-free sweetening process) is used to subject the gasoline feedstock to sweetening treatment, where an operating pressure of the reactor may be controlled at about 0.3 MPa, a reaction temperature is controlled at about 60 C., a feeding space velocity is 1.5 h.sup.1 and a volume ratio of an air flow rate to a feeding rate is about 1.0, thereby obtaining sweetened gasoline.

(98) The sweetened gasoline is cut into light, medium and heavy gasoline fractions, where a cutting temperature of the light and the medium gasoline fractions is 50 C., and a cutting temperature of the medium and the heavy gasoline fractions is 90 C.

(99) Introducing the medium gasoline fraction from a middle lower part of an extraction tower and sulfolane from a top of the extraction tower, and meanwhile injecting isopentane to a backflow device at the bottom of the extraction tower, controlling a temperature at the top of the extraction tower at 60 C., a temperature at the bottom of the extraction tower at 40 C., and a pressure (absolute pressure) at the top of the extraction tower at 0.2 MPa, controlling a weight ratio of sulfolane to the medium gasoline fraction at 1.0, and controlling a weight ratio of isopentane to the medium gasoline fraction at 0.1, thereby collecting first desulfurized medium gasoline fraction and sulfur-rich oil content respectively.

(100) Introducing the first desulfurized medium gasoline fraction into a fixed bed reactor filled with the catalyst for the aromatization/hydroisomerization reaction as prepared above, and carrying out an aromatization/hydroisomerization reaction for 200 hours in the fixed bed reactor successively in a condition where a reaction temperature is 400 C., a reaction pressure is 2 MPa, a weight hourly space velocity is 6 h.sup.1, and a volume ratio of hydrogen to oil is 800:1, thereby obtaining second desulfurized medium gasoline fraction;

(101) Filling the selective hydrodesulfurization catalyst prepared in Example 5 into a fixed bed reactor, subjecting the heavy gasoline fraction incorporated with the extracted oil and the sulfur-rich component to selective hydrodesulfurization in a condition where a reaction temperature is 300 C., a reaction pressure is 2.5 MPa, a liquid hourly space velocity is 2.0 h.sup.1, and a volume ratio of hydrogen to oil is 400, thereby obtaining a desulfurized heavy gasoline fraction. The desulfurized heavy gasoline fraction is blended with the light gasoline fraction and the second desulfurized medium gasoline fraction to prepare upgraded gasoline, reference may be made to Table 6 for its composition.

(102) TABLE-US-00006 TABLE 6 Composition of Gasoline before and after Upgrading Desulfurized Desulfurized Gasoline gasoline in gasoline in Item feedstock Example 7 Example 8 Density (20 C.), g/cm.sup.3 0.7562 0.7764 0.7783 Sulfur content, ppmw 421 10 10 Group Paraffin 25.6 37.3 33.8 composition, Olefins 30.9 15.6 13.6 m % Naphthene 8.9 11.5 14.4 Aromatics 34.6 35.6 38.2 Octane RON 89.2 91.7 92.4 number MON 80.1 82.2 82.5

(103) It can be seen from Table 6 that:

(104) The method for upgrading gasoline as described in Example 7 and Example 8 of the present invention not only can reduce sulfur content in the gasoline feedstock below 10 ppm, but also can control olefins content below 24%, and octane number is increased significantly.

Comparative Example 1

(105) After preparing a ZSM-5 type zeolite subjected to alkali treatment according to the method as described in Example 5, the ZSM-5 type zeolite after alkali treatment is sequentially subjected to incipient wetness impregnation with a K.sub.2SO.sub.4 solution and a NiSO.sub.4 solution according to the method described in Example 5, washing, drying and calcinating the impregnated material, thereby preparing a desulfurization adsorbent. Upon detection, a sulfur capacity of the desulfurization adsorbent is 0.286, and its lifespan is only 3-4 h.

Comparative Example 2

(106) After preparing an active carbon subjected to alkali treatment according to the method as described in Example 5, the active carbon after alkali treatment is sequentially subjected to incipient wetness impregnation with a K.sub.2SO.sub.4 solution and a NiSO.sub.4 solution according to the method described in Example 5, washing, drying and calcinating the impregnated material, thereby preparing a desulfurization adsorbent. Upon detection, a sulfur capacity of the desulfurization adsorbent is 0.236, and its lifespan is only 3-4 h.

Comparative Example 3

(107) A ZSM-5 type zeolite (without alkali treatment) and an active carbon (without alkali treatment) according to Example 5 are directly placed into a mortar and grounded after being blended at a weight ratio of 40:60, then placing the grounded material in an oven at a temperature of 120 C. to be dried for 6 h, thereby preparing a composite carrier.

(108) The composite carrier is subjected to incipient wetness impregnation sequentially with a K.sub.2SO.sub.4 solution and a NiSO.sub.4 solution according to the method described in Example 5, washing, drying and calcinating the impregnated material, thereby preparing a desulfurization adsorbent. Upon detection, a sulfur capacity of the desulfurization adsorbent is 0.155, and its lifespan is only 2-3 h.

(109) Finally, it should be noted that the foregoing examples are merely intended for describing technical solutions of the present invention rather than limiting the present invention. Although the present invention is described in detail with reference to the foregoing examples, persons of ordinary skill in the art should understand that they may still make modifications to the technical solutions described in the foregoing examples, or make equivalent replacements to some or all technical features therein; however, these modifications or replacements do not make the essence of corresponding technical solutions depart from the scope of the technical solutions in the examples of the present invention.