CN108329944B

CN108329944B - Method for co-producing desulfurized low-olefin gasoline and chemical products by using catalytic cracking gasoline

Info

Publication number: CN108329944B
Application number: CN201810130514.7A
Authority: CN
Inventors: 郝天臻; 赵亮; 高金森; 陈丰; 张宇豪
Original assignee: Hebei Refining Technologies Co ltd; China University of Petroleum Beijing
Current assignee: Hebei Refining Technologies Co ltd; China University of Petroleum Beijing
Priority date: 2018-02-08
Filing date: 2018-02-08
Publication date: 2020-09-22
Anticipated expiration: 2038-02-08
Also published as: CN108329944A

Abstract

The invention provides a method for co-producing desulfurized low-olefin gasoline and chemical products by utilizing catalytic cracking gasoline. The method of the invention comprises the following steps: pre-hydrogenating the catalytic cracking gasoline to obtain pre-hydrogenated catalytic cracking gasoline; cutting the prehydrogenation catalytic cracking gasoline into light fraction, medium fraction and heavy fraction; carrying out solvent extraction on the middle distillate to obtain raffinate oil rich in olefin and extract oil rich in aromatic hydrocarbon; carrying out mild aromatization or catalytic cracking on at least part of the light fraction and/or at least part of raffinate oil to obtain a chemical product; recovering light olefin from the extracted oil to obtain light olefin and sulfur-rich oil; returning at least part of the light olefin to the system for solvent extraction for backwashing; and carrying out selective hydrodesulfurization on the heavy fraction and the sulfur-rich oil to obtain a desulfurized heavy fraction. The method can efficiently convert the catalytic cracking gasoline into high-value chemical products, and can co-produce high-quality desulfurized low-olefin gasoline components.

Description

Method for co-producing desulfurized low-olefin gasoline and chemical products by using catalytic cracking gasoline

Technical Field

The invention belongs to the technical field of petrochemical industry, and particularly relates to a method for co-producing desulfurized low-olefin gasoline and chemical products by using catalytic cracking gasoline.

Background

With the increasing weight of petroleum resources and the increasing influence of automobile exhaust emission on the atmospheric environment, the requirements on the quality of the motor gasoline are increasingly strict worldwide. The national VI automotive gasoline standard which is about to be implemented in 2019, 1 and 1 requires that the sulfur content of gasoline is lower than 10ppm, the olefin content is lower than 15v percent, and the octane number is maintained to be more than 93. Thus, the production of high quality gasoline is marked by an increase in octane number with a simultaneous decrease in the sulfur content and the olefin content.

At present, aiming at the production of low-sulfur, low-alkene and high-octane gasoline, developed countries mainly achieve corresponding quality standards by blending gasoline produced by various processes; generally, the catalytic cracking gasoline containing olefin is less than 1/3, the reformed gasoline containing aromatic hydrocarbon but no olefin is more than 1/3, and the other clean gasoline components such as alkylation, isomerization and etherification containing no olefin and no aromatic hydrocarbon are less than 1/3, and the blended gasoline has low sulfur content and olefin content and high octane number.

The catalytic cracking gasoline (i.e. FCC gasoline) is the main component of motor gasoline in China, and accounts for about 75% of gasoline pools. The catalytic cracking gasoline has the characteristics of high olefin content (30-45 v%), high sulfur content (150-1000ppm) and the like. As is known, 85-95 wt% of sulfur and 95 v% of olefin in the commodity gasoline in China come from catalytic cracking gasoline, which is the main reason that the gasoline for vehicles in China is difficult to meet the requirements that the sulfur content is lower than 10ppm and the olefin content is lower than 15-18 v%.

China mainly depends on a hydrodesulfurization technology aiming at the processing of catalytic cracking gasoline, the technology can meet the requirements that the sulfur content is lower than 10ppm and the olefin content is reduced, however, the olefin content is reduced in a mode of changing hydrogenation saturation into alkane, so that the octane number of a gasoline product is reduced, the aim of desulfurizing, reducing the olefin and protecting the octane number cannot be met, and in addition, the economic benefit of an enterprise is seriously influenced.

In the hydrodesulfurization process, octane number loss caused by olefin saturation cannot be effectively inhibited by optimizing a catalyst or process conditions of the hydrodesulfurization process, and olefin components are prevented from entering a hydrodesulfurization unit from a hydrogenation raw material, so that the method is a fundamental method for protecting olefins. At present, relevant research at home and abroad mainly focuses on distillation cutting of FCC gasoline and hydrotreatment of high-sulfur components, and the mode can prevent high-octane olefins from being subjected to hydrogenation saturation, but cannot convert the high-octane olefins into high-octane aromatics.

Meanwhile, the market demand of chemical products such as ethylene, propylene, benzene, toluene and xylene (abbreviated as BTX) is very large. Ethylene and propylene are very important organic chemical basic raw materials, wherein the ethylene is mainly used for producing polyethylene, ethylene propylene rubber, polyvinyl chloride and the like, and the propylene can be used for generating synthetic resin, synthetic rubber, various fine chemicals and the like; BTX can be directly used as a chemical production raw material, and has great market value. However, the existing research mainly focuses on producing gasoline blending components, and cannot be converted into various chemical products urgently needed by the market.

Therefore, how to efficiently combine the production of high octane gasoline fraction with the preparation of bulk chemical products is a problem to be solved.

Disclosure of Invention

The invention provides a method for co-producing desulfurized low-olefin gasoline and chemical products by utilizing catalytically cracked gasoline, which can efficiently convert catalytically cracked gasoline into high-value chemical products and can co-produce high-quality desulfurized low-olefin gasoline components.

The invention provides a method for co-producing desulfurized low-olefin gasoline and chemical products by utilizing catalytic cracking gasoline, which comprises the following steps:

pre-hydrogenating the catalytic cracking gasoline to obtain pre-hydrogenated catalytic cracking gasoline;

cutting the prehydrogenated catalytically cracked gasoline into light, medium and heavy fractions;

performing solvent extraction on the middle distillate to obtain raffinate oil rich in olefin and extract oil rich in aromatic hydrocarbon;

carrying out mild aromatization or catalytic cracking on at least part of the light fraction and/or at least part of the raffinate oil to obtain a chemical product;

recovering light olefin from the extracted oil to obtain light olefin and sulfur-rich oil;

returning at least a portion of the light olefins to the system undergoing the solvent extraction for backwashing;

and carrying out selective hydrodesulfurization on the heavy fraction and the sulfur-rich oil to obtain a desulfurized heavy fraction.

The catalytically cracked gasoline (i.e., FCC gasoline) of the present invention is not strictly limited and may be the conventional catalytically cracked gasoline of the present invention. In the present invention, unless otherwise specified, the pressure refers to gauge pressure and the content refers to mass content.

The invention prehydrogenation is carried out on the catalytic cracking gasoline, and the catalytic cracking gasoline is used for reacting light sulfide in the catalytic cracking gasoline with dialkene to form high-boiling sulfide, thereby avoiding the conditions of coking and the like in the subsequent process of the dialkene, and ensuring the long-term operation of heavy fraction hydrodesulfurization; during the pre-hydrogenation process, the olefins in the catalytically cracked gasoline are not saturated.

The prehydrogenation process of the present invention is not critical and, for example, an alkali-free deodorization process or Prime-G + prehydrogenation process conventional in the art may be employed.

In a particular embodiment of the invention, the prehydrogenation is carried out in the presence of a prehydrogenation catalyst; wherein the pre-hydrogenation catalyst is Ni-Mo/Al₂O₃(nickel-molybdenum bimetallic catalyst), the composition thereof may be, for example, (% by mass): al (Al)₂O₃90.5 percent of (carrier), 6 percent of Ni and 3.5 percent of Mo; the pre-hydrogenation process conditions may be: the hydrogen partial pressure is 2.2MPa, and the volume space velocity is 3.0h^-1The volume ratio of hydrogen to oil is 10: 1, and the reaction temperature is 110 ℃.

In the invention, the cutting is to cut the prehydrogenation catalytic cracking gasoline into light, medium and heavy fractions according to the distillation range from low to high; the cleavage may be performed by a method conventional in the art, and for example, a distillation cleavage or the like may be used.

In a specific scheme of the invention, the cutting temperature of the light fraction and the middle fraction is 35-65 ℃, and further 50-60 ℃; the cutting temperature of the middle fraction and the heavy fraction is 100-160 ℃. At this time, the distillation range of the middle distillate is 35-65 ℃ to 100-160 ℃.

In the present invention, the chemical products include BTX (including benzene, toluene, and xylene), ethylene, propylene, and the like; wherein, the mild aromatization can produce BTX, and the catalytic cracking can produce ethylene and propylene. In addition, the process can be adjusted according to actual needs; if the chemical products are required to be produced maximally, all of the light fraction and all of the raffinate oil can be subjected to mild aromatization or catalytic cracking; if the desulfurized low-olefin gasoline needs to be produced to the maximum extent, all the light fraction and all the raffinate oil can be blended with the desulfurized heavy fraction; if chemical products and desulfurized low-olefin gasoline are required to be obtained, mild aromatization or catalytic cracking can be carried out on part of the light fraction and/or part of the raffinate oil according to the requirement. In addition, the partial BTX may also be reconciled as desired.

In a specific embodiment of the invention, a part of the light fraction and a part of the raffinate oil are subjected to mild aromatization or catalytic cracking, and the other part of the light fraction and the other part of the raffinate oil are blended with the desulfurized heavy fraction to form desulfurized low-olefin gasoline; wherein the volume ratio of the part subjected to mild aromatization or catalytic cracking to the part subjected to blending in the light fraction is (0.5-4): 1, the volume ratio of the part subjected to mild aromatization or catalytic cracking to the part subjected to blending in the raffinate oil is (0.5-3): 1. in addition, a portion of the light fraction may be returned to the system in which the solvent extraction is carried out for backwashing, if necessary.

Further, a portion of the light olefins may be returned to the system undergoing the solvent extraction for backwashing while another portion of the light olefins is subjected to mild aromatization or catalytic cracking; the amount of the light olefin returned to the solvent extraction is not particularly limited, and the amount of the light olefin returned to the solvent extraction may be 20 to 100% (by volume, 100% means the whole amount is returned to the solvent extraction) of the amount of the recovered light olefin, and further may be 40 to 60%.

In the invention, the solvent extraction mainly utilizes the solvent to realize the directional separation of aromatic hydrocarbon, olefin, alkane and cyclane in middle distillate; the solvent used for solvent extraction in the present invention is not particularly limited as long as the above-mentioned directional separation can be achieved, and for example, one or a combination of two or more of diethylene glycol, triethylene glycol, tetraethylene glycol, dimethyl sulfoxide, sulfolane, N-formylmorpholine, N-methylpyrrolidone, polyethylene glycol, propylene carbonate, and the like can be used. In particular, the water content of the solvent is preferably < 1.0% by weight, and more preferably 0.5 to 0.8% by weight.

In a specific embodiment of the present invention, the solvent extraction is performed using a composite solvent of sulfolane and N-methylpyrrolidone (i.e., using the composite solvent as a solvent), wherein the volume content of N-methylpyrrolidone in the composite solvent is 5-40%, and further 5-20%.

The research shows that: when the composite solvent is adopted for solvent extraction, the mass content of olefin in raffinate oil is 40-45%, and the mass content of aromatic hydrocarbon in extract oil is 60-70%; when sulfolane is adopted for solvent extraction, the mass content of olefin in raffinate oil is 35-40%, and the mass content of aromatic hydrocarbon in extract oil is 50-55%. Therefore, the composite solvent has high selectivity, and when the composite solvent is used for solvent extraction, the mass content of olefin in raffinate oil is increased by about 5 percent, and the mass content of aromatic hydrocarbon in extract oil is increased by about 10-15 percent, so that the directional separation of the aromatic hydrocarbon and the olefin in middle distillate is facilitated.

In the present invention, solvent extraction may be carried out in a manner conventional in the art; specifically, the solvent extraction may include:

the middle fraction enters from the middle-lower part of the extraction tower, the solvent enters from the upper part of the extraction tower, the temperature of the top of the extraction tower is controlled to be 50-105 ℃, the temperature of the bottom of the extraction tower is controlled to be 35-80 ℃, the pressure (absolute pressure) of the top of the extraction tower is 0.2-0.8MPa, and the feeding ratio of the solvent to the middle fraction is 1.0-5.0.

Further, the overhead temperature of the extraction column is preferably 50 to 70 ℃, the overhead pressure (absolute pressure) is preferably 0.5 to 0.6MPa, and the feed ratio of the solvent to the middle distillate is preferably controlled to 2.0 to 3.0.

In the present invention, mild aromatization is aromatization carried out under relatively mild conditions (low temperature, normal pressure) and is mainly used for converting olefins into aromatic hydrocarbons.

Specifically, the mild aromatization of the present invention may be carried out in the presence of an aromatization catalyst; the aromatization catalyst is obtained by loading active ingredients on a carrier. Further, the carrier of the aromatization catalyst comprises a zeolite molecular sieve and pseudoboehmite, the active ingredients comprise a first ingredient, a second ingredient, a third ingredient and a fourth ingredient, the first ingredient is Na or K, the second ingredient is P, the third ingredient is Zn, the fourth ingredient is La, the loading amount of the first ingredient is 0.2-0.5%, the loading amount of the second ingredient is 1-3%, the loading amount of the third ingredient is 5-8%, and the loading amount of the fourth ingredient is 0-3%.

Further, the mass ratio of the zeolite molecular sieve to the pseudo-boehmite in the carrier of the aromatization catalyst may be (1-9): 1; the zeolite molecular sieve may be, for example, an HZSM-5 molecular sieve. Further, the supported amount of the fourth component is further 1.5 to 3%.

In the present invention, the above-mentioned method for preparing an aromatization catalyst comprises the following steps in order:

mixing a zeolite molecular sieve with pseudo-boehmite to obtain a catalyst precursor;

carrying out ion exchange modification on the catalyst precursor to enable the first component to be loaded on the catalyst precursor;

subjecting the catalyst precursor to a first modification treatment so that the second component or the fourth component is supported on the catalyst precursor;

carrying out active metal modification on the catalyst precursor to enable a third component to be loaded on the catalyst precursor;

the catalyst precursor is subjected to a second modification treatment to support a second component on the catalyst precursor.

Further, the ion exchange modification may include:

the catalyst precursor is subjected to ion exchange modification using a salt solution or an alkali solution containing sodium ions or potassium ions as the ion exchange solution, the ion exchange modification being controlled to last at 60-120 ℃ for at least 30 minutes, then dried at 60-280 ℃ for at least 3 hours, and finally calcined at 450-700 ℃ for at least 1 hour.

The first modification treatment, the active metal modification and the second modification treatment are not strictly limited, and conventional methods in the field, such as an isometric immersion method, can be adopted; further, the modification conditions may be conventional in the art.

In the invention, the temperature of the mild aromatization can be controlled to be 280-330 ℃, the pressure is normal pressure, and the volume space velocity is 1.0-2.0h^-1. The mild aromatization can be carried out by adopting a fixed bed reactor, and can be carried out under the conditions of hydrogenation and non-hydrogenation; preferably under non-hydrogen conditions.

The above-described mild aromatization of the present invention is easily achieved by using the above-described aromatization catalyst and aromatization conditions, thereby converting olefins into aromatics.

The mild aromatization of the invention is carried out by adopting the aromatization catalyst, the aromatization catalyst has high aromatization activity, the aromatization reaction can be carried out under the mild conditions of temperature not higher than 400 ℃ (particularly not higher than 330 ℃) and normal pressure, the selectivity of olefin selective conversion into aromatic hydrocarbon is higher, the selectivity can reach more than 60% under the condition that the liquid yield is ensured to be higher than 98.5%, the generated aromatic hydrocarbon is mainly C7-C9 aromatic hydrocarbon, reaches about 90%, and the generation rate of benzene is lower; in addition, the aromatization catalyst has good anti-carbon deposition capability, so that the service life and the stability are longer, the single-pass activity is 8-10 days (the activity of olefin conversion rate is maintained to be more than 50 percent), and the liquid yield is maintained to be more than 98.5 percent, so that the oil loss is effectively avoided, and the long-period stable operation can be kept.

The mild aromatization of the invention not only can effectively reduce the olefin content in the aromatization product, obviously improve the aromatic hydrocarbon content, especially the C7-C9 aromatic hydrocarbon content and lower the benzene content, and achieve the effects of low olefin, high octane number and low benzene content, thereby being beneficial to obtaining high-quality gasoline meeting national VI standards, but also being beneficial to saving production energy consumption, having very good industrial amplification adaptability, and being really used in actual industrial production.

In the present invention, the catalytic cracking may be carried out using a fluidized reactor; in addition, the catalytic cracking can be carried out in the presence of a catalytic cracking catalyst, the catalytic cracking catalyst comprises a ZSM-5 molecular sieve and a RE-USY molecular sieve, and the mass ratio of the ZSM-5 molecular sieve to the RE-USY molecular sieve is (1-3): 1; further, the temperature of the catalytic cracking can be controlled to be 600-700 ℃, and the mass ratio of water to the raw material is (0.5-2): 1, the mass ratio of the catalytic cracking catalyst to the raw material is 1: (2-5).

In the invention, the light olefin (light olefin for short) can be recovered from the extracted oil by adopting a conventional mode; wherein the recovered light olefins comprise primarily C5 olefins.

Specifically, the light olefin recovery may be carried out in a recovery column, wherein the overhead temperature of the recovery column may be controlled to be 80 to 95 ℃, the overhead pressure may be controlled to be 0.05 to 0.2MPa, the bottom temperature may be controlled to be 150-.

In the present invention, at least part of the light olefins are returned to the system in which the solvent extraction is carried out, and backwashed (i.e., back extraction) is carried out for displacing the large molecular olefins from the extract oil into the raffinate oil, thereby flowing out from the top of the extraction column. Specifically, the light olefins may enter from the lower portion of the extraction column. At the moment, after the middle distillate and the solvent are subjected to multi-stage countercurrent contact at the upper section of the extraction tower, raffinate oil (desulfurized middle distillate) flows out from the top of the tower; meanwhile, the recovered light olefin is contacted with a solvent at the bottom of the tower, so that the macromolecular olefin is replaced from the extract oil to raffinate oil, and then flows out of the tower top together with the desulfurized middle distillate, and the sulfur-rich oil containing sulfide, aromatic hydrocarbon and cycloolefin (namely, the sulfur-rich middle distillate) flows out of the tower bottom.

The research shows that: in the solvent extraction process, the smaller the carbon number of the same hydrocarbon is, the higher the solubility of the solvent to the solvent is, and the larger the carbon number is, the opposite is realized (namely, the lower olefin has higher solubility in the solvent); the light olefin is returned to the solvent extraction step for back extraction, so that the high-carbon olefin can be separated and replaced into the raffinate oil, the raffinate oil with higher olefin content and the extract oil with higher aromatic hydrocarbon content are obtained, and the separation effect of the solvent on the olefin and the aromatic hydrocarbon is obviously improved.

The results show that: after light olefin is adopted for back washing, the mass content of olefin in raffinate oil is 45-50%; when the light olefin is not adopted for backwashing, the mass content of the olefin in the raffinate oil is 40-45%. The light olefin is adopted for backwashing, so that the mass content of the olefin in the raffinate oil can be improved by about 5 percent, and the separation effect of the olefin and the aromatic hydrocarbon is further improved.

In the present invention, selective hydrodesulfurization can be carried out in a manner conventionally practiced in the art, for example, S-zorb, RSDS, OCT-M, Prime-G can be used⁺Selective desulfurization techniques such as CODS and the like and other selective deep desulfurization techniques.

In the embodiment of the present invention, the selective hydrodesulfurization is performed in the presence of a selective hydrodesulfurization catalyst, and the selective hydrodesulfurization catalyst is not limited in the present invention, and may be a catalyst that is conventional in the art, for example, a catalyst disclosed in chinese patent publication No. CN 104673376A.

Specifically, the selective hydrodesulfurization catalyst can be obtained by loading an active metal component on a carrier; wherein the carrier may be a molecular sieve (e.g., X-type, Y-type, or ZSM-5-type) or a metal oxide (e.g., alumina), and the active metal may include Co and Mo, and the total mass content of Co and Mo in the selective hydrodesulfurization catalyst may be 5 to 20%. Further, the mass ratio of Co to Mo supported on the carrier may be (0.2 to 0.8): 1.

in the present invention, the selective hydrodesulfurization may be carried out in a fixed bed reactor. Further, the temperature of the selective hydrodesulfurization is 200-305 ℃, the pressure is 1.5-3.0MPa, and the volume space velocity is 1-5h^-1The volume ratio of hydrogen to oil is 300-600. The sulfur content of the desulfurized heavy fraction obtained by the selective hydrodesulfurization is less than 10ppm, and the desulfurized heavy fraction can be used as a gasoline blending component.

As the sulfide, the aromatic hydrocarbon and the cycloolefin are main components forming the sulfur-rich oil, the sulfide is decomposed and removed when the sulfur-rich oil is subjected to selective hydrodesulfurization, the aromatic hydrocarbon does not participate in the reaction, and the octane number is improved by the hydrogenation saturation of the cycloolefin, so that the octane number is not lost.

According to the invention, through the research on the group composition distribution such as sulfur content, olefin content and aromatic hydrocarbon content in the catalytic cracking gasoline and the octane value distribution of narrow fractions, the catalytic cracking gasoline subjected to pre-hydrogenation is divided into three fractions, namely light fraction, medium fraction and heavy fraction, and specific conditions of impurity content distribution and octane value distribution of each fraction are adopted to carry out comprehensive quality upgrading and product structure adjustment on the catalytic cracking gasoline by adopting a specific treatment mode, so that deep desulfurization is realized, the sulfur content of the treated gasoline fraction is reduced to less than 10ppm, the olefin content is reduced to below 18 v%, the octane value of a gasoline product is greatly improved, and the aims of reducing sulfur, reducing olefin and improving the octane value are realized; in addition, the method also can produce high-value chemical products such as benzene, toluene, xylene, ethylene, propylene and the like as byproducts, and has good application prospect.

Drawings

FIG. 1 is a flow chart of a process for co-producing desulfurized low-olefin gasoline and chemical products using catalytically cracked gasoline in accordance with one embodiment of the present invention;

FIG. 2 is a flow chart of a process for co-producing desulfurized low-olefin gasoline and chemical products using catalytically cracked gasoline in accordance with another embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings and the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

1. Preparation of aromatization catalyst

1) Preparation of catalyst precursor

Under the room temperature environment, the ratio of silicon to aluminum is 25, the HZSM-5 molecular sieve and the pseudo-boehmite are mixed according to the ratio of 4: 1 to obtain the catalyst precursor.

2) Modification by ion exchange

The catalyst precursor is subjected to ion exchange treatment by adopting a constant-temperature water bath method, specifically, sodium hydroxide is dissolved in deionized water, is mixed with the catalyst precursor, is placed in a 90 ℃ water bath environment and is stirred for 2 hours, so that the loading capacity of sodium is about 0.2 wt%, and then is dried for about 8 hours at about 120 ℃ and is roasted for about 4 hours at about 540 ℃.

3) First modification treatment

Adopting an isometric impregnation method to carry out first modification treatment on the catalyst precursor subjected to ion exchange treatment, specifically dissolving ammonium dihydrogen phosphate in deionized water, then impregnating the catalyst precursor, and controlling the mass ratio of an aqueous solution of ammonium dihydrogen phosphate to the catalyst precursor to be (1.0 +/-0.2): 1, the loading amount of phosphorus is about 1 wt%; after the impregnation is completed, the mixture is aged at a temperature of about 20 ℃ for about 6 hours, dried at about 120 ℃ for about 8 hours, and calcined at about 540 ℃ for about 4 hours.

4) Reactive metal modification

The catalyst precursor subjected to the first modification treatment is subjected to hydrothermal treatment at a temperature of about 300 ℃ in a 100% steam atmosphere for about 6 hours, and then the catalyst precursor subjected to the hydrothermal treatment is subjected to active metal loading by an isometric immersion method: dissolving zinc nitrate in a citric acid solution with the concentration of about 0.1mol/L to obtain a steeping fluid; controlling the mass ratio of the impregnation liquid to the catalyst precursor to be (1.0 +/-0.2): 1. the dipping temperature is about 20 ℃, the dipping time is about 10 hours, and the loading amount of zinc is about 5 wt%; after the impregnation is completed, the mixture is aged at about 25 ℃ for 4 hours, dried at about 120 ℃ in an air atmosphere for about 10 hours, and baked at 540 ℃ for about 4 hours.

5) Second modification treatment

And (3) performing second modification treatment on the catalyst precursor subjected to active metal loading by adopting an isometric impregnation method, and referring to the step 3) to obtain the aromatization catalyst.

The aromatization catalyst comprises a zeolite molecular sieve (HZSM-5 molecular sieve) and pseudo-boehmite, wherein the mass ratio of the zeolite molecular sieve to the pseudo-boehmite is 4: 1; the active ingredients comprise Na, P and Zn, wherein the loading amount of Na is 0.2 wt%, the loading amount of P is 2 wt%, and the loading amount of Zn is 5 wt%.

2. Mild aromatization test

The C5 cut catalytic cracking gasoline (the family composition is shown in table 1) produced by the North China petrochemical through catalytic cracking is used as a raw material, and the aromatization catalyst is adopted to carry out a mild aromatization test under the non-hydrogenation condition.

In the presence of aromatization catalyst, the above-mentioned C5 cut stage catalytic cracking gasoline is undergone the process of mild aromatization in fixed bed, in which the temperature for controlling mild aromatization is 290 deg.C, pressure is normal pressure and volume space velocity is 1.5h^-1(ii) a The mild aromatization results are shown in table 2.

TABLE 1C 5 cut fraction catalytically cracked gasoline family composition

TABLE 2C 5 cut segment moderated aromatization product family composition

The results show that:

the mild aromatization of the C5 cut catalytic cracking gasoline was performed in the manner of this example, with a liquid yield of 99.5%, an olefin conversion of 58%, and an aromatics content increase of 12%.

In addition, the aromatization catalyst has longer service life and stability, the single-pass activity is 8-10 days (the conversion rate of olefin is maintained at the activity of more than 50 percent), the liquid yield is maintained at more than 98.5 percent, the oil loss can be effectively avoided, and the long-period stable operation can be kept.

Example 2

1. Preparation of aromatization catalyst

1) Preparation of catalyst precursor

Under the room temperature environment, the HZSM-5 molecular sieve with the silica-alumina ratio of 25 and the nano-scale and the pseudo-boehmite are mixed according to the weight ratio of 9: 1 to obtain the catalyst precursor.

2) Modification by ion exchange

The catalyst precursor is subjected to ion exchange treatment by adopting a constant-temperature water bath method, specifically, sodium hydroxide is dissolved in deionized water, is mixed with the catalyst precursor, is placed in a 90 ℃ water bath environment and is stirred for 2 hours, so that the loading capacity of sodium is about 0.5 wt%, and then is dried for about 8 hours at about 120 ℃ and is roasted for about 4 hours at about 540 ℃.

3) First modification treatment

Adopting an isometric impregnation method to carry out first modification treatment on the catalyst precursor subjected to ion exchange treatment, specifically dissolving lanthanum nitrate in deionized water, and then impregnating the catalyst precursor to ensure that the loading capacity of lanthanum is 2 wt%; aging at about 23 deg.C for about 6 hr; then dried at about 120 ℃ for about 8 hours and finally calcined at about 540 ℃ for about 8 hours.

4) Reactive metal modification and second modification treatment

The catalyst precursor subjected to the first modification was subjected to hydrothermal treatment at a temperature of about 300 ℃ for about 6 hours in a 100% steam atmosphere.

Carrying out active metal loading and second modification treatment on the catalyst precursor after the hydrothermal treatment by adopting an isometric impregnation method: dissolving ammonium dihydrogen phosphate and zinc nitrate in a citric acid solution with the concentration of about 0.1mol/L to obtain a steeping fluid; controlling the mass ratio of the impregnation liquid to the catalyst precursor to be (1.0 +/-0.2): 1. the impregnation temperature is about 30 ℃, the impregnation time is about 15 hours, and the loading amount of phosphorus is about 1 wt%, and the loading amount of zinc is about 8 wt%; after the impregnation is finished, the aromatization catalyst is obtained by aging for 6 hours at about 28 ℃, drying for about 8 hours at about 120 ℃ in the air atmosphere and roasting for about 4 hours at 540 ℃.

The aromatization catalyst comprises a zeolite molecular sieve (HZSM-5 molecular sieve) and pseudo-boehmite, wherein the mass ratio of the zeolite molecular sieve to the pseudo-boehmite is 9: 1; the active ingredients comprise Na, La, Zn and P, wherein the loading amount of Na is 0.5 wt%, the loading amount of La is 2 wt%, the loading amount of Zn is 8 wt%, and the loading amount of P is 1 wt%.

2. Mild aromatization test

The C6/7 cut catalytic cracking gasoline (the family composition is shown in table 3) produced by the North China petrochemical through catalytic cracking is used as a raw material, and the aromatization catalyst is adopted to carry out a mild aromatization test under the non-hydrogenation condition.

In the presence of aromatization catalyst, the above-mentioned C5 cut stage catalytic cracking gasoline is undergone the process of mild aromatization in fixed bed, in which the temperature for controlling mild aromatization is 310 deg.C, pressure is normal pressure and volume space velocity is 1.0h^-1(ii) a The mild aromatization results are shown in table 4.

TABLE 3C 6/7 cut fraction catalytically cracked gasoline family composition

TABLE 4C 6/7 cut segment moderated aromatization product family composition

The results show that:

the mild aromatization of the C6/7 cut segment catalytically cracked gasoline was carried out in the manner of this example with a liquid yield of 99.5%.

Example 3

As shown in fig. 1, the method for co-producing desulfurized low-olefin gasoline and chemical products by using catalytically cracked gasoline of the embodiment includes the following steps:

1. prehydrogenation

The composition of the catalytically cracked gasoline feedstock of this example is shown in table 5.

TABLE 5 composition of catalytically cracked gasoline feedstock

Pre-hydrogenating the catalytic cracking gasoline in the presence of a pre-hydrogenation catalyst to obtain pre-hydrogenated catalytic cracking gasoline; wherein the pre-hydrogenation catalyst is Ni-Mo/Al₂O₃The composition thereof is as follows (mass content%): al (Al)₂O₃90.5 percent, Ni 6 percent and Mo 3.5 percent; the pre-hydrogenation process conditions are as follows: the hydrogen partial pressure is 2.2MPa, and the volume space velocity is 3.0h^-1The volume ratio of hydrogen to oil is 10: 1, and the reaction temperature is 110 ℃.

After the pre-hydrogenation, light sulfides in the catalytically cracked gasoline react with diolefin to form sulfides with high boiling point, and the olefin is not saturated.

2. Cutting of

Cutting the pre-hydrocatalytic cracked gasoline into light fraction, medium fraction and heavy fraction, wherein the cutting temperature of the light fraction and the medium fraction is 60 ℃, and the cutting temperature of the medium fraction and the heavy fraction is 130 ℃, namely: the distillation range of the middle distillate is 60 ℃ to 130 ℃.

3. Solvent extraction

The solvent used for solvent extraction is a mixed solvent of sulfolane and N-methyl pyrrolidone, wherein the volume content of the N-methyl pyrrolidone in the mixed solvent is 10%.

And (3) allowing the middle distillate to enter from the middle-lower part of the extraction tower, allowing the mixed solvent to enter from the upper part of the extraction tower, controlling the top temperature of the extraction tower to be 70 ℃, the bottom temperature of the extraction tower to be 45 ℃, the top pressure (gauge pressure) to be 0.5MPa, and controlling the feeding ratio of the mixed solvent to the middle distillate to be 2.0 to obtain raffinate oil rich in olefin and extract oil rich in aromatic hydrocarbon.

4. Light olefin recovery and backwashing

And (3) delivering the extract oil into a recovery tower for recovering the light olefin, wherein the tower top temperature of the recovery tower is controlled to be 88 ℃, the tower top pressure is controlled to be 0.07MPa, the tower bottom temperature is controlled to be 168 ℃, and the tower bottom pressure is controlled to be 0.095MPa, so that the light olefin and the sulfur-rich oil are obtained.

Returning 40% of the light olefin to the extraction tower for backwashing, and performing mild aromatization on the rest light olefin, part of light fraction and part of raffinate oil.

5. Mild aromatization

A portion of the light ends, a portion of the raffinate and the remaining light olefins were mildly aromatized in the non-hydrogenation condition using the aromatization catalyst of example 1.

Specifically, mild aromatization was carried out in the presence of the aromatization catalyst of example 1, wherein the temperature of the mild aromatization was controlled to 290 ℃, the pressure was normal pressure, and the volume space velocity was 1.5h^-1The reaction time is about 200 hours, and an aromatization product BTX is obtained.

6. Selective hydrodesulfurization

Firstly adopting CoSO₄Soaking ZSM-5 type molecular sieve (carrier) in the solution in the same volume, washing, drying, roasting, and then adopting (NH)₄)₆Mo₇O₂₄.4H₂Aqueous solution of O to impregnated CoSO₄Soaking the ZSM-5 type molecular sieve in the solution in the same volume, and washing, drying and roasting to prepare the selective hydrodesulfurization catalyst; the total specific surface area of the prepared selective hydrodesulfurization catalyst is 168m through detection²About/g, the total pore volume is about 0.378mL/g, the loading of Co on the carrier is about 7%, the loading of Mo on the carrier is about 10%, and the mass ratio of Co to Mo loaded on the carrier is 0.7: 1.

in the presence of the selective hydrodesulfurization catalyst, selectively hydrodesulfurization is carried out on the heavy fraction and the sulfur-rich oil, wherein the temperature of the selective hydrodesulfurization is controlled to be 260 ℃, the pressure is controlled to be 1.8MPa, and the volume space velocity is controlled to be 3.0h^-1And the volume ratio of the hydrogen to the oil (namely the volume ratio of the hydrogen to the total volume of the heavy fraction and the sulfur-rich oil) is 500, so as to obtain the desulfurized heavy fraction.

7. Oil blending

Blending the other part of the light fraction, the other part of the raffinate oil and the desulfurized heavy fraction, wherein: the volume ratio of the portion subjected to mild aromatization to the portion subjected to blending in the light fraction was 1: 1, the volume ratio of the part subjected to mild aromatization to the part subjected to blending in the raffinate oil is 2: 1, obtaining a high-quality gasoline product; the composition of the aromatization product BTX and the composition of the desulfurized low-olefin gasoline are respectively shown in table 6.

Example 4

1. prehydrogenation

The composition of the catalytically cracked gasoline feedstock of this example was the same as in example 3.

2. Cutting of

Cutting the pre-hydrocatalytic cracked gasoline into light fraction, medium fraction and heavy fraction, wherein the cutting temperature of the light fraction and the medium fraction is 50 ℃, and the cutting temperature of the medium fraction and the heavy fraction is 130 ℃, namely: the distillation range of the middle distillate is 50 ℃ to 130 ℃.

3. Solvent extraction

The solvent used for solvent extraction is a mixed solvent of sulfolane and N-methyl pyrrolidone, wherein the volume content of the N-methyl pyrrolidone in the mixed solvent is 5%.

And (3) allowing the middle distillate to enter from the middle-lower part of the extraction tower, allowing the mixed solvent to enter from the upper part of the extraction tower, controlling the top temperature of the extraction tower to be 50 ℃, the bottom temperature of the extraction tower to be 35 ℃, the top pressure (gauge pressure) to be 0.6MPa, and controlling the feed ratio of the mixed solvent to the middle distillate to be 3.0 to obtain raffinate oil rich in olefin and extract oil rich in aromatic hydrocarbon.

4. Light olefin recovery and backwashing

And (3) delivering the extract oil into a recovery tower for recovering the light olefin, wherein the temperature of the top of the recovery tower is controlled to be 80 ℃, the pressure of the top of the recovery tower is controlled to be 0.05MPa, the temperature of the bottom of the recovery tower is controlled to be 150 ℃, and the pressure of the bottom of the recovery tower is controlled to be 0.08MPa, so that the light olefin and the sulfur-rich oil are obtained.

50% of the light olefin is returned to the extraction tower for backwashing, and the rest light olefin, part of the light fraction and part of raffinate oil are subjected to mild aromatization.

5. Mild aromatization

A portion of the light ends, a portion of the raffinate and the remaining light olefins were mildly aromatized in the non-hydrogenation condition using the aromatization catalyst of example 2.

Specifically, mild aromatization was carried out in the presence of the aromatization catalyst of example 2, wherein the temperature of the mild aromatization was controlled to 290 ℃, the pressure was normal pressure, and the volume space velocity was 1.5h^-1The reaction time is about 200 hours, and an aromatization product BTX is obtained.

6. Selective hydrodesulfurization

A selective hydrodesulfurization catalyst was prepared according to the method of example 3, except that the loading of Co on the carrier was controlled to be about 4%, the loading of Mo on the carrier was controlled to be about 10%, and the mass ratio of Co to Mo loaded on the carrier was controlled to be 0.4: 1.

in the presence of the selective hydrodesulfurization catalyst, selectively hydrodesulfurization is carried out on the heavy fraction and the sulfur-rich oil, wherein the temperature of the selective hydrodesulfurization is controlled to be 300 ℃, the pressure is controlled to be 2.5MPa, and the volume space velocity is controlled to be 2.0h^-1And the volume ratio of the hydrogen to the oil (namely the volume ratio of the hydrogen to the total volume of the heavy fraction and the sulfur-rich oil) is 400, so as to obtain the desulfurized heavy fraction.

7. Oil blending

Blending the other part of the light fraction, the other part of the raffinate oil and the desulfurized heavy fraction, wherein: the volume ratio of the portion subjected to mild aromatization to the portion subjected to blending in the light fraction was 2: 1, the volume ratio of the part subjected to mild aromatization to the part subjected to blending in the raffinate oil is 1: 1, obtaining a high-quality gasoline product; the composition of the aromatization product BTX and the composition of the desulfurized low-olefin gasoline are respectively shown in table 6.

Example 5

As shown in fig. 2, the method for co-producing desulfurized low-olefin gasoline and chemical products by using catalytically cracked gasoline of the present embodiment includes the following steps:

1. prehydrogenation

2. Cutting of

Cutting the pre-hydrocatalytic cracked gasoline into light fraction, medium fraction and heavy fraction, wherein the cutting temperature of the light fraction and the medium fraction is 50 ℃, and the cutting temperature of the medium fraction and the heavy fraction is 160 ℃, namely: the distillation range of the middle distillate is 50 ℃ to 160 ℃.

3. Solvent extraction

The solvent used for solvent extraction is a mixed solvent of sulfolane and N-methyl pyrrolidone, wherein the volume content of the N-methyl pyrrolidone in the mixed solvent is 15%.

And (3) allowing the middle distillate to enter from the middle-lower part of the extraction tower, allowing the mixed solvent to enter from the upper part of the extraction tower, controlling the tower top temperature of the extraction tower to be 105 ℃, the tower bottom temperature to be 80 ℃, the tower top pressure (gauge pressure) to be 0.4MPa, and controlling the feeding ratio of the mixed solvent to the middle distillate to be 3.0 to obtain raffinate oil rich in olefin and extract oil rich in aromatic hydrocarbon.

4. Light olefin recovery and backwashing

And (3) delivering the extract oil into a recovery tower for recovering the light olefin, wherein the temperature of the top of the recovery tower is controlled to be 95 ℃, the pressure of the top of the recovery tower is 0.08MPa, the temperature of the bottom of the recovery tower is controlled to be 180 ℃, and the pressure of the bottom of the recovery tower is 0.09MPa, so that the light olefin and the sulfur-rich oil are obtained.

Returning 60% of light olefin to the extraction tower for backwashing, and carrying out catalytic cracking on the rest light olefin, part of light fraction and part of raffinate oil.

5. Catalytic cracking

Carrying out catalytic cracking on part of the light fraction, part of raffinate oil and the rest of light olefins (the catalytic cracking raw material consisting of part of the light fraction, part of raffinate oil and the rest of the light olefins) in the presence of a catalytic cracking catalyst; the catalytic cracking catalyst consists of a ZSM-5 molecular sieve and an RE-USY molecular sieve, wherein the mass ratio of the ZSM-5 molecular sieve to the RE-USY molecular sieve is 2: 1; controlling the catalytic cracking temperature to be 650 ℃, and controlling the mass ratio of water to the raw material to be 2: 1, the mass ratio of the catalytic cracking catalyst to the raw material is 1: 4, obtaining catalytic cracking products of ethylene and propylene.

6. Selective hydrodesulfurization

Selective hydrodesulfurization was carried out using the selective hydrodesulfurization catalyst of example 3.

In the presence of a selective hydrodesulfurization catalyst, selectively hydrodesulfurization is carried out on the heavy fraction and the sulfur-rich oil, wherein the temperature of the selective hydrodesulfurization is controlled to be 250 ℃, the pressure is controlled to be 2.0MPa, and the volume space velocity is controlled to be 3.0h^-1And the volume ratio of the hydrogen to the oil (namely the volume ratio of the hydrogen to the total volume of the heavy fraction and the sulfur-rich oil) is 300, so as to obtain the desulfurized heavy fraction.

7. Oil blending

Blending the other part of the light fraction, the other part of the raffinate oil and the desulfurized heavy fraction, wherein: the volume ratio of the portion subjected to catalytic cracking to the portion subjected to blending in the light fraction was 1: 1, the volume ratio of the part for catalytic cracking to the part for blending in the raffinate oil is 1: 1, obtaining a high-quality gasoline product; the composition of the catalytic cracking product and the composition of the desulfurized low-olefin gasoline are shown in Table 6, respectively.

Example 6

1. prehydrogenation

2. Cutting of

3. Solvent extraction

And (3) allowing the middle distillate to enter from the middle-lower part of the extraction tower, allowing the composite solvent to enter from the upper part of the extraction tower, controlling the top temperature of the extraction tower to be 80 ℃, the bottom temperature of the extraction tower to be 60 ℃, the top pressure (gauge pressure) to be 0.3MPa, and controlling the feeding ratio of the composite solvent to the middle distillate to be 2.0, so as to obtain raffinate oil rich in olefin and extract oil rich in aromatic hydrocarbon.

4. Light olefin recovery and backwashing

Returning 50% of the light olefin to the extraction tower for backwashing, and carrying out catalytic cracking on the rest light olefin, part of light fraction and part of raffinate oil.

5. Catalytic cracking

Carrying out catalytic cracking on part of the light fraction, part of raffinate oil and the rest of light olefins (the catalytic cracking raw material consisting of part of the light fraction, part of raffinate oil and the rest of the light olefins) in the presence of a catalytic cracking catalyst; the catalytic cracking catalyst consists of a ZSM-5 molecular sieve and an RE-USY molecular sieve, wherein the mass ratio of the ZSM-5 molecular sieve to the RE-USY molecular sieve is 3: 1; controlling the catalytic cracking temperature to be 700 ℃, and controlling the mass ratio of water to the raw material to be 1: 1, the mass ratio of the raw material to the catalytic cracking catalyst is 3: 1, obtaining catalytic cracking products of ethylene and propylene.

6. Selective hydrodesulfurization

Selective hydrodesulfurization was carried out using the selective hydrodesulfurization catalyst of example 4.

7. Oil blending

Blending the other part of the light fraction, the other part of the raffinate oil and the desulfurized heavy fraction, wherein: the volume ratio of the portion subjected to catalytic cracking to the portion subjected to blending in the light fraction was 3: 1, the volume ratio of the part for catalytic cracking to the part for blending in the raffinate oil is 2: 1, obtaining a high-quality gasoline product; the composition of the catalytic cracking product and the composition of the desulfurized low-olefin gasoline are shown in Table 6, respectively.

Comparative example 1

This control is the same as example 3 except that the mild aromatization of example 3 is replaced with conventional aromatization. Specifically, the preparation method of the aromatization catalyst used in this comparative example was substantially the same as that of example 1 except that: the catalyst precursor is not subjected to the ion exchange treatment of step 2), and is directly subjected to step 3), step 4), and step 5).

Performing conventional aromatization in the presence of the aromatization catalyst, wherein the temperature of the conventional aromatization is 450 ℃, the pressure is normal pressure, and the volume space velocity is 1.0h^-1The reaction time is about 200 hours, and an aromatization product is obtained.

Through calculation, the yield of the conventional aromatization solution is about 70 percent, and the selectivity is about 20 percent; the once-through activity is only 3-4 days (once-through activity is an activity in which the olefin conversion remains above 50%).

TABLE 6 composition of the product System

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for co-producing desulfurized low-olefin gasoline and chemical products by utilizing catalytic cracking gasoline is characterized by comprising the following steps:

carrying out selective hydrodesulfurization on the heavy fraction and the sulfur-rich oil to obtain a desulfurized heavy fraction;

the light olefin is recovered in a recovery tower, the temperature at the top of the recovery tower is controlled to be 80-95 ℃, the pressure at the top of the recovery tower is controlled to be 0.05-0.2MPa, the temperature at the bottom of the recovery tower is controlled to be 150-.

2. The method as claimed in claim 1, wherein the cutting temperature of the light fraction and the middle fraction is 35-65 ℃, and the cutting temperature of the middle fraction and the heavy fraction is 100-160 ℃.

3. The method according to claim 1, wherein the solvent extraction is performed by using a composite solvent of sulfolane and N-methylpyrrolidone, wherein the volume content of N-methylpyrrolidone in the composite solvent is 5-40%.

4. The method of claim 1 or 3, wherein the solvent extraction comprises:

the middle fraction enters from the middle-lower part of the extraction tower, the solvent enters from the upper part of the extraction tower, the temperature of the top of the extraction tower is controlled to be 50-105 ℃, the temperature of the bottom of the extraction tower is controlled to be 35-80 ℃, the pressure of the top of the extraction tower is 0.2-0.8MPa, and the feeding ratio of the solvent to the middle fraction is 1.0-5.0.

5. The method according to claim 1, wherein the mild aromatization is carried out in the presence of an aromatization catalyst, the support of the aromatization catalyst comprising a zeolite molecular sieve and pseudoboehmite, the active ingredients comprising a first ingredient, a second ingredient, a third ingredient and a fourth ingredient, the first ingredient being Na or K, the second ingredient being P, the third ingredient being Zn, the fourth ingredient being La, and the loading amount of the first ingredient being 0.2-0.5%, the loading amount of the second ingredient being 1-3%, the loading amount of the third ingredient being 5-8%, and the loading amount of the fourth ingredient being 0-3%.

6. The method as claimed in claim 1 or 5, wherein the temperature for controlling mild aromatization is 280-330 ℃, the pressure is normal pressure, and the volume space velocity is 1.0-3.0h^-1。

7. The process of claim 1, wherein the catalytic cracking is conducted in the presence of a catalytic cracking catalyst, wherein the catalytic cracking catalyst comprises a ZSM-5 molecular sieve and a RE-USY molecular sieve, and the mass ratio of ZSM-5 molecular sieve to RE-USY molecular sieve is (1-3): 1, controlling the temperature of the catalytic cracking to be 600-700 ℃, wherein the mass ratio of water to raw materials is (0.5-2): 1, the mass ratio of the catalytic cracking catalyst to the raw material is 1: (2-5).

8. The process according to claim 1, characterized in that the selective hydrodesulfurization is carried out in the presence of a selective hydrodesulfurization catalyst obtained by supporting an active metal component on a support; wherein the carrier is a molecular sieve or a metal oxide, the active metal comprises Co and Mo, and the total mass content of the Co and the Mo in the selective hydrodesulfurization catalyst is 5-20%.

9. The method as claimed in claim 1, wherein the temperature of the selective hydrodesulfurization is 200-^-1The volume ratio of hydrogen to oil is 300-600.