CN108018076B

CN108018076B - Method for deep desulfurization of gasoline and equipment for deep desulfurization of gasoline

Info

Publication number: CN108018076B
Application number: CN201610964557.6A
Authority: CN
Inventors: 潘光成; 常春艳; 李涛; 唐文成; 习远兵; 赵丽萍; 田龙胜; 褚阳; 李明丰; 胡志海
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2016-10-28
Filing date: 2016-10-28
Publication date: 2020-08-18
Anticipated expiration: 2036-10-28
Also published as: CN108018076A

Abstract

The invention relates to the field of refining of hydrocarbon materials, and discloses a method for deep desulfurization of gasoline and equipment for deep desulfurization of gasoline, wherein the method comprises the following steps: (1) fractionating a gasoline feedstock; (2) contacting the light fraction with an extraction solvent to effect solvent extraction, and then separating the sulfur-containing solvent from the sulfides contained therein by distillation; (3) contacting the light fraction after solvent extraction with alkali liquor to perform alkali liquor extraction or contacting the light fraction after solvent extraction with an adsorbent; (4) contacting the heavy fraction with a hydrodesulfurization catalyst to perform a selective hydrodesulfurization reaction to obtain a hydrogenated heavy fraction; (5) and (3) mixing the hydrogenated heavy fraction with the light fraction extracted by alkali liquor or with the absorbed light fraction to obtain a gasoline product. The method provided by the invention can obtain a gasoline product with lower sulfur on the premise of avoiding larger loss of octane number.

Description

Method for deep desulfurization of gasoline and equipment for deep desulfurization of gasoline

Technical Field

The invention relates to the field of refining of hydrocarbon materials, in particular to a gasoline deep desulfurization method and equipment for gasoline deep desulfurization, and more particularly relates to a deep desulfurization process for sulfur-containing gasoline by combining a hydrogenation mode and a non-hydrogenation mode.

Background

As is well known, the emission of toxic and harmful substances in automobile exhaust seriously affects the air quality, and therefore, increasingly strict standards are defined in all countries in the world for the quality of oil products as engine fuels. China has implemented No. IV emission standard nationwide from 1 month and 1 day in 2013, and has implemented No. V emission standard in big cities such as Beijing, Shanghai, and the like. Emission standards IV and V respectively stipulate that the sulfur content of the motor gasoline is not more than 50 mu g/g and 10 mu g/g.

The sulfur in gasoline mainly comes from catalytic cracking gasoline, and the sulfur content of the catalytic cracking gasoline is further increased along with the development of oil processing raw materials to the heavy state. Therefore, reducing the sulfur content of catalytically cracked gasoline is the key to reducing the sulfur content of finished gasoline.

The sulfur in gasoline mainly comprises thiols, thioethers, dithioethers and thiophenes (including thiophene and thiophene derivatives). The maximum limit of the mercaptan sulfur content and the total sulfur content of a gasoline standard as a fuel is specified. When the sulfur content of mercaptan exceeds the standard or the total sulfur content exceeds the standard, the gasoline must be subjected to mercaptan removal or desulfurization refining.

As the catalytic cracking gasoline used as the blending component of the gasoline pool for the automobile is rich in olefin, the octane number loss is easily caused by the saturation of the olefin by adopting the conventional hydrogenation mode. In order to avoid the great loss of octane number in the processing process, the catalytic cracking gasoline is usually desulfurized and refined by adopting a sectional treatment mode.

US3957625 reports a process for the desulfurization of gasoline. The method is characterized in that gasoline is cut into a light part and a heavy part, and the sulfur content in the gasoline is reduced by carrying out selective hydrogenation treatment on heavy gasoline fraction. And US6610197 reports a process for the desulfurization of gasoline by cutting the gasoline into a light fraction and a heavy fraction, subjecting the light fraction to non-hydrotreating, and subjecting the heavy fraction to hydrotreating, thereby reducing the sulfur content in the gasoline.

US6623627 reports a process for the production of low sulphur gasoline by cutting gasoline into three fractions of low, medium and high boiling point, in which the low boiling point fraction containing mercaptans is contacted with alkali liquor to selectively remove mercaptans, the medium boiling point fraction containing thiophenes is desulfurized by extraction, the extraction liquid containing thiophenes of the medium boiling point fraction and the high boiling point fraction are subjected to a desulfurization reaction in a hydrodesulfurization zone, and then the light, medium and heavy fractions after the respective treatments are mixed to obtain a gasoline product with reduced sulphur content. The contact of the low boiling point fraction and the alkali liquor is carried out by adopting an alkali liquor extraction mode, the alkali liquor is oxidized and regenerated after mercaptan is extracted, and disulfide generated in the oxidation process is separated by a sedimentation mode and then recycled. However, this prior art does not disclose a process for the solvent extraction of the medium-boiling fractions containing thiophene.

CN102851069A reports a method for desulphurizing gasoline, which comprises cutting gasoline into heavy fraction with relatively high boiling range and light fraction with relatively low boiling range; under the condition of selective hydrodesulfurization, contacting the heavy fraction and hydrogen with a hydrodesulfurization catalyst to perform selective hydrodesulfurization to obtain desulfurized heavy fraction; contacting the light fraction with alkali liquor to desulfurize the light fraction, contacting the obtained alkali liquor and oxidant which absorb sulfide with oxidation catalyst and a part of the desulfurized heavy fraction, and simultaneously performing alkali liquor regeneration and alkali liquor desulfurization to oxidize the sulfide salt in the alkali liquor into disulfide, simultaneously extracting the disulfide in the alkali liquor into the desulfurized heavy fraction, then performing phase separation, and discharging tail gas; returning at least a portion of said disulfide-absorbed heavy fraction obtained to said selective hydrodesulfurization; and mixing the desulfurized heavy fraction with the desulfurized light fraction to obtain a product.

CN103555359A discloses a deep desulfurization method for catalytically cracked gasoline, which also removes sulfides in gasoline fractions by means of solvent extraction. The solvent extraction part adopts a liquid-liquid extraction desulfurization mode.

CN103740405A discloses an alkali washing-extraction-hydrogenation combined process for producing low-sulfur gasoline, which comprises the steps of cutting gasoline into light and heavy fractions, refining the light fraction with alkali, then carrying out extraction desulfurization, mixing the extracted sulfur-containing components with the heavy fraction for selective hydrogenation, and mixing the light fraction after extraction desulfurization and the heavy fraction after selective hydrogenation into a low-sulfur gasoline product. The alkali refining is carried out by adopting a simple alkali washing mode, and the alkali consumption is inevitably serious. The extraction desulfurization mode also adopts a liquid-liquid extraction mode.

In the above disclosed desulfurization method or process, the alkali treatment is aimed at removing mercaptans of relatively small molecular mass, such as mercaptans having a carbon number of not more than 4, from the gasoline fraction, and the solvent extraction is aimed at removing sulfides other than mercaptans, mainly thiophene compounds, from the gasoline fraction. When the mass fraction of the gasoline fraction subjected to the alkali treatment and the solvent treatment is increased and the mass fraction of the gasoline fraction subjected to the hydrotreatment is correspondingly decreased, the octane number loss caused by the hydrotreatment is undoubtedly relatively reduced. However, the conventional liquid-liquid solvent extraction generally has low desulfurization efficiency, absorbs more non-sulfide hydrocarbons, and needs to be washed and separated subsequently, and the separated sulfur-containing material also carries more impurities, which is not favorable for being sent into a hydrogenation device for treatment, and particularly, the recovered solvent is not completely regenerated, so that the sulfide extraction capacity is reduced when the solvent is recycled.

In order to obtain a gasoline product with lower sulfur and avoid a large loss of octane number, it is necessary to provide a new process which overcomes the aforementioned drawbacks of the prior art.

Disclosure of Invention

The object of the present invention is to overcome the drawbacks of the prior art and to provide a new process for the deep desulfurization of gasoline and a plant for the process, which allow to obtain a gasoline product with lower sulfur, while avoiding a greater loss of octane number.

The inventor of the invention finds that micromolecule mercaptan is difficult to be completely extracted by an extraction solvent, and finds that the extraction distillation has higher sulfide removal efficiency compared with the conventional liquid-liquid extraction, and the extraction solvent has less absorption on olefin in the extraction distillation process compared with the conventional liquid-liquid extraction, so that the method is beneficial to keeping more olefin, reducing octane value loss caused by hydrogenation treatment of the olefin in subsequent (merged into heavy fraction) after sulfide extraction, and on the other hand, reducing the harmful influence of oxidative polymerization and the like on solvent recycling of the olefin, and avoiding frequent regeneration of the extraction solvent due to accumulation of harmful impurities. If the gasoline fraction is treated by solvent extraction, the thiophene sulfides in the gasoline fraction can be removed completely, but some non-thiophene mercaptan sulfides can not be removed, so that further subsequent treatment is required. In the present invention, this subsequent treatment is performed by alkali extraction or adsorption treatment which is industrially easily carried out. The inventors of the present invention have provided the following method for deep desulfurization of gasoline according to the present invention based on the aforementioned studies.

In order to achieve the above object, in a first aspect, the present invention provides a method for deep desulfurization of gasoline, comprising:

(1) fractionating a gasoline raw material at a cutting point temperature of 70-140 ℃ to obtain a light fraction and a heavy fraction;

(2) contacting the light fraction with an extraction solvent to perform solvent extraction through distillation to obtain a sulfur-containing solvent and a solvent-extracted light fraction, and then separating the sulfur-containing solvent from sulfides contained in the sulfur-containing solvent through reduced pressure distillation to obtain a solvent-extracted sulfur-containing material and a recovered solvent from which the sulfides are removed;

(3) a mercaptan-removing treatment which is carried out in the following manner 1 or manner 2,

the mode 1 includes: contacting the light fraction after solvent extraction with alkali liquor to perform alkali liquor extraction to obtain sulfur-containing alkali liquor and the light fraction after alkali liquor extraction, then performing oxidation treatment on the sulfur-containing alkali liquor to obtain oxidized sulfur-containing alkali liquor, and contacting the oxidized sulfur-containing alkali liquor with a hydrocarbon solvent to perform reverse extraction treatment to obtain sulfur-containing materials after alkali liquor extraction and regenerated alkali liquor capable of being recycled;

the mode 2 includes: contacting the light fraction after solvent extraction with an adsorbent to obtain an adsorbed light fraction;

(4) contacting the heavy fraction with a hydrodesulfurization catalyst to perform selective hydrodesulfurization reaction to obtain hydrogenated heavy fraction;

(5) and (3) mixing the sweetening light fraction obtained in the step (3) with the hydrogenated heavy fraction obtained in the step (4) to obtain a gasoline product, wherein the sweetening light fraction is the alkali liquor extracted light fraction obtained in the mode 1 or the adsorbed light fraction obtained in the mode 2.

In a second aspect, the present invention provides an apparatus for deep desulfurization of gasoline, comprising:

a fractionation system through which the gasoline fraction is fractionated to obtain a light fraction and a heavy fraction;

the solvent extraction system comprises a solvent extraction distillation unit and a solvent recovery unit, wherein the solvent extraction distillation unit is used for carrying out solvent extraction on the light fraction from the fractionation system to obtain a sulfur-containing solvent and the light fraction after solvent extraction; the solvent recovery unit is used for separating the sulfur-containing solvent from the sulfide contained in the sulfur-containing solvent to obtain a sulfur-containing material subjected to solvent extraction and a recovered solvent from which the sulfide is removed;

the system comprises a light fraction desulfurization system, a solvent extraction system and an alkali liquor reverse extraction system, wherein the alkali liquor extraction system comprises a mercaptan extraction unit, an alkali liquor oxidation unit and an alkali liquor reverse extraction unit, the mercaptan extraction unit is used for contacting the light fraction extracted by a solvent from the solvent extraction system with alkali liquor to perform alkali liquor extraction to obtain the light fraction extracted by the alkali liquor and sulfur-containing alkali liquor, and the alkali liquor oxidation unit is used for performing oxidation treatment on the sulfur-containing alkali liquor to obtain oxidized sulfur-containing alkali liquor; the alkali liquor reverse extraction unit is used for performing reverse extraction treatment on the oxidized sulfur-containing alkali liquor to obtain a sulfur-containing material after alkali liquor extraction and a regenerated alkali liquor capable of being recycled; and the adsorption system is used for contacting the light fraction after solvent extraction from the solvent extraction system with an adsorbent contained in the adsorption system to obtain an adsorbed light fraction;

the selective hydrogenation system is used for introducing the heavy fraction from the fractionation system into the selective hydrogenation system through a pipeline to perform selective hydrodesulfurization reaction so as to obtain hydrogenated heavy fraction;

and mixing the hydrogenated heavy fraction with the mercaptan removal light fraction, and taking the mixture as a gasoline product to be led out through a pipeline, wherein the mercaptan removal light fraction is the light fraction extracted by alkali liquor or the light fraction after adsorption.

In order to obtain a gasoline product with lower sulfur and avoid large loss of octane number, the method flexibly applies non-hydrogenation modes such as adsorbent adsorption, alkali liquor extraction, solvent extraction and the like while adopting a hydrogenation mode, so that the gasoline product with lower sulfur can be obtained on the premise of avoiding large loss of the octane number.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred flow charts only and do not provide details as to vessels, heaters, coolers, pumps, compressors, mixers, valves, process control equipment, etc., and do not constitute a limitation of the invention. In the drawings:

FIG. 1 is a schematic structural diagram of a gasoline deep desulfurization apparatus according to a preferred embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a gasoline deep desulfurization apparatus according to another preferred embodiment of the present invention.

Description of the reference numerals

1. Gasoline raw material 2, fractionation system

3. Heavy fraction 4, light fraction

5. Solvent extraction system 6, light fraction after solvent extraction

7. Extraction system for sulfur-containing material 81 and alkali liquor after solvent extraction

82. Adsorption system 9, light fraction after alkali liquor extraction

91. Light fraction 10 after adsorption, and sulfur-containing material after alkali liquor extraction

11. Mixing the sulfur-containing material 12, and extracting the light fraction with alkali liquor for reverse extraction

13. Etherification system 14, light ends after etherification

15. Selective hydrogenation system 16, heavy fraction after hydrogenation

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the invention provides a method for deep desulfurization of gasoline, comprising the following steps:

The light fraction is a fraction with a relatively light distillation range, and the heavy fraction is a fraction with a relatively heavy distillation range. The light fraction of the invention concentrates most of the mercaptans and olefins in the gasoline feedstock, and the heavy fraction concentrates most of the other relatively high boiling sulfides, primarily thiophenes, in the gasoline feedstock.

In the step (3) of the present invention, the light fraction after solvent extraction may be desulfurized by means of alkali liquor extraction or adsorbent adsorption.

The solvent extraction in a preferred case in connection with the present invention is provided below:

the solvent extraction enables the sulfide mainly containing thiophene in the light fraction to be transferred into the extraction solvent to form the sulfur-containing solvent.

Preferably, the solvent extraction is performed in an extractive distillation tower, the light fraction obtained after the fractionation enters the extractive distillation tower from the middle part of the extractive distillation tower, the extraction solvent enters the extractive distillation tower from the upper part of the extractive distillation tower, and under the selective action of the solvent, thiophene and thioether compounds with relatively high boiling points in the light fraction enter the bottom of the extractive distillation tower along with the extraction solvent. And part of the low-sulfur light fraction distilled from the top of the extractive distillation tower is refluxed and circulated at the top of the tower, and part of the low-sulfur light fraction is discharged outside to be the light fraction extracted by the solvent. And a part of the sulfur-rich solvent at the bottom of the extractive distillation tower circulates at the bottom of the tower, and a part of the sulfur-rich solvent is discharged to a solvent recovery unit for treatment.

The weight ratio of the extraction solvent to the light fraction after fractionation is (0.5-20): 1, more preferably (1-5): 1. the inventor finds that in the liquid-liquid extraction mode, the sulfur-containing solvent absorbs sulfur in the light fraction and also absorbs other components much more than the sulfur, so that the problems of a solvent recovery system in a distillation mode are brought, such as increased energy consumption, more residual components in the recovered solvent, and rapid reduction of solvent extraction capacity caused by returning to the solvent extraction system. In the solvent extraction distillation desulfurization mode, the extraction solvent absorbs fewer components of the material to be treated, and the extraction capacity of the recovered solvent can be effectively recovered.

Preferably, the solvent extraction is carried out in an extractive distillation column, the conditions in the extractive distillation column comprising: the pressure at the top of the column is 100kPa to 500kPa, preferably 110kPa to 300 kPa; the temperature of the tower top is 50-180 ℃; the temperature of the tower bottom is 80-260 ℃, and preferably 140-200 ℃.

Preferably, the sulfur content in the light fraction obtained after solvent extraction is not more than 10 mu g/g.

Preferably, the extraction solvent contains a main extraction solvent, and the boiling point of the main extraction solvent is 175-320 ℃, and more preferably 175-250 ℃.

Preferably, the primary extraction solvent is selected from sulfolane, 3-methylsulfolane, 2, 4-dimethylsulfolane, 3-ethylsulfolane, methylethylsulfone, dimethylsulfone, diethylsulfone, dipropylsulfone, dibutylsulfone, dimethylsulfoxide, furfural, furfuryl alcohol, α -pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, at least one of N-propyl-2-pyrrolidone, N-formyl morpholine, dimethylformamide, triethylene glycol, tetraethylene glycol, pentaethylene glycol, triethylene glycol methyl ether, tetraethylene glycol methyl ether, ethylene carbonate, propylene carbonate, acetonitrile, nitrobenzene, polyethylene glycol having a relative molecular mass of 200 to 400, and polyethylene glycol methyl ether having a relative molecular mass of 200 to 400; more preferably, the main extraction solvent is selected from at least one of sulfolane, N-formyl morpholine, N-methyl-2-pyrrolidone, tetraethylene glycol and pentaethylene glycol.

In the solvent extraction distillation tower, both gas phase and liquid phase exist, the liquid phase is a single liquid phase, namely, in the liquid phase interval, the solvent of the liquid phase and the light fraction of the liquid phase are in a dissolved state, so that the sulfide in the light fraction is favorably transferred into the extraction solvent, and once a multi-liquid phase state is formed, the extraction of the sulfide is not favorably realized. In order to improve the sulfide absorption capacity of the extraction solvent and help the liquid phase region of the extractive distillation column to maintain a single liquid phase, it is preferable that the extraction solvent further contains an auxiliary agent, wherein the auxiliary agent is at least one of alcohols, ketones, organic acids and organic nitrides, and/or water, which is miscible with the main extraction solvent and has a boiling point or a dry point not higher than that of the main extraction solvent, and the organic nitrides are at least one of amines, ureas and alcamines.

Preferably, the auxiliary agent is at least one of alcohols with the boiling point or the dry point not higher than that of the main extraction solvent and with the carbon number not more than 6, ketones with the carbon number not more than 6, organic acids with the carbon number not more than 6 and organic nitrides with the carbon number not more than 6, and/or water, wherein the organic nitrides are at least one of amines, ureas and alcohol amines.

Preferably, the alcohol having no more than 6 carbon atoms is at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butanol, n-pentanol, and cyclohexanol.

Preferably, the ketone having no more than 6 carbon atoms is acetone and/or methyl ethyl ketone.

Preferably, the organic acid with the carbon number not more than 6 is at least one of isobutyric acid, oxalic acid, malonic acid and succinic acid.

Preferably, the organic nitrogen compound having not more than 6 carbon atoms is selected from at least one of urea, ethylenediamine, monoethanolamine, N-methyl monoethanolamine, N-ethyl monoethanolamine, N-dimethylethanolamine, N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, N-propanolamine, isopropanolamine, and diglycolamine.

More preferably, the solvent contains at least one of water, methanol, ethanol, N-propanol, isopropanol, acetone, methyl ethyl ketone, isobutyric acid, oxalic acid, malonic acid, succinic acid, urea, ethylenediamine, monoethanolamine, N-methyl monoethanolamine, N-ethyl monoethanolamine, N-dimethylethanolamine, N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, N-propanolamine, isopropanolamine, and diglycolamine. Particularly preferably, the auxiliary agent is selected from at least one of water, methanol, acetone, methyl ethyl ketone, isobutyric acid, oxalic acid, malonic acid, succinic acid, ethylenediamine, monoethanolamine, N-methyl monoethanolamine, isopropanolamine and diglycolamine.

Preferably, in the extraction solvent, the content of the auxiliary agent is 0.1-20 wt%, and more preferably 0.5-15 wt%; particularly preferably, the content of the auxiliary agent is 1-10 wt%.

Preferably, the adjuvant is a mixture containing water. However, water greatly affects the formation of multiple phases, and when the water content in the solvent is large, a multiple phase state tends to be formed in the extractive distillation column. Therefore, when the auxiliary is a mixture containing water, the content of water in the extraction solvent is preferably 0.1 to 5% by weight, more preferably 0.1 to 3% by weight.

Preferably, the extraction solvent contains a defoaming agent, and the defoaming agent is selected from at least one of siloxane compounds, alkyl sulfonate compounds, polyether compounds, polyethylene glycol compounds, polyester compounds, amide compounds and fatty alcohol compounds.

The inventor of the present invention found that when an extraction solvent containing an auxiliary agent is used in the solvent extractive distillation process, the effective utilization rate of the extraction solvent can be increased, and the regeneration frequency of the solvent can be reduced, thereby causing relative reduction of energy consumption and relative reduction of operation cost.

The following provides solvent recovery in relation to a preferred aspect of the invention:

the sulfur-containing solvent rich in sulfide can be recycled after the absorbed sulfide is removed, and the sulfide removal mode is called solvent recovery. The solvent recovery is carried out in a distillation mode, namely, a sulfur-containing solvent from the solvent extraction process is heated to evaporate a sulfur-containing material, the sulfur-containing material comprises aromatic hydrocarbon, thiophene and thioether compounds from light fractions, and the sulfur-containing material is discharged to be the sulfur-containing material after the solvent extraction. The solvent after the sulfide removal becomes a recovered solvent and returns to the solvent extraction distillation process for recycling.

Preferably, the solvent recovery is performed by vacuum distillation, and the conditions for separating the sulfur-containing solvent from the sulfide contained therein by vacuum distillation include: the pressure at the top of the solvent recovery tower is 10 kPa-100 kPa, the temperature at the top of the tower is 50-100 ℃, the temperature at the bottom of the tower is 100-250 ℃, more preferably the temperature at the bottom of the tower is 120-200 ℃, and the weight ratio of stripping steam to the sulfur-containing solvent is (0.01-5.0): 1.

the sulfur-containing hydrocarbon materials are removed from the recovered solvent, but side reactions such as oxidation and decomposition can occur during the operation process, so that some soluble high-boiling compounds such as stable salts, organic polymers, sediments and other impurities are formed, and the existence and accumulation of the substances in the solvent can undoubtedly reduce the dissolving capacity of the extraction solvent, thereby reducing the efficiency of gasoline extraction and desulfurization, so that the solvent needs to be regenerated, and the purity of the solvent is improved.

Preferably, the method further comprises: at least part of the recovered solvent is subjected to water injection purification treatment in a solvent regeneration tower for regeneration.

The following provides solvent regeneration in relation to a preferred aspect of the invention:

the water-injected purification treatment can be carried out by distilling the solvent under reduced pressure with water injected, wherein the residual hydrocarbon material of relatively light weight in the recovered solvent is azeotroped with water and discharged from the top of the column, the high boiling point compound impurity of relatively heavy weight in the recovered solvent is discharged as a residue from the bottom of the solvent regeneration column, and the purified solvent is discharged from the lower side of the solvent regeneration column to be used as the regenerated solvent. Preferably, the water in the water injection purification treatment is from condensed water collected in the solvent extraction distillation process and the solvent recovery process. The regenerated solvent can be directly returned to the solvent recovery tower or directly mixed with the recovered solvent flowing out of the solvent recovery tower for recycling.

Preferably, the regeneration conditions in the solvent regeneration column include: the pressure at the top of the tower is 1 kPa-10 kPa, the temperature at the top of the tower is 90-110 ℃, the temperature at the top of the tower is preferably 96-105 ℃, the temperature at the bottom of the tower is 120-200 ℃, the temperature at the bottom of the tower is preferably 150-200 ℃, and the weight ratio of the injected water to the recovered solvent is (0.1-10): 1, preferably the weight ratio of (0.5-5): 1.

preferably, the recovery solvent used for regeneration accounts for 1 to 10 wt% of the total recovery solvent, and more preferably accounts for 1 to 5 wt% of the total recovery solvent.

The mercaptan removal treatment of the invention can be carried out by alkali extraction in the mode 1 or by an adsorbent adsorption in the mode 2.

The lye extraction of the present invention comprises three successive basic processes, namely: mercaptan extraction, sulfur-containing alkali liquor oxidation and alkali liquor back extraction.

The following provides a preferred aspect of the invention regarding the mercaptan extraction step:

the light fraction after solvent extraction containing mercaptan and olefin is contacted with alkali liquor which does not contain disulfide and oxygen basically, mercaptan in the light fraction after solvent extraction is absorbed into the alkali liquor to generate thiolate, and the light fraction after solvent extraction, which is subjected to mercaptan removal and has reduced sulfur content, is separated from the extracted alkali liquor and flows out to become the light fraction after alkali liquor extraction. The light fraction after the alkaline extraction contains essentially no more mercaptans and the sulphur content is correspondingly reduced.

Preferably, in the mercaptan extraction process, the light fraction is contacted with the alkali liquor in a counter-current manner after the solvent extraction, and the contacting can be carried out in various manners, equipment or containers which are known to be favorable for the contacting of two immiscible fluids, for example, in a cocurrent manner, and the equipment or container for contacting can be a static mixer or a vertical tower provided with a contacting device, for example, a plate tower, a packed tower, a fiber membrane contactor provided with stainless steel wire fiber bundles and the like, so as to generate close contact between the two injected fluids.

The alkaline liquor in the mercaptan extraction comprises any known alkaline agent having the ability to extract mercaptans from a gasoline feedstock. Preferably, the alkali solution in the alkali solution extraction is aqueous ammonia and/or an aqueous solution of alkali metal hydroxide, such as an aqueous solution of sodium hydroxide, potassium hydroxide, and lithium hydroxide. And the concentration of the alkali liquor is 1-50 wt%, and more preferably 5-25 wt%. If necessary, an aqueous solution of an alkaline earth metal hydroxide such as calcium hydroxide or barium hydroxide, or an aqueous solution of an organic quaternary ammonium base may be used.

Preferably, the mercaptan extraction conditions comprise: the temperature is 5-100 ℃, and preferably 15-65 ℃; the pressure is 0.1 MPa-2.0 MPa, and the dosage volume ratio of the alkali liquor to the light fraction contacted with the alkali liquor after solvent extraction is (1-50): 100, preferably (5-40): 100.

the following provides the oxidation treatment steps in a preferred case of the present invention:

and oxidizing the sulfur-containing alkali liquor, so that mercaptide in the sulfur-containing alkali liquor is oxidized into disulfide after oxidation. The oxidant used in the oxidation process is preferably oxygen from air. The air injected in the oxidation process of the sulfur-containing alkali liquor is preferably purified air, and the air amount is greater than or equal to the stoichiometric amount required for oxidizing thiolate contained in the sulfur-containing alkali liquor into disulfide, and is usually 2-4 times of the stoichiometric amount.

Preferably, the conditions of the oxidation treatment include: the temperature is 5-100 ℃, preferably 15-65 ℃, the pressure is 0.1-2.0 MPa, preferably 0.1-0.8 MPa, and the pressure in the oxidation process of the sulfur-containing alkali liquor is generally lower than that in the extraction process of the alkali liquor.

Preferably, the oxidation treatment is carried out in the presence of a fixed bed oxidation catalyst of a metal phthalocyanine. Preferably, in the metal phthalocyanine fixed bed oxidation catalyst, the supported amount of the metal phthalocyanine compound is 0.01 to 10% by weight, preferably 0.05 to 3% by weight, based on the metal phthalocyanine fixed bed oxidation catalyst.

Preferably, the metal phthalocyanine is selected from at least one of magnesium phthalocyanine, titanium phthalocyanine, hafnium phthalocyanine, vanadium phthalocyanine, tantalum phthalocyanine, molybdenum phthalocyanine, manganese phthalocyanine, iron phthalocyanine, cobalt phthalocyanine, platinum phthalocyanine, palladium phthalocyanine, copper phthalocyanine, silver phthalocyanine, zinc phthalocyanine, and tin phthalocyanine; more preferably, the metal phthalocyanine is a cobalt phthalocyanine and/or a vanadium phthalocyanine.

Preferably, the metal phthalocyanine is selected from the group consisting of sulfonates, carboxylates, and quaternaries of metal phthalocyanines,

The compound is preferably a sulfonated cobalt phthalocyanine, and includes at least one of a monosulfonate of cobalt phthalocyanine (cobalt monosulfonated phthalocyanine), a bissulfonate of cobalt phthalocyanine (cobalt bissulfonated phthalocyanine), a trisulfonate of cobalt phthalocyanine (cobalt trisulfonated phthalocyanine), and a tetrasulfonate of cobalt phthalocyanine (cobalt tetrasulfonated phthalocyanine).

The back extraction treatment in the preferred case of the present invention is provided below:

the oxidized alkali liquor contains disulfide, the disulfide must be removed for recycling, the mode of removing the disulfide is reverse extraction treatment, namely, the oxidized sulfur-containing alkali liquor containing the disulfide is contacted with a hydrocarbon solvent, the disulfide is transferred into the hydrocarbon solvent and separated from the alkali liquor, and the regenerated alkali liquor obtained after the reverse extraction is returned to the mercaptan extraction process for recycling. Before the reverse extraction treatment, the oxidized alkali liquor can be separated from redundant air tail gas in a settling mode, then the hydrocarbon solvent is contacted, the hydrocarbon solvent absorbing the disulfide can be continuously recycled with the oxidized sulfur-containing alkali liquor, and is discharged intermittently or continuously to become the sulfur-containing material after the alkali liquor is extracted. Preferably, the volume ratio of the hydrocarbon solvent to the oxidized alkali liquor is (0.1-10): the sulfide-absorbed hydrocarbon solvent may be discharged intermittently or continuously. The pressure during the stripping is generally lower than the pressure of the oxidation of the lye.

Preferably, the hydrocarbon solvent in the reverse extraction treatment is selected from at least one of the heavy fraction after hydrogenation, the light fraction after solvent extraction, the light fraction after alkali liquor extraction, the light fraction after adsorption, the light fraction after etherification and the gasoline product.

The following provides the adsorbent adsorption step in relation to the preferred case of the present invention:

the adsorbent adsorption step is carried out by contacting the solvent-extracted light fraction with an adsorbent to obtain an adsorbed light fraction. And (3) adsorbing and removing the sulfide in the light fraction after solvent extraction by using an adsorbent.

As long as various materials having an adsorption ability for sulfides can be used as the adsorbent in the present invention, a porous material having a physical adsorption effect for sulfides and a transition metal material having a chemical adsorption effect for sulfides are preferably used as the adsorbent in the present invention, and the adsorbent is preferably used in the form of a solid.

The adsorbent used may be a physical adsorbent and/or a chemical adsorbent.

The physical adsorbent is preferably a porous material including at least one selected from the group consisting of silica, alumina, zeolite, clay and activated carbon.

The chemical adsorbent preferably includes a metal, a metal oxide, or a metal ion compound containing a transition metal element selected from at least one of an iron element, a cobalt element, a nickel element, a copper element, and a zinc element. Preferably, the chemical adsorbent further contains at least one adsorbent aid selected from the group consisting of alkali metal elements and alkaline earth metal elements.

Preferably, the conditions under which the light fraction is contacted with the adsorbent after the solvent extraction include: the temperature is 10-300 ℃; the pressure is 0.1-2 MPa, and the liquid hourly space velocity is 0.1-1 h^-1. More preferably, the temperature of the contact is 15 to 200 ℃.

The present invention is not particularly limited in the method for producing the adsorbent, and is not particularly limited in the shape of the adsorbent.

Preferably, the sulfur content in the light fraction after adsorption obtained after the adsorbent adsorption step is not more than 10 mu g/g.

Preferably, the method of the present invention further comprises: before mixing with the hydrogenated heavy fraction obtained in the step (4), carrying out etherification reaction on the sweetening light fraction obtained in the step (3) to obtain an etherified light fraction; and then mixing the etherified light fraction with the hydrogenated heavy fraction of step (4) to obtain the gasoline product.

The etherification reaction of the present invention allows the production of etherified light fractions with reduced olefin content and increased octane number.

The following provides the etherification reactions in the preferred case of the present invention:

preferably, the etherification reaction is carried out by contacting the light sweetening fraction with a lower alcohol having no more than 6 carbon atoms.

Preferably, the lower alcohol used for the etherification reaction is at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butanol, n-pentanol and cyclohexanol; methanol is particularly preferred.

Preferably, the etherification reaction conditions include: the molar ratio of the low-carbon alcohol to the olefin in the mercaptan-removed light fraction is (0.5-3): 1, preferably (1.0-1.2): 1, the contact temperature is 20-100 ℃, and the pressure is 0.3-1.0 MPa.

Preferably, the etherification reaction is carried out in the presence of an etherification catalyst which is a strongly acidic ion exchange resin. The strongly acidic ion exchange resin may be, for example, a sulfonic acid type ion exchange resin.

More preferably, the conditions for contacting the light fraction after the removal of mercaptans with the lower alcohol are such that the removal rate of olefins from the light fraction after etherification is not less than 35%.

Preferably, the method of the present invention further comprises: before the etherification reaction, the sweetening light fraction is subjected to adsorption pretreatment and/or selective hydrogenation pretreatment.

In particular, the adsorptive pretreatment and/or the selective hydrogenation pretreatment carried out before the etherification reaction are carried out in order to remove the diolefins and basic nitrides that may be present in the fractions, in order to prevent the diolefins and basic nitrides that may be present in the fractions from causing deactivation of the etherification catalyst. The adsorbent used in the adsorption pretreatment is not necessarily the same as the adsorbent used for the removal of the sulfur compounds in the light ends (in the mercaptan-removal treatment) described above. The person skilled in the art is able to carry out desulfurization operations or adsorption pretreatment operations before etherification, according to the objectives of desulfurization provided by the present invention and of removing diolefins and basic nitrides that may be present in the fractions and the adsorbent provided by the present invention. Preferably, the adsorbent used in the adsorption pretreatment is an acidic porous molecular sieve material, and the adsorption pretreatment may be performed at normal temperature and pressure. Also, unless otherwise specified, all the adsorbents mentioned herein are adsorbents used for removing sulfides in the light fraction after solvent extraction to obtain an adsorbed light fraction.

In the invention, after the light fraction is subjected to solvent extraction and alkali liquor extraction, or solvent extraction and adsorbent adsorption, most of sulfides are removed, and the selective hydrogenation pretreatment can be carried out under milder conditions, for example, a high-activity noble metal catalyst which is easily poisoned by sulfur can be adopted to carry out the pretreatment under the conditions of lower temperature, lower pressure and lower hydrogen-oil volume ratio so as to effectively avoid the loss of octane number caused by hydrogenation of monoolefine.

Preferably, the selective hydrogenation pretreatment is carried out in the presence of a transition metal supported catalyst. The selective hydrogenation pretreatment catalyst used for selective hydrogenation pretreatment can be a hydrogenation or hydrogenation catalyst capable of saturating diolefins and avoiding mono-olefin saturation under certain reaction conditions, and the selective hydrogenation pretreatment catalyst comprises a transition metal supported catalyst, a non-noble metal supported catalyst, a noble metal supported catalyst or a combination of the two catalysts. The transition metal supported catalyst comprises a carrier and a metal active component supported on the carrier, wherein the carrier is selected from at least one of alumina, silicon oxide, aluminosilicate, titanium oxide, zeolite and activated carbon, and the metal active component is selected from at least one of nickel, cobalt, molybdenum, platinum and palladium.

According to a preferred embodiment, the carrier in the transition metal supported catalyst is alumina, and the loading amount of the metal active component in terms of oxide is 0.05-15 wt%.

Preferably, the conditions of the selective hydrogenation pretreatment include: the hydrogen partial pressure is 0.1MPa to 2.0MPa, the temperature is room temperature to 250 ℃, and the liquid hourly volume space velocity is 1.0h^-1～10.0h^-1The volume ratio of hydrogen to oil is 1-100.

According to a preferred embodiment of the present invention, the method of the present invention further comprises: and (3) carrying out selective hydrodesulfurization reaction on the sulfur-containing material extracted by the solvent in the step (2) and/or the sulfur-containing material extracted by the alkali liquor in the step (3) and the heavy fraction.

According to a preferred embodiment of the present invention, the method of the present invention further comprises: introducing the sulfur-containing material extracted by the solvent in the step (2) and/or the sulfur-containing material extracted by the alkali liquor in the step (3) into a catalytic cracking device for catalytic cracking reaction to obtain at least part of the gasoline raw material used in the step (1).

The following provides a selective hydrodesulfurization reaction in a preferred case in connection with the present invention:

preferably, the selective hydrodesulfurization reaction is performed in a first reaction zone and a second reaction zone which are connected in sequence, a first hydrodesulfurization catalyst and a second hydrodesulfurization catalyst are respectively filled in the first reaction zone and the second reaction zone, the first hydrodesulfurization catalyst and the second hydrodesulfurization catalyst respectively and independently contain an alumina carrier and/or a silica-alumina carrier and a hydrogenation active metal component loaded on the carrier, and the hydrogenation active metal component is a non-noble metal element from group VIB of molybdenum and/or tungsten and/or a non-noble metal element from group VIII of nickel and/or cobalt.

Preferably, the first and second hydrodesulfurization catalysts each independently contain molybdenum and/or tungsten, nickel and/or cobalt, an alumina matrix, and a large pore zeolite and/or a medium pore zeolite.

Preferably, based on the total amount of the hydrodesulfurization catalyst, the content of the group VIB non-noble metal element calculated by oxides is 2 to 25 wt%, and the content of the group VIII non-noble metal element calculated by oxides is 0.2 to 6 wt%. The "hydrodesulfurization catalyst" here is the first hydrodesulfurization catalyst or the second hydrodesulfurization catalyst.

Preferably, the desulfurization activity of the first hydrodesulfurization catalyst is lower than the desulfurization activity of the second hydrodesulfurization catalyst. The desulfurization activity of the present invention is expressed by "the reaction temperature (T) per unit volume of the hydrodesulfurization catalyst when the same feedstock is treated to achieve the same desulfurization effect", and the greater the T, the lower the activity.

Preferably, the reaction conditions of the first reaction zone and the second reaction zone each independently comprise: the hydrogen partial pressure is 0.1MPa to 4.0MPa, the reaction temperature is 200 ℃ to 440 ℃, and the liquid hourly volume space velocity is 1.0h^-1～10.0h^-1The volume ratio of hydrogen to oil is 200-1000. More preferably, the reaction conditions of the first reaction zone and the second reaction zone each independently comprise: the hydrogen partial pressure is 1.0MPa to 3.2MPa, the reaction temperature is 200 ℃ to 300 ℃, and the liquid hourly volume space velocity is 2.0h^-1～6.0h^-1The volume ratio of hydrogen to oil is 200-600.

Preferably, the conditions of the selective hydrodesulfurization reaction are such that the sulfur content in the obtained hydrogenated heavy fraction is no more than 10 mu g/g.

Preferably, the cut points of the light fraction and the heavy fraction are 80-120 ℃.

Preferably, the dry point of the light fraction is not higher than the lower limit of the boiling range temperature range of the extraction solvent.

Preferably, the yield of the light fraction is 40-60 wt% and the yield of the heavy fraction is 40-60 wt% based on the gasoline raw material.

Preferably, the gasoline feedstock is selected from at least one of catalytically cracked gasoline, straight run gasoline, coker gasoline, pyrolysis gasoline, and thermally cracked gasoline.

Preferably, in step (5), the sulfur content of the obtained gasoline product is not more than 10 mu g/g. Particularly, the gasoline product in step (5) of the present invention is a product obtained by mixing the heavy fraction after hydrogenation with the light fraction after alkali liquor extraction or the light fraction after adsorption, or a product obtained by mixing the heavy fraction after hydrogenation with the light fraction after etherification.

Preferably, the equipment further comprises an etherification system, and the light mercaptan removal fraction from the light fraction desulfurization system is firstly introduced into the etherification system through a pipeline to carry out etherification reaction so as to obtain light fraction after etherification; and then mixing the etherified light fraction with the hydrogenated heavy fraction to be taken as a gasoline product to be led out through a pipeline.

According to a preferred embodiment, the apparatus further comprises a line for introducing said alkali extracted sulfur-containing material and/or said solvent extracted sulfur-containing material into a selective hydrogenation system.

According to another preferred embodiment, the apparatus further comprises a cracking system, wherein the sulfur-containing material after solvent extraction from the solvent extraction system and/or the sulfur-containing material after alkali liquor extraction from the light fraction desulfurization system are introduced into the cracking system through a pipeline to perform catalytic cracking reaction, and the products in the cracking system are introduced into the fractionation system through a pipeline.

Preferably, the solvent extraction system further comprises a solvent regeneration unit, and the solvent regeneration unit is used for introducing the recovered solvent from the solvent recovery unit into the solvent regeneration unit through a pipeline for water injection purification treatment so as to regenerate.

Preferably, the selective hydrogenation system comprises a first reaction zone and a second reaction zone connected in series to perform the selective hydrodesulfurization reaction.

According to a preferred embodiment, the device for deep desulfurization of gasoline of the present invention has a schematic structure shown in fig. 1, and the light fraction desulfurization system of the embodiment is a lye extraction system, specifically:

the gasoline raw material 1 enters a fractionation system 2 through a pipeline, and heavy fraction 3 and light fraction 4 are fractionated. The heavy fraction 3 flows out through a pipeline, is mixed with hydrogen to enter a selective hydrogenation system 15, is subjected to selective hydrogenation reaction under the action of a first hydrodesulfurization catalyst with relatively low activity in a first reaction zone, then enters a second reaction zone to be subjected to selective hydrogenation reaction under the action of a second hydrodesulfurization catalyst with relatively high activity, and flows out of the pipeline to obtain a hydrogenated heavy fraction 16. The light fraction 4 from the fractionation system 2 enters a solvent extraction system 5 through a pipeline to contact with an extraction solvent, and sulfide remaining in the light fraction is transferred to the extraction solvent to obtain a light fraction 6 after solvent extraction and a sulfur-containing solvent. The sulfur-containing solvent absorbing the sulfide enters a solvent recovery unit for solvent recovery, the absorbed sulfide is separated from the extraction solvent under the distillation condition to obtain a sulfur-containing material 7 after solvent extraction, the sulfur-containing material 7 after solvent extraction is mixed with a sulfur-containing material 10 after alkali liquor extraction to form a mixed sulfur-containing material 11, the mixed sulfur-containing material 11 and the heavy fraction 3 enter a selective hydrogenation system 15 together or are merged into a cracking system for cracking reaction, and the gasoline fraction obtained after cracking is used as a part of the gasoline raw material 1. Meanwhile, a part of the recovered solvent flows into a solvent regeneration unit to contact with water for purification and regeneration, the hydrocarbons (azeotropic with water) absorbed in the solvent, heavy residual liquid rich in impurities and the regenerated solvent are separated, the regenerated solvent is merged into the recovered solvent, and the recovered solvent is continuously contacted with the light fraction obtained after fractionation for recycling.

The light fraction 6 after solvent extraction enters an alkali liquor extraction system 81 to contact with alkali liquor, mercaptan in the light fraction after solvent extraction is transferred into the alkali liquor to obtain an alkali liquor extracted light fraction 9, the alkali liquor extracted light fraction leaves the alkali liquor extraction system 81 through a pipeline, the sulfur-containing alkali liquor which absorbs the mercaptan is oxidized by air under the action of a fixed bed oxidation catalyst, the absorbed mercaptan is oxidized into disulfide, the oxidized alkali liquor separates redundant air, and contacting with a reverse extraction solvent to perform reverse extraction operation, transferring disulfide in the alkali liquor into the reverse extraction solvent and separating the disulfide from the alkali liquor to obtain a sulfur-containing material 10 and a regenerated alkali liquor after the alkali liquor is extracted, the sulfur-containing material 10 after the alkaline extraction leaves the alkaline extraction system 81 through a pipeline, and the regenerated alkaline solution which is deprived of disulfide and basically has no air after the reverse extraction is continuously contacted with the light fraction after the solvent extraction for recycling. The reverse extraction solvent is heavy fraction 16 after hydrogenation which comes from a selective hydrogenation system 15 and flows out through a pipeline, light fraction 9 after alkali liquor extraction from an alkali liquor extraction system 81, light fraction 12 after alkali liquor extraction for reverse extraction or a final low-sulfur gasoline product, wherein the light fraction 12 after alkali liquor extraction for reverse extraction is light fraction after alkali liquor extraction from the alkali liquor extraction system 81.

Preferably, the lye oxidation unit and the lye back-extraction unit can be combined into an oxidation desulfurization unit for operation, as long as the oxidation of the lye and the separation of the air and the sulfur-containing material can be realized in one system, such as a vertical tower or a vertical tower with a horizontal tank connected to the bottom of the tower, and then the regenerated lye from which the sulfide and air are removed can be recycled in the lye extraction system 81.

Preferably, the light fraction 9 after the alkaline extraction is fed via a line to an etherification system 13.

The light fraction 9 after the alkali liquor extraction in the etherification system 13 is preferably subjected to pre-hydrogenation treatment and is contacted with a lower alcohol after treatment, so that the olefin in the light fraction after the alkali liquor extraction is reacted with the lower alcohol to generate ether, and an etherified light fraction 14 is obtained.

The hydrogenated heavy fraction 16 and the etherified light fraction 14 are mixed to form a gasoline product with low sulfur, low olefins and increased octane number; or the hydrogenated heavy fraction 16 and the alkali liquor extracted light fraction 9 are mixed to form a gasoline product with low sulfur, low olefin and less octane number loss.

According to another preferred embodiment, the device for deep desulfurization of gasoline of the present invention has a schematic structure shown in fig. 2, and the light fraction desulfurization system of the embodiment is an adsorption system, specifically:

the gasoline raw material 1 enters a fractionation system 2 through a pipeline, and heavy fraction 3 and light fraction 4 are fractionated. The heavy fraction 3 flows out through a pipeline, is mixed with hydrogen to enter a selective hydrogenation system 15, is subjected to selective hydrogenation reaction under the action of a first hydrodesulfurization catalyst with relatively low activity in a first reaction zone, then enters a second reaction zone to be subjected to selective hydrogenation reaction under the action of a second hydrodesulfurization catalyst with relatively high activity, and flows out of the pipeline to obtain a hydrogenated heavy fraction 16. The light fraction 4 from the fractionation system 2 enters a solvent extraction system 5 through a pipeline to contact with an extraction solvent, and sulfide remaining in the light fraction is transferred to the extraction solvent to obtain a light fraction 6 after solvent extraction and a sulfur-containing solvent. The sulfur-containing solvent absorbing the sulfide enters a solvent recovery unit for solvent recovery, the absorbed sulfide is separated from the extraction solvent under the distillation condition to obtain a sulfur-containing material 7 after solvent extraction, the sulfur-containing material 7 after solvent extraction and the heavy fraction 3 enter a selective hydrogenation system 15 together or are merged into a cracking system for cracking reaction, and the gasoline fraction obtained after cracking is used as a part of the gasoline raw material 1. Meanwhile, a part of the recovered solvent flows into a solvent regeneration unit to contact with water for purification and regeneration, the hydrocarbons (azeotropic with water) absorbed in the solvent, heavy residual liquid rich in impurities and the regenerated solvent are separated, the regenerated solvent is merged into the recovered solvent, and the recovered solvent is continuously contacted with the light fraction obtained after fractionation for recycling.

The light fraction 6 after solvent extraction flows into the adsorption system 82 through a pipeline, and contacts with the adsorbent, and the trace sulfide remaining in the light fraction 6 after solvent extraction is adsorbed by the adsorbent, so that the light fraction 91 after adsorption is obtained.

Preferably, the absorbed light fraction 91 is fed to the etherification system 13 through a pipeline.

The adsorbed light fraction 91 entering the etherification system 13 is preferably subjected to pre-hydrogenation treatment and is contacted with a lower alcohol after treatment, so that olefins in the adsorbed light fraction react with the lower alcohol to generate ether, and the etherified light fraction 14 is obtained.

The hydrogenated heavy fraction 16 and the etherified light fraction 14 are mixed to form a gasoline product with low sulfur, low olefins and increased octane number; or the hydrogenated heavy fraction 16 and the adsorbed light fraction 91 are mixed to form a low sulfur, low olefin and octane number loss gasoline product.

The gasoline deep desulfurization process provided by the invention has the following specific advantages:

the invention adopts a way of sectionalized treatment of sulfur-containing gasoline, and adopts the treatment ways of solvent extraction, alkali liquor extraction or adsorbent adsorption and selective hydrogenation respectively for gasoline of each sectionalized treatment.

The invention disposes the alkali liquor extraction after the solvent extraction, because of the improvement of the solvent extraction efficiency, the non-mercaptan sulfur compounds and partial mercaptan in the light fraction are removed by the solvent extraction, the residual trace amount of mercaptan can be conveniently removed by the alkali liquor extraction mode, and the severity of the alkali liquor extraction operation can be reduced.

In order to effectively reduce the sulfur content of the gasoline fraction, the invention adopts the extraction solvent which has obvious selective absorption to sulfide, and the method adopts the mode of extractive distillation to extract and remove sulfide in the gasoline fraction and the mode of reduced pressure distillation to recover the extraction solvent, the light fraction after solvent extraction is completely separated from the extraction solvent (basically without entrainment), no subsequent treatment is needed, the extraction solvent can be well separated from the absorbed sulfide and sulfur-containing materials during recovery, part of the recovered solvent is regenerated, the defect of incomplete regeneration of the conventional solvent is overcome, residual hydrocarbon materials dissolved in the solvent are separated through the azeotropic action with water, but also removes impurities such as high boiling point polymers, sediments and the like accumulated in the solvent, has obvious purification effect when the solvent is regenerated, thereby effectively recovering the circulating extraction capacity after the recovered solvent is mixed with a part of regenerated solvent.

The dry point of the light fraction can be properly increased due to the improvement of the desulfurization efficiency, so that the yield of the light fraction can be increased and the yield of the heavy fraction can be reduced during the gasoline fractionation, the treatment amount of the heavy fraction entering a hydrogenation system is reduced, and the octane number loss caused by the hydrogenation of the heavy fraction can be effectively reduced.

Meanwhile, the solvent extraction is prepared before the alkali liquor extraction, the alkali liquor extraction process can be even simplified, for example, the usage amount of a reverse extraction solvent for alkali liquor reverse extraction is reduced, or the oxidation step and the reverse extraction step are combined into one step of oxidation desulfurization step operation (namely, the alkali liquor oxidation is realized in the oxidation step, the separation of air and a sulfur-containing material (a reverse extraction solvent phase containing disulfide) after the alkali liquor extraction is completed, the separated alkali liquor returns to the alkali liquor extraction mercaptan step), the mercaptan with relatively low boiling point is only needed to be removed during the light fraction alkali liquor extraction, and whether the disulfide converted from the mercaptan is completely separated from the light fraction or not is not influenced by the subsequent solvent extraction effect. Because under the condition of solvent extractive distillation, the sulfide remained in the light fraction from which the mercaptan is removed is mainly thiophene, and can be easily absorbed by the extraction solvent and enriched to the bottom of the extraction tower, and the disulfide (converted from the mercaptan with low boiling point) contained in the light fraction has higher boiling point, and can be easily separated from the hydrocarbon component of the light fraction due to the boiling point difference under the tray effect and enriched to the bottom of the extraction tower although the disulfide is not necessarily well absorbed by the extraction solvent. Obviously, such optimization can reduce the number and quantity of the discharged spent caustic of the caustic extraction system. However, if the liquid-liquid solvent extraction and the positive pressure solvent distillation recovery are adopted, the solvent having higher selective absorption efficiency for the thiophenic compounds generally has poor effect in absorbing the sulfur of the thioether, and is difficult to deeply desulfurize, and due to mutual entrainment, the gasoline fraction after extraction often needs subsequent treatment such as water washing, and the solvent after extraction is difficult to completely recover due to relatively more absorbed materials, and is not beneficial to the effective use of the solvent.

In the present invention, both alkaline extraction and solvent extraction will produce a sulfur-rich material. Under the conditions of the present invention, these sulfur-rich materials can be subjected to selective hydrodesulfurization along with the heavy fraction with little effect on the hydrogenation system and without causing a large loss in octane number. Meanwhile, the materials rich in sulfur can also be merged into the catalytic cracking riser tube for cracking reaction, and the operation is more beneficial.

The gasoline desulfurization process provided by the invention has the following other remarkable advantages: the selective hydrodesulfurization system provided by the invention adopts the matching of two hydrogenation catalysts, and the catalytic hydrodesulfurization reaction is respectively carried out in the first hydrogenation reaction zone and the second hydrogenation reaction zone, so that a gasoline product with the sulfur content of not more than 10 mu g/g can be stably obtained, and the octane number loss is smaller.

In order to reduce the loss of octane number, the invention preferably configures an etherification step after the alkali liquor extraction step or the adsorbent adsorption step, so that the olefin in the light fraction reacts with the low carbon alcohol to generate ether compounds with high octane number. Because most of sulfide and other heteroatom compounds in the light fraction are removed by solvent extraction, pretreatment before etherification can be carried out under mild conditions, and the operation cost is favorably reduced.

Compared with the conventional process containing conventional liquid-liquid extraction, the method of the invention has the advantage that the liquid yield of the obtained gasoline product is higher by adopting extraction distillation and matching with other process means. Moreover, in the prior art, the situation of oil carrying agent and carrier oil is easy to occur in the liquid-liquid extraction process, further treatment by water washing and the like is needed, and the liquid recovery loss is easy to cause.

In summary, the deep desulfurization process of the present invention is superior in terms of desulfurization effect, reduction of octane number loss, feasibility and stability of plant operation, and environmental protection effect, which cannot be compared with the prior art.

The present invention will be described in detail below by way of examples. In the following examples, various raw materials used are commercially available without specific description.

One of the selective hydrodesulfurization catalysts used below is a commercial RSDS-11 catalyst provided by catalyst division ChangLing catalyst works of petrochemical Co., Ltd.

Composition of another selective hydrodesulfurization catalyst Cat 1: the content of cobalt oxide was 4.3 wt%, the content of molybdenum oxide was 12.4 wt%, and the balance was an alumina carrier.

The composition of the selective hydrogenation pretreatment catalyst Cat2 used below was: 0.5 wt% Pd, balance Al₂O₃And (3) a carrier.

The metal phthalocyanine fixed bed oxidation catalyst used below was supplied by Guangzhou Daorefined plant under the trade designation ARC-01.

The following adsorbents used in the mercaptan removal treatment were provided by Guangzhou Daorefined plant under the trade designation SSA-01.

The lye used is hereinafter an aqueous sodium hydroxide solution having a concentration of 25% by weight.

Example 1

This example uses the apparatus shown in FIG. 1 to carry out a deep desulfurization treatment of a gasoline feedstock A in Table 1.

Gasoline feed a was fractionated at a cut point temperature of 95 ℃ to give a light fraction with a yield of 50 wt% and a heavy fraction with a yield of 50 wt%.

In the solvent extraction system, the light fraction after fractionation is subjected to solvent extraction distillation in a solvent extraction distillation tower to obtain the light fraction after solvent extraction and a sulfur-containing solvent, wherein the sulfur-containing solvent accounts for 5 wt% of the total weight of the light fraction. Then separating the sulfur-containing solvent from the sulfides contained therein in a solvent recovery column by distillation under reduced pressure to obtain a solvent-extracted sulfur-containing material and a sulfide-removed recovered solvent:

in a solvent extractive distillation column: the feed weight ratio of the extraction solvent to the light fraction was 3: 1, the bottom temperature of the tower is 170 ℃, the top temperature of the tower is 80 ℃, the pressure of the top of the tower is 180kPa, the main extraction solvent in the extraction solvent is N-formyl morpholine, the auxiliary agent is water and methanol, the content of the auxiliary agent is 5 wt% of the extraction solvent, and the content of water in the extraction solvent is 1 wt%.

In the solvent recovery column: the bottom temperature of the tower is 180 ℃, the top temperature of the tower is 80 ℃, the top pressure of the tower is 40kPa, and the weight ratio of the steam stripping steam to the sulfur-containing solvent is 0.2: 1.

in a solvent regeneration column: the recovered solvent used for regeneration is 3 weight percent of the total recovered solvent, the temperature at the bottom of the tower is 180 ℃, the temperature at the top of the tower is 100 ℃, the pressure at the top of the tower is 10kPa, residual liquid is discharged from the bottom of the tower, the regenerated solvent and the recovered solvent are mixed and then recycled, and the used stripping water is from condensed water collected by a solvent extraction distillation tower and a solvent recovery tower. The content of non-mercaptan sulfur in the light fraction after solvent extraction is no more than 5 mu g/g.

In an alkali liquor extraction system, the volume ratio of the light fraction after solvent extraction to the alkali liquor when the light fraction is contacted with the alkali liquor is 8: 2, obtaining light fraction after alkali liquor extraction and sulfur-containing alkali liquor at the temperature of 25 ℃ and the pressure of 0.6 MPa; oxidizing the sulfur-containing alkali liquor absorbing the mercaptan under the action of an ARC-01 catalyst, wherein the injection amount of air in the oxidation process is 2.4 times of the theoretical amount, the pressure in the oxidation process is 0.5MPa, and the temperature is 40 ℃; the oxidized sulfur-containing alkali liquor is prepared by mixing the following components in a volume ratio of 1: 10, mixing the heavy fraction with hydrogenation from a selective hydrogenation system to reversely extract and remove disulfide in the oxidized sulfur-containing alkali liquor to obtain regenerated alkali liquor and alkali liquor extracted sulfur-containing materials, wherein the regenerated alkali liquor is recycled; and continuously discharging the sulfur-containing materials extracted by the alkali liquor.

Carrying out selective hydrogenation pretreatment and etherification treatment on the light fraction after alkali liquor extraction, wherein the selective hydrogenation pretreatment conditions are as follows: the catalyst Cat2 is pretreated by selective hydrogenation, the reaction temperature is 80 ℃, the reaction pressure is 1.0MPa, and the liquid hourly space velocity is 4.0h^-1Hydrogen to oil volume ratio 1. The etherification reaction is carried out by contacting the light fraction after the alkali liquor extraction with methanol, and the etherification conditions are as follows: using sulfonic acid type ion exchange resin as an etherification catalyst, wherein the molar ratio of methanol to olefin in the light fraction after alkaline liquor extraction is 1.02: 1, liquid hourly space velocity of 2.0h^-1The reaction temperature is 70 ℃, and the reaction pressure is 1.0MPa, so as to obtain the etherified light fraction.

In a selective hydrogenation system aiming at heavy fractions, carrying out selective hydrodesulfurization reaction on a sulfur-containing material extracted by alkali liquor, a sulfur-containing material extracted by a solvent and the heavy fractions after fractionation, wherein the conditions of the selective hydrodesulfurization reaction are as follows: the hydrogen partial pressure is 1.6MPa, the first reaction zone adopts RSDS-11 catalyst, the reaction temperature is 200 ℃, the second reaction zone adopts Cat1 catalyst, the reaction temperature is 300 ℃, and the liquid hourly space velocity is 3.0h^-1The volume ratio of hydrogen to oil was 400. And (3) selectively hydrogenating to obtain hydrogenated heavy fraction, wherein the sulfur content in the hydrogenated heavy fraction is 8 mu g/g.

Mixing the light fraction extracted by the alkali liquor and the hydrogenated heavy fraction into a low-sulfur gasoline product B; or the etherified light fraction and the hydrogenated heavy fraction are mixed into a low-sulfur low-olefin gasoline product C.

The properties of gasoline product B and gasoline product C are shown in table 1.

As can be seen from Table 1, the desulfurization rate of the gasoline product B is as high as 98.7%, the sulfur content of the product is only 8 mug/g, the requirement that the sulfur content of the national emission standard V gasoline product is not more than 10 mug/g is met, the olefin saturation rate is 12.0%, and the RON loss value is 1.1 unit.

As can be seen from Table 1, the desulfurization rate of the gasoline product C is as high as 98.8%, the sulfur content of the product is only 7 mug/g, the requirement that the sulfur content of the national emission standard V gasoline product is not more than 10 mug/g is met, the olefin removal rate is 42.0%, and the RON is increased by 0.8 unit.

Therefore, the combined process has good desulfurization effect and octane number loss reduction effect, the olefin saturation rate is low and the octane number loss is low if the light fraction etherification treatment is not carried out, and the olefin content can be greatly reduced and the octane number can be effectively recovered and even increased after the light fraction etherification treatment.

In addition, in this embodiment, the extraction solvent containing the auxiliary agent is used during the extractive distillation, so that the effective utilization rate of the extraction solvent is significantly increased, the regeneration frequency of the solvent is reduced, and the relative reduction of energy consumption and the relative reduction of operation cost are caused.

TABLE 1

Comparative example 1

The comparative example, which was carried out using parameters similar to those of example 1, was a gasoline feedstock as feedstock a in table 1, except that the gasoline feedstock was fractionated first to obtain a light fraction and a heavy fraction, then the light fraction was subjected to alkali extraction, and the heavy fraction was subjected to hydrodesulfurization:

the cut point of the gasoline feedstock in example 1 was defined as 65 ℃ and the yield after fractionation was 30 wt% for the light fraction and 70 wt% for the heavy fraction;

and treating the light fraction by adopting an alkali liquor extraction method, wherein the alkali liquor extraction conditions are as follows: the volume ratio of the light fraction to the alkali liquor is 8: 2, obtaining light fraction after alkali liquor extraction at the temperature of 25 ℃ and the pressure of 0.6 MPa; the sulfur-containing alkali liquor absorbing the mercaptan is oxidized under the action of a metal phthalocyanine catalyst suspended in the alkali liquor, the adding amount of the metal phthalocyanine (sulfonated cobalt phthalocyanine, a commercial product) in the alkali liquor is 500 mu g/g, the injection amount of air in the oxidation process is 2.4 times of the theoretical amount, the pressure in the oxidation process is 0.5MPa, and the temperature is 40 ℃; the oxidized sulfur-containing alkali liquor is prepared by mixing the following components in a volume ratio of 1: 10, mixing the heavy fraction with hydrogenation from a selective hydrogenation system to reversely extract and remove disulfide in the oxidized sulfur-containing alkali liquor to obtain regenerated alkali liquor and alkali liquor extracted sulfur-containing materials, wherein the regenerated alkali liquor is recycled; and continuously discharging the sulfur-containing materials extracted by the alkali liquor.

The comparative example only adopts the steps of performing alkali liquor extraction on the light fraction after fractionation without solvent extraction, and performing selective hydrogenation reaction on the heavy fraction after fractionation; the comparative example did not involve solvent extraction and etherification of the light ends.

Only one hydrogenation catalyst RSDS-11 is used in the selective hydrogenation system aiming at the heavy fraction, and the hydrogenation temperature is 320 ℃.

The sulfur content of the light fraction is not more than 10 mu g/g after the alkali liquor extraction, and the sulfur content of the heavy fraction is 9 mu g/g after the hydrogenation.

In this comparative example, the light fraction after the alkali extraction and the heavy fraction after the hydrogenation were mixed to produce a low sulfur gasoline product D, and the results are shown in table 2.

As can be seen from Table 2, in order to obtain a gasoline product D having a sulfur content of not more than 10. mu.g/g, the combined process of comparative example 1 had an olefin saturation of up to 41.0% and an octane RON loss of up to 3.8 units, as compared to the combined process of example 1, which obtained gasoline product B.

TABLE 2

Oil name	Starting materials A	Light fraction after fractionation	Heavy fraction after fractionation	Gasoline product D
					Density (20 ℃ C.)/(g/cm)³)	0.7302	0.6650	0.7512	0.7254
Sulfur content/(μ g/g)	600	107	811	9
					Mercaptan sulfur content/(μ g/g)	60	98	37	4
Olefin content/volume%	30.0	41.5	25.0	17.7
					RON	92.0	-	-	88.2
Desulfurization rate/%)	-	-	-	98.5
					Olefin saturation/removal rate/%)	-	-	-	41.0
△RON	-	-	-	-3.8

Example 2

This example uses the apparatus shown in FIG. 2 to carry out a deep desulfurization treatment of a gasoline feedstock E.

Gasoline feedstock E was fractionated at a cut point temperature of 120 ℃ to give a light fraction with a yield of 60 wt% and a heavy fraction with a yield of 40 wt%.

In the solvent extraction system, the light fraction after fractionation is subjected to solvent extraction distillation in a solvent extraction distillation tower to obtain the light fraction after solvent extraction and a sulfur-containing solvent, wherein the sulfur-containing solvent accounts for 7 wt% of the total amount of the light fraction. The sulfur-containing solvent is then separated from the sulfides contained therein by distillation in a solvent recovery column to yield a solvent-extracted sulfur-containing material and a sulfide-depleted recovered solvent:

in a solvent extractive distillation column: the feed weight ratio of the extraction solvent to the light fraction after fractionation was 4: 1, the temperature of the bottom of the tower is 150 ℃, the temperature of the top of the tower is 95 ℃, the pressure of the top of the tower is 200kPa, the main extraction solvent in the extraction solvent is N-methyl-2-pyrrolidone, the auxiliary agent is acetone, and the content of the auxiliary agent is 4.2 percent by weight of the extraction solvent.

In the solvent recovery column: the bottom temperature is 200 ℃, the top temperature is 90 ℃, the top pressure is 40kPa, the weight ratio of the stripping steam to the sulfur-containing solvent is 0.25: 1.

in a solvent regeneration column: the recovered solvent used for regeneration is 5 weight percent of the total recovered solvent, the temperature at the bottom of the tower is 170 ℃, the temperature at the top of the tower is 100 ℃, the pressure at the top of the tower is 8kPa, residual liquid is discharged from the bottom of the tower, the regenerated solvent and the recovered solvent are mixed and then recycled, and the used stripping water is from condensed water collected by a solvent extraction distillation tower and a solvent recovery tower. The content of thiophene sulfur in the light fraction after solvent extraction was 3. mu.g/g.

In the adsorption system for the light fraction after solvent extraction, the adsorbent SSA-01 is used. The temperature of adsorption contact is 140 ℃, the pressure is 0.6MPa, and the liquid hourly space velocity is 0.5h^-1. The sulfur content of the light fraction after adsorption is no more than 1 mu g/g.

And carrying out selective hydrogenation pretreatment and etherification treatment on the adsorbed light fraction, wherein the selective hydrogenation pretreatment conditions are as follows: the catalyst Cat2 is pretreated by selective hydrogenation, the reaction temperature is 100 ℃, the reaction pressure is 1.2MPa, and the liquid hourly space velocity is 5h^-1And the volume ratio of hydrogen to oil is 5. The etherification reaction is carried out by contacting the absorbed light fraction with methanol under the etherification conditions: using sulfonic acid type ion exchange resin as etherification catalyst, the molar ratio of methanol to olefin in the adsorbed light fraction is 1.05: 1, liquid hourly space velocity of 2.0h^-1The reaction temperature is 80 ℃, and the reaction pressure is 1.0MPa, so as to obtain the etherified light fraction.

In a selective hydrogenation system aiming at heavy fractions, carrying out selective hydrodesulfurization reaction on the sulfur-containing material subjected to solvent extraction and the heavy fractions subjected to fractionation, wherein the conditions of the selective hydrodesulfurization reaction are as follows: the hydrogen partial pressure is 1.6MPa, the first reaction zone adopts RSDS-11 catalyst, the reaction temperature is 220 ℃, the second reaction zone adopts Cat1 catalyst, the reaction temperature is 295 ℃, and the liquid hourly volume space velocity is 3.0h^-1The volume ratio of hydrogen to oil was 400. And (3) selectively hydrogenating to obtain hydrogenated heavy fraction, wherein the sulfur content in the hydrogenated heavy fraction is 6 mu g/g.

Mixing the adsorbed light fraction and the hydrogenated heavy fraction into a low-sulfur gasoline product F; or the etherified light fraction and the hydrogenated heavy fraction are mixed into a low-sulfur low-olefin gasoline product G.

The properties of gasoline product F and gasoline product G are shown in table 3.

As can be seen from Table 3, the desulfurization rate of the gasoline product F is as high as 99.0%, the sulfur content of the product is only 3 mug/g, the requirement that the sulfur content of the national emission standard V gasoline product is not more than 10 mug/g is met, the olefin saturation rate is 13.5%, and the RON loss value is 0 and 5 units.

As can be seen from Table 3, the desulfurization rate of the gasoline product G is as high as 99.4%, the sulfur content of the product is only 2 mug/G, the requirement that the sulfur content of the national emission standard V gasoline product is not more than 10 mug/G is met, the olefin removal rate is 58.1%, and the RON is increased by 0.7 unit.

TABLE 3

Example 3

This example was carried out using the same feedstock E and the same combined desulfurization process and the same process parameters as in example 2, except that:

the extraction solvent used in the solvent extraction process of this example contained no auxiliary agent, and the rest was the same as in example 2, with the result that the thiophene sulfur content in the light fraction after solvent extraction was 5 μ g/g.

And (3) selectively hydrogenating to obtain hydrogenated heavy fraction, wherein the sulfur content in the hydrogenated heavy fraction is 6 mu g/g.

Mixing the absorbed light fraction and hydrogenated heavy fraction into a low-sulfur gasoline product H; or the etherified light fraction and the hydrogenated heavy fraction are mixed into a low-sulfur low-olefin gasoline product I.

The properties of gasoline product H and gasoline product I are shown in table 4.

As can be seen from Table 4, the desulfurization rate of the gasoline product H is as high as 99.0%, the sulfur content of the product is only 3 mug/g, the requirement that the sulfur content of the national emission standard V gasoline product is not more than 10 mug/g is met, the olefin saturation rate is 13.5%, and the RON loss value is 0.5 unit.

As can be seen from Table 4, the desulfurization rate of the gasoline product I is as high as 99.4%, the sulfur content of the product is only 2 mug/g, the requirement that the sulfur content of the national emission standard V gasoline product is not more than 10 mug/g is met, the olefin removal rate is 58.1%, and the RON is increased by 0.7 unit.

Comparing the results of this example and example 2, it can be seen that the use of the extraction solvent containing an auxiliary agent in the solvent extraction process can make the sulfur content of the thiophene after solvent extraction of the present invention lower, but the sulfur content of the product tends to be the same after the subsequent adsorption treatment.

However, in view of solvent extraction, in this example, since no auxiliary agent is used, the effective utilization rate of the extraction solvent is lowered at the time of extractive distillation, which is disadvantageous for a long period of extraction.

TABLE 4

From the above results, it can be seen that the process of the present invention can obtain a lower sulfur gasoline product while avoiding a large loss in octane number. In addition, in the solvent extraction process, the use of the auxiliary agent has a certain promotion effect on the solvent extraction, and further, when the solvent is recycled for a long time, the effect of the auxiliary agent on the solvent extraction of the sulfide is more favorable particularly when the solvent is decomposed and the content of impurities is increased. Particularly, the matching of the etherification reaction process can lead the octane number of the gasoline product to be increased, the sulfur content to be further reduced, and simultaneously, the olefin is greatly reduced, thereby being beneficial to meeting the requirements of the VI gasoline standard of the future.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A method for deep desulfurization of gasoline, comprising:

(2) contacting the light fraction with an extraction solvent to perform solvent extraction through distillation to obtain a sulfur-containing solvent and a solvent-extracted light fraction, and then separating the sulfur-containing solvent from sulfides contained in the sulfur-containing solvent through reduced pressure distillation to obtain a solvent-extracted sulfur-containing material and a recovered solvent from which the sulfides are removed; in the solvent extraction process, the weight ratio of the extraction solvent to the light fraction is (0.5-20): 1; the solvent extraction is carried out in an extractive distillation column under conditions comprising: the pressure at the top of the tower is 100 kPa-500 kPa; the temperature of the tower top is 50-180 ℃; the temperature of the tower bottom is 80-260 ℃; the extraction solvent contains a main extraction solvent and 0.1-20 wt% of an auxiliary agent, wherein the main extraction solvent is at least one of tetraethyleneglycol, pentaethylene glycol, furfural, furfuryl alcohol, dimethylformamide, triethylene glycol monomethyl ether, acetonitrile and a solvent with a boiling point of 175-320 ℃; the auxiliary agent is at least one of alcohols, ketones, organic acids and organic nitrides which can be mutually dissolved with the main extraction solvent and have the boiling point or the dry point not higher than that of the main extraction solvent and/or water, and the organic nitrides are at least one of amines, ureas and alcohol amines;

the conditions for separating the sulfur-containing solvent from the sulfides contained therein by distillation under reduced pressure include: the pressure at the top of the solvent recovery tower is 10-100 kPa, the temperature at the top of the tower is 50-100 ℃, the temperature at the bottom of the tower is 100-250 ℃, and the weight ratio of stripping steam to the sulfur-containing solvent is (0.01-5.0): 1;

(5) mixing the sweetening light fraction obtained in the step (3) with the hydrogenated heavy fraction obtained in the step (4) to obtain a gasoline product, wherein the sweetening light fraction is the alkali liquor extracted light fraction obtained in the mode 1 or the adsorbed light fraction obtained in the mode 2;

the method further comprises the following steps: performing water injection purification treatment on at least part of the recovered solvent in a solvent regeneration tower to regenerate, wherein the recovered solvent for regeneration accounts for 1-10 wt% of the total recovered solvent; the regeneration conditions in the solvent regeneration column include: the pressure at the top of the tower is 1 kPa-10 kPa, the temperature at the top of the tower is 90-110 ℃, the temperature at the bottom of the tower is 120-200 ℃, and the weight ratio of the injected water to the recovered solvent is (0.1-10): 1.

2. the method of claim 1, wherein the method further comprises: before mixing with the hydrogenated heavy fraction obtained in the step (4), carrying out etherification reaction on the sweetening light fraction to obtain an etherified light fraction; and then mixing the etherified light fraction with the hydrogenated heavy fraction of step (4) to obtain the gasoline product.

3. The process according to claim 2, wherein the etherification reaction is carried out by contacting the light mercaptans-removed fraction with a lower alcohol having no more than 6 carbon atoms.

4. The method according to claim 3, wherein the lower alcohol is at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, t-butanol, n-pentanol, and cyclohexanol.

5. The process of claim 3, wherein the etherification reaction conditions include: the molar ratio of the low-carbon alcohol to the olefin with the carbon number not more than 6 is (0.5-3): 1, the contact temperature is 20-100 ℃, and the pressure is 0.3-1.0 MPa.

6. The process of claim 5, wherein the etherification reaction conditions comprise: the molar ratio of the low-carbon alcohol to the olefin with the carbon number not more than 6 is (1.0-1.2): 1.

7. the process according to claim 2, wherein the etherification reaction is carried out in the presence of a strongly acidic ion exchange resin as etherification catalyst.

8. The method of any of claims 2-7, wherein the method further comprises: before the etherification reaction, the sweetening light fraction is subjected to adsorption pretreatment and/or selective hydrogenation pretreatment.

9. The method according to claim 8, wherein the selective hydrogenation pretreatment is carried out in the presence of a transition metal supported catalyst comprising a carrier selected from at least one of alumina, silica, aluminosilicate, titania, zeolite and activated carbon and a metal active component selected from at least one of nickel, cobalt, molybdenum, platinum and palladium supported on the carrier.

10. The method according to claim 9, wherein the carrier in the transition metal supported catalyst is alumina, and the loading amount of the metal active component in terms of oxide is 0.05-15 wt%.

11. The method of claim 8, wherein the conditions of the selective hydrogenation pretreatment comprise: the hydrogen partial pressure is 0.1MPa to 2.0MPa, the temperature is room temperature to 250 ℃, and the liquid hourly volume space velocity is 1.0h^-1～10.0h^-1The volume ratio of hydrogen to oil is 1-100.

12. The method of any of claims 1-5, wherein the method further comprises: carrying out selective hydrodesulfurization reaction on the sulfur-containing material extracted by the solvent in the step (2) and/or the sulfur-containing material extracted by the alkali liquor in the step (3) and the heavy fraction; or

Introducing the sulfur-containing material extracted by the solvent in the step (2) and/or the sulfur-containing material extracted by the alkali liquor in the step (3) into a catalytic cracking device for catalytic cracking reaction to obtain at least part of the gasoline raw material used in the step (1).

13. The method of any one of claims 1 to 7, wherein in the solvent extraction process, the weight ratio of the extraction solvent to the light fraction is (1-5): 1.

14. the method of any of claims 1-7, wherein the conditions in the extractive distillation column comprise: the pressure at the top of the tower is 110 kPa-300 kPa; the temperature of the tower top is 50-180 ℃; the temperature of the tower bottom is 140-200 ℃.

15. The process according to any one of claims 1 to 7, wherein the boiling point of the solvent in the main extraction solvent is 175 to 250 ℃.

16. The method of any one of claims 1-7, the main extraction solvent is at least one selected from sulfolane, 3-methyl sulfolane, 2, 4-dimethyl sulfolane, 3-ethyl sulfolane, methyl ethyl sulfone, dimethyl sulfone, diethyl sulfone, dipropyl sulfone, dibutyl sulfone, dimethyl sulfoxide, alpha-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone, N-formyl morpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol, tetraethylene glycol methyl ether, ethylene carbonate, propylene carbonate, nitrobenzene, polyethylene glycol with the relative molecular mass of 200-400 and polyethylene glycol methyl ether with the relative molecular mass of 200-400.

17. The process according to any one of claims 1 to 7, wherein the main extraction solvent is selected from at least one of sulfolane, N-formylmorpholine, N-methyl-2-pyrrolidone, tetraethylene glycol and pentaethylene glycol.

18. The method according to any one of claims 1 to 7, wherein the number of carbon atoms of the alcohol, ketone, organic acid and organonitride in the auxiliary is not more than 6.

19. The method according to any one of claims 1 to 7, wherein the content of the auxiliary in the extraction solvent is 0.5 to 15% by weight.

20. The method of any one of claims 1-7, wherein the adjuvant is selected from at least one of water, methanol, ethanol, N-propanol, isopropanol, acetone, methyl ethyl ketone, isobutyric acid, oxalic acid, malonic acid, succinic acid, urea, ethylenediamine, monoethanolamine, N-methyl monoethanolamine, N-ethyl monoethanolamine, N-dimethylethanolamine, N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, N-propanolamine, isopropanolamine, and diglycolamine.

21. The method of any one of claims 1-7, wherein the adjuvant is selected from at least one of water, methanol, acetone, methyl ethyl ketone, isobutyric acid, oxalic acid, malonic acid, succinic acid, ethylenediamine, monoethanolamine, N-methyl monoethanolamine, isopropanolamine, and diglycolamine.

22. The method according to any one of claims 1 to 7, wherein the auxiliary is a mixture containing water, and the content of water in the extraction solvent is 0.1 to 5 wt%.

23. The method according to claim 22, wherein the auxiliary agent is a mixture containing water, and the content of water in the extraction solvent is 0.1-3 wt%.

24. The process according to any one of claims 1 to 7, wherein the conditions for separating the sulfur-containing solvent from the sulfides contained therein by distillation under reduced pressure comprise: the temperature of the tower bottom is 120-200 ℃.

25. The method of any of claims 1-7, wherein the regeneration conditions in the solvent regeneration column comprise: the temperature of the top of the tower is 96-105 ℃, the temperature of the bottom of the tower is 150-200 ℃, and the weight ratio of the injected water to the recovered solvent is (0.5-5): 1.

26. the method according to any one of claims 1 to 7, wherein the recovered solvent used for regeneration accounts for 1 to 5 wt% of the total recovered solvent.

27. The method according to any one of claims 1 to 7, wherein the selective hydrodesulfurization reaction is carried out in a first reaction zone and a second reaction zone which are connected in sequence, wherein the first reaction zone and the second reaction zone are respectively filled with a first hydrodesulfurization catalyst and a second hydrodesulfurization catalyst, and the first hydrodesulfurization catalyst and the second hydrodesulfurization catalyst respectively and independently comprise an alumina carrier and/or a silica-alumina carrier and a hydrogenation active metal component loaded on the carrier, wherein the hydrogenation active metal component is a non-noble metal element from the group VIB of molybdenum and/or tungsten and/or a non-noble metal element from the group VIII of nickel and/or cobalt.

28. The process of claim 27, wherein the first and second hydrodesulfurization catalysts each independently contain molybdenum and/or tungsten, nickel and/or cobalt, an alumina matrix, and a large pore zeolite and/or a medium pore zeolite.

29. The process of claim 27, wherein the group VIB non-noble metal element is present in an amount of 2 to 25 wt.% as oxide and the group VIII non-noble metal element is present in an amount of 0.2 to 6 wt.% as oxide, based on the total amount of the hydrodesulfurization catalyst.

30. The process of claim 27, wherein the reaction conditions of the first and second reaction zones each independently comprise: the hydrogen partial pressure is 0.1MPa to 4.0MPa, the reaction temperature is 200 ℃ to 440 ℃, and the liquid hourly volume space velocity is 1.0h^-1～10.0h^-1The volume ratio of hydrogen to oil is 200-1000.

31. The process of claim 30, wherein the reaction conditions of the first and second reaction zones each independently comprise: the hydrogen partial pressure is 1.0MPa to 3.2MPa, the reaction temperature is 200 ℃ to 300 ℃, and the liquid hourly volume space velocity is 2.0h^-1～6.0h^-1The volume ratio of hydrogen to oil is 200-600.

32. The method of claim 1, wherein the alkali solution in the alkali solution extraction is ammonia water and/or an aqueous solution of alkali metal hydroxide, and the concentration of the alkali solution is 1-50 wt%.

33. The method of claim 1, wherein the alkali solution in the alkali solution extraction is ammonia water and/or an aqueous solution of alkali metal hydroxide, and the concentration of the alkali solution is 5-25 wt%.

34. The method of claim 1, wherein the adsorbent is a physical adsorbent and/or a chemical adsorbent.

35. The method of claim 34, wherein the physical adsorbent is a porous material comprising at least one selected from the group consisting of silica, alumina, zeolite, clay, and activated carbon; the chemical adsorbent comprises an adsorbent aid and a metal, metal oxide or metal ion compound containing a transition metal element, wherein the transition metal element is at least one selected from iron, cobalt, nickel, copper and zinc, and the adsorbent aid is at least one selected from alkali metal and alkaline earth metal.

36. The process of claim 1, wherein the conditions under which the solvent extracted light ends are contacted with the adsorbent comprise: the temperature is 10-300 ℃; the pressure is 0.1-2 MPa, and the liquid hourly space velocity is 0.1-1 h^-1。

37. The method according to claim 1, wherein the cut points of the light fraction and the heavy fraction are 80-120 ℃.

38. The process as claimed in claim 37, wherein the yield of the light fraction is 40-60 wt% and the yield of the heavy fraction is 40-60 wt% based on the gasoline feedstock.

39. The process of claim 37, wherein the gasoline feedstock is selected from at least one of catalytically cracked gasoline, straight run gasoline, coker gasoline, pyrolysis gasoline, and thermally cracked gasoline.

40. The method according to any one of claims 1 to 7, wherein in step (5), the sulfur content of the obtained gasoline product is no more than 10 μ g/g.