CN108003931B

CN108003931B - Method for deep desulfurization of gasoline and equipment for deep desulfurization of gasoline

Info

Publication number: CN108003931B
Application number: CN201610972973.0A
Authority: CN
Inventors: 潘光成; 李涛; 赵杰; 赵丽萍; 习远兵; 唐文成; 褚阳; 常春艳; 吴明清; 陶志平; 田龙胜; 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: 2020-09-22
Anticipated expiration: 2036-10-28
Also published as: CN108003931A

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) carrying out pre-hydrogenation reaction on a gasoline raw material to obtain a pre-hydrogenated gasoline raw material; (2) fractionating the pre-hydrogenated gasoline feedstock to obtain a light fraction, a medium fraction and a heavy fraction; (3) contacting the middle fraction with an extraction solvent to obtain a sulfur-containing solvent and a solvent-extracted middle fraction, and then separating the sulfur-containing solvent from sulfides contained in the sulfur-containing solvent to obtain a solvent-extracted sulfur-containing material and a recovered solvent from which the sulfides are removed; (4) carrying out selective hydrodesulfurization reaction on the heavy fraction to obtain hydrogenated heavy fraction; (5) and mixing the light fraction, the medium fraction after solvent extraction and the heavy fraction after hydrogenation 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.

CN103725323A discloses a deodorization-extraction-washing-hydrogenation combined process for producing low-sulfur gasoline. The process comprises deodorizing catalytically cracked gasoline, cutting into light and heavy fractions, extracting, desulfurizing and washing the light fraction, mixing the extracted sulfur-containing component with the heavy fraction, selectively hydrogenating, and mixing the washed light fraction and the selectively hydrogenated heavy fraction to obtain the low-sulfur gasoline product. 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 operation of the lye extraction process with lye regeneration and the solvent extraction process with solvent recovery will produce a sulfur-rich material, which is usually mixed with the heavy fraction and then processed in the hydrogenation unit. However, researches find that sulfur-rich materials generated in the alkali liquor extraction process usually carry trace amounts of alkali and colloid, and enter a hydrogenation system to easily cause the poisoning and coking of a hydrogenation catalyst, while sulfur-containing materials generated in the solvent extraction process often contain unstable impurities and are not beneficial to direct hydrotreatment, especially under the high-temperature hydrogenation condition of pursuing higher desulfurization rate; on the other hand, conventional liquid-liquid solvent extraction usually does not have selectivity for all sulfides, and the extracted material and the extraction solvent are often entrained with each other (usually further subsequent treatment is required, such as water washing of the extracted material is performed, etc.) when being contacted and separated, while the solvent with the extracted material under positive pressure (higher than standard atmospheric pressure) is difficult to distill, so that the extraction solvent is well recovered, even side reactions such as high-temperature degradation of the extraction solvent occur, and the capacity of the solvent to continuously extract sulfides is reduced.

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 gasolines and a plant for use in this 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 organic solvent, and finds that the extraction distillation has higher sulfide removal efficiency compared with the conventional liquid-liquid extraction, and the absorption of the extraction solvent to olefin in the extraction distillation process is less than that of the conventional liquid-liquid extraction, so that the method is beneficial to keeping more olefin, reducing octane value loss caused by subsequent (merged into heavy fraction) hydrogenation treatment after the olefin is extracted along with sulfide, 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. In order to remove small molecular mercaptan sulfur, a mode of alkali liquor extraction can be adopted, however, the alkali discharge problem is caused, and therefore, the invention adopts a hydrogenation mode to remove the mercaptan in the gasoline under the condition of unsaturated olefin as much as possible, and combines with solvent extraction to realize deep desulfurization of the gasoline. 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) in the presence of a pre-hydrogenation catalyst, carrying out a pre-hydrogenation reaction on a gasoline raw material to obtain a pre-hydrogenated gasoline raw material;

(2) fractionating the pre-hydrogenated gasoline raw material to obtain a light fraction, a medium fraction and a heavy fraction, wherein the cutting point temperature of the light fraction and the medium fraction is 40-65 ℃, and the cutting point temperature of the medium fraction and the heavy fraction is 80-150 ℃;

(3) contacting the middle fraction with an extraction solvent to perform solvent extraction through distillation to obtain a sulfur-containing solvent and a solvent-extracted middle 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;

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

(5) and (3) mixing the light fraction obtained in the step (2), the medium fraction obtained after solvent extraction in the step (3) and the heavy fraction obtained after hydrogenation in the step (4) to obtain a gasoline product.

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

the pre-hydrogenation system is used for carrying out pre-hydrogenation reaction on the gasoline raw material to obtain a pre-hydrogenated gasoline raw material;

a fractionation system through which the pre-hydrogenated gasoline feedstock from the pre-hydrogenation system is fractionated to obtain a light fraction, a medium 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 middle distillate from the fractionation system to obtain a sulfur-containing solvent and the middle distillate 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 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 the light fraction, the middle fraction after solvent extraction and the heavy fraction after hydrogenation are mixed and are taken as a gasoline product to be led out through a pipeline.

In order to obtain a gasoline product with lower sulfur and avoid great loss of octane number, the method flexibly uses non-hydrogenation modes such as solvent extraction and the like while adopting a hydrogenation mode, so that the method provided by the invention can obtain the gasoline product with lower sulfur on the premise of avoiding great 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.

Description of the reference numerals

1. Gasoline raw material 2, pre-hydrogenation system

3. Gasoline raw material 4 after pre-hydrogenation and fractionation system

5. Heavy fraction 6, light fraction

7. Middle distillate 8 and solvent extraction system

9. Middle distillate 10 after solvent extraction, sulfur-containing material after solvent extraction

11. Mixed fraction 12, etherification system

13. Fraction 14 after etherification and selective hydrogenation system

15. 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:

In the present invention, the light fraction is a fraction having a relatively light distillation range, the heavy fraction is a fraction having a relatively heavy distillation range, and the middle fraction is a fraction having a distillation range between the light fraction and the heavy fraction.

It has been found that the presence of small molecule mercaptans in gasoline is detrimental to the solvent extractive distillation desulfurization operation of the present invention, primarily because the low boiling small molecule mercaptans tend to remain in the extracted gasoline fraction during the extractive distillation. In order to solve the problem, the gasoline raw material is firstly treated by adopting a pre-hydrogenation mode, so that mercaptan in light fraction is converted into thioether sulfide with relatively high boiling point, and then the thioether is basically transferred into middle and heavy fractions after being subjected to fractionation and cutting, thereby reducing the sulfur content in the light fraction.

The prehydrogenation reaction step in the preferred case relating to the invention is provided below:

according to the invention, a gasoline feedstock containing mercaptans and diolefins is contacted with hydrogen over a prehydrogenation catalyst, the mercaptans and diolefins are reacted to form thioether sulfides and the diolefins are saturated, and the prehydrogenation conditions are such that the reaction is highly selective, i.e. the reaction of the saturation of the monoolefins with the hydrogenolysis of the sulfides is suppressed or made difficult in addition to the above-mentioned reactions. Preferably, the pre-hydrogenation catalyst comprises a transition metal supported catalyst, which can be a non-noble metal supported catalyst, a noble metal supported catalyst, or a combination of the two catalysts.

Preferably, the pre-hydrogenation catalyst is a transition metal supported catalyst, the transition metal supported catalyst comprises a carrier and a metal active component loaded on the carrier, the carrier is selected from at least one of alumina, silica, aluminosilicate, titania, zeolite and activated carbon, and the metal active component is selected from at least one of nickel, cobalt, molybdenum, platinum and palladium.

Preferably, 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 pre-hydrogenation reaction 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 1.0 to 10.0h^-1The volume ratio of hydrogen to oil is 1-100.

The mercaptans contained in the light fraction are converted to higher-boiling thioethers in the prehydrogenation. The light fraction after pre-hydrogenation is contacted with an extraction solvent, and the contained thioether compounds and thiophene sulfides are transferred into the extraction solvent.

The mercaptans contained in the gasoline feedstock are converted to high boiling thioethers during the pre-hydrogenation process. And fractionating the pre-hydrogenated gasoline raw material to obtain a light fraction, a medium fraction and a heavy fraction.

Preferably, the cut point temperatures of the light fraction and the medium fraction are such that the non-mercaptan sulfur content in the light fraction is no more than 10 μ g/g.

Preferably, the cut points of the medium fraction and the heavy fraction are 80-130 ℃.

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

Preferably, the yield of the light fraction is 10-30 wt%, the yield of the medium fraction is 20-40 wt%, and the yield of the heavy fraction is 30-70 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.

After prehydrogenation, the mercaptan with relatively low boiling point in gasoline is converted into thioether sulfide with relatively high boiling point, and after fractional distillation and cutting, the mercaptan in light fraction is converted into thioether sulfide with relatively high boiling point and transferred into medium and heavy fractions, so that the sulfur content in light fraction is reduced, and the sulfur content in medium and heavy fractions is raised. The sulfides in the light fraction are mainly thiophene sulfides other than mercaptan sulfur and have a content of not more than 10 mug/g, while the sulfides contained in the medium and heavy fractions, besides thiophene sulfides, also include disulfides converted from mercaptans, which are easily removed by solvent extraction and selective hydrogenation, respectively.

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

and the solvent extraction enables sulfide mainly comprising thiophene in the middle distillate obtained after fractionation to be transferred into the extraction solvent to form the sulfur-containing solvent.

Preferably, the solvent extraction is carried out in an extractive distillation tower, the middle distillate enters the tower from the middle part of the extractive distillation tower, the extraction solvent enters the 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 middle distillate enter the tower bottom of the extractive distillation tower along with the extraction solvent. Part of the low-sulfur middle distillate 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 middle distillate is discharged to be the middle distillate after solvent extraction. 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 middle distillate 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 middle distillate 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 middle distillate after solvent extraction obtained after solvent extraction is not more than 10 mu g/g.

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

Preferably, the organic solvent is selected from sulfolane, 3-methylsulfolane, 2, 4-dimethylsulfolane, 3-ethylsulfolane, methylethylsulfone, dimethylsulfone, diethylsulfone, dipropylsulfone, dibutylsulfone, dimethylsulfoxide, furfural, furfuryl alcohol, alpha-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 organic 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 a gas phase and a liquid phase exist, the liquid phase is a single liquid phase, namely, in a liquid phase interval, a solvent of the liquid phase and a middle distillate of the liquid phase are in a dissolved state, so that the sulfide in the middle distillate is favorably transferred into an organic 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 organic solvent and help the liquid phase region of the extractive distillation column to maintain a single liquid phase, it is preferable that the extractive solvent contains an auxiliary agent, and the auxiliary agent contains at least one of alcohols, ketones, organic acids and organonitrides, which are miscible with the organic solvent and have a boiling point or a dry point not higher than that of the extractive solvent, and the organonitrides are at least one of amines, ureas and alcamines.

Preferably, the auxiliary agent contains at least one of alcohols having a boiling point or a dry point which is mutually soluble with the organic solvent and has no more than 6 carbon atoms, ketones having no more than 6 carbon atoms, organic acids having no more than 6 carbon atoms and organic nitrides having no more than 6 carbon atoms, 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 auxiliary agent contains at least one of 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 contains at least one of 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 auxiliary agent further contains 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 contains water, the content of water in the extraction solvent is preferably 0.1 to 5% by weight, and 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 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 distilled to obtain a sulfur-containing material under the heating condition, the sulfur-containing material comprises aromatic hydrocarbon, thiophene and thioether compounds from middle distillate, 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.

Preferably, the method of the present invention further comprises: before mixing with the hydrogenated heavy fraction in the step (4), carrying out etherification reaction on the light fraction in the step (2) and a mixed fraction formed by the middle fraction after solvent extraction in the step (3) to obtain an etherified fraction; and then mixing the etherified 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 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 mixed fraction with a lower alcohol having not 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 lower alcohol to the olefin in the mixed fraction is (0.5-3): 1, preferably (1.0-1.2): 1, the contact temperature is 20-100 ℃, and the pressure is 0.3-2.0 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 under which the mixed fraction is contacted with the lower alcohol are such that the olefin removal rate of the fraction after etherification is not less than 35%.

According to a preferred embodiment of the present invention, the method of the present invention further comprises: and (4) carrying out selective hydrodesulfurization reaction on the sulfur-containing material extracted by the solvent in the step (3) and the heavy fraction.

According to another 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 (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, in step (5), the sulfur content of the obtained gasoline product is not more than 10 mu g/g. In particular, the gasoline product of step (5) of the present invention is a product obtained by mixing a light fraction, a medium fraction after solvent extraction and a heavy fraction after hydrogenation, or a product obtained by mixing a heavy fraction after hydrogenation and a fraction after etherification.

Preferably, the equipment further comprises an etherification system, wherein the light fraction from the fractionation system and the solvent-extracted middle fraction from the solvent extraction system are firstly introduced into the etherification system through a pipeline to carry out etherification reaction so as to obtain etherified fraction; and then mixing the etherified fraction with the hydrogenated heavy fraction to be taken as a gasoline product to be led out through a pipeline.

According to a preferred aspect, the apparatus further comprises a line for introducing said solvent extracted sulfur-containing feed to a selective hydrogenation system.

According to another preferred case, the equipment further comprises a cracking system, the sulfur-containing material after solvent extraction from the solvent extraction system is introduced into the cracking system through a pipeline to carry out catalytic cracking reaction, and products in the cracking system are introduced into the pre-hydrogenation 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 the deep desulfurization of gasoline according to the invention has a schematic structural diagram shown in fig. 1, in particular:

the gasoline raw material 1 enters a pre-hydrogenation system 2 through a pipeline and contacts with hydrogen under the action of a pre-hydrogenation catalyst, and mercaptan in the gasoline raw material reacts with diene to generate thioether sulfides with high boiling point, so that a pre-hydrogenated gasoline raw material 3 is obtained.

The prehydrogenated gasoline feed 3 from the prehydrogenation system 2 is introduced into the fractionation system 4 through a line to fractionate the heavy fraction 5, the light fraction 6 and the middle fraction 7. The heavy fraction 5 flows out through a pipeline, is mixed with hydrogen to enter a selective hydrogenation system 14, 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 15.

And (3) enabling the middle distillate 7 from the fractionation system 4 to enter a solvent extraction system 8, contacting with an extraction solvent, and transferring the residual sulfide in the middle distillate 7 into the extraction solvent to obtain a middle distillate 9 after solvent extraction. 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 10 after solvent extraction, the sulfur-containing material 10 after solvent extraction and a heavy fraction 5 enter a selective hydrogenation system 14 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 and the heavy residual liquid rich in impurities are separated from the regenerated solvent, and the regenerated solvent is merged into the recovered solvent and is continuously contacted with the middle distillate for recycling.

Preferably, a mixed fraction 11 formed from the light fraction 6 and the solvent-extracted middle fraction 9 is fed via a line to an etherification system 12. The mixed fraction 11 entering the etherification system 12 contacts with lower alcohol, so that the olefin in the mixed fraction 11 reacts with the lower alcohol to generate ether, and the fraction 13 after etherification is obtained.

The hydrogenated heavy fraction 15 and the etherified fraction 13 are mixed to form a gasoline product which is low in sulfur and olefin and has an increased octane number; or the light fraction 6, the hydrogenated heavy fraction 15 and the solvent-extracted middle fraction 9 are mixed to form a gasoline product with low sulfur, low olefin and less octane number loss.

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

in order to effectively reduce the sulfur content of the gasoline fraction, the invention adopts an extraction solvent combination which has obvious selective absorption on sulfides on the basis of pre-hydrogenation, and adopts an extraction distillation mode to extract and remove the sulfides in the gasoline fraction and a reduced pressure distillation mode to recover the extraction solvent, the middle fraction after solvent extraction and the extraction solvent are completely separated (basically do not carry with each other) without subsequent treatment, the extraction solvent, the absorbed sulfides and sulfur-containing materials can also be well separated during recovery, and a part of the recovered solvent is regenerated, thereby overcoming the defect of incomplete regeneration of the conventional solvent, not only separating the residual hydrocarbon materials dissolved in the solvent through the azeotropic action with water, but also removing the high boiling point polymers, sediments and other impurities accumulated in the solvent, and having obvious purification effect during solvent regeneration, thereby effectively recovering the cyclic extraction capability after the recovered solvent is mixed with a part of the regenerated solvent . The dry point of the middle distillate in the invention can be properly increased due to the improvement of the desulfurization efficiency, so that the yield of the middle distillate in the gasoline fractionation process can be increased, the yield of the heavy distillate can be reduced, the treatment amount of the heavy distillate entering a hydrogenation system is reduced, and the octane number loss caused by the hydrogenation of the heavy distillate can be effectively reduced.

If the modes of liquid-liquid solvent extraction and positive pressure solvent distillation recovery are adopted, the solvent with higher selective absorption efficiency on the thiophene compounds generally has poor effect on the aspect of sulfur sulfide absorption, deep desulfurization is difficult to realize, extracted gasoline fractions often need subsequent treatment such as water washing and the like due to mutual entrainment, and the extracted solvent is difficult to completely recover due to relatively more absorbed materials, so that the effective use of the solvent is not facilitated. In the invention, the sulfur-containing gasoline raw material is pre-hydrogenated, so that the problems of caustic sludge discharge and treatment caused by an alkali liquor extraction mode can be avoided, the sulfide content in the light fraction can be conveniently reduced to 10 mu g/g after fractionation, and meanwhile, the heavy fraction treatment amount entering a selective hydrogenation system is relatively reduced through the desulfurization operation of the middle fraction, so that the octane number loss is effectively reduced.

In the present invention, solvent extraction produces a sulfur-rich feedstock. Under the conditions of the invention, these sulfur-rich materials can be subjected to selective hydrodesulfurization, and have little effect on the hydrogenation system and do not cause major octane number loss. At the same time, the sulfur-rich materials can be preferably combined into a 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 two hydrogenation catalysts to be matched, and the catalytic hydrodesulfurization reaction is respectively carried out in the first reaction zone and the second 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.

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.

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.

Carrying out pre-hydrogenation reaction on a gasoline raw material A, wherein the conditions of the pre-hydrogenation reaction are as follows: using a pre-hydrogenation catalyst Cat2, wherein the reaction temperature is 80 ℃, the reaction pressure is 1.0MPa, and the liquid hourly space velocity is 4.0h^-1And 5, obtaining the gasoline raw material after pre-hydrogenation.

And (3) fractionating the pre-hydrogenated gasoline raw material into light fraction, medium fraction and heavy fraction, wherein the fractionation temperature of the light fraction and the medium fraction is 60 ℃, and the fractionation temperature of the medium fraction and the heavy fraction is 120 ℃. The yields (in mass fraction) of the light fraction, the middle fraction and the heavy fraction after fractionation were about 20%, 45% and 35%, respectively.

In the solvent extraction system, the middle distillate is subjected to solvent extraction distillation in a solvent extraction distillation tower to obtain the middle distillate and a sulfur-containing solvent after solvent extraction, wherein the sulfur-containing solvent accounts for 5 wt% of the total weight of the middle distillate. 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 middle distillate is 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 organic 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 sulfur content in the middle distillate after solvent extraction is not more than 5 mu g/g.

The etherification reaction is carried out by contacting the mixed fraction formed by the light fraction and the solvent-extracted middle 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 mixed fraction 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 fraction after etherification.

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 200 ℃, the second reaction zone adopts Cat1 catalyst, the reaction temperature is 302 ℃, 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 not more than 10 mu g/g.

Mixing the light fraction, the middle fraction after solvent extraction and the heavy fraction after hydrogenation into a low-sulfur gasoline product B; or mixing the etherified fraction and the hydrogenated heavy fraction to obtain the low-sulfur and 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 99.0%, 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 saturation rate is 21.8%, and the RON loss value is 1.6 units.

As can be seen from Table 1, the desulfurization rate of the gasoline product C is as high as 99.2%, the sulfur content of the product is only 6 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 55.9%, and the RON is increased by 0.4 unit.

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

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 60 c 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 light fraction after the alkali liquor extraction and the heavy fraction after the selective hydrogenation are mixed into a gasoline product.

This comparative example only used a combination of the alkaline extraction step of the light fraction with the selective hydrogenation step of the heavy fraction, and did not use the solvent extraction step and the etherification step for the light fraction. The results are shown in Table 2.

The sulfur content of the light fraction after alkaline extraction is not more than 10 mug/g, and the sulfur content of the heavy fraction after hydrogenation is controlled at a level equivalent to that of example 1: 9. mu.g/g (not more than 10. mu.g/g). In addition, only one hydrogenation catalyst RSDS-11 is used in the selective hydrogenation system, and the hydrogenation temperature is 320 ℃.

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 47.9% and an octane RON loss of up to 4.4 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)	0.7235	0.6443	0.7848	0.7216
Sulfur content/(μ g/g)	716	100	980	9
					Mercaptan sulfur content/(μ g/g)	48	90	30	<3
Olefin content/volume%	34.0	47.6	28.0	17.7
					RON	91.8	-	-	87.4
Desulfurization rate/%)	-	-	-	98.7
					Olefin saturation/removal rate/%)	-	-	-	47.9
△RON	-	-	-	-4.4

Example 2

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

Carrying out pre-hydrogenation reaction on a gasoline raw material E, wherein the conditions of the pre-hydrogenation reaction are as follows: using a pre-hydrogenation catalyst Cat2, the reaction temperature is 100 ℃, the reaction pressure is 1.2MPa, and the liquid hourly space velocity is 5.0h^-1And 5, obtaining the gasoline raw material after pre-hydrogenation.

And (3) fractionating the pre-hydrogenated gasoline raw material into light fraction, medium fraction and heavy fraction, wherein the fractionation temperature of the light fraction and the medium fraction is 55 ℃, and the fractionation temperature of the medium fraction and the heavy fraction is 120 ℃. The yields (in mass fraction) of the light fraction, the middle fraction and the heavy fraction after the fractionation were about 25%, 35% and 40%, respectively.

In the solvent extraction system, the middle distillate obtained after fractionation is subjected to solvent extraction distillation in a solvent extraction distillation tower to obtain the middle distillate after solvent extraction and a sulfur-containing solvent, wherein the sulfur-containing solvent accounts for 7 wt% of the total weight of the middle distillate. 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 middle distillate is 4: 1, the bottom temperature of the tower is 150 ℃, the top temperature of the tower is 95 ℃, the pressure of the top of the tower is 200kPa, the organic 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 sulfur content in the middle distillate after solvent extraction is not more than 5 mu g/g.

The etherification reaction is carried out by contacting the mixed fraction formed by the light fraction and the solvent-extracted middle 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 mixed fraction is 1.05: 1, the liquid hourly space velocity is 2.0h^-1The reaction temperature is 80 ℃, and the reaction pressure is 1.0MPa, so as to obtain the fraction after etherification.

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 catalyst Cat1,the reaction temperature is 297 ℃ 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 7 mu g/g.

Mixing the light fraction, the middle fraction after solvent extraction and the heavy fraction after hydrogenation into a low-sulfur gasoline product F; or mixing the etherified fraction and the hydrogenated heavy fraction to obtain the low-sulfur and 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 98.8%, the sulfur content of the product is only 5 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 3, the desulfurization rate of the gasoline product G is as high as 99.0%, the sulfur content of the product is only 4 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 0.1 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 does not contain an auxiliary agent, and the rest is the same as that in example 2, and as a result, the sulfur content in the middle distillate after solvent extraction is no more than 10 μ g/g.

And (3) selectively hydrogenating to obtain hydrogenated heavy fraction, wherein the sulfur content in the hydrogenated heavy fraction is not more than 10 mu g/g.

Mixing the light fraction, the middle fraction after solvent extraction and the heavy fraction after hydrogenation into a low-sulfur gasoline product H; or the etherified 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 98.5%, the sulfur content of the product is only 6 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 98.8%, the sulfur content of the product is only 5 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 0.1 unit.

Comparing the results of this example with those of example 2, it can be seen that the use of an extraction solvent containing an adjuvant during the solvent extraction process enables the gasoline product obtained by the process of the present invention to have a somewhat lower sulfur content. If the sulfur content of the product is to be made completely uniform, the hydrogenation degree of the heavy fraction is increased in this example, which results in a decrease in the olefin content of the product H (as compared with the product I), and a greater octane number loss than in example 2.

In addition, in this embodiment, since no auxiliary agent is used, the effective utilization rate of the extraction solvent is lowered during the extractive distillation, which is not favorable for the long-term 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:

(3) contacting the middle fraction with an extraction solvent to perform solvent extraction through distillation to obtain a sulfur-containing solvent and a solvent-extracted middle 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 middle distillate is (0.5-20): 1, the solvent extraction being carried out in an extractive distillation column, the conditions in the extractive distillation column 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 tetraethylene glycol, pentaethylene glycol, furfural, furfuryl alcohol, dimethylformamide, triethylene glycol methyl ether, acetonitrile and an organic solvent with a boiling point of 175-320 ℃, the auxiliary agent is at least one of alcohols, ketones, organic acids and organic nitrides and/or water, the boiling point or the dry point of the auxiliary agent is not higher than that of the main extraction solvent, 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 light fraction of step (2), the medium fraction after solvent extraction of step (3) and the heavy fraction after hydrogenation of step (4) to obtain a gasoline product;

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 in the step (4), carrying out etherification reaction on the light fraction in the step (2) and a mixed fraction formed by the middle fraction after solvent extraction in the step (3) to obtain an etherified fraction; and then mixing the etherified fraction with the hydrogenated heavy fraction of step (4) to obtain the gasoline product.

3. The process of claim 2, wherein the etherification reaction is carried out by contacting the mixed 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 lower alcohol to the olefin in the mixed fraction is (0.5-3): 1, the contact temperature is 20-100 ℃, and the pressure is 0.3-2.0 MPa.

6. The process of claim 5, wherein the etherification reaction conditions comprise: the molar ratio of the lower alcohol to the olefin in the mixed fraction 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 according to any one of claims 1 to 7, wherein the pre-hydrogenation catalyst is 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.

9. The method according to claim 8, 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%.

10. The process of any one of claims 1-7, wherein the conditions of the pre-hydrogenation reaction 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 1.0 to 10.0h^-1The volume ratio of hydrogen to oil is 1-100.

11. The method of any of claims 1-7, wherein the method further comprises: carrying out selective hydrodesulfurization reaction on the sulfur-containing material extracted by the solvent in the step (3) and the heavy fraction; or

Introducing the sulfur-containing material extracted by the solvent 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).

12. The method according to any one of claims 1 to 7, wherein in the solvent extraction process, the weight ratio of the extraction solvent to the middle distillate is (1-5): 1.

13. 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 ℃.

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

15. 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.

16. The process of claim 15, wherein the primary extraction solvent is selected from at least one of sulfolane, N-formylmorpholine, N-methyl-2-pyrrolidone, tetraethylene glycol, and pentaethylene glycol.

17. 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.

18. 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.

19. The method of any one of claims 1-7, wherein the adjuvant comprises at least one of 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.

20. The method of claim 19, wherein the adjuvant comprises at least one of methanol, acetone, methyl ethyl ketone, isobutyric acid, oxalic acid, malonic acid, succinic acid, ethylenediamine, monoethanolamine, N-methyl monoethanolamine, isopropanolamine, and diglycolamine.

21. The method according to any one of claims 1 to 7, wherein the auxiliary further comprises water, and the content of water in the extraction solvent is 0.1 to 5 wt%.

22. The method according to claim 21, wherein the content of water in the extraction solvent is 0.1 to 3% by weight.

23. 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 ℃.

24. 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;

the recovery solvent for regeneration accounts for 1-5 wt% of the total recovery solvent.

25. 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.

26. The process of claim 25, 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.

27. The process of claim 25, 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.

28. The process of claim 25, 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.

29. The process of claim 28, 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.

30. The method according to claim 1, wherein the cut point temperatures of the light fraction and the medium fraction are such that the non-thiol sulphur content in the light fraction is no more than 10 μ g/g.

31. The method according to claim 30, wherein the cut points of the medium and heavy fractions are 80-130 ℃.

32. The process as claimed in claim 30, wherein the yield of the light fraction is 10 to 30 wt%, the yield of the middle fraction is 20 to 40 wt%, and the yield of the heavy fraction is 30 to 70 wt% based on the gasoline feedstock.

33. The process of claim 30, 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.

34. 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.