CN108003930B

CN108003930B - Method for deep desulfurization of gasoline and equipment for deep desulfurization of gasoline

Info

Publication number: CN108003930B
Application number: CN201610971960.1A
Authority: CN
Inventors: 潘光成; 赵杰; 李涛; 习远兵; 褚阳; 唐文成; 赵丽萍; 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: CN108003930A

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 to obtain a light fraction and a heavy fraction; (2) carrying out pre-hydrogenation reaction on the light fraction to obtain pre-hydrogenated light fraction; (3) carrying out solvent extraction on the light fraction after pre-hydrogenation to obtain a sulfur-containing solvent and the light fraction after solvent extraction, and then separating the sulfur-containing solvent from sulfides contained in the sulfur-containing solvent by distillation to obtain a sulfur-containing material after solvent extraction 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 hydrogenated heavy fraction with the solvent-extracted 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. The process comprises the steps of cutting gasoline into light and heavy fractions, refining the light fraction by alkali, then carrying out extraction desulfurization, mixing the extracted sulfur-containing component with the heavy fraction for selective hydrogenation, and mixing the light fraction subjected to extraction desulfurization and the heavy fraction subjected to selective hydrogenation to form 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 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. For removing small molecule mercaptan sulfur, alkali liquor extraction can be adopted, however, alkali discharge problems can be caused, and therefore, the invention adopts hydrogenation to remove the mercaptan under the condition of unsaturated olefin as much as possible and combines solvent extraction to realize deep desulfurization of 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) fractionating a gasoline raw material at a cutting point temperature of 70-140 ℃ to obtain a light fraction and a heavy fraction;

(2) in the presence of a pre-hydrogenation catalyst, carrying out a pre-hydrogenation reaction on the light fraction to obtain a pre-hydrogenated light fraction;

(3) contacting the pre-hydrogenated 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;

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

(5) and (3) mixing the hydrogenated heavy fraction in the step (4) with the solvent-extracted light fraction in the step (3) to obtain a gasoline product.

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

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

a pre-hydrogenation system, wherein the light fraction from the fractionation system is subjected to a pre-hydrogenation reaction in the pre-hydrogenation system to obtain a pre-hydrogenated light 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 pre-hydrogenated light fraction from the pre-hydrogenation system to obtain a sulfur-containing solvent and the solvent-extracted light fraction; 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;

the hydrogenated heavy fraction is mixed with the solvent extracted light fraction and is led out as a gasoline product 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 embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit 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, fractionation system

3. Heavy fraction 4, light fraction

5. Pre-hydrogenation system 6, pre-hydrogenated light fraction

7. Solvent extraction system 8, sulfur-containing material after solvent extraction

9. Light fraction 10 after solvent extraction and heavy fraction after hydrogenation

11. Etherification system 12, light ends after etherification

13. Selective hydrogenation system

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.

The inventors of the present invention have found that the presence of small molecule mercaptans in the gasoline feedstock 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 the light fraction is converted into thioether sulfide with a relatively high boiling point, and then the thioether sulfide is absorbed by an extraction solvent by adopting a solvent extraction distillation mode and is separated from the light fraction, so that the sulfur content in the light fraction is reduced.

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 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 after the pre-hydrogenation 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 pre-hydrogenated light fraction 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 pre-hydrogenated 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 pre-hydrogenated light fraction 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 sulfide in the light fraction after pre-hydrogenation, and often absorbs other components much more than the sulfide, so that a plurality of problems are brought to a solvent recovery system in a distillation mode, such as increased energy consumption, more residual components in the recovered solvent, and the return to the solvent extraction system is easy to cause rapid reduction of solvent extraction capacity. 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 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, and the liquid phase is a single liquid phase, namely, in a liquid phase interval, a solvent of the liquid phase and a light fraction of the liquid phase are in a dissolved state, so that the sulfide in the light fraction 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 heated to evaporate a sulfur-containing material, the sulfur-containing material comprises aromatic hydrocarbon, thiophene and thioether compounds from the pre-hydrogenated light fraction, 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 obtained in the step (4), carrying out etherification reaction on the light fraction obtained in the step (3) after solvent extraction 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 fraction after solvent extraction 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 mol ratio of the low-carbon alcohol to the olefin in the light fraction after solvent extraction 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 light fraction is contacted with the lower alcohol after the solvent extraction are such that the olefin removal rate in the light 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, 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. In particular, the gasoline product of step (5) of the present invention is a product obtained by mixing a heavy fraction after hydrogenation with a light fraction after solvent extraction, or a product obtained by mixing a heavy fraction after hydrogenation with a light fraction after etherification.

Preferably, the equipment further comprises an etherification system, and the light fraction after solvent extraction from the solvent extraction 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 aspect, the apparatus further comprises a line for introducing said solvent extracted sulfur-containing feed to a selective hydrogenation system.

According to another preferred aspect, the apparatus further comprises a cracking system, the sulfur-containing material extracted by the solvent from the solvent extraction system is introduced into the cracking system through a pipeline to perform catalytic cracking reaction, and the product in the cracking system is 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 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 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 13, 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 the hydrogenated heavy fraction 10.

The light fraction 4 from the fractionation system 2 enters a pre-hydrogenation system 5 through a pipeline and contacts with hydrogen under the action of a pre-hydrogenation catalyst, and mercaptan in the light fraction reacts with diene to generate high-boiling-point thioether sulfides, so that pre-hydrogenated light fraction 6 is obtained.

The light fraction 6 after pre-hydrogenation from the pre-hydrogenation system 5 enters a solvent extraction system 7, contacts with an extraction solvent, and the sulfide remained in the light fraction 6 after pre-hydrogenation is transferred into the extraction solvent to obtain a light fraction 9 after solvent extraction, and preferably, the light fraction 9 after solvent extraction enters an etherification system 11 through a pipeline.

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 8 after solvent extraction, the sulfur-containing material 8 after solvent extraction and the heavy fraction 3 enter a selective hydrogenation system 13 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 light fraction after the pre-hydrogenation for recycling.

And (3) contacting the light fraction 9 subjected to solvent extraction in the etherification system 11 with a lower alcohol, so that the olefin in the light fraction 9 subjected to solvent extraction reacts with the lower alcohol to generate ether, and obtaining an etherified light fraction 12.

The hydrogenated heavy fraction 10 and the etherified light fraction 12 are mixed to form a gasoline product with low sulfur, low olefin and increased octane number; or the hydrogenated heavy fraction 10 and the solvent extracted light 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 in the gasoline raw material, the invention adopts an extraction solvent combination which has obvious selective absorption on sulfide on the basis of pre-hydrogenation, and adopts an extraction distillation mode to extract and remove sulfide in gasoline fraction and a reduced pressure distillation mode to recover the extraction solvent, the light fraction after solvent extraction is completely separated from the extraction solvent (basically without entrainment) without subsequent treatment, the extraction solvent can be well separated from the absorbed sulfide and sulfur-containing materials 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 residual hydrocarbon materials dissolved in the solvent through the azeotropic action with water, but also removing high boiling point polymers, sediments and other impurities accumulated in the solvent, and having obvious purification effect during solvent regeneration, thereby effectively recovering the circulating extraction capability after the recovered solvent is mixed with a part of the regenerated solvent And (5) repeating. 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.

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. The invention adopts pre-hydrogenation to pre-treat the light fraction, can avoid the problem of caustic sludge treatment caused by adopting alkali liquor extraction, and is particularly beneficial to further treatment of the light fraction, such as etherification operation and the like.

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. 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 adopts two kinds of 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.

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%.

Carrying out pre-hydrogenation reaction on the light fraction after fractionation, 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 the volume ratio of hydrogen to oil is 5.

In a solvent extraction system, carrying out solvent extraction distillation on the pre-hydrogenated light fraction in a solvent extraction distillation tower to obtain the solvent extracted light fraction and a sulfur-containing solvent, wherein the sulfur-containing solvent accounts for 5 wt% of the total weight of the pre-hydrogenated 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 weight ratio of the extraction solvent to the pre-hydrogenated light fraction 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 light fraction after solvent extraction is no more than 5 mu g/g.

The etherification reaction is carried out by contacting the light fraction after the solvent extraction with methanol under the etherification conditions: using sulfonic acid type ion exchange resin as an etherification catalyst, wherein the molar ratio of methanol to olefin in the light fraction after solvent 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 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 after solvent extraction 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 99.3%, 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 23.8%, and the RON loss value is 1.9 units.

As can be seen from Table 1, the desulfurization rate of the gasoline product C is as high as 99.4%, 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 55.9%, and the RON is increased by 0.1 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

This comparative example was run using the same feed oil a and the same combined desulfurization process, the same process parameters as in example 1, except that:

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.

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%.

Carrying out pre-hydrogenation reaction on the light fraction after fractionation, 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 the volume ratio of hydrogen to oil is 5.

In a solvent extraction system, carrying out solvent extraction distillation on the pre-hydrogenated light fraction in a solvent extraction distillation tower to obtain the solvent extracted light fraction and a sulfur-containing solvent, wherein the sulfur-containing solvent is 7 wt% of the total weight of the pre-hydrogenated 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 weight ratio of the extraction solvent to the light fraction after pre-hydrogenation 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 light fraction after solvent extraction was 3. mu.g/g.

The etherification reaction is carried out by contacting the light fraction after the solvent extraction with methanol under the etherification conditions: using sulfonic acid type ion exchange resin as etherification catalyst, the mol ratio of methanol to olefin in the light fraction after solvent extraction is 1.05: 1, the 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, and 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 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 after solvent extraction 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 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 saturation rate is 16.0%, and the RON loss value is 0.7 unit.

As can be seen from Table 3, the desulfurization rate of the gasoline product G is as high as 99.3%, 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 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 of this example contained no auxiliary agent, and the rest was the same as in example 2, with the result that the sulfur content in the light fraction after solvent extraction was 5. mu.g/g.

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 after solvent extraction and the 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 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 16.0%, and the RON loss value is 0.7 unit.

As can be seen from Table 4, the desulfurization rate of the gasoline product I 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.

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. In particular, the matching of the etherification reaction process can lead the octane number of the gasoline product of the invention to be increased and the sulfur content to be further reduced.

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 pre-hydrogenated 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 pre-hydrogenated 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 an organic solvent and 0.1-20 wt% of an auxiliary agent, wherein the organic solvent is at least one of tetraethyleneglycol, pentaethylene glycol, furfural, furfuryl alcohol, dimethylformamide, triethylene glycol methyl ether, acetonitrile and a solvent with a boiling point of 175-320 ℃; the auxiliary agent contains at least one of alcohols, ketones, organic acids and organic nitrides which can be mutually dissolved with the organic solvent and have the boiling point or the dry point not higher than that of the organic solvent, wherein 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 hydrogenated heavy fraction of step (4) with the solvent extracted light fraction of step (3) 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 obtained in the step (4), carrying out etherification reaction on the light fraction obtained in the step (3) after solvent extraction 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 of claim 2, wherein the etherification reaction is carried out by contacting the solvent extracted light 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 mol ratio of the low-carbon alcohol to the olefin in the light fraction after solvent extraction 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 mol ratio of the low-carbon alcohol to the olefin in the light fraction after solvent extraction 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 pre-hydrogenated light fraction 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 method according to any one of claims 1 to 7, wherein the organic solvent has a boiling point of 175 to 250 ℃.

15. The method according to claim 1, wherein the organic solvent is selected from at least one of 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-formylmorpholine, triethylene glycol, tetraethylene glycol, pentaethylene glycol methyl ether, ethylene carbonate, propylene carbonate, nitrobenzene, polyethylene glycol having a relative molecular mass between 200 and 400, and polyethylene glycol methyl ether having a relative molecular mass between 200 and 400.

16. The process of claim 15, wherein the organic solvent is selected from at least one of sulfolane, N-formyl morpholine, 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, the ketone, the organic acid, and the organonitride in the auxiliary contained in the extraction solvent 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 according to claim 1, wherein 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.

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 claim 1, wherein the auxiliary agent further comprises water, and the content of water in the extraction solvent is 0.1-5 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.

25. 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.

26. 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.

27. The process of claim 26, 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.

28. The process of claim 26, 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.

29. The process of claim 26, 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.

30. The process of claim 29, wherein the reaction conditions of the first and second reaction zones are eachIndependently comprising: 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.

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

32. The process of claim 1, wherein the yield of the light fraction is 40 to 60 wt% and the yield of the heavy fraction is 40 to 60 wt% based on the gasoline feedstock.

33. The process of claim 1, 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.