CN111218301A

CN111218301A - An extraction solvent for deep desulfurization of sulfur-containing raw materials

Info

Publication number: CN111218301A
Application number: CN202010061175.9A
Authority: CN
Inventors: 潘光成; 赵杰; 常春艳; 赵丽萍; 李涛; 吴明清; 陶志平
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: 2020-06-02
Also published as: CN108018066A; CN108018066B

Abstract

The invention relates to the field of refining of hydrocarbon materials, and discloses an extraction solvent for deep desulfurization of a sulfur-containing raw material, which comprises a main extraction solvent and 0.1-20 wt% of an auxiliary agent. When the extraction solvent is used for deep desulfurization of a sulfur-containing feedstock, the sulfur-containing feedstock such as gasoline can be deeply desulfurized even under the condition of no hydrogen source or insufficient hydrogen source, and the octane number is basically not lost.

Description

Extraction solvent for deep desulfurization of sulfur-containing raw material

The application case is a divisional application of Chinese patent application with the application date of 2016, 10 and 28 and the application number of 201610971957.X, which is named as a method for deep desulfurization of sulfur-containing raw materials.

Technical Field

The invention relates to the field of refining of hydrocarbon materials, in particular to an extraction solvent for deep desulfurization of a sulfur-containing raw material.

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.

Since the catalytic cracking gasoline as the blending component of the gasoline pool for the automobile is rich in olefin, the octane number loss caused by olefin saturation is large when the catalytic cracking gasoline is subjected to hydrotreating. In order to avoid the great loss of octane number, the currently common mode is to perform staged treatment on the catalytic cracking gasoline, i.e. fractionating the catalytic cracking gasoline into multiple fractions, for example, a light fraction containing more sulfides of thiols and a heavy fraction containing more sulfides of thiophenes, performing alkaline extraction on the light fraction, and performing hydrotreating on the heavy fraction.

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.

CN1142258A discloses a method for removing sulfides in gasoline fraction by solvent extraction. The method also removes the sulfide in the gasoline fraction by means of solvent extraction. The solvent extraction part adopts a liquid-liquid extraction desulfurization mode.

CN1460121A discloses a method for removing sulfur compounds from gasoline. The method is to remove sulfide in gasoline fraction by means of solvent extraction distillation, and to recover solvent by stripping. CN103555359A reports a deep desulfurization method for catalytically cracked gasoline, which also removes sulfides in gasoline fractions by solvent extraction, and the solvent extraction part adopts a liquid-liquid extraction desulfurization method.

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

In the desulfurization method or process disclosed above, solvent extraction is used for the purpose of removing sulfides from gasoline without or in the absence of a hydrogen source. The solvent extraction step mainly comprises extraction, recovery and regeneration, namely, the solvent is adopted to extract gasoline, and then the solvent absorbing sulfide is recovered and regenerated. As long as a proper organic solvent is selected, the sulfide mainly comprising thiophene in the gasoline can be extracted and removed, the olefin change is not large, and the octane number can be well maintained.

The gasoline is extracted and desulfurized by adopting a selective organic solvent, and liquid-liquid extraction is a common mode. However, during liquid-liquid extraction, the organic solvent and the extracted gasoline are difficult to separate effectively and often carry with each other, the extracted gasoline usually needs further subsequent treatment such as water washing, and the solvent carries with more gasoline hydrocarbon materials while absorbing sulfides, which is not beneficial to the maintenance of octane number, nor the subsequent solvent recovery and regeneration, thereby reducing the capability of the solvent to continuously extract sulfides.

In the recycling process of the organic solvent, the purity of the solvent is reduced (compared with that of a fresh solvent) and the desulfurization efficiency is reduced rapidly because of the dissolution of more hydrocarbon materials and the pyrolysis or oxidation of the solvent to form more polymers, sediments, stable salts and the like, so that the regeneration treatment amount and frequency of the solvent have to be increased. In particular, the conventional solvent regeneration method mostly adopts a simple flash evaporation method, and some soluble hydrocarbon materials are easy to accumulate in the regenerated solvent (the flash evaporation only removes residues with boiling points higher than that of the solvent, and residual hydrocarbon materials with boiling points lower than or close to that of the solvent cannot be removed), so that the desulfurization effect during the recycling of the solvent is inevitably not facilitated.

Disclosure of Invention

The object of the present invention is to overcome the drawbacks of the prior art and to provide a process for the deep desulfurization of a new sulfur-containing feedstock which allows to obtain a product with lower sulfur, while ensuring a substantial octane number loss.

The inventor of the invention finds that for a sulfur-containing raw material, the removal efficiency of sulfide is higher in an extractive distillation phase compared with the conventional liquid-liquid extraction, and the absorption of an extraction solvent to olefin is lower in the extractive distillation process compared with the conventional liquid-liquid extraction, so that on one hand, the method is beneficial to more retaining olefin, reducing octane number loss caused by subsequent (merged into heavy fraction) hydrogenation treatment of the olefin after sulfide extraction, on the other hand, the method can reduce the harmful influence of oxidative polymerization and the like on solvent recycling in the extraction solvent by dissolving less olefin in the extraction solvent, and avoids frequent regeneration of the extraction solvent due to accumulation of harmful impurities. The addition of the auxiliary agent into the solvent can effectively adjust the property of the solvent and improve the long-period use efficiency of the solvent. The inventors of the present invention have provided a process for deep desulfurization of a sulfur-containing raw material as follows according to the present invention based on the foregoing studies.

In order to achieve the above object, the present invention provides a method for deep desulfurization of a sulfur-containing raw material, comprising: contacting a sulfur-containing raw material with an extraction solvent to perform solvent extraction through distillation to obtain a sulfur-containing solvent and a desulfurization product; the extraction solvent contains a main extraction solvent and an auxiliary agent, the auxiliary agent is at least one of alcohols, ketones, organic acids and organic nitrides and/or water, the auxiliary agent can be mutually soluble with the main extraction solvent, and the boiling point or 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 method can deeply remove the sulfide in the gasoline even under the condition of no hydrogen source or insufficient hydrogen source, and has no octane value loss basically.

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 process flow diagram of gasoline deep desulfurization according to a preferred embodiment of the present invention.

Description of the reference numerals

1. Gasoline raw material 2, extraction distillation tower

3. Hydrocarbon product 4, first reflux drum

5. The regenerated solvent 6 after the second water washing and the first circulating material

7. Desulfurized gasoline product 8 and first water

9. Sulfur-containing solvent 10, solvent recovery column

11. The sulfur-containing material 12 after solvent extraction, a second reflux tank

13. The regenerated solvent 14 after the first water washing and the second circulating material

15. Washed with water, regenerated solvent 16 and second water

17. Hydrocarbon material 18, recovery solvent

19. Solvent water scrubber 20, solvent regenerator

21. Washing water 22, regenerated solvent

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.

The invention provides a method for deep desulfurization of a sulfur-containing raw material, which comprises the following steps: contacting a sulfur-containing raw material with an extraction solvent to perform solvent extraction through distillation to obtain a sulfur-containing solvent and a desulfurization product; the extraction solvent contains a main extraction solvent and an auxiliary agent, the auxiliary agent is at least one of alcohols, ketones, organic acids and organic nitrides and/or water, the auxiliary agent can be mutually soluble with the main extraction solvent, and the boiling point or 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 purpose of adding the auxiliary agent into the extraction solvent is to adjust the physical and chemical properties of the main extraction solvent in the extraction solvent, improve the absorption capacity of the extraction solvent on sulfides, and help a liquid phase region of an extractive distillation tower to keep a single liquid phase, and is particularly beneficial to the long-period use efficiency of the extraction solvent under the condition of the existence of water.

Preferably, the sulfur-containing feedstock is a gasoline feedstock.

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.

The invention carries out solvent extraction by distillation, so that gasoline and an extraction solvent are contacted in an extraction distillation tower, and sulfide in the gasoline is transferred into the solvent to obtain the sulfide-rich solvent and a desulfurization product.

The sulfide contained in the gasoline raw material comprises hydrogen sulfide, mercaptan, thioether, thiophene and the like, and the thiophene sulfide is taken as the main component. After the gasoline feedstock contacts the extraction solvent, the sulfides contained are transferred into the extraction solvent. Preferably, the contacting is carried out in a countercurrent manner in the extractive distillation column, that is, the gasoline raw material enters the extractive distillation column from the middle part of the extractive distillation column, the extraction solvent enters the extractive distillation column from the upper part of the extractive distillation column, under the selective action of the solvent, the sulfide such as thiophene with relatively high boiling point in the gasoline raw material flows into the bottom of the extractive distillation column along with the solvent and is discharged, and a part of the sulfide circulates at the bottom of the extractive distillation column.

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

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

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

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

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

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

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

Preferably, the adjuvant is a mixture containing water. However, water greatly affects the formation of multiple phases, and when the water content in the solvent is large, a multiple phase state tends to be formed in the extractive distillation column. Therefore, when the auxiliary 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 boiling point of the main extraction solvent is 175-320 ℃, and more preferably, the boiling point is 175-250 ℃.

Preferably, the main extraction solvent is selected from at least one of sulfolane, 3-methylsulfolane, 2, 4-dimethylsulfolane, 3-ethylsulfolane, methylethylsulfone, dimethylsulfone, diethylsulfone, dipropylsulfone, dibutylsulfone, dimethylsulfoxide, furfural, furfuryl alcohol, α -pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone, N-formylmorpholine, 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 between 200 and 400, and polyethylene glycol methyl ether having a relative molecular mass between 200 and 400, more preferably, the main extraction solvent is selected from at least one of sulfolane, N-formylmorpholine, N-methyl-2-pyrrolidone, tetraethylene glycol, and pentaethylene glycol.

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

Preferably, in the solvent extraction process, the weight ratio of the extraction solvent to the sulfur-containing raw material is (0.5-20): 1, preferably (1-5): 1. the inventor finds that in the liquid-liquid extraction mode, the sulfur-containing solvent absorbs not only the sulfides in the gasoline raw material but also other components much more than the sulfides, so that various problems are brought to a solvent recovery system in a subsequent distillation mode, 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 overhead pressure is 100kPa to 500kPa, more preferably 110kPa to 300 kPa; the temperature of the tower top is 65-180 ℃; the temperature of the tower bottom is 80-260 ℃, and the preferable temperature is 140-200 ℃.

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 by adopting a reduced pressure distillation mode, namely, a sulfur-containing solvent from the solvent extraction process is distilled out to obtain a sulfur-containing material under the heating condition, the sulfur-containing material comprises aromatic hydrocarbon, thiophene and thioether compounds from a gasoline raw material, 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.

A part of the extraction solvent in the solvent extraction distillation tower is discharged to a solvent recovery tower for recovery treatment. And condensing a part of desulfurized gasoline fraction distilled from the top of the distillation tower to be used as tower top reflux circulation, and discharging a part of desulfurized gasoline fraction to be discharged as a desulfurized product. And the liquid water collected after the condensation at the top of the extractive distillation tower can be used for the subsequent washing of possible regenerated solvents after being separated from the desulfurization products.

The extractive distillation column may be a vertical column, such as a tray column, a packed column, etc., for bringing the two fluids to be injected into contact with and separated from each other.

Preferably, the aforementioned method of the present invention further comprises: separating the sulfur-containing solvent from the sulfides contained therein by reduced pressure distillation in a solvent recovery column to obtain a solvent-extracted sulfur-containing material and a recovered solvent which is freed of sulfides and can be recycled for the solvent extraction.

Specifically, the sulfur-containing solvent from the extractive distillation tower enters a solvent recovery tower, sulfide in the sulfur-containing solvent is evaporated from the top of the solvent recovery tower to form a sulfur-containing material, the solvent after the sulfide removal is discharged from the bottom of the solvent recovery tower to form a recovered solvent, and the recovered solvent can be returned to the extractive distillation tower for recycling. Preferably, the conditions in the solvent recovery column 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 solvent recovery may be effected in a vertical column equipped with contacting means, such as a tray column, packed column or the like, for separating the introduced fluid mixture under reduced pressure due to the difference in boiling range.

The recovered solvent is removed of sulfur-containing compounds, but still contains a very small amount of residual hydrocarbon materials, and meanwhile, side reactions such as oxidation and decomposition can occur during operation, so that impurities such as soluble high-boiling-point compounds, such as stable salts, organic polymers, sediments and the like are formed, and the existence and accumulation of the impurities in the solvent can reduce the dissolving capacity of the solvent undoubtedly, so that the efficiency of gasoline extraction and desulfurization is reduced, and therefore, the regeneration treatment of the solvent is required, and the purity of the solvent is improved. The regeneration method is to distill a part of the recovered solvent, the distillation is performed in a way of reducing pressure, the distilled impurities are discharged from the bottom of the solvent regenerator in the form of heavy residual liquid, and the distilled solvent (mixture of water) is discharged from the top of the regenerator to become the regenerated solvent. The solvent regeneration can make a part of the recovered solvent from the solvent recovery tower enter a solvent regeneration unit for distillation regeneration, and the solvent without heavy residual liquid is discharged to be the regenerated solvent. Preferably, the aforementioned method of the present invention further comprises: introducing at least part of the recovered solvent into a solvent regeneration unit for reduced pressure distillation to obtain a regenerated solvent.

Preferably, the regeneration conditions in the solvent regeneration unit include: the pressure is 1kPa to 10kPa, the temperature is 120 ℃ to 200 ℃, and more preferably 150 ℃ to 200 ℃.

And (3) contacting the regenerated solvent from the solvent regeneration unit with condensed water from an extractive distillation tower and/or a solvent recovery tower, washing off residual hydrocarbon materials and water-insoluble precipitates in the regenerated solvent to obtain the regenerated solvent after water washing, wherein the regenerated solvent after water washing is preferably introduced into the solvent recovery tower for recycling. Preferably, the recovery solvent used for regeneration accounts for 1 to 10 wt% of the total recovery solvent, and preferably accounts for 1 to 5 wt% of the total recovery solvent.

The regenerated solvent is preferably directly returned to the solvent recovery tower (flowing from the lower side of the recovery tower) for recycling, so as to further remove impurities in the sulfur-containing solvent and improve the efficiency of solvent extraction desulfurization.

Although impurities with boiling points higher than that of the solvent are removed from the regenerated solvent after the regeneration treatment, the regenerated solvent still contains hydrocarbon materials with boiling points not higher than that of the regenerated solvent, and the like, and the hydrocarbon materials are gradually accumulated, so that the extraction desulfurization effect of the solvent is still influenced. For this reason, the regenerated solvent is preferably further treated to remove dissolved hydrocarbon materials contained therein. The invention adopts a water washing mode to further treat the regenerated solvent. The water is dissolved in the regenerated solvent, so that the hydrocarbon material contained in the regenerated solvent is separated because the hydrocarbon material is insoluble in the water phase, and is periodically discharged from the upper part of the water scrubber. During the contact of the regeneration solvent and water, water-insoluble sediments can be generated and discharged. The water for washing is preferably liquid water condensed from the top of the extractive distillation column and/or liquid water condensed from the top of the solvent recovery column, in addition to water introduced from outside the apparatus. The washing may be carried out in various ways known in the literature, such as by using a tray column, a packed column, a static mixer, or a combination thereof, and the washing operation should have a settling time such that the water-insoluble hydrocarbon material in the solvent can be separated from the aqueous solvent by separation. Preferably, the method further comprises: and washing at least part of the regenerated solvent with water to obtain a washed regenerated solvent and hydrocarbon materials.

Preferably, the conditions under which at least part of the regenerated solvent is subjected to water washing include: the pressure is 100kPa to 1000 kPa; the temperature is 25-140 ℃, and more preferably 25-80 ℃; the weight ratio of water to the regenerative solvent for water washing is (0.1-10): 1, more preferably (0.5 to 10): 1.

preferably, the regenerated solvent used for water washing accounts for 1-10 wt% of the total regenerated solvent.

The hydrocarbon material remained in the regenerated solvent can be evaporated by azeotropy with water, therefore, the invention also provides a method for purifying the regenerated solvent by carrying out secondary regeneration. The secondary regeneration is carried out in a reduced pressure distillation mode as well as the primary regeneration, but the purpose of the distillation is different, and the primary regeneration is mainly to remove heavy residues or sediments with boiling points higher than that of the solvent. And the secondary regeneration is mainly to remove residual hydrocarbon materials which are dissolved in the solvent and have boiling points lower than or close to the solvent, and the accumulation of the hydrocarbon materials in the solvent is not beneficial to the extraction of the sulfide by the solvent. The secondary regeneration may be performed simultaneously with the primary regeneration or may be performed alternately. Preferably, the method further comprises: at least part of the regeneration solvent is contacted with water for secondary regeneration.

Preferably, the conditions of the secondary regeneration include: the pressure is 1 kPa-10 kPa; the temperature is 90-110 ℃, and more preferably 96-105 ℃; the weight ratio of water to the regeneration solvent for secondary regeneration is (0.1-10): 1, more preferably (0.5 to 5): 1.

in the invention, the regenerated solvent can be returned to the solvent recovery tower for recycling after being washed by water, so that the treatment capacity or load of a subsequent solvent regeneration unit can be reduced, the energy consumption is reduced, and the regenerated solvent after being washed by water can be sent to the solvent regeneration unit for secondary regeneration treatment and then returned to the solvent recovery tower for recycling, so that the solvent can be further purified, high-boiling-point compounds (including insoluble sediments or sediments in the solvent) accumulated in the solvent are reduced, and the method is very favorable for improving the efficiency of solvent extraction and desulfurization.

The inventors of the present invention have found that under an oxygen atmosphere, the extraction solvent may undergo oxidative decomposition and polymerization, and that unsaturated hydrocarbons and heteroatom compounds in the treated gasoline hydrocarbon stream may also undergo oxidation, especially at higher temperatures, which may affect the extraction of sulfides by the solvent. According to the present invention, in order to improve the efficiency of solvent desulfurization and reduce the consumption of solvent, the solvent desulfurization of gasoline feedstocks is carried out in an oxygen-free environment and all the materials entering the desulfurization operation are essentially free of air or previously subjected to a deoxygenation treatment, including a physical or chemical deoxygenation treatment of the extraction solvent during the desulfurization operation. Preferably, the process of the present invention is carried out in an oxygen-free environment.

The sulfur-containing material and the hydrocarbon material after solvent extraction are subjected to further processing, and according to a preferred aspect, the process further comprises: and (3) carrying out hydrotreating on the sulfur-containing material and/or the hydrocarbon material after solvent extraction to obtain a mixture capable of being used as the desulfurization product.

According to another preferred aspect, the method further comprises: introducing the sulfur-containing material and/or the hydrocarbon material after solvent extraction into a catalytic cracking device for catalytic cracking reaction to obtain a product capable of being used as the sulfur-containing raw material.

In order to effectively control the water content in the recovered solvent which is discharged from the bottom of the solvent recovery tower and returned to the extractive distillation tower and improve the solvent recovery efficiency, besides water is selected as a stripping medium, a low-carbon hydrocarbon, preferably a low-carbon hydrocarbon stream with the carbon number not more than 4 after desulfurization, can be used as the stripping medium.

Preferably, the method further comprises: and (3) carrying out selective hydrogenation treatment on the desulfurization product to obtain a refined product with the sulfur content of not more than 10 mu g/g.

Preferably, the method further comprises: introducing the desulfurization product into at least one unit selected from an etherification unit, a reforming unit, an isomerization unit, an alkylation unit and a polymerization unit for further treatment to obtain a refined product with improved octane number.

Preferably, the method further comprises: the sulfur-containing feedstock is pretreated prior to the solvent extraction, the pretreatment being selected from at least one of oxidation, adsorption, alkylation, hydrotreating and fractionation. That is, in the present invention, the sulfur-containing raw material to be contacted with the extraction solvent includes oxidative sweetening or oxidative desulfurized gasoline, hydrodediolefinic or hydrodesulfurized gasoline, and gasoline fractionation products, and the like.

According to a preferred embodiment, the process for the deep desulfurization of sulfur-containing feedstocks according to the invention, which are gasoline feedstocks, in particular:

the gasoline raw material 1 enters an extractive distillation tower 2 through a pipeline, is contacted with a pumped fresh extraction solvent and a pumped recovery solvent 18 in the extractive distillation tower 2, a sulfur-containing solvent 9 is discharged through a pipeline, a sulfide-removed hydrocarbon product 3 is discharged from the top of the extractive distillation tower 2 through a pipeline, the hydrocarbon product 3 is condensed and then enters a first reflux tank 4, then is extracted through a pipeline, one part of the hydrocarbon product is used as a first circulating material 6 to return to the top of the extractive distillation tower 2 for circulation, and the other part of the hydrocarbon product is used as a desulfurized gasoline product 7 to be led out. The sulfur-containing solvent 9 flows into a solvent recovery tower 10 to be subjected to reduced pressure stripping treatment, so as to obtain a sulfur-containing material 11 subjected to solvent extraction and a recovered solvent 18, the sulfur-containing material 11 subjected to solvent extraction is condensed and then enters a second reflux tank 12, the condensed sulfur-containing material is led out through a pipeline, one part of the condensed sulfur-containing material is used as a second circulating material 14 and returns to the top of the solvent recovery tower 10 for circulation, and the other part of the condensed sulfur-containing material is discharged through. The recovered solvent 18 from which the sulfide is distilled off in the solvent recovery column 10 flows out from the bottom of the solvent recovery column 10 through a line. A part of the recovered solvent is returned to the extractive distillation column 2 through a line for recycling, and a part thereof flows into the solvent regenerator 20 through a line for regeneration treatment. The high boiling residue is discharged from the pipeline, the evaporated regenerated solvent 22 is discharged from the pipeline, and flows into the solvent water scrubber 19 to contact with water, and water washing is performed, the water being condensed water formed by the water washing water 21 formed by merging the first water 8 introduced from the first reflux drum 4 via the pipeline and the second water 16 discharged from the second reflux drum 12 via the pipeline. The hydrocarbon material 17 produced in the solvent water scrubber 19 is drawn out from the upper part, and the insoluble sediment or deposit which may be produced in a trace amount after washing is drawn out from the bottom of the solvent water scrubber 19, the obtained washed regenerated solvent 15 is divided into two parts, which are a first washed regenerated solvent 13 and a second washed regenerated solvent 5, respectively, the first washed regenerated solvent 13 returns to the solvent recovery tower 10 through a pipeline, and the second washed regenerated solvent 5 flows into the solvent regenerator 20 through a pipeline.

The present invention will be described in detail below by way of examples.

In the following examples, various starting materials used are commercially available without specific reference.

Test example 1

This test example serves to illustrate the effect of the process for the deep desulfurization of sulfur-containing feedstocks according to the present invention.

In the test example, the sulfur-containing raw material was subjected to total reflux distillation in the absence of a solvent, a main extraction solvent, and an extraction solvent containing an auxiliary agent, respectively, until equilibrium was reached, and then the gas phase was taken to analyze the sulfide content, thereby analyzing the solvent extraction effect of the present invention.

The sulfur-containing feedstock used in this test example was a catalytically cracked gasoline from the chinese petrochemical long ridge division: the volume fraction of olefin was 22.5%, the volume fraction of aromatic hydrocarbon was 40%, and the sulfur content was 470. mu.g/g.

The selected extraction solvents were of the following species:

extraction solvent RJ-1: n-formyl morpholine (NFM);

extraction solvent RJ-2: n-formyl morpholine containing 5 wt% water (mixture labeled 95% NFM + 5% H)₂O)；

Extraction solvent RJ-3: n-formyl morpholine containing methanol (MeOH) and water (where the mass fraction of water is 5 wt%, the mass fraction of methanol (MeOH) is 5 wt%, and the mixture is labeled 90% NFM + 5% H)₂O+5％MeOH)；

Extraction solvent RJ-4: n-formyl morpholine with ethanolamine (MEA) (where the mass fraction of ethanolamine is 5 wt%, and the mixture is labeled 95% NFM + 5% MEA);

extraction solvent RJ-5: n-formyl morpholine containing isobutyric acid (IBA) (where the mass fraction of isobutyric acid is 5 wt%, and the mixture is labeled 95% NFM + 5% IBA);

extraction solvent RJ-6: a mixed solvent of Sulfolane (SULF) and N-methyl-2-pyrrolidone (NMP) (wherein the mass fraction of sulfolane is 75 wt%, the mass fraction of N-methyl-2-pyrrolidone is 25 wt%, and the mixed solvent is labeled as 75% SULF + 25% NMP);

extraction solvent RJ-7: a mixed solvent of sulfolane containing acetone (DMK) and N-methyl-2-pyrrolidone (where the mass fraction of acetone is 5 wt% and the mixture is labeled 95% (75SULF/25NMP) + 5% DMK);

extraction solvent RJ-8: a mixed solvent of sulfolane containing Ethylenediamine (EDA) and N-methyl-2-pyrrolidone (wherein the mass fraction of ethylenediamine is 5 wt%, and the mixture is labeled 95% (75SULF/25NMP) + 5% EDA);

extraction solvent RJ-9: a mixed solvent of sulfolane containing Succinic Acid (SA) and N-methyl-2-pyrrolidone (wherein the mass fraction of succinic acid is 5 wt%, and the mixture is marked as 95% (75SULF/25NMP) + 5% SA)

In a distillation test, the mass ratio of the extraction solvent to the sulfur-containing raw material is 1: 1. the results are shown in tables 1 and 2.

TABLE 1

TABLE 2

As can be understood from tables 1 and 2, when the sulfide is subjected to extractive distillation, the use of a mixed solvent of N-formylmorpholine or sulfolane and N-methyl-2-pyrrolidone as the extraction solvent can significantly reduce the proportion of the sulfide in the vapor phase material in the extractive distillation column, as compared with the case where no solvent is used, and when a certain amount of water is added to the solvent, it is also helpful to evaporate more sulfide into the vapor phase.

As can be seen from the results of tables 1 and 2, when the water content in the extraction solvent is controlled to not more than 5% by weight, preferably not more than 3% by weight, the extraction of the sulfide by the solvent is more facilitated.

It can also be seen from tables 1 and 2 that the addition of an adjuvant to the extraction solvent promotes solvent extraction, especially in the presence of excess water. Furthermore, it is further presumed that, when the solvent is used in a circulating manner for a long period of time, the effect of the auxiliary agent on the extraction of the sulfide with the solvent is more advantageous, particularly when the solvent is decomposed and the content of impurities is increased.

Example 1

This example uses the process flow shown in FIG. 1 to carry out a deep desulfurization treatment on a gasoline feedstock A.

The distillation range of the gasoline raw material A is 60-120 ℃, and the sulfur content is 400 mu g/g.

In a solvent extraction system, the gasoline raw material is subjected to solvent extraction distillation in a solvent extraction distillation tower to obtain a desulfurized gasoline product and a sulfur-containing solvent. 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 feeding weight ratio of the extraction solvent to the gasoline raw material 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 main extraction solvent in the extraction solvent is N-formyl morpholine, the auxiliary agent is water and methanol, and the content of the auxiliary agent is 5 wt% of the extraction solvent, wherein the content of the water is 0.5 wt% of the extraction solvent.

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.

And (3) water washing: the regeneration solvent used for water washing was 3% by weight of the total regeneration solvent, and the pressure was 500 kPa; the temperature is 75 ℃; the weight ratio of water to the regenerated solvent is 5: 1.

as a result, the sulfur content of the obtained gasoline product is not more than 5 mu g/g.

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.

Example 2

In this example, the process flow shown in FIG. 1 was used to carry out deep desulfurization of gasoline feedstock B.

The distillation range of the gasoline raw material B is 27-100 ℃, the sulfur content is 450 mu g/g, and the mercaptan sulfur content is 50 mu g/g.

And carrying out alkali washing pretreatment on the gasoline raw material B, washing off part of light mercaptan, wherein alkali liquor for alkali washing is NaOH aqueous solution with the mass fraction of 15 wt%. The gasoline raw material obtained after the alkaline washing has the sulfur content of 425 mu g/g, wherein the mercaptan sulfur content is 25 mu g/g.

In a solvent extraction system, carrying out solvent extraction distillation on the gasoline raw material subjected to alkaline washing in a solvent extraction distillation tower to obtain a desulfurized gasoline product and a sulfur-containing solvent. 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 feeding weight ratio of the extraction solvent to the gasoline raw material is 4: 1, the temperature of the bottom of the tower is 150 ℃, the temperature of the top of the tower is 95 ℃, the pressure of the top of the tower is 200kPa, the main extraction solvent in the extraction solvent is N-methyl-2-pyrrolidone, the auxiliary agent is acetone, and the content of the auxiliary agent is 4.2 percent by weight of the extraction solvent.

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

in a solvent regeneration column: the recovered solvent used for regeneration is 5 weight percent of the total recovered solvent, the temperature at the bottom of the tower is 170 ℃, the temperature at the top of the tower is 100 ℃, the pressure at the top of the tower is 8kPa, residual liquid is discharged from the bottom of the tower, the regenerated solvent and the recovered solvent are mixed and then recycled, and the used stripping water is from condensed water collected by a solvent extraction distillation tower and a solvent recovery tower.

And (3) water washing: the regeneration solvent used for water washing was 4% by weight of the total regeneration solvent, and the pressure was 600 kPa; the temperature is 80 ℃; the weight ratio of water to the regenerated solvent is 6: 1.

Example 3

This example was carried out using a similar process flow to that of example 1, except that:

the raw material used in the embodiment is a gasoline raw material C, the distillation range of the gasoline raw material C is 33-205 ℃, and the sulfur content is 253 mu g/g.

The extraction solvent used was a mixed solvent of sulfolane containing Ethylenediamine (EDA) and N-methyl-2-pyrrolidone (where the mass fraction of ethylenediamine is 5 wt%, and the mixture is labeled 95% (75SULF/25NMP) + 5% EDA).

The rest is the same as in example 1.

As a result, the sulfur content of the obtained gasoline product is not more than 10 mu g/g.

Example 4

This example was carried out using a similar process flow to that of example 2, except that:

in this embodiment, an oxidation treatment (metal phthalocyanine catalytic oxidation) is adopted to pretreat the gasoline raw material B in advance, so as to oxidize the mercaptan contained in the gasoline raw material B into a disulfide with a higher boiling point, and the sulfur content in the gasoline raw material obtained after the oxidation treatment is not changed, wherein the sulfur content of the mercaptan is not more than 5 μ g/g.

And the extraction solvent used was N-formyl morpholine containing ethanolamine (MEA) (where ethanolamine is present in a mass fraction of 5 wt%, and the mixture is labeled 95% NFM + 5% MEA).

The rest is the same as in example 2.

Example 5

in the embodiment, the gasoline raw material B is pretreated by adopting pre-hydrogenation treatment so as to enable mercaptan contained in the gasoline raw material B to react with diene substances to generate thioether substances, and the sulfur content of the gasoline raw material obtained after the pre-hydrogenation treatment is 335 mug/g, wherein the sulfur content of the mercaptan is not more than 3 mug/g.

And the extraction solvent used was N-formylmorpholine containing 5 wt.% water (mixture labeled 95% NFM + 5% H)₂O)。

The rest is the same as in example 2.

From the above results, it can be seen that deep desulfurization can be performed without octane number reduction by using the selective extraction solvent containing an auxiliary according to the present invention.

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. an extraction solvent for the deep desulfurization of sulfur-containing raw materials, characterized in that the extraction solvent contains a main extraction solvent and an auxiliary agent of 0.1 to 20% by weight, and the auxiliary agent is selected from methanol, Ethanol, n-propanol, isopropanol, acetone, methyl ethyl ketone, isobutyric acid, oxalic acid, malonic acid, succinic acid, urea, ethylenediamine, monoethanolamine, N-methylmonoethanolamine, N-ethyl Monoethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, n-propanolamine, isopropanolamine and diethylene glycolamine At least one substance, or the auxiliary agent is selected from 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,N-dimethylethanolamine, N,N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, normal A mixture of at least one of propanolamine, isopropanolamine and diethylene glycol amine and water.

2. The extraction solvent according to claim 1, wherein the auxiliary agent is selected from methanol, acetone, methyl ethyl ketone, isobutyric acid, oxalic acid, malonic acid, succinic acid, ethylenediamine, monoethanolamine , at least one material in N-methylmonoethanolamine, isopropanolamine and diethylene glycol amine, or the auxiliary agent is selected from methanol, acetone, methyl ethyl ketone, isobutyric acid, oxalic acid, malonic acid, A mixture of at least one of succinic acid, ethylenediamine, monoethanolamine, N-methylmonoethanolamine, isopropanolamine and diethylene glycolamine and water.

3 . The extraction solvent according to claim 1 , wherein the content of the auxiliary agent is 0.5 to 15% by weight. 4 .

4. The extraction solvent according to claim 1, wherein the auxiliary agent is a mixture containing water.

5 . The extraction solvent according to claim 4 , wherein the content of water in the extraction solvent is 0.1 to 5% by weight. 6 .

6 . The extraction solvent according to claim 5 , wherein the content of water in the extraction solvent is 0.1 to 3% by weight. 7 .

7 . The extraction solvent according to claim 1 , wherein the boiling point of the main extraction solvent is 175 to 250° C. 8 .

8. The extraction solvent according to claim 7, wherein the main extraction solvent is selected from sulfolane, 3-methyl sulfolane, 2,4-dimethyl sulfolane, 3-ethyl sulfolane, methyl ethyl sulfolane Sulfone, dimethyl sulfone, diethyl sulfone, dipropyl sulfone, dibutyl sulfone, dimethyl sulfoxide, furfural, furfuryl alcohol, alpha-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl- 2-pyrrolidone, N-propyl-2-pyrrolidone, N-formylmorpholine, dimethylformamide, triethylene glycol, tetraethylene glycol, pentaethylene glycol, triethylene glycol methyl ether, tetraethylene glycol methyl ether, Ethylene carbonate, propylene carbonate, propylene carbonate, acetonitrile, nitrobenzene, polyethylene glycol with relative molecular mass between 200 and 400 and polyethylene glycol methyl ether with relative molecular mass between 200 and 400 at least one of them.

9. The extraction solvent according to claim 8, wherein the main extraction solvent is at least selected from the group consisting of sulfolane, N-formylmorpholine, N-methyl-2-pyrrolidone, tetraethylene glycol and pentaethylene glycol A sort of.