C4 hydrocarbon fraction fine desulfurization method and reaction device

Abstract

The invention relates to a C4 hydrocarbon fraction fine desulfurization method and a reaction device. The C4 hydrocarbon fraction fine desulfurization method comprises the following steps: (1) mixing an oxidant with naphtha to obtain oxidant carrying oil; (2) mixing the C4 hydrocarbon fraction with the oxidant carrying oil, then adding a mercaptan conversion auxiliary agent, entering an oxidation reactor to be in contact with an oxidation catalyst to carry out oxidation reaction, and converting mercaptan into disulfide; and (3) carrying out rectification separation on the material flow after the oxidation reaction to obtain a fine desulfurized C4 hydrocarbon fraction and sulfur-containing naphtha. According to the method provided by the invention, the safety of the C4 hydrocarbon fraction oxygen dissolving process is improved by virtue of the oxidant carrying oil, the boiling point difference between sulfide and C4 hydrocarbons is increased by virtue of the mercaptan oxidation reaction, the fine desulfurized C4 hydrocarbon fraction with the total sulfur content not greater than 1mg / kg is obtained by adopting a rectification method, and a high-quality raw material can be provided for chemical utilization of the C4 hydrocarbon fraction.

Description

Technical Field

[0001] This invention relates to a method for removing sulfides from hydrocarbon materials, specifically a method for fine desulfurization of C4 hydrocarbon fractions. Background Technology

[0002] Liquefied petroleum gas (LPG) is a mixture of hydrocarbons primarily composed of C3 and C4 alkanes and alkenes. Its sources are mainly three categories: refinery LPG, chemical plant LPG, and LPG produced as a byproduct of natural gas or associated gas from oil fields. Alkenes in LPG are important organic synthesis monomers with wide applications, and alkanes are good cracking feedstocks and can also be dehydrogenated to produce olefins. In the past, LPG production in my country was mainly for civilian use. However, with the widespread use of natural gas and the transformation of oil refining into chemical processing, there is a surplus of civilian LPG, while the demand for chemical synthesis monomers continues to increase. Therefore, based on the characteristics of the hydrocarbon composition in LPG, there is a tendency to separate the components and utilize the separated components in depth according to different needs. In the process of deep application of liquefied petroleum gas (LPG), in addition to paying attention to the characteristics of hydrocarbon composition, the impurity content in LPG is also a key focus, especially the sulfide content. Some processes have stringent requirements for the total sulfur content in LPG, and conventional desulfurization measures can no longer meet these requirements. Therefore, it is necessary to develop LPG fine desulfurization technology to meet the needs of special circumstances.

[0003] Refinery liquefied petroleum gas (LPG) is the main source of liquefied petroleum gas (LPG). Refining units that produce LPG mainly include catalytic cracking units, catalytic pyrolysis units, delayed coking units, hydrocracking units, and catalytic reforming units. Based on the source of refinery LPG, it can be divided into unsaturated LPG and saturated LPG. Saturated LPG mainly comes from hydrocracking and catalytic reforming units. Except for hydrocracking LPG, which requires hydrogen sulfide removal, saturated LPG generally has no desulfurization pressure. Unsaturated LPG produced by catalytic cracking, catalytic pyrolysis, and delayed coking units accounts for the majority of refinery LPG. Unsaturated LPG contains a significant amount of hydrogen sulfide and mercaptans, among other sulfides. Industrially, a two-step method is typically used to remove hydrogen sulfide and mercaptans: first, hydrogen sulfide is removed using an alkanolamine solvent, and then mercaptans are removed using alkali extraction. The total sulfur content in the LPG after this two-step desulfurization process is typically about 10 mg / kg. The desulfurized LPG then... The gas separation unit separates the C3 and C4 hydrocarbon fractions. While hydrogen sulfide and carbonyl sulfide, which have lower boiling points, enter the C3 fraction, most sulfides, such as thiols and thioethers, enter the C4 fraction. The total sulfur content in the C4 fraction is significantly higher than that in the liquefied petroleum gas (LPG) components, typically rarely falling below 20 mg / kg. The sulfides in the C4 fraction can cause problems for subsequent MTBE, butadiene selective hydrogenation, and alkylation units. Besides potentially increasing energy consumption in the MTBE unit, it may also cause catalyst poisoning in selective hydrogenation or increased acid consumption in liquid acid alkylation units. Therefore, subsequent processing units aim for the lowest possible sulfur content in the C4 fraction. In addition, in certain special applications of C4 hydrocarbon fractions, such as when used as feedstock in isononanol units or solid acid alkylation units, the total sulfur content in the C4 hydrocarbon fraction is required to be no more than 1 mg / kg. Therefore, the C4 hydrocarbon fraction, which has undergone conventional two-step desulfurization and has been separated into C3 hydrocarbon fractions by a gas separation unit, needs to be finely desulfurized to meet the requirements of special processes.

[0004] CN1330126A discloses a method for removing organic sulfur from liquefied petroleum gas (LPG). When LPG, after hydrogen sulfide removal, passes through a desulfurizing agent bed, the organic sulfides are physically adsorbed by the desulfurizing agent. The desulfurizing agent used is a modified X-type or Y-type molecular sieve. The sulfur content of the LPG after adsorption desulfurization can be less than 1 mg / kg, achieving fine desulfurization of LPG. This method significantly improves the breakthrough sulfur capacity of the desulfurizing agent through modification of the molecular sieve desulfurizing agent, but the breakthrough sulfur capacity is still relatively low, generally maintained within the range of 1.5–2.2 wt%. To maintain long-term operation of the device, a large amount of desulfurizing agent is used. This method proposes regenerating the desulfurizing agent with high-temperature nitrogen or catalytic dry gas, or superheated steam. However, the waste gas or waste liquid generated during desulfurizing agent regeneration is difficult to treat due to its very high sulfide content.

[0005] CN104194833A discloses a deep desulfurization process for liquefied petroleum gas (LPG). LPG that has undergone hydrogen sulfide removal via amine extraction is mixed with hydrogen. In a reactor packed with a sulfur transfer catalyst, mercaptans and olefins in the LPG react to produce high-boiling-point sulfides. A stabilization tower is then used to separate the LPG from the high-boiling-point sulfides. The top of the tower yields an ultra-low sulfur content LPG product, while the bottom yields sulfur-rich waste liquid. In this method, thiols react with olefins in liquefied petroleum gas (LPG), and some hydrogen also participates in the thiols conversion reaction. During the conversion of thiols into high-boiling-point sulfides, there is a significant loss of olefins. Under the reaction temperature conditions proposed in this method, the reaction stream in the sulfur conversion reactor is in the gas phase. The gasification process before the LPG enters the reactor requires a large amount of energy, and the energy consumption for the distillation and separation of the reaction products is also high. Therefore, the energy cost of obtaining ultra-low sulfur LPG by this method is relatively high. The hydrogen mixed with LPG in this method should be in excess, but the inventors have not described the separation of excess hydrogen from LPG, which will also cause a loss in the yield of LPG during the separation process. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a safe, environmentally friendly, and long-term stable desulfurization method for C4 hydrocarbon fractions, based on the existing technology.

[0007] In a first aspect, the present invention provides a method for the fine desulfurization of C4 hydrocarbon fractions, comprising:

[0008] (1) Oxidant is mixed with naphtha to obtain oxidant-carrying oil;

[0009] (2) The C4 hydrocarbon fraction is mixed with the oxidant-carrying oil, and then a mercaptan conversion aid is added. The mixture enters the oxidation reactor and comes into contact with the oxidation catalyst to undergo an oxidation reaction, where the mercaptan is converted into disulfide.

[0010] (3) The stream after oxidation reaction is separated by distillation to obtain desulfurized C4 hydrocarbon fraction and sulfur-containing naphtha.

[0011] The preferred option also includes: (4) the sulfur-containing naphtha is contacted with the hydrorefining catalyst to carry out a hydrodesulfurization reaction, and the desulfurized naphtha is recycled.

[0012] Secondly, the present invention provides a C4 hydrocarbon fraction desulfurization reaction apparatus for the aforementioned C4 hydrocarbon fraction desulfurization method, comprising: a first static mixer for mixing an oxidant with naphtha to obtain an oxidant-carrying oil; a second static mixer for mixing the C4 hydrocarbon fraction, the oxidant-carrying oil, and a mercaptan conversion aid; the second static mixer being connected to the first static mixer; an oxidation reactor filled with an oxidation catalyst bed, having a feed inlet and an outlet, the outlet of the second static mixer being connected to the feed inlet of the oxidation reactor; and a distillation column for fractionating the C4 hydrocarbon fraction and naphtha after the oxidation reaction; the distillation column having an inlet, a top outlet, and a bottom outlet, the outlet of the oxidation reactor being connected to the inlet of the distillation column.

[0013] Compared with the prior art, the beneficial effects of the C4 hydrocarbon fraction desulfurization method and reaction apparatus provided by the present invention are as follows:

[0014] The present invention provides a method for fine desulfurization of C4 hydrocarbon fractions. (1) The oxidant is first dissolved in the oxidant-carrying oil, and then the oxidant-carrying oil is mixed with the C4 hydrocarbon fraction. This avoids the possibility of C4 hydrocarbon fractions being directly mixed with the oxidant and forming explosive gases, and greatly improves the safety of the mixing process of C4 hydrocarbon fractions and oxidant. (2) The sulfide forms in C4 hydrocarbon fractions are relatively complex, mainly consisting of thiols, thioethers, disulfides and polysulfides. After oxidizing thiols to disulfides, the boiling points of the sulfides are much higher than the boiling points of various hydrocarbons in the C4 hydrocarbon fractions, and fine desulfurized C4 hydrocarbon fractions are obtained by fractionation. (3) The main function of the catalyst packed in the oxidation reactor is to convert thiols into disulfides. It is not an adsorption desulfurization mechanism. Frequent regeneration is not required, and long-term stable operation of the device can be achieved. The catalyst replacement cycle can be matched with the plant shutdown and maintenance cycle. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0016] Figure 1 This is a schematic flowchart of the C4 hydrocarbon fraction desulfurization method provided by the present invention.

[0017] in:

[0018] 1-C4 hydrocarbon fraction 2-naphtha 3-oxidizing agent

[0019] 4-Mitol conversion aid; 5-Oxidant carrying oil; 6, 7, 8, 10-Pipelines

[0020] 9-Refined desulfurized C4 hydrocarbon fraction

[0021] A - First static mixer; B - Second static mixer; C - Oxidation reactor

[0022] D-Distillation Column Detailed Implementation

[0023] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0024] All pressures mentioned in this article are gauge pressures.

[0025] In a first aspect, the present invention provides a method for the fine desulfurization of C4 hydrocarbon fractions, comprising:

[0026] (1) Oxidant is mixed with naphtha to obtain oxidant-carrying oil;

[0027] (2) The C4 hydrocarbon fraction is mixed with the oxidant-carrying oil, and then a mercaptan conversion aid is added. The mixture enters the oxidation reactor and comes into contact with the oxidation catalyst to undergo an oxidation reaction, where the mercaptan is converted into disulfide.

[0028] (3) The stream after oxidation reaction is separated by distillation to obtain desulfurized C4 hydrocarbon fraction and sulfur-containing naphtha.

[0029] Preferably, the method provided by the present invention further includes: (4) contacting sulfur-containing naphtha with a hydrorefining catalyst to carry out a hydrodesulfurization reaction, and recycling the obtained naphtha.

[0030] In this invention, the oxidant is oxygen or a mixture of oxygen and an inert gas, such as air after removing moisture and carbon dioxide; the naphtha has a distillation range of 30-170°C; and the oxygen content of the oil carried by the oxidant is 10-500 mg / kg.

[0031] In one specific embodiment, the oxidant is air with moisture and carbon dioxide removed. The method for removing moisture and carbon dioxide is conventional, such as dehydration by molecular sieve adsorption and decarbonization by activated carbon adsorption. The moisture content and carbon dioxide content in the treated air are no more than 10 ppmv and no more than 10 ppmv, respectively. The air, after being dehydrated and decarbonized, is thoroughly mixed with naphtha to obtain an oxidant-carrying oil with an oxygen content of 50-300 mg / kg.

[0032] Preferably, the naphtha is selected from light naphtha with a distillation range of 30-80℃; or from topped oil from a reforming unit, raffinate from a benzene extraction unit, or light naphtha from a hydrorefining unit.

[0033] Preferably, the C4 hydrocarbon fraction comprises not less than 95.0 wt% C4 hydrocarbons and the balance C3 and C5 hydrocarbons, wherein the C4 hydrocarbons include isobutane, n-butane, isobutene, 1-butene, cis-2-butene, trans-2-butene, and butadiene. The C4 hydrocarbon fraction originates from a catalytic cracking unit, a catalytic pyrolysis unit, or a delayed coking unit. The mercaptan sulfur content in the C4 hydrocarbon fraction is not greater than 50 mg / kg, and the total sulfur content is not greater than 100 mg / kg; wherein the C4 hydrocarbon fraction contains one or more of methanethiol, ethanethiol, propanethiol, dimethyl sulfide, methyl ethyl sulfide, dimethyl disulfide, methyl ethyl disulfide, diethyl disulfide, and dimethyl polysulfide.

[0034] In this invention, the thiol conversion aid is selected from one or more of diethanolamine, methyldiethanolamine, diisopropanolamine, ethylenediamine, and ethanol.

[0035] Preferably, the naphtha comprises 5-40% by weight of the C4 hydrocarbon fraction; the amount of thiol conversion aid added to the C4 hydrocarbon fraction is 10-100 mg / kg; the oxidation reaction temperature is 30-80℃, the reaction pressure is 0.3-2.0 MPa, and the volume hourly space velocity (VHSV) of the C4 hydrocarbon fraction is 0.5-5.0 h⁻¹. -1 .

[0036] In this invention, the oxidation catalyst is a support and an active component supported on the support. The support is selected from one or more of activated carbon, alumina, and molecular sieves, and the active component is one or more metal phthalocyanine compounds selected from Co, Fe, Mo, and Cu.

[0037] Preferably, in step (2), the oxidation reactor is one or more fixed-bed reactors. When multiple fixed-bed reactors are used, the fixed-bed reactors are connected in series or in parallel.

[0038] In the oxidation reactor, the oxidation catalyst is packed in a fixed bed. The oxidation reactor can be a single unit, or two or more reactors connected in series, or two or more reactors connected in parallel. A single oxidation reactor contains one, two, or more catalyst beds.

[0039] Preferably, the oxidation reactor is provided with a material inlet distributor at the top and an outlet collector at the bottom.

[0040] In step (3), the outlet stream of the oxidation reactor enters the distillation column, where it is distilled and separated into desulfurized C4 hydrocarbon fraction and sulfur-containing naphtha. The total sulfur content of the desulfurized C4 hydrocarbon fraction is no more than 1 mg / kg.

[0041] In this invention, the sulfur-containing naphtha and hydrogen enter the hydrogenation reactor and come into contact with the hydrogenation refining catalyst to carry out a hydrogenation desulfurization reaction to obtain desulfurized naphtha. The desulfurized naphtha is returned to step (1) for recycling as recycled naphtha.

[0042] In specific industrial implementations, sulfur-containing naphtha can be refined using existing naphtha hydrotreating units in oil refineries, without requiring additional investment in such equipment. The hydrodesulfurization reaction employs conventional hydrorefining catalysts, and this invention is not limited in this regard. Typically, the hydrorefining catalyst consists of a heat-resistant oxide support and a metal active component supported on the support. The heat-resistant oxide support is alumina and / or silica, and the metal active component is selected from one or more of Co, Mo, W, and Ni. Alumina is preferred as the heat-resistant oxide support.

[0043] The hydrogenation reaction conditions are as follows: reaction temperature 250-300℃, reaction pressure 1.5-2.5MPa, and volume hourly space velocity 4-10h. -1 The hydrogen-to-oil volume ratio is 50-100;

[0044] Preferably, the sulfur content of the naphtha obtained after hydrodesulfurization is no more than 0.5 mg / kg.

[0045] The advantages of the C4 hydrocarbon fraction desulfurization method provided by this invention are further explained below:

[0046] First, the oxidation reaction of thiols and sulfides in the C4 hydrocarbon fraction requires oxygen. Since the saturated vapor pressure of each hydrocarbon component in the C4 hydrocarbon fraction is relatively high at room temperature, directly adding oxygen to the C4 hydrocarbon fraction can easily lead to the formation of explosive gases in localized areas, posing an explosion hazard if exposed to static electricity or an open flame. The method provided by this invention employs a method of first dissolving oxygen in naphtha, preferably light naphtha, as an oxidant carrier oil, and then mixing the oxidant carrier oil with the C4 hydrocarbon fraction. This ensures that the oxygen previously dissolved in the naphtha is evenly distributed in the mixture stream, thereby achieving a sufficient amount of oxygen in the C4 hydrocarbon fraction required for the thiols oxidation reaction. Introducing oxygen into naphtha is a commonly used and safe method in conventional naphtha alkali-free deodorization processes. The method provided by this invention, by transferring the oxidant to the C4 hydrocarbon fraction through the oxidant carrier oil, significantly improves the safety of the oxygen dissolution process in the C4 hydrocarbon fraction.

[0047] The method provided by this invention uses naphtha as the oxidant carrier oil. Besides improving the safety of the oxygen dissolution process in the C4 hydrocarbon fraction, it also extracts and concentrates sulfides from the C4 hydrocarbon fraction. Because the sulfides in the C4 hydrocarbon fraction, after being oxidized to disulfides, have boiling points significantly higher than those of the other C4 hydrocarbon components, the transfer of sulfides from the C4 hydrocarbon fraction to the naphtha is achieved during the distillation separation process, thus realizing the fine desulfurization of the C4 hydrocarbon fraction without affecting its yield. After distillation separation, the oxidant carrier oil dissolves most of the sulfides and can be sent to a conventional naphtha hydrotreating unit for refining. The resulting desulfurized naphtha is recycled. Simultaneously, the sulfides are converted to hydrogen sulfide, and finally, a sulfur recovery unit converts the sulfides back into sulfur. The removal of sulfides and the recovery of sulfur do not produce environmentally friendly waste gas or waste liquid.

[0048] Compared with the light hydrocarbon fraction adsorption desulfurization process used in the prior art, the oxidation catalyst in this invention has a long service life, does not require frequent regeneration, can achieve long-term stable operation of the device, and the catalyst replacement cycle can be matched with the plant shutdown and maintenance cycle.

[0049] Secondly, the present invention provides a C4 hydrocarbon fraction desulfurization reaction apparatus, comprising: a first static mixer for mixing an oxidant with naphtha to obtain an oxidant-carrying oil; a second static mixer for mixing the C4 hydrocarbon fraction, the oxidant-carrying oil, and a mercaptan conversion aid; the second static mixer being connected to the first static mixer; an oxidation reactor filled with an oxidation catalyst bed, having a feed inlet and an outlet, the outlet of the second static mixer being connected to the feed inlet of the oxidation reactor; and a distillation column for fractionating the C4 hydrocarbon fraction and naphtha after the oxidation reaction; the distillation column having an inlet, a top outlet, and a bottom outlet, the outlet of the oxidation reactor being connected to the inlet of the distillation column.

[0050] Preferably, it also includes a naphtha hydrogenation unit for hydrogenating and desulfurizing sulfur-containing naphtha from a distillation column. The naphtha hydrogenation unit includes a hydrogenation reactor, a gas-liquid separator, and a stripping column. The hydrogenation reactor has a feed inlet and an outlet. The bottom outlet of the distillation column is connected to the feed inlet of the hydrogenation reactor. The outlet of the hydrogenation reactor is connected to the gas-liquid separator. The gas-liquid separator has a gas phase outlet and a liquid phase outlet. The liquid phase outlet of the gas-liquid separator is connected to a first static mixer via the stripping column.

[0051] In this invention, the hydrogenation reactor is filled with a hydrogenation refining catalyst for the hydrodesulfurization reaction of sulfur-containing naphtha; the gas-liquid separator is used for preliminary gas-liquid separation of the reaction stream; the stripping tower is used to remove gases such as hydrogen sulfide from the naphtha, and the bottom of the stripping tower is provided with a bottom outlet, which is connected to a first static mixer.

[0052] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings, but the drawings do not constitute a limitation of the present invention.

[0053] Appendix Figure 1 This is a schematic flow diagram of the C4 hydrocarbon fraction desulfurization method provided by the present invention. (See attached diagram.) Figure 1 As shown, oxidant 3 and naphtha 2 are mixed in the first static mixer A, causing the oxidant to dissolve in the naphtha to obtain oxidant-carrying oil 5. The oxidant 3 is oxygen or air stripped of moisture and carbon dioxide. C4 hydrocarbon fraction 1 is mixed with oxidant-carrying oil 5. Since C4 hydrocarbon fraction and oxidant-carrying oil 5 are miscible, after mixing, the oxidant originally dissolved in the oxidant-carrying oil is uniformly distributed in the mixture stream. The mixture of C4 hydrocarbon fraction and oxidant-carrying oil flows through pipeline 6 and is mixed with thiol conversion aid 4. The mixture is then forcibly mixed uniformly in the second static mixer B to obtain the inlet stream of the oxidation reactor. The thiol conversion aid 4 is an alkanolamine compound. The inlet stream of the oxidation reactor enters the oxidation reactor C from the top via pipeline 7, where it comes into contact with the catalyst and undergoes a thiol oxidation reaction. This converts trace amounts of thiols in the C4 hydrocarbon fraction into disulfides with higher boiling points. With the assistance of the thiol conversion aid, the thiols in the C4 hydrocarbon fraction are completely converted into disulfides. The stream in the oxidation reactor C is in the liquid phase. After the thiol oxidation conversion, the effluent from the oxidation reactor is introduced into the distillation column D via pipeline 8. After the thiols in the C4 hydrocarbon fraction are completely converted into disulfides, the boiling points of various sulfides in the C4 hydrocarbon fraction are significantly higher than the boiling points of various C4 hydrocarbons. After distillation separation, the sulfides in the mixture stream are concentrated to the bottom stream, thus obtaining a finely desulfurized C4 hydrocarbon fraction 9 at the top of the column and sulfur-containing naphtha at the bottom of the column, which is led out via pipeline 10. This achieves the fine desulfurization of the C4 hydrocarbon fraction. The sulfur-containing naphtha at the bottom of the column is sent to a conventional naphtha hydrotreating unit for refining, and the obtained naphtha is recycled. The sulfides in the naphtha are converted into hydrogen sulfide, and finally, the hydrogen sulfide is converted into sulfur in the sulfur recovery unit, realizing the recovery and utilization of sulfides.

[0054] The following detailed description of the C4 hydrocarbon fraction desulfurization method provided by the present invention is based on specific examples, but this does not limit the scope of the invention.

[0055] The C4 hydrocarbon fraction feedstock is a liquefied petroleum gas fraction from which C3 hydrocarbons have been removed. It is taken from Shijiazhuang Refining & Chemical Branch of China Petroleum & Chemical Corporation. Its composition and sulfide content are shown in Table 1.

[0056] The naphtha used is the topping oil from the reforming unit of China Petroleum & Chemical Corporation Guangzhou Branch. Because it has undergone hydrorefining treatment in the reforming pre-hydrogenation unit, the topping oil is basically free of impurities such as sulfur and nitrogen. Its composition data is shown in Table 2.

[0057] The oxidation catalyst is the HUS-C01 desulfurization catalyst produced by Guangzhou Dayou Fine Chemical Plant.

[0058] Example 1

[0059] Adopting attachment Figure 1 The process flow is shown below. Oxygen and naphtha are mixed in a first static mixer to obtain an oxidant-carrying oil with an oxygen content of 90 mg / kg. The C4 hydrocarbon feedstock is mixed with the oxidant-carrying oil and a thiol conversion aid to obtain the inlet stream for the oxidation reactor. The thiol conversion aid is a compound solution containing 60 wt% diethanolamine and 40 wt% ethanol. The inlet stream enters the oxidation reactor and contacts the oxidation catalyst, where a thiol oxidation reaction occurs. With the assistance of the thiol conversion aid, the thiols in the C4 hydrocarbon fraction are completely converted into disulfides. The post-oxidation stream is introduced into a distillation column for separation. The distillation column is a variable diameter column, with the upper diameter of the feed tray smaller than the lower diameter. The top of the distillation column yields a desulfurized C4 hydrocarbon fraction, and the bottom yields sulfur-containing naphtha. The activity of the oxidation catalyst can meet the requirements of an operating cycle of not less than 3 years, which can match the shutdown and maintenance cycle of other units in the plant.

[0060] The main operating conditions for the oxidation reaction are shown in Table 3, and the main operating conditions for the distillation column are shown in Table 4; the material balance of the unit is shown in Table 5; and the sulfur balance of the unit is shown in Table 6.

[0061] The main effects of Example 1 are as follows: (1) The total sulfur content of the C4 hydrocarbon fraction feedstock was reduced from 41 mg / kg to 0.5 mg / kg by the fine desulfurization method of the present invention, thus achieving fine desulfurization of the C4 hydrocarbon fraction. (2) During the fine desulfurization process of the C4 hydrocarbon fraction, the yield of the C4 hydrocarbon fraction was 100%, and there was no loss of the C4 hydrocarbon fraction. (3) The desulfurization adsorbent in the existing adsorption desulfurization process needs to be frequently regenerated, and the operating cycle of the device is 8-12 days. The method of Example 1 has a long operating cycle and is easy to operate.

[0062] Example 2

[0063] The process flow, oxidation catalyst, mercaptan conversion aid, C4 hydrocarbon feedstock, and topping oil of Example 1 were adopted.

[0064] Unlike Example 1, the feed rate of the topping oil was increased from 1000 kg / h to 2000 kg / h, the oxidant was air with water and carbon dioxide removed, and the oxygen content in the oxidant-carrying oil obtained by mixing the oxidant and naphtha was 46 mg / kg; the amount of mercaptan conversion aid added was increased from 0.4 kg / h to 0.6 kg / h, and the amount of oxidation catalyst loaded was reduced from 10000 kg to 6000 kg.

[0065] The main operating conditions for the oxidation reaction are shown in Table 3, and the main operating conditions for the distillation column are shown in Table 4; the material balance of the unit is shown in Table 5; and the sulfur balance of the unit is shown in Table 6.

[0066] The main effects of Example 2 are: (1) The total sulfur content of the C4 hydrocarbon fraction feedstock was reduced from 41 mg / kg to 0.7 mg / kg by using the fine desulfurization method of the present invention, thus achieving fine desulfurization of the C4 hydrocarbon fraction. (2) During the fine desulfurization process of the C4 hydrocarbon fraction, the yield of the C4 hydrocarbon fraction was 100%, and there was no loss of the C4 hydrocarbon fraction.

[0067] In Example 2, the sulfur-containing topping oil obtained from the bottom of the distillation column was fed into a hydrotreating reactor for hydrorefining. The desulfurized topping oil was returned to the first static mixer for recycling. The hydrorefining catalyst used was RS-1 catalyst produced by the Catalyst Division of China Petroleum & Chemical Corporation. The main reaction conditions for hydrorefining were: reaction temperature 260℃, reaction pressure 1.8MPa, and volume hourly space velocity 8h⁻¹. -1 The hydrogen-to-oil volume ratio is 80. After hydrorefining, the sulfur content of the sulfur-containing topping oil is reduced from 201.7 mg / kg to 0.3 mg / kg.

[0068] Table 1

[0069]

[0070] Table 2

[0071]

[0072]

[0073] Table 3 Process conditions of the oxidation reactor

[0074] Instance number Example 1 Example 2 C4 hydrocarbon fraction feed rate, kg / h 10000 10000 Naphtha feed rate, kg / h 1000 2000 Oxygen feed rate, kg / h 0.09 / Air feed rate, kg / h / 0.40 Thiol conversion aid feed rate, kg / h 0.40 0.60 Oxidation reaction temperature, °C 40 52 Oxidation reaction pressure, MPa 1.20 1.50 Catalyst loading in oxidation reactor, kg 10000 6000

[0075] Table 4 Operating conditions of the distillation column

[0076]

[0077]

[0078] * A variable diameter distillation column is used. The column diameter (upper / lower) refers to the column diameter at the top of the feed plate and the column diameter at the bottom of the feed plate.

[0079] Table 5

[0080]

[0081] Table 6

[0082]

Claims

1. A method for the fine desulfurization of C4 hydrocarbon fractions, characterized in that, include: (1) Oxidant is mixed with naphtha to obtain oxidant-carrying oil; (2) The C4 hydrocarbon fraction is mixed with the oxidant-carrying oil, and then a mercaptan conversion aid is added. The mixture enters the oxidation reactor and comes into contact with the oxidation catalyst to undergo an oxidation reaction, where the mercaptan is converted into disulfide. (3) The stream after oxidation reaction is separated by distillation to obtain desulfurized C4 hydrocarbon fraction and sulfur-containing naphtha.

2. The C4 hydrocarbon fraction desulfurization method according to claim 1, characterized in that, Also includes: (4) Sulfur-containing naphtha is contacted with a hydrorefining catalyst to carry out a hydrodesulfurization reaction, and the desulfurized naphtha is recycled.

3. The C4 hydrocarbon fraction desulfurization method according to claim 1 or 2, characterized in that, The oxidant is oxygen or a mixture of oxygen and an inert gas; the naphtha has a distillation range of 30-170℃; and the oxygen content of the oil carried by the oxidant is 10-500 mg / kg. Preferably, the naphtha is selected from light naphtha with a distillation range of 30-80℃; or from topped oil from a reforming unit, raffinate from a benzene extraction unit, or light naphtha from a hydrorefining unit.

4. The C4 hydrocarbon fraction desulfurization method according to claim 1 or 2, characterized in that, The C4 hydrocarbon fraction contains not less than 95.0 wt% C4 hydrocarbons and the balance of C3 and C5 hydrocarbons, with a mercaptan sulfur content of not more than 50 mg / kg and a total sulfur content of not more than 100 mg / kg; the mercaptan conversion aid is selected from one or more of diethanolamine, methyldiethanolamine, diisopropanolamine, ethylenediamine and ethanol. Preferably, the C4 hydrocarbon fraction contains one or more of the following: methanethiol, ethanethiol, propanethiol, dimethyl sulfide, methyl ethyl sulfide, dimethyl disulfide, methyl ethyl disulfide, diethyl disulfide, and dimethyl polysulfide.

5. The C4 hydrocarbon fraction desulfurization method according to claim 1 or 2, characterized in that, The naphtha comprises 5-40% by weight of the C4 hydrocarbon fraction; the amount of thiol conversion aid added to the C4 hydrocarbon fraction is 10-100 mg / kg; the oxidation reaction temperature is 30-80℃, the reaction pressure is 0.3-2.0 MPa, and the volume hourly space velocity (VHSV) of the C4 hydrocarbon fraction is 0.5-5.0 h⁻¹. -1 ; Preferably, the naphtha comprises 10-20% by weight of the C4 hydrocarbon fraction; the amount of thiol conversion aid added to the C4 hydrocarbon fraction is 30-60 mg / kg; the oxidation reaction temperature is 40-60°C, the reaction pressure is 1.0-2.0 MPa, and the volume hourly space velocity (VHSV) of the C4 hydrocarbon fraction is 1.0-2.0 h⁻¹. -1 .

6. The C4 hydrocarbon fraction desulfurization method according to claim 1 or 2, characterized in that, The oxidation catalyst is a support and an active component supported on the support. The support is selected from one or more of activated carbon, alumina and molecular sieves, and the active component is one or more metal phthalocyanine compounds selected from Co, Fe, Mo and Cu.

7. The C4 hydrocarbon fraction desulfurization method according to claim 1 or 2, characterized in that, The oxidation reactor is one or more fixed-bed reactors. When multiple fixed-bed reactors are used, the fixed-bed reactors are connected in series or in parallel. Preferably, the oxidation reactor is provided with a material inlet distributor at the top and an outlet collector at the bottom.

8. The C4 hydrocarbon fraction desulfurization method according to claim 1 or 2, characterized in that, The total sulfur content of the desulfurized C4 hydrocarbon fraction obtained in step (3) is no more than 1 mg / kg.

9. The C4 hydrocarbon fraction desulfurization method according to claim 2, characterized in that, The hydrogenation refining catalyst is a heat-resistant inorganic oxide support and a metal active component supported on the support. The heat-resistant inorganic oxide support is alumina and / or silicon oxide, and the metal active component is selected from one or more of Co, Mo, W and Ni.

10. The C4 hydrocarbon fraction desulfurization method according to claim 9, characterized in that, The hydrogenation reaction conditions are as follows: reaction temperature 250-300℃, reaction pressure 1.5-2.5MPa, and volume hourly space velocity (VHSV) 4-10h. -1 The hydrogen-to-oil volume ratio is 50-100. Preferably, the sulfur content of the naphtha obtained after hydrodesulfurization is no more than 0.5 mg / kg.

11. A C4 hydrocarbon fraction desulfurization reaction apparatus, used in the C4 hydrocarbon fraction desulfurization methods of claims 1-10, comprising: The first static mixer is used to mix the oxidant with naphtha to obtain an oxidant-carrying oil. The second static mixer is used for mixing C4 hydrocarbon fractions, oxidant-carrying oil and mercaptan conversion aids; The second static mixer is connected to the first static mixer; An oxidation reactor is filled with an oxidation catalyst bed and has a raw material inlet and an outlet. The outlet of the second static mixer is connected to the raw material inlet of the oxidation reactor. A distillation column is used for fractionating C4 hydrocarbon fractions and naphtha after oxidation reaction; the distillation column is provided with an inlet, a top outlet and a bottom outlet, and the outlet of the oxidation reactor is connected to the inlet of the distillation column; Preferably, it further includes a hydrogenation reactor, a gas-liquid separator, and a stripping tower for hydrogenating and desulfurizing sulfur-containing naphtha from a distillation column; the hydrogenation reactor is provided with a feed inlet and an outlet, the bottom outlet of the distillation column is connected to the feed inlet of the hydrogenation reactor, the outlet of the hydrogenation reactor is connected to the gas-liquid separator, the gas-liquid separator is provided with a gas phase outlet and a liquid phase outlet, and the liquid phase outlet is connected to a first static mixer via the stripping tower.

Images