Method for treating high acetylene carbon four tail gas and application thereof

Abstract

The application relates to the field of petroleum chemical industry and discloses a high-acetylene carbon four tail gas treatment method and application thereof, which comprises the following steps: (1) contacting a mixture of raw materials containing high-acetylene carbon four tail gas and N-methyl pyrrolidone with hydrogen, and performing a hydrogenation reaction under catalytic hydrogenation reaction conditions to obtain a mixture containing reaction products; and (2) separating the mixture containing the reaction products to obtain a gas phase recovery stream and the reaction products respectively. The method takes increasing butadiene yield as the main purpose, uses high-acetylene carbon four diluted by NMP as hydrogenation raw materials, improves the activity and selectivity of a hydrogenation catalyst, prolongs the service life of the hydrogenation catalyst, and makes the butadiene content in a hydrogenation product high, so that the carbon four fraction is more reasonably utilized.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, specifically to a method for treating high-acetylene C4 tail gas and its application. Background Technology

[0002] In the process of producing ethylene via naphtha steam cracking, the yield of C4 hydrocarbons can reach 20%-25% of the ethylene production. The cracked mixed C4 hydrocarbons contain approximately 40-60% by weight of 1,3-butadiene, 0.5-2.0% by weight of vinylacetylene (VA) and ethylacetylene (EA), and the remaining components are butane, butene, and small amounts of 1,2-butadiene, C3 and C5 hydrocarbons. The most valuable component is 1,3-butadiene.

[0003] Industrially, butadiene is obtained by refining cracked mixed C4 fractions through two-stage solvent extraction distillation and direct distillation processes, with a butadiene yield typically ranging from 97-98.5%. The separated alkynes contain 20-40 wt% VA and EA, as well as 3-60 wt% 1,3-butadiene. This fraction is known as high-alkyne C4. In industrial production, for safety reasons, the C4 fraction is usually diluted and then flared, resulting in resource waste and environmental pollution.

[0004] Selective hydrogenation is an effective way to treat high-alkyne C4 streams and avoid resource waste and environmental pollution. It involves using a selective hydrogenation catalyst to convert alkynes in the C4 stream into butadiene, butene, and a small amount of butane. This hydrogenation reaction is exothermic, releasing a large amount of heat that causes a rapid rise in catalyst bed temperature. Furthermore, substances such as vinylacetylene and butadiene in the C4 stream are highly unstable and prone to polymerization on the catalyst, leading to coking and deactivation. The exothermic hydrogenation reaction raises the reaction temperature, which further accelerates polymer deposition. This selective hydrogenation process for alkynes is not only extremely unsafe but also has a very short catalyst lifespan. The consequences are even more severe if the concentration of alkynes and butadiene in the C4 stream is higher. Therefore, selecting a suitable selective hydrogenation process for alkyne removal is crucial.

[0005] The existing high-acetylene C4 selective hydrogenation process flow is shown below. Figure 2The high-alkyne C4 stream and hydrogen 1, along with the circulating stream 4, from the butadiene extraction unit are fed into one or more reactors connected in series, transforming the high-alkyne C4 stream into a C4 stream containing a low concentration of alkyne. If several reactors are used in series, coolers must be installed between each reactor section, and appropriate amounts of hydrogen must be introduced. The hydrogenated stream 3 is sent to a vapor-liquid separator II. A portion of the liquid stream 4 from the vapor-liquid separator is pumped back to the inlet of the first / several reactors I for dilution of the high-alkyne C4 2. The other portion, stream 5, is the hydrogenated product, which can be used as feedstock for the butadiene extraction unit. The non-condensable gaseous stream 6 from the vapor-liquid separator is sent to the recovery system.

[0006] CN110963878A discloses a method for recovering C4 alkyne tail gas, which is generated by a DMF-based 1,3-butadiene extraction device. The impurities in the C4 alkyne tail gas include butadiene dimer, DMF solvent, and water. The method includes the following steps: (1) Tail gas liquefaction: The C4 alkyne tail gas is pressurized by a two-stage compression process involving a compressor stage 1 and a compressor stage 2; (2) Impurity removal: S1, the discharge from the compressor stage 2 cooler enters the compressor stage 2 discharge buffer tank for impurity removal to obtain liquefied C4 alkyne material; S2, the liquefied C4 alkyne material is mixed with raffinate C4 and then impurity removed to obtain coalescing feed; (3) Hydrogenation reaction: The coalescing feed is mixed with hydrogen and then subjected to a selective hydrogenation reaction; (4) Light component removal: The hydrogenated material is de-lightened, and part of it is sent to the reactor inlet as a circulating diluent, and part of it is sent to the product cooler for cooling to obtain hydrogenated product, which is then sent to a mixed C4 storage tank.

[0007] CN108927173A discloses a selective catalyst for alkyne hydrogenation, its preparation method, and its application. The catalyst consists of an active component, a co-catalyst component, and a support. The active component is palladium, and a co-catalyst component is added to improve the catalyst's hydrogenation stability and selectivity. The co-catalyst component is introduced into the catalyst in different ways to achieve reasonable control of the catalyst surface acidity and promote the dispersion of the active component palladium, thereby forming more active sites. This catalyst is suitable for the selective hydrogenation of alkyne-containing materials, especially for the selective hydrogenation of high-alkyne-content C4 materials emitted from butadiene extraction units, converting vinylacetylene and ethylacetylene into butadiene and butene. The hydrogenated product is returned to the feedstock storage tank or the butadiene extraction unit recovers butadiene and butene. The catalyst of this invention exhibits mild hydrogenation reaction conditions, high activity and selectivity, particularly good stability, and a long operating cycle, making it suitable for the hydrogenation of materials with high alkyne content.

[0008] CN107522587B discloses a method for selective hydrogenation of alkynes in mixed C4 hydrocarbons to recover 1,3-butadiene, comprising the following steps: selecting a hypergravity reactor; feeding hydrogen and mixed C4 materials into the feed chamber for efficient gas-liquid two-phase mixing, dispersing sparingly soluble hydrogen into a large number of nano-microbubbles in the mixed C4, achieving supersaturation of hydrogen solubility in the mixed C4, forming a gas-liquid mixture; conveying the gas-liquid mixture into the hypergravity reactor through a liquid distributor, and carrying out a gas-liquid-solid catalytic hydrogenation reaction in a rotor containing catalyst and packing; the reaction products and unreacted hydrogen leave the reactor, the products are cooled to room temperature by a condenser, and then enter a gas-liquid separator, with hydrogen collected from the top and liquid products collected from the bottom of the gas-liquid separator; the reactor used in this method can achieve supersaturation of sparingly soluble hydrogen solubility in the liquid phase, efficiently utilize hydrogen, enhance gas-liquid-solid phase mass transfer, and achieve a butadiene yield of ≥80%.

[0009] The invention makes some optimizations in terms of process flow and hydrogenation catalyst, but in essence, it still uses C4 and alkynes as raw materials and carries out hydrogenation reaction in a fixed-bed reactor in the presence of hydrogenation catalyst. In actual process, the service life and lifespan of the catalyst are relatively short, and no substantial improvement has been made to the hydrogenation method.

[0010] Furthermore, the inventors of this invention have discovered through research that in the prior art, as the reaction proceeds, the temperature of the catalyst bed along the material feed direction increases due to the heat released by the reaction. At higher reaction temperatures, excessive hydrogenation causes a decrease in product selectivity, and the polymerization of unsaturated C4 can clog catalyst pores and cover active centers, leading to a decrease in catalyst lifespan and service life.

[0011] Therefore, how to provide a new process to improve the service life and lifespan of catalysts in process applications is a technical problem that needs to be solved. Summary of the Invention

[0012] In view of the problems in the prior art, the purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a method for treating high-alkyne C4 tail gas and its application. The method aims to increase butadiene production. It uses high-alkyne C4 diluted with N-methylpyrrolidone (NMP) as hydrogenation feedstock, which improves the activity and selectivity of the hydrogenation catalyst, extends the service life of the hydrogenation catalyst, and results in a higher butadiene content in the hydrogenation product, thus making more rational use of the C4 fraction.

[0013] One objective of this invention is to provide a method for treating high-acetylene C4 tail gas, comprising the following steps:

[0014] (1) The mixture of raw material containing high-alkyne C4 tail gas and N-methylpyrrolidone is contacted with hydrogen and hydrogenated under catalytic hydrogenation reaction conditions to obtain a mixture containing reaction products.

[0015] (2) The mixture containing the reaction products is separated to obtain the gas phase recovery stream and the reaction products respectively.

[0016] Given the wide applicability of the high-acetylene C4 tail gas source, in a preferred embodiment of the present invention, the high-acetylene C4 tail gas originates from the residual fraction containing C4 acetylene discharged from the acetylene washing stage in the butadiene extraction secondary extraction stage, preferably mainly from the residual fraction containing high concentrations of vinyl acetylene and ethyl acetylene discharged from the acetylene washing tower in the secondary extraction section of the butadiene extraction unit.

[0017] According to the present invention, the component content of the high-acetylsene C4 tail gas has a wide selection range. Preferably, based on the weight percentage of the C4 components, the high-acetylsene C4 tail gas contains 0-5% by weight of butene, 3-60% by weight of 1,3-butadiene, and 20-50% by weight of C4-acetylsene. In addition, the high-acetylsene C4 tail gas may also contain other components, such as n-butane, isobutane, 1-butene, cis-2-butene, trans-2-butene, isobutene, and 1,2-butadiene. The content of these components has a relatively small impact on the selection of hydrogenation reaction; therefore, the present invention does not impose any particular limitations on the specific content of these components.

[0018] According to the present invention, the range of C4-acetylene hydrocarbons is relatively wide. Preferably, the C4-acetylene hydrocarbons include vinyl acetylene and / or ethyl acetylene, that is, vinyl acetylene and ethyl acetylene coexist, or one of vinyl acetylene and ethyl acetylene.

[0019] The range of possible ratios for N-methylpyrrolidone and the feedstock containing high-acetylene C4 tail gas is relatively wide. In a preferred embodiment of the present invention, the high-acetylene C4 and NMP are mixed and then fed into selective hydrogenation reactor I. To improve the activity and selectivity of the catalyst in the hydrogenation reaction, the mass ratio of N-methylpyrrolidone to the feedstock containing high-acetylene C4 tail gas is (0.1-40):1, preferably (1-20):1, and more preferably (2-10):1. In this preferred embodiment, the hydrogenation product has a higher butadiene content, better butadiene selectivity, and a longer service life and service cycle of the hydrogenation catalyst.

[0020] According to the present invention, the mass ratio of N-methylpyrrolidone to the raw material containing high-acetylsene C4 tail gas is (0.1-40):1, preferably (1-20):1, more preferably (2-10):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and any value between 2 and 10 or any range of two numbers to 1.

[0021] In a preferred embodiment of the present invention, based on the total weight of the raw material containing high-acetylene C4 tail gas as 100%, the vinyl acetylene content in the raw material containing high-acetylene C4 tail gas before the reaction is 1-6% by weight, preferably 2-4% by weight; in this preferred embodiment, the temperature rise can be reduced more effectively, and the service life and service cycle of the hydrogenation catalyst can be improved.

[0022] According to the present invention, preferably, the hydrogenation reaction is carried out under continuous feeding of the mixture. Under continuous feeding, the mixture can continuously flush the catalyst, which can further maintain the catalytic activity and selectivity of the catalyst. Compared with the prior art, this improves the activity and selectivity of the catalyst and further extends the service life and cycle of the catalyst.

[0023] The vinylacetylene content in the high-acetylene C4 tail gas feedstock can be controlled by dilution, and the present invention does not have any particular restrictions on the source of the diluent. Under the hydrogenation conditions used in the above-mentioned hydrogenation reaction, the hydrogenated C4 fraction contains only a small amount of alkynes, which can be returned as feedstock for the butadiene extraction unit. Preferably, after selective hydrogenation reaction, a portion of the hydrogenated product is returned to the inlet of the hydrogenation reactor as a circulating stream to dilute the concentration of alkynes in the high-acetylene C4, and the remainder is collected as product.

[0024] In a preferred embodiment of the present invention, the method further includes step (3): a portion of the reaction product obtained in step (2) is returned to step (1) as recycled material to dilute the alkynes in the high-alkyne C4 tail gas in step (1) before hydrogenation; the other reaction products are collected. In this way, no additional dilution gas is required, and the high-alkyne C4 tail gas can be diluted in the process flow of the present invention, controlling the vinyl acetylene content in the raw materials within a preferred range, making the process more economical.

[0025] According to the present invention, the range of selectable conditions for the catalytic hydrogenation reaction is relatively wide. In a preferred embodiment of the present invention, the catalytic hydrogenation reaction conditions include a hydrogenation reaction temperature of 20-80°C.

[0026] According to the present invention, the molar ratio of hydrogen gas to alkyne content in the mixture before reaction can also be adjusted within a wide range. In a preferred embodiment of the present invention, the molar ratio of hydrogen gas to alkyne content in the mixture before reaction is (0.5-2):1.

[0027] According to the present invention, the catalytic hydrogenation reaction pressure has a wide selection range. In a preferred embodiment of the present invention, the reaction pressure is 0.6-4 MPa; preferably, the liquid hourly space velocity is 1-100 h⁻¹. -1 .

[0028] According to the present invention, the hydrogenation conditions used in the hydrogenation reactor can be appropriately varied according to the compositional properties of the C4 fraction stream being treated and the proportion of NMP added. The temperature should be as low as possible to further prevent the polymerization of unsaturated hydrocarbons in the C4 fraction. In a more preferred embodiment of the present invention, the conditions include: a reactor inlet temperature of 20-80°C, a molar ratio of hydrogen to alkynes in the mixture stream at the inlet of 0.5-2:1, a reaction pressure of 0.6-4 MPa, and a liquid hourly space velocity of 1-100 h⁻¹. -1 .

[0029] According to the present invention, the catalyst used in the catalytic hydrogenation reaction can be a conventional catalyst in the art. In a preferred embodiment of the present invention, the catalyst used in the catalytic hydrogenation reaction is a supported hydrogenation catalyst. Preferably, the supported hydrogenation catalyst contains a support, an active metal component supported on the support, and optional auxiliary agents.

[0030] The range of component content for supported hydrogenation catalysts is relatively wide. Preferably, in the supported selective hydrogenation catalyst, the content of active metal component, based on the total weight of the catalyst, can be 0.008-1% by weight, preferably 0.01-0.5% by weight; and the content of the auxiliary agent, based on the element, can be 0-10% by weight.

[0031] According to the present invention, the selection range of the active metal component is relatively wide. In a preferred embodiment of the present invention, the active metal component is selected from at least one of palladium, platinum, and nickel.

[0032] According to the present invention, the range of selection of the auxiliary agent is relatively wide. In a preferred embodiment of the present invention, the auxiliary agent is selected from at least one of potassium, sodium, lithium, calcium, magnesium, barium, fluorine, copper, silver, gold, zinc, tin, lead, manganese, bismuth, molybdenum, zirconium and rare earth elements.

[0033] According to the present invention, the range of the carrier is relatively wide. In a preferred embodiment of the present invention, the carrier is selected from at least one of alumina, silicon dioxide, spinel, diatomaceous earth, titanium dioxide, zinc oxide, tin oxide and molecular sieve.

[0034] Preferably, in order to give the supported selective hydrogenation catalyst the advantages of higher activity, better selectivity and longer lifespan, the supported selective hydrogenation catalyst may contain a support and an active metal component and an auxiliary agent supported on the support. The active metal component may contain at least palladium, the auxiliary agent may contain at least silver or lead, and the support may be alumina.

[0035] According to the present invention, the bulk density, specific surface area, and other parameters of the catalyst can be selected over a wide range. In a preferred embodiment of the present invention, the bulk density of the catalyst is 0.5-1.5 g / cm³. 3 and / or, with a specific surface area of ​​5-350 m² 2 / g.

[0036] According to the present invention, in the supported selective hydrogenation catalyst, the shape of the support can be chosen conventionally in the art. For example, the shape of the support can be one or more of spherical, cylindrical, clover-shaped, serrated, or extruded. The bulk density of the catalyst can be 0.5-1.5 g / cm³. 3 When the support is spherical, cylindrical, or extruded, the diameter of the catalyst (spherical diameter, cylindrical diameter, or extruded diameter) can be 1-6 mm, and the specific surface area can be 5-350 m². 2 / g.

[0037] According to the present invention, the preparation method of the supported selective hydrogenation catalyst can be a method well known to those skilled in the art. The preparation method includes, for example, a step of loading components, including the active component, onto a catalyst support and then calcining it; wherein the loading can be performed by impregnating or spraying components, including an active component solution, onto the catalyst support.

[0038] According to the present invention, in order to realize the selective hydrogenation method of alkynes in C4 high-alkyne hydrocarbons, the method is carried out in a reaction apparatus including a selective hydrogenation reactor I, which is an adiabatic fixed-bed reactor or a tubular isothermal fixed-bed reactor, and the reactant flow direction is from top to bottom or from bottom to top.

[0039] According to the present invention, the hydrogenation technology can adopt a suitable reactor form. For example, the hydrogenation reactor can be an adiabatic or isothermal fixed-bed reactor. More preferably, the fixed-bed hydrogenation reactor can be a bubbling bed reactor (material flows from bottom to top) or a trickling bed reactor (material flows from top to bottom).

[0040] In a more preferred embodiment of the invention, such as Figure 1As shown, a selective hydrogenation method for alkynes in high-alkyne C4 is carried out in a fixed-bed hydrogenation reactor I. The method includes: mixing high-alkyne C4 stream 1 with N-methylpyrrolidone 3, diluting with recycled material 5, and then adding a metered hydrogen stream 2. The mixture is then introduced into the hydrogenation reactor I for selective hydrogenation to obtain hydrogenated product 4. This product is separated by a separator II, with a portion of the hydrogenated product returned to the inlet of the hydrogenation reactor as recycled material 5 to dilute the concentration of alkynes in the high-alkyne C4. The remaining portion is collected as product 6, and the gaseous recovery stream 7 is collected from above. Figure 2 As shown, the catalyst hydrogenation reaction does not contain N-methylpyrrolidone 3.

[0041] The second objective of this invention is to provide an application of the method described above in the selective hydrogenation of alkynes in high-alkyne C4 tail gas.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] (1) Catalytic hydrogenation is carried out according to the process of the present invention, wherein the content of vinylacetylene in the hydrogenation product is not more than 1.5% by weight, preferably not more than 1.3% by weight, the selectivity of vinylacetylene hydrogenation to 1,3-butadiene is not less than 50%, and the content of 1,3-butadiene in the product is significantly increased. The increased butadiene content in the hydrogenation product allows for more rational utilization of the C4 fraction.

[0044] (2) The service life and service cycle of hydrogenation catalysts have been significantly increased.

[0045] (3) The above-mentioned catalytic hydrogenation process is simple, controllable, and has high application value.

[0046] The inventors of this invention discovered through research that, in the prior art, along the material feeding direction, as the reaction proceeds, the catalyst bed temperature increases due to the heat released by the reaction. At higher reaction temperatures, excessive hydrogenation causes a decrease in product selectivity, and the polymerization of unsaturated C4 can clog catalyst pores and cover active centers, leading to a decrease in catalyst lifespan and service life.

[0047] This invention adds NMP to the hydrogenation process. The inventors unexpectedly discovered that this significantly increases the lifespan and service life of the hydrogenation catalyst, and the catalytic effect is superior to existing technologies. Specifically, hydrogenation of the high-acetylsyl C4 fraction in the presence of NMP not only does not cause a decrease or deactivation of the hydrogenation catalytic activity, but also improves the selectivity for 1,3-butadiene. Through further research, the inventors believe this is because the continuously flowing NMP can scour the catalyst surface, significantly reducing coking. Furthermore, the addition of NMP also reduces temperature rise.

[0048] In the method provided by this invention, the high-alkyne C4 feedstock stream and the NMP stream are mixed and then subjected to a hydrogenation reaction to finally obtain the target C4 fraction product. Because the concentration of alkyne is reduced after the C4 fraction is diluted by NMP, the temperature rise during the hydrogenation process can be significantly reduced, over-hydrogenation reaction can be suppressed, and the selectivity of the hydrogenation catalyst can be improved. At the same time, due to the continuous scouring of the catalyst surface by NMP, the deposition of polymer on the catalyst surface is greatly reduced, which can extend the service life of the hydrogenation catalyst. Attached Figure Description

[0049] Figure 1 This is a schematic flowchart of the selective hydrogenation method for alkynes in high-alkyne C4 tail gas provided by the present invention.

[0050] Figure 2 This is a schematic flowchart of the selective hydrogenation method for alkynes in the high-alkyne C4 tail gas described in Comparative Example 1.

[0051] Explanation of reference numerals in the attached figures

[0052] 1. High-acetylene C4 material

[0053] 2. Hydrogen logistics

[0054] 3. N-methylpyrrolidone

[0055] 4. Hydrogenation products

[0056] 5. Circulating materials

[0057] 6. Products

[0058] 7. Gas phase recovery logistics

[0059] I. Selection of Hydrogenation Reactor

[0060] II. Separation Tank Detailed Implementation

[0061] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0062] In the following examples and comparative examples, the contents of alkynes, alkenes and alkanes in the C4 fraction were determined by a gas chromatograph (model 7890) purchased from Agilent Technologies; the contents of alkynes, alkenes and alkanes in the hydrogenated product were calculated as weight percentages after deducting NMP and hydrogen content.

[0063] In the following examples and comparative examples, the inlet and outlet temperatures of each hydrogenation reactor were measured using thermocouples.

[0064] In the following examples and comparative examples, N-methylpyrrolidone was obtained from commercially available sources.

[0065] Example 1

[0066] The raw material used in this embodiment is the high-acetylene C4 tail gas discharged from the butadiene extraction unit. The specific contents are shown in Table 1, which lists the contents of each component in the high-acetylene tail gas. The catalyst used is a palladium-silver supported hydrogenation catalyst, with Al2O3 as the catalyst support. The active metal components are: palladium 0.3% by weight, silver 0.15% by weight. The active components are loaded onto the support using an equal-volume impregnation method, dried at 120°C for 6 hours, and then decomposed in air at 450°C for 8 hours. Before use, the catalyst is reduced in the reactor by passing hydrogen gas at 100-120°C for 4 hours. Figure 1 The process flow shown uses a trickle-bed hydrogenation reactor loaded with 50 ml of catalyst. Based on the total weight of the high-acetylene C4 fraction feedstock from the butadiene extraction unit, 2 parts by weight of NMP are mixed and fed into selective hydrogenation reactor I. Specifically, the weight ratio of NMP to the high-acetylene C4 fraction feedstock in the feed stream entering selective hydrogenation reactor I is 2:1. The inlet temperature of selective hydrogenation reactor I is 42°C, the pressure is 1.0 MPa, and the molar ratio of hydrogen to alkyne content in the mixed stream at the inlet is 0.86:1. Assuming a total C4 component content of 100%, the vinylacetylene content at the reactor inlet is 3.12% by weight, and the liquid hourly space velocity (LHSV) calculated based on the C4 feed rate at the reactor inlet is 40 h⁻¹. -1 ;

[0067] The hydrogenation reaction was carried out under the above conditions. The reaction mixture entered the separator II. After separation, a gaseous recovery stream was obtained above the separator II, and the hydrogenation product was obtained below. Part of the hydrogenation product was returned to the inlet of the hydrogenation reactor as a circulating stream to dilute the concentration of alkynes in the high-alkyne C4, so as to control the vinyl acetylene content at the reactor inlet within the target range of 2%-4%. The remaining part was collected as product. The results are shown in Table 1.

[0068] Example 2

[0069] This embodiment uses the same high-alkyne tail gas and catalyst as in Example 1 for the hydrogenation reaction. Specifically, it uses the following... Figure 1The process flow shown uses a trickle-bed reactor for hydrogenation, loaded with 50 ml of catalyst. Based on the total weight of the high-acetylene C4 feedstock discharged from the butadiene extraction unit, 4 parts by weight of NMP are mixed with it and fed into selective hydrogenation reactor I. That is, the weight ratio of NMP to the high-acetylene C4 feedstock in the feed stream entering selective hydrogenation reactor I is 4:1. The inlet temperature of selective hydrogenation reactor I is 42°C, the pressure is 1.0 MPa, the molar ratio of hydrogen to alkyne content in the mixed stream at the inlet is 0.92:1, the vinylacetylene content at the reactor inlet is 3.05% by weight, and the liquid hourly space velocity (LHSV) calculated based on the C4 feed rate at the reactor inlet is 40 h⁻¹. -1 The subsequent separation steps were the same as in Example 1, and the results are shown in Table 1.

[0070] Example 3

[0071] This embodiment uses the same C4 feedstock and catalyst as in Example 1 for the hydrogenation reaction. Specifically, it uses the following... Figure 1 The process flow shown uses a trickle-bed reactor for hydrogenation, loaded with 50 ml of catalyst. Based on the total weight of high-acetylene C4 from the butadiene extraction unit of the hydrocarbon steam cracking unit, 10 parts by weight of NMP are mixed with it and fed into selective hydrogenation reactor I. That is, the weight ratio of NMP to high-acetylene C4 feed stream in the feed to selective hydrogenation reactor I is 10:1. The inlet temperature of selective hydrogenation reactor I is 42°C, the pressure is 1.0 MPa, the molar ratio of hydrogen to alkyne in the mixed stream at the inlet is 0.90:1, the vinylacetylene content at the reactor inlet is 2.98% by weight, and the liquid hourly space velocity (LHSV) calculated based on the C4 feed rate at the reactor inlet is 20 h⁻¹. -1 The subsequent separation steps were the same as in Example 1, and the results are shown in Table 1.

[0072] Example 4

[0073] The raw materials used in this embodiment are the same as in Example 1. The catalyst is a palladium-lead selective hydrogenation catalyst, with Al2O3 as the catalyst support. The active metal component content is: palladium 0.3% by weight, lead 0.1% by weight. The active components are loaded onto the support using an equal-volume impregnation method, dried at 120°C for 6 hours, and then decomposed in air at 450°C for 8 hours. Before use, the catalyst is reduced with hydrogen gas in the reactor at 100-120°C for 4 hours. Figure 1The process flow shown uses a bubble bed reactor for hydrogenation, loaded with 50 ml of catalyst. Based on the total weight of high-acetylene C4 from the butadiene extraction unit, 10 parts by weight of NMP are mixed with it and fed into selective hydrogenation reactor I. That is, the weight ratio of NMP to high-acetylene C4 feed stream in the feed to selective hydrogenation reactor I is 10:1. The inlet temperature of selective hydrogenation reactor I is 42°C, the pressure is 1.2 MPa, the molar ratio of hydrogen to alkyne in the mixture at the inlet is 0.94:1, the vinylacetylene content at the reactor inlet is 3.07% by weight, and the liquid hourly space velocity (LHSV) calculated based on the C4 feed rate at the reactor inlet is 40 h⁻¹. -1 The subsequent separation steps were the same as in Example 1, and the results are shown in Table 1.

[0074] Comparative Example 1

[0075] This comparative example uses the same high-acetylene C4 tail gas and catalyst as Example 1. Figure 2 The process flow shown uses a trickle-bed hydrogenation reactor, loaded with 50 ml of catalyst. The inlet temperature of hydrogenation reactor I is selected as 40 °C, the pressure as 1.2 MPa, the molar ratio of hydrogen to alkyne in the mixed stream at the inlet is 0.83:1, the vinylacetylene content at the reactor inlet is 3.07% by weight, and the liquid hourly space velocity (LHSV) calculated based on the C4 feed rate at the reactor inlet is 40 h⁻¹. -1 The subsequent separation steps were the same as in Example 1, and the results are shown in Table 1.

[0076] Detection example

[0077] The reaction materials (corresponding to high-acetylene tail gas) and results of the above-described embodiments and comparative examples were tested according to the method described above. The high-acetylene tail gas was calculated with a total content of all C4 components of 100%, and the products in the embodiments and comparative examples were calculated with a total content of all C4 components of 100%.

[0078] The method for calculating the selectivity of butadiene is as follows:

[0079]

[0080] Table 1

[0081]

[0082] As shown in Table 1, the method provided by this invention, by adding NMP to high-acetylene C4 and selecting hydrogenation reactor I, along with appropriate selection of the recycle ratio, the flow ratio of NMP to C4 fraction feedstock entering the hydrogenation reactor, the hydrogen / acetylene ratio, and the reaction temperature, improves the activity and selectivity of the hydrogenation catalyst and extends its service life. After hydrogenation, the vinylacetylene content in the target C4 fraction product does not exceed 1.3% by weight, and the selectivity for 1,3-butadiene is not less than 50%.

[0083] Comparing Example 1 and Comparative Example 1, it can be seen that, with the same total catalyst dosage and high-alkyne C4 feedstock processing capacity, the 1,3-butadiene selectivity of Example 1 is significantly higher than that of Comparative Example 1.

[0084] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for treating high-acetylene C4 tail gas, comprising the following steps: (1) The mixture of raw material containing high-acetylsene C4 tail gas and N-methylpyrrolidone is contacted with hydrogen and hydrogenated under catalytic hydrogenation reaction conditions to obtain a mixture containing reaction products. (2) The mixture containing the reaction products is separated to obtain the gaseous recovery stream and the reaction products respectively; The treatment method can increase the production of 1,3-butadiene; the selectivity of the hydrogenation of vinylacetylene in the feedstock to 1,3-butadiene is not less than 50%. The mass ratio of N-methylpyrrolidone to the feedstock containing high-acetylene C4 tail gas is (2-10):1; The hydrogenation reaction is carried out in a selective hydrogenation reactor, and the process of carrying out the hydrogenation reaction is carried out under continuous feeding of the mixture, under continuous feeding conditions, the mixture can continuously scour the catalyst; Based on the weight percentage of the C4 components, the high-acetylsene C4 tail gas contains 0-5% by weight of butene, 3-60% by weight of 1,3-butadiene, and 20-50% by weight of C4 acetylsene. It also includes step (3): a portion of the reaction products obtained in step (2) are returned to step (1) as recycled material to dilute the alkynes in the high-alkyne C4 tail gas in step (1) before hydrogenation; the other reaction products are collected.

2. The processing method according to claim 1, characterized in that: The high-alkyne C4 tail gas comes from the residual fraction containing C4 alkynes discharged during the alkyne washing stage of the butadiene extraction secondary extraction stage.

3. The processing method according to claim 1, characterized in that: The C44 hydrocarbons include vinyl acetylene and / or ethyl acetylene.

4. The processing method according to claim 1, characterized in that... include: Based on the total weight of the raw material containing high-acetylene C4 tail gas as 100%, the vinyl acetylene content in the raw material containing high-acetylene C4 tail gas before the reaction is 1-6 by weight.

5. The processing method according to claim 1, characterized in that... include: Based on the total weight of the raw material containing high-acetylene C4 tail gas as 100%, the vinyl acetylene content in the raw material containing high-acetylene C4 tail gas before the reaction is 2-4% by weight.

6. The processing method according to claim 1, characterized in that... include: The vinyl acetylene content in the feedstock containing high-acetylene C4 tail gas is controlled by diluting the high-acetylene C4 tail gas.

7. The processing method according to any one of claims 1-6, characterized in that: The catalytic hydrogenation reaction conditions include: The hydrogenation reaction temperature is 20-80℃; and / or, the molar ratio of hydrogen to alkyne content in the mixture before the reaction is (0.5-2):1; and / or, the reaction pressure is 0.6-4MPa; and / or, the liquid hourly space velocity is 1-100h. -1 .

8. The processing method according to any one of claims 1-6, characterized in that: The catalyst used in the catalytic hydrogenation reaction is a supported hydrogenation catalyst, which contains a support, an active metal component supported on the support, and optional auxiliary agents.

9. The processing method according to claim 8, characterized in that: In the supported hydrogenation catalyst, the content of the active metal component, calculated by element, is 0.008-1% by weight based on the total weight of the catalyst; and the content of the auxiliary agent, calculated by element, is 0-10% by weight.

10. The processing method according to claim 8, characterized in that: In the supported hydrogenation catalyst, the content of the active metal component, calculated by element, is 0.01-0.5% based on the total weight of the catalyst. The content of the additive, calculated by element, is 0-10% by weight.

11. The processing method according to claim 8, characterized in that: The active metal component is selected from at least one of palladium, platinum, and nickel; and / or, The additive is selected from at least one of potassium, sodium, lithium, calcium, magnesium, barium, fluorine, copper, silver, gold, zinc, tin, lead, manganese, bismuth, molybdenum, zirconium, and rare earth elements; and / or, The carrier is selected from at least one of alumina, silicon dioxide, spinel, diatomaceous earth, titanium dioxide, zinc oxide, tin oxide, and molecular sieves; and / or, The bulk density of the catalyst is 0.5-1.5 g / cm³. 3 and / or, with a specific surface area of ​​5-350 m² 2 / g.

12. The processing method according to any one of claims 1-6, characterized in that: The hydrogenation reactor used for the hydrogenation reaction is an adiabatic fixed-bed reactor or a tubular isothermal fixed-bed reactor.

13. The processing method according to any one of claims 1-6, characterized in that: The reaction flow direction is either from top to bottom or from bottom to top.

14. The application of any one of the processing methods according to claims 1-13 in the selective hydrogenation of alkynes in high-alkyne C4 tail gas.

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