A method and separation system for selectively removing acetylene impurities from dry gas

Abstract

The present invention discloses a method for selectively removing acetylene impurities from dry gas and a separation method. The method comprises: S1, removing hydrogen sulfide from the raw dry gas to obtain desulfurized purified dry gas; S2, extracting and stripping the desulfurized purified dry gas using a membrane extraction component provided with a deacetylene extraction membrane; wherein the deacetylene extraction membrane is a hollow fiber membrane, and the desulfurized purified dry gas and the acetylene stripping lean liquid flow through the inner cavity and outer wall of the hollow fiber respectively to obtain deacetylene purified dry gas and acetylene stripping rich liquid; S3, the deacetylene purified dry gas is washed with water in a water washing tower to obtain water-washed purified dry gas. The method of the present invention can solve the problems of high acetylene impurity content in the existing dry gas raw material that affects the ethylbenzene alkylation catalyst, short operation cycle of the alkylation catalyst, and large ethylene loss in conventional selective hydrogenation deacetylation. The acetylene impurities in the dry gas raw material are extracted by an efficient continuous membrane, so that the operation cycle of the alkylation catalyst is greatly improved, and the production cost of ethylbenzene is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of preparing ethylbenzene from dry gas, and relates to a method and a separation system for selectively removing acetylene impurities from dry gas. Background Art

[0002] Dry gas refers to the tail gas that cannot be liquefied in the process of oil refining. It mainly comes from the secondary processing of crude oil and is generally used as fuel. In order to make full use of the dilute ethylene in dry gas, improve the utilization rate of oil resources, and solve the current shortage of ethylbenzene / styrene market, various countries have developed the process of producing ethylbenzene from dry gas. Dry gas to produce ethylbenzene is generally carried out under the action of a catalyst at a reaction temperature of 200℃-500℃, so that the ethylene and a small amount of propylene and butene in the dry gas react with benzene to produce ethylbenzene, propylbenzene, butylbenzene and polyalkylbenzenes.

[0003] Ethylbenzene alkylation catalysts generally use acidic molecular sieves. Alkyne impurities in the dry gas feedstock are easily adsorbed on the active center to form coke, resulting in a rapid decrease in catalyst activity. According to the literature "The Effect of Process Impurities on Ethylbenzene Alkylation Reaction by Dilute Ethylene Process" (Industrial Catalysis, Issue 08, 2014), in order to prevent serious coking and deactivation of the catalyst, the volume content of acetylenic impurities is generally controlled to be less than 20ppm. However, due to fluctuations in the operating process of the catalytic cracking unit, the volume content of acetylenes in the catalytic dry gas can exceed 60ppm, or even exceed 100ppm.

[0004] CN101704701A discloses a method for reducing alkynes to cis-olefins, wherein Pd(OAc) 2 , Pd / C, Pd / C and PdCl 2 (PPh 3 ) 2 Under the catalysis of at least one of the following, N,N-dimethylformamide is reacted with potassium hydroxide in situ to produce formic acid for reducing alkynes. This method, for catalytic dry gas containing a large amount of ethylene, will cause ethylene to be reduced to ethane, resulting in a large loss of high-value ethylene.

[0005] CN102249834B discloses a method for selective hydrogenation of alkynes and dienes in an olefin stream. Under the action of a palladium-based catalyst, an olefin stream containing alkynes and dienes is fed together with hydrogen into a hydrogenation reactor equipped with a supported palladium catalyst. At an inlet temperature of 10 to 80°C, a molar ratio of hydrogen to the sum of alkynes and dienes of 1 to 10, and a reaction pressure of 0.1 to 4 MPa, alkynes and dienes in the olefin stream are selectively hydrogenated to olefins and removed. In this method, when the hydrogen content in the catalytic cracking dry gas is 10% to 50%, the selectivity of acetylene hydrogenation is reduced, resulting in a large amount of ethylene being reduced.

[0006] CN102408293A discloses a method for selective hydrogenation of dienes and alkynes, wherein the carrier is treated by adding 0.05wt% to 25wt% of silane groups to improve the conversion stability of dienes and alkynes when the raw material contains trace amounts of water. The method has a certain beneficial effect on hydrogenation under conditions where the existing dry gas contains saturated water, but still cannot solve the problem of acetylene hydrogenation selectivity under high hydrogen content conditions.

[0007] CN1034226C discloses a method and an absorption tower for absorbing acetylene from a crude gas mixture, wherein acetylene is removed from a crude gas mixture mainly containing two-carbon hydrocarbons by washing with an absorbent in an absorption tower composed of multiple layers of tower plates. In this method, the crude gas mixture is fed into the lower area of ​​the absorption tower, regenerated absorbent is fed from the upper area of ​​the absorption tower, the absorbed absorbent is discharged from the bottom of the absorption tower and sent for regeneration, and a product gas stream free of acetylene is obtained at the top of the absorption tower. This method has a high effect on removing acetylene from the gas, but for catalytic dry gas containing a large amount of ethylene, part of the ethylene will be dissolved and carried out, resulting in a certain loss.

[0008] In summary, the existing technology has the main problems of difficult selective removal of acetylenes and high ethylene loss during the removal of acetylenes for high hydrogen content refinery dry gas. If the problem of high acetylenes content in dry gas is not solved, the alkylation catalyst will continue to deactivate slowly or quickly. Therefore, the selective removal of acetylenes impurities in high hydrogen content dry gas is one of the important issues that need to be solved in ethylbenzene plants. Summary of the invention

[0009] The technical problem to be solved by the present invention is that the acetylenic impurities in the high hydrogen-containing dry gas in the prior art are high in content and difficult to selectively remove, and a method and a separation system for selectively removing acetylenic impurities in dry gas are provided. The method of the present invention is used to separate acetylenic impurities in dry gas that affect the activity of ethylbenzene alkylation catalyst, effectively eliminate the cumulative effect of trace acetylenic impurities on the catalyst, and is conducive to extending the operating cycle of the alkylation catalyst, and realizing low-cost and continuous production of ethylbenzene.

[0010] The first aspect of the present invention provides a method for selectively removing acetylene impurities from dry gas, comprising:

[0011] S1, the raw dry gas is subjected to the removal of hydrogen sulfide to obtain desulfurized purified dry gas;

[0012] S2, extracting and stripping the desulfurized purified dry gas using a membrane extraction assembly having a deacetylide extraction membrane therein; wherein the deacetylide extraction membrane is a hollow fiber membrane, and the desulfurized purified dry gas and the acetylide stripping lean liquid flow through the inner cavity and outer wall of the hollow fiber, respectively, to obtain the deacetylide purified dry gas and the acetylide stripping rich liquid;

[0013] S3, the deacetylated purified dry gas is washed with water in a water washing tower to obtain washed purified dry gas.

[0014] In the above technical scheme, the deacetylation extraction membrane described in step S2, wherein the deacetylation extraction membrane is a modified hollow fiber membrane, including a base membrane, a grafted layer and an outer layer, the base membrane has an imine content of 1.4 to 3.0 mmol / g, and an amine content of 4.4 to 11.8 mmol / g; the grafted layer has an imine content of 2.3 to 4.5 mmol / g, and an amine content of 6.9 to 17.7 mmol / g; the outer layer is a polydimethylsiloxane layer with a thickness of 100 to 200 microns.

[0015] In the above technical solution, the grafted layer is covered on the inner surface of the base film, and the outer layer is covered on the outer surface of the base film.

[0016] In the above technical solution, in the dealkyne extraction membrane described in step S2, the imine content and amine content in the base membrane and the imine content and amine content in the grafted layer are based on per gram of modified hollow fiber membrane (ie, dealkyne extraction membrane).

[0017] In the above technical solution, in the deacetylation extraction membrane described in step S2, preferably, the inner diameter of the deacetylation extraction membrane is 0.3 to 1.0 mm.

[0018] In the above technical solution, in the deacetylation extraction membrane described in step S2, preferably, the base film thickness of the deacetylation extraction membrane is 0.4 to 0.8 mm.

[0019] In the above technical solution, in the dealkyne extraction membrane described in step S2, the viscosity of the polydimethylsiloxane is 7000-12000 centipoise.

[0020] In the above technical solution, in the deacetylation extraction membrane described in step S2, the base membrane is a polypropylene membrane modified by a first modifier. The first modifier is polyetherimide and polyacrylamide, wherein the mass ratio of polyetherimide to polyacrylamide is (10-18): (4-8). The molecular weight of polyetherimide is 6300-9100, and the molecular weight of polyacrylamide is 8300-12000. The molecular weight of polypropylene is 40000-50000.

[0021] In the above technical scheme, the method for preparing the dealkyne extraction membrane described in step S2 includes: preparing a base membrane, coating the inner surface of the base membrane with a grafting layer, and then coating the outer surface of the base membrane with an outer wall, i.e., a polydimethylsiloxane layer, to obtain a modified hollow fiber membrane, i.e., a dealkyne extraction membrane.

[0022] In the above technical scheme, in the method for preparing the deacetylenic extraction membrane described in step S2, preferably, the process for preparing the base membrane is preferably: preparing a casting liquid, a core liquid and an outer gel bath containing a first modifier, and then using hollow fiber spinning and drying to obtain a hollow fiber membrane, i.e., a base membrane.

[0023] In the above technical solution, in the method for preparing the dealkyne extraction membrane described in step S2, preferably, the hollow fiber membrane is swollen, treated with the second modifier, and treated with the third modifier to be coated with a graft layer.

[0024] In the above technical solution, in the method for preparing the dealkyne extraction membrane described in step S2, preferably, the hollow fiber membrane covered with the grafted layer is subjected to a third modification post-treatment to coat the outer layer, i.e., a polydimethylsiloxane layer, to obtain a modified hollow fiber membrane, i.e., a dealkyne extraction membrane.

[0025] In the above technical scheme, in the preparation method of the deacetylated extraction membrane described in step S2, the first modifier is polyetherimide and polyacrylamide, wherein the mass ratio of polyetherimide to polyacrylamide is (10-18): (4-8). Wherein, the molecular weight of polyetherimide is 6300-9100, and the molecular weight of polyacrylamide is 8300-12000. The preparation method of the hollow fiber membrane comprises: polypropylene (molecular weight is 40000-50000), N-methylpyrrolidone, diethylene glycol, and the first modifier, in a mass ratio of (20-30): (100-150): (2-6): (14-26), stirring at 90-130°C for 24-48 hours, and then standing and degassing for 5-10 hours to obtain a casting solution containing the first modifier. The core liquid composition is N-methylpyrrolidone: water = (2-8): (92-98) in a mass ratio. The outer gel bath is composed of desalted water. The hollow fiber spinning conditions are as follows: the inner diameter and outer diameter of the spinneret are adjusted according to the inner diameter of the hollow fiber membrane and the thickness of the base membrane, the temperature of the core liquid and the outer gel bath is 0-3°C, the air gap height is 2-4 cm, the fiber collection rate is free fall, the casting liquid flow rate is 7-10 ml / min, the casting liquid pressure in the spinneret is 100-300 kPa (gauge pressure), the core liquid flow rate is 3-7 ml / min, the ambient temperature is 20-30°C, the ambient humidity is 50%-70%, the casting liquid and the core liquid and the outer gel bath undergo solvent exchange and phase solidification to form a hollow fiber membrane blank. The hollow fiber blank is washed with desalted water 4-8 times, washed with low-carbon alcohol (such as at least one of methanol or ethanol) 4-8 times, and washed with n-hexane 4-8 times, and then dried in a nitrogen atmosphere at 20-30°C to obtain a hollow fiber membrane.

[0026] In the above technical scheme, in the preparation method of the deacetylation extraction membrane described in step S2, the hollow fiber swelling agent is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene, the swelling temperature is 80-120°C, the swelling time is 5-12 hours, and the volume ratio of the swelling agent to the hollow fiber membrane is 2-5.

[0027] In the above technical scheme, in the preparation method of the deacetylated extraction membrane described in step S2, the second modifier is 1,3,5-trichlorobenzene, a catalyst and a solvent; the catalyst is selected from one of a Lewis acid or a Lewis base, preferably at least one of anhydrous zinc chloride, anhydrous tin tetrachloride, and anhydrous aluminum chloride; the solvent is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene; in terms of mass fractions, 1,3,5-trichlorobenzene: anhydrous zinc chloride: toluene = (5-15): (1-3): (100-200).

[0028] In the above technical solution, in the preparation method of the deacetylated extraction membrane described in step S2, the conditions for the treatment with the second modifier are as follows: the second modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line speed is 0.2 m / s to 0.5 m / s, the treatment temperature is 30° C. to 60° C., and the treatment time is 20 to 40 minutes. After the hollow fiber membrane is treated with the second modifier, a modified hollow fiber membrane intermediate is obtained.

[0029] In the above technical scheme, in the method for preparing the dealkyne extraction membrane described in step S2, the modified hollow fiber membrane intermediate is subjected to a third modification treatment and a third modification post-treatment to obtain a modified hollow fiber membrane (i.e., a dealkyne extraction membrane). The third modifier is poly(propylene imine-hexadecylamine), sodium hydroxide and a solvent, wherein the solvent is selected from at least one of toluene, p-xylene, m-xylene and o-xylene; in terms of mass fractions, poly(propylene imine-hexadecylamine): sodium hydroxide: solvent = (8-18): (2-5): (100-200). Wherein, the molecular weight of poly(propylene imine-hexadecylamine) is 1600-1700.

[0030] In the above technical scheme, in the preparation method of the deacetylated extraction membrane described in step S2, the conditions for the third modifier treatment are as follows: the third modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line velocity is 0.2 m / s to 0.5 m / s, the treatment temperature is 40°C to 80°C, and the treatment time is 5 to 15 minutes.

[0031] In the above technical scheme, in the preparation method of the deacetylated extraction membrane described in step S2, the third post-modification treatment comprises: using a polydimethylsiloxane solution with a mass concentration of 4% to 8% (the solvent is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene) to dip-coat the outer wall of the hollow fiber membrane for 2 to 7 seconds, followed by drying in a vacuum drying oven at 50°C to 70°C, the pressure (absolute pressure) of the vacuum drying oven being 50 to 80 kPa, and the drying time being 4 to 8 hours; then using a low-carbon alcohol (such as The polydimethylsiloxane is soaked in at least one of methanol or ethanol at a temperature of 40°C to 60°C, 1 to 5 times, and 1 to 4 hours for each soaking; then soaked in an alkali aqueous solution with a mass concentration of 5% to 15% (the alkali is selected from at least one of sodium hydroxide and potassium hydroxide) at a temperature of 40°C to 60°C, 1 to 5 times, and 1 to 4 hours for each soaking; soaked in desalted water at a temperature of 70°C to 90°C, 1 to 5 times, and 2 to 6 hours for each soaking. The viscosity of polydimethylsiloxane is 7000 to 12000 centipoise.

[0032] In the above technical scheme, in step S1, the raw dry gas is derived from catalytic cracking, thermal cracking, delayed coking, and hydrocracking in a refinery. The raw dry gas includes, but is not limited to, ethylene, methane, ethane, propane, propylene, isobutane, n-butane, trans-butene, n-butene, isobutene, cis-butene, oxygen, nitrogen, hydrogen, carbon monoxide, carbon dioxide, 1,3-butadiene, alkanes or alkenes with carbon five or more, and also includes acetylene impurities. In the raw dry gas, the volume content of ethylene is 5% to 40%, preferably 10% to 20%, and the volume content of hydrogen is 5% to 50%. In the raw dry gas, the volume content of acetylene is not less than 60ppm, preferably not less than 150ppm, and further preferably, the volume content is not higher than 300ppm.

[0033] In the above technical scheme, in step S1, the desulfurization of hydrogen can be carried out using a conventional plate tower or packed tower in the art. The desulfurizer and the raw dry gas are in countercurrent contact in the tower body. The theoretical number of plates of the desulfurization tower is 5 to 11, the desulfurization temperature is 20 to 50°C, and the desulfurization pressure is 0.5 to 1.0 MPaG. The desulfurizer is a conventional desulfurizer alcohol amine in the art, preferably at least one of diethanolamine and N-methyldiethanolamine. The dosage ratio of the raw dry gas to the desulfurizer is 50 to 100 by volume, and the mass concentration of the desulfurizer is 20% to 35%.

[0034] In the above technical scheme, in step S2, the interior of the membrane extraction component is filled with the modified hollow fiber membrane, i.e., the deacetylenic extraction membrane, and the acetylenes in the desulfurized purified dry gas are permeated and extracted through the modified hollow fiber membrane to reach the main body and the outside of the modified hollow fiber membrane, and then mass transfer is achieved through the acetylenic back-extraction lean liquid under the promotion of the concentration gradient, and finally the acetylenes in the desulfurized purified dry gas are transferred to the acetylenic back-extraction lean liquid, so that the acetylenes in the desulfurized purified dry gas are effectively removed.

[0035] In the above technical solution, in step S2, the feed amount of the desulfurized purified dry gas is 10000~50000Nm 3 / hour, the filling volume of the deacetylation extraction membrane regularization module is 30-40m 3 The cross-sectional arrangement density of the dealkyne extraction membrane in the dealkyne extraction membrane regularization module is 30,000 to 60,000 pieces / m 2 The contact temperature of the desulfurized purified dry gas passing through the inner cavity of the modified hollow fiber membrane is 20-50°C, and the contact pressure (gauge pressure) is 500-1000 kPa.

[0036] In the above technical scheme, in step S2, the composition of the acetylene stripping lean solution includes N,N-dimethylformamide and 1,2-propylene glycol, wherein the mass content of N,N-dimethylformamide is 78% to 90%, and the mass content of 1,2-propylene glycol is 10% to 22%.

[0037] In the above technical solution, in step S2, the temperature at which the acetylene stripping lean liquid contacts the deacetylene extraction membrane is 20-50° C., and the pressure is 0.5-1.0 MPaG.

[0038] In the above technical solution, in step S2, the gas-liquid volume ratio of the desulfurized purified dry gas to the acetylene stripping lean liquid is 300-800.

[0039] In the above technical solution, in step S2, after the deacetylated purified dry gas contacts the deacetylated extraction membrane, it can pass through a cyclone, and / or a coalescer, and / or a demister, and then enter a water washing tower. The separation accuracy of the cyclone, coalescer or demister is 5 to 10 microns.

[0040] In the above technical solution, in step S3, the number of theoretical plates of the water washing tower is 4 to 10, the water washing temperature is 20 to 50°C, and the water washing pressure is 0.5 to 1.0 MPaG. The water washing water is industrial fresh water and / or desalted water. The gas-water ratio is 40 to 70 by volume.

[0041] In the above technical solution, after step S3, the method further includes:

[0042] S4, the acetylene stripping rich liquid is subjected to hydrogenation and deacetylation to obtain an acetylene stripping lean liquid. Preferably, the obtained acetylene stripping lean liquid can be returned to step S2 for further use.

[0043] In the above technical solution, preferably, in step S4, the acetylene stripping rich liquid is mixed with the preheated hydrocarbonation tail gas after heat exchange and enters the hydrogenation reactor to remove the acetylene in the acetylene stripping rich liquid, and after gas-liquid separation, the acetylene stripping lean liquid is obtained.

[0044] In the above technical scheme, in step S4, the acetylene stripping rich liquid is contacted with the acetylene stripping lean liquid after thermal degassing to recover heat, and then heated to 50-80°C by a heat exchanger, and then mixed with the hydrocarbonized tail gas heated to 50-80°C by a heat exchanger, and then enters the hydrogenation reactor. The hydrocarbonized tail gas originates from a dry gas alkylation reactor, and its composition includes but is not limited to ethylene, methane, ethane, propane, propylene, isobutane, n-butane, trans-butene, n-butene, isobutene, cis-butene, oxygen, nitrogen, hydrogen, carbon monoxide, carbon dioxide, 1,3-butadiene, and alkanes or alkenes with a carbon content of more than five. In the hydrocarbonized tail gas, the volume content of hydrogen is 6.3% to 60%.

[0045] In the above technical scheme, in step S4, the hydrogenation reactor is equipped with a nickel-iron-copper alloy catalyst. The nickel-iron-copper alloy catalyst is calculated by mass fraction, nickel: iron: copper = (80-90): (5-10): (0.8-3.5). The preparation method of the nickel-iron-copper alloy catalyst is: aluminum, nickel, iron, copper, calculated by mass fraction, aluminum: nickel: iron: copper = (300-500): (80-90): (5-10): (0.8-3.5), mixed, heated to 1600-1800°C to melt uniformly, quenched at 100-150°C, broken into 10-50 mesh, and then treated with a sodium hydroxide aqueous solution with a mass concentration of 30%-50% at 20-40°C for 4-8 hours to obtain a nickel-iron-copper alloy catalyst.

[0046] In the above technical scheme, in step S4, the reaction temperature of the hydrogenation reactor is 50-80°C, and the reaction mass space velocity is 1-3h based on the rich liquid of acetylene stripping. -1 The ratio of the hydrocarbon tail gas to the alkyne stripping rich liquid is, in terms of the molar ratio of hydrogen to alkyne, hydrogen:alkyne=(5-20):1.

[0047] In the above technical solution, preferably, the acetylenic content in the deacetylenic purified dry gas obtained in step S2 is not higher than 10 ppm, preferably not higher than 5 ppm.

[0048] In the above technical solution, the deacetylated purified dry gas obtained in step S2 can meet the requirements of long-term operation of the ethylbenzene alkylation catalyst.

[0049] A second aspect of the present invention provides a separation system for selectively removing acetylene impurities from dry gas, comprising:

[0050] 1) Hydrogen sulfide removal tower, used to remove hydrogen sulfide and solid dust from raw dry gas;

[0051] 2) A membrane extraction component, used to extract and remove acetylene impurities from the dry gas raw material, and transfer mass to the acetylene stripping lean liquid;

[0052] 3) A hydrogenation reactor for removing acetylene impurities from the acetylene stripping rich solution;

[0053] 4) Water washing tower, used to remove trace alkaline impurities in the deacetylated purified dry gas.

[0054] Compared with the prior art, the present invention has the following advantages:

[0055] 1. The inventors of the present invention have found through research that there are acetylene impurities in the dry gas raw material that have a significant impact on the ethylbenzene alkylation catalyst, and these impurities will continue to accumulate in the catalyst, resulting in coking of the ethylbenzene catalyst, decreased activity, and shortened operating cycle. Conventional deacetylation is mainly carried out through selective hydrogenation and solvent absorption. Since the refinery dry gas often contains 5% to 50% hydrogen by volume, while the volume fraction of acetylene is only 50 to 200 ppm and the volume fraction of ethylene is 5% to 40%, the hydrogen is greatly excessive relative to acetylene, resulting in conventional selective hydrogenation of acetylene. It is difficult, and it is inevitable that high value-added ethylene is hydrogenated to ethane. The solvent absorption method generally uses N, N-dimethylformamide and N-methylpyrrolidone to absorb acetylene, but a small amount of ethylene will be absorbed and discharged, causing losses. The inventors of the present invention further discovered that by using a modified hollow fiber membrane, the permeation and selective absorption of acetylene impurities in the raw dry gas are improved, and then the concentrated acetylene impurities permeate to the other side of the dense film under the driving force of the concentration difference and are taken away by the acetylene stripping lean solution; the acetylene stripping lean solution is added with a certain amount of 1,3-propylene glycol on the basis of N,N-dimethylformamide to adjust the polarity of the solution, further increase the acetylene / ethylene distribution system, improve the permeation selectivity of the dense film to acetylene, and reduce the loss of ethylene. Therefore, through the high-selective membrane extraction and high-selective stripping of acetylene impurities in the raw dry gas, the separation of acetylene impurities and ethylene is achieved, and the difficulty of acetylene hydrogenation removal is reduced.

[0056] 2. The present invention preferably uses the hydrocarbon tail gas from the outlet of an ethylbenzene alkylation reactor as a hydrogen source for hydrogenation removal of acetylene impurities, thereby reducing the hydrogen consumption cost of the enterprise and realizing the regeneration and recycling of the acetylene stripping rich liquid.

[0057] 3. The present invention solves the problems of high acetylene impurity content in the existing dry gas raw materials that affect the ethylbenzene alkylation catalyst and short operating cycle of the alkylation catalyst. By extracting acetylene impurities in the dry gas raw materials through efficient continuous membrane, the operating cycle of the alkylation catalyst is greatly improved, thereby reducing the production cost of ethylbenzene. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of a separation system for selectively removing acetylene impurities from dry gas according to the present invention;

[0059] The reference numerals are described as follows:

[0060] 101 is a dehydrogen sulfide tower, 102 is a dehydrogen sulfide tower kettle circulation pump, 103 is a membrane extraction component, 104 is an acetylene stripping rich liquid buffer tank, 112 is a hydrogenation reaction inlet and outlet heat exchanger, 105 is a hydrogenation reaction feed heater, 106 is a hydrocarbonation tail gas heater, 107 is a hydrogenation reactor, 108 is a hydrogenation product gas-liquid separation tank, 109 is a hydrogenation liquid phase product material delivery pump, 113 is an acetylene stripping lean liquid cooler, 110 is a water washing tower, 111 is a water washing tower kettle circulation pump, 201 is a raw material dry gas inlet, 202 is a desulfurizer inlet, 203 is a desulfurizer outlet, 204 is a hydrocarbonation tail gas inlet, 205 is a hydrocarbonation tail gas outlet, 206 is a water washing tower fresh water replenishment port, 207 is a water washing water discharge port, and 208 is a water washing purified dry gas outlet. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention.

[0062] In the present invention, the low-carbon hydrocarbon component analysis adopts gas chromatography Agilent 7890A GC (Agilent, USA), equipped with HP-PLOT Al 2 O 3 KCl (50m×0.53mm×15μm) capillary column, column temperature 100℃ for 10 minutes, then increased to 120℃ at 30℃min, maintained for 3 minutes. Carrier gas He flow rate 3mL / min, injection volume 0.1mL (quantitative loop), split ratio 5:1, injection port temperature 250℃, detector (FID) temperature 250℃.

[0063] In the present invention, the content of amine groups is determined by titration, and the content of imine groups is determined by Vertex-70 Fourier transform infrared spectrometer. Part of the hollow fiber is cut, fully ground, and pressed into KBr tablets with a scanning range of 4000-400 cm-1 , resolution 4cm -1 , the number of scans is 2 times.

[0064] The separation system for selectively removing acetylene impurities from dry gas of the present invention (such as Figure 1, comprising: 101 is a dehydrogen sulfide tower, 102 is a dehydrogen sulfide tower kettle circulation pump, 103 is a membrane extraction component, 104 is an acetylene stripping rich liquid buffer tank, 112 is a hydrogenation reaction inlet and outlet heat exchanger, 105 is a hydrogenation reaction feed heater, 106 is a hydrocarbonation tail gas heater, 107 is a hydrogenation reactor, 108 is a hydrogenation product gas-liquid separation tank, 109 is a hydrogenation liquid product material delivery pump, 113 is an acetylene stripping lean liquid cooler, 110 is a water washing tower, 111 is a water washing tower kettle circulation pump, 201 is a raw material dry gas inlet, 202 is a desulfurizer inlet, 203 is a desulfurizer outlet, 204 is a hydrocarbonation tail gas inlet, 205 is a hydrocarbonation tail gas outlet, 206 is a water washing tower fresh water replenishment port, 207 is a water washing water discharge port, and 208 is a water washing purified dry gas outlet. The separation process is as follows: the raw dry gas enters the dehydrogen sulfide tower 101 through the raw dry gas inlet 201 (for example, from catalytic cracking, thermal cracking, delayed coking, and hydrocracking in a refinery), contacts with the desulfurizer that enters the dehydrogen sulfide tower through the desulfurizer inlet 202, separates and removes hydrogen sulfide impurities and solid dust in the dry gas raw material, and the desulfurized and purified dry gas at the top of the dehydrogen sulfide tower 101 enters the inner cavity of the modified hollow fiber membrane of the membrane extraction component 103, and the acetylene impurities in the dry gas are penetrated and absorbed by the hollow fiber membrane, and the modified The dry gas coming out of the inner cavity of the hollow fiber membrane is collected and then enters the acetylene stripping rich liquid buffer tank 104 for gas-liquid separation and foam removal, and then enters the water washing tower 110, wherein the water washing medium enters the water washing tower through the fresh water replenishment port 206 of the water washing tower, and the water washing medium after work is discharged from the water washing water discharge port 207. The purified dry gas after removing the trace alkaline impurities in the deacetylated purified dry gas is discharged from the water washing purified dry gas outlet 208, and then enters the subsequent alkylation reaction system to react with benzene to produce ethylbenzene, propylbenzene, butylbenzene, etc. The acetylene stripping lean liquid enters the shell side of the membrane extraction component 103, contacts the outer wall of the modified hollow fiber membrane, and the absorbed acetylene impurities are permeated and mass transferred to the acetylene stripping lean liquid under the promotion of concentration difference, so as to obtain acetylene stripping rich liquid, and then enters the acetylene stripping rich liquid buffer tank 104, is heated by the hydrogenation reaction inlet and outlet heat exchanger 112 and the hydrogenation reaction feed heater 105 in sequence, and is mixed with the alkylated tail gas (from the alkylated tail gas inlet 204) heated by the alkylated tail gas heater 106, and enters the hydrogenation reactor 107 to remove the acetylene impurities in the acetylene stripping rich liquid. The gas-liquid mixture from the outlet of the hydrogenation reactor 107 enters the hydrogenation product gas-liquid separation tank 108 for separation, and the hydrocarbonized tail gas after the reaction and the ethylene, ethane and other components generated by the reaction are transported to the outside through the hydrocarbonized tail gas outlet 205. The liquid phase material of the hydrogenation product gas-liquid separation tank 108, that is, the acetylene stripping rich liquid after regeneration, is transported to the hydrogenation reaction inlet and outlet heat exchanger 112 through the hydrogenation liquid phase product material delivery pump 109, and is heat exchanged with the feed of the hydrogenation reactor 107, and then cooled by the acetylene stripping lean liquid cooler 113 and enters the membrane extraction component 103.

[0065] [Example 1]

[0066] The dry gas raw material described in this embodiment is derived from catalytic cracking in a refinery, and the dry gas composition, by volume ratio, includes: 17.6329% methane, 9.0708% ethane, 18.3310% ethylene, 0.2080% propane, 1.0190% propylene, 0.0996% isobutane, 0.0153% normal butane, 0.0058% trans-butene, 0.0178% normal butene, 0.0418% isobutene, 0.0001% cis-butene, 0.1530% oxygen, 16.2566% nitrogen, 30.3531% hydrogen, 1.6817% carbon monoxide, 2.9997% carbon dioxide, 0.0001% 1,3-butadiene, 1.2722% alkanes or alkenes with a carbon content of more than five, 0.0002% ammonia, 0.0008% hydrogen sulfide, 0.0114% acetylene, and 0.8289% other components.

[0067] The separation process of this embodiment is the same as Figure 1 As shown, the method for selectively removing acetylene impurities from dry gas comprises:

[0068] S1, the raw dry gas is subjected to the removal of hydrogen sulfide to obtain desulfurized purified dry gas;

[0069] S2, extracting and stripping the desulfurized purified dry gas using a membrane extraction assembly having the deacetylide extraction membrane therein; wherein the desulfurized purified dry gas and the acetylide stripping lean liquid flow through the inner cavity and outer wall of the modified hollow fiber, respectively, to obtain the deacetylide purified dry gas and the acetylide stripping rich liquid;

[0070] S3, the deacetylated purified dry gas is washed with water in a water washing tower to obtain washed purified dry gas;

[0071] S4, the acetylene stripping rich liquid is mixed with the preheated hydrocarbonation tail gas after heat exchange and enters the hydrogenation reactor to remove the acetylene in the acetylene stripping rich liquid, and the acetylene stripping lean liquid is obtained after gas-liquid separation; the obtained acetylene stripping lean liquid can be returned to step S2 for continued use.

[0072] In step S1, the desulfurization tower is a conventional packed tower. The desulfurizer and the raw dry gas are in countercurrent contact in the tower body. The number of theoretical plates of the desulfurization tower is 8, the desulfurization temperature is 35°C, and the desulfurization pressure is 0.7MPaG. The desulfurizer is N-methyldiethanolamine. The dosage ratio of the raw dry gas to the desulfurizer is, by volume, 75, and the mass concentration of the desulfurizer is 27.5%.

[0073] In step S2, the interior of the membrane extraction component is filled with a deacetylenic extraction membrane, i.e., a modified hollow fiber membrane, and the acetylenes in the desulfurized purified dry gas are infiltrated and extracted through the modified hollow fiber membrane to reach the main body and the outside of the modified hollow fiber membrane. Mass transfer is achieved with the acetylenic back-extraction lean liquid under the promotion of the concentration gradient, and finally the acetylenes in the desulfurized purified dry gas are transferred to the acetylenic back-extraction lean liquid, so that the acetylenes in the desulfurized purified dry gas are effectively removed.

[0074] The preparation method of the modified hollow fiber membrane comprises: preparing a casting solution containing a first modifier, a core solution and an outer gel bath, and then performing hollow fiber spinning and drying by a conventional method to obtain a hollow fiber membrane. Then, the hollow fiber membrane is swollen, treated with a second modifier, treated with a third modifier and post-modification treatment to obtain a modified hollow fiber membrane.

[0075] The first modifier is polyetherimide and polyacrylamide, wherein the mass ratio of polyetherimide to polyacrylamide is 14:6; the molecular weight of polyetherimide is 7700, and the molecular weight of polyacrylamide is 10100. The preparation conditions of the hollow fiber membrane are as follows: polypropylene (molecular weight is 45000), N-methylpyrrolidone, diethylene glycol, and the first modifier are in a mass ratio of 25:125:4:20, stirred at 110°C for 36 hours, and then allowed to stand and degas for 7.5 hours to obtain the casting solution. The core liquid composition is N-methylpyrrolidone: water = 5:95 in a mass ratio. The outer gel bath composition is desalted water. The inner diameter of the spinneret is 0.6 mm, the outer diameter is 1.8 mm, the temperature of the core liquid and the outer gel bath is 1.5°C, the air gap height is 3 cm, the collection rate is free fall, the casting liquid flow rate is 8.5 ml / min, the casting liquid pressure in the spinneret is 200 kPa (gauge pressure), the core liquid flow rate is 5 ml / min, the ambient temperature is 25°C, the ambient humidity is 60%, the casting liquid and the core liquid, the outer gel bath undergo solvent exchange and phase solidification to form a hollow fiber membrane blank. The hollow fiber embryo is washed with desalted water 6 times, methanol 6 times, and n-hexane 6 times, and then dried in a nitrogen atmosphere at 25°C to obtain a hollow fiber membrane.

[0076] The hollow fiber swelling agent was toluene, the swelling temperature was 100° C., the swelling time was 8.5 hours, and the volume ratio of the swelling agent to the hollow fiber membrane was 3.5.

[0077] The second modifier is 1,3,5-trichlorobenzene, anhydrous zinc chloride and toluene, and the mass fraction is 1,3,5-trichlorobenzene: anhydrous zinc chloride: toluene = 10:2:150. The conditions for treating with the second modifier are as follows: the second modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line velocity is 0.35 m / s, the treatment temperature is 45°C, and the treatment time is 30 minutes. After treating the hollow fiber membrane with the second modifier, a modified hollow fiber membrane intermediate is obtained.

[0078] The modified hollow fiber membrane intermediate is subjected to a third modification treatment and a third modification post-treatment to obtain a modified hollow fiber membrane. The third modifier is poly(propylene imine)-hexadecylamine, sodium hydroxide and toluene, and the weight fractions are poly(propylene imine)-hexadecylamine: sodium hydroxide: toluene = 13:3.5:150. The molecular weight of the poly(propylene imine)-hexadecylamine is 1685. The conditions for the third modifier treatment are as follows: the third modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line velocity is 0.35 m / s, the treatment temperature is 60°C, and the treatment time is 10 minutes.

[0079] The third post-modification treatment includes: dip coating the outer wall of the hollow fiber membrane with a toluene solution of 5.7% polydimethylsiloxane by mass for 4.5 seconds, followed by drying in a 60°C vacuum drying oven with a pressure (absolute pressure) of 65kPa for 6 hours; then soaking in ethanol at a temperature of 50°C for 3 times and each soaking time of 2.5 hours; then soaking in a sodium hydroxide aqueous solution with a mass concentration of 10% at a temperature of 50°C for 3 times and each soaking time of 2.5 hours; soaking in desalted water at a temperature of 80°C for 3 times and each soaking time of 4 hours. The viscosity of polydimethylsiloxane is 9000 centipoise.

[0080] In the prepared modified hollow fiber membrane, the inner diameter of the modified hollow fiber is 0.6 mm, the thickness of the base membrane is 0.6 mm, the imine content in the base membrane is 2.1 mmol / g, and the amine content is 8.0 mmol / g; the imine content in the grafted layer is 3.4 mmol / g, the amine content is 12.2 mmol / g, and the thickness of the polydimethylsiloxane is 150 microns.

[0081] In step S2, the feed amount of the desulfurized purified dry gas is 30000Nm 3 / hour, the filling capacity of the modified hollow fiber membrane regular module is 35m 3 The cross-sectional arrangement density of the modified hollow fiber membrane in the modified hollow fiber membrane regular module is 45,000 pieces / m 2 The contact temperature of the dry gas passing through the inner cavity of the modified hollow fiber membrane was 35°C and the contact pressure (gauge pressure) was 700 kPa.

[0082] After the desulfurized and purified dry gas contacts the modified hollow fiber membrane, it can pass through the coalescer and then enter the water scrubber. The separation accuracy of the coalescer is 7 microns.

[0083] In step S2, the composition of the acetylene stripping lean solution includes N,N-dimethylformamide and 1,2-propylene glycol, wherein the mass content of N,N-dimethylformamide is 85%, and the mass content of 1,2-propylene glycol is 15%. The temperature at which the acetylene stripping lean solution and the modified hollow fiber membrane are in contact is 35°C and the pressure is 0.7MPaG. The gas-liquid volume ratio of the desulfurized purified dry gas to the acetylene stripping lean solution is 550.

[0084] In step S3, the number of theoretical plates of the water washing tower is 7, the water washing temperature is 35°C, the water washing pressure is 0.7MPaG, the water washing water is industrial fresh water, and the gas-water ratio is 55 by volume.

[0085] In step S4, the acetylene stripping rich liquid is contacted with the acetylene stripping lean liquid after thermal degassing to recover heat, and then heated to 65°C by a heat exchanger, and then mixed with the hydrocarbon tail gas of the ethylbenzene unit heated to 65°C by a heat exchanger, and then enters the hydrogenation reactor. The hydrogenation reactor is equipped with a nickel-iron-copper alloy catalyst. The nickel-iron-copper alloy catalyst is calculated by mass fraction, nickel: iron: copper = 85:7.5:2.1. The preparation method of the nickel-iron-copper alloy catalyst is: aluminum, nickel, iron, and copper are calculated by mass fraction, aluminum: nickel: iron: copper = 400:85:7.5:2.1, mixed, heated to 1700°C to melt evenly, quenched at 125°C, broken into 30 mesh, and then treated with a sodium hydroxide aqueous solution with a mass concentration of 40% at 30°C for 6 hours to obtain a nickel-iron-copper alloy catalyst. The reaction temperature of the hydrogenation reactor is 65°C, and the reaction mass space velocity is 2h based on the acetylene stripping rich liquid. -1 The ratio of the hydrocarbon tail gas to the alkyne stripping rich liquid is, in terms of the molar ratio of hydrogen to alkyne, hydrogen:alkyne=12.5:1.

[0086] The acetylenic content in the deacetylened purified dry gas obtained in step S2 is 6 ppm, and the deacetylened purified dry gas can meet the requirements for long-term operation of the ethylbenzene alkylation catalyst.

[0087] [Example 2]

[0088] The dry gas raw material described in this embodiment is the same as that in embodiment 1. The separation process of this embodiment is the same as that in embodiment 1.

[0089] In step S1, the desulfurization tower is a conventional packed tower. The desulfurizer and the raw dry gas are in countercurrent contact in the tower body. The number of theoretical plates of the desulfurization tower is 10, the desulfurization temperature is 45°C, and the desulfurization pressure is 0.9MPaG. The desulfurizer is N-methyldiethanolamine. The dosage ratio of the raw dry gas to the desulfurizer is, by volume, 55, and the mass concentration of the desulfurizer is 33%.

[0090] In step S2, the interior of the membrane extraction component is filled with a deacetylated extraction membrane, i.e., a modified hollow fiber membrane, and the modified hollow fiber membrane is used to permeate and extract the acetylide in the desulfurized purified dry gas, so that the acetylide reaches the main body and the outside of the modified hollow fiber membrane, and then the mass transfer is achieved by the acetylide stripping lean solution under the promotion of the concentration gradient, and finally the acetylide in the desulfurized purified dry gas is transferred to the acetylide stripping lean solution, so that the acetylide in the desulfurized purified dry gas is effectively removed. The preparation method of the modified hollow fiber membrane comprises: preparing a casting liquid, a core liquid, and an external gel bath containing a first modifier, and then performing hollow fiber spinning and drying by a conventional method to obtain a hollow fiber membrane. Subsequently, the hollow fiber membrane is swollen, treated with a second modifier, treated with a third modifier, and treated after modification to obtain a modified hollow fiber membrane.

[0091] The first modifier is polyetherimide and polyacrylamide, wherein the mass ratio of polyetherimide to polyacrylamide is 17:5; the molecular weight of polyetherimide is 6400, and the molecular weight of polyacrylamide is 8500. The preparation conditions of the hollow fiber membrane are as follows: polypropylene (molecular weight is 45000), N-methylpyrrolidone, diethylene glycol, and the first modifier are in a mass ratio of 22:145:5:25, stirred at 125°C for 45 hours, and then allowed to stand and degas for 9 hours to obtain a casting solution. The core liquid composition is N-methylpyrrolidone: water = 3:97 by mass ratio. The outer gel bath composition is desalted water. The inner diameter of the spinneret is 0.4 mm, the outer diameter is 1.8 mm, the temperature of the core liquid and the outer gel bath is 0.5°C, the air gap height is 3.5 cm, the collection rate is free fall, the casting liquid flow rate is 7.5 ml / min, the casting liquid pressure in the spinneret is 150 kPa (gauge pressure), the core liquid flow rate is 4 ml / min, the ambient temperature is 22°C, the ambient humidity is 65%, the casting liquid and the core liquid, the outer gel bath undergo solvent exchange and phase separation solidification to form a hollow fiber membrane blank. The hollow fiber blank was washed with desalted water 7 times, methanol 7 times, and n-hexane 7 times, and then dried in a nitrogen atmosphere at 22°C to obtain a hollow fiber membrane.

[0092] The hollow fiber swelling agent was toluene, the swelling temperature was 110° C., the swelling time was 11 hours, and the volume ratio of the swelling agent to the hollow fiber membrane was 4.

[0093] The second modifier is 1,3,5-trichlorobenzene, anhydrous zinc chloride and toluene, and the mass fraction is 1,3,5-trichlorobenzene: anhydrous zinc chloride: toluene = 14:2.5:120. The conditions for treatment with the second modifier are as follows: the second modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line velocity is 0.25 m / s, the treatment temperature is 55°C, and the treatment time is 35 minutes. After the hollow fiber membrane is treated with the second modifier, a modified hollow fiber membrane intermediate is obtained.

[0094] The modified hollow fiber membrane intermediate is subjected to a third modification treatment and a third modification post-treatment to obtain a modified hollow fiber membrane. The third modifier is poly(propylene imine)-hexadecylamine, sodium hydroxide and toluene, and the weight fractions are poly(propylene imine)-hexadecylamine: sodium hydroxide: toluene = 17:4.5:120. The molecular weight of the poly(propylene imine)-hexadecylamine is 1685. The conditions for the third modifier treatment are as follows: the third modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line velocity is 0.25 m / s, the treatment temperature is 78°C, and the treatment time is 14 minutes.

[0095] The third post-modification treatment includes: dip coating the outer wall of the hollow fiber membrane with a toluene solution of 4.2% polydimethylsiloxane by mass for 3 seconds, followed by drying in a 55°C vacuum drying oven with a pressure (absolute pressure) of 75kPa for 7 hours; then soaking in ethanol at a temperature of 55°C for 4 times and each soaking for 3 hours; then soaking in a sodium hydroxide aqueous solution with a mass concentration of 13% at a temperature of 55°C for 4 times and each soaking for 3 hours; soaking in desalted water at a temperature of 85°C for 4 times and each soaking for 5 hours. The viscosity of polydimethylsiloxane is 8300 centipoise.

[0096] In the prepared modified hollow fiber membrane, the inner diameter of the modified hollow fiber is 0.4 mm, the thickness of the base membrane is 0.7 mm, the imine content in the base membrane is 2.8 mmol / g, and the amine content is 11.3 mmol / g; the imine content in the grafted layer is 4.4 mmol / g, the amine content is 17.5 mmol / g, and the thickness of the polydimethylsiloxane is 120 microns.

[0097] In step S2, the feed amount of the desulfurized purified dry gas is 20000Nm 3 / hour, the filling capacity of the modified hollow fiber membrane regular module is 38m 3 The cross-sectional arrangement density of the modified hollow fiber membrane in the modified hollow fiber membrane regular module is 55,000 pieces / m 2 The contact temperature of the dry gas passing through the inner cavity of the modified hollow fiber membrane is 45°C and the contact pressure (gauge pressure) is 900 kPa.

[0098] After the desulfurized and purified dry gas contacts the modified hollow fiber membrane, it can pass through the coalescer and then enter the water scrubber. The separation accuracy of the coalescer is 6 microns.

[0099] In step S3, the number of theoretical plates of the water washing tower is 9, the water washing temperature is 25°C, the water washing pressure is 0.9 MPaG, the water washing water is industrial fresh water, and the gas-water ratio is 45 by volume.

[0100] In step S2, the composition of the acetylene stripping lean solution includes N,N-dimethylformamide and 1,2-propylene glycol, wherein the mass content of N,N-dimethylformamide is 86%, and the mass content of 1,2-propylene glycol is 14%. The temperature at which the acetylene stripping lean solution and the modified hollow fiber membrane are in contact is 45° C. and the pressure is 0.9 MPaG. The gas-liquid volume ratio of the desulfurized purified dry gas to the acetylene stripping lean solution is 400.

[0101] In step S4, the acetylene stripping rich liquid is contacted with the acetylene stripping lean liquid after thermal degassing to recover heat, and then heated to 75°C by a heat exchanger, and then mixed with the hydrocarbon tail gas of the ethylbenzene unit heated to 75°C by a heat exchanger, and then enters the hydrogenation reactor. The hydrogenation reactor is equipped with a nickel-iron-copper alloy catalyst. The nickel-iron-copper alloy catalyst is calculated by mass fraction, nickel: iron: copper = 87:9.5:3.3. The preparation method of the nickel-iron-copper alloy catalyst is: aluminum, nickel, iron, and copper, calculated by mass fraction, aluminum: nickel: iron: copper = 450:87:9.5:3.3, mixed, heated to 1750°C to melt evenly, quenched at 110°C, broken into 40 mesh, and then treated with a sodium hydroxide aqueous solution with a mass concentration of 45% at 35°C for 7 hours to obtain a nickel-iron-copper alloy catalyst. The reaction temperature of the hydrogenation reactor is 75°C, and the reaction mass space velocity is 1.5h based on the acetylene stripping rich liquid. -1 The ratio of the hydrocarbon tail gas to the alkyne stripping rich liquid is, in terms of the molar ratio of hydrogen to alkyne, hydrogen:alkyne=18:1.

[0102] The acetylenic content in the deacetylated purified dry gas obtained in step S2 is 3 ppm, and the deacetylated purified dry gas can meet the requirements for long-term operation of the ethylbenzene alkylation catalyst.

[0103] [Example 3]

[0104] The dry gas raw material described in this embodiment is the same as that in Example 1.

[0105] In step S1, the desulfurization tower is a conventional packed tower. The desulfurizer and the raw dry gas are in countercurrent contact in the tower body. The number of theoretical plates of the desulfurization tower is 6, the desulfurization temperature is 25°C, and the desulfurization pressure is 0.6MPaG. The desulfurizer is N-methyldiethanolamine. The dosage ratio of the raw dry gas to the desulfurizer is, by volume, 90, and the mass concentration of the desulfurizer is 25%.

[0106] In step S2, the interior of the membrane extraction component is filled with a deacetylated extraction membrane, i.e., a modified hollow fiber membrane, and the modified hollow fiber membrane is used to permeate and extract the acetylide in the desulfurized purified dry gas, so that the acetylide reaches the main body and the outside of the modified hollow fiber membrane, and then the mass transfer is achieved by the acetylide stripping lean solution under the promotion of the concentration gradient, and finally the acetylide in the desulfurized purified dry gas is transferred to the acetylide stripping lean solution, so that the acetylide in the desulfurized purified dry gas is effectively removed. The preparation method of the modified hollow fiber membrane comprises: preparing a casting liquid, a core liquid, and an external gel bath containing a first modifier, and then performing hollow fiber spinning and drying by a conventional method to obtain a hollow fiber membrane. Subsequently, the hollow fiber membrane is swollen, treated with a second modifier, treated with a third modifier, and treated after modification to obtain a modified hollow fiber membrane.

[0107] The first modifier is polyetherimide and polyacrylamide, wherein the mass ratio of polyetherimide to polyacrylamide is 11:7; the molecular weight of polyetherimide is 9000, and the molecular weight of polyacrylamide is 11300. The preparation conditions of the hollow fiber membrane are as follows: polypropylene (molecular weight is 45000), N-methylpyrrolidone, diethylene glycol, and the first modifier are in a mass ratio of 27:115:3:15, stirred at 95°C for 30 hours, and then allowed to stand and degas for 6 hours to obtain a casting solution. The core liquid composition is N-methylpyrrolidone: water = 7:93 by mass ratio. The outer gel bath composition is desalted water. The inner diameter of the spinneret is 0.8 mm, the outer diameter is 1.8 mm, the temperature of the core liquid and the outer gel bath is 2.5°C, the air gap height is 2.5 cm, the collection rate is free fall, the casting liquid flow rate is 9.5 ml / min, the casting liquid pressure in the spinneret is 250 kPa (gauge pressure), the core liquid flow rate is 6 ml / min, the ambient temperature is 28°C, the ambient humidity is 55%, the casting liquid and the core liquid, the outer gel bath undergo solvent exchange and phase separation solidification to form a hollow fiber membrane blank. The hollow fiber embryo is washed with desalted water 5 times, methanol 5 times, and n-hexane 5 times, and then dried in a nitrogen atmosphere at 28°C to obtain a hollow fiber membrane.

[0108] The hollow fiber swelling agent is toluene, the swelling temperature is 90° C., the swelling time is 6 hours, and the volume ratio of the swelling agent to the hollow fiber membrane is 3.

[0109] The second modifier is 1,3,5-trichlorobenzene, anhydrous zinc chloride and toluene, and the mass fraction is 1,3,5-trichlorobenzene: anhydrous zinc chloride: toluene = 6:1.5:180. The conditions for treatment with the second modifier are as follows: the second modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line velocity is 0.45 m / s, the treatment temperature is 35°C, and the treatment time is 25 minutes. After the hollow fiber membrane is treated with the second modifier, a modified hollow fiber membrane intermediate is obtained.

[0110] The modified hollow fiber membrane intermediate is subjected to a third modification treatment and a third modification post-treatment to obtain a modified hollow fiber membrane. The third modifier is poly(propylene imine)-hexadecylamine, sodium hydroxide and toluene, and the ratio of poly(propylene imine)-hexadecylamine: sodium hydroxide: toluene is 9:2.5:180 by weight. The molecular weight of the poly(propylene imine)-hexadecylamine is 1685. The conditions for the third modifier treatment are as follows: the third modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line velocity is 0.45 m / s, the treatment temperature is 45°C, and the treatment time is 6 minutes.

[0111] The third post-modification treatment includes: dip coating the outer wall of the hollow fiber membrane with a toluene solution of 7.5% polydimethylsiloxane by mass for 6 seconds, followed by drying in a 65°C vacuum drying oven, the pressure (absolute pressure) of the vacuum drying oven is 55kPa, and the drying time is 5 hours; then soaking in ethanol at a temperature of 45°C, the number of soaking times is 2 times, and the soaking time is 2 hours each time; then soaking in a sodium hydroxide aqueous solution with a mass concentration of 6%, the soaking temperature is 45°C, the number of soaking times is 2 times, and the soaking time is 2 hours each time; soaking in desalted water at a temperature of 75°C, the number of soaking times is 2 times, and the soaking time is 2.5 hours each time. Among them, the viscosity of polydimethylsiloxane is 11000 centipoise.

[0112] In the prepared modified hollow fiber membrane, the inner diameter of the modified hollow fiber is 0.8 mm, the thickness of the base membrane is 0.5 mm, the imine content in the base membrane is 1.5 mmol / g, and the amine content is 4.6 mmol / g; the imine content in the grafted layer is 2.5 mmol / g, the amine content is 7.1 mmol / g, and the thickness of the polydimethylsiloxane is 180 microns.

[0113] In step S2, the feed amount of the desulfurized purified dry gas is 40000Nm 3 / hour, the filling capacity of the modified hollow fiber membrane regular module is 32m 3 The cross-sectional arrangement density of the modified hollow fiber membrane in the modified hollow fiber membrane regular module is 35,000 pieces / m 2 The contact temperature of the dry gas passing through the inner cavity of the modified hollow fiber membrane was 25°C and the contact pressure (gauge pressure) was 600 kPa.

[0114] After the desulfurized and purified dry gas contacts the modified hollow fiber membrane, it can pass through the coalescer and then enter the water scrubber. The separation accuracy of the coalescer is 8 microns.

[0115] In step S3, the number of theoretical plates of the water washing tower is 5, the water washing temperature is 45°C, the water washing pressure is 0.6MPaG, the water washing water is industrial fresh water, and the gas-water ratio is 65 by volume.

[0116] In step S2, the composition of the acetylene stripping lean solution includes N,N-dimethylformamide and 1,2-propylene glycol, wherein the mass content of N,N-dimethylformamide is 82% and the mass content of 1,2-propylene glycol is 18%. The temperature at which the acetylene stripping lean solution and the modified hollow fiber membrane are in contact is 25° C. and the pressure is 0.6 MPaG. The gas-liquid volume ratio of the desulfurized purified dry gas to the acetylene stripping lean solution is 700.

[0117] In step S4, the acetylene stripping rich liquid is contacted with the acetylene stripping lean liquid after thermal degassing to recover heat, and then heated to 55°C by a heat exchanger, and then mixed with the hydrocarbon tail gas of the ethylbenzene unit heated to 55°C by a heat exchanger, and then enters the hydrogenation reactor. The hydrogenation reactor is equipped with a nickel-iron-copper alloy catalyst. The nickel-iron-copper alloy catalyst is calculated by mass fraction, nickel: iron: copper = 82:6:1. The preparation method of the nickel-iron-copper alloy catalyst is: aluminum, nickel, iron, and copper are calculated by mass fraction, aluminum: nickel: iron: copper = 350:82:6:1, mixed, heated to 1650°C to melt evenly, quenched at 140°C, broken into 20 meshes, and then treated with a sodium hydroxide aqueous solution with a mass concentration of 35% at 25°C for 5 hours to obtain a nickel-iron-copper alloy catalyst. The reaction temperature of the hydrogenation reactor is 55°C, and the reaction mass space velocity is 2.5h based on the acetylene stripping rich liquid. -1 The ratio of the hydrocarbon tail gas to the alkyne stripping rich liquid is, in terms of the molar ratio of hydrogen to alkyne, hydrogen:alkyne=7:1.

[0118] The acetylenic content in the deacetylened purified dry gas obtained in step S2 is 9.6 ppm, and the deacetylened purified dry gas can meet the requirements for long-term operation of the ethylbenzene alkylation catalyst.

[0119] [Example 4]

[0120] The separation process for the dry gas raw material in this embodiment is the same as that in embodiment 2. The only difference between this embodiment and embodiment 2 is the dry gas raw material used. The dry gas composition, by volume, includes: methane 14.9171%, ethane 9.0558%, ethylene 16.0016%, propane 0.1716%, propylene 0.8819%, isobutane 0.0888%, n-butane 0.0130%, trans-butene 0.0052%, n-butene 0.0159%, isobutene 0.0375%, cis-butene 0.0001%, oxygen 0.1461%, nitrogen 13.9689%, hydrogen 28.6106%, carbon monoxide 1.3302%, carbon dioxide 2.6619%, 1,3-butadiene 0.0001%, alkanes or alkenes with a carbon content of more than five carbon atoms 1.2283%, ammonia 0.0002%, hydrogen sulfide 0.0006%, acetylene 0.0069%, and other components 0.7861%.

[0121] The acetylenic content in the deacetylated purified dry gas obtained in step S2 is 0.2 ppm, and the deacetylated purified dry gas can meet the requirements for long-term operation of the ethylbenzene alkylation catalyst.

[0122] [Example 5]

[0123] The separation process for the dry gas raw material in this embodiment is the same as that in embodiment 2. The only difference between this embodiment and embodiment 2 is the dry gas raw material used. The dry gas composition, by volume, includes: methane 17.4240%, ethane 10.0384%, ethylene 19.2733%, propane 0.2123%, propylene 0.9130%, isobutane 0.0909%, n-butane 0.0149%, trans-butene 0.0058%, n-butene 0.0198%, isobutene 0.0385%, cis-butene 0.0001%, oxygen 0.1567%, nitrogen 14.5237%, hydrogen 30.2879%, carbon monoxide 1.6499%, carbon dioxide 3.1818%, 1,3-butadiene 0.0001%, alkanes or alkenes with a carbon content of more than five carbon atoms 1.2416%, ammonia 0.0002%, hydrogen sulfide 0.0008%, acetylene 0.0183%, and other components 0.9076%.

[0124] The acetylenic content in the deacetylated purified dry gas obtained in step S2 is 9.3 ppm, and the deacetylated purified dry gas can meet the requirements for long-term operation of the ethylbenzene alkylation catalyst.

[0125] [Comparative Example 1]

[0126] Referring to the catalytic hydrogenation method of patent CN101704701A, 42.0 mg of potassium hydroxide, 89.0 mg of mixed dry gas, and 22.3 mg of Pd(OAc) were added to a 50 mL glass reaction tube with a lid, and the air in the reaction tube was replaced with nitrogen. 1 mL of DMF was added under a nitrogen atmosphere, and then the reaction tube was sealed, and the reaction tube was placed in an oil bath and heated to 145°C. After stirring and keeping warm for 6 hours, it was cooled to room temperature. The raw dry gas was deacetylenic components, and the dry gas raw material was the same as in Example 1. Acetylene was reduced from 0.0114% to less than 1 ppm, ethylene content was reduced from 18.3310% to 15.3980%, and ethane content was increased from 9.0708% to 12.2132%. Ethylene loss was large.

[0127] The above describes the specific implementation of the present invention in detail, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the various technical features being combined in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for selectively removing acetylene impurities from dry gas, comprising: S1, the raw dry gas is subjected to the removal of hydrogen sulfide to obtain desulfurized purified dry gas; S2, extracting and stripping the desulfurized purified dry gas using a membrane extraction assembly having a deacetylide extraction membrane therein; wherein the deacetylide extraction membrane is a hollow fiber membrane, and the desulfurized purified dry gas and the acetylide stripping lean liquid flow through the inner cavity and outer wall of the hollow fiber, respectively, to obtain the deacetylide purified dry gas and the acetylide stripping rich liquid; S3, the deacetylated purified dry gas is washed with water in a water washing tower to obtain washed purified dry gas; The deacetylation extraction membrane described in step S2 is a modified hollow fiber membrane, including a base membrane, a grafted layer and an outer layer, wherein the base membrane has an imine content of 1.4 to 3.0 mmol / g and an amine content of 4.4 to 11.8 mmol / g; the grafted layer has an imine content of 2.3 to 4.5 mmol / g and an amine content of 6.9 to 17.7 mmol / g; and the outer layer is a polydimethylsiloxane layer with a thickness of 100 to 200 microns.

2. The method according to claim 1, characterized in that The inner diameter of the deacetylation extraction membrane in step S2 is 0.3-1.0 mm, and / or the thickness of the base membrane is 0.4-0.8 mm.

3. The method according to claim 1, characterized in that In the dealkyne extraction membrane described in step S2, the viscosity of the polydimethylsiloxane is 7000-12000 centipoise.

4. The method according to claim 1, characterized in that In the deacetylation extraction membrane described in step S2, the base membrane is a polypropylene membrane modified by a first modifier; the first modifier is polyetherimide and polyacrylamide, wherein the mass ratio of polyetherimide to polyacrylamide is (10-18): (4-8).

5. The method according to claim 4, characterized in that In the deacetylation extraction membrane described in step S2, the molecular weight of polyetherimide is 6300-9100, and the molecular weight of polyacrylamide is 8300-12000.

6. The method according to claim 4, characterized in that In the deacetylening extraction membrane described in step S2, the molecular weight of the polypropylene is 40,000-50,000.

7. The method according to claim 1, characterized in that The preparation method of the deacetylated extraction membrane described in step S2 comprises: preparing a casting liquid, a core liquid and an outer gel bath containing a first modifier, and then adopting hollow fiber spinning and drying to obtain a hollow fiber membrane, i.e., a base membrane; swelling the hollow fiber membrane, treating it with a second modifier, and treating it with a third modifier to coat it with a grafting layer; and then performing a third modification post-treatment on the hollow fiber membrane coated with the grafting layer to coat it with a polydimethylsiloxane layer to obtain a deacetylated extraction membrane.

8. The method according to claim 7, characterized in that In the method for preparing the deacetylation extraction membrane described in step S2, the first modifier is polyetherimide and polyacrylamide, wherein the mass ratio of polyetherimide to polyacrylamide is (10-18): (4-8).

9. The method according to claim 8, characterized in that In the first modifier described in step S2, the molecular weight of polyetherimide is 6300-9100, and the molecular weight of polyacrylamide is 8300-12000.

10. The method according to claim 7, characterized in that The casting liquid containing the first modifier includes: polypropylene, N-methylpyrrolidone, diethylene glycol, and the first modifier, in a mass ratio of (20-30): (100-150): (2-6): (14-26); the core liquid composition is N-methylpyrrolidone: water = (2-8): (92-98) in a mass ratio; and the outer gel bath composition is desalted water.

11. The method according to claim 10, characterized in that In the casting solution containing the first modifier, the molecular weight of the polypropylene is 40,000-50,000.

12. The method according to claim 7, characterized in that In the method for preparing the deacetylated extraction membrane described in step S2, the swelling agent used for swelling is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene, the swelling temperature is 80 to 120° C., the swelling time is 5 to 12 hours, and the volume ratio of the swelling agent to the hollow fiber membrane is 2 to 5; And / or, the second modifier is 1,3,5-trichlorobenzene, a catalyst and a solvent; the catalyst is selected from one of Lewis acids or Lewis bases; the solvent is selected from at least one of toluene, p-xylene, m-xylene and o-xylene; by mass, 1,3,5-trichlorobenzene: catalyst: solvent = (5-15): (1-3): (100-200); And / or, the conditions for the second modifier treatment are as follows: the second modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line velocity is 0.2 m / s to 0.5 m / s, the treatment temperature is 30°C to 60°C, and the treatment time is 20 to 40 minutes.

13. The method according to claim 12, characterized in that In the second modifier, the catalyst is at least one of anhydrous zinc chloride, anhydrous tin tetrachloride, and anhydrous aluminum chloride.

14. The method according to claim 7, characterized in that In the method for preparing the deacetylated extraction membrane described in step S2, the third modifier is poly(propyleneimine-hexadecylamine), sodium hydroxide and a solvent, and the solvent is selected from at least one of toluene, p-xylene, m-xylene and o-xylene; in terms of mass fractions, poly(propyleneimine-hexadecylamine): sodium hydroxide: solvent = (8-18): (2-5): (100-200).

15. The method according to claim 14, characterized in that In the third modifier, the molecular weight of polypropylene imine-hexadecylamine is 1600-1700.

16. The method according to claim 14, characterized in that The conditions for the third modifier treatment are as follows: the third modifier solution passes through the inner cavity of the hollow fiber membrane, the flow line speed is 0.2 m / s to 0.5 m / s, the treatment temperature is 40° C. to 80° C., and the treatment time is 5 to 15 minutes.

17. The method according to claim 7, characterized in that In the preparation method of the dealkyne extraction membrane described in step S2, the post-treatment agent used in the third modification post-treatment is a polydimethylsiloxane solution with a mass concentration of 4% to 8%, and the solvent is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene; the outer wall thickness of the modified hollow fiber membrane obtained by the third modification post-treatment is polydimethylsiloxane of 100 to 200 microns.

18. The method according to claim 17, characterized in that In the post-treatment agent used in the third modification post-treatment, the viscosity of polydimethylsiloxane is 7000-12000 centipoise.

19. The method according to claim 1, characterized in that In step S1, the volume content of acetylene in the raw dry gas is not less than 60 ppm.

20. The method according to claim 19, characterized in that In step S1, the volume content of acetylene in the raw dry gas is not less than 150 ppm.

21. The method according to claim 19 or 20, characterized in that In step S1, the volume content of acetylene in the raw dry gas is not higher than 300 ppm.

22. The method according to claim 1, characterized in that In step S1, a plate tower or a packed tower is used for desulfurization of hydrogen; the desulfurizer and the raw dry gas are in countercurrent contact in the tower body; the theoretical number of plates of the desulfurization tower is 5 to 11, the desulfurization temperature is 20 to 50° C., and the desulfurization pressure is 0.5 to 1.0 MPaG; the dosage ratio of the raw dry gas to the desulfurizer is 50 to 100 by volume; the desulfurizer is an alcohol amine; and the mass concentration of the desulfurizer is 20% to 35%.

23. The method according to claim 22, characterized in that The desulfurizing agent is at least one of diethanolamine and N-methyldiethanolamine.

24. The method according to claim 1, characterized in that In step S2, the contact temperature of the desulfurized purified dry gas when passing through the inner cavity of the modified hollow fiber membrane is 20-50° C., and the contact pressure is 500-1000 kPa; And / or, in step S2, the acetylene stripping lean solution comprises N,N-dimethylformamide and 1,2-propylene glycol, wherein the mass content of N,N-dimethylformamide is 78% to 90%, and the mass content of 1,2-propylene glycol is 10% to 22%; and / or, in step S2, the temperature at which the alkyne stripping lean solution contacts the deacetylening extraction membrane is 20-50° C. and the pressure is 0.5-1.0 MPaG; And / or, in step S2, the gas-liquid volume ratio of the desulfurized purified dry gas to the acetylene stripping lean liquid is 300-800.

25. The method according to claim 1, characterized in that In step S3, the theoretical plate number of the water washing tower is 4 to 10, the water washing temperature is 20 to 50° C., the water washing pressure is 0.5 to 1.0 MPaG; and the gas-water usage ratio is 40 to 70 by volume.

26. The method according to claim 1, characterized in that The method further comprises: S4, the acetylene stripping rich liquid is subjected to hydrogenation and deacetylation to obtain the acetylene stripping lean liquid.

27. The method according to claim 26, characterized in that In step S4, the acetylene stripping rich liquid is mixed with the preheated hydrocarbonation tail gas after heat exchange and enters the hydrogenation reactor to remove the acetylene in the acetylene stripping rich liquid.

28. The method according to claim 26, characterized in that In step S4, the obtained acetylene stripping lean solution is returned to step S2 for further use.

29. The method according to claim 27, characterized in that In step S4, the volume content of hydrogen in the alkylated tail gas is 6.3% to 60%; And / or, in step S4, the hydrogenation reactor is equipped with a nickel-iron-copper alloy catalyst; the nickel-iron-copper alloy catalyst has a mass fraction of nickel: iron: copper = (80-90): (5-10): (0.8-3.5); And / or, in step S4, the reaction temperature of the hydrogenation reactor is 50-80°C, and the reaction mass space velocity is 1-3h based on the acetylene stripping rich liquid. -1 ; The ratio of hydrocarbon tail gas to alkyne stripping rich liquid is calculated based on the molar ratio of hydrogen to alkyne, hydrogen:alkyne = (5-20):1.

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