Treatment method suitable for separating crude isopentene from cracked C5

Abstract

The method comprises the following steps: firstly, carrying out dimerization reaction to polymerize cyclopentadiene in C5 into dicyclopentadiene, carrying out rectification to remove dicyclopentadiene and part of m-pentadiene, and carrying out extractive distillation by using acetonitrile as a solvent to obtain crude isopentene in C5 cracking. The method comprises the following steps of: removing crude m-pentadiene and crude dicyclopentadiene from which isoprene is removed, separating high-purity isoprene from C5 components with very close boiling points, obtaining crude isopentene, mixing catalytic light gasoline, methanol and crude isopentene, respectively carrying out first-stage etherification reaction, catalytic distillation and etherification product separation, second-stage deep etherification, and methanol recovery, thereby obtaining the isoprene. The method has the advantages that the crude isopentene can be introduced into the light gasoline for etherification, high-quality gasoline blending components are produced, the additional value of the crude isopentene is increased, and the economic benefit of a whole plant is effectively improved; the processing technology and flow are simple and easy to implement, and the operability is high.

Description

Technical Field

[0001] The invention relates to a processing method, and more specifically, to a processing method suitable for separating crude isopentene by cracking carbon five, and belongs to the field of petrochemical industry. Background Art

[0002] At present, in the cracking carbon five separation operation process, when one ton of polymerization grade isoprene is produced, about 1.8 tons of crude isopentene can be produced as a byproduct. Crude isopentene is currently mainly used in gasoline, and less than 5% enters some fine chemical plants for secondary processing. However, when crude isopentene is added to gasoline, it cannot be added too much because it is rich in olefins and affects the saturated vapor pressure of gasoline. Therefore, it is easy to cause waste and reduce economic benefits. Although fine chemical plants can extract crude isopentene as a raw material for synthesizing petroleum resins, they can only extract a small part of the components to synthesize petroleum resins. The current utilization rate of crude isopentene is low. Therefore, in the field of petrochemicals, how to improve the utilization of crude isopentene is a trend of research and development. Summary of the invention

[0003] In order to solve the above-mentioned problems in the prior art, the present invention provides a method for separating crude isopentene by cracking C5, which has the technical characteristics of being able to convert crude isopentene into etherified gasoline to become a high-quality gasoline blending component and having significant economic benefits.

[0004] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0005] A method for separating crude isopentene by cracking C5, the method comprising the following steps:

[0006] Step 1) using cracked C5 introduced from the tank area as a raw material, and sending it into a double-ring polymerization reactor for dimerization reaction to polymerize cyclopentadiene in C5 into dicyclopentadiene; the double-ring polymerization reactor then enters a decarbonization tower through a pipeline, the upper end of the decarbonization tower is connected to a C4 refining tower through a pipeline, and the lower end of the decarbonization tower is connected to a pre-deweighting tower through a pipeline;

[0007] Step 2) obtaining isopentadiene and dicyclopentadiene products from the bottom of the pre-deweighting tower and sending them to a deweighting tower through a pipeline, preheating the C5 fraction of dimers extracted from the top of the pre-deweighting tower to 70° C., removing dicyclopentadiene and part of isopentadiene through an extraction feed water washing tower into which washing water is introduced, and then sending them to the upper part of an isoprene extraction distillation tower, introducing an acetonitrile solvent containing 5.0% (by weight) of water into the isoprene extraction distillation tower, discharging C5 alkanes, monoolefins and a small amount of isoprene with part of acetonitrile and water from the top of the isoprene extraction distillation tower, and sending them to a residual C5 water washing tower into which washing water is introduced, washing away the entrained acetonitrile through the residual C5 water washing tower, wherein the upper end of the residual C5 water washing tower is connected to a pipeline to send crude isopentene to a crude isopentene tank area and to a diene reactor as a raw material, and the lower end of the residual C5 water washing tower is connected to a pipeline to recover the solvent;

[0008] Step 3) firstly mix the catalytic light gasoline, methanol and the crude isopentene obtained at the upper end of the residual carbon five water washing tower, and send them into a methanol evolution device to obtain a mixture;

[0009] Step 4) The mixture is sent to the first etherification reactor and the second etherification reactor to carry out a first stage of etherification reaction, and then sent to the catalytic distillation tower with supplementary methanol, the gas phase discharged from the top of the catalytic distillation tower enters the bottom of the third etherification reactor to achieve a deep etherification reaction between the unreacted tertiary amylene in the catalytic distillation tower and methanol, and the etherified product generated after the reaction is cooled to 40° C. and then flows out from the top of the third etherification reactor into the methanol extraction tower, and the methanol is extracted from the residual carbon five into the water phase through the methanol extraction tower, and the residual carbon five flowing out from the top of the methanol extraction tower is dehydrated through a filter and a residual carbon five agglomerator, and then sent to a blending tank with the etherified gasoline flowing out from the bottom of the catalytic distillation tower to achieve mixing and then exit the device;

[0010] Step 5) The mixture of extraction water and methanol flowing out from the bottom of the methanol extraction tower is first purified by an extraction water purification tower, and then enters a methanol recovery tower after heat exchange to separate the extraction water and methanol. The extraction water flowing out from the bottom of the methanol recovery tower is cooled to 40°C and then circulated to the methanol extraction tower to achieve countercurrent contact between the extraction water from the bottom of the methanol recovery tower and the etherified product in the methanol extraction tower. Methanol flows out from the top of the methanol recovery tower and serves as methanol feed for the methanol evolver.

[0011] Preferably, the molar ratio of methanol after purification by the methanol purifier to tertiary carbon olefins in light gasoline is (1.3-1.5):1. After mixing and filtering according to this ratio, they enter the bottom of the No. 1 etherification reactor, and the tertiary carbon olefins and methanol are first subjected to etherification reaction in the catalyst bed of the No. 1 etherification reactor. The reaction products flow out from the top of the No. 1 etherification reactor and enter the No. 2 etherification reactor in series for heat exchange to continue the reaction, so that the tertiary carbon olefins in the gasoline continue to be converted into ether products. The reactants flowing out from the top of the No. 2 etherification reactor enter the catalytic distillation tower.

[0012] Preferably, the crude isopentene is stored in a pressure storage tank, the temperature is controlled to be ≮40° C., and the crude isopentene is mixed with catalytic light gasoline at a blending ratio of 10%.

[0013] Preferably, in step 4), the flow rate of methanol replenished in the catalytic distillation tower is controlled according to the methanol content in the material produced from the top of the catalytic distillation tower, and the etherified product oil produced from the bottom of the catalytic distillation tower is first cooled to 40° C. through heat exchange, and then mixed with the residual carbon five from the residual carbon five agglomerator, and then discharged from the device as the etherified gasoline product.

[0014] Preferably, the flow rate of crude isopentene is controlled to be no higher than 15% of the total feed flow rate of the methanol purifier.

[0015] Beneficial effects: Crude isopentene can be introduced into light gasoline for etherification to produce high-quality gasoline blending components, thereby increasing the added value of crude isopentene and effectively improving the economic benefits of the entire plant; the processing technology and process are simple and easy to implement, and have strong operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a crude isopentene production flow chart of the present invention.

[0017] Figure 2 The present invention is a flow chart of a light gasoline etherification device utilizing crude isopentene. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings, but the present invention is not limited to the following embodiments.

[0019] like Figure 1-2 The figure shows a specific embodiment of a method for separating crude isopentene by cracking C5. The embodiment is a method for separating crude isopentene by cracking C5, and the method comprises the following steps:

[0020] Step 1) using cracked C5 introduced from the tank area as a raw material, sending it into a double-ring polymerization reactor for dimerization reaction to polymerize cyclopentadiene in C5 into dicyclopentadiene; the double-ring polymerization reactor then enters a decarbonization tower through a pipeline, the upper end of the decarbonization tower is connected to a C4 refining tower through a pipeline, the upper end of the C4 refining tower sends refined C4 to the tank area, the lower end of the C4 refining tower sends other components to water washing, and the lower end of the decarbonization tower is connected to a pre-deweighting tower through a pipeline;

[0021] Step 2) obtain isoprene and dicyclopentadiene products from the bottom of the pre-deweighting tower and send them to a deweighting tower through a pipeline, preheat the C5 fraction of dimers taken out from the top of the pre-deweighting tower to 70° C., pass through an extraction feed water washing tower with washing water to remove dicyclopentadiene and part of isoprene (the bottom of the extraction feed water washing tower is connected to a sewage treatment device through a pipeline), and then send it to the upper part of an isoprene extraction distillation tower, pass an acetonitrile solvent containing 5.0% (by weight) water into the isoprene extraction distillation tower, and remove part of the C5 alkanes, monoolefins and a small amount of isoprene entrained Acetonitrile and water are discharged from the top of the isoprene extraction and distillation tower (the bottom of the isoprene extraction and distillation tower is connected to the solvent removal and analysis tower through a pipeline), and sent to a residual carbon five water washing tower into which washing water is introduced, and the entrained acetonitrile is washed away by the residual carbon five water washing tower, wherein the crude isopentene is sent to the crude isopentene tank area through a pipeline at the upper end of the residual carbon five water washing tower and is sent to the diene reactor as a raw material, and the solvent is recovered through a pipeline at the lower end of the residual carbon five water washing tower; the crude isopentene is stored in a pressure storage tank, the temperature is controlled to be ≮40° C., and the crude isopentene is mixed with catalytic light gasoline at a blending ratio of 10%;

[0022] Step 3) firstly mix the catalytic light gasoline, methanol and the crude isopentene obtained at the upper end of the residual carbon five water washing tower, and send them into a methanol evolution device to obtain a mixture;

[0023] Step 4) the mixture is sent to the first etherification reactor and the second etherification reactor to carry out a first stage of etherification reaction, and then sent to the catalytic distillation tower with supplementary methanol, the gas phase discharged from the top of the catalytic distillation tower enters the bottom of the third etherification reactor to achieve deep etherification reaction between the unreacted tertiary amylene in the catalytic distillation tower and methanol, the etherified product generated after the reaction is cooled to 40°C and then flows out from the top of the third etherification reactor into the methanol extraction tower, and the methanol is extracted from the residual carbon five to the water phase through the methanol extraction tower, the residual carbon five flowing out from the top of the methanol extraction tower is dehydrated through a filter and a residual carbon five agglomerator, and then is mixed with the etherified gasoline flowing out of the bottom of the catalytic distillation tower to achieve mixing and then exiting the device; in step 4), the flow rate of supplementary methanol in the catalytic distillation tower is controlled according to the methanol content in the material produced from the top of the catalytic distillation tower, the etherified product oil produced from the bottom of the catalytic distillation tower is first cooled to 40°C through heat exchange, and then mixed with the residual carbon five from the residual carbon five agglomerator, and then exits the device as an etherified gasoline product;

[0024] Step 5) The mixture of extraction water and methanol flowing out from the bottom of the methanol extraction tower is first purified by an extraction water purification tower, and then enters a methanol recovery tower after heat exchange to separate the extraction water and methanol. The extraction water flowing out from the bottom of the methanol recovery tower is cooled to 40°C and then circulated to the methanol extraction tower to achieve countercurrent contact between the extraction water from the bottom of the methanol recovery tower and the etherified product in the methanol extraction tower. Methanol flows out from the top of the methanol recovery tower and serves as methanol feed for the methanol evolver.

[0025] In a preferred embodiment, the molar ratio of methanol purified by a methanol purifier to tertiary olefins in light gasoline is (1.3-1.5):1. After being mixed and filtered according to this ratio, they enter the bottom of a No. 1 etherification reactor, and the tertiary olefins and methanol are first subjected to an etherification reaction on a catalyst bed of the No. 1 etherification reactor. The reaction products flow out from the top of the No. 1 etherification reactor and enter the No. 2 etherification reactor in series for heat exchange to continue the reaction, so that the tertiary olefins in the gasoline continue to be converted into ether products. The reactants flowing out from the top of the No. 2 etherification reactor enter a catalytic distillation tower.

[0026] In a preferred embodiment, the flow rate of crude isopentene is controlled to be no higher than 15% of the total feed flow rate of the methanol purifier.

[0027] The production of polymerization-grade isoprene in the technical case of this application is based on the cracking of C5 as raw material. First, a dimerization reaction is carried out to polymerize the cyclopentadiene in C5 into dicyclopentadiene. Dicyclopentadiene and part of isoprene are removed by distillation. Then, acetonitrile is used as a solvent and crude isoprene and dicyclopentadiene are removed by extractive distillation. High-purity isoprene is separated from the C5 components with very close boiling points, and crude isopentene is obtained. Crude isopentene is produced from the C5 water washing tower ( Figure 1 ), the properties of crude isopentene in this application are shown in the following tables (Table 1, Table 2).

[0028] Table 1 Composition and properties of crude isopentene

[0029] Analyze Project unit composition Isopentane %(mass fraction) 39.09 1,4-Pentadiene %(mass fraction) 3.03 2-Butyne %(mass fraction) 0.07 n-pentene %(mass fraction) 5.69 2-Methyl-1-butene %(mass fraction) 16.65 n-Pentane %(mass fraction) 24.27 Isoprene %(mass fraction) 1.65 trans-2-pentene %(mass fraction) 3.91 1-Penten-3-yne %(mass fraction) <0.01 1-Pentyne %(mass fraction) <0.01 Cis-2-Pentene %(mass fraction) 2.06 2-Methyl-2-butene %(mass fraction) 3.25 trans-1,3-pentadiene %(mass fraction) <0.01 Cyclopentadiene %(mass fraction) <0.01 Cyclopentane %(mass fraction) C5 conjugated diene + dicyclopentadiene %(mass fraction) 1.67 C5 monoolefins %(mass fraction) Diolefin Index gI / 100g 0.7

[0030] Table 2 Composition and properties of catalytic light gasoline

[0031]

[0032]

[0033] Table 3 Comparison of properties of crude isopentene and catalytic light gasoline

[0034]

[0035]

[0036] The tertiary carbon olefins of carbon five and six in light gasoline are converted into TAME and THxME by etherification reaction with methanol to produce etherified light gasoline. After the etherified light gasoline is blended with heavy gasoline, the olefin content of catalytic gasoline is reduced by about 10 percentage points, the octane number is increased by about 1 unit, and the vapor pressure is reduced by 10-20 kPa. The etherification process can convert low-value methanol equivalent to 9% to 10% of light gasoline into high-value gasoline components, which is a gasoline increment production process. By comparing the properties of crude isopentene and catalytic light gasoline, it is analyzed that the etherification unit can blend part of crude isopentene, the olefin content of crude isopentene is about 40%, the diene index value is 0.7gI / 100g, and the nitrogen content and sulfur content meet the feed requirements. Further blending crude isopentene through light gasoline etherification has innovative significance and provides a new research direction for the development of the industry.

[0037] Brief description of the method of the present invention

[0038] 1) Raw material pretreatment

[0039] The catalytic light gasoline from the gasoline hydrogenation unit is mixed with methanol and sent to the light gasoline-methanol purifier to remove catalyst poisoning substances such as acetonitrile, propionitrile, and metal ions contained in the light gasoline. Fresh methanol from outside the boundary area and the circulating methanol from the top of the methanol recovery tower of the methanol recovery part enter the methanol buffer tank together, and are mixed with light gasoline and sent to the light gasoline-methanol purifier together. Then the light gasoline-methanol mixture enters the first stage etherification reaction-catalytic distillation and etherification product separation-second stage deep etherification part.

[0040] 2) First stage etherification reaction - catalytic distillation and etherification product separation - second stage deep etherification

[0041] The purified methanol is mixed with the molar ratio of tertiary carbon olefins in light gasoline (1.3-1.5):1 and filtered, and then enters the bottom of the No. 1 etherification reactor, and the tertiary carbon olefins and methanol are etherified through the catalyst bed of the No. 1 etherification reactor. The reaction product flows out from the top of the No. 1 etherification reactor and enters the No. 2 etherification reactor in series for further reaction after heat exchange, so that the tertiary carbon olefins in gasoline are further converted into ether products. The reactants flowing out from the top of the No. 2 etherification reactor enter the catalytic distillation tower. The gas phase discharged from the top of the lower tower of the catalytic distillation tower enters the No. 3 etherification reactor, and the reaction product flows out from the top of the No. 3 etherification reactor and enters the methanol extraction tower. The flow rate of methanol supplemented in the catalytic distillation tower is controlled according to the methanol content in the material produced from the top of the catalytic distillation tower. The etherification product oil produced from the bottom of the lower tower of the catalytic distillation tower is cooled to 40°C through heat exchange, and then mixed with the remaining carbon five from the remaining carbon five agglomerator, and is used as the etherification light gasoline product to exit the device.

[0042] 3) Methanol recovery part

[0043] The reaction product from the No. 3 etherification reactor is cooled to 40°C and then enters the lower part of the methanol extraction tower, where it countercurrently contacts the extraction water from the bottom of the methanol recovery tower to extract methanol from the residual carbon five into the water phase. The residual carbon five flowing out of the top of the methanol extraction tower is dehydrated through the filter and the residual carbon five agglomerator, and then mixed with the etherification product oil and then exits the device. The extraction water / methanol mixture is purified by the extraction water purification tower, and then enters the methanol recovery tower after heat exchange to separate the extraction water and methanol. The extraction water flows out from the bottom of the methanol recovery tower, is cooled to 40°C, and then circulated to the upper part of the methanol extraction tower for recycling.

[0044] In this application, crude isopentene is stored in a pressure storage tank, and the daily temperature is controlled to be ≮40°C. Crude isopentene is mixed with catalytic light gasoline in front of the buffer tank at a blending ratio of 10%, and then directly enters the methanol purifier. After etherification reaction, etherified gasoline blending components are obtained (see Table 4 for main operating conditions).

[0045] Table 4 Main operating conditions

[0046]

[0047]

[0048] After the etherification unit was blended with 10% crude isopentene, the temperature rise of the etherification reactor did not change significantly, and the related operations of the catalytic distillation tower did not change significantly. The crude isopentene was blended at 12.7t / h. The following table shows the changes in the properties of the etherified gasoline before and after blending in the etherification unit.

[0049] Table 5 Properties of etherified gasoline before and after blending with crude isopentene

[0050] Analyze Project unit Before blending crude isopentene After blending with crude isopentene (10%) Distillation ℃ IBP ℃ 28.7 26.4 10% recovery temperature ℃ 40.8 40.1 30% recovery temperature ℃ 47.6 45.3 50% recovery temperature ℃ 53.2 50.2 70% recovery temperature ℃ 68.3 62.1 90% recovery temperature ℃ 83.4 81.3 FBP ℃ 107.7 107.4 Family composition Wt% Alkanes Wt% 64.3 65.0 Olefins Wt% 19.4 17.8 Aromatics Wt% 0.97 1.03 Ether Wt% 15.3 16.2 Octane 96.7 96.3 Vapor pressure KPa 97.2 100.1 Density at 20℃ <![CDATA[kg / m 3 ]]> 671.3 667.4

[0051] After crude isopentene is blended in the catalytic light gasoline etherification unit, part of the olefins in the crude isopentene react with methanol to produce etherified gasoline. Compared with direct oil blending with crude isopentene, the octane number is increased and the saturated vapor pressure is reduced, making it a high-quality gasoline blending component.

[0052] Table 6 Product Distribution

[0053]

[0054] Benefit calculation of adopting the technical solution of this application:

[0055] Crude isopentene passes through the light gasoline etherification unit: benefit increment (75317-70746)*24=109704 yuan / d

[0056] The processing fee of crude isopentene through the light gasoline etherification unit is about 49.5 yuan / ton, so the comprehensive benefit is: 109704-12.7*24*49.5=94616 yuan / d.

[0057] Comprehensively comparing the new process, the monthly economic benefit can reach: 94616 yuan / d*30d=2.838 million yuan.

[0058] Finally, it should be noted that the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A method for separating crude isopentene by cracking C5, Features The method comprises the following steps: Step 1) using cracked C5 introduced from the tank area as a raw material, and sending it into a double-ring polymerization reactor for dimerization reaction to polymerize cyclopentadiene in C5 into dicyclopentadiene; the double-ring polymerization reactor then enters a decarbonization tower through a pipeline, the upper end of the decarbonization tower is connected to a C4 refining tower through a pipeline, and the lower end of the decarbonization tower is connected to a pre-deweighting tower through a pipeline; Step 2) obtaining isopentadiene and dicyclopentadiene products from the bottom of the pre-deweighting tower and sending them to a deweighting tower through a pipeline, preheating the C5 fraction of dimers extracted from the top of the pre-deweighting tower to 70° C., removing dicyclopentadiene and part of isopentadiene through an extraction feed water washing tower into which washing water is introduced, and then sending them to the upper part of an isoprene extraction distillation tower, introducing an acetonitrile solvent containing 5.0% (by weight) of water into the isoprene extraction distillation tower, discharging C5 alkanes, monoolefins and a small amount of isoprene with part of acetonitrile and water from the top of the isoprene extraction distillation tower, and sending them to a residual C5 water washing tower into which washing water is introduced, washing away the entrained acetonitrile through the residual C5 water washing tower, wherein the upper end of the residual C5 water washing tower is connected to a pipeline to send crude isopentene to a crude isopentene tank area and to a diene reactor as a raw material, and the lower end of the residual C5 water washing tower is connected to a pipeline to recover the solvent; Step 3) firstly mix the catalytic light gasoline, methanol and the crude isopentene obtained at the upper end of the residual carbon five water washing tower, and send them into a methanol evolution device to obtain a mixture; Step 4) The mixture is sent to the first etherification reactor and the second etherification reactor to carry out a first stage of etherification reaction, and then sent to the catalytic distillation tower with supplementary methanol, the gas phase discharged from the top of the catalytic distillation tower enters the bottom of the third etherification reactor to achieve a deep etherification reaction between the unreacted tertiary amylene in the catalytic distillation tower and methanol, and the etherified product generated after the reaction is cooled to 40° C. and then flows out from the top of the third etherification reactor into the methanol extraction tower, and the methanol is extracted from the residual carbon five into the water phase through the methanol extraction tower, and the residual carbon five flowing out from the top of the methanol extraction tower is dehydrated through a filter and a residual carbon five agglomerator, and then sent to a blending tank with the etherified gasoline flowing out from the bottom of the catalytic distillation tower to achieve mixing and then exit the device; Step 5) The mixture of extraction water and methanol flowing out from the bottom of the methanol extraction tower is first purified by an extraction water purification tower, and then enters a methanol recovery tower after heat exchange to separate the extraction water and methanol. The extraction water flowing out from the bottom of the methanol recovery tower is cooled to 40°C and then circulated to the methanol extraction tower to achieve countercurrent contact between the extraction water from the bottom of the methanol recovery tower and the etherified product in the methanol extraction tower. Methanol flows out from the top of the methanol recovery tower and serves as methanol feed for the methanol evolver.

2. A method for separating crude isopentene by cracking C5 according to claim 1, Features: The molar ratio of methanol purified by the methanol purifier to tertiary olefins in light gasoline is (1.3-1.5):

1. After being mixed and filtered according to the ratio, they enter the bottom of the No. 1 etherification reactor, and the tertiary olefins and methanol are first subjected to etherification reaction in the catalyst bed of the No. 1 etherification reactor. The reaction products flow out from the top of the No. 1 etherification reactor and enter the No. 2 etherification reactor in series for heat exchange to continue the reaction, so that the tertiary olefins in the gasoline continue to be converted into ether products. The reactants flowing out from the top of the No. 2 etherification reactor enter the catalytic distillation tower.

3. A method for separating crude isopentene by cracking C5 according to claim 1, Features: The crude isopentene is stored in a pressure tank, the temperature of which is controlled to be ≮40°C, and the crude isopentene is mixed with catalytic light gasoline at a blending ratio of 10%.

4. A method for separating crude isopentene by cracking C5 according to claim 1, 2 or 3, Features: In step 4), the flow rate of methanol added to the catalytic distillation tower is controlled according to the methanol content in the material produced from the top of the catalytic distillation tower. The etherified product oil produced from the bottom of the catalytic distillation tower is first cooled to 40° C. through heat exchange, and then mixed with the remaining carbon five from the remaining carbon five agglomerator, and then discharged from the device as an etherified gasoline product.

5. A method for separating crude isopentene by cracking C5 according to claim 1 or 3, Features: The flow rate of crude isopentene was controlled to be no higher than 15% of the total feed flow rate of the methanol purifier.

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