A method for removing olefins from a cyclohexane based on production of ethylene-propylene rubber

Abstract

This invention relates to the field of organic chemical engineering, and particularly to a method for removing olefins from recycled hexane in the production of ethylene propylene rubber. The method includes the following steps: drawing hexane from an HX storage tank, removing olefins through two adsorption beds or either one of them, and then returning it to the HX storage tank. The operating temperature of the two adsorption beds is 10℃~50℃, the operating pressure is 0.1MPa~2.0MPa, and the operating space velocity is 0.01h⁻¹. ‑1 ~5.0h ‑1 The two adsorption beds are regenerable. This invention uses two adsorption beds to remove C6-C9 olefins from hexane, reducing the bromine value of hexane, thus enabling continuous hexane refining and improving the quality of ethylene propylene rubber products.

Description

Technical fields:

[0001] This invention relates to the field of organic chemical technology, and in particular to a method for removing olefins from recycled hexane in the production of ethylene propylene rubber. Background technology:

[0002] The production method for ethylene propylene rubber (EPR) employs solvent polymerization using n-hexane (HX) as the solvent, which is recyclable. The hexane from the solvent recovery unit of the EPR production plant contains trace amounts of C6-C9 olefins. As these components accumulate, the bromine value of the hexane in the system increases from 200 mg / kg to 1000 mg / kg. When the bromine value reaches 700 mg / kg, the hexane containing a high concentration of olefins is discharged from the solvent recovery unit to a storage tank for temporary storage. The storage tank level determines the timing of the discharge, with approximately 1000 tons discharged annually at a cost of 3,000-4,000 RMB / ton. With increased production time, the concentration of C6-C9 olefins in the hexane increases, affecting the quality of the EPR product. This process is characterized by a long process route, complex operation, unstable hydrogen content in the system, low safety performance, and high cost.

[0003] In his article "Industrial Application of ROC-Z1 Reforming Oil Deolefins Adsorbent in Aromatic Hydrocarbon Complex," Ma Xiaojin of the Research Institute of Urumqi Petrochemical Company of China National Petroleum Corporation discusses the industrial application of ROC-Z1 reforming oil deolefins adsorbent in replacing kaolin in the aromatic hydrocarbon complex of Urumqi Petrochemical Company. Under unchanged process conditions, ROC-Z1 reforming oil deolefins adsorbent has a long service life, with an actual operating life of over 200 days, which is 3.5 times that of ordinary kaolin.

[0004] In their study, "Research on the Removal of Trace Olefins from Reformate Using Molecular Sieve Catalysts," Li Keming et al. of the Tianjin Branch of China Petroleum & Chemical Corporation (Sinopec) used Hβ molecular sieve, HY molecular sieve, and HY molecular sieve treated with steam as the active catalysts for olefin removal. They investigated the effects of different molecular sieves, sieve acidity, and steam treatment time on the olefin removal performance of the catalysts. The results showed that the surface acidity of the catalyst has a significant impact on its olefin removal performance. Beta acid (B acid) is the main active center, while Lewis acid (L acid) acts as an auxiliary catalyst. Excessive density of B acid centers accelerates catalyst coking and deactivation. Steam treatment can effectively improve the surface acidity and acid strength of the molecular sieve, extending the catalyst's single-pass life by up to six times that of industrial clay. The olefin removal catalyst exhibits better coking capacity, and the carbon deposits on its surface are light coke, making them easy to regenerate.

[0005] In their study, "Research on Alkane / Olefin Separation Technology Using Porous Materials," Zhao Chuang and Li Ben et al. from CNOOC Tianjin Chemical Research and Design Institute Co., Ltd. investigated the adsorption and separation performance of porous materials such as silica gel, γ-Al₂O₃, 13X molecular sieve, Y molecular sieve, and ZSM-5 molecular sieve for alkanes / olefins using simulated oil as raw material in a small fixed-bed (200mL) reactor. Silica gel showed the best alkane / olefin separation effect, achieving a maximum separation degree of 0.81 under the conditions of an adsorption temperature of 40℃, a pressure of 0.5MPa, and n-octane / methylcyclohexane as the desorbent. Compared with other types of silica gel, type B silica gel with an average pore size of 4–6 nm exhibited better mass transfer and a more readily equilibrated adsorption-desorption process. The separation effect of the adsorbent after calcination and solvent regeneration did not show a significant decrease compared to the fresh adsorbent.

[0006] In his article "Research Progress on Trace Olefin Removal Process in Reformed Aromatics", Han Qinghua of Luoyang Ruize Petrochemical Engineering Co., Ltd. pointed out that the olefin removal process widely used in the aromatics units of refineries has problems such as rapid deactivation, short lifespan, frequent replacement, and environmental pollution.

[0007] Michael B. Russ reported a process combining hydrorefining and clay refining. Stephen H. Brown et al. designed a composite production process that includes three methods: activated clay refining, molecular sieve refining, and hydrorefining. Axens' Arofining TMR selective hydrogenation process, Changling Institute's FITS hydrogenation process, and Tianjin Institute's molecular sieve refining process can all be used in conjunction with activated clay refining.

[0008] Chen Yingchao of CNPC Tianjin Branch reported that the replacement cycle of bleached clay with the molecular sieve catalyst TCDTO-1 has been extended to approximately 20 times. A molecular sieve catalyst developed by CNOOC Tianjin Chemical Research and Design Institute for the deolefination of C6-C7 mixed aromatics has a single-pass life of 12-15 months and can be regenerated 3-4 times; another molecular sieve catalyst for the deolefination of C8 components has a single-pass life of 8-10 months when the bromine index of the feedstock is <600mgBr / 100g, and can also be regenerated 3-4 times. This shows that under the same operating conditions, the single-pass life of molecular sieves is more than 8 times that of bleached clay, effectively mitigating the safety hazards caused by frequent replacement and disposal of waste bleached clay. Through regeneration, it can be reused repeatedly, reducing solid waste emissions by 85%-90%.

[0009] Based on the above similar literature, it can be concluded that the clay refining process is the earliest and most outdated process; utilizing the abundant pores, large specific surface area and acidity of the adsorbent is currently the most competitive process for adsorbing olefins in recycled hexane. Summary of the Invention:

[0010] The technical problem this invention aims to solve is to provide a method for removing olefins from recycled hexane in the production of ethylene propylene rubber (EPR). This method employs two adsorption beds to remove C6-C9 olefins from hexane, reducing the bromine value of hexane and enabling continuous hexane purification, thereby improving the quality of EPR products. It overcomes the shortcomings of existing hydrogenation-adsorption processes for olefin removal, which suffer from poor olefin removal efficiency, high processing costs, and negative impacts on EPR product quality.

[0011] The technical solution adopted in this invention is: a method for removing olefins from recycled hexane during the production of ethylene propylene rubber. This method uses n-hexane as the polymerization solvent. Hexane vapor generated during the production of ethylene propylene rubber enters an HX storage tank. Hexane is drawn from the HX storage tank, passes through two adsorption beds or either one of them to remove olefins, and then returns to the HX storage tank. The operating temperature of the two adsorption beds is 10℃~50℃, the operating pressure is 0.1MPa~2.0MPa, and the operating space velocity is 0.01h⁻¹. -1 ~5.0h -1 The two adsorption beds can be regenerated.

[0012] Furthermore, the two adsorption beds can be connected in series or in parallel, and one adsorption bed can be used while the other is on standby.

[0013] Furthermore, the inlet hexane bromine value of the two adsorption beds is 130 mgBr / 100g to 700 mgBr / 100g.

[0014] Furthermore, the operating temperature of the two adsorption beds is 30℃~40℃.

[0015] Furthermore, the operating pressure of the two adsorption beds is 0.4 MPa to 0.7 MPa.

[0016] Furthermore, the operating space velocity of the two adsorption beds is 0.2 h⁻¹. -1 ~0.5h -1 .

[0017] Furthermore, the two adsorption beds are regenerated using both online and offline methods. The first and second regenerations are performed online using steam, while the third regeneration is performed offline. The adsorbent in the adsorption beds has a service life of 2 years and can be regenerated 3 times.

[0018] Furthermore, the two adsorption beds undergo first and second online steam regeneration for 4 to 6 days at a steam temperature of 180°C to 220°C. After regeneration, they are dried and replaced with nitrogen at room temperature and set aside for later use. For the third offline regeneration, the adsorption beds are first purged with nitrogen at room temperature, then the adsorption beds are opened, the adsorbent is unloaded, and calcined at a temperature of 500°C to 550°C for 4 to 6 hours.

[0019] Furthermore, when either of the two adsorption beds enters the later stage of adsorption, i.e., when the olefin adsorption rate is less than 50%, they can be connected in series.

[0020] Furthermore, when the adsorption capacity of either of the two adsorption beds is less than 70% to 80%, i.e., the olefin adsorption rate is less than 20% to 30%, the other adsorption bed is switched.

[0021] The beneficial effects of this invention are:

[0022] (1) The present invention adopts the adsorption method, which has a high olefin adsorption capacity, a low bromine value of hexane in HX storage tank, and a good olefin removal effect.

[0023] (2) Compared with the existing hydrogenation-adsorption process for refining hexane, this invention can improve the quality of ethylene propylene rubber products and enhance the market competitiveness of ethylene propylene rubber among similar products in China. Attached image description:

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] Figure 1 This is a schematic diagram illustrating the use of the present invention.

[0026] Figure 2 This is a schematic diagram of the existing hydrogenation-adsorption process for refining hexane. Detailed implementation method:

[0027] The two adsorption beds in this invention are arranged as follows: Figure 1 As shown in the figure, the following is in conjunction with the appendix. Figure 1 The present invention will be described in detail with reference to specific embodiments.

[0028] Example 1

[0029] Open valves 7 and 4, and close valves 8, 11, 6, 5, 12, and 13. Adsorption bed 1 is operational, adsorption bed 2 is on standby, and the displacement system is shut down. The adsorption pressure of adsorption bed 1 is 0.1 MPa, the temperature is 20℃, and the space velocity is 0.2 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 1 was 200 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 1 was 70 mgBr / 100g, and the bromine value of the hexane in storage tank 3 of HX was 100 mgBr / 100g.

[0030] Example 2

[0031] Open valves 8 and 11, and close valves 7, 4, 10, 9, 5, 6, 12, and 13. Adsorption bed 2 will operate, while adsorption bed 1 will remain in standby mode. The displacement system will be shut down. The adsorption pressure of adsorption bed 2 is 0.2 MPa, the temperature is 30°C, and the space velocity is 0.5 h⁻¹. -1The bromine value of the circulating hexane at the inlet of adsorption bed 2 was 210 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 2 was 80 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 was 130 mgBr / 100g.

[0032] Example 3

[0033] Open valves 8 and 11, and close valves 7, 4, 10, 9, 5, 6, 12, and 13. Adsorption bed 2 will operate, while adsorption bed 1 will remain in standby mode. The displacement system will be shut down. The adsorption pressure of adsorption bed 2 is 0.7 MPa, the temperature is 40 °C, and the space velocity is 0.5 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 2 was 180 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 2 was 60 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 was 130 mgBr / 100g.

[0034] Example 4

[0035] Open valves 7 and 4, and close valves 8, 11, 6, 5, 12, and 13. Adsorption bed 1 is operational, adsorption bed 2 is on standby, and the displacement system is shut down. The adsorption pressure of adsorption bed 1 is 2.0 MPa, the temperature is 50℃, and the space velocity is 2.5 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 1 was 200 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 1 was 70 mgBr / 100g, and the bromine value of the hexane in storage tank 3 of HX was 150 mgBr / 100g.

[0036] Example 5

[0037] Open valves 11, 4, and 12, and close valves 8, 9, 5, 7, 13, 10, and 6. Adsorption beds 2 and 1 operate in series, and the displacement system is shut down. The adsorption pressure of adsorption beds 2 and 1 is 1.5 MPa, the temperature is 40℃, and the space velocity is 1.0 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 2 is 200 mgBr / 100g, and the bromine value of the circulating hexane at the inlet of adsorption bed 1 is 130 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 1 is 50 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 is 120 mgBr / 100g.

[0038] Example 6

[0039] Open valves 8, 4, 11, and 7; close valves 12, 13, 9, 10, 5, and 6. Adsorption beds 2 and 1 operate in parallel, and the displacement system is shut down. The adsorption pressure of adsorption beds 2 and 1 is 0.5 MPa, the temperature is 10 °C, and the space velocity is 0.01 h⁻¹. -1The bromine value of the circulating hexane at the inlet of adsorption beds 2 and 1 was 500 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption beds 2 and 1 was 70 mgBr / 100g, and the bromine value of the hexane in storage tank 3 of HX was 120 mgBr / 100g.

[0040] Example 7

[0041] Open valves 11, 4, and 12, and close valves 8, 9, 5, 7, 13, 10, and 6. Adsorption beds 2 and 1 operate in series, and the displacement system is shut down. The adsorption pressure of adsorption beds 2 and 1 is 0.5 MPa, the temperature is 40℃, and the space velocity is 0.2 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 2 is 400 mgBr / 100g, and the bromine value of the circulating hexane at the inlet of adsorption bed 1 is 260 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 1 is 60 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 is 130 mgBr / 100g.

[0042] Example 8

[0043] Open valves 8 and 11, and close valves 7, 4, 10, 9, 5, 6, 12, and 13. Adsorption bed 2 will operate, while adsorption bed 1 will remain in standby mode. The displacement system will be shut down. The adsorption pressure of adsorption bed 2 is 0.5 MPa, the temperature is 20°C, and the space velocity is 0.1 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 2 was 300 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 2 was 110 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 was 140 mgBr / 100g.

[0044] Example 9

[0045] Open valves 8 and 11, and close valves 7, 4, 10, 9, 5, 6, 12, and 13. Adsorption bed 2 will operate, while adsorption bed 1 will remain in standby mode. The displacement system will be shut down. The adsorption pressure of adsorption bed 2 is 0.6 MPa, the temperature is 30°C, and the space velocity is 5.0 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 2 was 150 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 2 was 70 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 was 135 mgBr / 100g.

[0046] Example 10

[0047] Open valves 4 and 7, and close valves 8, 11, 6, 5, 12, and 13. Adsorption bed 1 will start operating, and adsorption bed 2 will undergo its first online regeneration. Open valves 9 and 10 to introduce 200℃ steam into adsorption bed 2 for online regeneration for 6 days. Then, purge and replace the gas with nitrogen at room temperature. The organic matter and water obtained after condensation of the regenerated gas will be sent to the waste hexane system. After regeneration, close valves 9, 10, 4, and 7, and open valves 8 and 11. Adsorption bed 2 will start operating, and adsorption bed 1 will be on standby. The adsorption pressure of adsorption bed 2 is 0.4 MPa, the temperature is 40℃, and the space velocity is 0.2 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 2 was 200 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 2 was 70 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 was 120 mgBr / 100g.

[0048] Example 11

[0049] Open valves 4 and 7, and close valves 8, 11, 6, 5, 12, and 13. Adsorption bed 1 will start operating, and adsorption bed 2 will undergo its second online regeneration. Open valves 9 and 10 to introduce 180°C steam into adsorption bed 2 for online regeneration for 6 days. Then, purge and replace the gas with nitrogen at room temperature. The organic matter and water obtained after condensation of the regenerated gas will be sent to the waste hexane system. After regeneration, close valves 9, 10, 4, and 7, and open valves 8 and 11. Adsorption bed 2 will start operating, and adsorption bed 1 will be on standby. The adsorption pressure of adsorption bed 2 is 0.4 MPa, the temperature is 40°C, and the space velocity is 0.2 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 2 was 200 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 2 was 80 mgBr / 100g, and the bromine value of the hexane in storage tank T7K01 of HX was 121 mgBr / 100g.

[0050] Example 12

[0051] Open valves 11 and 8, and close valves 7, 4, 10, 9, 12, and 13. Adsorption bed 2 will start operating, and adsorption bed 1 will undergo its first online regeneration. Open valves 5 and 6 to introduce 200℃ steam into adsorption bed 1 for online regeneration for 4 days. Then, purge and replace the gas with nitrogen at room temperature. The organic matter and water obtained after condensation of the regenerated gas will be sent to the waste hexane system. After regeneration, close valves 5, 6, 11, and 8, and open valves 4 and 7. Adsorption bed 1 will start operating, and adsorption bed 2 will be on standby. The adsorption pressure of adsorption bed 1 is 0.3 MPa, the temperature is 40℃, and the space velocity is 0.5 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 1 was 210 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 1 was 80 mgBr / 100g, and the bromine value of the hexane in storage tank 3 of HX was 125 mgBr / 100g.

[0052] Example 13

[0053] Open valves 11 and 8, and close valves 7, 4, 10, 9, 12, and 13 to start adsorption bed 2. Adsorption bed 1 undergoes a second online regeneration. Open valves 5 and 6 to introduce 220℃ steam into adsorption bed 1 for 4 days of online regeneration. Then, purge and replace the gas with room temperature nitrogen. The organic matter and water obtained after condensation of the regenerated gas are sent to the waste hexane system. After regeneration, close valves 5, 6, 11, and 8, and open valves 4 and 7 to start adsorption bed 1. Adsorption bed 2 is on standby. The adsorption pressure of adsorption bed 1 is 0.5 MPa, the temperature is 40℃, and the space velocity is 0.5 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 1 was 210 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 1 was 70 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 was 128 mgBr / 100g.

[0054] Example 14

[0055] Open valves 11 and 8, and close valves 7, 4, 10, 9, 12, and 13 to start adsorption bed 2. After six months of second regeneration, adsorption bed 1 undergoes offline regeneration. Open valves 5 and 6, purge with nitrogen at room temperature, then open adsorption bed 1 to remove the adsorbent for calcination at 500℃ for 6 hours. After calcination, the adsorbent is refilled into adsorption bed 1. The regenerated gas is condensed in a condenser, and the resulting organic matter and water are sent to the waste hexane system. Open valves 4 and 7, and close valves 8, 11, 5, and 6 to start adsorption bed 1. The adsorption pressure is 0.7 MPa, the temperature is 40℃, and the space velocity is 0.1 h⁻¹. -1 The bromine value of the circulating hexane at the inlet of adsorption bed 1 was 700 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 1 was 68 mgBr / 100g, and the bromine value of the hexane in storage tank 3 of HX was 135 mgBr / 100g.

[0056] Example 15

[0057] Open valves 4 and 7, and close valves 8, 11, 6, 5, 12, and 13 to start adsorption bed 1. After six months of second regeneration, adsorption bed 2 undergoes offline regeneration. Open valves 9 and 10, purge with nitrogen at room temperature, then open adsorption bed 2. Discharge the adsorbent and calcine it at 550℃ for 4 hours. After calcification, refill adsorption bed 2. The regenerated gas is condensed in a condenser, and the resulting organic matter and water are sent to the waste hexane system. Open valves 8 and 11, and close valves 4, 7, 9, and 10 to start adsorption bed 2. The adsorption pressure is 0.7 MPa, the temperature is 40℃, and the space velocity is 0.2 h⁻¹. -1The bromine value of the circulating hexane at the inlet of adsorption bed 2 was 600 mgBr / 100g. After one month of calibration, the bromine value of the circulating hexane at the outlet of adsorption bed 2 was 76 mgBr / 100g, and the bromine value of the hexane in HX storage tank 3 was 130 mgBr / 100g.

[0058] Comparative Example

[0059] like Figure 2 As shown, when the bromine value of hexane in the HX storage tank reaches 700 mg / kg, the valve is opened, and a hydrogenation-adsorption method is used. Hexane is first hydrogenated in the gas phase at a reaction temperature of 320℃, then distilled to remove heavy and light components, and then adsorbed with clay until the bromine value reaches 50 mgBr / 100g. The hexane is then returned to the new HX storage tank via pipeline. After one month of calibration, the bromine value of hexane in the ENB and diene recovery tower increased from 130 mgBr / 100g to 700 mgBr / 100g, increasing the cost of hexane by 50-80 yuan per ton.

[0060] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.

Claims

1. A method for removing olefins from recycled hexane during the production of ethylene propylene rubber, wherein the method uses n-hexane as a polymerization solvent, and the hexane vapor generated during the production of ethylene propylene rubber enters an HX storage tank; characterized in that: Recycled hexane is drawn from the HX storage tank, passes through either of two regenerable adsorption beds to remove olefins, and then returns to the HX storage tank. These two regenerable adsorption beds can perform adsorption and regeneration in a single cycle. The bromine value of the recycled hexane entering the adsorption beds is 130 mgBr / 100 g to 700 mgBr / 100 g. The operating temperatures of the two adsorption beds are 30℃ to 40℃, the operating pressures are 0.4 MPa to 0.7 MPa, and the operating space velocities are 0.2 h⁻¹. -1 ~0.5 h -1 When the olefin adsorption rate of the adsorption bed is less than 30%, switch to another adsorption bed. The regeneration of both adsorption beds adopts online regeneration and offline regeneration: the first and second regenerations are carried out by online steam regeneration for 4 to 6 days, with a steam temperature of 180℃ to 220℃. After regeneration, the bed is purged with nitrogen at room temperature. The third regeneration is carried out offline. The bed is first purged with nitrogen at room temperature, and then the adsorbent is removed from the adsorption bed and calcined at a temperature of 500℃ to 550℃ for 4 to 6 hours. The adsorbents in the two adsorption beds have a service life of 2 years and can be regenerated 3 times.

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