Method and system for producing hydrogenated terphenyl

Abstract

The invention provides a method and a system for producing hydrogenated terphenyl. The method comprises the following steps: (1) carrying out hydroalkylation reaction on a benzene-containing raw material and hydrogen under the action of a catalyst to obtain a reaction product; and (2) carrying out C6 removal treatment on the reaction product to obtain a circulating C6 material flow containing benzene, methyl cyclopentane and cyclohexane and a material flow containing hydrogenated terphenyl, and carrying out heat exchange on the circulating C6 material flow and the reaction product in the step (1) after the circulating C6 material flow is cooled. According to the method and the system disclosed by the invention, heat removal and heating are realized at the same time in a self-heat-exchange manner of reactants such as circulating C6 material flow and reaction products, reaction heat is fully utilized, and the problem of high energy consumption in a hydrogenated terphenyl production process is well solved.

Description

Technical Field

[0001] The present invention belongs to the field of chemical synthesis, and particularly relates to a method and a system for producing hydrogenated terphenyls. Background Art

[0002] With the continuous development of new technologies such as photovoltaic power generation, energy storage, and polyester in China, the demand for synthetic high-temperature heat transfer oils with long cycle service life and service temperature (≥330°C), such as L-QD340, has increased significantly. However, domestic heat transfer oils mainly consist of mineral oil-based heat transfer oils applicable to temperatures below 300°C, which cannot meet the high-temperature use requirements. Hydrogenated terphenyl is the main base oil raw material of L-QD340, and currently, this product mainly relies on imports.

[0003] The traditional production method of hydrogenated terphenyl is the high-temperature cracking of benzene (≥800°C). Patent CN103804114A reports that benzene is cracked at high temperature to produce a reaction product containing benzene, biphenyl, and terphenyl. The product is cooled and rectified to obtain terphenyl, and the terphenyl is hydrogenated in a hydrogenation autoclave to obtain hydrogenated terphenyl. This production method has a high reaction temperature, high energy consumption, and low total yield.

[0004] Patent CN115991631A uses a multi-stage (unit) fixed-bed alkylation reactor and a catalyst unequal loading reaction process. Using benzene, biphenyl, and cyclohexane as raw materials, an alkylation reaction occurs with hydrogen in the reactor to produce hydrogenated terphenyl. However, compared with the benzene high-temperature cracking method, although the reaction temperature of this method is low and the yield of hydrogenated terphenyl is also increased, this method uses inter-stage addition of raw materials to control the reaction temperature, and the utilization of reaction heat is insufficient. The energy consumption required to heat the raw materials fed in the first stage to the initial reaction temperature is relatively high. For example, 62% of the raw materials need to be heated from 56°C to 150°C, resulting in high costs. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and a system for producing hydrogenated terphenyl to significantly reduce the reaction energy consumption and save production costs on the premise of ensuring the yield of hydrogenated terphenyl in view of the above technical problems existing in the prior art.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] In the first aspect, the present invention provides a method for producing hydrogenated terphenyl, comprising the following steps:

[0008] (1) Subjecting a benzene-containing raw material and hydrogen to a hydroalkylation reaction under the action of a catalyst to obtain a reaction product;

[0009] (2) Perform C6 removal treatment on the reaction product to obtain a recycled C6 stream containing benzene, methylcyclopentane and cyclohexane and a stream containing hydrogenated terphenyl, wherein the recycled C6 stream is cooled and then undergoes heat exchange with the reaction product in step (1).

[0010] The benzene-containing raw material described in the present invention can be fresh benzene or a mixture of benzene, methylcyclopentane, cyclohexane, etc.

[0011] In some embodiments, the hydroalkylation reaction in step (1) is carried out in the tubes of a shell-and-tube reactor, and the recycled C6 stream in step (2) enters the shell side of the shell-and-tube reactor after cooling treatment to undergo heat exchange with the reaction product in the tubes.

[0012] In some embodiments, the shell side of the shell-and-tube reactor is provided with N (N≥2) outlets in sequence from top to bottom, wherein the first outlet (from top to bottom) is located at the center of the shell side, and the distance between the Nth outlet and the (N - 1)th outlet is 0.05 - 0.25 times, preferably 0.16 - 0.24 times, more preferably 0.18 - 0.22 times the length of the tubes of the shell-and-tube reactor. In some embodiments, N = 3.

[0013] In some embodiments, in step (2), the C6 removal treatment is carried out in a C6 removal tower. In some embodiments, the C6 removal tower includes a benzene-containing raw material feed inlet, a reaction product feed inlet and preferably three recycled C6 side draw ports. Among them, the reaction product enters the C6 removal tower from the reaction product feed inlet for C6 removal treatment, and a recycled C6 stream containing benzene, methylcyclopentane and cyclohexane is side drawn at the recycled C6 side draw ports, and a stream containing hydrogenated terphenyl is obtained at the bottom of the tower.

[0014] In some embodiments, in step (2), the cooling treatment is carried out in a cooler. In some embodiments, the cooling treatment includes cooling the recycled C6 stream side drawn from the C6 removal tower.

[0015] In some embodiments, the outlet of the cooler is connected to the inlet of the shell side of the shell-and-tube reactor so that the cooled recycled C6 stream enters the shell side of the shell-and-tube reactor to undergo heat exchange with the reaction product in the tubes.

[0016] In some embodiments, the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 2.0 to 4.0, for example, it can be 2.0, 2.5, 3.0, 3.5, 4.0 or any value therebetween. In some specific embodiments, the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 2.0 to 2.5. In some specific embodiments, the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 2.5 to 3.0. In some specific embodiments, the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 3.0 to 4.0.

[0017] In some embodiments, the temperature of the hydroalkylation reaction is 140 to 200 °C, preferably 150 to 190 °C. In some embodiments, the pressure of the hydroalkylation reaction is 1.5 to 2.0 MPaG, preferably 1.6 to 1.8 MPaG. In some embodiments, in the benzene-containing feedstock, the content of benzene is 68 wt% to 72 wt%.

[0018] In some embodiments, the temperature of the recycled C6 stream obtained in step (2) is 75 to 110 °C, and the temperature of the recycled C6 stream after cooling treatment is 20 to 100 °C, for example, 20 to 60 °C or 60 to 90 °C or 90 to 100 °C.

[0019] In some embodiments, the recycled C6 stream after heat exchange in step (2) is heated and then returned to step (1) for the hydroalkylation reaction. Preferably, the heating of the recycled C6 stream in step (3) is carried out in a heater. Preferably, the recycled C6 stream is heated to 140 to 200 °C, preferably 150 to 190 °C.

[0020] In some embodiments, the recycled C6 stream after heat exchange in step (2) is directly returned to step (1) for the hydroalkylation reaction without heating.

[0021] In some embodiments, the shell side of the shell-and-tube reactor is provided with a first outlet, a second outlet and a third outlet in sequence from top to bottom, the first outlet is located at the center of the shell side, and

[0022] When the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 2.0 to 2.5, the recycled C6 stream is drawn from the 3rd tray side of the C6 stripper, the outlet temperature of the cooler is 20 to 60 °C, and the recycled C6 stream after heat exchange flows out from the first outlet of the shell side of the shell-and-tube reactor;

[0023] When the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 2.5 to 3.0, the recycled C6 stream is drawn from the 5th tray side of the C6 stripper, the outlet temperature of the cooler is 60 to 90 °C, and the recycled C6 stream after heat exchange flows out from the second outlet of the shell side of the shell-and-tube reactor;

[0024] When the molar ratio of benzene to hydrogen in the benzene-containing raw material is 3.0 to 4.0, a circulating C6 stream is extracted from the 7th tray side of the C6 removal column, the outlet temperature of the cooler is 90 to 100 °C, and the circulating C6 stream after heat exchange flows out from the third outlet of the shell side of the tubular reactor.

[0025] In a second aspect, the present invention provides a system for producing hydrogenated terphenyls, comprising:

[0026] (1) A tubular reactor, which includes tubes and a shell side, and the tubes are used to carry out hydroalkylation reaction on the benzene-containing raw material and hydrogen under the action of a catalyst to obtain a reaction product;

[0027] (2) A C6 removal column, which includes a benzene-containing raw material feed inlet, a reaction product feed inlet, and multiple circulating C6 side draw ports. Among them, the reaction product enters the C6 removal column from the reaction product feed inlet for C6 removal treatment, a circulating C6 stream containing benzene, methylcyclopentane and cyclohexane is side-drawn at the circulating C6 side draw port, and a stream containing hydrogenated terphenyls is obtained at the bottom of the column;

[0028] (3) A cooler, which is used to cool the circulating C6 stream side-drawn from the C6 removal column and make the cooled circulating C6 stream enter the shell side of the tubular reactor for heat exchange with the reaction product in the tubes;

[0029] (4) A heater, which is used to heat the benzene-containing raw material or the circulating C6 stream flowing out from the shell side to the hydroalkylation reaction temperature.

[0030] In some embodiments, the shell side of the tubular reactor is provided with 1 inlet and N outlets from top to bottom in sequence, N≥2, preferably 2≤N≤4, more preferably N = 3. In some embodiments, the first outlet is located at the center of the shell side, and the distance between the Nth outlet and the (N - 1)th outlet is 0.05 to 0.25 times the length of the tubes of the tubular reactor, preferably 0.16 to 0.24 times, more preferably 0.18 to 0.22 times. In some embodiments, the distance between every two outlets is the same.

[0031] In some embodiments, the C6 removal column includes one benzene-containing raw material feed inlet, one reaction product feed inlet, and three circulating C6 side draw ports. In some embodiments, the C6 removal column is a plate column, the circulating C6 side draw port is located on the tray above the benzene-containing raw material feed inlet, and the reaction product feed inlet is located on the tray below the benzene-containing raw material feed inlet.

[0032] In some embodiments, the operating pressure at the top of the C6 removal column is 101 - 200 kPaA, preferably 120 - 160 kPaA. A C6 mixture containing benzene, methylcyclopentane and cyclohexane can be obtained from the top of the C6 removal column, and the content of benzene in the C6 mixture is 60 wt% - 64 wt%.

[0033] In some embodiments, the content of benzene in the recycled C6 is 68 wt% - 72 wt%.

[0034] In some embodiments, the temperature of the side draw from the C6 removal column is 75 - 110 °C, for example, it can be 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, etc.

[0035] In some embodiments, the total number of trays of the C6 removal column is denoted as N′, N′ is an integer of ≥10, preferably ≥15. The topmost tray of the C6 removal column is denoted as the 1st tray. The benzene-containing raw material feed inlet is located on the 0.4N′ - 0.6N′ tray, the reaction product feed inlet is located on the 0.6N′ - 0.8N′ tray, and the recycled C6 side draw inlet is located on the 0.15N′ - 0.2N′ or 0.25N′ - 0.35N′ or 0.35N′ - 0.5N′ tray.

[0036] In some embodiments, the number of trays of the C6 removal column is 15 - 20. The topmost tray of the C6 removal column is denoted as the 1st tray. The benzene-containing raw material feed inlet is located on the 8th - 10th tray, the reaction product feed inlet is located on the 11th - 13th tray, and the recycled C6 side draw inlet is located on the 2nd - 4th or 4th - 6th or 6th - 8th tray.

[0037] In some specific embodiments, the number of trays of the C6 removal column is 15 - 20. The topmost tray of the C6 removal column is denoted as the 1st tray. The benzene-containing raw material feed inlet is located on the 7th tray, the reaction product feed inlet is located on the 12th tray, and the recycled C6 side draw inlet is located on the 3rd or 5th or 7th tray.

[0038] In some embodiments, the cooler is provided with a temperature control device which contains a cooling medium, and the temperature at the outlet of the cooler is controlled by adjusting the flow rate of the cooling medium. In some embodiments, the outlet of the cooler is connected to the inlet of the shell side of the shell-and-tube reactor, so that the cooled circulating C6 stream enters the shell side of the shell-and-tube reactor to exchange heat with the reaction products in the tubes. In some embodiments, the temperature at the outlet of the cooler is 20 to 100 °C. In some embodiments, the temperature at the outlet of the cooler is 20 to 60 °C. In some embodiments, the temperature at the outlet of the cooler is 60 to 90 °C. In some embodiments, the temperature at the outlet of the cooler is 90 to 100 °C.

[0039] In some embodiments, the shell side of the shell-and-tube reactor is provided with a first outlet, a second outlet and a third outlet in sequence from top to bottom. The first outlet is located at the center of the shell side. The distance between the second outlet and the first outlet is 0.05 to 0.25 times the length of the tubes of the shell-and-tube reactor, preferably 0.16 to 0.24 times, more preferably 0.18 to 0.22 times. The distance between the second outlet and the third outlet is 0.05 to 0.25 times the length of the tubes of the shell-and-tube reactor, preferably 0.16 to 0.24 times, more preferably 0.18 to 0.22 times. The number of trays of the C6 stripper is 15 to 20. When the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 2.0 to 2.5, the circulating C6 stream is withdrawn from the side of the 3rd tray of the C6 stripper. The temperature at the outlet of the cooler is 20 to 60 °C. After heat exchange, the circulating C6 stream flows out from the first outlet of the shell side of the shell-and-tube reactor. When the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 2.5 to 3.0, the circulating C6 stream is withdrawn from the side of the 5th tray of the C6 stripper. The temperature at the outlet of the cooler is 60 to 90 °C. After heat exchange, the circulating C6 stream flows out from the second outlet of the shell side of the shell-and-tube reactor. When the molar ratio of benzene to hydrogen in the benzene-containing feedstock is 3.0 to 4.0, the circulating C6 stream is withdrawn from the side of the 7th tray of the C6 stripper. The temperature at the outlet of the cooler is 90 to 100 °C. After heat exchange, the circulating C6 stream flows out from the third outlet of the shell side of the shell-and-tube reactor.

[0040] It should be noted that in the above system for producing hydrogenated terphenyls according to the present invention, when the circulating C6 material flowing out from the outlet of the shell side of the shell-and-tube reactor is heated to the initial reaction temperature (for example, 140 to 200 °C) after heat exchange, the heater can be deactivated, and the circulating C6 material is mixed with hydrogen through the heater bypass line and then enters the tubes of the shell-and-tube reactor for hydroalkylation reaction.

[0041] The method and system of the present invention use benzene in a benzene-containing raw material (such as recycled C6) and hydrogen to undergo a hydroalkylation reaction under heating conditions to synthesize hydrogenated terphenyl. The reaction temperature is 140 - 200 °C, and the conditions are mild. Compared with the high-temperature cracking process of benzene, it is a brand-new synthetic route for hydrogenated terphenyl. The preferred reaction temperature in the present invention is 150 - 190 °C, which indicates that: 1) The initial temperature for the reaction of recycled C6 and fresh hydrogen needs to reach 140 °C, preferably 150 °C, for the reaction to occur; 2) The heat released by the hydroalkylation reaction cannot heat the materials in the reaction process to exceed 200 °C, preferably not exceed 190 °C, that is, the temperature of the reaction product needs to be lower than 200 °C, preferably lower than 190 °C, which is more favorable for the selectivity of hydrogenated terphenyl. Therefore, recycled C6 needs to be provided with heat to be heated to the initial reaction temperature of about 140 °C, preferably 150 °C. At the same time, the reaction product needs to be cooled to below 200 °C, preferably 190 °C.

[0042] Based on this, the method and system of the present invention couple heat and cold, and through the self-heat exchange of the reaction raw material (recycled C6) and the reaction product in the reaction system, simultaneously achieve heat removal and heating of the materials, making full use of the heat generated in the reaction and the cold brought by recycled C6, and hardly consuming external energy in the entire reaction system.

[0043] When the hydrogen feed is a fixed value, the heat released by the reaction is a fixed value (hydrogen can be considered to be completely converted). Analyzing from the entire reaction system, the heat released by the reaction essentially heats hydrogen and recycled C6. Therefore, the flow rate of recycled C6 and (the temperature of the reaction product - the temperature of recycled C6 entering the tubular reactor) are in an inverse proportion relationship. As previously mentioned, the temperature of the reaction product is recommended to be controlled at 190 °C. Then, the flow rate of recycled C6 and the temperature entering the tubular reactor are in a direct proportion relationship, and there is a temperature such that when the flow rate of recycled C6 changes, the inlet temperature of the tubular reactor remains at a fixed value, such as 150 °C. Therefore, when the benzene-hydrogen ratio is low, the temperature of recycled C6 entering the tubular reactor (the outlet temperature of the cooler) needs to be reduced. At this time, the logarithmic temperature difference of the heat exchange between the hot and cold fluid streams in the tubular reactor increases, and the heat exchange area needs to be reduced, and vice versa. In addition, the extraction temperature of recycled C6 increases with the increase in the number of trays. In order to minimize (or even not consume) the external cold energy consumed by the cooler, when the benzene-hydrogen ratio is low, it needs to be extracted from trays with a low numerical value, and vice versa.

[0044] In addition, the system of the present invention can adjust the side extraction and outlet positions according to the high or low benzene-hydrogen ratio by setting multiple side extraction positions of recycled C6 and the outlet position of the shell side of the tubular reactor, so as to maintain the optimal reaction conditions, greatly improving the stability and operating flexibility of the system.

[0045] In the third aspect, the present invention provides the application of the method described in the first aspect or the system described in the second aspect in the production of hydrogenated terphenyl.

[0046] Adopting the technical solution of the present invention, when the system operates stably, almost zero energy consumption operation of the reaction system can be achieved. For example, when the benzene-hydrogen ratio is 3.0, the pressure of the C6 removal tower is 120 kPaA, the recycled C6 is withdrawn from the 5th plate, the side draw temperature is 84 °C, and the distance from the shell side outlet of the shell-and-tube reactor to the center of the shell side is 1.3 m, the energy consumption of the heater is 0, the cooling water consumption of the cooler is 0, while the inlet temperature of the shell-and-tube reactor is 150 °C and the outlet temperature is 190 °C, achieving very good technical effects. Brief Description of the Drawings

[0047] Figure 1 It is a system and process flow diagram for producing hydrogenated terphenyl of the present invention.

[0048] The reference numerals in the drawings are as follows: 1: fresh benzene; 2: C6 mixture; 3: stream containing hydrogenated terphenyl; 4: recycled C6; 5: fresh hydrogen; 6: reactants; 7: reaction products; R-101: shell-and-tube reactor; E-101: recycled C6 heater; E-102: recycled C6 cooler; T-101: C6 removal tower; ①: first outlet of the shell-and-tube reactor; ②: second outlet of the shell-and-tube reactor; ③: third outlet of the shell-and-tube reactor. Detailed Embodiments

[0049] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments and drawings. The specific embodiments described herein are only used to explain the present invention and do not constitute any limitation to the present invention.

[0050] As a specific embodiment of the present invention, the method for producing hydrogenated terphenyl includes the following steps:

[0051] 1) Provide a system for producing hydrogenated terphenyl as shown in Figure 1 , including a shell-and-tube reactor R-101, a recycled C6 heater E-101, a recycled C6 cooler E-102 and a C6 removal tower T-101;

[0052] In this system, fresh benzene 1 and reaction products 7 enter T-101 from different trays, and a C6 mixture 2 containing benzene, methylcyclopentane and cyclohexane is obtained at the top of the tower, and a stream 3 containing hydrogenated terphenyl is obtained at the bottom of the tower;

[0053] 2) The side stream of T-101 (at the 3rd, 5th or 7th tray) withdraws the recycled C6 containing benzene, methylcyclopentane and cyclohexane. The recycled C6 enters the shell side of R-101 after passing through E-102, flows in parallel with the material in the tubes of R-101, and undergoes heat exchange. The material in the tubes of R-101 is cooled, and the recycled C6 is heated. The heated recycled C6 flows out from one of the outlets ①, ② and ③ at the shell side of R-101. Outlet ① is located at the center of the shell side, and the distance between adjacent two outlets is 0.18 - 0.22 times the length of the tubes of the tubular reactor.

[0054] It should be noted that during the first startup, the benzene-containing raw material (fresh benzene 1) enters T-101 from the 9th tray, is withdrawn from the side stream of T-101, then enters E-101 through the shell side of R-101, is heated to the initial reaction temperature, and then enters the tubes of R-101 after being mixed with fresh hydrogen to carry out the hydroalkylation reaction to obtain the reaction product. The reaction product enters T-101 from the 12th tray for C6 removal treatment.

[0055] 3) The recycled C6 then enters E-101 and is heated to the initial reaction temperature, and then enters the tubes of R-101 filled with catalyst after being mixed with fresh hydrogen 5, and the hydroalkylation reaction occurs. The reaction releases heat, and the material in the tubes exchanges heat with the recycled C6 in the shell side. The recycled C6 is gradually heated, and the reaction material is gradually cooled. Finally, the reaction product 7 is obtained at the outlet of the tube side of R-101;

[0056] It should be noted that in the above step 2), when the outlet temperature of the shell side of R-101 reaches the initial reaction temperature (140 - 200 °C), then in step 3), E-101 is deactivated, and the recycled C6 passes through the bypass line of E-101 (without further heating), and then enters the tube side of R-101 after being mixed with fresh hydrogen 5, and the hydroalkylation reaction occurs in the tubes filled with catalyst. The reaction product 7 enters T-101 to achieve separation.

[0057] The present invention does not make special limitations on the type and dosage of the catalyst, and conventional hydrocatalysts in the art can be used. For example, the catalyst can be the catalyst in Example 1 of Patent CN114130421A.

[0058] Example 1

[0059] A 10,000-ton / year system for producing hydrogenated terphenyls adopts Figure 1 the system and process flow shown and the above specific implementation manners. In the initial stage of the system operation, E-101 is put into use. When the outlet temperature of the shell side of R-101 reaches 168 °C, E-101 is deactivated, the bypass line of E-101 is enabled and E-102 is put into use simultaneously. The main process operation parameters during stable operation are listed in Table 1.

[0060] Table 1

[0061]

[0062]

[0063] Example 2

[0064] A production system of hydrogenated terphenyl with an annual output of 10,000 tons adopts the system and process flow shown in Figure 1 and the above specific implementation manners. In the initial stage of the system operation, E-101 is put into use. When the outlet temperature of the shell side of R-101 reaches 173 °C, E-101 is stopped, the cross-line of E-101 is enabled and E-102 is put into use at the same time. The main process operation parameters during stable operation are listed in Table 2.

[0065] Table 2

[0066]

[0067]

[0068] Example 3

[0069] A production system of hydrogenated terphenyl with an annual output of 10,000 tons adopts the system and process flow shown in Figure 1 and the above specific implementation manners. In the initial stage of the system operation, E-101 is put into use. When the outlet temperature of the shell side of R-101 reaches 168 °C, E-101 is stopped, the cross-line of E-101 is enabled and E-102 is put into use at the same time. The main process operation parameters during stable operation are listed in Table 3.

[0070] Table 3

[0071]

[0072] Comparative Example 1

[0073] Comparative Example 1 is Example 1 in Patent CN115991631A, with a hydrogen conversion rate of 93%, a cyclohexylbenzene selectivity of 72%, and a hydrogenated terphenyl selectivity of 9%. However, this example does not give the specific energy consumption. Through calculation, the electric power required to heat 6100 kg / h of the first-stage feed from 56 °C to 155 °C is 904 kW, and the energy consumption is relatively high.

[0074] From the operation parameters of Example 2 and Comparative Example 1, it can be seen that under the condition of comparable selectivity of hydrogenated terphenyl, the method and device of the present invention hardly consume energy, and the coupling of heat and cold is well achieved, obtaining good technical effects.

[0075] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A method for producing hydrogenated terphenyl, comprising the following steps: (1) subjecting a benzene-containing raw material to a hydroalkylation reaction with hydrogen in the presence of a catalyst to obtain a reaction product; (2) The reaction product is subjected to a C6 removal treatment to obtain a circulating C6 logistics containing benzene, methylcyclopentane and cyclohexane and a logistics containing hydrogenated terphenyl, wherein the circulating C6 logistics is subjected to a cooling treatment and then heat exchanged with the reaction product in step (1).

2. The method according to claim 1, characterized in that The hydroalkylation reaction in step (1) is carried out in the tubes of a shell-and-tube reactor, and the circulating C6 stream in step (2) enters the shell side of the shell-and-tube reactor after cooling treatment to perform heat exchange with the reaction products in the tubes; preferably, the shell side of the shell-and-tube reactor is provided with N outlets from top to bottom, N ≥ 2, the first outlet is located at the center of the shell side, and the spacing between the Nth outlet and the N-1th outlet is 0.05 to 0.25 times, preferably 0.16 to 0.24 times, and more preferably 0.18 to 0.22 times the length of the tubes of the shell-and-tube reactor; and / or, In step (2), the C6 removal treatment is carried out in a C6 removal tower; preferably, the C6 removal tower comprises a benzene-containing raw material feed port, a reaction product feed port and a plurality of preferably three circulating C6 side withdrawal ports, wherein the reaction product enters the C6 removal tower from the reaction product feed port for C6 removal treatment, and a circulating C6 logistics containing benzene, methylcyclopentane and cyclohexane is obtained by side withdrawal at the circulating C6 side withdrawal port, and a logistics containing hydrogenated terphenyl is obtained at the bottom of the tower; and / or, In step (2), the cooling treatment is carried out in a cooler. Preferably, the cooling treatment includes cooling the circulating C6 logistics extracted from the side of the C6 removal tower; preferably, the outlet of the cooler is connected to the shell side inlet of the shell and tube reactor, so that the cooled circulating C6 logistics enters the shell side of the shell and tube reactor and performs heat exchange with the reaction products in the shell and tube.

3. The method according to claim 1 or 2, characterized in that In step (1), the molar ratio of benzene to hydrogen in the benzene-containing raw material is 2.0 to 4.0; and / or, The temperature of the hydroalkylation reaction is 140-200° C., preferably 150-190° C., and the pressure is 1.5-2.0 MPaG, preferably 1.6-1.8 MPaG; and / or, The benzene content in the benzene-containing raw material is 68 wt% to 72 wt%.

4. The method according to any one of claims 1 to 3, characterized in that In step (2), the operating pressure of the C6 removal treatment is 101 to 200 kPaA, preferably 120 to 160 kPaA; and / or, The benzene content in the circulating C6 stream is 68 wt% to 72 wt%; and / or, The temperature of the circulating C6 logistics is 75-110°C, and the temperature of the circulating C6 logistics after cooling treatment is 20-100°C, preferably 20-60°C or 60-90°C or 90-100°C.

5. The method according to any one of claims 1 to 4, characterized in that The method further comprises step (3): the circulating C6 stream after heat exchange in step (2) is returned to step (1) for hydroalkylation reaction with or without heating; Preferably, the heating of the circulating C6 logistics in step (3) is carried out in a heater; preferably, the circulating C6 logistics is heated to 140-200°C, preferably 150-190°C.

6. A system for producing hydrogenated terphenyl, comprising: (1) a shell-and-tube reactor comprising a shell and tube side, wherein the shell and tube side is used to carry out a hydroalkylation reaction of a benzene-containing raw material with hydrogen under the action of a catalyst to obtain a reaction product; (2) a C6 removal tower, comprising a benzene-containing raw material feed port, a reaction product feed port, and a plurality of preferably three circulating C6 side extraction ports, wherein the reaction product enters the C6 removal tower from the reaction product feed port for C6 removal treatment, and a circulating C6 stream containing benzene, methylcyclopentane, and cyclohexane is obtained by side extraction at the circulating C6 side extraction port, and a stream containing hydrogenated terphenyl is obtained at the bottom of the tower; (3) a cooler for cooling the circulating C6 stream drawn from the side of the C6 removal tower, and allowing the cooled circulating C6 stream to enter the shell side of the tubular reactor to perform heat exchange with the reaction products in the tubular reactor; (4) A heater for heating the benzene-containing feedstock or the circulating C6 stream flowing out of the shell side to the hydroalkylation reaction temperature.

7. The system according to claim 6, characterized in that The C6 removal tower is a plate tower, the circulating C6 side extraction port is located on the upper tray of the benzene-containing raw material feed port, and the reaction product feed port is located on the lower tray of the benzene-containing raw material feed port; Preferably, the total number of plates of the C6 removal tower is recorded as N', N' is an integer ≥10, the topmost plate of the C6 removal tower is recorded as the first plate, the benzene-containing raw material feed port is located at the 0.4N' to 0.6N' plate, the reaction product feed port is located at the 0.6N' to 0.8N' plate, and the circulating C6 side extraction port is located at the 0.15N' to 0.2N' or the 0.25N' to 0.35N' or the 0.35N' to 0.5N' plate; Preferably, the number of trays of the C6 removal tower is 15 to 20, the top tray of the C6 removal tower is marked as the first tray, the benzene-containing raw material feed port is located on the 8th to 10th trays, the reaction product feed port is located on the 11th to 13th trays, and the circulating C6 side extraction port is located on the 2nd to 4th or 4th to 6th or 6th to 8th trays; Preferably, the number of plates of the C6 removal tower is 15 to 20, the topmost plate of the C6 removal tower is marked as the first plate, the benzene-containing raw material feed port is located on the seventh plate, the reaction product feed port is located on the 12th plate, and the circulating C6 side extraction port is located on the third, fifth or seventh plate.

8. The system according to claim 6 or 7, characterized in that The cooler is provided with a temperature control device containing a cooling medium, and the temperature of the cooler outlet is controlled by adjusting the flow of the cooling medium.

9. The system according to any one of claims 6 to 8, characterized in that: The shell side of the shell and tube reactor is provided with N outlets from top to bottom, N ≥ 2, the first outlet is located at the center of the shell side, and the spacing between the Nth outlet and the N-1th outlet is 0.05 to 0.25 times the length of the shell and tube reactor, preferably 0.16 to 0.24 times, more preferably 0.18 to 0.22 times; Preferably, the shell side of the tubular reactor is provided with a first outlet, a second outlet and a third outlet in sequence from top to bottom, the first outlet is located at the center of the shell side, and When the molar ratio of benzene to hydrogen in the benzene-containing raw material is 2.0-2.5, a circulating C6 stream is extracted from the side of the third tray of the C6 removal tower, the outlet temperature of the cooler is 20-60°C, and the circulating C6 stream after heat exchange flows out from the first outlet of the shell side of the tubular reactor; When the molar ratio of benzene to hydrogen in the benzene-containing raw material is 2.5 to 3.0, a circulating C6 stream is extracted from the side of the fifth tray of the C6 removal tower, the outlet temperature of the cooler is 60 to 90° C., and the circulating C6 stream after heat exchange flows out from the second outlet of the shell side of the tubular reactor; When the molar ratio of benzene to hydrogen in the benzene-containing raw material is 3.0-4.0, a circulating C6 stream is extracted from the side of the 7th tray of the C6 removal tower, the cooler outlet temperature is 90-100°C, and the circulating C6 stream after heat exchange flows out from the third outlet of the shell side of the shell and tube reactor.

10. Use of the method according to any one of claims 1 to 5 or the system according to any one of claims 6 to 9 in the production of hydrogenated terphenyl.

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