A method for producing hydrogenated terphenyl, a reaction system and a multi-stage composite reactor and hydrogenated terphenyl obtained thereby

Abstract

A method, reaction system, multi-stage composite reactor, and resulting hydrogenated terphenyl are disclosed. The method includes feeding, reaction, and discharging. The reaction includes contacting the feed with a catalyst. The reaction comprises n stages in series, with catalysts in each stage loaded in a gradient manner, wherein n ≥ 3. The feed is divided into n groups and enters each of the n stages of the reaction. The feed includes raw materials and hydrogen, wherein the raw materials contain benzene. The system and method for producing hydrogenated terphenyl of this invention can produce hydrogenated terphenyl at different scales, can adapt to catalysts at different reaction temperatures, and ensures the same selectivity of hydrogenated terphenyl in each reactor.

Description

Technical Field

[0001] This invention relates to the field of terphenyl production technology, and more specifically to a method for producing hydrogenated terphenyl, a reaction system, a multi-stage composite reactor, and the resulting hydrogenated terphenyl. Background Technology

[0002] Heat transfer oil, also known as organic heat carrier, is a heat transfer medium. Due to its advantages such as uniform heating, accurate temperature control, good heat transfer effect, energy saving, and convenient transportation and operation, it is widely used in petroleum and petrochemical industries, chemical fiber industries, polysilicon, aerospace, and other fields. As its applications expand, its usage is also increasing. Hydrogenated terphenyl is currently the highest quality liquid-phase high-temperature heat transfer oil. Hydrogenated terphenyl is obtained by partially hydrogenating a mixture of ortho, meta, and para-terphenyls in different proportions (with a saturation of 40%). Hydrogenated terphenyl can operate at higher temperatures, with a flash point as high as 190℃, a pour point below -30℃, and low evaporation loss. Currently, the market price of hydrogenated terphenyl heat transfer oil is relatively high, and there is limited research on the reaction and distillation of hydrogenated terphenyl.

[0003] Patent CN103804114A discloses a method for preparing hydrogenated terphenyl, including steps such as biphenyl synthesis, first distillation, second distillation, and hydrogenation. This invention utilizes a high-performance, energy-saving tubular reactor. The biphenyl synthesis process includes: ① Mixing: Pure benzene and catalyst are mixed in a circulating tank and then pumped into a benzene evaporator for evaporation; ② Cracking: A measured amount of benzene vapor is preheated in a heat exchanger and then enters a tubular reactor, where the benzene vapor reacts; ③ Cooling: The reaction gas enters a heat exchanger from the tubular reactor, and after heat exchange, it is cooled to liquefy the gaseous benzene, biphenyl, and terphenyl. Then, the mixture undergoes a first distillation: the benzene and biphenyl liquid are placed in a distillation vessel, and benzene is recovered under atmospheric pressure as a synthesis raw material. Then, the mixture is distilled under reduced pressure to obtain biphenyl. A second distillation is then performed: the residue at the bottom of the distillation vessel is distilled a second time, and the low-boiling components are sent to the distillation vessel to obtain terphenyl. Finally, the terphenyl is hydrogenated in a high-pressure hydrogenation vessel to obtain the hydrogenated terphenyl product.

[0004] Patent CN111018652A discloses a method for preparing high-purity hydrogenated terphenyl heat transfer oil. The method mainly includes connecting a vacuum distillation column after a terphenyl hydrogenation reactor; sampling the product after the terphenyl hydrogenation reaction for chromatographic analysis to determine the components and their contents; evacuating the vacuum distillation column; allowing the material from the hydrogenation reactor to be drawn into the vacuum distillation column by self-priming; closing the inlet valve after loading; opening the top valve; collecting the top material through vacuum distillation; and then cooling the top material through a heat exchanger before it enters a product storage tank. This invention uses a reactor for preparing hydrogenated terphenyl heat transfer oil but does not disclose the reactor's operating conditions or feeding conditions.

[0005] To scale up industrial operations and approximate actual industrial applications, it is essential to have reaction systems capable of producing hydrogenated terphenyl at different scales. Summary of the Invention

[0006] In view of the problems existing in the prior art, one of the objectives of the present invention is to provide a method for producing hydrogenated terphenyl, which achieves the production capacity of hydrogenated terphenyl through n-stage series reaction operation. This method has the advantages of simple operation and easy control.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for producing hydrogenated terphenyl includes feeding, reaction, and discharging. The reaction includes contacting the feed with a catalyst. The reaction comprises n stages of reaction in series, with catalysts for each stage loaded in a gradient manner, wherein n ≥ 3. The feed is divided into n groups and fed into the n stages of reaction respectively. The feed includes raw materials and hydrogen, wherein the raw materials contain benzene; preferably, it is a mixture of benzene and at least one of biphenyl and cyclohexane; more preferably, it is benzene, or a mixture of benzene and biphenyl, or a mixture of benzene, biphenyl, and cyclohexane; more preferably, it is a mixture of benzene, biphenyl, and cyclohexane, wherein the biphenyl content preferably does not exceed 10 wt%. The n-stage feeding means that the feed is fed separately into the first, second, ..., nth stages of the reaction.

[0009] In the above technical solution, the feed amount of raw materials entering the first stage of reaction is 30%-70 wt% of the total feed amount; the feed amount of raw materials entering each stage of reaction from the second stage to the penultimate stage is 8-16 wt% of the total feed amount; and the feed amount of raw materials entering the final stage of reaction is 15-25 wt% of the total feed amount.

[0010] In the above technical solution, the amount of hydrogen entering the first stage of reaction is 8%-13wt% of the total hydrogen feed; the amount of hydrogen entering each stage of reaction from the second stage to the penultimate stage is 1.1-1.3 times the amount of hydrogen entering the previous stage of reaction; and the amount of hydrogen entering the final stage of reaction is 1.1-1.45 times the amount of hydrogen entering the penultimate stage of reaction.

[0011] In the above technical solution, the gradient loading of catalysts in each stage of the reaction includes: the catalyst loading height of each stage from the second stage to the penultimate stage is 1.1-1.3 times that of the catalyst loading height of the previous stage; the catalyst loading height of the last stage is 1.1-1.45 times that of the catalyst loading height of the previous stage.

[0012] In the above technical solution, the raw material further includes at least one of biphenyl and cyclohexane; and / or,

[0013] The inlet temperature for each reaction stage is 140℃-180℃, with a temperature rise of 20℃-50℃; and / or,

[0014] The inlet temperature difference for each reaction stage is ±3℃, and the temperature rise difference for each reaction stage is ±3℃; and / or,

[0015] The reaction pressure in each stage is 300 kPa to 800 kPa.

[0016] A second objective of this invention is to provide a reaction system for producing hydrogenated terphenyl using the method described above, comprising a feed heater, a feed distributor, and n hydrogenation alkylation reactors connected in series.

[0017] In the above technical solution, the raw material is heated by the feed heater and then mixed with hydrogen before entering the reactor from the top of the first hydrogenation alkylation reactor. The reaction product is discharged from the reactor and enters the next hydrogenation alkylation reactor. The discharge from each hydrogenation alkylation reactor is mixed with the raw material and hydrogen from the next stage of reaction and then enters the reactor from the top of the next hydrogenation alkylation reactor. The resulting hydrogenated terphenyl product is discharged from the last hydrogenation alkylation reactor.

[0018] In the above technical solution, the feed rate into the first hydrogenation alkylation reactor is preferably 35%-65 wt% of the total feed rate; more preferably 40-55 wt% of the total feed rate; the inlet temperature of the first hydrogenation alkylation reactor is controlled by the feed heater, and the inlet temperature of the second to n-1 hydrogenation alkylation reactors is controlled by the feed rate into each of the second to n-1 hydrogenation alkylation reactors, which is 8%-16 wt% of the total feed rate; preferably 10-15 wt% of the total feed rate; the inlet temperature of the last hydrogenation reactor is controlled by the feed rate into the last hydrogenation alkylation reactor, which is 15%-25 wt% of the total feed rate; preferably 16-22 wt% of the total feed rate.

[0019] In the above technical solution, the temperature rise of the first reactor is controlled by the amount of hydrogen entering the first hydrogenation alkylation reactor, which is 8%-13% of the total hydrogen amount; preferably 8.5%-10 wt% of the total hydrogen amount; the temperature rise of the second to n-1th hydrogenation alkylation reactors is controlled by the amount of hydrogen entering the second to n-1th hydrogenation alkylation reactors, wherein the amount of hydrogen entering the second to n-1th hydrogenation alkylation reactors is 1.1-1.3 times the amount of hydrogen in the previous reactor; preferably 1.15-1.25 times the amount of hydrogen in the previous stage reaction; the temperature rise of the last hydrogenation alkylation reactor is controlled by the amount of hydrogen entering the last hydrogenation alkylation reactor, which is 1.1-1.45 times the amount of hydrogen entering the penultimate stage hydrogenation alkylation reactor; preferably 1.15-1.4 times.

[0020] In the above technical solution, the feed distributor is set at the inlet of each alkylation reactor, and is used to mix the feed from the previous hydrogenation alkylation reactor, the raw materials of this stage reaction and hydrogen, and then enter the next hydrogenation alkylation reactor at the top of the reactor.

[0021] In the above technical solution, the catalyst in each alkylation reactor is loaded according to the gradient.

[0022] A third objective of this invention is to provide a multi-stage composite reactor for producing hydrogenated terphenyl using the method described above. The reactor includes a feed heater, a hydrogenation alkylation reactor, a reactor feed distributor, and an inter-stage feed distributor. The raw materials and hydrogen are fed in stages. The alkylation reactor includes n catalyst beds, with the catalyst gradient-loaded. Specifically, the raw materials and hydrogen are fed in stages, i.e., feed is performed separately in the first, second, third, ... (n-1)th reactor beds.

[0023] In the above technical solution, the feed heater is located outside the reactor, before the reactor inlet; the reactor feed distributor is located at the reactor inlet; and the inter-stage feed distributor is located between every two catalyst bed sections inside the reactor.

[0024] In the above technical solution, the raw material is heated by the feed heater and then enters the reactor. It, along with the first-stage hydrogen, enters the first-stage catalyst bed of the reactor via the top reactor feed distributor. The second-stage raw material, the reaction product from the first-stage bed, and the hydrogen enter the second-stage catalyst bed of the reactor via the second-stage inter-stage feed distributor. Similarly, the (n-1)th stage bed raw material, the reaction product from the (n-2)th stage bed, and the hydrogen enter the (n-1)th stage catalyst bed of the reactor via the (n-1)th stage inter-stage feed distributor. The nth stage catalyst bed of the hydroalkylation reactor serves as a protective bed to ensure complete reaction of the feed hydrogen.

[0025] In the above technical solution, the feed rate into the first bed of the hydroalkylation reactor is 30%-70 wt% of the total feed rate; more preferably, it is 40-60 wt% of the total feed rate; the inlet temperature of the first bed of the reactor is controlled by the feed heater, and the inlet temperature of the second to (n-1)th beds of the reactor is controlled by the feed rate of each bed segment entering the second to (n-1)th beds of the reactor, which is 9%-15 wt% of the total feed rate, preferably 10%-15 wt% of the total feed rate.

[0026] In the above technical solution, the reactor temperature rise is controlled by the amount of hydrogen entering each bed section of the reactor. The amount of hydrogen entering the first bed section is 7%-14 wt% of the total hydrogen, preferably 8%-12 wt% of the total hydrogen. The amount of hydrogen entering each bed section from the second to the (n-2)th bed section is 1.05-1.35 times the amount of hydrogen in the previous section, preferably 1.1-1.25 times. The amount of hydrogen entering the (n-1)th bed section is 1.05-1.45 times the amount of hydrogen entering the (n-2)th bed section, preferably 1.1-1.4 times the amount of hydrogen entering the (n-2)th bed section.

[0027] In the above reaction, the catalyst loading of each bed section of the reactor is gradient-loaded, including: the catalyst loading height of each bed section from the second bed to the penultimate bed section is 1.05-1.35 times the catalyst loading height of the previous bed section; preferably 1.15-1.25 times; the catalyst loading height of the last bed section is 1.05-1.45 times the catalyst loading height of the penultimate bed section; preferably 1.1-1.4 times.

[0028] The fourth objective of this invention is to provide a method for producing hydrogenated terphenyl, or a reaction system for producing hydrogenated terphenyl, or a reactor prepared from the aforementioned method, or a method described above.

[0029] The beneficial effects of the present invention are at least in the following two aspects:

[0030] Firstly, the system for producing hydrogenated terphenyl of the present invention can produce hydrogenated terphenyl at different scales, can adapt to catalysts at different reaction temperatures, and ensures that the selectivity of hydrogenated terphenyl is the same in each reactor.

[0031] Secondly, since the raw materials themselves are used to control the inlet temperature and temperature rise of the reactor, the device has low energy consumption and saves a lot of costs. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of the reaction system in Example 2;

[0033] Figure 1The reference numerals in the attached figures are explained as follows: I represents the first hydroalkylation reactor; A1 represents the catalyst in the first hydroalkylation reactor; H1 represents the catalyst loading height in the first hydroalkylation reactor; II represents the second hydroalkylation reactor; A2 represents the catalyst in the second hydroalkylation reactor; H2 represents the catalyst loading height in the second hydroalkylation reactor; III represents the third hydroalkylation reactor; A3 represents the catalyst in the third hydroalkylation reactor; H3 represents the catalyst loading height in the third hydroalkylation reactor; IV represents the fourth hydroalkylation reactor; A4 represents the catalyst in the fourth hydroalkylation reactor; H4 represents the catalyst loading height in the fourth hydroalkylation reactor; V represents the fifth hydroalkylation reactor; A5 represents the catalyst in the fifth hydroalkylation reactor; H5 represents the catalyst loading height in the fifth hydroalkylation reactor; B represents the feed heater;

[0034] 1 represents hydrogen from outside the reactor; 2 represents the feedstock; 3 represents the feed to the first hydrogenation alkylation reactor after heat exchange and mixing with hydrogen; 4 represents the effluent from the first hydrogenation alkylation reactor; 5 represents the feed to the second hydrogenation alkylation reactor after mixing with feedstock and hydrogen; 6 represents the effluent from the second hydrogenation alkylation reactor; 7 represents the feed to the third hydrogenation alkylation reactor after mixing with feedstock and hydrogen; 8 represents the effluent from the third hydrogenation alkylation reactor; 9 represents the feed to the fourth hydrogenation alkylation reactor after mixing with feedstock and hydrogen; 10 represents the fourth hydrogenation alkylation reactor. 11-15 are the discharge from the alkylation reactor, and 16 is the hydrogen feed to the first to fifth hydrogenation alkylation reactors, respectively; 17 is the feed to the fifth hydrogenation alkylation reactor after the feed and hydrogen are mixed; 18 is the feed to the first hydrogenation alkylation reactor after being heated by heater B; 21-25 are the feed to the first to fifth hydrogenation alkylation reactors; C1, C2, C3, C4, and C5 are the feed distributors for the first, second, third, fourth, and fifth hydrogenation alkylation reactors, respectively.

[0035] Figure 2 The process flow diagram of the multi-stage composite reactor in Example 4 is shown.

[0036] Figure 2 The reference numerals in the attached figures are explained as follows: A is a six-stage hydroalkylation reactor; B is a feed heater; C is a feed distributor; D, E, F, and G are the inter-stage feed distributors for the second to fifth stages of the reactor, respectively; A1-A6 are the catalyst beds for the first to sixth stages of the hydroalkylation reactor; H1-H6 are the catalyst loading heights for the first to sixth stages of the reactor.

[0037] 1 is the raw material feed; 2 is hydrogen from outside the boundary; 3 is the heat carrier feed to the heat exchanger; 4 is the heat carrier discharge from the heater; 5 is the discharge from the hydroalkylation reactor; 21-25 are hydrogen feed; 11-15 are the raw material feeds for the first to fifth stages of the hydroalkylation reactor. Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0039] Example 1

[0040] Example 1 describes the reaction system for producing hydrogenated terphenyl according to the present invention. It employs a four-reactor system in series, including a feed heater, a first hydrogenation alkylation reactor, a second hydrogenation alkylation reactor, a third hydrogenation alkylation reactor, a fourth alkylation alkylation reactor, and reactor feed distributors. The first reactor feed distributor is located after the feed heater and before the first alkylation reactor, used to mix the raw material with hydrogen before feeding. The second to fourth reactor feed distributors are located between every two hydrogenation alkylation reactors. Each reactor bed is gradient-loaded with catalyst, and each reactor is gradient-fed; the feed rates are shown in Table 1. The catalyst gradient loading height is 30 cm for the first alkylation reactor, 33 cm for the second alkylation reactor, 36 cm for the third alkylation reactor, and 40 cm for the fourth alkylation reactor.

[0041] The raw materials (a mixture of benzene, biphenyl, and cyclohexane) are heated by a feed heater and mixed with hydrogen through a reactor feed distributor before entering the first hydrogenation alkylation reactor from the top of the reactor. The raw materials, the effluent from the first hydrogenation alkylation reactor, and hydrogen are then mixed and enter the second hydrogenation alkylation reactor from the top of the reactor. The raw materials, the effluent from the second hydrogenation alkylation reactor, and hydrogen are then mixed and enter the third hydrogenation alkylation reactor from the top of the reactor. Finally, the raw materials, the effluent from the third hydrogenation alkylation reactor, and hydrogen are mixed and enter the fourth hydrogenation alkylation reactor from the top of the reactor.

[0042] The reaction system for hydrogenating terphenyl with a capacity of 10,000 tons / year (8,000 operating hours per year) has a reactor reaction pressure of 500 kPa, a feed hydrogen temperature of 30°C, and a feed material consisting of a mixture of biphenyl, benzene, and cyclohexane at a feed temperature of 56°C. The weight percentages of biphenyl, benzene, and cyclohexane are 8%, 25%, and 67%, respectively. The outlet temperature of the feed heater is 155°C.

[0043] Table 1

[0044]

[0045] Under the above reaction and feed conditions, the inlet temperature of each reactor is controlled at 150°C, and the bed temperature of each of the four reactors is increased by 33°C, that is, the outlet temperature of each reactor is controlled at 183°C, so as to achieve the optimal efficiency of each reactor. Under these conditions, the hydrogen conversion rate is 93%, the cyclohexylbenzene selectivity is 72%, and the hydrogenated terphenyl selectivity is 9%. The system for producing hydrogenated terphenyl of the present invention can produce hydrogenated terphenyl of different scales, can adapt to catalysts with different reaction temperatures, and ensures that the selectivity of hydrogenated terphenyl is the same in each reactor.

[0046] Example 2

[0047] Example 2 uses the reaction method and a similar reaction system as in Example 1, with a scale of 10,000 tons / year of hydrogenated terphenyl. The difference lies in the excess of benzene and biphenyl reactants in the actual reaction. Because Example 1 only used four reactors and a temperature rise of 33°C, it resulted in more benzene recycling, leading to higher recycled benzene levels and increased energy consumption. Therefore, this example uses... Figure 1 The reaction system shown comprises five reactors: a feed heater B, a first hydrogenation alkylation reactor I, a second hydrogenation alkylation reactor II, a third hydrogenation alkylation reactor III, a fourth hydrogenation alkylation reactor IV, a fifth hydrogenation alkylation reactor V, and reactor feed distributors C1, C2, C3, C4, and C5. Feed distributor C1 is located after feed heater B and before the first alkylation reactor I, used to mix the feedstock with hydrogen before feeding. C2, C3, C4, and C5 are located between every two hydrogenation alkylation reactors. Each reactor bed is gradient-loaded with catalyst, and each reactor is gradient-fed; the feed rates are shown in Table 2. The catalyst gradient loading height is 20 cm for the first alkylation reactor, 22 cm for the second alkylation reactor, 24 cm for the third alkylation reactor, 26 cm for the fourth alkylation reactor, and 33 cm for the fifth alkylation reactor.

[0048] In this process, raw material 21 is heated by feed heater B and mixed with hydrogen 11 by reactor feed distributor 3 and enters the first hydrogenation alkylation reactor I from the top of the reactor. Raw material 22, the discharge 4 from the first hydrogenation alkylation reactor, and hydrogen 12 are mixed and then enter the second hydrogenation alkylation reactor II from the top of the reactor. Raw material 23, the discharge 6 from the second hydrogenation alkylation reactor, and hydrogen 13 are mixed and then enter the third hydrogenation alkylation reactor III from the top of the reactor. Raw material 24, the discharge 8 from the third hydrogenation alkylation reactor, and hydrogen 14 are mixed and then enter the fourth hydrogenation alkylation reactor IV from the top of the reactor. Raw material 25, the discharge 10 from the fourth hydrogenation alkylation reactor, and hydrogen 15 are mixed and then enter the fourth hydrogenation alkylation reactor IV from the top of the reactor.

[0049] The reactor reaction pressure is 500 kPa, the feed hydrogen temperature is 30℃, the feed material is a mixture of biphenyl, benzene and cyclohexane at a feed temperature of 56℃, and the weight percentages of biphenyl, benzene and cyclohexane are 8%:25%:67%. The feed heater outlet temperature is 152℃.

[0050] Table 2

[0051]

[0052] Under the above reaction and feed conditions, the inlet temperature of each reactor is controlled at 150°C, and the bed temperature rise of each of the five reactor stages is 30°C, meaning the outlet temperature of each reactor stage is controlled at 180°C. This allows each reactor to achieve its optimal efficiency. Under these conditions, the hydrogen conversion rate is 92%, the cyclohexylbenzene selectivity is 70%, and the hydrogenated terphenyl selectivity is 11%. Because five reactors are used, the feed rates of benzene and biphenyl are reduced, thereby decreasing the amount of unreacted benzene and biphenyl circulating. Simultaneously, the reactor temperature rise is also lower than in Example 1.

[0053] Example 3

[0054] Example 3 describes a multi-stage composite reactor for producing hydrogenated terphenyl, employing a five-stage fixed-bed hydrogenation alkylation reactor. The reactor includes a feed distributor, a feed heater, the hydrogenation alkylation reactor, a second-stage inter-stage feed distributor, a third-stage inter-stage feed distributor, and a fourth-stage inter-stage feed distributor. The catalyst is packed in a five-stage gradient, with the first four stages forming the reaction bed and the fifth stage forming the protective bed. The catalyst loading height is 22 cm for the first stage, 24 cm for the second stage, 26 cm for the third stage, 28 cm for the fourth stage, and 36 cm for the fifth stage protective layer. Each stage is fed in a gradient, and the feed rates are shown in Table 3.

[0055] In this process, the raw material is heated by the feed heater and mixed with hydrogen through the reactor feed distributor before entering the fixed-bed hydroalkylation reactor from the top. The raw material feed is mixed with the effluent from the first-stage hydroalkylation reactor and hydrogen, and then enters the second-stage bed of the hydroalkylation reactor through the second-stage inter-stage feed distributor. The raw material feed is mixed with the effluent from the second-stage hydroalkylation reactor and hydrogen, and then enters the third-stage bed of the hydroalkylation reactor through the third-stage inter-stage feed distributor. The raw material feed is mixed with the effluent from the third-stage hydroalkylation reactor and hydrogen, and then enters the fourth-stage bed of the hydroalkylation reactor through the fourth-stage inter-stage feed mixing distributor. Finally, the hydrogenation reaction is completed by passing through the protection bed of the hydroalkylation reactor.

[0056] A multi-stage composite reactor for hydrogenating terphenyl with a capacity of 10,000 tons / year (8,000 operating hours per year) has a reactor reaction pressure of 500 kPa, a feed hydrogen temperature of 30°C, and a feed material consisting of a mixture of biphenyl, benzene, and cyclohexane at a feed temperature of 56°C. The weight percentages of biphenyl, benzene, and cyclohexane are 8%, 25%, and 67%, respectively. The outlet temperature of the feed heater is 150°C.

[0057] Table 3

[0058]

[0059]

[0060] Under the above reaction and feed conditions, the inlet temperature of each reactor is controlled at 148°C, and the temperature rise of each section of the reactor bed is the same at 31°C, that is, the outlet temperature of each section of the reactor is controlled at 179°C, so as to maximize the efficiency of the catalyst in each section of the reactor bed. Under these conditions, the hydrogen conversion rate is 93%, the cyclohexylbenzene selectivity is 72%, and the hydrogenated terphenyl selectivity is 11%.

[0061] Example 4

[0062] Example 4 uses the reactor and reaction method from Example 3, maintaining a scale of 10,000 tons / year of hydrogenated terphenyl. The difference lies in the excess of benzene and biphenyl in the actual reaction. Because Example 3 only reduced the reactor inlet temperature to 148°C and increased the temperature of each reactor bed by 31°C, it resulted in excessive benzene recycling, leading to high circulating benzene levels and increased operating energy consumption. Therefore, this example employs... Figure 2The fixed-bed reactor shown has six bed layers: the first five are reaction beds, and the sixth is a protective bed. It includes a feed heater B, a six-stage hydroalkylation reactor A, a reactor feed distributor C, a second-stage inter-stage feed distributor D, a third-stage inter-stage feed distributor E, and a fourth-stage inter-stage feed distributor F. The catalyst is packed in six gradient stages (A1-A6), with the first five stages being reaction beds and the sixth stage being a protective bed. The catalyst loading height is 20 cm for the first stage, 22 cm for the second, 24 cm for the third, 26 cm for the fourth, 28 cm for the fifth, and 35 cm for the sixth protective bed. The feed rates for each reaction stage are shown in Table 4.

[0063] In this process, raw material 1 is heated by feed heater B and mixed with hydrogen 21 via reactor feed distributor C, then enters the fixed-bed hydroalkylation reactor from the top of the reactor. Raw material feed 12 is mixed with the effluent from the first-stage hydroalkylation reactor and hydrogen 22, then enters the second-stage bed of the hydroalkylation reactor via the second-stage inter-stage feed distributor D. Raw material feed 13 is mixed with the effluent from the second-stage hydroalkylation reactor and hydrogen 23, then enters the third-stage bed of the hydroalkylation reactor via the third-stage inter-stage feed distributor E. Raw material feed 14 is mixed with the effluent from the third-stage hydroalkylation reactor and hydrogen 24, then enters the fourth-stage bed of the hydroalkylation reactor via the fourth-stage inter-stage feed mixing distributor F. Finally, the hydrogenation reaction is completed by passing through the protection bed of the hydroalkylation reactor.

[0064] The reactor reaction pressure remains at 500 kPa, the feed hydrogen temperature is 30°C, the feed material is a mixture of biphenyl, benzene and cyclohexane at a feed temperature of 56.4°C, and the weight percentages of biphenyl, benzene and cyclohexane are 8%:25%:67%. The feed heater outlet temperature is 151.7°C.

[0065] Table 4

[0066]

[0067] Under the above reaction and feed conditions, the inlet temperature of each reactor is controlled at 150°C, and the temperature rise of each bed section is controlled at 30°C, meaning the outlet temperature of each reactor section is controlled at 180°C. This allows each reactor to achieve optimal efficiency. Under these conditions, the hydrogen conversion rate is 95%, the cyclohexylbenzene selectivity is 71%, and the hydrogenated terphenyl selectivity is 12%. Because the composite reactor uses 5 reaction bed sections and 1 protective bed section, the feed rates of benzene and biphenyl are reduced, thereby reducing the amount of unreacted benzene and biphenyl circulating. At the same time, the temperature rise of the reactor is also lower than in Example 3.

[0068] Comparative Example 1

[0069] Compared with the reaction system for producing hydrogenated terphenyl in Example 1, a four-reactor system in series was used, including a feed heater, a first hydrogenation alkylation reactor, a second hydrogenation alkylation reactor, a third hydrogenation alkylation reactor, a fourth alkylation alkylation reactor, and a reactor feed distributor. The first reactor feed distributor was located after the feed heater and before the first alkylation reactor, and was used to mix the feedstock with hydrogen before feeding. The second to fourth reactor feed distributors were located between every two hydrogenation alkylation reactors. Each reactor was fed with equal amounts of feed, and the catalyst was non-gradiently packed, with a catalyst packing height of 33 cm in each alkylation reactor.

[0070] In this process, the raw materials (including cyclohexane in addition to benzene and biphenyl) are heated by the feed heater and mixed with hydrogen through the reactor feed distributor before entering the first hydrogenation alkylation reactor from the top of the reactor. The raw materials, the effluent from the first hydrogenation alkylation reactor, and hydrogen are then mixed and enter the second hydrogenation alkylation reactor from the top of the reactor. The raw materials, the effluent from the second hydrogenation alkylation reactor, and hydrogen are then mixed and enter the third hydrogenation alkylation reactor from the top of the reactor. Finally, the raw materials, the effluent from the third hydrogenation alkylation reactor, and hydrogen are mixed and enter the fourth hydrogenation alkylation reactor from the top of the reactor.

[0071] The reaction system for hydrogenating terphenyl with a capacity of 10,000 tons / year (8,000 operating hours per year) has a reactor reaction pressure of 500 kPa, a feed hydrogen temperature of 30°C, and a feed material consisting of a mixture of biphenyl, benzene, and cyclohexane at a feed temperature of 56°C. The weight percentages of biphenyl, benzene, and cyclohexane are 8%, 25%, and 67%, respectively. The outlet temperature of the feed heater is 155°C.

[0072] Table 5

[0073]

[0074] Under the above reaction and feeding conditions, the inlet temperature of the first reactor was controlled at 146℃. The temperature rise of each of the four reactors was different, at 50℃, 61℃, 70℃, and 82℃ respectively. This completely failed to achieve the optimal efficiency of each reactor, exceeding the optimal reaction temperature of 180℃-210℃ that the catalyst could tolerate, resulting in production not proceeding normally. This comparative example verifies the effectiveness of the method of the present invention, indicating that the method of the present invention can maximize the performance of the catalyst in each stage of the reactor.

[0075] Comparative Example 2

[0076] A five-stage fixed-bed hydroalkylation reactor is adopted, including a reactor feed distributor, a feed heater, a hydroalkylation reactor, a second-stage inter-stage feed distributor, a third-stage inter-stage feed distributor, and a fourth-stage inter-stage feed distributor. Each stage of the reactor is fed with equal amounts of catalyst, and the catalyst is non-gradiently packed. The catalyst packing height of each alkylation reactor is 30 cm. The feed rates are shown in Table 6.

[0077] In this process, the raw material is heated by the feed heater and mixed with hydrogen through the reactor feed distributor before entering the fixed-bed hydroalkylation reactor from the top. The raw material feed is mixed with the effluent from the first-stage hydroalkylation reactor and hydrogen, and then enters the second-stage bed of the hydroalkylation reactor through the second-stage inter-stage feed distributor. The raw material feed is mixed with the effluent from the second-stage hydroalkylation reactor and hydrogen, and then enters the third-stage bed of the hydroalkylation reactor through the third-stage inter-stage feed distributor. The raw material feed is mixed with the effluent from the third-stage hydroalkylation reactor and hydrogen, and then enters the fourth-stage bed of the hydroalkylation reactor through the fourth-stage inter-stage feed mixing distributor. Finally, the hydrogenation reaction is completed by passing through the protection bed of the hydroalkylation reactor.

[0078] A multi-stage composite reactor for hydrogenating terphenyl with a capacity of 10,000 tons / year (8,000 operating hours per year) has a reactor reaction pressure of 500 kPa, a feed hydrogen temperature of 30°C, a feed material consisting of a mixture of biphenyl, benzene, and cyclohexane at a feed temperature of 56°C, and a weight percentage of biphenyl, benzene, and cyclohexane of 8%, 25%, and 67%. The outlet temperature of the feed heater is 150°C.

[0079] Table 6

[0080]

[0081]

[0082] Under the above reaction and feeding conditions, the inlet temperature of the first stage of the reactor is controlled at 148℃. The temperature rise of each bed section of the reactor is different, at 49℃, 60℃, 69℃, and 80℃ respectively. This completely fails to achieve the optimal efficiency of each bed section of the reactor, and completely exceeds the optimal reaction temperature that the catalyst can tolerate, 180℃-210℃, resulting in the inability to carry out normal production. This comparative example verifies the effectiveness of the method of the present invention, indicating that the method of the present invention can maximize the performance of the catalyst in each stage of the reactor.

[0083] Comparative Example 3

[0084] A two-reactor system in series is employed, comprising a feed heater, a first hydrogenation alkylation reactor, a second hydrogenation alkylation reactor, and a reactor feed distributor. The first reactor feed distributor is located after the feed heater and before the first alkylation reactor, used to mix the feedstock with hydrogen before feeding. The second reactor feed distributor is located between the two alkylation reactors, with gradient feeding to each reactor; the feed rates are shown in Table 7. The catalyst is gradient-loaded, with a catalyst loading height of 65 cm in the first alkylation reactor and 75 cm in the second alkylation reactor.

[0085] In this process, the raw materials (a mixture of benzene, biphenyl, and cyclohexane) are heated by the feed heater and mixed with hydrogen by the reactor feed distributor before entering the first hydrogenation alkylation reactor from the top of the reactor. The raw materials, the effluent from the first hydrogenation alkylation reactor, and hydrogen are mixed and then enter the second hydrogenation alkylation reactor from the top of the reactor.

[0086] The reaction system for hydrogenating terphenyl with a capacity of 10,000 tons / year (8,000 operating hours per year) has a reactor reaction pressure of 500 kPa, a feed hydrogen temperature of 30°C, and a feed material consisting of a mixture of biphenyl, benzene, and cyclohexane at a feed temperature of 56°C. The weight percentages of biphenyl, benzene, and cyclohexane are 8%, 25%, and 67%, respectively. The outlet temperature of the feed heater is 155°C.

[0087] Table 7

[0088]

[0089]

[0090] Under the above reaction and feeding conditions, the inlet temperature of the first reactor is controlled at 150°C, the temperature rise of the first reactor is 42°C, and the temperature rise of the second reactor reaches 120°C. Under these conditions, the optimal efficiency of the catalyst in the reactor bed cannot be fully utilized, and the optimal reaction temperature that the catalyst can tolerate, 180°C-210°C, is completely exceeded, resulting in the inability to carry out normal production. This comparative example verifies the effectiveness of the method of the present invention, indicating that the method of the present invention can maximize the performance of the catalyst in each stage of the reactor.

Claims

1. A method for producing hydrogenated terphenyl, comprising feeding, reacting, and discharging, wherein the reaction comprises contacting the feed with a catalyst; wherein, The reaction comprises n stages in series, with catalysts for each stage loaded in a gradient manner, where n ≥ 3. The feed is divided into n groups and enters each of the n stages. The feed includes raw materials and hydrogen, wherein the raw materials contain benzene, biphenyl, and cyclohexane. The amount of raw material entering the first stage is 30%-70 wt% of the total raw material feed. The amount of raw material entering each of the second to penultimate stages is 8-16 wt% of the total raw material feed. The amount of raw material entering the final stage is 15-25 wt% of the total raw material feed. The amount of hydrogen entering the first stage is 8%-13 wt% of the total hydrogen feed. The amount of hydrogen entering each of the second to penultimate stages is 1.1-1.3 times the amount of hydrogen entering the previous stage. The amount of hydrogen entering the final stage is 1.1-1.45 times the amount of hydrogen entering the penultimate stage.

2. The method according to claim 1, characterized in that, The gradient loading of catalysts in each stage of the reaction includes: the catalyst loading height of each stage from the second stage to the penultimate stage is 1.1-1.3 times that of the catalyst loading height of the previous stage; the catalyst loading height of the last stage is 1.1-1.45 times that of the catalyst loading height of the penultimate stage.

3. The method according to any one of claims 1-2, characterized in that: The inlet temperature of each reaction stage is 140℃-180℃, and the temperature rise is 20℃-50℃.

4. The method according to any one of claims 1-2, characterized in that: The inlet temperature difference for each reaction stage is ±3℃, and the temperature rise difference for each reaction stage is ±3℃.

5. The method according to any one of claims 1-2, characterized in that: The reaction pressure in each stage is 300 kPa to 800 kPa.

6. The method according to claim 1, characterized in that, After being heated by the feed heater, the raw material is mixed with hydrogen and enters the reactor from the top of the first hydrogenation alkylation reactor. The reaction product is discharged from the reactor and enters the next hydrogenation alkylation reactor. The effluent from each hydrogenation alkylation reactor is mixed with the raw material and hydrogen from the next stage of reaction and enters the reactor from the top of the next hydrogenation alkylation reactor. The resulting hydrogenated terphenyl product is discharged from the last hydrogenation alkylation reactor.

7. The method according to claim 6, characterized in that, After being heated by the feed heater, the raw materials are mixed with hydrogen and then enter the reactor from the top of the first hydrogenation alkylation reactor through the feed distributor. The reaction products are discharged from the reactor and enter the next hydrogenation alkylation reactor.

8. The method according to claim 7, characterized in that, The effluent from each hydroalkylation reactor is mixed with the feedstock and hydrogen from the next stage of reaction and then fed into the next hydroalkylation reactor from the top via a feed distributor; the resulting hydrogenated terphenyl product is discharged from the last hydroalkylation reactor.

9. The method according to claim 6, characterized in that, The raw materials, after being heated by the feed heater, enter the reactor and, together with the first-stage hydrogen, enter the first-stage catalyst bed of the reactor via the reactor top feed distributor. The second-stage raw materials of the hydroalkylation reactor, the reaction effluent from the first-stage bed, and the hydrogen enter the second-stage catalyst bed of the reactor via the second-stage inter-stage feed distributor. The (n-1)th-stage bed raw materials of the hydroalkylation reactor, the reaction effluent from the (n-2)th-stage bed, and the hydrogen enter the (n-1)th-stage catalyst bed of the reactor via the (n-1)th-stage inter-stage feed distributor.

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