A method for continuous production of diisopropyl naphthalene

Abstract

This invention relates to the field of fine chemical technology and proposes a method for the continuous production of diisopropylnaphthalene. The method utilizes a feeding unit, a multi-tandem alkylation reaction unit, a reaction liquid separation unit, a distillation and crystallization purification unit, and a dedicated catalyst preparation unit. This method employs a continuous feeding, continuous discharging, and online catalyst separation and regeneration cycle, fundamentally solving the problems of frequent catalyst replacement and difficulty in long-term stable continuous operation in traditional fixed-bed processes. This effectively improves product yield and successfully achieves stable, industrial-scale continuous production of diisopropylnaphthalene.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a method for the continuous production of diisopropylnaphthalene. Background Technology

[0002] 2,6-Diisopropylnaphthalene is an important organic chemical raw material. It is oxidized to produce 2,6-naphthalenedicarboxylic acid, which is then esterified and polycondensed to produce polyethylene naphthalate (PEN). Compared with 2,6-dimethylnaphthalene, PEN has the advantages of readily available raw materials, mild reaction conditions, and low cost, making it the most ideal raw material for the industrial production of PEN.

[0003] Currently, the alkylation process (a gas-liquid-solid three-phase reaction system) using naphthalene and propylene as raw materials and solid molecular sieves as catalysts is mainly carried out in industrial applications using batch and fixed-bed continuous processes. Batch processes suffer from long reaction cycles, low production efficiency, and poor product quality stability, making them unsuitable for large-scale production. Foreign companies have largely achieved continuous production processes, and many domestic institutions are also conducting research and development on fixed-bed continuous processes, focusing on key technologies such as catalyst preparation, optimization of alkylation reaction conditions, and post-treatment purification. However, existing fixed-bed continuous processes generally suffer from short catalyst lifetimes, mostly around 300 hours, requiring frequent catalyst replacements during industrialization, making it difficult to achieve long-term stable operation and large-scale production. To date, China has not achieved a breakthrough in the industrialization of continuous alkylation processes, and no related industrial continuous plants have been built and put into operation as reported in public documents or literature. Therefore, developing highly automated continuous alkylation processes and complete sets of equipment is of great significance for breaking foreign technological monopolies, overcoming key technological bottlenecks, and promoting the domestic production and independent control of my country's PEN industry.

[0004] Existing patents related to fixed-bed processes mostly focus on the improvement of molecular sieve catalysts and the optimization of process parameters. For example, Sinopec proposed a three-bed tandem process of MCM-56 / ZSM-5 / MCM-22 in patent CN112661587A, which improves the selectivity of 2,6-diisopropylnaphthalene to 30% by stepwise control of alkylation and isomerization pathways. However, due to the limitations of the fixed-bed reactor structure, the catalyst activity decreases by more than 15% after 200 hours of continuous operation, requiring shutdown for regeneration. Another Sinopec patent, CN105272801A, uses organosilicon zeolite catalysts to suppress alkyl side reactions. Although it controls the triisopropylnaphthalene content below 11%, the catalyst life still does not exceed 300 hours, and the regeneration process requires interruption of feed, resulting in less than 80% of the annual effective production time.

[0005] ExxonMobil's US20030004625A1 patent uses high-silica H-MOR molecular sieves as its core, achieving a 64% selectivity for 2,6-diisopropylnaphthalene through pore confinement. However, this catalyst is prone to pore blockage due to carbon buildup in a fixed bed, and literature data shows its half-life is only 250 hours. Furthermore, catalyst replacement requires reactor disassembly, resulting in equipment downtime and losses. Dalian University of Technology's CN114558611A patent prepares a La / Ce-MOR / SAPO-5 catalyst through rare earth modification, extending its lifespan to over 300 hours. However, the catalyst cannot be replenished online in a fixed bed, and the naphthalene conversion rate still drops from 90% to 65% at the end of the reaction, with significant fluctuations in product purity.

[0006] In-depth analysis reveals that the catalyst lifetime bottleneck in fixed-bed processes stems from inherent structural defects: Firstly, the catalyst in a fixed bed is in a static, stacked state, and carbon deposits generated during naphthalene alkylation easily accumulate at the active sites. Commercial fixed-bed reactors (such as the tubular reactor used in patent CN107954812A) cannot achieve online catalyst replacement and regeneration, requiring frequent shutdowns, which reduces production efficiency and increases energy consumption. Secondly, to meet the requirements of fixed-bed packing, the catalyst must be made into 2-5 mm particles, leading to increased internal diffusion resistance. Heavy components generated during propylene over-alkylation easily adhere to the particle surface, accelerating catalyst deactivation. Although some patents delay deactivation through silanization modification (CN107954812A) or hydrogenation processes (CN100364941C), none fundamentally solve the problem of the inability to dynamically renew the catalyst in fixed-bed processes.

[0007] Therefore, in order to address the problems of frequent catalyst replacement and difficulty in long-term stable continuous operation of existing traditional fixed-bed processes, a novel continuous production process for diisopropylnaphthalene was developed. This process extends the stable operating cycle of the catalyst, while improving the yield and product quality stability of diisopropylnaphthalene, and successfully realizes the stable industrial continuous production of diisopropylnaphthalene. This has significant scientific research value and engineering application significance. Summary of the Invention

[0008] This invention proposes a method for continuous production of diisopropylnaphthalene, aiming to improve product yield and overcome the shortcomings of traditional fixed-bed processes, such as frequent catalyst replacement and difficulty in long-term stable continuous operation. At the same time, it solves the problems of low automation level, difficulty in large-scale safe production, inability to achieve long-term stable continuous operation, and difficulty in industrial production in gas-liquid-solid three-phase reaction systems.

[0009] The technical solution of this invention is as follows: This invention proposes a method for continuous production of diisopropylnaphthalene. The method utilizes a feeding unit, a multi-tandem alkylation reaction unit, a reaction liquid separation unit, a distillation and crystallization purification unit, and a dedicated catalyst preparation unit. The steps include: mixing raw materials and catalyst to obtain a mixture, which is continuously fed into the alkylation primary reactor of the multi-tandem alkylation reaction unit. Simultaneously, 60%~70% propylene is introduced into the primary reactor. After the material reaches a certain liquid level, it overflows into the secondary reactor, and the remaining propylene is added to continue the reaction. The material also overflows into the tertiary reactor to continue the reaction until the propylene is completely converted. The reaction material is continuously separated, the deactivated solid catalyst is recovered and regenerated for reuse, and the filtered reaction liquid is successively purified by distillation and crystallization to obtain high-purity 2,6-diisopropylnaphthalene. The raw materials include one or both of solid naphthalene and monoisopropylnaphthalene.

[0010] In this invention, after the mixture is reacted in the primary reactor, the conversion rate of the raw materials can reach more than 70%, and after the mixture is reacted in the secondary reactor, the conversion rate of the raw materials can reach 90%~95%, and the final conversion rate of propylene can reach 95%~100%.

[0011] As a further technical solution, the mass ratio of the solid naphthalene to the monoisopropyl naphthalene is 1~5:2~10, and the monoisopropyl naphthalene includes one or two of α-isopropyl naphthalene and β-isopropyl naphthalene.

[0012] As a further technical solution, the mass ratio of α-isopropylnaphthalene to β-isopropylnaphthalene is 1:3~6.

[0013] As a further technical solution, the catalyst is a preheated catalyst, the preheating temperature of the preheated catalyst is 120~220℃, the preheating time is 20~120min, the stirring speed is 100~400r / min, the mass ratio of the solid naphthalene to the monoisopropylnaphthalene to the preheated catalyst is 100:1~7, and the catalyst is suspended in the mixture.

[0014] As a further technical solution, the mixture needs to be preheated before being fed into the reactor. The preheating treatment is a pipeline preheating treatment. After being preheated by the pipeline preheater to the reaction initiation temperature, the mixture is fed into the first-stage reactor. The pipeline preheater is either a single-tube preheater or a multi-tube preheater. The heat medium for the preheating treatment is heat transfer oil. The temperature of the heat medium is 260~280℃. The temperature of the mixture after the preheating treatment is 200~220℃.

[0015] In this invention, the mixture needs to be preheated before being fed into the pipeline. The outlet temperature of the pipeline preheater reaches the reaction initiation temperature, and the heat generated by the reaction is carried away by the low-temperature heat transfer oil circulation to maintain a stable temperature.

[0016] As a further technical solution, the rotation speed of each of the primary, secondary, and tertiary reactors is independently 120~500 r / min, the reaction temperature is independently 240~280℃, and the reaction pressure is independently 0.2~0.6 MPa. The primary, secondary, and tertiary reactors are connected in a step-by-step low-overflow manner, and a pulse flushing method is set between the overflow pipes of every two reactors. The total residence time of the mixture in the three reactors is controlled according to the feed flow rate of the mixture.

[0017] In this invention, a novel multi-layer combined agitator is used for mixing during the reaction in the primary reactor, which enables the catalyst to be uniformly suspended. The novel multi-layer combined agitator employs a combination of four blades, inclined vanes, and propeller-type gas siphon stirring in its upper, middle, and lower layers. The siphon mainly draws unreacted propylene gas from the upper part of the reactor into the stirring shaft, and then throws it out from the bottom blades, increasing the utilization efficiency of propylene.

[0018] In this invention, when the mixture is continuously fed into the alkylation primary reactor, a feed pump is used. The feed pump includes one of a single screw pump, a gear pump, and a diaphragm metering pump. The feed pump will not be blocked by solid catalyst deposits. During the conveying of materials containing solid particles, the screw pump, because its pitch is larger than the diameter of the catalyst particles, can protect the characterization properties of the catalyst to the greatest extent and solve the problem of the inability to operate stably for a long time due to catalyst deposits blocking the pump outlet.

[0019] In this invention, propylene is fed submerged, and the propylene feed distributor is a microporous gas distributor, which can disperse the introduced propylene into bubbles with a diameter of 0.1μm to 5μm. Under the stirring conditions of the multi-layer combined stirrer in the reactor, the reaction rate can be accelerated.

[0020] As a further technical solution, the separator used in the separation includes one of a positive pressure drum separator and a negative pressure drum separator. The filter cloth pore size of the separator is 0.5~1μm, the separation speed is 0.5~12.5r / min, the separation temperature is 80~150℃, and the working pressure of the separator is 0.2~1.0MPa.

[0021] In this invention, the reactants are directly drawn from the reactor under pressure into a collection tank and then pressed into a separator. When the pressure is insufficient to complete filtration, nitrogen is continuously added to the collection tank. Nitrogen serves as a protective gas, ensuring safety and providing a pressure source. The separator has desorption, purging, and nitrogen protection functions. Trace amounts of non-condensable gases dissolved in the reaction liquid are blown by nitrogen to the tail gas treatment system for safe processing. The filter cake, which is the deactivated catalyst, is desorbed by nitrogen backflushing to remove residual organic matter and then discharged by a scraper into the deactivated catalyst silo for recycling.

[0022] As a further technical solution, the distillation is a two-column continuous distillation. The temperature of the first column is 120~150℃, the pressure is 1~5KPa, and the theoretical plate number is 40~80. The temperature of the second column is 170~220℃, the pressure is 1~5KPa, and the theoretical plate number is 60~100. After distillation, the crude 2,6-diisopropylnaphthalene contains 60%~80% 2,6-diisopropylnaphthalene.

[0023] As a further technical solution, the crystallization purification includes the following steps: purifying the crude 2,6-diisopropylnaphthalene by crystallization, wherein the crystallization method employs a single-stage dynamic crystallization and a three-stage static crystallization. The dynamic crystallization is carried out in a crystallizer equipped with a stirrer, the crystallizer rotation speed is 5~50 r / min, and the cooling rate is 1~5℃ / h. Then, the three-stage static crystallization is carried out at a cooling rate of 0.5~3.5℃ / h to obtain 2,6-diisopropylnaphthalene with a purity ≥99.8%.

[0024] As a further technical solution, the catalyst is a modified mordenite catalyst, and the preparation method of the modified mordenite catalyst includes the following steps: D1. Soak the mordenite in a 0.1-2 mol / L acid solution for 2-4 hours, filter and wash until neutral, dry at 80-120℃ for 6-8 hours, calcine the dried mordenite in air at 350-400℃ for 1.5-2 hours, then calcine in air at 450-480℃ for 1.5-2 hours, and finally calcine in air at 500-550℃ for 1-2 hours. After cooling, the pretreated mordenite is obtained. D2. Disperse the modifier in a solvent, add the pretreated mordenite zeolite, stir and dry to obtain the modified mordenite zeolite catalyst.

[0025] As a further technical solution, the modifier is composed of phenyltrimethoxysilane and dodecyltrimethoxysilane in a mass ratio of 1:1~2.

[0026] In this invention, phenyltrimethoxysilane and dodecyltrimethoxysilane are used to modify the catalyst. Both silanes combine with the hydroxyl groups on the catalyst surface through hydrolysis of alkoxy groups, forming a dense and uniform organosilicon graft layer on the catalyst surface. The C12 long-chain alkyl group introduced by dodecyltrimethoxysilane is a strongly hydrophobic and oleophilic group, which can significantly reduce the surface free energy of the catalyst. The benzene ring group introduced by phenyltrimethoxysilane is also a hydrophobic group, forming a synergistic complementarity with the aliphatic long-chain alkyl group of dodecyltrimethoxysilane. The combination of the two makes the hydrophobic and oleophilic effect of the catalyst surface more suitable for the reaction system, reduces the solid-liquid interface resistance, and promotes the dispersion and suspension of the modified catalyst in the organic phase.

[0027] As a further technical solution, in step D2, the mass ratio of the phenyltrimethoxysilane and dodecyltrimethoxysilane to the pretreated mordenite is 4~5:50.

[0028] As a further technical solution, in step D2, the stirring time is 1 to 3 hours, preferably 2 hours.

[0029] As a further technical solution, in step D2, the solvent is composed of anhydrous ethanol and water in a mass ratio of 5:1.

[0030] As a further technical solution, in step D2, the mass ratio of the solvent to the pretreated mordenite is 4:1.

[0031] The modified mordenite zeolite catalyst prepared by this invention has the following characteristics: (1) Particle size and morphology: The particles are spherical with a particle size distribution of 5~50μm. The particles are evenly dispersed without obvious agglomeration. The settling rate is reduced by optimizing the particle size, thereby improving the suspension persistence. (2) Structural stability: Mordenite has excellent mechanical strength and thermal stability. There is no pulverization or breakage during the continuous reaction process, which ensures the long-term maintenance of suspension stability.

[0032] The catalyst prepared by this invention is suitable for continuous alkylation reaction in a batch reactor, has excellent suspension stability, can achieve uniform mixing of raw materials and catalyst, and is convenient for pipeline transportation, continuous feeding and overflow of reaction system.

[0033] The working principle and beneficial effects of this invention are as follows: In this invention, a continuous production method for diisopropylnaphthalene employs a three-stage continuous process. Naphthalene, monoisopropylnaphthalene, and propylene are reacted continuously in a primary, secondary, and tertiary reactor under catalytic conditions. This process not only yields 2,6-diisopropylnaphthalene with a purity ≥99.8%, but also effectively improves the yield of 2,6-diisopropylnaphthalene. Compared to traditional fixed-bed processes, where catalyst deactivation necessitates a complete shutdown for regeneration or replacement, severely impacting continuous production efficiency and operational stability, this process utilizes a suspended catalyst. This catalyst is uniformly dispersed and suspended within the reaction system, preventing sedimentation and clogging of equipment pipelines. Furthermore, it allows for the timely removal of deactivated catalyst due to pore blockage for regeneration and recycling, ensuring continuous, stable, and long-term operation of the equipment. Attached Figure Description

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] Figure 1 This is a process route diagram for the synthesis of 2,6-diisopropylnaphthalene according to the present invention. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] In the following examples and comparative examples: Mordenite zeolite: Si / A ratio of 150, particle size Dv10 of 1.5 μm, Dv50 of 8 μm, Dv90 of 26 μm; bulk density of 0.4 g / cm³. 3 ; Yield of 2,6-diisopropylnaphthalene = (mass of 2,6-diisopropylnaphthalene × content of 2,6-diisopropylnaphthalene) / (mass of alkylation reaction solution × content of 2,6-diisopropylnaphthalene in alkylation reaction solution) × 100%.

[0038] Example 1 A method for continuous production of diisopropylnaphthalene includes the following steps: S1. Place solid naphthalene in a premixing vessel, heat to 120°C to melt, then add monoisopropyl naphthalene and stir for 60 min to obtain mixture A; the mass ratio of solid naphthalene to monoisopropyl naphthalene is 1:1, and monoisopropyl naphthalene is composed of α-isopropyl naphthalene and β-isopropyl naphthalene in a mass ratio of 1:4. S2. Heat the catalyst to 150℃ and keep it at that temperature for 120 min. Then add the preheated catalyst to mixture A and stir at 100 r / min to obtain mixture B. The mass ratio of mixture A to preheated catalyst is 100:1. S3. Mixture B is preheated to 200°C via a pipeline preheater using 260°C heat transfer oil as the preheating medium. Subsequently, it is continuously fed into the alkylation primary reactor via a raw material pump at a flow rate of 0.9 kg / h. When the liquid level in the reactor exceeds the gas feed distributor, propylene is introduced into the primary reactor in the form of bubbles at a flow rate of 0.24 kg / h through a microporous gas distributor with a bubble diameter of 0.1 μm. Stirring is started at a speed of 120 r / min, and the reaction is carried out at 0.2 MPa and 240°C. After the material reaches a certain liquid level, it overflows into the secondary reactor. At the same time, the remaining propylene is introduced at a flow rate of 0.16 kg / h and also overflows into the tertiary reactor to continue the reaction until the propylene is completely converted. Pressurized reactants are fed into a positive pressure rotary drum separator for solid-liquid separation. The separator operates at a speed of 0.5 r / min, a separation temperature of 90℃, and a pressure of 0.3 MPa. The pressure difference allows the liquid to pass through a filter cloth (0.5 μm pore size), intercepting the deactivated catalyst. The separator has desorption, purging, and nitrogen protection functions. Propylene dissolved in the reaction liquid is purged with nitrogen and sent to the tail gas system for treatment. The deactivated catalyst filter cake is desorbed by nitrogen backflushing to remove residual organic matter and then discharged by a scraper to the deactivated catalyst silo for recycling. S4. The filtered reaction liquid is subjected to a two-column continuous distillation process. Unreacted naphthalene and light components such as monoisopropylnaphthalene are collected from the top of the first column, while mixed diisopropylnaphthalene is collected from the bottom and fed into the second column. The top temperature of the first column is 120℃, the pressure is 2.0 kPa (absolute pressure), the bottom temperature is 133℃, and the number of trays is 50. The top of the second column yields crude 2,6-diisopropylnaphthalene, while high-boiling-point heavy components are collected from the bottom. The top temperature of the second column is 178℃, the pressure is 2.5 kPa (absolute pressure), and the bottom temperature is... Distillation at 208℃ with 80 trays yielded crude 2,6-diisopropylnaphthalene with a purity of 60.87%. Purification was then carried out using a combination of single-stage dynamic crystallization and three-stage static crystallization. Dynamic crystallization was conducted in a crystallizer equipped with a stirrer at a rotation speed of 30 r / min and a cooling rate of 3℃ / h. Three-stage static crystallization was then performed at a cooling rate of 2℃ / h to obtain high-purity 2,6-diisopropylnaphthalene and residual liquid (such as 2,7-diisopropylnaphthalene). The catalyst is mordenite; In this embodiment, all equipment, including the premixing kettle, catalyst preheating, three-stage reaction kettle, separator, and distillation column, operates continuously without interruption. Starting from step S1, the equipment operates continuously for 12 hours before all equipment is stopped and production ends. During the 12-hour continuous operation, the total feed rate of mixture B is 10.8 kg, and the total feed rate of propylene is 4.8 kg. The 2,6-diisopropylnaphthalene after distillation and crystallization is continuously collected. The purity of the crystallized 2,6-diisopropylnaphthalene is 99.8%, and the yield of 2,6-diisopropylnaphthalene is 76.35%.

[0039] Example 2 A method for continuous production of diisopropylnaphthalene includes the following steps: S1. Place solid naphthalene in a premixing vessel, heat to 120°C to melt, and stir for 45 minutes to obtain molten naphthalene; S2. Heat the catalyst to 180℃ and hold for 70 min. Then add the preheated catalyst to the molten naphthalene and stir at 300 r / min to obtain mixture B. The mass ratio of naphthalene to preheated catalyst is 100:3. S3. Mixture B is preheated to 210℃ via a pipeline preheater using 270℃ heat transfer oil as the preheating medium. Subsequently, it is continuously fed into the alkylation primary reactor via a feed pump at a flow rate of 0.9 kg / h. When the liquid level in the reactor exceeds the gas feed distributor, propylene is introduced into the primary reactor at a flow rate of 0.37 kg / h via a microporous gas distributor in the form of bubbles with a bubble diameter of 2 μm. Stirring is then started at 300 r / min, and the reaction proceeds at 0.4 MPa and 260℃. After the material reaches a certain liquid level, it overflows into the secondary reactor. Simultaneously, the remaining propylene is introduced at a flow rate of 0.20 kg / h, also overflowing into the tertiary reactor, where the reaction continues until the propylene is completely converted. The pressurized reactants are then fed into a positive pressure rotary drum separator for solid-liquid separation at a speed of 1.5 r / min, a separation temperature of 110℃, and a separator pressure of 0.4 MPa. The pressure difference forces the liquid through a filter cloth (0.8 μm pore size) to intercept the deactivated catalyst. The separator has desorption, purging and nitrogen protection functions. Propylene dissolved in the reaction liquid is purged with nitrogen and sent to the tail gas system for treatment. After the deactivated catalyst filter cake is desorbed by nitrogen backflushing, the residual organic matter is discharged by scraper to the deactivated catalyst silo for recycling. S4. The filtered reaction liquid is subjected to a two-column continuous distillation process. Unreacted naphthalene and light components such as monoisopropylnaphthalene are collected from the top of the first column, while mixed diisopropylnaphthalene is collected from the bottom and fed into the second column. The top temperature of the first column is 120℃, the pressure is 2.0 kPa (absolute pressure), the bottom temperature is 133℃, and the number of trays is 50. The top of the second column yields crude 2,6-diisopropylnaphthalene, while high-boiling-point heavy components are collected from the bottom. The top temperature of the second column is 178℃, the pressure is 2.5 kPa (absolute pressure), and the bottom temperature is... Distillation at 208℃ with 80 trays yielded crude 2,6-diisopropylnaphthalene with a purity of 62.58%. Purification was then carried out using a combination of single-stage dynamic crystallization and three-stage static crystallization. Dynamic crystallization was conducted in a crystallizer equipped with a stirrer at a rotation speed of 5 r / min and a cooling rate of 1℃ / h. Three-stage static crystallization was then performed at a cooling rate of 0.5℃ / h to obtain high-purity 2,6-diisopropylnaphthalene and residual liquid (such as 2,7-diisopropylnaphthalene). The catalyst is mordenite; In this embodiment, all equipment, including the premixing kettle, catalyst preheating, three-stage reaction kettle, separator, and distillation column, operates continuously without interruption. Starting from step S1, the equipment operates continuously for 12 hours before all equipment is stopped and production ends. During the 12-hour continuous operation, the total feed rate of mixture B is 10.8 kg, and the total feed rate of propylene is 6.9 kg. The 2,6-diisopropylnaphthalene after distillation and crystallization is continuously collected. The purity of the crystallized 2,6-diisopropylnaphthalene is 99.82%, and the yield of 2,6-diisopropylnaphthalene is 77.21%.

[0040] Example 3 A method for continuous production of diisopropylnaphthalene includes the following steps: S1. Place monoisopropylnaphthalene in a premixing vessel, heat to 120°C, and stir for 60 minutes to obtain mixture A; monoisopropylnaphthalene is composed of α-isopropylnaphthalene and β-isopropylnaphthalene in a mass ratio of 1:4. S2. Heat the catalyst to 200℃ and keep it at that temperature for 20 min. Then add the preheated catalyst to mixture A and stir at 400 r / min to obtain mixture B. The mass ratio of monoisopropylnaphthalene to the preheated catalyst is 100:7. S3. Mixture B is preheated to 220℃ via a pipeline preheater using 280℃ heat transfer oil as the preheating medium. Subsequently, it is continuously fed into the alkylation primary reactor via a feed pump at a flow rate of 0.9 kg / h. When the liquid level in the reactor exceeds the gas feed distributor, propylene is introduced into the primary reactor at a flow rate of 0.15 kg / h via a microporous gas distributor in the form of bubbles, with a bubble diameter of 5 μm. Stirring is started at 500 r / min, and the reaction proceeds at 0.6 MPa and 280℃. After the material reaches a certain liquid level, it overflows into the secondary reactor. Simultaneously, the remaining propylene is introduced at a flow rate of 0.06 kg / h, also overflowing into the tertiary reactor, where the reaction continues until the propylene is completely converted. The pressurized reactants are then fed into a positive pressure rotary drum separator for solid-liquid separation. The separator operates at a speed of 2.5 r / min, a separation temperature of 120℃, and a separator pressure of 0.6 MPa. The pressure difference forces the liquid through a filter cloth (1.0 μm pore size), intercepting the deactivated catalyst. The separator has desorption, purging and nitrogen protection functions. Propylene dissolved in the reaction liquid is purged with nitrogen and sent to the tail gas system for treatment. After the deactivated catalyst filter cake is desorbed by nitrogen backflushing, the residual organic matter is discharged by scraper to the deactivated catalyst silo for recycling. S4. The collected reaction liquid after filtration is subjected to a two-column continuous distillation process. Unreacted monoisopropylnaphthalene and other light components are collected from the top of the first column, while mixed diisopropylnaphthalene is collected from the bottom and fed into the second column. The top temperature of the first column is 120℃, the pressure is 2.0 kPa (absolute pressure), the bottom temperature is 133℃, and the number of trays is 50. The top of the second column yields crude 2,6-diisopropylnaphthalene, while high-boiling-point heavy components are collected from the bottom. The top temperature of the second column is 178℃, the pressure is 2.5 kPa (absolute pressure), and the bottom temperature is 20℃. Distillation at 8℃ with 80 trays yielded crude 2,6-diisopropylnaphthalene with a purity of 60.84%. Purification was then carried out using a combination of single-stage dynamic crystallization and three-stage static crystallization. Dynamic crystallization was conducted in a crystallizer equipped with a stirrer at a rotation speed of 50 r / min and a cooling rate of 5℃ / h. Three-stage static crystallization was then performed at a cooling rate of 3.5℃ / h to obtain high-purity 2,6-diisopropylnaphthalene and residual liquid (such as 2,7-diisopropylnaphthalene). The catalyst is mordenite; In this embodiment, all equipment, including the premixing kettle, catalyst preheating, three-stage reaction kettle, separator, and distillation column, operates continuously without interruption. Starting from step S1, the equipment operates continuously for 12 hours before all equipment is stopped and production ends. During the 12-hour continuous operation, the total feed rate of mixture B is 10.8 kg, and the total feed rate of propylene is 2.5 kg. The 2,6-diisopropylnaphthalene after distillation and crystallization is continuously collected. The purity of the crystallized 2,6-diisopropylnaphthalene is 99.81%, and the yield of 2,6-diisopropylnaphthalene is 77.2%.

[0041] Example 4 The difference between Example 4 and Example 2 is that the continuous operation time is 24 hours. In this embodiment, during 24 hours of continuous operation, the total feed rate of mixture B was 21.6 kg, the total feed rate of propylene was 13.8 kg, and the 2,6-diisopropylnaphthalene after distillation and crystallization was continuously collected. Distillation yielded crude 2,6-diisopropylnaphthalene with a content of 64.12%, and the purity of 2,6-diisopropylnaphthalene after crystallization was 99.83%, with a yield of 78.07%.

[0042] Example 5 The difference between Example 2 and Example 5 is that the continuous operation time is 48 hours; In this embodiment, during continuous operation for 48 hours, the total feed rate of mixture B was 43.2 kg, the total feed rate of propylene was 27.5 kg, and the 2,6-diisopropylnaphthalene after distillation and crystallization was continuously collected. Distillation yielded crude 2,6-diisopropylnaphthalene with a content of 64.7%, and the purity of 2,6-diisopropylnaphthalene after crystallization was 99.83%, with a yield of 78.07%.

[0043] Example 6 The difference between Example 2 and Example 6 is that the continuous operation time is 72 hours; In this embodiment, during 72 hours of continuous operation, the total feed amount of raw materials was 64.8 kg, the total feed amount of propylene was 41.3 kg, and the 2,6-diisopropylnaphthalene after distillation and crystallization was continuously collected. Distillation yielded crude 2,6-diisopropylnaphthalene with a content of 66.32%, and the purity of 2,6-diisopropylnaphthalene after crystallization was 99.84%, with a yield of 78.92%.

[0044] Example 7 Compared with Example 2, Example 7 differs in that a pilot-scale amplification experiment was conducted in this example. In step S3, the feed flow rate of mixture B was 50 kg / h. During continuous operation for 72 hours, the total feed amount of raw materials was 3600 kg, and the total feed amount of propylene was 2293.7 kg. 2,6-Diisopropylnaphthalene was continuously collected after distillation and crystallization. Distillation yielded crude 2,6-diisopropylnaphthalene with a content of 68.89%. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.87%, and the yield of 2,6-diisopropylnaphthalene was 80.65%.

[0045] Example 8 The difference between Example 2 and Example 8 is that the catalyst is replaced with an equal amount of the modified mordenite catalyst prepared by the following preparation method; The preparation method of the modified mordenite zeolite catalyst includes the following steps: D1. Soak mordenite in a 1 mol / L acid solution for 3 hours, filter and wash until neutral, dry at 100℃ for 8 hours, cool, and then calcine at 550℃ in air atmosphere for 5 hours to obtain pretreated mordenite. D2. Disperse the pretreated mordenite zeolite in the modifier, stir for 2 hours and then dry to obtain the modified mordenite zeolite catalyst. The modifier is phenyltrimethoxysilane; The mass ratio of the modifier to the pretreated mordenite zeolite is 4:50; The solvent consists of anhydrous ethanol and water in a mass ratio of 5:1; The mass ratio of solvent to pretreated mordenite is 4:1; In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 64.43% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.83%, and the yield of 2,6-diisopropylnaphthalene was 78.07%.

[0046] Example 9 The difference between Example 9 and Example 8 is that the mass ratio of the modifier to the pretreated mordenite is 1:10. In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 65.23% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.82%, and the yield of 2,6-diisopropylnaphthalene was 78.98%.

[0047] Example 10 The difference between Example 10 and Example 9 is that the modifier is dodecyltrimethoxysilane; In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 65.99% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.85%, and the yield of 2,6-diisopropylnaphthalene was 78.93%.

[0048] Example 11 The difference between Example 11 and Example 9 is that the modifier is composed of phenyltrimethoxysilane and dodecyltrimethoxysilane in a mass ratio of 1:1. In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 69.21% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.87%, and the yield of 2,6-diisopropylnaphthalene was 79.8%.

[0049] Example 12 The difference between Example 12 and Example 11 is that phenyltrimethoxysilane is replaced with an equal amount of tert-butyldiphenylmethoxysilane; In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 60.70% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.81%, and the yield of 2,6-diisopropylnaphthalene was 78.05%.

[0050] Example 13 The difference between Example 13 and Example 11 is that dodecyltrimethoxysilane is replaced with an equal amount of hexadecyltrimethoxysilane; In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 63.16% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.83%, and the yield of 2,6-diisopropylnaphthalene was 77.15%.

[0051] Example 14 The difference between Example 14 and Example 11 is that dodecyltrimethoxysilane is replaced with an equal amount of octyltrimethoxysilane; In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 62.11% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.82%, and the yield of 2,6-diisopropylnaphthalene was 77.14%.

[0052] Example 15 Compared with Example 11, the difference in Example 15 is that in the preparation method of the modified mordenite catalyst, step D1 includes the following: mordenite is soaked in a 1 mol / L acid solution for 3 h, filtered and washed until neutral, dried at 100°C for 8 h, cooled, first heated to 400°C and calcined in air atmosphere for 3 h, then heated to 550°C and calcined in air atmosphere for 2 h to obtain pretreated mordenite; In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 71.44% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.86%, and the yield of 2,6-diisopropylnaphthalene was 80.64%.

[0053] Example 16 Compared with Example 11, Example 16 differs in that, in the preparation method of the modified mordenite catalyst, step D1 includes the following: mordenite is soaked in a 1 mol / L acid solution for 3 hours, filtered, washed until neutral, dried at 100°C for 8 hours, cooled, first heated to 400°C and calcined in air for 2 hours, then heated to 480°C and calcined in air for 2 hours, and finally heated to 550°C and calcined in air for 1 hour to obtain pretreated mordenite. In this embodiment, crude 2,6-diisopropylnaphthalene with a content of 72.99% was obtained by distillation. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.88%, and the yield of 2,6-diisopropylnaphthalene was 81.13%.

[0054] Example 17 The difference between Example 17 and Example 16 is that the continuous operation time is 24 hours. In this embodiment, during continuous operation for 24 hours, the total feed rate of mixture B was 21.6 kg, the total feed rate of propylene was 13.8 kg, and the 2,6-diisopropylnaphthalene after distillation and crystallization was continuously collected. Distillation yielded crude 2,6-diisopropylnaphthalene with a content of 74.61%, and the purity of 2,6-diisopropylnaphthalene after crystallization was 99.90%, with a yield of 82.48%.

[0055] Example 18 The difference between Example 18 and Example 17 is that the continuous operation time is 48 hours. In this embodiment, during continuous operation for 48 hours, the total feed rate of mixture B was 43.2 kg, the total feed rate of propylene was 27.5 kg, and the 2,6-diisopropylnaphthalene after distillation and crystallization was continuously collected. Distillation yielded crude 2,6-diisopropylnaphthalene with a content of 76.5%, and the purity of 2,6-diisopropylnaphthalene after crystallization was 99.92%, with a yield of 83.84%.

[0056] Example 19 The difference between Example 19 and Example 17 is that the continuous operation time is 72 hours. In this embodiment, during continuous operation for 72 hours, the total feed rate of mixture B was 64.8 kg, the total feed rate of propylene was 41.3 kg, and the 2,6-diisopropylnaphthalene after distillation and crystallization was continuously collected. Distillation yielded crude 2,6-diisopropylnaphthalene with a content of 77.56%, and the purity of 2,6-diisopropylnaphthalene after crystallization was 99.93%, with a yield of 84.82%.

[0057] Example 20 Compared with Example 19, Example 20 differs in that a pilot-scale amplification experiment was conducted in this example. In step S3, the feed flow rate of mixture B was 50 kg / h. During continuous operation for 72 hours, the total feed amount of raw materials was 3600 kg, and the total feed amount of propylene was 2293.7 kg. 2,6-Diisopropylnaphthalene was continuously collected after distillation and crystallization. Distillation yielded crude 2,6-diisopropylnaphthalene with a content of 80.0%. After crystallization, the purity of 2,6-diisopropylnaphthalene was 99.95%, and the yield of 2,6-diisopropylnaphthalene was 88.16%.

[0058] The catalyst prepared in Example 16 of this application was subjected to a suspension test. The test method and results are as follows: 1. Characterization and verification of catalyst suspension: The catalyst was dispersed in a naphthalene-monoisopropylnaphthalene mixture according to the reaction system ratio. After continuous stirring for 24 hours at the reaction temperature (240℃) and stirring speed (300r / min), the suspension rate of the catalyst in Example 16 was ≥90%, indicating that the catalyst has excellent suspension performance.

[0059] 2. X-ray diffraction (XRD) characterization: Verify the integrity of the mordenite structure.

Claims

1. A method for continuous production of diisopropylnaphthalene, characterized in that, The method utilizes a feeding unit, a multi-tandem alkylation reaction unit, a reaction liquid separation unit, a distillation and crystallization purification unit, and a dedicated catalyst preparation unit. The steps include: mixing raw materials and catalyst to obtain a mixture, which is continuously fed into the primary alkylation reactor of the multi-tandem alkylation reaction unit. Simultaneously, 60%–70% propylene is introduced into the primary reactor. Once the material reaches a certain level, it overflows into the secondary reactor, and the remaining propylene is added to continue the reaction. The material also overflows into the tertiary reactor, where the reaction continues until the propylene is completely converted. The reactants are continuously separated, and the deactivated solid catalyst is recovered, regenerated, and reused. After filtration, the reaction liquid is sequentially purified by distillation and crystallization to obtain high-purity 2,6-diisopropylnaphthalene. The raw materials include one or both of solid naphthalene and monoisopropylnaphthalene.

2. The method for continuous production of diisopropylnaphthalene according to claim 1, characterized in that, The mass ratio of the solid naphthalene to the monoisopropyl naphthalene is 1~5:2~10, and the monoisopropyl naphthalene includes one or both of α-isopropyl naphthalene and β-isopropyl naphthalene.

3. The method for continuous production of diisopropylnaphthalene according to claim 1, characterized in that, The catalyst is a preheating catalyst, the preheating temperature of the preheating catalyst is 120~220℃, the preheating time is 20~120min, the mass ratio of the raw material to the preheating catalyst is 100:1~7, and the catalyst is suspended in the mixture.

4. The method for continuous production of diisopropylnaphthalene according to claim 1, characterized in that, The mixture needs to be preheated before being fed into the reactor. The preheating treatment is performed by a pipeline preheater. After being preheated by the pipeline preheater to the reaction initiation temperature, the mixture is fed into the first-stage reactor. The pipeline preheater is either a single-tube preheater or a multi-tube preheater. The heat medium for the preheating treatment is heat transfer oil. The temperature of the heat medium is 260~280℃. The temperature of the mixture after preheating treatment is 200~220℃.

5. The method for continuous production of diisopropylnaphthalene according to claim 1, characterized in that, In the primary, secondary, and tertiary reactors, the reaction speed is independently 120~500 r / min, the reaction temperature is independently 240~280℃, and the reaction pressure is independently 0.2~0.6 MPa. The primary, secondary, and tertiary reactors are connected by a step-by-step low-overflow method, and a pulse flushing method is set between the overflow pipes of every two reactors.

6. The method for continuous production of diisopropylnaphthalene according to claim 1, characterized in that, The separator used in the separation includes one of a positive pressure drum separator and a negative pressure drum separator. The filter cloth pore size of the separator is 0.5~1μm, the separation speed is 0.5~12.5r / min, the separation temperature is 80~150℃, and the working pressure of the separator is 0.2~1.0MPa.

7. The method for continuous production of diisopropylnaphthalene according to claim 1, characterized in that, The distillation is a two-column continuous distillation. The temperature of the first column is 120~150℃, the pressure is 1~5KPa, and the number of theoretical plates is 40~80. The temperature of the second column is 170~220℃, the pressure is 1~5KPa, and the number of theoretical plates is 60~100.

8. The method for continuous production of diisopropylnaphthalene according to claim 1, characterized in that, The crystallization purification includes the following steps: The crude 2,6-diisopropylnaphthalene obtained by distillation is purified by crystallization using a single-stage dynamic crystallization and a three-stage static crystallization. The dynamic crystallization is carried out in a crystallizer equipped with a stirrer at a rotation speed of 5-50 r / min and a cooling rate of 1-5 °C / h. Then, the three-stage static crystallization is carried out at a cooling rate of 0.5-3.5 °C / h to obtain 2,6-diisopropylnaphthalene with a purity ≥99.8%.

9. A method for continuous production of diisopropylnaphthalene according to claim 1, characterized in that, The catalyst is a modified mordenite catalyst, and the preparation method of the modified mordenite catalyst includes the following steps: D1. Soak the mordenite in a 0.1-2 mol / L acid solution for 2-4 hours, filter and wash until neutral, dry at 80-120℃ for 6-8 hours, calcine the dried mordenite in air at 350-400℃ for 1.5-2 hours, then calcine in air at 450-480℃ for 1.5-2 hours, and finally calcine in air at 500-550℃ for 1-2 hours. After cooling, the pretreated mordenite is obtained. D2. Disperse the modifier in a solvent, add the pretreated mordenite zeolite, stir and dry to obtain the modified mordenite zeolite catalyst.

10. A method for continuous production of diisopropylnaphthalene according to claim 9, characterized in that, In step D2, the modifier is composed of phenyltrimethoxysilane and dodecyltrimethoxysilane in a mass ratio of 1:1~2.

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