Methylnaphthalene alkylation catalyst as well as preparation method and application thereof

Abstract

The invention provides a methylnaphthalene alkylation catalyst as well as a preparation method and application thereof. The preparation method of the methylnaphthalene alkylation catalyst comprises the following steps: carrying out high-temperature steam treatment on an MCM-22 molecular sieve, carrying out acid treatment on the MCM-22 molecular sieve subjected to high-temperature steam treatment in an acid solution, and further drying and roasting to obtain the methylnaphthalene alkylation catalyst. The invention also provides the catalyst prepared by the method and a method for preparing 2, 6-dimethylnaphthalene by alkylation of 2-methylnaphthalene and methanol based on the catalyst. According to the MCM-22 molecular sieve provided by the invention, the conversion rate of dimethylnaphthalene and the selectivity of 2, 6-dimethylnaphthalene are improved.

Description

Technical Field

[0001] The present invention relates to a methylnaphthalene alkylation catalyst, a preparation method thereof and an application thereof, belonging to the technical field of chemical engineering. Background Art

[0002] 2,6-Dimethylnaphthalene (2,6-DMN) is a bicyclic aromatic hydrocarbon molecule with high added value. Its oxidation product 2,6-naphthalenedicarboxylic acid (2,6-NDA) reacts with ethylene glycol to obtain the high-performance polyester material polyethylene naphthalate (PEN). Due to the high symmetry of the polymer monomer, PEN has the characteristics of a linear polymer, and at the same time has excellent mechanical properties, heat resistance, gas barrier properties, chemical stability, modulus and dimensional stability, and all properties are superior to polyethylene terephthalate (PET) commonly used at present. In terms of material applications, PEN can be made into a 0.8-μm biaxially stretched ultra-thin film, which can be used in high-density tapes, capacitors, transformers, automotive sensors, etc.; PEN can also be used in food canning and packaging materials. Replacing the current glass bottles with the new PEN material can not only meet the practical requirements such as the airtightness and shelf life of beer packaging, but also will not explode and is not easy to break; PEN fiber filaments have excellent strength, rigidity and thermal stability, and can be used in high-temperature gas filters, screen printing, electrical insulation materials, industrial filaments, etc.

[0003] The synthesis process of 2,6-DMN is very complex and the cost is difficult to control. At present, its large-scale production mainly adopts the traditional process route using o-xylene and butadiene as raw materials. The technology and equipment are mainly concentrated in countries such as Europe, America and Japan. For example, in 1996, Amoco Corporation of the United States established a 30,000-ton / year industrial production device in Decatur, Alabama. There is no production device for 2,6-DMN in China, which greatly restricts the large-scale production of PEN, and the raw materials are basically dependent on imports.

[0004] 2,6-DMN can be directly separated and extracted from raw materials containing DMN such as coal tar and petroleum cracking heavy aromatics. Since the abundance of 2,6-DMN in the raw materials is limited (0.5-5%), simply separating and purifying it still cannot meet the needs of downstream PEN polyester; at the same time, in the process of separating and extracting 2,6-DMN, other naphthalene components such as naphthalene, methylnaphthalene, dimethylnaphthalene, etc. are also effectively enriched. Through alkylation and isomerization, the above naphthalene components can be converted into 2,6-DMN, thereby increasing the product yield. Among petrochemical raw materials, catalytic cracking cycle oil (LCO) and ethylene tar are both rich in naphthalene-based bicyclic aromatic hydrocarbons, and the yields are respectively above tens of millions of tons and millions of tons. At present, the utilization routes of LCO mainly include blending gasoline and diesel, and obtaining chemical products of BTX through hydroconversion. The utilization routes of ethylene tar mainly include producing petroleum resins, polycondensing to produce carbon fibers or directly using them as fuels, etc.

[0005] While separating and purifying 2,6-DMN from LCO or ethylene tar, other naphthalene-rich components are catalytically converted to obtain 2,6-DMN, forming a complete process route, which can effectively ensure the yield of 2,6-DMN, further increase the added value of raw materials, meet the current demand for refining transformation to improve high-value-added products, and solve the bottleneck technology of refining transformation.

[0006] The content disclosed in CN01138989 was compared and studied on the preparation method of methylnaphthalene alkylation catalyst by modifying HZSM-5, HY zeolite, HM mordenite or Hβ zeolite with BaO, partially exchanging with Co 2+ , Mn 2+ , Ce 2+ or Mg 2+ and activating at 500 - 600 °C for 1 - 5 hours, but the preparation time of this technology for the catalyst is long and the conversion rate of 2-MN and the selectivity of 2,6-DMN are low. Summary of the Invention

[0007] To solve the above technical problems, the object of the present invention is to provide a methylnaphthalene alkylation catalyst, its preparation method and application, and this methylnaphthalene alkylation catalyst can improve the conversion rate of 2-MN and the selectivity of 2,6-DMN.

[0008] To achieve the above object, the present invention provides a preparation method of a methylnaphthalene alkylation catalyst, which includes the following steps: performing high-temperature steam treatment on MCM-22 molecular sieve; placing the MCM-22 molecular sieve after high-temperature steam treatment in an acid solution for acid treatment, and then performing drying and calcination to obtain the methylnaphthalene alkylation catalyst.

[0009] According to a specific embodiment of the present invention, preferably, the temperature of the high-temperature steam treatment is 200 - 400 °C, preferably 250 - 300 °C, and the time is 1 - 12 hours.

[0010] According to a specific embodiment of the present invention, preferably, the liquid-solid mass ratio of the acid solution to the MCM-22 molecular sieve after high-temperature steam treatment is 25:1; the acid solution is citric acid, the concentration of the acid solution is 1% - 10%, preferably 5% - 8%, and the time of the acid treatment is 2 - 8 hours.

[0011] According to a specific embodiment of the present invention, preferably, the temperature of the drying is 90 - 120 °C, preferably 90 - 100 °C, and the time is 12 - 24 hours.

[0012] According to a specific embodiment of the present invention, preferably, the temperature of the calcination is 300 - 550 °C, preferably 350 - 450 °C, and the time is 5 - 10 hours.

[0013] The present invention also provides a methylnaphthalene alkylation catalyst, which is prepared by the preparation method of the above-mentioned methylnaphthalene alkylation catalyst.

[0014] The present invention also provides a method for preparing 2,6-dimethylnaphthalene by alkylation of 2-methylnaphthalene with methanol. In this method, the above-mentioned methylnaphthalene alkylation catalyst is used, and the method comprises the following steps:

[0015] Loading the catalyst into a fixed-bed reactor;

[0016] Mixing 2-methylnaphthalene, methanol and a solvent uniformly to obtain a raw material liquid; wherein, the ratio of 2-methylnaphthalene, methanol and the solvent is 10-70:5-40:25-70; introducing the raw material liquid into the reactor to contact with the catalyst bed for reaction to generate a product containing 2,6-dimethylnaphthalene;

[0017] According to a specific embodiment of the present invention, preferably, after loading the catalyst into the fixed-bed reactor, the catalyst is subjected to in-situ activation pretreatment in a nitrogen atmosphere at 300-500 °C for 1-24 h.

[0018] According to a specific embodiment of the present invention, preferably, the solvent includes one or a combination of two or more of benzene, toluene, xylene, trimethylbenzene, and tetramethylbenzene; preferably, the solvent includes mesitylene and / or durene.

[0019] According to a specific embodiment of the present invention, preferably, the reaction temperature is 280-500 °C, and the reaction pressure is 0-5 MPa; the feeding rate of the raw material liquid into the reactor is 0.02-0.10 ml / min.

[0020] According to a specific embodiment of the present invention, preferably, the reaction temperature is 280-470 °C, and the reaction pressure is 2-4 MPa; the feeding rate of the raw material liquid into the reactor is 0.03-0.08 ml / min.

[0021] According to a specific embodiment of the present invention, preferably, the method for preparing 2,6-dimethylnaphthalene by alkylation of 2-methylnaphthalene with methanol provided by the present invention comprises the following specific steps:

[0022] The MCM-22 molecular sieve modified by high-temperature steam treatment and acid treatment is used to catalyze the alkylation reaction of 2-methylnaphthalene. The specific steps are as follows: First, the molecular sieve catalyst prepared above is loaded into a fixed-bed reactor, and then in a nitrogen atmosphere, it is in-situ activated and pretreated at 300-500 °C for 1-24 h; Second, 2-methylnaphthalene, methanol and a solvent are mixed evenly according to the ratio of 10-70:5-40:25-70 to obtain a raw material liquid. The solvent can be one or a combination of two or more of benzene, toluene, xylene, mesitylene, and durene; Finally, the raw material liquid is introduced into the reactor by a metering pump to contact the catalyst bed for reaction to generate a product containing 2,6-dimethylnaphthalene. The reaction temperature is 280-500 °C, the reaction pressure is 0-5 MPa, and the feeding rate of the raw material liquid into the reactor is 0.02-0.10 ml / min.

[0023] According to a specific embodiment of the present invention, preferably, the method for preparing 2,6-dimethylnaphthalene by alkylation of 2-methylnaphthalene and methanol provided by the present invention comprises the following specific steps:

[0024] First, the molecular sieve catalyst is loaded into a fixed-bed reactor, and then in a nitrogen atmosphere, it is in-situ activated and pretreated at 200-300 °C for 1-24 h; Second, 2-methylnaphthalene, methanol and a solvent are mixed evenly according to the ratio of 20-50:10-40:30-65 to obtain a raw material liquid, wherein the solvent is mesitylene and / or durene; Finally, the raw material liquid is introduced into the reactor by a metering pump to contact the catalyst bed for reaction to generate a product containing 2,6-dimethylnaphthalene. The reaction temperature is 280-470 °C, the reaction pressure is 2-4 MPa, and the feeding rate of the raw material liquid into the reactor is 0.03-0.08 ml / min.

[0025] The synthesis of 2,6-DMN by alkylation of 2-methylnaphthalene and methanol catalyzed by a molecular sieve is a promising synthetic route. However, the MCM-22 molecular sieve currently used for catalyzing the alkylation reaction has problems of low selectivity for DMN and 2,6-DMN, resulting in low yield of 2,6-DMN. The MCM-22 molecular sieve provided by the present invention through high-temperature steam treatment and acid treatment modification can improve the conversion rate of 2-MN and the selectivity of 2,6-DMN, and can solve the above technical problems.

[0026] The present invention has the following advantages:

[0027] (1) The raw materials used in the present invention are composed of 2-methylnaphthalene, methanol and a solvent. The alkylation reaction is a multiphase continuous reaction. The reaction product containing 2,6-dimethylnaphthalene is easy to separate from the catalyst, the operation is simple, and it is convenient for industrial production;

[0028] (2) The molecular sieve catalyst used in the present invention can specifically modify the acidic sites on the catalyst surface by first performing high-temperature steam treatment and then pickling, and specifically modify both the acid strength and the density of acidic sites of the acidic sites of the catalyst. The modified acidic sites serve as active sites for the reaction to occur, and their catalytic behavior changes, manifested as an increase in the conversion rate of 2-MN and the selectivity of 2,6-DMN. Detailed implementation mode

[0029] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0030] Sources of raw materials used in the examples and comparative examples of the present invention:

[0031] Industrial pure MCM-22 molecular sieve: Beijing Huawei Ruike Chemical Co., Ltd.;

[0032] Analytical pure citric acid: Sinopharm Group.

[0033] The evaluation and analysis method used in the examples and comparative examples of the present invention: Take 30 g of the treated molecular sieve sample, at 200 °C - 600 °C, with nitrogen as the carrier gas, introduce 2-MN, and continue for 100 hours. Record the conversion rate of 2-MN and the selectivity of 2,6-DMN.

[0034] Comparative Example 1

[0035] Take 30 g of the MCM-22 catalyst without high-temperature steam and pickling treatment, activate it at 400 °C by introducing nitrogen carrier gas at a flow rate of 25 ml / min for 12 h, then keep the nitrogen flow rate, and introduce a mixed raw material with a ratio of 2-MN:methanol:mesitylene = 20:15:65 at a flow rate of 0.06 ml / min. Under a pressure of 2 MPa, continue for 100 hours. At the 50th hour and the 100th hour, the conversion rates of 2-MN are 30% and 29% respectively, and the selectivities of 2,6-DMN are 15% and 14% respectively.

[0036] Example 1

[0037] The MCM-22 catalyst was treated in high-temperature steam at 250 °C for 1 hour, and then stirred in an aqueous citric acid solution with a concentration of 5% for 2 hours. Subsequently, the molecular sieve was dried at 90 °C for 24 hours and then calcined at 350 °C for 5 hours to obtain Sample 1. 30 g of Sample 1 was taken, and at 450 °C, nitrogen carrier gas was introduced at a flow rate of 25 ml / min for 12 h for activation. After that, while maintaining the nitrogen flow rate, a mixed raw material with a ratio of 2-MN: methanol: mesitylene = 20:15:65 was introduced at a rate of 0.05 ml / min. Under a pressure of 2 MPa, it continued for 100 hours. At the 50th hour and the 100th hour, the 2-MN conversion rates were 42% and 41% respectively, and the 2,6-DMN selectivities were 21% and 20% respectively.

[0038] Example 2

[0039] The MCM-22 catalyst was treated in high-temperature steam at 250 °C for 2 hours, and then stirred in an aqueous citric acid solution with a concentration of 6% for 4 hours. Subsequently, the molecular sieve was dried at 90 °C for 24 hours and then calcined at 350 °C for 5 hours to obtain Sample 2. 30 g of Sample 2 was taken, and at 470 °C, nitrogen carrier gas was introduced at a flow rate of 20 ml / min for 15 h for activation. After that, while maintaining the nitrogen flow rate, a mixed raw material with a ratio of 2-MN: methanol: mesitylene = 20:20:60 was introduced at a rate of 0.08 ml / min. Under a pressure of 2.2 MPa, it continued for 100 hours. At the 50th hour and the 100th hour, the 2-MN conversion rates were 44% and 43% respectively, and the 2,6-DMN selectivities were 20% and 19% respectively.

[0040] Example 3

[0041] The MCM-22 catalyst was treated in high-temperature steam at 300 °C for 1.5 hours, and then stirred in an aqueous citric acid solution with a concentration of 5% for 2.5 hours. Subsequently, the molecular sieve was dried at 95 °C for 24 hours and then calcined at 350 °C for 5 hours to obtain Sample 3. 30 g of Sample 3 was taken, and at 380 °C, nitrogen carrier gas was introduced at a flow rate of 40 ml / min for 18 h for activation. After that, while maintaining the nitrogen flow rate, a mixed raw material with a ratio of 2-MN: methanol: mesitylene = 40:20:40 was introduced at a rate of 0.03 ml / min. Under a pressure of 2.5 MPa, it continued for 100 hours. At the 50th hour and the 100th hour, the 2-MN conversion rates were 44% and 43% respectively, and the 2,6-DMN selectivities were 23% and 22% respectively.

[0042] Example 4

[0043] The catalyst was treated in high-temperature steam at 300 °C for 8 hours, and then stirred in an aqueous citric acid solution with a concentration of 8% for 6 hours. Subsequently, the molecular sieve was dried at 100 °C for 12 hours and then calcined at 450 °C for 2 hours to obtain Sample 2. Take 30 g of Sample 2, at 470 °C, nitrogen carrier gas was passed in at a flow rate of 30 ml / min for 10 h for activation. After that, while maintaining the nitrogen flow rate, a mixed raw material with a ratio of 2-MN:methanol:mesitylene = 30:40:30 was passed in at 0.03 ml / min. Under a pressure of 3.5 MPa, it continued for 100 hours. At the 50th hour and the 100th hour, the 2-MN conversion rates were 46% and 43% respectively, and the 2,6-DMN selectivities were 20% and 19% respectively.

[0044] Example 5

[0045] The catalyst was treated in high-temperature steam at 250 °C for 12 hours, and then stirred in an aqueous citric acid solution with a concentration of 6% for 8 hours. Subsequently, the molecular sieve was dried at 100 °C for 16 hours and then calcined at 450 °C for 2 hours to obtain Sample 5. Take 30 g of Sample 5, at 280 °C, nitrogen carrier gas was passed in at a flow rate of 35 ml / min for 24 h for activation. After that, while maintaining the nitrogen flow rate, a mixed raw material with a ratio of 2-MN:methanol:mesitylene = 40:20:40 was passed in at 0.05 ml / min. Under a pressure of 4 MPa, it continued for 100 hours. At the 50th hour and the 100th hour, the 2-MN conversion rates were 45% and 43% respectively, and the 2,6-DMN selectivities were 21% and 20% respectively.

[0046] Example 6

[0047] The catalyst was treated in high-temperature steam at 300 °C for 8 hours, and then stirred in an aqueous citric acid solution with a concentration of 8% for 6 hours. Subsequently, the molecular sieve was dried at 100 °C for 12 hours and then calcined at 450 °C for 2 hours to obtain Sample 2. Take 30 g of Sample 2, at 450 °C, nitrogen carrier gas was passed in at a flow rate of 25 ml / min for 12 h for activation. After that, while maintaining the nitrogen flow rate, a mixed raw material with a ratio of 2-MN:methanol:mesitylene = 50:10:40 was passed in at 0.03 ml / min. Under a pressure of 3 MPa, it continued for 100 hours. At the 50th hour and the 100th hour, the 2-MN conversion rates were 36% and 36% respectively, and the 2,6-DMN selectivities were 24% and 23% respectively.

[0048] The conversion rate of 2-MN of the MCM-22 molecular sieve after high-temperature steam treatment and acid treatment basically did not decrease within 100 h of the catalytic alkylation reaction, indicating that the modified molecular sieve improved the 2-MN conversion rate and the 2,6-DMN yield.

[0049] The above results are significantly higher than the results reported in the professional literature in the current field, and have significant industrial application value.

Claims

1. A preparation method of a methylnaphthalene alkylation catalyst, which comprises the following steps: Performing high-temperature steam treatment on MCM-22 molecular sieve; Placing the MCM-22 molecular sieve after high-temperature steam treatment in an acid solution for acid treatment, and further performing drying and calcination to obtain the methylnaphthalene alkylation catalyst.

2. The preparation method according to claim 1, wherein, the temperature of the high-temperature steam treatment is 200 - 400 °C, and the time is 1 - 12 hours.

3. The preparation method according to claim 1, wherein, the liquid-solid mass ratio of the acid solution to the MCM-22 molecular sieve after high-temperature steam treatment is 10 - 50:1; the acid solution is citric acid, the concentration of the acid solution is 1% - 10%, and the time of the acid treatment is 2 - 8 hours.

4. The preparation method according to claim 1, wherein, the temperature of the drying is 90 - 120 °C, and the time is 12 - 24 hours.

5. The preparation method according to claim 1, wherein, the temperature of the calcination is 300 - 550 °C, and the time is 5 - 10 hours.

6. A methylnaphthalene alkylation catalyst, which is prepared by the preparation method according to any one of claims 1 - 5.

7. A method for preparing 2,6-dimethylnaphthalene by alkylation of 2-methylnaphthalene and methanol, wherein, this method is carried out using the catalyst according to claim 6, and this method comprises the following steps: Loading the catalyst into a fixed-bed reactor; Mixing 2-methylnaphthalene, methanol and a solvent uniformly to obtain a raw material liquid; wherein, the mass ratio of 2-methylnaphthalene, methanol and the solvent is 10 - 70:5 - 40:25 - 70; Introducing the raw material liquid into the reactor to contact with the catalyst bed for reaction to generate a product containing 2,6-dimethylnaphthalene.

8. The method according to claim 7, wherein, after loading the catalyst into the fixed-bed reactor, subjecting the catalyst to in-situ activation pretreatment in a nitrogen atmosphere at 300 - 500 °C for 1 - 24 h.

9. The method according to claim 7, wherein, the solvent includes one or a combination of two or more of benzene, toluene, xylene, mesitylene, tetramethylbenzene; preferably, the solvent includes mesitylene and / or durene.

10. The method according to claim 7, wherein, the temperature of the reaction is 280 - 500 °C; the reaction pressure is 0 - 5 MPa; the feeding rate of the raw material liquid into the reactor is 0.02 - 0.10 ml / min.