Catalyst for preparing 2, 6-dimethylnaphthalene through alkylation of 2-methylnaphthalene as well as preparation method and application of catalyst
Through rare earth metal ion exchange modification and hydrothermal aging treatment of MCM-22 molecular sieve, a catalyst for 2-methyl decalination was prepared, which solved the problems of low selectivity and yield of 2,6-dimethyl naphthalene in existing catalysts, and achieved efficient 2,6-DMN production, with significant industrial application value.
Patent Information
- Application Number
- CN202311602246.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-28
- Publication Date
- 2025-05-30
AI Technical Summary
After the existing rare earth metal-modified MCM-22 molecular sieve catalyzed with 2-methylnaphthalene and methanol alkylation reaction, the selectivity of dimethylnaphthalene and 2,6-dimethylnaphthalene is low, limiting the industrial application of 2,6-dimethylnaphthalene.
A catalyst for 2-methyl denaphthalene preparation was prepared by ion exchange modification with the MCM-22 molecular sieve with a rare earth metal aqueous solution and hydrothermal aging treatment. The catalyst improves the conversion rate of 2-MN and the selectivity of 2,6-DMN by adjusting the acidity and structure of the molecular sieve.
This catalyst significantly improved the conversion rate of 2-MN and the selectivity of 2,6-DMN, and the yield of Σ2,6-DMN was also significantly improved. The experimental results were better than those reported in the same field at this stage, and had significant innovation and industrial application value.
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Abstract
Description
Technical Field
[0001] The present invention relates to a catalyst for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene, a preparation method thereof and an application thereof, belonging to the technical field of chemical engineering. Background Art
[0002] The method of ion-exchange modification of MCM-22 molecular sieve with rare earth metals improves the conversion rate of 2-methylnaphthalene (2-MN) and the stability of alkylation reaction of the molecular sieve. However, the selectivity of dimethylnaphthalene (DMN) and the yield of Σ2,6-DMN are low after the alkylation reaction of 2-MN with methanol, which limits the industrial application and production of 2,6-dimethylnaphthalene. Summary of the Invention
[0003] To solve the above technical problems, the purpose of the present invention is to provide a catalyst for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene, a preparation method thereof and an application thereof, and this catalyst can improve the conversion rate of 2-MN and the selectivity of 2,6-DMN.
[0004] To achieve the above purpose, the present invention provides a preparation method of a catalyst for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene, which comprises the following steps:
[0005] Adding the original powder of MCM-22 molecular sieve into an aqueous solution of rare earth metal with a concentration of 0.01-5 mol / L for ion exchange, then filtering, washing, drying and calcining to obtain a rare earth metal-modified MCM-22 molecular sieve; performing hydrothermal aging treatment on the rare earth metal-modified MCM-22 molecular sieve to obtain the catalyst; wherein: the solid-liquid ratio of the MCM-22 molecular sieve to the aqueous solution of rare earth metal is 1:5-20 (g:ml), the hydrothermal aging is carried out by using water vapor, and the temperature of the hydrothermal aging is 300-700 °C and the time is 1-10 hours.
[0006] According to a specific embodiment of the present invention, preferably, the temperature of the ion exchange is 50-90 °C and the time is 5-10 h.
[0007] According to a specific embodiment of the present invention, preferably, the temperature of the calcination is 300-600 °C and the time is 5-10 h.
[0008] According to a specific embodiment of the present invention, preferably, the rare earth metal includes one or a combination of two or more of lanthanum, scandium, yttrium, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium.
[0009] According to a specific embodiment of the present invention, preferably, before hydrothermal aging, the rare earth metal-modified MCM-22 molecular sieve is activated by heating at a rate of 5-30 °C / min to 200-400 °C and activating for 1-4 hours.
[0010] According to a specific embodiment of the present invention, preferably, in the hydrothermal aging process, the rare earth metal-modified MCM-22 molecular sieve is placed in the reaction tube of the hydrothermal aging device, and 10%-100% of water vapor is introduced into the reaction tube at a pressure of 0.1-1 MPa and a rate of 1-10 ml / h for hydrothermal aging.
[0011] According to a specific embodiment of the present invention, preferably, the preparation method further includes the following steps: sequentially adding a binder, a shaping aid, and a peptizing agent to the hydrothermally aged molecular sieve for kneading, repeatedly extruding three times with a shaping machine to make it uniformly mixed, drying the obtained bar-shaped catalyst at room temperature, drying at 120 °C, calcining at 550 °C for 4 h, cooling to room temperature, and grinding to a suitable particle size to obtain the catalyst for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene.
[0012] The present invention also provides a catalyst for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene, which is prepared by the above catalyst preparation method.
[0013] According to a specific embodiment of the present invention, preferably, by mass percentage, the catalyst contains the following components: 70-99.99% of MCM-22 molecular sieve, 0.01-30% of rare earth metal, preferably 0.01-2% of rare earth metal.
[0014] The present invention also provides a method for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene, which is carried out by the above catalyst.
[0015] According to a specific embodiment of the present invention, preferably, the method for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene provided by the present invention includes the following steps:
[0016] Loading the catalyst into a fixed-bed reactor, and performing in-situ activation pretreatment at 300-500 °C in a nitrogen atmosphere for 5-10 h;
[0017] Mixing 2-methylnaphthalene, methanol, and a solvent to obtain a raw material liquid; wherein, the molar ratio of methanol to 2-methylnaphthalene is 0.5-4, and the mass ratio of 2-methylnaphthalene to (2-methylnaphthalene + solvent) is 0.1-1; the solvent is one or more of toluene, xylene, trimethylbenzene, and tetramethylbenzene;
[0018] The raw material liquid is introduced into a reactor to contact with a catalyst bed for reaction to generate a product containing 2,6-dimethylnaphthalene; wherein, the reaction temperature is 300-500 °C; based on the mass hourly space velocity of 2-methylnaphthalene, the mass hourly space velocity of the raw material liquid feed is 0.2-6.0 h -1 ; the reaction pressure is 0-10 MPa.
[0019] The present invention has the following advantages:
[0020] The problem that the excessive initial activity caused by the large number of acid sites and high acid strength on the surface of MCM-22 molecular sieve leads to too fast carbon deposition rate on the catalyst and affects the stability. After modification for this problem, there will be a problem of low selectivity of DMN and low yield of Σ2,6-DMN (1,5-DMN + 1,6-DMN + 2,6-DMN). The present invention further reduces the acidity of the molecular sieve by a hydrothermal aging modification method to ensure that the crystal phase structure of the molecular sieve does not change, so as to improve its selectivity to the target product. The obtained experimental results are significantly higher than the results reported in the literature in the same field at the present stage, and have significant innovation and industrial application value. Description of the Drawings
[0021] Figure 1 It is the NH 3 -TPD diagram of Example 5.
[0022] Figure 2 It is the DMN selectivity result diagram of Example 7.
[0023] Figure 3 It is the Σ2,6-DMN selectivity result diagram of Example 7. Detailed Embodiments
[0024] In order to have 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 implementable scope of the present invention.
[0025] Example 1
[0026] The MCM-22 molecular sieve (purchased from Huawei Ruike) is exchanged in a 1 mol / L ammonium chloride solution (99.5% ammonium chloride, purchased from Sinopharm Chemical Reagent Co., Ltd.), the water bath heating temperature is 80 °C, the exchange time is 4 h, the exchanged molecular sieve is fully washed with deionized water, filtered, dried in an oven at 105 °C to remove moisture, and then calcined in a muffle furnace at a programmed temperature of 550 °C for 4 h to obtain the H-type MCM-22 molecular sieve raw powder.
[0027] Example 2
[0028] The MCM-22 zeolite powder was preliminarily modified by rare earth metal ion exchange. The zeolite powder was placed in a beaker with lanthanum nitrate solution of the same mass fraction (99.5% lanthanum(III) nitrate hexahydrate, purchased from Sinopharm Chemical Reagent Co., Ltd.) at a solid-liquid ratio (g:ml) of 1:10, and heated and stirred at 80 °C for 7 h.
[0029] The exchanged solution was washed thoroughly with deionized water, filtered, and then dried in an oven at 105 °C to remove moisture, and then calcined in a muffle furnace at 500 °C for 3 h to obtain the La element-modified MCM-22 catalyst (La-MCM-22). Calculated by mass percentage, the zeolite contained 0.6% lanthanum element.
[0030] Example 3
[0031] The MCM-22 zeolite was placed in the middle of a stainless steel reaction tube of a hydrothermal aging experimental device, heated to 200 °C at a rate of 5 °C / min, and activated for 2 h; then, the high-pressure pump was started to introduce 10% (0.1 MPa) steam into the reaction tube at a rate of 5 ml / h. The modification experimental conditions were 2 h at 350 °C, 7 h at 350 °C, and 2 h at 650 °C to obtain the hydrothermally aged zeolite.
[0032] Example 4
[0033] The hydrothermally aged zeolite was successively added with a binder, a forming aid, and a peptizing agent for kneading, and repeatedly extruded three times with a forming machine to make it evenly mixed. The obtained bar-shaped catalyst was air-dried at room temperature, dried at 120 °C, calcined at 550 °C for 4 h, cooled to room temperature, and ground to a suitable particle size for standby.
[0034] Example 5
[0035] The MCM-22 zeolite modified by lanthanum nitrate ion exchange and further hydrothermal aging was subjected to NH 3 -TPD characterization. The results are shown in Figure 1 .
[0036] Example 6
[0037] The catalytic performance of La-MCM-22 zeolite in the alkylation reaction of 2-methylnaphthalene was investigated in a continuous flow fixed-bed reaction device. A stainless steel reactor with an inner diameter of 10 mm was used, and the reaction pressure was 3.2 MPa.
[0038] A certain amount of catalyst was loaded in the middle of the isothermal reaction tube. The feed solution was prepared according to the ratio of methanol / 2-methylnaphthalene = 1.02 (mol / mol) and 2-methylnaphthalene / (mesitylene + 2-methylnaphthalene) = 0.8 (wt / wt). The mixed solution of raw materials 2-methylnaphthalene, methanol and mesitylene was introduced into the reactor by a micro liquid pump at a certain flow rate under the condition of nitrogen as the carrier gas for reaction. The reaction conditions were: temperature 350 °C, pressure 3.2 MPa, and space velocity (calculated based on 2-methylnaphthalene) of 0.3 h -1 。
[0039] The liquid-phase products were collected in the collection tube at the same interval for gas chromatography analysis, and the obtained sample data were the average values within this time.
[0040] Example 7
[0041] The alkylation reaction performance of the shaped hydrothermally aged molecular sieve prepared in Example 4 for 2-methylnaphthalene was investigated in a continuous-flow fixed-bed reaction device. A stainless-steel reactor with an inner diameter of 10 mm was used, and the reaction pressure was 3.2 MPa.
[0042] A certain amount of catalyst was loaded in the middle of the isothermal reaction tube. The feed solution was prepared according to the ratio of methanol / 2-methylnaphthalene = 1.02 (mol / mol) and 2-methylnaphthalene / (mesitylene + 2-methylnaphthalene) = 0.8 (wt / wt). The mixed solution of raw materials 2-methylnaphthalene, methanol and mesitylene was introduced into the reactor by a micro liquid pump at a certain flow rate under the condition of nitrogen as the carrier gas for reaction. The reaction conditions were: temperature 350 °C, pressure 3.2 MPa, and space velocity (calculated based on 2-methylnaphthalene) of 0.3 h -1 。
[0043] The liquid-phase products were collected at the same interval for gas chromatography analysis, and the obtained sample data were the average values within this time. The reaction results are shown in Figure 2 and Figure 3 。
[0044] In the present invention, the rare earth metal ion-exchanged modified and hydrothermally aged molecular sieves after modification were evaluated for their performance in a fixed-bed reactor. The results showed that the modification effectively solved the problems of low selectivity to DMN and low yield of Σ2,6-DMN in the alkylation reaction of 2-MN with methanol over MCM-22 molecular sieve. Within 200 h, the conversion of 2-MN over lanthanum-modified MCM-22 molecular sieve was stably maintained at about 50%, the selectivities to DMN and Σ2,6-DMN were about 65% and 23% respectively, and the yield of Σ2,6-DMN was 12.7%. Within 200 h, the conversion of 2-MN over the shaped molecular sieve prepared in Example 4 after hydrothermal aging was stably maintained at about 47.5%, the selectivities to DMN and Σ2,6-DMN were about 72% and 25% respectively, and the yield of Σ2,6-DMN was 13.1%. The above results are significantly higher than those reported in the current professional literature in this field and have significant industrial application value.
Claims
1. A preparation method of a catalyst for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene, which comprises the following steps: Adding the original powder of MCM-22 molecular sieve into an aqueous solution of rare earth metal with a concentration of 0.01-5 mol / L for ion exchange, and then filtering, washing, drying and calcining to obtain the rare earth metal-modified MCM-22 molecular sieve; subjecting the rare earth metal-modified MCM-22 molecular sieve to hydrothermal aging treatment to obtain the catalyst; Wherein: The solid-liquid ratio of the MCM-22 molecular sieve to the aqueous solution of rare earth metal is 1:5-20 (g:ml); The hydrothermal aging is carried out by using water vapor, and the temperature of the hydrothermal aging is 300-700 °C and the time is 1-10 hours.
2. The preparation method according to claim 1, Wherein, The temperature of the ion exchange is 50-90 °C and the time is 5-10 h.
3. The preparation method according to claim 1, Wherein, The temperature of the calcination is 300-600 °C and the time is 5-10 h.
4. The preparation method according to claim 1, wherein the rare earth metal comprises one or a combination of two or more of lanthanum, scandium, yttrium, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium.
5. The preparation method according to claim 1, Wherein, In the hydrothermal aging process, the rare earth metal-modified MCM-22 molecular sieve is placed in the reaction tube of the hydrothermal aging device, and 10%-100% of water vapor is introduced into the reaction tube at a pressure of 0.1-1 MPa and a rate of 1-10 ml / h for hydrothermal aging.
6. A catalyst for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene, which is prepared by using the preparation method according to any one of claims 1-5.
7. The catalyst according to claim 6, Wherein, By mass percentage, the catalyst comprises the following components: 70-99.99% of MCM-22 molecular sieve, 0.01-30% of rare earth metal.
8. The catalyst according to claim 6, Wherein, The Si / Al atomic ratio of the catalyst is 1 - 600:1; the specific surface area is 140 - 700 m 2 / g; the pore volume is 0.02 - 1.5 cm 3 / g.
9. A method for the alkylation of 2-methylnaphthalene to prepare 2,6-dimethylnaphthalene, which is carried out by using the catalyst according to any one of claims 6-8.
10. The method according to claim 9, which comprises the following steps: Loading the catalyst into a fixed-bed reactor, and carrying out in-situ activation pretreatment at 300-500 °C for 5-10 h in a nitrogen atmosphere; Mixing 2-methylnaphthalene, methanol and a solvent to obtain a raw material liquid; wherein, the molar ratio of methanol to 2-methylnaphthalene is 0.5-4, and the mass ratio of 2-methylnaphthalene to (2-methylnaphthalene + solvent) is 0.1-1; the solvent is one or several of toluene, xylene, trimethylbenzene, tetramethylbenzene; Introducing the raw material liquid into the reactor to contact with the catalyst bed layer for reaction to generate a product containing 2,6-dimethylnaphthalene; Among them, the reaction temperature is 300 - 500 °C; based on the mass space velocity of 2-methylnaphthalene, the feed mass space velocity of the raw material liquid is 0.2 - 6.0 h -1 ; the reaction pressure is 0 - 10 MPa.