A magnesium modified catalyst, its preparation method and application

Abstract

This invention belongs to the field of lubricating oil technology and discloses a magnesium-modified catalyst, its preparation method, and its application. The magnesium-modified catalyst includes an MCM-22 molecular sieve and magnesium supported on the MCM-22 molecular sieve. Based on the total mass of magnesium metal salt and MCM-22 molecular sieve as 100%, the mass percentage of magnesium metal salt is 1wt% to 8wt%, preferably 3wt% to 8wt%. In this invention, magnesium-modified MCM-22 molecular sieve is used. The modified MCM-22 molecular sieve has higher catalytic activity than the unmodified MCM-22 molecular sieve. Under preferred conditions, the conversion rate of monoisopropylnaphthalene can reach 95%, and the selectivity of diisopropylnaphthalene in the product can reach 65%. Furthermore, the magnesium-modified catalyst prepared using this invention is pollution-free, easy to separate, and can be reused.

Description

Technical Field

[0001] This invention relates to the field of lubricating oil technology, specifically to a magnesium-modified catalyst, its preparation method and application, and more specifically to a magnesium-modified MCM-22 molecular sieve catalyst, its preparation method and a method for preparing diisopropylnaphthalene using alkyl transfer reaction. Background Technology

[0002] Alkyl naphthalenes possess excellent thermal oxidation stability, hydrolytic stability, good additive solubility, and demulsification properties, making them widely used in hydraulic oils, gear oils, heat transfer oils, transformer oils, compressor oils, and liquid crystals. Among them, isopropyl naphthalene series products can be used as heat transfer oils. Isopropyl naphthalene series heat transfer oils have advantages such as being odorless, non-corrosive to metals, having good thermal stability, excellent low-temperature performance, and being recyclable. The isopropyl naphthalene series mainly includes monoisopropyl naphthalene (MIPN), diisopropyl naphthalene (DIPN), and triisopropyl naphthalene (TIPN). DIPN is an important organic chemical raw material and a raw material for high-performance engineering plastics. Due to its many advantages, such as being colorless, odorless, having a high boiling point, low toxicity, low pour point, and strong fuel solubility, DIPN has been widely used as a solvent in printing, coatings and paints, adhesives, and other industries. It can also be used as a plant growth regulator in agricultural production. Furthermore, it is a high-performance high-temperature synthetic heat transfer oil and electrical insulating oil.

[0003] Traditional methods for producing DIPN involve alkylation reactions of naphthalene and propylene or isopropanol under acidic catalytic conditions. These methods often employ hydrofluoric acid, sulfuric acid, or anhydrous aluminum trichloride as catalysts. However, liquid alkylation catalysts are highly corrosive and cause severe environmental pollution, resulting in very low DIPN content in the product. Therefore, research on DIPN synthesis both domestically and internationally primarily focuses on finding environmentally friendly catalysts, and exploring novel catalytic reaction technologies is currently a key research area. Furthermore, current production methods generate significant amounts of MIPN and TIPN during the process, leading to low selectivity for DIPN. Therefore, using MIPN and TIPN as raw materials to further produce DIPN via alkyl transfer reactions has significant application value. Summary of the Invention

[0004] The technical problem to be solved by this invention is that existing DIPN synthesis techniques generate a large amount of MIPN and TIPN, resulting in low selectivity of DIPN, strong catalyst corrosivity, and serious environmental pollution. This invention provides a magnesium-modified catalyst, its preparation method, and its application. The prepared magnesium-modified MCM-22 molecular sieve exhibits good catalytic performance, can be used in alkyl transfer reactions with high conversion and selectivity, and good reproducibility. Furthermore, by using MIPN and TIPN as raw materials to prepare DIPN via alkyl transfer reactions, this method can further utilize the MIPN and TIPN generated during the production process, thereby increasing the yield of DIPN.

[0005] To solve the above-mentioned technical problems, the first aspect of the present invention provides a method for preparing a magnesium-modified catalyst, comprising: adding a magnesium metal salt solution dropwise into an MCM-22 molecular sieve, calcining it to obtain the magnesium-modified catalyst; wherein the MCM-22 molecular sieve is subjected to dehydration treatment.

[0006] In this invention, the modification principle of the magnesium-modified catalyst is mainly to deactivate some acidic sites of the MCM-22 molecular sieve, while the introduction of magnesium increases the active sites for dealkylation of triisopropylnaphthalene, thereby improving the selectivity of diisopropylnaphthalene. After modification, the pore structure of the MCM-22 molecular sieve remains unchanged, the silicon-to-aluminum ratio increases, and the performance is improved.

[0007] According to some embodiments of the present invention, the water absorption rate of the MCM-22 molecular sieve after dehydration treatment is 15% to 25%, preferably 20% to 25%.

[0008] According to some embodiments of the present invention, the dehydration treatment includes drying and calcination II; preferably, the drying conditions include: a drying temperature of 100℃~150℃ and a drying time of 24h~36h; the calcination II conditions include: a calcination II temperature of 500℃~600℃ and a calcination II time of 7h~8h.

[0009] According to some embodiments of the present invention, the concentration of the magnesium metal salt solution is 0.1 mol / L to 3.0 mol / L;

[0010] And / or, the magnesium metal salt is selected from at least one of magnesium nitrate, magnesium chloride, and magnesium sulfate.

[0011] According to some embodiments of the present invention, the mass percentage of magnesium metal salt is 1 wt% to 8 wt%, preferably 3 wt% to 8 wt%, based on the total mass of magnesium metal salt and MCM-22 molecular sieve as 100%.

[0012] According to some embodiments of the present invention, the conditions for calcination I include: calcination I temperature of 500℃~600℃ and calcination I time of 4h~6h.

[0013] According to some embodiments of the present invention, a drying step is included before the roasting I; preferably, the drying conditions include: a drying temperature of 120°C to 150°C and a drying time of 4h to 6h.

[0014] According to some embodiments of the present invention, stirring is performed simultaneously with the dripping;

[0015] And / or, after the addition, the mixture is stirred for 3 to 5 hours at a temperature of 25°C to 30°C, and then allowed to stand for 20 to 24 hours;

[0016] According to some embodiments of the present invention, the volume of magnesium metal salt solution added is the product of the mass of the MCM-22 molecular sieve and its water absorption rate.

[0017] A second aspect of this invention provides a magnesium-modified catalyst prepared by the above-described method, comprising an MCM-22 molecular sieve and magnesium supported on the MCM-22 molecular sieve; the magnesium mass percentage is 0.16 wt% to 2.04 wt% based on 100% of the magnesium-modified catalyst. In the magnesium-modified catalyst of this invention, magnesium mainly exists in the form of oxides.

[0018] In the magnesium-modified catalyst of the present invention, magnesium is not only adsorbed on the surface of MCM-22 molecular sieve, but also enters the pores of MCM-22 molecular sieve because magnesium has a smaller atomic radius than calcium, strontium and other elements in the same group, thereby deactivating some acidic sites and improving the performance of magnesium-modified catalyst.

[0019] According to some embodiments of the present invention, the MCM-22 molecular sieve is a white powdery crystal with an MWW structure.

[0020] According to some embodiments of the present invention, the molar ratio of SiO2 to Al2O3 in the MCM-22 molecular sieve is 20 to 35;

[0021] And / or, the pore size of the MCM-22 molecular sieve is 0.55 nm to 2.0 nm.

[0022] A third aspect of the present invention provides a method for synthesizing diisopropylnaphthalene, wherein monoisopropylnaphthalene and triisopropylnaphthalene undergo an alkyl transfer reaction in the presence of an inert atmosphere and a magnesium-modified catalyst prepared by the preparation method provided in the first aspect or a magnesium-modified catalyst provided in the second aspect, to obtain diisopropylnaphthalene.

[0023] According to some embodiments of the present invention, the inert atmosphere is selected from at least one of nitrogen, helium, and argon.

[0024] According to some embodiments of the present invention, the molar ratio of monoisopropylnaphthalene to triisopropylnaphthalene is (0.25-4):1, preferably (0.25-0.5):1.

[0025] According to some embodiments of the present invention, the added mass of the magnesium-modified catalyst is 2% to 5% of the total mass of monoisopropylnaphthalene and triisopropylnaphthalene.

[0026] According to some embodiments of the present invention, the conditions for the alkyl transfer reaction include: a reaction temperature of 200°C to 250°C, a reaction pressure of 1.5 MPa to 2.5 MPa, and a reaction time of 3 h to 5 h.

[0027] According to some embodiments of the present invention, the diisopropylnaphthalene further includes a purification step; preferably, the purification is carried out by vacuum distillation; more preferably, the conditions for vacuum distillation include: a vacuum degree of 500 Pa to 1500 Pa, a bottom temperature of 170°C to 200°C, a top temperature of 160°C to 170°C, and a reflux ratio of 1:(0.5 to 2); even more preferably, the purity of the purified diisopropylnaphthalene is >99%.

[0028] Beneficial effects:

[0029] The magnesium-modified catalyst prepared by this invention uses magnesium-modified MCM-22 molecular sieve. Compared with the unmodified MCM-22 molecular sieve, the modified MCM-22 molecular sieve has higher catalytic activity. Under preferred conditions, the conversion rate of monoisopropylnaphthalene can reach up to 95%, and the selectivity of diisopropylnaphthalene in the product can reach up to 65%. Moreover, the magnesium-modified catalyst prepared by this invention is pollution-free, easy to separate, and can be reused.

[0030] The preparation of diisopropylnaphthalene via alkyl transfer reaction in this invention can further improve the utilization rate of monoisopropylnaphthalene and polyisopropylnaphthalene, and increase the yield of diisopropylnaphthalene. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to these embodiments.

[0032] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of the present invention are commercially available.

[0033] In the preparation examples, comparative preparation examples, examples, and comparative examples:

[0034] Magnesium nitrate hexahydrate was purchased from Sinopharm Chemical Reagent Co., Ltd., analytical grade, ≥99.0%.

[0035] MCM-22 molecular sieve was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and is a white powder crystal with an MWW structure; MCM-22 molecular sieve pore size (nm): 0.55-1.0; silicon-to-aluminum ratio: 30.

[0036] Monoisopropylnaphthalene and triisopropylnaphthalene were obtained by distillation purification of crude isopropylnaphthalene produced by Sinopec Maoming Branch, with a purity of over 95.0%.

[0037] In the specific embodiments of the present invention, unless otherwise specified, the room temperature is 25°C.

[0038] The conversion rate of monoisopropylnaphthalene and the selectivity of diisopropylnaphthalene in the various embodiments and comparative examples of the present invention are calculated as follows:

[0039] Conversion rate of monoisopropylnaphthalene = (number of moles of monoisopropylnaphthalene converted / total number of moles of monoisopropylnaphthalene) * 100%;

[0040] Selectivity of diisopropylnaphthalene = (number of moles of diisopropylnaphthalene in the product / total number of moles of the product) * 100%.

[0041] Preparation Example 1

[0042] This preparation example illustrates the magnesium-modified catalyst and its preparation method described in this invention.

[0043] Weigh 50g of MCM-22 molecular sieve with a water absorption rate of 20% after dehydration treatment (the dehydration treatment consisted of drying at 120℃ for 24h and then calcining at 500℃ for 8h). Weigh 0.86g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 10mL magnesium nitrate solution, resulting in a 0.337mol / L magnesium nitrate aqueous solution. Add this magnesium nitrate aqueous solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, stir magnetically at 300r / min for 3h at room temperature. After stirring, let the mixture stand at room temperature for 24h. Place the mixture in an oven at 120℃ for 24h to obtain the dried sample. The dried sample was calcined in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified catalyst M1 (wherein, based on the total mass of magnesium nitrate and MCM-22 molecular sieve used to prepare the magnesium-modified catalyst being 100%, the mass percentage of magnesium nitrate is 1 wt%; the calculation process is as follows: when the mass percentage of magnesium nitrate is 1 wt%, the mass of magnesium nitrate added is 0.5 g, and the molar mass is (0.5 g ÷ 148.3 g / mol) ÷ 0.01 mL = 0.337 mol / L, then the mass of magnesium nitrate hexahydrate weighed is 0.337 mol / L × 10 -2 mL×256.41g / mol=0.86g), which is magnesium-modified MCM-22 molecular sieve M1.

[0044] Preparation Example 2

[0045] This preparation example illustrates the magnesium-modified catalyst and its preparation method described in this invention.

[0046] Weigh 50g of MCM-22 molecular sieve with a water absorption rate of 20% after dehydration treatment (the dehydration treatment consisted of drying at 120℃ for 24h and then calcining at 500℃ for 8h). Weigh 1.73g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 10mL magnesium nitrate solution, resulting in a 0.674mol / L magnesium nitrate aqueous solution. Add this magnesium nitrate aqueous solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, stir magnetically at 300r / min for 3h at room temperature. After stirring, let the mixture stand at room temperature for 24h. Place the mixture in an oven at 120℃ for 24h to obtain the dried sample. The dried sample was calcined in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified catalyst M2 (wherein, based on the total mass of magnesium nitrate and MCM-22 molecular sieve used to prepare the magnesium-modified catalyst being 100%, the mass percentage of magnesium nitrate is 2wt%; the calculation process is as follows: when the mass percentage of magnesium nitrate is 2wt%, the mass of magnesium nitrate added is 1.0g, and the molar mass is (1.0g ÷ 148.3g / mol) ÷ 0.01mL = 0.674mol / L, then the mass of magnesium nitrate hexahydrate weighed is 0.674mol / L × 10 -2 mL×256.41g / mol=1.73g), which is magnesium-modified MCM-22 molecular sieve M2.

[0047] Preparation Example 3

[0048] This preparation example illustrates the magnesium-modified catalyst and its preparation method described in this invention.

[0049] Weigh 50g of MCM-22 molecular sieve with a water absorption rate of 20% after dehydration treatment (specifically, drying at 120℃ for 24h followed by calcination at 500℃ for 8h). Weigh 2.59g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 10mL magnesium nitrate solution, resulting in a 1.011mol / L magnesium nitrate aqueous solution. Add this magnesium nitrate aqueous solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, stir magnetically at 300r / min for 3h at room temperature. After stirring, let the mixture stand at room temperature for 24h. Place the mixture in an oven at 120℃ for 24h to obtain the dried sample. The dried sample was calcined in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified catalyst M3 (wherein, based on the total mass of magnesium nitrate and MCM-22 molecular sieve used to prepare the magnesium-modified catalyst being 100%, the mass percentage of magnesium nitrate is 3wt%; the calculation process is as follows: when the mass percentage of magnesium nitrate is 3wt%, the mass of magnesium nitrate added is 1.5g, and the molar mass is (1.5g ÷ 148.3g / mol) ÷ 0.01mL = 1.011mol / L, then the mass of magnesium nitrate hexahydrate weighed is 1.011mol / L × 10 -2 mL×256.41g / mol=2.59g), which is magnesium-modified MCM-22 molecular sieve M3.

[0050] Preparation Example 4

[0051] This preparation example illustrates the magnesium-modified catalyst and its preparation method described in this invention.

[0052] Weigh 50g of MCM-22 molecular sieve with a water absorption rate of 20% after dehydration treatment (the dehydration treatment consisted of drying at 120℃ for 24h and then calcining at 500℃ for 8h). Weigh 3.46g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 10mL magnesium nitrate solution, resulting in a 1.349mol / L magnesium nitrate aqueous solution. Add this magnesium nitrate aqueous solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, stir magnetically at 300r / min for 3h at room temperature. After stirring, let the mixture stand at room temperature for 24h. Place the mixture in an oven at 120℃ for 24h to obtain the dried sample. The dried sample was calcined in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified catalyst M4 (wherein, based on the total mass of magnesium nitrate and MCM-22 molecular sieve used to prepare the magnesium-modified catalyst being 100%, the mass percentage of magnesium nitrate is 4wt%; the calculation process is as follows: when the mass percentage of magnesium nitrate is 4wt%, the mass of magnesium nitrate added is 2.0g, and the molar mass is (2.0g ÷ 148.3g / mol) ÷ 0.01mL = 1.349mol / L, then the mass of magnesium nitrate hexahydrate weighed is 1.349mol / L × 10 -2 mL×256.41g / mol=3.46g), which is magnesium-modified MCM-22 molecular sieve M4.

[0053] Preparation Example 5

[0054] This preparation example illustrates the magnesium-modified catalyst and its preparation method described in this invention.

[0055] Weigh 50g of MCM-22 molecular sieve with a water absorption rate of 20% after dehydration treatment (the dehydration treatment consisted of drying at 120℃ for 24h and then calcining at 500℃ for 8h). Weigh 5.19g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 10mL magnesium nitrate solution, resulting in a 2.023mol / L magnesium nitrate aqueous solution. Add this magnesium nitrate aqueous solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, stir magnetically at 300r / min for 3h at room temperature. After stirring, let the mixture stand at room temperature for 24h. Place the mixture in an oven at 120℃ for 24h to obtain the dried sample. The dried sample was calcined in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified catalyst M5 (wherein, based on the total mass of magnesium nitrate and MCM-22 molecular sieve used to prepare the magnesium-modified catalyst being 100%, the mass percentage of magnesium nitrate is 6wt%; the calculation process is as follows: when the mass percentage of magnesium nitrate is 6wt%, the mass of magnesium nitrate added is 3.0g, and the molar mass is (3.0g ÷ 148.3g / mol) ÷ 0.01mL = 2.023mol / L, then the mass of magnesium nitrate hexahydrate weighed is 2.023mol / L × 10 -2 mL×256.41g / mol=5.19g), which is magnesium-modified MCM-22 molecular sieve M5.

[0056] Preparation Example 6

[0057] This preparation example illustrates the magnesium-modified catalyst and its preparation method described in this invention.

[0058] Weigh 50g of MCM-22 molecular sieve with a water absorption rate of 20% after dehydration treatment (the dehydration treatment consisted of drying at 120℃ for 24h and then calcining at 500℃ for 8h). Weigh 6.92g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 10mL magnesium nitrate solution, resulting in a 2.697mol / L magnesium nitrate aqueous solution. Add this magnesium nitrate aqueous solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, stir magnetically at 300r / min for 3h at room temperature. After stirring, let the mixture stand at room temperature for 24h. Place the mixture in an oven at 120℃ for 24h to obtain the dried sample. The dried sample was calcined in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified catalyst M6 (wherein, based on the total mass of magnesium nitrate and MCM-22 molecular sieve used to prepare the magnesium-modified catalyst being 100%, the mass percentage of magnesium nitrate is 8wt%; the calculation process is as follows: when the mass percentage of magnesium nitrate is 8wt%, the mass of magnesium nitrate added is 4.0g, and the molar mass is (4.0g ÷ 148.3g / mol) ÷ 0.01mL = 2.697mol / L, then the mass of magnesium nitrate hexahydrate weighed is 2.697mol / L × 10 -2 mL×256.41g / mol=6.92g), which is magnesium-modified MCM-22 molecular sieve M6.

[0059] Comparative Preparation Example 1

[0060] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0061] Weigh 50g of untreated MCM-22 molecular sieve with a water absorption rate of 10%. Weigh 0.86g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 5mL magnesium nitrate solution with a concentration of 0.674mol / L. Add the magnesium nitrate solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, magnetically stir at 300r / min for 3 hours at room temperature. Let the mixture stand at room temperature for 24 hours after stirring. Place the mixture in an oven at 120℃ for 24 hours to obtain a dried sample. Calcine the dried sample in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified untreated catalyst DM1 (based on a total mass of 100% magnesium nitrate and MCM-22 molecular sieve, with magnesium nitrate accounting for 1wt%), i.e., magnesium-modified untreated MCM-22 molecular sieve DM1.

[0062] Comparative Preparation Example 2

[0063] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0064] Weigh 50g of untreated MCM-22 molecular sieve with a water absorption rate of 10%. Weigh 1.73g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 5mL magnesium nitrate solution with a concentration of 1.349mol / L. Add the magnesium nitrate solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, stir magnetically at 300r / min for 3 hours at room temperature. Let the mixture stand at room temperature for 24 hours after stirring. Place the mixture in an oven at 120℃ for 24 hours to obtain a dried sample. Calcine the dried sample in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified untreated catalyst DM2 (based on a total mass of 100% magnesium nitrate and MCM-22 molecular sieve, with magnesium nitrate accounting for 2wt%), i.e., magnesium-modified untreated MCM-22 molecular sieve DM2.

[0065] Comparative preparation example 3

[0066] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0067] Weigh 50g of untreated MCM-22 molecular sieve with a water absorption rate of 10%. Weigh 2.59g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 5mL magnesium nitrate solution with a concentration of 2.023mol / L. Add the magnesium nitrate solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, magnetically stir at 300r / min for 3 hours at room temperature. Let the mixture stand at room temperature for 24 hours after stirring. Place the mixture in an oven at 120℃ for 24 hours to obtain a dried sample. Calcine the dried sample in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified untreated catalyst DM3 (based on a total mass of 100% magnesium nitrate and MCM-22 molecular sieve, with magnesium nitrate accounting for 3wt%), i.e., magnesium-modified untreated MCM-22 molecular sieve DM3.

[0068] Comparative preparation example 4

[0069] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0070] Weigh 50g of untreated MCM-22 molecular sieve with a water absorption rate of 10%. Weigh 3.46g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 5mL magnesium nitrate solution with a concentration of 2.697mol / L. Add the magnesium nitrate solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, magnetically stir at 300r / min for 3 hours at room temperature. Let the mixture stand at room temperature for 24 hours after stirring. Place the mixture in an oven at 120℃ for 24 hours to obtain a dried sample. Calcine the dried sample in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified untreated catalyst DM4 (based on a total mass of 100% magnesium nitrate and MCM-22 molecular sieve, with magnesium nitrate accounting for 4wt%), i.e., magnesium-modified untreated MCM-22 molecular sieve DM4.

[0071] Comparative preparation example 5

[0072] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0073] Weigh 50g of untreated MCM-22 molecular sieve with a water absorption rate of 10%. Weigh 5.19g of magnesium nitrate hexahydrate and add it to deionized water to prepare a 5mL magnesium nitrate solution with a concentration of 4.044mol / L. Add the magnesium nitrate solution dropwise to the MCM-22 molecular sieve under stirring. After the addition is complete, magnetically stir at 300r / min for 3 hours at room temperature. Let the mixture stand at room temperature for 24 hours after stirring. Place the mixture in an oven at 120℃ for 24 hours to obtain a dried sample. Calcine the dried sample in a muffle furnace at 550℃ for 4 hours in air atmosphere to obtain magnesium-modified untreated catalyst DM5 (based on a total mass of 100% magnesium nitrate and MCM-22 molecular sieve, with magnesium nitrate accounting for 6wt%), i.e., magnesium-modified untreated MCM-22 molecular sieve DM5.

[0074] Comparative preparation example 6

[0075] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0076] 50g of untreated MCM-22 molecular sieve with a water absorption rate of 10% was weighed. 6.92g of magnesium nitrate hexahydrate was added to deionized water to prepare a 5mL magnesium nitrate solution with a concentration of 5.392mol / L. This magnesium nitrate solution was added dropwise to the MCM-22 molecular sieve under stirring. After the addition was complete, the mixture was magnetically stirred at 300r / min for 3 hours at room temperature. The mixture was then left to stand at room temperature for 24 hours. The mixture was then placed in an oven at 120℃ for 24 hours to obtain a dried sample. The dried sample was calcined in a muffle furnace at 550℃ for 4 hours in air to obtain magnesium-modified untreated catalyst DM6 (based on a total mass of 100% magnesium nitrate and MCM-22 molecular sieve, with magnesium nitrate accounting for 8wt%), i.e., magnesium-modified untreated MCM-22 molecular sieve DM6.

[0077] Comparative preparation example 7

[0078] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0079] The experimental method was the same as in Preparation Example 4, except that the modifier added was an aqueous solution of calcium nitrate, which yielded calcium-modified catalyst DM7, namely calcium-modified MCM-22 molecular sieve DM7.

[0080] Comparative Preparation Example 8

[0081] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0082] The experimental method was the same as that in Preparation Example 4, except that the modifier added was an aqueous solution of strontium nitrate, which yielded strontium-modified catalyst DM8, namely strontium-modified MCM-22 molecular sieve DM8.

[0083] Comparative preparation example 9

[0084] This comparative preparation example is used to illustrate the magnesium-modified catalyst and its preparation method described in this invention.

[0085] The experimental method was the same as that in Preparation Example 4, except that the silicon-to-aluminum ratio of the added MCM-22 molecular sieve was 15, resulting in magnesium-modified catalyst DM9, namely magnesium-modified MCM-22 molecular sieve DM9.

[0086] Example 1

[0087] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0088] Monoisopropylnaphthalene and triisopropylnaphthalene were added to the reactor at a molar ratio of 1:2, along with 5% (4 wt%) of magnesium-modified MCM-22 molecular sieve M4 prepared in Preparation Example 4. All exhaust valves of the reactor were closed, and nitrogen gas was introduced into the reactor. After pressurizing to 0.2 MPa–0.5 MPa, the nitrogen valve was closed, and the vacuum pump was started to evacuate the reactor for 5 minutes, displacing the gas in the reactor with nitrogen. Nitrogen gas was then introduced into the reactor to raise the pressure to the reaction pressure of 2.5 MPa. The reactor was stirred and heated to 230°C for 4 hours, after which heating was stopped. The reactor was allowed to cool to 40°C, and stirring was stopped. The reactor was then depressurized, the material was removed, and the magnesium-modified MCM-22 molecular sieve was filtered out.

[0089] Gas chromatography analysis revealed a conversion rate of 94.7% for monoisopropylnaphthalene and a selectivity of 65.1% for diisopropylnaphthalene in the product.

[0090] Subsequently, diisopropylnaphthalene was purified by vacuum distillation. Under vacuum conditions of 1000 Pa, bottom temperature of 180 °C, top temperature of 165-170 °C, and reflux ratio of 1:1, diisopropylnaphthalene with a purity of over 99% was collected.

[0091] Comparative Example 1

[0092] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0093] The experimental method was the same as in Example 1, except that the catalyst added was MCM-22 molecular sieve that was only dehydrated and not modified. The conversion rate of monoisopropylnaphthalene was 50.8%, and the selectivity of diisopropylnaphthalene in the product was 29.1%.

[0094] Comparative Example 2

[0095] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0096] The experimental method was the same as in Example 1, except that the catalyst added was an undehydrated and unmodified MCM-22 molecular sieve, and the conversion rate of monoisopropylnaphthalene was 50.2%, with a selectivity of 28.8% for diisopropylnaphthalene in the product.

[0097] Comparative Examples 1 and 2 show that the catalytic performance of MCM-22 molecular sieve in the synthesis of diisopropylnaphthalene is not significantly affected by dehydration treatment if it is not modified with magnesium. This indicates that dehydration treatment of MCM-22 molecular sieve is more conducive to the magnesium modification process and improves the catalytic performance of magnesium-modified catalyst.

[0098] Comparative Example 3

[0099] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0100] The experimental method was the same as in Example 1, except that the catalyst added was the magnesium-modified MCM-22 molecular sieve DM9 (silicon-to-aluminum ratio of 15) prepared in Comparative Preparation Example 9. The conversion rate of monoisopropylnaphthalene was 45.6%, and the selectivity of diisopropylnaphthalene in the product was 36.9%.

[0101] As can be seen from Comparative Example 3, the performance of the magnesium-modified catalyst prepared by the low silicon-to-aluminum ratio of MCM-22 molecular sieve is generally poor, which is not conducive to improving the conversion rate and selectivity of monoisopropylnaphthalene in the synthesis of diisopropylnaphthalene.

[0102] Comparative Example 4

[0103] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0104] The experimental method was the same as in Example 1, except that the catalyst added was the calcium-modified MCM-22 molecular sieve DM7 prepared in Comparative Preparation Example 7. The conversion rate of monoisopropylnaphthalene was 62.6%, and the selectivity of diisopropylnaphthalene in the product was 32.3%.

[0105] Comparative Example 5

[0106] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0107] The experimental method was the same as in Example 1, except that the catalyst added was the strontium-modified MCM-22 molecular sieve DM8 prepared in Comparative Preparation Example 8. The conversion rate of monoisopropylnaphthalene was 51.2%, and the selectivity of diisopropylnaphthalene in the product was 30.6%.

[0108] As can be seen from Comparative Examples 4 and 5, the conversion rate and selectivity of monoisopropylnaphthalene were significantly reduced when calcium-modified MCM-22 molecular sieve and strontium-modified MCM-22 molecular sieve were used to synthesize diisopropylnaphthalene. This is mainly because calcium and strontium have larger atomic radii, making it more difficult for them to enter the pores of MCM-22 molecular sieve, thus resulting in poor modification effects.

[0109] Comparative Example 6

[0110] This comparative example is used to illustrate the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0111] The experimental method was the same as in Example 1, except that the catalyst added was the magnesium-modified MCM-22 molecular sieve DM4 prepared in Comparative Preparation Example 4. The conversion rate of monoisopropylnaphthalene was 60.7%, and the selectivity of diisopropylnaphthalene in the product was 31.8%.

[0112] Example 2

[0113] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0114] The experimental method was the same as in Example 1, except that the catalyst added was the magnesium-modified MCM-22 molecular sieve M1 (magnesium mass percentage of 1 wt%) prepared in Example 1. The conversion rate of monoisopropylnaphthalene was 64.8%, and the selectivity of diisopropylnaphthalene in the product was 33.5%.

[0115] Example 3

[0116] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0117] The experimental method was the same as in Example 1, except that the catalyst added was the magnesium-modified MCM-22 molecular sieve M2 (magnesium mass percentage of 2 wt%) prepared in Preparation Example 2. The conversion rate of monoisopropylnaphthalene was 74.9%, and the selectivity of diisopropylnaphthalene in the product was 45.1%.

[0118] Example 4

[0119] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0120] The experimental method was the same as in Example 1, except that the catalyst added was the magnesium-modified MCM-22 molecular sieve M3 (magnesium mass percentage of 3 wt%) prepared in Preparation Example 3. The conversion rate of monoisopropylnaphthalene was 80.3%, and the selectivity of diisopropylnaphthalene in the product was 56.2%.

[0121] Example 5

[0122] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0123] The experimental method was the same as in Example 1, except that the catalyst added was the magnesium-modified MCM-22 molecular sieve M5 (magnesium mass percentage of 6 wt%) prepared in Preparation Example 5. The conversion rate of monoisopropylnaphthalene was 95.4%, and the selectivity of diisopropylnaphthalene was 67.1%.

[0124] Example 6

[0125] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0126] The experimental method was the same as in Example 1, except that the catalyst added was the magnesium-modified MCM-22 molecular sieve M6 (magnesium mass percentage of 8 wt%) prepared in Preparation Example 6, and the conversion rate of monoisopropylnaphthalene was 89.9% and the selectivity of diisopropylnaphthalene was 60.3%.

[0127] Table 1. Statistical analysis of the effect of the magnesium-modified catalyst described in this invention on the synthesis of diisopropylnaphthalene.

[0128]

[0129]

[0130] Example 7

[0131] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0132] Monoisopropylnaphthalene and triisopropylnaphthalene were added to the reactor at a molar ratio of 1:1, along with 5% (by mass) of magnesium-modified MCM-22 molecular sieve M3 prepared in Preparation Example 3 (magnesium mass percentage 3 wt%). All exhaust valves of the reactor were closed, and nitrogen gas was introduced into the reactor. After pressurizing to 0.2 MPa–0.5 MPa, the nitrogen valve was closed, and the vacuum pump was started to evacuate the reactor for 5 minutes, displacing the gas in the reactor with nitrogen. Then, nitrogen gas was introduced into the reactor, increasing the pressure to the reaction pressure of 2.5 MPa. The reactor was stirred and heated to 230°C for 4 hours, after which heating was stopped. The reactor was allowed to cool to 40°C, and stirring was stopped. The reactor was then depressurized, the material was removed, and the magnesium-modified MCM-22 molecular sieve was filtered out.

[0133] Gas chromatography analysis revealed a conversion rate of 69.8% for monoisopropylnaphthalene and a selectivity of 52.6% for diisopropylnaphthalene in the product.

[0134] Example 8

[0135] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0136] The experimental method was the same as in Example 7, except that monoisopropylnaphthalene and triisopropylnaphthalene were mixed in a molar ratio of 1:1.5, resulting in a conversion rate of 74.7% for monoisopropylnaphthalene and a selectivity of 54.6% for diisopropylnaphthalene in the product.

[0137] Example 9

[0138] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0139] The experimental method was the same as in Example 7, except that monoisopropylnaphthalene and triisopropylnaphthalene were used in a molar ratio of 1:3, resulting in a conversion rate of 85.1% for monoisopropylnaphthalene and a selectivity of 57.9% for diisopropylnaphthalene in the product.

[0140] Example 10

[0141] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0142] The experimental method was the same as in Example 7, except that monoisopropylnaphthalene and triisopropylnaphthalene were used in a molar ratio of 1:4, resulting in a conversion rate of 90.2% for monoisopropylnaphthalene and a selectivity of 59.8% for diisopropylnaphthalene in the product.

[0143] Example 11

[0144] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0145] The experimental method was the same as in Example 7, except that the molar ratio of monoisopropylnaphthalene and triisopropylnaphthalene was 2:1, resulting in a conversion rate of 59.7% for monoisopropylnaphthalene and 78.2% for triisopropylnaphthalene, with a selectivity of 56.8% for diisopropylnaphthalene in the product.

[0146] Example 12

[0147] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0148] The experimental method was the same as in Example 7, except that the molar ratio of monoisopropylnaphthalene and triisopropylnaphthalene was 3:1, resulting in a conversion rate of 43.2% for monoisopropylnaphthalene and 87.1% for triisopropylnaphthalene, with a selectivity of 58.4% for diisopropylnaphthalene in the product.

[0149] Example 13

[0150] This embodiment illustrates the synthesis method of diisopropylnaphthalene using the magnesium-modified catalyst described in this invention.

[0151] The experimental method was the same as in Example 7, except that the molar ratio of monoisopropylnaphthalene and triisopropylnaphthalene was 4:1, resulting in a conversion rate of 32.1% for monoisopropylnaphthalene and 91.1% for triisopropylnaphthalene, with a selectivity of 60.3% for diisopropylnaphthalene in the product.

[0152] Table 2. Statistical analysis of the effect of the magnesium-modified catalyst described in this invention on the synthesis of diisopropylnaphthalene.

[0153]

[0154] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a magnesium-modified catalyst, characterized in that, The process includes adding a magnesium metal salt solution dropwise into an MCM-22 molecular sieve, followed by calcination (I) to obtain the magnesium-modified catalyst. The MCM-22 molecular sieve has undergone dehydration treatment.

2. The preparation method according to claim 1, characterized in that, The dehydration treatment includes drying and calcination II; more preferably, the drying conditions include: a drying temperature of 100℃~150℃ and a drying time of 24h~36h; the calcination II conditions include: a calcination II temperature of 500℃~600℃ and a calcination II time of 7h~8h; even more preferably, the water absorption rate of the MCM-22 molecular sieve after the dehydration treatment is 15%~25%, preferably 20%~25%.

3. The preparation method according to claim 2, characterized in that, The concentration of the magnesium metal salt solution is 0.1 mol / L to 3.0 mol / L; And / or, the magnesium metal salt is selected from at least one of magnesium nitrate, magnesium chloride, and magnesium sulfate; And / or, based on the total mass of magnesium metal salt and MCM-22 molecular sieve as 100%, the mass percentage of magnesium metal salt is 1wt% to 8wt%, preferably 3wt% to 8wt%.

4. The preparation method according to any one of claims 1-3, characterized in that, The conditions for calcination I include: calcination I temperature of 500℃~600℃, and calcination I time of 4h~6h; And / or, the roasting I is preceded by a drying step; preferably, the drying conditions include: a drying temperature of 120℃~150℃ and a drying time of 4h~6h.

5. The preparation method according to any one of claims 1-4, characterized in that, The addition is performed while stirring; And / or, after the addition, the mixture is stirred for 3 to 5 hours at a temperature of 25°C to 30°C, and then allowed to stand for 20 to 24 hours.

6. A magnesium-modified catalyst, comprising an MCM-22 molecular sieve and magnesium supported on the MCM-22 molecular sieve; characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

7. The magnesium-modified catalyst according to claim 6, characterized in that, The molar ratio of SiO2 to Al2O3 in the MCM-22 molecular sieve is 20–35. And / or, the pore size of the MCM-22 molecular sieve is 0.55 nm to 2.0 nm.

8. A method for synthesizing diisopropylnaphthalene, characterized in that, Under an inert atmosphere and in the presence of the magnesium-modified catalyst prepared by any one of claims 1-5 or the magnesium-modified catalyst described in claim 6 or 7, monoisopropylnaphthalene and triisopropylnaphthalene react to obtain diisopropylnaphthalene.

9. The synthesis method according to claim 8, characterized in that, The inert atmosphere is selected from at least one of nitrogen, helium, and argon; And / or, the molar ratio of the monoisopropylnaphthalene to the triisopropylnaphthalene is (0.25–4):1, preferably (0.25–0.5):1; And / or, the added mass of the magnesium-modified catalyst is 2% to 5% of the total mass of monoisopropylnaphthalene and triisopropylnaphthalene; And / or, the reaction conditions include: a reaction temperature of 200℃~250℃, a reaction pressure of 1.5MPa~2.5MPa, and a reaction time of 3h~5h.

10. The synthesis method according to claim 8, characterized in that, The diisopropylnaphthalene further includes a purification step; preferably, the purification is carried out by vacuum distillation; more preferably, the conditions for vacuum distillation include: a vacuum degree of 500 Pa to 1500 Pa, a bottom temperature of 170°C to 200°C, a top temperature of 160°C to 170°C, and a reflux ratio of 1:(0.5 to 2); even more preferably, the purity of the purified diisopropylnaphthalene is >99%.

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