Method for synthesizing alkyl tetrahydronaphthalene by using rare earth modified solid acid catalyst

Abstract

The invention discloses a method for synthesizing alkyl tetrahydronaphthalene by using a rare earth modified solid acid catalyst, which comprises the following steps: dissolving soluble salt of active metal and soluble salt of rare earth element lanthanum in water, then adding ammonia water to adjust the pH value, stirring, aging, washing and carrying out suction filtration to obtain a precipitate, drying the precipitate, then dipping with H2SO4 solution, carrying out suction filtration, and drying to obtain the alkyl tetrahydronaphthalene. Then roasting to obtain a rare earth modified solid acid catalyst; the preparation method comprises the following steps: mixing tetrahydronaphthalene, a rare earth modified solid acid catalyst and a solvent, heating, then adding alpha-olefin, and reacting to obtain a reaction product; and adding carclazyte and calcium hydroxide into the product, heating, stirring and filtering to remove the catalyst used in the reaction, and then carrying out distillation and reduced pressure distillation to obtain the alkyl tetrahydronaphthalene. The rare earth modified solid acid catalyst provided by the invention is a multi-component carrier composite solid superacid, has better catalytic effect and higher thermal stability, and has the characteristic of long service life.

Description

Technical Field

[0001] The invention belongs to the field of synthesis methods of alkyltetralin, and in particular relates to a method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst. Background Art

[0002] As an efficient blending component of high-grade base oil, alkyl naphthalene base oil can significantly improve the high thermal stability of oil products, the solubility and effectiveness of additives, greatly reduce the amount of additives, extend the service life of oil products, and meet the requirements of high temperature and high heat conditions. The currently developed alkyl naphthalene lubricant products have a single structure, and their molecular structure is mostly composed of a single long-chain alkyl naphthalene. The physicochemical properties and uses of alkyl naphthalene chemicals depend on the molecular structure and number of side chains, and the lubrication performance of the products is limited. Therefore, the synthesis of a series of polyalkyl naphthalenes with different numbers, lengths and structures is of great significance to enrich the types and uses of alkyl naphthalene lubricants. In recent years, the structure of the lubricant industry has been upgraded, and the demand for Class V alkyl naphthalene base oil has increased significantly. Domestic alkyl naphthalene base oil mainly relies on imports, and my country's research on alkyl naphthalene has just started in recent years.

[0003] Chinese patent CN 112694379 A discloses a method for preparing alkyltetralin, wherein under the condition of an ionic liquid catalyst, tetralin is subjected to an alkylation reaction with an olefin of different carbon numbers to generate an alkyltetralin product. However, the ionic liquid catalyst used in the method is more expensive than conventional solid catalysts, has a more complicated structure, is easily destroyed by reactants during the catalytic reaction, and loses catalytic activity, and the stability of the catalyst cannot be guaranteed. Moreover, recovery has a certain difficulty, and unlike conventional catalysts, ionic liquid catalysts require special recovery conditions and equipment, which easily causes waste of resources and pollution of the environment.

[0004] Chinese patent CN 113388430 A discloses a method and application of preparing alkyl naphthalene from mixed olefins, wherein a plurality of mixed α-olefins are used to replace single carbon number olefins in the traditional process, and alkyl naphthalene products are prepared by the synergistic preparation of solid acid catalysts and reaction conditions. However, the solid acid catalyst used in this method has poor strength, which is not conducive to long-term reaction.

[0005] Chinese patent CN 114478157 A discloses a method for preparing a long-chain dialkylnaphthalene type lubricating oil base oil, which first prepares high-purity monoalkylnaphthalene, and then uses the monoalkylnaphthalene as a raw material to prepare polyalkylnaphthalene. However, the monoalkylnaphthalene in the raw material of this method is highly toxic and causes great harm to the human body and the environment. It is difficult to ensure that the method is non-toxic and harmless to the environment during the synthesis process.

[0006] Chinese patent CN 114790407 A discloses a method for preparing alkylnaphthalene lubricant base oil from α-olefins. Alkylnaphthalene is obtained by using coal-based α-olefins, naphthalene and / or methylnaphthalene as raw materials and catalyzing with a solid acid catalyst. However, the solid acid catalyst used in this method has poor mechanical strength and is difficult to pass long-term industrial tests.

[0007] Chinese patent CN 103508834 A discloses a method for highly selectively synthesizing 1,1-phenyltetrahydronaphthylethane isomers as a heat transfer fluid, wherein solid metatitanic acid is added to a zirconium oxychloride solution, stirred evenly, and then slowly added with ammonia water for adjustment, and the ground powder is added to a sulfuric acid solution of cerium sulfate for soaking; under stirring and heating conditions, a superacid catalyst and an organic fluorine sulfonic acid are first added to tetralin in their mass ratio, and styrene is added dropwise when the temperature reaches above 30°C, and the reaction is stopped when GC detects that there is no styrene. However, the superacid catalyst synthesized by this method is extremely harmful to the human body and the environment, so strict protective measures are required during the production process, and the superacid catalyst is highly corrosive to most metals, non-metals and organic matter, which can easily cause damage and pollution to the equipment. Therefore, the equipment needs to be specially treated and protected before use, and these factors indirectly increase the economic and management costs.

[0008] Chinese patent CN 1935373A discloses a rare earth-containing composite solid superacid catalyst, which is composed of a ZrO2 carrier containing sulfate ions, a TiO2 carrier, a rare earth metal oxide and an aluminum halide, wherein the content of sulfate ions is 10-20 (parts by weight), the content of aluminum halide is (parts by weight), the moisture content in the catalyst is 0-1 (parts by weight), the ZrO2 carrier is 43-80 (parts by weight), the TiO2 carrier is 43-80 (parts by weight), the rare earth metal oxide accounts for 3-10 (parts by weight), the specific surface area of ​​the catalyst is 100-300m / g, and the aluminum halide is selected from aluminum fluoride or aluminum chloride or a mixture of the two. However, the catalyst is used for the polycondensation reaction of naphthalene to obtain naphthalene polycondensate, and it is not disclosed that it can be used for the alkylation reaction of naphthalene. In addition, metals such as Zr, Ti, rare earth metals, and Al are added to the catalyst, and the added metals are of various types, the preparation process is cumbersome, the cost is high, and the by-products after the reaction contain metal elements, which makes it difficult to handle and is not conducive to environmental protection.

[0009] Chinese patent CN 105195179A discloses a solid superacid catalyst and a preparation method thereof. The solid superacid catalyst is zirconium dioxide loaded with sulfuric acid, abbreviated as SO4 2- / ZrO2, the ZrO2 is prepared by calcining a zirconium-based coordination polymer, and the zirconium-based coordination polymer involved is UTO-66 and its analogs. However, the catalyst is used for esterification and isomerization reactions, and it does not show that it can catalyze the alkylation reaction of alkyltetralin; and the purpose of modifying the catalyst with metal, transition metal or rare earth metal is only to stabilize the tetragonal phase of ZrO2 crystal form, and the catalyst structure is not significantly improved.

[0010] The prepared SO4 was characterized by XRD, SEM, NH3-TPD and other methods. 2- / TiO2 solid superacid catalyst, and investigated its catalytic performance in the reaction of naphthalene and 1-tetradecene to synthesize long-chain alkylnaphthalene. 2- / TiO2 solid superacid catalyst has the disadvantages of poor strength and insufficient stability.

[0011] "Alkylation of Tetralin with Butene / Propylene Catalyzed by Ionic Liquid and Its Lubricating Properties" uses tetralin and short-chain α-olefins (C3 / C4) as raw materials and Et3NHCl-AlCl3 ionic liquid as catalyst to successfully synthesize alkyl tetralin similar to cycloalkyl base oil. However, compared with traditional solid catalysts, the ionic liquid catalyst used in this method is more expensive and has a more complex structure. It is easily destroyed by reactants during the catalytic reaction and loses its catalytic activity. The stability of the catalyst cannot be guaranteed. In addition, it is difficult to recycle. Unlike traditional catalysts, ionic liquid catalysts require special recycling conditions and equipment, which can easily cause waste of resources and environmental pollution.

[0012] 《Alkyl-tetralin base oils synthesized from coal-based chemicals and evaluation of their lubricating properties》 Alkyl-tetralin products similar to cycloalkyl base oils were successfully synthesized by Friedel-Crafts alkylation reaction using short-chain α-olefins (C3 / C4) as raw materials. Using Et3NHCl-AlCl3 ionic liquid (IL) as catalyst, the alkylation reaction of tetralin with n-butene or propylene showed excellent catalytic performance. However, compared with traditional solid catalysts, the ionic liquid catalyst used in this method is more expensive and has a more complex structure. It is easily destroyed by reactants during the catalytic reaction and loses its catalytic activity, and the stability of the catalyst cannot be guaranteed. In addition, it is difficult to recycle. Unlike traditional catalysts, ionic liquid catalysts require special recycling conditions and equipment, which easily causes waste of resources and environmental pollution.

[0013] In the current methods, the catalysts used in the synthesis of alkyl naphthalene base oil are mostly solid acids, and the raw materials are naphthalene. The raw material naphthalene is highly toxic and causes great harm to the human body and the environment, and it is difficult to ensure that it is non-toxic and harmless to the environment during the synthesis process. In addition, the mechanical strength of unmodified solid acid catalysts is generally low, the catalyst life is short, and it is difficult to pass the test of long-term industrial tests, and the actual application prospects are not good. Summary of the invention

[0014] The main purpose of the present invention is to provide a method for synthesizing alkyltetralin by using rare earth modified solid acid catalyst. The introduction of rare earth lanthanum element into solid acid can make the catalyst surface produce new L acid center while maintaining B acid center, improve the thermal stability of B acid in the catalyst, adjust the strength and density of surface acid center, increase the ability of anti-poison, improve mechanical strength and extend the service life of the catalyst. Alkyltetralin has good physical properties, good thermal oxidation stability, good compatibility with additives, and its molecular structure is similar to typical cycloalkyl base oil in petroleum resources. Therefore, alkyltetralin can be used as a substitute for cycloalkyl base oil, which is an important member of the lubricating oil family. As a lubricating base oil, the performance of alkyltetralin is closely related to the molecular structure of the side chain and the number of alkyl groups on the naphthalene ring.

[0015] To achieve the above object, the present invention provides a method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst, the preparation method comprising the following steps:

[0016] (1) dissolving a soluble salt of an active metal and a soluble salt of a rare earth element lanthanum in water, then adding aqueous ammonia to adjust the pH value, stirring, aging, washing, and filtering to obtain a precipitate, drying the precipitate, then impregnating it with a H2SO4 solution, filtering, drying, and then calcining to obtain a rare earth-modified solid acid catalyst;

[0017] (2) mixing tetralin, a rare earth-modified solid acid catalyst, and a solvent, heating the mixture, and then adding an α-olefin to react to obtain a reaction product;

[0018] (3) adding clay and calcium hydroxide to the product of step (2), heating, stirring and filtering to remove the catalyst used in the reaction, and then distilling and distilling under reduced pressure to obtain alkyltetralin.

[0019] The method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention, wherein the active metal is one of Zr, Sn, Ti, Al and Fe; the rare earth modified solid acid catalyst is SO4 2－ / ZrO2-La2O3 catalyst, SO4 2－ / SnO2-La2O3 catalyst, SO4 2－ / TiO2-La2O3 catalyst, SO4 2－ / Al2O3-La2O3 catalyst, SO4 2－ / One of the Fe2O3-La2O3 catalysts.

[0020] In the method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention, the active metal is preferably one of Fe, Ti and Al.

[0021] In the method for synthesizing alkyltetralin using rare earth modified solid acid catalyst of the present invention, the soluble salt of La is selected from at least one of La(NO3)3·6H2O, La2(CO3)3.xH2O and La2(SO4)3·9H2O.

[0022] The method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention comprises the following steps: in step (1), the soluble salt of the active metal is calculated as the active metal element, the soluble salt of La is calculated as the La element, and the mass ratio of the active metal to La is 15 to 19.

[0023] In the method for synthesizing alkyltetralin using rare earth modified solid acid catalyst of the present invention, in step (1), the pH value is adjusted to 8-10.

[0024] The method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention comprises the following steps: in step (1), the temperature for drying the precipitate is 90 to 120° C. and the drying time is 2 to 6 hours.

[0025] In the method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention, in step (1), the concentration of the H2SO4 solution and the amount thereof added are not particularly limited.

[0026] In the method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention, in step (2), the molar ratio of tetralin to alpha-olefin is 1:12 to 12:1, preferably 1:4 to 4:1.

[0027] In the method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention, in step (2), the molar ratio of the rare earth modified solid acid catalyst to tetralin is 1:2 to 1:20, preferably 1:1 to 1:12.

[0028] In the method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention, in step (2), the molar ratio of the tetralin to the solvent is 1:2 to 1:8, preferably 1:5 to 1:7.

[0029] In the method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention, in step (2), the α-olefin is selected from at least one of 1-octene, 1-nonene, 1-decene, 1-dodecene and 1-tetradecene.

[0030] In the method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst of the present invention, in step (2), the solvent is selected from at least one of n-decane and cyclohexane.

[0031] The method for synthesizing alkyltetralin using rare earth modified solid acid catalyst of the present invention comprises the following steps: in step (2), the reaction temperature is 80-150° C., preferably 100-120° C., and the reaction time is 1-6 hours, preferably 2-4 hours.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] (1) The rare earth modified solid acid catalyst of the present invention is a multi-component carrier composite solid superacid, which has good catalytic effect, high thermal stability and mechanical strength, and a long service life of the catalyst. The introduction of rare earth lanthanum element into the solid acid of the present invention can make the catalyst surface produce new L acid center while maintaining the B acid center, thereby regulating the BL acid position. The present invention uses the rare earth lanthanum modified solid acid catalyst to catalyze tetralin, successfully alkylates tetralin with α-olefins, and synthesizes a series of alkyl tetralin products. The raw material tetralin has low toxicity and is liquid, which is beneficial to the reaction. At the same time, the rare earth lanthanum modified solid acid catalyst of the present invention has the advantages of simple preparation method, environmental friendliness, high catalytic activity and stability, easy separation of product and catalyst, easy recycling, no corrosion pollution to equipment, etc., making the alkylation process more green. The alkyl tetralin synthesized by the present invention has a lower pour point.

[0034] (2) The alkyltetralin synthesized by the present invention has a typical cycloalkyl structure, and its product has the performance advantages of cycloalkyl, has good low-temperature fluidity, solubility and thermal stability, etc., and is widely used in various fields. Alkyltetralin as a synthetic lubricant has a similar structure to cycloalkyl lubricant, and alkyltetralin base oil is gradually used in various fields due to its excellent oxidation stability and additive solubility, etc., and has the potential to supplement or replace cycloalkyl lubricant. The solid acid catalyst modified by rare earth lanthanum can improve the reaction conversion rate and the catalyst has stronger mechanical strength and can be used for a long period of time. It is easy to recycle and regenerate after the reaction, saving technical and time costs, having good industrial application value, breaking the technical bottleneck that domestic alkyltetralin base oil mainly relies on imports. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 XRD spectra of solid acid catalysts with different rare earth doping amounts. DETAILED DESCRIPTION

[0036] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention. The raw materials used in the following examples and comparative examples, unless otherwise specified, are all commercially available.

[0037] Source of raw materials:

[0038] Table 1 Source of raw materials

[0039] name Specification Manufacturer Tetralin 99％ Aladdin Chemical Reagent Co., Ltd. 1-Octene Analytical grade Aladdin Chemical Reagent Co., Ltd. 1-Decene Analytical grade Aladdin Chemical Reagent Co., Ltd. 1-Nonene Analytical grade Aladdin Chemical Reagent Co., Ltd. 1-Dodecene Analytical grade Aladdin Chemical Reagent Co., Ltd. 1-Tetradecene Analytical grade Aladdin Chemical Reagent Co., Ltd. n-Decane 99％ Aladdin Chemical Reagent Co., Ltd. Cyclohexane 99％ Aladdin Chemical Reagent Co., Ltd.

[0040] Evaluation and analysis methods:

[0041] Table 2 Evaluation methods

[0042]

[0043]

[0044] Embodiment 1:

[0045] Weigh AlCl3 and La(NO3)3·6H2O and dissolve them in distilled water, where the mass ratio of Al to La is 15.2. Then, add ammonia water to adjust the pH value to 8 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2－ / Al2O3-La2O3.

[0046] Tetralin (1 mol), catalyst SO4 2－ / Al2O3-La2O3 (0.1 mol) and n-decane (4 mol) are added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reaches 80°C, 1-octene (0.125 mol) is slowly added thereto, the reaction temperature is controlled at 80°C, and the mixture is mixed and stirred for 5 hours. After the reaction is completed, appropriate amounts of clay and calcium hydroxide are added, heated, stirred and filtered to remove the catalyst in the reaction. The product is distilled and vacuum distilled, and the obtained product is the alkyltetralin product. The obtained product is subjected to performance testing, and its performance is listed in Table 3.

[0047] Embodiment 2:

[0048] Weigh TiCl4 and La(NO3)3·6H2O and dissolve them in distilled water, where the mass ratio of Ti to La is 16.7. Then, add ammonia water to adjust the pH value to 8.5 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2- / TiO2-La2O3.

[0049] Tetralin (1.5 mol), catalyst SO4 2- / TiO2-La2O3 (0.1 mol) and n-decane (6 mol) are added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reaches 90°C, 1-decene (6 mol) is slowly added thereto, the reaction temperature is controlled at 90°C, and the mixture is mixed and stirred for 4 hours. After the reaction is completed, appropriate amounts of clay and calcium hydroxide are added, heated, stirred and filtered to remove the catalyst in the reaction. The product is distilled and vacuum distilled, and the obtained product is the alkyltetralin product. The obtained product is subjected to performance testing, and its performance is listed in Table 3.

[0050] Embodiment 3:

[0051] Weigh AlCl3 and La2(SO4)3·9H2O and dissolve them in distilled water, where the mass ratio of Al to La is 15.2. Then, add ammonia water to adjust the pH value to 8 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2－ / Al2O3-La2O3.

[0052] Tetralin (1 mol), catalyst SO4 2－ / Al2O3-La2O3 (0.05 mol) and cyclohexane (8 mol) were added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reached 100°C, 1-nonene (2 mol) was slowly added thereto, the reaction temperature was controlled at 100°C, and the mixture was mixed and stirred for 3 hours. After the reaction was completed, appropriate amounts of clay and calcium hydroxide were added, heated, stirred and filtered to remove the catalyst in the reaction. The product was distilled and vacuum distilled, and the obtained product was the alkyltetralin product. The obtained product was subjected to performance testing, and its performance is listed in Table 3.

[0053] Embodiment 4:

[0054] Weigh FeCl3 and La(NO3)3·6H2O and dissolve them in distilled water, where the mass ratio of Fe to La is 18.6. Then, add ammonia water to adjust the pH value to 9 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2－ / Fe2O3-La2O3.

[0055] Tetralin (1 mol), catalyst SO4 2－ / Fe2O3-La2O3 (0.0625 mol) and cyclohexane (4 mol) were added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reached 110°C, 1-dodecene (1.6 mol) was slowly added thereto, the reaction temperature was controlled at 110°C, and the mixture was mixed and stirred for 2 hours. After the reaction was completed, appropriate amounts of clay and calcium hydroxide were added, heated, stirred and filtered to remove the catalyst in the reaction. The product was distilled and vacuum distilled, and the obtained product was the alkyltetralin product. The obtained product was subjected to performance testing, and its performance is listed in Table 3.

[0056] Embodiment 5:

[0057] Weigh TiCl4 and La(NO3)3·6H2O and dissolve them in distilled water, where the mass ratio of Ti to La is 16.7. Then, add ammonia water to adjust the pH value to 8.5 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2- / TiO2-La2O3.

[0058] Tetralin (1 mol), catalyst SO4 2- / TiO2-La2O3 (0.071 mol) and n-decane (6 mol) are added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reaches 120°C, 1-octene (1 mol) is slowly added thereto, the reaction temperature is controlled at 120°C, and the mixture is mixed and stirred for 2 hours. After the reaction is completed, appropriate amounts of clay and calcium hydroxide are added, heated, stirred and filtered to remove the catalyst in the reaction. The product is distilled and vacuum distilled, and the obtained product is the alkyltetralin product. The obtained product is subjected to performance testing, and its performance is listed in Table 3.

[0059] Embodiment 6:

[0060] Weigh ZrCl4 and La(NO3)3·6H2O and dissolve them in distilled water, where the mass ratio of Zr to La is 16.2. Then, add ammonia water to adjust the pH value to 8.5 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2- / ZrO2-La2O3.

[0061] Tetralin (2 mol), catalyst SO4 2- / ZrO2-La2O3 (0.5 mol) and n-decane (8 mol) are added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reaches 130°C, 1-decene (4 mol) is slowly added thereto, the reaction temperature is controlled at 130°C, and the mixture is mixed and stirred for 4 hours. After the reaction is completed, appropriate amounts of clay and calcium hydroxide are added, heated, stirred and filtered to remove the catalyst in the reaction. The product is distilled and vacuum distilled, and the obtained product is the alkyltetralin product. The obtained product is subjected to performance testing, and its performance is listed in Table 3.

[0062] Embodiment 7:

[0063] Weigh TiCl4 and La2(SO4)3·9H2O and dissolve them in distilled water, where the mass ratio of Ti to La is 16.7. Then, add ammonia water to adjust the pH value to 8.5 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2- / TiO2-La2O3.

[0064] Tetralin (2 mol), catalyst SO4 2- / TiO2-La2O3 (0.2 mol) and cyclohexane (4 mol) are added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reaches 110°C, 1-dodecene (1 mol) is slowly added thereto, the reaction temperature is controlled at 110°C, and the mixture is stirred for 5 hours. After the reaction is completed, appropriate amounts of clay and calcium hydroxide are added, heated, stirred and filtered to remove the catalyst in the reaction. The product is distilled and vacuum distilled, and the obtained product is the alkyltetralin product. The obtained product is subjected to performance testing, and its performance is listed in Table 3.

[0065] Embodiment 8:

[0066] Weigh FeCl3 and La(NO3)3·6H2O and dissolve them in distilled water, where the mass ratio of Fe to La is 18.6. Then, add ammonia water to adjust the pH value to 9 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl －The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2－ / Fe2O3-La2O3.

[0067] Tetralin (2 mol), catalyst SO4 2－ / Fe2O3-La2O3 (0.17 mol) and cyclohexane (6 mol) are added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reaches 120°C, 1-tetradecene (0.5 mol) is slowly added thereto, the reaction temperature is controlled at 120°C, and the mixture is mixed and stirred for 2 hours. After the reaction is completed, appropriate amounts of clay and calcium hydroxide are added, heated, stirred and filtered to remove the catalyst in the reaction. The product is distilled and vacuum distilled, and the obtained product is the alkyltetralin product. The obtained product is subjected to performance testing, and its performance is listed in Table 3.

[0068] Embodiment 9:

[0069] Weigh TiCl4 and La(NO3)3·6H2O and dissolve them in distilled water, where the mass ratio of Ti to La is 16.7. Then, add ammonia water to adjust the pH value to 8.5 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2- / TiO2-La2O3.

[0070] Tetralin (2 mol), catalyst SO4 2- / TiO2-La2O3 (0.14 mol) and n-decane (8 mol) are added to a 250 mL three-necked flask with a condensation reflux device and mixed evenly. When the temperature reaches 140°C, 1-dodecene (0.4 mol) is slowly added thereto, the reaction temperature is controlled at 140°C, and the mixture is mixed and stirred for 4 hours. After the reaction is completed, appropriate amounts of clay and calcium hydroxide are added, heated, stirred and filtered to remove the catalyst in the reaction. The product is distilled and vacuum distilled, and the obtained product is the alkyltetralin product. The obtained product is subjected to performance testing, and its performance is listed in Table 3.

[0071] Embodiment 10:

[0072] Weigh AlCl3 and La(NO3)3·6H2O and dissolve them in distilled water, where the mass ratio of Al to La is 15.2. Then, add ammonia water to adjust the pH value to 8 under rapid stirring. Continue stirring for 1 hour, age for 24 hours, and repeatedly wash and filter to remove Cl － The precipitate was dried at 110°C for 4 hours, and then impregnated with 0.5 mol / L H2SO4 solution at a ratio of 10 mL / g precipitate for 1 hour, and then the impregnation solution was removed by suction filtration, dried, and then calcined to obtain a rare earth modified catalyst SO4 2－ / Al2O3-La2O3.

[0073] Tetralin (2 mol), catalyst SO4 2－ / Al2O3-La2O3 (0.11 mol) and cyclohexane (6 mol) are added to a 250 mL three-necked flask with a condensing reflux device and mixed evenly. When the temperature reaches 150°C, 1-tetradecene (0.25 mol) is slowly added thereto, the reaction temperature is controlled at 150°C, and the mixture is mixed and stirred for 5 hours. After the reaction is completed, appropriate amounts of clay and calcium hydroxide are added, heated, stirred and filtered to remove the catalyst in the reaction. The product is distilled and vacuum distilled, and the obtained product is the alkyltetralin product. The obtained product is subjected to performance testing, and its performance is listed in Table 3.

[0074] Comparative Example 1:

[0075] The difference from Example 1 is that the rare earth modified catalyst SO4 2－ / Al2O3-La2O3 is replaced by the ionic liquid catalyst prepared in Example 1 of CN112694379 A. The specific preparation steps of the ionic liquid catalyst are as follows:

[0076] To prepare an ionic liquid catalyst, FeCl3 (3.0 mmol), triethylamine hydrochloride (1.5 mmol) and an inert organic solvent n-decane (5 mL) were sequentially added into a three-necked round-bottom flask and stirred continuously in a constant temperature oil bath at 60°C for 1 h.

[0077] The rest is the same as in Example 1.

[0078] The obtained product was subjected to performance testing, and its performance is listed in Table 3.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that the rare earth modified catalyst SO4 2－ / Al2O3-La2O3 is replaced by the super acid catalyst prepared in Example 1 of CN10350883 A. The preparation steps of the super acid catalyst are as follows:

[0081] In a 1000ml three-necked flask with a mechanical stirrer, first add 500ml of distilled water, add 10g of zirconium oxychloride under stirring, dissolve it, then add 100g of metatitanic acid solid, stir evenly, slowly add dilute ammonia water (mass concentration is 12-14wt%), until the pH>9, let it stand for 12 hours, filter, wash with distilled water until it is neutral and there is no chloride ion, dry it in a 100-120℃ oven for 3 hours, and grind it to 100-200 mesh. Separately weigh 1g of cerium sulfate and dissolve it in 450ml of distilled water, then slowly add 50g of concentrated sulfuric acid; add the above-mentioned dried solid powder and soak it for more than 24 hours. Filter until there is no water dripping, place the solid in a beaker and dry it in a 100-120℃ oven for 3 hours, grind it; bake it in a muffle furnace at 350℃ for 1 hour; bake it at 550-600℃ for 3 hours, cool it naturally to about 100℃, take it out and store it in a dryer for use. The rest is the same as in Example 1.

[0082] The obtained product was subjected to performance testing, and its performance is listed in Table 3.

[0083] Table 3 Alkyl naphthalene product properties

[0084]

[0085] Figure 1 The XRD spectra of solid acid catalysts with different rare earth doping amounts are shown in Figure 1, where a is 0% La2O3; b is 2% La2O3; c is 6% La2O3; and d is 4% La2O3. In order to illustrate that the internal structure of the modified solid acid catalyst has changed, Figure 1 The XRD analysis spectra of different rare earth doping amounts when the catalyst was calcined at 600°C. The XRD analysis of the catalyst was carried out using a Japanese Rigaku D / max-2200 X-ray diffractometer, Cu target, Kα line (λ=0.15406nm), tube voltage 40kV, tube current 30mA, scanning rate 10° / min, 10°~80° scanning. Figure 1 It can be seen that the catalyst with 0% rare earth element La addition has only two broad dispersion peaks, indicating that its crystallization degree is not high, and its ZrO2 crystal phase is basically an amorphous structure. The introduction of rare earth element La significantly increases its crystallization degree, indicating that the tetragonal crystal phase structure of ZrO2 can be stabilized when an appropriate amount of rare earth element exists. Therefore, an appropriate amount of doping with rare earth elements can significantly improve the structural crystallinity of solid acid, increase its stability and service life.

[0086] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for synthesizing alkyltetralin using a rare earth modified solid acid catalyst, characterized in that: The following steps are involved: (1) dissolving a soluble salt of an active metal and a soluble salt of a rare earth element lanthanum in water, then adding aqueous ammonia to adjust the pH value, stirring, aging, washing, and filtering to obtain a precipitate, drying the precipitate, then impregnating it with a H2SO4 solution, filtering, drying, and then calcining to obtain a rare earth-modified solid acid catalyst; (2) mixing tetralin, a rare earth-modified solid acid catalyst, and a solvent, heating the mixture, and then adding an α-olefin to react to obtain a reaction product; (3) adding clay and calcium hydroxide to the product of step (2), heating, stirring and filtering to remove the catalyst used in the reaction, and then distilling and distilling under reduced pressure to obtain alkyltetralin.

2. The method according to claim 1, characterized in that: The active metal is one of Zr, Sn, Ti, Al and Fe.

3. The method according to claim 2, characterized in that The active metal is one of Fe, Ti and Al.

4. The method according to claim 1, characterized in that The soluble salt of La is selected from at least one of La(NO3)3·6H2O and La2(SO4)3·9H2O.

5. The method according to claim 1, characterized in that In step (1), the soluble salt of the active metal is calculated as the active metal element, the soluble salt of La is calculated as the La element, and the mass ratio of the active metal to La is 15 to 19.

6. The method according to claim 1, characterized in that In step (1), the pH value is adjusted to 8-10.

7. The method according to claim 1, characterized in that In step (2), the molar ratio of tetralin to α-olefin is 1:12 to 12:

1.

8. The method according to claim 1, characterized in that: In step (2), the molar ratio of the rare earth modified solid acid catalyst to tetralin is 1:2 to 1:

20.

9. The method according to claim 1, characterized in that: In step (2), the molar ratio of tetralin to solvent is 1:2 to 1:

8.

10. The method according to claim 1, characterized in that In step (2), the α-olefin is selected from at least one of 1-octene, 1-nonene, 1-decene, 1-dodecene and 1-tetradecene.

11. The method according to claim 1, characterized in that In step (2), the reaction temperature is 80 to 150° C. and the reaction time is 1 to 6 hours.

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