Hierarchical porous mordenite catalyst as well as preparation method and application thereof

Abstract

The invention discloses a graded porous mordenite catalyst as well as a preparation method and application thereof, and belongs to the technical field of heterogeneous catalysis and chemistry and chemical engineering. The preparation method comprises the following steps: carrying out hydrolysis-polycondensation reaction on a silicon source, an aluminum source, an alkali source and water, after the reaction is completed, adding an alpha, omega-biquaternary ammonium salt surfactant as a template agent, and carrying out template-oriented self-assembly reaction to obtain gel; carrying out hydrothermal crystallization treatment on the gel to obtain zeolite raw powder; roasting the zeolite raw powder for the first time to remove the template agent so as to obtain roasted zeolite; and carrying out ion exchange treatment on the roasted zeolite, and roasting again to obtain the graded porous mordenite catalyst. According to the invention, the alpha, omega-biquaternary ammonium salt surfactant is used as the template agent to prepare the hierarchical porous structure catalyst with both inherent micropores and uniform mesopores, so that mass transfer can be improved and acidic sites can be optimized.

Description

Technical Field

[0001] This invention relates to the fields of heterogeneous catalysis and chemical engineering, and more specifically to a hierarchical porous mordenite zeolite catalyst, its preparation method, and its application. Background Technology

[0002] Polyethylene naphthalate (PAN) is a high-performance aromatic polyester material. Due to its unique naphthalene ring structure in its molecular chain, PAN exhibits superior thermal stability, mechanical strength, gas barrier properties, and chemical resistance compared to polyethylene terephthalate (PET). Based on these performance advantages, PAN shows significant application potential in high-value-added fields such as aerospace, high-end optoelectronic thin films, specialty fibers, and advanced medical devices.

[0003] 2,6-Diisopropylnaphthalene is a key monomer in the synthesis of polyethylene naphthalate (PEG), and its efficient and selective synthesis process is a core bottleneck restricting the industrialization of PEG. Currently, the industrial synthesis of 2,6-diisopropylnaphthalene faces several challenges: for example, the isopropylation reaction of naphthalene generates various diisopropylnaphthalene isomers such as 2,7-diisopropylnaphthalene and 1,6-diisopropylnaphthalene, as well as multiple isopropylation byproducts. The target product, 2,6-diisopropylnaphthalene, and the main byproduct, 2,7-diisopropylnaphthalene, have extremely similar physicochemical properties, such as boiling point and solubility, leading to high energy consumption and significant yield loss when separated and purified using traditional distillation or crystallization methods. Furthermore, early industrial use of liquid-phase acid catalysts, such as hydrofluoric acid, concentrated sulfuric acid, and aluminum trichloride, while possessing catalytic activity, exhibits strong corrosiveness and high toxicity, placing stringent requirements on equipment materials, necessitating the use of special corrosion-resistant materials. The post-reaction treatment generates a large amount of acidic wastewater and aluminum-containing residue, and the cost of treating these three wastes is high, which does not meet the development requirements of green chemical processes.

[0004] To overcome the aforementioned problems, shape-selective zeolite catalysts, especially mordenite, have become an ideal alternative to liquid acids due to their unique pore structure and tunable acidity. Mordenite possesses a twelve-membered ring main channel with a pore size of approximately 0.65 nm × 0.70 nm. This pore size highly matches the kinetic diameter of naphthalene molecules, enabling shape-selective confinement to regulate the formation of reaction products. Theoretically, this creates favorable conditions for the formation of 2,6-diisopropylnaphthalene, which has relatively low steric hindrance. Nevertheless, conventional mordenite catalysts in existing technologies still face significant challenges in practical applications, including substantial mass transfer confinement, rapid deactivation due to carbon deposition, and insufficient control over acidic sites.

[0005] In recent years, the construction of hierarchical zeolites has been regarded as an effective means to solve the problem of mass transfer limitation. Hierarchical zeolites, while retaining their own microporous structure, introduce a second-level pore system composed of mesopores (2 nm–50 nm) or macropores (>50 nm). The mesoporous system acts as a molecular highway, significantly shortening the diffusion path for molecules to enter and exit the active sites in the micropores, thereby improving catalytic efficiency and stability. In existing technologies, the construction of hierarchical pores typically employs post-treatment methods such as desilication, dealumination, or template methods. However, post-treatment methods often damage the zeolite's framework structure, resulting in acid loss and decreased crystallinity; while traditional template methods often use monocationic surfactants such as hexadecyltrimethylammonium bromide, which have limited guiding effect on the zeolite microporous structure and limited ability to regulate the final acidic sites during mesopore formation, making it difficult to achieve synergistic optimization of pore structure and acidic function.

[0006] Therefore, it is necessary to develop a catalyst that can construct an efficient microporous-mesoporous composite mass transfer network and finely control the distribution and intensity of acidic sites, thereby achieving high activity, high selectivity and high stability in the naphthalene alkylation reaction. Summary of the Invention

[0007] To address the above problems, this invention provides a hierarchical porous mordenite catalyst, its preparation method, and its application. This invention utilizes α,ω-bisquaternary ammonium salt surfactants as template agents to prepare a hierarchical porous catalyst that combines inherent micropores with uniform mesopores, which can improve mass transfer and optimize acidic sites.

[0008] The first objective of this invention is to provide a method for preparing a hierarchical porous mordenite zeolite catalyst, comprising the following steps: A silicon source, an aluminum source, an alkali source, and water undergo a hydrolysis-condensation reaction to form an aluminosilicate polymer. After the reaction is complete, an α,ω-bisquaternary ammonium salt surfactant is added as a template agent to induce a template-directed self-assembly reaction. During the reaction, the α,ω-bisquaternary ammonium salt surfactant self-assembles to form micelles, and the aluminosilicate polymer is adsorbed on the surface of the micelles to obtain a gel.

[0009] The gel is subjected to hydrothermal crystallization treatment. During the hydrothermal crystallization process, a condensation reaction continues to occur. The Si-O-Si bonds and Si-O-Al bonds in the aluminosilicate polymer self-assemble around the template agent to form micropores, thus obtaining zeolite raw powder.

[0010] The zeolite powder is first calcined to remove the template agent and form a hierarchical pore structure, thus obtaining the calcined zeolite.

[0011] The calcined zeolite was subjected to ion exchange to remove Na from the zeolite. + Exchange for NH4 +Then, a second calcination is carried out, during which acid sites are formed and impurities are removed to obtain a hierarchical porous mordenite catalyst.

[0012] The preparation mechanism of the present invention will be explained in detail below: In the zeolite synthesis process, a silicon source, an aluminum source, and an alkali source are first dissolved in water. The OH groups released from the alkali source... - The ions attack the covalent bonds in the silicon and aluminum sources, causing them to hydrolyze and hydroxylate, generating soluble silanol groups Si(OH)4 and aluminum hydroxy groups [Al(OH)4]. - Species. Subsequently, a condensation reaction occurs between these species, the specific condensation reaction formula of which is shown below:

[0013] Si–OH+HO–Si→Si–O–Si+H2O.

[0014] Si–OH+HO–Al→Si–O–Al+H2O.

[0015] Through condensation reactions, Si–O–Si and Si–O–Al bonds are formed, and the polymers gradually polymerize to form amorphous aluminosilicate polymers, causing the system to change from a clear solution to a turbid gel.

[0016] An α,ω-bisquaternary ammonium salt surfactant is added to the formed gel. The α,ω-bisquaternary ammonium salt surfactant, with its amphiphilic structure consisting of two hydrophilic quaternary ammonium cationic head groups and a hydrophobic long carbon chain, self-assembles into micelles in the aqueous phase via hydrophobic interactions. The negatively charged aluminosilicate polymer precursor is adsorbed onto the positively charged micelle surface through electrostatic interactions, forming a micelle-aluminosilicate composite unit.

[0017] Subsequently, hydrothermal crystallization treatment is carried out. Under high temperature and high pressure conditions, the hydroxyl groups in the aluminosilicate framework undergo further condensation reactions, making the arrangement of Si-O-Si bonds and Si-O-Al bonds tend to be highly ordered, and finally self-assembled around the template agent to form zeolite crystals with regular microporous channel structure, namely zeolite raw powder.

[0018] The zeolite powder is then subjected to a first calcination, primarily to remove the structure-directing agent α,ω-bisquaternary ammonium salt. In air, the template agent decomposes through oxidation into gaseous products such as CO2, H2O, and nitrogen oxides, releasing the space it previously occupied within the crystals. This creates mesoporous channels within the zeolite, forming a hierarchical porous structure. Simultaneously, this process also facilitates further solidification of the zeolite framework.

[0019] To further prepare the acidic catalyst, ion exchange is required. The calcined zeolite is contacted with an ammonium salt solution, allowing the Na+ in the framework to balance its charge. + Exchange for NH4 + .

[0020] Zeolite-Na + +H4 + →Zeolite–NH4 + +Na + .

[0021] After the exchange is completed, a second calcination is performed. Under heating conditions, NH4 + Decomposition produces H + .

[0022] Zeolite–NH4 + →Zeolite–H + +NH3↑.

[0023] H⁺ combines with the negatively charged centers of the framework to form Brønsted acid sites, which are the core active centers for acid-driven reactions such as alkylation. Furthermore, this step removes surface-adsorbed impurities, such as residual salts and moisture, and further enhances the thermal stability of the framework, ensuring the hierarchical pore structure remains stable under high-temperature reaction conditions. Ultimately, a mordenite zeolite catalyst with abundant Brønsted acid sites and a microporous-mesoporous hierarchical pore structure is obtained, suitable for the alkylation reaction of naphthalene and propylene.

[0024] The hierarchical mordenite zeolite catalyst prepared by this invention can simultaneously solve the two core problems of mass transfer and acidity, thereby achieving high selectivity, high yield and long lifetime of 2,6-diisopropylnaphthalene in the naphthalene alkylation reaction. It overcomes the problems of low catalytic activity and low product yield caused by severely limited microporous mass transfer in conventional mordenite zeolite catalysts in the naphthalene alkylation reaction, the problem of rapid carbon deposition and deactivation rate caused by limited mass transfer and inappropriate acidity, and the problem of poor selectivity of target product caused by non-shape-selective reactions and serious side reactions.

[0025] In a preferred embodiment of the present invention, the general formula of the α,ω-bisquaternary ammonium salt surfactant is [R1R2N]. + -(CH2) n -NR3R4]2X - .

[0026] In the formula, R1, R2, R3, and R4 are independently selected from C1-C4 alkyl groups such as methyl, ethyl, n-propyl, and isopropyl; n is the number of carbon atoms in the methylene chain connecting the two quaternary ammonium head groups, which is an integer from 6 to 12; X - To counteract the anions, halogen anions or hydroxide ions are preferred, such as C. - or Br - .

[0027] The preparation method of α,ω-bisquaternary ammonium salt surfactant is as follows: In alcohol solvents, dibromoalkane and nitrogen-containing compounds undergo nucleophilic substitution reactions to yield α,ω-bisquaternary ammonium salt surfactants containing quaternary ammonium cationic head groups and long carbon chain amphiphilic structures.

[0028] In a preferred embodiment of the present invention, the molar ratio of dibromoalkane to nitrogen-containing compound is 1:2.2 to 2.3.

[0029] The nucleophilic substitution reaction is carried out at a temperature of 80℃ to 85℃ and for a reaction time of 40h to 48h.

[0030] When the reaction conditions for nucleophilic substitution are below the parameter range, the nucleophilic substitution reaction is difficult to proceed fully and is prone to generating unilateral quaternary ammonium salts, which affects the formation efficiency of the target product. When the reaction conditions are above the parameter range, it will increase the difficulty of subsequent product separation and purification, which is not conducive to the smooth progress of the experimental procedure.

[0031] The dibromoalkane is 1,6-dibromohexane or 1,6-dibromooctane.

[0032] The nitrogen-containing compounds are triethylamine or N-methylpyrrolidone. Both triethylamine and N-methylpyrrolidone are substances containing nitrogen atoms, which have a lone pair of electrons, serving as the site for nucleophilic substitution reactions.

[0033] In a preferred embodiment of the present invention, the molar ratio of SiO2 to Al2O3 in the gel is 15–50:1; the molar ratio of α,ω-bisquaternary ammonium salt surfactant to SiO2 is 0.04–0.2:1; and the molar ratio of H2O to SiO2 is 20–50:1. In actual preparation, the silica-to-alumina ratio of mordenite has certain requirements; excessively high or low ratios of silica to alumina are detrimental to the synthesis of mordenite.

[0034] Insufficient use of α,ω-bisquaternary ammonium salt surfactant leads to insufficient structure-directing ability, making it difficult to form the target zeolite phase and slowing down the ordered polymerization rate of silica-alumina species. This also results in a decrease in the specific surface area and pore volume of the zeolite. Excessive use of α,ω-bisquaternary ammonium salt surfactant prevents uniform contact and directional assembly of silica-alumina species, leading to excessive local aggregation and the formation of numerous crystal agglomerates. This disrupts the uniform pore structure of the zeolite and leaves template agent residue, affecting product performance.

[0035] In a preferred embodiment of the present invention, the reaction temperature in the hydrothermal crystallization treatment is 150℃~200℃, and the reaction time is 48h~120h. During hydrothermal crystallization, if the synthesis temperature is too low, the crystallization rate is slow, and the synthesis cycle is prolonged, resulting in insufficient crystallinity of the product. If the synthesis temperature is too high, the target zeolite phase is easily decomposed, leading to the formation of more impurities and amorphous phases. If the synthesis time is too short, crystallization is incomplete, and the product is mainly composed of amorphous phases or low crystallinity. If the time is too long, excessive crystal growth occurs, resulting in uncontrolled morphology and size. The zeolite phase dissolves and recrystallizes, generating impurities.

[0036] In a preferred embodiment of the present invention, the conditions for the first calcination are: a calcination temperature of 550℃~600℃ and a calcination time of 5h~6h. During the first calcination, if the calcination temperature is too low, the template agent and impurities are not completely removed, the pores are blocked, the active sites are not fully exposed, and the function cannot be activated. If the temperature is too high, the zeolite framework collapses, the pore structure is damaged, the framework undergoes severe dealuminization, the active sites are lost, the crystal morphology is damaged, and the zeolite strength decreases.

[0037] In a preferred embodiment of the present invention, the ion exchange reaction time is 4 to 6 hours, and the number of ion exchanges is 2 to 3 times. If the exchange time is too short, the ion exchange efficiency is low, and the target ion loading is insufficient. If the exchange time is too long, the zeolite structure is dissolved, and the integrity of the framework is destroyed. Impurity ions are introduced, and the purity of the product decreases.

[0038] In a preferred embodiment of the present invention, the conditions for the second calcination are: calcination temperature of 550℃~600℃ and calcination time of 3h~4h.

[0039] During the second calcination, if the calcination temperature is too low, ammonium ions cannot be completely decomposed, resulting in insufficient acidity and low catalyst activity. If the calcination temperature is too high, the framework structure begins to partially collapse or the lattice undergoes dealuminization, leading to an increase in the silicon-to-aluminum ratio, a decrease in strong acid sites, and a drop in total acidity; the specific surface area and pore volume decrease, diffusion is restricted, and catalytic activity declines.

[0040] A second objective of this invention is to provide a hierarchical porous mordenite zeolite catalyst prepared by the above-described method. The total specific surface area of ​​the hierarchical porous mordenite zeolite catalyst is 350 m². 2 / g~450m 2 The total pore volume is 0.25 cm³ / g. 3 / g~0.35cm 3 / g, of which the mesoporous pore volume reaches 0.10cm³. 3 / g~0.20cm 3 / g, the molar ratio of Brønsted acid sites to Lewis acid sites is 5-10.

[0041] The hierarchical porous mordenite zeolite catalyst is a hydrogen-form hierarchical porous mordenite zeolite catalyst, which has the following unique physicochemical characteristics: a) Unique pore structure: Nitrogen adsorption-desorption isotherm analysis reveals typical type I and type IV composite characteristics, accompanied by an H4 type hysteresis loop, indicating that it possesses both microporous and mesoporous structures. Its total specific surface area ranges from 350 m² / g. 2 / g~450m 2 / g, of which the external specific surface area contributed by mesopores accounts for 30% to 50% of the total specific surface area, significantly higher than that of conventional mordenite. Its total pore volume is 0.25 cm³. 3 / g~0.35cm 3 / g, of which the mesoporous pore volume reaches 0.10cm³. 3 / g~0.20cm 3 / g provides an efficient transport channel for reactants and products.

[0042] b) Optimized acidity distribution: Pyridine adsorption infrared spectroscopy analysis showed that, under desorption conditions at 150℃, the acidity distribution was approximately 1545 cm⁻¹. -1 The characteristic peaks at approximately 1455 cm⁻¹ belong to pyridine ions adsorbed on Brønsted acid sites. -1 The integral area molar ratio of the characteristic peaks attributable to coordinated pyridine adsorbed on Lewis acid sites was controlled in a relatively high range of 5–10. Temperature-programmed desorption analysis using ammonia showed that the peak temperature of its high-temperature desorption peak was lower than that of conventional mordenite, indicating that the strength of the strong acid centers was appropriately controlled.

[0043] The third objective of this invention is to provide the application of the above-mentioned hierarchical porous mordenite catalyst in the preparation of 2,6-diisopropylnaphthalene, characterized in that naphthalene and propylene are used as raw materials, added to a fixed-bed reactor packed with hierarchical porous mordenite catalyst, and an alkylation reaction is carried out to prepare 2,6-diisopropylnaphthalene.

[0044] The alkylation reaction was carried out at temperatures ranging from 200°C to 325°C and pressures from 1.0 MPa to 5.0 MPa. The molar ratio of naphthalene to propylene was 1:2 to 6, and the mass ratio of naphthalene to hierarchical mordenite catalyst was 0.43 to 2.16:1. The mass hourly space velocity (HHSV) was 1 h⁻¹. −1 ~5h −1 .

[0045] Currently, the yield of 2,6-diisopropylnaphthalene is below 40%, the single-pass life is <100h, and the molar ratio of 2,6-diisopropylnaphthalene to 2,7-diisopropylnaphthalene is usually less than 3. However, the catalyst prepared in this invention exhibits a selectivity of 2,6-diisopropylnaphthalene higher than 47% in alkylation reactions, and the naphthalene conversion rate decreases by less than 10% after 200 hours of continuous operation. The molar ratio of 2,6-diisopropylnaphthalene to 2,7-diisopropylnaphthalene reaches 5–7.

[0046] 2,6-Diisopropylnaphthalene is denoted as 2,6-DIPN, 2,7-Diisopropylnaphthalene is denoted as 2,7-DIPN, and the molar ratio of 2,6-diisopropylnaphthalene to 2,7-diisopropylnaphthalene is abbreviated as 2,6- / 2,7-DIPN.

[0047] Compared with the prior art, the present invention has the following beneficial effects: This invention introduces an α,ω-biquaternary ammonium salt bifunctional template agent, which forms hierarchical pores through hydrothermal crystallization and a first calcination, and then forms acid sites through a second calcination, thus preparing a mordenite catalyst with hierarchical pore structure and optimized acidity.

[0048] The hierarchical porous silica zeolite catalyst prepared by this invention has the following advantages: (1) Significantly improved catalytic selectivity: The catalyst of this invention has a unique microporous-mesoporous hierarchical pore structure. The microporous-mesoporous molecular sieve overcomes the limitations of single microporous / mesoporous materials through the synergistic effect of precise micropore screening and provision of high active sites and mesoporous-assisted mass transfer and improved site accessibility. It not only alleviates the carbon deposition and deactivation problems caused by pore blockage in traditional microporous molecular sieves, but also achieves highly efficient catalysis of macromolecular preconversion and small molecule shape selection by virtue of the multi-level pores, thereby significantly improving the shape selection efficiency and catalyst lifetime. Large naphthalene molecules and diisopropylnaphthalene product molecules can quickly approach or leave the active sites in the micropores through mesoporous channels, significantly shortening the residence time of molecules in the channels, thereby effectively inhibiting side reactions such as excessive alkylation and isomerization of the products.

[0049] (2) Significantly extended catalytic life: The efficient mass transfer channels effectively prevent the accumulation and deep transformation of reactants within the channels, inhibiting the formation of carbon precursors at the source. Therefore, the catalyst of this invention exhibits excellent anti-carbon deposition ability and catalytic stability. In a continuous fixed-bed reactor, its single-pass life can exceed 200 hours, with a maximum of 280 hours, which is 3 to 5 times that of conventional mordenite catalysts. This significantly reduces the catalyst regeneration frequency and operating costs, making it more promising for industrial applications.

[0050] (3) Improved catalytic activity and yield: Due to the breakthrough of the mass transfer bottleneck, more catalytic active sites can be effectively utilized, resulting in a significant improvement in the apparent activity of the catalyst. Under optimized reaction conditions, the conversion rate of naphthalene can be stabilized at over 90%, and combined with the significantly improved selectivity, the single-pass yield of the target product 2,7-diisopropylnaphthalene exceeds 65%, which is far higher than the level reported in the prior art. Attached Figure Description

[0051] Figure 1 The X-ray diffraction patterns are those of the catalysts in Examples 1 to 4 and Comparative Examples 1 to 2 of this invention.

[0052] Figure 2 The nitrogen adsorption-desorption isotherm of C6-NEt-MOR prepared in Example 1 of the present invention is shown in the inset as a pore size distribution diagram.

[0053] Figure 3 The nitrogen adsorption-desorption isotherm of C8-NEt-MOR prepared in Example 2 of the present invention is shown in the inset as a pore size distribution diagram.

[0054] Figure 4 The nitrogen adsorption-desorption isotherm of C6-NMP-MOR prepared in Example 3 of the present invention is shown in the inset as a pore size distribution diagram.

[0055] Figure 5 The nitrogen adsorption-desorption isotherm of C8-NMP-MOR prepared in Example 4 of this invention is shown in the inset as a pore size distribution diagram.

[0056] Figure 6 The inset shows the nitrogen adsorption-desorption isotherm of CTAB-MOR prepared in Comparative Example 1 of this invention, wherein the inset is a pore size distribution diagram.

[0057] Figure 7 The figure shows the nitrogen adsorption-desorption isotherm of TEABr-MOR in Comparative Example 2 of this invention, wherein the inset is a pore size distribution diagram.

[0058] Figure 8 Scanning electron microscope images of the catalysts in Examples 1 to 4 and Comparative Examples 1 to 2 of this invention.

[0059] Figure 9 This is the ammonia desorption curve of the catalyst in Example 1 of the present invention.

[0060] Figure 10 This is the ammonia desorption curve of the catalyst in Example 2 of the present invention.

[0061] Figure 11 This is the ammonia desorption curve of the catalyst in Example 3 of the present invention.

[0062] Figure 12 This is the ammonia desorption curve of the catalyst in Example 4 of the present invention.

[0063] Figure 13 This is the ammonia desorption curve of the catalyst in Comparative Example 1 of this invention.

[0064] Figure 14 This is the ammonia desorption curve of the catalyst in Comparative Example 2 of this invention. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] Conventional mordenite catalysts still suffer from problems such as mass transfer limitation, rapid deactivation due to carbon deposition, and insufficient control over acidic sites. Specifically, mordenite is a typical one-dimensional microporous material. For large aromatic molecules like naphthalene with a kinetic diameter of approximately 0.69 nm, the diffusion rate within the narrow micropores is extremely low. On the one hand, reactants struggle to reach the active sites; on the other hand, the generated diisopropylnaphthalene product molecules, due to their even larger size (kinetic diameter > 0.8 nm), are even more difficult to desorb rapidly from the pores. This severe mass transfer limitation not only significantly reduces the apparent activity and utilization efficiency of the catalyst but also leads to excessively long residence times of product molecules within the pores, triggering side reactions such as deep alkylation and isomerization, ultimately resulting in a decrease in the selectivity of 2,6-diisopropylnaphthalene. Due to the mass transfer limitation, reaction intermediates and products are prone to condensation and dehydrogenation reactions at the catalyst pore openings and within the pores, forming large polycyclic aromatic hydrocarbons. These carbon deposits clog the pores and cover the acidic active sites, causing a rapid decline in catalyst activity within a short period. Existing research indicates that the single-pass lifetime of conventional mordenite catalysts is typically less than 100 hours, and frequent regeneration operations significantly increase the complexity and cost of industrial operation. Furthermore, the outer surface and pores of conventional mordenite contain numerous non-shape-selective strong acid centers, which readily catalyze non-shape-selective reactions, generating a large number of non-target isomers. Simultaneously, the excessively strong acidity within the pores exacerbates carbon deposition and side reactions. Therefore, the molar ratio of 2,6-DIPN to 2,7-DIPN in the product is typically less than 3, far from the ideal level for industrial applications.

[0067] While existing technologies have addressed the mass transfer limitation by constructing hierarchical porous zeolites, there remains a challenge in achieving synergistic optimization of pore structure and acidic function. Based on this, this invention studies a hierarchical porous mordenite catalyst that can construct an efficient microporous-mesoporous composite mass transfer network and finely control the distribution and intensity of acidic sites.

[0068] The synthesis scheme of the bisquaternary ammonium salt template agent used in the examples is as follows: C6H 12 The preparation method of (NEt3)2Br2 is as follows: 24.3 g of 0.1 mol of 1,6-dibromohexane and 22.2 g of 0.22 mol of triethylamine are dissolved in 200 mL of anhydrous ethanol, and the mixture is heated under reflux at 80 °C for 48 h. After cooling, the solvent is evaporated to obtain a white solid. The white solid is washed with diethyl ether and dried to obtain the product N,N,N,N′,N′,N′−hexaethylhexane−1,6−diammonium dibromide, abbreviated as C6-NEt3 template agent, with a yield of approximately 90%.

[0069] C8H 16 The preparation method of (NEt3)2Br2 is as follows: 27.2 g of 0.1 mol of 1,6-dibromooctane and 22.2 g of 0.22 mol of triethylamine are dissolved in 200 mL of anhydrous ethanol, and the mixture is heated under reflux at 80 °C for 48 h. After cooling, the solvent is evaporated to obtain a white solid. The white solid is washed with diethyl ether and dried to obtain the product N,N,N,N′,N′,N′−hexaethyloctane−1,6−diammonium dibromide, abbreviated as C8-NEt3 template agent, with a yield of approximately 92%.

[0070] C6H 12 The preparation method of (NMP)₂Br₂ is as follows: 24.3 g (0.1 mol) of 1,6-dibromohexane and 18.73 g (0.22 mol) of 1-methylpyrrolidine are dissolved in 200 mL of anhydrous ethanol, and the mixture is heated under reflux at 80 °C for 48 h. After cooling, the solvent is evaporated to obtain a white solid. The white solid is washed with diethyl ether and dried to obtain the product, abbreviated as C6-NMP template agent, with a yield of approximately 94%.

[0071] C8H 16 The preparation method of (NMP)₂Br₂ is as follows: 27.2 g of 0.1 mol of 1,6-dibromooctane and 18.73 g of 0.22 mol of 1-methylpyrrolidine are dissolved in 200 mL of anhydrous ethanol, and the mixture is heated under reflux at 80 °C for 48 h. After cooling, the solvent is evaporated to obtain a white solid. The white solid is washed with diethyl ether and dried to obtain the product, abbreviated as C8-NMP template agent, with a yield of approximately 90%.

[0072] The silica sol used in this invention contains 30 wt% SiO2. 2,6-Diisopropylnaphthalene is abbreviated as 2,6-DIPN.

[0073] Example 1 Graded porous mordenite was prepared using C6-NEt3 template agent.

[0074] (1) Gel preparation: Weigh 2.14g of sodium aluminate and 80g of deionized water, and add sodium hydroxide to adjust the synthesis solution to an alkaline solution with a pH of 10. Mix and stir until the solution is clear. Under rapid stirring at room temperature, slowly add 50g of silica sol to the above solution and continue stirring for ten minutes. Then add 4.47g of C6-NEt3 template agent and continue stirring for 4 hours to form a uniform white gel. The final molar ratio of the gel is: 1SiO2:0.05Al2O3:0.05Na2O:0.04C6-NEt3 template agent:25.5H2O.

[0075] (2) Hydrothermal crystallization: The gel was transferred to a 200 mL hydrothermal reactor with a polytetrafluoroethylene liner and subjected to static hydrothermal reaction at 170 °C for 120 hours.

[0076] (3) Post-processing: The crystal product is cooled, filtered, washed with deionized water until neutral, and then dried at 110℃ to obtain zeolite powder.

[0077] (4) Template agent removal and ion exchange: 4.1. The raw zeolite powder is calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours to remove the template agent, thereby obtaining raw zeolite powder with the template agent removed.

[0078] 4.2. 10g of template-removed zeolite powder was added to a single-necked flask containing 200mL of 1mol / L NH4Cl solution and stirred at 85℃ for 6h to perform ion exchange. This step was repeated a total of 3 times to obtain the exchanged sample. After drying, the exchanged sample was calcined again in a muffle furnace under air atmosphere at 550℃ for 4h to obtain the final graded porous mordenite, denoted as C6-NEt3-MOR.

[0079] Example 2 Graded porous mordenite was prepared using C8-NEt3 template agent.

[0080] (1) Gel preparation: Weigh 2.14g of sodium aluminate and 80g of deionized water, and add sodium hydroxide to adjust the synthesis solution to an alkaline solution with a pH of 10. Mix and stir until the solution is clear. Under rapid stirring at room temperature, slowly add 50g of silica sol to the above solution and continue stirring for ten minutes. Then add 4.75g of C8-NEt3 template agent and continue stirring for 4 hours to form a uniform white gel. The final molar ratio of the gel is: 1SiO2:0.05Al2O3:0.05Na2O:0.04C8-NEt3 template agent:25.5H2O.

[0081] (2) Hydrothermal crystallization: The gel was transferred to a 200 mL hydrothermal reactor with a polytetrafluoroethylene liner and subjected to static hydrothermal reaction at 170 °C for 120 hours.

[0082] (3) Post-processing: The crystal product is cooled, filtered, washed with deionized water until neutral, and then dried at 110℃ to obtain zeolite powder.

[0083] (4) Template agent removal and ion exchange: 4.1. The raw zeolite powder is calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours to remove the template agent, thereby obtaining raw zeolite powder with the template agent removed.

[0084] 4.2. 10g of template-removed zeolite powder was added to a single-necked flask containing 200mL of 1mol / L NH4Cl solution and stirred at 85℃ for 6h to perform ion exchange. This step was repeated a total of 3 times to obtain the exchanged sample. After drying, the exchanged sample was calcined again in a muffle furnace under air atmosphere at 550℃ for 4h to obtain the final graded porous mordenite, denoted as C8-NEt3-MOR.

[0085] Example 3 Graded porous mordenite was prepared using C6-NMP template agent.

[0086] (1) Gel preparation: Weigh 2.14g of sodium aluminate and 80g of deionized water, and add sodium hydroxide to adjust the synthesis solution to an alkaline solution with a pH of 10. Mix and stir until the solution is clear. Under rapid stirring at room temperature, slowly add 50g of silica sol to the above solution and continue stirring for ten minutes. Then add 4.4g of C6-NMP template agent and continue stirring for 4 hours to form a uniform white gel. The final molar ratio of the gel is: 1SiO2:0.05Al2O3:0.05Na2O:0.04C6-NMP template agent:25.5H2O.

[0087] (2) Hydrothermal crystallization: The gel was transferred to a 200 mL hydrothermal reactor with a polytetrafluoroethylene liner and subjected to static hydrothermal reaction at 170 °C for 120 hours.

[0088] (3) Post-processing: The crystal product is cooled, filtered, washed with deionized water until neutral, and then dried at 110℃ to obtain zeolite powder.

[0089] (4) Template agent removal and ion exchange: 4.1. The raw zeolite powder is calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours to remove the template agent, thereby obtaining raw zeolite powder with the template agent removed.

[0090] 4.2. 10g of template-removed zeolite powder was added to a single-necked flask containing 200mL of 1mol / L NH4Cl solution and stirred at 85℃ for 6h to perform ion exchange. This step was repeated a total of 3 times to obtain the exchanged sample. After drying, the exchanged sample was calcined again in a muffle furnace under air atmosphere at 550℃ for 4h to obtain the final graded porous mordenite zeolite, denoted as C6-NMP-MOR.

[0091] Example 4 Graded porous mordenite was prepared using C8-NMP template agent.

[0092] (1) Gel preparation: Weigh 2.14g of sodium aluminate and 80g of deionized water, and add sodium hydroxide to adjust the synthesis solution to an alkaline solution with a pH of 10. Mix and stir until the solution is clear. Under rapid stirring at room temperature, slowly add 50g of silica sol to the above solution and continue stirring for ten minutes. Then add 4.7g of C8-NMP template agent and continue stirring for 4 hours to form a uniform white gel. The final molar ratio of the gel is: 1SiO2:0.025Al2O3:0.05NaOH:0.04C8-NMP template agent:23H2O.

[0093] (2) Hydrothermal crystallization: The gel was transferred to a 200 mL hydrothermal reactor with a polytetrafluoroethylene liner and subjected to static hydrothermal reaction at 170 °C for 120 hours.

[0094] (3) Post-processing: The crystal product is cooled, filtered, washed with deionized water until neutral, and then dried at 110℃ to obtain zeolite powder.

[0095] (4) Template agent removal and ion exchange: 4.1. The raw zeolite powder is calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours to remove the template agent, thereby obtaining raw zeolite powder with the template agent removed.

[0096] 4.2. 10g of template-removed zeolite powder was added to a single-necked flask containing 200mL of 1mol / L NH4Cl solution and stirred at 85℃ for 6h to perform ion exchange. This step was repeated a total of 3 times to obtain the exchanged sample. After drying, the exchanged sample was calcined again in a muffle furnace under air atmosphere at 550℃ for 4h to obtain the final graded porous mordenite zeolite, denoted as C8-NMP-MOR.

[0097] Example 5 Graded porous mordenite was prepared using C6-NEt3 template agent.

[0098] (1) Gel preparation: Weigh 0.82g of sodium aluminate and 55g of deionized water, and add sodium hydroxide to adjust the synthesis solution to an alkaline solution with a pH of 10. Mix and stir until the solution is clear. Under rapid stirring at room temperature, slowly add 50g of silica sol to the above solution and continue stirring for ten minutes. Then add 4.47g of C6-NEt3 template agent and continue stirring for 4 hours to form a uniform white gel. The final molar ratio of the gel is: 1SiO2:0.02Al2O3:0.014Na2O:0.2C6-NEt3 template agent:20H2O.

[0099] (2) Hydrothermal crystallization: The gel was transferred to a 200 mL hydrothermal reactor with a polytetrafluoroethylene liner and subjected to static hydrothermal reaction at 150 °C for 100 hours.

[0100] (3) Post-processing: The crystal product is cooled, filtered, washed with deionized water until neutral, and then dried at 110℃ to obtain zeolite powder.

[0101] (4) Template agent removal and ion exchange: 4.1. The raw zeolite powder is calcined in an air atmosphere in a muffle furnace at 600°C for 5 hours to remove the template agent, thereby obtaining raw zeolite powder with the template agent removed.

[0102] 4.2. 10g of template-removed zeolite powder was added to a single-necked flask containing 200mL of 1mol / L NH4Cl solution and stirred at 85℃ for 4h to perform ion exchange. This step was repeated twice to obtain the exchanged sample. After drying, the exchanged sample was calcined again in a muffle furnace under air atmosphere at 600℃ for 3h to obtain the final graded porous mordenite zeolite.

[0103] Example 6 Graded porous mordenite was prepared using C6-NEt3 template agent.

[0104] (1) Gel preparation: Weigh 2.46g of sodium aluminate and 190g of deionized water, and add sodium hydroxide to adjust the synthesis solution to an alkaline solution with a pH of 12. Mix and stir until the solution is clear. Under rapid stirring at room temperature, slowly add 50g of silica sol to the above solution and continue stirring for ten minutes. Then add 4.47g of C6-NEt3 template agent and continue stirring for 4 hours to form a uniform white gel. The final molar ratio of the gel is: 1SiO2:0.06Al2O3:0.05NaOH:0.00.1C6-NEt3 template agent:50H2O.

[0105] (2) Hydrothermal crystallization: The gel was transferred in batches to a 200 mL hydrothermal reactor with a polytetrafluoroethylene liner and subjected to static hydrothermal reaction at 200 °C for 48 hours.

[0106] (3) Post-processing: The crystal product is cooled, filtered, washed with deionized water until neutral, and then dried at 110℃ to obtain zeolite powder.

[0107] (4) Template agent removal and ion exchange: 4.1. The raw zeolite powder is calcined in an air atmosphere in a muffle furnace at 580°C for 5.5 hours to remove the template agent, thereby obtaining raw zeolite powder with the template agent removed.

[0108] 4.2. 10g of template-removed zeolite powder was added to a single-necked flask containing 200mL of 1mol / L NH4Cl solution and stirred at 85℃ for 5h to perform ion exchange. This step was repeated twice to obtain the exchanged sample. After drying, the exchanged sample was calcined again in a muffle furnace under air atmosphere at 580℃ for 3.5h to obtain the final graded porous mordenite zeolite.

[0109] Comparative Example 1 Graded porous mordenite was prepared using CTAB template agent.

[0110] (1) Gel preparation: Weigh 2.14g of sodium aluminate and 80g of deionized water, and add sodium hydroxide to adjust the synthesis solution to an alkaline solution with a pH of 10. Mix and stir until the solution is clear. Under rapid stirring at room temperature, slowly add 50g of silica sol to the above solution and continue stirring for ten minutes. Then add 4g of CTAB template agent and continue stirring for 4 hours to form a uniform white gel. The final molar ratio of the gel is: 1SiO2:0.05Al2O3:0.05Na2O:0.04CTAB template agent:25.5H2O.

[0111] (2) Hydrothermal crystallization: The gel was transferred to a 200 mL hydrothermal reactor with a polytetrafluoroethylene liner and subjected to static hydrothermal reaction at 170 °C for 120 hours.

[0112] (3) Post-processing: The crystal product is cooled, filtered, washed with deionized water until neutral, and then dried at 110℃ to obtain zeolite powder.

[0113] (4) Template agent removal and ion exchange: 4.1. The raw zeolite powder is calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours to remove the template agent, thereby obtaining raw zeolite powder with the template agent removed.

[0114] 4.2. 10g of template-removed zeolite powder was added to a single-necked flask containing 200mL of 1mol / L NH4Cl solution and stirred at 85℃ for 6h to perform ion exchange. This step was repeated a total of 3 times to obtain the exchanged sample. After drying, the exchanged sample was calcined again in a muffle furnace under air atmosphere at 550℃ for 4h to obtain the final graded porous mordenite, denoted as CTAB-MOR.

[0115] Comparative Example 2 Graded porous mordenite was prepared using TEABr template agent.

[0116] (1) Gel preparation: Weigh 2.14g of sodium aluminate and 80g of deionized water, and add sodium hydroxide to adjust the synthesis solution to an alkaline solution with a pH of 10. Mix and stir until the solution is clear. Under rapid stirring at room temperature, slowly add 50g of silica sol to the above solution and continue stirring for ten minutes. Then add 3.2g of TEABr3 template agent and continue stirring for 4 hours to form a uniform white gel. The final molar ratio of the gel is: 1SiO2:0.05Al2O3:0.05Na2O:0.04TEABr template agent:25.5H2O.

[0117] (2) Hydrothermal crystallization: The gel was transferred to a 200 mL hydrothermal reactor with a polytetrafluoroethylene liner and subjected to static hydrothermal reaction at 170 °C for 120 hours.

[0118] (3) Post-processing: The crystal product is cooled, filtered, washed with deionized water until neutral, and then dried at 110℃ to obtain zeolite powder.

[0119] (4) Template agent removal and ion exchange: 4.1. The raw zeolite powder is calcined in an air atmosphere in a muffle furnace at 550°C for 6 hours to remove the template agent, thereby obtaining raw zeolite powder with the template agent removed.

[0120] 4.2. 10g of template-removed zeolite powder was added to a single-necked flask containing 200mL of 1mol / L NH4Cl solution and stirred at 85℃ for 6h to perform ion exchange. This step was repeated a total of 3 times to obtain the exchanged sample. After drying, the exchanged sample was calcined again in a muffle furnace under air atmosphere at 550℃ for 4h to obtain the final graded porous mordenite, denoted as TEABr-MOR.

[0121] The alkylation reaction of naphthalene and propylene will be evaluated below.

[0122] Naphthalene and propylene were added to a fixed-bed reactor containing 2.5g of the catalysts prepared in Examples 1 to 4 and Comparative Examples 1 to 2, respectively, and an alkylation reaction was carried out to obtain 2,6-diisopropylnaphthalene.

[0123] The alkylation reaction was carried out at a temperature of 250°C, a pressure of 1.5 MPa, and a mass hourly space velocity (H₂S) of 2 h⁻¹. −1 .

[0124] Characterization and performance results: The physicochemical properties and performance data of the catalyst are summarized in Tables 1 and 2.

[0125] Results Analysis and Discussion 1. Characterization and analysis of catalyst structure like Figure 1 As shown, the C6-NEt3-MOR, C8-NEt3-MOR, C6-NMP-MOR, and C8-NMP-MOR prepared in Examples 1 to 4, as well as Comparative Examples 1 to 2, have the same characteristic diffraction peaks of mordenite as commercially available H-MOR, and the peaks are sharp, indicating that the synthesized samples all have good crystallinity, and the introduction of the template agent did not destroy the basic framework structure of the zeolite.

[0126] Figures 2-7As shown in Table 1, the nitrogen adsorption-desorption isotherms of the catalysts in Examples 1 to 4 exhibit a composite isotherm of type I and type IV, and a significant H4-type hysteresis loop appears within the relative pressure P / P0 range of 0.4 to 0.9, which strongly demonstrates the successful introduction of the mesoporous structure. The pore structure data in Table 1 show that the catalysts synthesized using the template method all have higher external specific surface area and considerable mesoporous pore volume. The catalysts prepared using α,ω-bisquaternary ammonium salt templates in Examples 1 to 4 have significantly higher external specific surface area ratios and mesoporous pore volumes than Comparative Example 1, which uses a single quaternary ammonium salt CTAB. This indicates that bisquaternary ammonium salt templates have unique advantages in constructing intergranular or intragranular mesopores. The mechanism of action may lie in the fact that the two hydrophilic cationic head groups of the bisquaternary ammonium salt molecule can interact with different zeolite nanocrystals or nuclei, while the intermediate hydrophobic alkyl chain acts as a bridge and support, naturally forming regular mesopores during grain aggregation. As the alkyl chain length n increases from 6 to 8, both the mesopore volume and the proportion of external specific surface area increase, indicating that longer alkyl chains are conducive to the formation of larger mesopores.

[0127] Table 1 Physicochemical properties of catalysts In Table 1, the total specific surface area is denoted as S. BET The specific surface area of ​​micropores is denoted as S. micro The outer surface area is denoted as S. externa The volume of the micropores is denoted as V. micro The volume of mesopores is denoted as V. meso .

[0128] Figure 8 Electron microscopy images visually confirmed the existence of the hierarchical pore structure. The C8-NEt-MOR in Example 2 was composed of stacked nanocrystals with a size of approximately 50 nm to 100 nm. A distinct sponge-like mesoporous network was formed between the nanocrystals, which is highly consistent with the results of nitrogen adsorption.

[0129] 2. Characterization and analysis of catalyst acidity The acidity of the catalyst is a key factor determining its selectivity in alkylation reactions. Figures 9-14 Table 2 shows the acidity properties of each catalyst.

[0130] from Figures 9-14 As can be seen from the NH3-TPD results in Table 2, all catalysts exhibit two main ammonia desorption peaks at approximately 220 °C and approximately 430 °C. It should be noted that 220 °C is a low-temperature peak, corresponding to weak acid and moderately strong acid sites, while approximately 430 °C is a high-temperature peak, corresponding to strong acid sites.

[0131] Compared to mordenite zeolites synthesized using traditional CTAB and TEAB as template agents, the catalysts prepared in this invention exhibit a reduced total acid content, but more importantly, the strength of their strong acid centers has changed. The high-temperature peak of CTAB-MOR reaches a high of 455°C, while the high-temperature peaks of the catalysts in Examples 1 to 4 have all shifted towards lower temperatures, to 420°C–430°C, indicating that the strength of their strongest acid centers has been appropriately controlled. Excessively strong acid sites are a major cause of side reactions such as deep alkylation and coking; therefore, appropriately reducing the strength of strong acids is beneficial for improving the selectivity of the target product and the stability of the catalyst.

[0132] Table 2. Properties of acidic sites of catalysts In Table 2, Brønsted acid is denoted as B acid, Lewis acid as L acid, and the molar ratio of Brønsted acid to Lewis acid is denoted as B / L molar ratio.

[0133] 3. Catalytic performance evaluation Table 3 shows the evaluation results of the catalytic performance, which ultimately verifies the superiority of the technical solution of this invention.

[0134] Table 3 Catalyst Performance Evaluation Table As can be seen from the data in Table 3, the TEABr-MOR catalyst of Comparative Example 2 exhibits the worst performance, with low selectivity, yield, and lifetime. This corresponds perfectly to the severe mass transfer limitations and unsuitable acidity distribution caused by its purely microporous structure. Although the CTAB-MOR catalyst of Comparative Example 2 introduces some mesopores, resulting in some performance improvement, it still lags significantly behind the examples of this invention. This highlights the uniqueness and superiority of the α,ω-bisquaternary ammonium salt template agent used in this invention.

[0135] Examples 1 through 4 of this invention all exhibit excellent catalytic performance. Among them, the C8-NMP-MOR catalyst of Example 4 shows the most outstanding performance, with a 2,6-DIPN selectivity as high as 47.1%, a 2,6- / 2,7-DIPN molar ratio of 4.51, and a catalyst lifetime as long as 237 hours. This result fully demonstrates that the hierarchical porous mordenite zeolite prepared by the method of this invention, with its optimal mesoporous network constructed by the C8-template agent and the synergistic effect of moderate strong acid strength and high B / L ratio, perfectly solves the bottleneck problems of the prior art.

[0136] Similar to Examples 1-4, the catalysts prepared in Examples 5 and 6 also possess abundant Brønsted acid sites and a microporous-mesoporous hierarchical pore structure, making them suitable for the alkylation reaction of naphthalene and propylene. The catalyst lifetimes of Examples 5 and 6 of this invention reached 220 h and 223 h, respectively.

[0137] In summary, this invention successfully prepared a mordenite catalyst with a hierarchical pore structure and optimized acidity by introducing a novel α,ω-bisquaternary ammonium salt bifunctional template agent. This catalyst fundamentally solves the two major problems of mass transfer and deactivation in the catalytic alkylation of macromolecular aromatic hydrocarbons using traditional mordenite, exhibiting unprecedented high selectivity, high yield, and high stability in the synthesis of 2,6-DIPN, demonstrating significant technological advancement and broad industrial application prospects.

[0138] This invention controls the optimized B / L ratio and moderately weakened strong acid centers by adjusting the Si / Al ratio of the gel (15-50), the pH of the synthesis solution (10-12), the type and amount of template agent, crystallization conditions, and post-treatment methods, thereby further suppressing non-shape-selective reactions. Under these combined effects, the selectivity of 2,6-diisopropylnaphthalene can be stably increased to over 75%, reaching a maximum of 82%. The molar ratio of 2,6-diisopropylnaphthalene to 2,7-diisopropylnaphthalene in the product can be improved from <3 in existing technologies to 5-7, greatly simplifying the subsequent separation and purification process.

[0139] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0140] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a hierarchical porous mordenite zeolite catalyst, characterized in that, Includes the following steps: Silicon source, aluminum source and water undergo hydrolysis-condensation reaction at pH 10-12 to form aluminosilicate polymer. After the reaction is complete, α,ω-bisquaternary ammonium salt surfactant is added as a template agent to carry out template-directed self-assembly reaction. During the reaction, α,ω-bisquaternary ammonium salt surfactant self-assembles to form micelles, and aluminosilicate polymer is adsorbed on the surface of the micelles to obtain a gel. The gel was subjected to hydrothermal crystallization. During the hydrothermal crystallization process, a condensation reaction continued to occur. The Si–O–Si bonds and Si–O–Al bonds in the aluminosilicate polymer self-assembled around the template agent to form micropores, thus obtaining zeolite raw powder. The zeolite powder is first calcined to remove the template agent and form a hierarchical pore structure, thus obtaining the calcined zeolite. The calcined zeolite is subjected to ion exchange to replace Na⁺ with NH⁺, followed by a second calcination. During the calcination process, acid sites are formed and impurities are removed, resulting in a hierarchical porous mordenite catalyst.

2. The method for preparing the hierarchical porous mordenite zeolite catalyst according to claim 1, characterized in that, The preparation method of α,ω-bisquaternary ammonium salt surfactant is as follows: In alcohol solvents, dibromoalkane and nitrogen-containing compounds undergo nucleophilic substitution reactions to yield α,ω-bisquaternary ammonium salt surfactants containing quaternary ammonium cationic head groups and long carbon chain amphiphilic structures.

3. The method for preparing the hierarchical porous mordenite zeolite catalyst according to claim 2, characterized in that, The molar ratio of dibromoalkane to nitrogen-containing compound is 1:2.2–2.3; The nucleophilic substitution reaction is carried out at a temperature of 80℃~85℃ for a reaction time of 40h~48h. The dibromoalkane is 1,6-dibromohexane or 1,6-dibromooctane.

4. The method for preparing the hierarchical porous mordenite zeolite catalyst according to claim 1, characterized in that, In the gel, the molar ratio of SiO2 to Al2O3 is 15–50:1; the molar ratio of α,ω-bisquaternary ammonium salt surfactant to SiO2 is 0.04–0.2:1; and the molar ratio of H2O to SiO2 is 20–50:

1.

5. The method for preparing the hierarchical porous mordenite zeolite catalyst according to claim 1, characterized in that, In the hydrothermal crystallization process, the reaction temperature is 150℃~200℃ and the reaction time is 48h~120h.

6. The method for preparing the hierarchical porous mordenite zeolite catalyst according to claim 1, characterized in that, The conditions for the first roasting are: roasting temperature of 550℃~600℃ and roasting time of 5h~6h.

7. The method for preparing the hierarchical porous mordenite zeolite catalyst according to claim 1, characterized in that, The ion exchange reaction takes 4 to 6 hours and involves 2 to 3 ion exchanges.

8. The method for preparing the hierarchical porous mordenite zeolite catalyst according to claim 1, characterized in that, The conditions for the second roasting are: roasting temperature of 550℃~600℃ and roasting time of 3h~4h.

9. A hierarchical porous silica zeolite catalyst prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The total specific surface area of ​​the hierarchical porous mordenite zeolite catalyst is 350 m². 2 / g~450m 2 / g, total pore volume is 0.25cm³ 3 / g~0.35cm 3 / g, of which the mesoporous pore volume reaches 0.10cm³. 3 / g~0.20cm 3 / g, the molar ratio of Brønsted acid sites to Lewis acid sites is 5-10.

10. The application of the hierarchical porous mordenite zeolite catalyst of claim 9 in the preparation of 2,6-diisopropylnaphthalene, characterized in that, 2,6-Diisopropylnaphthalene was prepared by adding naphthalene and propylene as raw materials into a fixed-bed reactor packed with a graded porous mordenite catalyst and undergoing an alkylation reaction.

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