Catalyst for producing 2, 6-dimethylnaphthalene as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for producing 2, 6-dimethylnaphthalene as well as a preparation method and application of the catalyst. The catalyst for producing the 2, 6-dimethylnaphthalene, disclosed by the invention, is a heteroatom-doped SAPO-11 molecular sieve catalyst containing gallium oxide. The catalyst for producing 2, 6-dimethylnaphthalene provided by the invention has the advantages of high conversion rate of the raw material 2-methylnaphthalene, high selectivity of the product 2, 6-dimethylnaphthalene, high ratio of 2, 6-dimethylnaphthalene to 2, 7-dimethylnaphthalene, long service cycle and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysis, and particularly relates to a catalyst for producing 2,6-dimethylnaphthalene, a preparation method thereof, and an application thereof. Background Art

[0002] 2,6-Dimethylnaphthalene (2,6-DMN) is a high-end polyester monomer. After oxidation, it is condensed with ethylene glycol to obtain poly(ethylene naphthalate) (PEN), a polyester material. Compared with polyethylene terephthalate (PET), PEN has higher strength, more excellent thermal properties, better gas barrier properties, stronger chemical stability, and radiation resistance, and is widely used in fields such as electronic components, instruments, insulation materials, and aerospace materials. However, the preparation technology of 2,6-dimethylnaphthalene is not yet mature, resulting in high costs and expensive prices, thus preventing PEN from entering the market on a large scale.

[0003] There are many methods for preparing 2,6-dimethylnaphthalene, which can be divided into two categories: direct extraction method and chemical synthesis method. From the perspective of reaction raw materials, they can be summarized into four process routes: direct extraction from coal tar, toluene acylation method, xylene alkylation method, and alkylation of naphthalene or methylnaphthalene. From the synthetic process, the alkylation reaction of naphthalene or methylnaphthalene to synthesize 2,6-dimethylnaphthalene has a simple route, providing a new way for the deep processing of naphthalene or methylnaphthalene, and has gradually become a research hotspot.

[0004] CN102746102A discloses a method for preparing 2,6-dimethylnaphthalene using SAPO-11 molecular sieve. The SAPO-11 molecular sieve synthesized by microwave radiation heating is activated, and naphthalene, an alkylating agent, and a solvent are mixed at a molar ratio of 1:(2-4):(6-12). Under the conditions of 350°C - 450°C and 2MPa - 5MPa, with a mass space velocity of 0.5h -1 ~2h -1 , and a carrier gas flow rate of 20 mL / min - 60 mL / min, the alkylation reaction is carried out to obtain 2,6-dimethylnaphthalene. This method has a high selectivity for 2,6-dimethylnaphthalene and a certain anti-coking ability. However, using only SAPO-11 molecular sieve as a catalyst, a large number of acid centers on its outer surface are prone to cause side reactions, and a large amount of coking substances will be formed after long-term operation. In addition, relying solely on the pore shape selectivity of SAPO-11 molecular sieve still cannot significantly improve the ratio of 2,6-dimethylnaphthalene to 2,7-dimethylnaphthalene.

[0005] CN102513146A discloses a catalyst for synthesizing 2,6-dimethylnaphthalene and a preparation method thereof. The weight ratio of the main components of the catalyst is: Na 2 O 0.25 parts - 0.5 parts, SiO 21 part, 0.05 part to 0.2 part of TPABr, Al 2 O 3 0.01 part to 0.03 part, Fe 2 O 3 0.01 part to 0.03 part, H 2 PO 4 - 0.03 part to 0.06 part and 22 parts to 45 parts of carbon aerogel. At 400 °C and a mass space velocity of 0.5 h -1 for 2 - methylnaphthalene, 2 - methylnaphthalene:methanol:mesitylene = 1:1:3 (molar ratio), the above catalyst is used in the reaction of alkylation of 2 - methylnaphthalene with methanol to synthesize 2,6 - dimethylnaphthalene. However, after partial substitution of Fe for Al element, the acid strength of the molecular sieve will be increased, and while increasing the catalytic activity, it is also easy to cause further polycondensation reaction of the target product to form coke. In addition, the addition amount of carbon aerogel is not easy to control, which is easy to cause pore blockage and affect the product diffusion.

[0006] CN105566052A discloses a method for catalytically preparing 2,6 - dimethylnaphthalene using CuSAPO - 11 molecular sieve. The catalyst used in this method is copper - aluminum - silicon phosphate molecular sieve CuSAPO - 11, which is synthesized by adding copper salt during the hydrothermal synthesis of aluminum - silicon phosphate molecular sieve SAPO - 11, and then a new type of copper - aluminum - silicon phosphate molecular sieve CuSAPO - 11 is synthesized. This molecular sieve has a more suitable acidity and a larger mesopore diameter, and shows higher catalytic reaction activity and 2,6 - dimethylnaphthalene selectivity in the alkylation reaction of naphthalene. However, the Cu element in the molecular sieve prepared by this method is unevenly distributed in its framework structure, and is prone to shedding and loss after long - term operation, that is, the service time is limited; in addition, the Cu element only has the function of modifying the pore diameter and acidity, and cannot improve the shape - selective catalytic ability of the catalyst from the intrinsic effects such as electron density, that is, it still cannot significantly increase the ratio of 2,6 - dimethylnaphthalene to 2,7 - dimethylnaphthalene. SUMMARY OF THE INVENTION

[0007] In order to overcome the deficiencies of the prior art, the present invention provides a catalyst for producing 2,6 - dimethylnaphthalene, its preparation method and application. The catalyst for producing 2,6 - dimethylnaphthalene provided by the present invention has the advantages of high conversion rate of raw material 2 - methylnaphthalene, high selectivity of product 2,6 - dimethylnaphthalene, high ratio of 2,6 - dimethylnaphthalene / 2,7 - dimethylnaphthalene, and long service life.

[0008] In the first aspect of the present invention, a catalyst for producing 2,6 - dimethylnaphthalene is provided, and the catalyst for producing 2,6 - dimethylnaphthalene is a heteroatom - doped SAPO - 11 molecular sieve catalyst containing gallium oxide.

[0009] Further, the heteroatoms include carbon and nitrogen elements, and preferably the heteroatoms are carbon, nitrogen, and sulfur.

[0010] Further, in the catalyst for producing 2,6-dimethylnaphthalene, based on the mass of the catalyst, the mass content of SAPO-11 molecular sieve is 80% - 90%, the mass content of carbon is 5% - 10%, the mass content of gallium oxide is 2% - 5%, the mass content of sulfur is 0% - 2.5%, preferably 0.1% - 2.5%, and the mass content of nitrogen is 1% - 2.5%.

[0011] Further, the gallium oxide is embedded in the SAPO-11 molecular sieve framework, and the sulfur and nitrogen heteroatoms are combined with the carbon layer and doped into the SAPO-11 molecular sieve framework.

[0012] Further, the specific surface area of the catalyst for producing 2,6-dimethylnaphthalene is 178 m 2 / g - 195 m 2 / g, the microporosity is 73% - 86%, and the average pore diameter is 0.64 nm - 0.83 nm.

[0013] Further, the total acid amount of the catalyst for producing 2,6-dimethylnaphthalene is 1.23 mmol / g - 1.45 mmol / g, the medium-strong acid amount is 0.52 mmol / g - 0.63 mmol / g, and the ratio of L acid amount to B acid amount (L / B) is 1.23 - 1.34.

[0014] Further, the electron cloud density value inside the pores of the catalyst for producing 2,6-dimethylnaphthalene is 0.325 - 0.387.

[0015] The second aspect of the present invention provides a preparation method of the above-mentioned catalyst for producing 2,6-dimethylnaphthalene, including the following steps:

[0016] (1) Mix a phosphorus source, an aluminum source, a gallium salt, and water to obtain a mixed solution, then dropwise add a silicon source, and then mix with a template agent and react to obtain a precursor;

[0017] (2) Perform a crystallization reaction on the precursor obtained in step (1), introduce an unsaturated hydrocarbon gas during the reaction, then wash and dry, and then perform two-stage calcination to obtain the catalyst.

[0018] Further, the phosphorus source in step (1) is preferably phosphoric acid, and the mass concentration of phosphoric acid is 80% - 90%.

[0019] Further, the aluminum source in step (1) is selected from one or more of sodium aluminate, aluminum sulfate, kaolin, and pseudoboehmite; preferably pseudoboehmite, and more preferably pseudoboehmite with a purity greater than 99.5%.

[0020] Further, the gallium salt described in step (1) is selected from one or more of gallium nitrate, gallium acetate, and gallium chloride, and preferably gallium acetate.

[0021] Further, in order to mix the slurry in step (1) more uniformly, it can be continuously stirred for a period of time. The preferred stirring speed is 600 rpm to 900 rpm, and the time is 15 min to 45 min.

[0022] Further, the mass ratio of the gallium salt, phosphoric acid, water, and aluminum source described in step (1) is 1:(0.05 - 0.8):(5 - 50):(0.1 - 1), and preferably 1:(0.23 - 0.57):(10 - 35):(0.18 - 0.49).

[0023] Further, the silicon source in step (1) is a silicate compound, selected from at least one of tetraethyl orthosilicate, isopropyl orthosilicate, or trimethylsilyloxy silicate, and preferably isopropyl orthosilicate.

[0024] Further, the dropping speed ratio of the gallium salt to the silicon source in step (1) is 1 g of gallium salt:(0.01 mL / min - 0.1 mL / min), and preferably 1 g of gallium salt:(0.04 mL / min - 0.07 mL / min).

[0025] Further, the addition of the silicon source and the template agent in step (1) is preferably carried out under stirring. The stirring speed is 800 rpm to 1000 rpm, and the time is 100 min to 180 min.

[0026] Further, the template agent in step (1) is selected from water-soluble amino acids containing amino groups, preferably amino acids containing sulfur elements and amino groups, and more preferably L-cysteine.

[0027] Further, the reaction temperature of the reaction in step (1) is 55°C to 105°C, preferably 70°C to 85°C, the stirring speed is 800 rpm to 1000 rpm, and the time is 30 min to 100 min.

[0028] Further, the mass ratio of the gallium salt, silicon source, and template agent in step (1) is 1:(0.03 - 0.75):(0.12 - 1.14), and preferably 1:(0.08 - 0.37):(0.46 - 0.89).

[0029] Further, the crystallization reaction temperature in step (2) is 105°C to 317°C, preferably 170°C to 240°C, the time is 10 h to 60 h, and preferably 35 h to 46 h.

[0030] Further, the unsaturated hydrocarbon gas described in step (2) is selected from one or more of ethylene, propylene, and acetylene, preferably acetylene.

[0031] Further, the ratio of the flow rate of the unsaturated hydrocarbon gas described in step (2) to the gallium salt is (0.5 mL / min to 10 mL / min): 1 g of gallium salt, preferably (1 mL / min to 5 mL / min): 1 g of gallium salt.

[0032] Further, the pressure of the reaction described in step (2) is 0.12 MPa to 0.49 MPa, preferably 0.18 MPa to 0.27 MPa.

[0033] Further, the crystallization reaction described in step (2) is dynamic crystallization, and the stirring speed is 100 rpm to 800 rpm, preferably 180 rpm to 260 rpm.

[0034] Further, after the reaction in step (2) is completed, the catalyst is obtained by washing, suction filtration, and drying using conventional methods in the art. The solvent for washing is an ethanol aqueous solution, and the mass content of ethanol is 55% to 68%; the drying temperature is 100 °C to 150 °C, and the time is 5 h to 10 h.

[0035] Further, the calcination process described in step (2) is two-stage calcination. The calcination temperature in the first stage is 350 °C to 500 °C, preferably 400 °C to 450 °C, and the time is 1 h to 12 h, preferably 4 h to 6 h. The calcination temperature in the second stage is 450 °C to 700 °C, preferably 510 °C to 580 °C, and the time is 1 h to 8 h, preferably 3 h to 5 h; wherein, the calcination temperature in the second stage is at least 100 °C higher than that in the first stage.

[0036] Further, the catalyst obtained in step (2) can be crushed before application, and the preferred crushing mesh number is 5 mesh to 70 mesh, preferably 20 mesh to 40 mesh.

[0037] The third aspect of the present invention provides an application of the catalyst for producing 2,6-dimethylnaphthalene as described above in the preparation of 2,6-dimethylnaphthalene in the methylation reaction of 2-methylnaphthalene.

[0038] Further, the reaction conditions of the reaction are as follows: the reaction temperature is 330 °C to 380 °C, the reaction pressure is atmospheric pressure, the mass space velocity is 1.5 h -1 ~3 h -1 ; relative to 0.5 g to 1 g of the catalyst mass, the flow rate of the carrier gas hydrogen is 20 mL / min to 40 mL / min; the mass ratio of 2-methylnaphthalene, methanol, and mesitylene is 1: (3 to 7): (3 to 7).

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) The catalyst provided by the present invention is a heteroatom-doped SAPO-11 molecular sieve catalyst containing gallium oxide. Among them, the gallium oxide is embedded in the SAPO-11 molecular sieve framework, and sulfur and nitrogen heteroatoms are combined with the carbon layer and doped into the SAPO-11 molecular sieve framework. This part of metal oxides and heteroatoms often cause certain lattice defects, generating a certain number of defect sites with local charges, and these defect sites will generate new catalytic active centers.

[0041] (2) In the process of preparing the SAPO-11 molecular sieve in the present invention, a gallium salt is introduced to undergo a complex coordination reaction with the template agent component, and the obtained porous coordination compound is automatically embedded in the SAPO-11 molecular sieve framework structure. After calcination treatment, gallium oxide and heteroatoms such as carbon, sulfur, and nitrogen in the template agent are firmly deposited in the molecular sieve catalyst framework; in addition, the present invention uses a segmented calcination method. During the carbonization process of the obtained porous coordination compound, a small amount of open active sites will still be retained in its metal active centers. This part of the sites can increase the electron density inside the pores of the SAPO-11 molecular sieve, which is beneficial to reducing the activity of carbocations, making it easier for reactants to contact and react with the 6-position with high electron density, and improving the ratio of 2,6-dimethylnaphthalene to 2,7-dimethylnaphthalene.

[0042] (3) Preferably, the present invention uses L-cysteine as the template agent. On the one hand, by virtue of its mild acidic characteristics, the amount of phosphoric acid is reduced, improving the environmental friendliness of the reaction. On the other hand, L-cysteine contains sulfur and nitrogen heteroatoms, which can be deposited in the carbonized product. Unsaturated hydrocarbon gases are introduced during the reaction process, which can undergo a re-coordination reaction with the porous coordination compound intermediate. After calcination treatment, the number of lattice defects in the product is increased, further increasing the number of new catalytic active centers.

[0043] (4) Most of the gallium oxide in the product after calcination treatment in the present invention is deposited in the molecular sieve pores, narrowing the pore diameter and increasing the number of L acids and medium-strong acids inside the molecular sieve pores, which is beneficial to the alkylation reaction. At the same time, a small amount of gallium oxide is dispersed on the outer surface of the molecular sieve, covering the acidic sites on the outer surface, reducing the probability of non-selective catalytic reactions, and increasing the yield of the target product.

[0044] (5) The present invention does not use noble metal catalysts, which is beneficial to reducing production costs, and the preparation process is simple, facilitating industrial batch production and application. Description of the Drawings

[0045] Figure 1 It is a reaction route diagram for the methylation of 2-methylnaphthalene;

[0046] Figure 2 It is a scanning electron microscope image (SEM) of the catalyst prepared in Example 1;

[0047] Figure 3 Scanning electron microscope image (SEM) of the catalyst prepared for Comparative Example 1;

[0048] Figure 4 Nitrogen adsorption - desorption isotherm curves of the catalysts prepared for Example 1 and Comparative Example 1;

[0049] Figure 5 X - ray diffraction pattern (XRD) of the catalyst prepared for Example 1;

[0050] Figure 6 Gas chromatogram (GC) of the product obtained after the reaction of the catalyst prepared for Example 1;

[0051] Figure 7 Gas chromatogram (GC) of the product obtained after the reaction of the catalyst prepared for Comparative Example 1. Detailed implementation mode

[0052] The following examples are used to further illustrate the preparation method and application of the catalyst for producing 2,6 - dimethylnaphthalene of the present invention. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation modes and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0053] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all purchased from regular biochemical reagent stores.

[0054] In the present invention, a 3H - 2000PM2 specific surface area tester produced by Beijing Beishide Company is used to measure the specific surface area and pore volume of the catalyst. Before the test, the sample is treated by vacuum degassing at 373K, and the nitrogen adsorption - desorption isotherm curve is measured at 77K. The specific surface area and pore volume of the sample are analyzed by the BET method. Among them, micropores refer to pores with a pore diameter less than 2nm.

[0055] Micropore rate % = (micropore pore volume / total pore volume) × 100%.

[0056] In the present invention, an American Micromeritics Autochem II 2920C chemisorption instrument is used to perform NH 3 -TPD experiments on the catalyst to measure its acidity and acid amount. During the measurement, first, 0.2g of the sample is placed at 500°C and purged and activated with nitrogen at a flow rate of 30 mL / min, then cooled to 100°C to adsorb ammonia. After adsorption saturation, the temperature is raised to 700°C at a rate of 10°C / min for desorption, and detection is carried out through a TCD detector.

[0057] In the present invention, a Rigaku D / A type X-ray diffractometer was used to analyze the phase of the catalyst. The diffraction source was a copper target (CuKα = 0.15418 nm), the current was 40 mA, the voltage was 40 kV, and the scanning speed was 2 min -1 .

[0058] In the present invention, a Bruker EQUINOX 55 Fourier transform infrared spectrometer was used to perform pyridine adsorption infrared spectroscopy experiments on the catalyst. The KBr pellet method was adopted, and the scanning wave number range was 4000 cm -1 ~400 cm -1 . The sample wafer was first vacuum-purified at 450 °C for 3 h, then adsorbed pyridine vapor at room temperature for 30 min, desorbed at 150 °C for 1 h and the infrared spectrum was recorded to obtain the amounts of Brønsted acid and Lewis acid of the catalyst.

[0059] In the present invention, the molecular orbital program MOPAC was used to calculate the electron cloud density values inside the pores of the catalyst. The MOPAC program calculates some chemical properties of molecules based on quantum chemical principles.

[0060] In the present invention, a Hitachi HITACHI 3-4800 field emission scanning electron microscope was used to observe the crystal grain size and morphological characteristics of the catalyst.

[0061] In the present invention, a Hewlett-Packard HP6890 gas chromatograph-HP5973 mass spectrometer was used for qualitative and quantitative analysis of the composition of the product. Among them, the size of the HP-5MS quartz capillary column was 30 m × 0.25 mm × 0.25 μm, the solvent was absolute ethanol, the inlet temperature was 310 °C, the interface temperature was 280 °C, the column temperature was raised from 120 °C to 310 °C at 20 °C / min, the injection volume was 1 μL, and the analysis time was 11 min.

[0062] In the present invention, the 2-methylnaphthalene methylation reaction was carried out in a fixed-bed reactor. The catalyst was loaded into the constant-temperature zone of the reactor and fixed with quartz sand up and down. Before the reaction, the catalyst was first activated at 450 °C under hydrogen for 1 h. After cooling to the reaction temperature, the prepared reaction solution (2-methylnaphthalene, methanol and mesitylene) was injected into the reactor using a feed pump. The reaction product was condensed by a condenser and collected, and the obtained sample was analyzed by gas chromatography.

[0063] Example 1

[0064] Take 2 g of phosphoric acid with a mass concentration of 83% and place it in a flask containing 100 g of deionized water. Add 2 g of pseudo-boehmite with a purity of 99.8% and 5 g of gallium acetate to form a mixed slurry. Stir continuously at 800 rpm for 30 min at 25 °C until the slurry is evenly mixed. Dropwise add 1 g of isopropyl orthosilicate at a dropping rate of 0.25 mL / min, continue to stir at 900 rpm for 130 min, then add 3 g of L-cysteine, and stir at 75 °C and 900 rpm for 50 min to obtain a seed precursor. Transfer the seed precursor to a stainless steel autoclave with a polytetrafluoroethylene lining, carry out a dynamic crystallization reaction at 210 °C and 200 rpm for 40 h. During the reaction process, acetylene gas is introduced at 15 mL / min, the pressure in the autoclave is 0.23 MPa. Take out the mixture and let it cool to 25 °C, wash it with an ethanol aqueous solution with an ethanol mass content of 60% and filter it by suction, dry it at 110 °C for 8 h, and then carry out two-stage calcination treatment. The first-stage calcination temperature is 410 °C and the time is 5 h, the second-stage calcination temperature is 550 °C and the time is 4 h to obtain a powdery molecular sieve. Press the powdery molecular sieve under 2 MPa, crush it to 30 mesh to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0065] Example 2

[0066] Take 1.15 g of phosphoric acid with a mass concentration of 83% and place it in a flask containing 50 g of deionized water. Add 0.9 g of pseudo-boehmite with a purity of 99.8% and 5 g of gallium acetate to form a mixed slurry. Stir continuously at 800 rpm for 30 min at 25 °C until the slurry is evenly mixed. Dropwise add 0.4 g of isopropyl orthosilicate at a dropping rate of 0.25 mL / min, continue to stir at 900 rpm for 130 min, then add 2.3 g of L-cysteine, and stir at 75 °C and 900 rpm for 50 min to obtain a seed precursor. Transfer the seed precursor to a stainless steel autoclave with a polytetrafluoroethylene lining, carry out a dynamic crystallization reaction at 210 °C and 200 rpm for 40 h. During the reaction process, acetylene gas is introduced at 15 mL / min, the pressure in the autoclave is 0.23 MPa. Take out the mixture and let it cool to 25 °C, wash it with an ethanol aqueous solution with an ethanol mass content of 60% and filter it by suction, dry it at 110 °C for 8 h, and then carry out two-stage calcination treatment. The first-stage calcination temperature is 410 °C and the time is 5 h, the second-stage calcination temperature is 550 °C and the time is 4 h to obtain a powdery molecular sieve. Press the powdery molecular sieve under 2 MPa, crush it to 30 mesh to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0067] Example 3

[0068] Same as Example 1, except that the purity of the pseudo-boehmite is reduced to 95%, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0069] Example 4

[0070] Same as Example 1, except that gallium nitrate is used to replace gallium acetate, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0071] Example 5

[0072] Same as Example 1, except that the masses of phosphoric acid and deionized water are increased to 4 g and 250 g respectively, and the mass of pseudo-boehmite is reduced to 0.5 g, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0073] Example 6

[0074] Same as Example 1, except that trimethylsilyloxy silicate is used to replace isopropyl orthosilicate, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0075] Example 7

[0076] Same as Example 1, except that the dropping rate of isopropyl orthosilicate is increased to 0.1 mL / min, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0077] Example 8

[0078] Same as Example 1, except that serine is used to replace L-cysteine, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0079] Example 9

[0080] Same as Example 1, except that the reaction temperature after adding L-cysteine is reduced to 55 °C, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0081] Example 10

[0082] Same as Example 1, except that the mass of isopropyl orthosilicate is increased to 3.75 g and the mass of L-cysteine is reduced to 0.6 g, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0083] Example 11

[0084] Same as Example 1, except that the crystallization reaction temperature is increased to 300 °C, the reaction time is shortened to 12 h, and the dynamic synthesis stirring speed is reduced to 100 rpm, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0085] Example 12

[0086] Same as Example 1, except that ethylene is used instead of acetylene, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0087] Example 13

[0088] Same as Example 1, except that the flow rate of acetylene gas is increased to 50 mL / min, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0089] Example 14

[0090] Same as Example 1, except that the seed precursor is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and the dynamic crystallization reaction is carried out at 210 °C and 200 rpm for 40 h. During the reaction, acetylene gas is charged at 15 mL / min, and the pressure in the autoclave is increased from 0.23 MPa to 0.4 MPa. Other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0091] Example 15

[0092] Same as Example 1, except that the calcination temperature in the first stage is increased to 500 °C and the time is extended to 12 h, and the calcination temperature in the second stage is decreased to 450 °C and shortened to 1 h. Other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0093] Example 16

[0094] Same as Example 1, except that the grinding mesh number is increased to 70 mesh. Other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0095] Comparative Example 1

[0096] Same as Example 1, except that gallium acetate is omitted. Other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0097] Comparative Example 2

[0098] Same as Example 1, except that di-n-propylamine is used as the template agent to replace L-cysteine in Example 1. Other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0099] Comparative Example 3

[0100] Same as Example 1, except that isopropyl orthosilicate is poured into the slurry at once, replacing the dropwise addition in Example 1, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0101] Comparative Example 4

[0102] Same as Example 1, except that the dynamic crystallization reaction is changed to a static crystallization reaction, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0103] Comparative Example 5

[0104] Same as Example 1, except that high-purity nitrogen is introduced during the reaction to increase the pressure, replacing acetylene gas, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0105] Comparative Example 6

[0106] Same as Example 1, except that the two-stage calcination in Example 1 is changed to one-stage calcination treatment at a temperature of 600 °C for 10 h, and other reaction conditions and material compositions remain unchanged, to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0107] Comparative Example 7

[0108] According to the method described in CN102746102A, an aluminum source, a silicon source, a phosphorus source, a template agent DPA, and water are stirred evenly at a molar ratio of Al 2 O 3 :SiO 2 :P 2 O 5 :DPA:H 2 O of 1:0.6:1:1:40 to obtain a gel. Among them, the aluminum source is pseudo-boehmite, the silicon source is silica sol, the phosphorus source is phosphoric acid with a mass percentage of 85%, and DPA is di-n-propylamine. The polytetrafluoroethylene inner liner containing the gel is placed in a ceramic outer liner and then put into a microwave oven. Under the conditions of a power of 600 W and a temperature of 170 °C, crystallization reaction is carried out for 2 h to obtain a solid-liquid mixture. After the solid phase obtained by filtration is washed, it is dried at 110 °C for 12 h and calcined at 650 °C for 7 h to obtain SAPO-11 molecular sieve. After being tableted and crushed to 30 mesh, a catalyst for producing 2,6-dimethylnaphthalene is obtained.

[0109] Comparative Example 8

[0110] According to the method described in CN102513146A, 100 g of water glass and 50 g of NaOH solution are mixed evenly, 5 g of TPAOH solution is added, and after stirring evenly, 3 g of Al(NO 3 ) 3 ·9H2 Mix the O solution evenly with the above mixed solution, and then add 3 g of Fe 2 (SO 4 ) 3 Stir evenly, add 3 g of NaH to the above mixed solution 2 PO 4 solution, stir evenly and then add 4500 g of dry carbon aerogel, stir evenly; age the above mixture to obtain a gel, crystallize to obtain a sample, filter, wash and dry the sample, and remove the template agent by roasting to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0111] Comparative Example 9

[0112] According to the method described in CN105566052A, add 102 g of aluminum isopropoxide and 3.9 g of silica sol to 58.2 g of a phosphoric acid aqueous solution with a mass concentration of 50% at 30 °C, stir for 3 h, then add 10.1 g of di-n-propylamine and 9.35 g of copper nitrate, stir for 2 h to obtain a reaction mixture. Transfer the reaction mixture to a stainless steel autoclave lined with polytetrafluoroethylene and crystallize at 170 °C for 24 h. Cool the crystallized product to room temperature with water, and repeatedly rinse with deionized water. The separated solid is dried and then roasted to obtain CuSAPO-11 molecular sieve, which is tableted and crushed to 30 mesh to obtain a catalyst for producing 2,6-dimethylnaphthalene.

[0113] Test Example 1

[0114] Determine the physical and chemical properties of the catalysts for producing 2,6-dimethylnaphthalene in Examples 1-16 and Comparative Examples 1-9. The specific results are shown in Table 1.

[0115] Table 1 Performance of the catalysts for producing 2,6-dimethylnaphthalene prepared in Examples and Comparative Examples

[0116]

[0117]

[0118] As can be seen from Table 1, the catalysts for producing 2,6-dimethylnaphthalene prepared in the present invention have good physical and chemical properties. The gallium oxide content, sulfur content and nitrogen content of the sample in Example 1 reach 5%, 2.5% and 2.5% respectively, and its specific surface area, microporosity and average pore diameter are 195 m 2 / g, 86% and 0.78 nm respectively, and the medium-strong acid amount and L / B value reach 0.63 mmol / g and 1.34 respectively. The corresponding parameters of the comparative example samples are significantly lower than those of the example samples. From Figure 2 and Figure 3It can be seen from the SEM photos that the surface of the catalyst in Example 1 shows an obvious porous structure with regular morphology, which is helpful for the 2-methylnaphthalene methylation reaction, while the morphology of the sample in Comparative Example 1 is poor. Figure 4 The N 2 adsorption-desorption isotherm comparison diagrams of the samples in Example 1 and Comparative Example 1 are given. It can be seen that the specific surface area of Example 1 is significantly higher than that of the sample in Comparative Example 1, and its adsorption isotherm is of type I, that is, it belongs to microporous materials; while the sample in Comparative Example 1 shows a hysteresis loop structure and belongs to type IV adsorption isotherm, and its pore size is larger than that of the sample in Example 1. Figure 5 The XRD diffraction peaks in

[0119] Test Example 2

[0120] The 2-methylnaphthalene methylation reaction effects and product compositions in Example 1, Example 2, Example 8, Comparative Example 1 and Comparative Example 2 were determined, and the specific results are shown in Table 2.

[0121] Table 2 Effects of 2-methylnaphthalene methylation reaction in Examples and Comparative Examples

[0122] Sample Conversion rate of 2-methylnaphthalene / % Selectivity of 2,6-dimethylnaphthalene / % 2,6- / 2,7- Yield of 2,6-dimethylnaphthalene / % Example 1 46 81 3.9 28 Example 2 42 78 3.6 25 Example 8 39 75 3.4 21 Comparative Example 1 17 54 1.3 7.5 Comparative Example 2 10 42 1.05 5.8

[0123] From Table 2 and Figure 6 , Figure 7 It can be seen that the catalyst prepared by the method of the present invention has good 2-methylnaphthalene methylation reaction effect, as well as high 2,6-dimethylnaphthalene yield and selectivity. The 2-methylnaphthalene conversion rate, 2,6-dimethylnaphthalene selectivity, 2,6- / 2,7- and 2,6-dimethylnaphthalene yields of the sample in Example 1 are 46%, 81%, 3.9 and 28% respectively. The reaction effect of the sample in Example 8 is lower than that of other examples because there is a lack of sulfur heteroatom deposition. The reaction results of the comparative example samples are lower than those of the example samples because metal oxides and heteroatoms often cause certain lattice defects, generating a certain number of defect sites with local charges, and these defect sites will generate new catalytic active centers. The comparative example samples lack metal oxides and heteroatoms, so the reaction effect will decrease significantly.

[0124] The specific embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including the combination of each technical feature in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A catalyst for producing 2,6 - dimethylnaphthalene, wherein the catalyst for producing 2,6 - dimethylnaphthalene is a heteroatom - doped SAPO - 11 molecular sieve catalyst containing gallium oxide.

2. The catalyst according to claim 1, characterized in that the heteroatoms include carbon and nitrogen elements, and preferably the heteroatoms are carbon, nitrogen and sulfur.

3. The catalyst according to claim 1 or 2, characterized in that in the catalyst for producing 2,6 - dimethylnaphthalene, based on the mass of the catalyst, the mass content of SAPO - 11 molecular sieve is 80% - 90%, the mass content of carbon is 5% - 10%, the mass content of gallium oxide is 2% - 5%, the mass content of sulfur is 0% - 2.5%, preferably 0.1% - 2.5%, and the mass content of nitrogen is 1% - 2.5%.

4. The catalyst according to claim 1 or 2, characterized in that the gallium oxide is embedded in the SAPO - 11 molecular sieve framework, and the sulfur and nitrogen heteroatoms are combined with the carbon layer and doped into the SAPO - 11 molecular sieve framework.

5. The catalyst according to claim 1 or 2, characterized in that The specific surface area of the catalyst for producing 2,6-dimethylnaphthalene is 178 m 2 / g to 195 m 2 / g, the microporosity is 73% to 86%, and the average pore diameter is 0.64 nm to 0.83 nm; optionally, the total acid amount of the catalyst for producing 2,6 - dimethylnaphthalene is 1.23 mmol / g - 1.45 mmol / g, the medium - strong acid amount is 0.52 mmol / g - 0.63 mmol / g, and the ratio of L - acid amount to B - acid amount is 1.23 - 1.34; optionally, the electron cloud density value inside the pore channels of the catalyst for producing 2,6 - dimethylnaphthalene is 0.325 - 0.

387.

6. A preparation method of the catalyst for producing 2,6 - dimethylnaphthalene according to any one of claims 1 - 5, comprising the following steps: (1) Mix a phosphorus source, an aluminum source, a gallium salt and water to obtain a mixed solution, then dropwise add a silicon source, and then mix with a template agent and react to obtain a precursor; (2) Carry out a crystallization reaction on the precursor in step (1), introduce an unsaturated hydrocarbon gas during the reaction, then wash, dry, and then carry out two - stage calcination to obtain the catalyst.

7. The preparation method according to claim 6, characterized in that the phosphorus source in step (1) is phosphoric acid, and the mass concentration of phosphoric acid is 80% - 90%; optionally, the aluminum source in step (1) is selected from one or more of sodium aluminate, aluminum sulfate, kaolin, and pseudoboehmite; optionally, the gallium salt in step (1) is selected from one or several of gallium nitrate, gallium acetate and gallium chloride; optionally, the silicon source in step (1) is a silicate compound, selected from at least one of tetraethyl orthosilicate, isopropyl orthosilicate or trimethylsilyloxy silicate, preferably isopropyl orthosilicate; optionally, the template agent in step (1) is selected from water - soluble amino - group - containing amino acids, preferably amino - group - containing amino acids containing sulfur elements, more preferably L - cysteine.

8. The preparation method according to claim 6, characterized in that the mass ratio of the gallium salt, phosphoric acid, water and aluminum source in step (1) is 1:(0.05 - 0.8):(5 - 50):(0.1 - 1).

9. The preparation method according to claim 6, It is characterized in that The dropping speed ratio of the gallium salt to the silicon source in step (1) is 1 g of gallium salt: (0.01 mL / min to 0.1 mL / min); Optionally, the mass ratio of the gallium salt, silicon source and template agent in step (1) is 1: (0.03 to 0.75): (0.12 to 1.14).

10. According to the preparation method described in claim 6, It is characterized in that The reaction temperature of the reaction in step (1) is 55 °C to 105 °C, the stirring speed is 800 rpm to 1000 rpm, and the time is 30 min to 100 min.

11. According to the preparation method described in claim 6, It is characterized in that The crystallization reaction temperature in step (2) is 105 °C to 317 °C, and the time is 10 h to 60 h; Optionally, the crystallization reaction in step (2) is dynamic crystallization, the stirring speed is 100 rpm to 800 rpm, preferably 180 rpm to 260 rpm.

12. According to the preparation method described in claim 6, It is characterized in that For the two-stage calcination in step (2), the first-stage calcination temperature is 350 °C to 500 °C, the time is 1 h to 12 h, the second-stage calcination temperature is 450 °C to 700 °C, and the time is 1 h to 8 h; preferably, the second-stage calcination temperature is at least 100 °C higher than the first-stage calcination temperature.

13. According to the preparation method described in claim 6, It is characterized in that The unsaturated hydrocarbon gas in step (2) is selected from one or more of ethylene, propylene and acetylene; Optionally, the flow rate ratio of the unsaturated hydrocarbon gas to the gallium salt in step (2) is (0.5 mL / min to 10 mL / min): 1 g of gallium salt.

14. Application of the catalyst for producing 2,6-dimethylnaphthalene according to any one of claims 1-5 in the production of 2,6-dimethylnaphthalene in the methylation reaction of 2-methylnaphthalene.

15. According to the application described in claim 14, It is characterized in that The reaction conditions of the said reaction are as follows: the reaction temperature is 330°C to 380°C, the reaction pressure is atmospheric pressure, and the mass space velocity is 1.5 h -1 to 3 h -1 ; relative to the catalyst mass of 0.5 g to 1 g, the flow rate of the carrier gas hydrogen is 20 mL / min to 40 mL / min; the mass ratio of 2-methylnaphthalene, methanol and mesitylene is 1:(3 to 7):(3 to 7).

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