A modified molecular sieve, its preparation method and application

Abstract

The present invention discloses a modified molecular sieve, a preparation method thereof and an application thereof. The modified molecular sieve contains Ca and P elements, and the pore volume of the modified molecular sieve reaches 0.15 - 0.60 cm 3 / g, and the mesoporous specific surface area reaches 30 - 100 m 2 / g; the ratio of the amount of weak acid to the amount of strong acid in the modified molecular sieve is (2 - 10):1, and the ratio of B acid to L acid is (2 - 10):1. The method includes: subjecting the molecular sieve to acid treatment and alkali treatment in sequence, then mixing with a Ca-containing compound and a P-containing compound, and finally calcining to obtain the modified molecular sieve. After the modified molecular sieve is formed, a catalyst for catalytic benzene and / or toluene in the aromatics shape-selective methylation reaction can be obtained, which has suitable catalytic activity and can reduce the problems of cumbersome operation and environmental pressure brought by the traditional impregnation method while obtaining high para selectivity.

Description

Technical Field

[0001] The present invention belongs to the field of molecular sieves, and particularly relates to a modified molecular sieve, a preparation method thereof and an application thereof. Background Art

[0002] p-Xylene is an important basic organic raw material and is widely used in fields such as polyester, synthetic fibers, and synthetic rubbers. The toluene methanol methylation reaction uses methanol and toluene as raw materials to produce xylene. When the concentration of p-xylene in the xylene product is greater than the thermodynamic equilibrium value (≈24 wt.%), this reaction is also called the toluene methanol shape-selective methylation reaction.

[0003] The methylation reaction of benzene / toluene is a typical acid-catalyzed reaction, and common catalytic materials are acidic zeolite molecular sieves. In the toluene methanol shape-selective methylation reaction, in order to improve the para-selectivity of the reaction product (the mass fraction of p-xylene in the xylene product), it is necessary to reasonably modify the outer surface and pores of the zeolite molecular sieve, inhibit the isomerization reaction catalyzed by the acidic sites on the outer surface, and enhance the shape-selective catalytic effect of the pores. It should be noted that the outer surface acid coverage and pore modification will respectively reduce the number of acidic sites and the diffusion rate of the molecular sieve, thereby inhibiting the toluene conversion rate of the reaction.

[0004] There are many reported and disclosed methods for modifying the outer surface and pores of molecular sieves for the toluene methanol shape-selective methylation reaction. For example, CN107758689A and the literature (Journal of Catalysis, 2006, 243(2): 389-394) disclose a Silicalite / ZSM-5 core-shell structured molecular sieve for toluene methanol shape-selective methylation and a synthesis method. This method uses acidic ZSM-5 as the core and inert Silicalite as the shell, and inhibits the acidity on the outer surface of the molecular sieve through Silicalite to achieve the shape-selective methylation catalytic effect. However, this method requires secondary crystallization, has a large operation difficulty, and it is very difficult to freely control the shell structure, and the regulation effect is limited.

[0005] The commonly used method at the present stage is to synchronously cover the outer surface and pores of the molecular sieve with oxides, inhibit the acidic sites on its outer surface, and shrink the pores to improve the para-selectivity of the molecular sieve. CN105344373A discloses a preparation method for a catalyst in the process of synthesizing p-xylene. This method uses a microporous molecular sieve ZSM-5 matrix, uses boric acid as a precursor, first adjusts the pore size of the microporous molecular sieve through wet impregnation, and then loads boron oxide on the outer surface of the microporous molecular sieve through a solid-phase reaction method.

[0006] Looking at the above-mentioned oxide modification methods, the introduction of the modifier during the modification process is all completed by the liquid-phase impregnation method. In order to achieve the para-selective modification effect, sometimes multiple modifications are required. This may cause problems such as a large amount of impregnation liquid discharge, and the entire impregnation process is relatively complex, with long operation steps and a series of problems such as wastewater discharge. In summary, it is necessary to develop a green and simple method for modifying zeolite molecular sieves to obtain a zeolite molecular sieve with high para-selectivity and activity for the shape-selective methylation reaction of toluene and methanol. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art, the present invention provides a modified molecular sieve and its preparation method and application. The method obtains the modified molecular sieve through acid treatment, alkali treatment, and element modification, which contains Ca and P elements. After the modified molecular sieve is formed, a catalyst for catalyzing the shape-selective methylation reaction of benzene and / or toluene can be obtained. This catalyst not only has suitable catalytic activity but also reduces the problems of cumbersome operation and environmental pressure brought by the traditional impregnation method while obtaining high para-selectivity.

[0008] One of the purposes of the present invention is to provide a modified molecular sieve, which contains Ca element and P element, and the pore volume of the modified molecular sieve (measured by the low-temperature nitrogen adsorption method) reaches 0.15 - 0.60 cm 3 / g, and the mesoporous specific surface area reaches 30 - 100 m 2 / g.

[0009] In a preferred embodiment, it is obtained by ammonia temperature-programmed desorption test that the ratio of the amount of weak acid to the amount of strong acid in the modified molecular sieve is (2 - 10):1, preferably (3 - 8):1.

[0010] For example, it is obtained by ammonia temperature-programmed desorption test that the ratio of the amount of weak acid to the amount of strong acid in the modified molecular sieve is 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1.

[0011] In a preferred embodiment, it is obtained by pyridine adsorption infrared measurement that the ratio of B acid to L acid in the modified molecular sieve is (2 - 10):1, preferably (2.5 - 6):1.

[0012] For example, it is obtained by pyridine adsorption infrared measurement that the ratio of B acid to L acid in the modified molecular sieve is 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1.

[0013] In a preferred embodiment, the pore volume of the modified molecular sieve (measured by the low-temperature nitrogen adsorption method) reaches 0.20 - 0.50 cm 3 / g, the mesoporous specific surface area reaches 40 - 70 m 2 / g.

[0014] For example, the pore volume of the modified molecular sieve (measured by the low-temperature nitrogen adsorption method) reaches 0.20, 0.30, 0.40 or 0.50 cm 3 / g, and the mesoporous specific surface area reaches 40, 50, 60 or 70 m 2 / g.

[0015] In a preferred embodiment, the molecular sieve is selected from at least one of ZSM-22, ZSM-35, and ZSM-5, preferably from ZSM-22 and / or ZSM-35.

[0016] Among them, the present invention is based on molecular sieves with ten-membered ring channels such as ZSM-22 and ZSM-35, and preferably ZSM-22 and ZSM-35 molecular sieves with pore mouth sizes slightly smaller than that of ZSM-5 molecular sieve.

[0017] In a preferred embodiment, based on 100 wt% of the modified molecular sieve, the content of Ca element is 0.1 - 5 wt%, and the content of P element is 0.1 - 10 wt%.

[0018] In a further preferred embodiment, based on 100 wt% of the modified molecular sieve, the content of Ca element is 0.2 - 2 wt%, and the content of P element is 0.5 - 5 wt%.

[0019] The second object of the present invention is to provide a preparation method of a modified molecular sieve, preferably for the preparation of the modified molecular sieve described in the first object of the present invention. The preparation method includes:

[0020] (1) Acid-treat and alkali-treat the molecular sieve in sequence to obtain a precursor;

[0021] (2) Mix the precursor with a Ca compound and a P compound, and grind to obtain a mixture;

[0022] (3) Calcine the mixture to obtain the modified molecular sieve.

[0023] In a preferred embodiment, the molecular sieve is selected from at least one of ZSM-22, ZSM-35, and ZSM-5, preferably from ZSM-22 and / or ZSM-35.

[0024] Among them, the present invention is based on molecular sieves with ten-membered ring channels such as ZSM-22 and ZSM-35, and preferably ZSM-22 and ZSM-35 molecular sieves with pore mouth sizes slightly smaller than that of ZSM-5 molecular sieve.

[0025] In a preferred embodiment, the acid used in the acid treatment is selected from at least one of inorganic acids and organic acids.

[0026] In a further preferred embodiment, the acid used in the acid treatment is selected from 1 - 6 organic acids (such as 2 - 4 organic acids), and at least one of inorganic acids, preferably selected from 2 - 4 organic acids, hydrochloric acid, sulfuric acid, and nitric acid.

[0027] In an even more preferred embodiment, the acid used in the acid treatment is selected from a combination of 2 - 4 organic acids and inorganic acids, preferably a combination of oxalic acid and hydrochloric acid, and more preferably the molar ratio of 2 - 4 organic acids to inorganic acids (or oxalic acid to hydrochloric acid) is (2 - 5):1.

[0028] For example, the molar ratio of 2 - 4 organic acids to inorganic acids (or oxalic acid to hydrochloric acid) is 2:1, 3:1, 4:1, or 5:1.

[0029] In one embodiment, the acid treatment is carried out using an acid solution with a concentration of 0.1 - 5 mol / L, preferably 0.1 - 0.5 mol / L.

[0030] For example, the concentration of the acid solution is 0.1, 0.2, 0.3, 0.4, or 0.5 mol / L.

[0031] In one embodiment, the mass ratio of the acid solution to the molecular sieve is 1 - 10, preferably 1.5 - 6.5.

[0032] Among them, the mass ratio of the acid solution to the molecular sieve is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0033] In a preferred embodiment, the acid treatment is carried out at 50 - 95 °C for 0.5 to 10 hours.

[0034] In a further preferred embodiment, the acid treatment is carried out at 70 - 95 °C for 0.5 to 5 hours.

[0035] For example, the acid treatment is carried out at 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, or 95 °C for 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours.

[0036] In a preferred embodiment, solid-liquid separation, washing, and drying are carried out after the acid treatment to obtain an acid-treated molecular sieve.

[0037] In a further preferred embodiment, the solid-liquid separation is suction filtration and / or centrifugal filtration, and / or the drying is carried out at 90-150 °C for 0.5-10 hours.

[0038] For example, the drying is carried out at 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, or 150 °C for 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours.

[0039] In a preferred embodiment, the base used in the base treatment is selected from at least one of inorganic bases and organic bases.

[0040] In a further preferred embodiment, the base used in the base treatment is selected from at least one of alkylammonium hydroxides and inorganic bases. Preferably, the alkylammonium hydroxide is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide, and the inorganic base is selected from at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0041] In an even more preferred embodiment, the base used in the base treatment is selected from a combination of an alkylammonium hydroxide and an inorganic base, preferably a combination of tetramethylammonium hydroxide and sodium hydroxide. Preferably, the molar ratio of the alkylammonium hydroxide to the inorganic base (or tetramethylammonium hydroxide to sodium hydroxide) is (1-5):1.

[0042] For example, the base used in the base treatment is selected from a combination of an alkylammonium hydroxide and an inorganic base, and the molar ratio of the alkylammonium hydroxide to the inorganic base (or tetramethylammonium hydroxide to sodium hydroxide) is 1:1, 2:1, 3:1, 4:1, or 5:1.

[0043] In a preferred embodiment, the base treatment is carried out using a base solution with a concentration of 0.1-1 mol / L, more preferably 0.2-0.4 mol / L.

[0044] For example, the concentration of the base solution is 0.1, 0.2, 0.3, or 0.4 mol / L.

[0045] In one embodiment, the mass ratio of the base solution to the molecular sieve is 2-10, preferably 3.5-4.5.

[0046] For example, the mass ratio of the base solution to the molecular sieve is 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0047] In a preferred embodiment, the base treatment is carried out at 50-95 °C for 0.5-10 hours.

[0048] In a further preferred embodiment, the alkali treatment is carried out at 70 - 95 °C for 0.5 to 5 hours.

[0049] For example, the alkali treatment is carried out at 50 °C, 60 °C, 70 °C, 80 °C, 90 °C or 95 °C for 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 hours.

[0050] In a preferred embodiment, solid-liquid separation, washing, drying and calcination are carried out after the alkali treatment to obtain an alkali-treated molecular sieve.

[0051] In a further preferred embodiment, the solid-liquid separation is suction filtration and / or centrifugal filtration, and / or, the drying is carried out at 90 - 150 °C for 0.5 to 10 hours, and / or, the calcination is carried out at 300 - 700 °C for 0.2 to 15 hours (preferably at 400 - 600 °C for 0.5 to 10 hours).

[0052] For example, the drying is carried out at 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C or 150 °C for 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 hours; the calcination is carried out at 400 °C, 450 °C, 500 °C, 550 °C or 600 °C for 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 hours.

[0053] Among them, the purpose of the acid treatment is to remove amorphous aluminum and adjust the acidity of the molecular sieve, and the purpose of the alkali treatment is to increase the pore volume and carbon capacity of the molecular sieve. The treatment sequence of acid first and then alkali in the present invention can avoid the influence of amorphous aluminum on the alkali treatment.

[0054] In a preferred embodiment, the Ca-containing compound is selected from one or more of calcium hydroxide, calcium halide, calcium carbonate, calcium acetate, calcium phosphate, and calcium hydrogen phosphate.

[0055] Among them, the role of introducing the Ca element is to improve the para-selectivity in the methylation reaction.

[0056] In a preferred embodiment, the weight ratio of the Ca-containing compound to the precursor is (0.1 - 5):100, preferably (0.2 - 2):100, where the weight of the Ca-containing compound is calculated based on the weight of the Ca element therein.

[0057] For example, the weight ratio of the Ca-containing compound to the precursor is 0.2:100, 0.4:100, 0.6:100, 0.8:100, 1:100, 1.2:100, 1.4:100, 1.6:100, 1.8:100 or 2:100, where the weight of the Ca-containing compound is calculated based on the weight of the Ca element therein.

[0058] In a preferred embodiment, the P-containing compound is selected from one or more of ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0059] In a preferred embodiment, the weight ratio of the P-containing compound to the precursor is (0.1 - 10):100, preferably (0.5 - 5):100, where the weight of the P-containing compound is calculated based on the weight of the P element therein.

[0060] For example, the weight ratio of the P-containing compound to the precursor is 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, or 5:100, where the weight of the P-containing compound is calculated based on the weight of the P element therein.

[0061] Among them, the role of P is to improve the hydrothermal stability of the molecular sieve and Ca.

[0062] In a preferred embodiment, in step (3), the calcination is carried out at 300 - 700 °C for 0.2 - 15 hours.

[0063] In a further preferred embodiment, in step (3), the calcination is carried out at 400 - 600 °C for 0.5 - 10 hours.

[0064] For example, in step (3), the calcination is carried out at 400 °C, 450 °C, 500 °C, 550 °C, or 600 °C for 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours.

[0065] The third object of the present invention is to provide a modified molecular sieve obtained by using the preparation method described in the second object of the present invention.

[0066] The fourth object of the present invention is a catalyst for catalytically aromatizing benzene and / or toluene in a shape-selective methylation reaction, which comprises the modified molecular sieve described in the first object of the present invention or the modified molecular sieve obtained by using the preparation method described in the second object of the present invention.

[0067] The fifth object of the present invention is to provide the application of the modified molecular sieve described in the first object of the present invention, or the modified molecular sieve obtained by using the preparation method described in the second object of the present invention, or the catalyst described in the fourth object of the present invention in the shape-selective methylation reaction of benzene and / or toluene aromatics.

[0068] A sixth object of the present invention is to provide a method for the shape-selective methylation reaction of benzene and / or toluene aromatic hydrocarbons, comprising: reacting benzene and / or toluene with methanol under hydrogenation conditions in the presence of the modified molecular sieve described in one of the objects of the present invention or the modified molecular sieve obtained by using the preparation method described in the second object of the present invention or the catalyst described in the fourth object of the present invention.

[0069] In a preferred embodiment, the reaction conditions for the shape-selective methylation reaction include: the reaction temperature is 350 to 550 °C, and / or the weight hourly space velocity of benzene and / or toluene is 1 to 10 h -1 , and / or the molar ratio of benzene and / or toluene to methanol is 1 to 6, and / or the molar ratio of hydrogen to benzene and / or toluene is 0.5 to 10, and / or the reaction pressure is 0.1 to 3.0 MPa.

[0070] In a further preferred embodiment, the reaction conditions for the shape-selective methylation reaction are: the reaction temperature is 400 to 500 °C, the weight hourly space velocity of benzene and / or toluene is 1.5 to 6.0 h -1 , the molar ratio of benzene and / or toluene to methanol is 1.5 to 3.0, the molar ratio of hydrogen to benzene and / or toluene is 1 to 8, and the reaction pressure is 0.3 to 1.5 MPa.

[0071] For example, the reaction conditions for the shape-selective methylation reaction are: the reaction temperature is 350 °C, 400 °C, 450 °C, 500 °C or 550 °C, and / or the weight hourly space velocity of benzene and / or toluene is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 h -1 , and / or the molar ratio of benzene and / or toluene to methanol is 1, 2, 3, 4, 5 or 6, and / or the molar ratio of hydrogen to benzene and / or toluene is 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, and / or the reaction pressure is 0.1, 1, 1.5, 2, 2.5, 3 or 3.0 MPa.

[0072] In the present invention, the endpoints and any values within the disclosed ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following text, the various technical solutions can be combined with each other in principle to obtain new technical solutions, which should also be regarded as specifically disclosed herein.

[0073] Compared with the prior art, the present invention has the following beneficial effects: The modified molecular sieve is obtained by acid treatment, alkali treatment and element modification. After the modified molecular sieve is formed, a catalyst for catalytically selective methylation of benzene and / or toluene in the aromatic hydrocarbon can be obtained. This catalyst not only has suitable catalytic activity, but also reduces the cumbersome operation and environmental pressure problems brought by the traditional impregnation method while obtaining high para selectivity. Detailed Embodiments

[0074] The present invention will be specifically described below with reference to specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0075] In addition, it should be noted that the various specific technical features described in the following detailed embodiments can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0076] Furthermore, any combination can be made between different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions formed thereby belong to a part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0077] If there is no special limitation on the raw materials used in the examples and comparative examples, they are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0078] In the present invention, the acid amount of the molecular sieve is measured by ammonia temperature-programmed desorption, and the test instrument is the AutoChem2920 fully automatic temperature-programmed chemisorption instrument of Micrometrics. The pore properties of the zeolite molecular sieve are measured by the low-temperature nitrogen adsorption method, and the instrument is the 3Flex-Physisorption type fully automatic specific surface and pore size distribution analyzer of Micromeritics.

[0079] Example 1

[0080] a. Take 40 g of the original powder of ZSM-22 molecular sieve with a silica-alumina ratio of 25, add 64 g of nitric acid with a concentration of 0.4 mol / L, stir at 80 °C for 2 h. After the obtained product is filtered, washed, and dried at 120 °C for 10 h, 28 g of sample Z2-A-1 is obtained.

[0081] b. Take 28 g of Z2-A-1 molecular sieve and contact it with 100 g of sodium hydroxide solution with a concentration of 0.2 mol / L at 70 °C for 1.5 hours. The obtained product is subjected to suction filtration, washing, drying at 90 °C for 6 h, and then calcined at 550 °C for 4 hours to obtain molecular sieve Z2-A-1-B.

[0082] c. Add 20 g of the Z2-A-1-B molecular sieve obtained in step b to an appropriate amount of calcium hydroxide (where the weight ratio of calcium element to Z2-A-1-B molecular sieve is 0.202:100) and diammonium hydrogen phosphate (where the weight ratio of phosphorus element to Z2-A-1-B molecular sieve is 0.6759:100), mix them in a mortar for about 1 hour, and then calcine them in a muffle furnace under an air atmosphere at 550 °C for 4 h to directly obtain molecular sieve ZSM-22-1-Ca 0.2-P 0.67, where the Ca element content is 0.2 wt% and the phosphorus element content is 0.67 wt%. After pressing the molecular sieve, take 20-40 mesh catalyst particles ZSM-22-1-Ca0.2-P 0.67 for evaluation. The total acid amount of molecular sieve ZSM-22-1-Ca0.2-P0.67 is 0.47 mmol / g, and the detailed pore structure data are shown in Table 1.

[0083] d. Using toluene and methanol as raw materials, carry out the methylation reaction of toluene with methanol over catalyst ZSM-22-1-Ca0.2-P 0.67 in a fixed-bed reactor under hydrogenation conditions. The inner diameter of the reactor is 30 mm and the length is 100 mm, made of stainless steel. The catalyst bed is filled with glass beads with a particle size of 3 mm at both the top and bottom to play a role in gas flow distribution and support, and 5 g of the above catalyst is filled in the reactor. The weight hourly space velocity of the reaction toluene is 4 h -1 , the reaction temperature is 460 °C, the pressure is 0.5 MPa, the molar ratio of toluene to methanol is 2:1, and the molar ratio of hydrogen to toluene is 6:1. The reaction performance is shown in Table 2.

[0084] Example 2

[0085] a. Take 40 g of the original powder of ZSM-35 molecular sieve with a silica-alumina ratio of 12, add 64 g of citric acid with a concentration of 0.5 mol / L, stir at 70 °C for 5 h. The obtained product is subjected to suction filtration, washing, drying at 150 °C for 0.5 h, and then 27.5 g of sample Z3-A-1 is obtained.

[0086] b. Take 27.5 g of Z3-A-1 molecular sieve and contact it with 100 g of tetrapropylammonium hydroxide solution with a concentration of 0.25 mol / L at 95 °C for 0.5 hour. The obtained product is subjected to suction filtration, washing, drying at 120 °C for 5 h, and then calcined at 550 °C for 4 hours to obtain molecular sieve Z3-A-1-B. The detailed pore structure data are shown in Table 1.

[0087] c. Add 20 g of the Z3-A-1-B molecular sieve obtained in step b to an appropriate amount of calcium chloride (where the weight ratio of calcium element to the Z2-A-1-B molecular sieve is 2.05:100) and diammonium hydrogen phosphate (where the weight ratio of phosphorus element to the Z2-A-1-B molecular sieve is 0.513:100), mix them in a mortar for about 1 hour, and then calcine them in a muffle furnace under an air atmosphere at 550 °C for 4 h to directly obtain the molecular sieve ZSM-35-1-Ca 2-P 0.5, where the Ca element content is 2 wt% and the phosphorus element content is 0.5 wt%. After pressing this molecular sieve, take 20-40 mesh catalyst particles ZSM-35-1-Ca2-P 0.5 for evaluation. The total acid amount of the molecular sieve ZSM-35-1-Ca2-P 0.5 is 0.42 mmol / g, and the detailed pore structure data are shown in Table 1.

[0088] d. Using toluene and methanol as raw materials, carry out the methylation reaction of toluene with methanol over the catalyst ZSM-35-1-Ca2-P 0.5 in a fixed-bed reactor under a hydrogen-containing condition. The inner diameter of the reactor is 30 mm, the length is 100 mm, and the material is stainless steel. Glass beads with a particle size of 3 mm are filled above and below the catalyst bed to play a role in gas flow distribution and support, and 5 g of the above catalyst is filled in the reactor. The weight hourly space velocity of the reaction toluene is 4 h -1 , the reaction temperature is 460 °C, the pressure is 0.5 MPa, the molar ratio of toluene to methanol is 2:1, and the molar ratio of hydrogen to toluene is 8:1. The reaction performance is shown in Table 2.

[0089] Example 3

[0090] a. Take 40 g of the ZSM-22 molecular sieve raw powder with a silica-alumina ratio of 25, add 64 g of oxalic acid with a concentration of 0.3 mol / L, stir at 95 °C for 0.5 h. After the obtained product is filtered, washed, and dried at 90 °C for 10 h, 29 g of Z2-A-2 is obtained.

[0091] b. Take 29 g of the Z2-A-2 molecular sieve and contact it with 120 g of a potassium hydroxide solution with a concentration of 0.4 mol / L at 85 °C for 3.0 h. After the obtained product is filtered, washed, and dried at 150 °C for 0.5 h, it is calcined at 550 °C for 4 h to obtain the molecular sieve Z2-A-2-B.

[0092] c. Add 20 g of the Z2-A-2-B molecular sieve obtained in step b to an appropriate amount of calcium chloride (where the weight ratio of calcium element to the Z2-A-1-B molecular sieve is 2.06:100) and ammonium phosphate (where the weight ratio of phosphorus element to the Z2-A-1-B molecular sieve is 0.979:100), mix them in a mortar for about 1 hour, and then calcine them in a muffle furnace under an air atmosphere at 550 °C for 4 h to directly obtain the molecular sieve ZSM-22-2-Ca2-P 0.95, where the Ca element content is 2 wt% and the phosphorus element content is 0.95 wt%. After pressing this molecular sieve, take 20-40 mesh catalyst particles ZSM-22-2-Ca2-P 0.95 for evaluation. The total acid amount of the molecular sieve ZSM-22-2-Ca2-P 0.95 is 0.46 mmol / g, and the detailed pore structure data are shown in Table 1.

[0093] d. Using toluene and methanol as raw materials, carry out the methylation reaction of toluene with methanol over the catalyst ZSM-22-2-Ca2-P 0.95 in a fixed-bed reactor under a hydrogen-containing condition. The inner diameter of the reactor is 30 mm and the length is 100 mm, made of stainless steel. The upper and lower parts of the catalyst bed are filled with glass beads with a particle size of 3 mm to play the role of gas flow distribution and support, and 5 g of the above catalyst is filled in the reactor. The weight hourly space velocity of the reaction toluene is 4 h -1 , the reaction temperature is 460 °C, the pressure is 0.5 MPa, the molar ratio of toluene to methanol is 2:1, and the molar ratio of hydrogen to toluene is 1:1. The reaction performance is shown in Table 2.

[0094] Example 4

[0095] a. Take 40 g of the ZSM-35 molecular sieve raw powder with a silica-alumina ratio of 10, add 64 g of nitric acid with a concentration of 0.1 mol / L, stir at 80 °C for 2 h. After the obtained product is filtered by suction, washed, and dried at 100 °C for 6 h, 25 g of Z3-A-2 is obtained.

[0096] b. Take 27.5 g of the Z3-A-1 molecular sieve and contact it with 100 g of ammonia water solution with a concentration of 0.3 mol / L at 70 °C for 5 hours. After the obtained product is filtered by suction, washed, and dried at 90 °C for 10 h, it is calcined at 550 °C for 4 hours to obtain the molecular sieve Z3-A-2-B. The detailed pore structure data are shown in Table 1.

[0097] c. Add 20 g of the Z3-A-2-B molecular sieve obtained in step b to an appropriate amount of calcium carbonate (where the weight ratio of calcium element to the Z2-A-1-B molecular sieve is 2.15:100) and ammonium dihydrogen phosphate (where the weight ratio of phosphorus element to the Z2-A-1-B molecular sieve is 5.376:100), mix them in a mortar for about 1 hour, and then calcine them in a muffle furnace under an air atmosphere at 550 °C for 4 h to directly obtain the molecular sieve ZSM-35-2-Ca 0.2-P 5, where the Ca element content is 0.20 wt% and the phosphorus element content is 5 wt%. Take 20-40 mesh catalyst particles ZSM-35-2-Ca0.2-P 5 of this molecular sieve after tabletting for evaluation. The total acid amount of the molecular sieve ZSM-35-2-Ca0.2-P 5 is 0.40 mmol / g, and the detailed pore structure data are shown in Table 1.

[0098] C. Using toluene and methanol as raw materials, the catalyst ZSM-35-2-Ca0.2-P 5 is used for the methylation reaction of toluene with methanol in a fixed-bed reactor under a hydrogen-containing condition. The inner diameter of the reactor is 30 mm and the length is 100 mm, made of stainless steel. Glass beads with a particle size of 3 mm are filled above and below the catalyst bed to play a role in gas flow distribution and support, and 5 g of the above catalyst is filled in the reactor. The weight hourly space velocity of the reaction toluene is 4 h -1 , the reaction temperature is 460 °C, the pressure is 0.5 MPa, the molar ratio of toluene to methanol is 2:1, and the molar ratio of hydrogen to toluene is 5:1. The reaction performance is shown in Table 2.

[0099] Example 5

[0100] Repeat the process of Example 1, with the difference that an equal amount of ZSM-5 molecular sieve is used to replace the ZSM-22 molecular sieve.

[0101] Example 6

[0102] Repeat the process of Example 1, with the difference that an equal weight of mixed acid is used to replace the nitric acid, where the mixed acid is a mixture of oxalic acid and hydrochloric acid, and the mixed molar ratio of the two is 2:1; in the mixed acid, the total concentration of oxalic acid and hydrochloric acid is 0.4 mol / L.

[0103] Example 7

[0104] Repeat the process of Example 1, with the difference that an equal weight of mixed acid is used to replace the nitric acid, where the mixed acid is a mixture of oxalic acid and hydrochloric acid, and the mixed molar ratio of the two is 4:1; in the mixed acid, the total concentration of oxalic acid and hydrochloric acid is 0.4 mol / L.

[0105] Example 8

[0106] Repeat the process of Example 1, with the difference that: an equal weight of mixed base is used to replace the sodium hydroxide solution therein, wherein the mixed base is a mixture of tetramethylammonium hydroxide and sodium hydroxide, and the mixed molar ratio of the two is 2:1; in the mixed base, the total concentration of tetramethylammonium hydroxide and sodium hydroxide is 0.2 mol / L.

[0107] Example 9

[0108] Repeat the process of Example 1, with the difference that: an equal weight of mixed base is used to replace the sodium hydroxide solution therein, wherein the mixed base is a mixture of tetramethylammonium hydroxide and sodium hydroxide, and the mixed molar ratio of the two is 4:1; in the mixed base, the total concentration of tetramethylammonium hydroxide and sodium hydroxide is 0.2 mol / L.

[0109] Example 10

[0110] Repeat the process of Example 1, with the differences that: (1) an equal weight of mixed acid is used to replace the nitric acid therein, wherein the mixed acid is a mixture of oxalic acid and hydrochloric acid, and the mixed molar ratio of the two is 3:1; in the mixed acid, the total concentration of oxalic acid and hydrochloric acid is 0.4 mol / L. (2) an equal weight of mixed base is used to replace the sodium hydroxide solution therein, wherein the mixed base is a mixture of tetramethylammonium hydroxide and sodium hydroxide, and the mixed molar ratio of the two is 3:1; in the mixed base, the total concentration of tetramethylammonium hydroxide and sodium hydroxide is 0.2 mol / L.

[0111] Comparative Example 1

[0112] Repeat the process of Example 1, with the difference that: the alkali treatment is carried out first and then the acid treatment is carried out, and other conditions remain unchanged.

[0113] Comparative Example 2

[0114] Repeat the process of Example 1, with the difference that: the alkali treatment is not carried out, and the precursor is obtained after the acid treatment, and the subsequent process is carried out.

[0115] Comparative Example 3

[0116] Repeat the process of Example 1, with the difference that: the acid treatment is not carried out, and the precursor is obtained after the alkali treatment, and the subsequent process is carried out.

[0117] Table 1 Detailed data of the pore structure of the samples in the examples and comparative examples

[0118]

[0119]

[0120] Table 2 Toluene methanol methylation reaction performance in the examples and comparative examples

[0121]

[0122]

[0123] The present invention has been described in detail above in connection with specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications, or improvements can be made to the technical solutions and their implementation manners of the present invention, and all of these fall within the scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. A modified molecular sieve containing Ca element and P element, and the pore volume of the modified molecular sieve reaches 0.15 - 0.60 cm 3 / g, the mesoporous specific surface area reaches 30 - 100 m 2 / g. The ratio of the amount of weak acid to the amount of strong acid in the modified molecular sieve is (4.2 - 10):1, and the ratio of B acid to L acid in the modified molecular sieve is (2 - 10):

1. The molecular sieve is selected from at least one of ZSM-22, ZSM-35, and ZSM-5. Based on 100 wt% of the modified molecular sieve, the content of Ca element is 0.1 - 5 wt%, and the content of P element is 0.1 - 10 wt%.

2. The modified molecular sieve according to claim 1, wherein, the ratio of the amount of weak acid to the amount of strong acid in the modified molecular sieve is (4.2 - 8):

1.

3. The modified molecular sieve according to claim 1, wherein, the ratio of Bronsted acid to Lewis acid in the modified molecular sieve is (2.5 - 6):

1.

4. The modified molecular sieve according to claim 1, wherein, The pore volume of the modified molecular sieve reaches 0.20 - 0.50 cm 3 / g, and the specific surface area of mesopores reaches 40 - 70 m 2 / g.

5. The modified molecular sieve according to claim 1, wherein, the molecular sieve is selected from ZSM - 22 and / or ZSM - 35.

6. A preparation method of a modified molecular sieve for preparing the modified molecular sieve according to any one of claims 1 - 5, the preparation method comprises: (1) performing acid treatment and alkali treatment on the molecular sieve in sequence to obtain a precursor; (2) mixing the precursor with a Ca - containing compound and a P - containing compound, and grinding to obtain a mixture; (3) calcining the mixture to obtain the modified molecular sieve.

7. The preparation method according to claim 6, wherein, the acid used in the acid treatment is selected from at least one of inorganic acids and organic acids; and / or, the acid treatment is carried out using an acid solution with a concentration of 0.1 - 5 mol / L; and / or, the acid treatment is carried out at 50 - 95 °C for 0.5 - 10 hours; and / or, solid - liquid separation, washing and drying are carried out after the acid treatment to obtain an acid - treated molecular sieve.

8. The preparation method according to claim 6, wherein, The acid used in the acid treatment is selected from at least one of organic acids having C 1 -C 6 , hydrochloric acid, sulfuric acid, nitric acid; and / or the acid treatment is carried out using an acid solution, and the mass ratio of the acid solution to the molecular sieve is 1 - 10.

9. The preparation method according to claim 6, wherein, the base used in the alkali treatment is selected from at least one of inorganic bases and organic bases; and / or, the alkali treatment is carried out using an alkali solution with a concentration of 0.1 - 1 mol / L; and / or, the alkali treatment is carried out at 50 - 95 °C for 0.5 - 10 hours; and / or, solid - liquid separation, washing, drying and calcining are carried out after the alkali treatment to obtain an alkali - treated molecular sieve.

10. The preparation method according to claim 6, wherein, the base used in the alkali treatment is selected from at least one of alkyl ammonium hydroxides and inorganic bases; and / or, the alkali treatment is carried out using an alkali solution, and the mass ratio of the alkali solution to the molecular sieve is 2 - 10.

11. The preparation method according to claim 10, wherein, the alkyl ammonium hydroxide is selected from at least one of tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide and tetrapropyl ammonium hydroxide, and the inorganic base is selected from at least one of sodium hydroxide, potassium hydroxide and ammonia water.

12. The preparation method according to claim 6, wherein, the molecular sieve is selected from at least one of ZSM - 22, ZSM - 35 and ZSM - 5; and / or, the Ca - containing compound is selected from one or more of calcium hydroxide, calcium halide, calcium carbonate, calcium acetate, calcium phosphate and calcium hydrogen phosphate; the P - containing compound is selected from one or more of ammonium phosphate, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

13. The preparation method according to claim 6, wherein, The molecule is selected from ZSM-22 and / or ZSM-35; and / or, The weight ratio of the Ca-containing compound to the precursor is (0.1-5):100, wherein the weight of the Ca-containing compound is calculated based on the weight of the Ca element therein; The weight ratio of the P-containing compound to the precursor is (0.1-10):100, wherein the weight of the P-containing compound is calculated based on the weight of the P element therein.

14. The preparation method according to any one of claims 6 to 13, characterized in that, In step (3), the calcination is carried out at 300-700 °C for 0.2-15 hours.

15. A modified molecular sieve obtained by using the preparation method according to any one of claims 6 to 14.

16. A catalyst for catalytically selective methylation of benzene and / or toluene in an aromatic hydrocarbon, which comprises the modified molecular sieve according to any one of claims 1 to 5 or the modified molecular sieve obtained by using the preparation method according to any one of claims 6 to 14.

17. The application of the modified molecular sieve according to any one of claims 1 to 5 or the modified molecular sieve obtained by using the preparation method according to any one of claims 6 to 14 or the catalyst according to claim 16 in the selective methylation of benzene and / or toluene in an aromatic hydrocarbon.

18. A method for selective methylation of benzene and / or toluene in an aromatic hydrocarbon, comprising: Reacting benzene and / or toluene with methanol under hydrogenation conditions in the presence of the modified molecular sieve according to any one of claims 1 to 5 or the modified molecular sieve obtained by using the preparation method according to any one of claims 6 to 14 or the catalyst according to claim 16.

19. The method according to claim 18, characterized in that, The reaction conditions of the shape-selective methylation reaction include: the reaction temperature is 350 to 550 °C, and / or the weight hourly space velocity of benzene and / or toluene is 1 to 10 h -1 , and / or the molar ratio of benzene and / or toluene to methanol is 1 to 6, and / or the molar ratio of hydrogen to benzene and / or toluene is 0.5 to 10, and / or the reaction pressure is 0.1 to 3.0 MPa.

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