BETA / MOR symbiotic molecular sieve and preparation method thereof

Abstract

The invention discloses a BETA / MOR symbiotic molecular sieve and a preparation method thereof. The atomic ratio of the surface aluminum SSAR in the BETA / MOR symbiotic molecular sieve to the internal aluminum ISAR in the molecular sieve is 0.1-0.8, preferably 0.5-0.8. The molecular sieve provided by the invention has the characteristics of strong phase composition proportion adjustability, silicon-rich surface and aluminum-rich interior, and can be used as a catalyst component for transalkylation and other reactions.

Description

Technical Field

[0001] The invention relates to the field of molecular sieves, and in particular to a BETA / MOR symbiotic molecular sieve and a preparation method thereof. Background Art

[0002] Symbiotic molecular sieves are a type of molecular sieve material with a composite structure of multiple components. Its pores and acid properties are an organic combination of the pores and acid properties of its constituent molecular sieves. It has multi-level pores and reasonable acid distribution that are superior to those of individual molecular sieves. When dealing with complex reactants with different molecular diameters, it can exert a synergistic catalytic effect, so it exhibits excellent catalytic performance. In addition, compared with simply mechanically mixed mixed molecular sieves, symbiotic molecular sieves have a higher degree of compositeness of their pores and acid properties, and often exhibit better catalytic performance.

[0003] At present, there are many reports on the synthesis of symbiotic molecular sieves. CN1397493A discloses a type of two-phase symbiotic molecular sieve with a twelve-membered ring structure and a synthesis method thereof. The method is to mix a silicon source, an aluminum source, an alkali source, a template agent, and water in a certain proportion and a batching order, and hydrothermally crystallize a symbiotic molecular sieve containing two components such as BETA and MOR zeolite. CN1648046A discloses a preparation method for a mixed crystal material of MOR zeolite and BETA molecular sieve. The method is to mix a silicon source, an aluminum source, an alkali source, a template agent, a fluoride, water, a seed, in a certain proportion and a batching order, and hydrothermally crystallize a symbiotic molecular sieve containing two components such as BETA and MOR zeolite. CN101177276A discloses a binary composite molecular sieve with a core-shell structure and a preparation method thereof. The implementation of the method is divided into two major steps. First, a BETA molecular sieve is synthesized using a template agent, and then aluminum, a template agent, and a base are added to hydrothermally crystallize a binary composite molecular sieve containing two components of BETA and mordenite. CN101514009A discloses a MOR zeolite / BETA molecular sieve / Y molecular sieve symbiotic material and a synthesis method thereof, wherein the method comprises mixing a silicon source, an aluminum source, an alkali source, a template agent, water, and a Y-type molecular sieve seed in a certain proportion and in a batching order, and hydrothermally crystallizing a symbiotic molecular sieve containing three components of MOR zeolite, BETA, and Y. CN101514010A discloses a MOR zeolite / BETA molecular sieve / analcimite porous symbiotic material and a preparation method thereof, wherein the method comprises mixing a silicon source, an aluminum source, an alkali source, a template agent, and water in a certain proportion and in a batching order, and hydrothermally crystallizing a symbiotic molecular sieve containing three components of MOR zeolite, BETA, and analcite. CN101514011A discloses a MOR zeolite / BETA molecular sieve / MCM-22 three-phase symbiotic molecular sieve and a synthesis method thereof, wherein the method comprises mixing a silicon source, an aluminum source, an alkali source, a template, water, and MCM-22 molecular sieve seeds in a certain proportion and a batching order, and hydrothermally crystallizing a composite molecular sieve containing three components of MOR zeolite, BETA, and MCM-22. CN101514024A discloses a BETA molecular sieve / Magadiite / MOR zeolite symbiotic material and a synthesis method thereof, wherein the method comprises mixing a silicon source, an aluminum source, an alkali source, a template, water, and mordenite zeolite seeds in a certain proportion and a batching order, and hydrothermally crystallizing a symbiotic molecular sieve containing three components of BETA, Magadiite, and MOR zeolite.

[0004] Although the symbiotic molecular sieves synthesized by the above method show better catalytic performance than mechanically mixed molecular sieves to a certain extent, for the BETA / MOR symbiotic molecular sieves, how to further exert the advantages of their pores and acid properties still needs further study. Summary of the invention

[0005] The present invention provides a new BETA / MOR symbiotic molecular sieve and a preparation method thereof to solve the problems of the prior art. The molecular sieve has the characteristics of strong adjustability of phase composition ratio, silicon-rich surface and aluminum-rich interior.

[0006] The first aspect of the present invention provides a BETA / MOR symbiotic molecular sieve, wherein the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of is 0.1 to 0.8, preferably 0.5 to 0.8.

[0007] Furthermore, the BETA / MOR symbiotic molecular sieve has the following schematic chemical composition, in terms of molar ratio: nSiO 2 / Al 2 O 3 , wherein 10≤n≤100, preferably 20≤n≤50.

[0008] Furthermore, in the BETA / MOR symbiotic molecular sieve, the mass ratio of BETA / MOR is 10 / 90 to 90 / 10, preferably 25 / 75 to 75 / 25.

[0009] Furthermore, the specific surface area of ​​the BETA / MOR symbiotic molecular sieve is 400 to 550 m 2 / g, pore volume is 0.10~0.30cm 3 / g, preferably 0.20 to 0.30 cm 3 / g.

[0010] The second aspect of the present invention provides a method for preparing the above-mentioned BETA / MOR symbiotic molecular sieve, comprising:

[0011] (1) mixing a silicon source, an aluminum source, a first template T1, a second template T2, an alkali source and water, adjusting the pH to 9-13, and then adding MOR seed crystals to obtain a molecular sieve precursor;

[0012] (2) The molecular sieve precursor described in (1) is first subjected to a first-stage hydrothermal crystallization, and then the temperature is increased to perform a second-stage hydrothermal crystallization to obtain the BETA / MOR symbiotic molecular sieve.

[0013] Furthermore, the MOR seed crystal in step (1) has a silicon-aluminum molar ratio (SiO 2 / Al 2 O 3 ) is a MOR molecular sieve seed crystal with a content of 15 to 25.

[0014] Furthermore, the silicon source in step (1) is selected from water glass, preferably containing 15 to 40 wt% SiO 2, water glass with a modulus of 3.0 to 3.5; the aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, boehmite, sodium aluminate, aluminum nitrate, aluminum isopropoxide, and aluminum hydroxide, preferably sodium aluminate and / or aluminum sulfate; the alkali source is selected from ammonia water and / or alkaline hydroxide, preferably NaOH; the first template is tetraethylammonium hydroxide (TEAOH) and / or tetraethylammonium bromide (TEABr); the second template is sodium fluoride.

[0015] Furthermore, the silicon source, aluminum source, first template T1, second template T2, alkali source and water in step (1) are prepared in a molar ratio of (1-6) alkali source: (30-55) SiO 2 :Al 2 O 3 :(8~15)T1:(100~1000)H 2 O: (2~8) T2 mixed to form a sol.

[0016] Furthermore, the mass content of the MOR seed crystals in the molecular sieve precursor in step (1) is 20% to 55%.

[0017] Furthermore, in step (2), the hydrothermal crystallization conditions of the first stage are: 100-130° C. hydrothermal crystallization for 24-48 hours; and the hydrothermal crystallization conditions of the second stage are 160-200° C. hydrothermal crystallization for 24-48 hours.

[0018] Furthermore, after the hydrothermal crystallization in the second stage of step (2), conventional washing and drying treatments in the art may be performed.

[0019] The third aspect of the present invention provides that the above-mentioned BETA / MOR symbiotic molecular sieve can be used in catalytic fields, such as alkyl transfer, lightweighting of heavy aromatics, toluene / benzyl alcohol methylation and other reactions.

[0020] The BETA / MOR symbiotic molecular sieve is preferably subjected to ammonium exchange before use in the catalytic field. The ammonium exchange can be carried out by conventional methods in the art.

[0021] The transalkylation reaction is preferably a transalkylation reaction of toluene and trimethylbenzene, and the reaction conditions are: temperature of 250-450°C, reaction pressure of 1-5 MPa, reaction hydrogen-to-hydrocarbon molar ratio of 1-5:1, toluene-to-trimethylbenzene molar ratio of 0.1-10:1 in the feed, and feed mass space velocity of toluene and trimethylbenzene of 1-6 h -1 .

[0022] In the prior art, due to the obvious confined catalytic effect of the acidic sites in the molecular sieve pores, it has obvious advantages in improving product selectivity and inhibiting the formation of carbon deposit precursors. In contrast, the non-pore acidity on the outer surface of the molecular sieve, because there is no obvious confined catalytic effect, will lead to the generation of macromolecular byproducts and even carbon deposit precursors, which will reduce the catalyst selectivity. The inventors have found that for the field of molecular sieve catalyst synthesis, the differentiation of aluminum distribution on the inner and outer surfaces of molecular sieve materials has become the key and challenge to solving the above problems. Although the existing methods for synthesizing molecular sieves involve preparation methods for symbiotic molecular sieves containing BETA and mordenite components, it has been found that there is a common defect, that is, the internal and external silicon and aluminum distribution of the prepared BETA / MOR symbiotic molecular sieves is basically the same, and there is no obvious concentration gradient. Although the BETA / MOR symbiotic molecular sieves obtained by this method can sometimes obtain better catalytic performance than mechanically mixed BETA and MOR molecular sieves, there is no obvious advantage in further exerting and improving the pore confined catalytic effect. In addition, for the synthesis of symbiotic molecular sieve materials, flexible and adjustable composition of the two phases is also an important direction of synthesis. Although the existing synthesis method can synthesize BETA / MOR symbiotic molecular sieves, the controllability of the composition ratio of BETA and MOR is insufficient.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] The BETA / MOR symbiotic molecular sieve provided by the present invention can effectively adjust the BETA / MOR phase ratio, so that the raw material complexity and applicability are higher. The aluminum distribution characteristics of the silicon-rich surface and the aluminum-rich interior can effectively reduce the non-selective catalytic reaction on the outer surface of the molecular sieve, inhibit the formation of macromolecular by-products and colloids, and improve the catalyst activity and selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the XRD pattern of the BETA / MOR symbiotic molecular sieve obtained in Example 1;

[0026] Figure 2 This is the SEM image of the BETA / MOR symbiotic molecular sieve obtained in Example 1;

[0027] Figure 3 The XRD pattern of the BETA molecular sieve containing a small amount of ZSM-5 impurity crystals obtained in Comparative Example 3;

[0028] Figure 4 This is a SEM image of the BETA molecular sieve containing a small amount of ZSM-5 impurity crystals obtained in Comparative Example 3;

[0029] Figure 5 This is the XRD pattern of the pure MOR molecular sieve obtained in Comparative Example 5;

[0030] Figure 6This is the SEM image of the pure MOR molecular sieve obtained in Comparative Example 5. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0032] The raw materials used in the examples and comparative examples of the present invention are commercially available and have an analytical purity (AR).

[0033] In the context of this specification, the aluminum distribution value characterized by XPS-argon ion etching technology is S, S is S SAR with I SAR The ratio of SAR is the atomic percentage of aluminum on the surface of the molecular sieve obtained by direct XPS testing, I SAR It is the atomic percentage of aluminum inside the molecular sieve tested by XPS after argon ion etching, and the argon ion etching depth is 20-50nm.

[0034] In the context of this specification, the so-called specific surface area refers to the total area of ​​a sample per unit mass, including the internal surface area and the external surface area. Non-porous samples only have external surface area, such as silicate cement, some clay mineral powders, etc.; porous and porous samples have external surface area and internal surface area, such as asbestos fiber, diatomaceous earth and molecular sieves, etc. In the context of this specification, the so-called pore volume refers to the volume of pores per unit mass of porous materials. The so-called total pore volume refers to the volume of all pores per unit mass of molecular sieves (generally only pores with a pore diameter of less than 50 nanometers are counted). The pore structure parameters of molecular sieves, such as total pore volume and total specific surface area, are measured by physical adsorption instrument (such as TriStar 3000 physical adsorption instrument of Mack Instruments, USA) to obtain nitrogen physical adsorption and desorption isotherms, and then calculated by BET method and t-plot method. The experimental conditions for molecular sieves are: measurement temperature -196°C, and the molecular sieves are vacuum pretreated at 300°C for 10 hours before measurement.

[0035] In the context of this specification, including in the following examples and comparative examples, the model of the scanning electron microscope (SEM) of the molecular sieve is S-4800II field emission scanning electron microscope.

[0036] In the context of this specification, the structure of the molecular sieve is determined by an X-ray diffraction spectrum (XRD), and the X-ray diffraction spectrum (XRD) is determined by an X-ray powder diffractometer, including in the following embodiments and comparative examples, the model of the X-ray powder diffractometer of the molecular sieve is a Panalytical X PERPRO X-ray powder diffractometer, the physical phase of the sample is analyzed, CuKα ray source nickel filter, 2θ scanning range 5 to 50°, operating voltage 40KV, current 40mA, scanning rate 10° / min.

[0037] In the present invention, the overall reaction conversion and xylene selectivity are defined as follows:

[0038]

[0039]

[0040] Example 1

[0041] BETA / MOR molecular sieve synthesis method: take the silicon-aluminum molar ratio (SiO 2 / Al 2 O 3 ) is 20 MOR molecular sieve as seed, water glass (containing 28% SiO 2 , modulus 3.0-3.5) as silicon source, sodium aluminate as aluminum source; tetraethylammonium hydroxide (TEAOH) as the first template, sodium fluoride as the second template, and NaOH as the alkali source. The molecular sieve synthetic glue composition is: n(Na 2 O) / n(SiO 2 ) / n(Al 2 O 3 ) / n(TEAOH / ) / n(H 2 O) / n(NaF)=1.5:40:1:10:700:5, adjust the pH to 12 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 20%. The above precursor is first hydrothermally crystallized at 120°C for 48 hours, and then hydrothermally crystallized at 180°C for 48 hours to obtain a symbiotic molecular sieve, namely BETA / MOR symbiotic molecular sieve. Among them, the mass ratio of BETA / MOR phase is 35 / 65, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO is 0.55. 2 / Al 2 O 3 The molar ratio is 29.

[0042] The XRD pattern of the intergrowth molecular sieve in this example is shown in Figure 1 ,Depend on Figure 1It can be seen that it has typical characteristic peaks of BETA and MOR molecular sieves.

[0043] The SEM image of the intergrowth molecular sieve in this example is shown in Figure 2 ,Depend on Figure 2 It can be seen that there is a morphology in which large MOR particles and small BETA molecular sieve particles coexist.

[0044] The specific surface area of ​​the BETA / MOR symbiotic molecular sieve in this case is 410m 2 / g, pore volume is 0.25cm 3 / g.

[0045] The above molecular sieve was used for the transalkylation reaction of toluene and trimethylbenzene after ammonium exchange. The reaction conditions were as follows: temperature of 350°C, reaction pressure of 3.0 MPa, reaction hydrogen-hydrocarbon molar ratio of 3:1 mol / mol, molar ratio of toluene to trimethylbenzene in the feed of 1:1 mol / mol, feed mass space velocity of toluene and trimethylbenzene of 3 h -1 The total reaction conversion rate is 48% and the xylene selectivity is 97%.

[0046] Example 2

[0047] BETA / MOR molecular sieve synthesis method: take the silicon-aluminum molar ratio (SiO 2 / Al 2 O 3 ) is 25 MOR molecular sieve as seed, water glass (containing 28wt% SiO 2 , modulus 3.0-3.5) as silicon source, aluminum sulfate as aluminum source; tetraethylammonium bromide (TEABr) as first template, sodium fluoride as second template, NaOH as alkali source. Molecular sieve synthetic glue composition: n(Na 2 O) / n(SiO 2 ) / n(Al 2 O 3 ) / n(TEABr / ) / n(H 2 O) / n(NaF)=2.0:55:1:12:980:6, adjust the pH to 11 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 35%. The above precursor is first hydrothermally crystallized at 130°C for 24 hours, and then hydrothermally crystallized at 170°C for 48 hours to obtain a BETA / MOR symbiotic molecular sieve. Among them, the BETA / MOR phase mass ratio is 56 / 44, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO is 0.60. 2 / Al 2 O 3 The molar ratio is 31.

[0048] The XRD pattern of the intergrowth molecular sieve in this example is similar to Figure 1 Similarly, the SEM images of the co-existing molecular sieves in this example are similar to Figure 2 Similarly, the specific surface area of ​​the BETA / MOR symbiotic molecular sieve in this example is 466m 2 / g, pore volume is 0.27cm 3 / g.

[0049] The above molecular sieve was used for the transalkylation reaction of toluene and trimethylbenzene after ammonium exchange. The reaction conditions were as follows: temperature of 350°C, reaction pressure of 3.0 MPa, reaction hydrogen-hydrocarbon molar ratio of 3:1 mol / mol, molar ratio of toluene to trimethylbenzene in the feed of 1:1 mol / mol, feed mass space velocity of toluene and trimethylbenzene of 3 h -1 The total reaction conversion rate is 46% and the xylene selectivity is 98%.

[0050] Example 3

[0051] BETA / MOR molecular sieve synthesis method: take the silicon-aluminum molar ratio (SiO 2 / Al 2 O 3 ) is 20 MOR molecular sieve as seed, water glass (containing 28wt% SiO 2 , modulus 3.0-3.5) as silicon source, sodium aluminate as aluminum source; tetraethylammonium hydroxide (TEAOH) as the first template, sodium fluoride as the second template, and NaOH as the alkali source. The molecular sieve synthetic glue composition is: n(Na 2 O) / n(SiO 2 ) / n(Al 2 O 3 ) / n(TEAOH / ) / n(H 2 O) / n(NaF)=2.5:55:1:12:800:4.5, adjust the pH to 13 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 40%. The above precursor is first hydrothermally crystallized at 100°C for 48 hours, and then hydrothermally crystallized at 160°C for 72 hours to obtain a BETA / MOR symbiotic molecular sieve. Among them, the BETA / MOR phase mass ratio is 72 / 28, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO is 0.78. 2 / Al 2 O 3 The molar ratio is 25.

[0052] The XRD pattern of the intergrowth molecular sieve in this example is similar to Figure 1 Similarly, the SEM images of the co-existing molecular sieves in this example are similar to Figure 2 Similarly, the specific surface area of ​​the BETA / MOR symbiotic molecular sieve in this example is 538m 2 / g, pore volume is 0.29cm 3 / g.

[0053] The above molecular sieve was used for the transalkylation reaction of toluene and trimethylbenzene after ammonium exchange. The reaction conditions were as follows: temperature of 350°C, reaction pressure of 3.0 MPa, reaction hydrogen-hydrocarbon molar ratio of 3:1 mol / mol, molar ratio of toluene to trimethylbenzene in the feed of 1:1 mol / mol, feed mass space velocity of toluene and trimethylbenzene of 3 h -1 The total reaction conversion rate is 49% and the xylene selectivity is 97%.

[0054] Comparative Example 1

[0055] BETA / MOR molecular sieve synthesis method: take the silicon-aluminum molar ratio (SiO 2 / Al 2 O 3 ) is 20 MOR molecular sieve as seed, water glass (containing 28wt% SiO 2 , modulus 3.0-3.5) as silicon source, sodium aluminate as aluminum source; tetraethylammonium hydroxide (TEAOH) as the first template, sodium fluoride as the second template, and NaOH as the alkali source. The molecular sieve synthetic glue composition is: n(Na 2 O) / n(SiO 2 ) / n(Al 2 O 3 ) / n(TEAOH / ) / n(H 2 O) / n(NaF)=1.5:40:1:10:700:5, adjust the pH to 12 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 20%. The above precursor is hydrothermally crystallized at 180°C for 48 hours to obtain a BETA / MOR symbiotic molecular sieve. Among them, the mass ratio of BETA / MOR phase is 18 / 82, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO is 0.90. 2 / Al 2 O 3 The molar ratio is 22.

[0056] The specific surface area of ​​the BETA / MOR symbiotic molecular sieve in this case is 384m 2 / g, pore volume is 0.14cm 3 / g.

[0057] The above molecular sieve was used for the transalkylation reaction of toluene and trimethylbenzene after ammonium exchange. The reaction conditions were as follows: temperature of 350°C, reaction pressure of 3.0 MPa, reaction hydrogen-hydrocarbon molar ratio of 3:1 mol / mol, molar ratio of toluene to trimethylbenzene in the feed of 1:1 mol / mol, feed mass space velocity of toluene and trimethylbenzene of 3 h -1 The total reaction conversion rate is 47% and the xylene selectivity is 93%.

[0058] Comparative Example 2

[0059] BETA / MOR molecular sieve synthesis method: take the silicon-aluminum molar ratio (SiO 2 / Al 2 O 3 ) of 40 MOR molecular sieve as seed, water glass (containing 28wt% SiO 2 , modulus 3.0-3.5) as silicon source, sodium aluminate as aluminum source; tetraethylammonium hydroxide (TEAOH) as the first template, sodium fluoride as the second template, and NaOH as the alkali source. The molecular sieve synthetic glue composition is: n(Na 2 O) / n(SiO 2 ) / n(Al 2 O 3 ) / n(TEAOH / ) / n(H 2 O) / n(NaF)=1.5:40:1:10:700:5, adjust the pH to 12 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 20%. The above precursor is first hydrothermally crystallized at 120°C for 48 hours, and then hydrothermally crystallized at 180°C for 48 hours to obtain a BETA / MOR symbiotic molecular sieve. Among them, the BETA / MOR phase ratio is 20 / 80, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO is 1.12. 2 / Al 2 O 3 The molar ratio is 51.

[0060] The specific surface area of ​​the BETA / MOR symbiotic molecular sieve in this case is 389m 2 / g, pore volume is 0.15cm 3 / g.

[0061] The above molecular sieve was used for the transalkylation reaction of toluene and trimethylbenzene after ammonium exchange. The reaction conditions were as follows: temperature of 350°C, reaction pressure of 3.0 MPa, reaction hydrogen-hydrocarbon molar ratio of 3:1 mol / mol, molar ratio of toluene to trimethylbenzene in the feed of 1:1 mol / mol, feed mass space velocity of toluene and trimethylbenzene of 3 h -1The total reaction conversion rate is 40% and the xylene selectivity is 94%.

[0062] Comparative Example 3

[0063] BETA / MOR molecular sieve synthesis method: Take water glass (containing 28wt% SiO 2 , modulus 3.0-3.5) as the silicon source, sodium aluminate as the aluminum source; tetraethylammonium hydroxide (TEAOH) as the first template, sodium fluoride as the second template, and NaOH as the alkali source. 2 O) / n(SiO 2 ) / n(Al 2 O 3 ) / n(TEAOH / ) / n(H 2 O) / n(NaF) with a molar ratio of 1.5:40:1:10:700:5 to form a molecular sieve synthesis glue, adjust the pH to 12 with ammonia water, and stir evenly to prepare a molecular sieve synthesis precursor. The above precursor is first hydrothermally crystallized at 120°C for 48 hours, and then hydrothermally crystallized at 180°C for 48 hours to obtain a BETA molecular sieve containing a small amount of ZSM-5 impurity crystals. Among them, the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO is 1.02. 2 / Al 2 O 3 The molar ratio is 37.

[0064] The XRD pattern of the BETA molecular sieve containing a small amount of ZSM-5 impurity crystals in this example is shown in Figure 3 ,Depend on Figure 3 It can be seen that it has typical BETA characteristic peaks and weak ZSM-5 diffraction peaks. The SEM image of the BETA molecular sieve containing a small amount of ZSM-5 impurity crystals in this example is shown in Figure 4 ,Depend on Figure 4 It can be seen that the morphology of BETA molecular sieve is uniform small particles, while ZSM-5 cannot be observed due to its small amount.

[0065] In this case, the specific surface area of ​​BETA molecular sieve with a small amount of ZSM-5 impurity crystals is 579m 2 / g, pore volume is 0.35cm 3 / g.

[0066] The above molecular sieve was used for the transalkylation reaction of toluene and trimethylbenzene after ammonium exchange. The reaction conditions were as follows: temperature of 350°C, reaction pressure of 3.0 MPa, reaction hydrogen-hydrocarbon molar ratio of 3:1 mol / mol, molar ratio of toluene to trimethylbenzene in the feed of 1:1 mol / mol, feed mass space velocity of toluene and trimethylbenzene of 3 h -1 The total reaction conversion rate is 44% and the xylene selectivity is 92%.

[0067] Comparative Example 4

[0068] BETA / MOR molecular sieve synthesis method: take the silicon-aluminum molar ratio (SiO 2 / Al 2 O 3 ) is 20 MOR molecular sieve as seed, silica sol (containing 30wt% SiO 2 ) as silicon source, sodium aluminate as aluminum source; tetraethylammonium hydroxide (TEAOH) as first template, sodium fluoride as second template, NaOH as alkali source. Molecular sieve synthetic glue composition: n(Na 2 O) / n(SiO 2 ) / n(Al 2 O 3 ) / n(TEAOH / ) / n(H 2 O) / n(NaF)=2.5:55:1:12:800:4.5, adjust the pH to 13 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve synthesis precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 40%. The above precursor is first hydrothermally crystallized at 100°C for 48 hours, and then hydrothermally crystallized at 160°C for 72 hours to obtain a BETA / MOR symbiotic molecular sieve. Among them, the BETA / MOR phase ratio is 71 / 29, and the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO is 0.95. 2 / Al 2 O 3 The molar ratio is 35.

[0069] The specific surface area of ​​the BETA / MOR symbiotic molecular sieve in this case is 455m 2 / g, pore volume is 0.38cm 3 / g.

[0070] The above molecular sieve was used for the transalkylation reaction of toluene and trimethylbenzene after ammonium exchange. The reaction conditions were as follows: temperature of 350°C, reaction pressure of 3.0 MPa, reaction hydrogen-hydrocarbon molar ratio of 3:1 mol / mol, molar ratio of toluene to trimethylbenzene in the feed of 1:1 mol / mol, feed mass space velocity of toluene and trimethylbenzene of 3 h -1 The total reaction conversion rate is 45% and the xylene selectivity is 91%.

[0071] Comparative Example 5

[0072] BETA / MOR molecular sieve synthesis method: take the silicon-aluminum molar ratio (SiO 2 / Al 2 O 3) is 20 MOR molecular sieve as seed, water glass (containing 28wt% SiO 2 , modulus 3.0-3.5) as silicon source, sodium aluminate as aluminum source; tetraethylammonium hydroxide (TEAOH) as the first template, sodium fluoride as the second template, and NaOH as the alkali source. The molecular sieve synthetic glue composition is: n(Na 2 O) / n(SiO 2 ) / n(Al 2 O 3 ) / n(TEAOH / ) / n(H 2 O) / n(NaF)=1.5:20:1:10:700:5, adjust the pH to 12 with ammonia water, then add MOR seed crystals, stir evenly to prepare a molecular sieve synthesis precursor, wherein the mass content of MOR seed crystals in the molecular sieve precursor is 20%. The above precursor is first hydrothermally crystallized at 120℃ for 48 hours, and then hydrothermally crystallized at 180℃ for 48 hours, and only pure MOR molecular sieve can be obtained. Among them, the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of SiO is 1.01. 2 / Al 2 O 3 The molar ratio is 18.

[0073] The XRD pattern of the MOR molecular sieve in this example is shown in Figure 5 ,Depend on Figure 5 It can be seen that it has typical characteristic peaks of MOR. The SEM image of the MOR molecular sieve in this example is shown in Figure 6 ,Depend on Figure 6 It can be seen that the MOR molecular sieve morphology exhibits large particle pure phase.

[0074] The specific surface area of ​​the MOR molecular sieve in this example is 277m 2 / g, pore volume is 0.12cm 3 / g.

[0075] The above molecular sieve was used for the transalkylation reaction of toluene and trimethylbenzene after ammonium exchange. The reaction conditions were as follows: temperature of 350°C, reaction pressure of 3.0 MPa, reaction hydrogen-hydrocarbon molar ratio of 3:1 mol / mol, molar ratio of toluene to trimethylbenzene in the feed of 1:1 mol / mol, feed mass space velocity of toluene and trimethylbenzene of 3 h -1 The total reaction conversion rate is 47% and the xylene selectivity is 89%.

[0076] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A BETA / MOR symbiotic molecular sieve, wherein the surface aluminum S SAR With the aluminum inside the molecular sieve SAR The atomic ratio of is 0.1 to 0.8, preferably 0.5 to 0.

8.

2. The BETA / MOR symbiotic molecular sieve according to claim 1, characterized in that: The BETA / MOR intergrowth molecular sieve has the following schematic chemical composition, in terms of molar ratio: nSiO2 / Al2O3, wherein 10≤n≤100, preferably 20≤n≤50.

3. The BETA / MOR symbiotic molecular sieve according to claim 1, characterized in that: In the BETA / MOR symbiotic molecular sieve, the mass ratio of BETA / MOR is 10 / 90 to 90 / 10, preferably 25 / 75 to 75 / 25.

4. The BETA / MOR symbiotic molecular sieve according to claim 1, characterized in that: The specific surface area of ​​the BETA / MOR symbiotic molecular sieve is 400-550 m 2 / g, pore volume is 0.10~0.30cm 3 / g.

5. The method for preparing the BETA / MOR symbiotic molecular sieve according to any one of claims 1 to 4, comprising: (1) mixing a silicon source, an aluminum source, a first template T1, a second template T2, an alkali source and water, adjusting the pH to 9 to 13, and then adding MOR seed crystals to obtain a molecular sieve precursor; (2) The molecular sieve precursor described in step (1) is first subjected to a first-stage hydrothermal crystallization, and then the temperature is increased to perform a second-stage hydrothermal crystallization to obtain the BETA / MOR symbiotic molecular sieve.

6. The preparation method according to claim 5, characterized in that: The SiO2 / Al2O3 molar ratio of the MOR seed crystal in step (1) is 15-25.

7. The preparation method according to claim 5, characterized in that: The silicon source in step (1) is selected from water glass; the aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, boehmite, sodium aluminate, aluminum nitrate, aluminum isopropoxide, and aluminum hydroxide, preferably sodium aluminate and / or aluminum sulfate; the alkali source is selected from ammonia water and / or alkaline hydroxide, preferably NaOH; the first template is tetraethylammonium hydroxide and / or tetraethylammonium bromide; and the second template is sodium fluoride.

8. The preparation method according to claim 5, characterized in that: The silicon source, aluminum source, first template T1, second template T2, alkali source and water in step (1) are mixed in a molar ratio of (1-6) alkali source: (30-55) SiO2: Al2O3: (8-15) T1: (100-1000) H2O: (2-8) T2 to prepare a sol.

9. The preparation method according to claim 5, characterized in that: The mass content of the MOR seed crystals in the molecular sieve precursor in step (1) is 20% to 55%.

10. The preparation method according to claim 5, characterized in that: Step (2) The hydrothermal crystallization conditions of the first stage are: 100-130° C. hydrothermal crystallization for 24-48 hours; the hydrothermal crystallization conditions of the second stage are 160-200° C. hydrothermal crystallization for 24-48 hours.

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