Thickness-controllable MCM-22 molecular sieve as well as synthesis method and application thereof

Abstract

The invention discloses a thickness-controllable MCM-22 molecular sieve as well as a synthesis method and application thereof, and belongs to the field of MCM-22 molecular sieves. According to the MCM-22 molecular sieve with the controllable thickness, the MCM-22 molecular sieve is a layered crystal, the single-layer thickness of the MCM-22 molecular sieve is 2-100 nm, and the silicon-aluminum molar ratio (SiO2 / Al2O3) of the MCM-22 molecular sieve is 1-200; the synthesis method of the MCM-22 molecular sieve comprises the following steps: mixing a silicon source, an aluminum source, an alkali source, a template agent and a solvent I, and crystallizing to obtain the MCM-22 molecular sieve, the alkali source is selected from a mixture of alkali metal halide and alkali metal hydroxide; according to the MCM-22 molecular sieve provided by the invention, the thickness control of the MCM-22 molecular sieve is realized through the pretreatment of the silicon source and the selection of the template agent, so that the crystal thickness of the MCM-22 molecular sieve is increased, and the MCM-22 molecular sieve presents a regular and uniform hexagonal flaky morphology, thereby enhancing the micropore crystallinity and micropore volume of the MCM-22 molecular sieve, and improving the micropore catalytic shape selectivity of the MCM-22 molecular sieve.

Description

Technical Field

[0001] The invention relates to the field of MCM-22 molecular sieve preparation, and in particular to a MCM-22 molecular sieve with controllable thickness, a synthesis method and application thereof. Background Art

[0002] Zeolite molecular sieve is a type of crystalline aluminosilicate with molecular pores or cages formed by sharing silicon, aluminum tetrahedrons or other element vertices such as boron. It has the functions of ion exchange, shape-selective catalysis, molecular sieving, etc., and is widely used in the fields of oil refining, petrochemicals, and the synthesis of fine or special chemicals. MCM-22 molecular sieve (MWW structure), MWW family molecular sieves have the same topological structure, and are a practical catalytic material with a unique crystal structure. It is a group of molecular sieves that were first successfully developed by Mobil Corporation in the United States in the 1990s and quickly put into industrial application. Leonowicz et al. confirmed the layered structure of MCM-22, with oxygen bridges connecting the layers, and it has a two-dimensional sinusoidal cross channel of ten-membered rings and a surface bowl-shaped twelve-membered ring semi-super cage structure (Science, 1994, 264: 1910-1913). This family of molecular sieves, as an important new catalytic material, has become a hot spot for research and development in the field of catalysis. Its main members include PSH-3, SSZ-25, MCM-22 (P), MCM-22 (C), MCM-36, MCM-49, MCM-56, borosilicate molecular sieve ERB-1, ITQ-1, ITQ-2 and other molecular sieves. The main difference between different members is the different interlayer distance and bonding degree. Among them, PSH-3, SSZ-25, MCM-22 (C), borosilicate molecular sieve ERB-1, ITQ-1 and MCM-49 are connected by oxygen bridges between layers, and the bonding is tight, and the interlayer distance cannot be changed under the action of the expansion agent: MCM-22 (P) (called MCM-22 molecular sieve precursor) has weak interlayer bonding, and the interlayer distance can be changed under the action of the expansion agent. Therefore, it can be used as a raw material for preparing layer columnar molecular sieve MCM-36: MCM-56 is a layered molecular sieve with a MWW single-layer structure, and the B acid position exposure ratio is higher. ITQ-2 is pure silicon MCM-22; ITQ-1 is a type of MCM-22 obtained by ultrasonic separation. Zeolite catalytic materials with three-dimensional structures have strong acidic active sites and shape-selective effects. Their pore diameters are generally less than 1nm and cannot accommodate larger reactant molecules. Clay-based layered catalytic materials have abundant diffusion channels, but they also have problems with poor activity and stability. MWW molecular sieves have a large proportion of B acid sites on the external surface. The special topological structure, good stability, simpler synthesis process and lower price of this type of molecular sieve make it possible to be applied in a wider range of fields.

[0003] DFT-D theory shows that MCM-22 molecular sieve has three types of pores: superpores, sinusoidal pores and holes. The huge differences in pore size and shape determine the spatial confinement and electrostatic stabilization effect, and play different catalytic roles. MCM-22 molecular sieves usually have more medium-strong acid active centers; at the same time, they contain higher The acid center ratio is conducive to the electrophilic activation of the benzene ring and the formation of carbon cations (ACS Catal. 2011, 1: 7-17). MCM-22, MCM-36 and ITQ-2 are all layered zeolite molecular sieves with MWW topological structure and two independent multidimensional pore systems of ten-membered rings and twelve-membered rings. Due to the characteristics of MWW molecular sieves with strong adsorption and desorption capabilities for macromolecules, they have shown high catalytic activity and stability in catalytic hydrocarbon reactions. HMCM-22 molecular sieves have independent ten-membered ring and twelve-membered ring pore structures. The twelve-membered large pore size is conducive to the isomerization reaction of carbon ions, and the relatively weak acidity also inhibits the cracking reaction. Compared with HMCM-22, HITQ-2 and HMCM-36 have larger specific surface areas than their parent bodies. Their stretched or broken super cages make it easier for the reaction molecules to approach the active sites and undergo isomerization reactions. The synthesis conditions of MCM-22 are relatively harsh, and special adjustments are often required to broaden its phase range. Layered zeolite is a solid acid catalytic material with a unique structure. It has a large specific surface area and strong acidic external surface active sites (equivalent to the acidity of the corresponding three-dimensional structure zeolite), and exhibits excellent adsorption and catalytic performance for macromolecules. By (1) optimizing the synthesis process, layered molecular sieves with high specific surface area and highly accessible external surface active sites for macromolecules can be prepared; (2) after appropriate modification, such as adjusting the silicon-aluminum ratio, introducing heteroatoms, loading suitable active components, etc., layered zeolite materials can be used as new high-efficiency catalyst materials in corresponding macromolecular reactions. MCM-22 molecular sieve is a type of catalytic material with great application prospects due to its unique pore structure and acid properties. At present, this molecular sieve has been industrially applied in alkylation reactions. It has also been widely studied in petrochemical applications such as methanol to hydrocarbons (MTO / MTA / MTH), methane aromatization (MDA), Friedel-Crafts alkylation, toluene disproportionation, transalkylation, alkyl isomerization, n-hexane cracking to produce propylene, and glycerol dehydration to produce acrolein. It can also be used for the lightening of heavy oils, the lightening of polycyclic aromatic hydrocarbons, and the synthesis of xylene isomerization.

[0004] In the process of lightweighting of heavy aromatics, the acid center of the molecular sieve cannot meet the reaction requirements of selective hydrogenation and dealkylation. The demand for the diversity of active sites usually requires the modification of transition metals or metal compounds on the surface of zeolite materials. The molecular sieve stabilizes the metal sites as an active framework, and their interaction depends on many factors. The acid-catalyzed reaction of MCM-22 molecular sieve usually tends to occur at the acid center of the surface of the pocket or super cage with stable crystal structure, but the overly strong acid center is prone to side reactions, resulting in a decrease in the selectivity of the product BTX. The biggest problem of lightweighting technology is that during the main reaction, hydrogen transfer is prone to occur during the hydrogenation reaction, resulting in excessive hydrogenation and cracking of aromatic rings, or condensation of aromatics to form condensed aromatic compounds (coke) and other side reactions, and it is easy to deposit on the catalyst surface, resulting in a decrease in lightweighting efficiency; at the same time, dealkylation is an exothermic process, and it is very easy to aggravate side reactions, causing the catalyst to deactivate. The reaction process is very complicated, involving the hydrogenation-isomerization-dehydrogenation mechanism, which requires the help of a bifunctional catalyst to complete. At the same time, side reactions such as cracking and disproportionation will also occur during the conversion process. From the development history of catalysts, the metal components have not changed much. Almost all catalysts use metal components with high hydrogenation and dehydrogenation activity, while the acid components have changed a lot. At present, various types of catalysts have their own characteristics and their performance is also improving day by day. However, compared with industrial requirements, their activity stability and selectivity are still insufficient. Summary of the invention

[0005] In order to overcome the above technical problems, the present invention provides a thickness-controllable MCM-22 molecular sieve and a synthesis method and application thereof. The MCM-22 layered molecular sieve is selected as the acidic component, and the diffusion shape selectivity of the molecular sieve micropores is improved by effectively controlling the thickness of the layered molecular sieve crystals. The catalyst made of the obtained MCM-22 molecular sieve is used in the selective dealkylation reaction of side-chain alkyl aromatics and exhibits excellent performance.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides an MCM-22 molecular sieve, wherein the MCM-22 molecular sieve is a layered crystal, the thickness of the single-layer crystal of the MCM-22 molecular sieve is 2nm to 100nm, and the silicon-aluminum molar ratio of the MCM-22 molecular sieve is SiO 2 / Al 2 O 3 The specific surface area S of the MCM-22 molecular sieve is 1 to 200; BET 420m 2 / g~600m 2 / g; micropore volume V micro 0.2cm 3 / g~0.4cm 3The MCM-22 molecular sieve presents a regular hexagonal layered morphology in a microscopic state, and the micropore diffusion, mass transfer and reaction performance of the MCM-22 molecular sieve are improved by adjusting the thickness.

[0007] According to some embodiments of the present invention, the monolayer crystal thickness of the MWW structured molecular sieve is 10 nm to 90 nm, and the silicon-aluminum molar ratio of the MCM-22 molecular sieve is SiO 2 / Al 2 O 3 The specific surface area S of the MCM-22 molecular sieve is 15 to 180; BET 420m 2 / g~496m 2 / g.

[0008] The second aspect of the present invention provides a method for synthesizing the above-mentioned MCM-22 molecular sieve, comprising the steps of mixing a silicon source, an aluminum source, an alkali source, a template and a solvent I, and crystallizing to obtain the MCM-22 molecular sieve; the silicon source is selected from a silicon source containing a structural unit;

[0009] In the ultraviolet Raman spectrum of the silicon source containing the structural unit, at the vibration frequency of 240cm -1 There are characteristic peaks nearby, with a vibration frequency no greater than 600cm -1 In the characteristic area, there is at least one non-240cm -1 Characteristic peaks near 240cm -1 The sum of the peak areas of the nearby characteristic peaks is no more than 600 cm -1 The total area of ​​the characteristic peaks in the characteristic region is ≥ 20% but not more than 98% (correspondingly, at 240 cm -1 The area of ​​the characteristic peaks near the -1 The total area of ​​characteristic peaks in the characteristic region is ≤80%).

[0010] In some embodiments of the present invention, in the ultraviolet Raman spectrum of the silicon source containing the structural unit, at a vibration frequency of no more than 600 cm -1 In the characteristic region, there is a vibration frequency of 335cm -1 、400cm -1 and 480cm -1 At least one characteristic peak in the vicinity.

[0011] In the present invention, the peak area of ​​each characteristic peak can be obtained by automatic (or manual if necessary) integration in a spectrometer. The present invention does not limit the specific peak area of ​​each characteristic peak. -1 The peak area of ​​the characteristic peaks near 240 cm -1 The relationship between the areas of nearby characteristic peaks has corresponding limitations.

[0012] In the present invention, the "silicon source containing structural units" refers to silicon-containing four-membered rings (4MR), five-membered rings (5MR) or six-membered rings (6MR) that can constitute the framework structure of the molecular sieve.

[0013] According to the present invention, 240cm -1 The characteristic peak near the silicon-containing eight-membered ring (8MR) is the characteristic signal of TOT bending vibration. When the ultraviolet Raman spectrum of the silicon source containing the structural unit is at 240cm -1 When there is a characteristic peak nearby, it means that the silicon atoms in the silicon source containing the structural unit have overcome the skeleton stress and formed more of the aforementioned 4MR, 5MR or 6MR active structural units.

[0014] According to the present invention, in the ultraviolet Raman spectrum of the silicon source containing the structural unit, 240cm -1 The characteristic peaks near the 8-membered ring (8MR) represent the bending vibration of TOT in the silicon-containing 8-membered ring; the vibration frequency is not more than 600 cm -1 In the characteristic region, the smaller rings correspond to higher vibration frequencies, not 240 cm -1 Among the characteristic peaks nearby, 335cm -1 、400cm -1 or 480cm -1 The characteristic peaks near 240cm represent the bending vibration of TOT in the six-membered ring (6MR), five-membered ring (5MR) and four-membered ring (4MR) containing silicon. -1 The sum of the peak areas of the nearby characteristic peaks is no more than 600 cm -1 The total area of ​​the characteristic peaks in the characteristic region is ≥20%, indicating that the silicon atoms in the silicon source containing the structural unit have more active structural units such as four-membered rings (4MR), five-membered rings (5MR) or six-membered rings (6MR).

[0015] According to some embodiments of the present invention, in the ultraviolet Raman spectrum of the silicon source containing the structural unit, at a vibration frequency of no more than 600 cm -1 In the characteristic area, non-240cm -1 The characteristic peak near is 335cm -1 、400cm -1 and 4480cm -1 At least one of the nearby characteristic peaks.

[0016] According to some embodiments of the present invention, at a vibration frequency of no more than 600 cm -1 In the characteristic area, non-240cm -1 The characteristic peak near 335cm -1 、400cm -1 and 480cm-1 The sum of the peak areas of at least one of the characteristic peaks nearby is no more than 600 cm -1 The total area of ​​characteristic peaks in the characteristic region is ≥50%.

[0017] Regarding the expression “near” in the above content, those skilled in the art will know that since each characteristic peak in the ultraviolet Raman spectrum usually has a displacement, the position of the characteristic peak defined in the present invention may have a deviation, such as 480cm -1 The nearby characteristic peak is at 450cm -1 ~500cm -1 However, the vibration represented by each characteristic peak can be determined by those skilled in the art.

[0018] In the present invention, the above-mentioned “no more than 600cm -1 The characteristic area generally refers to 0cm -1 ~600cm -1 (e.g. 150cm -1 ~600cm -1 ) in the ultraviolet Raman spectrum region. Those skilled in the art will understand that if a characteristic peak appears in a region where the characteristic peak is not easy to appear in the silicon source containing the structural unit, it should be verified whether it is an impurity peak formed by contamination.

[0019] According to some embodiments of the present invention, the specific surface area of ​​the silicon source containing the structural unit is 200m 2 / g~980m 2 / g, preferably 550m 2 / g~980m 2 / g.

[0020] According to some embodiments of the present invention, in the silicon source containing the structural unit, SiO 2 The mass fraction is >90%, preferably >95%, and more preferably >98%.

[0021] According to some embodiments of the present invention, the pore volume of the silicon source containing the structural unit is 0.2 cm 3 / g~3.0cm 3 / g.

[0022] The method for preparing the silicon source containing the structural unit comprises the following steps:

[0023] S1, providing a mixed solution I containing a treatment reagent and a solvent II;

[0024] S2, mixing the silicon-containing raw material with the mixed solution I to obtain a mixed solution II;

[0025] S3, performing activation treatment on the mixed solution II to obtain an activated product;

[0026] S4, calcining the activated product to obtain the silicon source containing the structural unit.

[0027] In some embodiments of the present invention, in step S1, the treatment reagent is selected from at least one of an inorganic base, a fluorine-containing substance, an organic base and an ionic liquid containing an organic anion; preferably ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, hydrofluoric acid, sodium fluoride, ammonium fluoride, silicon tetrafluoride, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF 6 ) at least one of.

[0028] In the present invention, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF 6 ) is an imidazolium-type ionic liquid.

[0029] In the present invention, the treatment reagent is preferably an organic quaternary ammonium base or fluoride, that is, at least one selected from hydrofluoric acid, sodium fluoride, ammonium fluoride, silicon tetrafluoride, tetramethylammonium hydroxide, tetraethylammonium hydroxide and tetrapropylammonium hydroxide.

[0030] In the present invention, when used, the treatment reagent is usually prepared into a solution of a certain concentration using water or alcohol as a solvent. For example, the organic base can be prepared into an aqueous solution or an alcohol solution. Those skilled in the art can make a selection based on actual conditions.

[0031] In some embodiments of the present invention, in step S1, the solvent II is selected from at least one of water, alcohols and ionic liquids; preferably deionized water, methanol, ethanol, isopropanol, ethylene glycol and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF 6 ) at least one.

[0032] In some embodiments of the present invention, in step S2, the silicon-containing raw material is selected from at least one of diatomaceous earth, water glass, (liquid phase) silica sol, white carbon black, gas phase silica sol, silicon powder, silicone resin microspheres, silicate (such as tetramethyl silicate, tetraethyl silicate or tetrapropyl silicate), silicon tetrachloride and silane; wherein the silane is preferably selected from tetramethylsilane Si (CH 3 ) 4 , methyltrimethoxysilane MTMS, isobutylene triethoxysilane, trichlorosilane SiHCl 3 and tetraethoxysilane Si(OC 2 H 5 ) 4 At least one of .

[0033] In the present invention, the silicon-containing raw material is preferably liquid silica sol, silicate or silane.

[0034] In the present invention, the optional silicon-containing raw materials mentioned above are all silicon-containing materials commonly used in the art.

[0035] In some embodiments of the present invention, the treatment reagent and the SiO in the silicon-containing raw material 2 The molar ratio (hereinafter referred to as treatment reagent / SiO 2 The molar ratio) is 0.0001 to 10:1, preferably 0.0001 to 0.1:1.

[0036] In some embodiments of the present invention, the solvent II and the SiO in the silicon-containing raw material 2 The molar ratio (hereinafter referred to as solvent II / SiO 2 The molar ratio) is 0.5 to 50:1.

[0037] In some embodiments of the present invention, the total hydroxide anions in the treatment reagent and the solvent II and the SiO in the silicon-containing raw material 2 The molar ratio (hereinafter referred to as OH- / SiO 2 ) is 2 to 60:1.

[0038] In some embodiments of the present invention, in step S2, the conditions for the mixing treatment include: a stirring speed of 0 to 5000 rpm, preferably 0 to 50 rpm; and a temperature of 0 to 50°C, preferably 5 to 30°C.

[0039] In some embodiments of the present invention, in step S3, the process for performing the activation treatment (also referred to as the gelling process) is selected from Process (Preparation of monodisperse SiO by alkaline hydrolysis of ethyl orthosilicate TEOS) 2 Microspheres), hydrolysis, oligomer precipitation, alkali dissolution and hot melting. To highlight the mineralization effect on silicon atoms.

[0040] The activated The process includes mixing and hydrolysis steps; the hydrolysis step of the activation treatment is mainly controlled by controlling the hydrolysis catalyst (promoter or inhibitor) and temperature, stirring / ultrasound / irradiation, time and other parameters; the oligomer precipitation of the activation treatment includes the steps of hydrolysis, solvent network bonding and growth; the alkali dissolution of the activation treatment includes adding a certain amount of ammonia water, sodium hydroxide or potassium hydroxide solution with a certain concentration into the above preparation process; the hot melt of the activation treatment refers to a single-stage or segmented high-temperature heat treatment at 300-1000°C for a certain period of time.

[0041] In the present invention, the activation treatment preferably uses an optimized Specifically, the amount of solvent, temperature and stirring speed can be used to control the hydrolysis, bonding and SiO2 Growth rate to achieve uniformity and controllability of silicon powder.

[0042] According to the present invention, The process, hydrolysis, oligomer precipitation, alkali dissolution and hot melting are all conventional methods of the present invention. The present invention does not strictly limit the various parameters involved in the process, and those skilled in the art can determine them according to actual conditions.

[0043] In some embodiments of the present invention, the conditions for the activation treatment include: a temperature not higher than 200°C (such as 0-200°C), preferably not higher than 100°C (such as 0-100°C); a treatment time of 1 hour to 500 days, preferably 12 hours to 12 days. Further preferably, the activation treatment is completed at a temperature of 0-10°C, a temperature of 10-30°C, a temperature of 30-80°C, and a temperature of 80-100°C (staged constant temperature heat treatment) for 0 to 120 hours (such as 1 to 120 hours).

[0044] In some embodiments of the present invention, after obtaining the activated product of step S3, before the calcination treatment of step S4, the activated product can also be subjected to impurity removal treatment, and water-soluble impurities and solvents, including all impurities such as physically adsorbed water, alcohols, salts and ionic liquids, can be removed by means of forced air drying, vacuuming, etc. At the same time, a maximum of Si, C, H, O, F, S, Br, Cl or MoO can be retained at the same time. x At least one composition.

[0045] In some embodiments of the present invention, in step S4, the conditions for the calcination treatment include: a temperature of 200 to 1000°C, preferably 400 to 600°C; a time of 0.05 to 500 hours; further preferably, within the temperature range of 200 to 1000°C (preferably 400 to 600°C), at least two calcination temperatures are selected from low to high in an air atmosphere and calcined for 0.05 to 2 hours respectively, for example, in an air atmosphere, calcined at 150 to 200°C, 250 to 350°C, 400 to 500°C, and 500 to 600°C in sequence for 0.05 to 2 hours.

[0046] In some embodiments of the present invention, during the calcination treatment, a programmed temperature increase of 0.5 to 5° C. / min is used to raise the temperature from room temperature to the calcination temperature (ie, 150 to 1000° C., preferably 400 to 600° C.).

[0047] In the present invention, the calcination treatment is used to remove the skeleton crystal water (the desorption temperature is usually ≥ 200°C at normal pressure), sublimable fluoride, sulfur or MoO x Impurities such as alkali or salt molecules of the organic template can be completely decomposed by high temperature oxidation.

[0048] According to some embodiments of the present invention, the aluminum source is selected from at least one of aluminum hydroxide, aluminum isopropoxide, aluminum sec-butoxide, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride, and aluminum oxide.

[0049] According to some embodiments of the present invention, the molar ratio of the alkali metal halide to the alkali metal hydroxide is 0.02-50, for example 0.5, 30; further preferably, the alkali metal is selected from at least one of Li, Na, K, Ru, and Cs.

[0050] According to some embodiments of the present invention, the template is selected from nitrogen heterocyclic compounds and / or unequal tetraalkylammonium compounds; the unequal tetraalkylammonium compound has the general formula R 1 R 2 NR 3 R 4 ; Among them, R 1 , R 2 The same or different, each independently selected from C1-C5 straight chain or branched alkyl, preferably, the R 1 For -(CH 2 ) m CH 3 , R 2 For -(CH 2 ) n CH 3 , m≥n, m is 1, 2, 3, 4; n is 0, 1, 2, 3, 4; R 3 , R 4 The same or different, each independently selected from C1-C4 straight chain or branched alkyl, preferably, the R 3 For -(CH 2 ) l CH 3 , R 4 For -(CH 2 ) k CH 3 , and m>1, m>k, l is 0, 1, 2, 3; k is 0, 1, 2, 3; further preferably, the unequal tetraalkylammonium is selected from at least one of dimethyldiethylammonium hydroxide, monomethyltriethylammonium hydroxide, monomethylmonoethyldipropylammonium hydroxide, dimethyldibutylammonium hydroxide, and N,N,N-trimethyl-1-adamantylammonium hydroxide; the nitrogen heterocyclic compound is selected from hexamethyleneimine.

[0051] According to some embodiments of the present invention, the solvent I is deionized water, ethanol, glycerol, acetone, n-butanol or imidazole ionic liquid, [bmim]PF 6 At least one of the ionic liquids.

[0052] According to some embodiments of the present invention, the silicon source, the aluminum source, the alkali source, the template and the solvent I are mixed to obtain a gelling solution; preferably, the molar ratio of the silicon source, the aluminum source, the alkali source, the template and the solvent I is (5-500):1:(0.01-1):(0-60):(50-50000), preferably (40-180):1:(0.03-0.8):(5-50):(200-10000);

[0053] According to some embodiments of the present invention, the crystallization adopts a segmented crystallization process, including pre-crystallization and crystallization; preferably, the pre-crystallization temperature is 30-120°C, for example, 90°C, and the pre-crystallization time is 0.5h-12h, for example, 6h; further preferably, the crystallization temperature is 30-200°C, for example, 150°C, and the crystallization time is 1h-400h, for example, 160h, 200h.

[0054] The third aspect of the present invention provides an MCM-22 molecular sieve catalyst, comprising a carrier and an active component. In the MCM-22 molecular sieve catalyst, the carrier is made of a molecular sieve and a binder, and the mass ratio of the molecular sieve to the binder in the carrier is (8-17): (3-12); the mass percentage of the active component in the catalyst is 00001% to 20%; the molecular sieve is the above-mentioned MCM-22 molecular sieve; and the active component is selected from at least one of rare earth elements or their oxides, magnetic metal elements or their oxides.

[0055] According to some embodiments of the present invention, the mass percentage of the active component to the catalyst is 0.25% to 1.5%.

[0056] According to some embodiments of the present invention, the rare earth element is selected from at least one of yttrium, lanthanum, cerium, praseodymium and neodymium.

[0057] According to some embodiments of the present invention, the magnetic metal element is at least one of iron, cobalt and nickel.

[0058] According to some embodiments of the present invention, the binder is selected from at least one of alumina, aluminum phosphate, pseudo-boehmite, and sesbania powder.

[0059] A fourth aspect of the present invention provides a method for preparing the above-mentioned MCM-22 molecular sieve catalyst, comprising the following steps:

[0060] 1) calcining the molecular sieve sodium type raw powder in an air atmosphere to obtain the MWW structure molecular sieve raw powder I; wherein the molecular sieve sodium type raw powder is the above-mentioned MCM-22 molecular sieve;

[0061] 2) washing the molecular sieve raw powder I obtained in step 1) with acid to obtain molecular sieve raw powder II;

[0062] 3) subjecting the molecular sieve raw powder II obtained in step 2) to at least one ammonium exchange to obtain molecular sieve raw powder III;

[0063] 4) kneading and shaping the molecular sieve powder III obtained in step 3) to obtain a catalyst precursor IV;

[0064] 5) calcining the catalyst precursor IV obtained in step 4) under air atmosphere to obtain a catalyst carrier V;

[0065] 6) The catalyst carrier V obtained in step 5) is impregnated in a solution containing an active component precursor, and then calcined in an air atmosphere to obtain a catalyst containing a layered molecular sieve with an MWW structure.

[0066] According to some embodiments of the present invention, in step 1), the calcination is carried out in stages, and the calcination is carried out at a temperature of 150°C to 200°C for 0.5h to 3h, then at a temperature of 250°C to 350°C for 0.5h to 3h, then at a temperature of 400°C to 500°C for 0.5h to 3h, and finally at a temperature of 550°C to 600°C for 0.5h to 3h.

[0067] According to some embodiments of the present invention, in step 2), the acid washing adopts an oxalic acid aqueous solution with a mass concentration of 5% to 10% at a temperature of 20°C to 80°C for 1h to 2h; preferably, the liquid-to-solid weight ratio of the MWW structured molecular sieve raw powder I to the acid solution is 0.5 to 100; further preferably, the acid washing also includes the steps of filtering, washing and drying.

[0068] According to some embodiments of the present invention, in step 3), the ammonium exchange is carried out using an ammonium nitrate solution with a mass concentration of 5% to 20% at a temperature of 20°C to 100°C for 0.5h to 2h; preferably, the liquid-to-solid weight ratio of the molecular sieve raw powder II to the ammonium nitrate solution is 4 to 10; further preferably, the ammonium exchange further includes the steps of filtering, washing and drying.

[0069] According to some embodiments of the present invention, in step 4), a binder is added before kneading; preferably, the binder is selected from at least one of alumina, aluminum phosphate, pseudo-boehmite, and sesbania powder; further preferably, the mass ratio of the molecular sieve raw powder III to the binder is (8-17): (3-12).

[0070] According to some embodiments of the present invention, in step 5), the calcination further includes room temperature aging and drying steps; the calcination temperature is 500°C to 600°C, and the calcination time is 1h to 6h; preferably, the room temperature aging time is 0.5h to 50h; the drying temperature is 80°C to 120°C, and the drying time is 0.5h to 50h.

[0071] According to some embodiments of the present invention, in step 6), the mass of the solution containing the active component precursor accounts for 0.10% to 1.5% of the mass of the catalyst carrier V; the mass concentration of the solution containing the active component precursor is 0.1% to 30%; preferably, the solution containing the active component precursor is an aqueous solution of a metal acid, a metal acid salt, a chloride, an amine complex, a carbonyl complex or a mixture thereof containing at least one of a rare earth element and a magnetic metal element; further preferably, the rare earth element is at least one of yttrium, lanthanum, cerium, praseodymium and neodymium, and the magnetic metal element is at least one of iron, cobalt and nickel; further preferably, the impregnation is carried out at room temperature, and the impregnation time is 12h to 24h; after the impregnation, a drying step is also included, and the drying temperature is 70°C to 110°C, and the drying time is 0.5h to 50h.

[0072] According to some embodiments of the present invention, in step 6), the calcination temperature is 400° C. to 550° C., and the calcination time is 2 h to 5 h.

[0073] The fifth aspect of the present invention provides a selective dealkylation reaction of side-chain alkyl aromatics, in which aromatics are mixed with hydrogen in the presence of a catalyst to undergo a selective dealkylation reaction; wherein the catalyst is the above-mentioned MCM-22 molecular sieve catalyst.

[0074] According to some embodiments of the present invention, the aromatic hydrocarbon is selected from at least one of toluene, xylene, methylethylbenzene, propylbenzene, isopropylbenzene, trimethylbenzene, butylbenzene, naphthalene, anthracene and tetralin.

[0075] According to some embodiments of the present invention, the catalyst includes a reduction step before the reaction; preferably, the reduction is carried out by hydrogen reduction, wherein the hydrogen flow rate is 8 ml / min to 800 ml / min; during the reduction, the temperature is first increased to 100°C to 280°C at a rate of 0.1°C / min to 20°C / min and kept constant at the temperature for 0h to 48h, and then the temperature is increased to 300°C to 750°C at a rate of 0.1°C / min to 50°C / min and kept constant at the temperature for 0h to 48h.

[0076] According to some embodiments of the present invention, the selective dealkylation reaction temperature is 250° C. to 650° C., and the pressure is 0 MPa to 60 MPa.

[0077] According to some embodiments of the present invention, the weight space velocity of the aromatic hydrocarbon is 0.01h -1 ~50h -1 , the hydrogen-to-oil molar ratio is 0-300.

[0078] Beneficial effects:

[0079] The MCM-22 molecular sieve of the present invention is a silicon-based silicon-aluminum porous material, wherein the selection of a silicon source and a template agent has a relatively important influence on the crystallization degree of the MCM-22 molecular sieve. The activity of the silicon source can be improved by hydrothermal pretreatment of the silicon source, or the crystallization degree of the MCM-22 molecular sieve can be improved by optimizing the type and quantity of the template agent. Conventionally synthesized MCM-22 molecular sieves tend to have a thin sheet morphology to increase the specific surface area and the mesopore volume, while the present invention achieves thickness control of the nano MCM-22 molecular sieve by pretreatment of the silicon source and selection of the template agent, thereby increasing the crystal thickness of the MCM-22 molecular sieve and presenting a regular and uniform hexagonal sheet morphology, thereby enhancing the microporous crystallinity and microporous volume of the MCM-22 molecular sieve and improving the microporous catalytic shape selectivity of the MCM-22 molecular sieve.

[0080] The MCM-22 molecular sieve catalyst prepared by the invention can be used for efficient selective dealkylation reaction of alkyl aromatics. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 The XRD spectrum of the MCM-22 molecular sieve with controllable thickness prepared in Example 1 of the present invention;

[0082] Figure 2 This is a HR-TEM photo of the MCM-22 molecular sieve with controllable thickness prepared in Example 1 of the present invention;

[0083] Figure 3 This is a TEM photo of the silicon source SG1 containing the structural unit prepared in Example 1 of the present invention;

[0084] Figure 4 UV-Raman spectra of silicon source SG1 and white carbon black A200 containing structural units prepared in Example 1 of the present invention;

[0085] Figure 5 The nitrogen low temperature adsorption-desorption (BET) curves of the silicon source SG1 and white carbon black A200 containing the structural unit prepared in Example 1 of the present invention;

[0086] Figure 6 FT-IR spectra of the silicon source SG1 and white carbon black A200 containing structural units prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0087] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to these embodiments.

[0088] The specific surface area S of the MCM-22 molecular sieve in the present invention is BET 、Micropore volume V micro The surface area of ​​the samples was measured by using a Tristar 3000 surface area analyzer produced by Micrometrics. 2 Adsorption-desorption analysis: The sample was pretreated with vacuum activation at 300°C for 6 hours before testing. The test temperature was -196°C. The specific surface area S of the test sample was obtained by analyzing the isotherm. BET 、Micropore volume V micro And other structural data.

[0089] The phase analysis (XRD spectrum) in the present invention is measured by using a Bruker D8Focus diffractometer, a graphite monochromator, a Cu target Kα ray light source, a wavelength λ of 0.154nm, a tube voltage of 40kV, a tube current of 40mA, and recording diffraction signals in the 2θ range of 3-90° (scanning speed of 2° / min);

[0090] The high-resolution scanning electron imaging (HR-TEM) photos in the present invention were taken using a NovaNanoSEM450 microscope from FEI Company;

[0091] Explanation of symbols in the present invention: NA is non-aromatic, B is benzene, T is toluene, EB is ethylbenzene, X is xylene, TMB is trimethylol (including 1,2,4-trimethylol, 1,3,5-mesitylene and mixtures);

[0092] The polytetrafluoroethylene-lined pressure steel autoclave used in the present invention was purchased from Shandong Yantai Muping Shuguang Precision Instrument Factory, with a specification of 100 mL;

[0093] The rotary oven used in the present invention was purchased from a 200L space rotary oven produced by Beijing Creaser Co., Ltd.

[0094] In the present invention, the specific surface area and pore volume of the silicon source containing the structural unit are measured by using a Tristar 3000 specific surface analyzer produced by Micrometrics Company to perform low temperature N 2 For adsorption-desorption analysis, the samples were pretreated at 300 °C for 6 h under vacuum activation before testing. The test temperature was -196 °C. The pore structure data such as specific surface area and pore volume of the test samples were obtained by analyzing the isotherms.

[0095] In the present invention, the SiO 2The mass fraction was measured by thermogravimetric TG-DTA analysis of the sample using TGA Q500analyzer instrument (test conditions were air atmosphere, heating rate 10°C / min).

[0096] In the present invention, the FT-IR spectrum test uses a Nexus670 Fourier transform infrared spectrometer (FT-IR) produced by Nicolet Company of the United States to analyze the skeleton vibration area of ​​the sample; during the test, the sample powder is first diluted with KBr to a mass fraction of about 3%, ground and mixed evenly with a mortar, and then pressed into a tablet to prepare a sample, which is then placed in a vacuum cell for testing, and the test resolution is 4cm- 1 , scanning times 32 times, test range 400~4000cm -1 .

[0097] In the following examples, all chemical reagents used are commercially available products and, unless otherwise specified, have not been specially purified.

[0098] Example 1

[0099] This embodiment provides a MCM-22 molecular sieve with controllable thickness, and the synthesis method is as follows:

[0100] First, NaOH, sodium bromide and sodium aluminate are dissolved in deionized water, and then a template (hexamethyleneimine / N,N,N-trimethyl-1-adamantyl ammonium hydroxide, i.e., HMI / TMAdaOH with a molar ratio of 2:1) is added, and finally methyltrimethoxysilane is added, and stirred evenly to obtain a milky white gelling solution; then the gelling solution is charged into a polytetrafluoroethylene-lined pressure steel autoclave, and pre-crystallized for 6 hours at a temperature of 90°C, and then placed in a rotary oven at a temperature of 150°C and a rotation speed of 20r / min for further hydrothermal crystallization for 160 hours, and finally cooled to room temperature with tap water, and the obtained product is filtered, washed and dried to obtain the thickness-controllable MCM-22 molecular sieve MS1, and the XRD test of MS1 is shown in the attached Figure 1 , which is a pure phase MWW configuration; the SEM photo of MS1 is attached Figure 2 The single molecular sieve crystal of MS1 presents a regular hexagonal flake morphology. The single layer thickness of MS1 is 50nm, the silicon-aluminum molar ratio is 42, and the specific surface area S BET 448m 2 / g, micropore volume V micro 0.21cm 3 / g.

[0101] The molar ratio of methyltrimethoxysilane, sodium aluminate, (NaOH and sodium bromide), (hexamethyleneimine / N,N,N-trimethyl-1-adamantyl ammonium hydroxide) and deionized water is 40:1:0.03:5:200; the molar ratio of sodium bromide to sodium hydroxide is 0.5; the methyltrimethoxysilane contains a structural unit; the preparation of the methyltrimethoxysilane containing the structural unit includes weighing sodium hydroxide, sodium fluoride, and 25% ammonia solution, adding them to deionized water to dissolve them uniformly, adding methanol, and placing the solution in a 5°C water bath; weighing methyltrimethoxysilane, uniformly adding it to the above solution under stirring at 30rpm, stirring for another 2 minutes, transferring it into a container and standing it at 30°C for 5 hours to obtain a sol, and rotary evaporating the solvent therein under vacuum conditions at 80°C until a solid block is precipitated, wherein the treatment reagent / SiO 2 The molar ratio is 0.05; solvent II / SiO 2 The molar ratio is 10; OH- / SiO 2 Molar ratio 10.

[0102] The solid block obtained in the above preparation was treated with 1% citric acid aqueous solution at a liquid-solid mass ratio of about 6:1, and then acid exchanged and activated at 80°C for 1.5 hours, washed with deionized water until electrically neutral, and dried at 120°C. The temperature was then raised to 600°C at a rate of 3°C / min, and calcined at a constant temperature for 1.5 hours to obtain methyltrimethoxysilane containing a structural unit, which was recorded as sample SG1.

[0103] The specific surface area of ​​sample SG1 is S BET 510m 2 / g, pore volume = 2.4 cm 3 / g,SiO 2 The mass fraction is 99%, Figure 4 It can be seen that compared with silica A200, sample SG1 has a vibration frequency of no more than 600 cm -1 There are more non-240cm areas in the characteristic area -1 Nearby characteristic peaks; UV-Raman detected its vibration frequency at 335cm -1 、400cm -1 and 4480cm -1 The peak area of ​​the characteristic peak near 240cm -1 Characteristic peaks near 240cm -1 The sum of the peak areas of the nearby characteristic peaks is no more than 600 cm -1 The total area of ​​characteristic peaks in the characteristic region is 78%. Figure 4 In the UV-Raman spectrum of sample SG1, due to peak overlap, 335cm -1 、400cm -1 and 480cm-1 Nearby characteristic peaks overlap.

[0104] Depend on Figure 3 It can be seen that the silicon oxide particles in sample SG1 are uniform and dispersed; Figure 5 It can be seen that compared with silica A200, sample SG1 has a larger low-temperature adsorption capacity for nitrogen, and the specific surface area and pore volume obtained from the curve are larger; Figure 5 It can be seen that the signal peak of silanol in the corresponding FT-IR spectrum of sample SG1 is stronger (usually, the larger the peak area at the characteristic position, the higher the surface silanol concentration of the sample).

[0105] Example 2

[0106] This embodiment provides a MCM-22 molecular sieve with controllable thickness, and the synthesis method is as follows:

[0107] Firstly, NaOH, sodium chloride and sodium aluminate are dissolved in deionized water, then the template agent hexamethyleneimine is added, and finally tetramethyl silicate is added, and the mixture is stirred evenly to obtain a milky white gelling solution; then the gelling solution is charged into a pressure steel autoclave lined with polytetrafluoroethylene, and pre-crystallized for 6 hours at a temperature of 90°C, and then placed in a rotary oven at a temperature of 150°C and a rotation speed of 20r / min for further hydrothermal crystallization for 200 hours, and finally cooled to room temperature with tap water, and the obtained product is filtered, washed and dried to obtain the thickness-controllable MCM-22 molecular sieve MS2, wherein MS2 is a pure phase MWW configuration; the single molecular sieve crystal of MS2 presents a regular hexagonal flake morphology, and the MS2 single layer thickness is 83nm; the MS2 silicon-aluminum molar ratio is 38, and the specific surface area S BET 425m 2 / g, micropore volume V micro 0.20cm 3 / g.

[0108] Wherein, the molar ratio of tetramethyl silicate, sodium aluminate, (NaOH and sodium chloride), hexamethyleneimine and deionized water is 35:1:0.03:30:5000; the molar ratio of sodium chloride to sodium hydroxide is 30; the preparation of tetramethyl silicate is the same as Example 1.

[0109] Comparative Example 1

[0110] This comparative example provides a MCM-22 molecular sieve

[0111] The gel solution was prepared according to the synthesis method of Example 1, except that the silicon source used was a silica sol (model Ludox-30) with a mass fraction of 30%, and MCM-22 molecular sieve DS1 was obtained.

[0112] DS1 is a pure phase MWW configuration; the silicon-aluminum molar ratio of DS1 is 38, and the specific surface area S BET 298m 2 / g, micropore volume V micro 0.15cm 3 / g, the specific surface area and micropore volume are both low, and the morphology is irregular layer / flake, with a thickness of 15nm and uneven.

[0113] Comparative Example 2

[0114] This comparative example provides a MCM-22 molecular sieve

[0115] A gelling solution was prepared according to the synthesis method of Example 1, except that the template was replaced by imidazole to obtain MCM-22 molecular sieve DS2.

[0116] DS2 is a product containing impurities of ZSM-35 molecular sieve, and the pure phase MWW configuration cannot be obtained; the silicon-aluminum molar ratio of DS2 is 43, and the specific surface area S BET 336m 2 / g, micropore volume V micro 0.17cm 3 / g, the morphology is layer / flake-like, and the thickness is 40nm.

[0117] Example 3

[0118] This embodiment provides a MCM-22 molecular sieve with controllable thickness

[0119] According to the synthesis method of Example 1, except that the molar ratio of tetramethoxysilane, sodium aluminate, (NaOH and sodium bromide), (hexamethyleneimine / N,N,N-trimethyl-1-adamantyl ammonium hydroxide) and deionized water is 57:1:0.8:40:500, the thickness-controllable MCM-22 molecular sieve MS3 is obtained; MS3 is a pure phase MWW configuration; a single molecular sieve crystal of MS3 presents a regular hexagonal flake morphology, and the single layer thickness is about 35nm; the silicon-aluminum molar ratio of MS3 is 57, and the specific surface area S BET 439m 2 / g, micropore volume V micro 0.22cm 3 / g.

[0120] Example 4

[0121] This embodiment provides a MCM-22 molecular sieve with controllable thickness

[0122] According to the synthesis method of Example 1, except that the molar ratio of tetramethoxysilane, sodium aluminate, (NaOH and sodium bromide), (hexamethyleneimine / N,N,N-trimethyl-1-adamantyl ammonium hydroxide) and deionized water is 164:1:0.23:32:10000, the thickness-controllable MCM-22 molecular sieve MS4 is obtained; MS4 is a pure phase MWW configuration; a single molecular sieve crystal of MS4 presents a regular hexagonal flake morphology, and the single layer thickness is about 38nm; the silicon-aluminum molar ratio of MS4 is 124, and the specific surface area S BET 443m 2 / g, micropore volume V micro 0.21cm 3 / g.

[0123] Example 5

[0124] This embodiment provides a MCM-22 molecular sieve with controllable thickness

[0125] The synthesis method of Example 1 is followed, except that the molar ratio of the template (HMI / TMAdaOH) is 1:1, and the molar ratio of the tetramethoxysilane, sodium aluminate, (NaOH and sodium bromide), (hexamethyleneimine / N,N,N-trimethyl-1-adamantyl ammonium hydroxide) and deionized water is 171:1:0.34:43:800, to obtain the thickness-controllable MCM-22 molecular sieve MS5; MS5 is a pure phase MWW configuration; a single molecular sieve crystal of MS5 presents a regular hexagonal flake morphology, and the MS5 single layer thickness is about 76nm; the silicon-aluminum molar ratio of MS5 is 141, and the specific surface area S BET 496m 2 / g, micropore volume V micro 0.24cm 3 / g.

[0126] Preparation Example 1

[0127] This preparation example provides a MCM-22 molecular sieve catalyst, and the preparation method is as follows:

[0128] The thickness-controllable MCM-22 molecular sieve MS1 prepared in Example 1 was calcined at 200°C for 1 h in an air atmosphere, then at 300°C for 1 h, then at 450°C for 1 h, and finally at 550°C for 3 h to obtain molecular sieve raw powder I; the molecular sieve raw powder I was then contacted with an aqueous solution of oxalic acid having a mass concentration of 5% at a liquid-to-solid weight ratio of 4 for acid washing at a temperature of 75°C for 2 h, and the obtained solid was filtered, washed, and dried to obtain molecular sieve raw powder II; the obtained molecular sieve raw powder II was then ammonium exchanged with an aqueous solution of ammonium nitrate having a mass concentration of 10% at a liquid-to-solid weight ratio of 4 at a temperature of 90°C for 2 h, and the obtained solid was filtered, washed, and dried, and the ammonium exchange was repeated once to obtain molecular sieve raw powder III.

[0129] Take 100g of the molecular sieve powder III obtained above, mix it evenly with 150g of pseudo-boehmite powder and 5g of sesbania powder. Then add 180ml of a dilute nitric acid solution with a mass concentration of 5%, mix well and extrude it into strips on an extruder, age it at room temperature for 12h, dry it at 110℃ for 3h, and finally calcine it at 550℃ in air atmosphere for 3h to obtain catalyst carrier V.

[0130] The catalyst carrier V obtained above is shaped into 800 g of particles were weighed, mixed evenly with 8 g of 5% neodymium nitrate solution, and then allowed to stand and impregnate at room temperature for 12 h. The impregnated catalyst carrier V was then transferred to an oven and dried at 110°C for 3 h. The dried catalyst carrier V was then calcined at 500°C in an air atmosphere for 3 h to obtain catalyst A1.

[0131] The present invention provides multiple groups of preparation examples according to the preparation method of Preparation Example 1, and the catalyst samples obtained by the multiple groups of Preparation Examples 2-8 are marked A2-A8 in sequence. The differences between the multiple groups of preparation examples are that the original powder of the molecular sieve sodium type is selected from Examples 1-5 respectively; the concentration of the pickling solution, the pickling temperature, and the pickling time; the concentration of the ammonium exchange solution, the liquid-solid weight ratio, the ammonium exchange temperature, the ammonium exchange time, and the number of ammonium exchanges; the type of active component, the mass percentage of the active component in the catalyst; the calcination temperature, the calcination (step 6) time, etc. The specific preparation conditions are shown in Table 1;

[0132] Table 1

[0133]

[0134] 5g of each of the catalysts A1-A9 prepared in the above preparation examples 1-8 were respectively taken and loaded into a stainless steel fixed bed tubular reactor, and reduced with pure hydrogen. The reduction conditions were as follows: hydrogen flow rate 80ml / min, temperature was raised to 180℃ at 2℃ / min and kept at this temperature for 2h, then the temperature was raised to 375℃ at 2.5℃ / min, and the raw material trimethylbenzene was added for selective dealkylation reaction. The product was analyzed by HP6890 gas chromatography. Reaction conditions: reaction temperature 375℃, reaction pressure 0.6MPa, raw material weight space velocity 3.35h -1 , hydrogen to oil molar ratio 3. The statistics of online 100h reaction results are shown in Table 2;

[0135] The catalyst performance index is calculated according to the following formula: the evaluation index is based on the activity (conversion rate C) and BTX selectivity (high-quality low-carbon aromatics yield) as the catalyst performance comparison evaluation index.

[0136] The relevant calculation formulas and definitions based on the mass content of the components are as follows:

[0137] (P is B, T, X)

[0138] Table 2

[0139] catalyst <![CDATA[C TMB ]]> <![CDATA[S BTX ]]> Catalyst A1 29.1 89.3 Catalyst A2 31.5 88.1 Catalyst A3 30.4 88.2 Catalyst A4 29.9 86.2 Catalyst A5 29.3 82.2 Catalyst A6 30.8 90.0 Catalyst A7 30.2 78.3 Catalyst A8 29.8 88.4 Catalyst A9 29.1 89.3

[0140] Among them, TMB is the abbreviation of the raw material trimethylbenzene, S BTX It is the total selectivity of the products benzene, toluene and xylene.

[0141] Preparation Example 9

[0142] This preparation example provides a MCM-22 molecular sieve catalyst

[0143] The preparation method of Preparation Example 1 is followed, except that a mixed solution of nickel nitrate and praseodymium nitrate is used to replace the 5% neodymium nitrate solution by mass concentration so that the molar amount of the loaded metal is the same. After stirring evenly, the mixture is allowed to stand and impregnate at room temperature for 12 hours. The impregnated catalyst carrier V is then transferred to an oven and dried at 120°C for 3 hours. The dried catalyst carrier V is then calcined at 500°C in an air atmosphere for 3 hours to obtain a catalyst B1 containing 0.3wt% nickel and 0.6wt% praseodymium.

[0144] The present invention provides multiple groups of preparation examples according to the preparation method of Preparation Example 9. The catalyst samples obtained from the multiple groups of Preparation Examples 10-19 are marked as B2-B11 respectively. The difference is that the molecular sieve sodium type raw powder and the molecular sieve sodium type raw powder are selected from Examples 1-5 respectively; the type of active component, the mass percentage of the active component in the catalyst, and the specific preparation conditions are shown in Table 3.

[0145] Table 3

[0146]

[0147]

[0148] 5g of each of the catalysts B1-B11 prepared in the above preparation examples 9-10 were respectively taken and loaded into a stainless steel fixed bed tubular reactor, and reduced with pure hydrogen. The reduction conditions were as follows: hydrogen flow rate 80ml / min, heating to 180℃ at 2℃ / min and constant temperature for 2h, then heating to 375℃ at 2.5℃ / min, and adding raw material trimethylbenzene for selective dealkylation reaction. The product was analyzed by HP6890 gas chromatography. Reaction conditions: reaction temperature 375℃, reaction pressure 0.6MPa, raw material weight space velocity 3.35h -1 , hydrogen to oil molar ratio 3. The statistics of online 100h reaction results are shown in Table 4;

[0149] The catalyst performance index is calculated according to the following formula: the evaluation index is based on the activity (conversion rate C) and BTX selectivity (high-quality low-carbon aromatics yield) as the catalyst performance comparison evaluation index.

[0150] The relevant calculation formulas and definitions based on the mass content of the components are as follows:

[0151]

[0152] (P is B, T, X)

[0153] Table 4

[0154] catalyst <![CDATA[C TMB ]]> <![CDATA[S BTX ]]> Catalyst B1 29.7 91.3 Catalyst B2 30.5 88.2 Catalyst B3 31.5 88.1 Catalyst B4 31.9 87.8 Catalyst B5 32.5 87.6 Catalyst B6 31.1 88.4 Catalyst B7 32.1 87.9 Catalyst B8 51.5 88.1 Catalyst B9 30.3 87.9 Catalyst B10 35.8 87.7 Catalyst B11 34.8 87.8

[0155] 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 MCM-22 molecular sieve, characterized in that: The MCM-22 molecular sieve is a layered crystal, the thickness of a single-layer crystal of the MCM-22 molecular sieve is 2nm to 100nm, the silicon-aluminum molar ratio of the MCM-22 molecular sieve is 1 to 200; the specific surface area S of the MCM-22 molecular sieve is BET 420m 2 / g~600m 2 / g; micropore volume V micro 0.2cm 3 / g~0.4cm 3 / g.

2. The MCM-22 molecular sieve according to claim 1, characterized in that The thickness of the single-layer crystal of the MWW structure molecular sieve is 10nm to 90nm, the silicon-aluminum molar ratio of the MCM-22 molecular sieve is 15 to 180; the specific surface area S of the MCM-22 molecular sieve is BET 425m 2 / g~496m 2 / g.

3. A method for synthesizing the MCM-22 molecular sieve according to claim 1 or 2, characterized in that: The method comprises the steps of mixing a silicon source, an aluminum source, an alkali source, a template and a solvent I, and crystallizing to obtain an MCM-22 molecular sieve; the silicon source is selected from a silicon source containing a structural unit; preferably, in an ultraviolet Raman spectrum of the silicon source containing the structural unit, at a vibration frequency of 240 cm -1 There are characteristic peaks nearby, with a vibration frequency no greater than 600cm -1 In the characteristic area, there is at least one non-240cm -1 Characteristic peaks near 240cm -1 The sum of the peak areas of the nearby characteristic peaks is no more than 600 cm -1 The characteristic peak area of ​​the characteristic region accounts for 20% to 98% of the total area.

4. The synthesis method according to claim 3, characterized in that The aluminum source is selected from at least one of aluminum hydroxide, aluminum isopropoxide, aluminum sec-butoxide, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride, and aluminum oxide; And / or, the alkali source is selected from a mixture of alkali metal halide and alkali metal hydroxide; preferably, the molar ratio of the alkali metal halide to the alkali metal hydroxide is 0.02-50, preferably 0.5-30; further preferably, the alkali metal is selected from at least one of Li, Na, K, Ru, and Cs; And / or, the template is selected from nitrogen heterocyclic compounds and / or unequal tetraalkylammonium; the general formula of the unequal tetraalkylammonium is R1R2NR3R4, wherein R1 and R2 are the same or different and are independently selected from C1-C5 straight chain or branched alkyl groups, preferably, R1 is -(CH2) m CH3, R2 is -(CH2) n CH3, m≥n, m is 1, 2, 3, 4; n is 0, 1, 2, 3, 4; R3 and R4 are the same or different, and are independently selected from C1-C4 straight chain or branched alkyl, preferably, R3 is -(CH2) l CH3, R4 is -(CH2) k CH3, and m>1, m>k, l is 0, 1, 2, 3; k is 0, 1, 2, 3; further preferably, the non-equivalent tetraalkylammonium is selected from at least one of dimethyldiethylammonium hydroxide, monomethyltriethylammonium hydroxide, monomethylmonoethyldipropylammonium hydroxide, dimethyldibutylammonium hydroxide, and N,N,N-trimethyl-1-adamantylammonium hydroxide; the nitrogen heterocyclic compound is selected from hexamethyleneimine; And / or, the solvent I is at least one of deionized water, ethanol, glycerol, acetone, n-butanol or imidazole-type ionic liquid, [bmim]PF6 ionic liquid.

5. The synthesis method according to claim 3, characterized in that The silicon source, aluminum source, alkali source, template and solvent I are mixed to obtain a gelling solution; preferably, the molar ratio of the silicon source, aluminum source, alkali source, template and solvent I is (5-500):1:(0.01-1):(0-60):(50-50000), preferably (40-180):1:(0.03-0.8):(5-50):(200-10000); And / or, the crystallization adopts a segmented crystallization process, including pre-crystallization and crystallization; preferably, the pre-crystallization temperature is 30-120°C, and the pre-crystallization time is 0.5h-12h; further preferably, the crystallization temperature is 30-200°C, and the crystallization time is 1h-400h.

6. An MCM-22 molecular sieve catalyst, comprising a carrier and an active component, characterized in that: In the MCM-22 molecular sieve catalyst, the carrier is made of molecular sieve and adhesive, and the mass ratio of molecular sieve to adhesive in the carrier is (8-17): (3-12); the mass percentage of the active component in the catalyst is 0.0001%-20%; the molecular sieve is the MCM-22 molecular sieve described in claim 1 or 2 or the MCM-22 molecular sieve prepared by the preparation method described in any one of claims 3-5; the active component is selected from at least one of rare earth elements or their oxides, magnetic metal elements or their oxides.

7. The MCM-22 molecular sieve catalyst according to claim 6, characterized in that: The mass percentage of the active component in the catalyst is 0.25% to 1.5%; And / or, the rare earth element is at least one selected from yttrium, lanthanum, cerium, praseodymium, and neodymium; And / or, the magnetic metal element is at least one of iron, cobalt and nickel; And / or, the binder is selected from at least one of alumina, aluminum phosphate, pseudo-boehmite, and sesbania powder.

8. A method for preparing the MCM-22 molecular sieve catalyst as claimed in claim 6 or 7, characterized in that: The steps include: 1) calcining a molecular sieve sodium type raw powder in an air atmosphere to obtain a molecular sieve raw powder I of MWW structure; the sodium type raw powder is the MCM-22 molecular sieve according to claim 1 or 2, or the MCM-22 molecular sieve prepared by the preparation method of any one of claims 3 to 5; 2) washing the molecular sieve raw powder I obtained in step 1) with acid to obtain molecular sieve raw powder II; 3) subjecting the molecular sieve raw powder II obtained in step 2) to at least one ammonium exchange to obtain molecular sieve raw powder III; 4) kneading and shaping the molecular sieve powder III obtained in step 3) to obtain a catalyst precursor IV; 5) calcining the catalyst precursor IV obtained in step 4) under air atmosphere to obtain a catalyst carrier V; 6) The catalyst carrier V obtained in step 5) is impregnated in a solution containing an active component precursor, and then calcined in an air atmosphere to obtain a catalyst containing a layered molecular sieve with an MWW structure.

9. The preparation method according to claim 8, characterized in that: In step 1), the calcination is carried out in stages, at a temperature of 150°C to 200°C for 0.5h to 3h, then at a temperature of 250°C to 350°C for 0.5h to 3h, then at a temperature of 400°C to 500°C for 0.5h to 3h, and finally at a temperature of 550°C to 600°C for 0.5h to 3h; And / or, in step 2), the acid washing adopts an oxalic acid aqueous solution with a mass concentration of 5% to 10% at a temperature of 20°C to 80°C for 1h to 2h; preferably, the liquid-to-solid weight ratio of the MWW structure molecular sieve raw powder I to the acid solution is 0.5 to 100; further preferably, the acid washing further includes the steps of filtering, washing and drying; And / or, in step 3), the ammonium exchange is carried out using an ammonium nitrate solution with a mass concentration of 5% to 20% at a temperature of 20°C to 100°C for 0.5h to 2h; preferably, the liquid-to-solid weight ratio of the molecular sieve raw powder II to the ammonium nitrate solution is 4 to 10; further preferably, the ammonium exchange further includes the steps of filtering, washing and drying; And / or, in step 4), a binder is added before kneading; preferably, the binder is selected from at least one of alumina, aluminum phosphate, pseudo-boehmite, and sesbania powder; further preferably, the mass ratio of the molecular sieve raw powder III to the binder is (8-17): (3-12); And / or, in step 5), the step of room temperature aging and drying is also included before the calcination; the calcination temperature is 500°C to 600°C, and the calcination time is 1h to 6h; preferably, the room temperature aging time is 0.5h to 50h; the drying temperature is 80°C to 120°C, and the drying time is 0.5h to 50h; And / or, in step 6), the mass of the solution containing the active component precursor accounts for 0.10% to 1.5% of the mass of the catalyst carrier V; the mass concentration of the solution containing the active component precursor is 0.1% to 30%; preferably, the solution containing the active component precursor is an aqueous solution of a metal acid, a metal acid salt, a chloride, an ammonia complex, a carbonyl complex or a mixture thereof containing at least one of a rare earth element and a magnetic metal element; further preferably, the rare earth element is at least one of yttrium, lanthanum, cerium, praseodymium and neodymium, and the magnetic metal element is at least one of iron, cobalt and nickel; further preferably, the impregnation is carried out at room temperature, and the impregnation time is 12h to 24h; after the impregnation, a drying step is also included, and the drying temperature is 70°C to 110°C, and the drying time is 0.5h to 50h; And / or, in step 6), the calcination temperature is 400° C. to 550° C., and the calcination time is 2 h to 5 h.

10. A selective dealkylation reaction of side chain alkyl aromatics, characterized in that: In the presence of a catalyst, aromatic hydrocarbons are mixed with hydrogen to undergo a selective dealkylation reaction; wherein the catalyst is the MCM-22 molecular sieve catalyst described in claim 6 or 7 or the MCM-22 molecular sieve catalyst prepared by the preparation method described in claim 8 or 9.

11. The reaction according to claim 10, characterized in that The aromatic hydrocarbon is selected from at least one of toluene, xylene, methyl ethyl benzene, propyl benzene, isopropyl benzene, trimethylbenzene, butyl benzene, naphthalene, anthracene and tetralin; And / or, the catalyst includes a reduction step before the reaction; preferably, the reduction is carried out by hydrogen reduction, wherein the hydrogen flow rate is 8 ml / min to 800 ml / min; during the reduction, the temperature is first increased to 100°C to 280°C at a rate of 0.1°C / min to 20°C / min and kept at a constant temperature for 0h to 48h, and then increased to 300°C to 750°C at a rate of 0.1°C / min to 50°C / min and kept at a constant temperature for 0h to 48h; and / or, the selective dealkylation reaction temperature is 250° C. to 650° C. and the pressure is 0 MPa to 60 MPa; And / or, the weight space velocity of the aromatics is 0.01h -1 ~50h -1 , the hydrogen-to-oil molar ratio is 0-300.

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