Modified molecular sieve, method for preparing same, and use thereof

Abstract

The present application relates to the technical field of molecular sieve preparation, and discloses a modified molecular sieve and a preparation method and application thereof.A modified molecular sieve, wherein the modified molecular sieve comprises a molecular sieve and a rare earth element, the modified molecular sieve has a beta cage and a supercage structure, the R value of the modified molecular sieve is 10-35%, and the K value of the modified molecular sieve is 1-20; wherein the R value represents the mass fraction of the rare earth element in the modified molecular sieve in terms of an oxide, and the K value represents the ratio of the content of the rare earth element in the beta cage to that in the supercage. The modified molecular sieve is loaded with a relatively large amount of the rare earth element, and the distribution of the rare earth element in the beta cage and the supercage is regulated, so that the performance of the molecular sieve in an alkylation reaction is improved, and the molecular sieve exhibits excellent performance in catalytic synthesis of a linear alkylbenzene target product in a molecular sieve alkylation reaction.

Description

Technical Field

[0001] This invention relates to the technical field of molecular sieve preparation, specifically to a modified molecular sieve, its preparation method, and its application. Background Technology

[0002] Traditional linear alkylbenzene production processes utilize liquid catalysts such as HF and AlCl3. These traditional catalyst processes have a long history of development, are technologically mature, and highly industrialized; currently, most linear alkylbenzene production in this field still employs this type of process. However, traditional processes also suffer from various drawbacks, including environmental pollution, severe equipment corrosion, difficulty in separating the product from the target product, and high investment costs. Therefore, the development of novel, green, and environmentally friendly solid acid catalyst processes is urgently needed.

[0003] UOP and a Spanish oil company jointly developed the Detal solid acid process, which overcomes some shortcomings of the HF and AlCl3 processes and was industrialized in the mid-1990s. However, because the Detal process uses an amorphous silica-alumina catalyst containing phosphorus (F), the process requires frequent regeneration, and F is lost during operation. The alkylation and catalyst regeneration processes are discontinuous, resulting in high operating costs, which limits the promotion and development of the Detal solid acid process (Modern Chemical Industry, 2016, 45(2):373-375).

[0004] Existing research on molecular sieves for the catalytic synthesis of straight-chain alkylbenzenes mainly focuses on Y, β and mordenite. The main problem is that the molecular sieves generally have short catalytic lifetimes and low straight-chain properties of the target products (Bull. Korean Chem. Soc., 2001, 22(9): 1056-1058).

[0005] Patent application CN101861290A discloses a layered zeolite catalyst for improving linearity in detergent alkylation, wherein the catalyst comprises a layered composition comprising an inner core and an outer layer bonded to the inner core, and the catalyst is capable of improving the performance of the target product to a certain extent.

[0006] Patent application CN102655932A discloses a rare earth modified molecular sieve catalyst. This catalyst, through secondary rare earth exchange, exhibits a greater susceptibility of linearity to the target product synthesized by the catalyst compared to catalysts with primary rare earth exchange. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of low linearity and short catalytic lifetime of the target product of linear alkylbenzene in the catalytic synthesis of molecular sieve alkylation reaction in the existing technology, and to provide a modified molecular sieve, its preparation method and application. The modified molecular sieve has a large rare earth element loading, and the content of rare earth elements in the β cage and supercage of the modified molecular sieve can be controlled, thereby exhibiting excellent alkylation performance in the alkylation reaction.

[0008] To achieve the above objectives, a first aspect of the present invention provides a modified molecular sieve having a β-cage and a supercage structure, wherein the modified molecular sieve comprises a molecular sieve and rare earth elements, and the modified molecular sieve has an R value of 10-35% and a K value of 1-20; wherein, based on the total amount of modified molecular sieve, the R value represents the mass fraction of rare earth elements in the modified molecular sieve as oxides, and the K value represents the ratio of the rare earth element content in the β-cage to that in the supercage of the modified molecular sieve.

[0009] Preferably, the B value of the modified molecular sieve is 1.1-1.5, more preferably 1.2-1.4, where the B value represents the mass fraction ratio of rare earth elements (calculated as oxides) in the surface phase and bulk phase of the modified molecular sieve.

[0010] The second aspect of the present invention provides a method for preparing a modified molecular sieve, wherein the method includes: (1) placing the molecular sieve in a rare earth element ion exchange solution, performing a first ion exchange and then calcining it, treating the calcined product with acid in an acid solution, repeating the above steps at least once to obtain a first ion exchange product;

[0011] (2) Place the first ion exchange product in a rare earth element ion exchange solution for a second ion exchange, and repeat the above steps at least once to obtain the second ion exchange product.

[0012] (3) The second ion exchange product is placed in a rare earth element ion exchange solution for rare earth oxide precipitation and adsorption. The above steps are repeated at least once to make the R value 10-35% to obtain a modified molecular sieve. The R value represents the mass fraction of rare earth elements in the modified molecular sieve as oxides. The modified molecular sieve has β-cage and supercage structures, and the K value is 1-20. The K value represents the ratio of the rare earth element content in the β-cage to the supercage in the modified molecular sieve.

[0013] A third aspect of the present invention provides a modified molecular sieve prepared by the preparation method described in the second aspect.

[0014] The fourth aspect of this invention provides the application of the modified molecular sieve described in the first or third aspect in the alkylation reaction of linear olefins and aromatics to prepare linear alkylbenzenes.

[0015] The modified molecular sieve provided by this invention has a suitable amount of rare earth elements loaded at specific positions, so that the modified molecular sieve has a high content of rare earth elements. Furthermore, by controlling the content of rare earth elements in the β cage and supercage of the modified molecular sieve, and preferably by controlling the content of rare earth elements in the surface phase and the bulk phase of the modified molecular sieve, the skeletal isomerization of linear olefins can be effectively inhibited, while exhibiting strong alkylation activity, thereby improving the catalytic lifetime of the modified molecular sieve. Attached Figure Description

[0016] Figure 1 This is the XRD pattern of the modified molecular sieve prepared in Example 1 of the present invention. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of the present invention provides a modified molecular sieve, wherein the modified molecular sieve comprises a molecular sieve and rare earth elements, the modified molecular sieve has a β-cage and a supercage structure, the modified molecular sieve has an R value of 10-35%, and a K value of 1-20; wherein the R value represents the mass fraction of rare earth elements in the modified molecular sieve as oxides, and the K value represents the ratio of the rare earth element content in the β-cage to that in the supercage of the modified molecular sieve.

[0019] In a preferred embodiment, the R value of the modified molecular sieve is 16-28%, for example, it can be 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, or any value between any two groups. The modified molecular sieve provided by this invention, by controlling the total amount of rare earth elements in the modified molecular sieve, has the advantages of modifying the molecular sieve channels, consolidating the molecular sieve structure, inhibiting the formation of reaction byproducts, and improving the selectivity of the main product.

[0020] In a preferred embodiment, the K value of the modified molecular sieve is 2-8, for example, it can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, or any value between two groups. By adopting the above preferred embodiment, and by controlling the distribution of rare earth elements in the β cage and supercage of the modified molecular sieve, it has the advantages of modifying the molecular sieve channels and improving the linearity of the target product.

[0021] This invention provides a modified molecular sieve, which, by loading a high content of rare earth elements onto the molecular sieve and having a specific distribution of rare earth elements on the molecular sieve, enables the modified molecular sieve to effectively inhibit the skeletal isomerization of linear olefins in the alkylation reaction to prepare linear alkylbenzenes, while also exhibiting strong alkylation activity, thereby improving the catalytic lifetime of the modified molecular sieve and increasing the linearity of the target product.

[0022] In this invention, the "R value" is measured by XRF. The instrument used is a Rigaku Electric Industrial Co., Ltd. 3271 X-ray fluorescence spectrometer. The test conditions are: the anode target material of the X-ray tube is a rhodium target; the laser voltage is 50kV; and the laser current is 50mA.

[0023] In this invention, the "K value" is obtained by XRD. The instrument used is Netherland, PANalytical Corporation. The test conditions are: tube voltage 40kV, tube current 40mA, Cu target Kα radiation, scanning speed 2° / min, scanning range 2θ=5°-35°. The "K value" is calculated by the ratio of the area of ​​the characteristic peak at 11.9° to the area of ​​the characteristic peak at 12.4° in the XRD spectrum.

[0024] In a preferred embodiment, the B value of the modified molecular sieve is 1.1-1.5, preferably 1.2-1.4. The B value represents the mass fraction ratio of rare earth elements (calculated as oxides) in the surface phase and bulk phase of the modified molecular sieve. The B value can be, for example, 1, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, or any value between any two groups. The advantage of this preferred embodiment is that it modifies the surface of the molecular sieve to suppress side reactions.

[0025] In this invention, it is understood that the "rare earth element content (mass fraction) in the bulk phase of the modified molecular sieve, calculated as oxides" refers to the mass fraction of rare earth elements in the modified molecular sieve, calculated as oxides, as described above, i.e., the R value. In this invention, the "rare earth element content (mass fraction) in the bulk phase of the modified molecular sieve, calculated as oxides" is measured by XRF. Specifically, the instrument used is a Rigaku Electric Industrial Co., Ltd. 3271 X-ray fluorescence spectrometer; the test conditions are: the anode target material of the X-ray tube is a rhodium target; the laser voltage is 50 kV; and the laser current is 50 mA. The "rare earth element content (mass fraction) in the modified molecular sieve surface phase, expressed as oxides," was calculated using XPS. Specifically, in this invention, the XPS testing conditions were as follows: Instrument used: ESCALAB250 X-ray photoelectron spectrometer, manufactured by Thermo Fisher Scientific; Testing conditions: monochromatic Al Kα X-rays, energy 1486.6 eV, power 150 W, with charge shift corrected using the C1s peak (284.8 eV) of contaminating carbon. In this invention, it is understood that the XPS test first obtains the mole fraction of surface rare earth elements as elements, and then calculates the mass fraction of surface rare earth elements as oxides.

[0026] In this invention, there is no particular limitation on the type of modified molecular sieve. Preferably, the modified molecular sieve is a silica-alumina molecular sieve.

[0027] In this invention, preferably, the silicon-to-aluminum molar ratio of the modified molecular sieve is 1-50, more preferably 1.5-9. It is understood that in this invention, the silicon-to-aluminum molar ratio refers to the molar ratio of silicon atoms to aluminum atoms.

[0028] In this invention, the modified molecular sieve can load rare earth elements at specific locations on the modified molecular sieve, while simultaneously modifying the pores and surface of the modified molecular sieve, thereby improving the shape selectivity of the modified molecular sieve for alkylation reactions.

[0029] In this invention, there is no particular limitation on the types of rare earth elements; all rare earth elements conventionally defined in the art are applicable to this invention. Preferably, the rare earth elements are selected from Sc, Y, and non-radioactive lanthanides.

[0030] In a preferred embodiment, the rare earth element is selected from at least one of Sc, Y, La, Ce, Pr, Nd, Sm, and Yb, more preferably La and / or Ce. Using rare earth elements within the above preferred range facilitates matching with the molecular sieve channels, achieving optimal shape-selective catalysis, protecting the molecular sieve structure, and improving catalyst lifetime and the linearity of the target product.

[0031] A second aspect of the present invention provides a method for preparing a modified molecular sieve, wherein the method includes:

[0032] (1) Place the molecular sieve in a rare earth element ion exchange solution and perform the first ion exchange calcination. Treat the calcination product with acid in an acid solution. Repeat the above steps at least once to obtain the first ion exchange product.

[0033] (2) The first ion exchange product is placed in the rare earth element ion exchange solution for a second ion exchange, and the above steps are repeated at least once to obtain the second ion exchange product.

[0034] (3) The second ion exchange product is placed in a rare earth element ion exchange solution for rare earth oxide precipitation and adsorption. The above steps are repeated at least once to make the R value 10-35% to obtain a modified molecular sieve. The R value represents the mass fraction of rare earth elements in the modified molecular sieve as oxides. The modified molecular sieve has β-cage and supercage structures, and the K value is 1-20. The K value represents the ratio of the rare earth element content in the β-cage to the supercage in the modified molecular sieve.

[0035] The preparation method of the present invention can achieve a specific rare earth element loading and regulate the distribution of rare earth elements in the β cage and supercage through at least two cross-linking and two baking processes and one rare earth oxide precipitation adsorption, thereby improving the lifetime of the modified molecular sieve and suppressing the occurrence of side reactions to improve the linearity of the target product.

[0036] In this invention, by controlling the operation steps, conditions and the number of repetitions of each step in steps (1)-(3), the R value and K value in the modified molecular sieve are made to satisfy the above-mentioned R value of 10-35% and K value of 1-20. In this invention, the preferred range of R value and K value and the determination method have been described in the first aspect and will not be repeated here.

[0037] The inventors of this invention discovered that by controlling the conditions, parameters, and number of repetitions of the first ion exchange calcination, the various process parameters work synergistically to allow rare earth elements to migrate into the β cage of the molecular sieve, while simultaneously exchanging rare earth elements out of the supercage. A second ion exchange is then performed, and by controlling the conditions of the second ion exchange, the element content in the β cage and supercage is regulated. Finally, rare earth oxide precipitation and adsorption are carried out, and by controlling the conditions of rare earth oxide precipitation and adsorption, the content of rare earth elements in the molecular sieve is regulated, ensuring that the R and K values ​​of the modified molecular sieve meet the aforementioned conditions.

[0038] In this invention, there is no particular limitation on the type of molecular sieve in step (1), as long as it meets the requirements for preparing modified molecular sieves. Preferably, in step (1), the molecular sieve is a silica-alumina molecular sieve.

[0039] In a preferred embodiment, the silicon-to-aluminum molar ratio of the molecular sieve in step (1) is 1-50, more preferably 1.5-9. In this invention, it is understood that the silicon-to-aluminum molar ratio refers to the molar ratio of silicon atoms to aluminum atoms.

[0040] In this invention, the silicon-aluminum molar ratio remains essentially unchanged before and after molecular sieve modification, both satisfying the above-mentioned molar ratio range requirements.

[0041] In a preferred embodiment, the molecular sieve in step (1) is in the form of hydrogen and / or ammonium, more preferably in the form of ammonium.

[0042] In a preferred embodiment, the molecular sieve in step (1) is an X-type molecular sieve and / or a Y-type molecular sieve.

[0043] By selecting the above-mentioned molecular sieves as raw materials to prepare modified molecular sieves, the advantage of the molecular sieves having a supercage structure that makes reactants easier to contact is utilized, which is beneficial to improving the lifespan of the modified molecular sieves.

[0044] In a preferred embodiment, the rare earth element ion exchange liquids in steps (1), (2), and (3) are each independently selected from solutions containing rare earth element compounds.

[0045] In this invention, there is no particular limitation on the type of rare earth element compound, as long as it contains rare earth element ions and can provide rare earth elements to meet the modification requirements. Preferably, the rare earth element compound is selected from at least one of the nitrate, sulfate and chloride salts of the corresponding rare earth element, and more preferably a nitrate.

[0046] In this invention, the concentration of the rare earth ion exchange solution is not particularly limited. Preferably, the concentration of the rare earth ion exchange solution in steps (1), (2) and (3) is 0.18-1 mol / L, and more preferably 0.35-0.8 mol / L.

[0047] In this invention, it is understood that the concentrations of the rare earth ion exchange solution in steps (1), (2), and (3) can be the same or different.

[0048] In a preferred embodiment, the ratio of the mass of the molecular sieve to the volume of the rare earth element ion exchange liquid in step (1) is 150-550 g / L, preferably 200-400 g / L.

[0049] In this invention, preferably, the first ion exchange in step (1) is carried out under stirring conditions.

[0050] In this invention, there are no particular limitations on the conditions for the first ion exchange in step (1). Preferably, the conditions for the first ion exchange in step (1) include: a temperature of 60-120℃, a time of 0.5-1.5h, and a stirring rate of 200-500r / min. More preferably, the temperature is 75-95℃, the time is 0.8-1.2h, and the stirring rate is 300-400r / min.

[0051] In this invention, preferably, after the molecular sieve undergoes the first ion exchange, it is subjected to solid-liquid separation followed by a first drying in step (1). The method of solid-liquid separation is not particularly limited in this invention; for example, filtration may be used. The conditions for the first drying are selected within a wide range in this invention. Preferably, the conditions for the first drying include: a temperature of 50-180℃ and a time of 2-10 hours.

[0052] In this invention, preferably, in step (1), the calcination is carried out under alkaline atmosphere and slightly positive pressure conditions.

[0053] In this invention, step (1) calcination is carried out under alkaline conditions. Preferably, the alkaline atmosphere in step (1) is provided by ammonia. In this invention, it is understood that ammonia can rapidly vaporize under calcination conditions, thereby providing an alkaline atmosphere for the calcination process.

[0054] In this invention, there is no particular limitation on the concentration of ammonia. Preferably, the concentration of ammonia in step (1) is 0.05-0.5 mol / L, and more preferably 0.08-0.3 mol / L.

[0055] In a preferred embodiment, the ammonia flow rate is 0.01-5 mL / min, more preferably 0.05-3 mL / min, compared to 50 g of molecular sieve. It is understood that the flow rate of the alkaline atmosphere (ammonia) is proportional to the throughput of the molecular sieve; for example, as the throughput of the molecular sieve increases, the flow rate of the alkaline atmosphere (ammonia) can be increased proportionally. Those skilled in the art can select the appropriate rate based on actual needs.

[0056] In this invention, the selection range for the calcination conditions in step (1) is relatively wide. Preferably, the calcination conditions in step (1) include: a temperature of 400-600℃, a time of 0.5-2h, and a pressure of 0.01-0.1MPa; more preferably, a temperature of 450-580℃, a time of 0.8-1.5h, and a pressure of 0.001-0.05MPa, with the pressure measured in gauge pressure. The advantage of this preferred embodiment is that it facilitates the diffusion of rare earth elements into the molecular sieve β cage.

[0057] In this invention, there is no particular limitation on the type of acid in the acid solution described in step (1), and acids conventionally defined in the art are all applicable to this invention. Preferably, the acid in the acid solution described in step (1) is selected from inorganic acids and / or organic acids, preferably inorganic acids, and more preferably at least one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and boric acid.

[0058] In this invention, the concentration of the acid solution in step (1) is not particularly limited, as long as the pH of the solution is satisfied. Preferably, the concentration of the acid solution in step (1) is 0.0001-0.1 mol / L, and more preferably 0.001-0.1 mol / L.

[0059] In this invention, the selection range for the acid treatment conditions in step (1) is relatively wide. Preferably, the acid treatment conditions in step (1) include: a temperature of 40-80℃, a time of 0.5-2h, and a stirring rate of 200-500r / min; more preferably, a temperature of 55-75℃, a time of 0.8-1.5h, and a stirring rate of 300-400r / min. In this invention, after the acid treatment in step (1), a second drying is performed following solid-liquid separation. The method of solid-liquid separation in this invention has been described above and will not be repeated here. In this invention, the selection range for the second drying conditions is relatively wide. Preferably, the second drying conditions include: a temperature of 50-180℃ and a time of 2-10h.

[0060] In a preferred embodiment, the repetition of step (1) is 1-3 times, preferably 1-2 times. The advantage of the above preferred embodiment is that rare earth elements are filled into the molecular sieve β cage.

[0061] In a preferred embodiment, the ratio of the mass of the first ion exchange product to the volume of the rare earth element ion exchange liquid in step (2) is 200-600 g / L, preferably 300-450 g / L.

[0062] In this invention, preferably, in step (2), the second ion exchange is carried out under stirring conditions.

[0063] In this invention, the selection range for the conditions of the second ion exchange is relatively wide. Preferably, the conditions for the second ion exchange include: a temperature of 80-130℃, a time of 0.5-3h, and a stirring rate of 200-500r / min; more preferably, a temperature of 80-100℃, a time of 0.8-1.2h, and a stirring rate of 300-400r / min. In this invention, after the second ion exchange in step (2), a third drying is performed following solid-liquid separation. The method of solid-liquid separation in this invention has been described above and will not be repeated here. In this invention, the selection range for the conditions of the third drying is relatively wide. Preferably, the conditions for the third drying include: a temperature of 50-180℃ and a time of 2-10h.

[0064] In a preferred embodiment, step (2) is repeated 1-3 times, preferably 1-2 times. The advantage of this preferred embodiment is that rare earth elements are filled into the supercage of the molecular sieve.

[0065] In a preferred embodiment, the ratio of the mass of the second ion exchange product to the volume of the rare earth element ion exchange liquid in step (3) is 100-400 g / L, preferably 250-350 g / L.

[0066] In this invention, by controlling the conditions and repetition frequency of rare earth oxide precipitation and adsorption in step (3), the B value of the modified molecular sieve is made to meet the following range. In a preferred embodiment, in step (3), the B value of the modified molecular sieve is 1.1-1.5, preferably 1.2-1.4, where the B value represents the mass fraction ratio of rare earth elements (calculated as compounds) in the surface phase and bulk phase of the modified molecular sieve. The range of B values ​​and the method for determining them have been described in the first aspect of this invention and will not be repeated here.

[0067] In this invention, preferably, the rare earth oxide precipitation and adsorption in step (3) is carried out under alkaline conditions. The advantage of this preferred embodiment is that it promotes the migration of rare earth ions from the supercage into the β-cage.

[0068] In a preferred embodiment, the alkaline conditions in step (3) are provided by an alkaline compound.

[0069] In this invention, there is no particular limitation on the type of alkaline compound. Preferably, the alkaline compound in step (3) is selected from at least one of ammonia, ammonium carbonate and urea, and more preferably ammonia.

[0070] In this invention, there is no particular limitation on the concentration of the alkaline compound. Preferably, the concentration of the alkaline compound in step (3) is 1-4 mol / L.

[0071] In this invention, the selection range of conditions for rare earth oxide precipitation and adsorption is relatively wide. Preferably, the conditions for rare earth oxide precipitation and adsorption include: temperature of 0-50℃, time of 0.2-1.5h, and stirring rate of 200-500r / min; more preferably, temperature of 5-30℃, time of 0.2-0.8h, and stirring rate of 300-400r / min. Under these conditions, the rare earth oxide precipitation and adsorption of the second ion exchange product has the advantage of quantitative adsorption. In this invention, after the rare earth oxide precipitation and adsorption in step (3), solid-liquid separation is performed followed by a fourth drying. The solid-liquid separation method in this invention has been described above and will not be repeated here. In this invention, the selection range of conditions for the fourth drying is relatively wide; preferably, the conditions for the fourth drying include: temperature of 50-180℃ and time of 2-10h.

[0072] In a preferred embodiment, the number of repetitions in step (3) is 1-3 times, preferably 1-2 times.

[0073] The third aspect of this invention provides a modified molecular sieve prepared by the preparation method described in any one of the second aspects.

[0074] The fourth aspect of this invention provides the application of the modified molecular sieve described in the first or third aspect in the alkylation reaction of linear olefins and aromatics to prepare linear alkylbenzenes.

[0075] The present invention will be described in detail below through embodiments. In the following embodiments, unless otherwise specified, all raw materials used are commercially available.

[0076] In the following examples, the rare earth element content in the bulk phase of the modified molecular sieve, calculated as oxides, was determined by XRF, the rare earth element content in the surface phase of the molecular sieve, calculated as oxides, was determined by XPS and then calculated, and the ratio of rare earth content in the β cage to the supercage of the molecular sieve was calculated by integrating the characteristic peak area of ​​XRD.

[0077] Example 1

[0078] Preparation of La-modified molecular sieves

[0079] (1) Prepare a 0.5 mol / L lanthanum nitrate solution, then mix it with NH4Y molecular sieve (silicon-aluminum molar ratio of 3.13) and stir evenly. Heat and stir at 85℃ for 1 h at a stirring rate of 400 r / min. The mass ratio of NH4Y molecular sieve to lanthanum nitrate solution is 350 g / L. After heating, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0080] (2) The filter cake was roasted at high temperature for 1 hour. The roasting conditions were: temperature 560℃, pressure 0.02MPa, and 0.1mol / L ammonia water was introduced at a flow rate of 0.1mL / min.

[0081] (3) The calcined sample was mixed with 0.005 mol / L HNO3 solution and stirred evenly. The mixture was heated and stirred at 75°C for 1 h at a stirring rate of 400 r / min. The mixture was then filtered, the filter cake was thoroughly washed, and the filter cake was dried at 110°C for 4 h.

[0082] (4) Repeat steps (1)-(3) once to obtain the first ion exchange product.

[0083] (5) Mix the sample with 0.5 mol / L lanthanum nitrate solution and stir evenly. Heat and stir at 85°C for 1 h at a stirring rate of 400 r / min. The mass ratio of the first ion exchange product to the volume of the lanthanum nitrate solution is 300 g / L. After heating, filter, wash the filter cake and dry at 110°C for 4 h.

[0084] (6) Repeat step (5) once to obtain the second ion exchange product.

[0085] (7) Mix the filter cake with 0.5 mol / L lanthanum nitrate solution, and adjust the pH of the slurry to 9 with 2 mol / L ammonia water. Stir at 25℃ for 0.4 h with a stirring rate of 400 r / min. After stirring, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0086] (8) Repeat step (7) once.

[0087] (9) The molecular sieve prepared above is numbered S1.

[0088] XRD, XRF, and XPS analyses were performed on molecular sieve S1 to obtain the mass fraction of La (calculated as oxide) loaded on the molecular sieve, the ratio of La content in the β cage to the supercage, the ratio of La mass fraction (calculated as oxide) in the surface phase to the bulk phase, and the silica-alumina molar ratio of the modified molecular sieve. The results are shown in Table 1, and the XRD patterns are shown in the figure. Figure 1 As shown, the ratio of the area of ​​the characteristic peak at 11.9° to that at 12.4° is the ratio of the La element content in the β cage and the supercage of the modified molecular sieve.

[0089] In Table 1, the mass fraction of La element loaded in the molecular sieve as oxides is represented by the R value, the ratio of La element content in the β cage to the supercage of the molecular sieve is represented by the K value, and the ratio of the mass fraction of La element in the surface phase to the bulk phase of the molecular sieve as oxides is represented by the B value.

[0090] Example 2

[0091] (1) Prepare a 0.8 mol / L lanthanum nitrate solution, then mix it with NH4Y molecular sieve (silicon-aluminum molar ratio of 3.13) and stir evenly. Heat and stir at 95℃ for 1.2 h at a stirring rate of 400 r / min. The mass ratio of NH4Y molecular sieve to lanthanum nitrate solution is 350 g / L. After heating, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0092] (2) The filter cake was roasted at high temperature for 1.5 hours. The roasting conditions were: temperature 580℃, pressure 0.05MPa, and 0.3mol / L ammonia water was introduced at a flow rate of 3mL / min.

[0093] (3) The calcined sample was mixed with 0.005 mol / L HNO3 solution and stirred evenly. The mixture was heated and stirred at 75°C for 1 h at a stirring rate of 400 r / min. The mixture was then filtered, the filter cake was thoroughly washed, and the filter cake was dried at 110°C for 4 h.

[0094] (4) Repeat steps (1)-(3) once to obtain the first ion exchange product.

[0095] (5) Mix the sample with 0.8 mol / L lanthanum nitrate solution and stir evenly. Heat and stir at 100℃ for 1.2 h at a stirring rate of 400 r / min. The mass ratio of the first ion exchange product to the volume of the lanthanum nitrate solution is 300 g / L. After heating, filter, wash the filter cake and dry at 110℃ for 4 h.

[0096] (6) Repeat step (5) once to obtain the second ion exchange product.

[0097] (7) Mix the filter cake with 0.5 mol / L lanthanum nitrate solution, and adjust the pH of the slurry to 9 with 2 mol / L ammonia water. Stir at 30℃ for 0.8 h with a stirring rate of 400 r / min. After stirring, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0098] (8) Repeat step (7) once.

[0099] (9) The molecular sieve prepared above is numbered S2.

[0100] Example 3

[0101] (1) Prepare a 0.35 mol / L lanthanum nitrate solution, then mix it with NH4Y molecular sieve (silicon-aluminum molar ratio of 3.13) and stir evenly. Heat and stir at 75℃ for 0.8 h at a stirring rate of 400 r / min. The mass ratio of NH4Y molecular sieve to lanthanum nitrate solution is 350 g / L. After heating, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0102] (2) The filter cake was roasted at high temperature for 0.8h. The roasting conditions were: temperature 450℃, pressure 0.01MPa, and 0.08mol / L ammonia water was introduced at a flow rate of 0.05mL / min.

[0103] (3) The calcined sample was mixed with 0.005 mol / L HNO3 solution and stirred evenly. The mixture was heated and stirred at 75°C for 1 h at a stirring rate of 400 r / min. The mixture was then filtered, the filter cake was thoroughly washed, and the filter cake was dried at 110°C for 4 h.

[0104] (4) Repeat steps (1)-(3) once to obtain the first ion exchange product.

[0105] (5) Mix the sample with 0.35 mol / L lanthanum nitrate solution and stir evenly. Heat and stir at 80°C for 0.8 h at a stirring rate of 400 r / min. The mass ratio of the first ion exchange product to the volume of the lanthanum nitrate solution is 300 g / L. After heating, filter, wash the filter cake and dry at 110°C for 4 h.

[0106] (6) Repeat step (5) once to obtain the second ion exchange product.

[0107] (7) Mix the filter cake with 0.5 mol / L lanthanum nitrate solution, and adjust the pH of the slurry to 9 with 2 mol / L ammonia water. Stir at 5℃ for 0.2 h with a stirring rate of 400 r / min. After stirring, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0108] (8) Repeat step (7) once.

[0109] (9) The molecular sieve prepared above is numbered S3.

[0110] Example 4

[0111] The method is the same as in Example 1, except that the concentration of the lanthanum nitrate solution in step (1) is replaced with 0.2 mol / L, and the concentration of the lanthanum nitrate solution in step (5) is replaced with 0.2 mol / L. The molecular sieve prepared above is designated as S4.

[0112] Example 5

[0113] The method is the same as in Example 1, except that the heating temperature in step (1) is replaced with 70°C and the stirring time is replaced with 0.6 h, and the heating temperature in step (5) is replaced with 80°C and the stirring time is replaced with 0.6 h. The molecular sieve prepared above is numbered S5.

[0114] Example 6

[0115] The method is the same as in Example 1, except that the concentration of the HNO3 solution in step (3) is replaced with 0.0001 mol / L. The molecular sieve prepared above is designated as S6.

[0116] Example 7

[0117] The method is the same as in Example 1, except that the calcination temperature in step (2) is replaced with 420°C. The molecular sieve prepared above is designated as S7.

[0118] Example 8

[0119] The method is the same as in Example 1, except that the lanthanum nitrate solution in step (1) is replaced with yttrium nitrate solution, the lanthanum nitrate solution in step (5) is replaced with yttrium nitrate solution, and the lanthanum nitrate solution in step (7) is replaced with yttrium nitrate solution. The molecular sieve prepared above is designated as S8.

[0120] Example 9

[0121] The method was followed as in Example 1, except that the 0.1 mol / L ammonia in step (2) was replaced with air as the calcination atmosphere. The molecular sieve prepared above was designated as S9.

[0122] Example 10

[0123] The method is the same as in Example 1, except that the NH4Y molecular sieve (silicon-to-aluminum molar ratio of 3.13) in step (1) is replaced with NH4X molecular sieve (silicon-to-aluminum molar ratio of 1.21). The molecular sieve prepared above is designated as S10.

[0124] Comparative Example 1

[0125] The method was followed as in Example 1, except that the concentration of the lanthanum nitrate solution used in steps (1), (5), and (7) was 0.15 mol / L. The obtained comparative molecular sieve was designated CS1.

[0126] Comparative Example 2

[0127] The method was followed as in Example 1, except that the concentration of the lanthanum nitrate solution used in steps (1), (5), and (7) was 1.3 mol / L. The resulting comparative molecular sieve was designated CS2.

[0128] Comparative Example 3

[0129] The method was followed as in Example 1, except that the mass ratio of NH4Y molecular sieve to lanthanum nitrate solution in step (1) was 150 g / L, and the mass ratio of NH4Y molecular sieve to lanthanum nitrate solution in step (5) was 100 g / L. The resulting comparative molecular sieve was designated CS3.

[0130] Comparative Example 4

[0131] The method described in Example 1 was followed, except that steps (4) and (6) were omitted. The resulting comparative molecular sieve was designated CS4.

[0132] Table 1

[0133]

[0134]

[0135] Performance testing

[0136] This performance test demonstrates that the molecular sieve sample provided by this invention can be used in the linear alkylbenzene preparation reaction.

[0137] The molecular sieve samples from the examples and comparative examples were subjected to an alkylation reaction of benzene with 1-dodecene at 130°C and 2.5 MPa, with a 1-dodecene feed mass hourly space velocity of 0.708 h⁻¹. -1 The molar ratio of benzene to 1-dodecene was 10. Under these reaction conditions, the conversion rate of 1-dodecene, the linearity of the target product, and the selectivity of isoolefins are shown in Table 2.

[0138] Conversion rate of 1-dodecene (%) = (Amount of 1-dodecene before reaction - Amount of 1-dodecene after reaction) / Amount of 1-dodecene before reaction × 100%.

[0139] Isomeric olefin selectivity (%) = Amount of isomeric olefin after reaction / Amount of all reaction products × 100%;

[0140] Linearity (%) = Amount of linear alkylbenzene after reaction / Amount of monoalkylbenzene after reaction × 100%.

[0141] Table 2

[0142]

[0143]

[0144] Note: In Table 2, "-" indicates that the modified molecular sieve has been deactivated.

[0145] As can be seen from the data in Table 2, in the embodiments of the present invention, when the R value, K value and B value of the molecular sieve are within the preferred range, it is more suitable for catalyzing the alkylation reaction of benzene and 1-dodecene: the linearity of the target product reaches more than 94%, the selectivity of isomeric olefins is less than 1%, and the catalytic life is longer, reaching more than 34 hours.

[0146] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A modified molecular sieve, characterized in that, The modified molecular sieve comprises a molecular sieve and rare earth elements. The modified molecular sieve has a β-cage and a supercage structure. The R value of the modified molecular sieve is 16-28%, and the K value is 2-8. Wherein, the R value represents the mass fraction of rare earth elements in the modified molecular sieve as oxides, and the K value represents the ratio of the rare earth element content in the β-cage to that in the supercage of the modified molecular sieve. The modified molecular sieve has a B value of 1.2-1.4, where the B value represents the mass fraction ratio of rare earth elements (calculated as oxides) in the surface phase and bulk phase of the modified molecular sieve. The rare earth element is selected from at least one of La, Ce, Pr, Nd, Sm and Yb; The method for preparing the modified molecular sieve includes: (1) Place the molecular sieve in a rare earth element ion exchange solution, perform the first ion exchange, and then calcine it. Treat the calcined product with acid in an acid solution. Repeat the above steps at least once to obtain the first ion exchange product. (2) Place the first ion exchange product in a rare earth element ion exchange solution for a second ion exchange, and repeat the above steps at least once to obtain the second ion exchange product. (3) Place the second ion exchange product in a rare earth element ion exchange solution for rare earth oxide precipitation and adsorption, repeat the above steps at least once, so that the R value is 16-28%, and obtain the modified molecular sieve. In step (1), the calcination is carried out under alkaline atmosphere and slightly positive pressure conditions; The alkaline atmosphere in step (1) is provided by ammonia water; In step (1), the calcination conditions include: a temperature of 450-580℃, a time of 0.8-1.5h, and a pressure of 0.01-0.05MPa, with the pressure measured by a gauge. The concentrations of the rare earth element ion exchange solutions in steps (1), (2), and (3) are each 0.35-1 mol / L. The conditions for ion exchange in step (1) include: a temperature of 75-95℃, a time of 0.8-1.2h, and a stirring rate of 300-400r / min; The concentration of the acid solution in step (1) is 0.005-0.1 mol / L; Step (1) The ratio of the molecular sieve mass to the volume of the rare earth element ion exchange liquid is 200-400 g / L; Step (2) The ratio of the mass of the first ion exchange product to the volume of the rare earth element ion exchange solution is 300-450 g / L; The conditions for the second ion exchange include: a temperature of 80-130℃, a time of 0.8-3h, and a stirring rate of 200-500r / min.

2. The modified molecular sieve according to claim 1, wherein, The modified molecular sieve is a silica-alumina molecular sieve.

3. The modified molecular sieve according to claim 1 or 2, wherein, The modified molecular sieve has a silicon-to-aluminum molar ratio of 1-50.

4. The modified molecular sieve according to claim 3, wherein, The modified molecular sieve has a silicon-to-aluminum molar ratio of 1.5-9.

5. The modified molecular sieve according to claim 1 or 2, wherein, The rare earth elements are La and / or Ce.

6. A method for preparing the modified molecular sieve according to claim 1, wherein, The method includes: (1) Place the molecular sieve in a rare earth element ion exchange solution, perform the first ion exchange, and then calcine it. Treat the calcined product with acid in an acid solution. Repeat the above steps at least once to obtain the first ion exchange product. (2) Place the first ion exchange product in a rare earth element ion exchange solution for a second ion exchange, and repeat the above steps at least once to obtain the second ion exchange product. (3) Place the second ion exchange product in a rare earth element ion exchange solution for rare earth oxide precipitation and adsorption, repeat the above steps at least once, so that the R value is 16-28%, and obtain the modified molecular sieve. In step (1), the calcination is carried out under alkaline atmosphere and slightly positive pressure conditions; The alkaline atmosphere in step (1) is provided by ammonia water; In step (1), the calcination conditions include: a temperature of 450-580℃, a time of 0.8-1.5h, and a pressure of 0.01-0.05MPa, with the pressure measured by a gauge. The concentrations of the rare earth element ion exchange solutions in steps (1), (2), and (3) are each 0.35-1 mol / L. The conditions for ion exchange in step (1) include: a temperature of 75-95℃, a time of 0.8-1.2h, and a stirring rate of 300-400r / min; The concentration of the acid solution in step (1) is 0.005-0.1 mol / L; Step (1) The ratio of the molecular sieve mass to the volume of the rare earth element ion exchange liquid is 200-400 g / L; Step (2) The ratio of the mass of the first ion exchange product to the volume of the rare earth element ion exchange solution is 300-450 g / L; The conditions for the second ion exchange include: a temperature of 80-130℃, a time of 0.8-3h, and a stirring rate of 200-500r / min.

7. The method according to claim 6, wherein, In step (1), the molecular sieve is a silica-alumina molecular sieve.

8. The method according to claim 7, wherein, The silicon-aluminum molar ratio of the molecular sieve in step (1) is 1-50.

9. The method according to claim 6, wherein, The molecular sieve in step (1) is of the ammonium type and / or hydrogen type.

10. The method according to claim 6, wherein, The molecular sieve in step (1) is an X-type molecular sieve and / or a Y-type molecular sieve.

11. The method according to any one of claims 6-10, wherein, In steps (1), (2), and (3), the rare earth element ion exchange solutions are each independently selected from solutions containing rare earth element compounds.

12. The method according to claim 11, wherein, The rare earth element compound is selected from at least one of the nitrate, sulfate and chloride salts of the corresponding rare earth element.

13. The method according to claim 11, wherein, Step (1) The first ion exchange is carried out under stirring conditions.

14. The method according to any one of claims 6-10, wherein, The concentration of ammonia in step (1) is 0.05-0.5 mol / L.

15. The method according to any one of claims 6-10, wherein, The acid in the acid solution in step (1) is an inorganic acid.

16. The method according to claim 15, wherein, The acid in the acid solution in step (1) is at least one of nitric acid, hydrochloric acid and sulfuric acid.

17. The method according to any one of claims 6-10, wherein, The acid treatment conditions in step (1) include: a temperature of 40-80℃, a time of 0.5-2h, and a stirring rate of 200-500r / min.

18. The method according to claim 17, wherein, The acid treatment conditions in step (1) include: a temperature of 55-75℃, a time of 0.8-1.5h, and a stirring rate of 300-400r / min.

19. The method according to any one of claims 6-10, wherein, Step (1) is repeated 1-3 times.

20. The method according to claim 19, wherein, The number of repetitions in step (1) is 1-2 times.

21. The method according to any one of claims 6-10, wherein, In step (2), the second ion exchange is carried out under stirring conditions.

22. The method according to claim 21, wherein, In step (2), the conditions for the second ion exchange include: a temperature of 80-100℃, a time of 0.8-1.2h, and a stirring rate of 300-400r / min.

23. The method according to any one of claims 6-10, wherein, Step (2) is repeated 1-3 times.

24. The method according to claim 23, wherein, The number of repetitions in step (2) is 1-2 times.

25. The method according to any one of claims 6-10, wherein, In step (3), the ratio of the mass of the second ion exchange product to the volume of the rare earth element ion exchange liquid is 100-400 g / L.

26. The method of claim 25, wherein, In step (3), the ratio of the mass of the second ion exchange product to the volume of the rare earth element ion exchange liquid is 250-350 g / L.

27. The method according to any one of claims 6-10, wherein, The rare earth oxide precipitation and adsorption in step (3) are carried out under alkaline conditions.

28. The method according to claim 27, wherein, The alkaline conditions described in step (3) are provided by an alkaline compound.

29. The method according to claim 28, wherein, The alkaline compound in step (3) is selected from at least one of ammonia, ammonium carbonate and urea.

30. The method according to claim 29, wherein, The concentration of the alkaline compound in step (3) is 1-4 mol / L.

31. The method according to any one of claims 6-10, wherein, The conditions for rare earth oxide precipitation and adsorption in step (3) include: temperature of 0-50℃, time of 0.2-1.5h, and stirring rate of 200-500r / min.

32. The method according to claim 31, wherein, The conditions for the rare earth oxide precipitation and adsorption in step (3) include: temperature of 5-30℃, time of 0.2-0.8h, and stirring rate of 300-400r / min.

33. The method according to any one of claims 6-10, wherein, Step (3) is repeated 1-3 times.

34. The method according to claim 33, wherein, The number of repetitions in step (3) is 1-2 times.

35. The application of the modified molecular sieve according to any one of claims 1-5 in the alkylation reaction for the preparation of linear alkylbenzenes from linear olefins and aromatics.

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