Rare earth modified molecular sieve, its preparation method and application

Abstract

The present application relates to the technical field of molecular sieve preparation, and discloses a rare earth modified molecular sieve and a preparation method and application thereof. The rare earth modified molecular sieve comprises a molecular sieve and a rare earth element loaded on the molecular sieve, the E value of the rare earth modified molecular sieve is greater than 10%, and the C value is 0.3-2.8, wherein the E value represents the mass fraction of the rare earth element in the rare earth modified molecular sieve in terms of an oxide, and the C value represents the ratio of the acid amount of B acid to L acid of the rare earth modified molecular sieve. The modified molecular sieve provided by the present application is loaded with a large content of rare earth elements, and the distribution characteristics of B acid and L acid of the molecular sieve are adjusted, which is conducive to improving the selectivity of linear alkylbenzene, improving the alkylation reaction activity and the linearity of the product, and the linearity of the alkylation product can reach more than 94%, and the isomerization olefin selectivity is less than 1%.

Description

Technical Field

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

[0002] Linear alkylbenzenes are mainly used to prepare linear alkylbenzene sulfonates, which are primarily used as anionic surfactants. The most widely used catalysts in existing linear alkylbenzene production processes are liquid catalysts such as HF and AlCl3. While liquid catalyst technology is mature, it also suffers from various drawbacks, including environmental pollution, severe equipment corrosion, difficulty in separating the product from the catalyst, and high investment costs. In today's context of advocating for environmentally friendly and safe production, there is a need to develop novel green catalysts for the catalytic production of linear alkylbenzenes.

[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 linear alkylbenzenes mainly focuses on Y, β and mordenite. The main problem is that the molecular sieves generally have short catalytic lifetimes and low linearity of the products (Bull. Korean Chem. Soc., 2001, 22(9): 1056-1058).

[0005] Patent application No. 201080056751.5 discloses an alkylation catalyst for aromatic compounds, which obtains the catalyst through a secondary exchange of rare earth elements, thereby improving the linearity of the product. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low catalytic activity and short service life of existing molecular sieves, and to provide a rare earth modified molecular sieve, its preparation method and application. The rare earth modified molecular sieve is loaded with a large content of rare earth elements, and the distribution characteristics of Brønsted acid and Lewis acid in the modified molecular sieve are controlled, which can improve the catalytic activity and service life of the modified molecular sieve.

[0007] To achieve the above objectives, the first aspect of the present invention provides a rare earth modified molecular sieve, wherein the rare earth modified molecular sieve comprises a molecular sieve and rare earth elements loaded on the molecular sieve, the rare earth modified molecular sieve has an E value greater than 10% and a C value of 0.3-2.8, wherein the E value represents the mass fraction of rare earth elements in the rare earth modified molecular sieve as oxides, and the C value represents the ratio of the amount of Brønsted acid to Lewis acid in the rare earth modified molecular sieve.

[0008] Preferably, the micropore specific surface area of ​​the rare earth modified molecular sieve is reduced by more than 7% compared with that of the molecular sieve.

[0009] Preferably, the micropore volume of the rare earth modified molecular sieve is reduced by more than 7% compared with that of the molecular sieve.

[0010] A second aspect of the present invention provides a method for preparing rare earth modified molecular sieves, wherein the method includes:

[0011] (1) The molecular sieve is placed in a solution containing rare earth element compounds for ion exchange, followed by solid-liquid separation and drying, and then subjected to a first calcination. The above steps are repeated at least once to obtain the ion exchange product.

[0012] (2) The ion exchange product is optionally subjected to at least one second calcination and then to at least one third calcination, so that the C value is 0.3-2.8, to obtain rare earth modified molecular sieve; the C value represents the ratio of the amount of Brønsted acid to L-acid in the rare earth modified molecular sieve, and the E value of the rare earth modified molecular sieve is greater than 10%, where the E value represents the mass fraction of rare earth elements in the rare earth modified molecular sieve as oxides.

[0013] The third aspect of this invention provides a rare earth 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 rare earth modified molecular sieve described in the first or third aspect in the alkylation reaction for preparing linear alkylbenzenes.

[0015] The inventors of this invention discovered in their research that the sites of both Brønsted (B) and Lewis (L) acids can serve as active sites for the catalytic synthesis of linear alkylbenzenes. The modified molecular sieve provided by this invention, by loading a large amount of rare earth elements, adjusts the distribution characteristics of Brønsted (B) and Lewis (L) acids in the molecular sieve. In preferred cases, it simultaneously controls the specific surface area and micropore volume of the molecular sieve micropores. The confinement effect provided by the appropriate specific surface area and micropore volume of the molecular sieve micropores is beneficial to improving the selectivity of linear alkylbenzenes, thereby increasing the alkylation reaction activity, inhibiting the olefin isomerization reaction, and ultimately achieving the goal of improving the linearity of the product. Attached Figure Description

[0016] Figure 1This is the Py-IR spectrum of the modified molecular sieve provided 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 rare earth modified molecular sieve, wherein the rare earth modified molecular sieve includes a molecular sieve and rare earth elements supported on the molecular sieve, the rare earth modified molecular sieve has an E value greater than 10% and a C value of 0.3-2.8, wherein the E value represents the mass fraction of rare earth elements in the rare earth modified molecular sieve as oxides, and the C value represents the ratio of the amount of Brønsted acid to Lewis acid in the rare earth modified molecular sieve.

[0019] According to a preferred embodiment of the present invention, the E value of the rare earth modified molecular sieve is 16-25%, 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%, and any value between any two groups.

[0020] According to a preferred embodiment of the present invention, the C value of the rare earth modified molecular sieve is 1-2.5, for example, it can be 1, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.5, and any value between any two groups.

[0021] In this invention, by introducing rare earth elements to regulate the ratio of Brønsted acid (B acid) to Lewis acid (L acid) in the modified molecular sieve, the ratio of B acid to L acid in the rare earth modified molecular sieve is made to be within the range described in this invention, thereby achieving the effect of synergistic catalysis of B acid and L acid and improving catalytic activity.

[0022] In this invention, the "E value" is measured by XRF. The specific 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 "C value" is obtained through Py-IR measurement. Specifically, the 1540 cm⁻¹ value in the Py-IR spectrum is... -1 The characteristic peak at 1450 cm⁻¹ is a characteristic peak of Brønsted acid. -1 The characteristic peak at this point is the characteristic peak of L acid, the desorption temperature is 200℃, and the "C value" is the ratio of the peak area of ​​the characteristic peak of B acid to the peak area of ​​the characteristic peak of L acid.

[0024] According to a preferred embodiment of the present invention, the micropore specific surface area of ​​the rare earth modified molecular sieve is reduced by more than 7% compared with that of the molecular sieve, and more preferably by 7-28%.

[0025] According to a preferred embodiment of the present invention, the micropore volume of the rare earth modified molecular sieve is reduced by more than 7% compared with that of the molecular sieve, and more preferably by 7-28%.

[0026] The advantage of this preferred embodiment is that it modifies the molecular sieve channels to suppress the formation of isomers.

[0027] According to a preferred embodiment of the present invention, the microporous specific surface area of ​​the rare earth modified molecular sieve is 400-600 m². 2 / g, further preferably 450-550m 2 / g.

[0028] According to a preferred embodiment of the present invention, the micropore volume of the rare earth modified molecular sieve is 0.16-0.26 cm³. 3 / g, further preferably 0.18-0.24cm 3 / g.

[0029] According to a preferred embodiment of the present invention, the micropore specific surface area of ​​the molecular sieve without rare earth element modification is 620-680 m². 2 / g, micropore volume is 0.27-0.31cm³ 3 / g, compared with molecular sieves without rare earth element modification, the modified molecular sieve of the present invention has a smaller micropore specific surface area and pore volume, and the molecular sieve channels are modified to suppress the formation of isomers.

[0030] In this invention, the microporous specific surface area and pore volume of modified molecular sieves and unmodified molecular sieves were measured by the BET method. Specifically, the instrument used was a Micromeritics ASAP2460 multi-station specific surface area and porosity analyzer. The testing procedure involved evacuating the sample to a vacuum of 330°C to 10... -3The catalyst was kept at low temperature for 9 hours to remove adsorbed water and other impurities. The specific surface area and micropore volume of the sample were calculated using the BET (Brunauer-Emmett-Teller) method.

[0031] In this invention, there is no particular limitation on the type of rare earth modified molecular sieve. Preferably, the rare earth modified molecular sieve is a silica-alumina molecular sieve.

[0032] According to a preferred embodiment of the present invention, the silicon-to-aluminum molar ratio of the rare earth modified molecular sieve is 0.5-50, preferably 1-8. In this invention, it is understood that the silicon-to-aluminum molar ratio refers to the molar ratio of silicon atoms to aluminum atoms.

[0033] 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.

[0034] According to a preferred embodiment of the present invention, the rare earth modified molecular sieve is selected from at least one of X-type molecular sieves, Y-type molecular sieves, β-type molecular sieves, mordenite, and MCM-22 type molecular sieves, and more preferably X-type molecular sieves and / or Y-type molecular sieves. The advantage of this preferred embodiment is that it facilitates the contact between aromatic hydrocarbons and straight-chain olefins.

[0035] In this invention, there is no particular limitation on the types of rare earth elements in the rare earth modified molecular sieve; 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.

[0036] According to a preferred embodiment of the present invention, the rare earth element is selected from at least one of Sc, Y, La, Ce, Pr, Nd, Sm and Yb, and more preferably La and / or Ce.

[0037] A second aspect of the present invention provides a method for preparing rare earth modified molecular sieves, wherein the method includes:

[0038] (1) The molecular sieve is placed in a solution containing rare earth element compounds for ion exchange, followed by solid-liquid separation and drying, and then subjected to a first calcination. The above steps are repeated at least once to obtain the ion exchange product.

[0039] (2) The ion exchange product is optionally subjected to at least one second calcination, followed by at least one third calcination, so that the C value is 0.3-2.8, to obtain a rare earth modified molecular sieve; the C value represents the ratio of the amount of Brønsted acid to L-acid in the rare earth modified molecular sieve, and the E value of the rare earth modified molecular sieve is greater than 10%, where the E value represents the mass fraction of rare earth elements in the rare earth modified molecular sieve as oxides.

[0040] The inventors of this invention discovered in their research that by using a combination of multiple ion exchanges and multiple calcinations, rare earth modified molecular sieves can be prepared with the advantage of inhibiting the formation of reaction byproducts and improving the linearity of the product by adjusting the acidity and pore size of the molecular sieve.

[0041] In this invention, by controlling the operation steps, conditions and the number of repetitions of each step in steps (1)-(2), the E value and C value in the rare earth modified molecular sieve are made to satisfy the above-mentioned E value being greater than 10% and C value being 0.3-2.8. In this invention, the preferred range of E value and C value (preferably, E value is 16-25% and C value is 1-2.5) and the determination method have been described in the first aspect and will not be repeated here.

[0042] In this invention, there is no particular limitation on the type of molecular sieve mentioned in step (1), and all molecular sieves defined in the art are applicable to this invention. Preferably, in step (1), the molecular sieve is a silica-alumina molecular sieve.

[0043] According to a preferred embodiment of the present invention, in step (1), the silicon-to-aluminum molar ratio of the molecular sieve is 0.5-50, preferably 1-8. It is understood in this invention that the silicon-to-aluminum molar ratio refers to the molar ratio of silicon atoms to aluminum atoms.

[0044] According to a preferred embodiment of the present invention, in step (1), the molecular sieve is in the hydrogen form and / or ammonium form, more preferably in the hydrogen form. The advantage of this preferred embodiment is that it can provide the Brønsted acid sites required for the molecular sieve.

[0045] According to a preferred embodiment of the present invention, in step (1), the molecular sieve is selected from at least one of X-type molecular sieve, Y-type molecular sieve, β-type molecular sieve, mordenite and MCM-22 type molecular sieve, and is more preferably X-type molecular sieve and / or Y-type molecular sieve.

[0046] In this invention, by selecting molecular sieves with the above-mentioned structure and properties as raw materials, it has the advantage of facilitating the contact between aromatic hydrocarbons and straight-chain olefins.

[0047] In this invention, the types of rare earth elements mentioned in step (1) are as described in the first aspect, and will not be repeated here.

[0048] In this invention, the range of rare earth element compounds selected in step (1) is relatively wide. Preferably, the rare earth element compound in step (1) is selected from at least one of the nitrates, sulfates, and chlorides of the corresponding rare earth elements, and more preferably a nitrate, such as lanthanum nitrate, yttrium nitrate, cerium nitrate, etc.

[0049] According to a preferred embodiment of the present invention, in step (1), the concentration of the solution containing the rare earth element compound is 0.15-1.5 mol / L, preferably 0.3-0.8 mol / L. The advantage of this preferred embodiment is that it facilitates the exchange of rare earth elements onto the molecular sieve, improving the exchange efficiency to achieve the target parameters.

[0050] According to a preferred embodiment of the present invention, in step (1), the volume ratio of the solution containing rare earth element compounds to the mass of the molecular sieve is 1-20 mL / g, preferably 3-9 mL / g.

[0051] According to a preferred embodiment of the present invention, in step (1), the ion exchange is carried out under stirring conditions.

[0052] In this invention, the conditions for ion exchange in step (1) are not particularly limited. Preferably, the conditions for ion exchange in step (1) include: a temperature of 60-125℃, a time of 0.3-1.4h, and a stirring rate of 200-510r / min; more preferably, a temperature of 75-95℃, a time of 0.7-1.1h, and a stirring rate of 300-450r / min. The advantage of this preferred embodiment is that it facilitates the contact and exchange between the molecular sieve and rare earth ions.

[0053] In this invention, the range of drying conditions in step (1) is relatively wide. Preferably, in step (1), the drying conditions include: a temperature of 60-200℃ and a time of 1-20h.

[0054] In this invention, a specific first calcination atmosphere and a first calcination atmosphere are selected to perform the first calcination and the second calcination, respectively. Preferably, in step (2), the first calcination and the second calcination are each carried out independently under an alkaline atmosphere and a slightly positive pressure. The advantage of this preferred embodiment is that it facilitates the migration of molecular sieve cations.

[0055] According to a preferred embodiment of the present invention, the alkaline atmosphere is provided by ammonia.

[0056] According to a preferred embodiment of the present invention, the concentration of the ammonia water is 0.05-0.5 mol / L, preferably 0.08-0.2 mol / L.

[0057] According to a preferred embodiment of the present invention, the ammonia water introduction rate is 0.02-5 mL / min compared to 50 g of the molecular sieve. It is understood that the introduction rate of the alkaline atmosphere (ammonia water) is proportional to the throughput of the molecular sieve; for example, as the throughput of the molecular sieve increases, the introduction rate of the alkaline atmosphere (ammonia water) can be increased proportionally. Those skilled in the art can select the appropriate rate based on actual needs.

[0058] According to a preferred embodiment of the present invention, in step (1), the first calcination conditions include: a temperature of 450-650°C, a time of 0.3-1.8 h, and a pressure of 0.01-0.1 MPa; preferably, a temperature of 500-580°C, a time of 0.6-1.5 h, and a pressure of 0.01-0.06 MPa, with the pressure measured in gauge pressure. The advantage of this preferred embodiment is that it promotes the migration of rare earth ions into the molecular sieve.

[0059] According to a preferred embodiment of the present invention, step (1) is repeated 1-5 times, preferably 1-2 times. The advantage of this preferred embodiment is that it allows for more complete ion exchange within the molecular sieve.

[0060] In this invention, the selection range for the second calcination conditions is relatively wide; they can be the same as or different from the selection range for the first calcination conditions. An advantage of this preferred embodiment is that it allows for further passivation treatment of the molecular sieve, thereby improving the stability of the rare earth modified molecular sieve.

[0061] According to a preferred embodiment of the present invention, in step (2), the conditions for the second calcination include: a temperature of 450-650°C, a time of 0.5-2h, and a pressure of 0.01-0.1MPa. Preferably, the temperature is 480-600°C, the time is 0.8-1.8h, and the pressure is 0.01-0.06MPa, with the pressure measured in gauge.

[0062] According to a preferred embodiment of the present invention, in step (2), the second roasting is repeated 1-5 times, preferably 1-2 times.

[0063] According to a preferred embodiment of the present invention, in step (2), the third calcination is carried out in an air atmosphere. Calcination in an air atmosphere has the advantage of further modulating the migration degree of rare earth ions, thereby controlling the distribution of Brønsted acid and Lewis acid in the modified molecular sieve.

[0064] In this invention, there is no particular limitation on the air introduction rate in step (2). Preferably, in step (2), the air introduction rate is 100-1000 mL / min, and more preferably 250-750 mL / min.

[0065] According to a preferred embodiment of the present invention, in step (2), the conditions for the third calcination include: a temperature of 450-650°C, a time of 0.8-3h, and a pressure of 0.01-0.1MPa. Preferably, the temperature is 500-620°C, the time is 0.8-2h, and the pressure is 0.01-0.06MPa, with the pressure measured in gauge.

[0066] According to a preferred embodiment of the present invention, the third roasting in step (2) is repeated 1-5 times, preferably 1-2 times.

[0067] The third aspect of this invention provides a rare earth modified molecular sieve prepared by the preparation method described in the second aspect.

[0068] The fourth aspect of this invention provides the application of the rare earth modified molecular sieve described in the first or second aspect in the alkylation reaction for preparing linear alkylbenzenes.

[0069] According to a preferred embodiment of the present invention, the raw materials for the alkylation reaction are straight-chain olefins and aromatics.

[0070] According to a preferred embodiment of the present invention, the linear olefin has 10-32 carbon atoms, preferably 10-24, and more preferably 11-16.

[0071] According to a preferred embodiment of the present invention, the unsaturated bond of the straight-chain olefin is located on the α carbon atom or an intermediate carbon atom of the straight-chain olefin, preferably, the unsaturated bond of the straight-chain olefin is located on the top carbon atom of the straight-chain olefin.

[0072] According to a preferred embodiment of the present invention, the aromatic hydrocarbon is selected from at least one of benzene, toluene, and ethylbenzene, preferably benzene. Benzene will be used illustratively to represent aromatic hydrocarbons in the following description.

[0073] In this invention, the alkylation reaction conditions can be selected from those conventionally chosen in the art, and will not be elaborated further here.

[0074] In the following embodiments, unless otherwise specified, all raw materials used are commercially available.

[0075] In the examples, the rare earth content of the modified molecular sieve was measured by XRF (based on rare earth oxides), the ratio of Brønsted acid to Lewis acid in the modified molecular sieve was calculated by Py-IR measurement, and the micropore specific surface area and micropore volume of the modified molecular sieve were determined by BET.

[0076] Example 1

[0077] (1) Prepare a 0.5 mol / L lanthanum nitrate solution, then mix it with HY 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 volume ratio of lanthanum nitrate solution to HY molecular sieve mass is 3 mL / g. After heating, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0078] (2) The filter cake was roasted at high temperature for 1 hour. The first roasting conditions were: temperature 560℃, pressure 0.02MPa, and 0.1mol / L ammonia water was introduced at a flow rate of 0.1mL / min.

[0079] (3) The calcined sample was mixed with 0.5 mol / L lanthanum nitrate solution and stirred evenly. The mixture was heated and stirred at 85°C for 1 h at a stirring rate of 400 r / min. After heating, the slurry was filtered and the filter cake was dried at 110°C for 4 h.

[0080] (4) The filter cake after the second drying is calcined at high temperature for 1 hour under the same calcination conditions as in step (2) to obtain the ion exchange product.

[0081] (5) The ion exchange product after calcination in step (4) is subjected to a second calcination under the same conditions as in step (2) for 1.5 h.

[0082] (6) The molecular sieve after calcination in step (5) is subjected to a third calcination at high temperature for 2 hours. The calcination conditions are: temperature 560℃, pressure 0.02MPa, and air is introduced at a flow rate of 500mL / min.

[0083] (7) The rare earth modified molecular sieve prepared above is numbered N1.

[0084] Rare earth modified molecular sieve N1 was subjected to XRF and Py-IR (e.g.) Figure 1 (As shown in the figure) BET analysis was performed to obtain the mass fraction of rare earth elements loaded on the molecular sieve, the ratio of B acid to L acid in the molecular sieve, the percentage decrease in micropore specific surface area, the percentage decrease in micropore volume, the specific surface area and micropore volume of the molecular sieve micropores, and the silicon-aluminum molar ratio. The results are shown in Table 1.

[0085] Py-IR spectrum as shown Figure 1 As shown, the 1540cm in the spectrum -1 The characteristic peak at 1450 cm⁻¹ is a characteristic peak of Brønsted acid. -1 The characteristic peak at this point is that of L acid, and the desorption temperature is 200℃.

[0086] In Table 1, the mass fraction of rare earth elements in rare earth modified molecular sieves is represented by the E value, and the ratio of B acid content to L acid content in rare earth modified molecular sieves is represented by the C value.

[0087] Example 2

[0088] (1) Prepare a 0.8 mol / L lanthanum nitrate solution, then mix it with HY molecular sieve (silicon-aluminum molar ratio of 3.13) and heat and stir at 85℃ for 1 h at a stirring rate of 400 r / min. The volume ratio of lanthanum nitrate solution to HY molecular sieve mass is 3 mL / g. After heating, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0089] (2) The filter cake was roasted at high temperature for 1.5 hours. The first roasting conditions were: temperature 580℃, pressure 0.06MPa, and 0.2mol / L ammonia water was introduced at a flow rate of 5mL / min.

[0090] (3) The calcined sample was mixed with 0.8 mol / L lanthanum nitrate solution and stirred evenly. The mixture was heated and stirred at 85°C for 1 h at a stirring rate of 400 r / min. After heating, the slurry was filtered and the filter cake was dried at 110°C for 4 h.

[0091] (4) The filter cake after the second drying is calcined at high temperature for 1.5 h under the same calcination conditions as in step (2) to obtain the ion exchange product.

[0092] (5) The ion exchange product after calcination in step (4) is subjected to a second calcination under the same conditions as in step (2) for 1.8 h.

[0093] (6) The molecular sieve after calcination in step (5) is subjected to a third calcination at high temperature for 2 hours. The calcination conditions are: temperature 620℃, pressure 0.02MPa, and air is introduced at a flow rate of 750mL / min.

[0094] (7) The rare earth modified molecular sieve prepared above is numbered N2.

[0095] Example 3

[0096] (1) Prepare a 0.3 mol / L lanthanum nitrate solution, then mix it with HY 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 volume ratio of lanthanum nitrate solution to HY molecular sieve mass is 3 mL / g. After heating, filter the slurry and dry the filter cake at 110℃ for 4 h.

[0097] (2) The filter cake was roasted at high temperature for 0.6h. The first roasting conditions were: temperature 500℃, pressure 0.01MPa, and 0.08mol / L ammonia water was introduced at a flow rate of 0.02ml / min.

[0098] (3) The calcined sample was mixed with 0.3 mol / L lanthanum nitrate solution and stirred evenly. The mixture was heated and stirred at 85°C for 1 h at a stirring rate of 400 r / min. After heating, the slurry was filtered and the filter cake was dried at 110°C for 4 h.

[0099] (4) The filter cake after the second drying was calcined at high temperature for 0.6 h under the same calcination conditions as in step (2) to obtain the ion exchange product.

[0100] (5) The ion exchange product after calcination in step (4) is subjected to a second calcination under the same conditions as in step (2) for 0.8 h.

[0101] (6) The molecular sieve after calcination in step (5) is subjected to a third calcination at high temperature for 0.8 h. The calcination conditions are: temperature 500℃, pressure 0.02MPa, and air is introduced at a flow rate of 250mL / min.

[0102] (7) The rare earth modified molecular sieve prepared above is numbered N3.

[0103] Example 4

[0104] The method is the same as in Example 1, except that the concentration of lanthanum nitrate solution in step (1) is replaced with 0.15 mol / L, and the concentration of lanthanum nitrate solution in step (3) is replaced with 0.15 mol / L.

[0105] The rare earth modified molecular sieve prepared above is designated as N4.

[0106] Example 5

[0107] The method is the same as in Example 1, except that the roasting temperature in step (2) is replaced with 550°C, the roasting temperature in step (5) is replaced with 500°C, and the roasting temperature in step (6) is replaced with 600°C.

[0108] The rare earth modified molecular sieve prepared above is designated as N5.

[0109] Example 6

[0110] The method is the same as in Example 1, except that the roasting temperature in step (2) is replaced with 450°C, the roasting temperature in step (5) is replaced with 450°C, and the roasting temperature in step (6) is replaced with 450°C.

[0111] The rare earth modified molecular sieve prepared above is designated as N6.

[0112] Example 7

[0113] The method is the same as in Example 1, except that the heating temperature in step (1) is replaced with 60°C and the heating temperature in step (3) is replaced with 60°C.

[0114] The rare earth modified molecular sieve prepared above is designated as N7.

[0115] Example 8

[0116] The method is the same as in Example 1, except that steps (3) and (4) are repeated twice.

[0117] The rare earth modified molecular sieve prepared above is designated as N8.

[0118] Example 9

[0119] The method is the same as in Example 1, except that the lanthanum nitrate solution in step (1) is replaced with samarium nitrate solution, and the lanthanum nitrate solution in step (3) is replaced with samarium nitrate solution.

[0120] The rare earth modified molecular sieve prepared above is designated as N9.

[0121] Example 10

[0122] The method is the same as in Example 1, except that the flow rate of 0.1 mL / min for 0.1 mol / L ammonia water in step (2) is replaced by the flow rate of 500 mL / min for air as the roasting atmosphere.

[0123] The rare earth modified molecular sieve prepared above is designated as N10.

[0124] Comparative Example 1

[0125] The HY molecular sieve from Example 1 was used without rare earth modification. The resulting comparative molecular sieve was designated CN1.

[0126] Comparative Example 2

[0127] The method was followed as in Example 1, except that the concentration of the lanthanum nitrate solution in step (1) was replaced with 0.1 mol / L, and step (6) was omitted. The resulting comparative molecular sieve was designated CN2.

[0128] Table 1

[0129]

[0130] Performance testing

[0131] The alkylation reaction performance of the above examples and comparative examples was tested under the following conditions: alkylation reaction of benzene with 1-dodecene was carried out 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 product, and the selectivity of isoolefins are shown in Table 2.

[0132] Conversion rate of 1-dodecene (%) = (Amount of 1-dodecene before reaction - Amount of 1-dodecene after reaction) / Amount of 1-dodecene before reaction × 100%.

[0133] Isomeric olefin selectivity (%) = Amount of isomeric olefin after reaction / Amount of all reaction products × 100%;

[0134] Straight-chain degree (%) = Amount of straight-chain alkylbenzene after reaction / Amount of monoalkylbenzene after reaction × 100%.

[0135] Table 2

[0136]

[0137]

[0138] Note: In Table 2, "-" indicates that the molecular sieve has been deactivated.

[0139] As can be seen from Table 2, when the content of rare earth elements and the distribution of Brønsted acid and Lewis acid in the modified molecular sieve are within the range of the embodiments of the present invention, it is beneficial to improve the quality of the product of the alkylation reaction of benzene and 1-dodecene, so that the linearity of the product is greater than 94%.

[0140] 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 rare earth modified molecular sieve, characterized in that, The rare earth modified molecular sieve includes a molecular sieve and rare earth elements supported on the molecular sieve. The rare earth modified molecular sieve has an E value of 16-25% and a C value of 1-2.

48. The E value represents the mass fraction of rare earth elements in the rare earth modified molecular sieve as oxides, and the C value represents the ratio of the amount of Brønsted acid to L-acid in the rare earth modified molecular sieve. The specific surface area of ​​the micropores in the rare earth modified molecular sieve is reduced by 15.11-28% compared to that of a regular molecular sieve. The micropore volume of the rare earth modified molecular sieve is reduced by 15.6-28% compared with that of a regular molecular sieve; The rare earth modified molecular sieve is selected from at least one of X-type molecular sieve, Y-type molecular sieve, β-type molecular sieve, mordenite zeolite and MCM-22 type molecular sieve; The rare earth elements are selected from Sc, Y, and non-radioactive lanthanide elements; The C value was calculated using Py-IR, and the value at 1540 cm⁻¹ in the Py-IR spectrum is shown. -1 The characteristic peak at 1450 cm⁻¹ is a characteristic peak of Brønsted acid. -1 The characteristic peak at this point is the characteristic peak of L acid, the desorption temperature is 200℃, and the C value is the ratio of the peak area of ​​the characteristic peak of Br acid to the peak area of ​​the characteristic peak of L acid. A method for preparing rare earth modified molecular sieves, wherein the method includes: (1) The molecular sieve is placed in a solution containing rare earth element compounds for ion exchange, followed by solid-liquid separation and drying, and then subjected to a first calcination. The above steps are repeated at least once to obtain the ion exchange product. (2) The ion exchange product is subjected to at least one second calcination and then at least one third calcination to obtain rare earth modified molecular sieve; The first and second calcinations were carried out independently under alkaline atmosphere and slightly positive pressure conditions.

2. The rare earth modified molecular sieve according to claim 1, wherein, The rare earth modified molecular sieve has a microporous specific surface area of ​​400-600 m². 2 / g.

3. The rare earth modified molecular sieve according to claim 2, wherein, The rare earth modified molecular sieve has a microporous specific surface area of ​​450-550 m². 2 / g.

4. The rare earth modified molecular sieve according to claim 1, wherein, The rare earth modified molecular sieve has a micropore volume of 0.16-0.26 cm³. 3 / g.

5. The rare earth modified molecular sieve according to claim 4, wherein, The rare earth modified molecular sieve has a micropore volume of 0.18-0.24 cm³. 3 / g.

6. The rare earth modified molecular sieve according to claim 5, wherein, The silicon-aluminum molar ratio of the rare earth modified molecular sieve is 0.5-50.

7. The rare earth modified molecular sieve according to claim 1, wherein, The rare earth modified molecular sieve is an X-type molecular sieve and / or a Y-type molecular sieve.

8. The rare earth modified molecular sieve according to claim 1, wherein, The rare earth element is selected from at least one of Sc, Y, La, Ce, Pr, Nd, Sm and Yb.

9. The rare earth modified molecular sieve according to claim 8, wherein, The rare earth elements are La and / or Ce.

10. A method for preparing the rare earth modified molecular sieve of claim 1, wherein, The method includes: (1) The molecular sieve is placed in a solution containing rare earth element compounds for ion exchange, followed by solid-liquid separation and drying, and then subjected to a first calcination. The above steps are repeated at least once to obtain the ion exchange product. (2) The ion exchange product is subjected to at least one second calcination and then at least one third calcination to obtain rare earth modified molecular sieve; The first and second calcinations were carried out independently under alkaline atmosphere and slightly positive pressure conditions.

11. The method according to claim 10, wherein, In step (1), the silicon-aluminum molar ratio of the molecular sieve is 0.5-50.

12. The method according to claim 10, wherein, The molecular sieve is an X-type molecular sieve and / or a Y-type molecular sieve.

13. The method according to claim 10, wherein, In step (1), the rare earth element compound is selected from at least one of the nitrate, sulfate and chloride salts of the corresponding rare earth element.

14. The method of claim 10, wherein, In step (1), the concentration of the solution containing rare earth element compounds is 0.15-1.5 mol / L.

15. The method according to claim 10, wherein, In step (1), the volume ratio of the solution containing rare earth element compounds to the mass of the molecular sieve is 1-20 mL / g.

16. The method according to claim 15, wherein, In step (1), the volume ratio of the solution containing rare earth element compounds to the mass of the molecular sieve is 3-9 mL / g; And / or, in step (1), the ion exchange is carried out under stirring conditions.

17. The method according to claim 10, wherein, In step (1), the conditions for ion exchange include: a temperature of 60-125℃, a time of 0.3-1.4h, and a stirring rate of 200-510r / min.

18. The method according to claim 17, wherein, The conditions for ion exchange include: a temperature of 75-95℃, a time of 0.7-1.1h, and a stirring rate of 300-450r / min.

19. The method according to claim 10, wherein, In step (1), the drying conditions include: a temperature of 60-200℃ and a time of 1-20h.

20. The method according to any one of claims 10-19, wherein, The alkaline atmosphere is provided by ammonia.

21. The method according to claim 20, wherein, The concentration of the ammonia water is 0.05-0.5 mol / L.

22. The method according to claim 20, wherein, Compared to 50g molecular sieve, the ammonia water flow rate is 0.02-5mL / min.

23. The method according to claim 10, wherein, In step (1), the conditions for the first calcination include: a temperature of 450-650℃, a time of 0.3-1.8h, and a pressure of 0.01-0.1MPa, with the pressure measured by a gauge.

24. The method according to claim 23, wherein, The conditions for the first calcination include: a temperature of 500-580℃, a time of 0.6-1.5h, and a pressure of 0.01-0.06MPa.

25. The method according to claim 10, wherein, The step (1) is repeated 1-5 times.

26. The method of claim 25, wherein, The step (1) is repeated 1-2 times.

27. The method according to claim 10, wherein, In step (2), the conditions for the second calcination include: a temperature of 450-650℃, a time of 0.5-2h, and a pressure of 0.01-0.1MPa, with the pressure measured by a gauge.

28. The method according to claim 27, wherein, The conditions for the second calcination include: a temperature of 480-600℃, a time of 0.8-1.8h, and a pressure of 0.01-0.06MPa.

29. The method according to claim 10, wherein, In step (2), the second roasting is repeated 1-5 times.

30. The method according to claim 29, wherein, The second roasting is repeated 1-2 times.

31. The method according to claim 10, wherein, In step (2), the third calcination is carried out in an air atmosphere.

32. The method according to claim 31, wherein, In step (2), the air introduction rate is 100-1000 mL / min.

33. The method according to claim 10, wherein, In step (2), the conditions for the third calcination include: a temperature of 450-650℃, a time of 0.8-3h, and a pressure of 0.01-0.1MPa, with the pressure measured in gauge.

34. The method according to claim 33, wherein, The conditions for the third calcination include: a temperature of 500-620℃, a time of 0.8-2h, and a pressure of 0.01-0.06MPa.

35. The method according to any one of claims 31-34, wherein, The third roasting step (2) is repeated 1-5 times.

36. The method according to claim 35, wherein, The third roasting step (2) is repeated 1-2 times.

37. The application of the rare earth modified molecular sieve according to any one of claims 1-9 in the alkylation reaction for the preparation of linear alkylbenzenes.

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