A highly dispersible Ce-loaded Beta molecular sieve and its preparation method and application

Abstract

The present invention discloses a highly dispersible Ce-loaded Beta molecular sieve and a preparation method and application thereof, and belongs to the field of fine chemical technology. The highly dispersible Ce-loaded Beta molecular sieve is characterized in that the silicon-aluminum ratio of the molecular sieve is 41 to 45, the loading amount of Ce in the molecular sieve is 0.28 to 2.47wt%, the average particle size of the Ce oxide cluster is 2.37 to 3.00nm, and the dispersibility index of the Ce oxide cluster is 1.059 to 1.071. The highly dispersible Ce-loaded Beta molecular sieve of the present invention has high dispersibility of Ce metal elements, can effectively improve the selectivity of 2-LAB, and prolong the service life of the catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemical industry, and more specifically to a highly dispersed Ce-loaded Beta molecular sieve and a preparation method and application thereof. Background Art

[0002] Long-chain alkylbenzene is an important fine chemical raw material and intermediate. Its sulfonation product, long-chain alkylbenzene sulfonic acid or long-chain alkylbenzene sulfonate, occupies a very important position in anionic surfactants.

[0003] Long-chain alkylbenzenes are divided into two categories according to their structure: linear alkylbenzenes and branched alkylbenzenes. Branched alkylbenzenes are formed by the condensation of propylene tetramers and benzene, and their sulfonated products are difficult to degrade in the environment. Linear alkylbenzenes are produced by Friedel-Crafts alkylation reaction of benzene and linear olefins, and their sulfonated products are degradable in the environment. When linear long-chain olefins are alkylated with benzene, affected by the migration of carbon cations, long-chain linear alkylbenzenes (LAB) have multiple isomers, among which the long-chain alkylbenzene sulfonate produced by 2-position linear alkylbenzenes (2-LAB) has the best solubility, decontamination ability and biodegradability. At present, the main technologies for industrial production of long-chain linear alkylbenzenes are HF process and Detal process. The selectivity of 2-LAB prepared by HF process is only 15-18%, while the selectivity of 2-LAB prepared by Detal process is only 30-35%. In addition, the catalyst life of Detal process using solid acid as catalyst is short and the operating cost is high.

[0004] The prior art discloses a solid acid catalyst for alkylation of linear olefins with benzene to produce linear alkylbenzene. The solid acid catalyst used is a compound of a trace amount of alkali metal or alkaline earth metal oxide on the basis of a common solid catalyst WO3 / ZrO2, wherein the conversion rate of 1-dodecene is >98%, and the selectivity of 2-LAB is 44-46%. However, the selectivity of the catalyst for 2-LAB is still very low. Moreover, it is only recorded that the performance of the catalyst does not decrease significantly after 90 minutes of use, and the service life of the catalyst is not given.

[0005] Therefore, it is necessary to study a new type of solid acid catalyst, which can not only improve the selectivity of 2-LAB, but also improve the catalytic efficiency and stability of the catalyst and extend the service life of the catalyst in the process of catalyzing the alkylation of benzene with long-chain linear olefins to prepare LAB. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing solid acid catalyst used for the alkylation of linear olefins and benzene to produce linear alkylbenzenes, such as low selectivity for 2-LAB and short service life of the catalyst, and to provide a highly dispersible Ce (cerium) supported Beta molecular sieve, which has high dispersibility of Ce metal elements, can effectively improve the selectivity of 2-LAB and extend the service life of the catalyst.

[0007] Another object of the present invention is to provide a method for preparing a highly dispersible Ce-loaded Beta molecular sieve.

[0008] Another object of the present invention is to provide a highly dispersed Ce-supported Beta molecular sieve for use as a catalyst in the preparation of linear alkylbenzene from linear long-chain olefins and benzene.

[0009] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0010] A highly dispersible Ce-loaded Beta molecular sieve, wherein the silicon-aluminum ratio of the molecular sieve is 41-45, the Ce loading amount in the molecular sieve is 0.28-2.47wt%, the average particle size of the Ce oxide clusters is 2.37-3.00nm, and the dispersion index of the Ce oxide clusters is 1.059-1.071.

[0011] In the present invention, the Ce loading is measured by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0012] In the present invention, the dispersibility index of Ce oxide clusters refers to the degree of uniform dispersion of particle sizes.

[0013] The closer the dispersion index (DI) is to 1, the better the dispersion.

[0014] In the Ce-loaded Beta molecular sieve of the present invention, the rare earth metal Ce adsorbs long-chain olefins through π complexation, so that the electron cloud density of the long-chain olefins is reduced, and the long-chain olefin carbon cations are prompted to attack the benzene ring with a relatively large electron cloud density, and an alkylation reaction occurs, thereby inhibiting the occurrence of olefin oligomerization side reactions and extending the service life of the catalyst. In addition, in the Ce-loaded Beta molecular sieve of the present invention, the dispersion index (DI) of the Ce oxide cluster is 1.059 to 1.071, which is very close to 1, indicating that it has very high dispersion.

[0015] Furthermore, the Ce-loaded Beta molecular sieve of the present invention has a unique three-dimensional twelve-membered ring pore structure, has shape-selective catalytic performance for 2-LAB, and can effectively improve the selectivity of 2-LAB.

[0016] In the present invention, the Ce loading directly affects the catalytic activity of the catalyst. Within a certain range, the increase of Ce loading is beneficial to improving the conversion rate of 1-dodecene.

[0017] Preferably, the loading amount of Ce in the molecular sieve is 0.933-2.47 wt%.

[0018] In the present invention, the dispersibility of Ce directly affects the reaction activity. Under the same loading amount, the better the dispersibility of Ce is, the more conducive it is to improving the conversion rate of 1-dodecene.

[0019] Preferably, the dispersion index of the Ce oxide clusters is 1.059, 1.069 or 1.071.

[0020] Preferably, the average particle size of the Ce oxide clusters is 2.67-3.00 nm.

[0021] The average particle size of the Ce oxide cluster is 2.37 nm, 2.67 nm or 3.00 nm.

[0022] The present invention also protects a method for preparing the above-mentioned highly dispersible Ce-loaded Beta molecular sieve, comprising the following steps:

[0023] S1. Mixing a Ce source, citric acid and water to obtain a solution A;

[0024] S2. Adding a template, an aluminum source and a silicon source to the solution A obtained in step S1 in sequence, and aging to obtain a gel B;

[0025] S3. The gel B obtained in step S2 is crystallized, washed, dried, and calcined to obtain a highly dispersed Ce-loaded Beta molecular sieve;

[0026] In S1, the molar ratio of citric acid and Ce source is (2-8):(0.5-5);

[0027] In S2, the aging temperature is 15 to 35° C., and the aging time is 5 to 10 hours;

[0028] In S3, the crystallization temperature is 130 to 160° C., and the crystallization time is 5 to 10 days.

[0029] Optionally, the molar ratio of citric acid to the template is (0.03-0.16):1.

[0030] Optionally, the Ce source in S1 is cerium (III) chloride heptahydrate, cerium (III) nitrate hexahydrate or cerium acetate.

[0031] Preferably, the Ce source in S1 is cerium (III) chloride heptahydrate and / or cerium (III) nitrate hexahydrate.

[0032] Optionally, the water is one or more of deionized water, ultrapure water and RO water.

[0033] Optionally, the template is tetraethylammonium hydroxide.

[0034] Optionally, the silicon source is fumed silicon dioxide.

[0035] Optionally, the aluminum source is aluminum isopropoxide.

[0036] Optionally, the molar ratio of the silicon source, the aluminum source, and the template is 100:(1-3):(30-70).

[0037] Optionally, after the crystallization is completed, the steps of washing, drying and calcining are further included, wherein the washing refers to repeated washing with the water described in S1 until it becomes neutral. The drying refers to drying at 100-120° C. for 8-15 hours. The calcining refers to calcining in an air atmosphere at 550-600° C. for 5-8 hours.

[0038] The invention adds citric acid to a Beta molecular sieve synthesis precursor, utilizes citric acid and a Ce component of a cerium source to form a stable organic ligand salt, and synthesizes a Ce-loaded Beta molecular sieve catalyst by a one-step hydrothermal method. This method can overcome the difficulty that metal species are easily precipitated and Ce active components are difficult to effectively disperse in the process of preparing metal-loaded molecular sieves by a hydrothermal method, thereby improving the dispersion of Ce active components, and further improving the reaction activity of Beta molecular sieve in the process of catalyzing the alkylation of benzene and long-chain linear olefins to prepare LAB.

[0039] When the Ce source is an organic Ce source such as cerium acetate and citric acid is not added, the Ce species will precipitate and a highly dispersed Ce-loaded Beta molecular sieve cannot be obtained.

[0040] In S2 of the present invention, the template is first added to the solution A, which is beneficial to the dissolution of the aluminum source.

[0041] In S2 of the present invention, after the silicon source is added, the entire solution will become gel-like, so the silicon source needs to be added last.

[0042] Preferably, the molar ratio of the citric acid to the Ce source is 5:(1-3).

[0043] More preferably, the molar ratio of the citric acid to the Ce source is 5:(2-3).

[0044] More preferably, the molar ratio of the citric acid to the Ce source is 5:3.

[0045] Preferably, in S2, the aging time is 6 to 7 hours.

[0046] If the aging time is too short, the molecular sieve crystallization time will be too long, or even the synthesis will fail.

[0047] The present invention also protects the use of the highly dispersed Ce-supported Beta molecular sieve as a catalyst for catalyzing the preparation of linear alkylbenzene from linear long-chain olefins and benzene.

[0048] Preferably, in the application, the carbon chain length of the linear long-chain olefin is 10-14.

[0049] The present invention particularly protects the use of the above-mentioned highly dispersed Ce-supported Beta molecular sieve as a catalyst for preparing 2-dodecylbenzene from 1-dodecene and benzene.

[0050] The highly dispersed Ce-loaded Beta molecular sieve of the present invention is a catalyst that can improve the reaction activity in the liquid phase alkylation process of benzene and long-chain linear olefins, and can be used as a catalyst for catalyzing the alkylation of benzene and long-chain linear olefins to prepare 2-dodecylbenzene (2-LAB).

[0051] In the application, the molar ratio of benzene to 1-dodecene can be 5-25, preferably 8-20.

[0052] In the application, the catalytic temperature may be 60-100°C.

[0053] The lower the catalytic temperature, the slower the reaction rate.

[0054] The higher the catalytic temperature, the more energy is required.

[0055] Preferably, in the application, the catalytic temperature is 70-90°C and the mass space velocity is 30-50h -1 The service life of the highly dispersed Ce-loaded Beta molecular sieve is 9 to 13 hours.

[0056] The pressure is normal pressure.

[0057] The highly dispersed Ce-loaded Beta molecular sieve of the present invention has the significant advantages of high catalytic activity and long service life. -1 Under the harsh reaction conditions, it has a 1-dodecene conversion rate of more than 10% and a service life of 9 to 13 hours.

[0058] The reaction is an alkylation reaction, which can be carried out in a fixed bed reactor, the catalytic temperature is the bed temperature, and the reaction pressure can be normal pressure.

[0059] More preferably, the mass space velocity is 40h -1 .

[0060] Preferably, in the application, the conversion rate of 1-dodecene is 10-37%, and the selectivity of 2-dodecylbenzene is 80-90%.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] The present invention discloses a highly dispersible Ce-loaded Beta molecular sieve, wherein the silicon-aluminum ratio of the molecular sieve is 41-45, the Ce loading amount in the molecular sieve is 0.28-2.47wt%, the average particle size of the Ce oxide cluster is 2.37-3.00nm, and the dispersibility index of the Ce oxide cluster is 1.059-1.071. The molecular sieve catalyst of the present invention can be used for catalyzing the alkylation of benzene and long-chain linear olefins to prepare 2-LAB, has high dispersibility of Ce metal elements, can effectively improve the selectivity of 2-LAB, and prolongs the service life of the catalyst.

[0063] The highly dispersible Ce-loaded Beta molecular sieve provided by the present invention is synthesized in one step by a hydrothermal method and has the characteristics of uniform dispersion of Ce active components and high activity.

[0064] The highly dispersible Ce-loaded Beta molecular sieve of the present invention is heated to 80°C and the mass space velocity is 40h -1 Under the harsh reaction conditions, the selectivity of 2-dodecylbenzene can reach 80-90% and the service life can reach 9-13h. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 (a-f) are transmission electron microscope images (TEM images) and particle size distribution histograms of the highly dispersed Ce-loaded Beta molecular sieve catalysts prepared in Examples 1-3 of the present invention.

[0066] Figure 2 The X-ray diffraction diagrams of the highly dispersed Ce-loaded Beta molecular sieve catalysts prepared in Examples 1 to 3 of the present invention and Comparative Example 1 are shown.

[0067] Figure 3 This is a pyridine infrared spectrum of the highly dispersed Ce-loaded Beta molecular sieve catalyst prepared in Examples 1 to 3 of the present invention and Comparative Example 1.

[0068] Figure 4 This is the infrared spectrum of 2,6-di-tert-butylpyridine of the highly dispersed Ce-loaded Beta molecular sieve catalyst prepared in Examples 1 to 3 of the present invention and Comparative Example 1.

[0069] Figure 5 The 1-dodecene conversion rate and 2-dodecylbenzene selectivity graph of the highly dispersed Ce-loaded Beta molecular sieve catalyst prepared in Examples 1 to 3 of the present invention and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0070] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0071] Example 1

[0072] A highly dispersed Ce-loaded Beta molecular sieve, wherein the silicon-aluminum ratio of the molecular sieve is 43, the Ce loading amount in the molecular sieve is 0.283wt%, and the dispersion index of the Ce oxide cluster is 1.071.

[0073] The average particle size of the Ce oxide clusters is 2.37 nm.

[0074] The preparation method of the above-mentioned highly dispersible Ce-loaded Beta molecular sieve comprises the following steps:

[0075] Weighing raw materials:

[0076] The Ce source is cerium (III) chloride heptahydrate, 0.3726 g.

[0077] Citric acid, 1.0560 g.

[0078] Water is deionized water, 5.0755g.

[0079] The template is tetraethylammonium hydroxide, 21.0429 g, 35 wt% aqueous solution.

[0080] The silicon source was fumed silica, 6.0084 g.

[0081] The aluminum source was aluminum isopropoxide, 0.4093 g.

[0082] S1. Mixing a Ce source, citric acid and water and stirring until the solution is clear to obtain a solution A;

[0083] S2. Adding a template, an aluminum source and a silicon source to the solution A obtained in step S1 in sequence, and aging to obtain a gel B;

[0084] S3. The gel B obtained in step S2 is transferred to a reactor for crystallization, washing, drying, and calcination to obtain a highly dispersed Ce-loaded Beta molecular sieve;

[0085] In S1, the molar ratio of citric acid and Ce source was 5:1;

[0086] In S2, the molar ratio of silicon source, aluminum source and template is 100:2:50.

[0087] The aging temperature is room temperature 25°C, and the aging time is 6h;

[0088] In S3, the crystallization temperature is 150° C. and the crystallization time is 6 days.

[0089] After the crystallization is completed, the steps of washing, drying and calcination are also included. After the product is filtered, it is repeatedly washed with deionized water until it is neutral. The calcination is drying in a drying oven at 120° C. for 12 hours and calcining in an air atmosphere at 550° C. for 5 hours.

[0090] Example 2

[0091] A highly dispersed Ce-loaded Beta molecular sieve, wherein the silicon-aluminum ratio of the molecular sieve is 41, the Ce loading amount in the molecular sieve is 0.933wt%, and the dispersion index of the Ce oxide cluster is 1.059.

[0092] The average particle size of the Ce oxide clusters is 2.67 nm.

[0093] The preparation method of the above-mentioned highly dispersible Ce-supported Beta molecular sieve is basically the same as that of Example 1, except that:

[0094] The Ce source is cerium (III) chloride heptahydrate, 0.7452 g.

[0095] Water is deionized water, 4.9494g.

[0096] In S1, the molar ratio of citric acid to Ce source is 5:2.

[0097] Example 3

[0098] A highly dispersed Ce-loaded Beta molecular sieve, wherein the silicon-aluminum ratio of the molecular sieve is 43, the Ce loading amount in the molecular sieve is 2.469wt%, and the dispersion index of the Ce oxide cluster is 1.069.

[0099] The average particle size of the Ce oxide clusters was 3.00 nm.

[0100] The preparation method of the above-mentioned highly dispersible Ce-supported Beta molecular sieve is basically the same as that of Example 1, except that:

[0101] The Ce source is cerium (III) chloride heptahydrate, 1.1177 g.

[0102] Water is deionized water, 4.8233g.

[0103] In S1, the molar ratio of citric acid to Ce source is 5:3.

[0104] Comparative Example 1

[0105] A Beta molecular sieve, wherein the silicon-aluminum ratio of the molecular sieve is 45 and the Ce loading amount in the molecular sieve is 0.

[0106] The preparation method of the Ce-loaded Beta molecular sieve is substantially the same as that of Example 1, except that the Beta molecular sieve is not loaded with Ce.

[0107] Results

[0108] (1) The highly dispersed Ce-loaded Beta molecular sieve catalysts prepared in Examples 1 to 3 were characterized using a FEI Talos 200S transmission electron microscope to obtain transmission electron microscope images and particle size distribution histograms. The test results are shown in Figure 2. Figure 1 (a~f) and shown in Table 1. Figure 1 (a~c) are transmission electron microscope images of Examples 1~3, respectively. Figure 1 (d-f) are the particle size distribution histograms of Ce active species in Examples 1-3, respectively. Figure 1 As can be seen from (a-c), the spherical objects are molecular sieve particles, and the bright spots are Ce active species. The average particle size of Ce oxide clusters is calculated by the formula d mean =∑d i / N, the calculation formula of Ce oxide cluster dispersity index (DI) is: Wherein, n is the nth Ce oxide cluster grain counted, d is the diameter of the Ce oxide cluster grain, and N is the number of all grains counted.

[0109] (2) The highly dispersed Ce-supported Beta molecular sieves prepared in Examples 1 to 3 and the Beta molecular sieve catalyst prepared in Comparative Example 1 were characterized using a D8 Advance X-ray diffractometer from Bruker, Germany. The test results are as follows: Figure 2 shown.

[0110] from Figure 2 It can be seen from the XRD patterns of Examples 1 to 3 that the characteristic peaks 2θ of the Beta molecular sieve XRD spectrum are 7.6° and 22.5°, and the characteristic peak of Ce oxide is not found at 2θ of 28.6°, indicating that a highly dispersed Ce-loaded Beta molecular sieve is prepared.

[0111] (3) Using pyridine and 2,6-di-tert-butylpyridine as probe molecules, data were collected on a German Bruker Vertex 70 Fourier transform infrared spectrometer for the highly dispersed Ce-loaded Beta molecular sieves prepared in Examples 1 to 3 and the Beta molecular sieve catalyst prepared in Comparative Example 1, and Beer's law was used to calculate Acid and Lewis acid concentration. The results are as follows Figure 3 , Figure 4 As shown in Table 1.

[0112] from Figure 3It can be seen that in the Fourier transform infrared spectrum of the Ce-loaded Beta molecular sieve of the present invention, ~1545cm -1 is the CC stretching vibration peak of the pyridinium ion, Characteristic peak of acid site; ~1455cm -1 and ~1445cm -1 is the CC stretching vibration peak of the pyridine complex, which is the characteristic peak of the Lewis acid site. Figure 4 It can be seen that in the Fourier transform infrared spectrum of the Ce-loaded Beta molecular sieve of the present invention, ~1616cm -1 For the outer surface Characteristic peaks of acid sites.

[0113] Table 1 Ce dispersion properties and acid concentration of molecular sieves in Examples 1 to 3 and Comparative Example 1

[0114]

[0115] (3) The catalysts prepared in Examples 1 to 3 and Comparative Example 1 were granulated and passed through a 20-40 mesh sieve. 0.25 g of the sample was placed in a fixed bed and activated at 400° C. for 3 h in an air atmosphere, and then cooled to 80° C. Benzene and 1-dodecene were prepared into a reaction solution at a molar ratio of 8.75:1, and a certain amount of ethylcyclohexane was added thereto as an internal standard. The flow rate of the reaction solution was adjusted to a mass space velocity of 40 h -1 , reaction at normal pressure, the catalyst conversion rate is considered to be deactivated when it is less than 10%. The test results of 1-dodecene conversion rate and 2-dodecylbenzene selectivity in Examples 1 to 3 and Comparative Example 1 are as follows: Figure 5 As shown in Tables 2 and 3.

[0116] Table 2 Catalytic activity of molecular sieves of Examples 1 to 3 and Comparative Example 1

[0117]

[0118] Table 3 Catalytic selectivity of molecular sieves of Examples 1 to 3 and Comparative Example 1

[0119]

[0120] It can be seen from Table 2 and Table 3 that the highly dispersed Ce-supported Beta molecular sieve of the present invention has a catalytic temperature of 80°C and a mass space velocity of 40 h -1 Under the conditions of , the conversion rate of 1-dodecene by highly dispersed Ce-loaded Beta molecular sieve is 10-37%, the selectivity of 2-dodecylbenzene can reach 80-90%, and the service life can reach 9-13h.

[0121] In the molecular sieve of Comparative Example 1, without adding Ce, the 1-dodecene conversion rate was 24.71%, 12.14% lower than that of Example 3, and the catalytic life was 7 h, 6 h shorter than that of Example 3.

[0122] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A highly dispersible Ce-supported Beta molecular sieve for catalyzing the preparation of linear alkylbenzene from linear long-chain olefins with a carbon chain length of 10 to 14 and benzene, characterized in that: The silicon-aluminum ratio of the molecular sieve is 41-45, the Ce loading in the molecular sieve is 0.933-2.47 wt %, the average particle size of the Ce oxide cluster is 2.37-3.00 nm, and the dispersion index of the Ce oxide cluster is 1.059-1.071; The method for preparing the highly dispersible Ce-loaded Beta molecular sieve comprises the following steps: S1. Mixing a Ce source, citric acid and water to obtain a solution A; S2. Adding a template, an aluminum source and a silicon source to the solution A obtained in step S1 in sequence, and aging to obtain a gel B; S3. The gel B obtained in step S2 is crystallized, washed, dried, and calcined to obtain a highly dispersed Ce-loaded Beta molecular sieve; In S1, the molar ratio of citric acid to Ce source is 5:(2-3); In S2, the molar ratio of citric acid to template is (0.03-0.16):1; In S2, the aging temperature is 15 to 35° C., and the aging time is 5 to 10 hours; In S3, the crystallization temperature is 130-160°C and the crystallization time is 5-10 days; In S3, the calcination temperature is 550-600°C, the atmosphere is air atmosphere, and the calcination time is 5-8h; The template agent is tetraethylammonium hydroxide.

2. The highly dispersible Ce-loaded Beta molecular sieve according to claim 1, characterized in that: The average particle size of the Ce oxide cluster is 2.67-3.00 nm.

3. An application of the highly dispersed Ce-supported Beta molecular sieve according to claim 1 or 2 as a catalyst for preparing linear alkylbenzene from linear long-chain olefins and benzene, wherein the carbon chain length of the linear long-chain olefins is 10 to 14; in the application, the catalytic temperature is 70 to 90°C and the mass space velocity is 30 to 50 h -1 The service life of the highly dispersed Ce-loaded Beta molecular sieve is 11 to 13 hours; the catalytic reaction is carried out in a fixed bed reactor.

4. The use according to claim 3, characterized in that: In the application, the linear long-chain olefin is 1-dodecene, and the linear alkylbenzene is 2-dodecylbenzene.

5. The use according to claim 4, characterized in that: The conversion rate of 1-dodecene is 10-37%, and the selectivity of 2-dodecylbenzene is 80-90%.

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