A method for the preparation of a fau / emt intergrowth molecular sieve adsorbent for liquid phase adsorptive separations

Abstract

The application discloses a preparation method of a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation, and belongs to the field of chemical material preparation and application. + 2+ ion exchange; then the exchanged molecular sieve is flash dried into a powder with an average particle size of less than 30 microns, and the powder is uniformly mixed with clay and an additive in a certain proportion to prepare adsorbent pellets with a diameter of 0.3-0.8 mm; finally, the adsorbent is dehydrated and activated to obtain an adsorbent product with a dry basis of 94.5-99.5%. The adsorbent is loaded into a simulated moving bed, and can be used for the adsorption separation and purification of m-cresol isomers, xylene isomers, diethylbenzene isomers, methyl-ethylbenzene isomers and the like, so that high-purity single-isomer products are obtained, and the complete separation and purification effect of isomers is realized.​

Description

Technical Field

[0001] This invention relates to a method for preparing FAU / EMT symbiotic molecular sieve adsorbents for liquid phase adsorption and separation, belonging to the field of chemical materials preparation. Background Technology

[0002] o-cresol, m-cresol, and p-cresol are all important fine chemical intermediates. With the continuous development of downstream cresol products, the market demand for the quality and purity of cresol monomers is gradually increasing, leading to a significant decrease in the use of mixed cresols and a growing demand for single isomers. Due to the difficulty in synthesizing and separating cresol monomers, production facilities are often small-scale, resulting in a significant supply-demand imbalance. Therefore, efficient separation and purification processes for mixed cresols are essential for the rational utilization of each monomer. Molecular sieve adsorption separation and purification of m-cresol and p-cresol is a relatively effective method, consuming less energy and causing less environmental pollution, making it a more energy-efficient and environmentally friendly approach.

[0003] Patent document US3014078 discloses the use of NaX molecular sieves as adsorbents for the separation and purification of p-cresol. Patent document US5149887A discloses the use of a barium-potassium exchanged X zeolite adsorbent for the selective adsorption of p-cresol and m-cresol. Patent document CN111689838A discloses a method for the adsorption and separation of p-cresol and m-cresol, using BaX, BaKX, and KY molecular sieves as the active components of the adsorbent, preferentially adsorbing p-cresol, with m-cresol obtained in the adsorbent residue. All of the above documents use X and Y molecular sieves as adsorbents, which results in a tailing phenomenon during the desorption of p-cresol from the adsorbent, affecting the purity of the intermediate cresol in the adsorbent residue.

[0004] Currently, the separation and adsorption methods reported in patent literature mainly use X or Y molecular sieves as the active component of the adsorbent for the separation and purification of m-p-cresol. These methods have the disadvantages of not being able to effectively increase the adsorption capacity, having a limited improvement in adsorption mass transfer efficiency, and not being able to further improve selectivity. Summary of the Invention

[0005] This invention provides a FAU / EMT symbiotic molecular sieve, which utilizes a countercurrent belt filter exchange to separate the molecular sieve with K... + The molecular sieve spherical adsorbent obtained by efficient and continuous exchange of ions and Ba2+ ions, followed by spherical formation and post-treatment, shows higher adsorption capacity, adsorption rate, separation coefficient and resolution in the separation and purification of m-p-cresol isomer mixtures.

[0006] This invention uses a mixture of m-cresol and p-cresol as raw materials. The adsorbent preferentially adsorbs p-cresol, and the adsorption separation produces high-purity p-cresol with high selectivity. The production process does not corrode equipment, has low energy consumption, does not generate a large amount of industrial wastewater, and is low in cost, making it an environmentally friendly green process.

[0007] The adsorbent described in this invention is packed in a countercurrent simulated moving bed, and the p-cresol and m-cresol isomers are separated from the extract and the residual liquid by applying the principle of industrial chromatography. This not only solves the shortcomings of the existing industrial alkylation method for separating m-p-cresol, such as the large number of by-products, long process flow, high energy consumption and limited production scale.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: This invention provides a method for preparing FAU / EMT symbiotic molecular sieves, comprising the following steps: 1) Gel A is obtained by mixing and dissolving silicon source, aluminum source, NaOH, KOH and deionized water, aging at 60~100℃ for 2~10 hours, and then crystallizing at 90~100℃ for 1~10 hours to obtain crystallized product B.

[0009] 2) Mix silicon source, aluminum source, NaOH, 18-crown ether-6 and deionized water to obtain gel C, age at room temperature for 12-36 hours, add crystallization product B obtained in step 1), stir and mix evenly, crystallize at 110℃-120℃ for 10-15 days, dry and calcine the product to obtain the FAU / EMT symbiotic molecular sieve.

[0010] The silicon source is calculated as SiO2, the aluminum source as Al2O3, Na as Na2O, and K as K2O. The molar composition of gel A is: Na2O: K2O: SiO2: Al2O3: H2O = 5.28~6.38: 1.21~1.87: 2.2: 1: 99~143.

[0011] The molar composition of gel C is: Na2O:SiO2:Al2O3:18-crown ether-6:H2O=2.3~2.8:10:1:0.1~1.0:120~160.

[0012] In the FAU / EMT symbiotic molecular sieve, the mass content of FAU structured molecular sieve is 35.0~80.0 wt%.

[0013] Furthermore, each of the aluminum sources is independently selected from at least one of sodium aluminate, boehmite, Al(OH)3, Al2(SO4)3, Al(NO3)3, AlCl3, and aluminum isopropoxide, and each of the silicon sources is independently selected from at least one of water glass, silica sol, methyl silicate, ethyl silicate, silica fume, fumed silica, coarse-porous silica, and chromatography silica.

[0014] Furthermore, in the above technical solution, the X-ray diffraction phase spectrum of the symbiotic molecular sieve has characteristic peaks at 2θ angles of 5.85±0.2°, 6.11±0.2°, 6.61±0.2°, 9.98±0.2°, 11.02±0.2°, 11.73±0.2°, 15.42±0.2°, 16.67±0.2°, 17.12±0.2°, 20.38±0.2°, 23.29±0.2°, 24.68±0.2°, 26.64±0.2°, 27.07±0.2°, and 30.93±0.2°.

[0015] A method for preparing a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation, comprising sequentially subjecting the prepared FAU / EMT symbiotic molecular sieve to K... + Ions, Ba 2+ After ion exchange, it is mixed with clay and binder, placed in a ball-forming device to form, and then calcined and activated to obtain the molecular sieve adsorbent.

[0016] Furthermore, potassium ion exchange can be performed using one or more of KCl, K2SO4, and KNO3; and barium ion exchange can be performed using one or more of BaCl2, Ba(NO3)2, Ba(OH)2, Ba(CHO2)2, and (CH3COO)2Ba.

[0017] Furthermore, the FAU / EMT symbiotic molecular sieves were subjected to K-type ... + Ions, Ba 2+ Ion exchange.

[0018] Furthermore, the binder is a biomass binder; FAU / EMT symbiotic molecular sieve, clay, and biomass binder are mixed in a weight percentage of 85~95:4.9~15:0.1~1.5.

[0019] Furthermore, the biomass binder is selected from one or more of guar gum, SG plant gum, myrica gum, xanthan gum, alginate, gelatin, gum arabic, and Indian gum.

[0020] Furthermore, clay includes one or more of palygorskite, halloysite, sepiolite, lithium saponite, hydrotalcite, illite, palygorskite, montmorillonite, and chlorite.

[0021] Furthermore, in the molecular sieve adsorbent, the weight percentage of barium ions, calculated as BaO, is 20wt% to 40wt%.

[0022] Furthermore, the clay is selected from one or more of palygorskite, halloysite, sepiolite, lithium saponite, hydrotalcite, illite, rettoite, montmorillonite, and chlorite.

[0023] A specific method for preparing FAU / EMT symbiotic molecular sieve adsorbent for liquid phase adsorption separation includes the following steps: 1) FAU / EMT symbiotic molecular sieves with a Si / Al atomic ratio in the range of 1.0~2.0 are prepared into a slurry with a solid content of 20~45wt%, which is then thoroughly mixed and fed into K. + The solution is pre-exchanged in an ion exchange vessel and then enters K. + The filter cake undergoes exchange using an ion countercurrent belt filter exchanger, and is washed in the tail-end washing zone until the pH is ≤11. The Na content in the filter cake is then measured. + The ion content is less than 0.5%; 2) Take the K obtained in 1) + The molecular sieve filter cake after ion exchange is conveyed to a Ba2+ ion pre-exchange tank for pulping, and then conveyed to Ba... 2+ The ion exchange is carried out on a countercurrent belt exchanger; after the exchange, the slurry is filtered and then washed with deionized water to make the pH value <11. 3) The filter cake obtained in 2) is flash-dried to obtain a symbiotic molecular sieve powder with a dry basis of more than 75%. The symbiotic molecular sieve is uniformly mixed with clay and biomass binder, wherein the average particle size of the molecular sieve powder is ≤30μm and the average particle size of the clay is ≤50μm. 4) Place the mixed powder from 3) into a ball rolling device and roll it into small balls of 0.1~0.2mm. Then, add the mixed powder in a timed and quantitative manner to gradually increase the diameter of the adsorbent balls to 0.2~2.5mm, preferably 0.3~0.8mm. After the balls formed in the first rolling are naturally air-dried at room temperature and then dried in a greenhouse until the dry basis reaches 75%~85%, they are then calcined at 400~600℃ for 4~16 hours to remove the biomass binder. 5) Place the small ball adsorbent obtained in 4) in a kiln and calcine at 80~550℃ in different temperature zones to dehydrate and activate it, and obtain an adsorbent product with a dry basis of 94.5~99.5%.

[0024] Furthermore, in the above technical solution, the total molecular sieve content in the molecular sieve adsorbent is ≥80wt%, the clay content is ≤20wt%, the Ba content (calculated as BaO weight percentage wt%) in the adsorbent is ≥15wt%, preferably 20wt%~40wt%; the K content (calculated as K2O weight percentage wt%) in the adsorbent is ≤15wt%, preferably 0.1wt%~10wt%; and the Na content (calculated as Na2O weight percentage wt%) in the adsorbent is ≤0.5wt%, preferably ≤0.3wt%.

[0025] Furthermore, in the above technical solution, the KBa type molecular sieve adsorbent is applied to the performance evaluation and analysis of single-column pulse feeding of m-cresol and p-cresol. The calculated selectivity coefficient β of p-cresol for m-cresol is >2.0, and the separation degree R of p-cresol for m-cresol is >1.5.

[0026] Furthermore, in the above technical solution, the KBa type molecular sieve adsorbent, in the application of p-cresol in the simulated moving bed adsorption separation chamber, obtains p-cresol with a purity ≥99.5% and a yield ≥95% from the extract; and obtains m-cresol with a purity ≥99.0% and a yield ≥96% from the adsorbate.

[0027] The application of the KBa-type FAU / EMT symbiotic molecular sieve adsorbent described in this invention involves adsorption-desorption of m-p-cresol on small spherical adsorbents at a temperature of 100–200°C, with a pressure of 5–20 bar (gauge pressure) during adsorption and desorption. The adsorbent is packed into 4–30 adsorption columns or adsorption beds connected in series. By periodically changing the sequence of material entering and exiting individual adsorption columns or adsorption beds, a countercurrent simulated moving chromatography process is formed. The m-p-cresol mixture contacts the adsorbent, with p-cresol preferentially adsorbed and desorbed to form an extract, while m-cresol is finally desorbed to form a residual extract.

[0028] Furthermore, in the above technical solution, the eluent of the present invention is a secondary or primary alcohol with a C4-C8 structure, including any one or more of 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 2-butanol, 2-pentanol, 3-pentanol, 2-hexanol, 3-hexanol, 2-heptanol, 3-heptanol, 4-heptanol, 2-octanol, 3-octanol, 4-octanol, 2-methyl-2-pentanol, 4-methyl-2-pentanol, and 3-ethyl-3-pentanol.

[0029] Furthermore, in the above technical solution, the primary / secondary alcohol is used alone or in combination with a monocycloalkyl alcohol, wherein the content of the monocycloalkyl alcohol in the mixed alcohol is 0.1-10% by weight, preferably 0.2-5% by weight, and particularly preferably 0.5-3% by weight. Preferably, it is any one or more of cyclopentanol, cyclohexanol, cycloheptanol, and 1-methylcyclopentanol.

[0030] The superior effects of this invention: In this invention, FAU / EMT symbiotic molecular sieves are used as the adsorption active carrier, which increases the density of active sites for exchange ions. More metal active ions can generate more adsorption sites, increasing the adsorption capacity of cresol. In particular, the preferential adsorption of cresol is more obvious, that is, the separation coefficient and separation degree of p-cresol / m-cresol are higher, which increases the load capacity of simulated moving bed separation and purification.

[0031] The metal ion exchange-exchanged FAU / EMT symbiotic molecular sieve adsorbent provided by this invention has a relatively rich microporous-mesoporous structure, which reduces the diffusion resistance of the adsorbent molecular sieve, has a moderate adsorption-desorption force, and increases the adsorption and desorption rate of p-cresol. Therefore, it reduces the phenomenon of p-cresol molecule desorption tailing, and requires complete desorption, thereby reducing the amount of desorbent used. Finally, high-purity p-cresol and m-cresol monomer components can be obtained.

[0032] The adsorbent provided by this invention adopts a scheme of exchanging FAU / EMT symbiotic molecular sieve powder and then reshaping it. It has high exchange efficiency and large output per unit time, which is conducive to the efficient utilization of metal ion salt solution, reduces raw material cost and production energy consumption. Moreover, this production method can form a scale production effect and is suitable for mass production.

[0033] The simulated moving bed (SMB) used in this invention offers advantages such as automated continuous operation, high yield, high purity, high efficiency, and low solvent consumption. The countercurrent flow of the simulated moving bed system results in higher separation efficiency than systems with fixed adsorption beds. In industrial chromatographic methods using continuous separation with a simulated moving bed, adsorption and desorption occur continuously, thus allowing for continuous generation of extract and retentate streams, as well as continuous supply of feed and eluent streams. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 A flowchart of the process for preparing adsorbents by molding after molecular sieve ion exchange.

[0035] Figure 2 XRD phase characterization of the FAU / EMT symbiotic molecular sieve in Example 1.

[0036] Figure 3 This is a flow chart of a countercurrent belt filter continuous exchange process for molecular sieve slurry. Detailed Implementation

[0037] The embodiments and comparative examples further illustrate the implementation methods and effects of the present invention, but the scope of protection of the present invention is not limited to the contents listed in the embodiments.

[0038] The symbiotic composite molecular sieve of this invention was analyzed using X-ray diffraction (XRD) to determine the interplanar spacing (d) from the XRD pattern. This data was then compared with data collected from the XRD database of the International Society for Synthetic Zeolites or the PDF (Powder Diffraction File) of ICDD (International Centre for Diffraction Data).

[0039] Pure-phase, highly crystallizable FAU-type molecular sieves and EMT molecular sieves were mechanically and uniformly mixed and ground at mass ratios of 50:50, 60:40, 70:30, 80:20, and 90:10, and the areas of characteristic peaks in XRD were measured. Five characteristic peaks at 2θ angles (9.98±0.2, 15.42±0.2, 23.29±0.2, 26.64±0.2, 30.93±0.2) correspond to FAU-type molecular sieves, and their total area is correlated with the mass percentage content of FAU-type molecular sieves. Six characteristic peaks at 2θ angles (11.02±0.2, 16.67±0.2, 17.12±0.2, 20.38±0.2, 24.68±0.2, 27.07±0.2) correspond to EMT-type molecular sieves, and their total area is correlated with the mass percentage content of EMT-type molecular sieves. This yields a function curve of the FAU / EMT peak area ratio versus the FAU / EMT molecular sieve mass ratio, which serves as a reference curve for calculating the relative proportions of the two molecular sieves in the sample to be tested.

[0040] This invention can use pulse adsorption evaluation testing equipment to dynamically test the separation coefficient and resolution of purified components on the adsorbent based on the principle of chromatographic separation, thereby measuring the relative separation effect of the raw material mixture components. It can also test various adsorbents and eluents with specific feed mixtures to measure the adsorbent performance in terms of their adsorption capacity, selectivity and exchange rate.

[0041] Single-column pulse adsorption-desorption experimental method: Molecular sieve beads with a particle size of φ0.3~0.8mm were used as adsorbent, with a dry basis concentration of 95.5wt%~99.5wt%. These beads were then packed into the adsorption column. The column was purged with nitrogen to remove air. Eluent was then pumped in to remove nitrogen from the adsorbent voids, and the temperature was raised to 140℃. After maintaining the column at 140℃, the feed inlet was switched to a syringe via a six-way valve, and 2 ml of p-cresol feedstock (p-cresol / m-cresol mass ratio = 65 / 35) was pulsed into a quantitative tube. The six-way valve was then switched back to a pump to introduce eluent at a flow rate of 1~2 ml / min. When the eluent flow reached 10 ml, 3~5 drops of liquid sample were collected every 2 minutes using an automatic fraction collector. Forty samples were collected consecutively for gas chromatography quantitative analysis of composition. The flow chart of the single-column pulse adsorption-desorption experimental device is shown below. Figure 3 As shown. Example 1

[0042] 1) Dissolve 1202.54g of sodium aluminate (Na2O% 31.54%, Al2O3% 38.54%) in 4000.0g of deionized water and stir until completely dissolved. Then add 990.0g of KOH and 1284.18g of NaOH and mix thoroughly. Next, add 2519.26g of water glass (Na2O% 7.35%, SiO2% 23.85%) solution and add 3725.98g of deionized water to form a gel with a molar ratio of 5.5Na2O:1.65K2O:2.2SiO2:Al2O3:122H2O. Then age the mixed gel at 70℃ for 3 hours and then raise the temperature to 100℃ for 2 hours to crystallize. 2) Weigh out 9097.69 g of silica sol (Na2O% 0.24%, SiO2% 30.38%), 714.97 g of aluminum hydroxide (Comio, 65.60% on a dry basis), 863.58 g of sodium hydroxide, 429.85 g of 18-Crown-6, and 5021.14 g of deionized water, and mix thoroughly and evenly. The molar composition of the prepared mixed gel is: 2.4Na2O·10.0SiO2·Al2O3·0.35(18-Crown-6)·140H2O The gel was aged at room temperature for 24 hours with stirring. The crystallized product obtained in step 1) was then added to the gel and stirred until homogeneous. The mixture was then transferred to a Teflon-lined stainless steel autoclave and crystallized at 110°C for 10 days. The filter cake was recovered by vacuum filtration and washed with deionized water until the pH reached 8.0. After drying, the filter cake was confirmed by X-ray diffraction to be a FAU / EMT eutectic molecular sieve. Chemical analysis revealed that the Si / Al atomic ratio of the molecular sieve was 1.65.

[0043] 3) The FAU / EMT symbiotic molecular sieve filter cake obtained in step 2) is prepared into a slurry with a solid content of 35 wt%, and then fed into K. + In the ion exchange tank, K is then pumped in. + Ion exchange (K) is performed on an ion countercurrent belt filter exchanger. + The ion exchange solution was a 0.5 mol / L K₂SO₄ solution. The filter cake was washed to pH 10.5 in the washing zone at the end of the filter press, and the Na₂O content in the filter cake was measured. + Ion content: 0.32%; 4) Take the K obtained in 3) + The molecular sieve filter cake after ion exchange is transported to the Ba... 2+ The pulp is prepared in an ion pre-exchange tank and then transported to Ba. 2+ The ion countercurrent belt exchange is used for exchange (Ba 2+The ion exchange solution was a 0.5 mol / L Ba(NO3)2 solution; after ion exchange, the mixture was subjected to slurry filtration and then washed with deionized water to achieve a pH of 10.5. 5) The filter cake obtained in step 4) is flash-dried to obtain symbiotic molecular sieve powder (average particle size ≤30μm) with a dry basis of 80.5%. The symbiotic molecular sieve is mixed evenly with montmorillonite and guar gum in a weight percentage ratio of 85.32:13.38:1.3, and then rolled into small spheres of 0.1~0.2mm. The mixed powder is then added in a timed and quantitative manner to gradually increase the diameter of the adsorbent spheres to 0.3~0.8mm. The freshly rolled spheres are allowed to air dry naturally at room temperature, and then dried at 120℃ for 24 hours, with a dry basis of 83.5%. 5) The small sphere adsorbent obtained in 4) is directly fed into the rotary kiln. A total of 6 temperature ranges are designed for heating, dehydration and activation, with a final dry basis of 97.45%. The product is then vacuum packaged as the final adsorbent product, denoted as XFJ-1. Example 2

[0044] First, prepare FAU / EMT symbiotic molecular sieves: 1) Dissolve 3306.99 g of sodium aluminate (Na2O% 31.54%, Al2O3% 38.54%) in 10000.0 g of deionized water and stir until completely dissolved. Then add 2359.50 g of KOH and 3314.46 g of NaOH and mix thoroughly. Next, add 6927.96 g of water glass (Na2O% 7.35%, SiO2% 23.85%) solution and add 16445.74 g of deionized water to form a gel with a molar ratio of 5.28Na2O:1.43K2O:2.2SiO2:Al2O3:100H2O. Then age the mixed gel at 70℃ for 3 hours and then raise the temperature to 100℃ for 2 hours to crystallize. 2) Weigh out 9097.69 g of silica sol (Na₂O content 0.24%, SiO₂ content 30.38%), 658.74 g of boehmite (71.20% on a dry basis), 900.76 g of sodium hydroxide, 614.08 g of 18-Crown-6, and 5903.16 g of deionized water, and mix thoroughly and evenly. The molar composition of the prepared mixed gel is: 2.5Na2O·10.0SiO2·Al2O3·0.5(18-Crown-6)·150H2O The gel was aged at room temperature for 24 hours with stirring. The crystallized product obtained in step 1) was added to it and stirred and mixed evenly. Then it was transferred to a stainless steel autoclave with a Teflon inner liner and crystallized at 110°C for 15 days.

[0045] The other steps are the same as in Example 1 for preparing the adsorbent. The difference is that during the spheroidizing process, the FAU / EMT eutectic molecular sieve, sepiolite, and SG plant gum are mixed evenly in a weight percentage ratio of 92.64:7.11:0.25. They are then subjected to countercurrent filtration exchange using fresh soluble salt solutions of 0.6 mol / L KCl and 0.49 mol / L BaCl2, respectively. The resulting product is vacuum-packed as the final adsorbent product, designated as XFJ-2. Its composition is shown in Table 1. Example 3

[0046] First, prepare FAU / EMT symbiotic molecular sieves: 1) Dissolve 5712.08g of sodium aluminate (Na2O% 31.54%, Al2O3% 38.54%) in 30000.0g of deionized water and stir until completely dissolved. Then add 4702.50g of KOH and 7260.22g of NaOH and mix thoroughly. Next, add 11966.47g of water glass (Na2O% 7.35%, SiO2% 23.85%) solution and add 10737.12g of deionized water to form a gel with a molar ratio of 6.16Na2O:1.65K2O:2.2SiO2:Al2O3:132H2O. Then age the mixed gel at 70℃ for 3 hours and then raise the temperature to 100℃ for 2 hours to crystallize. 2) Weigh out 9097.69 g of silica sol (Na2O content 0.24%, SiO2 content 30.38%), 1216.97 g of sodium aluminate (Na2O content 31.54%, Al2O3 content 38.54%), 439.43 g of sodium hydroxide, 982.52 g of 18-Crown-6, and 6556.23 g of deionized water, and mix thoroughly and evenly. The molar composition of the prepared mixed gel is: 2.6Na2O·10.0SiO2·Al2O3·0.8(18-Crown-6)·160H2O The gel was aged at room temperature for 24 hours with stirring. The crystallized product obtained in step 1) was added to it and stirred and mixed evenly. Then it was transferred to a stainless steel autoclave with a Teflon inner liner and crystallized at 115°C for 10 days.

[0047] The other steps are the same as in Example 1 for preparing the adsorbent. The difference is that during the spherical molding process, the FAU / EMT eutectic molecular sieve, halloysite, and xanthan gum are mixed evenly in a weight percentage ratio of 90.33:9.10:0.57. A countercurrent belt filtration exchange is carried out using a fresh soluble salt solution of 0.8 mol / L KNO3 and 0.37 mol / L Ba(NO3)2. The product is then vacuum packaged as the final adsorbent product, denoted as XFJ-3. Its composition is shown in Table 1. Example 4

[0048] First, prepare FAU / EMT symbiotic molecular sieves: 1) Dissolve 865.83g of sodium aluminate (Na2O% 31.54%, Al2O3% 38.54%) in 5000.0g of deionized water and stir until completely dissolved. Then add 712.80g of KOH and 1158.67g of NaOH and mix thoroughly. Next, add 1813.87g of water glass (Na2O% 7.35%, SiO2% 23.85%) solution and add 1822.31g of deionized water to form a gel with a molar ratio of 6.38Na2O:1.65K2O:2.2SiO2:Al2O3:143H2O. Then age the mixed gel at 70℃ for 3 hours and then raise the temperature to 100℃ for 2 hours to crystallize. 2) Weigh out 9097.69g of silica sol (Na2O content 0.24%, SiO2 content 30.38%), 1979.36g of Al(NO3)3 (Comio, 99%), 975.10g of sodium hydroxide, 798.30g of 18-Crown-6, and 5903.16g of deionized water and mix thoroughly. The molar composition of the prepared mixed gel is: 2.7Na2O·10.0SiO2·Al2O3·0.65(18-Crown-6)·135H2O The gel was aged at room temperature for 24 hours with stirring. The crystallized product obtained in step 1) was added to it and stirred and mixed evenly. Then it was transferred to a stainless steel autoclave with a Teflon inner liner and crystallized at 120°C for 10 days.

[0049] The other steps are the same as in Example 1 for preparing the adsorbent. The difference is that during the spherical molding process, the FAU / EMT eutectic molecular sieve, hydrotalcite, and alginate are mixed evenly in a weight ratio of 94.38:5.33:0.29. The mixture is then subjected to countercurrent filtration exchange using a fresh soluble salt solution of 0.5 mol / L K2SO4 and 0.21 mol / L (CH3COO)2Ba. The final adsorbent product is vacuum packaged and designated as XFJ-4. Its composition is shown in Table 1. Example 5

[0050] First, prepare FAU / EMT symbiotic molecular sieves: 1) Dissolve 865.83g of sodium aluminate (Na₂O % 31.54%, Al₂O₃ % 38.54%) in 3000.0g of deionized water and stir until completely dissolved. Then add 807.84g of KOH and 1153.49g of NaOH and mix thoroughly. Next, add 1423.99g of silica sol (Na₂O % 0.24%, SiO₂ % 30.38%) solution and add 2099.23g of deionized water to form a gel with a molar ratio of 5.72Na₂O:1.87K₂O:2.2SiO₂:Al₂O₃:110H₂O. The mixed gel is then aged at 70℃ for 3 hours and then heated to 100℃ for crystallization for 2 hours. 3.27 2) Weigh out 9679.98g of tetraethyl orthosilicate (Sinopharm Group, 99%), 1897.99g of aluminum isopropoxide (Comio, 99%), 1040.73g of sodium hydroxide, 307.04g of 18-Crown-6, and 9806.74g of deionized water again, and mix thoroughly. The molar composition of the prepared mixed gel is: 2.8Na2O·10.0SiO2·Al2O3·0.25(18-Crown-6)·120H2O The gel was aged at room temperature for 24 hours with stirring. The crystallized product obtained in step 1) was added to it and stirred and mixed evenly. Then it was transferred to a stainless steel autoclave with a Teflon inner liner and crystallized at 110°C for 12 days.

[0051] The other steps are the same as in Example 1 for preparing the adsorbent. The difference is that during the spherical molding process, the FAU / EMT eutectic molecular sieve, lithium saponite, and gum arabic are mixed evenly in a weight ratio of 88.00:11.08:0.92. The mixture is then subjected to countercurrent filtration exchange using a fresh soluble salt solution of 0.6 mol / L KNO3 and 0.24 mol / L Ba(CHO2)2. The mixture is then vacuum-packed as the final adsorbent product, designated as XFJ-5. Its composition is shown in Table 1.

[0052] Table 1. Results of each component of the adsorbent prepared in the examples and after exchange and activation.

[0053]

[0054] Comparative Example 1 According to the preparation method in the embodiment of patent document CN110511121B: 1) Mix 90 kg (dry basis) of NaX / Silicalite-1 core / shell molecular sieve powder with a particle size of 0.6–1.2 μm with 8 kg of kaolin (kaolinite mass fraction of 92%). Place the mixture in a turntable and spray an appropriate amount of deionized water while rolling to agglomerate the solid powder into small balls. The amount of water sprayed during the rolling process should be 8% of the solid powder. Then sieve the mixture and take small balls with a particle size of 300–850 μm. Dry the balls at 80℃ for 12 hours and calcine them at 540℃ for 4 hours.

[0055] 2) Ion Exchange: 130 mL of the spheres obtained in step 1) were loaded into an ion exchange column for cation exchange. The exchange was performed continuously for 8 hours at atmospheric pressure and 94 °C using a mixed solution of 0.18 mol / L barium nitrate and 0.08 mol / L potassium chloride at a volume hourly space velocity (VHSV) of 6.0 h⁻¹. The total volume of the mixed solution used was 5000 mL. After the exchange was complete, the spheres were washed with 700 mL of deionized water at 70 °C, dried under nitrogen atmosphere at 70 °C for 24 hours, and then dehydrated and activated under nitrogen atmosphere at 180 °C for 6 hours. The resulting adsorbent was designated VS-1.

[0056] Comparative Example 2 According to the preparation method in the embodiment of patent document CN111689838B: 1) Mix 9.2 kg of NaY molecular sieve with a silica / alumina molar ratio of 5.1, 0.8 kg of kaolin and 0.4 kg of corn starch evenly, put them into a sugar coating pot, and roll and spray 1.9 kg of water to form small balls with a diameter of 0.3 mm to 0.8 mm. Then dry at 100℃ for 4 h and calcine at 540℃ for 6 h.

[0057] 2) The calcined microspheres were soaked in 20 liters of 1.5 mol / L NaOH aqueous solution at 98°C for 5 hours for alkali treatment. The microspheres after alkali treatment were washed with deionized water until the pH value of the washing solution was lower than 10 to obtain the basic microspheres.

[0058] 3) The above-mentioned basic microspheres were subjected to ion exchange with potassium chloride solution at 95℃ and a volume hourly space velocity of 6 h⁻¹ for 8 hours until the potassium ion exchange rate was greater than 97 mol%. Then, they were activated in dry air at 190℃ for 2 hours to obtain adsorbent VS-2. The adsorbent contained 92.5% KY molecular sieve by mass, with the remainder being kaolin. The water content, measured after calcination at 600℃ for 2 hours, was 2.8% by mass. The adsorbent was designated VS-2.

[0059] Examples 6-12 m-p-cresol (purity 99.5%) and cyclohexane were mixed at a mass ratio of 7:3 as the pulse feed component, and n-pentanol was used as the eluent. The single-column pulse adsorption-desorption evaluation method was adopted.

[0060] Plot the envelopes of the above components with the volume of the eluent for desorption on the x-axis and the concentrations of each component in the pulsed feed solution on the y-axis. Similarly, plot the volume of the eluent for desorption on the x-axis and the concentrations of cyclohexane, m-cresol, and p-cresol on the y-axis. Cyclohexane, as a non-delayed inert compound, is not adsorbed and can be used as a tracer to obtain the dead volume of the adsorption system. Using the midpoint of the tracer's half-peak width as the zero point, measure the net retention volume from the midpoint of the half-peak width to the zero point for each component. The net retention volume of any component is proportional to the partition coefficient at adsorption equilibrium, reflecting the interaction force between each component and the adsorbent material. The ratio of the net retention volumes of the two components is the selectivity coefficient β. For example, the ratio of the net retention volume of p-cresol to that of m-cresol represents the ratio of the adsorption performance of the adsorbent material for p-cresol and m-cresol, and is the adsorption selectivity of p-cresol relative to m-cresol, denoted as βp-cresol / m-cresol.

[0061] Vmc is defined as the net retention volume of m-cresol, calculated by subtracting the volume of eluent consumed by cyclohexane elution from the volume of eluent consumed by m-cresol elution; similarly, Vpc is defined as the net retention volume of p-cresol, calculated by subtracting the volume of eluent consumed by cyclohexane elution from the volume of eluent consumed by p-cresol elution; W 1 / 2MC The full width at half maximum (FWHM) of the m-cresol envelope peak. 1 / 2PC The full width at half maximum (FWHM) of the p-cresol envelope peak is given; the separation coefficient β is the ratio of the net retention volumes of the two separated components. Resolution (R) is used to evaluate the degree of separation between the analyte and the separated substances, and is a key indicator of the separation efficiency of a chromatographic system. The formula for calculating resolution (R) is: Vmc is the retention volume of p-cresol in the first of two adjacent peaks; Vpc is the retention volume of p-cresol in the second of two adjacent peaks; W 1 / 2MC and W 1 / 2PC These are the half-widths (WHMs) of the peaks for m-cresol and p-cresol, respectively. The exchange rate of the eluent with p-cresol is specified by the WHM of the p-cresol peak distribution; the narrower the peak width, the higher the desorption rate.

[0062] Table 2 Comparison of single-column pulse adsorption-desorption evaluation results between the adsorbents prepared in Examples 1-5 and those prepared in Comparative Examples 1-2

[0063] By comparing Table 2 and Figure 2The pulse envelope results show that the adsorbent obtained using the embodiments of the present invention exhibits a clear preferential adsorption characteristic for m-cresol. The selectivity coefficient β for p-cresol to m-cresol is >2.1, and the resolution R value for p-cresol to m-cresol is >1.5. In contrast, the adsorbents VS-1 and VS-2 prepared in Comparative Examples 1 and 2 clearly preferentially adsorb p-cresol, while m-cresol can only be extracted from the adsorbate, reducing the purity of m-cresol. Furthermore, the selectivity coefficient β for p-cresol to m-cresol is <2.0, and the resolution R value for p-cresol to m-cresol is <1.1. The results clearly demonstrate the advantages of using the adsorbent according to the present invention to separate cresol isomers: fast desorption rate, large separation coefficient and resolution, which is more conducive to obtaining high-purity p-cresol and m-cresol products.

[0064] Examples 13-19 Separation of m-cresol was carried out using an adsorbent on a continuous countercurrent simulated moving bed.

[0065] The small-scale simulated moving bed device consists of 24 adsorption columns connected in series, each 160 mm long and 22 mm in inner diameter, with a total adsorbent loading of 1459 ml. The two ends of the adsorption columns are connected by a circulation pump to form a closed loop. The device has four material streams entering and exiting at different positions on the adsorption columns, with the feed position changing periodically. Four material lines are led out from the connecting lines between adjacent adsorption columns for material input or output. These four basic material streams are: eluent (D), feed (F), extract (E), and adsorbate (R). The 24 columns are divided into four sections: the 7 columns between the feed and adsorbate form the adsorption zone; the 9 columns between the extract and feed form the purification zone; the 5 columns between the eluent and extract form the elution zone; and the 3 columns between the adsorbate and eluent form the isolation zone. The temperature of the entire adsorption system is controlled at 140°C, and the pressure at 8 bar.

[0066] The p-cresol feedstock (34.8 wt% p-cresol, 64.7 wt% m-cresol, 0.2 wt% 2-ethylphenol, 0.1 wt% dimethylphenol, and 0.2 wt% other hydrocarbons) enters through feed port F, while the desorbent (n-pentanol) is continuously added through feed line D. The step-through time is set to 90 s. At the end of the step-through time, all four material streams simultaneously move one adsorption column in the same direction as the liquid flow. This step-through continues until a cycle of 24 columns is completed, with a cycle time of 2160 s. The system operates at 140°C and 8 bar. Table 2 shows the feed rate, eluent dosage, extract volume, residual liquid volume, adsorption zone flow rate, purification zone flow rate, elution zone flow rate, and isolation zone flow rate after the system stabilizes. Examples 13-17 used adsorbents XFJ-1-XFJ-5 of the present invention, obtaining p-cresol with a purity >99.5 wt% and a yield >94 wt% from the extract stream E; simultaneously, m-cresol with a purity >99.2 wt% and a yield >95 wt% could be obtained through the discharge line of the adsorbate R. Examples 18-19 used adsorbents VS-1-VS-2 prepared in the comparative example, obtaining p-cresol with a purity <99.0 wt% and a yield <94 wt% from the extract stream E under the same feed load; simultaneously, m-cresol with a purity <98.0 wt% and a yield <93 wt% could be obtained from the adsorbate stream R. The results of the simulated separation of m-p-cresol isomers on a moving bed are shown in Table 3.

[0067] Table 3. Experimental parameters and separation results of p-cresol isomers in the continuous countercurrent simulated moving bed.

[0068] The above-described embodiments are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing FAU / EMT symbiotic molecular sieves, characterized in that, Includes the following steps: 1) Gel A is obtained by mixing and dissolving silicon source, aluminum source, NaOH, KOH and deionized water, aging at 60~100℃ for 2~10 hours, and then crystallizing at 90~100℃ for 1~10 hours to obtain crystallized product B; 2) Mix silicon source, aluminum source, NaOH, 18-crown ether-6 and deionized water to obtain gel C, age at room temperature for 12-36 hours, add crystallization product B obtained in step 1), stir and mix evenly, crystallize at 110℃-120℃ for 10-15 days, dry and calcine the product to obtain the FAU / EMT symbiotic molecular sieve. The silicon source is calculated as SiO2, the aluminum source as Al2O3, the sodium as Na2O, and the potassium as K2O. The molar composition of gel A is: Na2O:K2O:SiO2:Al2O3:H2O = 5.28~6.38: 1.21~1.87: 2.2: 1: 99~143. The molar composition of gel C is: Na2O:SiO2:Al2O3:18-crown ether-6:H2O=2.3~2.8:10:1:0.1~1.0:120~160; In the FAU / EMT symbiotic molecular sieve, the mass content of FAU structured molecular sieve is 35.0~80.0 wt%.

2. The method for preparing a FAU / EMT symbiotic molecular sieve according to claim 1, characterized in that: The aluminum source is each independently selected from at least one of sodium aluminate, boehmite, Al(OH)3, Al2(SO4)3, Al(NO3)3, AlCl3, and aluminum isopropoxide, and the silicon source is each independently selected from at least one of water glass, silica sol, methyl silicate, ethyl silicate, silica fume, fumed silica, coarse-porous silica, and chromatography silica.

3. A method for preparing a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation, characterized in that: The FAU / EMT symbiotic molecular sieve prepared by the method described in claim 1 or 2 is sequentially subjected to K... + Ions, Ba 2+ After ion exchange, it is mixed with clay and binder, placed in a ball-forming device to form, and then calcined and activated to obtain the molecular sieve adsorbent.

4. The method for preparing a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation according to claim 3, characterized in that: Potassium ion exchange can be performed using one or more of KCl, K2SO4, and KNO3. Barium ion exchange is performed using one or more of BaCl2, Ba(NO3)2, Ba(OH)2, Ba(CHO2)2, and (CH3COO)2Ba.

5. The method for preparing a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation according to claim 3, characterized in that: FAU / EMT symbiotic molecular sieves were subjected to K-type ... + Ions, Ba 2+ Ion exchange.

6. The method for preparing a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation according to claim 5, characterized in that: The adhesive used is a biomass adhesive; FAU / EMT symbiotic molecular sieves, clay, and biomass binder are mixed at a weight percentage of 85~95:4.9~15:0.1~1.

5.

7. The method for preparing a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation according to claim 6, characterized in that: The biomass binder is selected from one or more of guar gum, SG plant gum, myrica gum, xanthan gum, alginate, gelatin, gum arabic, and Indian gum.

8. The method for preparing a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation according to claim 3, characterized in that: The clay is selected from one or more of palygorskite, halloysite, sepiolite, lithium saponite, hydrotalcite, illite, rettoite, montmorillonite, and chlorite.

9. The method for preparing a FAU / EMT symbiotic molecular sieve adsorbent for liquid-phase adsorption separation according to claim 3, characterized in that: In the molecular sieve adsorbent, the weight percentage of barium ions, calculated as BaO, is 20wt%~40wt%.

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