A method for preparing an adsorbent for separating and purifying meta-cresol isomers

Abstract

The application discloses a preparation method of an m-p-cresol isomer separation and purification adsorbent, relates to an adsorption and desorption treatment process on a zeolite molecular sieve adsorbent, and belongs to the field of chemical separation applications. The LSX molecular sieve with the Si / Al atomic ratio in the range of 1.0-1.1 is fully stirred and mixed with a pillared bentonite and polyacrylamide, is formed into a ball, is exchanged with metal cations of group IA and group IIA, and is treated through drying, dehydration activation and the like to obtain a formed adsorbent. The formed adsorbent is loaded into a countercurrent simulated moving bed, continuous m-p-cresol material, a desorption agent and continuous extraction liquid, raffinate material are realized, and finally high-purity m-cresol and p-cresol products are obtained. The method is efficient, low in energy consumption, can obtain single cresol isomers, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing an adsorbent for the separation and purification of m- and p-cresol isomers, and more specifically, to a method for adsorbing and desorbing a mixture of m- and p-cresol isomers using a zeolite adsorbent, which belongs to the field of chemical separation applications. Background Technology

[0002] The cresol isomers, mesocresol and p-cresol, cannot be effectively separated using traditional distillation methods due to their boiling point difference of less than 1°C. Although m-cresol and p-cresol have significantly different melting points, the presence of a eutectic zone and their high viscosity as fluids limit the application of conventional crystallization methods. Using molecular sieve adsorbents to separate m-cresol and p-cresol is a relatively energy-efficient and environmentally friendly method with less pollution. However, this method places very high demands on the molecular sieves; the screening and preparation of molecular sieves with excellent cresol adsorption performance constitute a major technical barrier to the widespread application of this method.

[0003] Patent document US5149887A discloses the selective adsorption of p-cresol and m-cresol using a barium-potassium exchanged X zeolite adsorbent. Patent document US3014078 discloses the separation and purification of p-cresol using NaX molecular sieve as an adsorbent. Patent document CN111689838A discloses a method for adsorbing and separating p-cresol and m-cresol, wherein the active component of the adsorbent is selected from any one of BaX, BaKX and KY molecular sieves, preferentially adsorbing p-cresol, and obtaining m-cresol from the adsorbent residue.

[0004] Molecular sieves with this type of structure exhibit strong adsorption of cresol as adsorbents, but complete desorption is difficult. A tailing phenomenon occurs during the desorption of p-cresol from the adsorbent, which affects the purity of the cresol in the residual liquid. Furthermore, the pore structure of these molecular sieve adsorbents is imperfect, lacking a microporous-mesoporous hierarchical distribution. This results in significant resistance during the adsorption-desorption molecular diffusion process, reducing adsorption efficiency. This is also the reason why preferentially adsorbed p-cresol is difficult to desorb, causing the tailing phenomenon. Summary of the Invention

[0005] This invention provides an LSX molecular sieve with a Si / Al atomic ratio in the range of 1.0 to 1.1, which, when mixed with pillared bentonite and polyacrylamide to form spheres, exhibits good pore size distribution and high wear resistance. After being exchanged with Group IA metal ions and Group IIA ions, it has higher adsorption capacity, adsorption rate and separation coefficient, showing good application prospects in the separation and purification of m-p-cresol isomer mixtures.

[0006] The adsorbent described in this invention is packed in a countercurrent simulated moving bed. Applying industrial chromatographic separation principles, it separates the p-cresol and m-cresol isomers from the extract and raffinate, respectively. This not only overcomes the shortcomings of existing industrially commonly used alkylation methods for separating m-cresol, such as numerous byproducts, long process flow, high energy consumption, and limited production scale, but also addresses these drawbacks. The simulated moving bed in this invention refers to a fixed bed within the adsorption tower where the molecular sieve does not move. Simultaneously, sequentially, and periodically changing the positions of several inlet and outlet ports on the adsorption tower achieves the same effect as continuous movement of the molecular sieve within the tower; hence, it is called a simulated moving bed (SMB).

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: a method for preparing a high-strength mesoporous adsorbent, wherein LSX molecular sieve, pillared bentonite, and polyacrylamide are mixed in a weight percentage of (85-95):(4-14):(1-2), and the mixture is placed in a pelletizing machine to form spherical adsorbent particles with a particle size of φ0.2-2.5mm, preferably φ0.3-0.8mm, and then dried and calcined to obtain the high-strength mesoporous adsorbent.

[0008] Specifically, the adsorbent particles obtained by spheroidizing in the spheroidizing machine are naturally air-dried and then dried at 80-150°C until the dry basis is not less than 80%, and then calcined at 400-600°C to obtain the high-strength mesoporous adsorbent.

[0009] A method for preparing an adsorbent for the separation and purification of m-p-cresol isomers includes the following steps:

[0010] 1) LSX molecular sieves with a Si / Al atomic ratio in the range of 1.0 to 1.1 are mixed with pillared bentonite and polyacrylamide in a weight percentage ratio of (85 to 95): (4 to 14): (1 to 2). The mixture is then placed in a pelletizing machine to form spherical adsorbent particles with a particle size of φ0.2 to 2.5 mm, preferably φ0.3 to 0.8 mm. The pellets formed in the first pelletizing are air-dried at room temperature, then dried at 80 to 150°C. After the dry basis reaches more than 80%, the pellets are calcined at 400 to 600°C for 4 to 10 hours.

[0011] 2) The spherical adsorbent particles obtained in 1) are sequentially exchanged with Group IA and Group IIA metal cations, wherein the Group IA metal cation is K. + Cs + One of them, preferably K + The Group IIA metal cation mentioned is Ba. 2+ 、Sr 2+ One of them, preferably Ba 2+ .

[0012] The original molecular sieve has a group IA metal ion exchange rate of ≥97% and a group IIA metal ion exchange rate of ≥60%.

[0013] 3) The adsorbent particles are dried, calcined, dehydrated and activated to obtain a final shaped adsorbent with a dry basis content of 95% to 99%.

[0014] Furthermore, in the preparation method, a group IA metal salt solution with a concentration of 0.05–2.0 mol / L and a group IIA metal salt solution with a concentration of 0.05–2.0 mol / L are respectively used to perform ion exchange with the high-strength mesoporous adsorbent. The ion exchange temperature is 60–100°C, and the volume of the exchange liquid used is 20–40 times the volume of the adsorbent, preferably 15–35 times.

[0015] Furthermore, the final shaped adsorbent preferably has a dry basis content of 95.5% to 99.5%, wherein the molecular sieve content is ≥80wt%, the clay content is ≤20%, and the molar ratio of Group IIA ions to Group IA ions in the adsorbent is 1.5∶1 to 100∶1.

[0016] Furthermore, in the above technical solution, the ion exchange process is as follows: the high-strength mesoporous adsorbent is saturated with water in air at a temperature of 25-30°C to achieve a moisture content ≥20wt%, and then wetted in deionized water to prepare a wetted material; the wetted material is loaded into an exchange column or tank and incubated for 0.5-5 hours. -1 The ion exchange is performed by introducing a soluble Group IA metal ion salt solution at a volume hourly space velocity (VHSV) until the degree of exchange is greater than 97%. Then, the solution is switched to a Group IIA metal ion salt solution for further exchange until the degree of exchange is greater than 65%. After the exchange is completed, the adsorbent is washed with deionized water. The resulting microsphere adsorbent is first dried at a programmed temperature of 80–200°C until the dry basis reaches more than 90%. Then, it is calcined at 300–550°C for dehydration and activation until the dry basis reaches 95.5–98.5%.

[0017] Furthermore, in the above technical solution, the pillared bentonite is selected from any one or more of the following: hydroxyaluminum pillared bentonite, hydroxyiron pillared bentonite, hydroxyaluminum iron pillared bentonite, hydroxyzirconium pillared bentonite, hydroxychromium pillared bentonite, and hydroxytitanium pillared bentonite.

[0018] The pillared bentonite described in this invention is a novel porous material with a large specific surface area, tunable pore size, and strong acidity. It utilizes the exchangeability of interlayer cations in a layered structure to introduce ionic compounds through an exchange reaction, thereby generating molecular-level support pillars in situ. After drying and calcination, it is transformed into a composite material with large pore size and thermal stability, exhibiting certain adsorption and catalytic properties. The pillared bentonite used in the preparation of the adsorbent described in this invention enriches its pore structure characteristics, reduces the molecular diffusion kinetics resistance of adsorption-desorption, and improves adsorption separation and purification efficiency.

[0019] The LSX molecular sieve adsorbent for metal ion exchange described in this invention was applied to the performance evaluation and analysis of single-column pulse feeding of p-cresol. The calculated selectivity coefficient β of p-cresol to m-cresol was >2.1, the separation degree R of p-cresol to m-cresol was >1.6, and the p-cresol desorption curve showed good symmetry with no obvious tailing phenomenon.

[0020] Furthermore, in the above technical solution, the application of the metal ion exchange LSX molecular sieve adsorbent in the simulated moving bed adsorption separation chamber for p-cresol yields p-cresol with a purity ≥99.5% and a yield ≥96% from the extract; and m-cresol with a purity ≥99.0% and a yield ≥96% from the adsorption residue.

[0021] Furthermore, in the above technical solutions, the simulated moving bed (SMB) process includes continuous SMB, semi-continuous SMB, time-varying SMB, sequential SMB, and / or pulsed SMB.

[0022] The application of the LSX molecular sieve adsorbent for metal ion exchange described in this invention involves adsorption-desorption of m-p-cresol 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 a extract, while m-cresol is finally desorbed to form a raffinate.

[0023] Furthermore, in the above technical solution, the desorbent of the present invention has a monocyclic alicyclic alcohol structure, including any one or a mixture of several of cyclopentanol, cyclohexanol, cycloheptenol, cycloheptenol, 1-methylcyclopentanol, and 1-methylcyclohexanol.

[0024] This invention provides a method for the efficient separation and recovery of meta- and para-cresols on an industrial scale using highly practical adsorption and desorption processes, comprising using an adsorbent and a desorbent determined as described above. To achieve the above objective, various combinations of adsorbents and desorbents have been selected, and the desorption mode of each isomer separated at the true feed concentration has been determined using pulse adsorption-desorption separation experiments.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) This invention uses LSX molecular sieves with a Si / Al atomic ratio of 1.0 to 1.1 as the main component of the adsorbent, which can provide more active sites for metal ion exchange and has a moderate adsorption-desorption force for m-cresol and p-cresol. This ensures both a large adsorption capacity and complete desorption of p-cresol, reducing the tailing phenomenon during p-cresol desorption.

[0027] 2) This invention uses pillar-supported bentonite as a binder and polyacrylamide as a molding aid, which can increase the compressive strength of the adsorbent spheres, reduce the wear rate of the adsorbent, and provide a richer mesoporous channel structure, which is beneficial to the adsorption and desorption kinetics of cresol on the molecular sieve adsorption active sites, thereby improving the adsorption and separation efficiency.

[0028] 3) This invention uses group IA and group IIA metal cations to exchange with sodium ions in molecular sieves, and the exchange rate of sodium ions reaches more than 97%, which improves the adsorption-desorption performance of the adsorbent and enhances the selectivity, separation degree and other performance parameters of p-cresol and m-cresol, thus obtaining high-purity products on a simulated moving bed. Detailed Implementation

[0029] 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.

[0030] 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 desorbents with specific feed mixtures to measure the adsorbent performance in terms of their adsorption capacity, selectivity and exchange rate.

[0031] Single-column pulse adsorption-desorption experimental method: The pre-made adsorbent beads are packed into the adsorption column and compacted. The column is purged with nitrogen to remove air. Then, desorbent is pumped in to purge nitrogen from the adsorbent voids, and the temperature is raised to 140℃. After the adsorption column is stabilized at 140℃, the column feed inlet is switched to a syringe and 2 ml of m-cresol feedstock (p-cresol / m-cresol weight ratio = 65 / 35) is pulsed in. Then, the pump is switched back to the desorbent feed, with a desorbent feed rate of 2 ml / min. When the desorbent outflow reaches 10 ml, 3-5 drops of liquid sample are collected every 2 minutes using an automatic fraction collector. Forty samples are collected continuously for gas chromatography quantitative analysis of composition. The envelope curves of the desorbent volume are plotted on the x-axis and the concentrations of cyclohexane, m-cresol, and p-cresol on the y-axis.

[0032] 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. Taking the midpoint of the tracer's half-peak width (HWHM) as zero, the net retention volume from the midpoint of each component's HWHM to zero is measured. 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.

[0033] In this embodiment of the invention, the molecular sieve wear rate is detected:

[0034] A certain amount of calcined sample is rotated inside a grinding cylinder under specified conditions, causing the sample to rub and collide within the cylinder. The percentage of sample pulverization is measured, representing its abrasion rate. The measurement steps are as follows:

[0035] ① Divide the sample into two parts using the quartering method, each part being approximately equal to the amount used in the abrasion test: 25±2g;

[0036] ② Weigh the two porcelain crucibles that have been fired to constant weight at 550℃ (accurate to 0.001g), and this mass is M0;

[0037] ③ Pour the two samples into a standard sieve with a aperture of 0.85mm to remove the powder before grinding, and transfer them to two weighed porcelain crucibles respectively;

[0038] ④ Place the porcelain crucible and crucible lid (without covering the crucible) into a box furnace and bake at 550℃ for 2 hours;

[0039] ⑤ Remove the porcelain crucible and place it in the vacuum desiccator. Immediately cover the crucible and the vacuum desiccator with the lid, turn on the vacuum pump, and set the air pressure to less than 1.0 × 10⁻⁶. 3 Under Pa conditions, turn off the vacuum pump and cool the sample to room temperature;

[0040] ⑥ Slowly rotate the piston on the vacuum dryer cover to allow air to slowly enter the dryer. Open the vacuum dryer, take out the porcelain crucible, and weigh it immediately (accurate to 0.001g). This mass is M1.

[0041] ⑦ Immediately load the samples into the two grinding cylinders respectively, tighten the caps, then symmetrically mount the grinding cylinders onto the abrasion tester, start the abrasion tester, and the grinding cylinders will start to rotate until they rotate 1000 times.

[0042] ⑧ Remove the grinding cylinder, sieve the sample through a 0.6mm standard sieve, and pour it back into the original porcelain crucible;

[0043] ⑨ Place the porcelain crucible and crucible lid (not on the crucible) into a box furnace and fire at 550℃ for 1 hour. Then, operate in the same way, weigh the porcelain crucible, grind it, and sieve it. The mass of the sample after calcination of the material on the sieve (accurate to 0.001g) is M2; the abrasion rate %X = (M2-M1) / (M1-M0).

[0044] In this embodiment of the invention, the method for testing the compressive strength of adsorbent microspheres is as follows:

[0045] ① Sift 20-40 mesh adsorbent beads and place them in the air to allow them to adsorb various gases and water vapor in the air until the quality stabilizes;

[0046] ② Accurately weigh the empty weight of column G in the sample cell and sieve out samples with a mesh size of 50 or larger;

[0047] ③ Measure 1.0 mL of sample and put it into the sample cell. Accurately weigh the total weight of the sample cell and the sample, Ginitial.

[0048] ④ Place the test pin in the sample cell, vertically close to the sample, and gently rotate it once to compact and flatten the accumulated sample particles. After pressing it once under 150N pressure, pour it out, sieve it through a 50-mesh standard sieve to remove the fragments, and put the remaining small balls back into the sample cell using a small glass funnel. Weigh the total weight G150N.

[0049] ⑤ Calculate the breakage rate of the small ball under 150N pressure based on the initial weight of the sample and the remaining weight after crushing. This is the breakage rate of the sample, K150N; K150N = (Ginitial - G150N) / (Ginitial - Gcolumn) * 100%.

[0050] The sample refilled in step ④ is subjected to a pressure of 250N. Steps ④ and ⑤ are repeated to calculate the breakage rate K250N at 250N. K250N = (G_initial - G250N) / (G_initial - G_column) * 100%. The breakage rates K150N and K250N at 150N and 250N are measured again for the same adsorbent particle sample.

[0051] Example A

[0052] Preparation of aluminum hydroxyl pillared bentonite in a specific embodiment:

[0053] Dissolve AlCl3·6H2O in a beaker placed in a 70℃ water bath, and stir continuously at a molar ratio of [OH] - ] / [Al 3 + A 0.5 mol / L NaOH solution was slowly injected using a peristaltic pump at a ratio of 2.2. After the addition was complete, the prepared columnar solution was left to stand at room temperature for 2 days, and then [Al] was added. 3+The column support solution was injected into the bentonite slurry at a ratio of 10 mmol / g using a peristaltic pump to carry out the ion exchange reaction. After the reaction, the solution was aged in a 70°C oven for 2 days, and then centrifuged and washed until no Cl was found. - The material was dried and ground at 70℃ and passed through a 100-mesh sieve. Finally, it was activated at 115℃ for 2 hours to obtain aluminum hydroxyl pillared bentonite.

[0054] Preparation of hydroxyl iron-aluminum pillared bentonite in a specific embodiment:

[0055] 1) Mix 0.2 mol / L FeCl3 and 0.2 mol / L AlCl3 with a Fe / Al molar ratio of 0.2. Then, slowly (200 mL / h) add 0.2 mol / L Na2CO3 dropwise while stirring at high speed to achieve the desired molar ratio. - / (Fe+Al)=2.4, after the addition is complete, continue stirring for 1 hour, and age in an 80℃ water bath for 2 days. During the aging process, add deionized water to the columnar solvent as needed to replenish the evaporated water and keep the liquid level stable to obtain the prepared columnar solvent.

[0056] 2) Prepare a 5% bentonite slurry. Then, under continuous stirring, add the columnarizing agent prepared in 1) dropwise into the slurry until [(Fe+Al)] / [bentonite] = 10 mmol / g. After the addition is complete, continue the reaction for 2 hours, age at 80℃ for 2 days, and then wash with deionized water until no Cl is present. - Dry the material, activate it at 105℃ for 1.0 h, grind it, and pass it through a 200-mesh sieve to obtain hydroxyl iron aluminum pillared bentonite.

[0057] Preparation of hydroxyl iron-pillared bentonite in a specific embodiment:

[0058] Fe(NO3)3 was dissolved in a beaker placed in a 70℃ water bath to prepare a concentration of 0.2 mol / L. The molar ratio of Na2CO3 / Fe(NO3)3 was 1 / 1. The 0.2 mol / L Na2CO3 solution was injected into the continuously stirred Fe(NO3)3 solution using a peristaltic pump and left at room temperature for 2 days. Then, according to [Fe...] 3+ The column support solution with a ratio of 10 mmol / g of [bentonite] was added dropwise to a 5% bentonite slurry. After the addition was complete, the reaction continued for 2 hours, and the mixture was aged at 80°C for 2 days. Finally, it was washed with deionized water until no NO3 was found. - Dry the bentonite until it is dry, activate it at 105℃ for 2 hours, grind it through a 200-mesh sieve, and you will get hydroxyl iron-supported bentonite.

[0059] Preparation of hydroxyl iron titanium pillared bentonite in a specific embodiment:

[0060] 1) Dissolve Fe(NO3)3 in a beaker in a 70℃ water bath to prepare a concentration of 0.2mol / L. With a molar ratio of Na2CO3 / Fe(NO3)3 = 2 / 1, inject the 0.2mol / L Na2CO3 solution into the Fe(NO3)3 solution under constant stirring using a peristaltic pump. After vigorous stirring for 8 hours, a reddish-brown hydroxyl iron columnar liquid is obtained. Then, add the same volume of TiO2 sol and mix and continue stirring for 12 hours. Add deionized water to the columnar liquid as needed to replenish the evaporated water and keep the liquid level stable to obtain the prepared iron-titanium composite columnar agent.

[0061] 2) Prepare a 5% bentonite slurry. Then, under continuous stirring, add the iron-titanium composite columnar agent prepared in 1) dropwise into the slurry so that [(Fe+Ti)] / [bentonite] = 10 mmol / g. After the addition is complete, continue stirring for 2 hours. Aging at 80℃ for 2 days, centrifugation, washing with deionized water until neutral, drying and grinding the wet cake at 80℃, calcining at 350℃ at 2℃ / min for 3 hours, and grinding through a 200-mesh sieve to obtain light yellow iron-titanium bimetallic columnar bentonite.

[0062] Note: Silver-gray titanium-pillared bentonite can be prepared using the same method described above.

[0063] Preparation of hydroxyzirconium-pillared bentonite in a specific embodiment:

[0064] Dissolve ZrOCl2·8H2O in a beaker placed in a 70℃ water bath to prepare a concentration of 0.2 mol / L. With a molar ratio of Na2CO3 / ZrOCl2 = 1 / 1, inject the 0.2 mol / L Na2CO3 solution into the continuously stirred ZrOCl2 solution using a peristaltic pump and let it stand at room temperature for 2 days. Then, according to [Zr...] 4+ Add this pillaring solution at a ratio of 10 mmol / g to 5% bentonite slurry. After adding all the solution, continue the reaction for 2 hours. Then, age it at 80°C for 2 days. Wash it with deionized water until no Cl- is present. Dry it, activate it at 115°C for 2 hours, grind it, and pass it through a 200-mesh sieve to obtain hydroxyzirconium pillared bentonite.

[0065] Example 1

[0066] 1) LSX molecular sieve with a Si / Al atomic ratio of 1.1, controlled to have a dry basis content of 80%, is mixed with aluminum hydroxide-pillared bentonite and polyacrylamide ((C3H5NO)n, where n = 2000) in a weight percentage of 88.67:9.97:1.36. The mixture is then rolled into small spheres of 0.1-0.2 mm in a pelletizing machine. The mixed powder is then added regularly and quantitatively to gradually increase the diameter of the adsorbent spheres to 0.3-0.8 mm. The freshly rolled spheres are then naturally air-dried at room temperature, followed by drying at 120°C for 24 hours until the dry basis content reaches 80%. Finally, they are calcined at 550°C for 6 hours to improve the strength of the spheres.

[0067] 2) The microsphere adsorbent prepared in 1) is saturated with water in air at a temperature of 25–30°C until the moisture content reaches 20 wt%. It is then wetted in deionized water to form a wetted material. The wetted material is then placed in an exchange tank and incubated for 1.5 hours. -1 The molecular sieve was subjected to K+ ion exchange with a 0.5 mol / L K2SO4 solution. The amount of K2SO4 solution used was 30 times the volume of the adsorbent. The concentration of the effluent K2SO4 solution was 0.492 mol / L. + The exchange rate reached 98.48%, and then the solution was switched to 0.5 mol / L Ba(NO3)2 solution for Ba... 2+ In ion exchange, the amount of Ba(NO3)2 solution used was 24 times the volume of the adsorbent. The concentration of the effluent Ba(NO3)2 solution was 0.489 mol / L. The Ba in the molecular sieve... 2+ The exchange rate reached 97.81%, and after the exchange was completed, the sample was washed with deionized water until the pH value reached 9.0.

[0068] 3) The small ball adsorbent obtained in 2) was first dried by a vibrating fluidized bed at a temperature of 80℃-150℃-200℃. The output was directly fed into a rotary kiln and heated and dehydrated in six temperature ranges: 250℃-350℃-400℃-500℃-550℃-250℃. The final dry basis content was controlled to be 97.52%. The adsorbent was vacuum packaged as the final adsorbent product, denoted as XFJ-1. Its composition is shown in Table 1 and its physicochemical characterization data are shown in Table 2.

[0069] Example 2

[0070] The adsorbent was prepared according to the method in Example 1, except that during the spherical forming process, LSX molecular sieves with a Si / Al atomic ratio of 1.05 were mixed with hydroxyl iron-pillared bentonite and polyacrylamide ((C3H5NO)n, where n = 2500) in a weight percentage of 90.74:8.26:1.0. The mixture was then exchanged using soluble salts of KCl and SrCl2, and fed into a 1.0 mol / L KCl solution at a space velocity of 1.5 h⁻¹ for KCl exchange.+ In ion exchange, the amount of KCl solution used was 30 times the volume of the adsorbent, resulting in an effluent KCl solution concentration of 0.985 mol / L. Then, a 0.5 mol / L SrCl2 solution was used for Sr exchange. 2+ Ion exchange was performed, with the amount of SrCl2 solution used being 15 times the volume of the adsorbent packing, resulting in an effluent SrCl2 solution concentration of 0.304 mol / L. Other subsequent treatment methods were the same as in Example 1. The final adsorbent product, designated XFJ-2, was vacuum-packed. Its composition is shown in Table 1, and its physicochemical characterization data are shown in Table 2.

[0071] Example 3

[0072] The adsorbent was prepared according to the method in Example 1, except that during the spherical molding process, LSX molecular sieves with a Si / Al atomic ratio of 1.07 were mixed uniformly with hydroxyl iron-aluminum pillared bentonite and polyacrylamide ((C3H5NO)n, where n = 1000) in a weight percentage of 92.53:6.0:1.47. Ion exchange was performed using soluble salts of KNO3 and Ba(NO3)2, and the mixture was fed into a 1.0 mol / L KNO3 solution at a space velocity of 1.5 h⁻¹ for K exchange. + In ion exchange, the amount of KNO3 solution used was 30 times the volume of the adsorbent, resulting in an effluent KNO3 solution concentration of 0.986 mol / L. Then, a 0.5 mol / L Ba(NO3)2 solution was used for Ba... 2+ Ion exchange was performed, with the amount of Ba(NO3)2 solution used being 19 times the volume of the adsorbent packing, resulting in an effluent Ba(NO3)2 solution concentration of 0.384 mol / L. Other subsequent treatment methods were the same as in Example 1. The final adsorbent product, designated XFJ-3, was vacuum-packed. Its composition is shown in Table 1, and its physicochemical characterization data are shown in Table 2.

[0073] Example 4

[0074] The adsorbent was prepared according to the method in Example 1, except that during the spherical forming process, LSX molecular sieves with a Si / Al atomic ratio of 1.025 were mixed with hydroxyl zirconium-pillared bentonite and polyacrylamide ((C3H5NO)n, where n = 1500) in a weight percentage of 94.48:4.26:1.26. The mixture was then exchanged using soluble salts of K2SO4 and BaCl2, and fed into a 0.5 mol / L K2SO4 solution at a space velocity of 1.5 h⁻¹. + In ion exchange, the amount of K₂SO₄ solution used was 30 times the volume of the adsorbent. The concentration of the effluent K₂SO₄ solution was 0.487 mol / L. Then, the solution was switched to 0.5 mol / L BaCl₂ solution for Ba… 2+Ion exchange was performed, with the amount of BaCl2 solution used being 20 times the volume of the adsorbent packing, resulting in an effluent BaCl2 solution concentration of 0.412 mol / L. Other subsequent treatment methods were the same as in Example 1. The final adsorbent product, designated XFJ-4, was vacuum-packed. Its composition is shown in Table 1, and its physicochemical characterization data are shown in Table 2.

[0075] Example 5

[0076] The adsorbent was prepared according to the method in Example 1, except that during the spherical forming process, LSX molecular sieves with a Si / Al atomic ratio of 1.01 were mixed with hydroxyl titanium pillared bentonite and polyacrylamide ((C3H5NO)n, where n = 3000) in a weight percentage of 85.29:12.8:1.91. KNO3 and Ba(CH02)2 soluble salts were used for exchange. K+ ion exchange was performed by introducing a 1.0 mol / L KNO3 solution at a space velocity of 1.5 h⁻¹. The amount of KNO3 solution used was 30 times the volume of the adsorbent. The effluent KNO3 solution concentration was 0.971 mol / L. Then, the solution was switched to a 0.5 mol / L Ba(CH02)2 solution for Ba+ ion exchange. 2+ Ion exchange was performed, with the amount of Ba(CHO2)2 solution used being 22 times the volume of the adsorbent packing, resulting in an effluent Ba(CHO2)2 solution concentration of 0.441 mol / L. Other subsequent treatment methods were the same as in Example 1. The final adsorbent product, designated XFJ-5, was vacuum-packed. Its composition is shown in Table 1, and its physicochemical characterization data are shown in Table 2.

[0077] Table 1. Content of each component of the adsorbent prepared in the examples

[0078]

[0079] Comparative Example 1

[0080] According to the preparation method in the embodiment of patent document CN110511121B:

[0081] 1) Mix 90 kg (based on ignition, the same below) 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 is 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.

[0082] 2) Ion exchange: 130 mL of the pellets 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 pellets 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 at 180 °C under nitrogen atmosphere for 6 hours. The resulting adsorbent was designated VS-1. Physicochemical characterization data are shown in Table 2.

[0083] Comparative Example 2

[0084] According to the preparation methods in Examples 1 and 2 of patent CN 110511122 B:

[0085] 1) Add 4.02 kg of sodium hydroxide, 7.81 kg of deionized water, 5.32 kg of low-alkalinity sodium aluminate solution (Al₂O₃ content 9.99% by mass, Na₂O content 10.93% by mass), and 23.24 kg of water glass (SiO₂ concentration 0.2017 g / g, Na₂O concentration 0.0632 g / g) to a reaction vessel, stir and mix thoroughly, and allow to stand at 35°C for 24 hours to age, thus obtaining the directing agent. The molar ratio of each material in the directing agent is SiO₂ / Al₂O₃ = 15, Na₂O / Al₂O₃ = 16, and H₂O / Al₂O₃ = 320.

[0086] 2) Add 2.46 kg of sodium hydroxide, 4.15 kg of potassium hydroxide, 56.90 kg of deionized water, 31.48 kg of low-alkalinity sodium aluminate solution (Al₂O₃ content 9.99%, Na₂O content 10.93%), 22.82 kg of water glass (SiO₂ content 20.17% g / g, Na₂O content 6.32%), and 0.24 kg of directing agent to the reactor and stir to mix evenly to form a molecular sieve synthesis system. The total molar ratio of each material in the molecular sieve synthesis system is SiO₂ / Al₂O₃ = 2.5, M₂O / SiO₂ = 1.90, H₂O / SiO₂ = 72, K₂O ... + / (K + +Na + The concentration of Al2O3 in the added directing agent was 0.25, where M represents Na and K, and the molar ratio of Al2O3 in the added directing agent to the total Al2O3 in the molecular sieve synthesis system was 0.1%. The molecular sieve synthesis system was stirred for another half hour to form a milky white sol, which was then transferred to a reaction vessel and hydrothermally crystallized at 95°C for 8 hours. After filtration, the resulting solid was washed with deionized water until the pH of the filtrate was 8-9, and then dried at 80°C for 12 hours to obtain nanoscale X molecular sieve crystallite spherical self-aggregates a. The molar ratio of SiO2 / Al2O3 measured by XRF was 2.33.

[0087] 3) Take 92 kg (based on ignition, the same below) of the powdered X molecular sieve spherical self-aggregate a from step 2) and mix it evenly with 8 kg of kaolin. Place it in a turntable and spray an appropriate amount of deionized water while rolling it to make the solid powder aggregate into small balls. The amount of water sprayed during the rolling process is 8% of the mass of the solid powder. After sieving, take small balls with a particle size of 300-850 μm, dry them at 80℃ for 10 hours, and calcine them at 540℃ for 4 hours.

[0088] 4) Place 64 kg of the calcined pellets from step 3) into a 200 L mixed solution of sodium hydroxide and potassium hydroxide. The hydroxide ion concentration in the mixed solution is 0.3 mol / L, and the K / (Na+K) molar ratio is 0.2. Crystallize in situ at 95 °C for 4 hours. Take the crystallized solid, wash it with water until the pH of the washing solution is less than 10, and dry it at 80 °C for 10 hours.

[0089] 5) Ion exchange: 130 mL of the dried beads from step 4) were loaded into an ion exchange column for cation exchange. A mixed solution of 0.18 mol / L barium nitrate and 0.09 mol / L potassium chloride was used for continuous exchange at 0.1 MPa and 94 °C for 8 hours at a volume hourly space velocity (VHSV) of 6.0 h⁻¹. The total volume of the mixed solution used was 5000 mL. After ion exchange, the solid was washed with 700 mL of deionized water at 70 °C, dried under nitrogen atmosphere at 70 °C for 30 hours, and then dehydrated and activated under nitrogen atmosphere at 180 °C for 6 hours to obtain adsorbent VS-2. The physicochemical characterization data are shown in Table 2.

[0090] Table 2 Comparison of physicochemical characterization parameters of adsorbents prepared in Examples 1-5 and Comparative Examples 1-2

[0091]

[0092] Examples 6-12

[0093] 99.5% pure m-p-cresol was mixed with cyclohexane in a 7:3 ratio as the pulse feed component, and n-pentanol was used as the desorbent. The single-column pulse adsorption-desorption evaluation method was adopted.

[0094] Vmc is defined as the net retention volume of m-cresol, calculated by subtracting the volume of desorbent consumed by cyclohexane desorption from the volume of desorbent consumed by m-cresol efflux; similarly, Vpc is defined as the net retention volume of p-cresol, calculated by subtracting the volume of desorbent consumed by cyclohexane desorption from the volume of desorbent consumed by p-cresol efflux; W 1 / 2MC The full width at half maximum (FWHM) of the m-cresol envelope peak. 1 / 2PCThe half-maximum width (FWHM) of the m-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:

[0095]

[0096] Vpc is the retention volume of p-cresol in the latter of two adjacent peaks; Vmc is the retention volume of inter-cresol in the former of two adjacent peaks; W 1 / 2pC and W 1 / 2mC These are the half-widths (WHMs) of the peaks for m-cresol and p-cresol, respectively. The exchange rate of the desorbent to p-cresol is specified by the WHM of the p-cresol peak distribution; the narrower the peak width, the higher the desorption rate. The closer the p-cresol desorption / adsorption time ratio is to 1.0, the more balanced the adsorption and desorption rates are, reducing desorption tailing.

[0097] Table 3 Comparison of single-column pulse adsorption-desorption evaluation results between the adsorbents prepared in Examples 1-5 and Comparative Examples 1-2

[0098]

[0099] By comparing Table 3, the results show that the selectivity coefficient β of p-cresol to m-cresol obtained by using the adsorbents of the embodiments of the present invention is >2.3, and the resolution R value of p-cresol to m-cresol is >1.6. 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 adsorbent residue, which reduces the purity of m-cresol. Furthermore, the selectivity coefficient β of p-cresol to m-cresol is <1.7, and the resolution R value of p-cresol to m-cresol is <1.0. Furthermore, desorption of p-cresol typically takes longer than adsorption and exhibits tailing. The degree of tailing can be determined by the "p-cresol desorption / adsorption time ratio." For example, the closer this value is to 1.0, the better the adsorption and desorption performance, and the absence of incomplete desorption. The "p-cresol desorption / adsorption time ratio" of the adsorbents prepared in the embodiments of this invention is close to 1.0, generally within the range of 1.0 to 1.2, while the corresponding value of the adsorbents prepared in the comparative examples is >1.5. These results clearly demonstrate the advantages of using the adsorbents according to the present invention to separate cresol isomers: fast desorption-desorption rate, less tendency to produce tailing, which affects the separation purity, and larger separation coefficient and resolution, which is more conducive to obtaining high-purity p-cresol and m-cresol products.

[0100] Example 13

[0101] Separation of m-cresol using XFJ-1 adsorbent in a continuous countercurrent simulated moving bed:

[0102] 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 circulation pumps 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: desorbent D, feed F, extract E, and residual liquid R. The 24 columns are divided into four sections: the 7 columns between the feed and the residual liquid form the adsorption zone; the 9 columns between the extract and the feed form the purification zone; the 5 columns between the desorbent and the extract form the desorption zone; and the 3 columns between the residual liquid and the desorbent form the isolation zone. The temperature of the entire adsorption system is controlled at 140°C, and the pressure at 8 bar.

[0103] 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 inlet F, while the desorbent (cyclopentanol) 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 feed streams simultaneously move one adsorption column in the same direction as the liquid flow. This step-through process 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. A p-cresol purity of 99.56 wt% and a p-cresol yield of 98.2 wt% are obtained from the extract stream E; simultaneously, a m-cresol purity of 99.52 wt% and a m-cresol yield of 96.5 wt% can be obtained through the discharge line of the adsorbate R.

[0104] 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. An application of a separation and purification adsorbent, characterized in that: The separation and purification adsorbent is used for the separation and purification of m-p-cresol isomers, and the preparation method of the separation and purification adsorbent includes the following steps: LSX molecular sieves with a Si / Al atomic ratio of 1.0 to 1.1 are mixed with pillared bentonite and polyacrylamide in a weight percentage ratio of (85 to 95): (4 to 14): (1 to 2). The mixture is then placed in a pelletizing machine to form spherical particles with a particle size of φ0.2 to 2.5 mm. The particles are then dried and calcined to obtain a high-strength mesoporous adsorbent. The pillared bentonite is selected from one or more of the following: hydroxyaluminum pillared bentonite, hydroxyiron pillared bentonite, hydroxyaluminum iron pillared bentonite, hydroxyzirconium pillared bentonite, hydroxychromium pillared bentonite, and hydroxytitanium pillared bentonite. The high-strength mesoporous adsorbent was sequentially ion-exchanged with Group IA and Group IIA metal salts, and then dried, calcined, and dehydrated to activate the adsorbent to obtain the separation and purification adsorbent. The Group IA metal salt is one of potassium salt and cesium salt; the Group IIA metal salt is one of barium salt and strontium salt. The high-strength mesoporous adsorbent has an exchange degree of ≥97% with Group IA metal ions and ≥60% with Group IIA metal ions.

2. The application according to claim 1, characterized in that: In a pelletizing machine, spherical particles with a diameter of φ0.3~0.8mm are obtained by ball forming.

3. The application according to claim 1, characterized in that: The Group IA metal salt is a potassium salt, and the Group IIA metal salt is a barium salt.

4. The application according to claim 1, characterized in that: The high-strength mesoporous adsorbent was subjected to ion exchange sequentially with a Group IA metal salt solution with a concentration of 0.05~2.0 mol / L and a Group IIA metal salt solution with a concentration of 0.05~2.0 mol / L. The ion exchange temperature was 60~100℃, and the volume of the exchange liquid used was 20~40 times the volume of the adsorbent.

5. The application according to claim 4, characterized in that, The ion exchange process is as follows: the high-strength mesoporous adsorbent is saturated with water in air at a temperature of 25~30℃ to achieve a moisture content ≥20wt%, and then wetted in deionized water to prepare a wetted material; the wetted material is then loaded into an exchange column or tank and incubated for 0.5~5 hours. -1 Ion exchange is performed by introducing a soluble Group IA metal ion salt solution at a volume hourly space velocity (VHSV) until the degree of exchange is greater than 97%. Then, the solution is switched to a Group IIA metal ion salt solution for further exchange until the degree of exchange is greater than 65%. After the exchange is completed, the adsorbent is washed with deionized water. The adsorbent is then dried at 80–200 °C until the dry basis content reaches more than 90%. Finally, it is calcined at 300–550 °C in stages to dehydrate and activate the adsorbent, resulting in a dry basis content of 95.5–98.5%.

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