Preparation of liquid-phase preferential adsorption m-cresol adsorbent and continuous separation and purification process method

Abstract

The invention discloses preparation of an adsorbent for preferentially adsorbing m-cresol by a liquid phase and a continuous separation and purification process method, and belongs to the technical field of chemical separation application. The process comprises the following steps: stirring and mixing a lithium-type ZSM-20 molecular sieve obtained by exchanging a LiOH solution with an ammonium-type ZSM-20 molecular sieve, organic bentonite and a pore-forming aid, molding in a ball forming mill to obtain spherical adsorbent particles with the particle size of 0.2-2.5 mm, drying, roasting, dehydrating and activating to obtain the m-cresol adsorbent for producing high-purity m-cresol. The method not only overcomes the defects of more byproducts, long process flow, large production energy consumption, limited production scale and the like in the existing industrial common alkylation method for separating the m-cresol and the p-cresol, but also changes the process route of preferentially adsorbing the p-cresol to separate the cresol mixture reported in the existing patent literature. According to the process method disclosed by the invention, the m-cresol is adsorbed preferentially, the high-purity m-cresol is produced with high selectivity, and the process method is an environment-friendly green process.

Description

Technical Field

[0001] The invention relates to a preparation method of a liquid phase preferentially adsorbing meta-cresol adsorbent and a continuous separation and purification process, belonging to the technical field of chemical separation application. Background Art

[0002] The boiling points of m-cresol (202.9℃) and p-cresol (202.5℃) are very close, and they cannot be separated by traditional distillation methods. The alkylation method is currently the only industrialized m / p mixed phenol separation technology in China. At present, the alkylation method requires the use of concentrated sulfuric acid, sulfonic acid or aluminum chloride as a dealkylation catalyst, and the equipment maintenance and wastewater treatment costs are high. In addition, the alkylation method requires alkylation, dealkylation and multiple distillation separation processes. The process flow is lengthy and the process energy consumption is high, which has also prompted researchers to develop a more environmentally friendly cresol isomer separation process. The method of using molecular sieves to separate m-cresol and p-cresol by adsorption is more effective, with less energy consumption in the separation process and less pollution to the environment. It is a relatively energy-saving and environmentally friendly method. However, this method has very high requirements for molecular sieves, and the selection and preparation of molecular sieves are relatively difficult. The key lies in the development of highly selective and high adsorption adsorbents and the research on desorption processes, which requires a lot of effort to study. The adsorption separation method started late in China, but it has attracted the attention of domestic researchers due to its high efficiency and environmental protection. This technology has sufficient potential to alleviate the problem of insufficient supply of high-purity cresol monomer in my country, generate greater economic and social benefits, and has a large room for development.

[0003] US Patent No. 19900624810 selectively adsorbs p-cresol and m-cresol by using a barium potassium exchanged X zeolite adsorbent, and desorbs with (C5-C6) aliphatic alcohol at about 20°C to 250°C to obtain a co-extract of m-cresol and p-cresol, and then separates m-cresol and p-cresol by a second stage adsorption-desorption process using barium potassium exchanged X / Y zeolite as an adsorbent and (C5-C6) aliphatic alcohol or a mixture thereof with aliphatic ketones as a desorbent. US Patent No. 3014078 discloses the use of NaX molecular sieve as an adsorbent and cresol as a desorbent to adsorb and separate p-cresol. Patent document CN108147945A discloses that a mixture of m-cresol and p-cresol is used as a raw material, sodium type X or Y molecular sieve is used, and after being formed with a slurry of a binder, it is first treated with a KOH solution, and then modified with metal ions (at least one of copper, potassium, and zinc) to obtain an adsorbent, and anisole, phenol, and 4-methylanisole are used as desorbents to produce m-cresol with high selectivity at an adsorption separation temperature of 80 to 180°C. Patent document CN110511118B discloses an adsorbent with an X molecular sieve as the core and a ZSM-5 molecular sieve as the shell, which is occupied by group IIA metal ions or co-occupied with group IA metal ions, preferentially adsorbs p-cresol, and obtains m-cresol in the raffinate. Patent document CN110511121A discloses an adsorbent X / Silicalite-1 core / shell molecular sieve, wherein the core is X molecular sieve and the shell is Silicalite-1 molecular sieve, the cation sites are occupied by Group IIA metal ions or jointly occupied by Group IIA metal ions, p-cresol is preferentially adsorbed, and m-cresol is obtained in the raffinate. Patent document CN110511122A discloses an adsorbent for liquid phase adsorption separation of cresol isomers, wherein the active component is X molecular sieve, and the cation sites are occupied by Group IIA metal ions or jointly occupied by Group IIA metal ions and Group IIA metal ions.

[0004] The molecular sieve adsorbents used in the above patent literature materials all preferentially adsorb p-cresol, while m-cresol is released as a component of the raffinate. Impurities in the m-cresol raw material, such as cresol and dimethylphenol, will be mixed into the raffinate. These impurities are difficult to remove during the subsequent refining of m-cresol, resulting in difficulty in improving the purity of m-cresol, affecting the purity of the final m-cresol product. In addition, the p-cresol in these adsorbents is not easily desorbed by fatty alcohol desorbents, and there is a desorption tailing phenomenon, which leads to an increase in the amount of desorbent used and increases the energy consumption of public works. At the same time, the p-cresol that has not been desorbed is mixed into the raffinate of m-cresol, further reducing the purity of m-cresol. Summary of the invention

[0005] The present invention provides a preparation method of an adsorbent for preferentially adsorbing meta-cresol for producing high-purity meta-cresol, which not only solves the shortcomings of the existing industrial alkylation method commonly used to separate meta-cresol, such as many by-products, long process flow, high production energy consumption, and limited production scale, but also changes the process path of preferentially adsorbing p-cresol to separate cresol mixtures reported in existing patent documents. The present invention uses a mixture of meta-cresol and p-cresol as raw materials, preferentially adsorbs meta-cresol, and produces high-purity meta-cresol with high selectivity. The production process has little corrosion to equipment, low energy consumption, and does not generate a large amount of industrial wastewater. It is an environmentally friendly green process.

[0006] In order to solve the above technical problems, the technical scheme of the present invention is: a method for preparing a liquid-phase meta-cresol adsorbent, exchanging a soluble lithium salt with an ammonium-type ZSM-20 molecular sieve to obtain a lithium-type ZSM-20 molecular sieve with an exchange degree of ≥90%; stirring and mixing the lithium-type ZSM-20 molecular sieve with an organic bentonite and a pore-forming aid according to weight percentages of 85-95%, 4.9-15%, and 0.1-1.5%, respectively, and placing the mixture in a spheroidizer to obtain spherical adsorbent particles with a particle size of 0.2-2.5 mm; and drying, roasting, and dehydrating and activating the adsorbent particles to obtain a meta-cresol adsorbent.

[0007] In some preparation methods, the pore-forming aid is one or more of polyacrylic acid latex, sesbania powder, cellulose, methyl cellulose, polyethylene glycol PEG, and polyvinyl alcohol PVA; and the particle size of the spherical adsorbent particles is 0.3-0.8 mm.

[0008] The present invention provides a method for preparing a liquid phase adsorbent for preferentially adsorbing m-cresol and for continuous separation and purification, which is characterized by: 1) A soluble lithium salt is subjected to a kettle-type exchange with ammonium-type ZSM-20 molecular sieve powder to obtain a lithium-type ZSM-20 molecular sieve with an exchange degree of ≥90%; 2) Dry the lithium ZSM-20 molecular sieve obtained above to a dry basis content of ≥75% and an average particle size of ≤30 μm, fully stir and mix with organic bentonite with an average particle size of ≤50 μm and a pore-forming aid, place in a ball forming machine and roll to form spherical adsorbent particles with a particle size of 0.2-2.5 mm, preferably 0.3-0.8 mm; 3) Drying, calcining, dehydrating and activating the adsorbent particles to obtain a shaped lithium sieve adsorbent with a dry basis content of 96% to 99%; 4) The above-mentioned shaped lithium sieve adsorbent is loaded into a countercurrent simulated moving bed adsorption column / bed layer, and the inlet and outlet materials are switched by a switch valve or a multi-channel valve, and multiple adsorption columns or beds are divided into four areas of adsorption, purification, elution, and buffering, so as to realize the process of continuously feeding m-cresol material and desorbent and continuously withdrawing extract and raffinate materials; 5) introducing the extract and the raffinate into distillation towers to remove the desorbent, thereby obtaining high-purity m-cresol and p-cresol products; Further, in the above technical solution, the preparation method of lithium ZSM-20 molecular sieve is as follows: 1) the ZSM-20 molecular sieve raw powder is mixed with soluble NH 4 + The ion salt solution was exchanged 2 to 4 times at 60 to 100 °C according to the solid-liquid ratio of 1: (5 to 10) to achieve NH 4 + The ion exchange degree reaches more than 95%; 2) the NH 4 + ZSM-20 molecular sieve filter cake is input into Li + In the ion exchange tank, add LiOH solution at 60-70℃, stir and exchange, and introduce air to bubble the generated NH 3 ·H 2 O was squeezed out, and the filter cake was filtered after 2-10 h of exchange, and then washed with deionized water to make the pH value <11. + Ion content is less than 0.5%, Li + Ion exchange degree ≥92%.

[0009] Furthermore, in the above technical solution, the specific preparation method of the obtained spherical particles is characterized by: 1) Li + The molecular sieve powder after ion exchange is uniformly mixed with organic bentonite and pore-forming additive according to the weight percentage of 85-95%, 4.9-15% and 0.1-1.5%, and then the mixed powder is placed in a rolling ball forming device, and deionized water is added during rotation to keep the dry basis of the mixture in the range of 70-80%, and the diameter of the ball is controlled to be less than 2.5 mm, and φ0.3-0.8 mm small balls are sieved; 2) the lithium adsorbent small balls obtained in 1) are controlled to be programmed to rise in temperature in the range of 80-600°C for negative pressure dehydration activation, the additive is completely removed, and the dry basis content of the adsorbent small balls is controlled to be 96%-99%, and then the temperature is reduced to 80-150°C in an isolated water vapor environment for sealed packaging to obtain the finished small ball adsorbent.

[0010] Furthermore, in the above technical solution, NH 4 + The ion salt is NH 4 Cl, (NH 4 ) 2 SO 4 NH 4 NO 3 Any one or more of; Furthermore, in the above technical solution, the auxiliary agent is one or more of polyacrylic acid emulsion, sesbania powder, SG plant gum, cellulose, methyl cellulose, polyethylene glycol PEG, polyvinyl alcohol PVA and their derivatives.

[0011] Furthermore, in the continuous separation and purification process method using the Li-type ZSM-20 molecular sieve adsorbent, the temperature of meta-cresol adsorption-desorption is 100-200°C, the pressure during adsorption and desorption treatment is 5-20kg / cm2 (gauge pressure), the adsorbent is loaded in 4-30 adsorption columns or adsorption beds connected in series, and a countercurrent simulated mobile chromatography process is formed by periodically changing the way in which materials enter and exit a single adsorption column or adsorption bed. The meta-cresol mixture contacts the adsorbent, wherein meta-cresol is preferentially adsorbed relative to para-cresol, and para-cresol is preferentially desorbed to form a raffinate for removal, and meta-cresol is finally desorbed to form an extract for removal.

[0012] Furthermore, in the above technical solution, the desorbent is at least one of a secondary alcohol of C4 to C8 and a primary alcohol of C4 to C8.

[0013] Further, the desorbent is selected from 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, 3-ethyl-3-pentanol, cyclopentanol, cyclohexanol, cycloheptenol, cycloheptanol, 1-methylcyclopentanol, and 1-methylcyclohexanol.

[0014] Furthermore, in the above technical scheme, the desorbent is used as a primary / secondary alcohol alone or as a mixture of a primary / secondary alcohol and a cycloalkyl alcohol, and the weight content of the cycloalkyl alcohol in the mixed alcohol is 0.1-10%, preferably 0.2-5%, and particularly preferably 0.5-3%; the cycloalkyl alcohol is preferably any one or more of cyclopentanol, cyclohexanol, cycloheptanol, and 1-methylcyclopentanol.

[0015] The present invention uses a simulated countercurrent moving bed system to carry out adsorption and desorption treatment of a cresol isomer mixture. The basic operations of the adsorption and desorption treatment include: (i) adsorption operation; (ii) purification operation; (iii) desorption operation; (iv) raffinate recovery operation, and these steps are continuously carried out using a circulation system.

[0016] In the adsorption step (i), a feed mixture containing cresol isomers is introduced and contacted with an adsorbent and a desorbent, m-cresol is selectively adsorbed, and slightly adsorbable p-cresol is recovered together with the desorbent as a raffinate desorbent.

[0017] In the purification step (ii), the adsorbent having selectively adsorbed m-cresol is contacted with a desorbent to remove the feed mixture and the like remaining on the adsorbent, thereby concentrating the adsorbed m-cresol.

[0018] In the desorption step (iii), the adsorbent concentrate containing m-cresol is contacted with a desorbent to elute the m-cresol from the adsorbent and recover the m-cresol together with the desorbent as an extract.

[0019] In the raffinate recovery step (iv), the adsorbent that has adsorbed only the desorbent is contacted with the raffinate desorbent, and the adsorbed desorbent and the p-cresol component are recovered as the raffinate. The simulated moving bed of the present invention means that the adsorbent in the adsorption tower or adsorption column does not need to be moved, and the positions of several inlets and outlets on the adsorption tower or multi-stage adsorption column are changed simultaneously, successively and periodically. Its effect is the same as the effect of the adsorbent moving continuously on the adsorption tower or multi-stage adsorption column, so it is called a simulated moving bed. The flow fraction containing the extract component is called the extract flow, and the fluid containing the raffinate component is called the raffinate flow.

[0020] The present invention adopts a simulated moving bed (SMB) to not only retain the advantages of the adsorption separation method, but also introduces cross-flow technology, which has the advantages of automatic continuous operation, high yield, high purity, high efficiency and low solvent consumption. The countercurrent moving bed or countercurrent simulated moving bed system has a higher separation efficiency than the fixed adsorption bed system. In the industrial chromatography method of simulated moving bed continuous separation, adsorption and desorption occur continuously, so that extracts and raffinate streams can be continuously produced, and feed and desorbent streams can be continuously supplied. The preferred operating mode of the method according to the present invention is the countercurrent chromatography with a simulated fixed bed movement known in the art. The cresol adsorbent reported in the existing literature usually preferentially adsorbs p-cresol, and m-cresol can only be separated from the raffinate stream with other trace impurity phenols. After further distillation and refining treatment, there are still trace impurity phenols that affect the purity of m-cresol, and it is usually difficult to obtain a high-purity m-cresol product. The invention provides a lithium ZSM-20 molecular sieve adsorbent capable of preferentially adsorbing the meta-cresol component, and the meta-cresol is released from the extract liquid flow, which not only increases the purity of the meta-cresol in the extract liquid, but also reduces the amount of the desorbent. Trace impurities contained in the raw material meta-cresol, such as dimethylphenol and ethylphenol, are not easily adsorbed on the adsorbent and are completely included in the raffinate, and the meta-cresol is completely included in the extract liquid, so that a high-purity meta-cresol product can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 This is the data envelope diagram of single column pulse adsorption-desorption evaluation of the adsorbent prepared by Example 1; Figure 2 This is the data envelope diagram of single column pulse adsorption-desorption evaluation of the adsorbent prepared by Example 2; Figure 3 This is the data envelope diagram of single column pulse adsorption-desorption evaluation of the adsorbent prepared by Example 3; Figure 4 This is the data envelope diagram of single column pulse adsorption-desorption evaluation of the adsorbent prepared by Example 4; Figure 5 This is the data envelope diagram of single column pulse adsorption-desorption evaluation of the adsorbent prepared by Example 5; Figure 6 This is the data envelope diagram of single column pulse adsorption-desorption evaluation of the adsorbent prepared by Comparative Example 1; Figure 7 This is the data envelope diagram of single-column pulse adsorption-desorption evaluation of the adsorbent prepared using Comparative Example 2. DETAILED DESCRIPTION

[0022] The embodiments of the present invention and the effects produced are further illustrated by examples and comparative examples, but the protection scope of the present invention is not limited to the contents listed in the examples.

[0023] The present invention can use pulse adsorption evaluation test equipment to dynamically test the separation coefficient β and separation degree R of the separated and purified components on the adsorbent according to the chromatographic separation principle, thereby measuring the relative separation effect of the raw material mixture components, and testing various adsorbents and desorbents with specific feed mixtures to measure the adsorbent performance in terms of their adsorption capacity, selectivity and exchange rate.

[0024] Single column pulse adsorption-desorption experimental method: Li-type molecular sieve bead adsorbent with a particle size of φ0.3~0.8mm and a dry basis of 96~99% is loaded into the adsorption column, the adsorption column is purged with nitrogen to expel the air, and then the desorbent is pumped in to expel the nitrogen in the adsorbent gap and the temperature is raised to 140°C. After the adsorption column is kept stable at 140°C, the feed port of the adsorption column is switched to a syringe to pulse in 2ml of m-cresol raw material (m-cresol / m-cresol mass ratio = 65 / 35) and cyclohexane tracer, and then switched to pumping in the desorbent, wherein the desorbent feed flow rate is 1~2ml / min. When the desorbent outflow reaches 10~20ml, 3~5 drops of liquid sample are taken every 2min using an automatic fraction collector, and 40 samples are taken continuously for gas chromatography quantitative analysis of the composition content.

[0025] The capacity index is the distance between the center of the meta-cresol peak envelope and the tracer peak envelope or some other known reference point (e.g., the volume of desorbent pumped). It is expressed in milliliters of desorbent pumped during this time interval. The relative selectivity (β) for meta-cresol over para-cresol is the ratio of the distance between the center of the meta-cresol peak envelope and the tracer peak envelope to the corresponding distance for the para-cresol isomer. The exchange rate of meta-cresol with the desorbent can be characterized by the width of the meta-cresol peak envelope at half intensity, the narrower the peak width, the faster the desorption rate. Example 1

[0026] 1) ZSM-20 molecular sieve (SiO 2 / Al 2 O 3 =8.0) to 0.5 mol / L (NH 4 ) 2 SO 4 The solution was slurried in a solution exchange tank with a solid-liquid ratio of 1:10, stirred and exchanged at 85°C for 4 hours, and then the slurry was filtered into a filter cake; according to the above method, a new 0.5 mol / L (NH 4 ) 2 SO 4 The solution was exchanged twice again, so that the Na 2 O% content is less than 0.5%; 2) The ammonium ZSM-20 molecular sieve filter cake exchanged in 1) is input into the lithium pre-exchange tank, and LiOH solution is added and stirred first. The outer tube of the exchange reactor is heated to maintain the exchange temperature between 70°C, and then air is introduced to bubble NH 3 ·H 2 O was completely expelled, and after about 5 h of exchange, the solution was washed with deionized water using a vertical plate frame to a pH value < 11. + The ion exchange degree reaches 97%; 3) After flash drying the Li-type ZSM-20 molecular sieve obtained in 2), the dry basis content is controlled to be in the range of 75-85%, and the organic bentonite YH-34 and methyl cellulose are evenly mixed according to the weight percentage of 87.44%, 12.04% and 0.52%, respectively, and rolled into 0.1-0.2 mm small mother balls, and then the mixed powder is added regularly and quantitatively to gradually increase the diameter of the adsorbent small balls to 0.3-0.8 mm; the small balls formed by rolling are naturally dried and cured at room temperature, and then dried at 120°C for 24 hours, and the dry basis reaches 85%; 4) The adsorbent pellets prepared in 3) are pre-calcined in a conventional rotary kiln at five temperature stages of 80°C - 120°C - 180°C - 250°C - 300°C, and the discharged material is directly input into a vacuum rotary kiln. While the relative vacuum is maintained in the range of -0.07 to -0.05 MPa, the vacuum kiln is heated and dehydrated and activated at a total of 6 temperature stages of 300°C - 350°C - 400°C - 500°C - 550°C - 250°C, and the final dry basis is controlled to be 97.25%; screening is performed in a dry nitrogen atmosphere, and pellets with 0.3 to 0.8 mm particles are taken. The adsorbent temperature is in the range of 140±10°C and vacuum packaged as the final adsorbent product, which is recorded as XFJ-1. Example 2

[0027] The method of Example 1 was used to prepare the 4 Cl solution for ammonium ion exchange, NH 4 + The ion exchange degree reaches 98%; Li-type ZSM-20 molecular sieve is mixed with organic bentonite YH-S2 and methyl cellulose according to the weight percentage of 88.76%, 10.99% and 0.25% to prepare adsorbent beads; the final dehydration activation dry basis is 98.43%, and vacuum packaging is used as the final adsorbent product, recorded as XFJ-2. Example 3

[0028] The method of Example 1 was used to prepare the 4 Cl solution for ammonium ion exchange, NH 4 + The ion exchange degree reaches 97%; Li-type ZSM-20 molecular sieve is mixed with organic bentonite YH-S2 and cellulose according to the weight percentage of 90.31%, 9.02% and 0.67% to prepare adsorbent beads; the final dehydration and activation dry basis is 97.17%, and vacuum packaging is used as the final adsorbent product, recorded as XFJ-3. Example 4

[0029] The method of Example 1 was used to prepare the 4 NO 3 The solution was exchanged with ammonium ions, NH 4 + The ion exchange degree reaches 97%; Li-type ZSM-20 molecular sieve is mixed with organic bentonite YH-34 and polyethylene glycol according to the weight percentage of 85.15%, 13.65% and 1.20% to prepare adsorbent beads; the final dehydration and activation dry basis is 96.91%, and vacuum packaging is carried out as the final adsorbent product, recorded as XFJ-4, and its composition is shown in Table 1. Example 5

[0030] The method of Example 1 was used to prepare the 4 ) 2 SO 4 The solution was exchanged with ammonium ions, NH 4 + The ion exchange degree reaches 98%; Li-type ZSM-20 molecular sieve is mixed with organic bentonite YH-34 and cellulose according to the weight percentage of 93.43%, 6.45% and 0.12% to prepare adsorbent beads; finally, the dry basis of dehydration and activation is 97.71%, and vacuum packaging is carried out as the final adsorbent product, which is recorded as XFJ-5. Its composition is shown in Table 1.

[0031] Table 1 Raw material composition, exchange, and activation statistics of adsorbents prepared in the examples

[0032] Comparative Example 1 According to the preparation method in the embodiment of patent CN110511121B: 1) Mix 90 kg (basis weight, the same below) of NaX / Silicalite-1 core / shell molecular sieve powder with a particle size of 0.6-1.2 microns and 8 kg of kaolin (kaolin mass fraction is 92%), put 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 rolling is 8% of the solid powder. Then sieve it, take small balls with a particle size of 300-850 microns, dry them at 80℃ for 12 hours, and roast them at 540℃ for 4 hours.

[0033] 2) Ion exchange: 130 ml of the beads obtained in step 1) were placed in an ion exchange column for cation exchange. A mixed solution of 0.18 mol / L barium nitrate and 0.08 mol / L potassium chloride was used for continuous exchange at a volume space velocity of 6.0 h-1 for 8 hours at normal pressure and 94°C. The total amount of the mixed solution was 5000 ml. After the exchange was completed, the beads were washed with 700 ml of deionized water at 70°C, dried at 70°C in a nitrogen atmosphere for 24 hours, and dehydrated and activated at 180°C in a nitrogen atmosphere for 6 hours to obtain an adsorbent denoted as VS-1.

[0034] Comparative Example 2 According to the preparation method in the embodiment of patent CN111689838B: 1) Mix 9.2 kg of NaY molecular sieve with a silicon oxide / aluminum oxide molar ratio of 5.1, 0.8 kg of kaolin and 0.4 kg of corn starch evenly, put them into a sugar coating pan, and roll them while spraying 1.9 kg of water to form small balls with a diameter of 0.3 mm to 0.8 mm. Then dry them at 100°C for 4 h and roast them at 540°C for 6 h.

[0035] 2) The calcined pellets were soaked in 20L of 1.5mol / L NaOH aqueous solution at 98°C for alkali treatment for 5h. The alkali-treated pellets were washed with deionized water until the pH value of the washing solution was lower than 10 to obtain base pellets.

[0036] 3) The above-mentioned basic beads were subjected to ion exchange with potassium chloride solution at 95°C and a volume space velocity of 6h-1 for 8 hours until the exchange degree of potassium ions was greater than 97 mol%, and then the temperature was raised to 190°C in dry air for activation for 2 hours to obtain adsorbent VS-2. The adsorbent contained 92.5% by mass of KY molecular sieve and the rest was kaolin. The water content measured after calcination at 600°C for 2 hours was 2.8% by mass. The adsorbent was recorded as VS-2.

[0037] Embodiments 6 to 13 Meta-cresol (p-cresol 34.8 wt%, m-cresol 64.7 wt%, 2-ethylphenol 0.2% wt%, dimethylphenol 0.1 wt% and other hydrocarbons 0.2 wt%) with a purity of 99.5% was mixed with cyclohexane in a ratio of 7:3 as the pulse feed component, and n-pentanol was used as the desorbent. A single-column pulse adsorption-desorption evaluation method was adopted.

[0038] The envelopes of the above components are plotted with the volume of desorbent used for desorption as the horizontal coordinate and the concentration of each component of cyclohexane, m-cresol and p-cresol as the vertical coordinate. 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. The midpoint of the half-peak width of the tracer is taken as the zero point, and the net retention volume from the midpoint of the half-peak width to the zero point of each component is measured. The net retention volume of any component is proportional to the distribution coefficient at adsorption equilibrium, reflecting the interaction between each component and the adsorbent material. The ratio of the net retention volume of the two components is the selectivity coefficient β. For example, the ratio of the net retention volume of p-cresol to the net retention volume of m-cresol is the ratio of the adsorption performance of the adsorbent material for p-cresol and m-cresol, which is the adsorption selectivity of p-cresol relative to m-cresol, recorded as β p-cresol / m-cresol.

[0039] Vmc is defined as the net retention volume of m-cresol, which is calculated by subtracting the volume of desorbent consumed by elution with cyclohexane from the volume of desorbent consumed by m-cresol; similarly, Vpc is defined as the net retention volume of p-cresol, which is calculated by subtracting the volume of desorbent consumed by elution with cyclohexane from the volume of desorbent consumed by p-cresol; W 1 / 2MCis the half-peak width FWHM of the m-cresol envelope peak, W 1 / 2PC is the half-peak width FWHM of the m-cresol envelope peak; the separation coefficient β is the ratio of the net retention volumes of the two separated components. The resolution (R) is used to evaluate the degree of separation between the substance to be tested and the substance to be separated, and is a key indicator for measuring the separation efficiency of the chromatographic system. The calculation formula for resolution (R) is:

[0040] Vmc is the retention volume of p-cresol of the former peak among the two adjacent peaks; Vpc is the retention volume of p-cresol of the latter peak among the two adjacent peaks; W 1 / 2MC and W 1 / 2PC The half-peak widths of the m-cresol and p-cresol peaks, respectively. The exchange rate of the desorbent for p-cresol is specified by the half-width of the p-cresol peak distribution. The narrower the peak width, the higher the desorption rate.

[0041] Table 2 Comparison of single column pulse adsorption-desorption evaluation results of adsorbents prepared in Examples 1 to 5 and adsorbents prepared in Comparative Examples 1 to 2

[0042] By comparing Table 2 and Figures 2 to 7 The pulse envelope curve of the invention shows that the adsorbent prepared by the embodiment of the invention can preferentially adsorb m-cresol, the selectivity coefficient β value of m-cresol for p-cresol>2.1, and the separation degree R value of m-cresol for p-cresol>1.6, while the adsorbents VS-1 and VS-2 prepared in comparative examples 1~2 obviously preferentially adsorb p-cresol, and m-cresol can only be extracted from the raffinate, which reduces the purity of m-cresol, and the selectivity coefficient β value of p-cresol for m-cresol <2.0, and the separation degree R value of p-cresol for m-cresol <1.1, and it is found that in comparative example 1, the desorption envelope curve of p-cresol has obvious tailing and peak asymmetry, which will seriously affect the purification and elution effect. The single-column pulse desorption envelope curve of the adsorbent prepared by the invention does not have the serious tailing phenomenon of the p-cresol component, and the envelope peak shape has good symmetry and a small half-peak width, which is conducive to obtaining high-purity and high-yield m-cresol. When the adsorbent according to the present invention is used to separate cresol isomers, the desorption rate is significantly reduced, a better separation effect is achieved, and there is no obvious tailing phenomenon of the delayed component m-cresol.

[0043] Embodiments 14 to 20 According to the methods described in CN110511121B, CN110511118B and CN110511122B, experiments on separation of m-cresol were carried out using adsorbents on a continuous countercurrent simulated moving bed.

[0044] The small simulated moving bed device includes 24 adsorption columns connected in series, each column is 200 mm long, the inner diameter of the column is 30 mm, and the total loading amount of the adsorbent is 3300 ml. The ends of the adsorption column are connected by a circulating pump to form a closed loop. The device has a total of 4 streams of materials entering and exiting at different positions of the adsorption column, and the feed position is changed periodically. There are 4 material pipelines between the connecting pipelines of adjacent adsorption columns for inputting or removing materials from the adsorption column. The 4 basic materials are: desorbent D, feed F, extract E and raffinate R. The 24 columns in series are divided into four sections, that is, the 7 adsorption columns between the adsorption raw material and the raffinate are the adsorption zone, the 9 adsorption columns between the extract and the adsorption raw material are the purification zone, the 5 adsorption columns between the desorbent and the extract are the elution zone, and the 3 adsorption columns between the raffinate and the desorbent are the buffer zone. The temperature of the entire adsorption system is controlled at 140°C and the pressure is 8 bar.

[0045] The m-cresol raw material (34.8 wt% of p-cresol, 64.7 wt% of m-cresol, 0.2% wt% of 2-ethylphenol, 0.1 wt% of dimethylphenol and 0.2 wt% of other hydrocarbons) enters through the F raw material pipe port, and the desorbent (n-pentanol) is continuously added through the feed D pipeline. The step time is set to 90 s. At the end of the step time, the four streams of materials move one adsorption column in the same direction as the liquid flow at the same time. This step is continued until the cycle of 24 columns is completed. The cycle period is 2160 s. The system operates at 140 ° C and 8 bar pressure. After the system is running stably, the raw material feed amount, desorbent dosage, extract amount, raffinate amount, adsorption zone flow, purification zone flow, elution zone flow, and buffer zone flow are shown in Table 2. In Examples 14 to 18, the adsorbents XFJ-1 to XFJ-5 of the present invention were used to obtain a purity of >99.5wt% and a yield of >95wt% of meta-cresol from the extraction stream E; at the same time, a purity of >99.2wt% and a yield of >95wt% of p-cresol were obtained through the discharge pipeline of the raffinate R. In Examples 19 to 20, the adsorbents VS-1 to VS-2 prepared in the comparative example were used. Under the same feed load, VS-1 and VS-2 obtained a purity of <99.0wt% and a yield of <94wt% of p-cresol from the extraction stream E; at the same time, a purity of <98.0wt% and a yield of <91wt% of meta-cresol were obtained from the raffinate stream R. The results of the separation of isomers of meta-cresol on the simulated moving bed are shown in Table 3.

[0046] Table 3 Experimental parameters and separation results of m-p-cresol isomers separation on continuous countercurrent simulated moving bed

[0047] The above-mentioned embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a liquid phase meta-cresol adsorbent, Features: The LiOH solution is exchanged with the ammonium ZSM-20 molecular sieve to obtain a lithium ZSM-20 molecular sieve with an exchange degree of ≥90%; the lithium ZSM-20 molecular sieve is stirred and mixed with an organic bentonite and a pore-forming aid according to weight percentages of 85-95%, 4.9-15%, and 0.1-1.5%, respectively, and placed in a spheroidizer to form spherical adsorbent particles with a particle size of 0.2-2.5 mm; The adsorbent particles are dried, calcined, dehydrated and activated to obtain the m-cresol adsorbent.

2. The preparation method according to claim 1, It is characterized in that The pore-forming aid is one or more of polyacrylic acid latex, sesbania powder, cellulose, methyl cellulose, polyethylene glycol, and polyvinyl alcohol; The particle size of the spherical adsorbent particles is 0.3~0.8 mm.

3. The preparation method according to claim 1, Features: 1) Mix ZSM-20 molecular sieve powder with NH 4 + A soluble ammonium salt solution with an ion concentration of 0.1-1.0 mol / L is exchanged 2-4 times at a solid-liquid ratio of 1:(5-10) at 60-100 °C to obtain an ammonium-type ZSM-20 molecular sieve; 2) The ammonium ZSM-20 molecular sieve obtained in step 1 is exchanged with a 0.1-1 mol / L LiOH solution at 60-80° C. under stirring to obtain a lithium ZSM-20 molecular sieve.

4. The preparation method according to claim 3, It is characterized in that Ammonium salt is NH 4 Cl, (NH 4 ) 2 SO 4 NH 4 NO 3 One or more of the .

5. The preparation method according to claim 1, It is characterized in that The adsorbent particles are heated in the range of 80-600 ℃ and dehydrated under negative pressure to activate, the additives are removed, the dry basis content of the adsorbent particles is controlled to be 96%-99%, and then the temperature is lowered to 80-150 ℃ in an isolated water vapor environment and sealed and packaged to obtain the m-cresol adsorbent.

6. A process for continuously separating a cresol mixture using a m-cresol adsorbent prepared by the preparation method according to any one of claims 1 to 5, It is characterized in that The meta-cresol adsorbent is loaded into an adsorption column or bed layer of a countercurrent simulated moving bed, and the inlet and outlet materials are switched by a switch valve or a multi-channel valve, and multiple adsorption columns or beds are divided into four areas of adsorption, purification, elution, and buffering, so as to realize a process of continuously feeding the meta-cresol material and the desorbent and continuously withdrawing the extract and the raffinate material; The obtained extract and raffinate are introduced into distillation towers to remove desorbent, respectively, to obtain high-purity m-cresol and p-cresol products.

7. The process according to claim 6, It is characterized in that The adsorption-desorption temperature of p-cresol in the adsorption column or bed of the countercurrent simulated moving bed is 100-200°C, the pressure during the adsorption and desorption treatment is 5-20 kg / cm2, the meta-cresol adsorbent is loaded in 4-30 adsorption columns or adsorption beds connected in series, and the way of materials entering and exiting a single adsorption column or adsorption bed is changed periodically and sequentially to form a countercurrent simulated mobile chromatography process, the meta-cresol mixture contacts the adsorbent, the meta-cresol is preferentially adsorbed, the cresol is taken out through the raffinate, and the meta-cresol is taken out through the extract.

8. The process according to claim 7, It is characterized in that The desorbent is at least one of a C4-C8 secondary alcohol and a C4-C8 primary alcohol.

9. The process according to claim 8, It is characterized in that The desorbent is 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, 3-ethyl-3-pentanol, cyclopentanol, cyclohexanol, cycloheptenol, cycloheptanol, 1-methylcyclopentanol, and 1-methylcyclohexanol.

10. Application of ZSM-20 molecular sieve in the preparation of m-cresol adsorbent.

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