Molecular sieve for m-p-cresol adsorptive separation and preparation method and application thereof

Abstract

The application provides a molecular sieve for adsorptive separation of m-cresol and p-cresol and a preparation method and application thereof, wherein the molecular sieve is a ZSM-5 molecular sieve whose cation sites are jointly occupied by metal cations of group IA and rare earth metal cations, or a ZSM-5 molecular sieve whose cation sites are jointly occupied by metal cations of group IIA and rare earth metal cations. The pore size of the molecular sieve is regulated by complex modification of rare earth ions to realize selective adsorption of m-cresol and p-cresol, so that high-purity m-cresol and p-cresol can be obtained.

Description

Technical Field

[0001] This invention belongs to the petroleum and chemical industry, and more specifically, it relates to a molecular sieve for the adsorption and separation of m- and p-cresols, its preparation method, and its application. Background Technology

[0002] m-Cresol and p-Cresol are important intermediates in fine chemicals. m-Cresol has a wide range of applications, commonly used in the synthesis of pesticides, fragrances, and dyes, while p-Cresol is an indispensable raw material for the synthesis of antioxidants and also has important applications in pharmaceuticals and pesticides. However, the atmospheric pressure boiling points of m-Cresol and p-Cresol are very close, differing by less than 1°C, making it difficult to effectively separate a mixture of m-Cresol and p-Cresol using traditional distillation methods.

[0003] Currently, the main methods for separating m- and p-cresol isomers include solvent extraction, complexation, alkylation, and adsorption separation. Solvent extraction and complexation require large amounts of organic solvents, causing environmental pollution; alkylation is a complex process with high energy consumption, and the strong acid catalysts used can easily corrode equipment; adsorption separation is achieved through pore size sieving. By modifying the molecular sieve using ion exchange or chemical liquid phase deposition to control its pore size, the molecular sieve can preferentially adsorb p-cresol, thus achieving separation. Adsorption separation has low energy consumption and high product purity. Industrially, the key technology for achieving adsorption separation of cresol isomers is the preparation of high-performance adsorbents.

[0004] CN110511122A discloses a method for liquid-phase adsorption and separation of cresol using X molecular sieves with cation sites occupied by Group IIA metal ions or jointly occupied by Group IIA and Group IA ions as adsorbents. This adsorbent has the ability to preferentially adsorb p-cresol. However, the adsorbent prepared by this method has low selectivity, and a complex simulated moving bed is required to achieve the separation of the two.

[0005] CN104815612A discloses a molecular sieve adsorbent for the adsorption and separation of m- and p-cresol and its preparation method. The method uses SiO2·H2O as a binder to roll or extrude the prepared molecular sieve powder, then uses Si(OCH3)4 as a liquid phase depositing agent to repeatedly subject the formed molecular sieve to chemical liquid phase deposition, high-temperature steam treatment, and calcination. The resulting adsorbent can achieve the separation of m- and p-cresol with high selectivity, but the preparation process is relatively cumbersome. Summary of the Invention

[0006] The purpose of this invention is to provide a molecular sieve for the adsorption and separation of m- and p-cresol, its preparation method and application. By modifying the molecular sieve with rare earth ions, the pore size can be controlled to achieve selective adsorption of m- and p-cresol, thereby obtaining high-purity m- and p-cresol.

[0007] This invention is achieved through the following technical solution:

[0008] A molecular sieve for the adsorption and separation of m- and p-cresol, wherein the molecular sieve is a ZSM-5 molecular sieve in which the cation sites are occupied by both Group IA metal cations and rare earth metal cations, or a ZSM-5 molecular sieve in which the cation sites are occupied by both Group IIA metal cations and rare earth metal cations.

[0009] Preferably, the Group IA metal cation is Li. + Na + and K + One of them; the Group IIA metal cation is Mg 2+ Ca 2+ and Ba 2+ One of them.

[0010] Preferably, the rare earth metal cation is Y. 3+ La 3+ and Ce 3+ One of them.

[0011] A method for preparing the molecular sieve for adsorption and separation of m- and p-cresols includes the following steps:

[0012] (1) Ion exchange was performed on HZSM-5 molecular sieve with a soluble salt solution of a Group IA metal or a Group IIA metal to obtain molecular sieves of the corresponding cation type.

[0013] (2) Dry the molecular sieve obtained in step (1) and heat it to the target temperature for calcination activation;

[0014] (3) The molecular sieve activated in step (2) is subjected to ion exchange with a soluble salt solution of rare earth metals, and then filtered, washed, dried and calcined to obtain a molecular sieve for adsorption and separation of m- and p-cresols.

[0015] Preferably, the soluble salt in step (1) is one of lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, barium chloride, lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, and barium nitrate.

[0016] Preferably, the conditions for ion exchange in step (1) are: soluble salt solution concentration of 0.05-1 mol / L, exchange temperature of 60-90℃, solid-liquid ratio of 1 g: (5-20) mL, number of exchanges of 2-4 times, and exchange time of 1-24 h for each exchange.

[0017] Preferably, the heating rate in step (2) is 3-5℃ / min, the target temperature is 400-600℃, and the calcination activation time is 3-6h.

[0018] Preferably, the soluble salt of the rare earth metal in step (3) is one of lanthanum chloride, yttrium chloride, cerium chloride, or lanthanum nitrate, yttrium nitrate, and cerium nitrate.

[0019] Preferably, the conditions for ion exchange in step (3) are: soluble salt solution concentration of 0.01-0.5 mol / L, exchange temperature of 70-90℃, solid-liquid ratio of 1g:(5-20)mL, number of exchanges of 1, and exchange time of 1-1.5h for each exchange; calcination activation temperature of 400-600℃ and calcination activation time of 3-6h.

[0020] The application of the molecular sieve in the adsorption and separation of m- and p-cresol.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The molecular sieve of this invention is a ZSM-5 molecular sieve in which the cation sites are occupied by both Group IA / IIA metal cations and rare earth metal cations. This molecular sieve can adsorb cresol up to 69.2 mg / g or more, and the adsorption selectivity of p-cresol to m-cresol is as high as 5.54, which shows good adsorption selectivity. The reasons are analyzed as follows: (1) The adsorption and separation of p-cresol by molecular sieve is mainly based on size sieving. The p-cresol molecule size is smaller than the pore size and can enter the molecular sieve. The m-cresol molecule size is larger and cannot enter the interior. A reasonable pore size can improve the adsorption selectivity. The pore size of the molecular sieve is related to the ionic radius, number and distribution position of the equilibrium cation inside it. The radius of rare earth metal ions and their distribution position on ZSM-5 make the pore size just larger than p-cresol and smaller than m-cresol. (2) Rare earth metals have a relatively special electronic layer structure. In addition to the electrons on the 6s and 5d orbitals of the outermost and second outermost layers being able to form bonds, the electrons on the 4f orbitals of the third outermost layer can also form bonds. Therefore, after rare earth ions coordinate with oxygen in the silicon-oxygen tetrahedron, the remaining coordination ability can interact with the lone pair electrons on the oxygen of cresol. The methyl group of p-cresol has a hyperconjugation effect and can easily release lone pair electrons, thus enhancing the interaction force. Attached Figure Description

[0023] Figure 1 A schematic flowchart illustrating a method for preparing a molecular sieve for the adsorption and separation of m- and p-cresols provided by the present invention.

[0024] Figure 2 The fixed-bed breakthrough curve of sample A1 in Example 1;

[0025] Figure 3 The fixed-bed breakthrough curve of sample B4 in Comparative Example 4;

[0026] Figure 4 The FTIR spectra of the molecular sieves prepared in Examples 1-3 of this invention and sample B4 of Comparative Example 4 are shown below.

[0027] Figure 5 The XRD curves are those of the molecular sieves prepared in Examples 1-3 of this invention and sample B4 of Comparative Example 4. Detailed Implementation

[0028] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0029] The kinetic diameter of p-cresol is smaller than that of m-cresol. By modifying it with ion exchange, a molecular sieve adsorbent with a pore diameter between that of m-cresol and p-cresol can be prepared. This allows p-cresol to be adsorbed into the pores of the molecular sieve, while only a small amount of m-cresol is adsorbed, thus achieving shape-selective separation of p- and m-cresol.

[0030] The principle of the molecular sieve adsorbent preparation method provided by this invention is: the raw materials are efficient and widely available, and the preparation method should be as simple and easy as possible to facilitate industrial production.

[0031] I. Rare Earth Compound Modified Molecular Sieves and Their Preparation

[0032] A molecular sieve for the adsorption and separation of meta- and p-cresol, wherein the molecular sieve is a ZSM-5 molecular sieve in which the cation sites are occupied by both Group IA or Group IIA metal cations and rare earth metal cations.

[0033] Preferably, the Group IA metal cation is Li. + Na + and K + One of them; the Group IIA metal cation is Mg 2+ Ca 2+ and Ba 2+ At least one of them.

[0034] Preferably, the rare earth metal cation is Y. 3+ La 3+ and Ce 3+ One of them.

[0035] like Figure 1 As shown, the method for preparing the molecular sieve of the present invention includes the following steps:

[0036] (1) Ion exchange of HZSM-5 molecular sieve with soluble salt solution of Group IA / IIA metal, then filter and wash the filter cake, and then perform a second ion exchange with the same soluble salt solution. After 2-4 exchanges, molecular sieve of the corresponding cation type can be obtained.

[0037] (2) Dry the molecular sieve obtained in step (1), then transfer it to a calcination furnace, gradually heat it from room temperature to the target temperature for calcination and activation, and then cool it down naturally.

[0038] (3) The molecular sieve activated in step (2) is subjected to ion exchange with a soluble salt solution of rare earth metals, and then filtered, washed, dried and calcined to obtain a rare earth compound modified molecular sieve for adsorption and separation of m- and p-cresols.

[0039] Preferably, the soluble salt of the Group IA / IIA metal mentioned in step (1) is one of lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, barium chloride, lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, and barium nitrate. More preferably, the soluble salt mentioned above is potassium chloride, magnesium chloride, potassium nitrate, or magnesium nitrate.

[0040] Preferably, the ion exchange conditions in step (1) are: an exchange solution concentration of 0.05-1 mol / L, an exchange temperature of 60-90℃, a solid-liquid ratio of 1 g:(5-20) mL, 2-4 exchanges, and an exchange time of 1-24 h for each exchange. More preferably, the exchange solution concentration is 0.5-1 mol / L, the exchange temperature is 70-90℃, the solid-liquid ratio is 1 g:(8-10) mL, 2-3 exchanges, and an exchange time of 1-3 h for each exchange.

[0041] Preferably, the drying temperature in step (2) is 100-120℃ and the drying time is 2-4h.

[0042] Preferably, the heating rate in step (2) is 3-5℃ / min, the target temperature is 400-600℃, and the calcination time is 3-6h.

[0043] Preferably, the soluble salt of the rare earth metal in step (3) is lanthanum chloride, yttrium chloride, cerium chloride, lanthanum nitrate, yttrium nitrate, or cerium nitrate. More preferably, the soluble salt of the rare earth metal mentioned above is selected from lanthanum chloride or lanthanum nitrate.

[0044] Preferably, the ion exchange conditions in step (3) are: an exchange solution concentration of 0.01-0.5 mol / L, an exchange temperature of 70-90℃, a solid-liquid ratio of 1 g:(5-20) mL, one exchange cycle, and an exchange time of 1-4 h per cycle. More preferably, the exchange solution concentration is 0.3-0.5 mol / L, the exchange temperature is 80-90℃, the solid-liquid ratio is 1 g:(8-10) mL, one exchange cycle, and an exchange time of 1-1.5 h per cycle.

[0045] Preferably, the drying temperature in step (3) is 100-120℃ and the drying time is 2-4h; the calcination temperature is 400-600℃ and the calcination time is 3-6h.

[0046] This invention does not impose specific limitations on the ion exchange process between molecular sieves and metal ions. For example, the molecular sieve and a soluble metal salt can be simultaneously dispersed in a solvent and mixed; the molecular sieve and solvent can be mixed first to obtain a molecular sieve dispersion, and then the soluble metal salt can be dispersed in the dispersion; the molecular sieve and the soluble metal salt can be separately dispersed in a solvent and then mixed; the soluble metal salt and solvent can be mixed first to obtain a salt solution, and then the molecular sieve can be dispersed in the salt solution. Of the above methods, the last method is preferred, i.e., first mixing the soluble metal salt and solvent to obtain a salt solution, and then dispersing the molecular sieve in the salt solution.

[0047] II. Evaluation of Molecular Sieve Performance by Static Liquid Phase Adsorption Method

[0048] The adsorption and separation performance of the molecular sieve for the m-cresol and p-cresol mixed system was determined by static liquid phase adsorption. The cresol adsorbate solution contained 10 wt% m-cresol and 10 wt% p-cresol, with the solvent being 80 wt%, specifically mesitylene. Mesitylene has a molecular size of 0.74 nm, significantly larger than the pore size of the ZSM-5 molecular sieve (0.55-0.6 nm), and will not be adsorbed by the molecular sieve; therefore, mesitylene was used as both the solvent and internal standard. Each time, 0.5 g of molecular sieve was weighed and placed in a 20 mL sample vial, followed by the addition of 3-4 mL of adsorbate solution. The sample was allowed to stand at 25 °C for 12 h until adsorption equilibrium was reached. Gas chromatography was used to analyze the concentration changes of m-cresol and p-cresol in the adsorbate solution before and after adsorption, thereby calculating the adsorption capacity of the molecular sieve sample for both. The specific calculation formula is as follows:

[0049]

[0050] In the formula, A i m0 represents the adsorption capacity of m-cresol or p-cresol, in g / g; m0 represents the mass of the adsorbate solution before adsorption, in g; m1 represents the mass of the residual liquid, in g; W i,0 W represents the mass fraction of m-cresol or p-cresol in the adsorbate solution. i,1 This represents the mass fraction of m-cresol or p-cresol in the absorbent.

[0051] Adsorption selectivity is another important indicator for evaluating the performance of an adsorbent. Adsorption selectivity is the ratio of the concentrations of the two components in the adsorbed phase to the concentration ratio of the same two components in the non-adsorbed phase at adsorption equilibrium. Adsorption equilibrium refers to the state where, after the naphthalene isomer mixture comes into contact with the molecular sieve, no net transfer of components occurs between the adsorbed and non-adsorbed phases. The specific calculation formula is as follows:

[0052]

[0053] Where C and D represent the two components to be separated, A C and A DU represents the concentrations of components C and D in the adsorbed phase, respectively. C and U D These represent the concentrations of components C and D in the non-adsorbed phase, respectively. When the selectivity β≈1 for both components, it indicates that the adsorption capacity of the adsorbent for both components is comparable, and no component is preferentially adsorbed. When β>1.0, the adsorbent preferentially adsorbs component C; when β<1.0, the adsorbent preferentially adsorbs component D. β also represents the ease of separation; the larger the β value, the easier the adsorption separation, which can improve product purity and yield, and reduce the operating costs of the adsorption separation device.

[0054] The present invention will be further described below with reference to the embodiments.

[0055] In this embodiment, the infrared spectrum was measured using a Thermo Nicolet Fourier transform infrared spectrometer, model Is50, with a test resolution of 4 cm⁻¹. -1 The wavelength range is 500-4000cm. -1 .

[0056] In this embodiment, the XRD pattern was determined using an instrument manufactured by Bruker (Germany), model Bruker D8 Advance, with a Cu target X-ray tube and a wavelength of [wavelength missing]. The voltage is 40KV, the current is 30mA, the 2θ scan range is 6-70°, and the scan rate is 10° / min.

[0057] Example 1

[0058] Molecular sieves for the separation of m- and p-cresols were prepared according to the method of the present invention, and their static liquid phase adsorption performance was tested.

[0059] Weigh 11.18g of potassium chloride and dissolve it in 150mL of pure water. Dissolve 8.13g of lanthanum nitrate in 50mL of pure water. Take 5g of HZSM-5 molecular sieve and 50mL of potassium chloride solution (liquid / solid ratio of 10mL:1g) and mix them thoroughly. Heat and stir at 90℃ for 1.5h, then filter. Wash the filter cake with 100mL of pure water each time, repeating the washing 2-3 times until no ions are present in the washing liquid. Disperse the washed filter cake again in 50mL of potassium chloride solution for a second ion exchange. Repeat the above steps for a total of three exchanges. After the final washing, dry the filter cake at 110℃ for 2h and then put it into a calcination furnace. Increase the calcination temperature from room temperature to 500℃ over 180min, and then maintain this temperature for 3h before allowing it to cool naturally. Mix the calcined molecular sieve with the prepared lanthanum nitrate solution thoroughly, heat and stir at 90℃ for 1h, then filter. Wash the filter cake with pure water until no anions remain in the washing liquid. The filter cake was dried at 110℃ for 2 hours, and then calcined. The calcination conditions were: heating from room temperature to 500℃ for 180 minutes, holding for 180 minutes, and then naturally cooling to obtain product A1. Its infrared spectrum is shown in [reference needed]. Figure 4 XRD pattern can be found Figure 5 .

[0060] The static liquid phase adsorption separation performance of adsorbent A1 for the m / p-cresol system was determined by static liquid phase adsorption method. The measured adsorption performance data are shown in Table 1.

[0061] Comparative Example 1

[0062] Molecular sieves were prepared according to the method in Example 1, and their static liquid-phase adsorption performance was tested. The difference was that after the molecular sieve powder was exchanged with potassium chloride solution three times, it was directly obtained as product B1 after filtration, washing, drying, and calcination, without further ion exchange with rare earth metal ions. Its infrared spectrum is shown below. Figure 4 XRD pattern can be found Figure 5 The measured adsorption performance data are shown in Table 1.

[0063] Example 2

[0064] Weigh 37.44g of barium chloride and dissolve it in 180mL of pure water. Dissolve 9.76g of lanthanum nitrate in 60mL of pure water. Take 6g of HZSM-5 molecular sieve and mix it thoroughly with 100mL of barium chloride solution. Heat and stir at 70℃ for 2 hours, then filter. Wash the filter cake with 100mL of pure water each time, repeating the washing 2-3 times until no ions are present in the washing liquid. Disperse the washed filter cake again in an equal volume of barium chloride solution for a second ion exchange. Repeat the above steps for a total of three exchanges. After the final washing, dry the filter cake at 110℃ for 2 hours and then place it in a calcination furnace. Increase the calcination temperature from room temperature to 500℃ over 180 minutes, and then maintain this temperature for 3 hours before allowing it to cool naturally. Mix the calcined molecular sieve thoroughly with the prepared lanthanum nitrate solution, heat and stir at 90℃ for 1 hour, then filter. Wash the filter cake with pure water until no anions remain in the washing liquid. The filter cake was dried at 110℃ for 2 hours, and then calcined. The calcination conditions were: heating from room temperature to 500℃ for 180 minutes, holding for 180 minutes, and then naturally cooling to obtain product A2. Its infrared spectrum is shown in [reference needed]. Figure 4 XRD pattern can be found Figure 5 .

[0065] The static liquid phase adsorption and separation performance of adsorbent A2 for the m / p-cresol system was determined by static liquid phase adsorption method. The adsorption performance data are shown in Table 1.

[0066] Comparative Example 2

[0067] Molecular sieves were prepared according to the method in Example 2, and their static liquid-phase adsorption performance was tested. The difference was that after the molecular sieve powder was exchanged with barium chloride solution three times, the product B2 was directly obtained after filtration, washing, drying, and calcination, without further ion exchange with rare earth metal ions. Its infrared spectrum is shown below. Figure 4 XRD pattern can be found Figure 5 The measured adsorption performance data are shown in Table 1.

[0068] Example 3

[0069] Weigh 35.04g of sodium chloride and dissolve it in 600mL of pure water. Dissolve 32.52g of lanthanum nitrate in 200mL of pure water. Take 20g of HZSM-5 molecular sieve and mix it evenly with 200mL of sodium chloride solution. Heat and stir at 80℃ for 1.5h, then filter. Wash the filter cake with 500mL of pure water each time, repeating the washing 2-3 times until no ions are present in the washing liquid. Disperse the washed filter cake again in an equal volume of sodium chloride solution for a second ion exchange. Repeat the above steps for a total of three exchanges. After the final washing, dry the filter cake at 110℃ for 2h and then put it into a calcination furnace. Increase the calcination temperature from room temperature to 500℃ over 180min, and then maintain this temperature for 3h before naturally cooling. Mix the calcined molecular sieve with the prepared lanthanum nitrate solution evenly, heat and stir at 80℃ for 1h, then filter. Wash the filter cake with pure water until no anions remain in the washing liquid. The filter cake was dried at 110℃ for 2 hours, and then calcined. The calcination conditions were: heating from room temperature to 500℃ for 180 minutes, holding for 180 minutes, and then naturally cooling to obtain product A3. Its infrared spectrum is shown in [reference needed]. Figure 4 XRD pattern can be found Figure 5 .

[0070] The static liquid phase adsorption separation performance of adsorbent A3 for the m / p-cresol system was determined by static liquid phase adsorption method. The measured adsorption performance data are shown in Table 1.

[0071] Comparative Example 3

[0072] Molecular sieves were prepared according to the method in Example 3, and their static liquid-phase adsorption performance was tested. The difference was that after the molecular sieve powder was exchanged with sodium chloride solution three times, it was directly obtained as product B3 after filtration, washing, drying, and calcination, without further ion exchange with rare earth metal ions. Its infrared spectrum is shown below. Figure 4 XRD pattern can be found Figure 5 The measured adsorption performance data are shown in Table 1.

[0073] Comparative Example 4

[0074] Commercially available HZSM-5 molecular sieve without any metal ion exchange was used as adsorbent B4. The static liquid phase adsorption separation performance of adsorbent B4 for the m / p-cresol system was determined by static liquid phase adsorption method. The measured adsorption performance data are shown in Table 1.

[0075] The performance of the adsorbent was evaluated using a fixed-bed breakthrough experiment.

[0076] The fixed-bed breakthrough experiment used a Φ17×200 mm chromatography column. 5 g of molecular sieve was mixed thoroughly with 20 mL of mesitylene and poured into the adsorption column. The outlet valve was opened to allow the mesitylene to flow out slowly, while the suspended molecular sieve gradually settled. When the liquid level dropped to only 5 mm above the bed, the adsorbate solution was injected at a rate of 1 mL / min. The adsorbate solution used in the experiment consisted of 2.5 wt% p-cresol, 2.5 wt% m-cresol, and 95 wt% mesitylene. The adsorbate residue was collected at the liquid outlet section of the apparatus. Three drops of the residue sample were taken every 1 mL and analyzed by gas chromatography.

[0077] Figure 2 and Figure 3 The fixed-bed breakthrough curves are for sample A1 of Example 1 and sample B4 of Comparative Example 4, respectively. The width of the interval between the two curves represents the degree of separation of the components; the wider the interval, the better the separation effect. The separation effect of sample A1 of Example 1 after compound exchange is significantly better than that before exchange.

[0078] Figure 4 The figures show the FTIR spectra of samples A1, A2, A3 from the embodiments of the present invention and sample B4 from the comparative example. As can be seen from the figures, at 550 cm⁻¹... -1 794cm -1 1098cm -1 1228cm -1 The absorption peak at 1228 cm⁻¹ is a characteristic vibrational peak of ZSM-5 molecular sieve. -1 and 1098cm -1 The antisymmetric stretching vibrations, respectively attributed to Si-O-Si and Si-O-Al, are 794 cm⁻¹. -1 The vibrational absorption peak of Si(Al)-O is at 550 cm⁻¹. -1 The nearby vibrational absorption peak is due to the characteristic vibrations of the double pentagonal rings in the molecular sieve MFI topology. Additionally, the peak at 3466 cm⁻¹ in the figure... -1 and 1632cm -1 These peaks can be attributed to the vibrational absorption of OH bonds in surface-adsorbed water and surface hydroxyl groups, respectively. The introduction of Group IA, Group IIA, and rare earth metal ions did not alter these characteristic absorption peaks of ZSM-5, indicating that the material's framework structure remained unchanged.

[0079] Figure 5The XRD curves of samples A1, A2, A3 and comparative sample B4 from the embodiments of this invention are shown. Strong diffraction peaks were observed at 2θ = 7.9°, 8.8°, 23.1°, and 23.8°, corresponding to the (101), (200), (051), and (501) crystal planes of the MFI-type molecular sieve, respectively. The characteristic peaks of lanthanum oxide were distributed around 28°, 43°, and 48°. No diffraction peaks of lanthanum oxide were found in the spectra, indicating that La is highly dispersed in ZSM-5, consistent with the characteristics of ion exchange. Furthermore, compared to the unmodified HZSM-5 molecular sieve, the diffraction intensity of each characteristic peak did not decrease, indicating that the ion exchange process does not damage the crystal structure of the molecular sieve and does not reduce its crystallinity.

[0080] Table 1 Adsorption performance of the adsorbent

[0081]

[0082] As can be seen from Table 1, K + Ba + and Na + The ZSM-5 molecular sieve after exchange with La 3+ After the second exchange, the selectivity improved again. Compared with B1-B3, the selectivity of A1-A3 was significantly improved, by 91.0%, 18.2%, and 40.7%, respectively.

Claims

1. Use of a molecular sieve for the adsorptive separation of m-cresol and p-cresol, characterized in that The molecular sieve is ZSM-5 molecular sieve with cation sites jointly occupied by Group IA metal cations and rare earth metal cations; the Group IA metal cation is one of Li + , Na + , and K + ; and the rare earth metal cation is one of Y 3+ , La 3+ , and Ce 3+ .

2. Use according to claim 1, characterized in that, The preparation method of the molecular sieve comprises the following steps: (1) ion exchange of HZSM-5 molecular sieve with a solution of soluble salt of Group IA metal to obtain a molecular sieve of corresponding cation type; (2) drying of the molecular sieve obtained in step (1) and heating to a target temperature for calcination activation; (3) ion exchange of the activated molecular sieve in step (2) with a solution of soluble salt of rare earth metal, followed by filtration, washing, drying and calcination activation to obtain a molecular sieve for adsorption separation of m-cresol and p-cresol.

3. Use according to claim 2, characterized in that, The soluble salt in step (1) is one of lithium chloride, sodium chloride, potassium chloride, lithium nitrate, sodium nitrate and potassium nitrate.

4. Use according to claim 2, characterized in that, The ion exchange conditions in step (1) are as follows: the concentration of the soluble salt solution is 0.05-1 mol / L, the exchange temperature is 60-90℃, the solid-liquid ratio is 1g:(5-20)mL, the exchange times are 2-4, and the exchange time of each exchange is 1-24h.

5. Use according to claim 2, characterized in that, The heating rate of the heating in step (2) is 3-5℃ / min, the target temperature is 400-600℃, and the calcination activation time is 3-6h.

6. Use according to claim 2, characterized in that, The soluble salt of rare earth metal in step (3) is one of lanthanum chloride, yttrium chloride, cerium chloride, lanthanum nitrate, yttrium nitrate and cerium nitrate.

7. Use according to claim 2, characterized in that, The ion exchange conditions in step (3) are as follows: the concentration of the soluble salt solution is 0.01-0.5mol / L, the exchange temperature is 70-90℃, the solid-liquid ratio is 1g:(5-20)mL, the exchange times are 1, and the exchange time of each exchange is 1-1.5h; the calcination activation temperature is 400-600℃, and the calcination activation time is 3-6h.

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