Separation method of m-cresol and p-cresol

Abstract

The invention discloses a method for separating m-cresol and p-cresol, which is characterized in that a bis (dipropoxy) pillar [5] arene crystal material and / or an adsorption material loaded with bis (dipropoxy) pillar [5] arene are / is used as an adsorbent to selectively adsorb m-cresol in a mixture of the m-cresol and the p-cresol so as to realize the separation of the m-cresol and the p-cresol; the chemical structural formula of the bis (dipropoxy) pillar [5] arene is as follows: # imgabs0 #. The separation process of the invention is simple to operate and low in equipment requirement; rectification operation is not needed in the separation process, energy consumption is low, energy is saved, and the production cost is reduced; the used crystal material is high in stability and can be recycled, and the separation effect cannot be reduced; a lot of organic solvents, strong acids and strong alkalis are not used, and the green chemistry concept is met.

Description

Technical Field

[0001] The invention relates to the technical field of adsorption separation, and in particular to a method for separating m-cresol and p-cresol. Background Art

[0002] Meta-cresol and p-cresol are two isomers of cresol, both of which are important fine chemical intermediates and are widely used in resins, medicines, pesticides, dyes, fragrances, antioxidants and other industries. One of the main uses of p-cresol is the synthesis of the antioxidant 2,6-di-tert-butyl-p-cresol, which is the most widely used and largest antioxidant in my country and an important support for the development of the plastics industry. On the other hand, meta-cresol can be used to produce intermediates such as m-phenoxybenzyl alcohol and m-phenoxybenzaldehyde, which can be further used to synthesize dichlorophenoxy ether pyrethroid insecticides. In addition, meta-cresol is also a key raw material for the synthesis of vitamin E intermediate 2,3,6-trimethylphenol. Therefore, separating high-purity meta-cresol and p-cresol can not only improve their application efficiency in the field of fine chemicals, but also optimize the quality and performance of related products, and has important industrial application value.

[0003] At present, the commonly used chemical synthesis methods for obtaining m-cresol and p-cresol include toluene sulfonation alkali fusion method, isopropyl toluene oxidation method, toluene chlorination hydrolysis method, phenol methanol alkylation method, toluene direct oxidation method, o-xylene oxidation method and m-toluidine diazo method. Among them, the main synthesis method of p-cresol is toluene sulfonation alkali fusion method, and the main synthesis method of m-cresol is isopropyl toluene oxidation method. However, there are some challenges in the production process of chemical synthesis: first, the process is complicated, usually requires multi-step reactions, and involves the use of a large amount of corrosive chemicals such as strong acids and strong bases; second, since these synthesis methods often cannot obtain a single product, most of them are mixtures containing multiple isomers, so the subsequent separation and purification of m-cresol and p-cresol is still faced.

[0004] In the modern chemical industry, the separation and extraction of m-cresol and p-cresol from low-temperature coal tar, an industrial byproduct rich in phenolic compounds, is often adopted. However, since the boiling points of m-cresol (202.23℃) and p-cresol (201.95℃) differ by only 0.28℃, the traditional distillation separation method faces great challenges in practical applications. Distillation separation relies on the difference in boiling points to achieve component separation. The difference in boiling points between m-cresol and p-cresol is so small that a large amount of energy is required to overcome this difference during the distillation process, resulting in extremely high energy consumption and extremely strict temperature control accuracy requirements during operation. Therefore, the distillation method is not only too expensive in industrial production, but also often cannot meet the large-scale, low-cost, and high-efficiency industrial needs due to its high energy consumption and long operation cycle. In addition, the separation efficiency in the distillation process is limited. Especially when high-purity products are required, the separation process may require repeated distillation, which further increases the production cost and limits industrial applications. Although the alkylation separation method, i.e., reacting m-cresol and p-cresol with an alkylation agent under the action of an acidic catalyst, can increase the boiling point difference of the products and facilitate distillation separation, the use of concentrated sulfuric acid as a catalyst will bring risks of equipment corrosion and environmental pollution, limiting its widespread application in the context of green environmental protection and sustainable development.

[0005] In recent years, with the rapid development of porous materials such as carbon materials and inorganic molecular sieves, the separation and purification of m-cresol and p-cresol by adsorption separation has gradually become an important research hotspot. For example, the patent specification with publication number EP0587949A1 discloses a method for selectively adsorbing p-cresol using X-type zeolite. The research results show that only when the water content is less than 2%, X-type zeolite can show selectivity for p-cresol.

[0006] Considering the above limitations, the development of more efficient, environmentally friendly and economical separation technologies to achieve highly selective purification of m-cresol and p-cresol remains an urgent need in the current chemical engineering field. Summary of the invention

[0007] [1] A method for separating m-cresol and p-cresol, using a bis(dipropoxy)-column[5]arene crystal material and / or an adsorbent material loaded with bis(dipropoxy)-column[5]arene as an adsorbent to selectively adsorb (trace amounts of) m-cresol in a mixture of m-cresol and p-cresol, thereby achieving separation of m-cresol and p-cresol;

[0008] The chemical structural formula of the bis(dipropoxy)-column[5]arene is as follows:

[0009]

[0010] Due to the difference in molecular structure between m-cresol and p-cresol, the bis-dipropoxy-column[5]arene crystal material and the bis-dipropoxy-column[5]arene in the adsorbent material can form a host-guest complex with m-cresol in a theoretical stoichiometric ratio of 1:2. The host-guest complex is unstable and will gradually decomplex when heated, releasing the adsorbed m-cresol. The bis-dipropoxy-column[5]arene crystal material and the bis-dipropoxy-column[5]arene in the adsorbent material are stable at the desorption temperature and can be reused after the desorption process is completed.

[0011] The bis(dipropoxy)-column[5]arene crystalline material can be obtained by activation after recrystallization in a poor solvent. The poor solvent can be acetone, but is not limited thereto. The bis(dipropoxy)-column[5]arene crystalline material obtained by recrystallization can be activated by removing solvent molecules by heating. The activated crystalline material can be directly used for the adsorption of m-cresol and / or p-cresol, as well as the adsorption separation of a mixture of m-cresol and p-cresol. Optionally, the activation temperature of the bis(dipropoxy)-column[5]arene crystalline material is not less than 100°C, and the activation time is not less than 1.5 hours.

[0012] The carrier of the adsorbent material loaded with bis(dipropoxy)-pillar[5]arene may include a molecular sieve, etc. The bis(dipropoxy)-pillar[5]arene may be immobilized in the pores of the molecular sieve, and the molecular sieve may include hydroxyl-modified mesoporous silica nanoparticles (MSN-OH), etc.

[0013] The preparation method of the adsorbent material loaded with bis(dipropoxy)-column[5]arene includes an impregnation method and the like.

[0014] In some embodiments, [1] the separation method may specifically be: placing the bis(dipropoxy)-column[5]arene crystal material and / or the adsorbent material loaded with bis(dipropoxy)-column[5]arene in a mixed vapor atmosphere of m-cresol and p-cresol at a temperature of 60 to 70°C, such as 65°C. The adsorption time may vary with factors such as the sample amount, adsorption temperature, and the proportion of m-cresol in the mixture. During the adsorption process, the bis(dipropoxy)-column[5]arene crystal material and the bis(dipropoxy)-column[5]arene in the adsorbent material may undergo a change in crystal form. Due to the multiple hydrogen bonds of CH···π, CH···O, and OH···O, the m-cresol in the mixed vapor may form a host-guest complex with the bis(dipropoxy)-column[5]arene.

[0015] In some embodiments, [1] the separation method may further include removing the mixture of m-cresol and p-cresol adsorbed on the surface of the adsorbent by vacuum heating after the adsorption separation is completed. Furthermore, the temperature of the vacuum heating may be 60 to 65°C. The heating time may be adjusted according to the sample quantity. During the process of vacuum heating to remove the mixture of m-cresol and p-cresol adsorbed on the surface of the adsorbent, the host-guest complex still exists stably, while the cresol mixture adsorbed on the surface can be gradually removed. By removing the mixture adsorbed on the surface, the purity of the m-cresol separated by adsorption is improved.

[0016] In some embodiments, [1] the separation method may further include vacuum heating the desorption adsorbent to adsorb the complexed m-cresol molecules to achieve adsorbent regeneration. Further, the vacuum heating desorption temperature may be 100-110°C. The vacuum heating desorption time may be adjusted according to the sample amount. During the vacuum heating desorption adsorbent adsorbing the complexed m-cresol molecules, the host-guest complex is unstable, and the adsorbed m-cresol molecules will gradually be released, while the bis(dipropoxy)-column[5]aromatic hydrocarbon crystal material and the adsorbent material loaded with bis(dipropoxy)-column[5]aromatic hydrocarbon are stable, and only the bis(dipropoxy)-column[5]aromatic hydrocarbon crystal form changes during the desorption process. After the desorption is completed, the regenerated adsorbent is obtained, which can continue to be used for the adsorption and separation of m-cresol and p-cresol for the next cycle, and the selectivity will not decrease.

[0017] [2] The application of bis(dipropoxy)column[5]aromatic hydrocarbons having the chemical structure shown below for adsorption of m-cresol and / or p-cresol:

[0018]

[0019] The application described in [2] can refer to the separation method described in [1] for further selection and optimization of technical solutions.

[0020] The bis-dipropoxy column [5] aromatic hydrocarbon can be used to selectively adsorb (trace) meta-cresol in a mixture of meta-cresol and para-cresol, thereby achieving separation of meta-cresol and para-cresol, and fine purification of para-cresol.

[0021] The bis(dipropoxy)-column[5]arene can be loaded on a carrier or formed into a crystalline material for selectively adsorbing (trace amounts of) m-cresol in a mixture of m-cresol and p-cresol.

[0022] The carrier may include a molecular sieve, etc. The bis(dipropoxy)-pillar[5]arene may be immobilized in the pores of the molecular sieve, etc. The molecular sieve may include hydroxyl-modified mesoporous silica nanoparticles (MSN-OH), etc.

[0023] The bis(dipropoxy)-column[5]arene can be loaded onto a carrier by an impregnation method or the like.

[0024] The dipropoxy column [5] aromatic hydrocarbon crystal material can be obtained by activation after recrystallization in a poor solvent. The poor solvent may be acetone, but is not limited thereto. The dipropoxy column [5] aromatic hydrocarbon crystal material obtained by recrystallization can be activated by removing solvent molecules by heating. The activated crystal material can be directly used for the adsorption of m-cresol and / or p-cresol, as well as the adsorption separation of a mixture of m-cresol and p-cresol. Optionally, the activation temperature of the dipropoxy column [5] aromatic hydrocarbon crystal material is not less than 100° C., and the activation time is not less than 1.5 hours.

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

[0026] In view of the defects of low efficiency, great environmental pollution and high energy consumption in the process of separating m-cresol and p-cresol, the present invention provides a method for separating m-cresol and p-cresol, which uses a bis(dipropoxy)-column[5] aromatic hydrocarbon crystal material and / or an adsorption material loaded with bis(dipropoxy)-column[5] aromatic hydrocarbon to highly selectively adsorb (trace) m-cresol in a mixture of m-cresol and p-cresol, has low energy consumption and simple operation process, and can achieve fine purification of p-cresol.

[0027] The separation process of the present invention is simple to operate and has low equipment requirements; the separation process does not require distillation operation, has low energy consumption, saves energy, and reduces production costs; the crystal material used is highly stable and can be recycled without reducing the separation effect; and a large amount of organic solvents and strong acids and alkalis are not used, which is in line with the concept of green chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The powder X-ray diffraction (PXRD) pattern of the bis(dipropoxy)-pillar[5]arene crystalline material of Examples 1 to 4;

[0029] Figure 2 This is a gas chromatography characterization result diagram of the bis-dipropoxy column [5] aromatic hydrocarbon crystal material after adsorption and separation of m-cresol and p-cresol in Example 3;

[0030] Figure 3 This is a diagram showing the adsorption and separation effect of p-cresol and p-cresol when the double dipropoxy column [5] aromatic hydrocarbon crystal material of Example 5 is recycled.

[0031] Figure 4 This is a gas chromatography characterization result diagram of the double dipropoxy column [5] aromatic modified molecular sieve of Example 6 before and after being used for fine purification of p-cresol. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0033] Embodiment 1:

[0034] The preparation method of bis(dipropoxy)-column[5]arene is as follows: bromopropane, anhydrous potassium carbonate and 1,4-benzenediol are added to acetonitrile at 85°C and N 2 Reflux under protection for 48 hours. Filter the reaction solution, and the filtrate is evaporated to remove the solvent to obtain a crude product, which is separated by column chromatography to obtain the monomer of bis(dipropoxy)-column[5]arene, p-dipropoxybenzene. Add p-dipropoxybenzene and polyformaldehyde to 1,2-dichloroethane, add Lewis acid, react at 25-30°C for 20-25 minutes, and then quench with saturated sodium bicarbonate solution. After extraction and separation, retain the organic phase, evaporate the organic phase to remove the solvent, and separate the bis(dipropoxy)-column[5]arene by column chromatography.

[0035] Preparation of bis(dipropoxy)-column[5]arene crystalline material: Weigh 2 g of bis(dipropoxy)-column[5]arene, place in 20 mL of acetone, heat to boiling, add acetone dropwise until all dissolved, store the solution at 0°C overnight, collect the precipitated crystals by filtration, and vacuum dry at 100°C for 1.5 hours to obtain a white powder, recorded as PrP5.

[0036] The product characterization data prepared in this example are as follows:

[0037] PrP5, 1 H NMR (500 MHz, CDCl 3 ,298K)δ(ppm):6.80(s,10H),3.94-3.63(m,30H),1.74(m,20H),1.00(t,30H).

[0038] The PXRD test results are as follows Figure 1 As shown, the obtained bis(dipropoxy)pillar[5]arene crystalline material has good crystallinity.

[0039] Embodiment 2:

[0040] Adsorption of meta-cresol or para-cresol by bis(dipropoxy)-column[5]aromatic crystal material: Take two 20mL culture bottles, add 1mL meta-cresol (MC) and 1mL para-cresol (PC), respectively, named PrP5-MC and PrP5-PC, take 20mg of bis(dipropoxy)-column[5]aromatic crystal material and place them in two 5mL culture bottles, place the two open 5mL culture bottles in two 20mL culture bottles, seal the 20mL culture bottles, and place them at 65℃ for 48 hours.

[0041] The product characterization data prepared in this example are as follows:

[0042] PrP5-MC, 1 H NMR (400 MHz, CDCl 3 ,298K)δ(ppm):7.16-7.07(t,1.30H),6.80(s,10H),6.74(d,1.30H),6.63( d,2.60H),3.86-3.70(m,30H),2.29(s,3.90H),1.74(m,20H),1.00(t,30H).

[0043] PrP5-PC, 1 H NMR (500 MHz, CDCl 3 ,298K)δ(ppm):7.08-6.98(m,1.60H),6.80(s,10H),6.73(d,1.60H),3.88-3.69(m,30H),2.27(s,2.40H),1.74(m,20H),1.00(t,30H).

[0044] 1 H NMR results showed that the bis(dipropoxy)-column[5]arene crystalline material adsorbed m-cresol in a stoichiometric ratio of approximately 1:1.3 and p-cresol in a stoichiometric ratio of approximately 1:0.8.

[0045] The PXRD test results are as follows Figure 1 As shown, compared with the PXRD spectrum of the initially activated bis(dipropoxy)-column[5]arene crystalline material, the PXRD spectrum of the bis(dipropoxy)-column[5]arene crystalline material after being placed in the vapor of m-cresol and p-cresol for a period of time has changed, which indicates that the corresponding unit cell parameters have changed, meaning that m-cresol and p-cresol have been adsorbed into the bis(dipropoxy)-column[5]arene crystalline material.

[0046] Embodiment 3:

[0047] Adsorption of a 1:1 mixture of m-cresol and p-cresol by bis(dipropoxy)-column[5]aromatic hydrocarbon crystal material: Take a 20mL culture bottle, add 0.5mL of m-cresol and 0.5mL of p-cresol, named PrP5-MIX, take 10mg of bis(dipropoxy)-column[5]aromatic hydrocarbon crystal material and place it in a 5mL culture bottle, place the open 5mL culture bottle in the above 20mL culture bottle, seal the 20mL culture bottle, place it at 65℃ for 48 hours, and place the adsorbed material at 60℃ under vacuum for 5 hours.

[0048] The product characterization data prepared in this example are as follows:

[0049] PrP5-MIX, 1 H NMR (500 MHz, CDCl 3 ,298K)δ(ppm):7.16-7.07(t,1.0H),7.08-6.98(d,0.22H),6.80(s,10H),6.74(d,1.22H),6.6 3(d,2.00H),3.84-3.71(m,30H),2.29(s,3.00H),2.27(s,0.33H),1.74(m,20H),1.00(t,30H).

[0050] exist 1 In the H NMR spectrum, a strong signal of hydrogen atoms corresponding to m-cresol and a weak signal of hydrogen atoms corresponding to p-cresol were found, which indicates that the bis(dipropoxy)-column[5]arene crystal material can adsorb m-cresol with high selectivity.

[0051] The PXRD test results are as follows Figure 1 As shown, compared with the PXRD spectrum of the initially activated bis(dipropoxy)-column[5]arene crystalline material, the PXRD spectrum of the bis(dipropoxy)-column[5]arene crystalline material after being placed in the mixed vapor of m-cresol and p-cresol for a period of time changes, and the spectrum change is the same as that of PrP5-MC, which indicates that the bis(dipropoxy)-column[5]arene crystalline material can selectively adsorb m-cresol in the mixture of m-cresol and p-cresol.

[0052] The results of gas chromatography are as follows Figure 2 As shown, the bis(dipropoxy)-column[5]aromatic crystal material can selectively adsorb m-cresol in a mixture of m-cresol and p-cresol with a selectivity of 94.00%.

[0053] Embodiment 4:

[0054] Regeneration of bis(dipropoxy)-column[5]arene crystalline material: 10 mg of bis(dipropoxy)-column[5]arene crystalline material saturated with m-cresol was heated in a vacuum oven at 110° C. for 1.5 hours. The sample was recorded as PrP5-D1.

[0055] The product characterization data prepared in this example are as follows:

[0056] PrP5-D1, 1 H NMR (400 MHz, CDCl 3 ,298K)δ(ppm):6.80(s,10H),3.94-3.63(m,30H),1.74(m,20H),1.00(t,30H).

[0057] exist 1 It was found in the H NMR spectrum that the signals of hydrogen atoms corresponding to m-cresol and p-cresol had disappeared, indicating that the bis(dipropoxy)-column[5] aromatic hydrocarbon crystal material had completed desorption and regeneration, and all cresol molecules had been released.

[0058] The PXRD test results are as follows Figure 1 As shown, compared with the PXRD spectrum of the initially activated bis(dipropoxy)-column[5]arene crystalline material, the PXRD spectrum of the desorbed bis(dipropoxy)-column[5]arene crystalline material changes very little, which indicates that the bis(dipropoxy)-column[5]arene crystalline material has completed the desorption process, proving the excellent structural stability of the bis(dipropoxy)-column[5]arene crystalline material.

[0059] Embodiment 5:

[0060] Recycling of the bis(dipropoxy)-column [5] aromatic hydrocarbon crystal material: Repeat Examples 3 and 4 with 10 mg of the regenerated bis(dipropoxy)-column [5] aromatic hydrocarbon crystal material.

[0061] The gas chromatography results of direct injection are as follows Figure 3 As shown, the bis(dipropoxy)-column[5]aromatic crystal material can adsorb m-cresol with high selectivity, and its selectivity does not decrease after being reused three times.

[0062] Embodiment 6:

[0063] Preparation of molecular sieves modified with bis(dipropoxy)-column[5]arene and fine purification of p-cresol: 100 mg of bis(dipropoxy)-column[5]arene was dissolved in dichloromethane, and then 100 mg of molecular sieve MSN-OH (obtained from Chem. Commun., 2013, 49, 9033) was added to the above solution. The mixture was subjected to ultrasonic treatment, the solvent was slowly evaporated, and the bis(dipropoxy)-column[5]arene remaining on the surface was washed with dichloromethane, and then dried at 80°C for 12 hours to obtain a molecular sieve adsorption material with bis(dipropoxy)-column[5]arene immobilized in the pores.

[0064] 60 mg of the modified molecular sieve was immersed in 500 μL of p-cresol solution containing m-cresol (initial p-cresol purity was 98.40%), and then sampled for testing after standing for 12 hours. The results of direct gas chromatography analysis showed (e.g. Figure 4 As shown), the purity of p-cresol solution was increased to 99.06%.

[0065] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for separating m-cresol and p-cresol, characterized in that: Using a bis(dipropoxy)-column[5]arene crystal material and / or an adsorbent material loaded with bis(dipropoxy)-column[5]arene as an adsorbent, selectively adsorbing m-cresol in a mixture of m-cresol and p-cresol, thereby achieving separation of m-cresol and p-cresol; The chemical structural formula of the bis(dipropoxy)-column[5]arene is as follows:

2. The separation method according to claim 1, characterized in that The bis(dipropoxy)-column[5]arene crystal material is obtained by recrystallization in a poor solvent and then activation; The carrier of the adsorption material loaded with bis(dipropoxy)-pillar[5]arene comprises a molecular sieve; the bis(dipropoxy)-pillar[5]arene is immobilized in the pores of the molecular sieve; The molecular sieve comprises hydroxyl-modified mesoporous silica nanoparticles; The preparation method of the adsorbent material loaded with bis(dipropoxy)-column[5]arene comprises an impregnation method.

3. The separation method according to claim 2, characterized in that The poor solvent is acetone; The activation temperature of the bis(dipropoxy)-column[5]arene crystal material is not less than 100° C., and the activation time is not less than 1.5 hours.

4. The separation method according to claim 1, characterized in that The separation method is specifically as follows: placing the bis(dipropoxy)-column[5]arene crystal material and / or the adsorbent material loaded with bis(dipropoxy)-column[5]arene in a mixed vapor atmosphere of m-cresol and p-cresol at a temperature of 60-70°C.

5. The separation method according to claim 1 or 4, characterized in that: The separation method further comprises removing the mixture of m-cresol and p-cresol adsorbed on the surface of the adsorbent by vacuum heating after the adsorption separation is completed.

6. The separation method according to claim 5, characterized in that The temperature of the vacuum heating is 60-65°C.

7. The separation method according to claim 1, characterized in that The separation method further comprises vacuum heating to desorb the adsorbent to adsorb the complexed meta-cresol molecules, thereby regenerating the adsorbent.

8. The separation method according to claim 7, characterized in that The vacuum heating desorption temperature is 100-110°C.

9. Application of bis(dipropoxy)-column[5]arene having the chemical structure shown below for adsorption of m-cresol and / or p-cresol:

10. The use according to claim 9, characterized in that: The bis-dipropoxy column [5] aromatic hydrocarbon is used to selectively adsorb m-cresol in a mixture of m-cresol and p-cresol, thereby achieving separation of m-cresol and p-cresol; Furthermore, the bis(dipropoxy)-column[5]arene is loaded on a carrier or formed into a crystalline material and used to selectively adsorb meta-cresol in a mixture of meta-cresol and para-cresol, thereby achieving separation of meta-cresol and para-cresol.

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