Preparation method of m-cresol and p-cresol

Abstract

The present invention relates to the technical field of m-cresol and p-cresol production, and specifically discloses a method for preparing m-cresol and p-cresol: (1) subjecting a raw material containing phenol oil to a first distillation to obtain mixed cresol I; (2) subjecting the mixed cresol I to a second distillation to obtain o-cresol and mixed cresol II; (3) contacting the o-cresol with an isomerization catalyst to carry out an isomerization reaction, and the obtained isomerized product is returned to the raw material; and (4) subjecting the mixed cresol II to adsorption separation to obtain m-cresol and p-cresol. The method provided by the present invention couples distillation, isomerization, and adsorption separation, and has the advantages of high phenol oil utilization, high o-cresol conversion rate, and high purity of m-cresol and p-cresol, and is suitable for industrial promotion.

Description

Technical Field

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

[0002] Cresol is an important intermediate in fine chemicals and consists of three isomers: o-cresol, m-cresol, and p-cresol. m-cresol can be used in analytical reagents and organic synthesis, and is a key raw material for antioxidants, vitamin E, synthetic resins, and color film developers. p-cresol is a key raw material for the production of antioxidants, fluorescent brighteners, plasticizers, medical disinfectants, dyes, fragrances, and curing agents. Currently, demand for m-cresol and p-cresol monomers in my country is strong (annual production of 10,000 tons). However, domestic supply of these monomers is severely insufficient, and a significant amount of these monomers must be imported annually to meet domestic market demand.

[0003] Direct extraction from natural resources and chemical synthesis are the main approaches to obtaining cresol. Currently, the most commonly used raw material for cresol production is phenol oil, an oil product obtained by processing the phenol-containing fraction obtained by distilling coal tar. Phenol oil has a relatively complex composition, containing phenol and various cresol components. If m-cresol and p-cresol can be separated from crude phenol and the o-cresol in the crude phenol can be converted into m-cresol and p-cresol, the added value of coal resources can be significantly increased, and the supply and demand pressure of m-cresol and p-cresol can be alleviated.

[0004] Because p-cresol and m-cresol have very similar boiling points (less than 1°C difference), conventional distillation methods are difficult to separate. Consequently, a mixture of three or two isomers is extracted from phenol oil, making it difficult to obtain high-purity cresol monomer. Currently available methods for isolating m-cresol include complexation, alkylation, and crystallization. While these methods offer high separation efficiency, they are complex and difficult to commercialize.

[0005] US4032581 discloses a high-pressure crystallization separation method for a mixture of m-cresol and p-cresol. The method involves pressurizing the mixture of m-cresol and p-cresol in a first pressure zone at a certain temperature to produce a crystalline solid phase and a liquid phase of p-cresol or m-cresol. The crystalline phase is then transferred to a second pressure zone at a lower pressure, where the temperature is increased to melt the crystalline solid. The liquefied crystalline phase is then discharged to obtain high-purity cresol isomers. However, high-pressure crystallization separation requires high equipment requirements and requires significant investment.

[0006] CN104098445B discloses a method for extracting meta-cresol from a meta-cresol mixture. The method involves combining meta-cresol with urea to form a solid, washing the solid with a mixed solvent, hydrolyzing the washed solid with water, separating the oil phase, and subjecting the oil phase to vacuum distillation to obtain meta-cresol with a purity of not less than 99.8% by mass. However, the complex crystallization separation requires a large amount of solvent washing, resulting in a complex process and high energy consumption.

[0007] Regarding the conversion of o-cresol, CN103333051B discloses a method for producing m-cresol. A feedstock containing o-cresol and / or p-cresol is added to an isomerization reactor. Over the action of an isomerization catalyst, the o-cresol or p-cresol is largely converted to m-cresol. While this method can increase the yield of m-cresol, it reduces the yield of p-cresol.

[0008] CN103342629A provides a fluidized bed method for isomerizing o-cresol to produce m- and p-cresol. The o-cresol is vaporized, mixed with a carrier gas, and preheated to a reaction temperature. The gas is then introduced into a fluidized bed reactor to contact a cresol isomerization catalyst. After an isomerization reaction, a reaction mixture rich in m- and p-cresol is obtained. The reaction mixture is then rectified and separated to obtain m- and p-cresol. However, this method utilizes a fluidized bed, which has the disadvantages of severe catalyst wear, uneven catalyst residence time within the bed, and poor operational stability.

[0009] CN103449976B discloses a moving bed method for isomerizing o-cresol to produce m- and p-cresol: a) vaporizing o-cresol and superheating it, then mixing it with a carrier gas to obtain a reaction material I; b) introducing the reaction material I into a moving bed reactor to contact it with a catalyst, and after an isomerization reaction, obtaining a reaction mixture II containing m- and p-cresol; c) fractionating the reaction mixture II to obtain a fraction A (phenol and o-cresol); a fraction B (m- and p-cresol); and a fraction C (heavy components); d) introducing the fraction B into a product storage tank, mixing the fractions A and C with the reaction material I, and introducing them into a moving bed reactor for an isomerization reaction; e) introducing the catalyst to be regenerated from the bottom of the moving bed reactor into a catalyst regenerator to contact it with a regeneration gas for char regeneration, and the regenerated catalyst is returned from the bottom of the catalyst regenerator to the moving bed reactor for recycling. This method overcomes the problems of short catalyst life and the need for frequent shutdowns for regeneration in previous fixed bed processes through catalyst regeneration. However, the moving bed process equipment is complex and requires a high degree of automation.

[0010] Therefore, there is an urgent need to provide a method for preparing high-purity m-cresol and p-cresol from phenol oil, which has the advantages of simple process, high yield, low energy consumption, etc. Summary of the Invention

[0011] The purpose of the present invention is to solve the problems of low yield and low purity in the preparation of m-cresol and p-cresol from phenol oil in the prior art, and to provide a preparation method of m-cresol and p-cresol.

[0012] In order to achieve the above object, the present invention provides a method for preparing m-cresol and p-cresol, which comprises the following steps:

[0013] (1) subjecting a raw material containing phenol oil to a first distillation to obtain mixed cresol I; wherein the mixed cresol I comprises o-cresol, m-cresol and p-cresol;

[0014] (2) subjecting the mixed cresol I to a second distillation to obtain o-cresol and mixed cresol II; wherein the mixed cresol II comprises m-cresol and p-cresol;

[0015] (3) contacting the o-cresol with an isomerization catalyst to perform an isomerization reaction, and returning the obtained isomerized product to the raw material;

[0016] The isomerization catalyst comprises 10-90 parts by weight of nano HEU-1 molecular sieve, 10-90 parts by weight of alumina, and 0.1-10 parts by weight of a modifying element; wherein the modifying element is selected from one or more of rare earth metals, alkaline earth metals, and non-metallic elements;

[0017] (4) subjecting the mixed cresol II to adsorption separation to obtain m-cresol and p-cresol.

[0018] Through the above technical scheme, the preparation method of m-cresol and p-cresol provided in the present invention couples phenol oil distillation, o-cresol isomerization and adsorption separation, and has the advantages of high phenol oil utilization, high o-cresol conversion rate, and high purity of m-cresol and p-cresol. In addition, the reaction and separation processes are simple, energy consumption is low, it is environmentally friendly, production efficiency is high, and it is suitable for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention provides a process flow chart for preparing m-cresol and p-cresol.

[0020] Description of Reference Numerals

[0021] 1. Light removal tower 2. Heavy removal tower 3. Ortho-cresol removal tower

[0022] 4. Fixed bed reactor 5. Small simulated mobile device DETAILED DESCRIPTION

[0023] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0024] The present invention provides a method for preparing m-cresol and p-cresol, which comprises the following steps:

[0025] (1) subjecting a raw material containing phenol oil to a first distillation to obtain mixed cresol I; wherein the mixed cresol I comprises o-cresol, m-cresol and p-cresol;

[0026] (2) subjecting the mixed cresol I to a second distillation to obtain o-cresol and mixed cresol II; wherein the mixed cresol II comprises m-cresol and p-cresol;

[0027] (3) contacting the o-cresol with an isomerization catalyst to perform an isomerization reaction, and returning the obtained isomerized product to the raw material;

[0028] The isomerization catalyst comprises 10-90 parts by weight of nano HEU-1 molecular sieve, 10-90 parts by weight of alumina, and 0.1-10 parts by weight of a modifying element; wherein the modifying element is selected from one or more of rare earth metals, alkaline earth metals, and non-metallic elements;

[0029] (4) subjecting the mixed cresol II to adsorption separation to obtain m-cresol and p-cresol.

[0030] In step (1):

[0031] In a preferred embodiment, phenol oil has a well-known meaning and is not particularly limited in the present invention. Preferably, the phenol oil is crude phenol refined oil.

[0032] In a preferred embodiment, the first distillation comprises a light-removal distillation and a heavy-removal distillation; wherein the light-removal distillation is used to remove components with a boiling point below 185°C from the phenol oil, and the heavy-removal distillation is used to remove components with a boiling point above 210°C from the phenol oil. In the present invention, the phenol oil is first subjected to light-removal distillation and then to heavy-removal distillation to obtain a mixed cresol I comprising o-cresol, m-cresol, and p-cresol.

[0033] In a preferred embodiment, the light removal distillation is carried out in a light removal tower, and the heavy removal distillation is carried out in a heavy removal tower; wherein the operating conditions of the light removal tower include: a tower top temperature of 100-200°C, a tower top pressure of 0.005-0.12 MPa, a theoretical plate number of 55-85, and a reflux ratio of 8-12; the operating conditions of the heavy removal tower include: a tower top temperature of 120-220°C, a tower top pressure of 0.005-0.12 MPa, a theoretical plate number of 40-65, and a reflux ratio of 3-5.

[0034] In step (2):

[0035] In a preferred embodiment, the second distillation is carried out in a de-o-cresol tower; wherein the top temperature of the de-o-cresol tower is 120° C.-200° C., the top pressure is 0.005-0.12 MPa, the theoretical plates are 35-65, and the reflux ratio is 3-15.

[0036] In step (3):

[0037] In a preferred embodiment, the isomerization catalyst is the catalyst disclosed in patent application number 202111296976.4 (o-cresol isomerization catalyst, preparation method thereof, and o-cresol isomerization method).

[0038] In a preferred embodiment, the isomerization catalyst comprises 50-80 parts by weight, preferably 60-70 parts by weight of nano HEU-1 molecular sieve, 20-50 parts by weight, preferably 30-40 parts by weight of alumina and 2-7 parts by weight, preferably 2-5 parts by weight of modifying elements.

[0039] In a preferred embodiment, the crystal size of the nano HEU-1 molecular sieve is 1-200 nm, preferably 20-100 nm, and more preferably 40-60 nm;

[0040] Preferably, the molar ratio of silicon dioxide to aluminum oxide in the nano-HEU-1 molecular sieve is 20-100:1, preferably 25-75:1, and more preferably 35-45:1.

[0041] In a preferred embodiment, the modifying element is selected from one or more of Y, Ce, La, Pr, Nd, Mg, Ca, Sr, Ba, P, Cl and F; further preferably, the modifying element is selected from one or more of Ce, La, Mg, P, Cl and F.

[0042] In a preferred embodiment, before the o-cresol contacts the isomerization catalyst, the isomerization catalyst is sulfurized;

[0043] In a preferred embodiment, the vulcanization operating conditions include: a vulcanization temperature of 110-140° C., a vulcanization time of 1-3 h; a vulcanization gas of a mixture of H 2 S and H 2 , and a vulcanization gas flow rate of 10-30 mL / min;

[0044] In a preferred embodiment, the volume fraction of H2 in the sulfide gas is ≥90%, preferably ≥95%. In the present invention, the conversion rate of o-cresol can be increased by sulfiding the isomerization catalyst. To improve the sulfidation effect, the isomerization catalyst can be purged with an inert gas such as nitrogen or helium before the sulfide gas is introduced.

[0045] In a preferred embodiment, the isomerization reaction is carried out in a fixed bed reactor; wherein the reaction temperature is 320-400°C, the reaction pressure is 0.1 MPa-2 MPa, the carrier gas is hydrogen, and the mass space velocity of o-cresol is 0.5 h -1 -4h -1 .

[0046] The o-cresol isomerization catalyst provided by the present invention uses nano-HEU-1 molecular sieve as the active component and is modified with a modifying element. This allows the o-cresol isomerization catalyst to achieve not only a high o-cresol conversion rate and a high m- and p-cresol yield, but also high catalyst stability, multiple regeneration capabilities, and a long catalyst life. The resulting isomerized product is returned to step (1) and mixed with phenol oil for a first distillation, thereby increasing the yields of m- and p-cresol and improving the conversion of o-cresol.

[0047] In step (4):

[0048] In a preferred embodiment, the adsorptive separation is performed according to the method disclosed in CN111689838A (A method for separating p-cresol and m-cresol by adsorptive separation).

[0049] In the present invention, m-cresol and p-cresol are separated by adsorption separation, so that m-cresol with a purity of ≥98wt% and p-cresol with a purity of ≥99wt% can be obtained.

[0050] The present invention will be described in detail below through examples. Figure 1 The system shown is carried out as follows: the system includes a light-removal column 1, a heavy-removal column 2, an o-cresol removal column 3, a fixed-bed reactor 4, and a small-scale simulated mobile device 5. The bottom of the light-removal column 1 is connected to the heavy-removal column 2, the top of the heavy-removal column 2 is connected to the o-cresol removal column 3, the bottom of the o-cresol removal column 3 is connected to the small-scale simulated mobile device 5, the top of the o-cresol removal column 3 is connected to the fixed-bed reactor 4, and the fixed-bed reactor 4 is also connected to the light-removal column 1.

[0051] Small-scale simulation mobile device 5 is identical with the device among the CN111689838A embodiment 4, comprises 12 adsorption columns connected in series, 377 millimeters of column length, 30 millimeters of column internal diameters, and the total volume of adsorbent is 3200mL.In the adsorption columns connected in series, 12 adsorption columns are filled with adsorbent, and between certain two pillars, a recycle pump is connected to provide the power of fluid circulation in the column.Desorbent, extract, adsorption raw material, four strands of materials of residual liquid are divided into four districts by these adsorption columns: between desorbent and the extract, 2 pillars are desorption zones, between extract and the raw material, 5 pillars are purification zones, between raw material and the residual liquid, 3 pillars are adsorption zones, and between the residual liquid and the desorbent, 2 pillars are buffer zones.

[0052] The compositions of the phenol oils in the Examples and Comparative Examples are shown in Table 1:

[0053] Table 1

[0054]

[0055]

[0056] The isomerization catalyst A in the embodiment includes 65 parts by weight of nano HEU-1 molecular sieve, 35 parts by weight of alumina and 2.24 parts by weight of La, and is prepared as follows:

[0057] (1) Nano-HEU-1 molecular sieve (average particle size of 50 nm, silica / alumina molar ratio of 35), pseudo-boehmite and 1 wt% dilute nitric acid were mixed, the mixed mixture was extruded to obtain shaped particles, the shaped particles were dried at 110° C. for 4 h, and then calcined for the first time, and calcined at 540° C. for 5 h to obtain a calcined product; wherein, based on the mass of alumina in the pseudo-boehmite, the mass ratio of nano-HEU-1 molecular sieve to pseudo-boehmite was 65:35, and the amount of dilute nitric acid added was 50% of the sum of the mass of nano-HEU-1 molecular sieve and pseudo-boehmite;

[0058] (2) The calcined product was mixed with a 4 wt % La(NO 3 ) 3 solution, stirred at 80° C. for 1.5 h, dried, and then dried at 110° C. for 4 h to obtain a loaded calcined product; the loaded calcined product was subjected to a second calcination at 520° C. for 5 h to obtain an o-cresol isomerization catalyst; wherein, based on the mass of the nano-HEU-1 molecular sieve in the calcined product and the mass of the La element in the La(NO 3 ) 3 solution, the mass ratio of the calcined product to the La(NO 3 ) 3 solution was 65:2.3;

[0059] (3) The above-mentioned o-cresol isomerization catalyst was treated with steam in an air atmosphere at a mass space velocity of 1 h -1 , the treatment temperature is 360℃, the treatment time is 6h, and o-cresol isomerization catalyst A is obtained.

[0060] The isomerization catalyst B in the embodiment includes 65 parts by weight of nano HEU-1 molecular sieve, 35 parts by weight of alumina, 1.88 parts by weight of La and 2.24 parts by weight of P, and is prepared as follows:

[0061] (1) Nano-HEU-1 molecular sieve (average particle size of 50 nm, silica / alumina molar ratio of 35), pseudo-boehmite and 1 wt% dilute nitric acid were mixed, the mixed mixture was extruded to obtain shaped particles, the shaped particles were dried at 110° C. for 4 h, and then calcined for the first time, and calcined at 540° C. for 5 h to obtain a calcined product; wherein, based on the mass of alumina in the pseudo-boehmite, the mass ratio of nano-HEU-1 molecular sieve to pseudo-boehmite was 65:35, and the amount of dilute nitric acid added was 50% of the sum of the mass of nano-HEU-1 molecular sieve and pseudo-boehmite;

[0062] (2) The above-mentioned calcined product was mixed with 8 wt% (NH4)2HPO4 solution, stirred at 90°C for 1 hour, dried, and dried at 110°C for 4 hours to obtain a loaded product containing P; the loaded product containing P was mixed with 4 wt% La(NO3)3 solution, stirred at 80°C for 1.5 hours, dried, and dried at 110°C for 4 hours to obtain a loaded calcined product; the loaded calcined product was calcined for a second time at 520°C for 5 hours to obtain an o-cresol isomerization catalyst; wherein, based on the mass of nano-HEU-1 molecular sieve in the calcined product, the mass of P element in the (NH4)2HPO4 solution, and the mass of La element in the La(NO3)3 solution, the mass ratio of the calcined product to the (NH4)2HPO4 solution was 65:2.3; the mass ratio of the calcined product to the La(NO3)3 solution was 65:1.9;

[0063] (3) The above-mentioned o-cresol isomerization catalyst was treated with steam in an oxygen atmosphere at a mass space velocity of 1 h -1 , the treatment temperature is 380℃, the treatment time is 8h, and o-cresol isomerization catalyst B is obtained.

[0064] The isomerization catalyst C in the embodiment includes 65 parts by weight of nano HEU-1 molecular sieve, 35 parts by weight of alumina, 2.54 parts by weight of F and 1.73 parts by weight of Ce, and is prepared as follows:

[0065] (1) Nano-HEU-1 molecular sieve (average particle size of 50 nm, silica / alumina molar ratio of 35), pseudo-boehmite and 1 wt% dilute nitric acid were mixed, the mixed mixture was extruded to obtain shaped particles, the shaped particles were dried at 110° C. for 4 h, and then calcined for the first time, and calcined at 540° C. for 5 h to obtain a calcined product; wherein, based on the mass of alumina in the pseudo-boehmite, the mass ratio of nano-HEU-1 molecular sieve to pseudo-boehmite was 65:35, and the amount of dilute nitric acid added was 50% of the sum of the mass of nano-HEU-1 molecular sieve and pseudo-boehmite;

[0066] (2) The above-mentioned calcined product was mixed with 10wt% NH4F solution in a mass ratio of 1:5, stirred at 80°C for 2h, dried, and dried at 110°C for 4h to obtain a loaded product containing F; the loaded product containing F was mixed with 4wt% Ce(NO3)3 solution, stirred at 80°C for 1.5h, dried, and dried at 110°C for 4h to obtain a loaded calcined product, and the loaded calcined product was calcined for a second time at 520°C for 5h to obtain an o-cresol isomerization catalyst; wherein, based on the mass of nano-HEU-1 molecular sieve in the calcined product and the mass of Ce element in the Ce(NO3)3 solution, the mass ratio of the calcined product to the Ce in the Ce(NO3)3 solution is 65:1.8.

[0067] (3) The above-mentioned o-cresol isomerization catalyst was treated with steam in an air atmosphere at a mass space velocity of 1.2 h -1 , the treatment temperature is 360℃, the treatment time is 8h, and o-cresol isomerization catalyst C is obtained.

[0068] Example 1

[0069] (1) introducing 2 kg / h of phenol oil into a light-removal column to remove components with a boiling point below 185° C., then introducing the remaining components from the light-removal column into a heavy-removal column to remove components with a boiling point above 210° C., completing the first distillation to obtain a mixed cresol I including o-cresol, m-cresol, and p-cresol;

[0070] (2) introducing the mixed cresol I into an o-cresol removal tower for a second distillation, obtaining o-cresol from the bottom of the o-cresol removal tower, and obtaining a mixed cresol II including m-cresol and p-cresol from the top of the o-cresol removal tower;

[0071] (3) The above o-cresol was introduced into a fixed bed reactor and contacted with isomerization catalyst A, with hydrogen as carrier gas, at 380°C, 0.5 MPa, and a mass space velocity of o-cresol of 2.0 h -1 isomerization reaction is carried out under the conditions of , to obtain an isomerized product, and the obtained isomerized product is returned to step (1) and mixed with phenol oil and then distilled together; wherein the conversion rate of o-cresol in the fixed bed reactor is 56.1%;

[0072] (4) The mixed cresol II was introduced into a small simulated moving device for adsorption separation. The adsorption column was filled with the adsorbent prepared according to Example 1 of CN111689838A, and the desorbent was a mixture of 95 wt% n-pentanol and 5 wt% n-octane, containing 80 ppm of water. The feed temperature of the adsorption raw material and the desorbent feed temperature were controlled at 165°C and 185°C, respectively. The simulated moving bed pressure was 1.2 MPa, the desorbent flow rate was 3318 g / h, the extract flow rate was 1801 g / h, the adsorption raw material flow rate was 948 g / h, the raffinate flow rate was 2465 g / h, and the feed volume space velocity of the adsorption raw material relative to the adsorbent was 0.327 h -1 The purity of the obtained m-cresol product was 98.5 wt % after the desorbent was removed from the extract, and the purity of the obtained p-cresol product was 99.7 wt % after the desorbent was removed from the raffinate.

[0073] Among them, the operating conditions and results of the light removal tower, heavy removal tower and o-cresol removal tower are shown in Table 2:

[0074] Table 2

[0075]

[0076] Example 2

[0077] (1) introducing 1.5 kg / h of phenol oil into a light-removal column to remove components with a boiling point below 185° C., then introducing the remaining components from the light-removal column into a heavy-removal column to remove components with a boiling point above 210° C., completing the first distillation to obtain a mixed cresol I including o-cresol, m-cresol, and p-cresol;

[0078] (2) introducing the mixed cresol I into an o-cresol removal tower for a second distillation, obtaining o-cresol from the bottom of the o-cresol removal tower, and obtaining a mixed cresol II including m-cresol and p-cresol from the top of the o-cresol removal tower;

[0079] (3) The above o-cresol was introduced into a fixed bed reactor and contacted with isomerization catalyst B, with hydrogen as carrier gas, at 390°C, 1.0 MPa, and a mass space velocity of o-cresol of 1.5 h -1 isomerization reaction is carried out under the conditions of , to obtain an isomerized product, and the obtained isomerized product is returned to step (1) and mixed with phenol oil and then distilled together; wherein the conversion rate of o-cresol in the fixed bed reactor is 55.5%;

[0080] (4) The mixed cresol II was introduced into a small simulated moving device for adsorption separation. The adsorption column was filled with the adsorbent prepared according to Example 2 of CN111689838A, and the desorbent was a mixture of 95 wt% n-pentanol and 5 wt% n-octane, containing 80 ppm of water. The feed temperature of the adsorption raw material and the desorbent feed temperature were controlled at 165°C and 185°C, respectively. The simulated moving bed pressure was 1.2 MPa, the desorbent flow rate was 3318 g / h, the extract flow rate was 1801 g / h, the adsorption raw material flow rate was 948 g / h, the raffinate flow rate was 2465 g / h, and the feed volume space velocity of the adsorption raw material relative to the adsorbent was 0.327 h -1 The desorbent in the extract was removed, and the purity of the obtained m-cresol product was 98.2wt%. The desorbent in the residual liquid was removed, and the purity of the obtained p-cresol product was 99.5wt%.

[0081] Among them, the operating conditions of the light-removal tower, heavy-removal tower and o-cresol removal tower and the reaction results are shown in Table 3:

[0082] Table 3

[0083]

[0084] Example 3

[0085] (1) introducing 1.6 kg / h of phenol oil into a light-removal column to remove components with a boiling point below 185° C., then introducing the remaining components from the light-removal column into a heavy-removal column to remove components with a boiling point above 210° C., completing the first distillation to obtain a mixed cresol I including o-cresol, m-cresol, and p-cresol;

[0086] (2) introducing the mixed cresol I into an o-cresol removal tower for a second distillation, obtaining o-cresol from the bottom of the o-cresol removal tower, and obtaining a mixed cresol II including m-cresol and p-cresol from the top of the o-cresol removal tower;

[0087] (3) The above o-cresol was introduced into a fixed bed reactor and contacted with isomerization catalyst C, with hydrogen as carrier gas, at 350°C, 0.8 MPa, and a mass space velocity of o-cresol of 1.5 h -1 isomerization reaction is carried out under the conditions of , to obtain an isomerized product, and the obtained isomerized product is returned to step (1) and mixed with phenol oil and then distilled together; wherein the conversion rate of o-cresol in the fixed bed reactor is 50.9%;

[0088] (4) The mixed cresol II was introduced into a small simulated moving bed apparatus for adsorption separation. The adsorption column was filled with the adsorbent prepared according to Example 3 of CN111689838A. The desorbent was a mixture of 95 wt% n-pentanol and 5% n-octane, containing 80 ppm of water. The feed temperature of the adsorption raw material and the desorbent feed temperature were controlled at 165°C and 185°C, respectively. The simulated moving bed pressure was 1.2 MPa, the desorbent flow rate was 3318 g / h, the extract flow rate was 1801 g / h, the adsorption raw material flow rate was 948 g / h, the raffinate flow rate was 2465 g / h, and the feed volumetric space velocity of the adsorption raw material relative to the adsorbent was 0.327 h -1 The desorbent in the extract was removed, and the purity of the obtained m-cresol product was 98.3wt%. The desorbent in the residual liquid was removed, and the purity of the obtained p-cresol product was 99.2wt%.

[0089] Among them, the operating conditions of the light-removal tower, heavy-removal tower and o-cresol removal tower and the reaction results are shown in Table 4:

[0090] Table 4

[0091]

[0092] Example 4

[0093] The same as Example 3, except that, in step (3), before o-cresol is contacted with isomerization catalyst A, isomerization catalyst A is sulfurized: isomerization catalyst A is first purged with helium at a flow rate of 15 mL / min at 120° C. for 0.5 h, and then a mixed gas (5 v% H2S and 95 v% H2) is introduced at a flow rate of 15 ml / min to perform sulfurization treatment on isomerization catalyst A. The sulfurization reaction time is 2 h.

[0094] The conversion rate of o-cresol in the fixed-bed reactor was 60.3%, the purity of the obtained m-cresol product was 98.6 wt %, and the purity of the obtained p-cresol product was 99.7 wt %.

[0095] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing m-cresol and p-cresol, characterized in that: The method comprises the following steps: (1) subjecting a raw material containing phenol oil to a first distillation to obtain mixed cresol I; wherein the mixed cresol I comprises o-cresol, m-cresol and p-cresol; (2) subjecting the mixed cresol I to a second distillation to obtain o-cresol and mixed cresol II; wherein the mixed cresol II includes m-cresol and p-cresol; (3) contacting the o-cresol with an isomerization catalyst to perform an isomerization reaction, and returning the obtained isomerized product to the raw material; The isomerization catalyst comprises 10-90 parts by weight of nano HEU-1 molecular sieve, 10-90 parts by weight of alumina, and 0.1-10 parts by weight of a modifying element; wherein the modifying element is selected from one or more of Y, Ce, La, Pr, Nd, P, Cl, and F; (4) The mixed cresol II is subjected to adsorption separation to obtain m-cresol and p-cresol.

2. The preparation method according to claim 1, wherein The first distillation includes light removal distillation and heavy removal distillation; wherein, the light removal distillation is used to remove components with a boiling point below 185°C in the phenol oil, and the heavy removal distillation is used to remove components with a boiling point above 210°C in the phenol oil.

3. The preparation method according to claim 2, wherein The light removal distillation is carried out in a light removal tower, and the heavy removal distillation is carried out in a heavy removal tower.

4. The preparation method according to claim 3, wherein The operating conditions of the lightness removal tower include: a tower top temperature of 100-200° C., a tower top pressure of 0.005-0.12 MPa, 55-85 theoretical plates, and a reflux ratio of 8-12.

5. The preparation method according to claim 2, wherein The de-weighting distillation is carried out in a de-weighting tower. The operating conditions of the de-weighting tower include: a tower top temperature of 120-220° C., a tower top pressure of 0.005-0.12 MPa, 40-65 theoretical plates, and a reflux ratio of 3-5.

6. The preparation method according to claim 1, wherein The second distillation is carried out in an o-cresol removal tower.

7. The preparation method according to claim 6, wherein The top temperature of the o-cresol removal tower is 120-200° C., the top pressure is 0.005-0.12 MPa, the theoretical plates are 35-65, and the reflux ratio is 3-15.

8. The preparation method according to claim 1, wherein The isomerization catalyst comprises 50-80 parts by weight of nano HEU-1 molecular sieve, 20-50 parts by weight of aluminum oxide and 2-7 parts by weight of a modifying element.

9. The preparation method according to claim 8, wherein The isomerization catalyst comprises 60-70 parts by weight of nano HEU-1 molecular sieve, 30-40 parts by weight of aluminum oxide and 2-5 parts by weight of a modifying element.

10. The preparation method according to claim 1, wherein The crystal size of the nano HEU-1 molecular sieve is 1-200 nm.

11. The preparation method according to claim 10, wherein The crystal size of the nano HEU-1 molecular sieve is 20-100 nm.

12. The preparation method according to claim 11, wherein The crystal size of the nano HEU-1 molecular sieve is 40-60 nm.

13. The preparation method according to claim 1, wherein The molar ratio of silicon dioxide to aluminum oxide in the nano HEU-1 molecular sieve is 20-100:

1.

14. The preparation method according to claim 13, wherein The molar ratio of silicon dioxide to aluminum oxide in the nano HEU-1 molecular sieve is 25-75:

1.

15. The preparation method according to claim 14, wherein The molar ratio of silicon dioxide to aluminum oxide in the nano HEU-1 molecular sieve is 35-45:

1.

16. The preparation method according to claim 1, wherein The modifying element is selected from one or more of Ce, La, P, Cl and F.

17. The preparation method according to claim 1, wherein Before the o-cresol contacts the isomerization catalyst, the isomerization catalyst is sulfurized.

18. The preparation method according to claim 17, wherein The vulcanization operating conditions include: a vulcanization temperature of 110-140° C., a vulcanization time of 1-3 hours, a vulcanization gas of a mixture of H 2 S and H 2 , and a vulcanization gas flow rate of 10-30 mL / min.

19. The preparation method according to claim 18, wherein The volume fraction of H2 in the sulfide gas is ≥90%.

20. The preparation method according to claim 19, wherein The volume fraction of H2 in the sulfide gas is ≥95%.

21. The preparation method according to any one of claims 1 to 20, wherein: The isomerization reaction is carried out in a fixed bed reactor; wherein the reaction temperature is 320-400°C, the reaction pressure is 0.1MPa-2MPa, the carrier gas is hydrogen, and the mass space velocity of o-cresol is 0.5h -1 -4h -1 .

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