阅读说明：本技术 一种固体酸催化剂及生产间甲酚的方法 (Solid acid catalyst and method for producing m-cresol ) 是由 朱志荣 关业军 赵国庆 贾文志 于 2021-06-23 设计创作，主要内容包括：本发明特别涉及一种固体酸催化剂及生产间甲酚的方法。一种生产间甲酚的方法,步骤1,将含有对甲酚和邻甲酚的混合物原料经过预热器加热后,通入固定床反应器或模拟移动床反应器进行反应；步骤2,在反应压力0.1-12.0MPa、温度180-450℃、重量空速WHSV 1.0–12.0h-1的反应条件下,在如根据权利要求1和6的所述固体酸催化剂作用下进行反应生成含有邻甲酚、间甲酚和对甲酚的反应产物；步骤3,将所述反应产物通过精馏塔分离得到邻甲酚和间、对混合甲酚,并将未反应转化的邻甲酚循环,作为反应原料进入反应器。本发明具有反应效率高,脱羟基/甲基副反应少,甲酚损失率小,催化剂表面结炭失活低,间甲酚含量更高,具有显著的经济效益。(The invention particularly relates to a solid acid catalyst and a method for producing m-cresol. A method for producing m-cresol, step 1, heat the mixture raw materials containing p-cresol and o-cresol through the preheater, introduce fixed bed reactor or simulation moving bed reactor to react; step 2, carrying out a reaction under the reaction conditions of a reaction pressure of 0.1-12.0MPa, a temperature of 180-450 ℃ and a weight space velocity WHSV of 1.0-12.0 h < -1 > under the action of the solid acid catalyst according to claims 1 and 6 to generate a reaction product containing o-cresol, m-cresol and p-cresol; and 3, separating the reaction product by a rectifying tower to obtain o-cresol and m-cresol and p-cresol mixture, and recycling the o-cresol which is not converted by reaction and is used as a reaction raw material to enter a reactor. The method has the advantages of high reaction efficiency, less dehydroxylation/methyl side reaction, low cresol loss rate, low coking and inactivation on the surface of the catalyst, higher m-cresol content and obvious economic benefit.)

1. A solid acid catalyst characterized by: the solid acid catalyst is selected from one or two of a sheet hydrogen type molecular sieve and a mesoporous silica supported tungstic acid solid acid, and a hydrogen active transition metal element is added into the solid acid catalyst for modification;

wherein the sheet-shaped hydrogen type molecular sieve is at least one selected from sheet-shaped HITQ-2, sheet-shaped HMOR, sheet-shaped HMCM-36 and sheet-shaped HUZM-8.

2. A solid acid catalyst according to claim 1, wherein: the specific surface area of the mesoporous silica in the mesoporous silica supported tungstic acid solid acid is 200-800m²The load content of the tungstic acid is 5.0 wt% -20.0 wt%.

3. A solid acid catalyst according to claim 1, wherein: the hydrogen active transition metal element is at least one of Re, Co, Ag and Pd, and the content of the hydrogen active transition metal element is 0.05 wt% -3.0 wt%.

4. A process for the production of m-cresol, characterized in that: use of the solid acid catalyst according to claims 1-3 starting from a mixture comprising p-cresol and o-cresol, comprising the following steps:

step 1a, heating a mixture raw material containing p-cresol and o-cresol by a preheater, and introducing the mixture raw material into a fixed bed reactor or a simulated moving bed reactor for reaction;

step 2a, reacting under the reaction conditions of 0.1-12.0MPa of reaction pressure, 180-450 ℃ of temperature and 1.0-12.0 h < -1 > of weight space velocity WHSV under the action of the solid acid catalyst to generate a reaction product containing o-cresol, m-cresol and p-cresol;

step 3a, separating the reaction product by a rectifying tower to obtain o-cresol and m-cresol and p-cresol mixture, and recycling the o-cresol which is not converted by reaction and is used as a reaction raw material to enter a reactor;

wherein, the mixed reaction product containing o, m and p is passed through a rectification separation tower, o-cresol collected at the tower top is used as a reaction raw material and is sent to the inlet of an isomerization reactor through a circulating compressor, and m and p mixed cresol is obtained by collection at the tower bottom.

5. The process for producing m-cresol according to claim 4, characterized in that: in a hydrogen/hydrocarbon molar ratio of 0.5: 1-10: 1. the reaction is carried out under the reaction conditions of 0.5-5.0MPa of pressure, 250-380 ℃ of temperature and WHSV of 2.0-8.0 h < -1 > of weight space velocity to generate a reaction product containing o-cresol, m-cresol and p-cresol.

6. A solid acid catalyst characterized by: the solid acid catalyst is at least one selected from hydrogen type eutectic hybrid molecular sieve, silicon oxide loaded fluorosulfonic acid resin and silicon oxide loaded niobic acid solid acid;

wherein the hydrogen-type eutectic hybrid molecule is selected from at least one of HZSM-5/HMOR molecular sieves, HZSM-5/HBeta, HMCM-36/HBeta and HBeta/HMOR molecular sieves, and the ratio range of two molecular sieves in the eutectic molecular sieves is selected from 1: 10-10: 1.

7. the solid acid catalyst according to claim 6, wherein: the specific surface area of the macroporous silicon oxide in the silicon oxide supported fluorosulfonic acid resin is 200-500m2/g, the specific surface area of the macroporous silicon oxide in the silicon oxide supported niobic acid is 200-500m2/g, and the supported content of the fluorosulfonic acid resin or niobic acid is 5.0-30.0 wt%.

8. A process for the production of m-cresol, characterized in that: use of the solid acid catalyst according to claims 6-7 starting from a mixture comprising p-cresol and o-cresol, comprising the following steps:

step 1b, heating a mixture raw material containing p-cresol and o-cresol by a preheater, and introducing the mixture raw material into a fixed bed reactor or a simulated moving bed reactor for reaction;

step 2b, under the reaction conditions of the reaction pressure of 0.1-12.0MPa, the temperature of 180-450 ℃ and the weight space velocity WHSV of 1.0-12.0 h < -1 >, the reaction is carried out under the action of the solid acid catalyst to generate a reaction product containing o-cresol, m-cresol and p-cresol;

step 3b, separating the reaction product by a rectifying tower to obtain o-cresol and m-cresol and p-cresol mixture, and recycling the o-cresol which is not converted by reaction and is used as a reaction raw material to enter a reactor; and (3) passing the reaction product through a rectification separation tower, taking o-cresol collected at the top of the tower as a reaction raw material, passing the o-cresol through a circulating compressor to an inlet of an isomerization reactor, and collecting m-cresol and p-cresol at the bottom of the tower.

9. The process for producing m-cresol according to claim 8, characterized in that: the reaction is carried out under the reaction conditions of the pressure of 4.0-10.0MPa, the temperature of 200-350 ℃ and the weight space velocity WHSV of 1.0-5.0 h < -1 >.

10. The process for producing m-cresol according to claim 8, characterized in that: wherein the adopted fixed bed reactor is selected from a group consisting of a fixed bed reactor with a height/diameter ratio of 1: 1-6: 1 or a tubular reactor with an inner diameter of 3.0-8.0cm, wherein the materials are 316L stainless steel.

Technical Field

The invention relates to the technical field of chemical production, in particular to a solid acid catalyst and a method for producing m-cresol.

Background

O-, m-and p-cresol are three isomers of cresol, are fine chemical raw materials with important application, relate to various fields of national economy, and can be used for producing various products such as antioxidant, pesticide, resin, dye, medicine, spice and the like. The cresol production has good development prospect and wide market prospect. The traditional cresol production is mainly obtained by rectifying and separating from coal liquefied oil. However, limited by limited resources of cresol and complicated separation process, the chemical synthesis route of cresol is gaining increasing attention, and the industrial production route of cresol which has been developed at present includes toluene sulfonation alkali fusion process, isopropyl toluene process, toluene chlorination hydrolysis process and phenol isomerization process. The selectivity of the three cresol isomer products in the above routes is respectively characterized. The traditional toluene sulfonation alkali fusion method has the advantages of relatively mature technology and simple process, but has great pollution to the environment and serious corrosion to equipment, and the product accounts for more than 85 percent of p-cresol. The product of the toluene chlorination hydrolysis method is mainly o-cresol and m-cresol, has good product quality, but has rigorous requirements on equipment and higher production cost, is produced by a batch method, and is not suitable for large-scale production. The meta-position product prepared by the oxidation method of the isopropyl toluene has high purity, but has the disadvantages of great technical difficulty, difficult raw material source, longer process flow, explosive safety risk in oxidation operation and high separation cost. The phenol isomerization method is widely applied to large-scale production because of simple process, higher product selectivity, lower cost and less environmental pollution, and is one of the main routes of cresol production at home and abroad. However, the main product of the prior phenol isomerization method is a mixture of p-cresol and o-cresol, and m-cresol has low selectivity and cannot meet the requirement of domestic markets for m-cresol.

U.S. Pat. No. 4,450, 3269 discloses HZSM-5 molecular sieve used in high pressure reactor and fixed bed reaction process of o-cresol isomerization reaction, and the yield of cresol is not higher than 50% in the two processes. Wherein the catalyst in the fixed bed process has obvious deactivation phenomenon and short service life. China CN103449976A discloses a moving bed method for producing m-cresol and p-cresol by using a molecular sieve as a catalyst, in the method, o-phenol is used as a raw material, a silica-alumina molecular sieve is used as the catalyst, the reaction is carried out under the reaction conditions that the reaction temperature is 280-500 ℃, the feeding weight space velocity WHSV is 0.2-15 h < -1 >, the conversion rate of o-cresol can reach 57.4 percent, and the meta-position yield can reach 41.8 percent. Chinese patent CN104815612A discloses a molecular sieve adsorbent for m-cresol and p-cresol adsorption separation and a preparation method thereof, but the patent does not specify the specific structure and separation effect of the molecular sieve catalyst. Chinese patent CN108147945A discloses a method for producing high-purity m-cresol, the yield of m-cresol can reach 98%, however, the process includes four steps of adsorption separation, desorption, regeneration and isomerization, and multiple working temperatures are required to realize product separation. Chinese patent CN111689838A discloses a method for separating p-cresol and m-cresol by adsorption, which also comprises a plurality of functional areas, and the purity of the obtained m-cresol product can reach 84.3 wt%. Therefore, the m-cresol production process provided by the patent has a certain promotion effect on the m-cresol production, however, the steps of the method are complicated, the operation process is complex, and a more economic process is urgently needed.

Disclosure of Invention

The invention aims to provide a catalyst for the isomerization reaction of p/o-cresol and a method for producing m-cresol by using the catalyst.

The above object of the present invention is achieved by the following technical solutions:

a solid acid catalyst is selected from one or two of a sheet hydrogen type molecular sieve and a mesoporous silica supported tungstic acid solid acid, and a hydrogen active transition metal element is added into the solid acid catalyst for modification;

wherein the sheet-shaped hydrogen type molecular sieve is at least one selected from sheet-shaped HITQ-2, sheet-shaped HMOR, sheet-shaped HMCM-36 and sheet-shaped HUZM-8.

Preferably, the specific surface area of the mesoporous silica in the mesoporous silica supported tungstic acid solid acid is 200-800m 2/g, and the supported content of tungstic acid is 5.0-20.0 wt%.

Preferably, the hydrogen active transition metal element is at least one selected from Re, Co, Ag and Pd, and the content of the hydrogen active transition metal element is 0.05 wt% to 3.0 wt%.

A method for producing m-cresol by using a solid acid catalyst and using a mixture containing p-cresol and o-cresol as raw materials comprises the following steps:

step 1a, heating a mixture raw material containing p-cresol and o-cresol by a preheater, and introducing the mixture raw material into a fixed bed reactor or a simulated moving bed reactor for reaction;

step 2a, reacting under the reaction conditions of 0.1-12.0MPa of reaction pressure, 180-450 ℃ of temperature and 1.0-12.0 h < -1 > of weight space velocity WHSV under the action of the solid acid catalyst to generate a reaction product containing o-cresol, m-cresol and p-cresol;

step 3a, separating the reaction product by a rectifying tower to obtain o-cresol and m-cresol and p-cresol mixture, and recycling the o-cresol which is not converted by reaction and is used as a reaction raw material to enter a reactor;

wherein, the mixed reaction product containing o, m and p is passed through a rectification separation tower, o-cresol collected at the tower top is used as a reaction raw material and is sent to the inlet of an isomerization reactor through a circulating compressor, and m and p mixed cresol is obtained by collection at the tower bottom.

Preferably, the molar ratio of hydrogen/hydrocarbon is 0.5: 1-10: 1. the reaction is carried out under the reaction conditions of 0.5-5.0MPa of pressure, 250-380 ℃ of temperature and WHSV of 2.0-8.0 h < -1 > of weight space velocity to generate a reaction product containing o-cresol, m-cresol and p-cresol.

A solid acid catalyst, wherein the solid acid catalyst is selected from at least one of hydrogen type eutectic hybrid molecular sieve, silicon oxide loaded fluorosulfonic acid resin or silicon oxide loaded niobic acid solid acid;

wherein the hydrogen-type eutectic hybrid molecule is selected from at least one of HZSM-5/HMOR molecular sieves, HZSM-5/HBeta, HMCM-36/HBeta and HBeta/HMOR molecular sieves, and the ratio range of two molecular sieves in the eutectic molecular sieves is selected from 1: 10-10: 1.

preferably, the specific surface area of the macroporous silicon oxide in the silicon oxide supported fluorosulfonic acid resin is 200-500m2/g, the specific surface area of the macroporous silicon oxide in the silicon oxide supported niobic acid is 200-500m2/g, and the supported content of the fluorosulfonic acid resin or niobic acid is 5.0-30.0 wt%.

A method for producing m-cresol by using a solid acid catalyst and using a mixture containing p-cresol and o-cresol as raw materials comprises the following steps:

step 1b, heating a mixture raw material containing p-cresol and o-cresol by a preheater, and introducing the mixture raw material into a fixed bed reactor or a simulated moving bed reactor for reaction;

step 2b, under the reaction conditions of the reaction pressure of 0.1-12.0MPa, the temperature of 180-450 ℃ and the weight space velocity WHSV of 1.0-12.0 h < -1 >, the reaction is carried out under the action of the solid acid catalyst to generate a reaction product containing o-cresol, m-cresol and p-cresol;

step 3b, separating the reaction product by a rectifying tower to obtain o-cresol and m-cresol and p-cresol mixture, and recycling the o-cresol which is not converted by reaction and is used as a reaction raw material to enter a reactor;

and (3) passing the reaction product through a rectification separation tower, taking o-cresol collected at the top of the tower as a reaction raw material, passing the o-cresol through a circulating compressor to an inlet of an isomerization reactor, and collecting m-cresol and p-cresol at the bottom of the tower.

Preferably, the reaction is carried out under the reaction conditions of pressure of 4.0-10.0MPa, temperature of 200-350 ℃ and weight space velocity WHSV of 1.0-5.0 h-1.

Preferably, the fixed bed reactor used therein is selected from a group consisting of those having a high/diameter ratio of 1: 1-6: 1 or a tubular reactor with an inner diameter of 3.0-8.0cm, wherein the materials are 316L stainless steel.

The invention has the beneficial effects that:

the method has the characteristics of high reaction efficiency, less dehydroxylation/methyl side reaction, small cresol loss rate, low coking and inactivation on the surface of the catalyst, good operation stability and environmental friendliness; the method not only can convert the o/p-cresol with relatively surplus market into m-cresol products with large demand through isomerization reaction, but also has higher m-cresol content in reaction products compared with other isomerization reaction process methods, and has obvious economic benefit.

Detailed Description

The present invention will be described in further detail below.

The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.

The invention aims to solve the technical problems of poor cresol selectivity, low yield, complex process, serious equipment corrosion, serious environmental pollution and high isomer separation cost in the cresol production process. The solid acid catalyst provided by the invention has an excellent isomer hydroisomerization transfer function, and is beneficial to selectively producing m-cresol from o-cresol and p-cresol in an isomerization transfer mode. Compared with the prior cresol isomerization preparation and separation technology, the solid acid catalyst for isomerization reaction and the method for producing m-cresol by using the solid acid catalyst have the advantages of high production efficiency, low energy consumption and material consumption, low cresol loss rate, high m-cresol yield and the like, and have more remarkable technical and economic advantages.

Example 1

O-cresol as a reaction raw material is fed into a preheater through a mass metering pump, the temperature of the preheater is set to 250 ℃, the o-cresol is fully preheated and then fully mixed with a hydrogen medium, and the molar ratio of hydrogen to phenol is 3: 1, entering a hydroisomerization reaction unit. The reaction conditions in the isomerization reaction system are that the reaction pressure is 1.5MPa, the reaction temperature is 380 ℃, and the weight space velocity WHSV1.0h-1 of raw material feeding is realized. The isomerization reaction unit is pre-filled with a hydrogen type sheet crystal form MOR molecular sieve, and 2.7 wt% of Re is added as a hydrogen active metal in the modification process of the molecular sieve. After the isomerization reaction, the reaction product is subjected to gas-liquid separation and condensation, the reaction product is separated by a plurality of rectifying towers, and the unreacted and converted o (p) cresol is recycled into a hydroisomerization reaction system to be used as a reaction raw material for further isomerization reaction. The reaction results are shown in Table 1.

Example 2

Mixing the components in a molar ratio of 2: 1, taking o-cresol and p-cresol as reaction raw materials, fully mixing, sending the mixture into a preheater through a mass metering pump, setting the temperature of the preheater to be 250 ℃, fully preheating, and fully mixing with a hydrogen medium, wherein the molar ratio of hydrogen to cresol is 3: 1, entering a hydroisomerization reaction unit. The reaction conditions in the isomerization reaction system are that the reaction pressure is 1.5MPa, the reaction temperature is 360 ℃, and the weight space velocity WHSV1.5h-1 of raw material feeding is realized. The isomerization reaction unit is pre-filled with hydrogen type flake HMCM-36 molecular sieve, which is added with 2.3 wt% of Re and 0.16% of Pd as hydrogen active metal in the modification process. After the isomerization reaction, the reaction product is subjected to gas-liquid separation and condensation, the reaction product is separated by a plurality of rectifying towers, and the o-cresol and a small amount of generated dimethylphenol are recycled to enter a hydroisomerization reaction system to be used as reaction raw materials for further isomerization reaction. The reaction results are shown in Table 1, with a purity of m-cresol of 99.2 wt%.

Example 3

O-cresol as a reaction raw material is fed into a preheater through a mass metering pump, the temperature of the preheater is set to 250 ℃, the o-cresol is fully preheated and then fully mixed with a hydrogen medium, and the molar ratio of hydrogen to cresol is 3: 1, entering a hydroisomerization reaction unit. Isomerization ofThe reaction conditions in the reaction system are that the reaction pressure is 1.5MPa, the reaction temperature is 380 ℃, and the weight space velocity WHSV1.5h of raw material feeding^-1. The isomerization reaction unit was pre-charged with a hydrogen-form, flaky HUZM-8 molecular sieve, which had 1.9 wt% Co and 0.62% Ag added as hydrogen active metals during the modification. After the isomerization reaction, the reaction product is subjected to gas-liquid separation and condensation, the reaction product is separated by a plurality of rectifying towers, and the unreacted and converted phenol and a small amount of generated dimethylphenol are recycled into a hydroisomerization reaction system to be used as reaction raw materials for further isomerization reaction. The reaction results are shown in Table 1, with a purity of m-cresol of 99.5 wt%.

Example 4

P-cresol as a reaction raw material is fed into a preheater through a mass metering pump, the temperature of the preheater is set to 250 ℃, the p-cresol is fully preheated and then fully mixed with a hydrogen medium, and the molar ratio of hydrogen to cresol is 3: 1, entering a hydroisomerization reaction unit. The reaction conditions in the isomerization reaction system are that the reaction pressure is 1.5MPa, the reaction temperature is 380 ℃, and the weight airspeed WHSV1.0h of raw material feeding is^-1. The isomerization reaction unit is pre-filled with a macroporous silicon oxide supported tungstic acid solid acid catalyst, and the specific surface area of the macroporous silicon oxide in the catalyst is 330m²The loading of tungstic acid is 13.8 wt%. In addition, 0.12 wt% of Pd was added as a hydrogen active metal to the catalyst system. After the isomerization reaction, the reaction product was subjected to gas-liquid separation and condensation, and then the reaction product was separated by a plurality of rectifying towers, the purity of the obtained m-cresol was 99.7 wt%, and the reaction results are shown in table 1.

Example 5

O-cresol is fed into a preheater through a mass metering pump, the temperature of the preheater is set to 250 ℃, and after full preheating, the o-cresol is fully mixed with a hydrogen medium, wherein the molar ratio of hydrogen to cresol is 3: 1, entering a hydroisomerization reaction unit. The reaction conditions in the isomerization reaction system are that the reaction pressure is 1.5MPa, the reaction temperature is 380 ℃, and the weight space velocity of raw material feeding is 2.0h^-1. The isomerization reaction unit is pre-filled with macropores loaded by fluorosulfonic acid resinA silica catalyst having a specific surface area of 385m of large pore silica²The loading of fluorosulfonic acid resin was 23.1 wt.%. After the isomerization reaction, the reaction product is subjected to gas-liquid separation and condensation, the reaction product is separated by a plurality of rectifying towers, the purity of m-cresol is 99.3 wt%, and the rest cresol isomers are recycled to enter a hydroisomerization reaction system to be used as reaction raw materials for further isomerization reaction. The reaction results are shown in Table 1.

Example 6

The reaction raw material o-cresol is sent into a preheater through a mass metering pump, the temperature of the preheater is set to 250 ℃, the reaction raw material o-cresol is fully preheated and then is fully mixed with a hydrogen medium, and the molar ratio of hydrogen to cresol is 3: 1, entering a hydroisomerization reaction unit. The reaction conditions in the isomerization reaction system are that the reaction pressure is 6MPa, the reaction temperature is 300 ℃, and the weight space velocity of raw material feeding is 2.0h^-1. The isomerization reaction unit is filled with a niobic acid loaded macroporous silicon oxide catalyst in advance, the specific surface area of the macroporous silicon oxide in the catalyst is 492m2/g, and the niobic acid loading is 14.7 wt%. In addition, 2.0 wt% of Re was added as a hydrogen active metal to the catalyst system. After isomerization reaction, gas-liquid separation and condensation are carried out on reaction products, and then the reaction products are separated through a plurality of rectifying towers, wherein the purity of the m-cresol product is 99.1 wt%. Other cresol isomers are recycled into a hydroisomerization reaction system to be used as reaction raw materials for further isomerization reaction. The reaction results are shown in Table 1.

Example 7

The reaction raw material p-cresol is sent into a preheater through a mass metering pump, the temperature of the preheater is set to be 250 ℃, and after full preheating, the reaction raw material p-cresol is fully mixed with a hydrogen medium, wherein the molar ratio of hydrogen to cresol is 3: 1, entering a hydroisomerization reaction unit. The reaction conditions in the isomerization reaction system are that the reaction pressure is 5MPa, the reaction temperature is 300 ℃, and the weight space velocity of raw material feeding is 2.0h^-1. The isomerization reaction unit is pre-filled with hydrogen type eutectic HZSM-5/HMOR molecular sieves, and the ratio of the two molecular sieves is 3: 7(wt/wt), 2.5w of the molecular sieve is added in the modification processt% Re and 0.5 wt% Pd as hydrogen active metals. After the isomerization reaction, the reaction product is subjected to gas-liquid separation and condensation, and the m-cresol product is separated by a plurality of rectifying towers, wherein the purity of the m-cresol product is 99.4 wt%. Other m-cresol is recycled into the hydroisomerization reaction system to be used as a reaction raw material for further isomerization reaction. The reaction results are shown in Table 1.

Example 8

O-cresol as a reaction raw material is fed into a preheater through a mass metering pump, the temperature of the preheater is set to 250 ℃, the o-cresol is fully preheated and then fully mixed with a hydrogen medium, and the molar ratio of hydrogen to cresol is 3: 1, entering a hydroisomerization reaction unit. The reaction conditions in the isomerization reaction system are that the reaction pressure is 5MPa, the reaction temperature is 250 ℃, and the weight space velocity of raw material feeding is 1.0h^-1. The isomerization reaction unit is pre-filled with hydrogen type HMCM-36 molecular sieve/hydrogen type Beta eutectic, the ratio of the two molecular sieves is 8: 2(wt/wt), the molecular sieve is added with 0.5 wt% of Pd and 3 wt% of Mo as hydrogen active metal during the modification process. After isomerization reaction, gas-liquid separation and condensation are carried out on reaction products, and then the reaction products are separated through a plurality of rectifying towers, wherein the purity of the m-cresol product is 99.6 wt%. Recycling the unreacted and converted cresol isomers and a small amount of generated dimethylphenol into a hydroisomerization reaction system as reaction raw materials for further isomerization reaction. The reaction results are shown in Table 1.

TABLE 1 results of o-p-cresol hydroisomerization reaction