Modified Al2O3 catalyst as well as preparation method and application thereof

Abstract

The invention provides a modified Al2O3 catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: roasting pseudo-boehmite to generate theta-Al2O3; gamma-Al2O3 and at least one of feldspar powder and nepheline powder are taken and mixed with theta-Al2O3 and water, grinding and dipping are carried out, and mixed slurry is obtained; drying and roasting the mixed slurry to form a roasted material; and finally, crushing and sieving the roasted material to obtain the modified Al2O3 catalyst. According to the preparation method, at least one of pseudo-boehmite, gamma-Al2O3, feldspar powder and nepheline powder is taken as a basic raw material, and the modified Al2O3 catalyst has good stability and relatively long service life through operations of roasting, drying, sieving and the like in multiple stages. The catalyst is used for preparing thymol by taking m-cresol and isopropanol as raw materials, the reaction condition is mild, the synthesis selectivity and conversion rate can be effectively improved, and the service life of the catalyst can be effectively prolonged.

Description

Technical Field

[0001] The present invention relates to the field of fine chemical synthesis, and in particular to a modified Al2O3 catalyst and a preparation method and application thereof. Background Art

[0002] Thymol (2-isopropyl-5-methylphenol) is a special substance with the aroma of thyme or musk. It is often used as a raw material for making spices and an important intermediate for synthesizing other spices. In addition, thymol has many other uses. For example, thymol is one of the 599 additives in cigarettes; it can also be used as a drug component to treat skin fungi and ringworm, as an indicator to determine the content of substances such as titanium, antimony, arsenic, nitrates, etc., as a preservative for book binding or to control the number of varroa mites on beehives, and it can also be added to trifluorochlorobromoethane as an anesthetic. Before the 1940s, the main source of thymol was extracted from nature. With the development of society, people's demand for thymol has increased, and the cost of natural extraction of thymol is very high, which cannot meet people's needs. At present, with the development of catalytic technology, synthetic thymol has gradually replaced natural thymol.

[0003] The synthesis of thymol is usually prepared by a series of reactions using m-cresol and various isopropylating agents, such as propylene, isopropanol and isopropyl halides. In the traditional method for synthesizing thymol, isopropyl halides and m-cresol are generally used as raw materials, aluminum chloride or sulfuric acid is used as a catalyst, and organic solvents such as ethylene dichloride are used as reaction solvents to prepare thymol, which has a high yield. However, the synthesis method requires the use of a large amount of organic solvents, has serious environmental pollution problems, and the post-reaction treatment of the preparation method is complicated, which is not suitable for industrial large-scale production.

[0004] US4086283 discloses a process for preparing thymol, which involves a continuous alkylation reaction of m-cresol with propylene at a temperature of 350-365°C and a pressure of 50 bar. Although the yield under the process conditions is relatively high, the conversion rate is not high. In addition, the process requires both a high temperature and a high pressure, and the reaction conditions are relatively harsh, which poses a great safety hazard in large-scale production.

[0005] Compared with the high temperature and high pressure synthesis method, the catalyst-based method for synthesizing thymol has the advantages of high conversion rate and mild conditions. Therefore, there are many studies on the catalyst used in the synthesis of thymol in the prior art. For example, a method for synthesizing 2-isopropyl-5-methylphenol by catalyzing the reaction of meta-cresol and isopropyl alcohol ethyl ester using Al-MCM-41 molecular sieve as a catalyst can make the meta-cresol conversion rate reach 70%, and the selectivity of the product can reach 70% to 88%. However, the catalyst life of the catalyst using Al-MCM-41 molecular sieve as a catalyst is very short, within the range of 72 to 100 hours, and the cost is relatively high in actual production and application.

[0006] At present, a suitable catalyst for catalytic synthesis of thymol has not been found, which can achieve high conversion rate and selectivity of thymol in the synthesis process, mild reaction conditions and long service life of the catalyst. Summary of the invention

[0007] The main purpose of the present invention is to provide a modified Al2O3 catalyst and a preparation method and application thereof, so as to solve the problem in the prior art that high conversion rate and selectivity, long catalyst service life and milder reaction conditions cannot be taken into account simultaneously when synthesizing thymol.

[0008] In order to solve the above problems, the present invention provides a method for preparing a modified Al2O3 catalyst, which comprises the following steps: step (1), sequentially performing first-stage calcination and second-stage calcination on pseudo-boehmite to generate θ-Al2O3, wherein the temperature of the second-stage calcination is higher than the temperature of the first-stage calcination; step (2), mixing γ-Al2O3 and at least one of feldspar powder and nepheline powder with θ-Al2O3 and water, grinding and impregnating the mixture to obtain a mixed slurry; step (3), drying the mixed slurry, performing a third-stage calcination to form a calcined product; and crushing and sieving the calcined product to obtain a modified Al2O3 catalyst.

[0009] Furthermore, the first stage roasting process includes: first heating the temperature to a first roasting temperature at a heating rate of 3 to 5°C / min, and then roasting at the first roasting temperature for 4 to 5 hours, and the first roasting temperature is 550 to 600°C; preferably, the second stage roasting process includes: first heating the temperature to a second roasting temperature at a heating rate of 3 to 5°C / min, and then roasting at the second roasting temperature for 4 to 5 hours, and the second roasting temperature is 1150 to 1300°C; preferably, the drying temperature in step (3) is 120 to 140°C, and the drying time is 4 to 10 hours; preferably, the third stage roasting process includes: first heating the temperature to a third roasting temperature at a heating rate of 3 to 5°C / min, and then roasting at the third roasting temperature for 4 to 10 hours, and the third roasting temperature is 500 to 650°C.

[0010] Furthermore, the amount of γ-Al2O3 added is 5% to 15% of the weight of θ-Al2O3; preferably, the amount of γ-Al2O3 added is 8% to 12% of the weight of θ-Al2O3.

[0011] Further, the total amount of feldspar powder and nepheline powder added is 0.5% to 1% of the weight of θ-Al2O3; preferably, the total amount of feldspar powder and nepheline powder added is 0.6% to 0.75% of the weight of θ-Al2O3; preferably, the amount of water added is 12% to 14% of the weight of θ-Al2O3; preferably, the particle size of the modified Al2O3 catalyst is 20 to 40 mesh.

[0012] Furthermore, the feldspar powder is potassium feldspar and / or sodium feldspar, and the nepheline powder is potassium nepheline; preferably, the feldspar powder is potassium feldspar; more preferably, feldspar powder and nepheline powder are added simultaneously in step (2), and the weight ratio of the two is 1:(2-5); or, only nepheline powder is added in step (2), without adding feldspar powder.

[0013] According to another aspect of the present invention, a modified Al2O3 catalyst is also provided, which is prepared by the above preparation method.

[0014] According to the third aspect of the present invention, a method for preparing thymol is also provided. The method uses meta-cresol and isopropanol as raw materials and the modified Al2O3 catalyst prepared as above as a reaction catalyst. The method comprises the following steps: S1, respectively passing meta-cresol and isopropanol into the preheating section of a fixed bed reactor; S2, mixing the preheated meta-cresol and isopropanol and passing the mixture into the reaction section of a fixed bed reactor containing the modified Al2O3 catalyst to obtain crude thymol; S3, purifying the crude thymol to obtain thymol.

[0015] Further, the molar ratio of m-cresol to isopropanol is 1:(1.5-3); preferably, the molar ratio of m-cresol to isopropanol is 1:(1.5-2).

[0016] Furthermore, in step S2, the absolute reaction pressure of the reaction zone is 0.10-0.11 MPa; preferably, the temperature of the preheating zone is controlled at 250-300°C; preferably, the temperature of the reaction zone is controlled at 230-280°C; more preferably, the temperature of the reaction zone is controlled at 250-270°C.

[0017] Furthermore, in step S2, the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6 to 3.2 h -1 .

[0018] The invention provides a method for preparing a modified Al2O3 catalyst. When preparing the modified Al2O3 catalyst, the method uses pseudo-boehmite, gamma-Al2O3, and at least one of feldspar powder and nepheline powder as basic raw materials, and performs multiple stages of roasting, drying, sieving and other operations, so that the obtained modified Al2O3 catalyst has good stability and a long service life. In addition, the modified Al2O3 catalyst prepared by the method is used to prepare thymol using meta-cresol and isopropanol as raw materials, and the synthesis process can be completed under relatively mild conditions, and the selectivity and conversion rate of the synthesis can be effectively improved, and the service life of the catalyst can also be greatly extended. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0020] As described in the background technology section, conventional methods for synthesizing thymol using organic solvents require the use of a large amount of organic solvents during synthesis, and there are problems such as complex post-reaction treatment and serious environmental pollution, which are not suitable for industrial large-scale production. The method for synthesizing thymol under high temperature and high pressure has a low conversion rate and harsh conditions, which is also not suitable for large-scale production. The method for synthesizing thymol using a catalyst has the advantages of high conversion rate and mild conditions, but the catalyst used for synthesizing thymol in the prior art often has problems such as low conversion rate and selectivity and short catalyst life.

[0021] In order to solve the above problems, the present invention provides a method for preparing a modified Al2O3 catalyst, which comprises the following steps: step (1), sequentially performing first-stage calcination and second-stage calcination on pseudo-boehmite to generate θ-Al2O3, wherein the temperature of the second-stage calcination is higher than the temperature of the first-stage calcination; step (2), mixing γ-Al2O3 and at least one of feldspar powder and nepheline powder with θ-Al2O3 and water, grinding and impregnating the mixture to obtain a mixed slurry; step (3), drying the mixed slurry, performing a third-stage calcination to form a calcined product; and crushing and sieving the calcined product to obtain a modified Al2O3 catalyst.

[0022] Specifically, when preparing the modified Al2O3 catalyst, the present application first performs two-stage roasting of the raw material pseudo-boehmite, during which multiple crystal transformations occur, and finally θ-Al2O3 is generated; then the generated θ-Al2O3 and γ-Al2O3, and at least one of feldspar powder and nepheline powder are mixed with water, and the mixed slurry is obtained by grinding, impregnation and other operations; finally, the mixed slurry is subjected to a series of operations such as drying, roasting, crushing, and screening to obtain the modified Al2O3 catalyst.

[0023] In particular, the present invention uses pseudo-boehmite as a raw material when preparing a modified Al2O3 catalyst. The composition of pseudo-boehmite is AlOOH·nH2O, n=0.08-0.62. It is a type of incompletely crystallized hydrated aluminum oxide, which not only has the characteristics of high crystal purity and high stability, but also has the characteristics of high specific surface area and large pore volume, and has a good application foundation in the field of catalysts. Based on the above-mentioned excellent characteristics of pseudo-boehmite, the preparation method of the present invention first performs two-stage roasting on pseudo-boehmite. During the roasting process of these two stages, the pseudo-boehmite undergoes multiple crystal transformations and finally generates θ-Al2O3. Among them, in the first stage of the roasting process, the crystal water molecules contained in the pseudo-boehmite are first removed and further converted into γ-Al2O3, and the second stage of the roasting process converts γ-Al2O3 into θ-Al2O3. The conversion of γ-Al2O3 to θ-Al2O3 can reduce the specific surface area of ​​pseudo-boehmite, further improve the catalyst stability and selective activity, and ensure the long life of the final catalyst. The present invention selects pseudo-boehmite as a raw material to synthesize θ-Al2O3, on the one hand because the crystal form of the pseudo-boehmite preparation process is easier to control, so that θ-Al2O3 can be better generated, and on the other hand because it is cheap and widely available, which can reduce production costs. The synthesized θ-Al2O3 is used as a catalyst carrier. Firstly, θ-Al2O3 has a higher specific surface area, which has a better promoting effect on the diffusion of reactants inside the catalyst particles during the catalytic process; secondly, due to its porosity and high dispersibility, it has higher catalytic activity and surface acidity, which is conducive to making the modified Al2O3 catalyst better play its catalytic role.

[0024] Further, the present invention also adds γ-Al2O3, and at least one of feldspar powder and nepheline powder when preparing modified Al2O3 catalyst using pseudo-boehmite. The main components of feldspar powder are SiO2, Al2O3, K2O, Na2O, CaO, etc., and the main component of nepheline powder is KNa3(AlSiO4)4. On the one hand, both types of substances contain alkali metal ions such as potassium ions and sodium ions. When preparing modified Al2O3 catalyst, relevant alkali metal ions can be introduced when modifying Al2O3 catalyst, so that in the process of thymol synthesis, the trace water produced by the reaction can be used to make the catalyst continuously release the contained alkali metal ions, increase the basic sites of the catalyst, improve the selectivity of the catalyst, and improve the stability and life of the catalyst. On the other hand, feldspar powder and / or nepheline powder participate in the further roasting of θ-Al2O3 together with γ-Al2O3, and can be fully compounded and complementary with θ-Al2O3 in structure, which is beneficial to the selectivity of the catalyst. In summary, the interaction between the components in the above-mentioned raw materials combined with the preparation method described in the present invention not only prolongs the life of the modified Al2O3 catalyst, but also increases the selectivity of the modified Al2O3 catalyst for the target product, and also makes the obtained modified Al2O3 catalyst more stable and active, so that the comprehensive performance of the modified Al2O3 catalyst is further improved.

[0025] In summary, the modified Al2O3 catalyst prepared by the technical solution of the present invention has good stability. When it is used to prepare thymol, it can not only make the raw material have a good conversion rate and selectivity, but also has good stability and a long service life. It can be reactivated and used repeatedly, which reduces the production cost and has obvious progressive significance in actual production.

[0026] In a preferred embodiment, the first stage calcination process includes: first heating to the first calcination temperature at a heating rate of 3 to 5 ° C / min, and then calcining at the first calcination temperature for 4 to 5 hours, wherein the first calcination temperature is 550 to 600 ° C. The first stage of calcination can remove the crystal water carried by the raw material pseudo-boehmite and further convert it into γ-Al2O3. Controlling the calcination temperature and calcination time of this stage within the above range can make the obtained product have better specific surface area and stability. Preferably, the second stage of calcination process includes: first heating to the second calcination temperature at a heating rate of 3 to 5 ° C / min, and then calcining at the second calcination temperature for 4 to 5 hours, wherein the second calcination temperature is 1150 to 1300 ° C. The second stage of calcination is to prepare θ-Al2O3. In this process, controlling the calcination temperature and the burning time within the above range can not only make the crystal transformation more complete, but also make the obtained θ-Al2O3 stable. Preferably, the third stage calcination process includes: first heating to the third calcination temperature at a heating rate of 3 to 5°C / min, and then calcining at the third calcination temperature for 4 to 10 hours, wherein the third calcination temperature is 500 to 650°C. The third stage of calcination is to make the mixture of γ-Al2O3, and at least one of feldspar powder and nepheline powder, and θ-Al2O3 and water combine in a more dispersed and more compact manner, which is conducive to making the properties of the prepared modified Al2O3 catalyst more stable and uniform, and the activity of the catalyst will also be better. Preferably, the drying temperature in step (3) is 120 to 140°C, and the drying time is 4 to 10 hours. The above drying conditions are to remove the water mixed therein and prepare for the subsequent calcination.

[0027] In a preferred embodiment, the amount of γ-Al2O3 added is 5% to 15% of the weight of θ-Al2O3. γ-Al2O3 is added when preparing the modified Al2O3 catalyst because it can enhance the acidity of θ-Al2O3 at high temperatures and improve the reaction efficiency. The appropriate amount of addition can be beneficial to the reaction. Controlling the amount of γ-Al2O3 added within the above range can better release the alkali metal ions in the modified Al2O3 catalyst, thereby making the modified Al2O3 catalyst have better selectivity and conversion rate when used to prepare thymol, and is also conducive to extending the service life of the catalyst. Preferably, the amount of γ-Al2O3 added is 8% to 12% of the weight of θ-Al2O3. Controlling the amount of γ-Al2O3 added within the above range can make the effect of the obtained modified Al2O3 catalyst better.

[0028] In a preferred embodiment, the total amount of feldspar powder and nepheline powder added is 0.5% to 1% of the weight of θ-Al2O3. One of the purposes of adding feldspar powder and nepheline powder is to introduce alkali metal ion content into the modified Al2O3 catalyst, increase the basic sites in the catalyst, and thus achieve the purpose of improving the selectivity and service life of the catalyst. The above effect can be achieved by controlling the total amount of feldspar powder and nepheline powder added within the above range. Preferably, the total amount of feldspar powder and nepheline powder added is controlled to be 0.6% to 0.75% of the weight of θ-Al2O3, and the effect of the obtained modified Al2O3 catalyst is better. Preferably, the amount of water added is 12% to 14% of the weight of θ-Al2O3. The addition of water helps to mix the various raw material components, and the amount of water added can be controlled within the above range. Further, controlling the particle size of the modified Al2O3 catalyst after crushing and sieving to 20 to 40 meshes helps to better exert the effect of the catalyst during use.

[0029] In a preferred embodiment, the feldspar powder is potassium feldspar and / or sodium feldspar, and the nepheline powder is potassium nepheline. The modified Al2O3 catalyst prepared by using the above-mentioned types of feldspar powder and nepheline powder will have a good use effect. Preferably, the feldspar powder is potassium feldspar, and the modified Al2O3 catalyst prepared by using potassium feldspar in the feldspar powder has a better use effect. Further preferably, the feldspar powder and the nepheline powder are added at the same time in step (2), and the weight ratio of the two is 1: (2 to 5); or, only nepheline powder is added in step (2), and no feldspar powder is added. The above conditions are further preferred conditions explored in a large number of experimental conditions, and have better use effects.

[0030] According to another aspect of the present invention, a modified Al2O3 catalyst is provided, which is prepared by the above-mentioned preparation method. Under preferred conditions, the continuous service life of the modified Al2O3 catalyst prepared is greater than 1800 hours. In fact, in actual application, after the activity of the modified Al2O3 catalyst decreases, it is placed in a dry atmosphere and calcined at 550-600°C for 4-8 hours, and then it can be activated and can continue to be used.

[0031] According to the third aspect of the present invention, a method for preparing thymol is also provided, wherein the method uses meta-cresol and isopropanol as raw materials, and the modified Al2O3 catalyst prepared by the above preparation method is used as a reaction catalyst. Specifically, the method for preparing thymol comprises the following steps: S1, passing meta-cresol and isopropanol into the preheating section of a fixed bed reactor respectively; S2, mixing the preheated meta-cresol and isopropanol and passing them into the reaction section of a fixed bed reactor equipped with the modified Al2O3 catalyst to obtain crude thymol; S3, purifying the crude thymol to obtain thymol.

[0032] Specifically, the method uses meta-cresol and isopropanol as reaction raw materials, a modified Al2O3 catalyst as a reaction catalyst, and a fixed bed reactor as a reaction device when preparing thymol, thereby realizing continuous production of thymol. The use of the modified Al2O3 catalyst can also further improve the selectivity and conversion rate of meta-cresol, and has multiple advantages such as high synthesis efficiency, low cost, and good safety. At the same time, the method uses the modified Al2O3 catalyst as a catalyst for the reaction, which can make the reaction proceed under milder conditions, and the method can be used for industrial large-scale production of thymol.

[0033] In a preferred embodiment, the molar ratio of meta-cresol to isopropanol is 1:(1.5-3). When preparing thymol from meta-cresol, the reaction raw material meta-cresol has multiple reaction sites. Too much addition of isopropanol will lead to the formation of multi-substituted by-products, while too little addition of isopropanol will not guarantee the conversion rate of meta-cresol. Controlling the molar ratio of meta-cresol to isopropanol within the above range can improve the selectivity while ensuring the conversion rate. Preferably, the molar ratio of meta-cresol to isopropanol is controlled to be 1:(1.5-2), and the conversion rate and selectivity of synthesizing thymol are better.

[0034] In a preferred embodiment, the absolute reaction pressure of the reaction section in step S2 is 0.10-0.11 MPa. Under the action of the modified Al2O3 catalyst, the absolute reaction pressure during the reaction is controlled to be around the normal pressure range to complete the synthesis process. Preferably, the temperature of the preheating section is controlled to be 250°C-300°C; preferably, the temperature of the reaction section is controlled to be 230-280°C. Before the reaction, the raw material meta-cresol and the raw material isopropanol are preheated separately and then mixed and passed into the reaction section of the fixed bed reactor, which can effectively avoid the problem of reduced synthesis efficiency caused by uneven heating of the reaction raw materials during the reaction. Controlling the temperature of the preheating section and the reaction section within the above range is conducive to improving the synthesis yield of thymol. More preferably, the temperature of the reaction section is controlled to be 250-270°C, and the synthesis yield is better at the above reaction temperature. The modified Al2O3 catalyst prepared by the present invention is used as a catalyst for preparing thymol, so that the reaction can be completed under relatively mild conditions. As mentioned above, the absolute reaction pressure is about 0.10-0.11 MPa, the preheating stage temperature and the reaction stage temperature are respectively 250-300° C. and 230-280° C., so that the selectivity and yield of preparing thymol can be at a high level. In particular, the process does not require harsh operations such as pressurization and high temperature, and has great progressive significance in the actual application in the process of producing thymol.

[0035] In a preferred embodiment, the mass space velocity when the mixed material is passed into the fixed bed reactor in step S2 is 1.6 to 3.2 h -1Controlling the mass flow rate of the reaction raw materials and the mass ratio of the catalyst in the reactor within the above range can make the reaction proceed more completely.

[0036] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0037] In order to better understand the technical solution of the present invention, it is necessary to further explain that: (1) unless otherwise specified, the size of the reaction section of the fixed bed reactor in the embodiments of the present invention and the comparative examples is: (2) The Al-MCM-41 catalyst used in Comparative Example 3 and the activated alumina catalyst used in Comparative Example 4 were purchased; (3) The specific statistical methods for the conversion rate of m-cresol, the selectivity of thymol and the service life of the catalyst are explained as follows: The reaction liquid is detected by a gas chromatograph Agilent 7890C, and the content of the compound in the reaction liquid is calculated (mol%) according to the detection results of the gas chromatograph. The calculation process of the conversion rate is based on the raw material m-cresol. Among them, the calculation method of the m-cresol conversion rate is: m-cresol conversion rate = (1-m-cresol molar percentage of reaction liquid) × 100%; the calculation method of thymol selectivity is: thymol selectivity = thymol molar percentage of reaction liquid / conversion rate × 100%; the service life test of the catalyst is the use time of the catalyst when the conversion rate and selectivity of m-cresol are not less than 95% during the preparation process.

[0038] Example 1

[0039] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0040] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0041] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0042] Example 2

[0043] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0044] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:1.5, and then pass the preheated m-cresol and isopropanol into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity of the mixed material when passing into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0045] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0046] Example 3

[0047] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 12g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0048] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0049] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0050] Example 4

[0051] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.75g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0052] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0053] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0054] Example 5

[0055] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 12g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0056] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 3.2h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0057] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0058] Example 6

[0059] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.75g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0060] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 280°C, and the mass space velocity of the mixed material when passing into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0061] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0062] Example 7

[0063] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 550℃ at a heating rate of 5℃ / min, and roast it for 5h, then heat it to 1300℃ at a heating rate of 5℃ / min, and roast it for 5h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 140g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 10h, then place it in a muffle furnace and heat it to 650℃ at a heating rate of 5℃ / min and roast it for 4h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0064] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 250°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0065] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0066] Example 8

[0067] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 140℃ for 4h, then place it in a muffle furnace and heat it to 500℃ at a heating rate of 3℃ / min and roast it for 10h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0068] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:2 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 300°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.11 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0069] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0070] Example 9

[0071] The difference from Example 1 is that when preparing the modified Al2O3 catalyst, the amount of γ-Al2O3 added is 8% of the weight of θ-Al2O3.

[0072] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 8g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0073] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0074] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0075] Example 10

[0076] The difference from Example 1 is that when preparing the modified Al2O3 catalyst, the amount of γ-Al2O3 added is 5% of the weight of θ-Al2O3.

[0077] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 5g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0078] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0079] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0080] Embodiment 11

[0081] The difference from Example 1 is that when preparing the modified Al2O3 catalyst, the amount of γ-Al2O3 added is 15% of the weight of θ-Al2O3.

[0082] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 15g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0083] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0084] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0085] Example 12

[0086] The difference from Example 1 is that the total amount of potassium pyroxene added is 0.5% of the weight of the θ-Al2O3.

[0087] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.5g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0088] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0089] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0090] Example 13

[0091] The difference from Example 1 is that the total amount of potassium pyroxene added is 1% of the weight of the θ-Al2O3.

[0092] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 1g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0093] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0094] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0095] Embodiment 14

[0096] The difference from Example 1 is that the potassium pyroxene is adjusted to potassium feldspar.

[0097] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium feldspar to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0098] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0099] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0100] Embodiment 15

[0101] The difference from Example 1 is that the potassium nephrite is adjusted to albite.

[0102] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of albite to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0103] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0104] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0105] Example 16

[0106] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, 0.6g of a mixture of potassium feldspar and potassium nephrite (wherein the mass ratio of potassium feldspar to potassium nephrite is 1:5), add it to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h, and after cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0107] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0108] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0109] Embodiment 17

[0110] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, 0.6g of a mixture of potassium feldspar and potassium nephrite (wherein the mass ratio of potassium feldspar to potassium nephrite is 1:2), add it to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h, and after cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0111] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0112] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0113] Embodiment 18

[0114] The difference from Example 1 is that the molar ratio of m-cresol to isopropanol is 1:3.

[0115] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0116] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:3, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0117] The crude thymol was detected by gas chromatography, and the meta-cresol conversion rate was 86%, the thymol selectivity was 94%, and the catalyst was continuously operated for 2000 hours, and the meta-cresol conversion rate and selectivity remained unchanged.

[0118] Embodiment 19

[0119] The difference from Example 6 is that the temperature of the reaction zone is 230°C.

[0120] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0121] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 230°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0122] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0123] Embodiment 20

[0124] The difference from Example 6 is that the temperature of the reaction zone is 250°C.

[0125] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0126] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 250°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0127] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0128] Embodiment 21

[0129] The difference from Example 6 is that the temperature of the reaction zone is 270°C.

[0130] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0131] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 270°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0132] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0133] Embodiment 22

[0134] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 400℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1000℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 3g of γ-Al2O3, add 0.2g of potassium pyroxene powder to θ-Al2O3 and mix well, take 100g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 500℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0135] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0136] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0137] Embodiment 23

[0138] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3, add 0.6g of potassium pyroxene powder to θ-Al2O3 and mix well, take 120g of water, gradually add it to the above mixture, and grind and impregnate it to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0139] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:3.5, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 230°C, the temperature of the reaction section is 230°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 3.5h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0140] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0141] Comparative Example 1

[0142] The difference from Example 1 is that no feldspar powder or nepheline powder is added when preparing the modified Al2O3 catalyst.

[0143] Take 102g of pseudo-boehmite in a muffle furnace, heat it to 600℃ at a heating rate of 3℃ / min, and roast it for 4h, then heat it to 1150℃ at a heating rate of 3℃ / min, and roast it for 4h to obtain 100gθ-Al2O3. Take 10g of γ-Al2O3 and add it to θ-Al2O3 and mix well. Take 120g of water and gradually add it to the above mixture, while grinding and impregnating to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min and roast it for 5h. After cooling, crush it and sieve it to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0144] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0145] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0146] Comparative Example 2

[0147] The difference from Example 4 is that no pseudo-boehmite sintered θ-Al2O3 is added when preparing the modified Al2O3 catalyst.

[0148] Take 100g of γ-Al2O3 and 0.75g of potassium pyroxene powder and mix them evenly, take 120g of water and gradually add it to the above mixture, grind and impregnate it at the same time to obtain a mixed slurry. Place the above mixed slurry in an oven and dry it at 120℃ for 6h, then place it in a muffle furnace and heat it to 600℃ at a heating rate of 3℃ / min for 5h, and then crush and sieve it after cooling to make its particle size 20-40 mesh to obtain a modified Al2O3 catalyst.

[0149] Weigh 15g of the modified Al2O3 catalyst obtained above and mix it with quartz sand in a mass ratio of 1:1 and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor in a molar ratio of 1:2, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor, wherein the temperature of the preheating section of the fixed bed reactor is 280°C, the temperature of the reaction section is 260°C, and the mass space velocity when the mixed material is passed into the fixed bed reactor is 1.6h -1 The absolute pressure of the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0150] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0151] Comparative Example 3

[0152] Weigh 15g of Al-MCM-41 catalyst and fill it into the fixed bed reaction section. Pass m-cresol and isopropanol into the preheating section of the fixed bed reactor at a molar ratio of 1:3, and then mix the preheated m-cresol and isopropanol and pass them into the reaction section of the fixed bed reactor. The temperature of the reaction section of the fixed bed reactor is 400°C, and the mass space velocity of the mixed material when passing into the fixed bed reactor is 2.77h -1 The pressure in the reaction section is 0.1 MPa, and crude thymol is obtained after the reaction is completed. The crude thymol obtained above is purified to obtain thymol.

[0153] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0154] Comparative Example 4

[0155] 12.2L of catalyst is filled into a reactor with a length of 2m and an inner diameter of 90mm, wherein the catalyst is activated alumina, and liquid cresol and liquid propylene preheated to 300°C are pumped into the reactor at a rate of 1.8L / h and 1.5L / h, respectively. The reaction temperature is 360-365°C, and the reaction pressure is 48-50bar. After the reaction is completed, crude thymol is obtained. The crude thymol obtained above is purified to obtain thymol.

[0156] The crude thymol was detected by gas chromatography to obtain relevant data on the meta-cresol conversion rate, thymol selectivity and service life of the catalyst. The results are shown in Table 1.

[0157] The relevant test results in Examples 1 to 23 and Comparative Examples 1 to 4 are summarized in Table 1.

[0158] Table 1

[0159]

[0160]

[0161] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: Embodiments 1 to 21 are modified Al2O3 catalysts prepared by the method for preparing modified Al2O3 catalysts of the present invention for preparing thymol, and the meta-cresol conversion rate in the catalytic preparation process is above 80%, the thymol selectivity is above 90%, and the continuous operation time of the catalyst can reach above 1800h, and even above 2200h under preferred conditions, showing a good comprehensive use effect. Embodiments 22 and 23 are when preparing the catalyst or when synthesizing thymol, the parameters in the preparation process are not within the preferred range, and the catalyst life is reduced, but the meta-cresol conversion rate and thymol selectivity are still at a good level.

[0162] In Comparative Example 1, no feldspar powder and / or nepheline powder was added when preparing the modified Al2O3 catalyst, and in Comparative Example 2, no pseudo-boehmite sintered θ-Al2O3 was added when preparing the modified Al2O3 catalyst. The comprehensive performance of the catalysts in these two comparative examples is far different from that of the catalyst of the present invention. In Comparative Examples 3 and 4, conventional catalysts were used to catalyze the reaction of the present invention, and the results were not ideal.

[0163] In summary, the modified Al2O3 catalyst prepared by the preparation method of the present invention is used to prepare thymol with m-cresol and isopropanol as raw materials. The synthesis process can be completed under relatively mild conditions, and the selectivity and conversion rate of the synthesis can be improved at the same time, and the service life of the catalyst can also be greatly extended.

[0164] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a modified Al2O3 catalyst, characterized in that: The preparation method comprises the following steps: Step (1), subjecting pseudo-boehmite to first-stage calcination and second-stage calcination in sequence to generate θ-Al2O3, wherein the temperature of the second-stage calcination is higher than the temperature of the first-stage calcination; Step (2), taking γ-Al2O3, and at least one of feldspar powder and nepheline powder, mixing with the θ-Al2O3 and water, grinding and impregnating to obtain a mixed slurry; Step (3), after drying the mixed slurry, performing a third stage of calcination to form a calcined product; crushing and sieving the calcined product to obtain the modified Al2O3 catalyst.

2. The method for preparing the modified Al2O3 catalyst according to claim 1, characterized in that: The first stage calcination process includes: firstly heating the temperature to a first calcination temperature at a heating rate of 3 to 5°C / min, and then calcining at the first calcination temperature for 4 to 5 hours, wherein the first calcination temperature is 550 to 600°C; Preferably, the second stage calcination process comprises: firstly heating to a second calcination temperature at a heating rate of 3-5°C / min, and then calcining at the second calcination temperature for 4-5h, wherein the second calcination temperature is 1150-1300°C; Preferably, the drying temperature in step (3) is 120-140° C., and the drying time is 4-10 hours; Preferably, the third stage calcination process comprises: firstly heating to a third calcination temperature at a heating rate of 3-5°C / min, and then calcining at the third calcination temperature for 4-10 hours, wherein the third calcination temperature is 500-650°C.

3. The method for preparing a modified Al2O3 catalyst according to any one of claims 1 or 2, characterized in that: The added amount of the γ-Al2O3 is 5% to 15% of the weight of the θ-Al2O3; Preferably, the added amount of the γ-Al2O3 is 8% to 12% of the weight of the θ-Al2O3.

4. The method for preparing a modified Al2O3 catalyst according to any one of claims 1 to 3, characterized in that: The total amount of the feldspar powder and the nepheline powder added is 0.5% to 1% of the weight of the θ-Al2O3; Preferably, the total amount of the feldspar powder and the nepheline powder added is 0.6% to 0.75% of the weight of the θ-Al2O3; Preferably, the amount of water added is 12% to 14% of the weight of the θ-Al2O3; Preferably, the particle size of the modified Al2O3 catalyst is between 20 and 40 meshes.

5. The method for preparing a modified Al2O3 catalyst according to any one of claims 1 to 3, characterized in that: The feldspar powder is potassium feldspar and / or sodium feldspar, and the nepheline powder is potassium nepheline; Preferably, the feldspar powder is potassium feldspar; More preferably, in the step (2), the feldspar powder and the nepheline powder are added simultaneously, and the weight ratio of the two is 1:(2-5); or, in the step (2), only the nepheline powder is added, and the feldspar powder is not added.

6. A modified Al2O3 catalyst, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing thymol, characterized in that: Using m-cresol and isopropanol as raw materials and the modified Al2O3 catalyst prepared according to any one of claims 1 to 5 as a reaction catalyst, the method comprises the following steps: S1, respectively introducing the m-cresol and the isopropanol into a preheating section of a fixed bed reactor; S2, mixing the preheated m-cresol and the isopropanol and passing the mixture into a reaction section of the fixed bed reactor containing the modified Al2O3 catalyst to obtain a crude thymol product; S3, purifying the crude thymol to obtain the thymol.

8. The method for preparing thymol according to claim 7, characterized in that: The molar ratio of the meta-cresol to the isopropanol is 1:(1.5-3); preferably, the molar ratio of the meta-cresol to the isopropanol is 1:(1.5-2).

9. The method for preparing thymol according to claim 7 or 8, characterized in that: The absolute reaction pressure of the reaction zone in step S2 is 0.10-0.11 MPa; Preferably, the temperature of the preheating section is controlled to be 250°C to 300°C; Preferably, the temperature of the reaction section is controlled at 230-280°C; more preferably, the temperature of the reaction section is controlled at 250-270°C.

10. The method for preparing thymol according to any one of claims 7 to 9, characterized in that: The mass space velocity when the mixed material is passed into the fixed bed reactor in step S2 is 1.6 to 3.2 h -1 .

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