Catalyst for synthesizing 2,6-dimethylphenol and preparation method thereof, and preparation method of 2,6-dimethylphenol

Abstract

The present invention relates to a preparation method of a catalyst for synthesizing 2,6-dimethylphenol, comprising the steps of: mixing iron salt, aluminum salt, magnesium salt, acidic substance and water to obtain solution A; mixing sodium silicate, template agent and water to obtain solution B; mixing solution A and solution B, after aging, then crystallizing, filtering, drying, calcining, obtaining catalyst precursor one; then mixing with alkaline solution, filtering to obtain catalyst precursor two; then mixing with acidic solution, filtering to obtain solid, then washing, calcining, obtaining catalyst; the preparation method of 2,6-dimethylphenol, comprising the steps of: under the condition of the presence of the above-mentioned catalyst, using methanol, phenol, water and benzoic acid as raw materials to prepare 2,6-dimethylphenol. The catalyst of the present invention has good catalytic activity, reduces carbon deposition problems, and when preparing 2,6-dimethylphenol, has good selectivity and high phenol conversion rate.

Description

Technical Field

[0001] The invention relates to the technical field of a preparation process for 2,6-dimethylphenol, and in particular to a catalyst for synthesizing 2,6-dimethylphenol and a preparation method thereof, and a preparation method for 2,6-dimethylphenol. Background Art

[0002] 2,6-Dimethylphenol is an important organic chemical raw material and intermediate. It is a monomer for preparing polyphenylene ether (PPO), one of the five major engineering plastics. It has important applications in pharmaceuticals, medicine, military industry, and aviation.

[0003] At present, the main method for producing ortho-methylated phenol compounds is the phenol-methanol alkylation gas phase method, which is to gasify phenol and methanol in the presence of a catalyst and then enter a catalytic reactor for reaction. The key to the gas phase synthesis of 2,6-dimethylphenol lies in the catalyst. This method generally uses molecular sieves or metal oxides as catalysts, among which metal oxide catalysts show good catalytic performance for this reaction. Therefore, metal oxides are the most widely studied catalysts in the alkylation reaction of phenol and methanol. For example, General Motors has studied and developed magnesium oxide catalysts, Asahi Kasei Corporation, URBK Corporation and others have developed V-Fe catalysts, Beijing Chemical Research Institute is committed to the development of MgO series catalysts, and Hunan Changling Petrochemical Technology Development Co., Ltd. uses coprecipitation to prepare Fe composite catalysts.

[0004] Improving the ortho-methylation catalyst helps to improve the synthesis selectivity and conversion rate of 2,6-dimethylphenol. The earliest developed and applied ortho-methylation catalyst is Al2O3, such as Japanese patent JP7853627. Due to its low catalytic activity and selectivity of ortho-methylation substitution, and the generation of a large amount of para- and meta-methylated phenol, it is gradually replaced by MgO-based catalysts, such as MgO-based catalysts disclosed in patents such as US3446856, US4041085, US4201880, and US4554267.

[0005] Since MgO-based catalysts have the defects of high reaction energy consumption and low catalytic activity, they are gradually replaced by newly emerging iron-based catalysts, such as the iron-based catalysts disclosed in patents such as USP3716589, USP3953529, USP4024195, USP4227024, and EP19476, which have made great improvements in lowering the reaction temperature, improving the selectivity of ortho-methylation and the conversion rate of phenol.

[0006] A basic Fe / Mg / M composite oxide catalyst is disclosed in the patents CN101513614A, CN101514144A and CN101514145A of Xinling Chemical Industry, with Fe2O3 and MgO as catalysts, adding a small amount of other transition metal oxides. This catalyst reaction runs for 500h, and the average conversion rate of phenol is 33.7%. At this time, the phenol conversion rate has been significantly reduced, so the stability of the catalyst needs to be further improved, and the catalyst activity is relatively low and is only suitable for catalytic synthesis of o-cresol. The Fe / Mg composite oxide catalyst disclosed in the subsequent patent CN102826960A overcomes the stability defect, and the catalyst can be stably operated for 2000h in a single pass and maintains high selectivity, but the phenol conversion rate is still not high.

[0007] Therefore, there is an urgent need to provide a method for synthesizing 2,6-dimethylphenol with high synthesis selectivity and phenol conversion rate. Summary of the invention

[0008] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a catalyst for synthesizing 2,6-dimethylphenol and a preparation method thereof, and a preparation method of 2,6-dimethylphenol, so as to solve the problems of low selectivity and low phenol conversion rate in the synthesis of 2,6-dimethylphenol in the prior art.

[0009] To achieve the above objectives and other related objectives, the present invention is achieved through the following technical solutions.

[0010] The first aspect of the present invention is to provide a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, the preparation method comprising the following steps:

[0011] (1) mixing an iron salt, an aluminum salt, a magnesium salt, an acidic substance and water to obtain a solution A;

[0012] (2) mixing sodium silicate, a template and water to obtain a solution B;

[0013] (3) mixing the solution A obtained in step (1) and the solution B obtained in step (2), and aging them to obtain a slurry;

[0014] (4) crystallizing the slurry obtained in step (3), filtering, drying, calcining, and screening to obtain a catalyst precursor 1; the crystallization time is greater than 3 hours;

[0015] (5) mixing the catalyst precursor 1 obtained in step (4) with the alkaline solution, and filtering to obtain the catalyst precursor 2;

[0016] (6) The catalyst precursor 2 is then mixed with the acidic solution, filtered to obtain a solid, and the solid is washed and calcined to obtain a catalyst.

[0017] The second aspect of the present invention is to provide a catalyst for synthesizing 2,6-dimethylphenol, which is prepared by the preparation method as described above.

[0018] The third aspect of the present invention provides a method for preparing 2,6-dimethylphenol, comprising the following steps: in the presence of the catalyst for synthesizing 2,6-dimethylphenol prepared by the preparation method described above or the catalyst for synthesizing 2,6-dimethylphenol described above, using methanol, phenol, water and benzoic acid as raw materials, preheating the raw materials and mixing them with a carrier gas, and preparing 2,6-dimethylphenol through an alkylation reaction.

[0019] As described above, the catalyst for synthesizing 2,6-dimethylphenol and the preparation method thereof, and the preparation method of 2,6-dimethylphenol of the present invention have the following beneficial effects:

[0020] (1) The catalyst prepared by the present invention is a mixed catalytic system of Si / Al / Mg and Fe. The Si / Al / Mg part activates methanol molecules, and the Fe part can promote methanol dehydrogenation and electrophilic substitution reaction with phenol substrate. The reaction temperature is reduced by the combined action of the two catalysts with different mechanisms.

[0021] (2) After preparation, the catalyst of the present invention is processed into a surface structure with 2-50 nm mesopores by alkali treatment and acid treatment. The alkali treatment and acid treatment increase the ratio of Mg to Fe on the catalyst surface and increase the catalyst activity. In addition to the increase in specific surface area, the mesoporous structure enables the catalyst to have better selectivity for the catalytic alkylation of substrate phenol, and the byproduct 2,4,6-trimethylphenol is reduced.

[0022] (3) The catalyst of the present invention is loaded with a small amount of copper catalyst by impregnation. This part of the catalyst can catalyze the reaction of free active carbon atoms with water to generate CO, thereby reducing carbon deposits generated by the reaction.

[0023] (4) When the catalyst prepared by the present invention is used to produce 2,6-dimethylphenol, benzoic acid is added at the same time. Benzoic acid competes with phenol / o-phenol / xylenol for reaction sites to hinder the reaction, thereby enhancing the reaction selectivity. It is difficult for xylenol to be further methylated to trimethylphenol, thereby improving the selectivity of 2,6-dimethylphenol. DETAILED DESCRIPTION

[0024] In order to make the purpose of the invention, technical solutions and beneficial technical effects of the present invention clearer, the present invention is further described in detail below in conjunction with embodiments. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0025] The first aspect of the present invention is to provide a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, the preparation method comprising the following steps:

[0026] (1) mixing an iron salt, an aluminum salt, a magnesium salt, an acidic substance and water to obtain a solution A;

[0027] (2) mixing sodium silicate, a template and water to obtain a solution B;

[0028] (3) mixing the solution A obtained in step (1) and the solution B obtained in step (2), and aging them to obtain a slurry;

[0029] (4) crystallizing the slurry obtained in step (3), filtering, drying, calcining, and screening to obtain a catalyst precursor 1; the crystallization time is greater than 3 hours;

[0030] (5) mixing the catalyst precursor 1 obtained in step (4) with the alkaline solution, and filtering to obtain the catalyst precursor 2;

[0031] (6) The catalyst precursor 2 is then mixed with the acidic solution, filtered to obtain a solid, and the solid is washed and calcined to obtain a catalyst.

[0032] The catalyst of the present invention is a composite catalyst system of Mg / Fe oxide, wherein the MgO part increases the nucleophilicity of phenol by activating the hydroxyl group of phenol, and promotes the selective attack of methanol on the ortho position to affect the methylation reaction. MgO activates methanol through its alkaline site to form a methoxy substance that can methylate phenol. The alkaline property of MgO can also inhibit overmethylation by reducing the reactivity of the methylation site, thereby facilitating selective dimethylation.

[0033] The Fe2O3 moiety helps activate methanol by promoting its dehydrogenation to formaldehyde or methoxy species, and can play a role in the reaction as an electrophilic reagent for phenol methylation. The Fe2O3 supported on the porous material can enhance the surface area and dispersion of the active iron sites, and its redox properties can regulate the release of methylated species in a controlled manner, thereby reducing polyalkylation. The addition of the Fe component can regulate the acidity of silica / alumina / magnesia to enhance the selective methylation activity of the 2,6-dimethylphenol position.

[0034] In step (3), solution A and solution B are mixed and continuously stirred to form a preliminary cross-linked gel, which is helpful for crystallization in the subsequent step.

[0035] The phenol-methanol gas phase alkylation method generally uses a Mg-based catalyst or a Fe-based catalyst, and uses an impregnation method to load other metal additives. However, the catalyst obtained by calcination has a dense structure and has formed a complete crystal form. During the alkali metal impregnation process, the interaction between the loaded metal and the main active component of the catalyst is weak, which affects the dispersion effect, and the alkali metal is easy to migrate and lose during the reaction, thereby reducing the stability and life of the main catalyst. Therefore, before loading the catalyst, the catalyst substrate needs to be subjected to a certain surface treatment.

[0036] Steps (5) and (6) of the present invention are to treat the catalyst in an alkaline solution, dissolve the Si and Al components on the solid surface, so that a mesoporous structure appears on the catalyst solid surface, and then treat the catalyst solid in an acidic solution to further expand and homogenize the pores on the catalyst solid surface. Specifically, the present invention first uses an alkaline environment to wash the catalyst containing Si / Al components, and as the Si / Al components dissolve to produce a pore structure, the Mg / Fe ratio on the catalyst surface also increases. Second, the catalyst after alkali treatment is treated in an acidic environment again. This step adjusts the pH of the catalyst surface, further expands the pore size and makes the pore size uniform. By this method, mesopores with a diameter of 5-50nm can be introduced into the catalyst, the specific surface area of ​​the catalyst is greatly increased, and the catalytic activity is enhanced. Compared with the microporous structure of conventional zeolite catalysts before treatment, the molecular diffusion resistance of the mesoporous catalyst is smaller, and the reactant molecules are more likely to contact the active sites inside the catalyst, thereby increasing the catalyst efficiency. At the same time, the product molecules diffuse out of the catalyst faster, reducing the possibility of secondary reactions and improving the selectivity of the main reaction. The change in pore size also improves the catalyst's ability to resist carbon deposition. The effective shape, size and tortuous structure of the pores can prevent the formation and accumulation of condensates, thereby increasing the catalyst's carbon capacity. In addition, the present invention also loads CuO on the catalyst through impregnation as a catalyst for eliminating carbon deposition, thereby further improving the catalyst's service life.

[0037] In some embodiments of the present invention, the iron salt in step (1) is selected from one or more of ferric sulfate, ferric nitrate, and ferric chloride; preferably, the iron salt is ferric nitrate;

[0038] In some embodiments of the present invention, the magnesium salt in step (1) is selected from one or more of magnesium sulfate, magnesium nitrate, and magnesium chloride; preferably, the magnesium salt is magnesium nitrate;

[0039] In some embodiments of the present invention, the aluminum salt in step (1) is selected from one or more of aluminum sulfate, aluminum nitrate, and aluminum chloride; preferably, the aluminum salt is selected from aluminum nitrate;

[0040] In some embodiments of the present invention, the molar ratio of magnesium salt, aluminum salt and iron salt in step (1) is 1:0.1-3:0.5-5; specifically, the molar ratio of magnesium salt, aluminum salt and iron salt can be 1:0.1-2:0.5-3, 1:2-3:3-5; typically but not limiting, for example, 1:0.1:0.5, 1:2:3, 1:3:5.

[0041] In some embodiments of the present invention, the amount of water added in step (1) is based on the dissolution of solid salt. Specifically, different solubilities are achieved according to different salt ratios. Generally, 250 g of total solid salt is added with 250-1250 g of water. The solubility varies according to different salt ratios. More specifically, the mass ratio of the mixed solid salt to water can be 1:1-5.

[0042] In some embodiments of the present invention, the acidic substance in step (1) is selected from one or more of sulfuric acid, nitric acid, hydrochloric acid, and ammonium chloride; preferably, the acidic substance is ammonium chloride.

[0043] In some embodiments of the present invention, the molar ratio of the aluminum salt to the acidic substance in step (1) is 1:5-30; specifically, the molar ratio of the aluminum salt to the acidic substance can be 1:5-10, 1:10-20, 1:20-30; typically but not limiting, for example, 1:5, 1:10, 1:20, 1:30.

[0044] In some embodiments of the present invention, the sodium silicate in step (2) is selected from one or more of sodium orthosilicate, sodium metasilicate, sodium orthosilicate hydrate, and sodium metasilicate hydrate; preferably, the sodium silicate is sodium silicate nonahydrate.

[0045] In some embodiments of the present invention, the template in step (2) is selected from one or more of tetrapropylammonium hydroxide, hexadecyltrimethylammonium bromide, and N-octadecyl-N'-hexyl-tetramethyl-1,6-hexanediammonium; preferably, the template is tetrapropylammonium hydroxide.

[0046] In some embodiments of the present invention, the molar ratio of aluminum salt to sodium silicate in step (2) is 1:5-50; specifically, the molar ratio of aluminum salt to sodium silicate can be 1:5-20, 1:20-40, 1:40-50; typically but not limiting, for example, 1:5, 1:20, 1:40, 1:50.

[0047] In some embodiments of the present invention, the molar ratio of sodium silicate to template in step (2) is 1:0.001-0.05; specifically, the molar ratio of sodium silicate to template can be 1:0.001-0.02, 1:0.02-0.04, 1:0.04-0.05; typically but not limiting, for example, 1:0.001, 1:0.02, 1:0.04, 1:0.05.

[0048] In some embodiments of the present invention, the amount of water added in step (2) is based on the standard of completely dissolving the sodium silicate. The sodium silicate concentration of the present invention has little effect on the subsequent gel crystallization. Specifically, according to the solubility of sodium silicate, 1500-2000g of water is required to completely dissolve 600g of sodium silicate at room temperature. More specifically, the mass ratio of sodium silicate to water can be 1:2-4.

[0049] In some embodiments of the present invention, the mixing temperature in step (3) is 20-25°C, specifically, the mixing temperature can be 20-23°C, 23-25°C; typically but not limitatively, for example, 20°C, 23°C, 25°C; the mixing time is 5-30min; specifically, the mixing time can be 5-15min, 15-30min, typically but not limitatively, for example, 5min, 15min, 30min.

[0050] In some embodiments of the present invention, the aging temperature in step (3) is 30-80°C, specifically, the aging temperature can be 30-50°C, 50-80°C; typically but not limitatively, for example, 30°C, 50°C, 80°C; the aging time is 0.5-3h; specifically, the aging time can be 0.5-2h, 2-3h, typically but not limitatively, for example, 0.5h, 2h, 3h.

[0051] In some embodiments of the present invention, the crystallization temperature in step (4) is 100-250°C, specifically, the crystallization temperature can be 100-150°C, 150-250°C; typically but not limiting, for example, 100°C, 150°C, 250°C; the crystallization time is 10-48h; specifically, the crystallization time can be 10-15h, 15-30h, 30-48h; typically but not limiting, for example, 10h, 15h, 30h, 48h. After the crystallization, the material is poured out and filtered to obtain a solid powder, and the solid is washed 3 times with deionized water and then dried.

[0052] In some embodiments of the present invention, the drying temperature in step (4) is 70-150°C, specifically, the drying temperature can be 70-110°C, 110-150°C; typically but not limiting, for example, 70°C, 110°C, 150°C; the drying time is 25-40 minutes. The drying is carried out in an oven.

[0053] In some embodiments of the present invention, the calcination temperature in step (4) is 500-650°C; specifically, the calcination temperature can be 500-550°C, 550-600°C, 600-650°C; typically but not limiting, for example, 500°C, 550°C, 600°C, 650°C; the calcination time is 1-5h; specifically, the calcination time can be 1-3h, 3-5h; typically but not limiting, for example, 1h, 3h, 5h. The calcination is carried out in a muffle furnace. The purpose of the calcination is to remove bound water in the catalyst.

[0054] In some embodiments of the present invention, the particle size of the catalyst precursor 1 in step (4) is ≤150 μm.

[0055] In some embodiments of the present invention, the alkaline solution in step (5) is one or more of a sodium hydroxide solution or a potassium hydroxide solution. Preferably, the molar concentration of the sodium hydroxide solution is 0.1-2 mol / L.

[0056] In some embodiments of the present invention, the alkaline solution in step (5) needs to soak the catalyst, and the alkaline solution can be excessive and can be used multiple times. Specifically, the mass ratio of the catalyst to the alkaline solution in step (5) can be 1:0.5-10;

[0057] In some embodiments of the present invention, the mixing temperature in step (5) is 50-100° C.; and the mixing time is 0.5-3 h.

[0058] In some embodiments of the present invention, the filtration in step (5) further requires washing and drying.

[0059] In some embodiments of the present invention, the drying temperature in step (5) is 70-150° C. and the drying time is 30-90 min.

[0060] In some embodiments of the present invention, the acidic solution in step (6) is selected from one or more of oxalic acid solution, nitric acid solution, and hydrochloric acid solution. Preferably, the acidic solution is oxalic acid solution. More preferably, the mass percentage concentration of the oxalic acid solution is 5-20%.

[0061] In some embodiments of the present invention, the acidic solution in step (6) is only needed to soak the catalyst precursor 2, and the acidic solution can be used in excess and multiple times. Specifically, the mass ratio of the catalyst precursor 2 to the acidic solution in step (6) is 1:0.5-10;

[0062] In some embodiments of the present invention, the mixing temperature in step (6) is 50-100° C.; the mixing time is 1-5 h;

[0063] In some embodiments of the present invention, the calcination temperature in step (6) is 500-650°C; specifically, the calcination temperature can be 500-550°C, 550-600°C, 600-650°C; typically but not limitatively, for example, 500°C, 550°C, 600°C, 650°C; the calcination time is 1-5h; specifically, the calcination time can be 1-3h, 3-5h; typically but not limitatively, for example, 1h, 3h, 5h.

[0064] In some embodiments of the present invention, the washing is performed until the pH of the washing solution is greater than 6.

[0065] In some embodiments of the present invention, step (6) further includes step (7), specifically, mixing the catalyst obtained in step (6) with a copper salt aqueous solution, adjusting the pH to alkaline, ultrasonicating, filtering to obtain a solid, washing, and calcining to obtain the solid.

[0066] Carbon deposition and deactivation of alkylation catalysts are inevitable. The main reason for catalyst deactivation is that the macromolecular polycyclic aromatic hydrocarbons generated during the alkylation reaction cover the active sites of the catalyst and block the pores. Selecting an ideal catalyst and optimizing the reaction conditions are the basic ways to inhibit carbon deposition.

[0067] In addition to the reactants phenol and methanol, there is also water in the reaction materials. On the one hand, it serves as a heat carrier. The ortho-methylation reaction of phenol is a strong exothermic reaction, which can reduce the occurrence of temperature runaway. On the other hand, the presence of water can inhibit coking and remove coke through the reaction C+H2O→CO+H2 when coking has already occurred on the catalyst surface. The presence of water can reduce the impact of catalyst carbon deposition to a certain extent, but during the long-term operation of the reaction, the coke accumulated in the pores will still reduce the catalyst surface area and affect the catalytic efficiency.

[0068] The present invention uses a CuO component loaded on a fired and surface-treated catalyst by impregnation as a catalyst for the coke oxidation process, thereby effectively inhibiting the carbon deposition process and further improving the service life of the catalyst.

[0069] In some embodiments of the present invention, the catalyst is added to the prepared copper salt solution, stirred for 1-15 minutes to make the solid and liquid mix evenly while the solution completely infiltrates the catalyst. Maintain stirring, slowly add alkaline water at a uniform speed within 10 minutes, then continue stirring for 5-30 minutes, and then use ultrasonic treatment for 2-30 minutes to ensure that the precipitate is evenly loaded on the catalyst surface, and then the material is sealed and placed at room temperature for 2-6 hours. The solution in the system is separated by pouring, distilled water is added to the remaining solid for washing, the pH value of the poured liquid is tested with pH test paper, and the pouring liquid is repeatedly washed until the pH of the poured liquid is less than 10. The washed solid is then filtered out and dried, and the solid is transferred to a muffle furnace. After calcination at 500-650°C for 1-5 hours, the powder solid is tableted and crushed, and 40-60 mesh particles are screened out using a sieve and stored in a dryer.

[0070] In some embodiments of the present invention, the copper salt in step (7) is selected from one or more of copper sulfate, copper nitrate and copper chloride; preferably, the copper salt is copper nitrate.

[0071] In some embodiments of the present invention, the mass percentage concentration of the copper salt solution in step (7) is 0.5-10%.

[0072] In some embodiments of the present invention, the molar ratio of the magnesium salt to the copper salt in step (7) is 1:0.02-2; specifically, the molar ratio may be 1:0.02-1, 1:1-2; typically but not limiting, for example, 1:0.02, 1:1, 1:2.

[0073] In some embodiments of the present invention, an alkaline substance is used to adjust the pH in step (7); preferably, the alkaline substance is selected from one or more of sodium hydroxide and potassium hydroxide; further preferably, the alkaline substance is sodium hydroxide; and the mass percentage concentration of the alkaline substance is 0.5-5%.

[0074] In some embodiments of the present invention, the power of ultrasound in step (7) is 200-1000w; the time of ultrasound is 2-30min; the instrument of ultrasound is an ultrasonic disperser; and ultrasonic treatment is used to assist dispersion so as to make the copper oxide evenly loaded on the catalyst surface.

[0075] In some embodiments of the present invention, after the ultrasound in step (7), the film is sealed and allowed to stand for 2-6 hours.

[0076] In some embodiments of the present invention, the washing in step (7) is washing until the pH of the washing solution is less than 10.

[0077] In some embodiments of the present invention, the calcination temperature in step (7) is 500-650°C; specifically, the calcination temperature can be 500-550°C, 550-600°C, 600-650°C; typically but not limitatively, for example, 500°C, 550°C, 600°C, 650°C; the calcination time is 1-5h; specifically, the calcination time can be 1-3h, 3-5h; typically but not limitatively, for example, 1h, 3h, 5h.

[0078] The second aspect of the present invention is to provide a catalyst for synthesizing 2,6-dimethylphenol, which is prepared by the preparation method as described above.

[0079] In some embodiments of the present invention, the ratio of elements Si:Al:Mg:Fe:Cu in the catalyst is 10-40:0.5-5:1:0.5-5:0.01-0.5. Specifically, the ratio of elements Si:Al:Mg:Fe:Cu in the catalyst can be 10-15:0.5-0.8:1:0.5-2:0.01-0.05, 15-25:0.8-1.2:1:2-3:0.05-0.2, 25-40:1.2-5:1:3-5:0.2-0.5; typically but not limiting, for example, 10:0.5:1:0.5:0.01, 15:0.8:1:2:0.05, 25:1.2:1:2:0.2, 40:5:1:5:0.5.

[0080] In some embodiments of the present invention, the catalyst has a specific surface area of ​​300-500 m 2 / g, bulk density is 0.5-1g / cm 3 .

[0081] The third aspect of the present invention is to provide a method for preparing 2,6-dimethylphenol, comprising the following steps: in the presence of the catalyst for synthesizing 2,6-dimethylphenol prepared by the preparation method described above or the catalyst for synthesizing 2,6-dimethylphenol described above, using methanol, phenol, water and benzoic acid as raw materials, preheating the raw materials and mixing them with a carrier gas, and preparing 2,6-dimethylphenol through an alkylation reaction.

[0082] Specifically, the present invention loads the prepared catalyst into a reactor, and the reaction raw materials are quantitatively fed through a metering pump after mixing. After preheating, the raw materials are gasified and mixed with a carrier gas to enter the reactor. After the raw gas is fully reacted in the catalyst layer, a small amount of product gas enters the detection device through a branch to detect and record the gas phase composition in real time, and the remaining gas is cooled and collected in liquid phase to enter the post-processing link to obtain the product 2,6-dimethylphenol. The detection device is a gas chromatograph.

[0083] The reaction mechanism of phenol and methanol on solid acid catalysts is generally accepted and controversial, which are two different reaction mechanisms, namely the step-by-step mechanism and the synergistic mechanism. Both mechanisms believe that methanol is first connected to the B acid site of the solid acid catalyst through physical adsorption (hydrogen bond), and further reacts with phenol adsorbed on the catalyst surface, thereby ensuring the selectivity of the alkylation reaction at the ortho position. The only difference lies in the intermediate state of the reaction. Phenol-o-cresol-xylenol, the alkylation reaction activity decreases in sequence, which is related to the difference in the ability of the three to bind to the catalyst. The main by-product of the reaction, 2,4,6-trimethylphenol, is obtained by the reaction of the product xylenol.

[0084] As the methanol ratio increases, the tendency of polymethylation increases. As the space velocity increases, the conversion rate and selectivity decrease. The space velocity of the phenol solution also affects the reaction. Not only will the reaction be incomplete if the space velocity is too high, but the production capacity will also decrease when the space velocity is too low, the amount of trimethylation products generated will increase, and the decomposition of methanol will also become serious.

[0085] The present invention can effectively increase the selectivity of the reaction and reduce the proportion of the byproduct 2,4,6-trimethylphenol by adding an auxiliary agent benzoic acid into the system to participate in the competition between phenol / o-cresol / xylenol and the catalyst.

[0086] In some embodiments of the present invention, the reaction temperature is 310-390°C; specifically, it can be 310-350°C, 350-390°C, typically but not limiting, for example, 310°C, 390°C.

[0087] In some embodiments of the present invention, the molar ratio of methanol, phenol, water and benzoic acid is 1:(0.5-5):(0.1-2):(0.01-0.5); specifically, it can be 1:0.5-2.4:0.1-0.4:0.01-0.2, 1:2.4-2.5:0:4-0.5:0.2-0.3, 1:2.5-2.6:0.5-0.6:0.3-0.4, 1:2.6-6:0.6-2:0.4-0.5; typical but non-limiting, for example, 1:0.5:0.1:0.01, 1:2.4:0.4:0.2, 1:2.5:0.5:0.3, 1:2.6:0.6:0.4, 1:5:2:0.5.

[0088] In some embodiments of the present invention, the preheating temperature is 200-350°C; specifically, the preheating temperature may be 200-280°C, 280-350°C; typically but not limiting, for example, 200°C, 280°C, 350°C.

[0089] In some embodiments of the present invention, the alkylation reaction is carried out in a fixed bed reactor.

[0090] In some embodiments of the present invention, the mass space velocity of the reaction is 1.2-1.5h -1 .

[0091] In some embodiments of the present invention, the carrier gas is selected from nitrogen or helium, and preferably, the carrier gas is nitrogen.

[0092] The present invention is further described below by way of examples, but the scope of the present invention is not limited thereto.

[0093] When the embodiment gives a numerical range, it should be understood that, unless otherwise specified in the present invention, the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. If specific conditions are not specified in the embodiment, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for all reagents or instruments, they are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, according to the grasp of the prior art by those skilled in the art and the record of the present invention, any method, equipment, and material of the prior art similar or equivalent to the method, equipment, and material in the embodiments of the present invention can also be used to realize the present invention.

[0094] In the following example, the yield calculation method is actual yield / theoretical yield × 100%, and the purity determination method is gas chromatography, chromatographic column SK-5, chromatographic column temperature 50°C, retention time 2min, heating rate 10°C / min to 150°C, and then heating rate 20°C / min to 300°C, and final temperature retention time 10min.

[0095] The crystallization kettle of the present invention is a 5L high-pressure hydrothermal reaction kettle.

[0096] The gas chromatograph of the present invention is Shimadzu GC-2010.

[0097] The catalytic reaction device of the present invention is a fixed bed reaction device. The present invention has no special limitation on the source and use conditions of the device. The reaction device commonly used in the art can be used. Specifically, the manufacturer of the fixed bed reaction device used in the present invention is Shanghai Yanzheng Experimental Instrument Co., Ltd.

[0098] The tetrapropylammonium hydroxide of the present invention is abbreviated as TPAOH.

[0099] Example

[0100] Example 1

[0101] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, comprising the following steps:

[0102] (1) 80.8 g of Fe(NO3)3·9H2O, 37.5 g of Al(NO3)3·9H2O, 25.6 g of Mg(NO3)2·6H2O and 107 g of ammonium chloride were dissolved in 500 g of water to prepare solution A;

[0103] (2) 568 g of Na2SiO3·9H2O and 5 g of TPAOH were added to 1500 g of water and dissolved to obtain solution B;

[0104] (3) slowly dropping solution A into solution B under normal temperature and stirring to obtain a reaction slurry, turning on the heating to heat the reaction slurry to 50° C., stirring and keeping the temperature for aging for 1 hour to obtain a slurry;

[0105] (4) The slurry was transferred to a 10L hydrothermal reactor and crystallized at 200°C for 12 hours. During this period, the reactor was slowly stirred for 5 minutes every 2 hours. The solid and liquid phases were then mixed by stirring. The material was filtered, washed, and dried, and then calcined in a muffle furnace at 540°C for 6 hours. Large catalyst particles larger than 100 mesh were sieved to obtain a catalyst precursor 1.

[0106] (5) suspending the catalyst precursor 1 in a 0.2 mol / L NaOH solution, stirring and treating at 80° C. for 3 h to obtain a mixture, then cooling the mixture, washing with deionized water, and then drying at 110° C. to obtain a catalyst precursor 2;

[0107] (6) treating the catalyst precursor 2 with acid in a 15% oxalic acid solution, stirring at 90° C. for 4 h, filtering out the solid, repeatedly washing the solid with distilled water until the acid is completely eliminated, filtering out the solid and drying it at 90° C., and finally calcining it at 550° C. for 1 h to obtain a catalyst;

[0108] (7) Dissolve 12.1 g of Cu(NO3)2·3H2O in 200 g of water to obtain a copper nitrate solution. Add the catalyst to the copper nitrate solution, stir and mix, then add 1% sodium hydroxide aqueous solution until the pH value of the solution is greater than 12. Keep stirring and ultrasonicate the system for 15 min. Seal the film and place it at room temperature for 4 h. Pour the liquid in the container to obtain a solid substance. Wash the solid substance with deionized water until the aqueous solution is neutral. Then calcine at 550°C for 3 h. Press the obtained powder solid into tablets and crush them. Use a sieve to screen out 40-60 mesh particles and store them in a desiccator to obtain a loaded catalyst.

[0109] (II) This application example provides a method for preparing 2,6-dimethylphenol, comprising the following steps:

[0110] Take 10g of the loaded catalyst prepared in Example 1 and load it into a stainless steel fixed bed reactor. The molar ratio of phenol, methanol, water and benzoic acid is 1:2.5:0.5:0.3. The raw materials are quantitatively fed through a metering pump after mixing. After preheating, the raw materials are mixed with a carrier gas and enter the catalyst bed for reaction. The reaction temperature is controlled at 310°C, nitrogen with a flow rate of 15mL / min is used as the carrier gas, the reaction pressure is normal pressure, and the flow rate of the metering pump is adjusted so that the mass space velocity of the raw material phenol is 1.2h -1 The reaction state was maintained to allow the reaction device to operate stably for 2500 h. The tail gas products were analyzed using a gas chromatograph internal standard method. The results are shown in Table 1.

[0111] After the reaction product is condensed and separated from gas and liquid, the gas phase product is washed with water and released, and the liquid phase product is distilled to remove methanol and water to obtain a crude product. The crude product is subjected to vacuum distillation to separate o-cresol and obtain pure 2,6-dimethylphenol product. The kettle residue is dissolved by adding water and sodium hydroxide solution is added to adjust the pH to precipitate benzoic acid and recover it. In the experiment, 30.4 kg (99%) of phenol was consumed in 2500 hours, and 32.0 kg (99.5%) of product was obtained, with a total yield of 80.8%.

[0112] Table 1 Detection results of tail gas products after stable operation for 2500h in Example 1 experiment

[0113]

[0114] Example 2

[0115] (i) The preparation method of a catalyst for synthesizing 2,6-dimethylphenol in this embodiment is exactly the same as that in Example 1.

[0116] (II) This embodiment provides a method for preparing 2,6-dimethylphenol, comprising the following steps: 10 g of the catalyst prepared in Example 1 is loaded into a stainless steel fixed bed reactor, the raw material molar ratio is phenol: methanol: water: benzoic acid = 1: 2.5: 0.5: 0.3, and the raw materials are quantitatively fed through a metering pump after mixing. After preheating, the raw materials are mixed with a carrier gas and enter the catalyst bed for reaction. The reaction temperature is controlled at 390°C, nitrogen with a flow rate of 20 mL / min is used as the carrier gas, the reaction pressure is normal pressure, and the flow rate of the metering pump is adjusted so that the mass space velocity of the raw material phenol is 1.5 h -1 , maintaining the reaction state so that the reaction device can run stably for 2500h, and the tail gas products are analyzed using the internal standard method of gas chromatography. The results are shown in the table below.

[0117] After the reaction product is condensed and separated from gas and liquid, the gas phase product is washed with water and released, and the liquid phase product is distilled to remove methanol and water to obtain a crude product. The crude product is subjected to vacuum distillation to separate o-cresol and obtain pure 2,6-dimethylphenol product. The still residue is dissolved by adding water and adjusting the pH to precipitate benzoic acid and recover it. In the experiment, 30.6 kg (99%) of phenol was consumed in 2500 hours, and 36.2 kg (99.5%) of product was obtained, with a total yield of 93.6%.

[0118] Table 2 Tail gas product detection results of Example 2 experimental stable operation for 2500h

[0119]

[0120]

[0121] In combination with Example 1 and Example 2, and in combination with Table 1 and Table 2, Example 1 uses the corresponding catalyst and reacts at 310°C, which is convenient for effectively reducing the influence of carbon deposition, greatly reducing the amount of byproduct 2,4,6-trimethylphenol, and even the amount of byproduct 2,4,6-trimethylphenol generated within 1000h of stable operation is almost negligible. Even when it is stably operated for 2500h, the content of byproduct 2,4,6-trimethylphenol is also extremely low, and the phenol and o-cresol recovered from the product can be combined into the next batch reaction, achieving a higher atomic utilization rate, which is in line with the concept of green production; Example 2 uses a higher reaction temperature compared to Example 1. Under this condition, the conversion rate of phenol is higher. At the same time, the reaction selectivity is taken into account, so that the content of byproduct 2,4,6-trimethylphenol is controlled at about 5%. The product post-treatment only needs to simply remove a small amount of raw materials in the distillation head to obtain a pure 2,6-dimethylphenol product. Under this condition, the catalyst works stably for at least 2000h, which can meet most production needs.

[0122] Example 3 Synthesis of 2,6-dimethylphenol without benzoic acid

[0123] (i) The preparation method of a catalyst for synthesizing 2,6-dimethylphenol in this embodiment is exactly the same as that in Example 1.

[0124] (II) This embodiment provides a method for preparing 2,6-dimethylphenol, comprising the following steps:

[0125] 10 g of the catalyst prepared in Example 1 was loaded into a stainless steel fixed bed reactor, the raw material molar ratio was phenol:methanol:water=1:2.5:0.5, and the raw materials were quantitatively fed through a metering pump after mixing. After preheating, the raw materials were mixed with a carrier gas and entered the catalyst bed for reaction. The reaction temperature was controlled at 310°C, nitrogen with a flow rate of 15 mL / min was used as the carrier gas, the reaction pressure was normal pressure, and the flow rate of the metering pump was adjusted so that the mass space velocity of the raw material phenol was 1.2 h -1 , maintaining the reaction state so that the reaction device can run stably for 2500h, and the tail gas products are analyzed using the internal standard method of gas chromatography. The results are shown in the table below.

[0126] After the reaction product was condensed and separated from gas and liquid, the gas phase product was released after washing with water, and the liquid phase product was distilled to remove methanol and water to obtain a crude product. The crude product was subjected to vacuum distillation to separate o-cresol and obtain pure 2,6-dimethylphenol product. In the experiment, 30.7 kg (99%) of phenol was consumed in 2500 hours, and 35.1 kg (99.5%) of product was obtained, with a total yield of 92.1%.

[0127] Table 3 Tail gas product detection results of Example 3 experiment stable operation 2500h

[0128]

[0129]

[0130] Combining Example 1 and Example 3, and combining the data in Table 1 and Table 3, it can be seen that Example 1 and Example 3 both use the catalyst prepared in Example 1. The difference between Example 1 and Example 3 is that benzoic acid is added in Example 1 when preparing 2,6-dimethylphenol, while benzoic acid is not added in Example 3. In Example 3, the phenol conversion rate is better and the yield of 2,6-dimethylphenol is better, indicating that the catalyst prepared by Example 1 has higher catalytic activity and anti-carbon deposition ability. Compared with Example 1, the addition of benzoic acid can effectively enhance the selectivity of the reaction. Example 3 removes the benzoic acid component in the raw material. Under the same reaction conditions, the conversion rate of phenol is improved but the selectivity of the product is reduced. The impurity o-cresol and the by-product trimethylol are present in large quantities in the components at the same time, requiring distillation twice or the use of a higher tower, which increases the difficulty of post-processing and causes waste of resources.

[0131] Example 4 Comparison of magnesium salt addition amount

[0132] Example 4a

[0133] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that the amount of Mg(NO3)2·6H2O added in step (1) is 20.5 g, and the rest is exactly the same as Embodiment 1.

[0134] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 4a. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0135] Example 4b

[0136] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that the amount of Mg(NO3)2·6H2O added in step (1) is 30.7 g, and the rest is exactly the same as Embodiment 1.

[0137] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 4b. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0138] Table 4 Tail gas product detection results of Example 1 and Example 4a-4b after stable operation for 1h

[0139]

[0140] Combining Example 1, Example 4a, Example 4b, and the data in Table 4, it can be seen that the performance of the catalysts in the process of preparing 2,6-dimethylphenol is not much different, and the 2,6-dimethylphenol prepared thereby contains very few by-products.

[0141] Example 5 Comparison of iron salt addition amount

[0142] Example 5a

[0143] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that the amount of Fe(NO3)3·9H2O added in step (1) is 64.6 g, and the rest is exactly the same as Embodiment 1.

[0144] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 5a. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0145] Example 5b

[0146] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that the amount of Fe(NO3)3·9H2O added in step (1) is 161.6 g, and the rest is exactly the same as Embodiment 1.

[0147] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 5b. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0148] Table 5 Tail gas product detection results of Example 1 and Example 5a-5b after stable operation for 1h

[0149]

[0150] Combining Example 1, Example 5a, Example 5b, and the data in Table 5, it can be seen that the performance of the catalysts in the process of preparing 2,6-dimethylphenol is not much different, and the 2,6-dimethylphenol prepared thereby contains very few by-products.

[0151] Example 6 Crystallization Time Comparison

[0152] Example 6a

[0153] (I) This comparative example provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Example 1 in that the crystallization time in step (4) is 3 h, and the rest is exactly the same as Example 1.

[0154] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 6a. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0155] Example 6b

[0156] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that the crystallization time in step (4) is 48 h, and the rest is exactly the same as Embodiment 1.

[0157] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 6b. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0158] Table 6 Tail gas product detection results of Example 1 and Example 6a-6b after stable operation for 1h

[0159]

[0160] Combining Example 1, Example 6a and Example 6b, and combining the data in Table 6, it can be seen that the content of o-cresol and phenol in the component of Example 6a is relatively high, mainly because the crystallization time of the catalyst of Example 6a is too short during the preparation process. Too short crystallization time can easily lead to poor crystal form of the catalyst and very few catalytic active sites, thereby reducing the activity of the catalyst.

[0161] Example 7 Acid-base treatment comparison

[0162] Example 7a

[0163] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that step (6) is omitted, i.e., no acid treatment is performed, and steps 1-5 and 7 are identical to those of Embodiment 1. Other steps are identical to those of Embodiment 1, as follows:

[0164] (5) suspending the catalyst precursor 1 in a 0.2 mol / L NaOH solution, stirring and treating at 80° C. for 3 h to obtain a mixture, then cooling the mixture, washing with deionized water until the alkali is completely eliminated, then drying at 110° C., and then calcining at 550° C. for 1 h to obtain a catalyst precursor 2;

[0165] (7) Dissolve 12.1 g of Cu(NO3)2·3H2O in 200 g of water to obtain a copper nitrate solution. Add the catalyst precursor II to the copper nitrate solution, stir and mix, then add 1% sodium hydroxide aqueous solution until the pH value of the solution is greater than 12. Keep stirring and ultrasonicate the system for 15 min. Seal the film and place it at room temperature for 4 h. Pour out the liquid in the container to obtain a solid substance. Wash the solid substance with deionized water until the aqueous solution is neutral. Then calcine at 550°C for 3 h. Press the obtained powder solid into tablets and crush them. Use a sieve to sieve out 40-60 mesh particles and store them in a desiccator.

[0166] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 7a. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0167] Example 7b

[0168] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that step (5) is omitted, no alkali treatment is performed, and steps 1-4, 6-7 are exactly the same as those in Embodiment 1, specifically as follows:

[0169] (6) treating the catalyst precursor 1 with acid in a 15% oxalic acid solution, stirring at 90° C. for 4 h, filtering out the solid, repeatedly washing the solid with distilled water until the acid is completely eliminated, filtering out the solid and drying it at 90° C., and finally calcining it at 550° C. for 1 h to obtain a catalyst;

[0170] (7) Dissolve 12.1 g of Cu(NO3)2·3H2O in 200 g of water to obtain a copper nitrate solution. Add the catalyst to the copper nitrate solution, stir and mix, then add 1% sodium hydroxide aqueous solution until the pH value of the solution is greater than 12. Keep stirring and ultrasonicate the system for 15 min. Seal the film and place it at room temperature for 4 h. Pour the liquid in the container to obtain a solid substance. Wash the solid substance with deionized water until the aqueous solution is neutral. Then calcine at 550°C for 3 h. Press the obtained powder solid into tablets and crush them. Use a sieve to screen out 40-60 mesh particles and store them in a desiccator.

[0171] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 7b. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0172] Example 7c

[0173] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that: Step (5) and Step (6) in the embodiment are omitted, that is, the catalyst is directly mixed with copper nitrate trihydrate, and Steps 1-4 and 7 are exactly the same as those in Embodiment 1.

[0174] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 7c. After the reaction device has been running stably for 1 hour, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0175] Table 7 Tail gas product detection results of Example 1 and Example 7a-7c after stable operation for 1h

[0176]

[0177] In combination with Example 1, Examples 7a-7c, and the data in Table 7, it can be seen that the phenol, o-cresol, and by-products in the components of Example 7c are all relatively high, and the yield of 2,6-dimethylphenol is relatively low. The catalyst in Example 7c was not subjected to acid and alkali treatment during preparation, and the specific surface area of ​​the catalyst was relatively small. The catalyst thus prepared was used in the preparation process of 2,6-dimethylphenol, and the catalytic efficiency was relatively low and the selectivity was relatively poor. When the catalyst in Example 1 was prepared, acid and alkali treatment was performed to erode the silicon and aluminum components, exposing more iron and magnesium components, and at the same time, providing the catalyst with surface pores with larger pore sizes. The catalyst activity increased while the selectivity also increased, and the 2,4,6-trimethylphenol by-product was also less.

[0178] Example 8 Comparison of copper salt addition amount

[0179] Example 8a

[0180] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which is different from Embodiment 1 in that: in the step (7), the amount of copper nitrate trihydrate added is 48.4 g, and the mass percentage concentration of the copper nitrate trihydrate aqueous solution is 10%, and the rest is exactly the same as Embodiment 1.

[0181] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 8a. After the reaction device has been running stably for 1 hour and 500 hours, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0182] Example 8b

[0183] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which is different from Embodiment 1 in that: in the step (7), the amount of copper nitrate trihydrate added is 0.5 g, and the mass percentage concentration of the copper nitrate trihydrate aqueous solution is 0.5%. The rest is exactly the same as Embodiment 1.

[0184] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 8b. After the reaction device has been running stably for 1 hour and 500 hours, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0185] Example 8c

[0186] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that step (7) in the embodiment is omitted, that is, the catalyst precursor 2 is directly tableted, crushed and sieved to obtain the catalyst, and steps 1-6 are exactly the same as those in Embodiment 1.

[0187] (II) This application example provides a method for preparing 2,6-dimethylphenol. The difference from Example 1 is that the catalyst used is the catalyst prepared in Example 8c. After the reaction device has been running stably for 1 hour and 500 hours, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Example 1.

[0188] Table 8 Tail gas product detection results of Example 1 and Example 8a-8c after stable operation for 1h and 500h

[0189]

[0190]

[0191] Combining Example 1 and Examples 8a-8c, and combining the data in Table 8, it can be seen that the catalyst in Example 8c has a greatly reduced conversion rate of phenol when the reaction time is 500 hours, and the components contain more phenol and o-cresol, and the yield of 2,6-dimethylphenol is extremely low. Therefore, the CuO loaded on the catalyst has a significant effect on extending the service life of the catalyst.

[0192] Example 9

[0193] (I) This embodiment provides a method for preparing a catalyst for synthesizing 2,6-dimethylphenol, which differs from Embodiment 1 in that: Steps (5) to (7) in the embodiment are omitted, that is, alkali treatment, acid treatment and copper salt treatment are omitted, that is, the catalyst precursor 1 obtained in step (4) is tableted, crushed and sieved to obtain the catalyst, and Steps 1-4 are exactly the same as in Embodiment 1.

[0194] (II) This embodiment provides a method for preparing 2,6-dimethylphenol, which is different from Embodiment 1 in that the catalyst is the catalyst prepared in Embodiment 9, and after the reaction device has been running stably for 1 h and 500 h, the components of the tail gas product are analyzed, and the reaction conversion rate and selectivity are calculated. The rest is exactly the same as Embodiment 1.

[0195] Table 9 Tail gas product detection results of Example 1 and Example 9 after stable operation for 1h and 500h

[0196]

[0197] Combining Example 1 and Example 9, and combining the data in Table 9, it can be seen that in the process of preparing 2,6-dimethylphenol in Example 9, the phenol conversion rate and the selectivity of 2,6-dimethylphenol are relatively low, and the residual amounts of phenol and o-cresol are relatively high, and the performance of each part is worse than that of Example 1. The difference between Example 9 and Example 1 is that the catalyst used in Example 9 is not subjected to alkali treatment, acid treatment and copper salt treatment during preparation, and the catalyst obtained thereby is used in the preparation of 2,6-dimethylphenol, and the overall performance is poor.

[0198] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing a catalyst for synthesizing 2,6-dimethylphenol, characterized in that: The preparation method comprises the following steps: (1) mixing an iron salt, an aluminum salt, a magnesium salt, an acidic substance and water to obtain a solution A; (2) mixing sodium silicate, a template and water to obtain a solution B; the template in step (2) is selected from one or more of tetrapropylammonium hydroxide, hexadecyltrimethylammonium bromide, and N-octadecyl-N'-hexyl-tetramethyl-1,6-hexanediammonium; (3) mixing the solution A obtained in step (1) and the solution B obtained in step (2), and aging them to obtain a slurry; (4) crystallizing the slurry obtained in step (3), filtering, drying, calcining, and screening to obtain a catalyst precursor 1; the crystallization time is greater than 3 hours; (5) mixing the catalyst precursor 1 obtained in step (4) with the alkaline solution, and filtering to obtain the catalyst precursor 2; In step (5), the alkaline solution is one or more of a sodium hydroxide solution or a potassium hydroxide solution; (6) The catalyst precursor 2 is then mixed with the acidic solution, filtered to obtain a solid, and the solid is washed and calcined to obtain a catalyst.

2. The method for preparing a catalyst for synthesizing 2,6-dimethylphenol according to claim 1, characterized in that: The method further comprises step (7) after step (6), wherein step (7) comprises mixing the catalyst obtained in step (6) with a copper salt aqueous solution, adjusting the pH to be alkaline, ultrasonicating, filtering to obtain a solid, washing, and calcining to obtain a supported catalyst.

3. A method for preparing a catalyst for synthesizing 2,6-dimethylphenol according to claim 1, characterized in that: Also includes one or more of the following characteristics: 11) The iron salt in step (1) is selected from one or more of ferric sulfate, ferric nitrate and ferric chloride; 12) The magnesium salt in step (1) is selected from one or more of magnesium sulfate, magnesium nitrate and magnesium chloride; 13) The aluminum salt in step (1) is selected from one or more of aluminum sulfate, aluminum nitrate, and aluminum chloride; 14) The acidic substance in step (1) is selected from one or more of sulfuric acid, nitric acid, hydrochloric acid, and ammonium chloride; 15) The molar ratio of the aluminum salt to the acidic substance in step (1) is 1:5-30; 16) In step (1), the molar ratio of magnesium salt, aluminum salt and iron salt is 1:0.1-3:0.5-5; 21) In step (2), the sodium silicate is selected from one or more of sodium orthosilicate, sodium metasilicate, sodium orthosilicate hydrate, and sodium metasilicate hydrate; 22) In step (2), the molar ratio of aluminum salt to sodium silicate is 1:5-50; 23) In step (2), the molar ratio of sodium silicate to template is 1:0.001-0.05; 31) The mixing temperature in step (3) is 20-25°C and the mixing time is 5-30min; 32) The aging temperature in step (3) is 30-80°C and the aging time is 0.5-3h; 41) In step (4), the crystallization temperature is 100-250° C. and the crystallization time is 10-48 h; 42) In step (4), the drying temperature is 70-150° C. and the drying time is 25-40 min; 43) The calcination temperature in step (4) is 500-650°C; the calcination time is 1-5h; 44) In step (4), the particle size of the catalyst precursor 1 is ≤150 μm.

4. The method for preparing a catalyst for synthesizing 2,6-dimethylphenol according to claim 1, characterized in that: Also includes one or more of the following characteristics: 51) The mixing temperature in step (5) is 50-100°C; the mixing time is 0.5-3h; 61) In step (6), the acidic solution is selected from one or more of oxalic acid solution, nitric acid solution and hydrochloric acid solution; 62) The mixing temperature in step (6) is 50-100°C; the mixing time is 1-5h; 63) In step (6), the calcination temperature is 500-650°C and the calcination time is 1-5h.

5. The method for preparing a catalyst for synthesizing 2,6-dimethylphenol according to claim 2, characterized in that: The step (7) also includes one or more of the following features: 71) In step (7), the copper salt is selected from one or more of copper sulfate, copper nitrate and copper chloride; 72) The mass percentage concentration of the copper salt solution in step (7) is 0.5-10%; 73) In step (7), the molar ratio of magnesium salt to copper salt is 1:0.02-2; 74) In step (7), an alkaline substance is used to adjust the pH; 75) In step (7), the power of ultrasound is 200-1000w; the time of ultrasound is 2-30min; 76) In step (7), washing is performed until the pH of the washing solution is less than 10; 77) In step (7), the calcination temperature is 500-650°C and the calcination time is 1-5h.

6. A catalyst for synthesizing 2,6-dimethylphenol, characterized in that: The method is prepared according to any one of claims 1 to 5.

7. A catalyst for synthesizing 2,6-dimethylphenol according to claim 6, characterized in that: The ratio of the elements Si:Al:Mg:Fe:Cu in the catalyst is 10-40:0.5-5:1:0.5-5:0.01-0.

5.

8. A catalyst for synthesizing 2,6-dimethylphenol according to claim 6, characterized in that: The specific surface area of ​​the catalyst is 300-500m 2 / g, bulk density is 0.5-1g / cm 3 .

9. A method for preparing 2,6-dimethylphenol, characterized in that: The method comprises the following steps: in the presence of a catalyst for synthesizing 2,6-dimethylphenol prepared by the preparation method according to any one of claims 1 to 5 or a catalyst for synthesizing 2,6-dimethylphenol according to any one of claims 6 to 8, using methanol, phenol, water and benzoic acid as raw materials, preheating the raw materials and mixing them with a carrier gas, and preparing 2,6-dimethylphenol through an alkylation reaction.

10. The method for preparing 2,6-dimethylphenol according to claim 9, characterized in that: Also includes one or more of the following characteristics: S1, the reaction temperature is 310-390°C; S2, the molar ratio of the methanol, phenol, water and benzoic acid is 1:(0.5-5):(0.1-2):(0.01-0.5); S3, the preheating temperature is 200-350°C; S4, the alkylation reaction is carried out in a fixed bed reactor; S5, the mass space velocity of the reaction is 1.2-1.5h -1 ; S6. The carrier gas is selected from nitrogen or helium.

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