A catalyst for synthesizing 2,6-dimethylphenol and a preparation method thereof

Abstract

The application provides a catalyst for synthesizing 2,6-dimethylphenol and a preparation method thereof. The catalyst comprises iron oxide, germanium oxide, aluminum oxide, and alkali metal and / or alkaline earth metal oxide. The preparation method comprises the following steps: dissolving germanium dioxide in a hot alkaline solution to obtain a germanium-containing solution; mixing the germanium-containing solution with a mixed solution of iron salt and aluminum salt, adding ammonia water for co-precipitation, so that the pH value of the reaction system reaches 7.0; after aging and solid-liquid separation, a precipitate is obtained; the precipitate is added into a solution of alkali metal salt and / or alkaline earth metal salt, and stirring is performed to form a slurry; and then, the slurry is subjected to standing, drying and calcination to obtain the catalyst. The catalyst has the advantages of high catalytic activity, high selectivity of 2,6-dimethylphenol, and the like, can reduce the methanol decomposition rate, and the preparation method of the catalyst is simple and has good repeatability.

Description

Technical Field

[0001] This invention relates to a catalyst for the synthesis of 2,6-dimethylphenol and its preparation method, belonging to the field of 2,6-dimethylphenol synthesis technology. Background Technology

[0002] 2,6-Dimethylphenol (2,6-DMP) is an important chemical raw material and fine chemical intermediate, used in the synthesis of engineering plastics polyphenylene oxide (PPO) and modified polyphenylene oxide (MPPO). PPO is an excellent thermoplastic, resistant to high temperatures and acids and alkalis, and is one of the five major engineering plastics. 2,6-DMP is also a raw material and intermediate for some pharmaceuticals, and can be used to synthesize 2,6-dimethylaniline and the antioxidant Lowinox 44M 26.

[0003] Currently, the vapor-phase alkylation of phenol with methanol is the main method for synthesizing 2,6-DMP. Catalysts for the synthesis of 2,6-DMP are mainly divided into two categories: Mg-based catalysts and Fe-based catalysts. Mg-based catalysts operate at high temperatures (above 400℃) and have high activity, but are prone to deactivation at high temperatures and have low selectivity. Fe-based catalysts operate at low temperatures (350℃), but have a high methanol decomposition rate and low catalyst stability. Existing technologies can improve catalyst stability by introducing components such as Mg, Cr, Mn, Zn, and In, but the problem of high methanol decomposition rate remains unresolved.

[0004] US4329517 discloses an Fe-Ge catalyst system. The preparation method of this catalyst system mainly involves first preparing an iron sol using a precipitation method, then mixing the iron sol with a germanium raw material, followed by drying and calcination to obtain the catalyst system. After 300 hours of operation, the phenol conversion rate and 2,6-DMP selectivity of this catalyst system showed a decreasing trend. This method first prepares an iron precipitate, then mixes and grinds the iron and germanium components to promote mixing. However, the effect of physical grinding and mixing is limited, resulting in insufficient germanium doping for optimal reaction performance. Furthermore, the fine powder forming process is complex, requiring the addition of binders and other forming aids, increasing the difficulty of catalyst forming and ultimately leading to low reproducibility and unstable catalyst performance.

[0005] CN109833878A discloses a Fe-Cr-Si-Ce-Ge-K six-membered iron-based catalyst. The preparation method of this catalyst includes adding germanium dioxide dispersed in water to a reacted iron precipitate system, stirring to ensure thorough mixing of the components, followed by drying and calcination. The resulting solid is then dispersed in a potassium-containing solution for impregnation, and subsequently dried, calcined, and granulated to obtain the catalyst. However, the catalyst exhibits a maximum selectivity of only 95.4% for 2,6-dimethylphenol after 200 hours of reaction, and its stability has not been verified.

[0006] Therefore, developing a novel catalyst for the synthesis of 2,6-dimethylphenol and its preparation method remains one of the urgent problems to be solved in this field. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a catalyst for the synthesis of 2,6-dimethylphenol and a method for its preparation. This catalyst possesses advantages such as high catalytic activity and high selectivity for 2,6-dimethylphenol, and its preparation method is simple and reproducible.

[0008] To achieve the above objectives, a first aspect of the present invention provides a catalyst for the synthesis of 2,6-dimethylphenol, the catalyst comprising the following components: iron oxide, germanium oxide, aluminum oxide, and alkali metal oxide and / or alkaline earth metal oxide, wherein the molar ratio of each component is iron:germanium:aluminum:alkali metal and / or alkaline earth metal = 100:(0.4-4):(0.4-4):(0.1-1).

[0009] In the catalyst described above, preferably, the molar ratio of each component is iron: germanium: aluminum: alkali metal and / or alkaline earth metal = 100:(1-3):(1-3):(0.1-1).

[0010] In the catalysts described above, preferably, the alkali metal oxides and / or alkaline earth metal oxides include one or more oxides of calcium, sodium, and potassium.

[0011] According to a specific embodiment of the present invention, preferably, the catalyst is prepared by the following steps:

[0012] (1) Dissolve germanium dioxide in a hot alkaline solution to obtain a germanium-containing solution;

[0013] (2) The germanium-containing solution is mixed with a mixed solution of iron and aluminum salts, and then ammonia is added to carry out a co-precipitation reaction to make the pH value of the reaction system reach 7.0. After aging and solid-liquid separation, the precipitate is obtained.

[0014] (3) The precipitate is added to a solution of alkali metal salt and / or alkaline earth metal salt and stirred to form a slurry. After standing, a catalyst precursor is obtained.

[0015] (4) The catalyst precursor is dried and calcined at least to obtain the catalyst.

[0016] A second aspect of the present invention provides a method for preparing the above-described catalyst for the synthesis of 2,6-dimethylphenol, comprising the following steps:

[0017] (1) Dissolve germanium dioxide in a hot alkaline solution to obtain a germanium-containing solution;

[0018] (2) The germanium-containing solution is mixed with a mixed solution of iron and aluminum salts, and then ammonia is added to carry out a co-precipitation reaction to make the pH value of the reaction system reach 7.0. After aging and solid-liquid separation, the precipitate is obtained.

[0019] (3) The precipitate is added to a solution of alkali metal salt and / or alkaline earth metal salt and stirred to form a slurry. After standing, a catalyst precursor is obtained.

[0020] (4) The catalyst precursor is dried and calcined at least to obtain the catalyst.

[0021] In some specific embodiments of the present invention, preferably, in step (1), the hot alkaline solution comprises a solution of NaOH and / or KOH at a temperature of 40-60°C.

[0022] In some specific embodiments of the present invention, preferably, in step (1), the mass fraction of alkali in the hot alkaline solution is ≥15%, more preferably ≥20%.

[0023] In some specific embodiments of the present invention, preferably, in step (2), the iron salt includes one or a combination of several of ferric nitrate, ferric chloride and ferric sulfate.

[0024] In some specific embodiments of the present invention, preferably, in step (2), the aluminum salt includes one or a combination of aluminum nitrate, aluminum chloride and aluminum sulfate.

[0025] In some specific embodiments of the present invention, preferably, in step (2), the aging is carried out under stirring conditions, and the aging time is 0.5-4h.

[0026] In some specific embodiments of the present invention, preferably, in step (3), the alkali metal salt includes one or a combination of several of sodium and / or potassium nitrates, chlorides, sulfates and carbonates; the alkaline earth metal salt includes calcium chloride and / or calcium nitrate.

[0027] In some specific embodiments of the present invention, preferably, in step (4), the calcination temperature is 500-700℃ and the time is 4-10h.

[0028] Existing iron-based phenol-methanol alkylation catalysts exhibit high initial activity and selectivity for ortho-products, but suffer from problems such as easy deactivation during the reaction and high methanol decomposition rate. This invention introduces germanium as a dopant into the iron-based catalyst system. By improving the redox performance of the iron-based main active component, the selectivity for 2,6-dimethylphenol is effectively increased, the methanol decomposition rate is reduced, and the catalyst stability is improved. However, in existing iron-based catalysts, germanium doping does not achieve optimal reaction performance. This invention first dissolves germanium dioxide in a hot alkaline solution, then mixes the resulting solution with solutions containing iron and aluminum salts for a co-precipitation reaction. During the reaction, iron, germanium, and aluminum co-precipitate in the solution, achieving deep mixing and doping at the atomic level. Germanium enters the iron oxide lattice, replacing some iron atoms, maximizing the redox performance of germanium. Furthermore, aluminum improves the catalyst strength and further enhances the redox performance of iron oxide. Therefore, the catalyst of the present invention, on the one hand, inhibits the transformation of the iron oxide active phase, maintaining high catalytic activity and selectivity for 2,6-dimethylphenol; on the other hand, it can effectively utilize the role of germanium in inhibiting methanol decomposition, thereby improving the stability and lifespan of the catalyst.

[0029] The technical solution of the present invention has at least the following beneficial effects:

[0030] The catalyst of this invention has advantages such as high catalytic activity and high selectivity for 2,6-dimethylphenol. It can also effectively reduce the activity of methanol decomposition, improve catalyst stability and lifespan, reduce raw material consumption, and improve process economy. Furthermore, the catalyst preparation method of this invention employs a one-step co-precipitation method, eliminating the need for mixing and kneading, simplifying the catalyst forming process, and offering advantages such as simple preparation process and good repeatability. Detailed Implementation

[0031] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0032] A specific embodiment of the present invention provides a catalyst for the synthesis of 2,6-dimethylphenol, the catalyst comprising the following components: iron oxide, germanium oxide, aluminum oxide, and alkali metal oxide and / or alkaline earth metal oxide, and the molar ratio of each component is iron:germanium:aluminum:alkali metal and / or alkaline earth metal = 100:(0.4-4):(0.4-4):(0.1-1).

[0033] In some specific embodiments, the molar ratio of each component is iron: germanium: aluminum: alkali metal and / or alkaline earth metal = 100:(1-3):(1-3):(0.1-1).

[0034] In some specific embodiments, the alkali metal oxide and / or alkaline earth metal oxide includes one or more oxides of calcium, sodium, and potassium.

[0035] In some specific embodiments, the catalyst comprises the following components: iron oxide, germanium oxide, aluminum oxide, and alkali metal oxide, and the molar ratio of each component is iron:germanium:aluminum:alkali metal = 100:(0.4-4):(0.4-4):(0.1-1), and the preferred molar ratio of each component is iron:germanium:aluminum:alkali metal = 100:(1-3):(1-3):(0.1-1). The alkali metal includes sodium and / or potassium.

[0036] According to a specific embodiment of the present invention, the catalyst is prepared by the following steps:

[0037] (1) Dissolve germanium dioxide in a hot alkaline solution to obtain a germanium-containing solution;

[0038] (2) The germanium-containing solution is added dropwise to the mixed solution of iron salt and aluminum salt, and stirred thoroughly to mix evenly. Then, ammonia water is added dropwise under stirring to carry out a co-precipitation reaction until the pH value of the reaction system reaches 7.0. Then, the addition of ammonia water is stopped. After aging, solid-liquid separation and washing, the precipitate is obtained.

[0039] (3) Disperse the precipitate in a solution of alkali metal salt and / or alkaline earth metal salt, stir to form a slurry, and let it stand to obtain a catalyst precursor.

[0040] (4) The catalyst precursor is dried and calcined at least to obtain the catalyst.

[0041] Another specific embodiment of the present invention provides a method for preparing the above-described catalyst for synthesizing 2,6-dimethylphenol, which includes the following steps:

[0042] (1) Dissolve germanium dioxide in a hot alkaline solution to obtain a germanium-containing solution;

[0043] (2) The germanium-containing solution is added dropwise to the mixed solution of iron salt and aluminum salt, and stirred thoroughly to mix evenly. Then, ammonia water is added dropwise under stirring to carry out a co-precipitation reaction until the pH value of the reaction system reaches 7.0. Then, the addition of ammonia water is stopped. After aging, solid-liquid separation and washing, the precipitate is obtained.

[0044] (3) Disperse the precipitate in a solution of alkali metal salt and / or alkaline earth metal salt, stir to form a slurry, and let it stand to obtain a catalyst precursor.

[0045] (4) The catalyst precursor is dried and calcined at least to obtain the catalyst.

[0046] In some specific embodiments, in step (1), the hot alkaline solution comprises a solution of NaOH and / or KOH at a temperature of 40-60°C.

[0047] In some specific embodiments, in step (1), the mass fraction of alkali in the hot alkaline solution is ≥15%, more preferably ≥20%.

[0048] In some specific embodiments, in step (2), the mixed solution of iron salt and aluminum salt is prepared by dissolving iron salt and aluminum salt in water according to the molar ratio of iron and aluminum in the catalyst.

[0049] In some specific embodiments, in step (2), the iron salt includes soluble iron salts, such as, but not limited to, one or a combination of several of ferric nitrate, ferric chloride and ferric sulfate.

[0050] In some specific embodiments, in step (2), the aluminum salt includes soluble aluminum salts, such as, but not limited to, one or a combination of several of aluminum nitrate, aluminum chloride and aluminum sulfate.

[0051] In some specific embodiments, in step (2), the aging is carried out under stirring conditions, and the aging time is 0.5h-4h.

[0052] In some specific embodiments, in step (3), the alkali metal salt includes sodium and / or potassium salt compounds, such as, but not limited to, one or more combinations of sodium and / or potassium nitrates, chlorides, sulfates and carbonates; the alkaline earth metal salt includes calcium soluble salt compounds, such as, but not limited to, calcium chloride and / or calcium nitrate.

[0053] In some specific embodiments, the stirring time in step (3) is 0.5h-1.5h.

[0054] In some specific embodiments, in step (3), the settling time is 10h-18h.

[0055] In some specific embodiments, step (3) may further include solid-liquid separation after settling, which may be performed in a manner conventional in the art, such as filtration. If step (3) disperses the precipitate in a solution of alkali metal salt and / or alkaline earth metal salt by an equal-volume impregnation method, solid-liquid separation may not be performed.

[0056] In some specific embodiments, the concentration of germanium in the germanium-containing solution in step (1), the concentration of iron and aluminum in the mixed solution of iron and aluminum salts in step (2), and the concentration of alkali metal and / or alkaline earth metal in the solution of alkali metal salt and / or alkaline earth metal salt in step (3) can all be conventionally adjusted by those skilled in the art according to the actual situation, as long as the molar ratio of each component defined by the present invention is met and the reaction proceeds smoothly.

[0057] In some specific embodiments, in step (4), the drying temperature is 120-180°C and the time is 6-12 hours.

[0058] In some specific embodiments, in step (4), the calcination temperature is 500-700℃ and the time is 4h-10h.

[0059] In some specific embodiments, step (4) may further include molding after calcination, which may be carried out in a manner conventional in the art, such as, but not limited to, tableting.

[0060] The technical solutions of the present invention are illustrated in detail below through embodiments and comparative examples. However, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the key points of the present invention.

[0061] Example 1

[0062] This embodiment provides a catalyst for the synthesis of 2,6-dimethylphenol, the preparation method of which includes the following steps:

[0063] Solution A is prepared by dissolving 100g Fe(NO3)3·9H2O and 1.39g Al(NO3)3·9H2O in 1000mL of deionized water; Solution B is prepared by dissolving 0.385g GeO2 in 20g of 20% by mass NaOH solution at 40℃.

[0064] Solution B was added dropwise to solution A and stirred thoroughly until homogeneous. Then, 10 wt% ammonia solution was added dropwise under stirring to carry out a co-precipitation reaction until the pH of the reaction system reached 7.0. The addition of ammonia solution was stopped, and the mixture was aged for 120 min under room temperature. The precipitate was washed with water and filtered to obtain a filter cake.

[0065] Dissolve 0.17 g of potassium carbonate in 200 mL of deionized water to prepare a solution. Disperse the filter cake in the potassium carbonate aqueous solution for an equal volume impregnation. Stir for 0.5 h and then let stand for 12 h. Then dry at 150 °C for 8 h and calcine at 500 °C for 6 h to obtain the catalyst sample.

[0066] Example 2

[0067] This embodiment provides a catalyst for the synthesis of 2,6-dimethylphenol, the preparation method of which includes the following steps:

[0068] Solution A was prepared by dissolving 70g Fe2(SO4)3·9H2O and 0.81g AlCl3·6H2O in 1000mL of deionized water; Solution B was prepared by dissolving 0.52g GeO2 in 20g of 20% by mass NaOH solution at 45℃.

[0069] Solution B was added dropwise to solution A and stirred thoroughly until homogeneous. Then, 10 wt% ammonia solution was added dropwise under stirring to carry out a co-precipitation reaction until the pH of the reaction system reached 7.0. The addition of ammonia solution was stopped, and the mixture was aged for 100 min under room temperature conditions. The precipitate was washed with water and filtered to obtain a filter cake.

[0070] Dissolve 0.1 g of potassium carbonate in 200 mL of deionized water to prepare a solution. Disperse the filter cake in the potassium carbonate aqueous solution for an equal volume impregnation. Stir for 0.5 h and then let stand for 12 h. Then dry at 150 °C for 8 h and calcine at 600 °C for 6 h to obtain the catalyst sample.

[0071] Example 3

[0072] This embodiment provides a catalyst for the synthesis of 2,6-dimethylphenol, the preparation method of which includes the following steps:

[0073] Solution A was prepared by dissolving 40.5g FeCl3·3H2O and 1.22g Al(NO3)3·9H2O in 1000mL of deionized water; Solution B was prepared by dissolving 0.52g GeO2 in 20g of 15% by mass NaOH solution at 50℃.

[0074] Solution B was added dropwise to solution A and stirred thoroughly until homogeneous. Then, 10 wt% ammonia solution was added dropwise under stirring to carry out a co-precipitation reaction until the pH of the reaction system reached 7.0. The addition of ammonia solution was stopped, and the mixture was aged for 120 min under room temperature. The precipitate was washed with water and filtered to obtain a filter cake.

[0075] Dissolve 0.1 g of potassium chloride in 200 mL of deionized water to prepare a solution. Disperse the filter cake in the potassium chloride aqueous solution for an equal volume impregnation. Stir for 0.5 h and then let stand for 12 h. Then dry at 150 °C for 8 h and calcine at 700 °C for 4 h to obtain the catalyst sample.

[0076] Comparative Example 1

[0077] This comparative example provides a catalyst for the synthesis of 2,6-dimethylphenol, the preparation method of which includes the following steps:

[0078] 100g of Fe2(SO4)3·9H2O and 1.39g of AlCl3·9H2O were dissolved in 1000mL of deionized water to prepare a mixed metal salt solution. Then, under stirring, 10wt% ammonia solution was added dropwise to the mixed metal salt solution to carry out a coprecipitation reaction until the pH value of the reaction system reached 7.0. The addition of ammonia solution was stopped, and the mixture was stirred at room temperature for 60min until precipitation was complete. The precipitate was washed with water and filtered to obtain a filter cake.

[0079] Dissolve 0.17 g of potassium carbonate in 200 mL of deionized water to prepare a solution. Disperse the filter cake in the potassium carbonate aqueous solution for an equal volume impregnation. Stir for 0.5 h and then let stand for 12 h. Then dry at 150 °C for 8 h and calcine at 500 °C for 6 h to obtain the catalyst sample.

[0080] Comparative Example 2

[0081] This comparative example provides a catalyst for the synthesis of 2,6-dimethylphenol, the preparation method of which includes the following steps:

[0082] 70g Fe2(SO4)3·9H2O, 0.81g AlCl3·9H2O, and 1.29g germanium nitrate were dissolved in 1000mL of deionized water to prepare a mixed metal salt solution. Then, under stirring, 10wt% ammonia solution was added dropwise to the mixed metal salt solution to carry out a coprecipitation reaction until the pH of the reaction system reached 7.0. The addition of ammonia solution was stopped, and the mixture was stirred at room temperature for 120min until precipitation was complete. The precipitate was washed with water and filtered to obtain a filter cake.

[0083] Dissolve 0.1 g of potassium carbonate in 200 mL of deionized water to prepare a solution. Disperse the filter cake in the potassium carbonate aqueous solution for an equal volume impregnation. Stir for 0.5 h and then let stand for 12 h. Then dry at 150 °C for 8 h and calcine at 500 °C for 6 h to obtain the catalyst sample.

[0084] Comparative Example 3

[0085] This comparative example provides a catalyst for the synthesis of 2,6-dimethylphenol, the preparation method of which includes the following steps:

[0086] A mixed metal salt solution was prepared by dissolving 70g Fe2(SO4)3·9H2O and 0.81g AlCl3·9H2O in 1000mL of deionized water. Then, a 10wt% ammonia solution was added dropwise to the mixed metal salt solution under stirring to carry out a coprecipitation reaction until the pH of the reaction system reached 7.0, at which point the addition of ammonia solution was stopped. 0.52g GeO2 was dispersed in 20g of deionized water and added dropwise to the above reaction system. The mixture was stirred at room temperature for 120min until precipitation was complete. The precipitate was washed with water and filtered to obtain a filter cake.

[0087] Dissolve 0.1 g of potassium carbonate in 200 mL of deionized water to prepare a solution. Disperse the filter cake in the potassium carbonate aqueous solution for an equal volume impregnation. Stir for 0.5 h and then let stand for 12 h. Then dry at 150 °C for 8 h and calcine at 500 °C for 6 h to obtain the catalyst sample.

[0088] Comparative Example 4

[0089] This comparative example provides a catalyst for the synthesis of 2,6-dimethylphenol, the preparation method of which includes the following steps:

[0090] 70g Fe2(SO4)3·9H2O, 0.81g AlCl3·9H2O, and 0.88g Cr(NO3)3 were dissolved in 1000mL of deionized water to prepare a mixed metal salt solution. Then, under stirring, 10wt% ammonia solution was added dropwise to the mixed metal salt solution to carry out a coprecipitation reaction until the pH value of the reaction system reached 7.0. The addition of ammonia solution was stopped, and the mixture was stirred at room temperature for 120min until precipitation was complete. The precipitate was washed with water and filtered to obtain a filter cake.

[0091] Dissolve 0.1 g of potassium carbonate in 200 mL of deionized water to prepare a solution. Disperse the filter cake in the potassium carbonate aqueous solution for an equal volume impregnation. Stir for 0.5 h and then let stand for 12 h. Then dry at 150 °C for 8 h and calcine at 500 °C for 6 h to obtain the catalyst sample.

[0092] Test case

[0093] The performance of the catalysts prepared in Examples 1-3 and Comparative Examples 1-4 was evaluated. The catalyst performance was evaluated using a small-scale phenol-methanol alkylation system. The reactants were a mixed solution of phenol, methanol, and water, with a molar ratio of phenol:methanol:water of 1:5:3. A fixed-bed reactor was used, with a catalyst loading of 10 mL and a liquid hourly space velocity (LISH) of 0.8 h⁻¹. -1The carrier gas nitrogen flow rate was 10 mL / min, the reaction temperature was 350 °C, and the reaction pressure was 0.1 MPa. The reaction was carried out for 800 h and 2000 h. The reaction products were analyzed by gas chromatography using the internal standard method to obtain the phenol conversion rate, o-cresol selectivity, 2,6-DMP selectivity, and methanol decomposition rate. The performance evaluation results of the catalysts provided in Examples 1-3 and Comparative Examples 1-4 are shown in Table 1.

[0094] Table 1

[0095]

[0096]

[0097] The data above show that this invention effectively improves the catalytic activity and 2,6-DMP selectivity of the catalyst. After 800 hours of single-pass operation, the phenol conversion rate is over 97%, and the 2,6-DMP selectivity is over 96%. Furthermore, the catalyst activity decays slowly with increasing operating time. Comparative Example 1 did not introduce germanium; Comparative Example 2 did not first dissolve germanium dioxide in a hot alkaline solution; Comparative Example 3 added germanium dioxide dispersed in water to the iron precipitate system after the reaction; and Comparative Example 4 introduced different doping elements. The experimental results show that the catalysts obtained in the four comparative examples have relatively low activity, and their activity decays significantly with increasing time. They also exhibit relatively low 2,6-DMP selectivity and high methanol decomposition rate. Therefore, the technical solution of this invention improves the stability and lifespan of the catalyst, and the effective doping of germanium can inhibit methanol decomposition, reduce raw material consumption, and improve process economy. Simultaneously, the catalyst preparation method of this invention uses a one-step co-precipitation method, eliminating the mixing operation and simplifying the catalyst forming process, offering advantages such as simple preparation process and good repeatability.

Claims

1. A catalyst for the synthesis of 2,6-dimethylphenol, said catalyst comprising: iron oxide, germanium oxide, aluminum oxide, and alkali metal oxide and / or alkaline earth metal oxide, wherein the molar ratio of each component is iron:germanium:aluminum:alkali metal and / or alkaline earth metal = 100:(0.4-4):(0.4-4):(0.1-1); The catalyst is prepared by the following steps: (1) Dissolve germanium dioxide in a hot alkaline solution to obtain a germanium-containing solution; (2) The germanium-containing solution is mixed with a mixed solution of iron and aluminum salts, and then ammonia is added to carry out a co-precipitation reaction to make the pH value of the reaction system reach 7.

0. After aging and solid-liquid separation, the precipitate is obtained. (3) The precipitate is added to a solution of alkali metal salt and / or alkaline earth metal salt and stirred to form a slurry. After standing, a catalyst precursor is obtained. (4) The catalyst precursor is dried and calcined to obtain the catalyst.

2. The catalyst according to claim 1, wherein, The molar ratio of each component is iron: germanium: aluminum: alkali metal and / or alkaline earth metal = 100: (1-3): (1-3): (0.1-1).

3. The catalyst according to claim 1, wherein, The alkali metal oxides and / or alkaline earth metal oxides include oxides of one or more of calcium, sodium, and potassium.

4. A method for preparing the catalyst for synthesizing 2,6-dimethylphenol according to any one of claims 1-3, comprising the following steps: (1) Dissolve germanium dioxide in a hot alkaline solution to obtain a germanium-containing solution; (2) The germanium-containing solution is mixed with a mixed solution of iron and aluminum salts, and then ammonia is added to carry out a co-precipitation reaction to make the pH value of the reaction system reach 7.

0. After aging and solid-liquid separation, the precipitate is obtained. (3) The precipitate is added to a solution of alkali metal salt and / or alkaline earth metal salt and stirred to form a slurry. After standing, a catalyst precursor is obtained. (4) The catalyst precursor is dried and calcined to obtain the catalyst.

5. The preparation method according to claim 4, wherein, In step (1), the hot alkaline solution comprises a solution of NaOH and / or KOH at a temperature of 40-60°C.

6. The preparation method according to claim 4, wherein, In step (1), the mass fraction of alkali in the hot alkaline solution is ≥15%.

7. The preparation method according to claim 4 or 6, wherein, In step (1), the mass fraction of alkali in the hot alkaline solution is ≥20%.

8. The preparation method according to claim 4, wherein, In step (2), the iron salt includes one or a combination of ferric nitrate, ferric chloride and ferric sulfate.

9. The preparation method according to claim 4, wherein, In step (2), the aluminum salt includes one or a combination of aluminum nitrate, aluminum chloride and aluminum sulfate.

10. The preparation method according to claim 4, wherein, In step (2), the aging is carried out under stirring conditions and the aging time is 0.5-4 h.

11. The preparation method according to claim 4, wherein, In step (3), the alkali metal salt includes one or a combination of several of sodium and / or potassium nitrates, chlorides, sulfates and carbonates; the alkaline earth metal salt includes calcium chloride and / or calcium nitrate.

12. The preparation method according to claim 4, wherein, In step (4), the calcination temperature is 500-700℃ and the time is 4-10 h.

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