A magnesium-aluminum- erbium composite oxide catalyst, its preparation method and application

Abstract

The present invention provides a magnesium-aluminum- erbium composite oxide catalyst, a preparation method thereof and an application thereof, belonging to the technical field of isophorone. In the magnesium-aluminum- erbium composite oxide catalyst, based on metal elements, the molar ratio of magnesium to aluminum is 2:1 to 1:2, and the molar ratio of the sum of magnesium and aluminum to erbium is 100:1 to 10:1. In addition, a preparation method of the catalyst and an application method of the catalyst in the reaction of gas-phase condensation of acetone to prepare isophorone are also disclosed. The catalyst has the advantages of high catalytic activity, high selectivity for isophorone and good stability in the reaction of gas-phase condensation of acetone to prepare isophorone.

Description

Technical Field

[0001] The present invention belongs to the technical field of isophorone preparation, and particularly relates to a magnesium-aluminum- erbium composite oxide catalyst, a preparation method thereof, and an application thereof in the catalytic condensation reaction of acetone to prepare isophorone. Background Art

[0002] Isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) is an important fine chemical. As a solvent, it has many advantages such as high boiling point, strong dissolving ability, good dispersibility, and good leveling property. Isophorone is widely used as an excellent solvent for some polymer materials, and also has relatively wide applications in the polymer industry and the pharmaceutical industry. Isophorone is also an important organic synthesis raw material, used to produce fine chemical products such as isophorone diamine and isophorone diisocyanate. In addition, isophorone can also be used to prepare pesticides such as 3,5-dimethylphenol. Therefore, isophorone has broad application prospects.

[0003] Isophorone can be mainly prepared by two methods. One is the mesityl oxide method, and the other is the acetone condensation method. The mesityl oxide method uses mesityl oxide and ethyl acetoacetate as raw materials to obtain isophorone under the action of a catalyst. Due to the high production cost, this method mainly remains in the laboratory stage and has not been industrially applied (CN110885286A). The acetone condensation method is the main method for industrial synthesis of isophorone. In this method, three molecules of acetone are condensed through a condensation reaction under the action of a catalyst to form one molecule of isophorone.

[0004] The acetone condensation method can be divided into two methods: liquid-phase condensation and gas-phase condensation. In the liquid-phase condensation method, inorganic strong bases such as sodium amide, calcium oxide (US2399976), alkali metal and alkaline earth metal hydroxides (US2344226, GB733650), or organic bases such as organic imidazole quaternary ammonium bases (CN106892807A), etc. are used as catalysts. The condensation reaction of acetone is carried out under high-temperature conditions by heating to prepare isophorone. In order to avoid stratification and promote full contact between acetone and the catalyst, a small amount of water is generally added to the reaction system. Using NaOH as the catalyst and a 90% aqueous acetone solution as the raw material liquid, a 14% acetone conversion rate and a 51% isophorone selectivity can be obtained at 170 °C (GB583863). Using KOH as the catalyst and reacting at about 200 °C, the acetone conversion rate and the isophorone selectivity can reach 40% and 68% respectively (GB583863). In the liquid-phase condensation method, the conversion rate of acetone and the selectivity of isophorone are generally low. At the same time, this method also has problems such as difficult separation of the catalyst from the product after the reaction, a large amount of alkali solution in the waste liquid, and serious pollution. In the gas-phase condensation method, solid bases are generally used as catalysts and the reaction is carried out at 200 °C - 400 °C. This method can use a fixed-bed reactor, enabling continuous production, and has many advantages such as a simple separation process, high production efficiency, low pollution, and easy scale-up. Using solid strong bases such as sodium methoxide as the catalyst in a fixed-bed reactor, at 110 - 280 °C, the acetone conversion rate is between 16 - 40%, and the optimal selectivity of isophorone does not exceed 70% (CN101050168A). Magnesium-aluminum hydrotalcite can be used as a heterogeneous catalyst for the preparation of isophorone. In the experiment carried out in a tubular reactor, the acetone conversion rate using the magnesium-aluminum hydrotalcite catalyst is 38%, and the isophorone selectivity is 51% (US5849957). Aristech Chemical Corporation has disclosed the activities of some magnesium-aluminum oxide catalysts in the reaction for the preparation of isophorone (WO9012645, WO9507255). In the reaction, the acetone conversion rate is generally controlled below 35%. An excessively high acetone conversion rate will reduce the selectivity of isophorone, and at the same time, it will also promote catalyst carbon deposition, thereby reducing the service life of the catalyst. When the acetone conversion rate is 30%, the isophorone selectivity can reach 76%. Using a calcium-aluminum oxide catalyst and reacting at 300 °C, the total selectivity of mesityl oxide and isophorone can reach about 80% (US4535187).

[0005] In the gas-phase condensation of acetone, the by-products are mainly mesityl oxide, pseudocumene, and tetramers and pentamers of acetone. To obtain a high isophorone selectivity, the conversion rate generally needs to be controlled below 35%, resulting in low production efficiency of isophorone. Even under the condition of a low conversion rate, the selectivity of isophorone is generally lower than 80%. On the other hand, the stability of most solid base catalysts is poor and they are easily deactivated during the reaction. Therefore, it is still necessary to develop catalysts with high activity and high stability to achieve the efficient production of isophorone. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a process for preparing isophorone by gas-phase condensation of acetone using a magnesium-aluminum- erbium composite oxide catalyst. This method overcomes the disadvantages of the existing catalyst system, such as low conversion rate, many by-products, and easy deactivation of the catalyst. The present invention has the advantages of simple catalyst preparation process, simple reaction process, continuous reaction, high conversion efficiency, high isophorone selectivity, and high catalyst stability.

[0007] One of the objectives of the present invention is to provide a magnesium-aluminum- erbium composite oxide catalyst.

[0008] Another objective of the present invention is to provide a method for preparing the magnesium-aluminum- erbium composite oxide catalyst.

[0009] A third objective of the present invention is to provide an application of the magnesium-aluminum- erbium composite oxide catalyst.

[0010] To achieve the above objectives of the present invention, the following technical solutions are specifically adopted:

[0011] In the first aspect, the present invention provides a magnesium-aluminum- erbium composite oxide catalyst, and the composition of the magnesium-aluminum- erbium composite oxide catalyst is (MgO) x (Al 2 O 3 ) y (Er 2 O 3 ) z , where x:y = 4:1 to 1:1, and (x + 2y):2z = 100:1 to 10:1;

[0012] Preferably, x is 0.1 - 0.12, y is 0.04 - 0.05, and z is 0.002 - 0.0035.

[0013] In particular, the molar ratio of magnesium, aluminum, and erbium is 0.1:0.1:0.007;

[0014] Preferably, the specific surface area of the magnesium-aluminum- erbium composite oxide catalyst is 100 - 150 m 2 ·g-1 with an average pore diameter of 5 - 20 nm, preferably 15 - 20 nm.

[0015] The catalyst comprises a composite oxide of magnesium oxide, aluminum oxide and erbium oxide.

[0016] In a second aspect, the present invention provides a method for preparing the above-mentioned magnesium-aluminum-erbium composite oxide catalyst, comprising the following steps:

[0017] (1) Dissolve soluble magnesium salts, aluminum salts and erbium salts in water to prepare a mixed magnesium-aluminum-erbium salt solution; in the mixed magnesium-aluminum-erbium salt solution, the molar ratio of magnesium to aluminum is 2:1 - 1:2, and the molar ratio of the sum of magnesium and aluminum to erbium is 100:1 - 10:1; preferably, the molar ratio of magnesium, aluminum and erbium is 0.1:0.1:0.007;

[0018] (2) Dropwise add ammonia water to the mixed magnesium-aluminum-erbium salt solution under stirring, and the amount of ammonia water added dropwise is 1 - 3 times the theoretical amount of ammonia water required for complete precipitation of metal ions in the mixed magnesium-aluminum-erbium salt solution;

[0019] (3) After the dropwise addition of ammonia water is completed, continue to stir, then transfer the solution to a hydrothermal autoclave for hydrothermal synthesis;

[0020] (4) After cooling, wash, separate and dry the precipitate, and then calcine it to obtain the magnesium-aluminum-erbium composite oxide catalyst.

[0021] The magnesium-aluminum-erbium composite oxide catalyst is synthesized by a hydrothermal method.

[0022] Preferably, in step (1), the magnesium salt is one or more selected from magnesium nitrate, magnesium sulfate, magnesium chloride or magnesium acetate, preferably magnesium nitrate;

[0023] The aluminum salt is one or more selected from aluminum nitrate, aluminum sulfate, aluminum chloride or aluminum acetate, preferably aluminum nitrate;

[0024] The erbium salt is one or more selected from erbium nitrate or erbium acetate, preferably erbium nitrate;

[0025] Preferably, in step (1), the molar concentration of the mixed magnesium-aluminum-erbium salt solution is 0.5 - 2 mol / L.

[0026] Preferably, in step (2), the stirring temperature is 30 - 60 °C, the dropping rate is 1 - 5 mL / min, and the mass concentration of ammonia water is 10 - 40%, preferably 28%.

[0027] Preferably, in step (3), continue to stir for 1 - 5 h, the hydrothermal synthesis temperature is 120 - 200 °C, and the hydrothermal synthesis time is 2 - 10 h.

[0028] Preferably, in step (4), the drying temperature is 80-130 °C and the drying time is 4-20 h; the calcination temperature is 300-700 °C and the calcination time is 2-6 h.

[0029] More preferably, a magnesium-aluminum-eryttrium composite oxide catalyst is synthesized by a secondary hydrothermal method.

[0030] In some preferred embodiments, a method for preparing a magnesium-aluminum-eryttrium composite oxide catalyst includes the following steps:

[0031] (1’) Dissolve soluble magnesium salt, aluminum salt and erbium salt in water to prepare a magnesium-aluminum-eryttrium mixed salt solution; in the magnesium-aluminum-eryttrium mixed salt solution, the molar ratio of magnesium to aluminum is 2:1-1:2, and the molar ratio of the sum of magnesium and aluminum to erbium is 100:1-10:1; preferably, the molar ratio of magnesium, aluminum and erbium is 0.1:0.1:0.007;

[0032] (2’) While stirring, add ammonia water dropwise to the magnesium-aluminum-eryttrium mixed salt solution, and the amount of ammonia water added is 1-3 times the theoretical amount of ammonia water required for complete precipitation of metal ions in the magnesium-aluminum-eryttrium mixed salt solution;

[0033] (3’) After the addition of ammonia water is completed, continue stirring, then transfer the solution to a hydrothermal reactor for hydrothermal synthesis;

[0034] (4’) After cooling, wash and separate the precipitate;

[0035] (5’) Put the precipitate into water, add ammonia water dropwise again, and the amount of ammonia water added is 30%-60% of the amount of ammonia water used in the first titration. After the addition is completed, continue stirring, then transfer the solution to a hydrothermal reactor for secondary hydrothermal synthesis;

[0036] (6’) Stop heating, after cooling, wash, separate and dry the precipitate, and then perform calcination to obtain a magnesium-aluminum-eryttrium composite oxide catalyst.

[0037] Preferably, in step (1’), the magnesium salt is one or more selected from magnesium nitrate, magnesium sulfate, magnesium chloride or magnesium acetate, preferably magnesium nitrate;

[0038] The aluminum salt is one or more selected from aluminum nitrate, aluminum sulfate, aluminum chloride or aluminum acetate, preferably aluminum nitrate;

[0039] The erbium salt is one or more selected from erbium nitrate or erbium acetate, preferably erbium nitrate;

[0040] Preferably, in step (1’), the molar concentration of the magnesium-aluminum-eryttrium mixed salt solution is 0.5-2 mol / L.

[0041] Preferably, in step (2’), the stirring temperature is 30-60°C, the dropping rate is 1-5 mL / min, the mass concentration of ammonia water is 10-40%, preferably 28%.

[0042] Preferably, in step (3’), continue stirring for 1-5 h, the hydrothermal synthesis temperature is 120-160°C, and the hydrothermal synthesis time is 2-10 h.

[0043] Preferably, in step (5’), the dropping rate is 1-5 mL / min, the mass concentration of ammonia water is 10-40%, preferably 28%, continue stirring for 1-5 h, the secondary hydrothermal synthesis temperature is 160-200°C, and the secondary hydrothermal synthesis time is 2-10 h.

[0044] Preferably, in step (6’), the drying temperature is 80-130°C, the drying time is 4-20 h; the calcination temperature is 300-700°C, and the calcination time is 2-6 h.

[0045] In a specific embodiment, a method for preparing a magnesium-aluminum- erbium composite oxide catalyst includes the following steps:

[0046] 1. According to the formula, weigh a certain amount of soluble magnesium salt, aluminum salt and erbium salt and dissolve them in 150-250 mL of distilled water to prepare a magnesium-aluminum-erbium mixed salt solution with a concentration of 0.5-2 mol / L; the molar ratio of magnesium to aluminum is 2:1-1:2, and the molar ratio of the sum of magnesium and aluminum to erbium is 100:1-10:1;

[0047] 2. Keep the magnesium-aluminum-erbium mixed salt solution at 30-60°C, and while stirring, gradually add ammonia water to the magnesium-aluminum-erbium mixed salt solution at a dropping rate of 1-5 mL / min; the amount of ammonia water added is 1-3 times the theoretical amount of ammonia water required for complete precipitation of metal ions in the magnesium-aluminum-erbium mixed salt solution;

[0048] 3. After the addition of ammonia water is completed, continue stirring for 1-5 h, then transfer the solution to a hydrothermal kettle, place it in an oven, and keep it at 120-160°C for 2-10 h for hydrothermal synthesis;

[0049] 4. After cooling to room temperature, wash, filter and centrifuge the precipitate, and stop washing the filtrate when the pH value reaches 7;

[0050] 5. Put the precipitate into 150-250 mL of distilled water, and add ammonia water with a mass concentration of 28% again at a dropping rate of 1-5 mL / min. The amount of ammonia water added is 30%-60% of the ammonia water dosage in the first titration. After the addition is completed, continue stirring for 1-5 h, then transfer the solution to a hydrothermal kettle, place it in an oven, and keep it at 160-200°C for 2-10 h for secondary hydrothermal synthesis;

[0051] 6. Stop heating, and after cooling to room temperature, wash, filter, and centrifuge the precipitate. Stop washing when the pH value of the filtrate reaches 7. The solid obtained after filtration is dried in an oven at 80-130 °C for 4-20 h, and then calcined in a muffle furnace under an air atmosphere at 300-700 °C for 2-6 h to obtain a magnesium-aluminum-erbium composite oxide catalyst.

[0052] The catalyst synthesized through a secondary hydrothermal process has a pore structure with larger pore diameters, higher activity, and selectivity for isophorone.

[0053] In a third aspect, the present invention provides an application of the above-mentioned magnesium-aluminum-erbium composite oxide catalyst in the gas-phase condensation of acetone to prepare isophorone.

[0054] Preferably, the application includes the following steps:

[0055] Load the magnesium-aluminum-erbium composite oxide catalyst into a fixed-bed reactor, use acetone as the raw material, and carry out the reaction at a reaction temperature of 200-400 °C, a reaction pressure of 0.1-3 MPa, and a mass space velocity of 0.5-3 h -1 to obtain isophorone.

[0056] Preferably, the reaction temperature is 300 °C, the reaction pressure is 0.1 MPa, and the mass space velocity is 1.2 h -1 .

[0057] Beneficial effects:

[0058] The magnesium-aluminum-erbium composite oxide catalyst prepared by the present invention is applied to the reaction of gas-phase condensation of acetone to prepare isophorone. Under the condition of obtaining a relatively high acetone conversion rate of more than 55%, an isophorone selectivity of about 92% can be obtained, significantly reducing the generation of by-products. At the same time, the catalyst has extremely high stability, and during the continuous 1000 h experiment, the catalytic activity does not decrease significantly. The present invention also has the advantages of simple catalyst preparation process, mild reaction conditions, and continuous reaction.

[0059] The present invention has been described in detail above, but the above embodiments are essentially illustrative and do not intend to limit the present invention. In addition, the present invention is not limited by any theory in the foregoing prior art or the invention content or the following examples. Specific embodiments

[0060] The following further illustrates the present invention with reference to embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation to the scope of the present invention claimed.

[0061] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the embodiments are all conventional raw materials, reagents, methods in the art.

[0062] Preparation Example 1

[0063] Weigh 25.6 g of magnesium nitrate hexahydrate (0.1 mol), 37.5 g of aluminum nitrate nonahydrate (0.1 mol), and 3.2 g of erbium nitrate pentahydrate (0.007 mol), dissolve them in 207 mL of distilled water, and prepare a 1 mol / L magnesium-aluminum-erbium mixed salt solution; keep the magnesium-aluminum-erbium mixed salt solution at 40 °C, and while stirring, add 59 mL of 28% by mass ammonia water dropwise to the magnesium-aluminum-erbium mixed salt solution at a dropping rate of 2 mL / min; after the addition of ammonia water is completed, continue stirring for 2 h, then transfer the solution to a hydrothermal autoclave, place it in an oven, and keep it at 140 °C for 4 h for hydrothermal synthesis; stop heating, after cooling to room temperature, wash, filter, and centrifuge the precipitate, stop washing when the pH value of the filtrate reaches 7, dry the obtained solid in an oven at 110 °C for 12 h, and then calcine it in a muffle furnace under an air atmosphere at 500 °C for 4 h to obtain a magnesium-aluminum-erbium composite oxide catalyst.

[0064] Preparation Example 2

[0065] Weigh 25.6 g of magnesium nitrate hexahydrate (0.1 mol), 37.5 g of aluminum nitrate nonahydrate (0.1 mol), and 3.2 g of erbium nitrate pentahydrate (0.007 mol), dissolve them in 207 mL of distilled water, and prepare a 1 mol / L magnesium-aluminum-erbium mixed salt solution; keep the magnesium-aluminum-erbium mixed salt solution at 40 °C, and while stirring, add 59 mL of 28% by mass ammonia water dropwise to the magnesium-aluminum-erbium mixed salt solution at a dropping rate of 2 mL / min; after the addition of ammonia water is completed, continue stirring for 2 h, then transfer the solution to a hydrothermal autoclave, place it in an oven, and keep it at 180 °C for 4 h for hydrothermal synthesis; stop heating, after cooling to room temperature, wash, filter, and centrifuge the precipitate, stop washing when the pH value of the filtrate reaches 7, dry the obtained solid in an oven at 110 °C for 12 h, and then calcine it in a muffle furnace under an air atmosphere at 500 °C for 4 h to obtain a magnesium-aluminum-erbium composite oxide catalyst.

[0066] Preparation Example 3

[0067] Weigh 25.6 g of magnesium nitrate hexahydrate (0.1 mol), 37.5 g of aluminum nitrate nonahydrate (0.1 mol), and 3.2 g of erbium nitrate pentahydrate (0.007 mol), dissolve them in 207 mL of distilled water to prepare a 1 mol / L mixed salt solution of magnesium, aluminum, and erbium; keep the mixed salt solution of magnesium, aluminum, and erbium at 40 °C, and while stirring, gradually add 59 mL of 28% ammonia water dropwise to the mixed salt solution of magnesium, aluminum, and erbium at a dropping rate of 2 mL / min; after the addition of ammonia water is complete, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 140 °C for 4 h for hydrothermal synthesis; stop heating, cool to room temperature, wash, filter, and centrifuge the precipitate, and stop washing when the pH of the filtrate reaches 7; put the precipitate into 200 mL of distilled water, and again add 25 mL of 28% ammonia water dropwise at a dropping rate of 2 mL / min, after the addition is complete, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 180 °C for 4 h for secondary hydrothermal synthesis; the solid obtained after filtration is dried in an oven at 110 °C for 12 h, and then calcined in a muffle furnace under an air atmosphere at 500 °C for 4 h to obtain a magnesium-aluminum-erbium composite oxide catalyst.

[0068] Preparation Example 4

[0069] Weigh 30.7 g of magnesium nitrate hexahydrate (0.12 mol), 30.0 g of aluminum nitrate nonahydrate (0.08 mol), and 3.2 g of erbium nitrate pentahydrate (0.007 mol), dissolve them in 207 mL of distilled water to prepare a 1 mol / L mixed salt solution of magnesium, aluminum, and erbium; keep the mixed salt solution of magnesium, aluminum, and erbium at 40 °C, and while stirring, gradually add 84 mL of 28% ammonia water dropwise to the mixed salt solution of magnesium, aluminum, and erbium at a dropping rate of 2 mL / min; after the addition of ammonia water is complete, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 140 °C for 4 h for hydrothermal synthesis; stop heating, cool to room temperature, wash, filter, and centrifuge the precipitate, and stop washing when the pH of the filtrate reaches 7; put the precipitate into 200 mL of distilled water, and again add 30 mL of 28% ammonia water dropwise at a dropping rate of 2 mL / min, after the addition is complete, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 180 °C for 4 h for secondary hydrothermal synthesis; the solid obtained after filtration is dried in an oven at 110 °C for 12 h, and then calcined in a muffle furnace under an air atmosphere at 500 °C for 4 h to obtain a magnesium-aluminum-erbium composite oxide catalyst.

[0070] Preparation Example 5

[0071] Weigh 25.6 g of magnesium nitrate hexahydrate (0.1 mol), 37.5 g of aluminum nitrate nonahydrate (0.1 mol), and 1.9 g of erbium nitrate pentahydrate (0.004 mol), dissolve them in 204 mL of distilled water, and prepare a 1 mol / L mixed salt solution of magnesium, aluminum, and erbium; keep the mixed salt solution of magnesium, aluminum, and erbium at 40 °C, and while stirring, gradually add 58 mL of 28% ammonia water to the mixed salt solution of magnesium, aluminum, and erbium at a dropping rate of 2 mL / min; after the addition of ammonia water is complete, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 140 °C for 4 h for hydrothermal synthesis; stop heating, cool to room temperature, then wash, filter, and centrifuge the precipitate, and stop washing when the pH of the filtrate reaches 7; put the precipitate into 200 mL of distilled water, and again add 25 mL of 28% ammonia water dropwise at a dropping rate of 2 mL / min, after the addition is complete, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 180 °C for 4 h for secondary hydrothermal synthesis; dry the solid obtained after filtration in an oven at 110 °C for 12 h, and then calcine it in a muffle furnace under an air atmosphere at 500 °C for 6 h to obtain a magnesium-aluminum-erbium composite oxide catalyst.

[0072] Prepare Comparative Example 1

[0073] Weigh 25.6 g of magnesium nitrate hexahydrate and 37.5 g of aluminum nitrate nonahydrate, dissolve them in 200 mL of distilled water, and prepare a 1 mol / L mixed salt solution of magnesium and aluminum; keep the mixed salt solution of magnesium and aluminum at 40 °C, and while stirring, gradually add 56 mL of 28% ammonia water to the mixed salt solution of magnesium and aluminum at a dropping rate of 2 mL / min; after the addition of ammonia water is complete, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 140 °C for 4 h; stop heating, cool to room temperature, then wash, filter, and centrifuge the precipitate, and stop washing when the pH of the filtrate reaches 7, dry the solid obtained after filtration in an oven at 110 °C for 12 h, and then calcine it in a muffle furnace under an air atmosphere at 500 °C for 4 h to obtain a magnesium-aluminum composite oxide catalyst.

[0074] Prepare Comparative Example 2

[0075] Weigh 25.6 g of magnesium nitrate hexahydrate and 37.5 g of aluminum nitrate nonahydrate, dissolve them in 200 mL of distilled water to prepare a 1 mol / L magnesium-aluminum mixed salt solution; keep the magnesium-aluminum mixed salt solution at 40 °C, and while stirring, gradually add 56 mL of 28% ammonia water to the magnesium-aluminum mixed salt solution at a dropping rate of 2 mL / min; after the addition of ammonia water is completed, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 140 °C for 4 h for hydrothermal synthesis; stop heating, after cooling to room temperature, wash, filter, and centrifuge the precipitate, and stop washing when the pH of the filtrate reaches 7; put the precipitate into 200 mL of distilled water, and again add 25 mL of 28% ammonia water dropwise at a dropping rate of 2 mL / min, after the addition is completed, continue stirring for 2 h, then transfer the solution to a hydrothermal reactor, place it in an oven, and keep it at 180 °C for 4 h for secondary hydrothermal synthesis; the solid obtained after filtration is dried in an oven at 110 °C for 12 h, and then calcined in a muffle furnace under an air atmosphere at 500 °C for 4 h to obtain a magnesium-aluminum composite oxide catalyst.

[0076] Application Example 1

[0077] The reaction was carried out in a fixed-bed reactor. The length of the fixed-bed reaction tube was 40 cm and the inner diameter was 10 mm. The catalyst prepared in Preparation Example 1 was loaded into the fixed bed, and the catalyst loading was 1 g. The feeding rate of acetone was 1.2 g h -1 , corresponding to a mass space velocity of 1.2 h -1 . The reaction was carried out at a temperature of 300 °C and a pressure of 0.1 MPa for 24 h, and the reaction solution at the 24th h was sampled and analyzed. The reaction results are shown in Table 1.

[0078] Application Example 2

[0079] Except that the loaded catalyst was changed to the catalyst prepared in Preparation Example 2, the experiment was carried out in the same method as Application Example 1. The reaction results are shown in Table 1.

[0080] Application Example 3

[0081] Except that the loaded catalyst was changed to the catalyst prepared in Preparation Example 3, the experiment was carried out in the same method as Application Example 1. The reaction results are shown in Table 1.

[0082] Application Example 4

[0083] Except that the loaded catalyst was changed to the catalyst prepared in Preparation Example 4, the experiment was carried out in the same method as Application Example 1. The reaction results are shown in Table 1.

[0084] Application Example 5

[0085] Except for changing the loaded catalyst to the catalyst prepared in Preparation Example 5, the experiment was carried out in the same manner as in Application Example 1. The reaction results are shown in Table 1.

[0086] Application Example 6

[0087] Except for changing the feed rate of acetone to 1.8 g / h -1 and the mass space velocity to 1.8 h -1 the experiment was carried out in the same manner as in Application Example 3. The reaction results are shown in Table 1.

[0088] Application Example 7

[0089] Except for changing the reaction temperature to 275 °C, the experiment was carried out in the same manner as in Application Example 3. The reaction results are shown in Table 1.

[0090] Application Example 8

[0091] Except for changing the reaction temperature to 325 °C, the experiment was carried out in the same manner as in Application Example 3. The reaction results are shown in Table 1.

[0092] Application Example 9

[0093] Except for extending the reaction experiment to 1000 h, the experiment was carried out in the same manner as in Application Example 3. The reaction solution at the 1000th hour was sampled and analyzed, and the reaction results are shown in Table 1.

[0094] Application Comparative Example 1

[0095] Except for changing the loaded catalyst to the catalyst prepared in Comparative Preparation Example 1, the experiment was carried out in the same manner as in Application Example 1. The reaction results are shown in Table 1.

[0096] Application Comparative Example 2

[0097] Except for changing the loaded catalyst to the catalyst prepared in Comparative Preparation Example 2, the experiment was carried out in the same manner as in Application Example 1. The reaction results are shown in Table 1.

[0098] Table 1 Experimental results of application examples and comparative examples

[0099]

[0100]

[0101] Comparing the experimental results of Application Example 1 and Application Comparative Example 1, as well as those of Application Example 3 and Application Comparative Example 2, it can be seen that under the same catalyst preparation conditions, the magnesium-aluminum- erbium composite oxide catalyst has higher activity and selectivity for isophorone than the traditional magnesium-aluminum oxide catalyst. The specific surface areas of the catalysts corresponding to Preparation Examples 1-3 are 135, 128, and 115 m 2 g -1 respectively, and the average pore diameters are 6.5, 7.0, and 16.6 nm. Compared with the catalyst synthesized through a single hydrothermal process, the specific surface area of the catalyst synthesized through a two-step hydrothermal process decreases slightly, but the average pore diameter increases significantly, indicating that the physical structure properties of the catalyst synthesized through a two-step hydrothermal process have changed greatly. From the experimental results of Application Examples 1-3, it can be seen that the catalyst synthesized through a two-step hydrothermal process has higher activity and selectivity for isophorone, indicating that the pore structure with a large pore diameter can promote the diffusion process and the reaction.

[0102] From the experimental results of Application Examples 3-5, it can be seen that the contents of the three components of magnesium, aluminum, and erbium have a great influence on the catalytic activity. Appropriate relative contents of magnesium, aluminum, and erbium can significantly improve the conversion rate of acetone and the selectivity for isophorone. From the experimental results of Application Example 3 and Application Examples 6-8, it can be seen that the magnesium-aluminum- erbium composite oxide catalyst has good activity under the reaction conditions of 300 °C and a mass space velocity of 1.2 h -1 . It can simultaneously obtain a high conversion rate of acetone and a selectivity for isophorone. From the experimental results of Application Example 3 and Application Example 9, it can be seen that the magnesium-aluminum- erbium composite oxide catalyst has high stability and no obvious deactivation occurs during the long-term reaction process.

[0103] The above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: within the scope of the spirit and essence defined by the claims of the present invention, the technical solutions described in the foregoing examples can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A magnesium-aluminum-erbium composite oxide catalyst, characterized in that: The composition of the magnesium-aluminum-erbium composite oxide catalyst is (MgO) x (Al2O3) y (Er2O3) z , wherein x:y=4:1-1:1, (x+2y):2z=100:1-10:1; the specific surface area of ​​the magnesium-aluminum-erbium composite oxide catalyst is 100-150m 2 ·g -1 , the average pore size is 15-20nm; The preparation method of the magnesium-aluminum-erbium composite oxide catalyst comprises the following steps: (1) dissolving soluble magnesium salt, aluminum salt and erbium salt in water to prepare a magnesium-aluminum-erbium mixed salt solution; in the magnesium-aluminum-erbium mixed salt solution, the molar ratio of magnesium to aluminum is 2:1 to 1:2, and the molar ratio of the sum of the amounts of magnesium and aluminum to the amount of erbium is 100:1 to 10:1; (2) adding ammonia water dropwise to the magnesium-aluminum-erbium mixed salt solution under stirring, wherein the amount of ammonia water added is 1 to 3 times the theoretical amount of ammonia water required for complete precipitation of metal ions in the magnesium-aluminum-erbium mixed salt solution; (3) After the addition of aqueous ammonia is completed, stirring is continued, and then the solution is transferred to a hydrothermal kettle for hydrothermal synthesis; (4) washing and separating the precipitate after cooling; (5) placing the precipitate in water and adding ammonia water again, wherein the amount of ammonia water added is 30% to 60% of the amount of ammonia water used in the first titration. After the addition is completed, stirring is continued, and then the solution is transferred to a hydrothermal kettle for a second hydrothermal synthesis; (6) Stop heating, cool, wash, separate, dry and calcine the precipitate to obtain a magnesium-aluminum-erbium composite oxide catalyst.

2. The magnesium-aluminum-erbium composite oxide catalyst according to claim 1, characterized in that: In step (1), the soluble magnesium salt is one or more selected from magnesium nitrate, magnesium sulfate, magnesium chloride or magnesium acetate; The aluminum salt is one or more selected from aluminum nitrate, aluminum sulfate, aluminum chloride or aluminum acetate; The erbium salt is one or more selected from erbium nitrate or erbium acetate.

3. The magnesium-aluminum-erbium composite oxide catalyst according to claim 2, characterized in that: In step (1), the soluble magnesium salt is magnesium nitrate; The aluminum salt is aluminum nitrate; The erbium salt is erbium nitrate.

4. The magnesium-aluminum-erbium composite oxide catalyst according to claim 1, characterized in that: The molar concentration of the magnesium-aluminum-erbium mixed salt solution in step (1) is 0.5-2 mol / L.

5. The magnesium-aluminum-erbium composite oxide catalyst according to claim 1, characterized in that: In step (2), the stirring temperature is 30-60° C., the dropping rate is 1-5 mL / min, and the mass concentration of the ammonia water is 10-40%.

6. The magnesium-aluminum-erbium composite oxide catalyst according to claim 1, characterized in that: In step (3), stirring is continued for 1 to 5 hours, the hydrothermal synthesis temperature is 120 to 160° C., and the hydrothermal synthesis time is 2 to 10 hours.

7. The magnesium-aluminum-erbium composite oxide catalyst according to claim 1, characterized in that: In step (5), the dropping acceleration rate is 1-5 mL / min, the mass concentration of ammonia water is 10-40%, stirring is continued for 1-5 h, the secondary hydrothermal synthesis temperature is 160-200° C., and the secondary hydrothermal synthesis time is 2-10 h.

8. The magnesium-aluminum-erbium composite oxide catalyst according to claim 1, characterized in that: In step (6), the drying temperature is 80-130° C., and the drying time is 4-20 hours; the roasting temperature is 300-700° C., and the roasting time is 2-6 hours.

9. Use of the magnesium-aluminum-erbium composite oxide catalyst according to any one of claims 1 to 8 in the preparation of isophorone by gas phase condensation of acetone.

10. The use according to claim 9, characterized in that: The following steps are involved: The magnesium-aluminum-erbium composite oxide catalyst is loaded into a fixed bed reactor, and acetone is used as a raw material at a reaction temperature of 200-400° C., a reaction pressure of 0.1-3 MPa, and a mass space velocity of 0.5-3 h -1 The reaction was carried out under the following conditions to obtain isophorone.

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