A catalyst for methanol oxidation to formaldehyde and a preparation method and application thereof

Abstract

The application provides a catalyst for methanol oxidation to formaldehyde, a preparation method and application thereof, and the catalyst comprises an active component and a carrier, the carrier is silicon carbide, and the active component is molybdenum trioxide and lanthanum oxide. The application can effectively improve the crushing strength and thermal conductivity of the catalyst, no "three wastes" are discharged in the preparation process, the catalyst has extremely high formaldehyde selectivity and yield, can meet the requirements of the existing "air excess method" methanol oxidation to formaldehyde process, and the proportion of molybdenum trioxide in the catalyst is low, and the catalyst has the advantages of low cost.

Description

Technical Field

[0001] This invention relates to catalysts for the oxidation of methanol to formaldehyde, and more particularly to a catalyst for the oxidation of methanol to formaldehyde, its preparation method, and its application. Background Technology

[0002] In modern industry, formaldehyde is produced by oxidizing methanol in air. The mainstream processes are divided into the "methanol excess method" using silver as a catalyst and methanol in excess, and the "air excess method" using iron-molybdenum oxide as a catalyst and air in excess. Among them, the "air excess method" has achieved significant development in recent years due to its advantages such as high product quality, safety and environmental protection, and ease of large-scale production.

[0003] In recent years, most publicly available catalysts for the "air excess method" of methanol oxidation to formaldehyde, both domestically and internationally, are iron-molybdenum catalysts. The classic preparation process for these catalysts is the co-precipitation method (CN111229242, CN110066, CN100413584, US3978136, US4420421, US4829042, etc.). Other methods mainly include the sol-gel method (FR1604707, GB1282949, US3846341, etc.) and the solvothermal method (CN108114744, CN108097259, CN102240554, etc.). These preparation methods also generate large amounts of wastewater or polluting gases, severely polluting the environment. Furthermore, these catalysts generally have poor strength, and because iron-molybdenum oxides are poor conductors of heat, heat dissipation is insufficient during the methanol oxidation reaction, resulting in excessively high hotspot temperatures, leading to numerous byproducts and low selectivity for formaldehyde. Moreover, existing iron-molybdenum catalysts have a high molybdenum content, usually around 80%. Due to the high cost of molybdenum oxide, the production cost of such catalysts is relatively high.

[0004] Therefore, the existing technology has the following drawbacks:

[0005] 1. The strength of iron-molybdenum catalysts is generally poor. Because iron-molybdenum oxides are poor conductors of heat, heat dissipation is not timely during the methanol oxidation reaction, and the hot spot temperature is too high, resulting in more by-products and lower formaldehyde selectivity.

[0006] 2. The production and preparation of iron-molybdenum catalysts generate large amounts of wastewater or polluting gases, which seriously pollute the environment;

[0007] 3. Iron-molybdenum catalysts have a high molybdenum content, resulting in high costs. Summary of the Invention

[0008] The purpose of this invention is to overcome the defects of the prior art and provide a catalyst for the oxidation of methanol to formaldehyde, its preparation method and application. It can effectively improve the catalyst's crush resistance and thermal conductivity, has no "three wastes" emissions, and has extremely high formaldehyde selectivity and yield. It can meet the requirements of the existing "air excess method" methanol oxidation to formaldehyde process. Moreover, the catalyst has a low proportion of molybdenum oxide, which has the advantage of low cost.

[0009] This invention provides the following technical solution:

[0010] This invention provides a catalyst for the oxidation of methanol to formaldehyde, comprising an active component and a support, wherein the support is silicon carbide and the active component is molybdenum trioxide and lanthanum oxide.

[0011] Furthermore, the mass percentage of each component in the catalyst is: MoO3 48.0-58.2%, SiC 9.1-20.0%, and the balance is La2O3.

[0012] The catalyst incorporates a silicon carbide support, resulting in high crush resistance after molding. The silicon carbide support also provides thermal conductivity, effectively removing heat and mitigating the problems of insufficient heat dissipation and excessively high hotspot temperatures during the methanol oxidation to formaldehyde reaction. The active component utilizes a composite of molybdenum trioxide and lanthanum oxide, significantly improving thermal conductivity. This effectively enhances the formaldehyde selectivity in the reaction while reducing the proportion of molybdenum trioxide. The mass ratio of MoO3 in the catalyst of this invention is only 48.0–58.2%, which is significantly lower than the approximately 80% molybdenum oxide content in existing iron-molybdenum catalysts, offering a cost advantage.

[0013] The present invention also provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0014] S1. Weigh a certain amount of molybdenum source and lanthanum source according to the catalyst mass ratio, add water and ball mill to obtain material A;

[0015] S2. Mix material A with silicon carbide powder until uniform to obtain material B;

[0016] S3. Dry and cool material B, then calcine it to obtain material C;

[0017] S4. Add a release agent to material C, compress and form into tablets to obtain material D;

[0018] S5. Roast material D to obtain the catalyst.

[0019] Furthermore, the molybdenum source is ammonium molybdate or molybdic acid, and the lanthanum source is lanthanum acetate or lanthanum oxalate.

[0020] Further, in step S1, the ball milling is: ball milling at a rotation speed of 500-1500 r / m for 60-600 min in a ball mill.

[0021] Further, in step S3, the drying is performed at 60-150°C for 2-12 hours, and the calcination is performed at 300-350°C for 2-6 hours.

[0022] Furthermore, the release agent is stearic acid.

[0023] Furthermore, in step S5, the calcination is carried out at 400–550°C for 2–6 hours.

[0024] The present invention also provides the application of the above-mentioned catalyst in the production of formaldehyde by excess air oxidation of methanol.

[0025] The present invention has the following beneficial effects:

[0026] 1. The catalyst active component of this invention utilizes a composite of molybdenum trioxide and lanthanum oxide, with the addition of silicon carbide support, which significantly improves thermal conductivity, effectively reduces the reaction hot spot temperature, reduces the occurrence of side reactions, and improves the selectivity of the product formaldehyde, thereby significantly increasing the yield of the final product formaldehyde. As the silicon carbide content increases, the reaction hot spot temperature gradually decreases, and the catalyst strength increases significantly.

[0027] 2. The mass ratio of MoO3 in the catalyst of this invention is only 48.0-58.2%, which significantly reduces the amount of MoO3 used and can significantly reduce the cost of the catalyst;

[0028] 3. The catalyst of this invention is applied to the methanol oxidation to formaldehyde via the "excess air method", achieving a formaldehyde selectivity of up to 98% and a formaldehyde yield of up to 97.2%.

[0029] 3. The preparation method of the present invention is simple, green and environmentally friendly, and has high production safety. Compared with the traditional co-precipitation method, the mechanical ball milling method greatly simplifies the preparation process. The entire preparation process does not involve flammable and explosive organic solvents or easily explosive chemicals such as nitrates, ensuring safety. Moreover, the preparation process does not discharge wastewater or other "three wastes", making it environmentally friendly. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention provides a catalyst for the oxidation of methanol to formaldehyde, comprising an active component and a support, wherein the support is silicon carbide, and the active component is molybdenum trioxide and lanthanum oxide. The mass percentage of each component in the catalyst is: MoO3 48.0-58.2%, SiC 9.1-20.0%, and the balance is La2O3.

[0032] The present invention also provides a method for preparing the catalyst, including the following steps:

[0033] S1. Weigh a certain amount of molybdenum source and lanthanum source according to the catalyst mass ratio, add water and ball mill to obtain material A;

[0034] S2. Mix material A with silicon carbide powder until uniform to obtain material B;

[0035] S3. Dry and cool material B, then calcine it to obtain material C;

[0036] S4. Add a release agent to material C, compress and form into tablets to obtain material D;

[0037] S5. Roast material D to obtain the catalyst.

[0038] In a specific embodiment, the molybdenum source is ammonium molybdate or molybdic acid, and the lanthanum source is lanthanum acetate or lanthanum oxalate.

[0039] In a specific embodiment, in step S1, the ball milling is: ball milling at a rotation speed of 500-1500 r / m for 60-600 min in a ball mill.

[0040] In a specific embodiment, in step S3, the drying is performed at 60-150°C for 2-12 hours, and the calcination is performed at 300-350°C for 2-6 hours.

[0041] In a specific embodiment, the release agent is stearic acid.

[0042] In a specific embodiment, in step S5, the calcination is carried out at 400-550°C for 2-6 hours.

[0043] The present invention will be further illustrated below through specific embodiments:

[0044] Example 1

[0045] The preparation method of the catalyst for the methanol oxidation to formaldehyde in this embodiment is as follows:

[0046] 1. Weigh out ammonium molybdate containing 60.0 g MoO3 and lanthanum acetate containing 40.0 g La2O3, transfer them to a ball mill, add 20 ml of pure water, and ball mill at 1000 rpm for 120 minutes to obtain material A;

[0047] 2. Transfer the material A obtained in step 1 into a kneader, add 15 grams of silicon carbide powder, knead thoroughly and evenly to obtain material B;

[0048] 3. Dry the material B obtained in step 2 at 120℃ for 4 hours, cool it, and then calcine it at 320℃ for 3 hours to obtain material C;

[0049] 4. Weigh 50.0 g of material C obtained in step 3, add 1.0 g of stearic acid, mix well, compress into tablets, and obtain material D;

[0050] 5. The material D obtained in step 4 is calcined at 450℃ for 2 hours to obtain the finished catalyst.

[0051] Example 2

[0052] The preparation method of the catalyst for the methanol oxidation to formaldehyde in this embodiment is as follows:

[0053] 1. Weigh molybdic acid containing 57.0 g of MoO3 and lanthanum acetate containing 43.0 g of La2O3, transfer them into a ball mill, add 25 ml of pure water, and ball mill at 1500 rpm for 60 minutes to obtain material A;

[0054] 2. Transfer the material A obtained in step 1 into a kneader, add 25 grams of silicon carbide powder, knead thoroughly and evenly to obtain material B;

[0055] 3. Dry the material B obtained in step 2 at 60℃ for 12 hours, cool it, and then calcine it at 350℃ for 2 hours to obtain material C;

[0056] 4. Weigh 50.0 g of material C obtained in step 3, add 1.0 g of stearic acid, mix well, compress into tablets, and obtain material D;

[0057] 5. The material D obtained in step 4 is calcined at 400℃ for 12 hours to obtain the finished catalyst.

[0058] Example 3

[0059] The preparation method of the catalyst for the methanol oxidation to formaldehyde in this embodiment is as follows:

[0060] 1. Weigh out ammonium molybdate containing 64.0 g of MoO3 and lanthanum oxalate containing 36.0 g of La2O3, transfer them into a ball mill, add 21 ml of pure water, and ball mill at 500 rpm for 600 minutes to obtain material A;

[0061] 2. Transfer material A obtained in step 1 into a kneader, add 10 grams of silicon carbide powder, knead thoroughly and evenly to obtain material B;

[0062] 3. Dry the material B obtained in step 2 at 150℃ for 2 hours, cool it, and then calcine it at 300℃ for 12 hours to obtain material C;

[0063] 4. Weigh 50.0 g of material C obtained in step 3, add 1.0 g of stearic acid, mix well, compress into tablets, and obtain material D;

[0064] 5. The material D obtained in step 4 is calcined at 550℃ for 2 hours to obtain the finished catalyst.

[0065] Example 4

[0066] The preparation method of the catalyst for the methanol oxidation to formaldehyde in this embodiment is as follows:

[0067] 1. Weigh molybdic acid containing 64.0 g of MoO3 and lanthanum oxalate containing 36.0 g of La2O3, transfer them into a ball mill, add 22 ml of pure water, and ball mill at 800 rpm for 300 minutes to obtain material A;

[0068] 2. Transfer the material A obtained in step 1 into a kneader, add 12 grams of silicon carbide powder, knead thoroughly and evenly to obtain material B;

[0069] 3. Dry the material B obtained in step 2 at 120℃ for 4 hours, cool it, and then calcine it at 340℃ for 4 hours to obtain material C;

[0070] 4. Weigh 50.0 g of material C obtained in step 3, add 1.0 g of stearic acid, mix well, compress into tablets, and obtain material D;

[0071] 5. The material D obtained in step 4 is calcined at 500℃ for 3 hours to obtain the finished catalyst.

[0072] Example 5

[0073] The preparation method of the catalyst for the methanol oxidation to formaldehyde in this embodiment is as follows:

[0074] 1. Weigh out ammonium molybdate containing 57.0 g of MoO3 and lanthanum acetate containing 43.0 g of La2O3, transfer them into a ball mill, add 25 ml of pure water, and ball mill at 1200 rpm for 120 minutes to obtain material A;

[0075] 2. Transfer material A obtained in step 1 into a kneader, add 10 grams of silicon carbide powder, knead thoroughly and evenly to obtain material B;

[0076] 3. Dry the material B obtained in step 2 at 100℃ for 6 hours, cool it, and then calcine it at 330℃ for 4 hours to obtain material C;

[0077] 4. Weigh 50.0 g of material C obtained in step 3, add 1.0 g of stearic acid, mix well, compress into tablets, and obtain material D;

[0078] 5. The material D obtained in step 4 is calcined at 430℃ for 4 hours to obtain the finished catalyst.

[0079] Example 6

[0080] The preparation method of the catalyst for the methanol oxidation to formaldehyde in this embodiment is as follows:

[0081] 1. Weigh out ammonium molybdate containing 60.0 g MoO3 and lanthanum acetate containing 40.0 g La2O3, transfer them to a ball mill, add 20 ml of pure water, and ball mill at 1000 rpm for 120 minutes to obtain material A;

[0082] 2. Transfer material A obtained in step 1 into a kneader, add 10 grams of silicon carbide powder, knead thoroughly and evenly to obtain material B;

[0083] 3. Dry the material B obtained in step 2 at 120℃ for 4 hours, cool it, and then calcine it at 320℃ for 3 hours to obtain material C;

[0084] 4. Weigh 50.0 g of material C obtained in step 3, add 1.0 g of stearic acid, mix well, compress into tablets, and obtain material D;

[0085] 5. The material D obtained in step 4 is calcined at 450℃ for 2 hours to obtain the finished catalyst.

[0086] Example 7

[0087] The preparation method of the catalyst for the methanol oxidation to formaldehyde in this embodiment is as follows:

[0088] 1. Weigh out ammonium molybdate containing 60.0 g MoO3 and lanthanum acetate containing 40.0 g La2O3, transfer them to a ball mill, add 20 ml of pure water, and ball mill at 1000 rpm for 120 minutes to obtain material A;

[0089] 2. Transfer the material A obtained in step 1 into a kneader, add 20 grams of silicon carbide powder, knead thoroughly and evenly to obtain material B;

[0090] 3. Dry the material B obtained in step 2 at 120℃ for 4 hours, cool it, and then calcine it at 320℃ for 3 hours to obtain material C;

[0091] 4. Weigh 50.0 g of material C obtained in step 3, add 1.0 g of stearic acid, mix well, compress into tablets, and obtain material D;

[0092] 5. The material D obtained in step 4 is calcined at 450℃ for 2 hours to obtain the finished catalyst.

[0093] Example 8

[0094] The preparation method of the catalyst for the methanol oxidation to formaldehyde in this embodiment is as follows:

[0095] 1. Weigh out ammonium molybdate containing 60.0 g MoO3 and lanthanum acetate containing 40.0 g La2O3, transfer them to a ball mill, add 20 ml of pure water, and ball mill at 1000 rpm for 120 minutes to obtain material A;

[0096] 2. Transfer the material A obtained in step 1 into a kneader, add 25 grams of silicon carbide powder, knead thoroughly and evenly to obtain material B;

[0097] 3. Dry the material B obtained in step 2 at 120℃ for 4 hours, cool it, and then calcine it at 320℃ for 3 hours to obtain material C;

[0098] 4. Weigh 50.0 g of material C obtained in step 3, add 1.0 g of stearic acid, mix well, compress into tablets, and obtain material D;

[0099] 5. The material D obtained in step 4 is calcined at 450℃ for 2 hours to obtain the finished catalyst.

[0100] Comparative Example 1

[0101] Using the commonly used iron-molybdenum catalyst in the prior art as a comparison, and referring to patent ZL201110106337.7, the preparation process is as follows:

[0102] 1. Dissolve 5 mol of ethylene glycol in 5000 ml of deionized water to obtain the base solution;

[0103] 2. Add molybdic acid containing 1 mol of molybdenum trioxide to the above base solution and mix thoroughly;

[0104] 3. Preheat the slurry to 90℃;

[0105] 4. Air is introduced into a storage tank containing 0.2 mol of ferric oxide at a rate of 0.5 L / min to obtain air saturated with ferric oxide.

[0106] 5. Pass the air saturated with carbonyl iron into the slurry preheated in step 3;

[0107] 6. After the iron pentacarbonyl has completely volatilized, the slurry after the reaction is aged at 90°C for 12 hours, and then filtered to obtain a filter cake;

[0108] 7. The filter cake is dried at 80℃, pulverized, pressed into tablets, and calcined at 450℃ to obtain the formaldehyde iron-molybdenum catalyst.

[0109] The performance of the catalysts prepared in Examples 1-8 and Comparative Example 1 was evaluated:

[0110] Catalyst activity testing was conducted using a stainless steel fixed-bed jacketed tubular reactor with a tube diameter of Φ25×2.0mm and a reactor length of 1000cm. The heat transfer oil was heated by an immersion electric heater, and the temperature was controlled by a regulator.

[0111] The evaluation conditions were as follows: original particle evaluation; system pressure was atmospheric pressure, reaction temperature was 280℃, and dry gas hourly space velocity was 10000 h⁻¹. -1 The imported methanol content is 8.0–10.0%, the oxygen content is 10.0–12.0%, and the catalyst dosage is 30 ml. Gas chromatography is used to analyze the composition of the liquid and gas at the reactor outlet, and the selectivity and yield of formaldehyde are calculated accordingly.

[0112] The specific catalyst composition and properties are shown in Table 1:

[0113] Table 1. Catalyst composition and properties in each embodiment.

[0114]

[0115] As shown in Table 1, the reaction hotspot temperatures in Examples 1-8 were significantly lower than those in Comparative Example 1, with a maximum reduction of 17°C (Example 8), and the crush resistance was significantly higher than that in Comparative Example 1, with a maximum increase of over 30% (Example 8). Furthermore, with the increase of silicon carbide addition, the reaction hotspot temperature gradually decreased, and the crush resistance gradually increased, showing a significant correlation. It is well known that improving crush resistance helps reduce the resistance of the catalyst bed in formaldehyde industrial production, reduces power consumption in industrial formaldehyde production, and helps reduce operating costs. Lowering the hotspot temperature helps reduce the occurrence of side reactions, improves the selectivity of the product formaldehyde, and thus significantly increases the yield of the final formaldehyde product, which can significantly improve the economic benefits of the plant. The above data demonstrate that the catalyst and its preparation method proposed in this invention have significant advantages.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A catalyst for the oxidation of methanol to formaldehyde, characterized in that, It includes an active component and a support, wherein the support is silicon carbide and the active component is molybdenum trioxide and lanthanum oxide; The mass percentage of each component in the catalyst is: MoO3 48.0-50.0%, SiC 16.7-20.0%, with the balance being La2O3; The method for preparing the catalyst for the methanol oxidation to formaldehyde includes the following steps: S1. Weigh a certain amount of molybdenum source and lanthanum source according to the catalyst mass ratio, add water and ball mill to obtain material A; S2. Mix material A with silicon carbide powder until uniform to obtain material B; S3. Dry and cool material B, then calcine it to obtain material C; S4. Add a release agent to material C, compress and form into tablets to obtain material D; S5. Calcining material D yields the catalyst. The molybdenum source is ammonium molybdate or molybdic acid, and the lanthanum source is lanthanum acetate or lanthanum oxalate; In step S3, the calcination is carried out at 300-350°C for 2-6 hours; The release agent is stearic acid; In step S5, the calcination is carried out at 400-550°C for 2-6 hours.

2. The method for preparing the catalyst for the methanol oxidation to formaldehyde according to claim 1, characterized in that, Includes the following steps: S1. Weigh a certain amount of molybdenum source and lanthanum source according to the catalyst mass ratio, add water and ball mill to obtain material A; S2. Mix material A with silicon carbide powder until uniform to obtain material B; S3. Dry and cool material B, then calcine it to obtain material C; S4. Add a release agent to material C, compress and form into tablets to obtain material D; S5. Calcining material D yields the catalyst. The molybdenum source is ammonium molybdate or molybdic acid, and the lanthanum source is lanthanum acetate or lanthanum oxalate; In step S3, the calcination is carried out at 300-350°C for 2-6 hours; The release agent is stearic acid; In step S5, the calcination is carried out at 400-550°C for 2-6 hours.

3. The method for preparing the catalyst for the methanol oxidation to formaldehyde as described in claim 2, characterized in that: In step S1, the ball milling is performed by ball milling at a speed of 500-1500 r / m for 60-600 min.

4. The method for preparing the catalyst for the methanol oxidation to formaldehyde as described in claim 2, characterized in that: In step S3, the drying process involves drying at 60–150°C for 2–12 hours.

5. The application of the catalyst according to claim 1 in the production of formaldehyde by excess air oxidation of methanol.

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