High-performance catalyst for methanol oxidation to formaldehyde and application thereof

Abstract

This invention relates to a method for preparing a catalyst for the oxidation of methanol to formaldehyde and its application. The catalyst is an iron-molybdenum-based composite element oxide catalyst, comprising an active metal component and composite elements. The active metal component is mainly iron and molybdenum, with composite elements doped in. The catalyst reacts in a fixed-bed reactor, with methanol pumped in, under normal pressure, at a reaction temperature of 200℃–450℃, and a volume hourly space velocity (VHSV) of 6000–13000 h⁻¹. ‑1 This method uses an iron-molybdenum doped composite element oxide catalyst for the oxidation of methanol to formaldehyde. The methanol conversion rate can reach 98%, and the formaldehyde selectivity is as high as 93%, exhibiting high activity and selectivity. The catalyst has a long lifespan and has great potential for industrial production applications.

Description

Technical Field

[0001] This invention belongs to the field of alcohol oxidation to aldehyde catalyst technology, specifically relating to a method for preparing and applying a methanol oxidation to formaldehyde catalyst. Background Technology

[0002] Formaldehyde's importance in industry lies in its wide range of applications and its role as a fundamental chemical raw material. Formaldehyde is an indispensable raw material in the production of synthetic resins and is widely used in the manufacture of electrical equipment, automotive parts, and mechanical components. Adhesives formed by the reaction of formaldehyde with compounds such as urea and melamine are widely used in the wood processing, construction, and automotive industries due to their excellent bonding properties and water resistance. Simultaneously, formaldehyde is also an important raw material for manufacturing coatings with excellent weather resistance, corrosion resistance, and decorative properties. Due to its bactericidal and insecticidal effects, formaldehyde is widely used as a preservative and insect repellent in the electronics, textile, leather, and construction industries. Because of its unique chemical properties and wide range of applications, formaldehyde plays a crucial role in modern industry.

[0003] Currently, formaldehyde production processes mainly include methanol oxidation, natural gas oxidation, dimethyl ether oxidation, and methanol dehydrogenation. Among these, methanol oxidation is the mainstream process, accounting for over 90% of global formaldehyde production. Commonly used catalysts in methanol oxidation include silver catalysts and iron-molybdenum oxide catalysts. The silver process operates with excess methanol, while the iron-molybdenum process operates with excess air. Patent CN111229242B discloses a method for preparing and applying an iron-molybdenum-based catalyst for methanol oxidation to formaldehyde. This catalyst is prepared by adjusting the pH of the raw materials and using a micro-flow pump to precisely control the mixing rate of molybdenum and iron salts, thereby accurately controlling the spatial relationship and ratio of the active components and co-catalysts. This achieves efficient methanol conversion while maintaining high stability. Patent CN116764643A discloses a doped copper-iron-molybdenum catalyst, its preparation method, and its application. This doped copper-iron-molybdenum catalyst has low copper doping, high catalyst activity, good stability, and remains active for 60 hours without deactivation.

[0004] The above catalyst preparation processes are complex, and there is a lack of long-term stable operation data, making industrial-scale scaling difficult. Therefore, developing a composite catalyst system for the methanol oxidation to formaldehyde reaction, doped with iron and molybdenum and other elements, is of great significance for improving its reactivity and lifetime stability. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high-performance catalyst for the oxidation of methanol to formaldehyde and its application.

[0006] This invention describes a catalyst for the methanol oxidation to formaldehyde, a molybdenum-based composite element oxide catalyst. The main active components are metallic iron and molybdenum, doped with one or more of the composite elements Cu, Co, Si, Ni, Ti, Mn, Cr, Sn, K, and W. The catalyst is prepared and synthesized by one or more of the following methods: co-precipitation, solid-phase ball milling, impregnation, or sol-gel method. The precursors for the active component metallic iron are one or more of Fe(NO3)3, FeCl3, Fe2(SO4)3, FePO4, Fe2O3, and Fe(C2H3O2)2; the precursors for the active component metallic molybdenum are (NH4)2MoO4, MoC, MoCl5, MoS2, MoO3, and H3[P(Mo3O4)2]. 10 The composite element is one or more of the following: [4]. The precursor of the composite element is one or more of the following: nitrate, chloride, sulfate, phosphate, oxide, citrate, stearate, and acetate of the corresponding element. The iron-molybdenum based composite element oxide catalyst has an active molybdenum oxide to iron oxide mass ratio of 1:1 to 8:1, and the composite element oxide content is 0.5 wt% to 75 wt%. This invention also relates to the application of the catalyst, which can be used in the methanol oxidation to formaldehyde reaction.

[0007] The process of using iron-molybdenum based composite element oxide catalyst in the methanol oxidation to formaldehyde reaction is as follows: The catalyst is loaded into a fixed-bed reactor with a loading height of 5 mm to 25 mm. The reaction is carried out at atmospheric pressure, and a nitrogen-oxygen mixture (oxygen volume concentration of 5%-15%) is introduced as the oxidant. Methanol is fed into the reactor to start the reaction. The volume ratio of methanol to nitrogen-oxygen mixture is 1:20 to 1:5, and the volume hourly space velocity (VHSV) is 6000 to 13000 h⁻¹. -1 The reaction temperature is 200℃~450℃.

[0008] The iron-molybdenum-based composite element oxide catalysts used for the methanol oxidation to formaldehyde have the following characteristics: (1) By doping other elements, the bulk structure of the iron-molybdenum catalyst can be changed, accelerating the oxidation process. The combination of the doped elements and iron-molybdenum produces a synergistic effect on methanol oxidation, improving the catalyst activity. (2) Under specific conditions, the doping of iron-molybdenum with other elements can help activate the methanol methoxy group, reduce the loss of active components in the catalyst, and thus improve the catalyst lifetime stability.

[0009] The advantages of this method are: (1) It significantly improves the activity of iron-molybdenum based composite element oxide catalysts, and has the advantages of low cost and excellent effect. (2) By optimizing the catalyst through doping elements, the stability of the oxidation reaction can be significantly improved, the service life of the catalyst can be extended, and the economic benefits are significant.

[0010] This method uses an iron-molybdenum doped composite element oxide catalyst for the oxidation of methanol to formaldehyde. The methanol conversion rate can reach 98%, and the formaldehyde selectivity is as high as 93%, showing high activity, selectivity and stability, and has great potential for industrial application. Detailed Implementation

[0011] To provide a more detailed description of the present invention, several specific implementation examples are given below, but the present invention is not limited to these embodiments.

[0012] After the iron-molybdenum based composite element oxide catalyst is prepared, it is directly extruded, granulated, sieved, and then packed into a fixed-bed reactor for methanol oxidation to formaldehyde reaction. The product obtained from the reaction is analyzed and calculated.

[0013] Example 1

[0014] The catalyst for the methanol oxidation to formaldehyde production was prepared by solid-phase ball milling. The specific operation process is as follows: 32.96 g of Fe2(MoO4), 1.29 g of MoO3, and 0.80 g of CoO were weighed and added to a ball mill jar. Then, milling beads were added, and the mixture was placed in a planetary ball mill at 500 r / min in one direction for 2 hours. The sample was then removed and calcined in a muffle furnace at 400℃ for 4 hours under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to a 40-60 mesh, and 0.9 mL was loaded into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under atmospheric pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity (VHSV) of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 98%, and the selectivity of formaldehyde was 93%. After 2000 hours of stable operation, the conversion rate of methanol was 96%, and the selectivity of formaldehyde was 87%.

[0015] Example 2

[0016] The catalyst for the methanol oxidation to formaldehyde production was prepared by impregnation. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. Then, 3.46 g of molybdenum oxide was weighed and added to the solution. The mixture was stirred and dried in an 80℃ water bath. The resulting solid was calcined in an air atmosphere at 400℃ for 4 hours to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to a 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 90%, and the selectivity of formaldehyde was 88%.

[0017] Example 3

[0018] The catalyst for the methanol oxidation to formaldehyde was prepared using the sol-gel method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. Citric acid solution (the concentration of citric acid and total metal ions were both 0.25 mol / L) was added, and the mixture was stirred evenly. The solution was evaporated in a water bath at 70 °C to obtain a transparent sol. After drying at 100 °C for 12 h, a dry gel was obtained. The gel was then calcined in a muffle furnace at 400 °C for 10 h under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to a mesh size of 40-60, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure, and anhydrous methanol was fed using a plunger pump. The volume ratio of methanol to the nitrogen-oxygen mixture was 1:10, and the volume hourly space velocity (HSV) was 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 94%, and the selectivity of formaldehyde was 87%.

[0019] Example 4

[0020] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in an air atmosphere at 400℃ for 10 h to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 98%, and the selectivity of formaldehyde was 93%. After 2000 hours of stable operation, the conversion rate of methanol was 97%, and the selectivity of formaldehyde was 93%.

[0021] Example 5

[0022] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 3.24 g of Cu(NO3)2·3H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in an air atmosphere at 400℃ for 10 h to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 92%, and the selectivity of formaldehyde was 81%.

[0023] Example 6

[0024] The catalyst for the methanol oxidation to formaldehyde production was prepared using the sol-gel method. The specific procedure is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 5.33 g of 20% silica sol were weighed and dissolved in 100 mL of water. Citric acid solution (with a concentration of 0.25 mol / L for both citric acid and total metal ions) was added, and the mixture was stirred until homogeneous. The solution was then evaporated in a water bath at 70°C to obtain a transparent sol. After drying at 100°C for 12 h, a dry gel was obtained. This gel was then calcined in a muffle furnace at 400°C for 10 h under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% SiO2. The catalyst was directly extruded and granulated, sieved to a mesh size of 40-60, and 0.9 mL was loaded into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320°C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure, and anhydrous methanol was fed using a plunger pump. The volume ratio of methanol to the nitrogen-oxygen mixture was 1:10, and the volume hourly space velocity (HSV) was 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 94%, and the selectivity of formaldehyde was 90%.

[0025] Example 7

[0026] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 4.15 g of Ni(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in an air atmosphere at 400℃ for 10 h to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% NiO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was loaded into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 82%, and the selectivity of formaldehyde was 78%.

[0027] Example 8

[0028] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 2.53 g of TiCl4 were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was then dried and calcined in a muffle furnace at 400 °C for 10 h under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% TiO2. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was loaded into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under atmospheric pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 87%, and the selectivity of formaldehyde was 79%.

[0029] Example 9

[0030] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 3.77 g of Mn(NO3)2·4H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in an air atmosphere at 400 °C for 10 h to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% MnO. The catalyst was directly extruded and granulated, sieved to a 40-60 mesh, and 0.9 mL was filled into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure, and anhydrous methanol was fed using a plunger pump. The volume ratio of methanol to the nitrogen-oxygen mixture was 1:10, and the volume hourly space velocity (HSV) was 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 96%, and the selectivity of formaldehyde was 83%.

[0031] Example 10

[0032] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 5.63 g of Cr(NO3)3·9H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in an air atmosphere at 400 °C for 10 h to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% Cr2O3. The catalyst was directly extruded and granulated, sieved to a 40-60 mesh, and 0.9 mL was filled into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure, and anhydrous methanol was fed using a plunger pump. The volume ratio of methanol to the nitrogen-oxygen mixture was 1:10, and the volume hourly space velocity (HSV) was 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 95%, and the selectivity of formaldehyde was 71%.

[0033] Example 11

[0034] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 1.68 g of Sn(CH3CO2)2 were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in a muffle furnace at 400 °C for 10 h under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% SnO2. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 97%, and the selectivity of formaldehyde was 82%.

[0035] Example 12

[0036] The methanol oxidation to formaldehyde catalyst was prepared by solid-phase ball milling. The specific operation process is as follows: 32.96 g of Fe2(MoO4), 1.29 g of MoO3, and 0.80 g of K2O were weighed and added to a ball mill jar. Then, grinding beads were added, and the mixture was placed in a planetary ball mill at 500 r / min in one direction for 2 hours. The sample was then removed and calcined in a muffle furnace at 400℃ for 4 hours under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% K2O. The catalyst was directly extruded and granulated, sieved to a 40-60 mesh, and 0.9 mL was loaded into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under atmospheric pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity (VHSV) of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 90%, and the selectivity of formaldehyde was 91%.

[0037] Example 13

[0038] The catalyst for the methanol oxidation to formaldehyde was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and (NH4)6W7O were weighed. 24 1.24 g of ·6H₂O was dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in a muffle furnace at 400 °C for 10 h in air to obtain a catalyst of 15 wt% Fe₂O₃-65 wt% MoO₃-20 wt% WO₃. The catalyst was directly extruded and granulated, sieved through a 40-60 mesh sieve, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 94%, and the selectivity of formaldehyde was 92%.

[0039] Example 14

[0040] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 3.26 g of (NH4)2MoO4, and 8.28 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in a muffle furnace at 400 °C for 10 h under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-45 wt% MoO3-40 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 96%, and the selectivity of formaldehyde was 68%.

[0041] Example 15

[0042] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 5.80 g of (NH4)2MoO, and 1.04 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in an air atmosphere at 400℃ for 10 h to obtain a catalyst of 15 wt% Fe2O3-80 wt% MoO3-5 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 83%, and the selectivity of formaldehyde was 89%.

[0043] Example 16

[0044] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in an air atmosphere at 400℃ for 10 h to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 400℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 98%, and the selectivity of formaldehyde was 83%.

[0045] Example 17

[0046] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in a muffle furnace at 400℃ for 10 h under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 350℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 98%, and the selectivity of formaldehyde was 88%.

[0047] Example 18

[0048] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in a muffle furnace at 400℃ for 10 h under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 210℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 76%, and the selectivity of formaldehyde was 93%.

[0049] Example 19

[0050] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in a muffle furnace at 400℃ for 10 h under air atmosphere to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 7000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 98%, and the selectivity of formaldehyde was 81%.

[0051] Example 20

[0052] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O, 4.71 g of (NH4)2MoO4, and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and then calcined in an air atmosphere at 400 °C for 10 h to obtain a catalyst of 15 wt% Fe2O3-65 wt% MoO3-20 wt% CoO. The catalyst was directly extruded and granulated, sieved to a 40-60 mesh, and 0.9 mL was filled into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure, and anhydrous methanol was fed using a plunger pump. The volume ratio of methanol to the nitrogen-oxygen mixture was 1:10, and the volume hourly space velocity (VHSV) was 11000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 89%, and the selectivity of formaldehyde was 93%.

[0053] Comparative Example 1

[0054] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O and 4.71 g of (NH4)2MoO4 were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was then dried and calcined in a muffle furnace at 400℃ for 10 h under air atmosphere to obtain a catalyst of 19 wt% Fe2O3-81 wt% MoO. The catalyst was directly extruded and granulated, sieved to a 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken and analyzed. The conversion rate of methanol was 96% and the selectivity of formaldehyde was 91%. After 2000 hours of stable operation, the conversion rate of methanol was 66% and the selectivity of formaldehyde was 86%.

[0055] Comparative Example 2

[0056] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.71 g of (NH4)2MoO4 and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was dried and calcined in a muffle furnace at 400 °C for 10 h under air atmosphere to obtain a catalyst of 76 wt% MoO3-24 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320 °C. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 61%, and the selectivity of formaldehyde was 41%.

[0057] Comparative Example 3

[0058] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 4.04 g of Fe(NO3)3·9H2O and 4.14 g of Co(NO3)2·6H2O were weighed and dissolved in 100 mL of water. The pH of the solution was adjusted to 10 with a 10% ammonia solution. The solution was filtered to obtain a solid, which was then dried and calcined in a muffle furnace at 400℃ for 10 h under air atmosphere to obtain a catalyst of 43 wt% Fe2O3-57 wt% CoO. The catalyst was directly extruded and granulated, sieved to 40-60 mesh, and 0.9 mL was loaded into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 320℃. A nitrogen-oxygen mixture (oxygen volume concentration of 10%) was simultaneously introduced under normal pressure. Anhydrous methanol was fed using a plunger pump, with a methanol-to-nitrogen-oxygen mixture volume ratio of 1:10 and a volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 47%, and the selectivity of formaldehyde was 37%.

[0059] The above descriptions are merely a few embodiments of this application and do not constitute any limitation on this application. Any changes or modifications made to the technical content disclosed above without departing from the scope of the technical solution of this application are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A high-performance iron-molybdenum based composite element oxide catalyst, characterized in that: The catalyst for the methanol oxidation to formaldehyde is an iron-molybdenum based composite element oxide catalyst, with the main active components being metallic iron and molybdenum, and doped with composite elements. The catalyst contains one or more of the following composite elements: Cu, Co, Si, Ni, Ti, Mn, Cr, Sn, K, and W.

2. The catalyst according to claim 1, characterized in that: The iron-molybdenum based composite element oxide catalyst is prepared and synthesized from corresponding element precursor raw materials using one or more of the following methods: co-precipitation, solid-phase ball milling, impregnation, or sol-gel method.

3. The catalyst according to claim 1 or 2, characterized in that: The precursor of the active ingredient metallic iron is one or more of Fe(NO3)3, FeCl3, Fe2(SO4)3, FePO4, Fe2O3, and Fe(C2H3O2)2. The precursors of the active ingredient, metallic molybdenum, are (NH4)2MoO4, MoC, MoCl5, MoS2, MoO3, and H3[P(Mo3O]]. 10 One or more of the following: )4] The precursor of the composite element is one or more of the following: nitrate, chloride, sulfate, phosphate, oxide, citrate, stearate, and acetate of the corresponding element.

4. The catalyst according to claim 1 or 2, characterized in that: The iron-molybdenum based composite element oxide catalyst has an active metal molybdenum oxide to iron oxide mass ratio of 1:1 to 8:1 and a composite element oxide content of 0.5wt% to 75wt%.

5. The catalyst according to claim 3, characterized in that: The preferred mass ratio of active molybdenum oxide to iron oxide in the iron-molybdenum based composite element oxide catalyst is 1:1 to 6:1, and the preferred content of composite element oxide is 2wt% to 60wt%.

6. The application of the iron-molybdenum based composite element oxide catalyst according to any one of claims 1-5, characterized in that: The process of the iron-molybdenum based composite element oxide catalyst in the methanol oxidation to formaldehyde reaction is as follows: The catalyst is transferred and packed into a fixed-bed reactor with a packing height of 5 mm to 25 mm. The reaction is carried out at atmospheric pressure, and a nitrogen-oxygen mixture is introduced as the oxidant (oxygen volume concentration of 5%-15%). Methanol is fed in to start the reaction, and the volume ratio of methanol to nitrogen-oxygen mixture is 1:20 to 1:

5. The volume hourly space velocity of the methanol-nitrogen-oxygen mixture is 6000 to 13000 h⁻¹. -1 The reaction temperature is 200℃~450℃.

7. The application according to claim 6, characterized in that: The preferred reaction conditions are: the catalyst is packed to a height of 10 mm to 20 mm in the fixed bed, and the reaction volume hourly space velocity is 7000 to 11000 h⁻¹. -1 .