A method for preparing formaldehyde by catalyzing methanol oxidation with an iron-vanadium-based oxide catalyst

Abstract

The present application relates to a kind of high efficient stable methanol oxidation method for preparing formaldehyde.The method uses anhydrous methanol as reactant, under the catalysis of iron-vanadium-based oxide catalyst, nitrogen-oxygen mixed gas as oxidant, and prepares formaldehyde by oxidation reaction.The reaction conditions are as follows:the reaction is carried out in a fixed bed reactor under normal pressure, the reaction temperature is 190 DEG C-420 DEG C, the volume space velocity is 5000-15000h ‑1 The main active component of iron-vanadium-based oxide catalyst is iron-vanadium metal oxide, doped with one or more element oxides, used for methanol oxidation to prepare formaldehyde, the methanol conversion rate can reach 97%, the formaldehyde selectivity is as high as 93%, the catalyst has strong long-term running stability, and has significant industrial economic benefits.

Description

Technical Field

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

[0002] Formaldehyde, as an important chemical raw material, has wide applications and significant value in the industrial field. It is one of the main raw materials for producing adhesives, especially phenolic resin adhesives, urea-formaldehyde resin adhesives, and melamine-formaldehyde resin adhesives. These adhesives are widely used in real estate, furniture, and building materials. In the textile industry, formaldehyde is used in the finishing process of clothing to achieve effects such as wrinkle prevention, shrinkage prevention, and flame retardancy, or to maintain the durability of printing and dyeing, and improve the feel. Formaldehyde is used to produce polyoxymethylene (POM), an engineering plastic with excellent comprehensive performance, known as "super steel" or "acetal," due to its high mechanical strength, good electrical insulation, high toughness, and high wear resistance, and is widely used in industrial machinery, automobile manufacturing, and electronics. Formaldehyde derivatives include paraformaldehyde, phenolic resins, urea-formaldehyde resins, amino resins, hexamethylenetetramine products, and polyols, which are widely used in pesticides, disinfectants, wood processing, water treatment, coatings, pharmaceuticals, and dyes.

[0003] Industrially, formaldehyde is mainly produced using air oxidation, primarily through silver catalyst and iron-molybdenum catalyst methods. The silver catalyst method uses methanol as a raw material, employing silver wire mesh or thin layers of silver particles as the catalyst. This process is simple, requires low investment, has strong adjustability, and produces a product with low formic acid content. The iron-molybdenum catalyst method produces formaldehyde with a larger production capacity, high methanol conversion rate (up to 95%-99%), low methanol consumption, no need for distillation equipment, and can produce high-concentration formaldehyde. The finished formaldehyde product has a low alcohol content, and the catalyst has a long lifespan. In recent years, there has been a focus on developing various catalysts for the direct oxidation of methanol to formaldehyde, including metals and their oxides, noble metal catalysts, and heteropoly acids. Patent CN117696068B discloses a methanol oxidation catalyst for formaldehyde, using multi-walled carbon nanotubes as a support and Mo, Fe, V, and Mn as active components, exhibiting excellent reactivity. Patent CN117772219A discloses a multi-metal oxide-doped calcium molybdate-based catalyst for the oxidation of methanol to formaldehyde. Using CaMoO4 with a mass ratio of over 95% as the active center, it lowers the reaction temperature for the methanol-to-formaldehyde oxidation process. The doped metal oxides can improve the conversion rate of the raw material methanol and the selectivity of the target product formaldehyde. Patent CN116943672A discloses a catalyst for the oxidation of methanol to formaldehyde, using Zr(MoO4)2 as the matrix. The matrix surface is covered from the inside out with MoO3 and Fe2(MoO4)3 phases, with Zr(MoO4)2 phase interspersed in the middle, forming a composite morphology with excellent activity, selectivity, and stability.

[0004] While the aforementioned catalysts achieved the oxidation of methanol to formaldehyde, their preparation processes were complex and costly. Therefore, developing solid catalyst systems that are economical, stable, highly reactive, and exhibit good selectivity is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing formaldehyde by catalytic oxidation of methanol using an iron-vanadium-based oxide catalyst. This method features a simple reaction process, a non-toxic catalyst with high selectivity for formaldehyde, good stability, long lifespan, and low economic cost.

[0006] The formaldehyde involved in this invention is prepared by the following method.

[0007] Methanol is reacted to formaldehyde in a fixed-bed reactor using nitrogen or an argon-oxygen mixture as the oxidant and an iron-vanadium-based oxide catalyst. Methanol is used as the raw material, the catalyst is packed in the fixed bed to a height of 4 mm–29 mm (preferably 11 mm–19 mm), nitrogen and / or an argon-oxygen mixture is introduced as the oxidant (oxygen volume concentration in the mixture is 3%–17%, preferably 7%–13%), the methanol to mixture volume ratio is 1:25–1:4, the reaction temperature is 190℃–480℃ (preferably 200℃–430℃), and the volume hourly space velocity (HSV) of methanol and the mixture is 5000–15000 h⁻¹. -1 (Preferred to be 7000~11000h) -1 ).

[0008] The iron-vanadium-based oxide catalyst is composed of active metallic iron, vanadium, and other composite elements, which are one or more of nickel, cobalt, silicon, potassium, cerium, barium, calcium, zirconium, molybdenum, and tungsten. The iron-vanadium-based oxide 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 content of active metallic iron is 3 wt% to 70 wt% (based on the weight of oxides), the content of active metallic vanadium is 5 wt% to 90 wt% (based on the weight of oxides), and the remainder is 2% to 65% of other composite element oxides. The precursor of the active component metallic iron in the catalyst is one or more of ferric nitrate, ferric chloride, ferric sulfate, ferric phosphate, ferric oxide, and ferric acetate; the precursor of the active component metallic vanadium is one or more of vanadium chloride, ammonium metavanadate, vanadium oxide, vanadium fluoride, vanadium carbide, vanadium sulfide, vanadium oxysulfate, vanadium trichloride, vanadium nitride, and vanadium oxalate.

[0009] The catalytic oxidation of methanol to formaldehyde by iron-vanadium-based oxide catalysts has the following characteristics: (1) The strong interaction between iron-vanadium and composite element oxides greatly enhances the redox properties of the catalyst, thus significantly improving the low-temperature activity of the catalyst and greatly widening the temperature window. (2) The doping of composite elements improves the interaction between the catalyst and the catalyst, which can reduce the loss of oxygen vacancies, thereby improving the catalytic activity and stability of the catalyst.

[0010] The advantages of this method are: (1) The iron-vanadium-based oxide catalyst has a long service life and good stability, which reduces the frequency and cost of catalyst replacement. (2) After the iron-vanadium catalyst is doped with other metals, it helps to activate methoxy groups, which can significantly improve the low-temperature activity and broaden the temperature window.

[0011] Iron-vanadium based oxide catalysts are used in the methanol oxidation to formaldehyde reaction, achieving a methanol conversion rate of up to 97% and a formaldehyde selectivity of up to 93%. The catalysts exhibit strong long-term operational stability and significant industrial economic benefits. Detailed Implementation

[0012] 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.

[0013] After the iron-vanadium-based 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 resulting reaction products are then analyzed and calculated.

[0014] Example 1

[0015] The catalyst for the methanol oxidation to formaldehyde production was prepared by solid-phase ball milling. The specific operation process is as follows: 1.60 g of Fe2O3, 2.40 g of V2O5, and 1.33 g of CeO2 were weighed and added to a ball mill jar. Then, milling beads were added, and the mixture was placed in a planetary ball mill. The milling was performed at 500 r / min in a single clockwise direction for 2 hours. The sample was then removed and calcined in a muffle furnace at 400℃ for 4 hours to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% CeO2. 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 290℃. 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 reaction 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 97%, and the selectivity of formaldehyde was 93%. After 3000 hours of stable operation, the conversion rate of methanol was 96%, and the selectivity of formaldehyde was 92%.

[0016] Example 2

[0017] The catalyst for the methanol oxidation to formaldehyde production was prepared by impregnation. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O and 3.35 g of Ce(NO3)3·6H2O were weighed and dissolved in 100 mL of water. Then, 2.40 g of vanadium oxide was weighed and added to the solution. The mixture was stirred and dried in an 80℃ water bath. The resulting solid was then calcined in a muffle furnace at 400℃ for 4 hours to obtain a catalyst of 30wt% Fe2O3-45wt% V2O5-25wt% CeO2. 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 290℃. 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 reaction 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 93%, and the selectivity of formaldehyde was 90%.

[0018] Example 3

[0019] The catalyst for the methanol oxidation to formaldehyde production was prepared using the sol-gel method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 3.35 g of Ce(NO3)3·6H2O 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 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 to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% CeO2. 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 290 °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 reaction volume hourly space velocity (VHSV) 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 88%.

[0020] Example 4

[0021] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 3.35 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% CeO2. 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 290℃. 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 reaction 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 98%, and the selectivity of formaldehyde was 93%. After 3000 hours of stable operation, the conversion rate of methanol was 96%, and the selectivity of formaldehyde was 93%.

[0022] Example 5

[0023] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 5.19 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 a muffle furnace at 400℃ for 10 h to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% NiO. 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 290℃. 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 reaction 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 91%, and the selectivity of formaldehyde was 85%.

[0024] Example 6

[0025] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 5.19 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 to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 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 290℃. 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 reaction 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 86%, and the selectivity of formaldehyde was 90%.

[0026] Example 7

[0027] The catalyst for the methanol oxidation to formaldehyde production was prepared by solid-phase ball milling. The specific operation process is as follows: 0.96 g of Fe2O3, 1.44 g of V2O5, and 0.80 g of K2O were weighed and added to a ball mill jar. Then, milling beads were added, and the mixture was placed in a planetary ball mill. The milling was performed at 500 r / min, unidirectional clockwise, for 2 hours. The sample was then removed and calcined in a muffle furnace at 400℃ for 4 hours to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 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 290℃. 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 reaction 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 81%, and the selectivity of formaldehyde was 87%.

[0028] Example 8

[0029] The catalyst for the methanol oxidation to formaldehyde production was prepared using the sol-gel method. The specific procedure is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 6.68 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 to obtain a catalyst containing 30 wt% Fe2O3, 45 wt% V2O5, and 25 wt% SiO2. The catalyst was directly extruded and granulated, sieved to a mesh size of 40-60, and 0.9 mL of the granulated solution was added to a fixed-bed reactor at a height of 15 mm. The reaction temperature was 290°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 reaction volume hourly space velocity (VHSV) was 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 91%, and the selectivity of formaldehyde was 92%.

[0030] Example 9

[0031] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 2.27 g of Ba(NO3)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 then dried and calcined in a muffle furnace at 400℃ for 10 h to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% BaO. 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 290℃. 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 reaction 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 86%.

[0032] Example 10

[0033] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 5.62 g of Ca(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 a muffle furnace at 400℃ for 10 h to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% CaO. 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 290℃. 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 reaction 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 89%, and the selectivity of formaldehyde was 90%.

[0034] Example 11

[0035] The catalyst for the methanol oxidation to formaldehyde was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and (NH4)6W7O were weighed. 24 1.55 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 to obtain a catalyst of 30 wt% Fe₂O₃-45 wt% V₂O₅-25 wt% WO₃. The catalyst was directly extruded and granulated, sieved through a 40-60 mesh screen, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 290 °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 reaction 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 88%.

[0036] Example 12

[0037] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 4.66 g of Zr(NO3)4·5H2O 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 to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% ZrO2. 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 290℃. 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 reaction 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 85%.

[0038] Example 13

[0039] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 3.26 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 dried and then calcined in a muffle furnace at 400℃ for 10 h to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% MoO3. 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 290℃. 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 reaction 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 91%.

[0040] Example 14

[0041] 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, 1.37 g of NH4VO3, and 8.75 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 15 wt% Fe2O3-20 wt% V2O5-65 wt% CeO2. 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 290℃. 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 reaction 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 91%, and the selectivity of formaldehyde was 81%.

[0042] Example 15

[0043] 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, 4.81 g of NH4VO3, and 2.02 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 15 wt% Fe2O3-70 wt% V2O5-15 wt% CeO2. 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 290℃. 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 reaction 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 87%.

[0044] Example 16

[0045] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 3.35 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% CeO2. 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 360℃. 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 reaction 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 75%.

[0046] Example 17

[0047] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 3.35 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% CeO2. 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 200℃. 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 reaction 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 71%, and the selectivity of formaldehyde was 93%.

[0048] Example 18

[0049] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 3.35 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% CeO2. 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 290℃. 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 reaction 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 87%.

[0050] Example 19

[0051] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O, 3.09 g of NH4VO3, and 3.35 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 30 wt% Fe2O3-45 wt% V2O5-25 wt% CeO2. 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 290℃. 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 reaction volume hourly space velocity of 11000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken for analysis. The conversion rate of methanol was 91%, and the selectivity of formaldehyde was 92%.

[0052] Comparative Example 1

[0053] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O and 3.09 g of NH4VO3 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 to obtain a catalyst of 40 wt% Fe2O3-60 wt% V2O5. The catalyst was directly extruded and granulated, sieved to a 40-60 mesh size, and 0.9 mL was packed into a fixed-bed reactor to a height of 15 mm. The reaction temperature was 290℃. 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 reaction 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 92%. After 3000 hours of stable operation, the conversion rate of methanol was 66%, and the selectivity of formaldehyde was 73%.

[0054] Comparative Example 2

[0055] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 8.08 g of Fe(NO3)3·9H2O and 3.35 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 55 wt% Fe2O3-45 wt% CeO2. 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 290℃. 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 reaction 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 31%.

[0056] Comparative Example 3

[0057] The catalyst for the methanol oxidation to formaldehyde production was prepared by a co-precipitation method. The specific operation process is as follows: 3.09 g of NH4VO3 and 3.35 g of Ce(NO3)3·6H2O 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 to obtain a catalyst of 64 wt% V2O5-36 wt% CeO2. 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 290℃. 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 reaction volume hourly space velocity of 9000 h⁻¹. -1 After 2 hours of reaction, gas and liquid samples were taken and analyzed separately. The conversion rate of methanol was 41%, and the selectivity of formaldehyde was 60%. The above descriptions are merely a few embodiments of this application and are not intended to limit this application in any way. Any changes or modifications made to the above-disclosed technical content without departing from the scope of this application are equivalent to equivalent implementations and fall within the scope of the technical solution.

Claims

1. A method for preparing formaldehyde by catalytic oxidation of methanol using an iron-vanadium-based oxide catalyst, characterized in that: Using nitrogen and / or a mixture of argon and oxygen as oxidants, methanol reacts to formaldehyde in a fixed-bed reactor under the action of an iron-vanadium-based oxide catalyst. The iron-vanadium-based oxide catalyst is composed of active metal iron, vanadium and other composite elements, wherein the other composite elements are one or more of nickel, cobalt, silicon, potassium, cerium, barium, calcium, zirconium, molybdenum and tungsten.

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

3. The method according to claim 1 or 2, characterized in that: The precursor of the active ingredient metallic iron is one or more of ferric nitrate, ferric chloride, ferric sulfate, ferric phosphate, ferric oxide, and ferric acetate. The precursor of the active ingredient metallic vanadium is one or more of vanadium chloride, ammonium metavanadate, vanadium oxide, vanadium fluoride, vanadium carbide, vanadium sulfide, vanadium oxysulfate, vanadium oxytrichloride, vanadium nitride, and vanadium oxyoxate. 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 method according to claim 1, characterized in that: The iron-vanadium-based oxide catalyst has an active metal iron content of 3wt% to 70wt% (based on oxide weight), an active metal vanadium content of 5wt% to 90wt% (based on oxide weight), and the remainder consists of other composite element oxides with a content of 2% to 65%.

5. The method according to claim 1 or 2, characterized in that: The iron-vanadium-based oxide catalyst preferably contains 10 wt% to 60 wt% (by weight of oxide) of active metal iron, 10 wt% to 75 wt% (by weight of oxide) of active metal vanadium, and the remainder consists of 2% to 55% of other composite element oxides.

6. The method according to claim 1, characterized in that: The process of catalytic oxidation of methanol to formaldehyde using the iron-vanadium-based oxide catalyst is as follows: Methanol is used as the raw material; the catalyst is packed in a fixed bed at a height of 4 mm to 29 mm (preferably 11 mm to 19 mm); nitrogen and / or a mixture of argon and oxygen are introduced as the oxidant (the oxygen volume concentration in the mixture is 3% to 17%, preferably 7% to 13%); the volume ratio of methanol to the mixture is 1:25 to 1:4; the reaction temperature is 190℃ to 480℃ (preferably 200℃ to 430℃); and the volume hourly space velocity (HSV) of the methanol and mixture is 5000 to 15000 h⁻¹. -1 (Preferred to be 7000~11000h) -1 ).