A high-temperature resistant catalyst for methanol oxidation to formaldehyde and its preparation method

Abstract

This invention provides a high-temperature resistant catalyst for the methanol-to-formaldehyde oxidation process and its preparation method, belonging to the field of catalysts. The catalyst comprises a high-temperature resistant material, an active component, an active additive, and a molding aid. The high-temperature resistant material includes a composite oxide of magnesium oxide and aluminum oxide or aluminum oxide and silicon oxide; the active component includes iron oxide and molybdenum oxide; the active additive includes silver oxide, niobium oxide, zinc oxide, and erbium oxide; and the molding aid includes aluminum stearate, calcium stearate, magnesium stearate, and graphite. This invention also provides a method for preparing the catalyst. By adding high-temperature resistant materials and active additives during the catalyst preparation process, this invention enables the catalyst to maintain high strength and catalytic activity even after long-term operation under high-temperature conditions, resulting in a high yield of formaldehyde from methanol oxidation, good thermal stability, and extended catalyst lifespan, thus showing broad application prospects in industry.

Description

Technical Field

[0001] A high-temperature resistant catalyst for the oxidation of methanol to formaldehyde and its preparation method are disclosed, belonging to the field of catalysts. Background Technology

[0002] Formaldehyde has a wide range of applications, serving as a raw material for resins (phenolic, urea-formaldehyde, melamine-formaldehyde, polyacetal), vinylon, hexamethylenetetramine, 1,4-butanediol, pentaerythritol, dyes, 4,4'-diphenylmethane diisocyanate, pyridine and its derivatives, pesticides, and disinfectants. It is also used in the synthesis of bulk chemicals such as acrylic acid (esters), poly(poly)oxymethylene, and polyoxymethylene dimethyl ether. The iron-molybdenum process for formaldehyde production offers advantages over the silver process, resulting in higher formaldehyde concentrations, and is widely used in industry.

[0003] Currently, there are many publicly reported patents for the preparation of formaldehyde using iron-molybdenum catalysts. CN100413584C adds chromium and vanadium oxides to the active component and uses a hollow cylindrical ring structure, resulting in a catalyst with good thermal stability and a long service life. CN103933998B lowers the reaction temperature and improves the low-temperature activity of the catalyst by adding elements such as Ni, Bi, Co, Ce, Cr, and Li, thereby improving the catalyst's stability to some extent. CN105457648B improves mass and heat transfer by adding Ni as a promoter and creating more pores, resulting in a catalyst with high stability. CN106693981B lowers the catalyst reaction temperature by adding V as a promoter. CN107262105A produces a catalyst with a high specific surface area, large pore size and volume, good low-temperature activity, and beneficial heat transfer. CN107537577B prepares a catalyst precursor with uniform particle size distribution through highly dispersed precipitation of raw materials, resulting in a catalyst with high conversion rate, selectivity, and stability. CN107952445A reduces free iron ions and extends catalyst life by adding a humectant during the drying step. CN108097259A uses macromolecular heterocyclic compounds such as iron porphyrin and molybdenum porphyrin as raw materials, and regulates the spacing, ratio, and distribution of the iron-molybdenum binary active centers through nano-self-assembly to achieve efficient methanol conversion. CN108114744A prepares iron-molybdenum active components within the channels of titanium-silicon molecular sieves, and the resulting catalyst can achieve efficient methanol conversion. CN108816241A obtains a precursor with uniform particle size and large crystal size through hydrothermal reaction at high temperature and pressure, resulting in a catalyst with high activity and high selectivity. CN109806881A adds an activator during synthesis to promote metal dispersion, resulting in a catalyst with good stability. CN1044339C uses a non-nitric acid acidified solution for washing, simplifying the process and resulting in a catalyst with high stability.

[0004] The oxidation of methanol to formaldehyde is a highly exothermic reaction, making the control of the heat of reaction crucial. The high heat of reaction leads to the sublimation of molybdenum oxide in the catalyst under feed gas conditions. With the continuous precipitation and loss of molybdenum oxide, ferric molybdate in the catalyst gradually decomposes into ferrous molybdate and ferric oxide. This not only causes catalyst deactivation but also significantly reduces catalyst strength, leading to gradual breakage, pulverization, and bed blockage, resulting in increased bed pressure drop and ultimately halting the reaction. Currently, industrial catalysts have a relatively short lifespan of 10-12 months. Therefore, maintaining both catalyst strength and activity at high temperatures is of paramount importance. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant catalyst for the oxidation of methanol to formaldehyde and its preparation method. This catalyst can maintain stable performance under high-temperature operating conditions and is suitable for the methanol-to-air oxidation reaction to formaldehyde in a tubular reactor, with operating conditions of 0–0.5 MPa, 240–400 °C, and a gas space velocity of 5000–12000 h⁻¹. -1 The reaction atmosphere is a nitrogen-oxygen mixture containing 5-10% methanol by volume.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A high-temperature resistant catalyst for the oxidation of methanol to formaldehyde includes a high-temperature resistant material, an active component, an active additive, and a molding aid. The high-temperature resistant material comprises magnesium oxide, aluminum oxide, and silicon oxide; the active component comprises iron oxide and molybdenum oxide; the active additive comprises silver oxide, niobium oxide, zinc oxide, and erbium oxide; and the molding aid comprises aluminum stearate, calcium stearate, magnesium stearate, and graphite. By weight, the catalyst comprises 20-60 parts of the high-temperature resistant material, 40-80 parts of the active component, 0.05-0.5 parts of the active additive, and 0.5-2 parts of the molding aid.

[0008] Furthermore, the high-temperature resistant material is magnesium aluminum spinel formed by magnesium oxide and aluminum oxide or magnesium silicate formed by magnesium oxide and silicon oxide. By weight fraction, the high-temperature resistant material includes 20-50 parts of magnesium oxide and 60-80 parts of aluminum oxide, or 30-58 parts of magnesium oxide and 48-70 parts of silicon oxide.

[0009] Furthermore, the active components are iron oxide and molybdenum oxide, which are prepared to form iron molybdate crystal phase and molybdenum oxide crystal phase. By weight, the active components contain 70-82 parts of molybdenum oxide and 18-30 parts of iron oxide.

[0010] Furthermore, the active additives are four types: silver oxide, niobium oxide, zinc oxide, and erbium oxide. By weight, the additive components include 20-50 parts of silver oxide, 10-30 parts of niobium oxide, 10-30 parts of zinc oxide, and 10-30 parts of erbium oxide.

[0011] Furthermore, the molding aid is one or more of aluminum stearate, calcium stearate, magnesium stearate, and graphite.

[0012] The high-temperature resistant methanol oxidation catalyst for formaldehyde production described above has a specific surface area of ​​1-20 m². 2 / g, average pore size 10-30nm, pore volume 0.05-0.3cm³ 3 / g.

[0013] A method for preparing a high-temperature resistant catalyst for the oxidation of methanol to formaldehyde includes the following steps:

[0014] 1) Mix ferric nitrate with silver nitrate, zinc nitrate and erbium nitrate to prepare a solution, and mix ammonium molybdate with niobium oxalate to prepare a solution. Mix the two solutions in a reaction vessel, control the reaction temperature at 40-80℃, control the pH in the range of 1.5-3.5, age for 2-6 hours, filter and wash, and dry the filter cake at 80-130℃ for 8-24 hours, calcine at 300-600℃ for 2-4 hours, grind and sieve to obtain active component powder A;

[0015] 2) Dissolve magnesium nitrate and aluminum nitrate in anhydrous methanol, stir for 3-5 hours, add propylene oxide and urea, continue stirring for 1-3 hours, age at room temperature for 2-5 hours, dry to form a gel, calcine at a certain temperature, grind with a ball mill, dry and sieve to obtain high temperature resistant material powder B.

[0016] 3) Alternatively, add anhydrous methanol and ammonium polyacrylate to magnesium nitrate, and then...

[0017] Stirring in a water bath at 40–70°C for 3–5 hours, adjusting the pH to a suitable level with glacial acetic acid, a magnesium source solution is obtained. Simultaneously, anhydrous methanol is added to tetraethyl orthosilicate (TEOS), and stirring is carried out for 3–5 hours to obtain a silicon source solution. The silicon source solution is slowly poured into the magnesium source solution, and the mixture is heated and stirred in a water bath for another 3–5 hours. After drying, a gel is formed, which is then calcined at a certain temperature, ground using a ball mill, dried, and sieved to obtain powder C of the high-temperature resistant material.

[0018] 4) After mixing high-temperature resistant material B or C with active component A in a certain proportion, add the molding aid and a certain amount of water and mix evenly. Then, use a tablet molding method to obtain a ring with an inner diameter of 1-3 mm, an outer diameter of 4-6 mm, and a height of 2-5 mm to obtain the methanol oxidation to formaldehyde catalyst D.

[0019] Furthermore, the concentrations of the nitrate and ammonium salts in the deionized water are both 0.01–1 mol / L.

[0020] Furthermore, in step 2), the ratio of the amount of propylene oxide added to the total amount of nitrate is 3 to 8, and the ratio of the amount of urea added to the total amount of nitrate is 0.5 to 0.8.

[0021] Furthermore, in step 3), the mass ratio of ammonium polyacrylate to magnesium nitrate is 0.01 to 0.2.

[0022] Furthermore, in steps 2) and 3), the calcination temperature of B and C is 600–1200℃, the calcination time is 3–5 h, and the ball milling time is 8–24 h.

[0023] The above-described application of the high-temperature resistant methanol-to-formaldehyde oxidation catalyst involves placing the catalyst in a tubular reactor to carry out the methanol-to-air oxidation reaction to formaldehyde. The operating conditions are 0–0.5 MPa, 260–400 °C, and a gas space velocity of 5000–12000 h⁻¹. -1 The methanol volume fraction is 5-10%.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This application provides a high-temperature resistant catalyst for the oxidation of methanol to formaldehyde. By adding magnesium aluminum spinel or magnesium silicate high-temperature resistant materials to the traditional active components, the catalyst performance can be kept stable under high-temperature operating conditions. First, magnesium aluminum spinel and magnesium silicate have excellent high-temperature resistance, maintaining stability at high temperatures and providing structural support to prevent catalyst breakage and pulverization at high temperatures. Second, the magnesium aluminum spinel and magnesium silicate materials prepared by the sol-gel method have good pore size and specific surface area, maintaining the catalyst activity and preventing a decrease in catalyst activity due to the addition of the high-temperature resistant materials. Simultaneously, four oxides—silver oxide, niobium oxide, zinc oxide, and erbium oxide—are used as active agents to improve catalyst stability, reduce molybdenum oxide sublimation under the reaction atmosphere, and improve catalyst strength. Attached Figure Description

[0026] Figure 1 Schematic diagram of catalyst performance testing device

[0027] Wherein 1—methanol storage tank, 2—plunger pump, 3—ball valve, 4—mass flow meter, 5—pressure reducing valve, 6—reactor, 7—needle valve, 8—venting absorbent storage tank, 9—primary absorption storage tank, 10—secondary absorption storage tank, 11—gas phase product analysis, 12—liquid phase product analysis. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] Example 1

[0030] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0031] 1) Dissolve 43.88g Fe(NO3)3·9H2O, 0.32g AgNO3·6H2O, 0.20g Zn(NO3)2·6H2O, and 0.30g Er(NO3)3·5H2O in 900ml of water to form a mixed aqueous solution. Mix this solution with 400ml of a solution containing 37.21g ammonium heptamolybdate and 0.37g ammonium niobate in a reaction vessel. Control the reaction temperature at 50℃ and the pH at 1.5. Aging for 3h, filtering and washing, the resulting filter cake is dried at 100℃ for 12h and calcined at 420℃ for 4h to prepare A;

[0032] 2) Dissolve 70.34g Mg(NO3)2·6H2O and 205.81g Al(NO3)3·9H2O in anhydrous methanol, stir for 4h, then add 286.78g propylene oxide and 29.66g urea, continue stirring for 2h, age at room temperature for 3h, dry to form a gel, calcine at 800℃ for 3h, and grind using a ball mill for 24h, sieve out particles larger than 200 mesh to obtain B;

[0033] 3) After mixing A and B, add 1.95g of aluminum stearate and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D001.

[0034] Example 2

[0035] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0036] 1) Dissolve 59.24g Fe(NO3)3·9H2O, 0.14g AgNO3·6H2O, 0.53g Zn(NO3)2·6H2O, and 0.82g Er(NO3)3·5H2O in 800ml of water to form a mixed aqueous solution. Mix this solution with 800ml of a solution containing 57.42g ammonium heptamolybdate and 0.22g ammonium niobate in a reaction vessel. Control the reaction temperature at 60℃ and the pH at 2.0. Aging for 3h, filter and wash, and dry the filter cake at 100℃ for 12h and calcine at 500℃ for 4h to prepare A.

[0037] 2) Dissolve 105.51g Mg(NO3)2·6H2O and 308.71g Al(NO3)3·9H2O in anhydrous methanol, stir for 5h, add 215.08g propylene oxide and 37.07g urea, continue stirring for 1h, age at room temperature for 4h, dry to form a gel, calcine at 1200℃ for 4h, and grind with a ball mill for 20h, sieve out particles larger than 200 mesh to obtain B;

[0038] 3) After mixing A and B, add 1.95g of graphite and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D002.

[0039] Example 3

[0040] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0041] 1) Dissolve 86.74g Fe(NO3)3·9H2O, 0.10g AgNO3·6H2O, 0.24g Zn(NO3)2·6H2O, and 0.18g Er(NO3)3·5H2O in 1400ml of water to form a mixed aqueous solution. Mix this solution with 400ml of a solution containing 75.90g ammonium heptamolybdate and 0.08g ammonium niobate in a reaction vessel. Control the reaction temperature at 80℃ and the pH at 3.0. Aging for 6h, filter and wash, and dry the filter cake at 100℃ for 18h and calcine at 360℃ for 4h to prepare A.

[0042] 2) Dissolve 35.62g Mg(NO3)2·6H2O and 104.23g Al(NO3)3·9H2O in anhydrous methanol, stir for 5h, then add 145.23g propylene oxide and 20.02g urea, continue stirring for 3h, age at room temperature for 5h, dry to form a gel, calcine at 1100℃ for 3h, and grind using a ball mill for 18h, sieve out particles larger than 200 mesh to obtain B;

[0043] 3) After mixing A and B, add 0.99g of calcium stearate and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D003.

[0044] Example 4

[0045] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0046] 1) Dissolve 52.30g Fe(NO3)3·9H2O, 0.27g AgNO3·6H2O, 0.27g Zn(NO3)2·6H2O, and 0.20g Er(NO3)3·5H2O in 1000ml of water to form a mixed aqueous solution. Mix this solution with 500ml of a solution containing 57.73g ammonium heptamolybdate and 0.08g ammonium niobate in a reaction vessel. Control the reaction temperature at 70℃ and the pH at 2.5. Aging for 6h, filter and wash, and dry the filter cake at 120℃ for 24h and calcine at 450℃ for 3h to prepare A.

[0047] 2) Dissolve 73.93g Mg(NO3)2·6H2O and 216.32g Al(NO3)3·9H2O in anhydrous methanol, stir for 4h, then add 301.42g propylene oxide and 31.17g urea, continue stirring for 2h, age at room temperature for 5h, dry to form a gel, calcine at 900℃ for 4h, and grind using a ball mill for 12h, sieve out particles larger than 200 mesh to obtain B;

[0048] 3) After mixing A and B, add 1.23g of magnesium stearate and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D004.

[0049] Example 5

[0050] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0051] 1) Dissolve 44.56g Fe(NO3)3·9H2O, 0.09g AgNO3·6H2O, 0.06g Zn(NO3)2·6H2O, and 0.09g Er(NO3)3·5H2O in 700ml of water to form a mixed aqueous solution. Mix this solution with 700ml of a solution containing 34.56g ammonium heptamolybdate and 0.07g ammonium niobate in a reaction vessel. Control the reaction temperature at 60℃ and the pH at 2.4. Aging for 3h, filtering and washing, the resulting filter cake is dried at 110℃ for 8h and calcined at 380℃ for 4h to prepare A.

[0052] 2) Mix 174.34g of Mg(NO3)2·6H2O with anhydrous methanol, add 8.72g of ammonium polyacrylate and 3.5g of glacial acetic acid, stir for 3h to obtain a magnesium source solution. At the same time, add anhydrous methanol to 118.76g of tetraethyl orthosilicate, stir for 3h to obtain a silicon source solution. Slowly pour the silicon source solution into the magnesium source solution, continue to heat and stir in a water bath for 3h, dry to form a gel, calcine at 700℃ for 4h to obtain C;

[0053] 3) After mixing A and C, add 1.23g of magnesium stearate and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D005.

[0054] Example 6

[0055] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0056] 1) Dissolve 61.93g Fe(NO3)3·9H2O, 0.09g AgNO3·6H2O, 0.22g Zn(NO3)2·6H2O, and 0.17g Er(NO3)3·5H2O in 1000ml of water to form a mixed aqueous solution. Mix this solution with 500ml of a solution containing 60.03g ammonium heptamolybdate and 0.21g ammonium niobate in a reaction vessel. Control the reaction temperature at 40℃ and the pH at 1.5. Aging for 5h, filter and wash, and dry the filter cake at 130℃ for 12h and calcine at 480℃ for 2h to prepare A.

[0057] 2) Mix 116.82g of Mg(NO3)2·6H2O with anhydrous methanol, add 5.84g of ammonium polyacrylate and 2.8g of glacial acetic acid, stir for 5h to obtain a magnesium source solution. At the same time, add anhydrous methanol to 63.66g of tetraethyl orthosilicate, stir for 5h to obtain a silicon source solution. Slowly pour the silicon source solution into the magnesium source solution, continue to heat and stir in a water bath for 3h, dry to form a gel, calcine at 900℃ for 3h to obtain C;

[0058] 3) After mixing A and C, add 1.84g of graphite and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D006.

[0059] Example 7

[0060] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0061] 1) Dissolve 52.47g Fe(NO3)3·9H2O, 0.16g AgNO3·6H2O, 0.60g Zn(NO3)2·6H2O, and 0.61g Er(NO3)3·5H2O in 1000ml of water to form a mixed aqueous solution. Mix this solution with 1000ml of a solution containing 35.60g ammonium heptamolybdate and 0.25g ammonium niobate in a reaction vessel. Control the reaction temperature at 80℃ and the pH at 2.0. Aging for 6h, filter and wash, and dry the filter cake at 100℃ for 18h and calcine at 550℃ for 2h to prepare A.

[0062] 2) Mix 205.8g of Mg(NO3)2·6H2O with anhydrous methanol, add 6.17g of ammonium polyacrylate and 4.2g of glacial acetic acid, stir for 4h to obtain a magnesium source solution. At the same time, add anhydrous methanol to 92.81g of tetraethyl orthosilicate, stir for 4h to obtain a silicon source solution. Slowly pour the silicon source solution into the magnesium source solution, continue to heat and stir in a water bath for 5h, dry to form a gel, calcine at 1000℃ for 3h to obtain C;

[0063] 3) After mixing A and C, add 0.99g of calcium stearate and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D007.

[0064] Example 8

[0065] This embodiment discloses a method for preparing the catalyst of the present invention, specifically as follows:

[0066] 1) Dissolve 40.79g Fe(NO3)3·9H2O, 0.18g AgNO3·6H2O, 0.68g Zn(NO3)2·6H2O, and 0.34g Er(NO3)3·5H2O in 800ml of water to form a mixed aqueous solution. Mix this solution with 800ml of a solution containing 38.43g ammonium heptamolybdate and 0.28g ammonium niobate in a reaction vessel. Control the reaction temperature at 55℃ and the pH at 2.2. Aging for 4h, filter and wash, and dry the filter cake at 130℃ for 16h and calcine at 460℃ for 4h to prepare A.

[0067] 2) Mix 150.44g of Mg(NO3)2·6H2O with anhydrous methanol, add 9.03g of ammonium polyacrylate and 2.5g of glacial acetic acid, stir for 5h to obtain a magnesium source solution. At the same time, add anhydrous methanol to 122.98g of tetraethyl orthosilicate, stir for 5h to obtain a silicon source solution. Slowly pour the silicon source solution into the magnesium source solution, continue to heat and stir in a water bath for 5h, dry to form a gel, calcine at 800℃ for 3h, and grind with a ball mill for 12h. Sieve out particles larger than 200 mesh to obtain C;

[0068] 3) After mixing A and C, add 0.99g of magnesium stearate and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D008.

[0069] Example 9

[0070] This embodiment is Comparative Example 1. Compared with Example 8, this embodiment does not use high-temperature resistant materials. Specifically:

[0071] 1) Dissolve 40.79g Fe(NO3)3·9H2O, 0.18g AgNO3·6H2O, 0.68g Zn(NO3)2·6H2O, and 0.34g Er(NO3)3·5H2O in 800ml of water to form a mixed aqueous solution. Mix this solution with 800ml of a solution containing 38.43g ammonium heptamolybdate and 0.28g ammonium niobate in a reaction vessel. Control the reaction temperature at 55℃ and the pH at 2.2. Aging for 4h, filter and wash, and dry the filter cake at 130℃ for 16h and calcine at 460℃ for 4h to prepare A.

[0072] 2) Add 0.99g of magnesium stearate and a certain amount of water to A and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm, and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D009.

[0073] Example 10

[0074] This example is Comparative Example 2. Compared with Example 8, this example does not use any active additives. Specifically:

[0075] 1) Dissolve 40.79g Fe(NO3)3·9H2O in 800ml of water to form a mixed aqueous solution, and mix it with 800ml of a solution containing 38.43g ammonium heptamolybdate in a reaction vessel. Control the reaction temperature at 55℃ and the pH at 2.2. Aging for 4h, filtering and washing, the filter cake is dried at 130℃ for 16h and calcined at 460℃ for 4h to prepare A;

[0076] 2) Mix 150.44g of Mg(NO3)2·6H2O with anhydrous methanol, add 9.03g of ammonium polyacrylate and 2.5g of glacial acetic acid, stir for 5h to obtain a magnesium source solution. At the same time, add anhydrous methanol to 122.98g of tetraethyl orthosilicate, stir for 5h to obtain a silicon source solution. Slowly pour the silicon source solution into the magnesium source solution, continue to heat and stir in a water bath for 5h, dry to form a gel, calcine at 800℃ for 3h, and grind with a ball mill for 12h. Sieve out particles larger than 200 mesh to obtain C;

[0077] 3) After mixing A and C, add 0.99g of magnesium stearate and a certain amount of water and mix evenly. Then, use a tableting method to make a ring with an inner diameter of 2mm, an outer diameter of 5mm and a height of 3mm, to obtain the methanol oxidation to formaldehyde catalyst D010.

[0078] Catalyst performance testing

[0079] Methanol enters the unit from the methanol storage tank via a plunger pump, and after being metered by a ball valve and mass flow meter, it enters the reactor. In the reactor, after preheating, it merges with the reaction gases and reacts in the catalyst bed. The generated formaldehyde and byproducts, along with unreacted methanol, are absorbed by a two-stage absorbent solution, and then analyzed separately by gas chromatography along with the unabsorbed gaseous substances.

[0080] The catalysts prepared in Examples 1-10 were placed in tubular reactors, and their catalytic performance and axial compressive strength before and after the reaction were tested. The catalyst bed hot spot temperature was controlled at 400℃, and the space velocity was 8000 h⁻¹. -1 The activity was evaluated under normal pressure in an air atmosphere containing 5.5% methanol by volume. The test results after 1000 h of reaction are detailed in Table 1.

[0081] Table 1. Results of catalyst performance and strength tests

[0082]

[0083]

[0084] As shown in Table 1 above, the catalyst of this invention still exhibits high formaldehyde yield and high strength after 1000 hours of operation. The high-temperature resistant material improves the catalyst's heat resistance and provides good structural support, while the active agent reduces the sublimation of molybdenum oxidation under high-temperature conditions. In contrast, the D009 and D010 catalysts in Comparative Examples 1 and 2 showed a significant decrease in both activity and strength after 1000 hours of operation. Specifically, D009, without the aforementioned high-temperature resistant material, experienced a larger decrease in strength; D010, without the aforementioned active agent, experienced a larger decrease in activity. This demonstrates the combined effect of the high-temperature resistant material and the active agent, enabling the catalyst to maintain high strength and catalytic activity even after long-term operation under high-temperature conditions, indicating that the catalyst of this invention can operate stably for a long period.

[0085] 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, and improvements 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 at elevated temperatures, characterized in that The catalyst comprises a high-temperature-resistant material, an active component, an active adjuvant and a molding adjuvant; the high-temperature-resistant material is magnesium-aluminum spinel formed by magnesium oxide and aluminum oxide, or composite oxide magnesium silicate composed of magnesium oxide and silicon oxide; the active component comprises iron oxide and molybdenum oxide; the active adjuvant comprises silver oxide, niobium oxide, zinc oxide and erbium oxide, and the molding adjuvant is any one or several of aluminum stearate, calcium stearate, magnesium stearate and graphite; the catalyst comprises 20-60 parts by weight of the high-temperature-resistant material, 40-80 parts by weight of the active component, 0.05-0.5 parts by weight of the active adjuvant and 0.5-2 parts by weight of the molding adjuvant; the active component is formed by preparing iron oxide and molybdenum oxide into iron molybdate crystal phase and molybdenum oxide crystal phase, and comprises 70-82 parts by weight of molybdenum oxide and 18-30 parts by weight of iron oxide; the active adjuvant is composed of silver oxide, niobium oxide, zinc oxide and erbium oxide, and comprises 20-50 parts by weight of silver oxide, 10-30 parts by weight of niobium oxide, 10-30 parts by weight of zinc oxide and 10-30 parts by weight of erbium oxide. The preparation method comprises the following steps: 1) mixing and preparing a solution by mixing iron nitrate with silver nitrate, zinc nitrate and erbium nitrate, mixing and preparing another solution by mixing ammonium molybdate with ammonium niobium oxalate, mixing the two solutions in a reaction kettle, controlling the reaction temperature to be 40-80 DEG C, controlling the pH to be in the range of 1.5-3.5, aging for 2-6 hours, filtering and washing to obtain a filter cake, drying the filter cake at 80-130 DEG C for 8-24 hours, calcining the filter cake at 300-600 DEG C for 2-4 hours, grinding and sieving to obtain powder A of the active component; 2) dissolving magnesium nitrate and aluminum nitrate in anhydrous methanol, stirring for 3-5 hours, then adding propylene oxide and urea, continuing to stir for 1-3 hours, aging at room temperature for 2-5 hours, drying to form a gel, sintering at a certain temperature, grinding by using a ball mill, drying and sieving to obtain powder B of the high-temperature-resistant material; 3) adding anhydrous methanol and ammonium polyacrylate to magnesium nitrate, stirring the solution in a water bath at 40-70 DEG C for 3-5 hours, adjusting to a proper pH by using glacial acetic acid to obtain a magnesium source solution, meanwhile adding anhydrous methanol to tetraethyl orthosilicate, stirring for 3-5 hours to obtain a silicon source solution, slowly pouring the silicon source solution into the magnesium source solution, continuing to stir in the water bath for 3-5 hours, drying to form a gel, sintering at a certain temperature, grinding by using a ball mill, drying and sieving to obtain powder C of the high-temperature-resistant material; 4) mixing the high-temperature-resistant material B or C with the active component A at a certain ratio, then adding the molding adjuvant and a certain amount of water, mixing uniformly, and adopting a tablet pressing molding method to obtain the methanol oxidation to formaldehyde catalyst D; the prepared catalyst is used in the reaction of methanol oxidation to formaldehyde under the working condition of a temperature of 240-400 DEG C; The sintering temperature of B and C in steps 2) and 3) is 600-1200 DEG C, the calcining time is 3-5 hours, and the ball milling time is 8-24 hours.

2. The high temperature resistant catalyst for oxidation of methanol to formaldehyde according to claim 1, characterized in that: The high-temperature-resistant material comprises 20-50 parts by weight of magnesium oxide and 60-80 parts by weight of aluminum oxide, or 30-58 parts by weight of magnesium oxide and 48-70 parts by weight of silicon oxide.

3. The catalyst for the oxidation of methanol to formaldehyde at high temperature according to claim 1, characterized in that, The concentration of the nitrate and ammonium salt in deionized water in the step 1) is 0.01-1 mol / L.

4. The catalyst for the oxidation of methanol to formaldehyde at high temperature according to claim 1, characterized in that, The ratio of the added amount of propylene oxide to the total amount of substance of the nitrate in the step 2) is 3-8, and the ratio of the added amount of urea to the total amount of substance of the nitrate is 0.5-0.

8.

5. The catalyst for the oxidation of methanol to formaldehyde at high temperature according to claim 1, characterized in that, The ratio of the added amount of the ammonium polyacrylate to the amount of substance of the magnesium nitrate in the step 3) is 0.01-0.

2.

6. The catalyst for the oxidation of methanol to formaldehyde at high temperature according to claim 1, characterized in that, The catalyst has a specific surface area of 1-20 m 2 / g, an average pore diameter of 10-30 nm, and a pore volume of 0.05-0.3 cm 3 / g.

7. The catalyst for the oxidation of methanol to formaldehyde at high temperature according to claim 1, characterized in that, The catalyst is placed in a column reactor for methanol oxidation to formaldehyde, the working conditions are pressure 0-0.5 MPa, temperature 240-400℃, gas space velocity 5000-12000h -1 , and the reaction atmosphere is a gas containing 5-10% methanol in nitrogen and oxygen.

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