A production process of formaldehyde

Abstract

This application relates to the technical field of organic synthesis, and specifically discloses a production process of formaldehyde. The production process of formaldehyde in this application includes the following steps: S1. Prepare the catalyst bed: successively fill the first layer, the second layer, and the third layer in the reactor to form the catalyst bed; S2. Pretreat the catalyst bed: introduce air into the catalyst bed obtained in step S1, first heat up, keep warm for a period of time, and then purge with nitrogen to obtain the pretreated catalyst bed; S3. Prepare formaldehyde: introduce a mixed gas of methanol, oxygen, inert gas and water vapor into the pretreated catalyst bed obtained in step S2, carry out an oxidation reaction, carry out alcohol removal after the reaction ends, and add an inhibitor to obtain formaldehyde; for the above production process, the steps are simple, the conversion rate of methanol and the yield of formaldehyde are both relatively high, and it is suitable for industrial production.

Description

Technical Field

[0001] This application relates to the field of organic synthesis technology, and more specifically, it relates to a production process of formaldehyde. Background Art

[0002] Formaldehyde (HCHO) is the simplest aldehyde. There are a carbonyl O atom and an α-H atom in its structure, and its chemical properties are very active. As an important organic chemical raw material and chemical intermediate, formaldehyde is widely used in the synthetic resin industry and the production of industries such as medicine, wood processing, textile, papermaking, and pesticides. Specifically, it can be used in the production of urea-formaldehyde resin, phenolic resin, melamine-formaldehyde resin, diphenylmethane diisocyanate, pentaerythritol, and polyoxymethylene.

[0003] Currently, the main method for producing formaldehyde is the air oxidation method of methanol. According to the types of catalysts used, it can be further divided into two processes: the silver method and the iron-molybdenum method. The silver method process is a traditional method for formaldehyde production. Compared with the silver method, the iron-molybdenum method is more advanced, with characteristics such as low reaction temperature, high catalyst activity and selectivity, long service life, insensitivity to poisons, and low unit consumption. Therefore, the iron-molybdenum method is highly favored in newly built formaldehyde plants and is the future development trend of the formaldehyde industry.

[0004] However, in actual production, when using the iron-molybdenum method to prepare formaldehyde, the conversion rate of methanol and the yield of formaldehyde still need to be further improved to better meet industrial requirements. Therefore, there is an urgent need to propose a production process of formaldehyde to solve the problem of low conversion rate of methanol and low yield of formaldehyde in the production process of formaldehyde. Summary of the Invention

[0005] To solve the problem of low conversion rate of methanol and low yield of formaldehyde in the existing production process of formaldehyde, this application provides a production process of formaldehyde.

[0006] This application provides a production process of formaldehyde, adopting the following technical scheme:

[0007] A production process of formaldehyde includes the following steps:

[0008] S1. Prepare a catalyst bed: Fill the first layer, the second layer, and the third layer in sequence in a reactor to form a catalyst bed;

[0009] S2. Pretreat the catalyst bed: Pass air into the catalyst bed obtained in step S1, first raise the temperature, keep it warm for a period of time, and then purge with nitrogen to obtain a pretreated catalyst bed;

[0010] S3. Prepare formaldehyde: Pass a mixed gas of methanol, oxygen, inert gas, and steam into the pretreated catalyst bed obtained in step S2 to carry out an oxidation reaction. After the reaction ends, carry out alcohol removal and add an inhibitor to obtain formaldehyde;

[0011] Both the first layer and the third layer are inert layers, and the second layer is a mixed layer; the inert layers are filled with ceramic micropowders; the mixed layer is filled with a mixture of ceramic micropowders and iron-molybdenum catalysts with a mass ratio of 1:3 - 6.

[0012] By adopting the above technical solution, the formaldehyde production process of the present application mainly includes three major steps: first, preparing a catalyst bed, then pre-treating the catalyst bed, and finally preparing formaldehyde; among them, in the process of preparing the catalyst bed, a reactor is filled to form a catalyst bed, and the filling substances are controlled to effectively reduce the resistance of the catalyst bed, improve the catalytic effect of the iron-molybdenum catalyst, and thus improve the conversion rate of methanol and the yield of formaldehyde; in the pre-treatment process of the catalyst bed, mainly activating the iron-molybdenum catalyst to keep the iron-molybdenum catalyst in good catalytic activity; in the process of preparing formaldehyde, a mixed gas of methanol, oxygen, inert gas and water vapor is introduced into the pre-treated catalyst bed to carry out an oxidation reaction, and a polymerization inhibitor is added to the generated formaldehyde to effectively remove the dissolved oxygen in the formaldehyde aqueous solution, avoid the oxidation of formaldehyde, reduce the acidic substances that can promote the polymerization of formaldehyde, and thus improve the yield of formaldehyde. The formaldehyde production process of the present application has simple steps, significantly improves the conversion rate of methanol and the yield of formaldehyde, and is suitable for industrial production.

[0013] Preferably, the height of the catalyst bed is 60 - 100 mm; the height ratio of the first layer, the second layer and the third layer is 6:16 - 20:1 - 2.

[0014] By adopting the above technical solution, in the process of preparing the catalyst bed in step S1 of the present application, controlling the height of the catalyst bed and the height ratio between each layer is more conducive to the iron-molybdenum catalyst to exert its catalytic activity, improve the catalytic efficiency of the iron-molybdenum catalyst, and further promote the oxidation of methanol to formaldehyde.

[0015] Preferably, the specific operation of step S2 is: with a space velocity of 8000 - 10000 h -1 , air is introduced into the catalyst bed obtained in step S1, and then it is first heated to 200 - 400 °C at a rate of 10 - 15 °C / min and kept warm for 1 - 2 h; then purged with nitrogen for 180 - 300 min, and the purge space velocity is 1000 - 2000 h -1 , to obtain a pre-treated catalyst bed.

[0016] By adopting the above technical solution, the present application controls the pre-treatment conditions of the catalyst bed in step S2, effectively preventing the iron-molybdenum catalyst from deactivating and enabling the iron-molybdenum catalyst to better catalyze the oxidation of methanol.

[0017] Preferably, the iron-molybdenum catalyst comprises the following raw materials in parts by weight: 18-20 parts of ferric sulfate, 38-45 parts of molybdenum oxide, 30-40 parts of dilute sulfuric acid, and 11-15 parts of a carrier.

[0018] Preferably, the iron-molybdenum catalyst is prepared by the following method:

[0019] S11. Dissolve ferric sulfate and molybdenum oxide in dilute sulfuric acid with a concentration of 10-30 wt%. After complete dissolution, adjust the pH of the solution to 1-2. Aging at 60-80 °C for 18-20 h, then perform suction filtration and wash until neutral to obtain a mixture.

[0020] S12. First, mix the mixture obtained in step S11 with the carrier evenly, then dry at 80-100 °C for 20-60 min. Then, under nitrogen protection, heat-treat at 300-400 °C for 4-5 h, grind, and pass through a 400-800 mesh sieve to obtain the iron-molybdenum catalyst.

[0021] By adopting the above technical solution, the present application uses ferric sulfate, molybdenum oxide, and a carrier as the main raw materials to prepare an iron-molybdenum catalyst. During the preparation process, each process parameter is controlled, so that iron atoms and molybdenum atoms are successfully loaded onto the carrier, forming an iron-molybdenum catalyst with high catalytic activity and selectivity, long service life. When applied to the reaction of methanol oxidation to produce formaldehyde, it can significantly improve the selectivity of producing formaldehyde, reduce side reactions, and thus improve the conversion rate of methanol and the yield of formaldehyde.

[0022] Preferably, the carrier is prepared by the following method:

[0023] By weight, first add 12-18 parts of bamboo charcoal powder to 6-8 parts of triethanolamine and grind thoroughly, then add 1-2 parts of Tween. Then, under the condition of a temperature of 40-80 °C, perform ultrasonic treatment for 1-2 h, and then filter, wash, and dry to obtain the carrier.

[0024] By adopting the above technical solution, under the combined action of triethanolamine and Tween, the number of active groups on the surface of bamboo charcoal powder increases, and at the same time the specific surface area also increases, forming a carrier with excellent performance, enabling iron atoms and molybdenum atoms to be better loaded onto the carrier. The iron-molybdenum catalyst of the present application is used for preparing formaldehyde, with a small dosage and good catalytic effect.

[0025] Preferably, the molar ratio of methanol, oxygen, inert gas, and water vapor is 1:1-2:8-14:0.1-0.12.

[0026] By adopting the above technical solution, the present application controls the molar ratio of methanol, oxygen, inert gas, and water vapor within a certain range, enabling methanol to be fully oxidized to produce formaldehyde and improving the conversion rate of methanol.

[0027] Preferably, the inert gas is at least one of nitrogen, helium, neon, and argon.

[0028] Preferably, the volumetric space velocity of the mixed gas in step S3 is 10,000 - 20,000 h -1 ; the reaction temperature is 360 - 400 °C.

[0029] By adopting the above technical solution, in step S3 of this application, the process parameters are controlled to enable the full reaction of methanol and oxygen, reduce the occurrence of side reactions, and thus improve the conversion rate of methanol and the yield of formaldehyde.

[0030] Preferably, the mass of the polymerization inhibitor is 0.1 - 0.5% of that of methanol.

[0031] Preferably, the polymerization inhibitor is obtained by mixing p - methoxy phenol and p - tert - butylcatechol in a mass ratio of 3 - 5:1.

[0032] By adopting the above technical solution, in step S3 of this application, after formaldehyde is generated and the alcohol is removed, a polymerization inhibitor is added, effectively preventing the self - polymerization reaction of the generated formaldehyde, and thereby reducing the product quality of formaldehyde; this application controls the mass of the polymerization inhibitor, and the polymerization inhibitor is obtained by mixing p - methoxy phenol and p - tert - butylcatechol in a certain mass ratio, and the two work synergistically to make the polymerization inhibitor have excellent polymerization inhibition effect.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. The production process of formaldehyde in this application mainly includes three major steps: preparing the catalyst bed, pre - treating the catalyst bed, and preparing formaldehyde. The steps are simple, the cost is low, the conversion rate of methanol and the yield of formaldehyde are significantly improved, and it is suitable for industrial production.

[0035] 2. In the preparation process of the catalyst bed in step S1 of this application, the first layer, the second layer, and the third layer are successively filled into the reactor to form a catalyst bed. The first layer and the third layer are both inert layers, and the second layer is a mixed layer filled with a mixture of ceramic micro - powder and iron - molybdenum catalyst; and the iron - molybdenum catalyst in this application is to load iron and molybdenum atoms onto the carrier. The iron - molybdenum catalyst has excellent catalytic activity, selectivity, and long service life, and can efficiently catalyze the oxidation of methanol to produce formaldehyde.

[0036] 3. In the preparation process of formaldehyde in step S3 of this application, after methanol is oxidized to produce formaldehyde, a polymerization inhibitor is added, effectively preventing the self - polymerization reaction of formaldehyde and improving the product quality of formaldehyde. Detailed Embodiments

[0037] The following further elaborates on this application with reference to examples.

[0038] Preparation Examples 1-5 provide methods for preparing the carrier.

[0039] Preparation Example 1

[0040] First, 120 g of bamboo charcoal powder was added to 60 g of triethanolamine and ground thoroughly. Then, 10 g of Tween was added. After that, ultrasonic treatment was carried out at 40 °C for 2 h, followed by filtration, washing, and drying to obtain the carrier.

[0041] Preparation Example 2

[0042] First, 140 g of bamboo charcoal powder was added to 65 g of triethanolamine and ground thoroughly. Then, 12 g of Tween was added. After that, ultrasonic treatment was carried out at 50 °C for 1.8 h, followed by filtration, washing, and drying to obtain the carrier.

[0043] Preparation Example 3

[0044] First, 150 g of bamboo charcoal powder was added to 70 g of triethanolamine and ground thoroughly. Then, 15 g of Tween was added. After that, ultrasonic treatment was carried out at 60 °C for 1.5 h, followed by filtration, washing, and drying to obtain the carrier.

[0045] Preparation Example 4

[0046] First, 165 g of bamboo charcoal powder was added to 75 g of triethanolamine and ground thoroughly. Then, 18 g of Tween was added. After that, ultrasonic treatment was carried out at 70 °C for 1.2 h, followed by filtration, washing, and drying to obtain the carrier.

[0047] Preparation Example 5

[0048] First, 180 g of bamboo charcoal powder was added to 80 g of triethanolamine and ground thoroughly. Then, 20 g of Tween was added. After that, ultrasonic treatment was carried out at 80 °C for 1 h, followed by filtration, washing, and drying to obtain the carrier.

[0049] Preparation Examples 6-10 and Comparative Preparation Examples 1 and 2 provide iron-molybdenum catalysts and their preparation methods.

[0050] Preparation Example 6

[0051] The iron-molybdenum catalyst comprises the following raw materials: 180 g of ferric sulfate, 380 g of molybdenum oxide, 300 g of dilute sulfuric acid, and 110 g of carrier;

[0052] Among them, the carrier was prepared from Preparation Example 1.

[0053] The iron-molybdenum catalyst was prepared by the following method:

[0054] S11. Dissolve ferric sulfate and molybdenum oxide in dilute sulfuric acid with a concentration of 10 wt%. After complete dissolution, adjust the pH of the solution to 1, age at 60 °C for 20 h, then carry out suction filtration and wash until neutral to obtain the mixture;

[0055] S12. First, mix the mixture obtained in step S11 with the carrier evenly, then dry it at 80 °C for 60 min; then, under nitrogen protection, heat-treat it at 300 °C for 5 h, grind it, and sieve it through a 400-mesh sieve to obtain the iron-molybdenum catalyst.

[0056] Preparation Example 7

[0057] The iron-molybdenum catalyst comprises the following raw materials: 185 g of iron sulfate, 400 g of molybdenum oxide, 320 g of dilute sulfuric acid, and 120 g of carrier;

[0058] Among them, the carrier is prepared from Preparation Example 2.

[0059] The iron-molybdenum catalyst is prepared by the following method:

[0060] S11. Dissolve iron sulfate and molybdenum oxide in dilute sulfuric acid with a concentration of 15 wt%, after fully dissolving, adjust the pH of the solution to 1.2, age it at 65 °C for 19.5 h, then carry out suction filtration and wash it until neutral to obtain a mixture;

[0061] S12. First, mix the mixture obtained in step S11 with the carrier evenly, then dry it at 85 °C for 50 min; then, under nitrogen protection, heat-treat it at 320 °C for 4.8 h, grind it, and sieve it through a 500-mesh sieve to obtain the iron-molybdenum catalyst.

[0062] Preparation Example 8

[0063] The iron-molybdenum catalyst comprises the following raw materials: 190 g of iron sulfate, 410 g of molybdenum oxide, 350 g of dilute sulfuric acid, and 130 g of carrier;

[0064] Among them, the carrier is prepared from Preparation Example 3.

[0065] The iron-molybdenum catalyst is prepared by the following method:

[0066] S11. Dissolve iron sulfate and molybdenum oxide in dilute sulfuric acid with a concentration of 20 wt%, after fully dissolving, adjust the pH of the solution to 1.5, age it at 70 °C for 19 h, then carry out suction filtration and wash it until neutral to obtain a mixture;

[0067] S12. First, mix the mixture obtained in step S11 with the carrier evenly, then dry it at 90 °C for 40 min; then, under nitrogen protection, heat-treat it at 350 °C for 4.5 h, grind it, and sieve it through a 600-mesh sieve to obtain the iron-molybdenum catalyst.

[0068] Preparation Example 9

[0069] The iron-molybdenum catalyst comprises the following raw materials: 195 g of iron sulfate, 430 g of molybdenum oxide, 380 g of dilute sulfuric acid, and 140 g of carrier;

[0070] Among them, the carrier is prepared from Preparation Example 4.

[0071] The iron-molybdenum catalyst is prepared by the following method:

[0072] S11. Dissolve ferric sulfate and molybdenum oxide in dilute sulfuric acid with a concentration of 25 wt%, after complete dissolution, adjust the pH of the solution to 1.8, age at 75 °C for 19.5 h, then carry out suction filtration and wash until neutral to obtain a mixture;

[0073] S12. First, mix the mixture obtained in step S11 with the carrier evenly, dry at 95 °C for 30 min; then, under nitrogen protection, heat-treat at 380 °C for 4.8 h, grind, and pass through a 700-mesh sieve to obtain the iron-molybdenum catalyst.

[0074] Preparation Example 10

[0075] The iron-molybdenum catalyst includes the following raw materials: 200 g of ferric sulfate, 450 g of molybdenum oxide, 400 g of dilute sulfuric acid, and 150 g of carrier;

[0076] Among them, the carrier is prepared by Preparation Example 5.

[0077] The iron-molybdenum catalyst is prepared by the following method:

[0078] S11. Dissolve ferric sulfate and molybdenum oxide in dilute sulfuric acid with a concentration of 30 wt%, after complete dissolution, adjust the pH of the solution to 2, age at 80 °C for 20 h, then carry out suction filtration and wash until neutral to obtain a mixture;

[0079] S12. First, mix the mixture obtained in step S11 with the carrier evenly, dry at 100 °C for 20 min; then, under nitrogen protection, heat-treat at 400 °C for 4 h, grind, and pass through an 800-mesh sieve to obtain the iron-molybdenum catalyst.

[0080] Comparative Preparation Example 1

[0081] Comparative Preparation Example 1 is the same as Preparation Example 6, the only difference being that the carrier is activated carbon.

[0082] Comparative Preparation Example 2

[0083] Comparative Preparation Example 2 is the same as Preparation Example 6, the only difference being that the carrier is zeolite.

[0084] Examples 1-5 provide a production process of formaldehyde.

[0085] Example 1

[0086] A production process of formaldehyde includes the following steps:

[0087] S1. Prepare the catalyst bed: successively fill the first layer, the second layer, and the third layer in the reactor to form a catalyst bed with a height of 60 mm, and the height ratio of the first layer, the second layer, and the third layer is 6:16:1;

[0088] The first layer and the third layer are both inert layers, and the second layer is a mixed layer; the inert layers are filled with ceramic micropowders; the mixed layer is filled with a mixture of ceramic micropowders and iron-molybdenum catalyst with a mass ratio of 1:3; and the iron-molybdenum catalyst is prepared according to Preparation Example 6;

[0089] S2. Pretreat the catalyst bed: With a space velocity of 8000 h -1 , introduce air into the catalyst bed obtained in step S1, then first heat it to 200 °C at a rate of 10 °C / min and keep it warm for 1 h; then purge it with nitrogen for 180 min, and the purge space velocity is 1000 h -1 , to obtain a pretreated catalyst bed;

[0090] S3. Prepare formaldehyde: With a space velocity of 10000 h -1 , introduce a mixed gas of 1 mol of methanol, 1 mol of oxygen, 8 mol of nitrogen and 0.1 mol of steam into the pretreated catalyst bed obtained in step S2, and carry out an oxidation reaction at a temperature of 360 °C. After the reaction is completed, remove the alcohol and add 0.032 g of inhibitor to obtain formaldehyde;

[0091] Among them, the inhibitor is obtained by mixing p-methoxy phenol and p-tert-butylcatechol with a mass ratio of 3:1.

[0092] Example 2

[0093] A production process of formaldehyde, comprising the following steps:

[0094] S1. Prepare the catalyst bed: In the reactor, successively fill the first layer, the second layer, and the third layer to form a catalyst bed with a height of 70 mm, and the height ratio of the first layer, the second layer, and the third layer is 6:17:1.2;

[0095] The first layer and the third layer are both inert layers, and the second layer is a mixed layer; the inert layers are filled with ceramic micropowders; the mixed layer is filled with a mixture of ceramic micropowders and iron-molybdenum catalyst with a mass ratio of 1:4; and the iron-molybdenum catalyst is prepared according to Preparation Example 7;

[0096] S2. Pretreat the catalyst bed: With a space velocity of 8500 h -1 , introduce air into the catalyst bed obtained in step S1, then first heat it to 250 °C at a rate of 12 °C / min and keep it warm for 1.2 h; then purge it with nitrogen for 210 min, and the purge space velocity is 1200 h -1 , to obtain a pretreated catalyst bed;

[0097] S3. Prepare formaldehyde: With a space velocity of 12000 h -1, introduce a mixed gas of 1 mol of methanol, 1.2 mol of oxygen, 9 mol of nitrogen and 0.105 mol of steam into the pretreated catalyst bed obtained in step S2. An oxidation reaction occurs at a temperature of 370 °C. After the reaction, alcohol is removed, and 0.064 g of inhibitor is added to obtain formaldehyde;

[0098] Among them, the inhibitor is obtained by mixing p-methoxyphenol and hydroquinone monobutyl ether with a mass ratio of 3.5:1.

[0099] Example 3

[0100] A production process of formaldehyde includes the following steps:

[0101] S1. Prepare the catalyst bed: Fill the first layer, the second layer, and the third layer in sequence in the reactor to form a catalyst bed with a height of 80 mm, and the height ratio of the first layer, the second layer, and the third layer is 2:9:0.5;

[0102] Both the first layer and the third layer are inert layers, and the second layer is a mixed layer; the inert layer is filled with ceramic micropowder; the mixed layer is filled with a mixture of ceramic micropowder and iron-molybdenum catalyst with a mass ratio of 1:5; and the iron-molybdenum catalyst is prepared according to Preparation Example 8;

[0103] S2. Pretreat the catalyst bed: With a volume space velocity of 9000 h -1 , introduce air into the catalyst bed obtained in step S1, then first heat it to 300 °C at a rate of 13 °C / min and keep it warm for 1.5 h; then purge it with nitrogen for 240 min, and the purge volume space velocity is 1500 h -1 , to obtain the pretreated catalyst bed;

[0104] S3. Prepare formaldehyde: With a volume space velocity of 15000 h -1 , introduce a mixed gas of 1 mol of methanol, 1.5 mol of oxygen, 11 mol of nitrogen and 0.11 mol of steam into the pretreated catalyst bed obtained in step S2. An oxidation reaction occurs at a temperature of 380 °C. After the reaction, alcohol is removed, and 0.094 g of inhibitor is added to obtain formaldehyde;

[0105] Among them, the inhibitor is obtained by mixing p-methoxyphenol and hydroquinone monobutyl ether with a mass ratio of 4:1.

[0106] Example 4

[0107] A production process of formaldehyde includes the following steps:

[0108] S1. Prepare the catalyst bed: Fill the first layer, the second layer, and the third layer in sequence in the reactor to form a catalyst bed with a height of 9 mm, and the height ratio of the first layer, the second layer, and the third layer is 6:19:1.8;

[0109] Both the first layer and the third layer are inert layers, and the second layer is a mixed layer; the inert layers are filled with ceramic micropowders; the mixed layer is filled with a mixture of ceramic micropowders and iron-molybdenum catalyst with a mass ratio of 1:5.5; and the iron-molybdenum catalyst is prepared according to Preparation Example 9;

[0110] S2. Pretreat the catalyst bed: With a space velocity of 9500 h -1 , introduce air into the catalyst bed obtained in step S1, then first heat it to 350 °C at a rate of 14 °C / min and keep it warm for 1.8 h; then purge it with nitrogen for 270 min, and the purge space velocity is 1800 h -1 , to obtain a pretreated catalyst bed;

[0111] S3. Prepare formaldehyde: With a space velocity of 18000 h -1 , introduce a mixed gas of 1 mol of methanol, 1.8 mol of oxygen, 13 mol of helium and 0.115 mol of steam into the pretreated catalyst bed obtained in step S2, and carry out an oxidation reaction at a temperature of 390 °C. After the reaction is completed, carry out alcohol removal, and add 0.128 g of inhibitor to obtain formaldehyde;

[0112] Among them, the inhibitor is obtained by mixing p-methoxy phenol and p-tert-butylcatechol with a mass ratio of 4.5:1.

[0113] Example 5

[0114] A production process of formaldehyde, comprising the following steps:

[0115] S1. Prepare the catalyst bed: In the reactor, fill the first layer, the second layer and the third layer in sequence to form a catalyst bed with a height of 100 mm, and the height ratio of the first layer, the second layer and the third layer is 3:10:1;

[0116] Both the first layer and the third layer are inert layers, and the second layer is a mixed layer; the inert layers are filled with ceramic micropowders; the mixed layer is filled with a mixture of ceramic micropowders and iron-molybdenum catalyst with a mass ratio of 1:6; and the iron-molybdenum catalyst is prepared according to Preparation Example 10;

[0117] S2. Pretreat the catalyst bed: With a space velocity of 10000 h -1 , introduce air into the catalyst bed obtained in step S1, then first heat it to 400 °C at a rate of 15 °C / min and keep it warm for 2 h; then purge it with nitrogen for 300 min, and the purge space velocity is 2000 h -1 , to obtain a pretreated catalyst bed;

[0118] S3. Prepare formaldehyde: With a space velocity of 20000 h -1, introduce a mixed gas of 1 mol of methanol, 2 mol of oxygen, 14 mol of neon, and 0.12 mol of steam into the pretreated catalyst bed obtained in step S2. At a temperature of 400 °C, an oxidation reaction occurs. After the reaction, the alcohol is removed, and 0.16 g of polymerization inhibitor is added to obtain formaldehyde;

[0119] Among them, the polymerization inhibitor is obtained by mixing p-methoxyphenol and monobutyl ether of hydroquinone in a mass ratio of 5:1.

[0120] To verify the conversion rate of methanol, the yield and purity of formaldehyde in a formaldehyde production process provided by this application, the applicant set Comparative Examples 1-14, among which:

[0121] Comparative Example 1

[0122] Comparative Example 1 is the same as Example 1, except that: the first layer, the second layer, and the third layer form a catalyst bed with a height of 30 mm.

[0123] Comparative Example 2

[0124] Comparative Example 2 is the same as Example 1, except that: the first layer, the second layer, and the third layer form a catalyst bed with a height of 200 mm.

[0125] Comparative Example 3

[0126] Comparative Example 3 is the same as Example 1, except that: the height ratio of the first layer, the second layer, and the third layer is 6:10:1.

[0127] Comparative Example 4

[0128] Comparative Example 4 is the same as Example 1, except that: the height ratio of the first layer, the second layer, and the third layer is 6:25:1.

[0129] Comparative Example 5

[0130] Comparative Example 5 is the same as Example 1, except that: the mixing layer is filled with a mixture of ceramic micro powder and iron-molybdenum catalyst in a mass ratio of 1:1.

[0131] Comparative Example 6

[0132] Comparative Example 6 is the same as Example 1, except that: the mixing layer is filled with a mixture of ceramic micro powder and iron-molybdenum catalyst in a mass ratio of 1:10.

[0133] Comparative Example 7

[0134] Comparative Example 7 is the same as Example 1, except that: the iron-molybdenum catalyst is prepared from Comparative Preparation Example 1.

[0135] Comparative Example 8

[0136] Comparative Example 8, same as Example 1, except that: the iron-molybdenum catalyst was prepared from Comparative Preparation Example 2.

[0137] Comparative Example 9

[0138] Comparative Example 9, same as Example 1, except that: the amount of oxygen used was 0.8 mol.

[0139] Comparative Example 10

[0140] Comparative Example 10, same as Example 1, except that: the amount of oxygen used was 3 mol.

[0141] Comparative Example 11

[0142] Comparative Example 11, same as Example 1, except that: the mass of the polymerization inhibitor was 0.02 g.

[0143] Comparative Example 12

[0144] Comparative Example 12, same as Example 1, except that: the mass of the polymerization inhibitor was 0.2 g.

[0145] Comparative Example 13

[0146] Comparative Example 13, same as Example 1, except that: the polymerization inhibitor was only p-hydroxyanisole.

[0147] Comparative Example 14

[0148] Comparative Example 14, same as Example 1, except that: the polymerization inhibitor was only butylhydroxyanisole.

[0149] The conversion rate of methanol and the yield of formaldehyde in Examples 1-5 and Comparative Examples 1-14 of the present application were calculated respectively, and the following result parameters were obtained, as shown in Table 1 specifically.

[0150] Table 1:

[0151]

[0152]

[0153] As can be seen from the data shown in Table 1 above: when Examples 1-5 of the present application were compared with Comparative Examples 1-14,

[0154] in the formaldehyde production process of Examples 1-5, the conversion rate of methanol and the yield of formaldehyde were relatively high, indicating that the formaldehyde production process of the present application has broad prospects for industrial production.

[0155] From Example 1 and Comparative Examples 1 and 2, it can be seen that: the height of the catalyst bed layer in Example 1 was 60 mm. Compared with Comparative Examples 1 and 2, the conversion rate of methanol and the yield of formaldehyde in Example 1 were both higher than those in Comparative Examples 1 and 2.

[0156] As can be seen from Example 1 and Comparative Examples 3 and 4: The height ratio of the first, second, and third layers of the catalyst bed in Example 1 is 6:16:1. Compared with Comparative Examples 3 and 4, the conversion rate of methanol and the yield of formaldehyde in Example 1 have been significantly improved.

[0157] As can be seen from Example 1 and Comparative Examples 5 and 6: The mixed layer of the catalyst bed in Example 1 is filled with a mixture of ceramic micro-powder and iron-molybdenum catalyst with a mass ratio of 1:3. Compared with Comparative Examples 5 and 6, the yield of formaldehyde in Example 1 is higher.

[0158] As can be seen from Example 1 and Comparative Examples 7 and 8: The iron-molybdenum catalyst in Example 1 is prepared by Preparation Example 6, and the carrier of Preparation Example 6 is prepared by Preparation Example 1; compared with Comparative Examples 7 and 8, the iron-molybdenum catalyst in Example 1 greatly improves the conversion rate of methanol and the yield of formaldehyde.

[0159] As can be seen from Example 1 and Comparative Examples 9 and 10: The amount of oxygen used in Example 1 is 1 mol. Compared with Comparative Examples 9 and 10, the catalytic oxidation of methanol in Example 1 is more complete, and the conversion rate of methanol and the yield of formaldehyde are higher.

[0160] As can be seen from Example 1 and Comparative Examples 11 and 12, the mass of the polymerization inhibitor in Example 1 is 0.032 g, which is 0.1% of the mass of formaldehyde. Compared with Comparative Examples 11 and 12, the yield of formaldehyde in Example 1 has been significantly improved.

[0161] As can be seen from Example 1 and Comparative Examples 13 and 14, the polymerization inhibitor in Example 1 is obtained by mixing p-hydroxyanisole and p-tert-butylcatechol. Compared with Comparative Examples 13 and 14, the yield of formaldehyde in Example 1 is higher.

[0162] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A production process of formaldehyde, characterized in that, The following steps are involved: S1. Preparing a catalyst bed: sequentially filling a first layer, a second layer, and a third layer in a reactor to form a catalyst bed; S2, pre-treating the catalyst bed: introducing air into the catalyst bed obtained in step S1, first heating it up, keeping it warm for a period of time, and then purging it with nitrogen to obtain a pre-treated catalyst bed; the height of the catalyst bed is 60-100 mm; the height ratio of the first layer, the second layer and the third layer is 6:16-20:1-2; S3, preparing formaldehyde: introducing a mixed gas of methanol, oxygen, inert gas and water vapor into the pretreated catalyst bed obtained in step S2 to cause an oxidation reaction, and after the reaction is completed, performing dealcoholization, and adding a polymerization inhibitor to obtain formaldehyde; The first layer and the third layer are both inert layers, and the second layer is a mixed layer; the inert layer is filled with ceramic micropowder; the mixed layer is filled with a mixture of ceramic micropowder and iron-molybdenum catalyst in a mass ratio of 1:3-6; The iron-molybdenum catalyst comprises the following raw materials in parts by weight: 18-20 parts of ferric sulfate, 38-45 parts of molybdenum oxide, 30-40 parts of dilute sulfuric acid, and 11-15 parts of a carrier; The carrier is prepared by the following method: According to weight, 12-18 parts of bamboo charcoal powder are first added to 6-8 parts of triethanolamine for sufficient grinding, and then 1-2 parts of Tween are added. Then, the mixture is ultrasonically treated at a temperature of 40-80° C. for 1-2 hours, filtered, washed and dried to obtain a carrier.

2. The production process of formaldehyde according to claim 1, characterized in that, The molar ratio of the methanol, oxygen, inert gas and water vapor is 1:1-2:8-14:0.1-0.

12.

3. The production process of formaldehyde according to claim 1, characterized in that, The iron-molybdenum catalyst is prepared by the following method: S11, dissolving iron sulfate and molybdenum oxide in dilute sulfuric acid with a concentration of 10-30wt%, adjusting the pH of the solution to 1-2 after sufficient dissolution, aging at 60-80°C for 18-20h, filtering with suction, and washing to neutrality to obtain a mixture; S12, firstly mix the mixture obtained in step S11 with the carrier uniformly, and then dry at 80-100° C. for 20-60 min; then heat-treat at 300-400° C. for 4-5 h under nitrogen protection, grind, and pass through a 400-800 mesh sieve to obtain an iron-molybdenum catalyst.

4. The production process of formaldehyde according to claim 1, characterized in that, The mass of the polymerization inhibitor is 0.1-0.5% of methanol.

5. The production process of formaldehyde according to claim 4, characterized in that, The polymerization inhibitor is obtained by mixing p-hydroxyanisole and hydroquinone monobutyl ether in a mass ratio of 3-5:1.

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