Process for the preparation of hcn by methanol ammoxidation

Abstract

The application discloses a process for preparing HCN by methanol ammonia oxidation. The process is characterized by using ammonia, methanol and air as raw materials to prepare HCN in a reactor loaded with catalyst A and catalyst B; the catalyst A and the catalyst B are loaded in the upper part and the lower part of the reactor in sections. The application is applied to the preparation of HCN by methanol ammonia oxidation, and the bed temperature under high load is controllable, the activity and HCN selectivity are excellent, the preparation cost is low, and the selectivity of by-products formaldehyde and hydroxyacetonitrile is low.

Description

Technical Field

[0001] This invention relates to a preparation method, and more particularly to a process for preparing HCN by methanol ammoxidation. Background Technology

[0002] Hydrogen cyanide (HCN) can be used to produce acetone cyanohydrin, adiponitrile, sodium cyanide, methionine, glycine, and chelating agents, and has wide applications in the fields of medicine, pesticides, dyes, and metallurgy.

[0003] Industrially, HCN is mainly produced through methods such as the acrylonitrile by-product method, the methane ammoxidation method (Angle process), and the methanol ammoxidation method. The acrylonitrile by-product method produces HCN as a by-product during the catalytic ammoxidation of acrylonitrile. This technology requires proximity to acrylonitrile production plants and has an HCN yield of only about 6%, limiting its application. The methane ammoxidation method produces HCN at temperatures above 1000℃, with an HCN yield of only about 60-70%. Due to the wide explosion limits of methane, high reaction temperature, large exothermic reaction, and low ammonia utilization (only 60-70%), this technology carries a high safety risk.

[0004] The methanol ammoxidation process uses methanol, ammonia, and air as raw materials. This process has advantages such as low reaction temperature, low energy consumption, and relatively safe operation. This technology has been reported in numerous patents, with research focusing primarily on catalysts. The main catalytic systems are Fe-Mo oxides, PV oxides, Mn-P oxides, and Pt-Rh catalysts, with most reported catalysts containing Fe and Mo as their active phase.

[0005] US3911089 discloses a Mo catalyst for ammonia oxidation. a Bi b Fe c X d Y e Z f O g X is one of Cr, Mn, Co, Ni, Zn, Cd, Sn, W, and Pb, and Y is one or more transition elements. The catalyst composition is complex, and the HCN yield is 86%. Patent EP0322796 discloses a general-purpose catalyst Mo for the ammoxidation of one or more organic compounds such as methanol, propylene, and isobutylene. e D f E g F h O y D is mainly selected from Mn, Fe, Ni, Bi and Zn, while the HCN yield is only 81%.

[0006] Chinese patent CN1112243 discloses Mo a Bi b Me c Ted Q e R f X g Y h O z The catalyst contains Mo / Bi and at least one element selected from iron and cerium. Patent US4461752 discloses a catalyst containing Fe. a Cu b Sb c Mo d Me e Te f Q g O h (SiO2) i The methanol ammonia oxidation catalyst disclosed in patent US5158787 is Fe. a Cu b Sb c V d Mo e W f P g Q h R i S j O k (SiO2) l The preparation of the above catalysts requires a wide variety of raw materials and involves a complex process. The yield of HCN decreases significantly when the composition deviates even slightly from the empirical formula.

[0007] Chinese patent CN106669705A discloses a catalyst for methanol ammonia oxidation reaction and its preparation method. The catalyst has a high content of active components, high cost, and low HCN selectivity.

[0008] Chinese patent CN114950462A discloses a catalyst for the ammoxidation of methanol to HCN and its preparation method. The catalyst first requires the preparation of Fe-Mo composite oxide and spherical support. The catalyst preparation process is complex. It has a high methanol conversion rate, but the HCN selectivity is low and the by-products such as formaldehyde and hydroxyacetonitrile are still too high.

[0009] Chinese patent CN116139872A discloses a catalyst for the ammoxidation of methanol to HCN and its preparation method. The catalyst has good activity, but only one type of catalyst is used, resulting in low HCN selectivity and excessive byproducts such as formaldehyde and hydroxyacetonitrile.

[0010] Furthermore, catalysts containing Fe and Mo have the ability to oxidize methanol to formaldehyde. The generated formaldehyde further reacts with HCN to produce hydroxyacetonitrile and other byproducts. Formaldehyde and hydroxyacetonitrile byproducts are highly reactive and easily polymerize, leading to blockage of subsequent separation systems. None of the aforementioned patents mention the impact of different catalyst compositions and particle sizes on the methanol ammonia oxidation conversion rate and the formation of formaldehyde / hydroxyacetonitrile byproducts.

[0011] Currently, methanol ammonia oxidation catalysts prepared using existing technologies suffer from problems such as complex catalyst composition, high preparation cost, poor reproducibility, and poor HCN selectivity. Therefore, developing methanol ammonia oxidation processes and catalysts with superior reaction performance is of great significance. Summary of the Invention

[0012] To address the above technical problems, this invention proposes a process for preparing HCN by methanol ammoxidation.

[0013] A process for preparing HCN by methanol ammoxidation includes preparing HCN using ammonia, methanol, and air as raw materials in a reactor simultaneously packed with catalyst A and catalyst B; wherein catalyst A and catalyst B are separately packed in the upper and lower parts of the reactor.

[0014] The catalyst A comprises an active component A consisting of Fe2O3 and MoO3, and a support A consisting of Al2O3, SiO2, and Mn2O3, with the total mass being 100%, wherein the mass ratio of each component is as follows:

[0015]

[0016] The catalyst B comprises an active component B consisting of Fe2O3, MoO3, and PdO, and a support B consisting of Al2O3, SiO2, and Mn2O3, with the total mass being 100%, and the mass ratio of each component being:

[0017]

[0018] The catalyst is packed in sections. The catalyst particles in the upper section are large, which helps to control hot spots in the bed and prevent overheating. The catalyst particles in the lower section are small and contain palladium, which helps to improve methanol conversion and deeply oxidize by-products.

[0019] In a preferred embodiment of the present invention, the mass ratio of catalyst A to catalyst B is (0.25-4):1. An excessively high proportion of catalyst A will result in insufficient methanol conversion and a higher production of byproducts such as formaldehyde, which is detrimental to HCN yield. An excessively high proportion of catalyst B will cause over-oxidation of methanol and related products, and may even lead to overheating of the catalyst bed, which will also negatively impact HCN yield.

[0020] As a preferred embodiment of the present invention, the molar ratio of ammonia, methanol and air in the reaction raw materials is 1:(0.8-1.2):(80-120);

[0021] Preferably, the total gas space velocity of ammonia, methanol, and air is 2000-5000 h⁻¹. -1 .

[0022] As a preferred embodiment of the present invention, the reaction temperature of ammonia, methanol and air is 350-390°C, and the reaction is carried out at atmospheric pressure.

[0023] As a preferred embodiment of the present invention, the particle size of carrier A is 4-5.5 mm; the particle size of carrier B is 2-3.5 mm. Different carrier particle sizes can be adjusted by using a pelletizing die, which is a known adjustment method for those skilled in the art.

[0024] As a preferred embodiment of the present invention, the preparation method of catalyst A includes:

[0025] A1. Al2O3 and Mn2O3 are mixed and then added to silica sol for bonding. The mixture is then extruded, granulated, dried, and calcined to obtain carrier A. The calcination temperature can be 400-600℃ (e.g., 400℃, 500℃, 550℃), and the calcination time can be 2-8h (e.g., 3h, 5h, 7h).

[0026] A2. Dissolve molybdenum-containing compounds and iron-containing compounds in water to obtain an aqueous metal solution;

[0027] A3. The above-mentioned aqueous metal solution is impregnated onto support A, and then dried and calcined to obtain catalyst A. The calcination temperature can be 450-650℃ (e.g., 450℃, 500℃, 550℃), and the calcination time can be 2-8h (e.g., 3h, 5h, 7h).

[0028] As a preferred embodiment of the present invention, the method for preparing catalyst B includes:

[0029] B1. Al2O3 and Mn2O3 are mixed and then bonded with silica sol. The mixture is then extruded, granulated, dried, and calcined to obtain carrier B. The calcination temperature can be 400-600℃ (e.g., 400℃, 500℃, 550℃), and the calcination time can be 2-8h (e.g., 3h, 5h, 7h). Mn2O3 has good oxidizing ability, which can deeply oxidize byproducts such as formaldehyde and hydroxyacetonitrile, reducing the impact of easily polymerizable formaldehyde and hydroxyacetonitrile on the operation of downstream separation systems.

[0030] B2. Dissolve molybdenum-containing compounds, iron-containing compounds, and palladium-containing compounds in water to obtain an aqueous metal solution;

[0031] B3. The above-mentioned aqueous metal solution is impregnated onto the support B, and then dried and calcined to obtain catalyst B. The calcination temperature can be 450-650℃ (e.g., 450℃, 500℃, 550℃), and the calcination time can be 2-8h (e.g., 3h, 5h, 7h).

[0032] As a preferred embodiment of the present invention, the silica sol has a particle size of 20-40 nm and a concentration of 20-40 wt%. When the silica sol concentration is too high, the particle size in the sol is too large, which is not conducive to the dispersion of active components. When the silica sol concentration is too low, the catalyst preparation efficiency is low and the energy consumption is high.

[0033] The preferred particle size of Al2O3 is 100-200 mesh. Larger particle size is beneficial to the mass transfer performance of the catalyst, but detrimental to the catalyst strength. Smaller particle size is beneficial to the catalyst strength, but detrimental to improving the mass transfer performance of the catalyst. Therefore, selecting Al2O3 with a suitable particle size can improve the mass transfer performance of the catalyst and reduce the occurrence of side reactions while ensuring the catalyst strength.

[0034] As a preferred embodiment of the present invention, the molybdenum-containing compound is selected from one or more of ammonium dimolybdate, ammonium tetramolybdate, and ammonium heptamolybdate;

[0035] And / or, the iron-containing compound is selected from one or more of ferric nitrate, ferric chloride, and ferric acetate;

[0036] And / or, the palladium-containing compound is selected from one or more of palladium nitrate, palladium chloride, and dichlorotetraamminepalladium.

[0037] Preferably, the mass concentration of the metal aqueous solution is 30-50 wt%. If the mass concentration is too low, the preparation process requires a large amount of water, resulting in resource waste; if the mass concentration is too high, it will be difficult to dissolve completely, and it will also affect the dispersion of the active metal.

[0038] This invention utilizes catalysts with different active components and particle sizes, which are loaded in stages in a reactor. When applied to the methanol-to-HCN ammoxidation process, the bed temperature is controllable under high load, exhibiting excellent activity and HCN selectivity (HCN selectivity > 91.0%). Moreover, the preparation cost is low, and the selectivity of by-products formaldehyde and hydroxyacetonitrile is < 0.03%, respectively. Detailed Implementation

[0039] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0040] The main raw materials used in this invention are as follows. Unless otherwise specified, other raw materials and reagents can be purchased commercially.

[0041] Methanol, analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] Ferric nitrate, analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0043] Ammonium molybdate, analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0044] α-Alumina, ≥98%, purchased from Beijing Innocare Technology Co., Ltd., particle size 100-200 mesh;

[0045] Silica sol, concentration 40wt%, particle size 20-30nm, purchased from Linyi Kehan ​​Silicon Products Co., Ltd.

[0046] Silica sol, concentration 30wt%, particle size 20-30nm, purchased from Linyi Kehan ​​Silicon Products Co., Ltd.

[0047] Mn2O3, purity ≥98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0048] Dichlorotetraamminepalladium, purity ≥98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0049] The main testing methods involved in the following embodiments of the present invention are as follows:

[0050] Methanol conversion rate and hydroxyacetonitrile selectivity were calculated after analysis using an Agilent 7820A gas chromatograph. The test conditions included: DB-5 column, FID detector, vaporization chamber temperature of 260℃, detector temperature of 260℃, carrier gas of high-purity N2, and flow rate of 30 ml / min.

[0051] The HCN generated during the reaction was absorbed by sodium hydroxide solution within a certain time, and the HCN selectivity was determined and calculated by silver nitrate titration.

[0052] [Quasi-Example 1]

[0053] Preparation of catalyst A-1:

[0054] (1) 96g of α-alumina and 92.1g of Mn2O3 powder were thoroughly mixed, and 218.3g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 400℃ for 4h to obtain cylindrical carrier A-1 with a particle size of 4.0mm.

[0055] (2) Add 14.3g of ammonium heptamolybdate and 65.3g of ferric nitrate to 97.3g of water and stir thoroughly until dissolved to obtain a metal aqueous solution;

[0056] (3) The above-mentioned metal aqueous solution was immersed on the support A-1, dried at 120°C for 4 hours and calcined at 450°C for 4 hours to obtain catalyst A-1 with a particle size of 4.0 mm.

[0057] Preparation of catalyst B-1:

[0058] (1) 96g of α-alumina and 92.1g of Mn2O3 powder were thoroughly mixed, and 218.3g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 400℃ for 4h to obtain cylindrical carrier B-1 with a particle size of 2.0mm.

[0059] (2) Add 14.3g ammonium heptamolybdate, 65.3g ferric nitrate and 0.6g dichlorotetraamminepalladium to 97.3g water and stir thoroughly until dissolved to obtain a metal aqueous solution.

[0060] (3) The above-mentioned aqueous metal solution was impregnated onto the support B-1, dried at 120°C for 4 hours and calcined at 450°C for 4 hours to obtain catalyst B-1 with a particle size of 2.0 mm.

[0061]

Preparation of Example 2

[0062] Preparation of catalyst A-2:

[0063] (1) 135.3g of α-alumina and 53.7g of Mn2O3 powder were thoroughly mixed, and 218.0g of silica sol (concentration 30wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 400℃ for 4h to obtain cylindrical carrier A-2 with a particle size of 4.5mm.

[0064] (2) Add 19.9g of ammonium heptamolybdate and 53.1g of ferric nitrate to 92.9g of water and stir thoroughly until dissolved to obtain a metal aqueous solution;

[0065] (3) The above-mentioned metal aqueous solution was immersed on the support A-2, dried at 120°C for 4 hours and calcined at 550°C for 4 hours to obtain catalyst A-2 with a particle size of 4.5 mm.

[0066] Preparation of catalyst B-2:

[0067] (1) 135.3g of α-alumina and 53.7g of Mn2O3 powder were thoroughly mixed, and 218.0g of silica sol (concentration 30wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 450℃ for 4h to obtain cylindrical carrier B-2 with a particle size of 2.5mm.

[0068] (2) Add 19.9g ammonium heptamolybdate, 53.1g ferric nitrate and 1.2g dichlorotetraamminepalladium to 92.9g water and stir thoroughly until dissolved to obtain a metal aqueous solution.

[0069] (3) The above-mentioned aqueous metal solution was immersed on the support B-2, dried at 120°C for 4 hours and calcined at 550°C for 4 hours to obtain catalyst B-2 with a particle size of 2.5 mm.

[0070] [Preparation Example 3]

[0071] Preparation of catalyst A-3:

[0072] (1) 119.7g of α-alumina and 79.5g of Mn2O3 powder were thoroughly mixed, and 188.3g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 500℃ for 4h to obtain cylindrical carrier A-3 with a particle size of 5.0mm.

[0073] (2) Add 11.0g of ammonium heptamolybdate and 83.5g of ferric nitrate to 141.8g of water and stir thoroughly until dissolved to obtain a metal aqueous solution;

[0074] (3) The above-mentioned aqueous metal solution was immersed on the support A-3, dried at 120°C for 4 hours and calcined at 500°C for 4 hours to obtain catalyst A-3 with a particle size of 5.0 mm.

[0075] Preparation of catalyst B-3:

[0076] (1) 119.7g of α-alumina and 79.5g of Mn2O3 powder were thoroughly mixed, and 188.3g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 500℃ for 4h to obtain cylindrical carrier B-3 with a particle size of 3.0mm.

[0077] (2) Add 11.0g ammonium heptamolybdate, 83.5g ferric nitrate and 1.8g dichlorotetraamminepalladium to 141.8g water and stir thoroughly until dissolved to obtain a metal aqueous solution.

[0078] (3) The above-mentioned metal aqueous solution was immersed on the support B-3, dried at 120°C for 4 hours and calcined at 500°C for 4 hours to obtain catalyst B-3 with a particle size of 3.0 mm.

[0079] [Preparation Example 4]

[0080] Preparation of catalyst A-4:

[0081] (1) 135.3g of α-alumina and 58.8g of Mn2O3 powder were thoroughly mixed, and 195.8g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 550℃ for 4h to obtain cylindrical carrier A-4 with a particle size of 5.5mm.

[0082] (2) Add 9.6g of ammonium heptamolybdate and 100.2g of ferric nitrate to 195.1g of water and stir thoroughly until dissolved to obtain a metal aqueous solution;

[0083] (3) The above-mentioned aqueous metal solution was immersed on the support A-4, dried at 120°C for 4 hours and calcined at 550°C for 4 hours to obtain catalyst A-4 with a particle size of 5.5 mm.

[0084] Preparation of catalyst B-4:

[0085] (1) 135.3g of α-alumina and 58.8g of Mn2O3 powder were thoroughly mixed, and 195.8g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 550℃ for 4h to obtain cylindrical carrier B-4 with a particle size of 3.5mm.

[0086] (2) Add 9.6g ammonium heptamolybdate, 100.2g ferric nitrate and 2.4g dichlorotetraamminepalladium to 195.1g of water and stir thoroughly until dissolved to obtain a metal aqueous solution.

[0087] (3) The above-mentioned aqueous metal solution was immersed on the support B-4, dried at 120°C for 4 hours and calcined at 550°C for 4 hours to obtain catalyst B-4 with a particle size of 3.5 mm.

[0088] [Preparation Example 5]

[0089] Preparation of catalyst A-5:

[0090] (1) 144.3g of α-alumina and 48.3g of Mn2O3 powder were thoroughly mixed, and 210.8g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 450℃ for 4h to obtain cylindrical carrier A-5 with a particle size of 5.0mm.

[0091] (2) Add 13.6g of ammonium heptamolybdate and 60.7g of ferric nitrate to 135.0g of water and stir thoroughly until dissolved to obtain a metal aqueous solution;

[0092] (3) The above-mentioned aqueous metal solution was immersed on the support A-5, dried at 120°C for 4 hours and calcined at 600°C for 4 hours to obtain catalyst A-5 with a particle size of 5.0 mm.

[0093] Preparation of catalyst B-5:

[0094] (1) 144.3g of α-alumina and 48.3g of Mn2O3 powder were thoroughly mixed, and 210.8g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 450℃ for 4h to obtain cylindrical carrier B-5 with a particle size of 3.0mm.

[0095] (2) Add 13.6g ammonium heptamolybdate, 60.7g ferric nitrate and 1.5g dichlorotetraamminepalladium to 135.0g water and stir thoroughly until dissolved to obtain a metal aqueous solution.

[0096] (3) The above-mentioned aqueous metal solution was impregnated onto the support B-5, dried at 120°C for 4 hours and calcined at 600°C for 4 hours to obtain catalyst B-5 with a particle size of 3.0 mm.

[0097] [Preparation Example 6]

[0098] Preparation of catalyst A-6:

[0099] (1) 120.3g of α-alumina and 82.5g of Mn2O3 powder were thoroughly mixed, and 188.3g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 500℃ for 4h to obtain cylindrical carrier A-6 with a particle size of 4.0mm.

[0100] (2) Add 11.4g of ammonium heptamolybdate and 63.8g of ferric nitrate to 142.7g of water and stir thoroughly until dissolved to obtain a metal aqueous solution;

[0101] (3) The above-mentioned aqueous metal solution was immersed on the support A-6, dried at 120°C for 4 hours and calcined at 620°C for 4 hours to obtain catalyst A-6 with a particle size of 4.0 mm.

[0102] Preparation of catalyst B-6:

[0103] (1) 120.3g of α-alumina and 82.5g of Mn2O3 powder were thoroughly mixed, and 188.3g of silica sol (concentration 40wt%, particle size 20-30nm) was added for bonding. Then the mixture was extruded, granulated, dried at 120℃ for 4h, and calcined at 500℃ for 4h to obtain cylindrical carrier B-6 with a particle size of 3.0mm.

[0104] (2) Add 11.4g ammonium heptamolybdate, 63.8g ferric nitrate and 2.1g dichlorotetraamminepalladium to 142.7g water and stir thoroughly until dissolved to obtain a metal aqueous solution.

[0105] (3) The above-mentioned aqueous metal solution was impregnated onto the support B-6, dried at 120°C for 4 hours and calcined at 620°C for 4 hours to obtain catalyst B-6 with a particle size of 3.0 mm.

[0106] [Prepare Comparison Example 1]

[0107] Catalysts were prepared under essentially the same conditions as in Example 1, except that Mn2O3 powder was not added during the preparation of the support. The prepared catalysts were designated as catalysts D-1 and D-2, respectively.

[0108]

Example 1

[0109] HCN was prepared according to the following method:

[0110] The reaction was conducted using a small-scale molten salt apparatus. The reaction tube had an inner diameter of 27 mm, and the catalyst loading was 50 ml (catalyst A-1 and catalyst B-1 were loaded at the top and bottom of the reaction tube, respectively, with a mass ratio of 1:3). The molten salt temperature was set at 390℃. The feedstock was introduced from the top of the reactor, with a molar ratio of ammonia, methanol, and air of 4:4.4:91.6. The reaction was carried out at atmospheric pressure, and the total gas hourly space velocity (GHSV) of ammonia, methanol, and air was 3000 h⁻¹. -1 Samples were taken for analysis 2 hours after the reaction feed stabilized. The results of the methanol ammoxidation reaction are shown in Table 2.

[0111]

Examples 2-6

[0112] HCN was prepared under essentially the same conditions as in Example 1, except that some reaction conditions were described in Table 1.

[0113] Table 1. Different reaction conditions in each example

[0114]

[0115] Comparative Example 1

[0116] HCN was prepared under essentially the same conditions as in Example 1, except that catalyst B-1 was not packed at the bottom of the reaction tube.

[0117] Comparative Example 2

[0118] HCN was prepared under essentially the same conditions as in Example 1, except that catalyst A-1 was not packed into the upper part of the reaction tube.

[0119] Comparative Example 3

[0120] HCN was prepared under essentially the same conditions as in Example 1, except that the catalyst packed in the upper part of the reaction tube was replaced with D-1, and the catalyst packed in the lower part of the reaction tube was replaced with D-2.

[0121] Table 2. Results of methanol ammoxidation reaction

[0122]

[0123]

[0124] As shown in Table 2, the catalysts prepared in Examples 1 to 6 have good activity and selectivity, while the catalysts described in Comparative Examples 1 to 4 either have low activity or poor HCN selectivity.

[0125] The comparison between Example 1 and Comparative Example 1 shows that using only catalyst A-1 with a larger particle size and no Pd, without using catalyst B-1, results in low methanol conversion and a large amount of byproducts such as formaldehyde and hydroxyacetonitrile.

[0126] The comparison between Example 1 and Comparative Example 2 shows that using only the smaller particle size, Pd-containing catalyst B-1, without using catalyst A-1, results in a higher methanol conversion rate but also a higher likelihood of over-oxidation, leading to lower HCN selectivity.

[0127] The comparison between Example 1 and Comparative Example 3 demonstrates that the introduction of Mn2O3 into the catalyst is beneficial for reducing the amount of byproducts such as formaldehyde.

[0128] The above results demonstrate that the catalyst prepared in this invention not only exhibits excellent activity and HCN selectivity when used for the ammoxidation of methanol to produce HCN, but also produces less formaldehyde and hydroxyacetonitrile as byproducts.

[0129] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A process for the production of HCN from methanol ammoxidation, characterized in that, HCN is prepared with ammonia, methanol and air as raw materials in a reactor filled with catalyst A and catalyst B at the same time; the catalyst A and catalyst B are filled in the upper and lower parts of the reactor in stages; The catalyst A comprises active component A with a composition of Fe2O3 and MoO3, and carrier A with a composition of Al2O3, SiO2 and Mn2O3, wherein the mass ratio of each component is: Fe2O3 3.0-7.0wt%, MoO3 2.0-6.0wt%, Al2O3 30-50wt%, SiO2 20-30wt%, Mn2O3 15-30wt%; The catalyst B comprises active component B with a composition of Fe2O3, MoO3 and PdO, and carrier B with a composition of Al2O3, SiO2 and Mn2O3, wherein the mass ratio of each component is: Fe2O3 3.0-7.0wt%, MoO3 2.0-6.0wt%, Al2O3 30-50wt%, SiO2 20-30wt%, Mn2O3 15-30wt%, PdO 0.05-0.5wt%; The filling mass ratio of the catalyst A and the catalyst B is (0.25-4):

1.

2. The process for the production of HCN by methanol ammoxidation according to claim 1, characterized by the fact that, In the reaction raw materials, the molar ratio of ammonia, methanol and air is 1:(0.8-1.2):(80-120).

3. The process for the production of HCN by methanol ammoxidation according to claim 2, characterized by the fact that, The total gas space velocity of ammonia, methanol and air in the reaction raw materials is 2000-5000h -1 .

4. Process for the preparation of HCN by methanol ammoxidation according to any one of claims 1-3, characterized in that, The reaction temperature of ammonia, methanol and air is 350-390℃, and the reaction is carried out under normal pressure.

5. The process for the preparation of HCN by methanol ammoxidation according to any one of claims 1-3, characterized in that, The particle size of the carrier A is 4-5.5mm; and the particle size of the carrier B is 2-3.5mm.

6. The process for the production of HCN by methanol ammoxidation according to claim 1, characterized by the fact that, The preparation method of the catalyst A comprises: A1, mixing Al2O3 and Mn2O3, then adding silica sol for bonding, then extruding, cutting, drying and calcining to obtain the carrier A; A2, dissolving a molybdenum-containing compound and an iron-containing compound in water to obtain a metal aqueous solution; A3, dipping the above metal aqueous solution into the carrier A, and then drying and calcining to obtain the catalyst A.

7. The process for the production of HCN by methanol ammoxidation according to claim 1, characterized by the fact that, The preparation method of the catalyst B comprises: B1, mixing Al2O3 and Mn2O3, then adding silica sol for bonding, then extruding, cutting, drying and calcining to obtain the carrier B; B2, dissolving a molybdenum-containing compound, an iron-containing compound and a palladium-containing compound in water to obtain a metal aqueous solution; B3, dipping the above metal aqueous solution into the carrier B, and then drying and calcining to obtain the catalyst B.

8. Process for the production of HCN by methanol ammoxidation according to claim 6 or 7, characterized in that, The particle size of the silica sol is 20-40nm, and the concentration is 20-40wt%.

9. Process for the production of HCN by methanol ammoxidation according to claim 6 or 7, characterized in that, The molybdenum-containing compound is selected from one or more of ammonium dimolybdate, ammonium tetramolybdate and ammonium heptamolybdate; and / or, the iron-containing compound is selected from one or more of ferric nitrate, ferric chloride and ferric acetate; and / or, the palladium-containing compound is selected from one or more of palladium nitrate, palladium chloride and palladium dichloride tetraammonium.

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