A catalyst for preparing HCN by methanol ammoxidation and its preparation method

Abstract

The invention discloses a catalyst for preparing HCN by ammoxidation of methanol and a preparation method thereof, wherein the catalyst comprises: 3.0-7.0wt% Fe2O3, 2.0-6.0wt% MoO3, 50-80wt% SiO2 and 15-40wt% TiO2. The catalyst has high dispersity of active components and good mass transfer performance, and has excellent activity and selectivity when used for preparing HCN by ammoxidation of methanol.

Description

Technical Field

[0001] The invention relates to a catalyst for preparing HCN through methanol ammoxidation and a preparation method thereof, belonging to the technical field of catalysis. Background Art

[0002] Hydrocyanic acid (HCN) is an important chemical intermediate with active properties. It is widely used in the fields of medicine, pesticides, dyes, additives and metallurgy. It can be used to produce acetone cyanohydrin, adiponitrile, sodium cyanide, methionine, glycine, glyphosate and chelating agents.

[0003] The main industrial HCN production methods include acrylonitrile by-product method, methane ammoxidation method (Angler method), light oil cracking method and methanol ammoxidation method.

[0004] The acrylonitrile by-product method uses propylene, air and ammonia as raw materials, and produces HCN as a by-product during the catalytic ammoxidation synthesis of acrylonitrile. This technology needs to be close to the acrylonitrile manufacturer and the HCN yield is only about 6%, so its application is limited.

[0005] The methane ammoxidation method uses methane, ammonia and air as raw materials, Pt-Rh as catalyst, and reacts at above 1000°C to obtain HCN, with an HCN yield of only about 60-70%. Due to the wide explosion limit range of raw methane, high reaction temperature, large reaction heat, and low ammonia utilization rate (only 60-70%), this technology has a high safety risk.

[0006] The light oil cracking method uses light oil, liquid ammonia, petroleum coke and nitrogen as raw materials, and reacts at normal pressure and 1450°C to obtain HCN. This process requires intermittent addition of solid coke, and the synthesis process is unstable. Since the raw materials, intermediates and products are mostly flammable, explosive or highly toxic compounds, the production process is very dangerous and has many potential accidents, so this route has not been promoted and applied.

[0007] Methanol ammoxidation is a process for preparing HCN using methanol, ammonia and air as raw materials. This process has the advantages of low reaction temperature, low energy consumption and relatively safe process. The catalyst is the core of this technology. Methanol ammoxidation catalysts have been reported in many patents. The main catalytic systems are Fe-Mo oxide, PV oxide, Mn-P oxide and Pt-Rh catalyst, etc. Most of the reported catalyst active phases contain Fe and Mo.

[0008] US patent US4425260 proposed an iron-molybdenum catalyst Fe a Mo b O c The patent adds molybdenum salt solution to iron salt solution to form precipitation first, and then adds silica sol, which is expected to be unfavorable for the dispersion of molybdenum and iron, and the yield of hydrocyanic acid is about 86.4%. Patent US3911089 discloses an ammonia oxidation catalyst Mo a Bib Fe c X d Y e Z f O g , X is one of Cr, Mn, Co, Ni, Zn, Cd, Sn, W and Pb, Y is one or more of transition elements, the catalyst composition is complex, and the HCN yield is 86%. Patent EP0322796 discloses a catalyst Mo commonly used in the ammoxidation reaction of one or more organic substances 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, and the HCN yield is only 81%. The above patents do not mention the catalyst molding method and the reaction performance of the catalyst with a whole particle size.

[0009] China's public patent CN1112243 proposed Mo a Bi b Me c Te d Q e R f X g Y h O z The catalyst comprises Mo / Bi and at least one element selected from iron and cerium. The catalyst proposed in US Pat. No. 4,461,752 is Fe a Cu b Sb c Mo d Me e Te f Q g O h (SiO2) i The methanol ammoxidation 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 many types of raw materials, the preparation process is complicated, and the HCN yield is significantly reduced when the preparation composition deviates slightly from the empirical formula.

[0010] Chinese patent CN106669705A discloses a catalyst for methanol ammoxidation reaction and its preparation and molding method. During extrusion molding, a binder needs to be added, which is not conducive to the diffusion of the catalyst. The patent does not examine the performance of the catalyst with a whole particle size, and the catalyst formed by conventional extrusion molding is of different lengths, which is not suitable for use in a tubular reactor (high loading uniformity requirements).

[0011] In addition, the Fe and Mo-containing catalyst has the ability to oxidize methanol to form formaldehyde, and the generated formaldehyde will further react with HCN to generate hydroxyacetonitrile, etc. The by-products such as formaldehyde and hydroxyacetonitrile are very active and easy to polymerize, which can easily lead to blockage of the subsequent separation system. None of the above patents mention the influence of catalyst composition and preparation process on the generation of formaldehyde and hydroxyacetonitrile.

[0012] At present, the methanol ammoxidation catalyst prepared by the existing technology has problems such as complex catalyst composition, high preparation cost, poor preparation repeatability, etc. Therefore, it is of great significance to develop a methanol ammoxidation catalyst with excellent reaction performance, simple preparation process and low cost. Summary of the invention

[0013] The purpose of the present invention is to provide a catalyst for preparing HCN by ammoxidation of methanol and a preparation method thereof. The catalyst prepared by this patent has low cost and excellent activity and selectivity.

[0014] To achieve the above object, the present invention adopts the following technical solution:

[0015] A catalyst for preparing HCN by methanol ammoxidation, wherein the total mass of the catalyst is 100wt%, the catalyst comprises the following components:

[0016]

[0017] In the catalyst, Fe and Mo are active components of the catalyst; SiO2 and TiO2 are catalyst carriers. The combination of SiO2 and TiO2 as catalyst carriers is beneficial to regulating the interaction between the carrier and the active components to obtain a highly active catalyst.

[0018] The present invention also provides a method for preparing the methanol ammoxidation catalyst, comprising the following steps, in proportion:

[0019] (a) first adding water into a reaction kettle, then adding a molybdenum-containing compound, and stirring thoroughly until dissolved; then adding an iron-containing compound, and stirring thoroughly until dissolved to obtain a mixed solution;

[0020] (b) mixing silica sol, titanium sol, quartz powder and a pore-forming agent and stirring them thoroughly to obtain a suspension;

[0021] (c) adding the mixed solution obtained in step (a) to the suspension obtained in step (b), stirring thoroughly, drying and calcining at low temperature;

[0022] (d) The dried solid is sieved (e.g., 20 mesh sieve), an inorganic pore-forming agent and a release agent are added, and then tabletted and calcined to obtain a methanol ammoxidation catalyst.

[0023] In the method of the present invention, the molybdenum-containing compound in step (a) 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.

[0024] In the method of the present invention, the mass concentration of the iron-containing compound and the molybdenum-containing compound in the mixed solution of step (a) is 30-50wt%. When the mass concentration of the molybdenum-containing compound and the iron-containing compound is too low, a large amount of water needs to be evaporated during the drying process, resulting in energy waste; when the mass concentration of the iron-containing compound and the molybdenum-containing compound is too high, on the one hand, it is difficult to fully dissolve, and on the other hand, it will also affect the dispersion of the active components Fe and Mo.

[0025] In the method of the present invention, the particle size of the quartz powder in step (b) is 80-150 meshes, and the portion of SiO2 in the catalyst product that comes from the quartz powder accounts for 20-40%. When the particle size of the quartz powder used is larger, it is beneficial to the mass transfer performance of the catalyst, but not to the catalyst strength; when the particle size of the quartz powder used is smaller, it is beneficial to the catalyst strength, but not to improve the mass transfer performance of the catalyst. Using quartz powder with an appropriate particle size can improve the mass transfer performance of the catalyst while ensuring the catalyst strength and reduce the occurrence of side reactions.

[0026] In the method of the present invention, the organic pore former described in step (b) is PP or PE powder, and the powder particle size is greater than 150 mesh. When the particle size of the pore former is too coarse, it is difficult to disperse evenly, and the pore-forming effect is poor; when the particle size of the pore former is too fine, the pores formed are small, and the effect on improving the mass transfer performance of the catalyst is limited. The mass ratio of the pore former to the quartz powder is 1:5-20.

[0027] In the method of the present invention, the silica sol described in step (b) is an acidic silica sol with a concentration of 20-40wt% and a particle size of 20-40nm; the titanium sol is an acidic titanium sol with a concentration of 10-20wt% and a particle size of 20-40nm. When the concentration of silica sol and titanium sol is too high, the particle size of the particles in the sol is large, which is not conducive to the dispersion of active components. When the concentration of silica sol and titanium sol is too low, the catalyst preparation efficiency is low and the energy consumption is high.

[0028] In the method of the present invention, the drying temperature in step (c) is 90-120°C, preferably 100-120°C, and the drying time is 4-12h; the low-temperature roasting temperature is 250-400°C, and the roasting time is 2-8h. The drying temperature is 90-120°C (e.g. 100°C, 110°C), and the drying time is 4-12h (e.g. 5h, 8h, 10h); the low-temperature roasting temperature is 250-400°C (e.g. 250°C, 300°C, 350°C), and the roasting time is 2-8h (e.g. 3h, 5h, 7h).

[0029] In the method of the present invention, the inorganic pore-forming agent in step (d) is one or more of ammonium carbonate, ammonium bicarbonate and ammonium nitrate; the amount of the inorganic pore-forming agent added is 3-10wt% of the solid mass after sieving. When the amount of the inorganic pore-forming agent added is small, it has no pore-forming effect, and when the amount of the inorganic pore-forming agent added is large, it has an adverse effect on the catalyst strength.

[0030] In the method of the present invention, the release agent in step (d) is graphite, and the added amount is 0.5-2.0% (e.g. 0.5%, 1.0%, 1.5%) of the mass of the sieved powder.

[0031] In the method of the present invention, the calcination temperature in step (d) is 450-650° C. (eg, 450° C., 500° C., 550° C.), and the calcination time is 2-8 h (eg, 3 h, 5 h, 7 h).

[0032] In the method of the present invention, the catalyst molding described in step (d) is a hollow ring with regular particle size, an outer diameter of 4-6 mm, an inner diameter of 1-3 mm, and a length of 4-8 mm.

[0033] The process conditions for using the catalyst of the present invention to prepare hydrocyanic acid by ammoxidation of methanol are as follows:

[0034] Catalyst evaluation was carried out using a small-scale molten salt test device. The inner diameter of the reaction tube was 25-40 mm, the loading amount of the whole-particle catalyst was 30-100 ml, and the molten salt temperature was set at 350-390 ° C. The molar ratio of the raw materials ammonia, methanol and air was 1: 0.8-1.2: 80-120. The reaction was carried out under normal pressure and the space velocity was 2000-5000 h -1 .

[0035] The beneficial effects of the present invention are:

[0036] In the preparation method of the catalyst, an iron-molybdenum mixed solution is first prepared, then quartz powder and an organic pore-forming agent are added to the carrier solution, and finally an inorganic pore-forming agent is added to obtain a catalyst for alcohol ammoxidation, which has the advantages of high dispersion of active components and unobstructed catalyst pores. When used for methanol ammoxidation to produce HCN, it not only has excellent activity and HCN selectivity, but also has low preparation cost and less by-products of formaldehyde and hydroxyacetonitrile. DETAILED DESCRIPTION

[0037] In order to understand the technical features and contents of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described here.

[0038] <Source of raw materials>

[0039] Methanol was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0040] Ferric nitrate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0041] Ammonium molybdate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0042] Quartz powder, purchased from Beijing Inokai Technology Co., Ltd., particle size > 200 mesh;

[0043] Silica sol was purchased from Linyi Kehan ​​Silica Products Co., Ltd.

[0044] Titanium sol was purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0045] Ammonium carbonate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0046] Graphite was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0047] <Test Method>

[0048] The methanol conversion rate and hydroxyacetonitrile selectivity were calculated after analysis using an Agilent 7820A gas chromatograph. The test conditions included: a DB-5 chromatographic column, a FID detector, a vaporization chamber temperature of 260°C, a detector temperature of 260°C, and a carrier gas of high-purity N2 at a flow rate of 30 ml / min.

[0049] The HCN generated by the reaction within a certain period of time is absorbed by sodium hydroxide solution, and the HCN selectivity is determined and calculated by silver nitrate titration.

[0050] Example 1

[0051] (1) First, add 102.3 g of water into a reaction kettle, then add 9.6 g of ammonium heptamolybdate, and stir thoroughly until dissolved; then add 45.5 g of ferric nitrate (ferric nitrate nonahydrate), and stir thoroughly until completely dissolved to obtain a mixed solution.

[0052] (2) 280.0 g of silica sol (concentration 30 wt %, particle size 20-30 nm), 316.0 g of titanium sol (concentration 20 wt %, particle size 20-30 nm), 36.0 g of quartz powder and 3.6 g of PP powder (>200 mesh) were mixed and stirred thoroughly to obtain a suspension.

[0053] (3) Add the mixed solution obtained in step (a) to the suspension obtained in step (b), stir thoroughly, dry at 100°C for 6 h and calcine at 250°C for 4 h.

[0054] (4) The dried solid was passed through a 20-mesh sieve and 2.0 g of graphite and 10 g of ammonium carbonate were added. The pellets were pressed and calcined at 500° C. for 4 h to obtain methanol ammoxidation catalyst A. The catalyst particles had an outer diameter of 4 mm, an inner diameter of 1.5 mm, and a length of 4 mm.

[0055] Catalyst performance evaluation:

[0056] The catalyst evaluation was carried out using a small-scale molten salt test device. The inner diameter of the reaction tube was 27 mm, the catalyst loading was 50 ml, and the molten salt temperature was set at 390 °C. The molar ratio of the raw materials ammonia, methanol and air was 4:4.4:91.6. The reaction was carried out at normal pressure and the air velocity was 3000 h -1 After the reaction feed was stable for 1-2 hours, samples were taken for analysis. The results of the ammoxidation reaction are shown in Table 1.

[0057] Example 2

[0058] (1) First, add 94.3 g of water into a reaction kettle, then add 11.0 g of ammonium heptamolybdate, and stir thoroughly until dissolved; then add 35.4 g of ferric nitrate, and stir thoroughly until completely dissolved to obtain a mixed solution.

[0059] (2) 289.3 g of silica sol (concentration 30 wt %, particle size 30-40 nm), 293.3 g of titanium sol (concentration 15 wt %, particle size 30-40 nm), 86.8 g of quartz powder and 4.3 g of PE powder (>300 mesh) were mixed and stirred thoroughly to obtain a suspension.

[0060] (3) Add the mixed solution obtained in step (a) to the suspension obtained in step (b), stir thoroughly, dry at 100°C for 12 h and calcine at 300°C for 4 h;.

[0061] (4) The dried solid was passed through a 20-mesh sieve and 2.0 g of graphite and 6 g of ammonium carbonate were added. The pellets were pressed and calcined at 550° C. for 6 h to obtain methanol ammoxidation catalyst B. The catalyst particles had an outer diameter of 3.5 mm, an inner diameter of 1.0 mm, and a length of 3.5 mm.

[0062] The process conditions and operation process of the ammoxidation reaction of catalyst B are the same as those in Example 1.

[0063] Example 3

[0064] (1) First, add 166.6 g of water into a reaction kettle, then add 7.4 g of ammonium heptamolybdate, and stir thoroughly until dissolved; then add 55.7 g of ferric nitrate, and stir thoroughly until completely dissolved to obtain a mixed solution.

[0065] (2) 211.3 g of silica sol (concentration 40 wt %, particle size 20-30 nm), 353.3 g of titanium sol (concentration 15 wt %, particle size 20-30 nm), 84.5 g of quartz powder and 5.6 g of PP powder (>400 mesh) were mixed and stirred thoroughly to obtain a suspension.

[0066] (3) Add the mixed solution obtained in step (a) to the suspension obtained in step (b), stir thoroughly, dry at 110°C for 6 hours and calcine at 350°C for 4 hours;.

[0067] (4) The dried solid was passed through a 20-mesh sieve and 2.0 g of graphite and 14 g of ammonium carbonate were added. The solid was pressed into tablets and calcined at 450° C. for 8 h to obtain methanol ammoxidation catalyst C. The catalyst particles had an outer diameter of 4.5 mm, an inner diameter of 2.0 mm, and a length of 4.5 mm.

[0068] The process conditions and operation process of the ammoxidation reaction of catalyst C are the same as those in Example 1.

[0069] Example 4

[0070] (1) First, add 110.3 g of water into a reaction kettle, then add 6.9 g of ammonium heptamolybdate, and stir thoroughly until dissolved; then add 60.7 g of ferric nitrate, and stir thoroughly until completely dissolved to obtain a mixed solution.

[0071] (2) 375.0 g of silica sol (concentration 30 wt %, particle size 30-40 nm), 162.0 g of titanium sol (concentration 20 wt %, particle size 30-40 nm), 112.5 g of quartz powder and 14.1 g of PE powder (>500 mesh) were mixed and stirred thoroughly to obtain a suspension.

[0072] (3) Add the mixed solution obtained in step (a) to the suspension obtained in step (b), stir thoroughly, dry at 110°C for 4 h and calcine at 400°C for 4 h;.

[0073] (4) The dried solid was passed through a 20-mesh sieve and 2.0 g of graphite and 18 g of ammonium carbonate were added. The solid was pressed into tablets and calcined at 600° C. for 3 h to obtain methanol ammoxidation catalyst D. The catalyst particles had an outer diameter of 5 mm, an inner diameter of 2 mm, and a length of 5 mm.

[0074] The process conditions and operation process of the ammoxidation reaction of catalyst D are the same as those of Example 1.

[0075] Example 5

[0076] (1) First, add 67.8 g of water into a reaction kettle, then add 8.6 g of ammonium heptamolybdate, and stir thoroughly until dissolved; then add 40.5 g of ferric nitrate, and stir thoroughly until completely dissolved to obtain a mixed solution.

[0077] (2) 280.0 g of silica sol (concentration 40 wt %, particle size 20-30 nm), 300 g of titanium sol (concentration 15 wt %, particle size 20-30 nm), 112.0 g of quartz powder and 16.8 g of PP powder (>200 mesh) were mixed and stirred thoroughly to obtain a suspension.

[0078] (3) Add the mixed solution obtained in step (a) to the suspension obtained in step (b), stir thoroughly, dry at 110°C for 8 h and calcine at 300°C for 4 h;.

[0079] (4) The dried solid was passed through a 20-mesh sieve and 2.0 g of graphite and 10 g of ammonium carbonate were added. The solid was pressed into tablets and calcined at 550° C. for 4 h to obtain methanol ammoxidation catalyst E. The catalyst particles had an outer diameter of 4 mm, an inner diameter of 2 mm, and a length of 4 mm.

[0080] The process conditions and operation procedures for the ammoxidation reaction of catalyst E are the same as those in Example 1.

[0081] Example 6

[0082] (1) First, add 85.7 g of water into a reaction kettle, then add 7.8 g of ammonium heptamolybdate, and stir thoroughly until dissolved; then add 42.5 g of ferric nitrate, and stir thoroughly until completely dissolved to obtain a mixed solution.

[0083] (2) 270.0 g of silica sol (concentration 40 wt %, particle size 30-40 nm), 176 g of titanium sol (concentration 20 wt %, particle size 30-40 nm), 108.0 g of quartz powder and 9.0 g of PE powder (>500 mesh) were mixed and stirred thoroughly to obtain a suspension.

[0084] (3) Add the mixed solution obtained in step (a) to the suspension obtained in step (b), stir thoroughly, dry at 120°C for 6 h and calcine at 350°C for 4 h.

[0085] (4) The dried solid was passed through a 20-mesh sieve and 2.0 g of graphite and 6 g of ammonium carbonate were added. The solid was pressed into tablets and calcined at 500° C. for 4 h to obtain methanol ammoxidation catalyst F. The catalyst particles had an outer diameter of 4.5 mm, an inner diameter of 1.5 mm, and a length of 4.5 mm.

[0086] The process conditions and operation process of the ammoxidation reaction of catalyst F are the same as those in Example 1.

[0087] Comparative Example 1

[0088] The steps for preparing the methanol ammoxidation catalyst are the same as those in Example 1, except that no titanium sol is added in step (2), and catalyst G is prepared.

[0089] The process conditions and operation process of the ammoxidation reaction of catalyst G are the same as those in Example 1.

[0090] Comparative Example 2

[0091] The steps for preparing the methanol ammoxidation catalyst are the same as those in Example 1, except that quartz powder is not added in step (2), and catalyst H is prepared.

[0092] The process conditions and operation process of the ammoxidation reaction of catalyst H are as follows:

[0093] Comparative Example 3

[0094] The steps for preparing the methanol ammoxidation catalyst are the same as those in Example 1, except that PP powder (>400 mesh) is not added in step (2), and catalyst I is prepared.

[0095] The process conditions and operation process of the ammoxidation reaction of catalyst I are the same as those of Example 1.

[0096] Comparative Example 4

[0097] (1) Add 63.9 g of water into a reaction kettle, then add 45.5 g of ferric nitrate, stir thoroughly until dissolved, then add 48 g of a 20 wt % aqueous solution of ammonium heptamolybdate, and then add ammonia water to adjust the pH of the system to 2.0 to obtain a slurry containing molybdenum and iron compounds.

[0098] (2) 280.0 g of silica sol (concentration 30 wt%, particle size 20-30 nm), 316.0 g of titanium sol (concentration 20 wt%, particle size 20-30 nm), 36.0 g of quartz powder and 3.6 g of pore-forming agent PP powder (>200 mesh) were mixed and stirred thoroughly to obtain a suspension.

[0099] (3) Add the slurry obtained in step (a) to the suspension obtained in step (b), stir thoroughly, dry at 100°C for 6 h and calcine at 250°C for 4 h.

[0100] The process conditions and operation process of the ammoxidation reaction of catalyst K are the same as those of Example 1.

[0101] Table 1 Catalyst evaluation results

[0102] Methanol conversion rate % HCN selectivity % Formaldehyde selectivity % Hydroxyacetonitrile selectivity % Catalyst A 99.0 89.3 0.033 0.22 Catalyst B 98.9 89.5 0.026 0.19 Catalyst C 99.2 89.4 0.0089 0.15 Catalyst D 98.7 89.5 0.012 0.17 Catalyst E 98.9 89.2 0.022 0.18 Catalyst F 99.1 89.5 0.017 0.20 Catalyst G 98.2 89.6 0.3 1.06 Catalyst H 96.9 87.0 0.15 0.82 Catalyst I 97.3 88.5 0.12 0.76 Catalyst K 95.9 87.3 0.37 1.23

[0103] As shown in Table 1, catalysts A to F have good activity and selectivity, while the catalysts described in Comparative Examples 1 to 4 have either low activity or poor selectivity. The above results show that the methanol ammoxidation catalyst prepared by the present invention has low preparation cost, high dispersion of active components, and smooth catalyst pores. When used for preparing HCN by methanol ammoxidation, it not only has excellent activity and HCN selectivity, but also produces less by-products of formaldehyde and hydroxyacetonitrile.

[0104] The comparison between Example 1 and Comparative Example 1 shows that the introduction of Ti into the catalyst is beneficial to improving the catalyst activity and reducing the amount of formaldehyde generated.

[0105] The comparison between Example 1 and Comparative Example 2 shows that the introduction of quartz powder with a suitable particle size improves the diffusion performance of the catalyst and increases the methanol conversion rate.

[0106] The comparison between Example 1 and Comparative Example 3 shows that the introduction of the pore-forming agent in the preparation process is beneficial to improving the mass transfer performance of the catalyst and increasing the methanol conversion rate.

[0107] By comparing Comparative Example 4 with Example 1, it is shown that the active components of the catalyst prepared by the method of Comparative Example 4 (slurry containing molybdenum and iron compounds) have poor dispersion, which is not good for the catalyst activity and also leads to an increase in by-product formaldehyde and hydroxyacetonitrile.

Claims

1. A method for preparing a catalyst for preparing HCN by ammoxidation of methanol, characterized in that: The following steps are included, in proportion: (a) first adding water into a reaction kettle, then adding a molybdenum-containing compound, and stirring thoroughly until dissolved; then adding an iron-containing compound, and stirring thoroughly until dissolved to obtain a mixed solution; (b) mixing silica sol, titanium sol, quartz powder and an organic pore-forming agent and stirring them thoroughly to obtain a suspension; (c) adding the mixed solution obtained in step (a) to the suspension obtained in step (b), stirring thoroughly, drying and calcining at low temperature; (d) sieving the dried solid, adding an inorganic pore-forming agent and a release agent, pressing into tablets, and calcining to obtain a methanol ammoxidation catalyst; Taking the total mass of the catalyst as 100wt%, the catalyst comprises the following components:

2. The method according to claim 1, characterized in that The molybdenum-containing compound in step (a) is 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.

3. The method according to claim 1 or 2, characterized in that: The mass concentration of the iron-containing compound and the molybdenum-containing compound in the mixed solution of step (a) is 30-50wt%.

4. The method according to claim 1, characterized in that: The particle size of the quartz powder in step (b) is 80-150 mesh, and the portion of SiO2 in the catalyst product coming from the quartz powder accounts for 20-40wt%.

5. The method according to claim 1, characterized in that The organic pore-forming agent described in step (b) is PP or PE powder, the powder particle size is greater than 150 mesh, and the mass ratio of the pore-forming agent to the quartz powder is 1:5-20.

6. The method according to claim 1, 4 or 5, characterized in that: The silica sol described in step (b) is an acidic silica sol with a concentration of 10-20wt% and a particle size of 20-40nm; the titanium sol is an acidic titanium sol with a concentration of 20-30wt% and a particle size of 20-40nm.

7. The method according to claim 1, characterized in that The drying temperature in step (c) is 100-120° C., and the drying time is 4-12 hours; the low-temperature roasting temperature is 250-400° C., and the roasting time is 2-8 hours.

8. The method according to claim 1, characterized in that The inorganic pore-forming agent in step (d) is one or more of ammonium carbonate, ammonium bicarbonate and ammonium nitrate; the amount of the inorganic pore-forming agent added is 3-10wt% of the solid mass after sieving.

9. The method according to claim 1, characterized in that: The calcination temperature in step (d) is 450-650° C. and the calcination time is 2-8 hours.

10. The method according to claim 1, 8 or 9, characterized in that: The catalyst molding described in step (d) is a hollow ring with regular particle size, an outer diameter of 3-5 mm, an inner diameter of 1-3 mm, and a length of 4-8 mm.

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