A catalyst loading method for preparing hydrocyanic acid by methanol ammoxidation

Abstract

The present invention provides a catalyst loading method for preparing hydrogen cyanide by methanol ammoxidation, wherein the oxidation stage catalyst, the transition stage catalyst and the deep oxidation stage catalyst are loaded in sequence according to the flow direction of methanol, and each of them is independently represented by X a Y b Z c O@A d B e By adjusting parameters such as a, b, and carrier particle size N, the resulting catalyst can be adapted to different reaction stages. The present invention also provides a method for producing hydrocyanic acid by ammoxidation of methanol, using the catalyst loading method described herein. The catalyst loading method provided herein can fully utilize the catalytic effects of each catalyst stage, improving the yield of the target product while avoiding the production of large amounts of byproducts. It also effectively reduces reaction exotherm, thereby increasing the load to 180% or even higher, avoiding the risk of temperature runaway and achieving the goal of reducing costs and increasing efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, in particular to a catalyst loading method for preparing hydrocyanic acid through the ammoxidation of methanol, and also to a method for preparing hydrocyanic acid through the ammoxidation of methanol. Background Art

[0002] Hydrocyanic acid is an important chemical raw material used in the production of adiponectin, MMA, methionine, and other chemical products. However, due to its highly toxic nature and the difficulty of transporting it, the country must meet its own needs.

[0003] The methanol process for producing hydrocyanic acid is a common production process. This process uses methanol, ammonia, and air as raw materials and produces hydrocyanic acid in a high-temperature environment under the action of a catalyst. However, in actual production, many problems make it difficult to maintain high-load operation for a long time. First, the process inevitably produces byproducts such as formaldehyde and hydroxyacetonitrile. These byproducts polymerize within the system, forming a black solid residue. This residue can clog filters, pipes, and other components, and decomposes to produce hydrocyanic acid during cleanup, making it more difficult to clean. Furthermore, the black residue can enter the ammonium sulfate system through the reaction system, causing the cyanide content in the ammonium sulfate product to exceed the standard. Second, the process is a highly exothermic oxidation reaction, which poses a significant risk of temperature fluctuations during startup and load increase.

[0004] Chinese patent CN 115445633A discloses a catalyst for preparing hydrogen cyanide by ammoxidation of methanol, its preparation method, and application. The catalyst's active components are composed of oxides corresponding to the elements iron, molybdenum, and lanthanum, and the carrier includes oxides of Al, Si, and Zr. The Al oxide comprises two crystalline phases, α and γ. Based on the mass of α-Al2O3, γ-Al2O3, and silicon dioxide as 100%, γ-Al2O3 accounts for 6%-15%, preferably 8%-12%, silicon dioxide accounts for 5%-15%, preferably 8%-12%, and the remainder is α-Al2O3. This catalyst is used in the process of preparing hydrogen cyanide by ammoxidation of methanol. Its outstanding features are very low amounts of byproducts, formaldehyde and hydroxyacetonitrile, while also exhibiting the advantages of high activity and high selectivity. However, the catalyst is not specifically configured for the ammoxidation process during use, and the specific composition requirements for the carrier are relatively strict, making its preparation cumbersome.

[0005] It can be seen that in view of the process characteristics of methanol ammoxidation to prepare hydrocyanic acid (such as high exotherm and a large number of by-products), there is still an urgent need to improve different process links in order to improve production efficiency and process safety. Summary of the Invention

[0006] To overcome the deficiencies in the prior art, an object of the present invention is to provide a catalyst loading method for the production of hydrocyanic acid by the oxidation of methanol to ammonia. By loading the catalyst in multiple stages, the process of producing hydrocyanic acid by the oxidation of methanol to ammonia can be stably operated under high load, maintaining a high yield of the target product, reducing the formation of by-products, and reducing the exothermic heat of the reaction.

[0007] Another object of the present invention is to provide a method for preparing hydrocyanic acid by ammoxidation of methanol.

[0008] The first aspect of the present invention provides a catalyst loading method for preparing hydrogen cyanide by methanol ammoxidation, wherein an oxidation stage catalyst, a transition stage catalyst and a deep oxidation stage catalyst are loaded in sequence according to the flow direction of methanol, each of which is independently represented by X a Y b Z c O@A d B e O;

[0009] Among them, X a Y b Z c O represents the active component, A d B e O represents a carrier having a carrier particle size represented by N (O represents an oxygen element, and the unit is 1); X and Y each independently represent an element of Zn, Fe, Mo or Cu, Z represents an element of Pt, Ni, Cr or La, A and B each independently represent an element of Al, Si, Zr or Ti, a to e represent the stoichiometric number of each element, a represents 2 to 6, b represents 1 to 8, c represents 0 to 3, d represents 40 to 80, and e represents 5 to 10;

[0010] In the oxidation stage catalyst, 0.9≤a / b≤1.1, 6≤N≤8mm;

[0011] In the transition zone catalyst, 1.1 < a / b ≤ 1.4, 4 ≤ N < 6 mm;

[0012] In the deep oxidation stage catalyst, 1.4<a / b≤1.8, 2≤N<4mm.

[0013] The inventors have found that the reaction of methanol ammoxidation to produce hydrocyanic acid can be divided into three stages, namely the oxidation stage, the transition stage and the deep oxidation stage. The reaction exotherms, intensity, etc. of the three stages are all different, so the activity requirements for the catalyst are also different. The loading method provided by the present invention provides catalysts with similar compositions but different activities for different reaction stages, which can be more adaptable to the progress of the reaction. Among them, the oxidation stage catalyst has the lowest activity, so it is possible to control the ammoxidation reaction to be relatively mild, reduce the heat release, and still have a lower hot spot temperature under high load. The deep oxidation stage catalyst has the highest activity, and can decompose the by-products such as formaldehyde and hydroxyacetonitrile produced in the oxidation stage, thereby reducing the impurity content. The transition stage catalyst has moderate activity, so that the reaction can smoothly transition from the oxidation stage to the deep oxidation stage. At the same time, the activity of each stage catalyst can also ensure that all three reaction stages have a higher hydrocyanic acid yield. Therefore, by the catalyst loading method of the present invention, the process load of methanol ammoxidation to produce hydrocyanic acid can be greatly improved, and good reaction efficiency and process stability can be maintained.

[0014] In the catalyst loading method provided by the present invention, X and Y represent the main catalyst components, and Z represents the optional co-catalyst component. They can all use common active ingredients used in similar catalysts in the field. In some preferred embodiments, X can represent Fe element, Y can represent Mo element, Z can represent La element, a can represent 2.5 to 4.5, b can represent 1.5 to 5, and c can represent 0 to 1.5 (more preferably, c can represent 0 or 1.1 to 1.3). That is, the active component of the catalyst used in the present invention is preferably Fe oxide a Mo b La c O or Fe a Mo b O, where a, b, and c represent the stoichiometric numbers of their respective elements, and the unit of the O element is 1.

[0015] In the catalyst loading method provided by the present invention, A and B represent carrier components, and common carrier components used for similar catalysts in the field can be used. In some preferred embodiments, A can represent Al or Zr elements, B can represent Si elements, d can represent 40 to 65, and e can represent 6.5 to 8. That is, the catalyst carrier component used in the present invention is preferably oxide Al d Si e O or Zr d Si e O, wherein d and e represent the stoichiometric numbers of their respective elements, and the unit of the element O is 1. In other preferred embodiments, the carrier particle size N in the oxidation stage catalyst may be 6 mm, the carrier particle size N in the transition stage catalyst may be 4 mm, and the carrier particle size N in the deep oxidation stage catalyst may be 2 mm.

[0016] In the catalyst loading method provided by the present invention, the loading ratios of the oxidation stage catalyst, transition stage catalyst, and deep oxidation stage catalyst can be 10-40%, 30-50%, and 10-60% by volume, respectively. In some preferred embodiments, the loading ratios of the oxidation stage catalyst, transition stage catalyst, and deep oxidation stage catalyst can be 30-40%, 30-40%, and 30-40% by volume, respectively. Generally speaking, the catalysts are loaded into a catalyst bed distributed vertically, with the oxidation stage, transition stage, and deep oxidation stage arranged from top to bottom.

[0017] In the catalyst loading method provided by the present invention, the catalyst can be prepared using an impregnation method commonly used in the art. In some preferred embodiments, the preparation of the catalyst may include the following steps:

[0018] S1: adding a soluble salt containing elements X, Y and Z to a dispersant solution to form an impregnation solution; and

[0019] S2: adding the carrier to the impregnation solution and allowing the solution to stand, then separating the solid matter, drying and calcining the solid matter to obtain the catalyst.

[0020] In some preferred embodiments, the dispersant in the dispersant solution can be selected from one or more of acetic acid, oxalic acid, oxalic acid, ammonia, and ethylenediamine, or other common types in the art. In some more preferred embodiments, the concentration of the dispersant can be 1 to 10% by mass, for example, 1 to 5%.

[0021] In some preferred embodiments, the soluble salt containing elements X, Y, and Z can be selected from soluble salts of the corresponding elements commonly used in the art, such as sulfates, nitrates, chlorides, etc., according to the needs of the catalyst active components. In some more preferred embodiments, the soluble salt containing elements X, Y, and Z can be selected from one or more of sulfates, nitrates, chlorides, ammonium molybdate of Zn, Fe, and Cu, and sulfates, nitrates, and chlorides of Pt, Ni, Cr, and La. In some most preferred embodiments, the soluble salt can be selected from ferric nitrate, ammonium molybdate, and lanthanum nitrate.

[0022] In some preferred embodiments, in step S2, the standing time may be 20 to 50 minutes. In some more preferred embodiments, the standing time may be 30 to 40 minutes.

[0023] In some preferred embodiments, in step S2, the drying temperature may be 80-150° C., and the drying time may be 1-5 hours. In some more preferred embodiments, the drying temperature may be 110-130° C., and the drying time may be 1-3 hours.

[0024] In some preferred embodiments, in step S2, the calcination temperature may be 400-800° C., and the calcination time may be 2-8 hours. In some more preferred embodiments, the calcination temperature may be 500-600° C., and the calcination time may be 3-6 hours.

[0025] In some preferred embodiments, step S2 may further include: repeating the operation of step S2 (i.e., "standing, drying, and calcining") on the obtained catalyst 1 to 5 times, for example, repeating the operation 2 to 3 times, so that the active components of the catalyst can be fully loaded on the carrier.

[0026] In some preferred embodiments, the preparation process of the carrier can be: kneading, extruding and pelletizing a precursor containing elements A and B, sesbania powder and cellulose, and then drying and roasting to obtain the carrier.

[0027] In some preferred embodiments, during the preparation of the carrier, the drying temperature may be 80-150° C., and the drying time may be 2-8 hours. In some more preferred embodiments, during the preparation of the carrier, the drying temperature may be 110-130° C., and the drying time may be 2-6 hours.

[0028] In some preferred embodiments, during the preparation of the carrier, the calcination temperature may be 400-600°C, and the calcination time may be 2-8 hours. In some more preferred embodiments, during the preparation of the carrier, the calcination temperature may be 500-600°C, and the calcination time may be 2-6 hours.

[0029] In some preferred embodiments, the precursor containing elements A and B can be selected from common precursors in the art, such as oxides and hydroxides containing the corresponding elements, according to the requirements of the catalyst support component. In some more preferred embodiments, the precursor containing elements A and B can be selected from one or more of Al2O3 (e.g., α-Al2O3), pseudo-boehmite, silica sol, water glass, zirconium oxide, and titanium oxide, according to actual needs.

[0030] In some preferred embodiments, the amount of the sesbania powder may be 1 to 10% by mass of the amount of the precursor.

[0031] In some preferred embodiments, the amount of the cellulose used may be 1 to 5% of the amount of the precursor used, calculated by mass percentage.

[0032] In the catalyst loading method provided by the present invention, the desired material can be obtained through a separation step, such as separating the solid matter after impregnation and absorption. The separation method can be a common method in the art, including but not limited to natural sedimentation, (normal pressure or vacuum) filtration, centrifugation, etc.

[0033] A second aspect of the present invention provides a method for preparing hydrocyanic acid by ammoxidation of methanol, wherein the catalyst is loaded using the catalyst loading method described in any one of the above technical solutions.

[0034] In the method for preparing hydrocyanic acid by methanol ammoxidation provided by the present invention, the reaction temperature can be 300-400°C, the reaction raw materials are methanol, ammonia and air, the feed molar ratio can be 1:0.5-5:10-100, and the reaction raw materials are preheated to 100-250°C before entering the reaction tube to start the reaction.

[0035] In the method for preparing hydrogen cyanide by methanol ammoxidation provided by the present invention, the reaction can be carried out at a load of 100-180% according to actual working conditions, and the corresponding volume space velocity is 3000-5400h -1 .

[0036] The technical solution provided by the present invention has the following advantages:

[0037] (1) The catalyst loading method provided by the present invention is specially designed for the three reaction stages of the methanol ammoxidation process to produce hydrocyanic acid. Different reaction stages are adapted to catalysts of different activities, thereby fully exerting the catalytic effect of the catalyst, improving the yield of the target product while avoiding the production of a large amount of by-products. Moreover, the catalyst loading method provided by the present invention can also effectively reduce the reaction exotherm, thereby enabling the reaction device to increase the load to 180% or even higher without adding any external devices and catalysts.

[0038] (2) The catalyst loading method provided by the present invention does not require the use of expensive and complex catalysts. The catalysts in the three reaction stages have similar compositions and preparation methods. By adjusting the proportion of the catalyst active components and the carrier particle size, the required catalysts with different activities can be easily obtained. The process is simple, the conditions are mild, the economy is good and it is easy to control, so it is suitable for large-scale production and application.

[0039] (3) The method for producing hydrocyanic acid by methanol ammoxidation provided by the present invention utilizes the catalyst loading method provided by the present invention, thereby significantly improving production efficiency and process safety, avoiding the risk of temperature runaway, and achieving the goal of reducing costs and increasing efficiency. At a load of 100-180%, the reaction hotspot can be controlled within 520°C, the hydrocyanic acid yield is greater than 80%, and the hydroxyacetonitrile content is less than 0.2%. Therefore, the method for producing hydrocyanic acid provided by the present invention has great application prospects. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described in detail below with reference to specific embodiments.

[0041] Unless otherwise specified, the raw materials or reagents used in the examples and comparative examples of the present invention are commercially available products.

[0042] Unless otherwise specified, the percentages used in the examples and comparative examples of the present invention are all percentages by mass.

[0043] In the Examples and Comparative Examples of the present invention, hydroxyacetonitrile was analyzed using gas chromatography under the following conditions: an Agilent HP-INNOWAX column, an inlet temperature of 280°C, a detector temperature of 240°C, a hydrogen flow rate of 35 ml / min, and an air flow rate of 350 ml / min. Hydrocyanic acid was analyzed using silver nitrate titration. The elemental composition of the catalyst was determined using ICP.

[0044] Example 1

[0045] (1) Preparation of carrier

[0046] Take 100g of α-Al2O3 powder, 5g of Tianqing powder and 1.5g of cellulose, mix them evenly with a mixer, place them in a kneader, add 50g of 40% silica sol and knead them, then extrude and pelletize them with 2mm, 4mm and 6mm circular molds respectively. The obtained particles are dried at 120℃ for 4h and finally calcined at 500℃ for 4h to obtain carrier particles.

[0047] (2) Preparation of catalyst

[0048] Take 120g of water, heat it to 60℃, add 2.4g of oxalic acid, mix well to form oxalic acid solution, and divide it into three parts. Take 40g of oxalic acid solution, add 12g of ferric nitrate, 5.4g of ammonium molybdate and 3g of lanthanum nitrate, stir well, and after fully dissolving, add 46g of 6mm carrier particles, let it stand for 30min to fully absorb, dry it at 120℃ for 2h, and calcine it at 540℃ for 4h. Repeat the process of "absorption, drying and calcination" twice to obtain catalyst Fe 2.8 Mo 2.6 La 1.2 O@(Al 44.2Si 7.8 O)-6mm, recorded as A1.

[0049] The mass of ammonium molybdate was changed to 4.32 g, the carrier particle size was selected to be 4 mm, and the above steps were repeated to obtain the catalyst Fe 2.8 Mo 2.08 La 1.2 O@(Al 44.2 Si 7.8 O)-4mm, recorded as A2.

[0050] The mass of ammonium molybdate was changed to 3.24 g, the carrier particle size was selected to be 2 mm, and the above steps were repeated to obtain the catalyst Fe 2.8 Mo 1.56 La 1.2 O@(Al 44.2 Si 7.8 O)-2mm, recorded as A3.

[0051] (3) Catalyst evaluation

[0052] The catalyst was evaluated using a molten salt apparatus. The loading scheme was: by volume, 30% A1 in the upper portion, 30% A2 in the middle, and 40% A3 in the lower portion, totaling 50 ml. The molten salt temperature was set at 360°C, and the molar ratio of methanol, ammonia, and air was 4:4.4:91.6. The reaction materials were preheated before entering the reaction tube at 120°C. The full load (space velocity 3000h) and the reaction temperature were evaluated separately. -1 ) and 180% load (5400h -1 ) and measured the reaction hotspots using thermocouples. The results are shown in Table 1.

[0053] Example 2

[0054] (1) Preparation of carrier

[0055] Take 100g of pseudo-boehmite powder, 10g of Tianqing powder and 5g of cellulose, mix them evenly with a mixer, place them in a kneader, add 50g of 40% silica sol and knead them, then extrude and pelletize them with 2mm, 4mm and 6mm circular molds respectively. The obtained particles are dried at 120℃ for 4h and finally calcined at 520℃ for 4h to obtain carrier particles.

[0056] (2) Preparation of catalyst

[0057] Take 120g of water, heat it to 60℃, add 6g of ammonia water, mix well to form an ammonia solution, and divide it into three parts. Take a 40g ammonia solution, add 12g of ferric nitrate and 6.3g of ammonium molybdate, stir well, and after fully dissolving, add 32g of 6mm carrier particles, let it stand for 30min to fully absorb, dry it at 120℃ for 2h, and calcine it at 550℃ for 4h. Repeat the process of "absorption, drying and calcination" three times to obtain catalyst Fe 4.3 Mo 4.75 O@(Al 44.2 Si 7.8 O)-6mm, recorded as B1.

[0058] The mass of ammonium molybdate was changed to 7.02 g, the carrier particle size was selected to be 4 mm, and the above steps were repeated to obtain the catalyst Fe 4.3 Mo 3.8 O@(Al 44.2 Si 7.8 O)-4mm, recorded as B2.

[0059] The mass of ammonium molybdate was changed to 6.24 g, the carrier particle size was selected to be 2 mm, and the above steps were repeated to obtain the catalyst Fe 4.3 Mo 2.85 O@(Al 44.2 Si 7.8 O)-2mm, recorded as B3.

[0060] (3) Catalyst evaluation

[0061] The catalyst was evaluated using a molten salt apparatus. The loading scheme was: by volume, 40% B1 in the upper portion, 30% B2 in the middle, and 30% B3 in the lower portion, totaling 50 ml. The molten salt temperature was set at 360°C, and the molar ratio of methanol, ammonia, and air was 4:4.4:91.6. The reaction materials were preheated before entering the reaction tube at 120°C. The full load (space velocity 3000h) and the reaction temperature were evaluated. -1 ) and 180% load (5400h -1 ) and measured the reaction hotspots using thermocouples. The results are shown in Table 1.

[0062] Example 3

[0063] (1) Preparation of carrier

[0064] Take 100g of zirconium dioxide powder, 10g of Tianqing powder and 5g of cellulose, mix them evenly with a mixer, place them in a kneader, add 50g of 40% silica sol and knead them, then extrude and pelletize them with 2mm, 4mm and 6mm circular molds respectively. The obtained particles are dried at 120℃ for 4h and finally calcined at 520℃ for 4h to obtain carrier particles.

[0065] (2) Preparation of catalyst

[0066] Take 120g of water, heat it to 60℃, add 6g of ammonia water, mix well to form an ammonia solution, and divide it into three parts. Take a 40g ammonia solution, add 12g of ferric nitrate and 7.8g of ammonium molybdate, stir well, and after fully dissolving, add 32g of 6mm carrier particles, let it stand for 30min to fully absorb, dry it at 120℃ for 2h, and calcine it at 550℃ for 4h. Repeat the process of "absorption, drying and calcination" three times to obtain catalyst Fe 4.3 Mo 4.75 O@(Zr 61.6 Si 7.8 O)-6mm, recorded as C1.

[0067] The mass of ammonium molybdate was changed to 7.02 g, the carrier particle size was selected to be 4 mm, and the above steps were repeated to obtain the catalyst Fe 4.3 Mo 3.8 O@(Zr 61.6 Si 7.8 O)-4mm, recorded as C2.

[0068] The mass of ammonium molybdate was changed to 6.24 g, the carrier particle size was selected to be 2 mm, and the above steps were repeated to obtain the catalyst Fe 4.3 Mo 2.85 O@(Zr 61.6 Si 7.8 O)-2mm, recorded as C3.

[0069] (3) Catalyst evaluation

[0070] The catalyst was evaluated using a molten salt apparatus. The loading scheme was: by volume, 40% C1 in the upper portion, 30% C2 in the middle, and 30% C3 in the lower portion, totaling 50 ml. The molten salt temperature was set at 360°C, and the molar ratio of methanol, ammonia, and air was 4:4.4:91.6. The reaction materials were preheated before entering the reaction tube at 120°C. The full load (space velocity 3000h) and the reaction temperature were evaluated separately. -1 ) and 180% load (5400h -1 ) and measured the reaction hotspots using thermocouples. The results are shown in Table 1.

[0071] Comparative Example 1

[0072] Catalysts A1 and A2 from Example 1 were loaded, with 30% A1 in the upper portion and 70% A2 in the lower portion, based on volume. The catalysts were evaluated using the conditions from Example 1, and the results are shown in Table 1.

[0073] Comparative Example 2

[0074] The catalysts B2 and B3 from Example 2 were loaded, with 70% B2 in the upper portion and 30% B3 in the lower portion, by volume. The catalysts were evaluated using the conditions from Example 1, and the results are shown in Table 1.

[0075] Comparative Example 3

[0076] A commercially available methanol ammoxidation catalyst for producing hydrocyanic acid was prepared using a conventional iron-molybdenum catalyst prepared by an impregnation method. The carrier, designated D, was alumina, with a loading rate of 100% by volume. The catalyst was evaluated using the conditions described in Example 1. The results are shown in Table 1.

[0077] Comparative Example 4

[0078] (1) Preparation of carrier

[0079] Take 100g of zirconium dioxide powder, 10g of Tianqing powder and 5g of cellulose, mix them evenly with a mixer, place them in a kneader, add 50g of 40% silica sol and knead them, then extrude and pelletize them with 2mm, 4mm and 6mm circular molds respectively. The obtained particles are dried at 120℃ for 4h and finally calcined at 520℃ for 4h to obtain carrier particles.

[0080] (2) Preparation of catalyst

[0081] Take 120g of water, heat it to 60℃, add 6g of ammonia water, mix well to form an ammonia solution, and divide it into three parts. Take a 40g ammonia solution, add 24g of ferric nitrate and 7.8g of ammonium molybdate, stir well, and after fully dissolving, add 32g of 6mm carrier particles, let it stand for 30min to fully absorb, dry it at 120℃ for 2h, and calcine it at 550℃ for 4h. Repeat the process of "absorption, drying and calcination" three times to obtain catalyst Fe 8.6 Mo 4.75 O@(Zr 61.6 Si 7.8 O)-6mm, recorded as E1.

[0082] The mass of ammonium molybdate was changed to 7.02 g, the carrier particle size was selected to be 4 mm, and the above steps were repeated to obtain the catalyst Fe 8.6 Mo 3.8 O@(Zr 61.6 Si 7.8 O)-4mm, recorded as E2.

[0083] The mass of ammonium molybdate was changed to 6.24 g, the carrier particle size was selected to be 2 mm, and the above steps were repeated to obtain the catalyst Fe 8.6 Mo 2.85 O@(Zr 61.6 Si 7.8 O)-2mm, recorded as E3.

[0084] (3) Catalyst evaluation

[0085] The catalyst was evaluated using a molten salt apparatus. The loading scheme was: by volume, 40% E1 in the upper portion, 30% E2 in the middle, and 30% E3 in the lower portion, totaling 50 ml. The molten salt temperature was set at 360°C, and the molar ratio of methanol, ammonia, and air was 4:4.4:91.6. The reaction materials were preheated before entering the reaction tube at 120°C. The full load (space velocity 3000h) and the reaction temperature were evaluated separately. -1 ) and 180% load (5400h -1 ) and measured the reaction hotspots using thermocouples. The results are shown in Table 1.

[0086] Table 1 Catalyst evaluation results of Examples and Comparative Examples

[0087]

[0088] The results in Table 1 show that, under the evaluation conditions, the reaction hotspot of the catalysts of Examples 1-3 can be controlled within 520° C., the hydrocyanic acid yields are greater than 80% at both loads, and the hydroxyacetonitrile contents are less than 0.2%.

[0089] By comparing Comparative Example 1 with Example 1, it can be seen that if the catalyst activity in the deep oxidation stage is low, the reaction hotspot decreases, but by-products such as hydroxyacetonitrile cannot be fully decomposed, the content increases significantly, and the yield of the target product is also affected.

[0090] By comparing Comparative Example 2 with Example 2, it can be seen that if the catalyst activity in the oxidation stage is too high, the reaction will be significantly intensified, the heat release will increase, the reaction hotspot will be uncontrollable, and the target product will also decompose into small molecular substances, so the yield will also be greatly reduced.

[0091] It can be seen from Comparative Example 3 that the multi-stage catalyst loaded according to the loading method of the present invention has obvious advantages under high load compared with the uniformly loaded commercial catalyst.

[0092] It can be seen from Comparative Example 4 that the ratio of a to b in the catalyst active components has a greater influence on the catalyst activity, and thus also has a significant impact on the reaction results.

[0093] Unless otherwise defined, the terms used in the present invention have the same meanings as those commonly understood by those skilled in the art.

[0094] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above-mentioned embodiments, but is only limited by the claims.

Claims

1. A catalyst loading method for preparing hydrocyanic acid by ammoxidation of methanol, characterized in that: According to the flow direction of methanol, the oxidation stage catalyst, transition stage catalyst and deep oxidation stage catalyst are loaded in sequence, and they are each independently represented by X a Y b Z c O@A d B e O; Among them, X a Y b Z c O represents the active component, A d B e O represents a carrier, which has a carrier particle size represented by N; X represents an Fe element, Y represents an Mo element, Z represents an La element, A represents an Al or Zr element, B represents an Si element, and a to e represent the stoichiometric number of each element, a represents 2 to 6, b represents 1 to 8, c represents 0 to 3, d represents 40 to 80, and e represents 5 to 10; In the oxidation stage catalyst, 0.9≤a / b≤1.1, 6≤N≤8mm; In the transition zone catalyst, 1.1<a / b≤1.4, 4≤N<6mm; In the deep oxidation stage catalyst, 1.4<a / b≤1.8, 2≤N<4mm; Calculated by volume percentage, the loading proportions of the oxidation stage catalyst, the transition stage catalyst and the deep oxidation stage catalyst are 10-40%, 30-50% and 10-60% respectively.

2. The catalyst loading method according to claim 1, characterized in that: a represents 2.5 to 4.5, b represents 1.5 to 5, and c represents 0 to 1.5; and / or The d represents 40 to 65, and the e represents 6.5 to 8.

3. The catalyst loading method according to claim 1 or 2, characterized in that: The preparation of the catalyst comprises the following steps: S1: adding a soluble salt containing elements X, Y and Z to a dispersant solution to form an impregnation solution; and S2: adding the carrier to the impregnation solution and allowing the solution to stand, then separating the solid matter, drying and calcining the solid matter to obtain the catalyst.

4. The catalyst loading method according to claim 3, characterized in that: In the dispersant solution, the dispersant is selected from one or more of acetic acid, oxalic acid, oxalic acid, ammonia water, and ethylenediamine, and its concentration is 1-10% by mass.

5. The catalyst loading method according to claim 3, characterized in that: The soluble salt containing element X is selected from one or more of sulfates, nitrates, and chlorides of Fe; the soluble salt containing element Y is selected from ammonium molybdate; and the soluble salt containing element Z is selected from one or more of sulfates, nitrates, and chlorides of La.

6. The catalyst loading method according to claim 3, characterized in that: In step S2, the standing time is 20 to 50 minutes; and / or The drying temperature is 80-150° C. and the drying time is 1-5 hours; and / or The calcination temperature is 400-800° C., and the calcination time is 2-8 hours.

7. The catalyst loading method according to claim 3, characterized in that: The step S2 further comprises: repeating the operation of step S2 1 to 5 times on the obtained catalyst.

8. The catalyst loading method according to claim 3, characterized in that: The preparation process of the carrier is as follows: a precursor containing elements A and B is kneaded, extruded and pelletized with sesbania powder and cellulose, and the carrier is obtained after drying and roasting.

9. The catalyst loading method according to claim 8, characterized in that: The drying temperature is 80-150° C. and the drying time is 2-8 hours; and / or The calcination temperature is 400-600° C., and the calcination time is 2-8 hours.

10. The catalyst loading method according to claim 8, characterized in that: The precursor containing element A is selected from one or more of Al2O3, pseudo-boehmite, and zirconia; the precursor containing element B is selected from one or more of silica sol and water glass; and / or In terms of mass percentage, the amount of the sesbania powder is 1-10% of the amount of the precursor, and the amount of the cellulose is 1-5% of the amount of the precursor.

11. The catalyst loading method according to claim 10, characterized in that: The precursor containing element A is selected from α-Al2O3.

12. A method for preparing hydrocyanic acid by ammoxidation of methanol, characterized in that: The method uses the catalyst loading method according to any one of claims 1 to 11 to load the catalyst.

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