High-purity molybdenum trioxide for catalyst and preparation method thereof

Abstract

The present invention provides a method for preparing high-purity molybdenum trioxide for catalyst, comprising the following steps: step 1, placing ammonium molybdate in a dryer for drying; step 2, crushing the dried ammonium molybdate to obtain ammonium molybdate powder; screening the ammonium molybdate powder through a sieve to obtain undersize material; step 3, placing the undersize material in a disc turbine dryer, and performing heat preservation roasting under an oxidizing atmosphere at a temperature of 520°C to 550°C, to obtain; the heat preservation roasting time is 80min to 90min, and the material discharge amount is 5.0kg / min to 6.0kg / min. The method of the present invention uses an existing disc turbine dryer as a preparation device, does not need to add new equipment, does not need to improve process pipeline equipment, has a large single furnace capacity, a high degree of automation, less dust leakage, and is simple to operate. The purity of the high-purity molybdenum trioxide finally obtained is greater than 99.95%, has good solubility, and can meet actual needs.

Description

Technical Field

[0001] The invention belongs to the technical field of target material preparation, and specifically relates to high-purity molybdenum trioxide for catalyst and a preparation method thereof. Background Art

[0002] As an important inorganic compound, molybdenum trioxide has a unique layered structure and framework, and is widely used in the fields of catalyst, dye and pigment preparation, electrochemical energy storage devices, chemical industry, optoelectronics and material science. At present, the commonly used roasting equipment for industrial roasting of ammonium molybdate to produce pure molybdenum trioxide in China includes rotary kiln, disc turbine dryer and mesh belt furnace. Different roasting equipment is used, and the parameter control of the roasting process varies greatly, and the process repeatability is not high. In recent years, as the chemical industry has begun to develop in the direction of high automation, cleanness and environmental protection, the disc turbine dryer with the advantages of large single furnace production capacity, high degree of automation and less dust leakage can better meet the production development and environmental protection requirements. However, the pure molybdenum trioxide prepared by the existing disc turbine dryer preparation process has the defects of poor uniformity and poor solubility, and the solubility of pure molybdenum trioxide is related to the preparation procedure, uniformity, catalytic active sites, mechanical strength, life, catalytic ability and preparation cost of the catalyst. Therefore, it is urgent to develop a method for preparing high-purity molybdenum trioxide for catalysts suitable for disc turbine dryers to solve the problems of poor uniformity and poor solubility of molybdenum trioxide prepared by the existing preparation process. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a high-purity molybdenum trioxide for catalyst and a preparation method thereof, so as to solve the technical problems that the high-purity molybdenum trioxide prepared by a disc turbine dryer in the prior art has low solubility, poor uniformity and is difficult to meet actual needs.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0005] A method for preparing high-purity molybdenum trioxide for catalyst comprises the following steps:

[0006] Step 1, drying ammonium molybdate in a dryer;

[0007] Step 2, crushing the dried ammonium molybdate to obtain ammonium molybdate powder; sieving the ammonium molybdate powder through a sieve to obtain undersize material;

[0008] Step 3, adding the undersize material into the dryer through the top feed port of the dryer, and performing heat preservation and roasting under an oxidizing atmosphere at a temperature of 520°C to 550°C to obtain high-purity molybdenum trioxide;

[0009] The heat preservation and roasting time is 80min-90min, and the feeding amount is 5.0kg / min-6.0kg / min;

[0010] During the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, performs countercurrent heat exchange with the screened material, and then flows out from the top of the dryer; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer.

[0011] The present invention also has the following technical features:

[0012] Specifically, the dryer is a disc-type turbine dryer.

[0013] Furthermore, in the high-purity molybdenum trioxide, the mass percentage of molybdenum trioxide is not less than 99.95%.

[0014] Furthermore, during the heat preservation roasting, the pressure inside the furnace of the disc-type turbo dryer is -5Pa to -10Pa.

[0015] Furthermore, the ammonium molybdate described in step 2 is one or more of ammonium dimolybdate, ammonium tetramolybdate, ammonium heptamolybdate, ammonium octamolybdate, and ammonium dodecomolybdate.

[0016] Furthermore, the mesh size of the sieve in step 2 is 60 to 120 meshes.

[0017] Furthermore, the method specifically comprises the following steps:

[0018] Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C;

[0019] Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the ammonium dimolybdate powder through a 60-mesh sieve to obtain undersize;

[0020] Step 3: Add the undersize material into the dryer through the feeding port at the top of the dryer, introduce the gas for drying and heat exchange into the dryer from the bottom of the dryer, and heat-insulate and roast in an oxidizing atmosphere at 520°C to obtain the product;

[0021] The heat preservation and roasting time is 80 minutes, the feeding rate is 6 kg / min, and the furnace pressure of the disc turbine dryer is -5Pa to -10Pa.

[0022] The present invention also protects a high-purity molybdenum trioxide prepared by the method for preparing high-purity molybdenum trioxide using the catalyst as described above.

[0023] Compared with the prior art, the present invention has the following technical effects:

[0024] (I) The method for preparing high-purity molybdenum trioxide of the present invention uses a disc-type turbine dryer as a preparation device, without adding new equipment or improving process pipeline equipment; high-purity molybdenum trioxide is prepared using ammonium molybdate powder with a particle size of 60 to 120 mesh as a raw material, and the particle size of the powder entering the disc-type turbine dryer is more uniform, which can fully react during the roasting process, thereby ensuring that the prepared pure molybdenum trioxide for the catalyst has fine particle size, good solubility and stable quality.

[0025] (II) The method of the present invention achieves the preparation of high-purity molybdenum trioxide by selecting the parameters of the heat preservation roasting, especially, by selecting the roasting time, the amount of material fed, the roasting temperature, and the pressure in the furnace. The purity of the high-purity molybdenum trioxide finally obtained is greater than 99.95%, and the solubility is good, which can meet the actual needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the high-purity molybdenum trioxide obtained in Example 1;

[0027] Figure 2 This is a SEM image of the high-purity molybdenum trioxide obtained by passing through a 40-mesh sieve in Example 1.

[0028] Figure 3 This is a SEM image of the black precipitate in the product obtained by the 40-mesh sieve used in Example 1;

[0029] Figure 4 This is a connection diagram of the high-purity molybdenum trioxide preparation equipment in Example 1.

[0030] The symbols in the figure represent:

[0031] 1- oven, 2- pulverizer, 3- vibrating screen, 4- raw material bin, 5- double screw feeding device, 6- disc turbine dryer, 7- fan, 8- electric heating furnace, 9- spiral discharging device, 10- vibrating screen, 11- high purity molybdenum trioxide silo, 12- heat exchanger, 13- absorption tower, 14- chimney, 15- collector.

[0032] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0033] It should be noted that all raw materials and devices in the present invention, unless otherwise specified, are raw materials and devices known in the prior art. For example:

[0034] The ammonium molybdate used to prepare molybdenum trioxide, such as ammonium dimolybdate, ammonium tetramolybdate, ammonium heptamolybdate, ammonium octamolybdate, and ammonium dodecomolybdate, are all ammonium molybdate products already available in the prior art.

[0035] The technical terms involved in this application are explained as follows:

[0036] The purity of high-purity molybdenum trioxide refers to mass purity.

[0037] The present invention uses a disc-type turbine dryer with the advantages of large single-furnace production capacity, high degree of automation, and less dust leakage. The overall structure of the disc-type turbine dryer is a vertical cylindrical structure with multiple layers of turntables. The material is added from the top and falls layer by layer to the bottom for release. Hot air is introduced from the bottom, and the air is circulated in sections by several blast turbine impellers arranged in the center of the cylinder. The generated exhaust gas flows out from the top with the hot air. This mode of operation causes the exhaust gas to pass through each layer of turntable during the discharge process, which increases the discharge resistance and prolongs the discharge time. During the decomposition of ammonium molybdate, the main reaction in the disc-type turbine dryer generates ammonia. If the generated ammonia cannot be discharged in time, side reactions will continue to occur, causing the ammonia to decompose and generate hydrogen. The generated hydrogen further reduces molybdenum trioxide to generate a small amount of by-product molybdenum dioxide or molybdenum metal, which in turn leads to a small amount of black precipitate in the solubility test. The specific reaction process is as follows:

[0038] Main reaction:

[0039] Side effects:

[0040] Therefore, it is urgent to use new preparation methods to effectively solve this problem and obtain products with qualified physicochemical indicators and qualified solubility.

[0041] The present invention provides a method for preparing high-purity molybdenum trioxide for catalyst, comprising the following steps:

[0042] Step 1, drying ammonium molybdate in a dryer;

[0043] Step 2, crushing the dried ammonium molybdate to obtain ammonium molybdate powder; sieving the ammonium molybdate powder through a sieve to obtain undersize material;

[0044] Preferably, the ammonium molybdate in step 2 is one or more of ammonium dimolybdate, ammonium tetramolybdate, ammonium heptamolybdate, ammonium octamolybdate and ammonium dodecomolybdate.

[0045] Preferably, the mesh size of the sieve is 60 to 120 meshes.

[0046] Step 3, adding the undersize material into the dryer through the top feed port of the dryer, and performing heat preservation and roasting under an oxidizing atmosphere at a temperature of 520°C to 550°C to obtain high-purity molybdenum trioxide;

[0047] The heat preservation and roasting time is 80min-90min, and the feeding amount is 5.0kg / min-6.0kg / min;

[0048] During the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, performs countercurrent heat exchange with the screened material, and then flows out from the top of the dryer; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer.

[0049] Preferably, the dryer is a disc-type turbo dryer.

[0050] Preferably, during the heat-insulating roasting, the pressure inside the furnace of the disc-type turbo dryer is -5Pa to -10Pa.

[0051] In the following embodiments of the present invention, the solubility of pure molybdenum trioxide product is judged as follows: the solution is colorless, clear and free of precipitate, and is judged as qualified by visual inspection. The test equipment used in the solubility test process includes: Changzhou Danrui HJ-4 multi-head magnetic stirrer (test speed 1000r / min); Mettler Toledo electronic balance (model: ME3002TE / 02).

[0052] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0053] Example 1

[0054] In accordance with the above technical scheme, this embodiment provides a method for preparing high-purity molybdenum trioxide for catalyst. Figure 4 The equipment shown includes an oven 1 for drying ammonium dimolybdate, a crusher 2 for crushing, a vibrating screen 3 for screening, a raw material bin 4 for placing ammonium dimolybdate, a double-screw feeding device 5, and a disc-type turbine dryer 6. After the raw material dimolybdic acid is dried in the oven 1, it enters the crusher 2 for crushing. After the crushed material is screened by the vibrating screen 3, it enters the raw material bin 4 and is sent to the disc-type turbine dryer 6 through the double-screw feeding device 5. During the preparation process, hot air is sent to the disc-type turbine dryer 6 with the help of a fan 7 and an electric heating furnace 8; the raw material reacts in the disc-type turbine dryer 6 to generate high-purity molybdenum trioxide and flue gas-containing waste gas, and the high-purity molybdenum trioxide for catalyst is sent to the vibrating screen 10 through the spiral discharging device 9, and then enters the high-purity molybdenum trioxide bin 11; the flue gas-containing waste gas enters the heat exchanger 12 through the collector 15 to achieve dust removal and cooling, and then is treated in the secondary absorption tower 13 and discharged through the chimney 14.

[0055] The preparation method specifically comprises the following steps:

[0056] Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C;

[0057] Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the multiple groups of ammonium dimolybdate powders through 40 mesh, 60 mesh, 80 mesh, 100 mesh and 120 mesh sieves respectively to obtain multiple groups of undersize materials;

[0058] Step 3, placing each group of undersize materials in a disc turbine dryer, and performing heat preservation and roasting under an oxidizing atmosphere of 520°C, wherein the heat preservation and roasting time is 80min, the feeding amount is 6kg / min, and the furnace pressure of the disc turbine dryer is -5Pa to -10Pa. During the heat preservation and roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, and flows out from the top of the dryer after countercurrent heat exchange with the undersize materials; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer, and 5 groups of high-purity molybdenum trioxide samples for catalyst are prepared using the obtained product.

[0059] The solubility test was conducted on each group of samples, specifically including: adding 40g of 25% sodium hydroxide and 15ml of distilled water into a 100ml beaker, stirring evenly, adding 14.4g of high-purity molybdenum trioxide, and stirring for 5 minutes. The pure molybdenum trioxide product has good solubility and meets the required standards: colorless clear solution, visually no precipitate, and the test results are shown in Table 1:

[0060]

[0061] Table 1. Solubility test results of high-purity molybdenum trioxide prepared from ammonium dimolybdate powder of different particle sizes

[0062] It can be seen from the above table that the raw material ammonium molybdate is passed through 40 mesh, 60 mesh, 80 mesh, 100 mesh and 120 mesh sieves respectively. When the sieve material of 60 mesh to 120 mesh is used for roasting, the solubility of the roasted product is good and meets the requirements. This is because: reducing the particle size of the raw material can increase the surface area of ​​the material, thereby increasing the active molecules per unit volume, improving the roasting reaction speed, accelerating the discharge of ammonia, and avoiding the reduction reaction of molybdenum trioxide.

[0063] In this example, electron microscope scanning images of the product prepared by the 60-mesh sieve material and the product prepared by the 40-mesh sieve material were obtained, as shown in FIG. Figure 1 and Figure 2 As shown in the figure, it can be seen that the product prepared by the 60-mesh sieve has regular crystal shape and smooth surface, and the product prepared by the 40-mesh sieve has a clear honeycomb structure on the surface. The black precipitate is chemically tested and its molybdenum content is between 66.87% and 81.76%, which is higher than the theoretical value of molybdenum in pure molybdenum trioxide, 66.67%.

[0064] Example 2

[0065] This embodiment provides a method for preparing high-purity molybdenum trioxide for catalyst, comprising the following steps:

[0066] Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C;

[0067] Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the multiple groups of ammonium dimolybdate powders through a 60-mesh sieve to obtain undersize;

[0068] Step 3, placing the undersize material in a disc turbine dryer, and performing heat preservation roasting under oxidizing atmosphere conditions of 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C and 550°C, wherein the heat preservation roasting time is 80min, the feed rate is 6kg / min, and the furnace pressure of the disc turbine dryer is -5Pa to -10Pa; during the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, and flows out from the top of the dryer after countercurrent heat exchange with the undersize material; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer.

[0069] The solubility test of the products prepared at different roasting temperatures was carried out in the same manner as in Example 1. The test results are as follows:

[0070]

[0071] It can be seen from the above table that when the roasting temperature increases from 480°C to 550°C, the black precipitate in the dissolution process of the pure molybdenum trioxide product gradually decreases. When the roasting temperature increases to above 520°C, the product has good solubility and meets the requirements. The above results show that temperature is the main factor affecting the decomposition rate of ammonium molybdate. Generally speaking, the chemical reaction rate increases by 2 to 4 times for every 10°C increase in reaction temperature. When the temperature rises to above 520°C, it can ensure that ammonium molybdate decomposes rapidly, and the generated ammonia can be removed in time, avoiding the reduction of the pure molybdenum trioxide product.

[0072] Example 3

[0073] This embodiment provides a method for preparing high-purity molybdenum trioxide for catalyst, comprising the following steps:

[0074] Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C;

[0075] Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the multiple groups of ammonium dimolybdate powders through a 60-mesh sieve to obtain undersize;

[0076] Step 3, placing the undersize material in a disc turbine dryer, and performing heat preservation roasting under an oxidizing atmosphere of 520°C, wherein the heat preservation roasting time is 80min, the feed rate is increased from 3.0kg / min to 7.5kg / min, and the furnace pressure of the disc turbine dryer is -5Pa to -10Pa; during the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, and flows out from the top of the dryer after countercurrent heat exchange with the undersize material; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer.

[0077] The solubility test of the products prepared under different feeding amounts was carried out in the same manner as in Example 1. The test results are as follows:

[0078]

[0079]

[0080] From the above table we can see

[0081] From the table above, we can see that when the feeding amount increases from 3.0kg / min to 7.5kg / min, the solubility changes from unqualified to qualified and then to unqualified. When the feeding amount is 5.0kg / min to 6.0kg / min, the solubility is good and meets the requirements. This is because: when the feeding amount is lower than 5.0kg / min, the material cannot be fully spread on the feeding plate, resulting in a small amount of rust on the turntable being brought into the product when the scraper is scraping the material, resulting in a reddish-brown precipitate. When the feeding amount is higher than 6.0kg / min, the amount of material on the feeding plate increases, and the amount of ammonia generated by the material reaction increases and cannot be discharged in time, resulting in the reduction of the produced molybdenum trioxide.

[0082] Example 4

[0083] This embodiment provides a method for preparing high-purity molybdenum trioxide for catalyst, comprising the following steps:

[0084] Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C;

[0085] Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the multiple groups of ammonium dimolybdate powders through a 60-mesh sieve to obtain undersize;

[0086] Step 3, placing the undersize material in a disc turbine dryer, and performing heat preservation roasting under an oxidizing atmosphere of 520°C, wherein the heat preservation roasting time is increased from 55min to 105min, the feed rate is 6kg / min, and the furnace pressure of the disc turbine dryer is -5Pa to -10Pa; during the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, and flows out from the top of the dryer after countercurrent heat exchange with the undersize material; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer.

[0087] The solubility test of the products prepared at different roasting times was carried out in the same manner as in Example 1. The test results are as follows:

[0088]

[0089]

[0090] It can be seen from the table above that when the roasting time increases from 55min to 105min, the solubility of the product changes from unqualified to qualified and then to unqualified. When the roasting time is 80min-90min, the solubility is good and meets the requirements. The reason is that when the roasting time is less than 80min, the roasting time of the material is insufficient and a small amount of ammonium molybdate is not completely decomposed; when the roasting time is greater than 90min, the material stays in the dryer for too long and the molybdenum trioxide undergoes a reduction reaction.

[0091] Example 5

[0092] This embodiment provides a method for preparing high-purity molybdenum trioxide for catalyst, comprising the following steps:

[0093] Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C;

[0094] Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the multiple groups of ammonium dimolybdate powders through a 60-mesh sieve to obtain undersize;

[0095] Step 3, placing the undersize material in a disc turbine dryer, and performing heat preservation roasting under an oxidizing atmosphere of 520°C, wherein the heat preservation roasting time is 80min, the material feeding amount is 6kg / min, and the furnace pressure of the disc turbine dryer is -20Pa~+20Pa; during the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, and flows out from the top of the dryer after countercurrent heat exchange with the undersize material; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer.

[0096] The solubility test of the products prepared under different furnace pressures was carried out in the same manner as in Example 1. The test results are as follows:

[0097]

[0098] It can be seen from the above table that when the dryer pressure increases from -20Pa to +20Pa, the solubility of the product changes from unqualified to qualified and then to unqualified. When the dryer pressure is -5 to -10Pa, the solubility of the product is good and meets the requirements. The possible reasons are: when the dryer pressure is lower than -10Pa, the heat propagation speed in the dryer is too fast, the temperature is reduced, and sufficient heat cannot be provided to the roasting process, resulting in a small amount of ammonium molybdate cannot react completely; when the dryer pressure is higher than -5Pa, the ammonia generated by roasting cannot be discharged in time, resulting in the reduction of the generated molybdenum trioxide.

[0099] Example 6

[0100] This embodiment provides a method for preparing high-purity molybdenum trioxide for catalyst, using three different batches of ammonium dimolybdate as raw materials to prepare high-purity molybdenum trioxide for catalyst, specifically comprising the following steps:

[0101] Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C;

[0102] Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the multiple groups of ammonium dimolybdate powders through a 60-mesh sieve to obtain undersize;

[0103] Step 3, placing the undersize material in a disc turbine dryer, and performing heat preservation roasting under an oxidizing atmosphere of 520°C, wherein the heat preservation roasting is 80min, the material feeding amount is 6kg / min, and the furnace pressure of the disc turbine dryer is -5Pa to -10Pa; during the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, and flows out from the top of the dryer after countercurrent heat exchange with the undersize material; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer.

[0104] The solubility test of the product prepared by this method was carried out in the same manner as in Example 1, and the test results were as follows:

[0105]

[0106] It can be seen from the above table that the product prepared in this embodiment has high purity and good solubility of molybdenum trioxide, which can meet the solubility requirements of catalyst production, is simple and feasible to operate, and the product particles are tightly bonded, basically free of pores, with regular crystal shape and smooth surface. The purity is 99.96%, which can meet the technical requirements of high-purity molybdenum trioxide, and has no effect on other control indicators, such as the contents of Mo, Cu, K, Na, Ca, etc.

[0107] Example 7

[0108] The present embodiment provides a method for preparing high-purity molybdenum trioxide for catalyst, comprising the following steps: placing ammonium dimolybdate in a disc turbine dryer, and performing heat preservation roasting under 520° C. oxidizing atmosphere conditions, wherein the heat preservation roasting is 80 min, the feed rate is 6 kg / min, and the furnace pressure of the disc turbine dryer is -5 Pa to -10 Pa; during the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, and flows out from the top of the dryer after countercurrent heat exchange with the screened material; the obtained high-purity molybdenum trioxide is discharged from the discharge port at the bottom of the dryer.

[0109] The prepared product was tested for chemical indicators and solubility using the same testing method as in Example 1. The test results are as follows:

[0110]

[0111] Compared with Example 1, Example 7 is as follows: the raw material ammonium dimolybdate is not pretreated in the method steps, and the process operation parameters are the same. The physical and chemical indicators of the produced product are qualified, but the solubility is unqualified. The reason is analyzed as follows: the particle size of the untreated raw material is large, the speed of heat transfer from the surface of the raw material to the inside is slowed down during the roasting process, the reaction speed and the ammonia emission speed are slowed down, resulting in side reactions and unqualified solubility.

[0112] Example 8

[0113] Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C;

[0114] Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the multiple groups of ammonium dimolybdate powders through a 60-mesh sieve to obtain undersize;

[0115] Step 3: Place the screened material in a disc turbine dryer and perform heat preservation and roasting in an oxidizing atmosphere at 500°C. The heat preservation and roasting time is 70 minutes, the material feeding rate is 7kg / min, and the furnace pressure of the disc turbine dryer is 0Pa to -5Pa;

[0116] The prepared product was tested for chemical indicators and solubility using the same testing method as in Example 1. The test results are as follows:

[0117]

[0118] Embodiment 8 is compared with embodiment 1:

[0119] The raw material ammonium dimolybdate was pretreated, and the process parameters were not optimized. The physical and chemical indicators of the produced product were qualified, but the solubility was unqualified. The reasons were analyzed as follows: the roasting temperature was low, the reaction time was short, the amount of material was large, the pressure in the furnace was high, the heat provided to the material during the reaction was reduced, the heat transfer between the material layers was slow, the reaction speed and the ammonia emission speed were slow, resulting in side reactions and unqualified solubility.

[0120] From the above comparison, it can be seen that by adopting the method for preparing high-purity molybdenum trioxide for catalyst of the present invention, using a disc turbine dryer and controlling relevant process parameters, high-purity molybdenum trioxide with high purity and good solubility can be finally prepared.

[0121] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0122] In addition, various embodiments of the present invention may be combined arbitrarily.

Claims

1. A method for preparing high-purity molybdenum trioxide for catalyst, characterized in that: The following steps are involved: Step 1, drying ammonium molybdate in a dryer; Step 2, crushing the dried ammonium molybdate to obtain ammonium molybdate powder; sieving the ammonium molybdate powder through a sieve to obtain undersize material; Step 3, adding the undersize material into the dryer through the top feed port of the dryer, and performing heat preservation and roasting under an oxidizing atmosphere at a temperature of 520°C to 550°C to obtain high-purity molybdenum trioxide; The heat preservation and roasting time is 80min-90min, and the feeding amount is 5.0kg / min-6.0kg / min; During the heat preservation roasting process, the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, performs countercurrent heat exchange with the screened material, and then flows out from the top of the dryer; the obtained high-purity molybdenum trioxide is discharged from the bottom discharge port of the dryer.

2. The method for preparing high-purity molybdenum trioxide for catalyst according to claim 1, characterized in that: The dryer is a disc-type turbine dryer.

3. The method for preparing high-purity molybdenum trioxide for catalyst according to claim 1, characterized in that: The mass percentage of the high-purity molybdenum trioxide is not less than 99.95%.

4. The method for preparing high-purity molybdenum trioxide for catalyst according to claim 1, characterized in that: During the heat preservation roasting, the pressure inside the furnace of the disc-type turbo dryer is -5Pa to -10Pa.

5. The method for preparing high-purity molybdenum trioxide for catalyst according to claim 1, characterized in that: The ammonium molybdate described in step 2 is one or more of ammonium dimolybdate, ammonium tetramolybdate, ammonium heptamolybdate, ammonium octamolybdate, and ammonium dodecomolybdate.

6. The method for preparing high-purity molybdenum trioxide for catalyst according to claim 1, characterized in that: The mesh size of the sieve in step 2 is 60 to 120 meshes.

7. The method for preparing high-purity molybdenum trioxide for catalyst according to claim 1, characterized in that: The method specifically comprises the following steps: Step 1, placing ammonium dimolybdate in a dryer and drying at a temperature of 200°C; Step 2, crushing the dried ammonium dimolybdate to obtain ammonium dimolybdate powder; sieving the ammonium dimolybdate powder through a 60-mesh sieve to obtain undersize; Step 3: Add the undersize material into the dryer through the top feed port of the dryer, and the gas used for drying and heat exchange enters the dryer from the bottom of the dryer, and heat-insulates and roasts in an oxidizing atmosphere at 520°C to obtain the product; The heat preservation and roasting time is 80 minutes, the feeding rate is 6 kg / min, and the furnace pressure of the disc turbine dryer is -5Pa to -10Pa.

8. High-purity molybdenum trioxide prepared by the method for preparing high-purity molybdenum trioxide for catalyst according to any one of claims 1 to 7.

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