A method for synthesizing molybdenum trichloride

Abstract

The application discloses a process for preparing molybdenum trichloride, comprising the following processes: ①excess molybdenum pentachloride and stannous chloride powder are mixed, and the mixture is heated in a reactor to generate a replacement reaction to form molybdenum trichloride and tin tetrachloride; ②the generated tin tetrachloride is vaporized out of the reactor and enters a cooling system to collect and cool to obtain tin tetrachloride liquid; ③after the reaction is completed, the cooling system is switched into a molybdenum pentachloride collector, the reactor is heated to a certain temperature, and the excess molybdenum pentachloride is vaporized into the molybdenum pentachloride collector; ④after the reactor is cooled, the molybdenum trichloride product is obtained; and ⑤the tin tetrachloride liquid is filtered in a closed manner to obtain tin tetrachloride product and molybdenum pentachloride filter residue, and the molybdenum pentachloride filter residue and the collected molybdenum pentachloride can be recycled as reaction raw materials. The application improves the yield of molybdenum trichloride, reduces the production cost, the purity of the by-product tin tetrachloride is more than 99%, the waste gas amount in the production process is greatly reduced, and the process belongs to a green and environment-friendly process.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for synthesizing molybdenum trichloride, in particular to a method for simultaneously synthesizing molybdenum trichloride and tin tetrachloride at low cost, and belongs to the field of rare metal material synthesis. BACKGROUND

[0002] Molybdenum trichloride is a dark red monoclinic crystal with a sublimation point lower than 400℃ and higher than 375℃. It is an important precursor of molybdenum-based catalysts used for nitrogen fixation in the current ammonia production process. Molybdenum-based catalysts can fix more nitrogen for catalytic ammonia production, and ammonia is an important raw material for nitrogen fertilizer production. Therefore, molybdenum trichloride has great application prospects. Molybdenum pentachloride has a boiling point of 268℃, tin tetrachloride has a melting point of -33℃ and a boiling point of 114.15℃, and stannous chloride has a melting point of 247℃ and a boiling point of 623℃. By taking advantage of the differences in boiling points, stannous chloride is a potential reducing agent, and the boiling point of the reduction product, tin tetrachloride, is relatively low, making it easy to separate from the reactants and products.

[0003] Currently, the main method for synthesizing molybdenum trichloride is to reduce molybdenum pentachloride with hydrogen gas to produce molybdenum trichloride. However, this method is prone to over-reduction or insufficient reduction, resulting in the formation of by-products such as molybdenum dichloride and molybdenum tetrachloride. Therefore, more separation steps are required. Due to the close boiling points of the by-products and molybdenum trichloride, the yield of molybdenum trichloride is very low, and the purity is at most 98%. Some attempts have also been made to use aluminum or sodium as reducing agents to reduce molybdenum pentachloride to produce molybdenum trichloride. However, the above-mentioned methods still have the problem of excessive by-products due to the difficulty in controlling the reduction intensity, resulting in low yield of molybdenum trichloride and difficulty in separating molybdenum trichloride from by-products, which affects the purity of molybdenum trichloride. Therefore, it is necessary to innovate the synthesis method of molybdenum trichloride to overcome the above-mentioned problems. SUMMARY

[0004] In view of the above problems, the present application aims to provide a method for synthesizing molybdenum trichloride with low cost, high raw material utilization rate, and high purity of molybdenum trichloride product. The present application effectively overcomes the current situation of low raw material utilization rate and low quality of molybdenum trichloride in the prior art, and realizes the synthesis of high-purity molybdenum trichloride from molybdenum pentachloride by stannous chloride reduction. The molybdenum resources of molybdenum pentachloride are fully utilized, and the reduction product, tin tetrachloride, can also be used as a qualified product.

[0005] The synthesis method of molybdenum trichloride according to the present application comprises the following specific steps:

[0006] 1) Mix excess molybdenum pentachloride and stannous chloride powder to obtain a mixture;

[0007] 2) Put the mixture obtained in step 1) into a reactor and react under a protective atmosphere. The generated tin tetrachloride gasifies and leaves the reactor to enter a cooling system for cooling and collection to obtain tin tetrachloride liquid.

[0008] 3) After the reaction of step 2) is completed, the reactor is heated, and the cooling system is switched into the molybdenum pentachloride collector, and the excess molybdenum pentachloride is gasified into the molybdenum pentachloride collector.

[0009] 4) After step 3) is completed, the reactor is cooled and discharged to obtain the molybdenum trichloride product.

[0010] 5) The tin tetrachloride liquid obtained from step 2) is filtered to obtain tin tetrachloride product and molybdenum pentachloride filter residue, and the molybdenum pentachloride filter residue and the molybdenum pentachloride collected in step 3) are recycled as reaction raw materials.

[0011] The key in the process of preparing molybdenum trichloride in the technical solution is to mix excess molybdenum pentachloride with stannous chloride, completely oxidize the stannous chloride to tin tetrachloride, and reduce the corresponding amount of molybdenum pentachloride to molybdenum trichloride. The boiling point of tin tetrachloride is low, and it can be separated from the reaction system within the reaction temperature range. Thus, there are mainly molybdenum trichloride and relatively low-boiling molybdenum pentachloride in the reaction system. After the reaction is completed, the excess molybdenum pentachloride is distilled out by heating. Thus, the last remaining substance in the reaction system is molybdenum trichloride.

[0012] As a preferred solution, the molar ratio of molybdenum pentachloride to stannous chloride is 1.01-5:1.

[0013] As a preferred solution, the protective gas is one or a combination of more than one of helium, argon, and nitrogen.

[0014] As a preferred solution, the reaction temperature of step 2) is 115-200°C.

[0015] As a preferred solution, the heating temperature of step 3) is 250-375°C.

[0016] As a preferred solution, the solid-liquid separation method of step 5) is one or a combination of more than one of centrifugation, filtration, decantation, and gravity sedimentation.

[0017] The advantages of the present application over the prior art and the beneficial technical effects brought about are as follows:

[0018] The technical advantages of the present application are as follows:

[0019] 1) The quality of molybdenum trichloride is improved, and the purity reaches more than 99%.

[0020] 2) The molybdenum element of molybdenum pentachloride can be completely converted into molybdenum trichloride. In this system, no molybdenum dichloride, molybdenum tetrachloride, or other molybdenum chloride by-products are formed during the reaction process, and the excess molybdenum pentachloride can also be recycled and eventually completely converted into molybdenum trichloride.

[0021] 3) The chlorine-containing waste gas is greatly reduced, and the two chlorine atoms lost in the oxidation of molybdenum pentachloride to molybdenum trichloride are basically fixed to form tin tetrachloride by stannous chloride, thereby fundamentally reducing the emission of chlorine-containing waste gas.

[0022] 4) The by-product also has high value, and the technology is extremely competitive. The purity of tin tetrachloride formed by oxidation of stannous chloride is more than 99%, which meets the product standard of tin tetrachloride.

[0023] The beneficial technical effects of the present application: Based on the technical advantages of the present application, the present application brings outstanding technical effects compared with the prior art, realizes the quality upgrading of molybdenum trichloride, complete utilization of raw materials, waste gas reduction and waste-to-resource (chlorine lost in the oxidation of molybdenum pentachloride to molybdenum trichloride is used as raw material for the synthesis of tin tetrachloride). On the one hand, the method overcomes the problems of low purity of traditional molybdenum trichloride and difficulty in efficient utilization of molybdenum source. The selectivity of molybdenum pentachloride to molybdenum trichloride is high, and molybdenum pentachloride can be recycled. On the other hand, the method also creates a new method for the collaborative preparation of molybdenum trichloride and tin tetrachloride. The method just uses the chlorine lost in molybdenum pentachloride for the synthesis of tin tetrachloride. In summary, the scheme of the present application is simple in operation, high in raw material utilization rate, high in product purity, friendly to the environment, conducive to the maximization of resource utilization, and meets the needs of industrial development. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The process flow chart of the present application. DETAILED EMBODIMENT

[0025] The following examples are intended to further illustrate the content of the present application and do not limit the protection scope of the claims of the present application.

[0026] Example 1

[0027] The molar ratio of molybdenum pentachloride to stannous chloride is 1.2:1. 2.4 mol of molybdenum pentachloride and 2 mol of stannous chloride are weighed and mixed, and then loaded into a displacement reactor. After argon displacement, the reactor is kept at 120℃, and the tin tetrachloride liquid is collected at the rear end of the reactor. After 4h of reaction, the exhaust gas is discharged from the molybdenum pentachloride cooling collector, and the temperature is raised to 250℃. After keeping warm for 4h, the reactor is cooled and collected to obtain 1.95 mol of molybdenum trichloride with a purity of 99.1%. The cooled and collected molybdenum pentachloride is 100g, and the tin tetrachloride liquid is filtered to obtain 1.98 mol of tin tetrachloride with a purity of 99.4%. The filter residue is 1g. The solid-liquid separation method is centrifugation or filtration. The molybdenum pentachloride and the filter residue can be reused as raw materials.

[0028] Example 2

[0029] The molar ratio of molybdenum pentachloride to stannous chloride is 2:1, 4 mol of molybdenum pentachloride and 2 mol of stannous chloride are weighed, mixed and then loaded into a displacement reactor, the volume ratio of argon to nitrogen is 1:1, after displacement, the reactor is kept at 140°C, the liquid tin tetrachloride at the back end of the reactor is collected after cooling, after 4 hours of reaction, the exhaust of the molybdenum pentachloride cooling collector is stopped, the temperature is raised to 280°C, after keeping for 4 hours, the reactor is cooled to collect the material, 1.98 mol of molybdenum trichloride with a purity of 99.3% is obtained, 540 g of molybdenum pentachloride is collected after cooling, 1.99 mol of tin tetrachloride with a purity of 99.6% is obtained by centrifugation of the liquid tin tetrachloride, and 1.3 g of centrifugal residue, the solid-liquid separation method is a combination of decantation and gravity sedimentation, and the molybdenum pentachloride and the centrifugal residue can be reused as raw materials.

[0030] Example 3

[0031] The molar ratio of molybdenum pentachloride to stannous chloride is 3:1, 6 mol of molybdenum pentachloride and 2 mol of stannous chloride are weighed, mixed and then loaded into a displacement reactor, after argon displacement, the reactor is kept at 160°C, the liquid tin tetrachloride at the back end of the reactor is collected after cooling, after 4 hours of reaction, the exhaust of the molybdenum pentachloride cooling collector is stopped, the temperature is raised to 320°C, after keeping for 4 hours, the reactor is cooled to collect the material, 1.96 mol of molybdenum trichloride with a purity of 99.5% is obtained, 1100 g of molybdenum pentachloride is collected after cooling, the liquid tin tetrachloride is gravity sedimentated for 1 day, the supernatant is extracted, the bottom suspension is filtered, a total of 1.99 mol of tin tetrachloride with a purity of 99.5% is obtained, and 3 g of filter residue, the solid-liquid separation method is filtration, and the molybdenum pentachloride and the filter residue can be reused as raw materials.

[0032] Example 4

[0033] The molar ratio of molybdenum pentachloride to stannous chloride is 4:1, 8 mol of molybdenum pentachloride and 2 mol of stannous chloride are weighed, mixed and then loaded into a displacement reactor, after helium displacement, the reactor is kept at 200°C, the liquid tin tetrachloride at the back end of the reactor is collected after cooling, after 5 hours of reaction, the exhaust of the molybdenum pentachloride cooling collector is stopped, the temperature is raised to 375°C, after keeping for 5 hours, the reactor is cooled to collect the material, 1.96 mol of molybdenum trichloride with a purity of 99.7% is obtained, 1100 g of molybdenum pentachloride is collected after cooling, the liquid tin tetrachloride is gravity sedimentated for 10 hours, the supernatant is decanted, the bottom suspension is filtered, a total of 1.99 mol of tin tetrachloride with a purity of 99.5% is obtained, and 3 g of filter residue, the solid-liquid separation method is gravity sedimentation, and the molybdenum pentachloride and the filter residue can be reused as raw materials.

Claims

1. A method for synthesizing molybdenum trichloride, characterized by, The method comprises the following steps: 1) mixing excess molybdenum pentachloride and stannous chloride powder to obtain a mixture; 2) placing the mixture obtained in step 1) into a reactor and reacting under a protective atmosphere, and the generated tin tetrachloride gas is taken out of the reactor and enters a cooling system to obtain tin tetrachloride liquid; 3) after the reaction in step 2) is completed, heating the reactor, and at the same time, switching the cooling system into a molybdenum pentachloride collector, and the excess molybdenum pentachloride is gasified into the molybdenum pentachloride collector; 4) after step 3) is completed, discharging the reactor after cooling to obtain a molybdenum trichloride product; 5) obtaining a tin tetrachloride product and molybdenum pentachloride residue through solid-liquid separation from the tin tetrachloride liquid obtained in step 2), and recycling the molybdenum pentachloride filter residue and the molybdenum pentachloride collected in step 3) as reaction raw materials.

2. The method of claim 1, wherein the molybdenum trichloride is synthesized by the reaction of molybdenum pentachloride and hydrogen chloride. In step 1), the molar ratio of molybdenum pentachloride to stannous chloride is 1.05-5:

1.

3. The method for synthesizing molybdenum trichloride according to claim 1, characterized in that, In step 2), the protective atmosphere gas is one or a combination of more than one of helium, argon and nitrogen.

4. The method of claim 1, wherein the molybdenum trichloride is synthesized by the process of: In step 2), the reaction temperature under the protective atmosphere is 115-200°C. ​ 5. The method for synthesizing molybdenum trichloride according to claim 1, characterized in that, In step 3), the heating temperature of the reactor is 250-375°C.

6. The method for synthesizing molybdenum trichloride according to claim 1, characterized in that, In step 5), the solid-liquid separation method is one or a combination of more than one of centrifugation, filtration, decantation and gravity sedimentation.

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