Vanadium catalysts, methods of making and use
By controlling the alkali metal content of the vanadium aqueous solution in the Na-KV system and using spray drying technology, the problem of poor low-temperature activity of traditional vanadium catalysts was solved, and a high-efficiency vanadium catalyst suitable for wet acid production processes was prepared.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-30
- Publication Date
- 2026-06-30
AI Technical Summary
Traditional vanadium catalysts exhibit poor catalytic activity at low temperatures, resulting in low efficiency in the oxidation of SO2 to SO3. Furthermore, uneven loading of alkali metal salts during the preparation process leads to poor catalyst performance.
By controlling the alkali metal content in the Na-KV system vanadium aqueous solution and employing spray drying and calcination processes, a vanadium catalyst with small and uniform active phase grains was prepared, ensuring that the alkali metal was uniformly loaded onto the diatomaceous earth support.
It improves the low-temperature catalytic activity and material drying efficiency of vanadium catalysts, enhances the strength of catalysts and the stability of active phase crystal grains, and is suitable for wet acid production processes.
Smart Images
Figure CN122298403A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sulfuric acid production technology using environmentally friendly equipment, specifically to a vanadium catalyst, its preparation method, and its application. Background Technology
[0002] Vanadium-based catalysts are used in the process of oxidizing SO2 to SO3 to produce sulfuric acid. Traditional vanadium catalysts are vanadium-potassium (sodium)-silicon systems, with vanadium pentoxide as the active component, potassium sulfate and sodium sulfate as auxiliary agents, and diatomaceous earth from Shandong, Northeast China, or a mixture of both as the support. Currently, the manufacturing method for vanadium catalysts involves dissolving KOH with steam and then heating it with V2O5 under hot conditions to obtain a suitable mixed solution of KVO3 and KOH (referred to as vanadium water). The vanadium water is then neutralized with sulfuric acid to obtain a colloidal precipitate of V2O5 and K2SO4. The colloidal precipitate, auxiliary agents (alkali metal sulfates), and refined diatomaceous earth are then added to a mill and mixed evenly according to a specified ratio. However, this process is prone to uneven mixing, and the alkali metal salts cannot be well loaded onto the diatomaceous earth support. Uneven alkali metal loading directly leads to poor low-temperature performance of the catalyst.
[0003] Traditional vanadium catalyst drying methods use oven drying, which is simple, easy to implement, and easy to automate. However, the disadvantages are that the material drying is prone to unevenness and takes a long time, resulting in reduced catalyst strength and larger active phase crystal grains. The operation process and operating conditions have a significant impact on the performance of the catalyst.
[0004] Vanadium catalysts are widely used in the chemical industry, but their catalytic activity is poor at low reaction temperatures. The SO2 content in the tail gas during the catalytic oxidation of SO2 to produce acid is relatively high. Therefore, measures need to be taken to improve the performance of vanadium catalysts to achieve their higher low-temperature catalytic activity. Summary of the Invention
[0005] The purpose of this invention is to overcome the problems of poor performance in vanadium catalysts prepared by traditional methods, such as large active phase grains, and to provide a vanadium catalyst, its preparation method, and its applications. The vanadium catalyst of this invention exhibits high activity and can be used in the industrial production of wet acid production.
[0006] To achieve the above objectives, the present invention provides a method for preparing a vanadium catalyst, the method comprising the following steps: (1) React an alkaline solution containing sodium and potassium ions with V2O5 under heating conditions to obtain a Na-KV system vanadium aqueous solution; (2) The Na-KV system vanadium aqueous solution is mixed with concentrated sulfuric acid to obtain a mixed colloidal substance, wherein the amount of concentrated sulfuric acid used is such that the pH value of the mixed colloidal substance is 2-3; (3) The mixed colloid is mixed with a carrier and additives, and the resulting mixture is extruded. (4) The product obtained after extrusion molding is spray-dried and then roasted.
[0007] Preferably, in step (1), the amount of alkaline solution containing sodium and potassium ions and V2O5 used is such that the K / V molar ratio in the prepared Na-KV system vanadium aqueous solution is (2.8-4):1 and the Na / V molar ratio is (1.5-2.8):1.
[0008] Preferably, in step (1), the preparation process of the alkaline solution containing sodium ions and potassium ions includes: mixing sodium hydroxide, potassium hydroxide and water.
[0009] Preferably, in step (1), the reaction conditions include: a temperature of 105-130°C and a time of 1-2 hours.
[0010] Preferably, in step (2), boric acid and / or phosphoric acid are also added during the mixing process.
[0011] Preferably, in step (2), the mass-to-volume ratio of the vanadium catalyst to the boric acid and the phosphoric acid is (90-110) kg: 1 L.
[0012] Preferably, the mass ratio of V2O5 to the vanadium catalyst in step (1) is (6.5-8):100.
[0013] Preferably, the mass ratio of the additive to the vanadium catalyst is (1-5):100.
[0014] Preferably, the carrier is diatomaceous earth.
[0015] Preferably, the auxiliary agent is at least one selected from cesium sulfate, lanthanum sulfate, and cerium sulfate.
[0016] Preferably, in step (4), the spray drying process includes: placing the product obtained after extrusion molding on a spray drying fluidized bed at 120-130℃, and using an airflow atomizer to spray hot gas at a speed of ≥300m / s to spray dry the product obtained after extrusion molding.
[0017] Preferably, the ejection velocity of the hot gas is 300-600 m / s.
[0018] Preferably, the hot gas is at least one of air, nitrogen, and superheated steam.
[0019] Preferably, the temperature of the hot gas is ≥150℃, and more preferably 160-180℃.
[0020] Preferably, in step (4), the calcination conditions include: a temperature of 530-560℃ and a time of 1-2h.
[0021] A second aspect of the present invention provides a vanadium catalyst prepared by the method described above.
[0022] Preferably, the size of the active component of the vanadium catalyst is 15-35 nm.
[0023] The third aspect of this invention provides the application of the vanadium catalyst described above in the wet acid production process.
[0024] According to the vanadium catalyst preparation method described in this invention, by precisely controlling the alkali metal content of the Na-KV vanadium solution, the alkali metal is better supported on the diatomaceous earth carrier, thereby resulting in a vanadium catalyst with high activity, especially at low temperatures. By employing spray drying, the drying efficiency and uniformity of the material are improved during the vanadium catalyst production process, thus enhancing the catalyst strength and the stability of the active phase crystal grains. Specifically, the vanadium catalyst prepared according to the method of this invention can achieve an activity as high as 36% at 390°C. Attached Figure Description
[0025] Figure 1 A scanning electron microscope image of the vanadium catalyst prepared in Example 1; Figure 2 Scanning electron microscope (SEM) image of the vanadium catalyst prepared for Comparative Example 1. Detailed Implementation
[0026] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.
[0027] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0028] The method for preparing the vanadium catalyst of the present invention includes the following steps: (1) React an alkaline solution containing sodium and potassium ions with V2O5 under heating conditions to obtain a Na-KV system vanadium aqueous solution; (2) The Na-KV system vanadium aqueous solution is mixed with concentrated sulfuric acid to obtain a mixed colloidal substance, wherein the amount of concentrated sulfuric acid used is such that the pH value of the mixed colloidal substance is 2-3; (3) The mixed colloid is mixed with a carrier and additives, and the resulting mixture is extruded. (4) The product obtained after extrusion molding is spray-dried and then roasted.
[0029] In step (1), the amount of alkaline solution containing sodium and potassium ions and V2O5 is such that the K / V molar ratio in the prepared Na-KV system vanadium aqueous solution can be (2.8-4):1, preferably (3-3.8):1, specifically, for example, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1 or 3.8:1.
[0030] In step (1), the amount of alkaline solution containing sodium and potassium ions and V2O5 is such that the Na / V molar ratio in the prepared Na-KV system vanadium aqueous solution is (1.5-2.8):1, preferably (1.8-2.7):1. Specifically, it can be, for example, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1 or 2.7:1.
[0031] In step (1), the preparation process of the alkaline solution containing sodium and potassium ions may include mixing sodium hydroxide, potassium hydroxide, and water. The mixing process may be carried out under stirring.
[0032] In step (1), the reaction conditions may include a temperature of 105-130°C and a time of 1-2 hours. Preferably, the reaction conditions include a temperature of 110-120°C and a time of 1.5-2 hours. The reaction can be carried out in various conventional reaction apparatuses in the art.
[0033] In step (2), preferably, boric acid and / or phosphoric acid are also added during the mixing process. The boric acid may be added in the form of an aqueous solution, and the concentration of the aqueous solution of boric acid may be 80-90 wt%, preferably 85-90 wt%. The phosphoric acid may be added in the form of an aqueous solution, and the concentration of the phosphoric acid may be 85-98 wt%, preferably 90-95 wt%.
[0034] In step (2), the mass-to-volume ratio of the vanadium catalyst to the boric acid and the phosphoric acid can be (90-110) kg:1 L. Specifically, in some embodiments of the present invention, when boric acid is added during the mixing process, the mass-to-volume ratio of the vanadium catalyst to the boric acid can be (90-110) kg:1 L. In other embodiments of the present invention, when phosphoric acid is added during the mixing process, the mass-to-volume ratio of the vanadium catalyst to the phosphoric acid can be (90-110) kg:1 L. In still other embodiments of the present invention, when boric acid and phosphoric acid are added during the mixing process, the mass-to-volume ratio of the vanadium catalyst to the boric acid and the phosphoric acid can be (90-110) kg:1 L.
[0035] In the method described in this invention, the mass ratio of V2O5 to the vanadium catalyst in step (1) can be (6.5-8):100, preferably (6.6-7.8):100.
[0036] In the method described in this invention, the mass ratio of the auxiliary agent to the vanadium catalyst can be (1-5):100, preferably (2-4):100.
[0037] In the method described in this invention, preferably, the support is diatomaceous earth. The SiO2 content in the support is ≥90%.
[0038] In the method described in this invention, the auxiliary agent may be at least one selected from cesium sulfate, lanthanum sulfate, and cerium sulfate. In the most preferred embodiment, the auxiliary agent is a mixture of cesium sulfate and lanthanum sulfate. In the mixture of cesium sulfate and lanthanum sulfate, the ratio of cesium sulfate to lanthanum sulfate may be (1-10):1.
[0039] In step (3), the mixing time can be 1-2 hours, preferably 1.2-1.8 hours. The mixing process can be carried out in a kneader.
[0040] In step (4), the spray drying process may include: placing the product obtained after extrusion molding on a spray drying fluidized bed at 120-130℃, and using an airflow atomizer to spray hot gas at a speed of ≥300m / s to spray dry the product obtained after extrusion molding.
[0041] In step (4), the ejection velocity of the hot gas can be 300-600 m / s, preferably 350-550 m / s. The hot gas can be at least one of air, nitrogen, and superheated steam. In the most preferred embodiment, the hot gas is air. The temperature of the hot air is ≥150°C, preferably 160-180°C.
[0042] In step (4), the calcination conditions may include a temperature of 530-560℃ and a time of 1-2 hours. Preferably, the calcination conditions include a temperature of 530-550℃ and a time of 1.2-1.8 hours. The calcination process can be carried out in a tunnel kiln.
[0043] The present invention also provides a vanadium catalyst prepared by the above method. This vanadium catalyst has high stability of the active phase crystal grains, can effectively catalyze the oxidation reaction of SO2, and can maintain high activation performance in low-temperature environments.
[0044] In this invention, the size of the active component of the vanadium catalyst can be 15-35 nm. Preferably, the size of the active component of the vanadium catalyst can be 18-32 nm. The shape of the vanadium catalyst can be strip-shaped, ring-shaped, or plum blossom-shaped, preferably plum blossom-shaped.
[0045] This invention also provides the application of the vanadium catalyst in a wet acid production process. In practical applications, the activity of the vanadium catalyst can reach up to 36% at 390°C. The vanadium catalyst is suitable for bed conditions with an inlet temperature of 370-380°C.
[0046] The following examples further illustrate the vanadium catalyst, its preparation method, and its applications according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.
[0047] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.
[0048] In the following examples and comparative examples, the relevant parameters of the vanadium catalyst were tested according to the following methods: Activity test: In the process of sulfur dioxide oxidation to sulfuric acid, sulfur trioxide is generated under the action of a catalyst. The volume fraction of sulfur dioxide in the gas before and after the reaction is determined by iodine standard titration solution, and the sulfur dioxide conversion rate is calculated to characterize the catalyst activity. The activity is expressed as the sulfur dioxide conversion rate E after heat resistance, and the value is expressed as a percentage. It is calculated according to formula (1): (1) In the formula: —The volume fraction of sulfur dioxide in the reactor inlet gas, expressed as a percentage (%). —The volume fraction of sulfur dioxide in the reactor outlet gas, expressed as a percentage (%).
[0049] The arithmetic mean of three consecutive measurements is taken as the measurement result. The absolute difference between the three measurement results should not exceed 2.0% for low-temperature catalysts and not exceed 1.0% for high-temperature catalysts.
[0050] Vanadium pentoxide (V₂O₅) mass fraction measurement: Weigh the product on a Mettler Toledo electronic scale, repeating the process three times and taking the average value. Calculate the vanadium pentoxide mass fraction of the product based on the amount of vanadium pentoxide used.
[0051] Example 1 (1) Add 16.2 kg KOH, 8.8 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 120 °C for 2 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.5, Na / V molar ratio of 2.6).
[0052] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 12.72 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of phosphoric acid with a concentration of 95wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.6.
[0053] (3) The mixed colloid obtained in step (2), 46.56 kg of diatomaceous earth, 5.5 kg of cesium sulfate and 1.5 kg of lanthanum sulfate are put into a kneader and mixed for 1.5 h. The resulting mixture is then extruded and molded.
[0054] (4) The product obtained after extrusion molding in step (3) is placed in a spray drying fluidized bed at a temperature of 125°C for spray drying. Air at 170°C is sprayed out at a speed of 350 m / s using an airflow atomizer. The dried sample is then placed in a tunnel kiln for calcination at a temperature of 530°C for 1.8 h to obtain the vanadium catalyst A1 of the present invention. The scanning electron microscope image of vanadium catalyst A1 is shown below. Figure 1 As shown.
[0055] The vanadium catalyst A1 of the present invention was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium pentoxide (V2O5) in vanadium catalyst A1 was 7.6 wt%; the activity of vanadium catalyst A1 was 36.5% at 390℃ and 58.3% at 410℃.
[0056] Example 2 (1) Add 13.8 kg KOH, 6.1 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 115 °C for 1.5 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.0, Na / V molar ratio of 1.8).
[0057] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 12.72 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of boric acid with a concentration of 90 wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.5.
[0058] (3) The mixed colloid obtained in step (2), 46.56 kg of diatomaceous earth, 5.5 kg of cesium sulfate and 1.5 kg of lanthanum sulfate are put into a kneader and mixed for 1.8 h. The resulting mixture is then extruded and molded.
[0059] (4) The product obtained after extrusion molding in step (3) is placed in a spray drying fluidized bed at a temperature of 130°C for spray drying. Air at 160°C is sprayed out at a speed of 400 m / s using an airflow atomizer. The dried sample is placed in a tunnel kiln for calcination at a temperature of 550°C for 1.5 h to obtain the vanadium catalyst A2 of the present invention.
[0060] The vanadium catalyst A2 of the present invention was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium pentoxide (V2O5) in vanadium catalyst A2 was 7.0 wt%; the activity of vanadium catalyst A2 was 36.2% at 390℃ and 56.5% at 410℃.
[0061] Example 3 (1) Add 17.5 kg KOH, 9.1 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 110 °C for 1.8 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.8, Na / V molar ratio of 2.7).
[0062] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 12.72 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of boric acid with a concentration of 88wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.6.
[0063] (3) The mixed colloid obtained in step (2), 46.56 kg of diatomaceous earth, 5.5 kg of cesium sulfate and 1.5 kg of lanthanum sulfate are put into a kneader and mixed for 1.2 h. The resulting mixture is then extruded and molded.
[0064] (4) The product obtained after extrusion molding in step (3) is placed in a spray drying fluidized bed at a temperature of 120°C for spray drying. Air at 180°C is sprayed out at a speed of 450 m / s using an airflow atomizer. The dried sample is placed in a tunnel kiln for calcination at a temperature of 540°C for 1.2 h to obtain the vanadium catalyst A3 of the present invention.
[0065] The vanadium catalyst A3 of the present invention was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium pentoxide (V2O5) in vanadium catalyst A3 was 7.5 wt%; the activity of vanadium catalyst A3 was 36.3% at 390°C and 57.1% at 410°C.
[0066] Example 4 (1) Add 13.8 kg KOH, 8.8 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 120 °C for 1.8 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.0, Na / V molar ratio of 2.6).
[0067] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 10.08 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of boric acid with a concentration of 85 wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.5.
[0068] (3) The mixed colloid obtained in step (2), 50.38 kg of diatomaceous earth, 5.5 kg of cesium sulfate and 1.5 kg of lanthanum sulfate are put into a kneader and mixed for 1.3 h. The resulting mixture is then extruded and molded.
[0069] (4) The product obtained after extrusion molding in step (3) is placed in a spray drying fluidized bed at a temperature of 128°C for spray drying. Air at 160°C is sprayed out at a speed of 350 m / s using an airflow atomizer. The dried sample is placed in a tunnel kiln for calcination at a temperature of 530°C for 1.8 h to obtain the vanadium catalyst A4 of the present invention.
[0070] The vanadium catalyst A4 of the present invention was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium pentoxide (V2O5) in vanadium catalyst A4 was 7.1 wt%; the activity of vanadium catalyst A4 was 34.7% at 390°C and 55.2% at 410°C.
[0071] Example 5 (1) Add 16.2 kg KOH, 4.95 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 120 °C for 2 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.5, Na / V molar ratio of 1.5).
[0072] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 10.07 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of boric acid with a concentration of 90 wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.2.
[0073] (3) The mixed colloid obtained in step (2), 53.85 kg of diatomaceous earth, 5.5 kg of cesium sulfate and 1.5 kg of lanthanum sulfate are put into a kneader and mixed for 1.5 h. The resulting mixture is then extruded and molded.
[0074] (4) The product obtained after extrusion molding in step (3) is placed on a spray drying fluidized bed at a temperature of 124°C for spray drying. Superheated steam at 170°C is sprayed out at a speed of 350 m / s using an airflow atomizer. The dried sample is placed in a tunnel kiln for calcination at a temperature of 540°C for 1.5 h to obtain the vanadium catalyst A5 of the present invention.
[0075] The vanadium catalyst A5 of the present invention was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium pentoxide (V2O5) in vanadium catalyst A5 was 7.4 wt%; the activity of vanadium catalyst A5 was 30.5% at 390℃ and 52.5% at 410℃.
[0076] Example 6 (1) Add 16.2 kg KOH, 9.23 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 120 °C for 1.5 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.5, Na / V molar ratio of 2.8).
[0077] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 12.98 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of boric acid with a concentration of 88 wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.4.
[0078] (3) The mixed colloid obtained in step (2), 45.75 kg of diatomaceous earth, 5.5 kg of cesium sulfate and 1.5 kg of lanthanum sulfate are put into a kneader and mixed for 1.6 h. The resulting mixture is then extruded and molded.
[0079] (4) The product obtained after extrusion molding in step (3) is placed on a spray drying fluidized bed at a temperature of 125°C for spray drying. Superheated steam at 180°C is sprayed out at a speed of 400 m / s using an airflow atomizer. The dried sample is placed in a tunnel kiln for calcination at a temperature of 550°C for 1.6 h to obtain the vanadium catalyst A6 of the present invention.
[0080] The vanadium catalyst A6 of the present invention was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium pentoxide (V2O5) in vanadium catalyst A6 was 7.6 wt%; the activity of vanadium catalyst A6 was 36.0% at 390℃ and 55.6% at 410℃.
[0081] Example 7 (1) Add 16.61 kg KOH, 8.8 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 120 °C for 2 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.5, Na / V molar ratio of 2.8).
[0082] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 12.99 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of boric acid with a concentration of 86 wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.8.
[0083] (3) The mixed colloid obtained in step (2), 45.42 kg of diatomaceous earth, 5.5 kg of cesium sulfate and 1.5 kg of lanthanum sulfate are put into a kneader and mixed for 1.5 h. The resulting mixture is then extruded and molded.
[0084] (4) The product obtained after extrusion molding in step (3) is placed in a spray drying fluidized bed at a temperature of 126°C for spray drying. Air at 160°C is sprayed out at a speed of 350 m / s using an airflow atomizer. The dried sample is placed in a tunnel kiln for calcination at a temperature of 550°C for 1.4 h to obtain the vanadium catalyst A7 of the present invention.
[0085] The vanadium catalyst A7 of the present invention was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium pentoxide (V2O5) in vanadium catalyst A7 was 7.5 wt%; the activity of vanadium catalyst A7 was 36.1% at 390℃ and 55.5% at 410℃.
[0086] Example 8 (1) Add 16.2 kg KOH, 8.8 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 120 °C for 2 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.5, Na / V molar ratio of 2.6).
[0087] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 12.72 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of boric acid with a concentration of 90 wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.5.
[0088] (3) The mixed colloid obtained in step (2), 46.56 kg of diatomaceous earth and 7 kg of cerium sulfate are put into a kneader and mixed for 1.5 h. The resulting mixture is then extruded and molded.
[0089] (4) The product obtained after extrusion molding in step (3) is placed in a spray drying fluidized bed at a temperature of 125°C for spray drying. Air at 170°C is sprayed out at a speed of 350 m / s using an airflow atomizer. The dried sample is placed in a tunnel kiln for calcination at a temperature of 540°C for 1.5 h to obtain the vanadium catalyst A8 of the present invention.
[0090] The vanadium catalyst A8 of the present invention was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium pentoxide (V2O5) in vanadium catalyst A8 was 7.2 wt%; the activity of vanadium catalyst A8 was 34.7% at 390°C and 54.5% at 410°C.
[0091] Example 9 (1) Add 16.2 kg KOH, 8.8 kg NaOH and water to the reaction apparatus to prepare 34 L of Na-K system alkaline solution. Then add 7.5 kg V2O5 and react at 120 °C for 1.5 h to obtain Na-KV system vanadium aqueous solution (concentration of 220 g / L, K / V molar ratio of 3.5, Na / V molar ratio of 2.6).
[0092] (2) The Na-KV system vanadium aqueous solution obtained in step (1) was mixed with 12.72 L of concentrated sulfuric acid with a mass fraction of 98% to prepare a mixed colloidal substance containing V2O5, K2SO4 and Na2SO4, and then 1 L of boric acid with a concentration of 90 wt% was added. The pH value of the mixed colloidal substance was tested with a pH meter and found to be 2.4.
[0093] (3) The mixed colloid obtained in step (2), 46.56 kg of diatomaceous earth, 3 kg of cerium sulfate and 4 kg of lanthanum sulfate are put into a kneader and mixed for 1.5 h. The resulting mixture is then extruded and molded.
[0094] (4) The product obtained after extrusion molding in step (3) is placed in a spray drying fluidized bed at a temperature of 127°C for spray drying. Air at 160°C is sprayed out at a speed of 380 m / s using an airflow atomizer. The dried sample is placed in a tunnel kiln for calcination at a temperature of 530°C for 2 hours to obtain the vanadium catalyst A9 of the present invention.
[0095] The vanadium catalyst A9 of the present invention was weighed and its activity was tested. The test results are as follows: the mass fraction of vanadium catalyst A8 was 7.5 wt%; the activity of vanadium catalyst A9 was 34.9% at 390°C and 55.9% at 410°C.
[0096] Comparative Example 1 The vanadium catalyst was prepared according to the method of Example 1, except that in step (4), the drying process included: placing the product obtained after extrusion molding in step (3) in a regular oven and drying it at 105°C for 2 hours. Vanadium catalyst D1 was finally obtained. A scanning electron microscope image of vanadium catalyst D1 is shown below. Figure 2 As shown.
[0097] The vanadium catalyst D1 was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium catalyst D1 was 7.6 wt%; the activity of vanadium catalyst D1 was 27.4% at 390℃ and 48.8% at 410℃.
[0098] Comparative Example 2 The vanadium catalyst was prepared according to the method of Example 1, except that in step (1), the pH value of the mixed colloid was tested with a pH meter and found to be 4.5, thus obtaining vanadium catalyst D2.
[0099] The vanadium catalyst D2 was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium catalyst D2 was 7.5 wt%; the activity of vanadium catalyst D2 was 25.6% at 390℃ and 41.3% at 410℃.
[0100] Example 3 The vanadium catalyst was prepared according to the method of Example 1, except that in step (1), NaOH was replaced with KOH to obtain vanadium catalyst D3.
[0101] The vanadium catalyst D3 was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium catalyst D3 was 7.6 wt%; the activity of vanadium catalyst D3 was 24.6% at 390℃ and 42.5% at 410℃.
[0102] Example 4 The vanadium catalyst was prepared according to the method of Example 1, except that in step (1), KOH was replaced with NaOH to obtain vanadium catalyst D4.
[0103] The vanadium catalyst D4 was weighed and its activity was tested. The results are as follows: the mass fraction of vanadium catalyst D4 was 7.6 wt%; the activity of vanadium catalyst D4 was 23.1% at 390℃ and 36.5% at 410℃.
[0104] By comparing the scanning electron microscope images of the vanadium catalysts prepared in Example 1 and Comparative Example 1, it can be seen that spray drying at specific temperatures and flow rates can affect the pore structure of the catalyst, giving it more micropore channels and a larger specific surface area, which is beneficial for the adsorption of active substances.
[0105] The test results of the examples and comparative examples are shown in Table 1.
[0106] Table 1
[0107] The technical requirements for catalysts used in sulfuric acid production are shown in Table 2 below.
[0108] Table 2
[0109] As can be seen from the results in Table 1 and the technical requirements in Table 2, the vanadium catalyst prepared according to the method described in this invention has high activity for heat-resistant SO2 and meets the relevant technical indicators for industrial production.
[0110] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing a vanadium catalyst, characterized in that, The method includes the following steps: (1) React an alkaline solution containing sodium and potassium ions with V2O5 under heating conditions to obtain a Na-KV system vanadium aqueous solution; (2) The Na-KV system vanadium aqueous solution is mixed with concentrated sulfuric acid to obtain a mixed colloidal substance, wherein the amount of concentrated sulfuric acid used is such that the pH value of the mixed colloidal substance is 2-3; (3) The mixed colloid is mixed with a carrier and additives, and the resulting mixture is extruded. (4) The product obtained after extrusion molding is spray-dried and then roasted.
2. The method according to claim 1, characterized in that, In step (1), the amount of alkaline solution containing sodium and potassium ions and V2O5 is such that the K / V molar ratio in the prepared Na-KV system vanadium aqueous solution is (2.8-4):1 and the Na / V molar ratio is (1.5-2.8):
1.
3. The method according to claim 1 or 2, characterized in that, In step (1), the preparation process of the alkaline solution containing sodium ions and potassium ions includes mixing sodium hydroxide, potassium hydroxide and water.
4. The method according to any one of claims 1-3, characterized in that, In step (1), the reaction conditions include a temperature of 105-130℃ and a time of 1-2h.
5. The method according to any one of claims 1-4, characterized in that, In step (2), boric acid and / or phosphoric acid are also added during the mixing process; Preferably, the mass-to-volume ratio of the vanadium catalyst to the boric acid and the phosphoric acid is (90-110) kg: 1 L.
6. The method according to any one of claims 1-5, characterized in that, In step (1), the mass ratio of V2O5 to the vanadium catalyst is (6.5-8):100; and / or The mass ratio of the additive to the vanadium catalyst is (1-5):
100.
7. The method according to claim 1 or 6, characterized in that, The carrier is diatomaceous earth; and / or The auxiliary agent is at least one of cesium sulfate, lanthanum sulfate, and cerium sulfate.
8. The method according to any one of claims 1-7, characterized in that, In step (4), the spray drying process includes: placing the product obtained after extrusion molding on a spray drying fluidized bed at 120-130℃, and using an airflow atomizer to spray hot gas at a speed of ≥300m / s to spray dry the product obtained after extrusion molding; Preferably, the ejection velocity of the hot gas is 300-600 m / s; Preferably, the hot gas is at least one of air, nitrogen, and superheated steam; Preferably, the temperature of the hot gas is ≥150℃, and more preferably 160-180℃.
9. The method according to any one of claims 1-8, characterized in that, In step (4), the calcination conditions include a temperature of 530-560℃ and a time of 1-2h.
10. A vanadium catalyst prepared by the method according to any one of claims 1-9.
11. The vanadium catalyst according to claim 10, characterized in that, The active component of the vanadium catalyst has a size of 15-35 nm.
12. The application of the vanadium catalyst according to claim 10 or 11 in the wet acid production process.