Regeneration method of catalyst for preparing maleic anhydride through benzene oxidation and method for preparing maleic anhydride through benzene oxidation

Abstract

The invention discloses a regeneration method of a catalyst for preparing maleic anhydride through benzene oxidation and a method for preparing maleic anhydride through benzene oxidation. The regeneration method comprises the following steps: heating the inactivated benzene oxidation maleic anhydride catalyst, spraying a phosphomolybdic acid solution to the surface of the catalyst, and then drying and regenerating. According to the method, the catalyst can be reused, environmental pollution is reduced, and the use cost of the catalyst is reduced.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and specifically, to a method for regenerating a catalyst for oxidizing benzene to maleic anhydride and a method for oxidizing benzene to maleic anhydride. Background Art

[0002] Maleic anhydride is a very important organic chemical raw material and is the second largest organic acid anhydride after phthalic anhydride. As a chemical intermediate, maleic anhydride has a very wide range of uses. It can be used to produce unsaturated polyester resin (UPR), 1,4-butanedioic acid, 1,4-butanediol, tetrahydrofuran, γ-butyrolactone, malic acid and other products, and can also be used to produce pharmaceuticals, pesticides and food additives. Unsaturated polyester resin (UPR) is the largest consumer product downstream of maleic anhydride, and its consumption can account for more than 60% of the total consumption of maleic anhydride.

[0003] In the process of producing maleic anhydride by the benzene method, the most important is the V-Mo series catalyst, which plays a very important role in the reaction of oxidizing benzene to maleic anhydride. The preparation of this catalyst involves spraying and activation processes, and inevitably generates dust and ammonia and other gases, bringing a series of pollutions to the environment. If the catalyst whose reaction is about to reach the end of its life can be regenerated to improve its performance and extend its service life, it can not only reduce costs for enterprises, but also reduce environmental pollution.

[0004] Patent CN101036891A introduces a method for preparing a fluidized bed catalyst for oxidizing n-butane to maleic anhydride. The main method is to capture the fine powder from the fluidized bed reaction, and spray-dry and regenerate the collected catalyst with a catalyst precursor and matrix powder, etc. The obtained catalyst is equivalent to the fresh catalyst in terms of activity, particle size and strength, etc. This method is actually a mixture of new and old catalysts. The old catalyst does not have a significant decrease in activity, but only the volume and mass of the catalyst decrease.

[0005] Patent CN111701624A introduces a regeneration method applicable to deactivated vanadium phosphorus oxygen catalysts. First, the catalyst is calcined at 550-750°C, and the calcined catalyst is heated under reflux in a mixed solvent of isobutanol and benzyl alcohol to obtain a regenerated catalyst. This activation process is similar to the preparation method of fresh catalysts. The regeneration of the catalyst includes the main steps and methods of fresh vanadium phosphorus oxygen catalysts, and the process is relatively complex, and also involves the use and treatment of a large amount of solvents such as benzyl alcohol and isobutanol.

[0006] Patent CN113413924A also invented a method for regenerating a catalyst, mainly for zeolite catalysts and metal oxide catalysts, and uses an oxygen-containing atmosphere for activation regeneration. This method is mainly aimed at the regeneration process of catalysts deactivated by carbon deposition on the catalyst surface. Summary of the Invention

[0007] The reaction of benzene oxidation to maleic anhydride is a strongly exothermic reaction. When the reaction occurs under long-term high-temperature conditions, important elements such as Mo and P in the V-Mo series catalyst will be lost, and this loss is usually irreversible. In terms of catalyst performance, over time, the conversion rate of benzene and the weight yield of maleic anhydride will decrease, and conventional methods such as calcination have no effect on catalyst regeneration.

[0008] To solve the problem of maleic anhydride catalyst regeneration in the above prior art, the present invention discovers that when an appropriate amount of molybdenum element and phosphorus element are added to the catalyst with decreased activity after the reaction, and then an appropriate regeneration method is adopted, the activity of the catalyst can be restored to the level of a fresh catalyst.

[0009] One object of the present invention is to provide a regeneration method for a benzene oxidation to maleic anhydride catalyst, comprising the following steps:

[0010] S1, heating the deactivated benzene oxidation to maleic anhydride catalyst;

[0011] S2, spraying a phosphomolybdic acid solution onto the surface of the catalyst;

[0012] S3, drying the catalyst obtained in step S2;

[0013] S4, regenerating the catalyst obtained in step S3, wherein the regeneration atmosphere is a mixed gas of trimethyl phosphate / ethanol / nitrogen.

[0014] The method of the present invention has no special limitation on the benzene oxidation to maleic anhydride catalyst, and it is a common V-Mo series catalyst in the art. Generally, the benzene oxidation to maleic anhydride catalyst includes a carrier and an active component, and the active component includes a main catalyst and an optional promoter. The contents of the main catalyst, promoter, and carrier are all common contents in the art.

[0015] According to some embodiments of the present invention, the main catalyst includes vanadium, molybdenum, and optionally one or more of sodium, phosphorus, or nickel. The promoter includes one or more of elements in Group III A, Group IV A, Group V A, Group VI, Group VIII, etc.

[0016] The carrier can be a common carrier such as silicon carbide, alumina, silica, etc. According to some embodiments of the present invention, the shape of the carrier is any one of spherical, cylindrical, annular, three-leaf clover-shaped, and four-leaf clover-shaped.

[0017] According to some embodiments of the present invention, the deactivated catalyst refers to the catalyst after being used for a period of time and evaluated under normal operating conditions (generally at a molten salt temperature of 350 - 360 °C and a space velocity of 2000 - 2500 h-1 , the benzene load is 40 - 55 g / Nm 3 ), corresponding to a benzene conversion rate of 92 - 96% and a maleic anhydride weight yield of less than 90%, which is no longer suitable for industrial applications.

[0018] According to some embodiments of the present invention, in step S1, it is heated to a temperature of 40 - 80°C.

[0019] According to some embodiments of the present invention, the regenerated molybdenum source and phosphorus source are phosphomolybdic acid solution, which can better enter the catalyst bulk phase to supplement the reduced molybdenum and phosphorus elements during catalyst use. The addition amounts of the molybdenum source and phosphorus source are crucial for catalyst regeneration. If the addition amounts of the molybdenum source and phosphorus source are insufficient, the catalyst activity improvement is not obvious; if the addition amounts of the molybdenum source and phosphorus source are excessive, the catalyst activity is too high, and the maleic anhydride selectivity significantly decreases, resulting in a significant decrease in yield.

[0020] According to some embodiments of the present invention, in step S2, the solvent of the phosphomolybdic acid solution is at least one of methanol and ethanol.

[0021] The concentration of the phosphomolybdic acid solution is 1 - 5 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc.

[0022] According to some embodiments of the present invention, the flow rate of the acid molybdic acid solution is 0.05 - 0.5 mL / min, such as 0.05 mL / min, 0.1 mL / min, 0.2 mL / min, 0.3 mL / min, 0.4 mL / min, 0.5 mL / min, etc.

[0023] According to some embodiments of the present invention, in step S2, the weight ratio of phosphomolybdic acid to the catalyst is 0.00001 - 0.001, preferably 0.00002 - 0.0002, such as 0.00001, 0.00002, 0.00005, 0.00008, 0.0001, 0.0002, 0.0005, 0.001, etc.

[0024] According to some embodiments of the present invention, in step S2, nitrogen or air is used as the gas medium.

[0025] According to some embodiments of the present invention, in step S2, the spraying time is 1 - 30 minutes.

[0026] According to some embodiments of the present invention, in step S3, it is dried at 80 - 100°C for 2 - 5 hours.

[0027] According to some embodiments of the present invention, the regeneration atmosphere is a mixed gas of trimethyl phosphate / ethanol / nitrogen, wherein the molar ratio of trimethyl phosphate, ethanol and nitrogen is (0.0001 - 0.1):(0.0001 - 0.1):1, preferably (0.0001 - 0.001):(0.001 - 0.1):1.

[0028] According to some embodiments of the present invention, in step S4, the regeneration temperature is 420 - 480 °C, the regeneration time is 4 - 10 hours, and the regeneration space velocity is 500 - 3000 h -1 ; preferably, the regeneration temperature is 440 - 475 °C, the regeneration time is 5 - 8 hours, and the regeneration space velocity is 500 - 1500 h -1 .

[0029] The regeneration process is crucial for the regeneration of the catalyst for the oxidation of benzene to maleic anhydride. The regeneration process of the present invention can better activate and regenerate the catalyst and improve the performance of the catalyst.

[0030] According to some preferred embodiments of the present invention, the regeneration includes: heating the catalyst from room temperature to 140 - 160 °C at a heating rate of 70 - 150 °C / h, holding for 5 - 30 minutes, then heating to 240 - 260 °C at a heating rate of 60 - 120 °C / h, at this time introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen, holding for 5 - 30 minutes, then heating to 340 - 360 °C at a heating rate of 50 - 100 °C / h, holding for 10 - 60 minutes, and finally heating to 420 - 480 °C at a heating rate of 40 - 90 °C / h, maintaining for 4 - 10 hours, and then cooling to room temperature at a rate of 40 - 80 °C / h.

[0031] A second object of the present invention is to provide a catalyst for the oxidation of benzene to maleic anhydride obtained by the regeneration method.

[0032] A third object of the present invention is to provide a method for the oxidation of benzene to maleic anhydride, using the catalyst for the oxidation of benzene to maleic anhydride obtained by the regeneration method.

[0033] In the method for producing maleic anhydride using the regenerated catalyst of the present invention, maleic anhydride is prepared by oxidizing a mixed gas of benzene and air through a fixed-bed reactor filled with the regenerated catalyst.

[0034] According to some embodiments of the present invention, in order to prevent the danger caused by too high benzene concentration, the concentration of benzene in the mixed gas is 40 - 55 g / Nm 3 .

[0035] According to some embodiments of the present invention, the volume space velocity of the mixed gas is 1500 - 3000 h -1 .

[0036] According to some embodiments of the present invention, the volumetric space velocity of the mixed gas is preferably 2000 - 2500 h -1 .

[0037] According to some embodiments of the present invention, a molten salt bath is used for heating and removing heat.

[0038] According to some embodiments of the present invention, the temperature of the molten salt is 340 - 360 °C.

[0039] According to some embodiments of the present invention, the reaction pressure is negative pressure, normal pressure or positive pressure.

[0040] According to some embodiments of the present invention, the reaction pressure is normal pressure.

[0041] According to some embodiments of the present invention, a fixed bed reactor is used in the process of the present invention, and a molten salt bath is used for heating and removing heat. During the evaluation of the reaction process, the temperatures at different positions from top to bottom in the catalyst bed are inconsistent. The highest value in the temperature region is called the hot spot temperature of the catalyst, and the corresponding bed height is the hot spot position of the catalyst. In the present invention, a thermocouple is used to measure the temperature by pulling the bed layer. The benzene concentration refers to the number of grams of benzene contained in unit volume of air. The higher the value, the higher the content of benzene in the air.

[0042] Advantages of the present invention:

[0043] (1) The catalyst regenerated by the present method can reuse the catalyst, reducing the treatment cost of a large amount of solid hazardous waste;

[0044] (2) The catalyst regenerated by the present method can reuse the catalyst, avoid treating a large amount of solid hazardous waste, and reduce environmental pollution;

[0045] (3) The catalyst regenerated by the present method saves metal resources such as vanadium and molybdenum, reducing the consumption of metal resources;

[0046] (4) The catalyst regenerated by the present method can reduce the use cost of the catalyst, saving costs for the enterprise. Specific embodiments

[0047] The present invention will be described in detail below in conjunction with embodiments, but the present invention is not limited by the following embodiments. The raw materials or components used in the present invention can be obtained through commercial channels or conventional methods without special instructions. In the following quantitative tests of the embodiments, three repeated experiments are set, and the results are averaged.

[0048] According to a preferred embodiment of the present invention, the regeneration method includes the following steps:

[0049] S1. Place the catalyst in a sieve and heat the catalyst to 40 - 80 °C;

[0050] S2. Take an ethanol solution of 1 - 5% phosphomolybdic acid and spray the above solution onto the surface of the catalyst through a nozzle, using nitrogen as the gas medium, with a duration of 1 - 30 minutes;

[0051] S3. Transfer the above catalyst to an oven and dry it at 80 - 100 °C for 2 - 5 hours;

[0052] S4. Transfer the catalyst to an activation furnace for activation and regeneration. The regeneration temperature is 420 - 480 °C. The regeneration atmosphere is a mixture of trimethyl phosphate / ethanol / nitrogen, and the molar ratio of the three substances is (0.0001 - 0.1):(0.0001 - 0.1):1. The regeneration time is 4 - 10 hours, and the regeneration space velocity is 500 - 3000 h -1 。

[0053] In the examples of the present invention, the deactivated catalyst is a fresh catalyst obtained from the following preparation method:

[0054] Step A: Dissolve 980 g of oxalic acid in 4800 mL of water at room temperature, add 689.0 g of ammonium metavanadate, and add it while stirring until the ammonium metavanadate is dissolved to form a dark green solution; dissolve 302.0 g of ammonium molybdate in 450 mL of water and add this solution to the above ammonium metavanadate solution; sequentially add 41.1 g of trisodium phosphate, 12.1 g of nickel nitrate, 11.0 g of bismuth nitrate, and 14.1 g of iron nitrate under stirring, and prepare a catalyst active mother liquor after mixing.

[0055] Step B: Place 3300 g of the carrier into a rotatable and heatable stainless - steel drum. A thermocouple sleeve is provided at the bottom of the carrier, and the internal thermocouple is connected to a temperature display instrument to display the temperature change during the spraying process in real - time. Adjust the drum rotation speed to 10 - 20 revolutions per minute. When the carrier temperature is heated to 250 °C, spray the above - mentioned catalyst active component mixture in a dark green slurry state onto the carrier through a special nozzle. The spraying temperature is 250 - 270 °C. After spraying, dry the catalyst precursor and weigh to obtain 3984 g of the catalyst precursor. Based on the total mass of the catalyst, the adhesion amount of the active substance is 17.2%.

[0056] Step C: Place 1500 g of the above catalyst precursor in an activation furnace. After sealing, raise the temperature from room temperature to 150 °C at a heating rate of 150 °C / h and hold for 5 minutes. Then raise the temperature to 250 °C at a heating rate of 120 °C / h and hold for 10 minutes. Next, raise the temperature to 350 °C at a heating rate of 100 °C / h and hold at 350 °C for 20 minutes. Then raise the temperature to 450 °C at a heating rate of 90 °C / h and hold at this temperature for 5 hours. Subsequently, gradually lower the temperature to room temperature to obtain a fresh catalyst.

[0057] The deactivated catalyst obtained after the reaction of the above catalyst is selected in the present invention.

[0058] Example 1

[0059] Step A: Place 200 g of the deactivated catalyst in a sieve. At a molten salt temperature of 350 °C, the corresponding benzene conversion rate of this catalyst is 92%. The sieve is placed in a heatable oven. A thermocouple sleeve is provided at the bottom of the catalyst, and the internal thermocouple is connected to a temperature display instrument to display the catalyst bed temperature in real time. Adjust the oven temperature to make the catalyst temperature reach 40 °C.

[0060] Step B: Use a liquid pump to transport an ethanol solution of 1% phosphomolybdic acid, and spray the above solution onto the catalyst surface through a nozzle. The nozzle is provided with two paths, one is a nitrogen gas path and the other is a liquid path. The pressure of nitrogen is set to 0.01 MPa, and the flow rate of the ethanol solution of phosphomolybdic acid is 0.1 mL / min. The spraying time is kept for 20 minutes. According to the humidity of the catalyst surface, the spraying process can be continuous or intermittent, and the total spraying duration is accumulated to 20 minutes. Transfer the above catalyst to the oven and dry it at 80 °C for 2 hours.

[0061] Step C: Transfer the catalyst to an activation furnace for activation and regeneration. Raise the temperature of the catalyst from room temperature to 150 °C at a heating rate of 70 °C / h and hold for 5 minutes. Then raise the temperature to 250 °C at a heating rate of 60 °C / h and hold for 5 minutes. At this time, introduce a mixed gas of trimethyl phosphate / ethanol / nitrogen, and the molar ratio of the three is 0.0001:0.001:1, and the space velocity is 500 h -1 , then raise the temperature to 350 °C at a heating rate of 50 °C / h and hold for 10 minutes. Finally, raise the temperature to 450 °C at a heating rate of 40 °C / h and maintain for 5 hours. Then lower the temperature to room temperature at a rate of 60 °C / h. Stop introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen during the cooling process to obtain the regenerated catalyst A.

[0062] Load catalyst A into the fixed-bed reactor for testing. Use a molten salt temperature of 350 °C, and the results are shown in Table 1.

[0063] Example 2

[0064] Step A: Place 200 g of the deactivated catalyst in a sieve. At a molten salt temperature of 350 °C, the corresponding benzene conversion rate of this catalyst is 94%. The sieve is placed in a heatable oven. A thermocouple sleeve is provided at the bottom of the catalyst, and the internal thermocouple is connected to a temperature display instrument to display the catalyst bed temperature in real time. Adjust the oven temperature to make the catalyst temperature reach 40 °C.

[0065] Step B: Use a liquid pump to transport an ethanol solution of 5% phosphomolybdic acid, and spray the above solution onto the surface of the catalyst through a nozzle. The nozzle is provided with two paths, one is a nitrogen gas path and the other is a liquid path. The pressure of nitrogen is set to 0.01 MPa, the flow rate of the ethanol solution of phosphomolybdic acid is 0.1 mL / min, and the spraying time is maintained for 5 minutes. According to the humidity of the catalyst surface, the spraying process can be continuous or intermittent, and the total spraying duration is accumulated to 5 minutes. Transfer the above catalyst to the oven and dry it at 80 °C for 2 hours.

[0066] Step C: Transfer the catalyst to an activation furnace for activation and regeneration. Heat the catalyst from room temperature to 150 °C at a heating rate of 70 °C / h and hold for 5 minutes, then heat it to 250 °C at a heating rate of 60 °C / h and hold for 5 minutes. At this time, introduce a mixed gas of trimethyl phosphate / ethanol / nitrogen, and the molar ratio of the three is 0.001:0.01:1, and the space velocity is 800 h -1 , then heat it to 350 °C at a heating rate of 50 °C / h and hold for 10 minutes, and finally heat it to 470 °C at a heating rate of 40 °C / h and maintain for 5 hours, and then cool it to room temperature at a rate of 60 °C / h. Stop introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen during cooling to obtain the regenerated catalyst B.

[0067] Load catalyst B into the fixed-bed reactor for testing. The molten salt temperature is 350 °C, and the results are shown in Table 1.

[0068] Example 3

[0069] Step A: Place 200 g of the deactivated catalyst in a sieve. At a molten salt temperature of 350 °C, the corresponding benzene conversion rate of this catalyst is 92%. The sieve is placed in a heatable oven. A thermocouple sleeve is provided at the bottom of the catalyst, and the internal thermocouple is connected to a temperature display instrument to display the catalyst bed temperature in real time. Adjust the oven temperature to make the catalyst temperature reach 40 °C.

[0070] Step B: Use a liquid pump to transport an ethanol solution of 5% phosphomolybdic acid, and spray the above solution onto the surface of the catalyst through a nozzle. The nozzle is provided with two paths, one is a nitrogen gas path and the other is a liquid path. The pressure of nitrogen is set to 0.01 MPa, the flow rate of the ethanol solution of phosphomolybdic acid is 0.5 mL / min, and the spraying time is maintained for 2 minutes. According to the humidity of the catalyst surface, the spraying process can be continuous or intermittent, and the total spraying duration is accumulated to 2 minutes. Transfer the above catalyst to an oven and dry it at 80 °C for 2 hours.

[0071] Step C: Transfer the catalyst to an activation furnace for activation and regeneration. Heat the catalyst from room temperature to 150 °C at a heating rate of 70 °C / h and hold for 5 minutes, then heat it to 250 °C at a heating rate of 60 °C / h and hold for 5 minutes. At this time, introduce a mixed gas of trimethyl phosphate / ethanol / nitrogen, and the molar ratio of the three is 0.0001:0.1:1, and the space velocity is 1500 h -1 , then heat it to 350 °C at a heating rate of 50 °C / h and hold for 10 minutes, and finally heat it to 440 °C at a heating rate of 40 °C / h and maintain for 8 hours, and then cool it to room temperature at a rate of 60 °C / h. Stop introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen during cooling to obtain the regenerated catalyst C.

[0072] Load the catalyst C into the fixed-bed reactor for testing. The molten salt temperature is 350 °C, and the results are shown in Table 1.

[0073] Example 4

[0074] Step A: Take 200 g of the deactivated catalyst and place it in a sieve. At a molten salt temperature of 350 °C, the corresponding benzene conversion rate of this catalyst is 96%. The sieve is placed in a heatable oven. There is a thermocouple sleeve at the bottom of the catalyst, and the internal thermocouple is connected to a temperature display instrument to display the catalyst bed temperature in real time. Adjust the oven temperature to make the catalyst temperature reach 40 °C.

[0075] Step B: Use a liquid pump to transport an ethanol solution of 1% phosphomolybdic acid, and spray the above solution onto the surface of the catalyst through a nozzle. The nozzle is provided with two paths, one is a nitrogen gas path and the other is a liquid path. The pressure of nitrogen is set to 0.01 MPa, the flow rate of the ethanol solution of phosphomolybdic acid is 0.1 mL / min, and the spraying time is maintained for 10 minutes. According to the humidity of the catalyst surface, the spraying process can be continuous or intermittent, and the total spraying duration is accumulated to 10 minutes. Transfer the above catalyst to an oven and dry it at 80 °C for 2 hours.

[0076] Step C: Transfer the catalyst to an activation furnace for activation and regeneration. Heat the catalyst from room temperature to 150 °C at a heating rate of 70 °C / h and hold for 5 minutes. Then, heat it to 250 °C at a heating rate of 60 °C / h and hold for 5 minutes. At this time, introduce a mixed gas of trimethyl phosphate / ethanol / nitrogen, with a molar ratio of 0.0001:0.01:1 and a space velocity of 1000 h -1 , then heat it to 350 °C at a heating rate of 50 °C / h and hold for 10 minutes. Finally, heat it to 440 °C at a heating rate of 40 °C / h and maintain for 8 hours. Then, cool it to room temperature at a rate of 60 °C / h. Stop introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen during cooling to obtain the regenerated catalyst D.

[0077] Load the catalyst D into the fixed-bed reactor for testing. Use a molten salt temperature of 350 °C. The results are shown in Table 1.

[0078] Example 5

[0079] Step A: Take 200 g of the deactivated catalyst and place it in a sieve. At a molten salt temperature of 350 °C, the corresponding benzene conversion rate of this catalyst is 96%. The sieve is placed in a heatable oven. There is a thermocouple sleeve at the bottom of the catalyst, and the internal thermocouple is connected to a temperature display instrument to display the catalyst bed temperature in real time. Adjust the oven temperature to make the catalyst temperature reach 40 °C.

[0080] Step B: Use a liquid pump to transport an ethanol solution of 3% phosphomolybdic acid. Spray the above solution onto the catalyst surface through a nozzle. The nozzle is provided with two paths, one is a nitrogen gas path and the other is a liquid path. The pressure of nitrogen is set to 0.01 MPa, and the flow rate of the ethanol solution of phosphomolybdic acid is 0.1 mL / min. The spraying time is maintained for 8 minutes. According to the humidity of the catalyst surface, the spraying process can be continuous or intermittent, and the total spraying duration is accumulated to 8 minutes. Transfer the above catalyst to the oven and dry it at 80 °C for 2 hours.

[0081] Step C: Transfer the catalyst to an activation furnace for activation and regeneration. Heat the catalyst from room temperature to 150 °C at a heating rate of 70 °C / h and hold for 5 minutes. Then, heat it to 250 °C at a heating rate of 60 °C / h and hold for 5 minutes. At this time, introduce a mixed gas of trimethyl phosphate / ethanol / nitrogen, with a molar ratio of 0.0001:0.01:1 and a space velocity of 1500 h -1 , then heat it to 350 °C at a heating rate of 50 °C / h and hold for 10 minutes. Finally, heat it to 460 °C at a heating rate of 40 °C / h and maintain for 8 hours. Then, cool it to room temperature at a rate of 60 °C / h. Stop introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen during cooling to obtain the regenerated catalyst E.

[0082] The catalyst E was loaded into the fixed-bed reactor for testing. The molten salt temperature was 350 °C, and the results are shown in Table 1.

[0083] Example 6

[0084] Step A: 200 g of the deactivated catalyst was placed in a sieve. At a molten salt temperature of 350 °C, the corresponding benzene conversion rate of this catalyst was 94%. The sieve was placed in a heatable oven. A thermocouple sleeve was provided at the bottom of the catalyst, and the internal thermocouple was connected to a temperature display instrument to continuously display the catalyst bed temperature. The oven temperature was adjusted to make the catalyst temperature reach 60 °C.

[0085] Step B: An ethanol solution of 3% phosphomolybdic acid was pumped using a liquid pump, and the above solution was sprayed onto the surface of the catalyst through a nozzle. The nozzle was provided with two paths, one was a nitrogen gas path, and the other was a liquid path. The pressure of nitrogen was set at 0.01 MPa, and the flow rate of the ethanol solution of phosphomolybdic acid was 0.05 mL / min. The spraying time was maintained for 10 minutes. According to the humidity of the catalyst surface, the spraying process could be continuous or intermittent, and the total spraying duration was cumulatively maintained for 10 minutes. The above catalyst was transferred to the oven and dried at 80 °C for 2 hours.

[0086] Step C: The catalyst was transferred to an activation furnace for activation and regeneration. The catalyst was heated from room temperature to 150 °C at a heating rate of 70 °C / h and held for 5 minutes, then heated to 250 °C at a heating rate of 60 °C / h and held for 5 minutes. At this time, a mixed gas of trimethyl phosphate / ethanol / nitrogen was introduced, and the molar ratio of the three was 0.0001:0.001:1, and the space velocity was 1000 h -1 , and then heated to 350 °C at a heating rate of 50 °C / h and held for 10 minutes. Finally, it was heated to 470 °C at a heating rate of 40 °C / h and maintained for 8 hours, and then cooled to room temperature at a rate of 60 °C / h. When cooling, the introduction of the mixed gas of trimethyl phosphate / ethanol / nitrogen was stopped, and the regenerated catalyst F was obtained.

[0087] The catalyst F was loaded into the fixed-bed reactor for testing. The molten salt temperature was 350 °C, and the results are shown in Table 1.

[0088] Example 7

[0089] Step A: 200 g of the deactivated catalyst was placed in a sieve. At a molten salt temperature of 350 °C, the corresponding benzene conversion rate of this catalyst was 92%. The sieve was placed in a heatable oven. A thermocouple sleeve was provided at the bottom of the catalyst, and the internal thermocouple was connected to a temperature display instrument to continuously display the catalyst bed temperature. The oven temperature was adjusted to make the catalyst temperature reach 80 °C.

[0090] Step B: Use a liquid pump to transport an ethanol solution of 1% phosphomolybdic acid, and spray the above solution onto the surface of the catalyst through a nozzle. The nozzle is provided with two paths, one is a nitrogen gas path, and the other is a liquid path. The pressure of nitrogen is set to 0.01 MPa, the flow rate of the ethanol solution of phosphomolybdic acid is 0.05 mL / min, the spraying time is maintained for 30 minutes. According to the humidity of the catalyst surface, the spraying process can be continuous or intermittent, and the total spraying duration is accumulated to 30 minutes. Transfer the above catalyst to an oven and dry it at 80 °C for 2 hours.

[0091] Step C: Transfer the catalyst to an activation furnace for activation and regeneration. Heat the catalyst from room temperature to 150 °C at a heating rate of 70 °C / h and hold for 5 minutes, then heat it to 250 °C at a heating rate of 60 °C / h and hold for 5 minutes. At this time, introduce a mixed gas of trimethyl phosphate / ethanol / nitrogen, and the molar ratio of the three is 0.001:0.001:1, and the space velocity is 500 h -1 , then heat it to 350 °C at a heating rate of 50 °C / h and hold for 10 minutes, and finally heat it to 475 °C at a heating rate of 40 °C / h and maintain for 8 hours, and then cool it to room temperature at a rate of 60 °C / h. Stop introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen during cooling to obtain the regenerated catalyst G.

[0092] Load the catalyst G into the fixed-bed reactor for testing. The molten salt temperature is 350 °C, and the results are shown in Table 1.

[0093] Example 8

[0094] Step A: Take 200 g of the deactivated catalyst and place it in a sieve. At a molten salt temperature of 350 °C, the corresponding benzene conversion rate of this catalyst is 92%. The sieve is placed in a heatable oven. A thermocouple sleeve is provided at the bottom of the catalyst, and the internal thermocouple is connected to a temperature display instrument to display the catalyst bed temperature in real time. Adjust the oven temperature to make the catalyst temperature reach 80 °C.

[0095] Step B: Use a liquid pump to transport an ethanol solution of 4% phosphomolybdic acid, and spray the above solution onto the surface of the catalyst through a nozzle. The nozzle is provided with two paths, one is a nitrogen gas path, and the other is a liquid path. The pressure of nitrogen is set to 0.01 MPa, the flow rate of the ethanol solution of phosphomolybdic acid is 0.5 mL / min, the spraying time is maintained for 10 minutes. According to the humidity of the catalyst surface, the spraying process can be continuous or intermittent, and the total spraying duration is accumulated to 30 minutes. Transfer the above catalyst to an oven and dry it at 80 °C for 2 hours.

[0096] Step C: Transfer the catalyst to an activation furnace for activation and regeneration. Heat the catalyst from room temperature to 150°C at a heating rate of 70°C / h and hold for 5 minutes. Then, heat it to 250°C at a heating rate of 60°C / h and hold for 5 minutes. At this time, introduce a mixed gas of trimethyl phosphate / ethanol / nitrogen with a molar ratio of 0.001:0.001:1 and a space velocity of 500 h -1 , and then heat it to 350°C at a heating rate of 50°C / h and hold for 10 minutes. Finally, heat it to 475°C at a heating rate of 40°C / h and maintain for 8 hours. After that, cool it to room temperature at a rate of 60°C / h. Stop introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen during cooling to obtain the regenerated catalyst H.

[0097] Load the catalyst H into the fixed-bed reactor for testing. Use a molten salt temperature of 350°C. The results are shown in Table 1.

[0098] Comparative Example 1: Do not add an ethanol solution of phosphomolybdic acid

[0099] Prepare catalyst A1 according to the same method as in Example 1, except that an ethanol solution of phosphomolybdic acid is not added.

[0100] Load the catalyst A1 into the fixed-bed reactor for testing. Use a molten salt temperature of 350°C. The results are shown in Table 1.

[0101] Comparative Example 2: Add an ethanol solution of excessive phosphomolybdic acid

[0102] Prepare catalyst A2 according to the same method as in Example 1, except that the flow rate of the ethanol solution of phosphomolybdic acid is 1.0 mL / min and the time is maintained for 35 minutes.

[0103] Load the catalyst A2 into the fixed-bed reactor for testing. Use a molten salt temperature of 350°C. The results are shown in Table 1.

[0104] Comparative Example 3: Adopt a common closed activation method

[0105] Prepare catalyst A3 according to the same method as in Example 1, except that a conventional activation method is used to activate and regenerate the regenerated catalyst, that is, the mixed gas of trimethyl phosphate / ethanol / nitrogen is not introduced.

[0106] Load the catalyst A3 into the fixed-bed reactor for testing. Use a molten salt temperature of 350°C. The results are shown in Table 1.

[0107] Catalyst evaluation

[0108] The catalyst was loaded into a 120 ml bubbling molten salt circulating reactor. There was an inert carrier at the bottom of the reactor for support. 120 ml of the catalyst was loaded in the middle, and an inert carrier of a certain height was installed at the upper part. When the molten salt was heated to the reaction temperature, air was supplied, and benzene was fed simultaneously. After the benzene concentration reached the required operating condition concentration, sampling and analysis were started after stabilizing for 1 hour. The sampling and evaluation results of each catalyst are shown in Table 1. The calculation methods for each index are as follows:

[0109] Benzene conversion rate (%) = (amount of substance of benzene at the reactor inlet per unit time - amount of substance of benzene at the reactor outlet per unit time) / amount of substance of benzene at the reactor inlet per unit time × 100%;

[0110] Maleic anhydride weight yield (%) = benzene conversion rate × maleic anhydride selectivity × 98 / 78 × 100%.

[0111] Table 1 120 mL single-tube activity evaluation results

[0112]

[0113] It can be seen from Table 1 that the activity of the catalyst regenerated by the present invention has been significantly improved. The corresponding benzene conversion rate can reach more than 98% commonly used in industry, and the optimal weight yield of maleic anhydride can reach more than 95.0%.

[0114] It should be noted that the above embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as stipulated, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A regeneration method for a catalyst for producing maleic anhydride by benzene oxidation, comprising the following steps: S1, heating the deactivated catalyst for producing maleic anhydride by benzene oxidation; S2, spraying a phosphomolybdic acid solution onto the surface of the catalyst; S3, drying the catalyst obtained in step S2; S4, regenerating the catalyst obtained in step S3, wherein the regeneration atmosphere is a mixed gas of trimethyl phosphate / ethanol / nitrogen.

2. The regeneration method according to claim 1, characterized in that In step S1: The catalyst for producing maleic anhydride by benzene oxidation is a V-Mo series catalyst; and / or, heating to a temperature of 40 - 80 °C.

3. The regeneration method according to claim 1, wherein In step S2: The solvent of the phosphomolybdic acid solution is at least one of methanol and ethanol; and / or, using nitrogen or air as the gas medium; and / or, the spraying time is 1 - 30 minutes.

4. The regeneration method according to claim 1, characterized in that In step S2: The concentration of the phosphomolybdic acid solution is 1 - 5 wt%; and / or, the weight ratio of phosphomolybdic acid to the catalyst is 0.00001 - 0.001, preferably 0.00002 - 0.0002.

5. The regeneration method according to claim 1, wherein In step S3: drying at 80 - 100 °C for 2 - 5 hours.

6. The regeneration method according to claim 1, wherein In step S4: The molar ratio of trimethyl phosphate, ethanol and nitrogen is (0.0001 - 0.1):(0.0001 - 0.1):1, preferably (0.0001 - 0.001):(0.001 - 0.1):1; and / or, The regeneration temperature is 420 - 480 °C, the regeneration time is 4 - 10 hours, and the regeneration space velocity is 500 - 3000 h -1 ; Preferably, the regeneration temperature is 440 - 475 °C, the regeneration time is 5 - 8 hours, and the regeneration space velocity is 500 - 1500 h -1 .

7. The regeneration method according to claim 6, characterized in that The regeneration includes: heating the catalyst from room temperature to 140 - 160 °C at a heating rate of 70 - 150 °C / h, holding for 5 - 30 minutes, then heating to 240 - 260 °C at a heating rate of 60 - 120 °C / h, at this time introducing the mixed gas of trimethyl phosphate / ethanol / nitrogen, holding for 5 - 30 minutes, then heating to 340 - 360 °C at a heating rate of 50 - 100 °C / h, holding for 10 - 60 minutes, and finally heating to 420 - 480 °C at a heating rate of 40 - 90 °C / h, maintaining for 4 - 10 hours, and then cooling to room temperature at a rate of 40 - 80 °C / h.

8. A catalyst for producing maleic anhydride by benzene oxidation obtained by the regeneration method according to any one of claims 1 - 7.

9. A method for producing maleic anhydride by benzene oxidation, using the catalyst for producing maleic anhydride by benzene oxidation obtained by the regeneration method according to any one of claims 1 - 7.

10. According to the method of claim 9, wherein: using a mixed gas of benzene and air to oxidize and prepare maleic anhydride, wherein, The concentration of benzene in the mixed gas is 40 - 55 g / Nm 3 ; The volumetric space velocity of the mixed gas is 1500-3000 h -1 ; using a molten salt bath for heating and removing heat, and the molten salt temperature is 340 - 360 °C; the reaction pressure is negative pressure, normal pressure or positive pressure.

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