Catalysts with the function of benzene oxidation to maleic anhydride, their preparation methods and applications

Abstract

This invention relates to the field of benzene oxidation to maleic anhydride technology, and discloses a catalyst with benzene oxidation to maleic anhydride function, its preparation method, and its application. The catalyst includes a support and an active component supported on the support. The active component has a rod-shaped crystal structure with a grain diameter of less than 70 nm. The method includes loading the active component precursor onto the support and then activating it; wherein the activation is carried out in a mixed atmosphere of an inactive gas and hydrogen, the hydrogen content of which is 0.1-50% by volume. The catalyst prepared by this invention improves the selectivity of maleic anhydride, reaching over 80%, with a weight yield greater than 98%.

Description

Technical Field

[0001] This invention relates to the field of benzene oxidation to maleic anhydride technology, specifically to a catalyst with benzene oxidation to maleic anhydride function, its preparation method, and its application. Background Technology

[0002] The partial oxidation of benzene to maleic anhydride is a highly exothermic reaction with an enthalpy change of 1850 kJ / mol. If benzene is excessively oxidized to carbon dioxide, the enthalpy change reaches as high as 3274 kJ / mol. Clearly, if a significant portion of benzene is converted to carbon dioxide and other byproducts, the heat generated will increase dramatically, and the catalyst surface temperature will rise sharply. If the heat cannot be removed promptly during the production process, the catalyst bed temperature may become excessively high, potentially leading to partial combustion of benzene and maleic anhydride, producing large amounts of carbon monoxide and carbon dioxide as byproducts. Therefore, timely removal of the heat generated during the reaction is crucial for the partial oxidation of benzene. A common heat removal method is to add an appropriate amount of inert heat carrier. This can also improve catalyst selectivity, thereby reducing the amount of carbon monoxide and carbon dioxide produced, essentially minimizing the heat of reaction. Catalyst selectivity is related to various factors, including catalyst composition and preparation process.

[0003] V-Mo catalysts are important catalysts for the oxidation of benzene to maleic anhydride. Their preparation process involves spraying an active slurry containing V, Mo, and additives onto a high-temperature support to form a catalyst precursor, which is then activated to obtain the catalyst. Currently, industrially, closed-loop activation is mainly used for catalyst activation. CN1579631A discloses an activation method using a closed atmosphere, where activation is achieved by adjusting the ratio of ammonia and air produced during decomposition. This requires a strictly sealed solid-phase reactor, and the ammonia-to-air ratio during the holding period needs to be controlled at 1:10-1:5 using chromatographic analysis. Ammonia is a highly corrosive gas, placing very high demands on the equipment and apparatus. CN102371187A employs an activation method with inlet and outlet vent pipes on both sides of the activation furnace wall. During activation, the inlet vent pipe needs to be closed, while the outlet remains open. CN103816931A uses nitrogen gas for activation, selecting the inert gas nitrogen for catalyst activation. Summary of the Invention

[0004] The partial oxidation of benzene to maleic anhydride is a vigorous reaction that generates a large amount of heat. If this heat is not removed in time during production, the catalyst bed temperature may become excessively high, potentially leading to partial combustion of benzene and maleic anhydride and producing large amounts of carbon monoxide and carbon dioxide as byproducts. Therefore, timely removal of the heat generated during the reaction is crucial for the partial oxidation of benzene. The purpose of this invention is to overcome the problems of high heat of reaction and low catalyst selectivity in the existing technology for the oxidation of benzene to maleic anhydride, and to provide a catalyst with the function of oxidizing benzene to maleic anhydride, its preparation method, and its application.

[0005] To achieve the above objectives, the first aspect of the present invention provides a catalyst for the oxidation of benzene to maleic anhydride, the catalyst comprising a support and an active component supported on the support, the active component having a rod-shaped crystal structure and a grain diameter of less than 70 nm.

[0006] A second aspect of the present invention provides a method for preparing a catalyst with the function of benzene oxidation to maleic anhydride, the method comprising loading an active component precursor onto a support and then activating it;

[0007] The activation is carried out in a mixed atmosphere of inactive gas and hydrogen, wherein the hydrogen content in the mixed atmosphere is 0.1-50% by volume.

[0008] The third aspect of the present invention provides a catalyst prepared by the method described in the second aspect.

[0009] The fourth aspect of the present invention provides the application of the catalysts described in the first and third aspects or the catalysts prepared by the method described in the second aspect in the preparation of maleic anhydride by benzene oxidation.

[0010] The fifth aspect of the present invention provides a method for the oxidation of benzene to maleic anhydride, the method comprising: contacting benzene with oxygen in the presence of the catalysts described in the first and third aspects;

[0011] Alternatively, the method may include: preparing a catalyst according to the method described in the second aspect, and then contacting benzene with oxygen in the presence of the catalyst.

[0012] (1) The activation method of the present invention uses hydrogen and nitrogen atmosphere for activation, which makes it easy to adjust the reducing atmosphere and control the vanadium valence state and catalyst crystal phase structure.

[0013] (2) The activation process of the present invention can promote the formation of nanoscale crystal rods by active components with a diameter of less than 50 nm.

[0014] (3) By using the activation method of the present invention, the size of the crystal grains is controlled, the contact area between benzene and the catalyst is increased, and the activity of the catalyst is improved.

[0015] (4) The catalyst prepared by the present invention reduces the diffusion path of benzene and maleic anhydride, improves the selectivity of maleic anhydride to more than 80%, and the weight yield is greater than 98%. Attached Figure Description

[0016] Figure 1 This is a scanning electron microscope image of the active component on the catalyst prepared in Example 1;

[0017] Figure 2 This is a scanning electron microscope image of the active components on the catalyst prepared in Comparative Example 3. Detailed Implementation

[0018] 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.

[0019] The first aspect of the present invention provides a catalyst for the oxidation of benzene to maleic anhydride, the catalyst comprising a support and an active component supported on the support, the active component having a rod-shaped crystal structure, and the crystallite diameter of the active component being less than 70 nm, preferably less than 50 nm.

[0020] According to the present invention, preferably, the grain diameter of the active component is distributed in the range of 20-43 nm.

[0021] According to the present invention, preferably, the active component includes a first active component and a second active component, wherein the first active component includes Group VB metal oxides, Group VIB metal oxides, Group IA metal oxides, Group VA nonmetal oxides and Group VIII metal oxides, and the second active component includes quasi-metal oxides and / or post-transition metal oxides.

[0022] According to the present invention, preferably, the content of the active component is 10-20% by weight and the content of the support is 80-90% by weight, based on the total amount of the catalyst.

[0023] According to the present invention, preferably, the first active component includes oxides of vanadium, molybdenum, sodium, phosphorus, and nickel.

[0024] According to the present invention, preferably, the second active component includes at least one selected from indium oxide, antimony oxide, and bismuth oxide.

[0025] According to the present invention, preferably, the molar ratio of the first active component and the second active component, calculated as non-oxygen elements, is 10-2000:1, more preferably 100-1000:1.

[0026] According to the present invention, preferably, the vanadium oxide contains vanadium with an average valence state of 4.5-4.8.

[0027] According to the present invention, preferably, the vanadium oxide contains V 5+ and V 3+ V 5+ and V 3+ The molar ratio is 1.8-3:1.

[0028] According to the present invention, preferably, the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide and the second active component in the active component is 1:(0.2-0.90):(0.001-0.2):(0.005-0.25):(0.0001-0.05):(0.0001-0.05), wherein the vanadium oxide is calculated as V2O5, the molybdenum oxide as MoO3, the sodium oxide as Na2O, the phosphorus oxide as P2O5, the nickel oxide as NiO, and the second active component is calculated as a metal oxide.

[0029] A second aspect of the present invention provides a method for preparing a catalyst with the function of benzene oxidation to maleic anhydride, the method comprising loading an active component precursor onto a support and then activating it;

[0030] The activation is carried out in a mixed atmosphere of inactive gas and hydrogen, wherein the hydrogen content in the mixed atmosphere is 0.1-50% by volume.

[0031] According to the present invention, preferably, the inert gas is selected from nitrogen and / or an inert gas. The inert gas may be at least one of helium, neon, and argon.

[0032] According to the present invention, the space velocity of the gas mixture can be selected within a wide range, but in order to improve the catalytic effect, the volumetric space velocity of the gas mixture is preferably 500-3000 h⁻¹. -1 .

[0033] According to the present invention, preferably, the hydrogen content in the mixed gas is 2-20% by volume.

[0034] According to the present invention, preferably, the activation temperature is 250-480°C and the time is 3-15h.

[0035] According to the present invention, preferably, the activation temperature control procedure includes:

[0036] First stage: Increase the temperature to 150-170℃ at a rate of 60-120℃ / h, and hold for 5-30 minutes.

[0037] Second stage: Then, increase the temperature to 250-280℃ at a rate of 50-110℃ / h, and hold for 5-30 minutes.

[0038] Third stage: Then, increase the temperature to 350-380℃ at a rate of 40-100℃ / h, and hold for 10-60 minutes.

[0039] Fourth stage: Increase the temperature to 400-480℃ at a rate of 30-90℃ / h and maintain it for 3-10 hours.

[0040] According to the present invention, preferably, the heating rate of the preceding stage in the activated temperature control program is 5-15°C higher than the heating rate of the following stage, more preferably 8-12°C. For example, the heating rate of the first stage is 5-15°C higher than the heating rate of the second stage, the heating rate of the second stage is 5-15°C higher than the heating rate of the third stage, and the heating rate of the third stage is 5-15°C higher than the heating rate of the fourth stage.

[0041] According to the present invention, taking into account both the effect of the catalyst and the utilization rate of raw materials, preferably, a mixture of inactive gas and hydrogen is provided at the beginning of the third stage of the activation temperature control procedure.

[0042] According to the present invention, preferably, the activation temperature control procedure further includes: a fifth stage: reducing the temperature to 15-40°C at a rate of 40-90°C / h. It is understood that the introduction of the mixed atmosphere of inactive gas and hydrogen is stopped at the end of the fourth stage, i.e., the fifth stage (cooling stage) no longer continues to introduce the mixed atmosphere of inactive gas and hydrogen.

[0043] By employing the activation method of the present invention, vanadium oxide in the active component can be made to contain V. 5+ and V 3+ V 5+ and V 3+ The molar ratio is 1.8-3:1.

[0044] According to the present invention, preferably, the active component precursor includes a first active component precursor and a second active component precursor, wherein the first active component precursor includes a Group VB metal oxide precursor, a Group VIB metal oxide precursor, a Group IA metal oxide precursor, a Group VA nonmetal oxide precursor, and a Group VIII metal oxide precursor, and the second active component precursor includes a quasi-metal oxide precursor and / or a post-transition metal oxide precursor.

[0045] According to the present invention, preferably, the amounts of the active component precursor and the support are such that, based on the total amount of the catalyst, the content of the active component is 10-20% by weight and the content of the support is 80-90% by weight.

[0046] According to the present invention, preferably, the first active component precursor includes a vanadium oxide precursor, a molybdenum oxide precursor, a sodium oxide precursor, a phosphorus oxide precursor, and a nickel oxide precursor.

[0047] According to the present invention, preferably, the second active component precursor includes at least one selected from indium oxide precursor, antimony oxide precursor and bismuth oxide precursor.

[0048] According to the present invention, preferably, the oxide precursor of indium is indium acetate.

[0049] According to the present invention, preferably, the oxide precursor of antimony is antimony trichloride.

[0050] According to the present invention, the vanadium oxide precursor can be any substance capable of providing vanadium and converting it into vanadium oxide. Preferably, the vanadium oxide precursor includes at least one of ammonium metavanadate, vanadium pentoxide, and sodium vanadate.

[0051] According to the present invention, the molybdenum oxide precursor can be any substance capable of providing molybdenum and converting it into molybdenum oxide. Preferably, the molybdenum oxide precursor includes at least one of ammonium molybdate, molybdenum trioxide, and calcium molybdate.

[0052] According to the present invention, the sodium oxide precursor can be any substance capable of providing sodium and converting it into sodium oxide. Preferably, the sodium oxide precursor includes sodium dihydrogen phosphate and / or trisodium phosphate.

[0053] According to the present invention, the phosphorus oxide precursor can be any substance capable of providing phosphorus and converting it into phosphorus oxide. Preferably, the phosphorus oxide precursor includes at least one of ammonium dihydrogen phosphate, phosphoric acid (concentration of 85-115% by weight), and phosphorus pentoxide.

[0054] According to the present invention, the nickel oxide precursor can be any substance capable of providing nickel and converting it into nickel oxide. Preferably, the nickel oxide precursor includes at least one of nickel nitrate, nickel sulfate, nickel chloride, and nickel oxide.

[0055] According to the present invention, the amount of the active component precursor can be selected within a wide range. Preferably, the amount of the active component precursor is such that the molar ratio of the first active component (calculated as non-oxygen element) to the second active component (calculated as non-oxygen element) in the prepared catalyst is 10-2000:1, more preferably 100-1000:1.

[0056] According to the present invention, preferably, the amount of the active component precursor is such that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide and the second active component in the prepared catalyst is 1:(0.2-0.90):(0.001-0.2):(0.005-0.25):(0.0001-0.05):(0.0001-0.05), wherein the vanadium oxide is calculated as V2O5, the molybdenum oxide as MoO3, the sodium oxide as Na2O, the phosphorus oxide as P2O5, the nickel oxide as NiO, and the second active component as a metal oxide.

[0057] According to the present invention, there are no restrictions on the loading method; conventional techniques in the prior art can be used. Preferably, the loading method is as follows: coating a carrier with a mother liquor containing an active component precursor, followed by drying. The preparation method of the mother liquor containing the active component precursor can be: adding a first active component precursor and a second active component precursor to a reducing agent solution. The reducing agent solution can be an aqueous solution of oxalic acid. The drying conditions can include: a temperature of 100-150°C and a time of 2-8 hours.

[0058] According to the present invention, the equipment used for coating is not particularly limited, as long as it can load the active component onto the carrier. Preferably, the coating is performed in a rotatable and heatable stainless steel drum. The stainless steel drum is equipped with a thermocouple sheath for heating the carrier. The temperature of the thermocouple sheath is controllable and has a temperature display, allowing for real-time monitoring of carrier temperature changes during the coating process. The active component is sprayed onto the carrier through a nozzle to complete the coating. More preferably, during the coating process, the stainless steel drum rotates at 15-40 rpm / min. When the carrier is heated to 250-270°C, the spraying temperature is 250-300°C, while maintaining the carrier temperature at 260-270°C.

[0059] The third aspect of the present invention provides a catalyst prepared by the method described in the second aspect.

[0060] The fourth aspect of the present invention provides the application of the catalysts described in the first and third aspects or the catalysts prepared by the method described in the second aspect in the preparation of maleic anhydride by benzene oxidation.

[0061] The fifth aspect of the present invention provides a method for the oxidation of benzene to maleic anhydride, the method comprising: contacting benzene with oxygen in the presence of the catalysts described in the first and third aspects;

[0062] Alternatively, the method may include: preparing a catalyst according to the method described in the second aspect, and then contacting benzene with oxygen in the presence of the catalyst.

[0063] According to the present invention, preferably, the oxygen is in contact with benzene in the form of air. More preferably, to prevent the danger caused by excessively high benzene concentration, the concentration of benzene in the benzene-air mixture is 45-55 g / Nm³. 3 Benzene concentration refers to the mass of benzene contained in a unit volume of air, expressed in grams. The higher the value, the higher the benzene content in the air.

[0064] According to the present invention, preferably, the volume hourly space velocity (VHSV) of the benzene-air mixture is 1800-2800 h⁻¹. -1 More preferably 2000-2500h -1 .

[0065] According to the present invention, a molten salt bath can be used for heating and removing reaction heat during the oxidation of benzene to maleic anhydride. Preferably, the molten salt temperature is 340-360°C, more preferably 345-355°C.

[0066] The pressure test for benzene to come into contact with oxygen can be performed under normal pressure or under pressure.

[0067] During the evaluation reaction, the temperature in the catalyst bed is not uniform from top to bottom. The highest temperature in the range is called the hot spot temperature of the catalyst, and the corresponding bed height is the hot spot position of the catalyst. In this invention, thermocouples are used to measure the hot spot temperature by pulling the bed temperature.

[0068] The present invention will be described in detail below through embodiments. In the following embodiments,

[0069] Preparation Example 1

[0070] This preparation example is used to illustrate the preparation of catalyst precursors.

[0071] (1) Dissolve 92g of oxalic acid in 470mL of water at room temperature, add 65.6g of ammonium metavanadate while stirring until the ammonium metavanadate dissolves and a homogeneous and stable solution is formed. At this time, the solution is dark green. Dissolve ammonium molybdate in 40mL of water at 40℃ and dissolve it evenly. Add this solution to the ammonium metavanadate solution. Add trisodium phosphate, diammonium hydrogen phosphate, nickel nitrate and indium acetate in sequence while stirring. After mixing, a mother liquor containing the active component precursor is obtained.

[0072] (2) Take 300g of the prepared silicon carbide support and place it in a rotating and heatable stainless steel drum. Heating is performed using liquefied petroleum gas or natural gas. A thermocouple sheath is installed at the bottom of the support, and the internal thermocouple is connected to a temperature display instrument to show the temperature changes during spraying in real time. Adjust the drum speed to 15-40 rpm. When the support temperature reaches 250℃, spray the dark green slurry-like mother liquor containing the active component precursor onto the support through a special nozzle. The spraying temperature is 250-300℃, and the support temperature is maintained between 260-270℃. After spraying, dry at 120℃ for 4 hours to obtain the catalyst precursor. The catalyst precursor weighs 361g.

[0073] Preparation Example 2

[0074] This preparation example is used to illustrate the preparation of catalyst precursors.

[0075] (1) Dissolve 92g of oxalic acid in 470mL of water at room temperature, add 65.6g of ammonium metavanadate while stirring until the ammonium metavanadate dissolves and a homogeneous and stable solution is formed. At this time, the solution is dark green. Dissolve ammonium molybdate in 40mL of water at 40℃ and make it dissolve evenly. Add this solution to the above ammonium metavanadate solution. Add trisodium phosphate, diammonium hydrogen phosphate, nickel nitrate and indium acetate in sequence while stirring. After mixing, a mother liquor containing the active component precursor is obtained.

[0076] (2) Same as in Preparation Example 1. The weight of the catalyst precursor was 360 g.

[0077] Preparation Example 3

[0078] This preparation example is used to illustrate the preparation of catalyst precursors.

[0079] (1) Dissolve 92g of oxalic acid in 470mL of water at room temperature, add 65.6g of ammonium metavanadate while stirring until the ammonium metavanadate dissolves and a homogeneous and stable solution is formed. At this time, the solution is dark green. Dissolve ammonium molybdate in 40mL of water at 40℃ and make it dissolve evenly. Add this solution to the above ammonium metavanadate solution. Add trisodium phosphate, diammonium hydrogen phosphate, nickel nitrate and antimony trichloride in sequence while stirring. After mixing, a mother liquor containing the active component precursor is obtained.

[0080] (2) Same as in Preparation Example 1. The weight of the catalyst precursor was 358 g.

[0081] Example 1

[0082] The catalyst precursor from Preparation Example 1 was placed in an activation furnace, sealed, and activation began. Activation consisted of the following five stages:

[0083] First stage: Increase the temperature from room temperature to 150℃ at a rate of 120℃ / h and hold for 5 minutes;

[0084] Second stage: Increase the temperature to 250℃ at a rate of 110℃ / h and hold for 10 minutes;

[0085] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 500 h⁻¹. -1 The hydrogen content in the mixed gas is 2% by volume, and then the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20min.

[0086] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, raise the temperature to 450°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 8 hours;

[0087] Fifth stage: Stop the flow of mixed gas and cool the temperature to room temperature (about 25°C) at a rate of 90°C / h to obtain the catalyst.

[0088] The prepared catalyst was weighed, and the content of the active component was calculated to be 16.1% by weight and the content of the support was 83.9% by weight, based on the total amount of catalyst.

[0089] XRF elemental analysis revealed that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, and indium oxide in the active components of the catalyst was 1:0.55:0.058:0.041:0.016:0.007. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, and indium oxide as In2O3.

[0090] The scanning electron microscope (SEM) image of the active component on the catalyst prepared in this embodiment is shown below. Figure 1 As shown, from Figure 1 It can be seen that the active component in this embodiment has a rod-shaped crystal structure with a diameter of less than 50 nm and distributed in the range of 20-43 nm.

[0091] Example 2

[0092] The catalyst precursor from Preparation Example 1 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operation of the fourth stage was changed.

[0093] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, and raise the temperature to 450°C at a rate of 90°C / h. At this point, adjust the hydrogen content in the mixture to 4% by volume and maintain it at this temperature and atmosphere for 5 hours.

[0094] Example 3

[0095] The catalyst precursor from Preparation Example 2 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operation of the fourth stage was changed.

[0096] Fourth stage: Maintaining the space velocity and hydrogen content of the mixture from the third stage, increase the temperature to 450°C at a rate of 90°C / h. At this point, adjust the space velocity to 1000 h⁻¹. -1 And keep it at that temperature and atmosphere for 5 hours.

[0097] The prepared catalyst was weighed, and the content of the active component was calculated to be 15.7% by weight and the content of the support was 84.3% by weight, based on the total amount of catalyst.

[0098] XRF elemental analysis revealed that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, and indium oxide in the active components of the catalyst was 1:0.55:0.054:0.041:0.015:0.004. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, and indium oxide as In2O3.

[0099] Example 4

[0100] The catalyst precursor of Preparation Example 3 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operations of the third and fourth stages were changed.

[0101] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 1000 h⁻¹. -1 The hydrogen content in the mixed gas is 2% by volume, and then the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20min.

[0102] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, raise the temperature to 450°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 5 hours.

[0103] The prepared catalyst was weighed, and the content of the active component was calculated to be 15.5% by weight and the content of the support was 84.5% by weight, based on the total amount of catalyst.

[0104] XRF elemental analysis revealed that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, and antimony oxide in the active components of the catalyst was 1:0.55:0.058:0.044:0.017:0.008. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, and antimony oxide as Sb2O3.

[0105] Example 5

[0106] The catalyst precursor of Preparation Example 3 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operations of the third and fourth stages were changed.

[0107] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 1000 h⁻¹. -1 The hydrogen content in the mixed gas is 4% by volume. Then, the temperature is increased to 350°C at a rate of 100°C / h and held at 350°C for 20 minutes.

[0108] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, raise the temperature to 450°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 5 hours.

[0109] Example 6

[0110] The catalyst precursor of Preparation Example 3 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operations of the third and fourth stages were changed.

[0111] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 1000 h⁻¹. -1 The hydrogen content in the mixed gas is 6% by volume, and then the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20min.

[0112] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, raise the temperature to 450°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 5 hours.

[0113] Example 7

[0114] The catalyst precursor of Preparation Example 3 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operations of the third and fourth stages were changed.

[0115] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 1000 h⁻¹. -1The hydrogen content in the mixed gas is 8% by volume. Then, the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20min.

[0116] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, raise the temperature to 450°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 5 hours.

[0117] Example 8

[0118] The catalyst precursor from Preparation Example 1 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operations of the third and fourth stages were changed.

[0119] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 2000 h⁻¹. -1 The hydrogen content in the mixed gas is 2% by volume, and then the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20min.

[0120] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, raise the temperature to 450°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 5 hours.

[0121] Example 9

[0122] The catalyst precursor of Preparation Example 3 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operations of the third and fourth stages were changed.

[0123] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 2000 h⁻¹. -1 The hydrogen content in the mixed gas is 2% by volume, and then the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20min.

[0124] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, raise the temperature to 420°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 5 hours.

[0125] Example 10

[0126] The catalyst precursor of Preparation Example 3 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operations of the third and fourth stages were changed.

[0127] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 2000 h⁻¹. -1The hydrogen content in the mixed gas is 2% by volume, and then the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20min.

[0128] Fourth stage: Maintain the space velocity and hydrogen content of the mixture from the third stage, raise the temperature to 470°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 5 hours.

[0129] Example 11

[0130] The catalyst precursor from Preparation Example 1 was placed in an activation furnace, sealed, and then activated according to the method of Example 1, except that the operation of the third stage was changed.

[0131] Phase 3: Begin introducing a mixture of hydrogen and nitrogen gas at a space velocity of 500 h⁻¹. -1 The hydrogen content in the mixed gas is 35% by volume. Then, the temperature is increased to 350°C at a rate of 100°C / h and held at 350°C for 20 minutes.

[0132] Example 12

[0133] The catalyst precursor of Preparation Example 1 was placed in an activation furnace, sealed, and then activation was started.

[0134] The activation conditions included: heating from room temperature to 485°C at a rate of 120°C / h, and initially introducing a mixture of hydrogen and nitrogen gas with a space velocity of 500 h⁻¹. -1 The hydrogen content in the mixed gas is 2% by volume, and the mixture is kept at this temperature and atmosphere for 8 hours. Then the flow of the mixed gas is stopped, and the temperature is cooled to room temperature (about 25°C) at a rate of 90°C / h to obtain the catalyst.

[0135] Example 13

[0136] The catalyst precursor was prepared according to the method of Preparation Example 1, except that indium acetate was replaced with an equal mass of nickel nitrate. The prepared catalyst precursor was then activated in an activation furnace according to the method of Example 1.

[0137] Comparative Example 1

[0138] Activation is carried out in a closed air atmosphere.

[0139] The catalyst precursor from Preparation Example 1 was placed in an activation furnace, sealed, and then activated in a closed air atmosphere. Activation included the following five stages:

[0140] First stage: Increase the temperature from room temperature to 150℃ at a rate of 120℃ / h and hold for 5 minutes;

[0141] Second stage: Increase the temperature to 250℃ at a rate of 110℃ / h and hold for 10 minutes;

[0142] The third stage: the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20 minutes;

[0143] Fourth stage: Increase the temperature to 450℃ at a rate of 90℃ / h and maintain this temperature for 8 hours;

[0144] Fifth stage: The temperature is cooled to room temperature (approximately 25°C) at a rate of 90°C / h to obtain the catalyst.

[0145] Comparative Example 2

[0146] Activation is carried out in a closed nitrogen atmosphere.

[0147] The catalyst precursor from Preparation Example 1 was placed in an activation furnace, sealed, and then activated under a closed nitrogen atmosphere. Activation included the following five stages:

[0148] First stage: Increase the temperature from room temperature to 150℃ at a rate of 120℃ / h and hold for 5 minutes;

[0149] Second stage: Increase the temperature to 250℃ at a rate of 110℃ / h and hold for 10 minutes;

[0150] The third stage: the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20 minutes;

[0151] Fourth stage: Increase the temperature to 450℃ at a rate of 90℃ / h and maintain this temperature for 8 hours;

[0152] Fifth stage: The temperature is cooled to room temperature (approximately 25°C) at a rate of 90°C / h to obtain the catalyst.

[0153] Comparative Example 3

[0154] Activation is carried out in a nitrogen atmosphere.

[0155] The catalyst precursor from Preparation Example 1 was placed in an activation furnace, sealed, and activation began. Activation consisted of the following five stages:

[0156] First stage: Increase the temperature from room temperature to 150℃ at a rate of 120℃ / h and hold for 5 minutes;

[0157] Second stage: Increase the temperature to 250℃ at a rate of 110℃ / h and hold for 10 minutes;

[0158] Phase 3: Begin introducing nitrogen gas at a space velocity of 2000 h⁻¹. -1Then, the temperature is increased to 350℃ at a rate of 100℃ / h and held at 350℃ for 20 minutes.

[0159] Fourth stage: Maintain the nitrogen space velocity of the third stage, raise the temperature to 450°C at a rate of 90°C / h, and maintain this temperature and atmosphere for 8 hours;

[0160] Fifth stage: Stop the nitrogen gas supply and cool the temperature to room temperature (about 25°C) at a rate of 90°C / h to obtain the catalyst.

[0161] Scanning electron microscope (SEM) images of the active components on the catalyst prepared in this comparative example are shown below. Figure 2 As shown, from Figure 2 It can be seen that the active component particles in this preparation example are aggregated together, and the crystal rod structure is not obvious.

[0162] Comparative Example 4

[0163] Activation is carried out in a nitrogen atmosphere.

[0164] The catalyst precursor from Preparation Example 1 was placed in an activation furnace, sealed, and then activated according to the method of Comparative Example 3, except that the nitrogen space velocity was 500 h⁻¹. -1 .

[0165] Comparative Example 5

[0166] The catalyst was prepared according to the method of Example 1, except that the hydrogen content in the third stage was 70% by volume.

[0167] Test Example 1

[0168] (1) The grain size of the active components of the catalysts prepared in the above examples and comparative examples was characterized by SEM, and the results are shown in Table 1.

[0169] (2) The average valence state and V of vanadium in the vanadium oxides of the catalysts prepared in the above examples and comparative examples were determined using an automatic titrator. 5+ and V 3+ The molar ratio, the test method includes: (a) preparation of the sample to be tested: dissolving the active component in the catalyst with nitric acid, and then making up to volume using a volumetric flask. (b) V 3+ Determination of the number of moles: Take a certain volume of the sample to be tested and place it in an automatic titrator for titration with potassium permanganate. Determine V based on the result displayed by the automatic titrator. 3+ The number of moles. (c)V 5+ Determination of the molar number: A certain volume of the sample to be tested is placed in an automatic titrator and titrated with ferrous sulfate. The molar number V is determined based on the result displayed by the automatic titrator. 5+ The number of moles of vanadium can be calculated. The average valence state of vanadium can also be determined. The results are shown in Table 1.

[0170] (4) The catalysts prepared in the above examples and comparative examples were used for the oxidation of benzene to maleic anhydride. The reaction was carried out in a bubble-type molten salt circulating reactor. 120 mL of catalyst was packed in the middle of the reactor, and inert supports were packed at the bottom and top of the reactor. When the molten salt temperature was heated to 350°C, air and benzene were introduced into the reactor at a concentration of 50 g / Nm³. 3 The volume hourly space velocity (VHSV) of the benzene-air mixture is 2200 h⁻¹. -1 After 1 hour of stable operation, samples were taken for analysis, and the results are shown in Table 1.

[0171] Benzene conversion rate (%) = (Amount of benzene at reactor inlet per unit time - Amount of benzene at reactor outlet per unit time) / Amount of benzene at reactor inlet per unit time × 100%;

[0172] Maleic anhydride selectivity (%) = Amount of benzene converted to maleic anhydride per unit time / (Amount of benzene at reactor inlet per unit time - Amount of benzene at reactor outlet per unit time) × 100%.

[0173] Maleic anhydride yield (%) = benzene conversion × maleic anhydride selectivity × 98 / 78 × 100%.

[0174] Table 1

[0175]

[0176] 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 catalyst for the oxidation of benzene to maleic anhydride, characterized in that, The catalyst includes a support and an active component supported on the support. The active component has a rod-shaped crystal structure and a grain diameter of less than 70 nm. The active component includes a first active component and a second active component. The first active component includes oxides of vanadium, molybdenum, sodium, phosphorus, and nickel. The second active component includes at least one of oxides of indium, antimony, and bismuth. The vanadium oxide contains vanadium with an average valence state of 4.5-4.

8. The vanadium oxide includes V... 5+ and V 3+ V 5+ and V 3+ The molar ratio is 1.8-3:

1.

2. The catalyst according to claim 1, wherein, Based on the total amount of the catalyst, the content of the active component is 10-20% by weight, and the content of the support is 80-90% by weight.

3. The catalyst according to claim 1, wherein, The molar ratio of the first active component to the second active component, calculated based on non-oxygen elements, is 10-2000:

1.

4. The catalyst according to claim 1, wherein, The molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, and the second active component in the active component is 1:(0.2-0.9):(0.001-0.2):(0.005-0.25):(0.0001-0.05):(0.0001-0.05), wherein the vanadium oxide is calculated as V2O5, the molybdenum oxide as MoO3, the sodium oxide as Na2O, the phosphorus oxide as P2O5, the nickel oxide as NiO, and the second active component is calculated as a metal oxide.

5. A method for preparing a catalyst with the function of phenyl oxidation to maleic anhydride, characterized in that, The method includes loading an active component precursor onto a support and then activating it; the active component includes a first active component and a second active component, the first active component precursor includes an oxide precursor of vanadium, an oxide precursor of molybdenum, an oxide precursor of sodium, an oxide precursor of phosphorus, and an oxide precursor of nickel; the second active component precursor includes at least one of an oxide precursor of indium, an oxide precursor of antimony, and an oxide precursor of bismuth. The activation is carried out in a mixed atmosphere of inactive gas and hydrogen, wherein the hydrogen content in the mixed atmosphere is 0.1-50% by volume. The activation temperature control program includes: First stage: Increase the temperature to 150-170℃ at a rate of 60-120℃ / h, and hold for 5-30 minutes. Second stage: Then, increase the temperature to 250-280℃ at a rate of 50-110℃ / h, and hold for 5-30 minutes. Third stage: Then, increase the temperature to 350-380℃ at a rate of 40-100℃ / h, and hold for 10-60 minutes. Fourth stage: Increase the temperature to 400-480℃ at a rate of 30-90℃ / h and maintain it for 3-10 hours.

6. The method according to claim 5, wherein, The volume hourly space velocity of the gas mixture is 500-3000 h⁻¹. -1 ; And / or, the hydrogen content in the mixture is 2-20% by volume.

7. The method according to claim 5, wherein, The amounts of the active component precursor and the support are such that, based on the total amount of catalyst, the content of the active component is 10-20% by weight and the content of the support is 80-90% by weight.

8. The method according to claim 5, wherein, The amount of the active component precursor is such that the molar ratio of the first active component (calculated as non-oxygen element) to the second active component (calculated as non-oxygen element) in the prepared catalyst is 10-2000:

1. And / or, the amount of the active component precursor is such that in the prepared catalyst, the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide and the second active component in the active component is 1:(0.2-0.90):(0.001-0.2):(0.005-0.25):(0.0001-0.05):(0.0001-0.05), wherein the vanadium oxide is calculated as V2O5, the molybdenum oxide as MoO3, the sodium oxide as Na2O, the phosphorus oxide as P2O5, the nickel oxide as NiO, and the second active component as a metal oxide.

9. The catalyst prepared by the method according to any one of claims 5-8.

10. The use of the catalyst according to any one of claims 1-4 or the catalyst prepared by the method according to any one of claims 5-8 in the oxidation of benzene to maleic anhydride.

11. A method for producing maleic anhydride by benzene oxidation, characterized in that, The method includes: contacting benzene with oxygen in the presence of the catalyst described in any one of claims 1-4; Alternatively, the method may include: preparing a catalyst according to any one of claims 5-8, and then contacting benzene with oxygen in the presence of the catalyst.

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