Vanadium-molybdenum maleic anhydride catalyst, preparation method and application thereof

Abstract

The present application relates to the technical field of phenoxy anhydride preparation, and discloses a vanadium-molybdenum series catalyzer for anhydride, a preparation method and application thereof, which comprises a carrier and active components loaded on the carrier, wherein the active components comprise first, second and third active components; the first active component comprises oxides of vanadium, molybdenum, sodium, phosphorus and nickel; the second active component comprises at least one of oxides of germanium, selenium and strontium; and the third active component comprises at least one of oxides of titanium, zirconium, iridium, rhodium, iron and niobium. The catalyzer can improve the selectivity and yield of anhydride.

Description

Technical Field

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

[0002] Maleic anhydride (maleic anhydride) is a very important organic chemical raw material, ranking second only to phthalic anhydride as the largest organic acid anhydride. As a chemical intermediate, maleic anhydride has a wide range of applications, including the production of unsaturated polyester resins (UPR), 1,4-succinic acid, 1,4-butanediol, tetrahydrofuran, γ-butyrolactone, malic acid, and other products. It can also be used in the production of pharmaceuticals, pesticides, and food additives. Unsaturated polyester resins (UPR) are the largest downstream consumer of maleic anhydride, accounting for over 60% of total maleic anhydride consumption.

[0003] Based on the source and type of raw materials, maleic anhydride production processes can be divided into the benzene method and the n-butane method. With the continuous improvement and development of n-butane technology, the more environmentally friendly n-butane oxidation process has seen its capacity expand rapidly. However, the n-butane method for producing maleic anhydride is more complex than the benzene method, especially involving solvent absorption, making operation relatively complicated. Therefore, the process using benzene as a raw material still has a significant market. Furthermore, the price of benzene has fluctuated in recent years, remaining at a relatively low level, while the price of n-butane has remained relatively stable. Considering the operating costs of both the benzene and butane methods for producing maleic anhydride, the benzene method still holds certain overall advantages.

[0004] In regions with relatively abundant coal resources but relatively scarce oil resources, such as western regions like Shanxi Province, coal chemical resources are plentiful, resulting in the production of large quantities of coking benzene. Therefore, maleic anhydride plants using coking benzene as a feedstock still have significant production capacity. Currently, manufacturers are striving to improve economic efficiency by minimizing production costs, optimizing processes to reduce benzene consumption, minimizing by-products, and improving the selectivity of maleic anhydride, thereby enhancing economic benefits.

[0005] Currently, there are numerous patent applications for catalysts for the oxidation of benzene to maleic anhydride. Some patent applications focus on the preparation of the support, others involve process technology optimization, and still others involve screening metal additives and optimizing formulations. For example, CN103816931A proposes a method for preparing a catalyst for the oxidation of benzene to maleic anhydride, using Group VIII copper as an additive and hydrochloric acid as a reducing agent. The mixed solution is sprayed onto an inert talc ceramic support, and then activated at 350-450℃ under an inert gas atmosphere to obtain an active catalyst. This patent application uses hydrochloric acid, which is a highly volatile and corrosive acid. It not only causes severe corrosion to equipment and increases equipment investment costs, but also harms the health of employees and generates a large amount of waste acid water, among other environmental problems. CN105536837A discloses a catalyst for the oxidation of benzene to maleic anhydride, using rare earth metal oxides as the main additives, such as one or more elements selected from lanthanum, cerium, terbium, and europium, with silicon carbide as the support, and preparing the catalyst using impregnation or spraying methods. CN102850306 proposes a two-stage bed catalyst for the oxidation of maleic anhydride from benzene. The two-stage bed technology involves an upper catalyst composed of a combination of transition metals and lanthanides, while the lower catalyst contains transition metals. The phosphorus-vanadium ratio between the upper and lower beds is adjusted. Although this two-stage bed process achieves a high yield, the catalyst loading is complex, and the benzene loading is higher than that of commonly used benzene-based maleic anhydride plants in China. Summary of the Invention

[0006] The oxidation of benzene to maleic anhydride is a gas-solid phase reaction. Gaseous benzene molecules diffuse to the catalyst surface, where adsorption, bond breaking, bond formation, and desorption occur. The adsorption and desorption of benzene and maleic anhydride play a crucial role in this reaction. Benzene adsorption is short and desorption is rapid, leading to a decrease in benzene conversion; maleic anhydride desorption is long and prone to deep oxidation, producing carbon dioxide and carbon monoxide. The main crystalline form of the catalyst in the benzene oxidation reaction is V₂MoO₈. The inventors discovered that by simultaneously introducing a second and third active component as an auxiliary agent into a catalyst with vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, and nickel oxide as the first active component, the valence state and crystal structure of the central vanadium atom can be altered, thereby improving the catalyst's performance.

[0007] Therefore, in order to achieve the above objectives, the first aspect of the present invention provides a vanadium-molybdenum maleic anhydride catalyst, the catalyst comprising a support and an active component supported on the support, the active component comprising a first active component, a second active component and a third active component;

[0008] The first active component includes oxides of vanadium, molybdenum, sodium, phosphorus, and nickel.

[0009] The second active component includes at least one of germanium oxide, selenium oxide, and strontium oxide;

[0010] The third active component includes at least one of titanium oxide, zirconium oxide, iridium oxide, rhodium oxide, iron oxide, and niobium oxide.

[0011] A second aspect of the present invention provides a method for preparing a vanadium-molybdenum maleic anhydride catalyst, the method comprising loading an active component precursor onto a support to obtain a catalyst precursor, and then activating it; wherein the active component precursor comprises a first active component precursor, a second active component precursor, and a third active component precursor;

[0012] The first active component precursor includes vanadium oxide precursor, molybdenum oxide precursor, sodium oxide precursor, phosphorus oxide precursor and nickel oxide precursor;

[0013] The second active component precursor includes at least one of selenium oxide precursor, germanium oxide precursor and strontium oxide precursor;

[0014] The third active component precursor includes at least one of titanium oxide precursor, zirconium oxide precursor, iridium oxide precursor, rhodium oxide precursor, iron oxide precursor, and niobium oxide precursor.

[0015] A third aspect of the present invention provides a catalyst prepared by the method described above.

[0016] The fourth aspect of the present invention provides the application of the catalyst described above or the catalyst prepared by the method described above in the oxidation of benzene to maleic anhydride.

[0017] 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 catalyst described above;

[0018] Alternatively, the method may include: preparing a catalyst according to the method described above, and then contacting benzene with oxygen in the presence of the catalyst.

[0019] This invention introduces second and third active components into catalysts containing vanadium oxides, molybdenum oxides, sodium oxides, phosphorus oxides, and nickel oxides. This alters the valence state of the central vanadium atom, improving catalyst performance. Furthermore, the catalyst of this invention achieves high benzene conversion, maleic anhydride selectivity, and gravimetric yield at lower reaction temperatures. Simultaneously, the catalyst of this invention also achieves high benzene conversion, maleic anhydride selectivity, and gravimetric yield when used alone (i.e., without being combined with other catalysts in a staged loading process).

[0020] In a preferred embodiment, the present invention further utilizes polyethylene glycol and stearate ester in the catalyst preparation process, which can further improve the selectivity and yield of maleic anhydride. Detailed Implementation

[0021] 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.

[0022] The first aspect of the present invention provides a vanadium-molybdenum maleic anhydride catalyst, the catalyst comprising a support and an active component supported on the support, the active component comprising a first active component, a second active component and a third active component;

[0023] The first active component includes oxides of vanadium, molybdenum, sodium, phosphorus, and nickel.

[0024] The second active component includes at least one of germanium oxide, selenium oxide, and strontium oxide;

[0025] The third active component includes at least one of titanium oxide, zirconium oxide, iridium oxide, rhodium oxide, iron oxide, and niobium oxide.

[0026] According to the present invention, preferably, the carrier is silicon carbide. The shape of the carrier can be any one of spherical, cylindrical, annular, clover-shaped, or tetraclover-shaped.

[0027] According to the present invention, preferably, the combination of the second active component and the third active component is selected from at least one of the following: a combination of strontium oxide and niobium oxide, a combination of germanium oxide and iridium oxide, a combination of selenium oxide and zirconium oxide, and a combination of strontium oxide and zirconium oxide. When the combination of the second active component and the third active component is selected from a combination of strontium oxide and niobium oxide, it can be understood that the second active component is selected from strontium oxide and the third active component is selected from niobium oxide.

[0028] 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 weight of the catalyst.

[0029] According to the present invention, preferably, the catalyst does not contain lanthanide metal elements.

[0030] According to the present invention, preferably, the molar ratio of the first active component, the second active component, and the third active component, calculated as non-oxygen elements, is 1:0.0001-0.1:0.0001-0.1.

[0031] According to the present invention, preferably, the molar ratio of vanadium oxide (calculated as V₂O₅), molybdenum oxide (calculated as MoO₃), sodium oxide (calculated as Na₂O), phosphorus oxide (calculated as P₂O₅), nickel oxide (calculated as NiO), the second active component (calculated as oxide), and the third active component (calculated as oxide) is 1:0.2-0.9:0.001-0.2:0.005-0.25:0.0001-0.05:0.000 1-0.06:0.0001-0.08, preferably 1:0.5-0.8:0.01-0.1:0.01-0.1:0.01-0.02:0.0005-0.05:0.005-0.05, more preferably 1:0.55-0.7:0.04-0.08:0.01-0.05:0.015-0.02:0.0005-0.05:0.005-0.05.

[0032] A second aspect of the present invention provides a method for preparing a vanadium-molybdenum maleic anhydride catalyst, the method comprising loading an active component precursor onto a support to obtain a catalyst precursor, and then activating it; wherein the active component precursor comprises a first active component precursor, a second active component precursor, and a third active component precursor;

[0033] The first active component precursor includes vanadium oxide precursor, molybdenum oxide precursor, sodium oxide precursor, phosphorus oxide precursor and nickel oxide precursor;

[0034] The second active component precursor includes at least one of selenium oxide precursor, germanium oxide precursor and strontium oxide precursor;

[0035] The third active component precursor includes at least one of titanium oxide precursor, zirconium oxide precursor, iridium oxide precursor, rhodium oxide precursor, iron oxide precursor, and niobium oxide precursor.

[0036] According to the present invention, preferably, the carrier is silicon carbide. The shape of the carrier can be any one of spherical, cylindrical, annular, clover-shaped, or tetraclover-shaped.

[0037] According to the present invention, preferably, the combination of the second active component precursor and the third active component precursor is selected from at least one of the following: a combination of strontium oxide precursor and niobium oxide precursor, a combination of germanium oxide precursor and iridium oxide precursor, a combination of selenium oxide precursor and zirconium oxide precursor, and a combination of strontium oxide precursor and zirconium oxide precursor.

[0038] According to the present invention, preferably, the amounts of the active component precursor and the support are such that, based on the total weight 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.

[0039] According to the present invention, preferably, the amounts of the first active component precursor, the second active component precursor and the third active component precursor are such that the molar ratio of the first active component, the second active component and the third active component in the catalyst, calculated as non-oxygen elements, is 1:0.0001-0.1:0.0001-0.1.

[0040] According to the present invention, preferably, the amount of the active component precursor is such that the molar ratio of vanadium oxide (calculated as V₂O₅), molybdenum oxide (calculated as MoO₃), sodium oxide (calculated as Na₂O), phosphorus oxide (calculated as P₂O₅), nickel oxide (calculated as NiO), the second active component (calculated as oxide), and the third active component (calculated as oxide) in the prepared catalyst is 1:0.2-0.9:0.001-0.2:0.005-0.25:0.0001. -0.05:0.0001-0.06:0.0001-0.08, preferably 1:0.5-0.8:0.01-0.1:0.01-0.1:0.01-0.02:0.0005-0.05:0.005-0.05, more preferably 1:0.55-0.7:0.04-0.08:0.01-0.05:0.015-0.02:0.0005-0.05:0.005-0.05.

[0041] According to the present invention, preferably, the load includes:

[0042] (1) Mix the solvent, active component precursor, polyethylene glycol and stearic acid to obtain a mixture containing the active component precursor;

[0043] (2) The mixture obtained in step (1) is coated onto a support to obtain a catalyst precursor.

[0044] According to the present invention, preferably, the amount of polyethylene glycol used is 0.1-5g relative to 100g of solvent, more preferably 0.4-2g.

[0045] According to the present invention, preferably, the polyethylene glycol has a weight-average molecular weight of 1500-2000 g / mol. For example, PEG-1500 (polyethylene glycol with a weight-average molecular weight of 1500) and PEG-2000 (polyethylene glycol with a weight-average molecular weight of 2000).

[0046] According to the present invention, preferably, the amount of stearic acid used is 2-10g relative to 100g of solvent.

[0047] According to the present invention, preferably, the stearic acid has a particle size of 10-50 micrometers.

[0048] According to the present invention, the vanadium oxide precursor is any substance capable of providing elemental vanadium, and preferably, the vanadium oxide precursor is ammonium metavanadate.

[0049] According to the present invention, the molybdenum oxide precursor is any substance capable of providing elemental molybdenum. Preferably, the molybdenum oxide precursor is selected from at least one of ammonium molybdate, molybdenum trioxide, and calcium molybdate, and more preferably ammonium molybdate.

[0050] According to the present invention, the sodium oxide precursor is any substance capable of providing elemental sodium, preferably, the sodium oxide precursor is selected from at least one of sodium dihydrogen phosphate and trisodium phosphate, more preferably trisodium phosphate.

[0051] According to the present invention, the phosphorus oxide precursor is any substance capable of providing elemental phosphorus. Preferably, the phosphorus oxide precursor is selected from at least one of ammonium dihydrogen phosphate, 85%-115% phosphoric acid, phosphorus pentoxide, sodium dihydrogen phosphate, and trisodium phosphate, and more preferably ammonium dihydrogen phosphate and / or trisodium phosphate.

[0052] According to the present invention, the nickel oxide precursor is any substance capable of providing elemental nickel, preferably selected from at least one of nickel nitrate, nickel sulfate, nickel chloride and nickel oxide, more preferably nickel nitrate.

[0053] According to the present invention, preferably, the second active component precursor is any substance capable of providing the element of the second active component.

[0054] According to the present invention, preferably, the third active component precursor is any substance capable of providing the third active component element.

[0055] According to the present invention, preferably, step (2) further includes ultrasonic treatment of the mixture before coating, wherein the conditions for ultrasonic treatment include: ultrasonic frequency of 30-40KHz and ultrasonic time of 1-20min.

[0056] According to the present invention, there are no restrictions on the coating method, and conventional techniques in the prior art can be used. Preferably, the coating method is as follows: coating the carrier with a mother liquor containing the active component precursor, and then drying it. The drying conditions may include: a temperature of 100-150°C and a time of 2-8 hours.

[0057] 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 carried out 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 precursor is sprayed onto the carrier through a nozzle, completing the coating. More preferably, during the coating process, the stainless steel drum rotates at a speed of 10-40 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.

[0058] According to the present invention, preferably, the activation temperature control procedure includes: raising the temperature to 150-170°C at a heating rate of 70-150°C / h and holding for 5-30 min; then raising the temperature to 250-280°C at a heating rate of 60-120°C / h and holding for 5-30 min; subsequently raising the temperature to 350-380°C at a heating rate of 50-100°C / h and holding for 10-60 min; finally raising the temperature to 420-480°C at a heating rate of 40-90°C / h and holding for 5-10 h; and then lowering the temperature to 15-40°C at a rate of 40-80°C / h.

[0059] According to the present invention, preferably, the activation is carried out in a sealed container. The sealed container is a cylindrical or cubical activation furnace body, the upper part of which is sealed by a flange to isolate the internal space from the outside. The outer wall of the furnace body is wrapped with heating wires, and the heating wires are covered with heat insulation cloth or heat insulation tiles. The heating temperature of the furnace body is controlled by an automated digital temperature controller. The furnace body has vents at the top and bottom, with the lower vent serving as the gas inlet and the upper vent serving as the gas outlet. The gas flow rate is controlled by a gas mass flow meter.

[0060] According to the present invention, preferably, activation can be carried out in a closed environment, and the activation atmosphere can be a nitrogen and / or helium atmosphere.

[0061] A third aspect of the present invention provides a catalyst prepared by the method described above.

[0062] The fourth aspect of the present invention provides the application of the catalyst described above or the catalyst prepared by the method described above in the oxidation of benzene to maleic anhydride.

[0063] 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 catalyst described above;

[0064] Alternatively, the method may include: preparing a catalyst according to the method described above, and then contacting benzene with oxygen in the presence of the catalyst.

[0065] 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 40-55 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.

[0066] According to the present invention, preferably, the volume hourly space velocity (VHSV) of the benzene-air mixture is 1500-3000 h⁻¹. -1 More preferably 2000-2500h -1 .

[0067] The contact between benzene and oxygen can be carried out under normal pressure, under pressure, or under negative pressure. Preferably, the contact between benzene and oxygen is carried out under normal pressure.

[0068] According to the present invention, a fixed-bed reactor is used in the process of benzene oxidation to maleic anhydride. A molten salt bath can be used for heating and removal of reaction heat. Preferably, the molten salt temperature is 340-360°C. During the reaction evaluation, the temperature varies from top to bottom in the catalyst bed. The highest temperature value in the range is called the hot spot temperature of the catalyst, and the corresponding bed height is the hot spot location. In this invention, thermocouples are used to determine the hot spot temperature by measuring the bed temperature.

[0069] The present invention will be described in detail below through embodiments. In the following embodiments,

[0070] The room temperature is approximately 25°C.

[0071] Example 1

[0072] Step A: Dissolve 98g of oxalic acid in 490mL of water at room temperature, add 69.6g of ammonium metavanadate while stirring until the ammonium metavanadate dissolves and a homogeneous and stable solution is formed. At this point, add 2.45g of PEG-1500. Dissolve ammonium molybdate in 50mL of water until it is homogeneous, and add this solution to the above ammonium metavanadate solution. While stirring, add trisodium phosphate, nickel nitrate, strontium nitrate, and niobium ammonium oxalate in sequence, and then add 3.0g of stearic acid (particle size of 10-20 micrometers). Sonicate for 5 minutes at a frequency of 35KHz. After mixing, a mixture containing the active component precursor is obtained.

[0073] Step B: Place 330g of carrier (silicon carbide) into a rotating and heated stainless steel drum. A thermocouple sheath is installed at the bottom of the carrier, and the internal thermocouple is connected to a temperature display instrument to monitor temperature changes in real time during the spraying process. Adjust the drum speed to 10-20 rpm. When the carrier temperature reaches 250℃, spray the mixture containing the active precursor onto the carrier through a nozzle at a spraying speed of 0.08 mL / min·gcat and a spraying temperature of 250-270℃. After spraying, dry at 120℃ for 4 hours to obtain the catalyst precursor. The catalyst precursor weighs 404g.

[0074] Step C: Take 180g of the above catalyst precursor and place it in an activation furnace. After sealing, raise the temperature from room temperature to 150℃ at a rate of 150℃ / h and hold for 5min. Then raise the temperature to 250℃ at a rate of 120℃ / h and hold for 10min. Next, raise the temperature to 350℃ at a rate of 100℃ / h and hold for 20min. Then raise the temperature to 450℃ at a rate of 90℃ / h and hold for 5h. Then gradually lower the temperature to room temperature to obtain the catalyst.

[0075] The prepared catalyst was weighed, and the content of the active component was calculated to be 18.0% by weight and the content of the support was 82.0% by weight, based on the total amount of catalyst.

[0076] XRF elemental analysis revealed that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, strontium oxide, and niobium oxide in the active components of the catalyst was 1:0.61:0.06:0.02:0.017:0.008:0.01. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, strontium oxide as SrO, and niobium oxide as Nb2O5.

[0077] Example 2

[0078] The catalyst was prepared according to the method of Example 1, except that the amount of PEG-1500 added was 9.8g.

[0079] Example 3

[0080] The catalyst was prepared according to the method of Example 1, except that the amount of PEG-1500 added was 9.8g, and the amount of strontium nitrate added was also changed.

[0081] The prepared catalyst was weighed, and the content of the active component was calculated to be 17.9% by weight and the content of the support was 82.1% by weight, based on the total amount of catalyst.

[0082] XRF elemental analysis revealed that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, strontium oxide, and niobium oxide in the active components of the catalyst was 1:0.61:0.06:0.02:0.017:0.003:0.01. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, strontium oxide as SrO, and niobium oxide as Nb2O5.

[0083] Example 4

[0084] The catalyst was prepared according to the method of Example 1, except that "strontium nitrate and niobium ammonium oxalate" were replaced with "germanium tetrachloride and chloroiridic acid", and the amounts of germanium tetrachloride and chloroiridic acid were different from those of strontium nitrate and niobium ammonium oxalate.

[0085] The prepared catalyst was weighed, and the content of the active component was calculated to be 17.8% by weight and the content of the support was 82.2% by weight, based on the total amount of catalyst.

[0086] XRF elemental analysis revealed that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, germanium oxide, and iridium oxide in the active components of the catalyst was 1:0.61:0.06:0.02:0.017:0.0009:0.03. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, germanium oxide as GeO2, and iridium oxide as IrO2.

[0087] Example 5

[0088] The catalyst was prepared according to the method of Example 1, except that "strontium nitrate and niobium ammonium oxalate" were replaced with "selenic acid and zirconium nitrate", and the amounts of selenic acid and zirconium nitrate were different from those of strontium nitrate and niobium ammonium oxalate.

[0089] The prepared catalyst was weighed, and the content of the active component was calculated to be 17.8% by weight and the content of the support was 82.2% by weight, based on the total amount of catalyst.

[0090] XRF elemental analysis revealed that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, selenium oxide, and zirconium oxide in the active components of the catalyst was 1:0.61:0.06:0.02:0.017:0.001:0.03. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, selenium oxide as SeO2, and zirconium oxide as ZrO2.

[0091] Example 6

[0092] The catalyst was prepared according to the method of Example 1, except that "niobium oxalate ammonium" was replaced with "zirconium nitrate", and the amount of zirconium nitrate was different from that of niobium oxalate ammonium.

[0093] The prepared catalyst was weighed, and the content of the active component was calculated to be 17.9% by weight and the content of the support was 82.1% by weight, based on the total amount of catalyst.

[0094] XRF elemental analysis revealed that the molar ratio of vanadium oxide, molybdenum oxide, sodium oxide, phosphorus oxide, nickel oxide, strontium oxide, and zirconium oxide in the active components of the catalyst was 1:0.61:0.06:0.02:0.017:0.008:0.017. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, strontium oxide as SrO, and zirconium oxide as ZrO2.

[0095] Example 7

[0096] The catalyst was prepared according to the method of Example 1, except that PEG-1500 was replaced with an equal mass of PEG-2000, and the amount of niobium ammonium oxalate added was changed.

[0097] The prepared catalyst was weighed, and the content of the active component was calculated to be 17.8% by weight and the content of the support was 82.1% 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, strontium oxide, and niobium oxide in the active components of the catalyst was 1:0.61:0.06:0.02:0.017:0.008:0.009. Among them, vanadium oxide was calculated as V2O5, molybdenum oxide as MoO3, sodium oxide as Na2O, phosphorus oxide as P2O5, nickel oxide as NiO, strontium oxide as SrO, and niobium oxide as Nb2O5.

[0099] Example 8

[0100] The catalyst was prepared according to the method of Example 7, except that the amount of PEG-2000 added was 6.1g.

[0101] Example 9

[0102] The catalyst was prepared according to the method of Example 7, except that the amount of PEG-2000 added was 9.8g.

[0103] Example 10

[0104] The catalyst was prepared according to the method of Example 1, except that PEG-1500 was not added.

[0105] Example 11

[0106] The catalyst was prepared according to the method of Example 1, except that stearic acid was not added.

[0107] Example 12

[0108] The catalyst was prepared according to the method in Example 1, except that 8g of stearic acid was added.

[0109] Example 13

[0110] The catalyst was prepared according to the method of Example 1, except that the stearic acid had a particle size of 30-40 micrometers.

[0111] Example 14

[0112] The catalyst was prepared according to the method of Example 1, except that PEG-1500 was replaced with an equal mass of PEG-6000.

[0113] Example 15

[0114] The catalyst was prepared according to the method of Example 1, except that stearic acid was replaced with an equal mass of methyl stearate.

[0115] Comparative Example 1

[0116] The catalyst was prepared according to the method of Example 1, except that niobium oxalate was not added.

[0117] Comparative Example 2

[0118] The catalyst was prepared according to the method of Example 1, except that strontium nitrate was not added.

[0119] Comparative Example 3

[0120] The catalyst was prepared according to the method of Example 1, except that strontium nitrate and PEG-1500 were not added.

[0121] Comparative Example 4

[0122] The catalyst was prepared according to the method of Example 1, except that niobium oxalate was replaced with an equimolar amount of strontium nitrate.

[0123] Comparative Example 5

[0124] The catalyst was prepared according to the method of Example 1, except that strontium nitrate was replaced with an equimolar amount of niobium ammonium oxalate.

[0125] Comparative Example 6

[0126] The catalyst was prepared according to the method of Example 1, except that strontium nitrate was replaced with an equimolar amount of chromium nitrate.

[0127] Test case

[0128] The catalysts prepared in the above examples and comparative examples were loaded into a 120 ml bubbling molten salt circulating reactor. The reactor was supported by an inert support at the bottom, with 120 ml of catalyst in the middle and an inert support of a certain height at the top. When the molten salt was heated to the required reaction temperature, air was introduced, and benzene was added simultaneously. The volume hourly space velocity (VHSV) of the benzene-air mixture was 2200 h⁻¹. -1 When the benzene concentration reaches the required operating concentration (benzene concentration is 45 g / Nm³), 3 After stabilization for 1 hour, sampling and analysis began. The evaluation results of each catalyst are shown in Table 1. The calculation methods for each index are as follows:

[0129] 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%;

[0130] 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%.

[0131] Maleic anhydride yield (%) = benzene conversion × maleic anhydride selectivity × 98 / 78 × 100%.

[0132] Table 1

[0133]

[0134] As shown in Table 1, the catalyst of this invention can improve the conversion rate of benzene, the selectivity of maleic anhydride, and the weight yield. Furthermore, comparing the examples and comparative examples in Table 1 reveals that when the prepared catalyst simultaneously contains the first active component, the second active component, and the third active component, the weight yield of maleic anhydride is significantly increased. Adding stearic acid and polyethylene glycol during catalyst preparation further enhances the catalyst's performance. Moreover, the catalyst of this invention can achieve higher benzene conversion rates, maleic anhydride selectivity, and weight yields at lower reaction temperatures.

[0135] 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 vanadium-molybdenum based maleic anhydride catalyst, characterized in that, The catalyst includes a support and an active component supported on the support, wherein the active component includes a first active component, a second active component, and a third active component; The first active component includes oxides of vanadium, molybdenum, sodium, phosphorus, and nickel. The second active component includes at least one of germanium oxide, selenium oxide, and strontium oxide; The third active component includes at least one of titanium oxide, zirconium oxide, iridium oxide, rhodium oxide, iron oxide, and niobium oxide.

2. The catalyst according to claim 1, wherein, The combination of the second and third active components is selected from at least one of the following: a combination of strontium oxide and niobium oxide, a combination of germanium oxide and iridium oxide, a combination of selenium oxide and zirconium oxide, and a combination of strontium oxide and zirconium oxide. And / or, based on the total weight 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; And / or, the catalyst does not contain lanthanide metal elements.

3. The catalyst according to claim 2, wherein, The molar ratio of the first active component, the second active component, and the third active component (based on non-oxygen elements) is 1:0.0001-0.1:0.0001-0.

1. And / or, the molar ratio of vanadium oxide (calculated as V2O5), molybdenum oxide (calculated as MoO3), sodium oxide (calculated as Na2O), phosphorus oxide (calculated as P2O5), nickel oxide (calculated as NiO), the second active component (calculated as oxide), and the third active component (calculated as oxide) is 1:0.2-0.9:0.001-0.2:0.005-0.25:0.0001-0.05:0.0001-0.06:0.0001-0.

08.

4. A method for preparing vanadium-molybdenum based maleic anhydride catalyst, characterized in that, The method includes loading an active component precursor onto a support to obtain a catalyst precursor, followed by activation; the active component precursor includes a first active component precursor, a second active component precursor, and a third active component precursor; The first active component precursor includes vanadium oxide precursor, molybdenum oxide precursor, sodium oxide precursor, phosphorus oxide precursor and nickel oxide precursor; The second active component precursor includes at least one of selenium oxide precursor, germanium oxide precursor and strontium oxide precursor; The third active component precursor includes at least one of titanium oxide precursor, zirconium oxide precursor, iridium oxide precursor, rhodium oxide precursor, iron oxide precursor, and niobium oxide precursor.

5. The method according to claim 4, wherein, The combination of the second active component precursor and the third active component precursor is selected from at least one of the following combinations: a combination of strontium oxide precursor and niobium oxide precursor, a combination of germanium oxide precursor and iridium oxide precursor, a combination of selenium oxide precursor and zirconium oxide precursor, and a combination of strontium oxide precursor and zirconium oxide precursor. And / or, the amounts of the active component precursor and the support are such that, based on the total weight 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.

6. The method according to claim 5, wherein, The amounts of the first active component precursor, the second active component precursor, and the third active component precursor are such that the molar ratio of the first active component, the second active component, and the third active component in the catalyst, calculated as non-oxygen elements, is 1:0.0001-0.1:0.0001-0.1; And / or, the amount of the active component precursor is such that the molar ratio of vanadium oxide (calculated as V2O5), molybdenum oxide (calculated as MoO3), sodium oxide (calculated as Na2O), phosphorus oxide (calculated as P2O5), nickel oxide (calculated as NiO), the second active component (calculated as oxide), and the third active component (calculated as oxide) in the prepared catalyst is 1:0.2-0.9:0.001-0.2:0.005-0.25:0.0001-0.05:0.0001-0.06:0.0001-0.

08.

7. The method according to claim 5, wherein, The load includes: (1) Mix the solvent, active component precursor, polyethylene glycol and stearic acid to obtain a mixture containing the active component precursor; (2) The mixture obtained in step (1) is coated onto a support to obtain a catalyst precursor.

8. The method according to claim 7, wherein, The amount of polyethylene glycol used is 0.1-5g relative to 100g of solvent; And / or, the weight-average molecular weight of the polyethylene glycol is 1500-2000 g / mol; And / or, the amount of stearic acid used is 2-10g relative to 100g of solvent; And / or, the stearic acid has a particle size of 10-50 micrometers.

9. The catalyst prepared by the method according to any one of claims 4-8.

10. The use of the catalyst according to any one of claims 1-3 or the catalyst prepared by the method according to any one of claims 4-8 in the oxidation of benzene to maleic anhydride.

11. A method for producing maleic anhydride by benzene oxidation, characterized in that, The method comprises: contacting benzene with oxygen in the presence of the catalyst described in any one of claims 1-3 and 9; Alternatively, the method may include: preparing a catalyst according to any one of claims 4-8, and then contacting benzene with oxygen in the presence of the catalyst.

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