Hydroxyl phosphoric acid type phosphorus molybdenum vanadium heteropolyacid catalyst for regulating and controlling oxygen vacancy through VOx as well as preparation method and application of hydroxyl phosphoric acid type phosphorus molybdenum vanadium heteropolyacid catalyst

Abstract

The invention discloses a hydroxyl phosphoric acid type phosphorus molybdenum vanadium heteropolyacid catalyst capable of regulating and controlling oxygen vacancies through VOx and a preparation method and application thereof, the structural general formula of the hydroxyl phosphoric acid type phosphorus molybdenum vanadium heteropolyacid catalyst capable of regulating and controlling the oxygen vacancies through VOx is HEDP-Mo12-xVx, HEDP is HEDP, and x is a real number of 1-5. The hydroxyl phosphoric acid type phosphorus molybdenum vanadium heteropolyacid catalyst for regulating and controlling the oxygen vacancy through VOx can efficiently complete deep desulfurization at low temperature, obviously widens the use temperature, is suitable for low-temperature regions, does not need additional heating, and is simple and convenient; the dosage of the catalyst and the oxidant is reduced, and the catalyst cost is reduced.

Description

Technical Field

[0001] The present invention relates to a method for x The invention relates to a hydroxyphosphoric acid-type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies, a preparation method thereof, and its catalytic oxidation desulfurization application, belonging to the cross-technical field of environmental protection technology and the deep processing industry of oil and chemical products. Background Art

[0002] In recent years, with the continuous progress of the economy and society, sulfur compounds in fuel, which release sulfur oxides (SOx) after combustion, have become a major cause of air pollution. Continuously reducing the sulfur content in fuel oil, and achieving "zero" sulfur content in fuel oil, is the inevitable trend for the future development of the fuel industry. Exhaust emissions from oil-powered locomotives can easily cause environmental problems and pose a threat to human health. To this end, many countries have introduced increasingly stringent standards and regulations for petroleum sulfur content. Producing ultra-low sulfur fuel oil is a key task in the refining industry, and the development of deep desulfurization technology has become a goal of researchers worldwide.

[0003] Currently, oxidative desulfurization is considered one of the most promising desulfurization technologies due to its low energy consumption. It works by oxidizing sulfur compounds such as thiophene sulfur in fuel into corresponding sulfoxides or sulfones. Because the oxidation products are more polar, they can be extracted with polar solvents, thereby achieving desulfurization. Oxidative desulfurization can be further categorized into organic oxidant desulfurization systems, inorganic oxidant desulfurization systems, photocatalytic oxidative desulfurization systems, and plasma oxidative desulfurization systems.

[0004] In oxidative desulfurization technology, there are many types of oxidants involved, among which the application of hydrogen peroxide as an oxidant occupies a dominant position. However, since hydrogen peroxide is insoluble in the oil phase, the oxidant cannot fully contact with the gasoline during the gasoline reaction, which slows down the reaction rate, resulting in unsatisfactory desulfurization effect and increasing the amount of oxidant used. The use of a phase transfer catalyst can promote the reaction of two reactants in two immiscible solvents (liquid-liquid two-phase system or solid-liquid two-phase system), allowing the reaction to proceed smoothly in two mutually soluble systems. During the reaction, the actual reactants will be transferred from one phase to another under the action of the catalyst, so that the reactants and the substrate are combined, thereby ensuring that the reaction proceeds smoothly and the effect is good.

[0005] As a new type of catalytic material, heteropolyacids have a relatively small surface area and are prone to agglomeration during the reaction, making it difficult to fully exert their catalytic effect. Supported heteropolyacid catalysts can overcome these shortcomings and have attracted widespread attention from researchers in the field of catalysis. Different supported catalysts are suitable for different reaction types. Heteropolyacid-supported catalysts for deep desulfurization have several problems, such as the catalyst's easy dissolution in the ionic liquid phase, making it difficult to recycle and reuse, or its toxicity and high cost. Furthermore, the desulfurization rate needs to be further improved. For example, patent application number 201810972636.0 requires a modified molecular sieve as a support and requires multiple steps to complete. The operation is relatively complex and the preparation cost is high. The reaction takes 3 hours to complete, and the desulfurization rate still has room for improvement, which still far exceeds the ever-increasing practical application needs. There are a few reports of good desulfurization effects, but they are not suitable for use in low-temperature environments. In low-temperature areas, heating is required to complete the desulfurization, which takes a long time, requires large amounts of catalyst and oxidant, and is costly. Summary of the Invention

[0006] The present invention provides a method for x The hydroxyphosphoric acid-type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies, its preparation method and its catalytic oxidation desulfurization application can efficiently complete deep desulfurization at low temperatures and is suitable for low-temperature areas; it also reduces the amount of catalyst and oxidant used and reduces the catalyst cost.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] A through VO x Regulating oxygen vacancy hydroxyphosphoric acid type phosphomolybdovanadium heteropoly acid catalyst, the general structural formula is HEDP-Mo 12- x V x , wherein HEDP is hydroxyethylidene diphosphate and x is a real number of 1-5.

[0009] The above-mentioned hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst with oxygen vacancies regulated by VOx is used for efficient desulfurization at low temperature, and can complete deep desulfurization within 15 minutes at ≤10°C. The mass dosage of the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst with oxygen vacancies regulated by VOx is 0.3-0.6% of the quality of the oil to be desulfurized.

[0010] When using the above-mentioned hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst with oxygen vacancies regulated by VOx: after mixing the oil to be desulfurized and 1-methyl-3-octylimidazole tetrafluoroborate, add the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst with oxygen vacancies regulated by VOx and hydrogen peroxide, and stir to desulfurize; the amount of hydrogen peroxide is calculated according to the O / S molar ratio ≤2.5.

[0011] The inventors found in experiments that the catalyst of the present application has a very excellent catalytic effect of oxidative desulfurization, can achieve efficient desulfurization at low temperatures, significantly broadens the operating temperature, and does not require additional heating even in low-temperature areas, which is convenient and fast; at the same time, it also significantly reduces the O / S ratio, reduces the amount of hydrogen peroxide used, and reduces the desulfurization cost.

[0012] In order to improve the desulfurization effect, during the reaction, the volume ratio of 1-methyl-3-octylimidazole tetrafluoroborate to the oil to be desulfurized is 1: (5-7).

[0013] The mass concentration of the hydrogen peroxide in this application is 25-35%.

[0014] The reaction temperature for desulfurization using the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst in which oxygen vacancies are regulated by VOx is 0-40° C., and the reaction time is 5-15 minutes.

[0015] The catalyst of the present application can desulfurize efficiently under lower environment, broaden the desulfurization temperature, improve adaptability, and improve desulfurization efficiency.

[0016] After desulfurization, the catalyst can be recovered and reused by filtering and drying, which is simple and convenient and has excellent catalytic performance.

[0017] A method according to claim 1, wherein the VO x The invention discloses a preparation method of a hydroxyphosphoric acid-type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies, which is prepared by reacting an aqueous solution of hydroxyethylidene diphosphoric acid with molybdenum trioxide (MoO3) and vanadium pentoxide (V2O5); wherein the molar ratio of hydroxyethylidene diphosphoric acid to molybdenum trioxide is 1:(2.2-3.2); and the molar ratio of hydroxyethylidene diphosphoric acid to vanadium pentoxide is 1:(0.4-0.9).

[0018] In order to further ensure the quality of the obtained hydroxyphosphoric acid-type phosphomolybdovanadium heteropolyacid catalyst in which oxygen vacancies are regulated by VOx, the molar ratio of molybdenum trioxide to vanadium pentoxide is (2.8-6):1 during preparation, and more preferably, the molar ratio of molybdenum trioxide to vanadium pentoxide is (2.7-2.9):1.

[0019] The preparation method of the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst by regulating oxygen vacancies by VOx comprises the following steps:

[0020] (1) Molybdenum trioxide (MoO3) and vanadium pentoxide (V2O5) were mixed, added to deionized water, stirred and heated to 90-100°C, and then a 50 wt% aqueous solution of hydroxyethylidene diphosphonic acid was added dropwise. After the addition was complete, the mixture was stirred at 90-100°C for 18-24 hours to obtain a HEDP-Mo7V5 catalyst solution;

[0021] (2) The HEDP-Mo7V5 catalyst solution prepared in step (1) is subjected to microwave drying to obtain a hydroxyphosphoric acid type heteropolyacid salt catalyst HEDP-Mo7V5.

[0022] In step (1), the dripping speed of the hydroxyethylidene diphosphonic acid aqueous solution is 0.5-1.5 mL / min.

[0023] In step (1), the mass amount of deionized water is 15 to 22 times the mass sum of MoO3 and V2O5.

[0024] In step (2), the microwave drying time is 3-5 minutes and the power is 800 W. Microwave drying has a short cycle, high efficiency, good safety, and high efficiency of the resulting catalyst, and does not require a special atmosphere. If the existing graphitization furnace is used, the temperature is too high and the catalyst will turn into oxides, which will not achieve the catalytic effect. If the temperature is too low, graphitization cannot be completed and the catalytic effect cannot be achieved.

[0025] The present application can utilize the principle of combining catalytic oxidation with extraction separation to remove sulfur compounds from oil products, and the extraction separation directly refers to existing mature technologies.

[0026] Unless otherwise specified in this application, all operations are carried out under normal pressure.

[0027] The percentages in this application, unless otherwise specified, are all percentages by mass.

[0028] In the O / S of this application, O refers to the O in H2O2 and does not include the O in water.

[0029] The technologies not mentioned in this invention are all referred to the prior art.

[0030] The present invention is through VO x The hydroxyphosphoric acid-type phosphomolybdenum-vanadium heteropolyacid catalyst with regulated oxygen vacancies can efficiently complete deep desulfurization at low temperatures, significantly broadening the operating temperature and making it suitable for areas with lower temperatures. It does not require additional heating and is simple and convenient. It also reduces the amount of catalyst and oxidant used, lowering the catalyst cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a scanning electron micrograph of the hydroxyphosphoric acid type heteropolyacid salt catalyst HEDP-Mo7V5 prepared in Example 1;

[0032] Figure 2 This is a scanning electron microscope image of the hydroxyphosphoric acid type heteropolyacid catalyst HEDP-Mo8V4 prepared in Example 2;

[0033] Figure 3 This is a scanning electron micrograph of the hydroxyphosphoric acid type heteropolyacid catalyst HEDP-Mo9V3 prepared in Example 3;

[0034] Figure 4 The Fourier transform infrared spectra of the hydroxyphosphoric acid type heteropoly acid salt catalyst HEDP-Mo7V5, the hydroxyphosphoric acid type heteropoly acid salt catalyst HEDP-Mo8V4 and the hydroxyphosphoric acid type heteropoly acid salt catalyst HEDP-Mo9V3 prepared in Examples 1, 2 and 3 are shown;

[0035] Figure 5 Graphs showing oxygen vacancy rates for the hydroxyphosphoric acid type heteropolyacid salt catalysts HEDP-Mo7V5, HEDP-Mo8V4, and HEDP-Mo9V3 prepared in Examples 1, 2, and 3;

[0036] Figure 6 This is a graph showing the change of desulfurization efficiency over time in Example 4;

[0037] Figure 7 This is a graph showing the results of recycling the hydroxyphosphoric acid type heteropolyacid catalyst HEDP-Mo7V5 in Example 4;

[0038] Figure 8 This is a graph showing the results of recycling the hydroxyphosphoric acid type heteropolyacid catalyst HEDP-Mo7V5 in Example 6;

[0039] Figure 9 This is a diagram of the desulfurization effect in Comparative Example 1;

[0040] Figure 10 This is a diagram showing the desulfurization effect in Comparative Example 2;

[0041] Figure 11 This is a diagram showing the desulfurization effect in Comparative Example 3; DETAILED DESCRIPTION

[0042] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0043] In each case, if the stirring speed is not specifically stated, it is carried out at a speed of 200 r / min. When the conversion rate reaches 99.999% or more, it is considered to be 100% conversion.

[0044] Example 1

[0045] Preparation of hydroxyphosphoric acid catalyst HEDP-Mo7V5:

[0046] 5.04 g of MoO3 and 2.27 g of V2O5 were mixed and added to 160 mL of deionized water. The mixture was heated to 100° C. under condensation and reflux with continuous stirring. 6.2 g of a 50 wt% aqueous solution of hydroxyethylidene diphosphonic acid was then added dropwise (1 mL / min) and stirred at 100° C. for 24 h to obtain a HEDP-Mo7V5 catalyst. The HEDP-Mo7V5 catalyst solution was subjected to a microwave reaction (800 W) for 5 min (the material was divided into 50 mL crucibles for drying, 5 mL per crucible) to obtain a hydroxyphosphoric acid-type catalyst HEDP-Mo7V5. The scanning electron microscopy (SEM) image is shown as follows: Figure 1 As shown by Figure 1 It can be seen that the obtained catalyst is a material with loose nanopores; the Fourier infrared spectrum is as follows Figure 4 As shown by Figure 4 It can be seen that 1065cm -1 , 962cm -1 , 865cm -1 and 782cm -1 The left and right are the characteristic peaks of Keggin structure heteropoly acid, indicating that the hydroxyphosphoric acid type catalyst HEDP-Mo7V5 was successfully prepared. Figure 5 As shown by Figure 5 As shown, g = 2.003 is the characteristic g value of oxygen vacancies, indicating that the prepared catalyst has oxygen vacancies.

[0047] Example 2

[0048] Preparation of hydroxyphosphoric acid catalyst HEDP-Mo8V4:

[0049] 5.76 g of MoO3 and 1.82 g of V2O5 were mixed and added to 130 mL of deionized water. The mixture was heated to 100° C. under condensation and reflux with continuous stirring. 6.2 g of a 50 wt% aqueous solution of hydroxyethylidene diphosphonic acid was then added dropwise. The mixture was stirred at 100° C. for 24 h to obtain a HEDP-Mo8V4 catalyst. The HEDP-Mo8V4 catalyst solution was microwave-dried (800 W) for 5 min (the material was divided into 50 mL crucibles for drying, 5 mL per crucible) to obtain a hydroxyphosphoric acid-type catalyst, HEDP-Mo8V4. The scanning electron microscopy (SEM) image is shown below. Figure 2 As shown by Figure 2 It can be seen that the obtained catalyst is a material with loose nanopores; the Fourier infrared spectrum is as follows Figure 4 As shown by Figure 4 It can be seen that 1065cm -1 , 962cm -1 , 865cm -1 and 782cm -1The left and right are the characteristic peaks of Keggin structure heteropoly acid, indicating that the hydroxyphosphoric acid type catalyst HEDP-Mo8V4 was successfully prepared. Figure 5 As shown by Figure 5 As shown, g = 2.003 is the characteristic g value of oxygen vacancies, indicating that the prepared catalyst has oxygen vacancies.

[0050] Example 3

[0051] Preparation of hydroxyphosphoric acid catalyst HEDP-Mo9V3:

[0052] 6.48 g of MoO3 and 1.36 g of V2O5 were mixed and added to 140 mL of deionized water. The mixture was heated to 100° C. under condensation and reflux with continuous stirring. 6.2 g of a 50 wt% aqueous solution of hydroxyethylidene diphosphonic acid was then added dropwise thereto. The mixture was stirred at 100° C. for 24 h to obtain a HEDP-Mo9V3 catalyst. The HEDP-Mo9V3 catalyst solution was subjected to a microwave reaction (800 W) for 5 min (the material was divided into 50 mL crucibles for drying, 5 mL per crucible) to obtain a hydroxyphosphoric acid type catalyst, HEDP-Mo9V3. The scanning electron microscopy (SEM) image is shown as follows: Figure 3 As shown by Figure 3 It can be seen that the obtained catalyst is a porous material with a micron structure; the Fourier infrared spectrum is as follows Figure 4 As shown by Figure 4 It can be seen that 1065cm -1 , 962cm -1 , 865cm -1 and 782cm -1 The left and right are the characteristic peaks of Keggin structure heteropoly acid, indicating that the hydroxyphosphoric acid type catalyst HEDP-Mo9V3 was successfully prepared. Figure 5 As shown by Figure 5 As shown, g = 2.003 is the characteristic g value of oxygen vacancies, indicating that the prepared catalyst has oxygen vacancies.

[0053] Example 4

[0054] Taking dibenzothiophene (DBT), a relatively difficult substance to remove during hydrodesulfurization, as a representative substance, DBT was dissolved in 100 mL of 92# gasoline to prepare a simulated system with a sulfur content of 500 ppm. 7 mL of the simulated system was taken at a time, 1 mL of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate was added, and the mixture was stirred. Then, hydrogen peroxide (30% by mass) was added, calculated at an O / S (molar ratio) of 2.5. The hydroxyphosphoric acid catalyst HEDP-Mo7V5 prepared in Example 1 was added, calculated at 0.6% by mass of the 92# gasoline. Figure 6As shown, after 15 minutes of reaction at 10°C, the conversion rate (desulfurization rate) of DBT in 92# gasoline reached nearly 100%.

[0055] The same method was used to test the removal effect of HEDP-M8V4 and HEDP-Mo9V3 on DBT. The results are as follows: Figure 6 As shown in the figure, the conversion rate (desulfurization rate) of DBT in 92# gasoline reached nearly 100% after reaction at 15℃ for 15 minutes. Among them, HEDP-Mo7V5 had the best effect.

[0056] The hydroxyphosphoric acid catalysts HEDP-Mo7V5, HEDP-M8V4 and HEDP-Mo9V3 in the desulfurized material are recovered by sedimentation, filtration and drying, with a recovery rate of more than 99.9%. Figure 7 As shown, after 25 cycles, the catalytic efficiency decreases by about 0.2%. Figure 6 The figure shows the cycling effect of HEDP-Mo7V5. The cycling effect values ​​of HEDP-M8V4 and HEDP-Mo9V3 are basically the same as those of HEDP-Mo7V5, so they are not repeated here.

[0057] Example 5

[0058] Taking dibenzothiophene (DBT), a difficult-to-remove sulfur compound during hydrodesulfurization, as a representative example, DBT was dissolved in 100 mL of 95# gasoline to create a simulated system with a sulfur content of 500 ppm. 7 mL of the simulated system was then added to 1 mL of the ionic liquid 1-octyl-3-methylimidazolium tetrafluoroborate, followed by stirring. Hydrogen peroxide (calculated at an O / S (molar ratio) of 2.5) was then added, along with the hydroxyphosphoric acid catalyst HEDP-Mo7V5 (Example 1) (calculated at 0.6% by mass of the 95# gasoline). After reacting at 10°C for 15 minutes, the DBT conversion in the 95# gasoline reached 100%.

[0059] Example 6

[0060] Taking 4,6-dimethyldibenzothiophene (4,6-DMDBT), a difficult-to-remove hydrodesulfurization agent, as a representative, a simulated system with a sulfur content of 500 ppm was prepared by dissolving 4,6-DMDBT in 100 mL of 95# gasoline. 7 mL of the simulated system was then added with 1 mL of the ionic liquid 1-octyl-3-methylimidazolium tetrafluoroborate and stirred. Hydrogen peroxide (30% by mass) was then added, calculated to achieve an O / S molar ratio of 2.5. The hydroxyphosphoric acid catalyst HEDP-Mo7V5 (Example 1) was also added, calculated to be 0.6% by mass of the 95# gasoline. After reacting at 10°C for 15 minutes, the conversion of 4,6-DMDBT in the 95# gasoline reached over 99.9%.

[0061] The hydroxyphosphoric acid type catalyst HEDP-Mo7V5 in the above materials is recovered by sedimentation, filtration and drying, with a recovery rate of more than 99.9%. Figure 8 As shown, after 25 cycles, the catalytic efficiency decreased by 0.3%.

[0062] Comparative Example 1

[0063] Taking dibenzothiophene (DBT), which is difficult to remove in hydrodesulfurization, as a representative substance, DBT was dissolved in 100 mL of 92# gasoline to prepare a simulation system with a sulfur content of 500 ppm. 7 mL of the simulation system was taken at a time, and hydrogen peroxide (mass concentration 30%) was added according to the O / S (molar ratio) = 3. Figure 9 As shown, after reacting at 30°C for about 20 minutes, the conversion rate of DBT in 92# gasoline is only about 1.8%.

[0064] Comparative Example 2

[0065] Taking dibenzothiophene (DBT), which is difficult to remove during hydrodesulfurization, as a representative compound, DBT was dissolved in 100 mL of 92# gasoline to prepare a simulation system with a sulfur content of 500 ppm. 7 mL of the simulation system was taken at a time, 1 mL of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate was added, and the mixture was stirred. Hydrogen peroxide (mass concentration 30%) was added at an O / S (molar ratio) of 3. Figure 10 As shown, the conversion rate of DBT in 92# gasoline is only about 37% after reacting at 30°C for about 20 minutes.

[0066] Comparative Example 3

[0067] The difference from Example 4 is that the ionic liquid is replaced by 1-octyl-3-methylimidazolium hexafluorophosphate, and the rest is the same as Example 4. The catalyst used is a hydroxyphosphoric acid type catalyst HEDP-Mo7V5, such as Figure 11 As shown, after reacting at 30°C for about 20 minutes, the conversion rate (desulfurization rate) of DBT in 92# gasoline is only 75%.

Claims

1. A through VO x The invention relates to a hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies, characterized by: The general structural formula is HEDP-Mo 12-x V x , wherein HEDP is hydroxyethylidene diphosphate and x is a real number of 1-5.

2. Use of the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies by VOx according to claim 1, characterized in that: It is used for efficient desulfurization at low temperature and can complete deep desulfurization within 15 minutes at ≤10°C. The mass dosage of the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst that regulates oxygen vacancies through VOx is 0.3-0.6% of the quality of the oil to be desulfurized.

3. The use of the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies by VOx according to claim 2, characterized in that: After mixing the oil to be desulfurized and 1-methyl-3-octylimidazole tetrafluoroborate, add a hydroxyphosphoric acid-type phosphomolybdovanadium heteropolyacid catalyst with oxygen vacancies regulated by VOx and hydrogen peroxide, and stir to desulfurize. The amount of hydrogen peroxide is calculated based on an O / S molar ratio of ≤2.

5.

4. The use of the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies by VOx according to claim 3, characterized in that: The volume ratio of 1-methyl-3-octylimidazole tetrafluoroborate to the oil to be desulfurized is 1:(5-7).

5. Use of the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies by VOx according to claim 3 or 4, characterized in that: The mass concentration of hydrogen peroxide is 25-35%.

6. Use of the hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies by VOx according to claim 3 or 4, characterized in that: The reaction temperature during desulfurization is 0-40°C; the reaction time is 5-15 minutes.

7. A method for preparing a hydroxyphosphoric acid-type phosphomolybdovanadium heteropolyacid catalyst for regulating oxygen vacancies by VOx according to claim 1, characterized in that: It is prepared by reacting an aqueous solution of hydroxyethylidene diphosphoric acid with molybdenum trioxide and vanadium pentoxide; wherein the molar ratio of hydroxyethylidene diphosphoric acid to molybdenum trioxide is 1:(2.2-3.2); and the molar ratio of hydroxyethylidene diphosphoric acid to vanadium pentoxide is 1:(0.4-0.9).

8. The method for preparing a hydroxyphosphoric acid-type phosphomolybdovanadium heteropolyacid catalyst by regulating oxygen vacancies through VOx according to claim 3 or 4, characterized in that: The molar ratio of molybdenum trioxide to vanadium pentoxide is (2.8-6):

1.

9. The method for preparing a hydroxyphosphoric acid type phosphomolybdovanadium heteropolyacid catalyst by regulating oxygen vacancies through VOx according to claim 8, characterized in that: The molar ratio of molybdenum trioxide to vanadium pentoxide is (2.7-2.9):1.

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