Catalyst, preparation method and application thereof

Abstract

The present invention relates to the technical field of terephthalaldehyde, and discloses a catalyst, its preparation method, and application. The catalyst comprises a carrier and an active component supported on the carrier, wherein the active component comprises molybdenum oxide, iron oxide, and rubidium oxide. The preparation method of the catalyst comprises supporting an active component precursor on the carrier, wherein the active component precursor comprises a molybdenum salt, an iron salt, and a rubidium salt. When used in the direct oxidation of p-xylene to produce terephthalaldehyde, the catalyst exhibits high conversion, selectivity, and yield.

Description

Technical Field

[0001] The present invention relates to the technical field of terephthalaldehyde, in particular to a catalyst and a preparation method and application thereof. Background Art

[0002] Terephthalaldehyde is an important chemical raw material for the dye, pharmaceutical, and fragrance industries. It is also a key fine chemical raw material for the downstream products of para-xylene. Due to its two active aldehyde groups in its molecular structure, it can self-polymerize or copolymerize with other monomers to form polymers. These materials are primarily used in the synthesis of fluorescent materials, catalyst supports, and other polymer products.

[0003] The traditional production method is to chlorinate p-xylene and then hydrolyze it under the action of nitric acid or metal oxides to obtain terephthalaldehyde. The production process consumes a large amount of toxic chlorine, nitric acid and sodium hydroxide, and produces hydrogen chloride, NO x Gases such as chloroalkylbenzenes can cause serious environmental pollution and equipment corrosion. Material leakage is also a potential danger and can cause harm to the human body.

[0004] In addition to the traditional chlorination method, other methods for synthesizing terephthalaldehyde include terephthalate hydrogenation, terephthaloyl chloride hydrogenation, and direct oxidation of p-xylene. Direct oxidation of p-xylene with air is considered an environmentally friendly, green process and has attracted the attention of numerous chemical companies. Their research focuses on catalyst preparation, with catalyst selectivity and aldehyde yield being the most important objectives.

[0005] Catalyst preparation technologies for the selective oxidation of p-xylene to aromatic aldehydes include impregnation, sol-gel, and chemical vapor deposition. From the 1970s to 2006, companies such as Kodak in the United States, Japan Catalyst, and LG in South Korea all used the impregnation method to prepare catalysts. Tungsten trioxide was used as the primary catalyst, supplemented with one or two of molybdenum oxide, bismuth oxide, iron oxide, antimony oxide, and rubidium oxide as co-catalysts. Inorganic fireproof supports such as α-alumina, silicon dioxide, titanium dioxide, and zirconium oxide were added to a solution containing soluble compounds of the aforementioned metal elements and then impregnated. The catalyst was then evaporated, dried, and calcined to obtain the catalyst. LG's patent US7429682 discloses a catalyst using a composite of tungsten oxide and rubidium oxide, achieving p-xylene conversions of 53-86%, selectivity for terephthalaldehyde of 60-80%, and yields of 40-64%.

[0006] The conversion rate of p-xylene and the selectivity and yield of terephthalaldehyde need to be further improved. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of low conversion rate of p-xylene and low selectivity and yield of terephthalaldehyde in the prior art, and to provide a catalyst and its preparation method and application. The catalyst has high conversion rate, selectivity and yield when used in the direct oxidation of p-xylene to prepare terephthalaldehyde.

[0008] To achieve the above objectives, the present invention provides a catalyst in a first aspect, comprising a carrier and an active component supported on the carrier, wherein the active component comprises molybdenum oxide, iron oxide and rubidium oxide.

[0009] A second aspect of the present invention provides a method for preparing a catalyst, which comprises loading an active component precursor on a carrier and calcining the carrier, wherein the active component precursor comprises a molybdenum precursor, an iron precursor and a rubidium precursor.

[0010] The third aspect of the present invention provides a use of the above catalyst in the direct oxidation of p-xylene to produce terephthalaldehyde.

[0011] Through the above technical solution, the present invention has the following beneficial effects:

[0012] (1) The molybdenum oxide, iron oxide and rubidium oxide in the catalyst of the present invention cooperate with each other, which not only improves the conversion rate of p-xylene but also improves the selectivity of terephthalaldehyde, thereby increasing the yield of terephthalaldehyde in the product.

[0013] (2) The present invention uses a sol-gel method to coat a gel of molybdenum salt, iron salt and rubidium salt on a carrier, and then calcines the catalyst to obtain the catalyst, the content of which active ingredients can be controlled as needed.

[0014] (3) The catalyst of the present invention can be used to directly oxidize p-xylene to produce terephthalaldehyde using air. During the reaction, no toxic gases (chlorine, hydrogen chloride, or nitrogen oxides) or waste acid are produced, resulting in virtually no environmental impact, making this an environmentally friendly, green process. When the catalyst is used to directly oxidize p-xylene to produce terephthalaldehyde, the conversion of p-xylene can reach over 98%, the selectivity for terephthalaldehyde can reach 78%, and the yield can reach 77.5%. DETAILED DESCRIPTION

[0015] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0016] In a first aspect, the present invention provides a catalyst comprising a carrier and an active component supported on the carrier, wherein the active component comprises molybdenum oxide, iron oxide and rubidium oxide.

[0017] The active components of the catalyst in the present invention do not include tungsten oxide and nickel oxide.

[0018] According to the present invention, preferably, the molar ratio of the molybdenum oxide, iron oxide and rubidium oxide, calculated as metal elements, is 3:0.8-1.5:0.01-0.1, preferably 3:1-1.2:0.02-0.05, and more preferably 3:1.1:0.02-0.05.

[0019] According to the present invention, preferably, the content of the active component is 5-16 g, preferably 9-13 g, per 100 g of the catalyst.

[0020] According to the present invention, preferably, the content of the carrier is 84-95 g, preferably 87-91 g, per 100 g of the catalyst.

[0021] In the present invention, the carrier can be a common carrier in the art. According to a preferred embodiment of the present invention, the carrier is at least one of talc, aluminum silicate, silicon dioxide, quartz, titanium dioxide, aluminum oxide, zirconium oxide, silicon carbide and ceramics, preferably talc.

[0022] A second aspect of the present invention provides a method for preparing a catalyst, which includes loading an active component precursor on a carrier and calcining the carrier, wherein the active component precursor includes a molybdenum precursor, an iron precursor and a rubidium precursor.

[0023] In the present invention, the method for loading the active component precursor on the carrier can be a commonly used method in the art, as long as the active component precursor can be loaded on the catalyst, for example, an impregnation method, a deposition precipitation method, an ion exchange method, a chemical vapor deposition method or a sol-gel method can be used.

[0024] According to the present invention, in order to improve the uniformity of the active components of the catalyst and ultimately improve the selectivity and yield of benzaldehyde, the present invention adopts a sol-gel method to prepare the catalyst. Preferably, the method includes the following steps: (1) heating an aqueous solution of an active component precursor to form a sol, which is then aged to form a gel; and (2) coating the gel on a carrier, which is then calcined to obtain the catalyst.

[0025] According to the present invention, preferably, the amount of the active component precursor used, calculated as metal elements, is such that the molar ratio of molybdenum oxide, iron oxide and rubidium oxide in the obtained catalyst is 3:0.8-1.5:0.01-0.1, preferably 3:1-1.2:0.02-0.05, and further preferably 3:1.1:0.02-0.05.

[0026] According to the present invention, preferably, the amount of the active component precursor used is such that the active component content in the obtained catalyst is 5-16 g, preferably 9-13 g, per 100 g of the catalyst.

[0027] According to the present invention, preferably, the amount of the carrier used is such that the content of the carrier in the obtained catalyst is 84-95 g, preferably 87-91 g, per 100 g of the catalyst.

[0028] In the present invention, the carrier can be a common carrier in the art. According to a preferred embodiment of the present invention, the carrier is at least one of talc, aluminum silicate, silicon dioxide, quartz, titanium dioxide, aluminum oxide, zirconium oxide, silicon carbide and ceramics, preferably talc.

[0029] In the present invention, the shape of the carrier is not particularly limited and can be any of spherical, ring-shaped, granular, and cylindrical.

[0030] According to the present invention, preferably, the molybdenum precursor is at least one of ammonium molybdate, sodium molybdate and phosphomolybdic acid.

[0031] According to the present invention, preferably, the iron precursor is ferric nitrate and / or ferric citrate.

[0032] According to the present invention, preferably, the rubidium precursor is at least one of rubidium nitrate, rubidium carbonate and rubidium chloride.

[0033] According to the present invention, preferably, the heating temperature is 70-100°C, preferably 80-85°C.

[0034] According to the present invention, the heating time is not particularly limited. Preferably, the water content in the aqueous solution of the active component precursor is evaporated to 1 / 3-2 / 3.

[0035] According to the present invention, the heating method is not particularly limited. Preferably, the heating method is water bath heating.

[0036] According to the present invention, preferably, the aging time is 8-12 hours.

[0037] According to the present invention, the aging temperature is not particularly limited and can be performed at room temperature or under heating conditions. Preferably, the aging is performed at room temperature.

[0038] In the present invention, room temperature refers to "15-40°C".

[0039] According to the present invention, the calcination temperature is 400-600° C. and the calcination time is 2-6 hours.

[0040] According to a preferred embodiment of the present invention, the method for preparing the aqueous solution of the active component precursor comprises: dissolving the active component precursors in water respectively, mixing them, adding an organic acid, and adjusting the pH value to 2-3.

[0041] According to the present invention, preferably, the organic acid is citric acid.

[0042] According to the present invention, preferably, the coating is carried out in an environment of 120-140° C., that is, during the coating process, hot air at 120-140° C. is used to dry the coated article immediately.

[0043] According to the present invention, in order to ensure a certain adhesion between the active ingredient and the carrier, preferably, the method further comprises adding an adhesive to the gel and then coating the carrier.

[0044] According to the present invention, preferably, the adhesive is an organic adhesive. Further preferably, the organic adhesive is one of a vinyl acetate-acrylate copolymer, a vinyl acetate-maleate copolymer, a vinyl acetate-ethylene copolymer, and an acrylic acid-maleic acid copolymer.

[0045] According to the present invention, the amount of the binder is not particularly limited, as long as the gel can be coated on the carrier. The binder is decomposed after calcination.

[0046] According to the most preferred embodiment of the present invention, the method for preparing the catalyst comprises: dissolving (NH4)2MoO4 in water, dissolving Fe(NO3)3·9H2O in water, dissolving rubidium nitrate in water, and then mixing an aqueous solution of ammonium molybdate, an aqueous solution of ferric nitrate and an aqueous solution of rubidium nitrate to produce a precipitate, reacting for 8-12 minutes and then adding citric acid until the precipitate is dissolved, stirring and adjusting the pH value to 1.5-2 with aqueous ammonia to obtain an aqueous solution of an active component precursor, heating and stirring the obtained aqueous solution of the active component precursor in a constant temperature water bath at 80-82°C until half of the water in the solution evaporates, and then aging at room temperature for 9.5-10.5h to form a gel, adding an organic binder vinyl acetate-acrylate copolymer to the gel and stirring evenly, coating the talc balls with the mixture of the gel and the organic binder, and drying the coating environment with hot air at 115-125°C immediately, and finally calcining the catalyst at 490-520°C for 3.5-4.4h to obtain the catalyst. In the most preferred embodiment, relative to 11.76 g of (NH4)2MoO4, the weight of Fe(NO3)3·9H2O is 8.5-9 g, the molar number of rubidium nitrate is 0.7-0.9 mmol, the weight of the organic binder vinyl acetate-acrylate copolymer is 2.25-2.35 g, and the weight gain of the carrier is 2.1-2.3 g when the coating is completed.

[0047] The third aspect of the present invention provides a catalyst prepared by the above method.

[0048] A fourth aspect of the present invention provides an application of the above catalyst in the direct oxidation of p-xylene to produce terephthalaldehyde.

[0049] In the present invention, the conditions for the catalytic reaction of the catalyst for direct oxidation of p-xylene to produce terephthalaldehyde are not particularly limited and may be the conditions for catalytic reactions commonly used in the art. According to a preferred embodiment of the present invention, the conditions for the catalytic reaction include: a p-xylene flow rate of 0.01-0.5 mL / min, an oxygen volume space velocity of 300-1200 h / min, and a catalytic reaction temperature of 100-2000 °C. -1 , the reaction temperature is 300-500°C, and the reaction pressure is normal pressure.

[0050] In the present invention, "normal pressure" refers to a gauge pressure of 0.1 MPa.

[0051] According to the present invention, the oxygen can be an oxygen-containing gas or pure oxygen. Preferably, air is used to oxidize paraxylene in the present invention.

[0052] According to the present invention, preferably, the volume space velocity of the air is 1500-6000h -1 .

[0053] In the present invention, the reactor for the catalytic reaction is not particularly limited and can be any reactor commonly used in the art. According to a preferred embodiment of the present invention, the reactor for the catalytic reaction is a fixed bed reactor, preferably a micro multi-channel fixed bed reactor; the reaction tube in the micro multi-channel fixed bed reactor is 200-300 mm long and has an inner diameter of 5-15 mm.

[0054] The present invention will be described in detail below by way of examples.

[0055] The catalytic products were analyzed on an Agilent 7890A gas chromatograph using the external standard method;

[0056]

[0057]

[0058]

[0059] Vinyl acetate-ethylene copolymer emulsion, Beijing Dongfang Petrochemical Co., Ltd. Organic Chemical Plant.

[0060] Example 1

[0061] 11.76g of (NH4)2MoO4 was dissolved in 25mL of water, 8.888g of Fe(NO3)3·9H2O was dissolved in 8mL of water, 8g of 0.1mmol / g rubidium nitrate aqueous solution was taken, and then the ammonium molybdate aqueous solution, the ferric nitrate aqueous solution and the rubidium nitrate aqueous solution were mixed to produce a precipitate. After reacting for 10min, citric acid was added until the precipitate dissolved, stirred and the pH value was adjusted to 2 with ammonia water to obtain an aqueous solution of the active component precursor. The obtained aqueous solution of the active component precursor was heated and stirred in a constant temperature water bath at 80°C until half of the water in the solution evaporated, and then aged at room temperature for 10h to form a gel. 2.3g of an organic binder vinyl acetate-acrylate copolymer was added to the gel and stirred evenly. 20g of talc balls were coated with the mixture of the gel and the organic binder. The coating environment was immediately dried with hot air at 120°C. When the coating was completed, the carrier weight increased by 2.2g. Finally, the catalyst was calcined at 500°C for 4h to obtain the catalyst Mo3Fe 1.1 Rb 0.04 .

[0062] Example 2

[0063] 11.76g of (NH4)2MoO4 was dissolved in 25mL of water, 8.08g of Fe(NO3)3·9H2O was dissolved in 8mL of water, 4g of 0.1mmol / g rubidium nitrate aqueous solution was taken, and then the ammonium molybdate aqueous solution, the ferric nitrate aqueous solution and the rubidium nitrate aqueous solution were mixed to form a precipitate. After reacting for 10min, citric acid was added until the precipitate dissolved, and the pH value was adjusted to 2.5 with ammonia water to obtain an aqueous solution of the active component precursor. The active component precursor aqueous solution was heated and stirred in a constant temperature water bath at 85℃ until half of the water in the solution evaporated, and then aged at room temperature for 9h to form a gel. 2.1g of an organic binder vinyl acetate-acrylate copolymer was added to the gel and stirred evenly. The mixture of the gel and the organic binder was coated on 20g of talc balls. The coating environment was immediately dried with hot air at 140℃. When the coating was completed, the carrier weight increased by 2.2g. Finally, the coated carrier was calcined at 550℃ for 3h to obtain the catalyst Mo3Fe1Rb 0.02 .

[0064] Example 3

[0065] 11.76g of (NH4)2MoO4 was dissolved in 25mL of water, 9.696g of Fe(NO3)3·9H2O was dissolved in 8mL of water, 10g of 0.1mmol / g rubidium nitrate aqueous solution was taken, and then the ammonium molybdate aqueous solution, the ferric nitrate aqueous solution and the rubidium nitrate aqueous solution were mixed to produce a precipitate. After reacting for 10min, citric acid was added until the precipitate dissolved, stirred and the pH value was adjusted to 3 with ammonia water to obtain an aqueous solution of the active component precursor. The active component precursor aqueous solution was heated and stirred in a constant temperature water bath at 80℃ until half of the water in the solution evaporated, and then aged at room temperature for 11h to form a gel. 2.4g of an organic binder vinyl acetate-acrylate copolymer was added to the gel and stirred evenly. The mixture of the gel and the organic binder was coated on 20g of talc balls. The coating environment was immediately dried with hot air at 130℃. When the coating was completed, the carrier weight increased by 2.2g. Finally, the coated carrier was calcined at 450℃ for 5h to obtain the catalyst Mo3Fe 1.2 Rb 0.05 .

[0066] Example 4

[0067] 11.76g of (NH4)2MoO4 was dissolved in 25mL of water, 6.464g of Fe(NO3)3·9H2O was dissolved in 8mL of water, 20g of 0.1mmol / g rubidium nitrate aqueous solution was taken, and then the ammonium molybdate aqueous solution, the ferric nitrate aqueous solution and the rubidium nitrate aqueous solution were mixed to produce a precipitate. After reacting for 10min, citric acid was added until the precipitate dissolved, stirred and the pH value was adjusted to 2.5 with ammonia water to obtain an aqueous solution of the active component precursor. The active component precursor aqueous solution was heated and stirred in a constant temperature water bath at 70°C until half of the water in the solution evaporated, and then aged at room temperature for 12h to form a gel. 2.6g of an organic binder vinyl acetate-acrylate copolymer was added to the gel and stirred evenly. The mixture of the gel and the organic binder was coated on 20g of talc balls. The coating environment was immediately dried with hot air at 120°C. When the coating was completed, the carrier weight increased by 2.2g. Finally, the coated carrier was calcined at 400°C for 6h to obtain the catalyst Mo3Fe 0.8 Rb 0.1 .

[0068] Example 5

[0069] 11.76g of (NH4)2MoO4 was dissolved in 25mL of water, 12.12g of Fe(NO3)3·9H2O was dissolved in 8mL of water, 4g of 0.1mmol / g rubidium nitrate aqueous solution was taken, and then the ammonium molybdate aqueous solution, the ferric nitrate aqueous solution and the rubidium nitrate aqueous solution were mixed to produce a precipitate. After reacting for 10min, citric acid was added until the precipitate dissolved, stirred and the pH value was adjusted to 3 with ammonia water to obtain an aqueous solution of the active component precursor. The active component precursor aqueous solution was heated and stirred in a constant temperature water bath at 100℃ until half of the water in the solution evaporated, and then aged at room temperature for 8h to form a gel. 2.2g of an organic binder vinyl acetate-acrylate copolymer was added to the gel and stirred evenly. The mixture of the gel and the organic binder was coated on 20g of talc balls. The coating environment was immediately dried with hot air at 130℃. When the coating was completed, the carrier weight increased by 2.2g. Finally, the coated carrier was calcined at 600℃ for 2h to obtain the catalyst Mo3Fe 1.5 Rb 0.02 .

[0070] Example 6

[0071] The catalyst was prepared according to the method of Example 1, except that the amount of rubidium nitrate aqueous solution was 4 g, and the catalyst Mo3Fe 1.1 Rb 0.02 .

[0072] Example 7

[0073] The catalyst was prepared according to the method of Example 1, except that the amount of rubidium nitrate aqueous solution was 6 g, and the catalyst Mo3Fe 1.1 Rb 0.03 .

[0074] Example 8

[0075] The catalyst was prepared according to the method of Example 1, except that the amount of rubidium nitrate aqueous solution was 10 g, and the catalyst Mo3Fe 1.1 Rb 0.05 .

[0076] Example 9

[0077] The catalyst was prepared according to the method of Example 1, except that the amount of rubidium nitrate aqueous solution was 20 g, and the catalyst Mo3Fe 1.1 Rb 0.1 .

[0078] Example 10

[0079] The catalyst was prepared according to the method of Example 1, except that 8.08 g of ferric nitrate was dissolved in 8 ml of water to obtain the catalyst Mo3Fe1Rb 0.04 .

[0080] Example 11

[0081] The catalyst was prepared according to the method of Example 1, except that 9.696 g of ferric nitrate was dissolved in 8 ml of water to obtain the catalyst Mo3Fe 1.2 Rb 0.04 .

[0082] Example 12

[0083] The catalyst was prepared according to the method of Example 1, except that the coated support was calcined twice, at 250° C. for 2 h and at 500° C. for 4 h.

[0084] Comparative Example 1

[0085] The catalyst was prepared according to the method of Example 1, except that no rubidium nitrate aqueous solution was added, and the catalyst Mo3Fe 1.1 .

[0086] Comparative Example 2

[0087] The catalyst was prepared according to the method of Example 7, except that cesium nitrate aqueous solution was used instead of rubidium nitrate aqueous solution, and the catalyst Mo3Fe 1.1 Cs 0.04 .

[0088] Comparative Example 3

[0089] The catalyst was prepared according to the method of Example 1, except that 14.88 g (NH4)6H2W 12 O 40 H2O was dissolved in 25mL water, 11.76g (NH4)2MoO4 was dissolved in 25mL water, 4g of 0.1mmol / g rubidium nitrate aqueous solution was taken, and then the tungsten salt aqueous solution, ammonium molybdate aqueous solution and rubidium nitrate aqueous solution were mixed to form a precipitate, and finally the catalyst W was obtained. 12 3Rb 0.02 .

[0090] Comparative Example 4

[0091] The catalyst was prepared according to the method of Example 1, except that 14.88 g (NH4)6H2W 12 O 40 H2O was dissolved in 25 mL of water, 1 g of 0.1 mmol / g rubidium nitrate aqueous solution was taken, and then the tungsten salt aqueous solution and the rubidium nitrate aqueous solution were mixed to form a precipitate, and finally the catalyst W was obtained. 12 Rb 0.02 .

[0092] Test Case

[0093] The catalysts prepared in Examples 1-13 and Comparative Examples 1-4 were used to directly oxidize p-xylene to produce terephthalaldehyde. The test conditions included: a micro multi-channel fixed-bed reactor was used, the reaction tube in the fixed-bed reactor was 230 mm long, 10 mm in inner diameter, and 140 mm in height, 5 g of catalyst was loaded, p-xylene was pumped into the vaporizer at 0.01 mL / min for vaporization, the temperature in the vaporizer was 300°C, and the volumetric air space velocity was 5000 h / min. -1 The reaction tube temperature was 450°C and the reaction pressure was normal pressure. After 3 hours of reaction, the product was collected in a test tube cooled with cold water and sampled for analysis. The analysis results are shown in Table 2.

[0094] Table 1

[0095] p-Xylene conversion rate (%) Terephthalaldehyde selectivity (%) Terephthalaldehyde yield (%) Example 1 98.8 78.4 77.5 Example 2 97.5 77.6 75.7 Example 3 98.6 77.9 76.8 Example 4 96.7 70.3 68.0 Example 5 98.2 65.7 64.5 Example 6 92.7 74.8 69.3 Example 7 94.6 77.1 72.9 Example 8 95.2 79.3 75.5 Example 9 89.1 71.5 63.7 Example 10 97.2 74.5 72.4 Example 11 98.0 75.1 73.6 Example 12 97.6 72.5 70.8 Comparative Example 1 88.4 53.2 47.0 Comparative Example 2 92.4 58.6 54.1 Comparative Example 3 87.2 57.9 50.5 Comparative Example 4 78.9 53.8 42.4

[0096] The results in Table 1 demonstrate that the coordination of molybdenum oxide, iron oxide, and rubidium oxide in the catalyst provided by the present invention not only increases the conversion of p-xylene but also enhances the selectivity for terephthalaldehyde, thereby increasing the yield of terephthalaldehyde in the product. Compared with Comparative Example 1, the addition of rubidium oxide to the catalyst of the present invention improves both the conversion of p-xylene and the selectivity for terephthalaldehyde. Compared with the tungsten oxide-containing catalysts of Comparative Examples 3-4, the catalysts of the present invention containing molybdenum oxide, iron oxide, and rubidium oxide exhibit higher p-xylene conversion and terephthalaldehyde selectivity.

[0097] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A catalyst, characterized in that The catalyst contains a carrier and active components supported on the carrier, wherein the active components are molybdenum oxide, iron oxide and rubidium oxide; the molar ratio of the molybdenum oxide, iron oxide and rubidium oxide is 3:0.8-1.5:0.01-0.1, calculated as metal elements; the content of the active components is 5-16g per 100g of the catalyst, the content of the carrier is 84-95g, and the carrier is at least one of talc, aluminum silicate, silicon dioxide, quartz, titanium dioxide, aluminum oxide, zirconium oxide, silicon carbide and ceramics.

2. The catalyst according to claim 1, wherein Calculated as metal elements, the molar ratio of the molybdenum oxide, the iron oxide and the rubidium oxide is 3:1-1.2:0.02-0.05; and / or, the content of the active component is 9-13 g per 100 g of the catalyst; And / or, the content of the carrier is 87-91 g per 100 g of the catalyst.

3. A method for preparing a catalyst, characterized in that: The method comprises loading active component precursors on a carrier and calcining the catalyst, wherein the active component precursors are a molybdenum precursor, an iron precursor and a rubidium precursor; wherein, calculated as metal elements, the amount of the active component precursors is such that the molar ratio of molybdenum oxide, iron oxide and rubidium oxide in the obtained catalyst is 3:0.8-1.5:0.01-0.1; the amount of the active component precursors and the carrier is such that, per 100g of the catalyst, the active component content is 5-16g and the carrier content is 84-95g; and the carrier is at least one of talc, aluminum silicate, silicon dioxide, quartz, titanium dioxide, aluminum oxide, zirconium oxide, silicon carbide and ceramics.

4. The method according to claim 3, wherein: The method comprises the following steps: (1) heating an aqueous solution of an active component precursor to form a sol, and then aging the solution to form a gel; (2) After coating the gel on the carrier, the catalyst is obtained by calcining.

5. The method according to claim 4, wherein The amount of the active component precursor used, calculated as metal elements, is such that the molar ratio of molybdenum oxide, iron oxide, and rubidium oxide in the resulting catalyst is 3:1-1.2:0.02-0.05; and / or, the amount of the active component precursor used is such that the active component content in the resulting catalyst is 9-13 g per 100 g of the catalyst; and / or, the amount of the carrier is such that the content of the carrier in the obtained catalyst is 87-91 g per 100 g of the catalyst; and / or, the molybdenum precursor is at least one of ammonium molybdate, sodium molybdate and phosphomolybdic acid; and / or, the iron precursor is ferric nitrate and / or ferric citrate; And / or, the rubidium precursor is at least one of rubidium nitrate, rubidium carbonate and rubidium chloride.

6. The method according to claim 4, wherein: The heating temperature is 70-100° C. And / or, the aging time is 8-12h; And / or, the calcination temperature is 400-600° C. and the calcination time is 2-6 hours.

7. The method according to claim 4, wherein: The heating temperature is 80-85°C.

8. The method according to claim 4, wherein The preparation method of the aqueous solution of the active component precursor comprises: dissolving the active component precursor in water respectively, adding organic acid after mixing, and adjusting the pH value to 2-3.

9. The method according to claim 8, wherein The organic acid is citric acid.

10. The method according to claim 4, wherein: The coating is carried out in an environment of 120-140°C.

11. The method according to claim 4, wherein The method further comprises adding a binder to the gel and then coating the carrier.

12. The method according to claim 11, wherein The adhesive is an organic adhesive.

13. The method according to claim 11, wherein The adhesive is one of a vinyl acetate-acrylate copolymer, a vinyl acetate-ethylene copolymer, a vinyl acetate-maleic acid copolymer, and an acrylic acid-maleic acid copolymer.

14. A catalyst prepared by the method according to any one of claims 4 to 13.

15. Use of the catalyst according to any one of claims 1 to 2 and 14 in the preparation of terephthalaldehyde by direct oxidation of p-xylene.

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