Vanadium-molybdenum-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a vanadium-molybdenum-based catalyst and a preparation method and application thereof.The catalyst comprises a carrier and active components loaded on the carrier, the active components comprise vanadium and / or an oxide thereof and molybdenum and / or an oxide thereof, and the molar ratio of molybdenum to vanadium on the surface of the catalyst is larger than the average molar ratio of molybdenum to vanadium in the catalyst. The surface of the catalyst has a relatively high vanadium-molybdenum ratio, and the catalyst has relatively high catalytic activity when being used for preparing aromatic aldehyde by oxidizing alkyl aromatic hydrocarbon (such as methyl substituted aromatic hydrocarbon), which is specifically reflected in relatively high conversion rate and relatively high yield.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, and particularly relates to a vanadium-molybdenum-based catalyst, its preparation method and application, which can be used in the reaction of oxidizing tert-butyltoluene to prepare p-tert-butylbenzaldehyde. Background Technology

[0002] p-tert-butylbenzaldehyde is an important intermediate in fine chemical products such as pharmaceuticals, dyes, and fragrances, especially in the synthesis of lily aldehyde in fragrances, where demand is particularly high. Lily aldehyde, due to its fresh aroma, long-lasting scent, and low skin irritation, is widely used in mid-to-high-end cosmetics and daily fragrances. Currently, developed countries such as the United States, Germany, the United Kingdom, Japan, and Switzerland all have large-scale lily aldehyde production companies. Givaudan of Switzerland holds a monopoly position globally due to the superior quality of its products. my country, however, mainly relies on imports for its lily aldehyde needs. As a key step in the synthesis of lily aldehyde, the preparation of p-tert-butylbenzaldehyde determines the technological level of subsequent lily aldehyde synthesis.

[0003] Traditional industrial production of p-tert-butylbenzaldehyde employs a chemical oxidation method, using MnO2 as an oxidant to directly oxidize p-tert-butyltoluene in concentrated sulfuric acid. While this process is favored due to its high product purity and pure, unblemished aroma, it suffers from drawbacks such as severe equipment corrosion and pollution, difficulty in recovering the large amounts of MnSO4 generated, high production costs, and difficulties in product separation. A new process for synthesizing p-tert-butylbenzaldehyde involves the hydrolysis of benzyl chloride. In this process, p-tert-butyltoluene is reacted with sulfuric acid, formaldehyde, and concentrated hydrochloric acid to produce p-tert-butylbenzyl chloride, which then reacts with hexamethylenetetramine in dilute acetic acid, followed by hydrolysis to obtain the final product. This method has mature process conditions, but it involves numerous reaction steps, resulting in a low yield. Furthermore, the product contains trace amounts of difficult-to-remove organochlorine compounds, which are carcinogenic. Subsequent treatment processes also generate large amounts of sodium chloride or calcium chloride wastewater, causing serious environmental pollution.

[0004] Air oxidation is a greener and more environmentally friendly process. This method uses oxygen as the oxygen source to remove methyl hydrogen in one step, generating the corresponding aldehyde group. Theoretically, the only byproduct is water, resulting in strong atom economy. Currently, the main oxidation reaction of p-tert-butyltoluene uses liquid-phase oxidation in a batch reactor. This method offers mild reaction conditions and high selectivity. However, batch reactors also have certain drawbacks. First, production is discontinuous, limiting efficiency. Second, solvents still need to be added during the reaction, and the solvent must be separated from the reaction products, increasing energy consumption and reducing economic efficiency. Gas-phase oxidation in a fixed-bed reactor significantly improves product purity and production efficiency. Furthermore, the heat of reaction can be collected and utilized, resulting in even greater economic benefits. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the present invention provides a vanadium-molybdenum-based catalyst, its preparation method and application. The catalyst has a high vanadium-molybdenum ratio on its surface and exhibits higher catalytic activity when used for the oxidation of alkyl aromatics (e.g., methyl-substituted aromatics) to prepare aromatic aldehydes, specifically manifested in higher conversion rate and higher yield.

[0006] One objective of this invention is to provide a vanadium-molybdenum-based catalyst comprising a support and an active component supported on the support, wherein the active component comprises vanadium and / or its oxides, molybdenum and / or its oxides, and wherein the molar ratio of molybdenum to vanadium on the catalyst surface is greater than the average molar ratio of molybdenum to vanadium in the catalyst.

[0007] The average molar ratio of molybdenum and vanadium in the catalyst refers to the average molar ratio of molybdenum and vanadium in the entire catalyst.

[0008] In a preferred embodiment, the support is selected from at least one of SiO2, Al2O3, and TiO2.

[0009] In a preferred embodiment, the average molar ratio of molybdenum to vanadium in the catalyst is 0.005 to 0.5, preferably 0.01 to 0.2, for example 0.005, 0.01, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.3, 0.4 or 0.5.

[0010] In a preferred embodiment, the molar ratio of molybdenum to vanadium on the catalyst surface is greater than 0.78, preferably greater than or equal to 0.8, more preferably 0.82 to 1.2, for example 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15 or 1.2.

[0011] In a preferred embodiment, the active component further includes an optional element X and / or its oxide, wherein the element X is selected from one or more elements of Group VIIB, Group VIII, Group IVA, and Group IB.

[0012] In a further preferred embodiment, element X is selected from one or more of Mn, Sn, Cu, Co, Ni, and Fe.

[0013] In a further preferred embodiment, the average molar ratio of element X to element vanadium is 0 to 1, preferably 0.01 to 0.5, for example, 0.005, 0.01, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.8 or 1.

[0014] In a preferred embodiment, the active component further includes, optionally, element Y and / or its oxide, wherein element Y is selected from one or more elements of Group IA and Group IIA.

[0015] In a further preferred embodiment, the Y element is selected from one or more of K, Rb, Cs, Mg, Sr, and Ba.

[0016] In a further preferred embodiment, the average molar ratio of Y to vanadium is 0 to 1, preferably 0.01 to 0.5, for example, 0.005, 0.01, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.8 or 1.

[0017] In this invention, most preferably, the active component includes V 1.0 X x Y y Mo z O w The values ​​of x, y, and z range from 0 to 1, 0 to 1, and 0.005 to 0.5, respectively. w represents the number of oxygen atoms required to satisfy the oxidation states of each element in the catalyst. Preferably, the values ​​of x, y, and z range from 0.01 to 0.5, 0.01 to 0.5, and 0.01 to 0.2, respectively. w represents the number of oxygen atoms required to satisfy the oxidation states of each element in the catalyst.

[0018] In a preferred embodiment, the active component is 0.3 to 20 wt% of 100 wt% of the catalyst, wherein the weight of the active component is based on the weight of the oxides corresponding to the elements (vanadium, molybdenum, X, Y).

[0019] For example, based on 100 wt% of the catalyst, the active component is 0.3 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%, wherein the weight of the active component is based on the weight of the oxides corresponding to the elements (vanadium, molybdenum, X, Y).

[0020] In a further preferred embodiment, the active component is 1 to 15 wt% of 100 wt% of the catalyst, wherein the weight of the active component is based on the weight of the oxide corresponding to the element.

[0021] A second objective of this invention is to provide a method for preparing a vanadium-molybdenum-based catalyst, preferably used for preparing the vanadium-molybdenum-based catalyst described in one objective of this invention. The preparation method includes:

[0022] (1) A vanadium source, an optional X source, and an optional Y source are loaded onto a support, and then dried and calcined to obtain a catalyst precursor;

[0023] (2) The molybdenum source is loaded onto the catalyst precursor and then dried and calcined to obtain the catalyst.

[0024] In a preferred embodiment, the vanadium source is selected from one or more of vanadium sulfate, vanadium oxysulfate, vanadium oxalate, ammonium metavanadate, and vanadium pentoxide.

[0025] When vanadium pentoxide is used, it can be dissolved in oxalic acid, with oxalic acid and vanadium pentoxide added in a molar ratio of 1:(0.5~5).

[0026] In a preferred embodiment, the X source and the Y source are each independently selected from the water-soluble salts corresponding to their elements, preferably from one or more of soluble chlorides, soluble sulfates, soluble nitrates, soluble acetates, and soluble oxalates.

[0027] In a preferred embodiment, the molybdenum source is selected from one or more of ammonium molybdate, ammonium molybdate-substrate, and ammonium paramolybdate.

[0028] In a preferred embodiment, the support is selected from at least one of SiO2, Al2O3, and TiO2.

[0029] In a preferred embodiment, the molar ratio of molybdenum source to vanadium source is 0.005 to 0.5, preferably 0.01 to 0.2, for example 0.005, 0.01, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.3, 0.4 or 0.5, wherein the molybdenum source is measured in moles of molybdenum and the vanadium source is measured in moles of vanadium.

[0030] In a preferred embodiment, the molar ratio of X source to vanadium source is 0 to 1, preferably 0.01 to 0.5, for example 0.005, 0.01, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.8 or 1, wherein X source is measured in moles of element X, and vanadium source is measured in moles of element vanadium.

[0031] In a preferred embodiment, the molar ratio of the Y source to the vanadium source is 0 to 1, preferably 0.01 to 0.5, for example, 0.005, 0.01, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.8 or 1, wherein the Y source is measured in moles of Y element and the vanadium source is measured in moles of vanadium element.

[0032] In a preferred embodiment, based on the total weight of the carrier, the oxide corresponding to the vanadium source, the oxide corresponding to the molybdenum source, the oxide corresponding to the X source, and the oxide corresponding to the Y source (100wt%), the total weight of the oxide corresponding to the vanadium source, the oxide corresponding to the molybdenum source, the oxide corresponding to the X source, and the oxide corresponding to the Y source is 0.3-20wt%, preferably 1-15wt%, for example 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, or 20wt%.

[0033] In a preferred embodiment, the loading in step (1) includes: mixing a vanadium source, an optional X source, an optional Y source, and water to obtain an impregnation solution one, and mixing the carrier with the impregnation solution one to perform the loading; preferably, the mixed impregnation is an equal-volume impregnation.

[0034] In a preferred embodiment, in step (1), the drying is performed by resting (air drying) and / or baking.

[0035] In a further preferred embodiment, the settling time is 4 to 48 hours; and / or the drying conditions include a temperature of 60 to 130°C (preferably 90 to 130°C) and a time of 4 to 12 hours.

[0036] For example, the settling time is 4h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h or 48h; and / or, the drying conditions include: a temperature of 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃ or 130℃, and a time of 4h, 6h, 8h, 10h or 12h.

[0037] In a preferred embodiment, in step (1), the calcination conditions include: a time of 1 to 10 hours and a temperature of 300 to 650°C.

[0038] For example, in step (1), the roasting conditions include: a time of 1h, 2h, 4h, 6h, 8h or 10h, and a temperature of 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃ or 650℃.

[0039] In a further preferred embodiment, in step (1), the calcination conditions include: a time of 2 to 8 hours and a temperature of 350 to 550°C.

[0040] In a further preferred embodiment, the calcination in step (1) is carried out under a protective atmosphere, preferably selected from one or more of nitrogen and inert gases.

[0041] In a preferred embodiment, the loading in step (2) includes: mixing a molybdenum source with water to obtain an impregnation solution II, and mixing the impregnation solution II with the catalyst precursor for impregnation; preferably, the mixed impregnation is an equal-volume impregnation.

[0042] In a preferred embodiment, in step (2), the drying is performed by resting (air drying) and / or baking.

[0043] In a further preferred embodiment, the settling time is 4 to 48 hours; and / or the drying conditions include a temperature of 60 to 130°C (preferably 90 to 130°C) and a time of 4 to 12 hours.

[0044] For example, the settling time is 4h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h or 48h; and / or, the drying conditions include: a temperature of 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃ or 130℃, and a time of 4h, 6h, 8h, 10h or 12h.

[0045] In a preferred embodiment, in step (2), the calcination conditions include: a time of 1 to 10 hours and a temperature of 300 to 650°C.

[0046] For example, in step (2), the roasting conditions include: a time of 1h, 2h, 4h, 6h, 8h or 10h, and a temperature of 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃ or 650℃.

[0047] In a further preferred embodiment, in step (2), the calcination conditions include: a time of 2 to 8 hours and a temperature of 350 to 550°C.

[0048] In a further preferred embodiment, the calcination in step (2) is carried out in an air atmosphere.

[0049] In a preferred embodiment, the preparation method includes:

[0050] (A) Mix a vanadium source, an optional X source, an optional Y source with water to obtain an impregnation solution one, and mix the carrier with the impregnation solution one for equal volume impregnation.

[0051] (B) The system after the equal-volume impregnation described in step (A) is left to stand at room temperature, dried, and calcined under a protective atmosphere to obtain the catalyst precursor;

[0052] (C) The molybdenum source is mixed with water to obtain impregnation solution two, and the impregnation solution two is mixed with the catalyst precursor for impregnation in equal volume;

[0053] (D) The system after the equal-volume impregnation described in step (C) is left to stand at room temperature, dried, and calcined in air to obtain the catalyst.

[0054] This invention prepares a Mo-enriched supported V oxide catalyst by a two-stage impregnation process followed by calcination in a protective atmosphere and then in air, thereby improving the catalyst's oxidation selectivity and increasing the yield of aromatic aldehydes.

[0055] The third objective of this invention is to provide the application of the vanadium-molybdenum-based catalyst described in the first objective of this invention or the vanadium-molybdenum-based catalyst obtained by the preparation method described in the second objective of this invention in the oxidation of alkyl aromatics (e.g., methyl-substituted aromatics) to prepare aromatic aldehydes, especially for the oxidation of p-tert-butyltoluene to prepare p-tert-butylbenzaldehyde.

[0056] The catalyst exhibits higher reactivity and is easier to separate, making it a reusable heterogeneous catalyst. This catalyst can be used for the oxidation of alkyl aromatics (e.g., methyl-substituted aromatics) to prepare the corresponding aromatic aldehydes, improving the yield of aromatic aldehydes. It is particularly suitable for the direct oxidation of various methyl-substituted aromatics to prepare aromatic aldehydes.

[0057] The resulting catalyst can be used in the industrial production of aromatic aldehydes (such as p-tert-butylbenzaldehyde), and has great potential for industrial application.

[0058] The fourth objective of this invention is to provide a method for preparing aromatic aldehydes from alkyl-substituted aromatic hydrocarbons, comprising: oxidizing the alkyl-substituted aromatic hydrocarbons in the presence of a catalyst; wherein the catalyst is selected from the vanadium-molybdenum-based catalyst described in the first objective of this invention or the vanadium-molybdenum-based catalyst obtained by the preparation method described in the second objective of this invention.

[0059] In a preferred embodiment, the alkyl-substituted aromatic hydrocarbon is selected from C1 to C5 alkyl-substituted aromatic hydrocarbons.

[0060] In a further preferred embodiment, the alkyl-substituted aromatic hydrocarbon is selected from methyl-substituted aromatic hydrocarbons.

[0061] In a further preferred embodiment, the alkyl-substituted aromatic hydrocarbon is selected from at least one of p-tert-butyltoluene, m-tert-butyltoluene, and o-tert-butyltoluene.

[0062] In a preferred embodiment, a fixed bed is used as the reactor.

[0063] In a preferred embodiment, air is introduced for pretreatment before the oxidation reaction.

[0064] In a further preferred embodiment, the pretreatment conditions include: a temperature of 300–700°C and a time of 0.1–10 h.

[0065] In a further preferred embodiment, the pretreatment conditions include: a temperature of 350–650°C and a time of 0.2–2 hours.

[0066] In a preferred embodiment, the molar ratio of air to alkyl-substituted aromatic hydrocarbons is 5 to 50, preferably 10 to 45, for example 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50.

[0067] In a preferred embodiment, the oxidation reaction is carried out at a temperature of 300–600°C, and the liquid hourly space velocity (LHSV) of the (alkyl-substituted aromatic hydrocarbon) oxidation reaction is 0.05–5 h⁻¹. -1 .

[0068] For example, the oxidation reaction temperature is 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, or 600℃, and the liquid hourly space velocity (LHSV) of the oxidation reaction is 0.05 h⁻¹. -1 0.1h -1 0.5h -1 1h -1 1.5h -1 2h -1 2.5h -1 3h -1 3.5h -1 4h -1 4.5h -1 or 5h -1 .

[0069] In a further preferred embodiment, the oxidation reaction is carried out at a temperature of 350–500°C, and the liquid hourly space velocity (LHSV) is 0.1–2 h⁻¹. -1 .

[0070] This invention primarily addresses the problems of poor reaction performance, high separation costs, and inability to achieve continuous production when using homogeneous catalysts in the oxidation of alkyl-substituted aromatics in existing technologies. It employs a fixed-bed reactor, loaded with a corresponding heterogeneous catalyst, for the oxidation of alkyl-substituted aromatics to prepare aromatic aldehydes, particularly for the oxidation of p-tert-butyltoluene to prepare p-tert-butylbenzaldehyde.

[0071] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; 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. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] (1) The vanadium-molybdenum-based catalyst can be used for the oxidation of alkyl-substituted aromatic hydrocarbons to prepare the corresponding aromatic aldehydes, which not only improves the oxidation selectivity but also increases the yield of aromatic aldehydes;

[0074] (2) The catalyst is a heterogeneous catalyst, and the fixed bed can be directly separated without catalyst separation and can be produced continuously. Detailed Implementation

[0075] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0076] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0077] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0078] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0079] In the examples, the surface Mo / V was obtained by XPS characterization, and the average Mo / V in the catalyst was obtained based on the amount of raw materials used.

[0080] In this embodiment of the invention, the conversion rate of p-tert-butyltoluene (PTBT) and the yield of p-tert-butylbenzaldehyde are defined as follows:

[0081]

[0082]

[0083] The preparation of p-tert-butylbenzaldehyde by oxidation of p-tert-butyltoluene in this invention was evaluated in a fixed-bed reactor with a diameter of 10 mm and a length of 800 mm.

[0084]

Example 1

[0085] According to the catalyst active phase composition V 1.0 Co0.2 Cu 0.1 Cs 0.1 Mo 0.1 O w An impregnation solution was prepared and loaded with the active phase at 6 wt% of the catalyst mass. First, the required amounts of NH4VO3, cobalt nitrate, copper nitrate, and cesium nitrate were weighed and dissolved in water, then impregnated onto the SiO2 support in equal volumes. After the first impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 100 °C for 4 h, and finally calcined in a tube furnace under N2 atmosphere at 480 °C for 4 h. Subsequently, the required amount of ammonium molybdate was weighed to prepare a solution for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 110 °C for 4 h, and finally calcined in a muffle furnace (air) at 450 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 0.92.

[0086] Reaction performance evaluation:

[0087] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 410 °C with a liquid hourly space velocity (LISH) of 0.5 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilizing for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 30.5%, and the yield of p-tert-butylbenzaldehyde was 26.4%.

[0088]

Example 2

[0089] According to the catalyst active phase composition V 1.0 Co 0.1 Mn 0.1 Cs 0.1 Mo 0.08 O w An impregnation solution was prepared and loaded with the active phase at 4 wt% of the catalyst mass. First, the required amounts of NH4VO3, cobalt nitrate, manganese nitrate, and cesium nitrate were weighed and dissolved in water, then impregnated onto the Al2O3 support in equal volumes. After the first impregnation, the catalyst was allowed to stand at room temperature for 16 h, then dried at 110 °C for 4 h, and finally calcined in a tube furnace at 480 °C for 6 h in a N2 atmosphere. Subsequently, the required amount of ammonium molybdate was weighed to prepare a solution for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 16 h, then dried at 110 °C for 4 h, and finally calcined in a muffle furnace at 480 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 0.87.

[0090] Reaction performance evaluation:

[0091] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced, and the reaction temperature was 420 °C with a liquid hourly space velocity (LISH) of 0.6 h⁻¹. -1The molar ratio of air to p-tert-butyltoluene was 25. After stabilization for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 32.2%, and the yield of p-tert-butylbenzaldehyde was 27.6%.

[0092]

Example 3

[0093] According to the catalyst active phase composition V 1.0 Co 0.1 K 0.1 Mo 0.15 O w An impregnation solution was prepared and loaded with the active phase at 4 wt% of the catalyst mass. First, the required amounts of NH4VO3, cobalt nitrate, and potassium acetate were weighed and dissolved in water, then impregnated onto the SiO2 support in equal volumes. After the first impregnation, the catalyst was allowed to stand at room temperature for 16 h, then dried at 110 °C for 4 h, and finally calcined in a tube furnace at 480 °C for 6 h in a N2 atmosphere. Subsequently, the required amount of ammonium molybdate was weighed to prepare a solution for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 16 h, then dried at 110 °C for 4 h, and finally calcined in a muffle furnace at 480 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 1.05.

[0094] Reaction performance evaluation:

[0095] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 420 °C with a liquid hourly space velocity (LISH) of 0.3 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilization for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 33.0%, and the yield of p-tert-butylbenzaldehyde was 26.4%.

[0096]

Example 4

[0097] According to the catalyst active phase composition V 1.0 Co 0.1 K 0.1 Mo 0.15 O w An impregnation solution was prepared and loaded with the active phase at 4 wt% of the catalyst mass. First, the required amounts of vanadium pentoxide, oxalic acid, cobalt nitrate, and potassium acetate were weighed and dissolved in water, then impregnated with an equal volume of SiO2 support. During the first impregnation dissolution process, oxalic acid and vanadium pentoxide were added in a 1:2 molar ratio. After impregnation, the solution was allowed to stand at room temperature for 16 h, then dried at 110 °C for 4 h, and finally calcined in a tube furnace at 480 °C for 4 h in a N2 atmosphere. Subsequently, the required amount of ammonium molybdate was weighed and a solution was prepared for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 16 h, then dried at 110 °C for 4 h, and finally calcined in a muffle furnace at 480 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 1.17.

[0098] Reaction performance evaluation:

[0099] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 420 °C with a liquid hourly space velocity (LISH) of 0.3 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilization for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 33.6%, and the yield of p-tert-butylbenzaldehyde was 27.0%.

[0100]

Example 5

[0101] According to the catalyst active phase composition V 1.0 Co 0.2 Cu 0.1 Cs 0.1 Mo 0.1 O w An impregnation solution was prepared and loaded with the active phase at 4 wt% of the catalyst mass. First, the required amounts of NH4VO3, cobalt nitrate, copper nitrate, and cesium nitrate were weighed and dissolved in water, then impregnated in equal volumes onto anatase TiO2 support. After the first impregnation, (due to the difficulty in forming TiO2), the impregnated support + active phase was sprayed onto the surface of a ceramic ring in slurry form, with the support + spray solution accounting for 30 wt% of the final formed total mass. The catalyst was allowed to stand at room temperature for 12 h, then dried at 100 °C for 4 h, and then calcined in a tube furnace at 480 °C for 4 h in a N2 atmosphere. Subsequently, the required amount of ammonium molybdate was weighed to prepare a solution for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 110 °C for 4 h, and then calcined in a muffle furnace at 450 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 1.00.

[0102] Reaction performance evaluation:

[0103] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 400 °C with a liquid hourly space velocity (LISH) of 0.5 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilizing for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 32.9%, and the yield of p-tert-butylbenzaldehyde was 27.5%.

[0104]

Example 6

[0105] According to the catalyst active phase composition V 1.0 Fe 0.1 Rb 0.1 Mo 0.1 O wAn impregnation solution was prepared and loaded with the active phase at 6 wt% of the catalyst mass. First, the required amounts of NH4VO3, ferric nitrate, and rubidium nitrate were weighed and dissolved in water, then impregnated onto the SiO2 support in equal volumes. After the first impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 100 °C for 4 h, and finally calcined in a tube furnace at 500 °C for 4 h in a N2 atmosphere. Subsequently, the required amount of ammonium molybdate was weighed to prepare a solution for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 110 °C for 4 h, and finally calcined in a muffle furnace at 450 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 0.95.

[0106] Reaction performance evaluation:

[0107] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 400 °C with a liquid hourly space velocity (LISH) of 0.5 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilizing for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 30.7%, and the yield of p-tert-butylbenzaldehyde was 25.9%.

[0108]

Example 7

[0109] According to the catalyst active phase composition V 1.0 Fe 0.5 K 0.2 Mo 0.1 O w An impregnation solution was prepared and loaded with the active phase at 6 wt% of the catalyst mass. First, the required amounts of NH4VO3, ferric nitrate, and potassium nitrate were weighed and dissolved in water, then impregnated onto the SiO2 support in equal volumes. After the first impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 100 °C for 4 h, and finally calcined in a tube furnace at 400 °C for 4 h in a N2 atmosphere. Next, the required amount of ammonium molybdate was weighed to prepare a solution for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 110 °C for 4 h, and finally calcined in a muffle furnace at 450 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 0.92.

[0110] Reaction performance evaluation:

[0111] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 400 °C with a liquid hourly space velocity (LISH) of 0.5 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilizing for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 31.2%, and the yield of p-tert-butylbenzaldehyde was 27.5%.

[0112]

Example 8

[0113] According to the catalyst active phase composition V 1.0 Fe 0.5 K 0.2 Mo 0.1 O w An impregnation solution was prepared and loaded with the active phase at 6 wt% of the catalyst mass. First, the required amounts of NH4VO3, ferric nitrate, and potassium nitrate were weighed and dissolved in water, then impregnated onto the SiO2 support in equal volumes. After the first impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 100 °C for 4 h, and finally calcined in a tube furnace at 550 °C for 4 h in a N2 atmosphere. Subsequently, the required amount of ammonium molybdate was weighed to prepare a solution for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 110 °C for 4 h, and finally calcined in a muffle furnace at 550 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 1.03.

[0114] Reaction performance evaluation:

[0115] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 400 °C with a liquid hourly space velocity (LISH) of 0.5 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilizing for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 32.3%, and the yield of p-tert-butylbenzaldehyde was 27.9%.

[0116] Comparative Example 1

[0117] According to the catalyst active phase composition V 1.0 Co 0.2 Cu 0.1 Cs 0.1 Mo 0.1 O w An impregnation solution was prepared, and the active phase was loaded at 6 wt% of the catalyst mass. First, the required amounts of NH4VO3, cobalt nitrate, copper nitrate, cesium nitrate, and ammonium molybdate were weighed out and dissolved in water. These were then used to impregnate the SiO2 support in equal volumes. After one impregnation, the catalyst was allowed to stand at room temperature for 12 h, then dried at 100 °C for 4 h, and finally calcined in a muffle furnace (air) at 450 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 0.72.

[0118] Reaction performance evaluation:

[0119] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 410 °C with a liquid hourly space velocity (LISH) of 0.5 h⁻¹. -1The molar ratio of air to p-tert-butyltoluene was 25. After stabilization for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 27.8%, and the yield of p-tert-butylbenzaldehyde was 16.4%.

[0120] Comparative Example 2

[0121] According to the catalyst active phase composition V 1.0 Co 0.1 K 0.1 Mo 0.15 O w An impregnation solution was prepared, and the active phase was loaded at 4 wt% of the catalyst mass. The required amounts of NH₄VO₃, cobalt nitrate, potassium acetate, and ammonium molybdate were dissolved in water and impregnated onto the SiO₂ support in equal volumes. After impregnation, the catalyst was allowed to stand at room temperature for 16 h, then dried at 110 °C for 4 h, calcined in a tube furnace under N₂ atmosphere at 480 °C for 6 h, and finally calcined in a muffle furnace at 480 °C for 4 h. The resulting catalyst had a surface Mo / V ratio of 0.76.

[0122] Reaction performance evaluation:

[0123] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 420 °C with a liquid hourly space velocity (LISH) of 0.3 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilization for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 29.0%, and the yield of p-tert-butylbenzaldehyde was 14.2%.

[0124] Comparative Example 3

[0125] According to the catalyst active phase composition V 1.0 Co 0.1 K 0.1 Mo 0.15 O w An impregnation solution was prepared and loaded with the active phase at 4 wt% of the catalyst mass. First, the required amounts of NH4VO3, cobalt nitrate, and potassium acetate were weighed and dissolved in water, then impregnated onto the SiO2 support in equal volumes. After the first impregnation, the solution was allowed to stand at room temperature for 16 h, followed by drying at 110 °C for 4 h, and then calcined in a muffle furnace at 480 °C for 4 h. Subsequently, the required amount of ammonium molybdate was weighed to prepare a solution for a second, equal-volume impregnation. After impregnation, the catalyst was allowed to stand at room temperature for 16 h, followed by drying at 110 °C for 4 h, and then calcined in a tube furnace at 480 °C for 6 h in a N2 atmosphere. The resulting catalyst had a surface Mo / V ratio of 0.65.

[0126] Reaction performance evaluation:

[0127] 1 g of catalyst was loaded into a fixed-bed reactor, air was introduced, and the reactor was pretreated at 500 °C for 1 h. Subsequently, p-tert-butyltoluene was introduced as the feedstock, and the reaction temperature was 420 °C with a liquid hourly space velocity (LISH) of 0.3 h⁻¹. -1 The molar ratio of air to p-tert-butyltoluene was 25. After stabilizing for 2 hours, samples were taken. The conversion rate of p-tert-butyltoluene was 24.9%, and the yield of p-tert-butylbenzaldehyde was 11.2%.

[0128] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A vanadium-molybdenum-based catalyst comprising a support and an active component supported on the support, said active component comprising vanadium and / or its oxides, molybdenum and / or its oxides, wherein, The molar ratio of molybdenum to vanadium on the catalyst surface is greater than the average molar ratio of molybdenum to vanadium in the catalyst.

2. The vanadium-molybdenum-based catalyst according to claim 1, characterized in that, The carrier is selected from at least one of SiO2, Al2O3, and TiO2.

3. The vanadium-molybdenum-based catalyst according to claim 1, characterized in that, The average molar ratio of molybdenum to vanadium in the catalyst is 0.005–0.5, preferably 0.01–0.2; and / or, The molar ratio of molybdenum to vanadium on the surface of the catalyst is greater than 0.78, preferably greater than or equal to 0.

8.

4. The vanadium-molybdenum-based catalyst according to claim 1, characterized in that, The active component further includes an optional element X and / or its oxide, wherein the element X is selected from one or more elements of Group VIIB, Group VIII, Group IVA, and Group IB, preferably one or more of Mn, Sn, Cu, Co, Ni, and Fe. More preferably, the average molar ratio of element X to element vanadium is 0 to 1, and more preferably 0.01 to 0.

5.

5. The vanadium-molybdenum-based catalyst according to any one of claims 1 to 4, characterized in that, The active component further includes optional element Y and / or its oxide, wherein element Y is selected from one or more elements of group IA and group IIA, preferably one or more of K, Rb, Cs, Mg, Sr, and Ba; More preferably, the average molar ratio of Y to vanadium is 0 to 1, and more preferably 0.01 to 0.

5.

6. The vanadium-molybdenum-based catalyst according to claim 5, characterized in that, Based on 100 wt% of the catalyst, the active component is 0.3 to 20 wt%, preferably 1 to 15 wt%, wherein the weight of the active component is based on the weight of the oxide corresponding to the element.

7. A method for preparing a vanadium-molybdenum-based catalyst, preferably used for preparing the vanadium-molybdenum-based catalyst according to any one of claims 1 to 6, the preparation method comprising: (1) A vanadium source, an optional X source, and an optional Y source are loaded onto a support, and then dried and calcined to obtain a catalyst precursor; (2) The molybdenum source is loaded onto the catalyst precursor and then dried and calcined to obtain the catalyst.

8. The preparation method according to claim 7, characterized in that, The vanadium source is selected from one or more of vanadium sulfate, vanadium oxysulfate, vanadium oxalate, ammonium metavanadate, and vanadium pentoxide; and / or, The X source and the Y source are each independently selected from the soluble salts corresponding to their respective elements, preferably from one or more of the following: soluble chlorides, soluble sulfates, soluble nitrates, soluble acetates, and soluble oxalates; and / or, The molybdenum source is selected from one or more of ammonium molybdate, ammonium molybdate-substrate, and ammonium paramolybdate.

9. The preparation method according to claim 7 or 8, characterized in that, In step (1), the calcination temperature is 300–650°C, preferably 350–550°C; and / or, The calcination in step (1) is carried out under a protective atmosphere, preferably selected from one or more of nitrogen and inert gases.

10. The preparation method according to claim 9, characterized in that, In step (2), the calcination temperature is 300–650°C, preferably 350–550°C; and / or, The roasting in step (2) is carried out in an air atmosphere.

11. The application of the vanadium-molybdenum-based catalyst according to any one of claims 1 to 6 or the vanadium-molybdenum-based catalyst obtained by the preparation method according to any one of claims 7 to 10 in the oxidation of alkyl aromatics to prepare aromatic aldehydes, especially for the oxidation of p-tert-butyltoluene to prepare p-tert-butylbenzaldehyde.

12. A method for preparing aromatic aldehydes from alkyl-substituted aromatic hydrocarbons, comprising: Alkyl-substituted aromatics undergo oxidation in the presence of a catalyst; wherein the catalyst is selected from the vanadium-molybdenum-based catalysts according to any one of claims 1 to 6 or the vanadium-molybdenum-based catalysts obtained by the preparation method according to any one of claims 7 to 10; Preferably, the alkyl-substituted aromatic hydrocarbon is selected from C1 to C5 alkyl-substituted aromatic hydrocarbons, more preferably from methyl-substituted aromatic hydrocarbons, and more preferably from at least one of p-tert-butyltoluene, m-tert-butyltoluene, and o-tert-butyltoluene.

13. The method according to claim 12, characterized in that, Before the oxidation reaction, air is introduced for pretreatment; the pretreatment conditions include: temperature of 300-700℃ and time of 0.1-10h; preferably, the conditions include: temperature of 350-650℃ and time of 0.2-2h. And / or, The oxidation reaction is carried out at a temperature of 300–600°C, and / or the liquid hourly space velocity (LHSV) is 0.05–5 h⁻¹. -1 .

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