A catalyst for preparing acrylic acid by acrolein oxidation, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a catalyst for the oxidation of acrolein to acrylic acid, its preparation method and application. The catalyst comprises a carrier and an active component, and the active component comprises a composite metal oxide containing V element, Mo element, Nb element, Tl element, transition metal element and alkali metal element. The catalyst of the present invention has the advantages of low abrasion and high acrylic acid yield.

Description

Technical Field

[0001] The present invention relates to the field of acrylic acid preparation, and particularly to a catalyst for the oxidation of acrolein to acrylic acid, a preparation method thereof, and an application thereof. Background Art

[0002] Acrylic acid is an important organic chemical raw material, mainly used to manufacture multifunctional polymer materials such as acrylic esters, and is widely used in fields such as papermaking, leather, coatings, textiles, plastics, rubber, oil additives, and oil extraction. In recent years, the market demand for acrylic acid has been continuously increasing worldwide, and the production of acrylic acid has always been a research hotspot.

[0003] The catalyst used for the synthesis of acrylic acid by the acrolein oxidation method is generally an oxide of the Mo-V series. In addition to Mo and V elements, other elements for improving the catalyst performance are generally added, such as Nb, Sn, Cr, W, Fe, Co, Ni, Sb, etc. US7220698 discloses a catalyst for catalytic gas-phase oxidation of acrolein and a method for producing acrylic acid by catalytic gas-phase oxidation using the catalyst. This method uses a catalyst with Mo-V as essential components, and by introducing trace amounts of catalyst poisons into the catalyst preparation process, the hot spot of the catalyst reaction bed layer is controlled, and the thermal degradation of the catalyst is inhibited, thereby improving the acrolein conversion rate. US7456129 discloses a support for a gas-phase oxidation catalyst suitable for the selective oxidation of acrolein to acrylic acid and a production method thereof. This method improves the catalyst performance by controlling the acid strength of the support, and improves the selectivity of acrylic acid, but the acrylic acid yield still needs to be further improved. CN111659408A discloses a preparation method of a catalyst for the oxidation of acrolein to acrylic acid. This method is based on Mo element, adds elements such as V, Ni, Cu, etc., and performs coprecipitation reaction or physical blending with their salts or corresponding oxides, and adopts geometric shapes such as spherical, cylindrical or special-shaped, and finally calcines to endow the catalyst with activity to form a catalyst product.

[0004] Through the above several methods, acrylic acid catalysts can be prepared and the catalyst performance can be improved, but the mechanical strength of the catalyst is poor and the catalytic activity is relatively low, which will be restricted in practical applications. Therefore, it is necessary to further study acrylic acid catalysts with high acrylic acid yield and low abrasion. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the present invention provides a catalyst for the oxidation of acrolein to acrylic acid, a preparation method thereof, and an application thereof. The catalyst of the present invention has the advantages of low abrasion and high acrylic acid yield.

[0006] The first aspect of the present invention provides a catalyst for the oxidation of acrolein to acrylic acid, which comprises a carrier and an active component, and the active component comprises a composite metal oxide containing V element, Mo element, Nb element, Tl element, transition metal element and alkali metal element.

[0007] The active component can be represented by formula (1):

[0008] VMo a Nb b Tl c X d Z e O f Formula (1)

[0009] In formula (1), X represents a transition metal element, Z represents an alkali metal element, and a, b, c, d, and e respectively represent the molar ratios of Mo, Nb, Tl, X, and Z to V. a is 1.0 to 10.0; b is 0.1 to 1.0; c is 0.1 to 1.0; d is 0.05 to 1.0; e is 0.05 to 1.0; f is the number of moles of oxygen atoms required to satisfy the valence of other elements in the active component. Preferably, a is 2.0 to 6.0; b is 0.2 to 0.6; c is 0.1 to 0.5; d is 0.1 to 0.5; e is 0.1 to 0.6. More preferably, a is 3.0 to 5.0; b is 0.3 to 0.5; c is 0.1 to 0.3; d is 0.1 to 0.3; e is 0.1 to 0.3.

[0010] Further, the transition metal element is one or more of Sc element, Tl element, Y element, Zr element, Hf element, Ta element, Cr element, W element, Mn element, Tc element, Re element, Fe element, Ru element, Os element, Co element, Rh element, Ir element, Ni element, Pd element, Pt element, Cu element, Ag element, Au element, Zn element and Cd element; preferably one or more of Ta element, Zr element, Y element, Hf element and W element. The alkali metal element is one or more of Li element, Na element, K element, Rb element and Cs element, preferably Na element and / or K element.

[0011] Further, the carrier is selected from one or several of lithium oxide, magnesium oxide, aluminum oxide, zirconium dioxide, silicon dioxide, titanium dioxide, vanadium dioxide, diatomite, kaolin and pumice.

[0012] Further, based on the weight of the catalyst, the content of the carrier is 20% to 60%, and the content of the active component is 40% to 80%.

[0013] Further, there are two desorption peaks in the ammonia temperature-programmed desorption curve of the catalyst, and the relative intensities of the two desorption peaks are different. Among them, the temperature corresponding to the highest position of the stronger desorption peak is 175°C to 250°C, and the temperature corresponding to the highest position of the weaker desorption peak is 300°C to 350°C.

[0014] Further, the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is (1.5 to 2.5):1.

[0015] Further, the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 90°C to 130°C; and / or the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is (10 to 50):1.

[0016] The second aspect of the present invention provides a method for preparing a catalyst for the oxidation of acrolein to acrylic acid, comprising the following steps:

[0017] 1) Mix a precursor containing Nb element and Tl element with a dispersion medium to obtain Solution I;

[0018] 2) Mix a precursor containing V element, Mo element, transition metal element and alkali metal element with a dispersion medium to obtain Solution II;

[0019] 3) Mix Solution I obtained in step 1) and Solution II obtained in step 2) to obtain Solution III;

[0020] 4) Impregnate a catalyst support with Solution III obtained in step 3), and then dry and calcine to obtain a catalyst.

[0021] Further, in step 1), the precursor containing Nb element is at least one of niobium oxalate, niobium oxide, and ammonium niobium oxalate hydrate; the precursor containing Tl element is at least one of thallium nitrate, thallium carbonate, and thallium oxide.

[0022] Further, the molar ratio of the Mo element to the V element is (1.0 to 10.0):1, preferably (2.0 to 8.0):1; and / or the molar ratio of the Nb element to the V element is (0.1 to 1.0):1, preferably (0.2 to 0.6):1; and / or the molar ratio of the Tl element to the V element is (0.1 to 1.0):1, preferably (0.1 to 0.5):1; and / or the molar ratio of the Nb element to the Tl element is (1 to 5):(5 to 1), preferably (1 to 3):(3 to 1), more preferably (1 to 3):1.

[0023] Further, the molar ratio of the transition metal element to the V element is (0.05 - 1.0):1, preferably (0.1 - 0.5):1; the molar ratio of the alkali metal element to the V element is (0.05 - 1.0):1, preferably (0.1 - 0.6):1.

[0024] Further, in step 2), the precursor containing the V element is ammonium metavanadate; the precursor containing the Mo element is ammonium molybdate; the precursor of the transition metal element is a nitrate and / or ammonium salt of the transition metal, and the precursor of the alkali metal element is a nitrate and / or ammonium salt of the alkali metal.

[0025] Further, the dispersion medium in both Solution I and Solution II is or mainly is water. When preparing Solution I and Solution II, the dispersion medium can be heated to 60°C - 90°C, and then the precursors of the corresponding elements are added.

[0026] Further, in step 3), it is preferred to add Solution I to Solution II.

[0027] Further, in step 3), the pH value of the obtained Solution III is controlled to be 1 - 6, preferably 2 - 4. An acidic solution can be used to adjust the pH value of Solution III. The acidic solution is selected from one or more of nitric acid, citric acid, and formic acid solutions.

[0028] Further, in step 3), before mixing, the temperature of Solution I is 10°C - 50°C, preferably 20°C - 30°C, and the temperature of Solution II is 10°C - 50°C, preferably 20°C - 30°C.

[0029] Further, in step 4), the catalyst support is first treated with a surface treatment liquid and then impregnated in Solution III. The surface treatment liquid is a mixture of polyacrylamide and water, and the treatment time is 10 min - 300 min, preferably 30 min - 100 min.

[0030] Preferably, the molecular weight of polyacrylamide is: 8 million - 20 million, preferably 8 million - 12 million; the mass concentration of the surface treatment liquid is: 1% - 25%, preferably 5% - 15%; the pH value of the surface treatment liquid is 6 - 10, preferably 7 - 9. The mass ratio of polyacrylamide to the catalyst support is 0.1 - 5:100, preferably 0.2 - 1:100.

[0031] Further, in step 4), the conditions for the drying treatment include: the temperature is 60°C to 150°C; the time is 1 h to 48 h. The conditions for the calcination treatment include: the temperature is 300°C to 500°C; the time is 1 h to 72 h. The atmosphere for the calcination is an inert atmosphere or an oxygen-containing atmosphere. Preferably, the inert atmosphere is a nitrogen atmosphere, and the oxygen content in the oxygen-containing atmosphere is 10 to 30%, preferably air.

[0032] The third aspect of the present invention provides an application of the above-mentioned catalyst or the catalyst prepared according to the above-mentioned preparation method in the selective oxidation of acrolein to acrylic acid.

[0033] The application is as follows: in the presence of the catalyst and a diluting gaseous material, acrolein is contacted with an oxygen-containing gas to obtain acrylic acid.

[0034] Further, the diluting gaseous material is water vapor. The oxygen-containing gas is air, pure oxygen or oxygen-enriched air.

[0035] Further, the conditions for the contact include: the temperature is 200°C to 350°C; the volume ratio of acrolein to the oxygen-containing gas is 1:(1 to 12); the volume ratio of acrolein to the diluting gaseous material is 1:(0.5 to 5), and the overall volume space velocity is 800 h -1 ~3000 h -1 .

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] When the catalyst of the present invention is used in the selective oxidation of acrolein to acrylic acid, the acrylic acid yield can reach more than 89%, and even up to 91%, and the abrasion can be below 1.5%, and even up to below 0.9%.

[0038] The preparation method of the present invention is simple, and through the mutual cooperation of each step, the acrylic acid yield of the catalyst can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is the ammonia temperature-programmed desorption (NH3-TPD) spectrum of the catalysts prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited to the following examples.

[0041] For those not specified in the examples, they are carried out under conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial channels.

[0042] In the present invention, the evaluation method of the catalyst performance is as follows:

[0043] Reactor: Fixed-bed micro reactor, with an inner diameter of 10 mm and a reactor length of 330 mm;

[0044] Catalyst loading: 1 g;

[0045] Reaction temperature: 270 °C;

[0046] Reaction time: 4 hours;

[0047] Volume ratio of raw materials: Acrolein: Air: Steam = 1:8:2;

[0048] Overall volume space velocity: 1300 h -1 .

[0049] In the present invention, the evaluation method of the catalyst attrition is as follows:

[0050] Put 20 g of the catalyst into the attrition index determination device, rotate and vibrate it. After 30 min, screen out the broken catalyst particles and weigh them. The proportion of the broken catalyst is the catalyst attrition.

[0051] In the present invention, the method for obtaining the NH3-TPD spectrum is as follows:

[0052] (1) Weigh 0.2 g of the 20-40 mesh sample and load it into a U-shaped quartz tube; (2) Purge with helium for 2 h and heat up to 400 °C; (3) Cool down to room temperature and adsorb ammonia for 30 min; (4) Heat up to 400 °C at a heating rate of 10 °C / min and record the curve simultaneously.

[0053] In the following embodiments, "g" represents the number of moles of oxygen atoms required to satisfy the valence of other elements in the active component.

[0054] Example 1

[0055] 1) Mix niobium oxalate (molecular formula: C 10 H5NbO 20 ) containing 0.04 moles of Nb with thallium nitrate (molecular formula: TlNO3) containing 0.02 moles of Tl and dissolve them in hot water at 80 °C. Cool to room temperature to obtain Solution I.

[0056] 2) Ammonium metavanadate (molecular formula: NH4VO3) containing 0.1 moles of V, ammonium molybdate (molecular formula: (NH4)2MoO4) containing 0.4 moles of Mo, ammonium tungstate (molecular formula: (NH4) 10 W 12 O 41), Sodium nitrate (formula: NaNO3) containing 0.02 moles of Na was dissolved in hot water at 80 °C and cooled to room temperature to obtain Solution II.

[0057] 3) At room temperature, Solution I was added to Solution II at a rate of 20 mL / min. After mixing evenly, 0.1 molar nitric acid was used to adjust the pH value of the solution to 3.0. Then, it was stirred and evaporated at 80 °C until the concentration of the active component VMo4Nb in the mixed material solution was 0.5 g / g to obtain Solution III. 0.4 Tl 0.2 W 0.2 Na 0.2 O g in the solution was 0.5 g / g to obtain Solution III.

[0058] 4) 1 g of polyacrylamide with a molecular weight of 8 million was mixed with 10 g of water. 0.1 molar ammonia water was used to adjust the pH value of the mixture to 8.0 to obtain a surface treatment solution. The surface treatment solution was mixed with 100 g of spherical silica carrier particles with a diameter of 5 mm, and then mixed with 300 g of Solution III to obtain a catalyst precursor.

[0059] The catalyst precursor was dried in an oven at 100 °C for 4 hours and then calcined in a muffle furnace at 400 °C for 5 hours to obtain a catalyst with the following composition:

[0060] 60 w% VMo4Nb 0.4 Tl 0.2 W 0.2 Na 0.2 O g + 40 w% SiO2.

[0061] The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, it has two desorption peaks. The temperature corresponding to the highest position of the stronger desorption peak is 208 °C, and the temperature corresponding to the highest position of the weaker desorption peak is 325 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.8:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 117 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 30:1.

[0062] Example 2

[0063] Example 2 is basically the same as Example 1, except that in step 4), 1 g of polyacrylamide with a molecular weight of 12 million is mixed with 10 g of water. The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 210 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 327 °C. The ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.6:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 117 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 28:1.

[0064] Example 3

[0065] Example 3 is basically the same as Example 1, except that in step 4), 1 g of polyacrylamide with a molecular weight of 20 million is mixed with 10 g of water. The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 210 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 328 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.6:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 118 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 27:1.

[0066] Example 4

[0067] Example 4 is basically the same as Example 1, except that in step 4), the pH value of the surface treatment solution is adjusted to 6. The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 222 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 338 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.8:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 116 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 29:1.

[0068] Example 5

[0069] Example 5 is basically the same as Example 1, except that the pH value of the surface treatment solution in step 4) is adjusted to 10. The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 220 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 336 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.7:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 16 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 28:1.

[0070] Example 6

[0071] Example 6 is basically the same as Example 1, except that the amounts of niobium oxalate and thallium nitrate in step 1) are adjusted so that the composition of the obtained catalyst is:

[0072] 60 w% VMo4Nb 0.2 Tl 0.4 W 0.2 Na 0.2 O g + 40 w% SiO2.

[0073] The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 218 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 335 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.8:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 117 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 28:1.

[0074] Example 7

[0075] Example 7 is basically the same as Example 1, except that the amounts of niobium oxalate and thallium nitrate are adjusted so that the composition of the obtained catalyst is:

[0076] 60 w% VMo4Nb 0.1 Tl 0.5 W 0.2 Na 0.2 O g + 40 w% SiO2.

[0077] The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 223 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 339 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 2.0:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 16 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 31:1.

[0078] Example 8

[0079] Example 8 was basically the same as Example 1, except that the amounts of niobium oxalate and thallium nitrate were adjusted so that the composition of the obtained catalyst was:

[0080] 60 w% VMo4Nb 0.5 Tl 0.1 W 0.2 Na 0.2 O g + 40 w% SiO2.

[0081] The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 212 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 329 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.7:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 117 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 26:1.

[0082] Example 9

[0083] Example 9 was basically the same as Example 1, except that in step 4), the surface treatment solution was mixed with 150 g of spherical silica carrier particles with a diameter of 5 mm, and then mixed with 200 g of the first solution to obtain a catalyst precursor. The composition of the obtained catalyst was:

[0084] 40 w% VMo4Nb 0.4 Tl 0.2 W 0.2 Na 0.2 O g + 60 w% SiO2.

[0085] The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 215 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 333 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.8:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 18 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 27:1.

[0086] Example 10

[0087] Example 10 was basically the same as Example 1, except that in step 4), the surface treatment solution was mixed with 100 g of spherical silica carrier particles with a diameter of 5 mm, and then mixed with 800 g of the first solution to obtain a catalyst precursor. The composition of the obtained catalyst was:

[0088] 80 w% VMo4Nb 0.4 Tl 0.2 W 0.2 Na 0.2 O g + 20 w% SiO2.

[0089] The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, the temperature corresponding to the highest position of its stronger desorption peak is 216 °C, and the temperature corresponding to the highest position of its weaker desorption peak is 335 °C; the ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is 1.8:1; the temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 19 °C; the ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is 28:1.

[0090] Comparative Example 1

[0091] Comparative Example 1 was basically the same as Example 1, except that the surface treatment solution was not added in step 2), and the composition of the obtained catalyst was:

[0092] 60 w% VMo4Nb 0.4 Tl 0.2 W 0.2 Na 0.2 O g + 40 w% SiO2.

[0093] The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, it has only one desorption peak, and the temperature corresponding to the highest position of the desorption peak is 190 °C.

[0094] Comparative Example 2

[0095] Comparative Example 2 was basically the same as Example 1, except that in steps 1)-3), the precursor solutions containing Nb element, Tl element, V element, Mo element, W element, and Na element were directly mixed to obtain a mixed solution. 1 g of polyacrylamide with a molecular weight of 8 million was mixed with 10 g of water, and the pH value of the mixed solution was adjusted to 8.0 using 0.1 mol / L ammonia water to obtain a surface treatment solution. The surface treatment solution was mixed with 100 g of spherical silica carrier particles with a diameter of 5 mm, and then mixed with 300 g of Solution III to obtain a catalyst precursor:

[0096] 60w% VMo4Nb 0.2 Tl 0.4 W 0.2 Na 0.2 O g +40w% SiO2.

[0097] The prepared catalyst was evaluated, and the results are shown in Table 1. Among them, according to the ammonia temperature-programmed desorption curve of the catalyst, it has only one desorption peak, and the temperature corresponding to the highest position of the desorption peak is 195 °C.

[0098] Table 1

[0099]

[0100]

[0101] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as specified, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A catalyst for the oxidation of acrolein to acrylic acid, which comprises a carrier and an active component, and the active component comprises a composite metal oxide containing V element, Mo element, Nb element, Tl element, transition metal element and alkali metal element; There are two desorption peaks in the ammonia temperature-programmed desorption curve of the catalyst, and the relative intensities of the two desorption peaks are different. Among them, The temperature corresponding to the highest position of the stronger desorption peak is 175°C to 250°C, and the temperature corresponding to the highest position of the weaker desorption peak is 300°C to 350°C; The active component is represented by formula (1): VMo a Nb b Tl c X d Z e O f Formula (1) Wherein, X represents a transition metal element, Z represents an alkali metal element, and a, b, c, d and e respectively represent the molar ratios of Mo, Nb, Tl, X, Z to V; a is 1.0 to 10.0; b is 0.1 to 1.0; c is 0.1 to 1.0; d is 0.05 to 1.0; e is 0.05 to 1.0; f is the number of moles of oxygen atoms required to satisfy the valence of other elements in the active component; The transition metal element is one or more of Ta element, Zr element, Y element, Hf element and W element; The ratio of the relative intensity corresponding to the highest position of the stronger desorption peak to the relative intensity corresponding to the highest position of the weaker desorption peak is (1.5 to 2.5):1; The ratio of the peak area of the stronger desorption peak to the peak area of the weaker desorption peak is (10 to 50):

1.

2. The catalyst according to claim 1, characterized in that: The alkali metal element is one or more of Li element, Na element, K element, Rb element and Cs element.

3. The catalyst according to claim 1, characterized in that: The temperature difference between the highest position of the stronger desorption peak and the highest position of the weaker desorption peak is 90°C to 130°C.

4. A method for preparing the catalyst according to any one of claims 1-3, comprising the following steps: 1) Mix a precursor containing Nb element and Tl element with a dispersion medium to obtain solution I; 2) Mix a precursor containing V element, Mo element, transition metal element and alkali metal element with a dispersion medium to obtain solution II; 3) Mix the solution I obtained in step 1) and the solution II obtained in step 2) to obtain solution III; 4) Immerse the catalyst carrier in the solution III obtained in step 3), and then dry and calcine to obtain the catalyst.

5. The method according to claim 4, wherein: The dispersion media in solution I and solution II are both water; when preparing solution I and solution II, first heat the dispersion medium to 60°C to 90°C, and then add the precursors of the corresponding elements.

6. The method according to claim 4, characterized in that: In step 3), control the pH value of the obtained solution III to be 1 to 6.

7. The method according to claim 6, characterized in that: In step 3), control the pH value of the obtained solution III to be 2 to 4.

8. The method according to claim 4, wherein: In step 3), before mixing, the temperature of solution I is 10°C to 50°C, and the temperature of solution II is 10°C to 50°C.

9. The method according to claim 8, characterized in that: In step 3), before mixing, the temperature of solution I is 20°C to 30°C, and the temperature of solution II is 20°C to 30°C.

10. The method according to claim 4, characterized in that: In step 4), first treat the catalyst carrier with a surface treatment solution, and then immerse it in solution III; the surface treatment solution is a mixture of polyacrylamide and water, and the treatment time is 10 min to 300 min.

11. The method according to claim 10, characterized in that: The molecular weight of the polyacrylamide is 8 million to 20 million; the concentration of the surface treatment liquid is 1% to 25%; the pH value of the surface treatment liquid is 6 to 10; the mass ratio of the polyacrylamide to the catalyst support is 0.1 to 5:

100.

12. The method according to claim 11, wherein: The molecular weight of the polyacrylamide is 8 million to 12 million; the concentration of the surface treatment liquid is 5% to 15%; the pH value of the surface treatment liquid is 7 to 9; the mass ratio of the polyacrylamide to the catalyst support is 0.2 to 1:

100.

13. Use of the catalyst according to any one of claims 1-3 or the catalyst prepared by the method according to any one of claims 4-12 in the selective oxidation of acrolein to acrylic acid.

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