Catalyst for synthesis of methyl methacrylate as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for synthesis of methyl methacrylate as well as a preparation method and application of the catalyst. The catalyst comprises an active component and a carrier, the active component and the carrier respectively have a general formula AuMaOn and a general formula Si10NbOx, M is at least one of Ni, Nb, Co, Fe and Bi, and N is at least one of Be, Mg, Ca, Sr and Ba; a is equal to 0.001 to 10; b is equal to 0.001 to 2; x and n are numerical values determined by the total valence of elements except oxygen in the general formula. The size of Au particles in the catalyst is reduced, the dispersity of the Au particles is improved, and high catalyst conversion rate and selectivity can be achieved under the condition of low alcohol-aldehyde ratio.

Description

Technical Field

[0001] The present invention relates to the field of methods for synthesizing methyl methacrylate, and more particularly, to a catalyst for synthesizing methyl methacrylate, a preparation method thereof, and an application thereof. Background Art

[0002] Methyl methacrylate (MMA) is an important organic chemical raw material. Its main downstream product, polymethyl methacrylate, is an important thermoplastic plastic that has been developed relatively early. It has the characteristics of beautiful appearance, excellent light transmittance, and chemical stability, and is widely used in industries such as automobiles, construction, sanitary ware, and public works.

[0003] In the current industrial MMA production processes, in the traditional ACH process route, the raw material hydrocyanic acid is greatly affected by the operation of acrylonitrile, and a large amount of ammonium sulfate by-products are generated, with relatively high treatment costs, resulting in a relatively high production cost of MMA and a reduced advantage. The BASF technology has unremarkable economic benefits, and the Alpha technology has just started industrialization, and its technical maturity and overall economy need to be further verified.

[0004] Compared with other processes, the direct oxidation method using C4 as the raw material has the advantages of wide raw material sources and good economy. In the traditional three-step method, isobutene is first oxidized to methacrolein, then further oxidized to methacrylic acid, and finally esterified with methanol to obtain methyl methacrylate. The two-step method oxidizes and esterifies methacrolein in one step to produce methacrylic acid, which is a huge innovation in the C4 route for producing MMA, and has many advantages such as a short reaction route, high atom utilization rate, good selectivity, mild reaction conditions, and environmental friendliness.

[0005] Currently, oxide-supported noble metal catalysts are mostly used, especially those supported with Au, which have the advantage of high selectivity. However, the catalyst cost is extremely high. For example, Suzuki et al. of Asahi Kasei Corporation in Japan loaded 1.1 wt% of Au nanoparticles on composite oxide supports such as SiO 2 -Al 2 O 3 -MgO, and the catalyst cost is as high as several million per ton.

[0006] The Au nanoparticles are very beneficial to improving the selectivity of this reaction, but the cost is high. How to reduce the amount of Au used has become a key issue. How to reduce the size of Au particles, improve the dispersion of Au particles, and find better promoters and supports to promote the activity of nano-gold particles are all directions worthy of exploration. Summary of the Invention

[0007] The technical problem to be solved by the present invention is the problem of low conversion rate and low single product yield of the catalyst used in the reaction of oxidizing and esterifying methacrolein to synthesize methyl methacrylate in the prior art, and to provide a bifunctional catalyst with high conversion rate and high yield of methyl methacrylate.

[0008] One of the objectives of the present invention is to provide a catalyst for synthesizing methyl methacrylate, which comprises an active component and a carrier. The active component and the carrier respectively have the general formula AuM a O n and Si 10 N b O x ,

[0009] wherein, M is at least one of Ni, Nb, Co, Fe, and Bi, and N is an element of the second main group, preferably at least one of Be, Mg, Ca, Sr, and Ba;

[0010] a = 0.001 - 10; b = 0.001 - 2;

[0011] x and n are values determined by the total valence of the elements other than oxygen in the general formula.

[0012] In the catalyst, based on the total mass of the catalyst, the Au content is 0.1 - 0.9 wt%, preferably 0.5 - 0.8 wt%.

[0013] In the catalyst, based on the total mass of the catalyst, the M content is 0.05 - 5 wt%, preferably 0.05 - 2.5 wt%.

[0014] In the catalyst, the size of the Au particles is 1 - 10 nm, for example, it can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc.

[0015] The specific surface area of the catalyst is 20 - 500 m 2 / g, preferably 30 - 100 m 2 / g, for example, 20 m 2 / g, 30 m 2 / g, 50 m 2 / g, 80 m 2 / g, 100 m 2 / g, 200 m 2 / g, 300 m 2 / g, 400 m 2 / g, 500 m 2 / g, etc.

[0016] The pore volume of the catalyst is 0.1 - 0.8 cm 3 / g, preferably 0.35 - 0.8 cm 3 / g, for example, 0.1 cm 3 / g, 0.2 cm 3 / g, 0.3 cm 3 / g, 0.35 cm 3 / g, 0.4 cm 3 / g, 0.5 cm 3 / g, 0.6 cm 3 / g, 0.7 cm 3 / g, 0.8 cm 3 / g, etc.

[0017] The most probable pore diameter range of the catalyst is 5 - 50 nm, preferably 20 - 50 nm, such as 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc.

[0018] The catalyst of the present invention has the general formula AuM a O n / Si 10 N b O x , and can be used in the reaction of oxidative esterification of methacrolein to synthesize methyl methacrylate, wherein Au is nanoparticles.

[0019] The second object of the present invention is to provide a preparation method of the catalyst for synthesizing methyl methacrylate, comprising the following steps:

[0020] (1) Dissolve the N salt in water to obtain solution A, then add solution A to the silica sol and stir for a period of time, and spray dry to obtain the carrier precursor;

[0021] (2) Calcinate the obtained carrier precursor to obtain the carrier;

[0022] (3) Mix the chloroauric acid solution or hydrogen tetrachloroaurate solution and the aqueous solution of the M salt to obtain solution B, add it to the carrier, stir for a period of time, wait until the color in solution B becomes transparent, filter, wash, and dry to obtain the catalyst precursor;

[0023] (4) After the obtained catalyst precursor is calcined once, perform a secondary calcination treatment in a water vapor-containing atmosphere.

[0024] In step (1) of the preparation method:

[0025] The N salt is selected from at least one of the oxygen-containing salts and / or oxygen-containing salt hydrates of Be, Mg, Ca, Sr, and Ba.

[0026] The M salt is selected from at least one of the oxygen-containing salts and / or oxygen-containing salt hydrates of Ni, Nb, Co, Fe, and Bi.

[0027] In step (2) of the preparation method:

[0028] The calcination temperature is 450 - 700 °C, and the calcination time is 2 - 100 hours.

[0029] Preferably, the calcination temperature is 500 to 650 °C and the calcination time is 3 to 24 hours.

[0030] In step (4) of the preparation method:

[0031] In the first calcination, the temperature is 200 to 600 °C and the first calcination time is 2 to 200 hours. Preferably, the first calcination temperature is 250 to 350 °C and the first calcination time is 3 to 24 hours.

[0032] In the first calcination, the heating rate can be 0.5 to 5 °C / min. Preferably, the heating rate is 2 to 4 °C / min.

[0033] In the first calcination, the atmosphere is an inert atmosphere or air.

[0034] In the second calcination, the atmosphere is an inert atmosphere containing water vapor or air, where the volume content of water vapor is 0.5 to 20%. Preferably, the volume content of water vapor is 5 to 15%, for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0035] In the second calcination, the treatment temperature is 100 to 800 °C and the treatment time is 0.5 to 200 hours. Preferably, the treatment temperature is 300 to 550 °C and the treatment time is 1 to 72 hours.

[0036] A third object of the present invention is to provide the application of the catalyst for synthesizing methyl methacrylate or the catalyst prepared by the preparation method in the synthesis of methyl methacrylate.

[0037] The application includes reacting methacrolein, methanol and an O-containing 2 atmosphere in the presence of the catalyst.

[0038] According to an embodiment of the present invention, the application includes reacting the catalyst with methacrolein, methanol and air in a batch reactor.

[0039] In the above reaction, preferably, the reaction temperature is 60 to 90 °C, the O 2 partial pressure is 0.02 to 3 MPa, the molar ratio of methanol to methacrolein is 10 to 40, and the reaction time is 0.5 to 24 h.

[0040] In the above reaction, more preferably, the reaction temperature is 60 to 80 °C, the O 2The partial pressure is 0.05 - 2.5 MPa, the molar ratio of methanol to methacrolein is 15 - 35, and the reaction time is 1 - 20 h.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] The catalyst obtained by the special preparation method of the technical solution of the present invention significantly reduces the size of Au particles in the catalyst, improves the dispersion of Au particles, and further improves the catalyst activity by adding additives. When the catalyst is used in the synthesis of methyl methacrylate, it can improve the conversion rate and selectivity of the catalyst under the condition of a lower alcohol - aldehyde ratio, achieving very good technical effects. Description of the Drawings

[0043] Figure 1 It is the electron micrograph of the catalyst prepared from the support without steam treatment for Comparative Example 2.

[0044] Figure 2 It is the electron micrograph of the catalyst prepared from the support with steam treatment for Example 1.

[0045] From Figure 1 and Figure 2 it can be seen that after steam treatment, a large number of pores appear in the support, the Au particles are more evenly dispersed, and the particle size becomes smaller. Detailed Embodiments

[0046] The present invention will be specifically described below in conjunction with specific drawings and embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be construed as limiting the protection scope 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 still fall within the protection scope of the present invention.

[0047] In addition, it should be noted that among the various specific technical features described in the following detailed embodiments, they can be combined in any suitable way without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0048] Furthermore, any combination can be made among various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions thus formed belong to a part of the original public content of this specification and also fall within the protection scope of the present invention.

[0049] The endpoints and any values within the ranges disclosed in this document are not limited to the exact 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 each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document.

[0050] For the raw materials used in the examples and comparative examples, if not specifically defined, they are all disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0051] The catalyst evaluation method used in the following examples is as follows:

[0052] The reactants methacrolein and methanol were added to a batch reactor filled with the catalyst to be tested. After heating to the required temperature, a certain amount of air was introduced, and then gas chromatography was used for analysis. During the analysis process, the carbon balance was calculated, and the data when the carbon balance was between 95% and 105% were selected as valid data. Among them, the reaction conditions were as follows:

[0053] Reactor: Batch reactor, volume 200 ml;

[0054] Catalyst filling amount: 2 g;

[0055] Reaction temperature: 65 °C;

[0056] Reaction time: 4 hours;

[0057] Molar ratio of raw materials: methanol / methacrolein = 30;

[0058] Feeding amount: 64 g of methanol and 4.7 g of methacrolein.

[0059] Air pressure: 3.5 Mpa.

[0060] Example 1:

[0061] (1) 40 g of strontium nitrate (Sr(NO 3 ) 2 ) was dissolved in water to obtain solution A, and then solution A was added to 280.8 g of silica sol (SiO 2 40 wt%) and stirred for a period of time, followed by spray drying to obtain the carrier precursor.

[0062] (2) The carrier precursor obtained in step (1) was calcined in air at 550 °C for 4 h to obtain the carrier.

[0063] (3) A mixed salt solution B was obtained by mixing 100 ml of chloroauric acid solution (Au content 0.005 g / ml) and 10 ml of bismuth nitrate solution (Bi content 0.005 g / ml), and it was added to 100 g of the carrier, stirred for a period of time. After the color of solution B became transparent, it was filtered, washed, and dried in a vacuum oven at 100 °C to obtain the catalyst precursor.

[0064] (4) The obtained catalyst precursor was calcined in air at 300 °C for 4 h, and then subjected to a second calcination at 350 °C for 2 h in air with a water vapor content of 10% (V / V) to obtain the catalyst for methyl methacrylate synthesis.

[0065] In the obtained catalyst, the average particle size of Au was 3.1 nm, the specific surface area was 82 m 2 / g, the pore volume was 0.67 cm 3 / g, and the most probable pore diameter was 38 nm.

[0066] Example 2:

[0067] 10 ml of nickel nitrate (Ni content 0.005 g / ml) was used to replace bismuth nitrate in Example 1, and the others were the same.

[0068] In the obtained catalyst, the size of Au was 3.5 nm, the specific surface area was 79 m 2 / g, the pore volume was 0.64 cm 3 / g, and the most probable pore diameter was 39 nm.

[0069] Example 3:

[0070] 10 ml of niobium tartrate (Nb content 0.005 g / ml) was used to replace bismuth nitrate in Example 1, and the others were the same.

[0071] In the obtained catalyst, the size of Au was 4.2 nm, the specific surface area was 67 m 2 / g, the pore volume was 0.67 cm 3 / g, and the most probable pore diameter was 41 nm.

[0072] Example 4:

[0073] 10 ml of cobalt nitrate (Co content 0.005 g / ml) was used to replace bismuth nitrate in Example 1, and the others were the same.

[0074] In the obtained catalyst, the size of Au was 2.9 nm, the specific surface area was 84 m 2 / g, the pore volume was 0.71 cm 3 / g, and the most probable pore diameter was 36 nm.

[0075] Example 5:

[0076] Replace bismuth nitrate in Example 1 with 10 ml of iron nitrate (Fe content: 0.005 g / ml), and keep other conditions the same.

[0077] In the obtained catalyst, the size of Au is 2.8 nm, the specific surface area is 77 m 2 / g, the pore volume is 0.66 cm 3 / g, and the most probable pore diameter is 37 nm.

[0078] Example 6:

[0079] Perform the second calcination in air with a water vapor content of 19.5% (V / V) at 350 °C, and keep other conditions the same as in Example 1.

[0080] In the obtained catalyst, the size of Au is 4.0 nm, the specific surface area is 52 m 2 / g, the pore volume is 0.91 cm 3 / g, and the most probable pore diameter is 49 nm.

[0081] Comparative Example 1:

[0082] (1) Spray-dry 280.8 g of silica sol (SiO 2 40 wt%) to obtain a support precursor.

[0083] (2) Calcinate the support precursor obtained in step (1) in air at 550 °C for 4 h to obtain a support.

[0084] (3) Add 100 ml of chloroauric acid solution (Au content: 0.005 g / ml) to 100 g of the support, stir for a period of time, wait until the color in solution B becomes transparent, filter and wash, and dry in a vacuum oven at 100 °C to obtain a catalyst precursor.

[0085] (4) Calcinate the obtained precursor in air at 300 °C for 4 h to obtain a catalyst for methyl methacrylate synthesis.

[0086] In the obtained catalyst, the size of Au is 9.3 nm, the specific surface area is 118 m 2 / g, the pore volume is 0.32 cm 3 / g, and the most probable pore diameter is 19 nm.

[0087] Comparative Example 2:

[0088] (1) Dissolve 40 g of strontium nitrate (Sr(NO 3 ) 2 ) in water to obtain solution A, and then add solution A to 280.8 g of silica sol (SiO 2 40 wt%), continue to stir for a period of time, and spray-dry to obtain a support precursor.

[0089] (2) The carrier precursor obtained in step (1) is calcined in air at 550 °C for 4 h to obtain the carrier.

[0090] (3) 100 ml of chloroauric acid solution (Au content 0.005 g / ml) and 10 ml of bismuth nitrate solution (Bi content 0.005 g / ml) are mixed to obtain a mixed salt solution B, which is added to 100 g of the carrier, stirred for a period of time, and when the color of solution B becomes transparent, it is filtered, washed, and dried in a vacuum oven at 100 °C to obtain the catalyst precursor.

[0091] (4) The obtained catalyst precursor is calcined in air at 300 °C for 4 h to obtain the catalyst for methyl methacrylate synthesis.

[0092] In the obtained catalyst, the size of Au is 7.1 nm, the specific surface area is 125 m 2 / g, the pore volume is 0.31 cm 3 / g, and the most probable pore diameter is 18 nm.

[0093] The obtained catalyst is evaluated and tested, and the results are shown in Table 1 below.

[0094] Table 1

[0095]

[0096] In Table 1, n is a value determined by the total valence of the elements other than oxygen in the general formula.

[0097] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions of the present invention and their implementation manners, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0098] All publications, patent applications, patents and other references mentioned in this specification are hereby incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0099] When this specification uses prefixes such as "well-known to those skilled in the art", "prior art" or their similar terms to derive materials, substances, methods, steps, devices or components, etc., the objects derived by such prefixes cover those commonly used in the art at the time when this application is filed, but also include those that are not commonly used at present but will become commonly recognized in the art as suitable for similar purposes.

[0100] In the context of this specification, any matter or thing not mentioned, other than what is expressly stated, shall directly apply those known in the art without any change.

Claims

1. A catalyst for methyl methacrylate synthesis, comprising an active component and a support, wherein the active component and the support have the general formulas AuM a O n and Si 10 N b O x , Among them, M is at least one of Ni, Nb, Co, Fe, and Bi, and N is at least one of Be, Mg, Ca, Sr, and Ba; a = 0.001 to 10; b = 0.001 to 2; x and n are values determined by the total valence of the elements other than oxygen in the general formula.

2. The catalyst for synthesizing methyl methacrylate according to claim 1, characterized in that Based on the total mass of the catalyst: The Au content is 0.1 to 0.9 wt%, preferably 0.5 to 0.8 wt%; and / or, The M content is 0.05 to 5 wt%, preferably 0.05 to 2.5 wt%.

3. The catalyst for synthesizing methyl methacrylate according to claim 1, characterized in that: In the catalyst, the size of Au is 0.5 to 10 nm.

4. The catalyst for synthesizing methyl methacrylate according to claim 1, characterized in that: The specific surface area of the catalyst is 20 to 500 m 2 / g, preferably 30 to 100 m 2 / g; and / or, The pore volume of the catalyst is 0.1 to 0.8 cm 3 / g, preferably 0.35 to 0.8 cm 3 / g; and / or, The most probable pore diameter of the catalyst is 5 to 50 nm, preferably 20 to 50 nm.

5. The preparation method of the catalyst according to any one of claims 1 to 4, comprising the following steps: (1) Dissolve the N salt in water to obtain solution A, then add solution A to the silica sol and stir, and spray dry to obtain the carrier precursor; (2) Calcinate the obtained carrier precursor to obtain the carrier; (3) Mix the solution of gold trichloride or chloroauric acid and the aqueous solution of the M salt to obtain solution B, add it to the carrier, filter, wash, and dry to obtain the catalyst precursor; (4) After the obtained catalyst precursor is calcined once, perform a secondary calcination treatment in an atmosphere containing water vapor.

6. The preparation method according to claim 5, characterized in that: The N salt is selected from at least one of the oxygen-containing salts and / or oxygen-containing salt hydrates of Be, Mg, Ca, Sr, and Ba; and / or, The M salt is selected from at least one of the oxygen-containing salts and / or oxygen-containing salt hydrates of Ni, Nb, Co, Fe, and Bi.

7. The preparation method according to claim 5, characterized in that In the step (2): The calcination temperature is 450 to 700 °C, and the calcination time is 2 to 100 hours.

8. The preparation method according to claim 5, characterized in that In the step (4): In the first calcination, the temperature is 200 to 600 °C, and the time is 2 to 200 hours; and / or, In the second calcination, the volume content of water vapor is 0.5 to 20%, the temperature is 100 to 800 °C, and the time is 0.5 to 200 hours.

9. The application of the catalyst for synthesizing methyl methacrylate according to any one of claims 1 to 4 and / or the catalyst prepared by the preparation method according to any one of claims 5 to 9 in the synthesis of methyl methacrylate.

10. The application according to claim 9, characterized in that Including reacting methacrolein, methanol and an O-containing atmosphere in the presence of the catalyst. Preferably, the reaction temperature is 60 to 90 °C, the partial pressure of O is 0.02 to 3 MPa, the molar ratio of methanol to methacrolein is 10 to 40, and the reaction time is 0.5 to 24 h. 2 Including reacting methacrolein, methanol and an O-containing atmosphere in the presence of the catalyst. Preferably, the reaction temperature is 60 to 90 °C, the partial pressure of O is 0.02 to 3 MPa, the molar ratio of methanol to methacrolein is 10 to 40, and the reaction time is 0.5 to 24 h. 2 Including reacting methacrolein, methanol and an O-containing atmosphere in the presence of the catalyst. Preferably, the reaction temperature is 60 to 90 °C, the partial pressure of O is 0.02 to 3 MPa, the molar ratio of methanol to methacrolein is 10 to 40, and the reaction time is 0.5 to 24 h.

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