Selective gold-based oxidation catalysts, their preparation methods and applications

Abstract

This invention relates to a selective gold-based oxidation catalyst, its preparation method, and its application; the catalyst comprises components represented by general formula (1): Au-Sc a / Si b Ce c X d O e In formula (1), a is the molar ratio of Sc to Au, with a value of 0.1 to 1.0; b is the molar ratio of Si to Au, with a value of 100 to 500; c is the molar ratio of Ce to Au, with a value of 1.0 to 30.0; d is the molar ratio of X to Au, with a value of 0.1 to 2.0; e is the number of oxygen atoms required to satisfy the oxidation states of each element in the active component; X is selected from at least one of Li, Na, K, Rb, and Cs. The catalyst of the present invention is used for selective oxidation, with high yield of target product and high conversion rate of raw materials. For example, it has the characteristics of high conversion rate of methacrolein and high yield of methyl methacrylate in the synthesis of alkyl acrylates.

Description

Technical Field

[0001] This invention relates to a selective gold-based oxidation catalyst, its preparation method, and its application. Background Technology

[0002] Methyl methacrylate (MMA), also known as methyl isobutylene acrylate, is mainly used as a monomer for plexiglass. It is also used in the manufacture of other resins, plastics, coatings, adhesives, lubricants, impregnating agents for wood and cork, paper varnishes, etc., and is an important organic chemical raw material.

[0003] Currently, among industrialized MMA production processes, the traditional ACH method is characterized by its simplicity and high maturity. However, the raw material used in this method, hydrogen cyanide, is highly toxic, and both hydrogen cyanide and sulfuric acid are highly corrosive. This places high demands on reaction equipment and results in large volumes of waste acid, potentially causing significant environmental harm. BASF's technology does not offer outstanding economic benefits, and Alpha technology is currently in its early stages of industrialization; its technological maturity and overall economic viability require further evaluation.

[0004] Using air or oxygen directly as an oxidant to oxidize methacrolein and methanol into the target product MMA in one step is undoubtedly a simple, green, and economically competitive process. This is because there is no intermediate formation of methacrylic acid or subsequent esterification of methylpropionic acid and methanol, significantly reducing production costs. Furthermore, the process's byproduct is water, making it environmentally friendly. However, the challenge lies in catalyst preparation, and therefore, considerable effort has been made to solve this problem.

[0005] Currently, oxide-supported noble metal catalysts, especially Au-supported catalysts, are commonly used. Au nanoparticles are very beneficial for improving the selectivity of this reaction, but their conversion rate is still significantly insufficient. Better gold-based catalysts for methyl methacrylate need to be developed to promote the production of methyl methacrylate. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of low conversion rate of methacrolein and low yield of methyl methacrylate in the prior art when the ratio of methanol to methacrolein is low. This invention provides a selective oxidation gold-based catalyst, its preparation method and application. This catalyst is used for selective oxidation and has a high yield of target product and a high conversion rate of raw materials. For example, it has the characteristics of high conversion rate of methacrolein and high yield of methyl methacrylate in the synthesis of alkyl acrylates.

[0007] According to a first aspect of the present invention, the present invention provides a selective gold oxidation-based catalyst, the catalyst comprising the components shown in general formula (1):

[0008] Au-Sc a / Si b Ce cX d O e Equation (1)

[0009] In equation (1),

[0010] 'a' represents the molar ratio of Sc to Au, and its value ranges from 0.1 to 1.0.

[0011] b is the molar ratio of Si to Au, and the value of b ranges from 100 to 500;

[0012] c is the molar ratio of Ce to Au, and the value of c ranges from 1.0 to 30.0;

[0013] d is the molar ratio of X to Au, and d ranges from 0.1 to 2.0;

[0014] e represents the number of moles of oxygen atoms required to satisfy the oxidation states of each element in the active component;

[0015] X is selected from at least one of Li, Na, K, Rb, and Cs.

[0016] According to a second aspect of the present invention, the present invention provides a method for preparing the selective gold-based oxidation catalyst of the present invention, the method comprising:

[0017] S1. The Si source, Ce source and X source are mixed under solution conditions, allowed to stand for aging, spray dried and calcined to obtain the support;

[0018] S2. Mix the Au source and the Sc source under solution conditions to obtain mixture I;

[0019] S3. Mix the mixture I with the support to obtain the catalyst precursor, which is then optionally dried and calcined.

[0020] According to a third aspect of the invention, the present invention provides the use of the catalyst described herein in the synthesis of alkyl acrylates, preferably in the selective oxidation of methacrolein to methyl methacrylate.

[0021] The catalyst of this invention is used for selective oxidation, with high yield of target product and high feed conversion rate. For example, it is used in the synthesis of alkyl acrylates and has the characteristics of high conversion rate of methacrolein and high yield of methyl methacrylate. Attached Figure Description

[0022] Figure 1 This is a TEM image of the selective gold oxide-based catalyst prepared in Example 1. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the 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.

[0024] This invention provides a selective gold-based oxidation catalyst, the catalyst comprising the components shown in general formula (1):

[0025] Au-Sc a / Si b Ce c X d O e Equation (1)

[0026] In equation (1),

[0027] 'a' represents the molar ratio of Sc to Au, and its value ranges from 0.1 to 1.0.

[0028] b is the molar ratio of Si to Au, and the value of b ranges from 100 to 500;

[0029] c is the molar ratio of Ce to Au, and the value of c ranges from 1.0 to 30.0;

[0030] d is the molar ratio of X to Au, and d ranges from 0.1 to 2.0;

[0031] e represents the number of moles of oxygen atoms required to satisfy the oxidation states of each element in the active component;

[0032] X is selected from at least one of Li, Na, K, Rb, and Cs. Na is used as an example in this embodiment, but is not limited to the scope of the invention. This catalyst is used for selective oxidation, achieving high yields of the target product and high feed conversion rates. For example, it is used in the synthesis of alkyl acrylates, exhibiting high conversion rates of methacrolein and methyl methacrylate.

[0033] According to a preferred embodiment of the present invention, b takes the value of 100 to 500, specifically, for example, 100, 200, 300, 400, 500. In this embodiment of the present invention, 200 is used as an example to illustrate the advantages of the present invention, but the present invention is not limited thereto.

[0034] According to a preferred embodiment of the present invention, c takes the value from 1.0 to 30.0, for example, 1, 5, 10, 15, 20, 25, 30. In this embodiment of the present invention, 10 is used as an example to illustrate the advantages of the present invention, but the present invention is not limited thereto.

[0035] According to a preferred embodiment of the present invention, the ratio of d to c is (0.01 to 0.5):1, preferably (0.05 to 0.3):1, more preferably (0.05 to 0.2):1, and even more preferably (0.1 to 0.2):1, for example 0.1:1, 0.15:1, 0.2:1.

[0036] According to a preferred embodiment of the present invention, the active components Au and / or Sc of the catalyst have a particle size of 3-6 nm, with 4-5 nm accounting for more than 80%, preferably 85-88%; and an average particle size of (4.5-4.7) nm ± 0.1 nm.

[0037] The catalyst of the present invention has a very uniform distribution of Au and / or Sc composite noble metals, a very narrow size distribution, and a particle size of 3-6 nm, wherein the proportion of 4-5 nm is more than 80%, preferably 85-88%; the average particle size is (4.5-4.7) nm ± 0.1 nm.

[0038] This invention does not impose any special requirements on the preparation method of the catalyst. Catalysts possessing the aforementioned characteristics of this invention can achieve the objectives of this invention. According to a preferred embodiment of this invention, a method for preparing a selective gold-based oxidation catalyst is provided, the method comprising:

[0039] S1. The Si source, Ce source and X source are mixed under solution conditions, allowed to stand for aging, spray dried and calcined to obtain the support;

[0040] S2. Mix the Au source and the Sc source under solution conditions to obtain mixture I;

[0041] S3. Mix the mixture I with the support to obtain the catalyst precursor, which is then optionally dried and calcined.

[0042] According to a preferred embodiment of the present invention, the mixing conditions of S1 include a temperature of 30-40°C. This can further improve the catalytic performance of the catalyst.

[0043] According to a preferred embodiment of the present invention, when the Si source, Ce source, and X source are each provided in solution, the solution temperature of each is 30-40°C, and the mixing temperature is also 30-40°C. This can further improve the catalytic performance of the catalyst.

[0044] According to a particularly preferred embodiment of the present invention, the mixing step S1 includes: mixing the Ce source and the X source under solution conditions, followed by adding the Si source; preferably, the X source solution is slowly added to the Ce source solution, followed by stirring for 10-60 min (e.g., 10 min, 20 min, 30 min, 40 min, 50 min, 60 min) to obtain a mixed solution M; then the Si source solution is slowly added to the mixed solution M, followed by stirring for 10-60 min (e.g., 10 min, 20 min, 30 min, 40 min, 50 min, 60 min). This can significantly improve the catalytic performance of the catalyst.

[0045] In this invention, there are no special requirements for the static aging steps and conditions. Preferably, for this invention, the static aging conditions for S1 include: a time of 12-48 hours (e.g., 12 hours, 24 hours, 36 hours, 48 ​​hours), and / or a temperature of 60-120°C (e.g., 60°C, 80°C, 100°C, 120°C). Using the aforementioned preferred static aging conditions can improve the catalytic performance of the catalyst.

[0046] In this invention, there are no special requirements for the mixing conditions of S2. According to a preferred embodiment of this invention, the mixing conditions of S2 include a temperature of 30-40°C.

[0047] According to a preferred embodiment of the present invention, when the Au source and the Sc source are each provided in solution, the temperature of each solution is 30-40°C, and the mixing temperature is 30-40°C.

[0048] In this invention, there are no special requirements for the mixing step of S2. According to one embodiment, the mixing step of S2 includes: under stirring conditions, slowly adding the Sc source solution to the Au source solution, and then stirring for 10-60 minutes.

[0049] In this invention, there are no special requirements for the mixing and contact conditions in S3, but preferably include: after mixing the mixture I with the carrier, continue stirring at 60-120°C (e.g., 60°C, 80°C, 100°C, 120°C) for 30-120 min (e.g., 30 min, 60 min, 80 min, 100 min, 120 min).

[0050] In this invention, the product is allowed to stand for aging, stirred evenly, and then spray-dried.

[0051] In this invention, there are no special requirements for the spray drying conditions. Commonly used spray drying conditions can be used in this invention. For this invention, the preferred spray drying conditions include: inlet temperature: 150-250℃, outlet temperature: 100-140℃.

[0052] In this invention, there are no special requirements for the source of each component; any commonly used source of each component can be used in this invention.

[0053] According to a preferred embodiment of the present invention, the Si source is preferably selected from one or more of silicon powder, silicon dioxide, silica sol, and silicates, and the solid content of the silica sol is preferably 0.5-5% by weight. Silica sol is used as an illustrative example in the embodiments of the present invention, but this does not limit the scope of the invention.

[0054] According to a preferred embodiment of the present invention, the Ce source is preferably selected from one or more of cerium nitrate, cerium ammonium nitrate, and cerium oxide.

[0055] According to a preferred embodiment of the present invention, the X source is preferably selected from one or more of nitrates, carbonates, sulfates, and oxides.

[0056] According to a preferred embodiment of the present invention, the Au source is preferably selected from one or more of chloroauric acid, ammonium tetrachloroaurate, and sodium chloroaurate.

[0057] According to a preferred embodiment of the present invention, the Sc source is preferably selected from one or more of scandium nitrate, scandium sulfate, and scandium trichloride.

[0058] In this invention, there are no special requirements for the drying and roasting conditions. Commonly used drying and roasting conditions in the art are applicable to this invention, and will not be described in detail here.

[0059] According to a preferred embodiment of the present invention, the drying conditions include: 60-120°C for 2-10 hours.

[0060] According to a preferred embodiment of the present invention, the calcination conditions include: 350-550℃, 2-10h.

[0061] The present invention provides the application of the catalyst in the synthesis of alkyl acrylates, preferably in the selective oxidation of methacrolein to methyl methacrylate.

[0062] In this invention, the purpose of slow operation is to ensure complete dissolution.

[0063] The formula for calculating the MAL conversion rate (%) includes: MAL conversion rate = MAL consumed in the reaction / MAL added to the reaction * 100%;

[0064] The formula for calculating the MMA yield (%) includes: Methyl methacrylate yield = Methacrolein consumed in the production of methyl methacrylate / Methacrolein added to the reaction.

[0065] In this invention, when the component sources are provided in solutions, there are no special requirements for the content of the component sources in the solutions, which is generally 0.5-5 wt%. The concentration of each solution is not the key focus of this invention, and will not be elaborated here. In the examples, the concentration of each solution or sol is 2% by weight.

[0066] In this invention, there are no special requirements for the stirring conditions; the purpose is to ensure that the stirring is uniform and thorough. This invention can use magnetic stirring or mechanical stirring.

[0067] Example 1

[0068] 1. The carrier is obtained by mixing the liquids of various elements.

[0069] Cerium nitrate (Ce(NO3)3) containing 0.1 mol Ce and sodium hydroxide (NaOH) containing 0.015 mol Na were dissolved separately in deionized water at 35°C. The sodium hydroxide solution was slowly added to the cerium nitrate solution under stirring, and stirring was continued for 30 min to obtain a mixed solution. Then, silica sol (SiO2) containing 2 mol Si was slowly added to the mixed solution, and stirring was continued for another 30 min. After homogeneous mixing, the mixture was allowed to stand at 80°C for 24 h for aging. After homogeneous mixing again, it was spray-dried (conditions including inlet temperature 200°C and outlet temperature 120°C) and calcined at 500°C for 5 h to obtain the carrier.

[0070] 2. Obtaining Mixed Solution I

[0071] Chloroauric acid (molecular formula: HAuCl) containing 0.01 mol Au and scandium nitrate (molecular formula: Sc(NO3)3) containing 0.005 mol Sc were dissolved separately in deionized water at 35°C. The scandium nitrate solution was slowly added to the chloroauric acid solution under stirring, and then stirring was continued for 30 min. After thorough mixing, mixture I was obtained.

[0072] 3. Mix solution I with the carrier, then dry and calcine.

[0073] The above mixture I and the above support were added to a flask and mixed thoroughly. The mixture was stirred in an oil bath at 80°C for 60 minutes. After cooling, the slurry was washed to obtain the catalyst precursor. The catalyst precursor was dried in an oven at 80°C for 3 hours, and then calcined in a muffle furnace at 400°C for 3 hours to obtain a catalyst with the following composition: Au-Sc 0.5 / Si 200 Ce 10 Na 1.5 O e。

[0074] Figure 1 This is a TEM image of the selective gold oxide-based catalyst prepared in Example 1. Figure 1 It can be seen that the composite noble metal particles of Au and / or Sc are very uniformly distributed, with a particle size of 3 to 6 nm, an average particle size of 4.5 nm, and 88% of the particles have a particle size of 4 to 5 nm.

[0075] Example 2

[0076] Following the method of Example 1, except for changing the feed ratio, a catalyst with the composition Au-Sc was prepared. 0.1 / Si 200 Ce 10 Na 1.5 O e The average particle size of the composite noble metal particles of Au and / or Sc in the catalyst was 4.7 nm, and the proportion of particles with a size of 4-5 nm was 85%. The results are shown in Table 1.

[0077] Example 3

[0078] Following the method of Example 1, except for changing the feed ratio, a catalyst with the composition Au-Sc was prepared. 1.0 / Si 200 Ce 10 Na 1.5 O e The average particle size of the composite noble metal particles of Au and / or Sc in the catalyst was 4.6 nm, and the proportion of particles with a size of 4-5 nm was 86%. The results are shown in Table 1.

[0079] Example 4

[0080] Following the method of Example 1, except for changing the feed ratio, a catalyst with the composition Au-Sc was prepared. 0.5 / Si 200 Ce 10 Na 0.1 O e The ratio of d to c is 0.01:1. The average particle size of the Au and / or Sc composite noble metal particles in the catalyst is 4.9 nm, and the proportion of particles with a size of 4-5 nm is 81%, as shown in Table 1.

[0081] Example 5

[0082] Following the method of Example 1, except for changing the feed ratio, a catalyst with the composition Au-Sc was prepared. 0.5 / Si 200 Ce 10 Na5O e The ratio of d to c is 0.5:1. The average particle size of the Au and / or Sc composite noble metal particles in the catalyst is 4.8 nm, and 80% of the particles are between 4 and 5 nm in size. The results are shown in Table 1.

[0083] Example 6

[0084] The method was followed as in Example 1, except that the individual solution temperatures in step S1 were both 50°C and the mixing temperature was 50°C. The results are shown in Table 1.

[0085] Example 7

[0086] The method is the same as in Example 1, except that the mixing step S1 is as follows:

[0087] Cerium nitrate (Ce(NO3)3) containing 0.1 mol Ce and sodium hydroxide (NaOH) containing 0.015 mol Na were dissolved separately in deionized water at 35°C. The sodium hydroxide solution and cerium nitrate solution were then added to 2 mol Si silica sol (SiO2) under stirring, and stirring was continued for 60 min to obtain a mixed solution. The remaining aging and settling steps were the same as in Example 1, and the results are shown in Table 1.

[0088] Example 8

[0089] The method is the same as in Example 1, except that aging is not performed.

[0090] Example 9

[0091] The method of Example 1 was followed, except that in step S3, the catalyst drying conditions were 150°C for 150 min, and the results are shown in Table 1.

[0092] Comparative Example 1

[0093] Following the method of Example 1, the feeding ratio was changed, and the results are shown in Table 1.

[0094] Comparative Example 2

[0095] The method of Example 1 was followed, except that the feeding ratio was changed. The results are shown in Table 1.

[0096] Comparative Example 3

[0097] The method of Example 1 was followed, except that the feeding ratio was changed. The results are shown in Table 1.

[0098] Comparative Example 4

[0099] The method of Example 1 was followed, except that the feeding ratio was changed. The results are shown in Table 1.

[0100] Table 1

[0101]

[0102] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A selective gold oxidation-based catalyst, characterized in that, The catalyst comprises the components shown in general formula (1): Au-Sc a / And b What c X d A e formula (1) In equation (1), 'a' represents the molar ratio of Sc to Au, and its value ranges from 0.1 to 1.

0. b is the molar ratio of Si to Au, and the value of b ranges from 100 to 500; c is the molar ratio of Ce to Au, and the value of c ranges from 1.0 to 30.0; d is the molar ratio of X to Au, and d ranges from 0.1 to 2.0; e represents the number of moles of oxygen atoms required to satisfy the oxidation states of each element in the active component; X is selected from at least one of Li, Na, K, Rb, and Cs; The ratio of d to c is (0.01~0.5):

1.

2. The catalyst according to claim 1, wherein, The ratio of d to c is (0.05~0.3):

1. The active components of the catalyst, Au and / or Sc, have a particle size of 3-6 nm, with Au and / or Sc having a particle size of 4-5 nm accounting for more than 80%; the average particle size of Au and / or Sc is (4.5-4.7) nm ± 0.1 nm.

3. The catalyst according to claim 2, wherein, The ratio of d to c is (0.05~0.2):

1. The particle size of the active components Au and / or Sc in the catalyst is 3~6 nm, and the proportion of Au and / or Sc with a particle size of 4~5 nm is 85-88%.

4. The catalyst according to claim 3, wherein, The ratio of d to c is (0.1~0.2):

1.

5. A method for preparing a selective gold oxide-based catalyst according to any one of claims 1-4, characterized in that, The method includes: S1. Si source, Ce source and X source are mixed under solution conditions, allowed to stand for aging, spray dried and calcined to obtain the support; S2. The Au source and the Sc source are mixed under solution conditions to obtain mixture I; S3. Mix the mixture I with the support to obtain the catalyst precursor, and then dry and calcine it.

6. The preparation method according to claim 5, wherein, The mixing conditions for S1 include a temperature of 30-40℃; When the Si source, Ce source and X source are each provided in solution, the solution temperature of each is 30-40℃, and the mixing temperature is 30-40℃. The conditions for spray drying include: inlet temperature: 150-250℃, outlet temperature: 100-140℃.

7. The preparation method according to claim 5 or 6, wherein, The mixing steps of S1 include: mixing the Ce source and the X source under solution conditions, followed by adding the Si source.

8. The preparation method according to claim 7, wherein, The mixing steps of S1 include: slowly adding the X source solution to the Ce source solution, then stirring for 10-60 min to obtain a mixed solution M; then slowly adding the Si source solution to the mixed solution M, and then stirring for 10-60 min.

9. The preparation method according to claim 5 or 6, wherein, The conditions for static aging of S1 include: a time of 12-48 hours and / or a temperature of 60-120℃.

10. The preparation method according to claim 5 or 6, wherein, The mixing conditions for S2 include a temperature of 30-40℃; When Au and Sc sources are provided in solutions, their respective solution temperatures are 30-40℃, and the mixing temperature is also 30-40℃.

11. The preparation method according to claim 5 or 6, wherein, The mixing steps for S2 include: slowly adding the Sc source solution to the Au source solution under stirring conditions, followed by stirring for 10-60 minutes.

12. The preparation method according to claim 5 or 6, wherein, The mixing contact conditions in S3 include: after mixing liquid I with the carrier, continue stirring at 60-120℃ for 30-120 min; Drying conditions include: 60-120℃, 2-10h; The roasting conditions include: 350-550℃, 2-10h.

13. The use of the catalyst according to any one of claims 1 to 4 in the synthesis of alkyl acrylates.

14. The use of the catalyst according to any one of claims 1 to 4 in the selective oxidation of methacrolein to methyl methacrylate.

Images