An oxidation esterification catalyst for methanol and methylpropyl aldehyde and its preparation method and application
By using TS-1 support to prepare a gold-based catalyst, Ti-O-Au bonds are formed to limit the size of gold particles and increase the specific surface area of the catalyst. This solves the problems of insufficient environmental protection and efficiency in the existing MMA production process and realizes a highly efficient methanol-methacrylaldehyde oxidative esterification reaction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2023-12-15
- Publication Date
- 2026-06-26
AI Technical Summary
Existing MMA production processes face challenges such as high environmental pressure, demanding equipment requirements, and insufficiently efficient catalysts. In particular, the ACH and C4 processes require the use of highly toxic raw materials, and catalysts such as ZSM-5 molecular sieves are insufficient in terms of both economy and environmental friendliness.
Gold-based catalysts were prepared using TS-1 as a support, forming smaller gold nanoparticles through Ti-O-Au bonds, thereby increasing the specific surface area and dispersibility of the catalyst and enhancing its catalytic activity and stability.
It improves the conversion rate and selectivity of the oxidative esterification reaction of methanol and methacrolein, making it suitable for the industrial production of methyl methacrylate while reducing environmental pollution and equipment requirements.
Smart Images
Figure CN117619432B_ABST
Abstract
Description
Technical fields:
[0001] This invention belongs to the field of catalytic synthesis technology, specifically relating to a catalyst for the oxidative esterification of methanol and methacrolein, its preparation method, and its application. Background technology:
[0002] Methyl methacrylate (MMA) is a colorless, transparent liquid with an ether-like odor. As an important organic chemical raw material, it is mainly used in the production of plexiglass and resin materials. To date, the main processes for producing MMA include the acetone-nitrogen alcohol process (ACH process), the isobutylene oxidation process (C4 process), the ethylene carbonylation process, and the Alpha process. The ACH process requires highly toxic raw materials, consumes large amounts of sulfuric acid during the reaction, has high equipment requirements, produces a large amount of ammonium bisulfate as a byproduct, has a long process flow, and poses significant environmental risks. The C4 process is divided into a three-step preparation method and a two-step preparation method. The three-step method involves oxidizing isobutylene to methacrolein (MAL), then oxidizing it to methacrylic acid (MAA), and finally esterifying it with methanol to produce MMA. The two-step method involves oxidizing isobutylene to MAL, followed by oxidative esterification to obtain MMA. The ethylene carbonylation method first produces propionaldehyde by catalytic carbonylation of ethylene, H2, and CO in the presence of a rhodium complex. Propanal then undergoes a condensation reaction with formaldehyde to generate MAL. Subsequently, methacrylic acid is generated in the gas phase under the action of a heteropolyacid catalyst, and finally, esterification with methanol produces MMA. The Alpha method mainly uses ethylene, CO, and methanol as raw materials to generate methyl propionate in the presence of a palladium catalyst, which then undergoes an aldol condensation reaction with formaldehyde to produce MMA. Chinese invention patent CN110981728B discloses a method for preparing MMA, but the catalyst used is a molecular sieve with a silica-to-alumina ratio of 80-120, including one of sodium-type ZSM-5, beta, 4A, and 5A molecular sieve spherical particles; the molecular sieve size is 50-100 μm. From economic and environmental perspectives, it is still necessary to develop new process routes and novel, efficient catalysts to improve the yield of MMA. Summary of the Invention
[0003] To address the problems existing in the background art, the present invention aims to provide a catalyst for the oxidative esterification of methanol and methacrolein, its preparation method, and its application.
[0004] The catalyst for the oxidative esterification of methanol methacrolein prepared in this invention uses TS-1 as a support to prepare a gold-based catalyst. The TS-1 support has better hydrophobicity and weaker acidity. The TS-1 support can not only stabilize gold salts, but also form Ti-O-Au bonds between the titanium species in the TS-1 support and the gold nanoparticles, which can improve the interaction between the gold metal and the support. It can also effectively limit the size of gold particles, forming smaller gold nanoparticles and good dispersion, so as to increase the specific surface area of the catalyst, thereby improving the catalyst activity and stability.
[0005] This invention is achieved through the following technical solution:
[0006] This invention provides a method for preparing a catalyst for the oxidative esterification of methanol and methacrolein, comprising the following steps:
[0007] (1) Mix silicon source, template agent and water evenly, and hydrolyze at 20-85℃ for 30-120 min to obtain silicon ester hydrolysate; add alcohol solution to titanium source, and hydrolyze at 25-85℃ for 10-60 min to obtain titanium ester hydrolysate; mix the obtained silicon ester hydrolysate and titanium ester hydrolysate evenly, heat to 50-90℃ to remove alcohol, and put the obtained titanium silicon sol into crystallization kettle, and crystallize at 150-200℃ for 10-48 h;
[0008] (2) Add aluminum sol or silica sol or silica-alumina sol and guar gum powder to the molecular sieve mother liquor obtained in step (1), age it at 50-90℃ for 10-72h under stirring, spray mold it, dry it, and calcine it at 300-600℃ for 2-24h to obtain the molecular sieve.
[0009] (3) Add the molecular sieve obtained in step (2) to the aqueous solution containing gold salt, add the template agent aqueous solution, mix well, put it into a crystallization kettle and treat it at 150-190℃ for 12-72h, filter, dry, and calcine at 400-600℃ for 1-10h to obtain the product.
[0010] Further, the silicon source mentioned in step (1) is one or a mixture of two or more of tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate; the template agent is one or a mixture of two or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide; the mass ratio of silicon source, template agent and water is 1:0.1-0.5:0.5-2.
[0011] Further, the titanium source in step (1) is one or a mixture of two or more of tetraethyl orthotitanate, tetrabutyl orthotitanate, tetraisopropyl orthotitanate, titanium trichloride, and titanium tetrachloride; the alcohol solution is isopropanol or ethanol; and the mass ratio of the titanium source to the alcohol solution is 1:10-20.
[0012] Furthermore, the mass ratio of the titanium source to the silicon source in step (1) is 1:10-50.
[0013] Furthermore, the alcohol removal process in step (1) takes 4 to 12 hours.
[0014] Further, in step (2), the mass ratio of the molecular sieve mother liquor to aluminum sol or silica sol or silica-alumina sol and guar gum powder is 1:0.1 to 1:0.02 to 0.08.
[0015] Furthermore, the drying temperature in step (2) is 100-180℃ and the time is 12-72h.
[0016] Further, the template agent mentioned in step (3) is one or a mixture of two or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide, and the molar concentration of the template agent is 0.01-0.1 mol / L.
[0017] Further, the gold salt mentioned in step (3) is one or a mixture of two or more of gold cyanide, potassium gold cyanide, gold chloride, gold chloride, chloroauric acid, chloroaurate, sodium gold sulfite or regrin; the mass ratio of gold salt to molecular sieve is 0.05 to 5:100, and the gold loading is 0.1 to 2 wt%.
[0018] In another aspect, the present invention provides a catalyst for the oxidative esterification of methanol and methacrolein prepared by the above preparation method.
[0019] The present invention also provides the application of the above-described catalyst in the reaction of methanol and methacrolein oxidative esterification to produce methyl methacrylate.
[0020] Further, the reaction specifically involves mixing the catalyst, methacrolein, and methanol in a reactor, introducing an oxygen-containing gas at the bottom of the reactor, reacting at a temperature of 70-160°C, a pressure of 0.5-2 MPa, and a reaction time of 1-12 h, to obtain methyl methacrylate.
[0021] Furthermore, the mass concentration of methacrolein is 10-55%; the rate of introduction of oxygen-containing gas is 1-2 L / min.
[0022] The beneficial effects of this invention are:
[0023] The catalyst for the oxidative esterification of methanol methacrolein prepared in this invention uses TS-1 as a support. The TS-1 support can not only stabilize the gold salt, but also form Ti-O-Au bonds between the titanium and gold nanoparticles in the TS-1 support, which can improve the interaction between the gold metal and the support. It can also effectively limit the size of the gold particles in order to increase the specific surface area of the catalyst. The larger specific surface area and better dispersibility increase the contact area between the reactants and the active sites, thereby improving the catalytic activity and making it suitable for industrial production. Attached Figure Description
[0024] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.
[0025] Figure 1 This is a SEM image of the titanium-silicon molecular sieve in Example 1;
[0026] Figure 2 This is a SEM image of the spray-formed titanium-silicon molecular sieve catalyst in Example 1;
[0027] Figure 3 This is a TEM image of the Au / TS-1 catalyst in Example 1. Detailed Implementation
[0028] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.
[0029] Example 1:
[0030] The preparation process of Au / TS-1(1) gold-based catalyst is as follows:
[0031] (a) Preparation of molecular sieve mother liquor
[0032] 100g of tetraethyl orthosilicate was added to a jacketed three-necked reactor. 90g of 20wt% TPAOH aqueous solution and 80g of deionized water were added under magnetic stirring at 25°C, allowing the tetraethyl orthosilicate to hydrolyze for 90 minutes. The mixture was then heated to 85°C to obtain a silicate hydrolysate. 30g of anhydrous isopropanol was added to 4g of tetrabutyl titanate, and hydrolyzed at room temperature for 30 minutes to obtain a titanium ester hydrolysate. The titanium ester hydrolysate was mixed with the silicate hydrolysate, and the reaction was continued at 85°C for 6 hours to remove the alcohol. The resulting clear titanium silicate sol was placed in a stainless steel sealed reactor with a polytetrafluoroethylene liner and crystallized at 170°C under autogenous pressure for 24 hours to obtain 300g of titanium silicate molecular sieve mother liquor, of which approximately 30g was titanium silicate molecular sieve.
[0033] (b) Take 200g of the above-mentioned titanium-silicon molecular sieve mother liquor, add 30g of aluminum sol with a mass concentration of 30% and 1g of guar gum powder, age at 70℃ for 24 hours under stirring, and then spray-form using a small spray molding machine. Dry the spray-formed catalyst at 100℃ for 12 hours and calcine at 540℃ for 12 hours to obtain the spray-formed TS-1 molecular sieve catalyst with a particle size of approximately 50-200μm.
[0034] (c) Dissolve 0.5 g of chloroauric acid in pure water, add TS-1 molecular sieve at room temperature, and then add a 0.1 mol / L tetrapropylammonium hydroxide aqueous solution (20 wt%). Add the above materials to a crystallization reactor. Rotate at 170°C for 24 hours, filter, dry, and calcine at 500°C for 2 hours.
[0035] Example 2:
[0036] The preparation process of Au / TS-1(2) gold-based catalyst is as follows:
[0037] (a) Preparation of molecular sieve mother liquor
[0038] Preparation of mother liquor for titanium-silicon molecular sieves and mother liquor for molecular sieves in Example 1.
[0039] (b) Take 200g of the above-mentioned titanium-silicon molecular sieve mother liquor, add 30g of silica sol with a mass concentration of 30% and 1g of guar gum powder, and age at 70℃ for 36 hours under stirring. Spray-form the catalyst using a small spray molding machine. Dry the spray-formed catalyst at 150℃ for 12 hours and calcine at 500℃ for 2 hours to obtain the spray-formed TS-1 molecular sieve catalyst with a particle size of approximately 50-200μm.
[0040] (c) Dissolve 1.0 mol / L chloroauric acid in pure water, add TS-1 molecular sieve at room temperature, and then add a 0.1 mol / L tetramethylammonium hydroxide aqueous solution (20 wt%). Add the above materials to a crystallization vessel and treat at 170°C for 24 hours. Filter, dry, and calcine at 400°C for 5 hours.
[0041] Example 3:
[0042] The preparation process of Au / TS-1(3) gold-based catalyst is as follows:
[0043] (a) Preparation of molecular sieve mother liquor
[0044] Preparation of mother liquor for titanium-silicon molecular sieves and mother liquor for molecular sieves in Example 1.
[0045] (b) Take 200g of the above-mentioned titanium-silicon molecular sieve mother liquor, add 30g of silica sol with a mass concentration of 30% and 1g of guar gum powder, and age at 70℃ for 72 hours under stirring. Spray-form the catalyst using a small spray molding machine. Dry the spray-formed catalyst at 150℃ for 12 hours and calcine at 500℃ for 2 hours to obtain the spray-formed TS-1 molecular sieve catalyst with a particle size of approximately 50-200μm.
[0046] (c) Dissolve 1.0 mol / L chloroauric acid in pure water, add TS-1 molecular sieve at room temperature, and then add a 0.01 mol / L tetraethylammonium hydroxide aqueous solution (20 wt%). Add the above materials to a crystallization vessel and treat at 180°C for 12 hours. Filter, dry, and calcine at 400°C for 12 hours.
[0047] Example 4:
[0048] The preparation process of Au / TS-1(4) gold-based catalyst is as follows:
[0049] (a) Preparation of molecular sieve mother liquor
[0050] Preparation of mother liquor for titanium-silicon molecular sieves and mother liquor for molecular sieves in Example 1.
[0051] (b) Take 200g of the above-mentioned titanium-silicon molecular sieve mother liquor, add 30g of 30% silica-alumina sol and 1g of guar gum powder, and age at 70℃ for 72 hours under stirring. Spray-form the catalyst using a small spray molding machine. Dry the spray-formed catalyst at 150℃ for 12 hours and calcine at 500℃ for 2 hours to obtain the spray-formed TS-1 molecular sieve catalyst with a particle size of approximately 50-200μm.
[0052] (c) Dissolve 0.5 g of chloroauric acid in pure water, add TS-1 molecular sieve at room temperature, and then add a 0.01 mol / L tetraethylammonium hydroxide aqueous solution (20 wt%). Add the above material to a crystallization kettle and treat it by rotation at 180°C for 12 hours. Filter, dry, and calcine at 400°C for 12 hours.
[0053] Example 5:
[0054] The preparation process of Au / TS-1(5) gold-based catalyst is as follows:
[0055] (a) Preparation of molecular sieve mother liquor
[0056] Preparation of mother liquor for titanium-silicon molecular sieves and mother liquor for molecular sieves in Example 1.
[0057] (b) Take 200g of the above-mentioned titanium-silicon molecular sieve mother liquor, add 30g of 30% silica-alumina sol and 1g of guar gum powder, and age at 70℃ for 72 hours under stirring. Spray-form the catalyst using a small spray molding machine. Dry the spray-formed catalyst at 150℃ for 12 hours and calcine at 500℃ for 2 hours to obtain the spray-formed TS-1 molecular sieve catalyst with a particle size of approximately 50-200μm.
[0058] (c) Dissolve 1.5g of chloroauric acid in pure water, add TS-1 molecular sieve at room temperature, and then add a 0.01mol / L tetraethylammonium hydroxide aqueous solution (20wt%). Add the above material to a crystallization kettle and treat it at 170℃ for 12 hours. Filter, dry, and calcine at 400℃ for 12 hours.
[0059] Example 6:
[0060] The preparation process of Au / TS-1(6) gold-based catalyst is as follows:
[0061] (a) Preparation of molecular sieve mother liquor
[0062] Preparation of mother liquor for titanium-silicon molecular sieves and mother liquor for molecular sieves in Example 1.
[0063] (b) Take 200g of the above-mentioned titanium-silicon molecular sieve mother liquor, add 30g of 30% silica-alumina sol and 1g of guar gum powder, and age at 70℃ for 72 hours under stirring. Spray-form the catalyst using a small spray molding machine. Dry the spray-formed catalyst at 150℃ for 12 hours and calcine at 500℃ for 2 hours to obtain the spray-formed TS-1 molecular sieve catalyst with a particle size of approximately 50-200μm.
[0064] (c) Dissolve 0.3 g of chloroauric acid in pure water, add TS-1 molecular sieve at room temperature, and then add a 0.01 mol / L tetraethylammonium hydroxide aqueous solution. Add the above materials to a crystallization reactor. Rotate at 170°C for 12 hours. Filter, dry, and calcine at 400°C for 12 hours.
[0065] Example 7:
[0066] 200g of the catalysts prepared in Examples 1-6 were weighed and added to a 1.2L stainless steel high-pressure reactor. 800mL of a mixture of methanol and methacrolein (30wt%) was added. Stirring was started and air was introduced. The reaction was initiated at a bath temperature of 80℃. After the reaction, the raw materials were continuously pumped into the reactor at a rate of 10mL / min, maintaining the reaction temperature at 80℃ for 1.5 hours. The generated products were continuously collected, and the effluent was analyzed using gas chromatography. n-Decane was used as an internal standard to calculate the conversion rate of methacrolein and the selectivity of methyl methacrylate. The results are shown in Table 1.
[0067] Table 1. Conversion and selectivity of methanol and methacrolein oxidative esterification catalyzed by catalysts in Examples 1-6
[0068] Example catalyst MAL conversion rate % MMA selectivity % 1 Au / TS-1(1) 92.0 99.0 2 Au / TS-1(2) 91.5 98.2 3 Au / TS-1(3) 90.4 98.6 4 Au / TS-1(4) 86.3 89.3 5 Au / TS-1(5) 88.2 90.7 6 Au / TS-1(6) 87.4 88.6
[0069] Table 1 shows that both excessively high and low gold loading of the Au / TS-1 gold catalyst negatively impact the conversion rate of MAL and the selectivity of MMA, resulting in a decrease in both. Therefore, appropriate gold loading and good interaction between the gold particles and the support are crucial for improving the conversion rate of MAL and the selectivity of MMA. The conversion and selectivity results in Table 1 demonstrate that TS-1, as a gold-supported catalyst, can significantly improve the yield and efficiency of the catalytic oxidative esterification of methanol and methacrolein to produce methyl methacrylate.
[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. The application of a catalyst for the oxidative esterification of methanol and methacrolein in the reaction of methanol and methacrolein to produce methyl methacrylate, characterized in that, The reaction specifically involves mixing the catalyst, methacrolein, and methanol in a reactor, introducing an oxygen-containing gas into the bottom of the reactor, maintaining a reaction temperature of 70-160℃, a reaction pressure of 0.5-2MPa, and a reaction time of 1-12h, and then separating to obtain methyl methacrylate. The method for preparing the catalyst includes the following steps: (1) Mix the silicon source, template agent and water evenly, and hydrolyze at 20~85℃ for 30~120min to obtain silicon ester hydrolysate; add alcohol solution to titanium source, and hydrolyze at 25~85℃ for 10~60min to obtain titanium ester hydrolysate; mix the obtained silicon ester hydrolysate and titanium ester hydrolysate evenly, heat to 50~90℃ to remove alcohol, and load the obtained titanium silica sol into crystallization kettle, and heat at 150℃. Crystallization at 200℃ for 10 48h; (2) Add aluminum sol or silica sol or silica-alumina sol and guar gum powder to the molecular sieve mother liquor obtained in step (1), age it at 50~90℃ for 10~72h under stirring, spray mold, dry it, and calcine it at 300~600℃ for 2~24h to obtain molecular sieve. (3) Add the molecular sieve obtained in step (2) to the aqueous solution containing gold salt, add the template agent aqueous solution, mix well, put it into a crystallization kettle and treat it at 150-190℃ for 12-72h, filter, dry, and calcine at 400-600℃ for 1-10h to obtain the product. The silicon source mentioned in step (1) is one or a mixture of two or more of tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate; the template agent is one or a mixture of two or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide; the mass ratio of silicon source, template agent and water is 1:0.1-0.5:0.5-2; The titanium source mentioned in step (1) is one or a mixture of two or more of tetraethyl orthotitanate, tetrabutyl orthotitanate, tetraisopropyl orthotitanate, titanium trichloride, and titanium tetrachloride; the alcohol solution is isopropanol or ethanol; the mass ratio of the titanium source to the alcohol solution is 1:10-20. The mass ratio of the titanium source to the silicon source in step (1) is 1:10-50; The template agent mentioned in step (3) is one or a mixture of two or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide, and the molar concentration of the template agent is 0.01-0.1 mol / L; the gold loading is 0.1-2 wt%.
2. The application according to claim 1, characterized in that, The alcohol removal process in step (1) takes 4 to 12 hours.
3. The application according to claim 1, characterized in that, The mass ratio of the molecular sieve mother liquor to aluminum sol or silica sol or silica-alumina sol and guar gum powder in step (2) is 1:0.1~1:0.02~0.08; the drying temperature is 100-180℃ and the time is 12-72h.
4. The application according to claim 1, characterized in that, The gold salt mentioned in step (3) is one or a mixture of two or more of gold cyanide, potassium gold cyanide, gold chloride, gold chloride, chloroauric acid, chloroaurate, sodium gold sulfite or regrin; the mass ratio of gold salt to molecular sieve is 0.05~5:
100.
5. The application according to claim 1, characterized in that, The mass concentration of methacrolein is 10-55%; the rate of introduction of oxygen-containing gas is 1-2 L / min.