Synthesis of methyl methacrylate reactor and its application

Abstract

The present application provides a kind of synthetic methyl methacrylate reactor, including reactor body, from bottom to top in turn including mixer one, mixer two, fluid distributor one, catalyst bed one, mixer three, fluid distributor two, catalyst bed two, mixer four, fluid distributor three and catalyst bed three, methanol delivery pump and methyl methacrylaldehyde delivery pump are arranged below the reactor body, gas pipeline one is arranged between mixer one and mixer two, gas pipeline two is arranged between catalyst bed one and mixer three, gas pipeline three is arranged between catalyst bed two and mixer four, gas one transported by gas pipeline one enters mixer two, gas two transported by gas pipeline two enters mixer three, gas three transported by gas pipeline three enters mixer four.The present application is mixed by multiple stages scheme, so that gas-liquid mixing is uniform, using multiple oxygen supply ensures that oxygen is not excessive in front stage, and oxygen concentration is sufficient in rear stage, improve the yield of methyl methacrylate.

Description

Technical Field

[0001] This invention relates to a reactor for synthesizing methyl methacrylate, and more specifically, a reactor for one-step oxidative esterification synthesis of methyl methacrylate. Background Technology

[0002] Methyl methacrylate (MMA) is an organic chemical raw material used in the production of PMMA (polymethyl methacrylate) acrylic glass, the manufacture of ACR (acetal methyl methacrylate) additives for polyvinyl chloride, and the production of acrylic fibers. It also finds wide application in the adhesives, coatings, resins, textiles, and paper industries.

[0003] The preparation methods of methyl methacrylate (MMA) are classified into C2, C3, and C4 methods based on the number of carbon atoms in the raw materials. Currently, the mainstream industrial methods are the C3 ACH method, the C4 two-step oxidative esterification method, and the C4 one-step oxidative esterification method. The C3 ACH method uses highly toxic hydrogen cyanide in the reaction process and large amounts of concentrated sulfuric acid in subsequent reactions, causing significant environmental pressure and production safety issues. The C4 two-step oxidative esterification method first oxidizes methacrolein (MAL) to methacrylic acid, which then reacts with methanol under acid catalysis to obtain MMA. Due to its multi-step reaction, the process is relatively complex, requiring oxidation, distillation, esterification, and further distillation, resulting in high energy consumption and high equipment investment. The C4 one-step oxidative esterification method involves the direct oxidative esterification of MAL and methanol to MMA under oxygen conditions using a gold catalyst. This process boasts low energy consumption, low equipment investment, and high product yield. Currently, the one-step oxidative esterification reaction primarily utilizes fixed-bed reactors. Fixed-bed reactors introduce the following problems: 1. Separation easily occurs in the gas-solid-liquid (gas: oxygen; liquid: methanol, methacrolein; solid: catalyst) three phases. Gas bubbles aggregate, and liquid aggregates, preventing effective oxygen transfer to the catalyst interface. This results in the methacrolein hemiacetal not being oxidized in time, further generating the byproduct methacrolein acetal. 2. If gases, methanol, and MAL are mixed in a single step, the oxygen concentration at the front of the bed will be high, while the oxygen concentration at the back will be low (the oxygen concentration needs to be higher at the back due to the decrease in the concentration of reactants). To solve this problem, the traditional approach is to use an excess of oxygen, which exacerbates the problem of excessively high oxygen concentration at the front of the bed and causes side reactions, such as the oxidation of MAL to methacrylic acid, or further oxidation to formic acid, carbon dioxide, etc. To solve the above two problems, a multi-stage oxygen supplementation mixing method is adopted, which can maintain a reasonable oxygen concentration at both the front and back of the catalyst bed, thus solving the above two problems. Summary of the Invention

[0004] The purpose of this invention is to overcome and supplement the shortcomings of existing technologies, and to provide a reactor for synthesizing methyl methacrylate and its application. This reactor has the advantages of high conversion rate and high selectivity in one-step oxidative esterification synthesis of MMA. The technical solution adopted by this invention is as follows:

[0005] A reactor for synthesizing methyl methacrylate, comprising: a reactor body, wherein the reactor body comprises, from bottom to top, a mixer 1, a mixer 2, a fluid distributor 1, a catalyst bed 1, a mixer 3, a fluid distributor 2, a catalyst bed 2, a mixer 4, a fluid distributor 3, and a catalyst bed 3; a methanol delivery pump and a methacrolein delivery pump are disposed below the reactor body; an inlet pipe 1 is disposed between mixer 1 and mixer 2; an inlet pipe 2 is disposed between catalyst bed 1 and mixer 3; and an inlet pipe 3 is disposed between catalyst bed 2 and mixer 4. Gas 1 delivered by inlet pipe 1 enters mixer 2; gas 2 delivered by inlet pipe 2 enters mixer 3; and gas 3 delivered by inlet pipe 3 enters mixer 4.

[0006] Preferably, in the methyl methacrylate synthesis reactor, the catalysts disposed on catalyst bed one, catalyst bed two, and catalyst bed three are all selected from one of particulate catalysts, straight-through honeycomb monolithic catalysts, and wall-flow honeycomb monolithic catalysts.

[0007] Preferably, in the methyl methacrylate synthesis reactor, the catalyst is selected from one of Au / SiO2-MgO-Al2O3, Au-Ni / SiO2-MgO-Al2O3, Au / CeO2-MgO-Al2O3, and Au-Ni / CeO2-MgO-Al2O3.

[0008] Preferably, in the methyl methacrylate synthesis reactor, the gas transported through the inlet pipe comprises 75% to 99.5% nitrogen and 0.5% to 25% oxygen.

[0009] Preferably, in the methyl methacrylate synthesis reactor, the gas supplied by the second inlet pipe comprises 0-60% nitrogen and 40%-100% oxygen.

[0010] Preferably, in the methyl methacrylate synthesis reactor, the gas supplied by the inlet pipe comprises 0-50% nitrogen and 50-100% oxygen.

[0011] Preferably, in the methyl methacrylate synthesis reactor: mixer one comprises a mixture of methanol and methacrolein; mixer two comprises a mixture of methanol, methacrolein and gas one; mixer three comprises a mixture of methanol, methacrolein and gas two; and mixer four comprises a mixture of methanol, methacrolein and gas three.

[0012] An application of a reactor for synthesizing methyl methacrylate, wherein: the reactor for synthesizing methyl methacrylate is used to synthesize methyl methacrylate.

[0013] Preferably, the application of the aforementioned methyl methacrylate synthesis reactor includes the following specific steps for synthesizing methyl methacrylate: methanol and methacrolein are respectively pumped to mixer one via a methanol transfer pump and a methacrolein transfer pump. The methanol and methacrolein are mixed in mixer one to obtain a mixed liquid. The mixed liquid and gas one are then mixed together in mixer two to obtain fluid one. Fluid one is then uniformly dispersed through fluid distributor one and enters catalyst bed one for reaction, generating a portion of methyl methacrylate. Fluid one, after passing through catalyst bed one, is then mixed with gas two and enters mixer three to obtain fluid two. Fluid two, after being uniformly dispersed through fluid distributor two, enters catalyst bed two for oxidative esterification reaction. After the reaction, the fluid and gas three are then mixed together in mixer four to obtain fluid three. Fluid three, after being uniformly dispersed through fluid distributor three, enters catalyst bed three for reaction, and finally, methyl methacrylate is obtained.

[0014] The reaction equation for the synthesis of methyl methacrylate from methanol and methacrolein is as follows:

[0015] C3H5CHO+CH3OH+0.5O2=C3H5COOCH3+H2O

[0016] Advantages of this invention:

[0017] The methyl methacrylate (MMA) synthesis reactor of the present invention employs a multi-stage mixing scheme. By setting up mixer one, mixer two, and mixer three in the middle and at the end, the gas-liquid mixing is uniform, and the oxygen mass transfer problem is solved. In addition, the use of a multi-stage oxygen supply method can ensure that the oxygen in the front stage is not excessive and the oxygen concentration in the rear stage is sufficient, thereby improving the yield of MMA. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the reactor used for synthesizing methyl methacrylate according to the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments.

[0020] Example 1

[0021] like Figure 1A reactor for synthesizing methyl methacrylate includes a reactor body, which, from bottom to top, comprises a mixer 3, a mixer 4, a fluid distributor 5, a catalyst bed 6, a mixer 7, a fluid distributor 8, a catalyst bed 9, a mixer 4, a fluid distributor 11, and a catalyst bed 12. A methanol delivery pump 1 and a methacrolein delivery pump 2 are installed below the reactor body. An inlet pipe 13 is installed between mixer 3 and mixer 4, an inlet pipe 24 is installed between catalyst bed 6 and mixer 7, and an inlet pipe 35 is installed between catalyst bed 9 and mixer 4. Gas 1 delivered by inlet pipe 13 enters mixer 2, gas 2 delivered by inlet pipe 24 enters mixer 5, and gas 3 delivered by inlet pipe 315 enters mixer 8.

[0022] Catalyst bed 1 (6), catalyst bed 2 (9), and catalyst bed 3 (12) are all particulate catalysts with a particle size of 1.7 mm. The catalyst is Au / SiO2-MgO-Al2O3. The gas transported by inlet pipe 1 includes 85% nitrogen and 15% oxygen; the gas transported by inlet pipe 2 includes 0% nitrogen and 100% oxygen; the gas transported by inlet pipe 3 includes 0% nitrogen and 100% oxygen. Mixer 1 (3) includes a mixture of methanol and methacrolein. Mixer 2 (4) includes a mixture of methanol, methacrolein, and gas 1. Mixer 3 (7) includes a mixture of methanol, methacrolein, and gas 2. Mixer 4 (10) includes a mixture of methanol, methacrolein, and gas 3.

[0023] The specific steps for synthesizing methyl methacrylate in a reactor are as follows: Methanol and methacrolein are pumped to mixer 3 via methanol pump 1 and methacrolein pump 2, respectively. The methanol and methacrolein are mixed in mixer 3 to obtain a mixed liquid. The mixed liquid and gas 1 are then mixed together in mixer 4 to obtain fluid 1. Fluid 1 is then uniformly dispersed through fluid distributor 5 and enters catalyst bed 6 to react, generating some methyl methacrylate. Fluid 1 passes through catalyst bed 7 and enters mixer 7 with gas 2 14 to obtain fluid 2. Fluid 2 is uniformly dispersed through fluid distributor 2 8 and enters catalyst bed 2 9 to undergo an oxidative esterification reaction. After the reaction, the fluid and gas 3 15 enter mixer 4 10 to obtain fluid 3. Fluid 3 is uniformly dispersed through fluid distributor 3 11 and enters catalyst bed 3 12 to react, ultimately yielding methyl methacrylate.

[0024] 9.4 g of Au / SiO2-MgO-Al2O3 (6.5 mL) was weighed. The particle size of the spheres was 1.7 mm. There were three catalyst layers. The catalyst layer 6 had a catalyst volume of φ20 mm * 10 mm, an oxygen partial pressure of 0.4 MPa, a nitrogen partial pressure of 2.67 MPa, and a temperature of 70 °C. The catalyst layer 9 had a catalyst volume of φ20 mm * 10 mm, and the oxygen partial pressure was supplemented to 0.4 MPa. The temperature was 70 °C. The catalyst layer 12 had a catalyst volume of φ20 mm * 10 mm, and the oxygen partial pressure was supplemented to 0.4 MPa. The temperature was 70 °C. The overall residence time of the reaction was 1 h. The reactants were methacrolein and methanol, and the molar ratio of methacrolein to methanol was 1:15.

[0025] Example 2

[0026] Weigh out 9.4 g of Au-Ni / SiO2-MgO-Al2O3 (6.5 mL), with a particle size of 1.7 mm. The catalyst consists of three layers: catalyst bed 1 (6) has a catalyst volume of φ20 mm * 10 mm, oxygen partial pressure of 0.4 MPa, nitrogen partial pressure of 2.67 MPa, and a temperature of 70 °C; catalyst bed 2 (9) has a catalyst volume of φ20 mm * 10 mm, with oxygen partial pressure supplemented to 0.4 MPa and a temperature of 70 °C; catalyst bed 3 (12) has a catalyst volume of φ20 mm * 10 mm, with oxygen partial pressure supplemented to 0.4 MPa and a temperature of 70 °C. The overall residence time of the reaction is 1 h. The reactants are methacrolein and methanol, with a molar ratio of methacrolein to methanol of 1:15.

[0027] Example 3

[0028] Weigh 9.4g of Au-Ni / SiO2-MgO-Al2O3 (6.5mL), with a particle size of 1.7mm. The catalyst consists of three layers: catalyst bed 1 (6) has a catalyst volume of φ20mm*10mm, oxygen partial pressure of 0.4MPa, nitrogen partial pressure of 1.6MPa, and temperature of 70℃; catalyst bed 2 (9) has a catalyst volume of φ20mm*10mm, with oxygen partial pressure supplemented to 0.5MPa and temperature of 70℃; catalyst bed 3 (12) has a catalyst volume of φ20mm*10mm, with oxygen partial pressure supplemented to 0.6MPa and temperature of 70℃. The overall residence time of the reaction is 1h. The reactants are methacrolein and methanol, with a molar ratio of methacrolein to methanol of 1:15.

[0029] Comparative Example 1

[0030] Weigh 9.4g of Au-Ni / SiO2-MgO-Al2O3 (6.5mL), the particle size of the spheres is 1.7mm, the catalyst is a single layer, the catalyst volume of the catalyst bed is φ20mm*30mm, the oxygen partial pressure is 0.4MPa, the nitrogen partial pressure is 2.67MPa, the temperature is 70℃, the reaction residence time is 1h, the reactants are methacrolein and methanol, and the molar ratio of methacrolein to methanol is 1:15.

[0031] Comparative Example 2

[0032] Weigh 9.4g of Au-Ni / SiO2-MgO-Al2O3 (6.5mL), the particle size of the spheres is 1.7mm, the catalyst is a single layer, the catalyst volume of the catalyst bed is φ20mm*30mm, the oxygen partial pressure is 0.6MPa, the nitrogen partial pressure is 2.67MPa, the temperature is 70℃, the reaction residence time is 1h, the reactants are methacrolein and methanol, and the molar ratio of methacrolein to methanol is 1:15.

[0033] The conversion rates and selectivity of methyl methacrylate synthesized from methacrolein and methanol in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1.

[0034] Table 1

[0035] Comparative Example 1 71.5 96.3 Comparative Example 2 88.6 93.1 Example 1 83.7 97.2 Example 2 82.9 98.3 Example 3 93.7 98.0

[0036] The data in Table 1 show that using a multi-stage oxygen supplementation method can effectively improve the conversion rate and selectivity of methacrolein, especially by increasing the oxygen concentration in the later stage, which further improves the conversion rate and selectivity.

[0037] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A reactor for synthesizing methyl methacrylate, characterized in that: The reactor body includes, from bottom to top, a mixer 1 (3), a mixer 2 (4), a fluid distributor 1 (5), a catalyst bed 1 (6), a mixer 3 (7), a fluid distributor 2 (8), a catalyst bed 2 (9), a mixer 4 (10), a fluid distributor 3 (11), and a catalyst bed 3 (12). A methanol delivery pump (1) and a methacrolein delivery pump (2) are installed below the reactor body. An air inlet pipe 1 (13) is installed between the mixer 1 (3) and the mixer 2 (4). An air inlet pipe 2 (14) is installed between the catalyst bed 1 (6) and the mixer 3 (7). An air inlet pipe 3 (15) is installed between the catalyst bed 2 (9) and the mixer 4 (10). Gas 1 delivered by the air inlet pipe 1 (13) enters the mixer 2 (4). Gas 2 delivered by the air inlet pipe 2 (14) enters the mixer 3 (7). Gas 3 delivered by the air inlet pipe 3 (15) enters the mixer 4 (10). The first gas transported by the first intake pipe (13) includes 75% to 99.5% nitrogen and 0.5% to 25% oxygen; the second gas transported by the second intake pipe (14) includes 0% to 60% nitrogen and 40% to 100% oxygen; the third gas transported by the third intake pipe (15) includes 0% to 50% nitrogen and 50% to 100% oxygen.

2. The reactor for synthesizing methyl methacrylate as described in claim 1, characterized in that: The catalysts placed on catalyst bed one (6), catalyst bed two (9) and catalyst bed three (12) are all selected from one of the following: particulate catalyst, direct-flow honeycomb monolithic catalyst and wall-flow honeycomb monolithic catalyst.

3. The methyl methacrylate synthesis reactor as described in claim 2, characterized in that: The catalyst is selected from one of Au / SiO2-MgO-Al2O3, Au-Ni / SiO2-MgO-Al2O3, Au / CeO2-MgO-Al2O3, and Au-Ni / CeO2-MgO-Al2O3.

4. The methyl methacrylate synthesis reactor as described in claim 1, characterized in that: The first mixer (3) comprises a mixture of methanol and methacrolein, the second mixer (4) comprises a mixture of methanol, methacrolein and gas one, the third mixer (7) comprises a mixture of methanol, methacrolein and gas two, and the fourth mixer (10) comprises a mixture of methanol, methacrolein and gas three.

5. The application of the reactor for synthesizing methyl methacrylate as described in any one of claims 1 to 4, characterized in that: The methyl methacrylate synthesis reactor is used for the synthesis of methyl methacrylate.

6. The application of the reactor for synthesizing methyl methacrylate as described in claim 5, characterized in that: The specific steps for synthesizing methyl methacrylate are as follows: Methanol and methacrolein are transported to mixer one (3) through methanol pump (1) and methacrolein pump (2) respectively. Methanol and methacrolein are mixed in mixer one (3) to obtain a mixture. The mixture and gas one enter mixer two (4) together to be mixed to obtain fluid one. Then fluid one is evenly dispersed through fluid distributor one (5) and enters catalyst bed one (6) to react and generate part of methyl methacrylate. After fluid one passes through catalyst bed one (6) and enters mixer three (7) together with gas two to obtain fluid two. Fluid two is evenly dispersed through fluid distributor two (8) and enters catalyst bed two (9) to undergo oxidative esterification reaction. After the reaction, fluid and gas three enter mixer four (10) together to obtain fluid three. Fluid three is evenly dispersed through fluid distributor three (11) and enters catalyst bed three (12) to react. After the reaction, methyl methacrylate is obtained.

Images