A process for the preparation of 2-methyl acrylic acid

Abstract

The application relates to the technical field of organic synthesis, in particular to a preparation method of 2-methacrylic acid, which uses cyclopropyl formic acid as raw material, stirs after adding a catalyst, carries out insulation reaction and reduced pressure rectification after heating to not less than 120 DEG C, and collects the fraction under the condition of 103-133 DEG C as the 2-methacrylic acid product. The preparation method has low production cost, short process route, and greatly improves the yield of 2-methacrylic acid.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing 2-methacrylic acid. Background Technology

[0002] 2-Methylacrylic acid is an important organic chemical raw material and polymer intermediate. Currently, there are several methods for synthesizing 2-methylacrylic acid: (1) According to patent EP0487853B1, acetone and methyl formate (or acetone, methanol and CO) are used as raw materials to synthesize 2-methylacrylic acid through a multi-step reaction including acetone cyanohydrin, α-hydroxyisobutyric acid amide, esterification, hydrolysis, and dehydration, and HCN is recycled. This process is complex, involves many steps, and has high energy consumption. In addition, due to the use of highly toxic HCN, the requirements for equipment and operational safety are high. (2) According to patent CN102049272A, isobutenaldehyde and oxygen are used as raw materials, and a heteropolyacid catalyst with a specific composition is used to catalyze the oxidation of isobutenaldehyde to prepare 2-methylacrylic acid in a fixed-bed reactor. The catalyst composition in this process is complex, containing multiple metal elements, and the cost is high. Impurities in the raw materials can easily affect the performance of the catalyst. (3) Patent US20100029979A1 reports the use of tetramethyl glycolide as raw material to prepare 2-methacrylic acid by ring-opening and depolymerization at 200-240℃ under the catalysis of potassium salt of α-hydroxyisobutyric acid. The generated 2-methacrylic acid is removed from the reaction system by gas phase and purified. This process has a low yield, the raw materials are not easy to obtain, the reaction temperature is high and there are many side reactions, and the amount of catalyst used is large. (4) Patent CN114195626A describes a method for synthesizing cyclopropyl formaldehyde: using acrolein as raw material, cyclopropyl formaldehyde is obtained by denitrification cyclization reaction. Then, cyclopropyl formaldehyde is reacted with diazonium methane in solvent under the action of Pd(oAc)2 catalyst to carry out denitrification cyclization reaction to obtain crude cyclopropyl formaldehyde. After acid washing, filtration and separation, and atmospheric distillation, a pure product with a content of more than 99% is obtained with a yield of more than 90%. The catalyst recovery is difficult, which increases the cost; a large amount of industrial wastewater is generated. (5) Patent CN114605252B reports the use of propionic acid (or propionic anhydride / methyl propionate and formaldehyde raw materials) under VPO catalyst catalysis. Propionic acid (or its derivatives) and formaldehyde source (such as formalin, trioxymethylene) are vaporized, diluted with inert gas, and then undergo aldol condensation reaction at high temperature (280-480℃) through a catalyst bed to generate 2-methacrylic acid (or methyl 2-methacrylate) and water. This process involves high-temperature reaction, and the catalyst preparation is complex, with many side reactions and low yield. (6) Patent CN118159513A reports the use of propane, propylene, and butane as raw materials, which are oxidized with oxygen under catalyst catalysis to generate a mixture containing 2-methacrylic acid, which is then purified by crystallization distillation and other methods. This process has poor reaction selectivity, many by-products, many separation and purification steps, and the problem of by-product enrichment. Therefore, in view of the above technical problems, this invention develops a method for preparing 2-methacrylic acid. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing 2-methacrylic acid, which has low production cost, short process route and greatly improves the yield of 2-methacrylic acid, in order to overcome the shortcomings of the prior art.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0005] A method for preparing 2-methylacrylic acid, wherein cyclopropionic acid is used as raw material, a catalyst is added and stirred, and the mixture is heated to a temperature not lower than 120°C for heat preservation reaction and vacuum distillation, and the fraction collected at 103-133°C is 2-methylacrylic acid product.

[0006] As an improved technical solution, the temperature is raised to 120-150℃, and the time for heat preservation reaction and vacuum distillation is 9-15 hours.

[0007] As an improved technical solution, the cyclopropionic acid and the catalyst are added at a molar ratio of 4.6:0.046-0.184, and the catalyst is hydrogen chloride, copper chloride, cuprous chloride, zinc chloride, or aluminum trichloride; wherein when the catalyst is hydrogen chloride, vacuum distillation is performed after the heat preservation reaction is completed; when the catalyst is copper chloride, cuprous chloride, zinc chloride, or aluminum trichloride, the heat preservation reaction is carried out simultaneously with vacuum distillation.

[0008] As a preferred technical solution, the cyclopropionic acid and the catalyst are added in a molar ratio of 4.6:0.138.

[0009] As a preferred technical solution, the temperature is raised to 140°C and the reaction is maintained for 13 hours.

[0010] The reaction equation involved in this invention is:

[0011]

[0012] After adopting the above technical solution, the beneficial effects of the present invention are:

[0013] This invention uses cyclopropionic acid as a raw material and hydrogen chloride, copper chloride, cuprous chloride, zinc chloride, and aluminum trichloride as catalysts to synthesize 2-methacrylic acid through a Lewis acid-catalyzed ring-opening reaction. The Lewis acid first abstracts electrons from a carbon atom, inducing the ring-opening of the cyclopropyl group, followed by a rearrangement reaction to generate 2-methacrylic acid. Compared with existing technologies, this process route offers readily available raw materials, relatively safe and environmentally friendly processes, high raw material utilization, and low product cost. Furthermore, the reaction route is shorter than traditional processes, making it suitable for industrial production. Attached Figure Description

[0014] Figure 1This is the mass spectrum of 2-methacrylic acid from Example 1 of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] Example 1

[0017] In a 500 ml four-necked flask at room temperature, 400.01 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 18.74 g (0.138 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 385.23 g, with a purity of 99.86% and a yield of 97.14%.

[0018] Example 2

[0019] In a 500 ml four-necked flask at room temperature, 400.02 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 13.80 g (0.138 mol) of cuprous chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 361.62 g, with a purity of 99.46% and a yield of 90.82%.

[0020] Example 3

[0021] In a 500ml four-necked flask at room temperature, 399.95 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by the introduction of 5.08 g (0.138 mol) of hydrogen chloride gas (99.00% purity) as a catalyst. The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140℃ and maintained at this temperature for 13 hours. After the reaction was completed, the product 2-methacrylic acid, with a top temperature of 123℃, was distilled off under reduced pressure (-0.075 MPa). The resulting 2-methacrylic acid was a colorless, transparent liquid weighing 346.46 g with a purity of 99.13% and a yield of 86.74%.

[0022] Example 4

[0023] In a 500ml four-necked flask at room temperature, 399.98g (4.6mol) of cyclopropionic acid (99.00% purity) was added, followed by 19.00g (0.138mol) of zinc chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140℃ and maintained at this temperature for 13 hours. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123℃, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 350.54g, with a purity of 99.35% and a yield of 87.95%.

[0024] Example 5

[0025] In a 500 ml four-necked flask at room temperature, 400.138 g (99.00% purity) of cyclopropionic acid (4.6 mol) was added, followed by 18.59 g (99.00% purity) of aluminum trichloride catalyst (0.138 mol), and the mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 359.07 g, with a purity of 99.23% and a yield of 89.97%.

[0026] Example 6

[0027] In a 500 ml four-necked flask at room temperature, 400.00 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 6.25 g (0.046 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 372.25 g, with a purity of 99.38% and a yield of 93.42%.

[0028] Example 7

[0029] In a 500 ml four-necked flask at room temperature, 399.95 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 12.49 g (0.092 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 380.75 g, with a purity of 99.49% and a yield of 95.67%.

[0030] Example 8

[0031] In a 500 ml four-necked flask at room temperature, 399.96 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 24.99 g (0.184 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 386.10 g with a purity of 99.56% and a yield of 97.08%.

[0032] Example 9

[0033] In a 500 ml four-necked flask at room temperature, 399.99 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 18.73 g (0.138 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 120 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 103 °C, was distilled off under reduced pressure (-0.090 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 353.52 g, with a purity of 99.31% and a yield of 88.66%.

[0034] Example 10

[0035] In a 500 ml four-necked flask at room temperature, 399.97 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 18.76 g (0.138 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 130 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 113 °C, was distilled off under reduced pressure (-0.084 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 376.24 g, with a purity of 99.75% and a yield of 94.78%.

[0036] Example 11

[0037] In a 500 ml four-necked flask at room temperature, 399.94 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 18.73 g (0.138 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 150 °C and maintained at this temperature for 13 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 133 °C, was distilled off under reduced pressure (-0.063 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 386.34 g, with a purity of 99.39% and a yield of 96.98%.

[0038] Example 12

[0039] In a 500 ml four-necked flask at room temperature, 400.05 g (99.00% purity) of cyclopropionic acid (4.6 mol) was added, followed by 18.74 g (99.00% purity) of copper chloride catalyst (0.138 mol), and the mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 9 hours. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 374.54 g, with a purity of 99.78% and a yield of 94.36%.

[0040] Example 13

[0041] In a 500 ml four-necked flask at room temperature, 399.98 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 18.72 g (0.138 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 11 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 382.67 g, with a purity of 99.69% and a yield of 96.34%.

[0042] Example 14

[0043] In a 500 ml four-necked flask at room temperature, 400.04 g (4.6 mol) of cyclopropionic acid (99.00% purity) was added, followed by 18.75 g (0.03 mol) of copper chloride catalyst (99.00% purity). The mixture was stirred until homogeneous. After the addition of the reactants, the reaction system was slowly heated to 140 °C and maintained at this temperature for 15 h. Simultaneously, the product 2-methylacrylic acid, with a top temperature of 123 °C, was distilled off under reduced pressure (-0.075 MPa) during the distillation process. The resulting 2-methylacrylic acid was a colorless, transparent liquid weighing 385.60 g, with a purity of 99.75% and a yield of 97.12%.

[0044] To better demonstrate that the preparation method of the present invention can improve the yield and purity of 2-methylacrylic acid, six comparative examples are given with reference to Example 1, and details are provided below.

[0045] Comparative Example 1

[0046] Unlike Example 1, the temperature was raised to 110°C, but the rest of the operation was the same. The resulting 2-methacrylic acid was a colorless, transparent liquid weighing 306.63 g, with a purity of 99.78% and a yield of 77.25%.

[0047] Comparative Example 2

[0048] Unlike Example 1, the temperature was increased to 160°C, but the rest of the operation was the same. The resulting 2-methacrylic acid was a colorless, transparent liquid weighing 345.64 g, with a purity of 99.05% and a yield of 86.45%.

[0049] Comparative Example 3

[0050] Unlike Example 1, the reaction was kept at a certain temperature for 7 hours, while the rest of the operation was the same. The resulting 2-methacrylic acid was a colorless, transparent liquid weighing 273.29 g, with a purity of 99.67% and a yield of 68.79%.

[0051] Comparative Example 4

[0052] Unlike Example 1, the reaction was kept at a certain temperature for 17 hours, while the rest of the operation was the same. The resulting 2-methacrylic acid was a colorless, transparent liquid weighing 385.59 g, with a purity of 99.64% and a yield of 97.02%.

[0053] Comparative Example 5

[0054] Unlike Example 1, cyclopropionic acid and copper chloride were added in a molar ratio of 4.6:0.023, with the remaining operations remaining the same. The resulting 2-methacrylic acid was a colorless, transparent liquid weighing 299.42 g, with a purity of 99.76% and a yield of 75.42%.

[0055] Comparative Example 6

[0056] Unlike Example 1, cyclopropionic acid and copper chloride were added in a molar ratio of 4.6:0.23, with the remaining operations remaining the same. The resulting 2-methacrylic acid was a colorless, transparent liquid weighing 385.17 g, with a purity of 99.84% and a yield of 97.12%.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing 2-methacrylic acid, characterized in that, The preparation method uses cyclopropionic acid as raw material. After adding a catalyst and stirring, the mixture is heated to a temperature not lower than 120°C for a heat preservation reaction and vacuum distillation. The fraction collected at 103-133°C is 2-methacrylic acid product. The cyclopropionic acid and the catalyst are added in a molar ratio of 4.6:0.046-0.

184. The catalyst is hydrogen chloride, cupric chloride, cuprous chloride, zinc chloride, or aluminum trichloride. When the catalyst is hydrogen chloride, vacuum distillation is performed after the heat preservation reaction. When the catalyst is cupric chloride, cuprous chloride, zinc chloride, or aluminum trichloride, the heat preservation reaction is carried out simultaneously with vacuum distillation.

2. The method for preparing 2-methacrylic acid according to claim 1, characterized in that, Heating to 120-150℃ and holding the reaction under heat and distilling under reduced pressure for 9-15 hours.

3. The method for preparing 2-methacrylic acid according to claim 2, characterized in that, The cyclopropionic acid and the catalyst were added in a molar ratio of 4.6:0.

138.

4. The method for preparing 2-methacrylic acid according to claim 3, characterized in that, Heat to 140℃ and maintain the temperature for 13 hours.

Images