CN-121990895-A - Method for preparing methacrolein by mild catalytic aldol condensation

Abstract

The invention belongs to the technical field of organic synthesis, and particularly discloses a method for preparing methacrolein by mild catalytic aldol condensation. The invention mixes the metal chelate ionic liquid catalyst, formaldehyde solution, propionaldehyde solution and water for reaction to obtain the methacrolein, wherein the reaction temperature is more than or equal to 60 ℃. The invention can realize high conversion rate and high selectivity preparation of the methacrolein under mild conditions.

Inventors

• ZHAO QIU
• CUI XUEYAN
• WANG GANG
• CHEN XINYAN
• Yang Shichong
• LI JIE
• ZHAO HUI
• ZHANG SUOJIANG

Assignees

• 中国科学院过程工程研究所

Dates

Publication Date

20260508

Application Date

20260312

Claims (5)

1. 1. A method for preparing methacrolein by mild catalytic aldol condensation, which is characterized by comprising the following steps: Mixing an ionic liquid catalyst, formaldehyde solution, propionaldehyde solution and water, and performing aldol condensation reaction to obtain methacrolein; The ionic liquid catalyst is metal chelating ionic liquid; the temperature of the reaction is more than or equal to 60 ℃.
2. 2. The method for preparing methacrolein by mild catalytic aldol condensation according to claim 1, wherein the molar ratio of the metal chelating ionic liquid, formaldehyde and propionaldehyde in the mixed system is 1-1.5:0.6-1.4:1.
3. 3. The method for preparing methacrolein by mild catalytic aldol condensation according to claim 2, wherein the mass fraction of water in the mixed system is 28-55% of the total reaction system.
4. 4. The method for preparing methacrolein by mild catalytic aldol condensation according to any one of claims 1 to 3, wherein the reaction temperature is 60 to 70 ℃, and the reaction time is not less than 30 minutes.
5. 5. The method for preparing methacrolein by mild catalytic aldol condensation according to claim 4, wherein said method for preparing metal chelating ionic liquid comprises: Reacting the ionic liquid with metal chloride to obtain metal chelate ionic liquid, namely obtaining the ionic liquid catalyst for preparing methacrolein by aldol condensation; The ionic liquid is protonated morpholine hydrochloride or 1-butyl-3-methylimidazole chloride.

Description

Method for preparing methacrolein by mild catalytic aldol condensation Technical Field The invention relates to the technical field of organic synthesis, in particular to a method for preparing methacrolein by mild catalytic aldol condensation. Background Methacrolein is widely used as an important chemical intermediate. Methacrolein is a basic chemical product, and is oxidized and esterified to give methacrylic acid (MAA) and Methyl Methacrylate (MMA), which are commonly used as monomers for the polymerization of polymethyl methacrylate. Polymethyl methacrylate is known as "plexiglass". In addition, the methacrolein can also be used as a modified additive of a polymer material product, and can obviously improve various service performances of the product. At present, three main methods for preparing methacrolein are an isobutene oxidation method, an isobutane oxidation method and a formaldehyde/propionaldehyde direct condensation method. Chinese patent application CN117399024A and Chinese patent application CN115260015B, CN114591156B, CN112871182B disclose a method for preparing methacrolein by oxidizing isobutene/isobutane, but the method has the problems of complex operation, harsh reaction conditions, high energy consumption, incapability of achieving both high conversion rate and high selectivity, and the like. Other technical problems still exist in the existing method for preparing the methacrolein by directly condensing formaldehyde/propionaldehyde, such as the preparation of the methacrolein by directly condensing formaldehyde/propionaldehyde in China patent application CN112638856A, CN113248359A, CN104311403A, CN101074192A and the like, but the problems of easy deactivation of a catalyst, poor selectivity and the like exist. Therefore, it is important to develop a process for preparing methacrolein by mild catalytic aldol condensation. Disclosure of Invention In view of the above, the invention provides a method for preparing methacrolein by mild catalytic aldol condensation, which aims to solve the problems that the existing methacrolein preparation method is complex in operation, harsh in reaction conditions, high in energy consumption, and incapable of achieving both high conversion rate and high selectivity. In order to achieve the above purpose, the invention adopts the following technical scheme: a method for preparing methacrolein by mild catalytic aldol condensation, comprising the following steps: Mixing an ionic liquid catalyst, formaldehyde solution, propionaldehyde solution and water, and performing aldol condensation reaction to obtain methacrolein; The ionic liquid catalyst is metal chelating ionic liquid; the temperature of the reaction is more than or equal to 60 ℃. Preferably, the molar ratio of the metal chelating ionic liquid, formaldehyde and propionaldehyde in the mixed system is 1-1.5:0.6-1.4:1. Preferably, in the mixed system, the mass fraction of water is 28-55% of the total reaction system. Preferably, the reaction temperature is 60-70 ℃, and the reaction time is more than or equal to 30min. Preferably, the preparation method of the metal chelating ionic liquid comprises the following steps: Reacting the ionic liquid with metal chloride to obtain metal chelate ionic liquid, namely obtaining the ionic liquid catalyst for preparing methacrolein by aldol condensation; The ionic liquid is protonated morpholine hydrochloride or 1-butyl-3-methylimidazole chloride. Compared with the prior art, the invention has the following beneficial effects: 1. the ionic liquid catalyst has simple synthesis operation, mild reaction conditions, no need of high-temperature roasting, high-pressure reaction or complex post-treatment, simple process flow, readily available raw materials and good industrial amplification potential; 2. the method effectively inhibits common side reactions in the aldol condensation process, thereby realizing high-selectivity synthesis of the methacrolein, and the highest selectivity reaches 98.30%; 3. according to the invention, the influence of reaction conditions on the catalytic performance is systematically researched, and a synergistic action mechanism among all parameters is disclosed. Detailed Description The invention provides a method for preparing methacrolein by mild catalytic aldol condensation, which comprises the following steps: Mixing an ionic liquid catalyst, formaldehyde solution, propionaldehyde solution and water, and carrying out aldol condensation reaction to obtain methacrolein. In classical aldol condensation reactions, two aldehyde molecules (or an aldehyde and a ketone) are catalyzed to first form an intermediate product containing both hydroxyl and aldehyde groups, which is known as β -hydroxyaldehyde. The reaction name is named according to its first stable product. In the invention, the ionic liquid catalyst is a metal chelating ionic liquid. In the invention, the temperature of the reaction is more than or equal to 60 ℃, and can be 65 ℃,