Application of a polymeric ionic liquid catalyst in aldol condensation reaction

Abstract

The present invention provides a polymerized ionic liquid heterogeneous catalyst, the preparation process of which includes: (1) synthesizing an ionic liquid monomer from an allyl secondary amine substance and an organic acid through an acid-base reaction; (2) synthesizing a polymerized ionic liquid catalyst from an ionic liquid monomer and a crosslinking agent under the action of an initiator, and applying the polymerized ionic liquid heterogeneous catalyst to prepare methacrolein by aldol condensation of formaldehyde and propionaldehyde. Compared with traditional homogeneous catalysts, the polymerized ionic liquid catalyst has less corrosion to equipment, lower equipment loss, is easy to separate and recover from reactants, reduces operation steps, and reduces energy consumption and cost.

Description

Technical Field

[0001] The invention discloses a heterogeneous polymerization ionic liquid heterogeneous catalyst for preparing methacrolein through aldol condensation of formaldehyde and propionaldehyde and a preparation method thereof. Background Art

[0002] Methacrolein has two active groups, olefin double bond and aldehyde group, and can be used as the raw material of various chemicals such as butyl phenylmorpholine. It is also a polymer monomer that can be used for synthetic resins, but the larger-scale use of methacrolein is to synthesize methacrylic acid and methyl methacrylate. Methyl methacrylate is an important monomer for synthesizing organic glass and acrylic resin. In addition, methyl methacrylate is also widely used in leather treatment agents, adhesives, ion exchange resins, coatings, lubricant additives, etc., and has a very wide range of uses. Therefore, methacrolein, as an intermediate for synthesizing methyl methacrylate, its production becomes very important. The commonly used production method of methacrolein is isobutylene / tert-butyl alcohol selective oxidation, which is to produce methacrolein under high temperature reaction conditions by reactants through solid catalysts. The disadvantage of this method is that the high reaction temperature leads to more by-products in the reaction, and the selectivity is difficult to control. In CN101074192A, ethylenediamine hydrochloride is used as a catalyst for catalyzing the liquid phase synthesis of methacrolein with formaldehyde and propionaldehyde. The ethylenediamine component has strong volatility under reaction conditions, which is potentially dangerous to the environment, equipment and operators, and hydrochloric acid is also highly volatile and acidic, and has high requirements for the corrosion resistance of the equipment. US4408079 discloses a catalyst using secondary amine and carboxylic acid, polyacid or carboxylic acid polymer. The patent details the effect of reaction pressure, feed sequence during the reaction process and catalyst water content on the reaction. CN104003856A discloses a method for preparing methacrolein by liquid phase aldol condensation of formaldehyde and propionaldehyde, wherein the catalyst is prepared by adding acetic acid aqueous solution to a mixture of diisopropanolamine, benzenesulfonic acid and an inhibitor, and catalyzes formaldehyde and propionaldehyde to synthesize methacrolein at a suitable temperature, and the catalyst has high conversion rate and selectivity. However, the corrosion of the equipment by homogeneous catalysts and the subsequent separation and recovery problems are still difficult to solve. Therefore, it is very necessary to develop a heterogeneous catalyst for synthesizing methacrolein from formaldehyde and propionaldehyde with high catalytic activity and high stability. Summary of the invention

[0003] The present invention provides a method for preparing a heterogeneous polymerization ionic liquid catalyst for preparing methacrolein by aldol condensation of formaldehyde and propionaldehyde. First, an ionic liquid monomer having a polymerizable functional group is synthesized by acid-base reaction. Then, the ionic liquid monomer and a crosslinking agent are synthesized into a polymerization ionic liquid catalyst under the action of an initiator. Compared with the existing homogeneous catalytic process, the catalyst is heterogeneous, which has the advantages of simple separation, mild catalytic conditions, stable properties and high methacrolein yield.

[0004] The present invention proposes a method for synthesizing methacrolein by using a polymerized ionic liquid as a catalyst in the aldol condensation of formaldehyde and propionaldehyde. The method uses a substance having a polymerizable group as a monomer, synthesizes a polymerizable ionic liquid monomer by acid-base neutralization, and synthesizes a polymerized ionic liquid catalyst by reacting the synthesized ionic liquid monomer with a crosslinking agent under the action of an initiator. Compared with the existing method, the catalyst in the method is a heterogeneous catalyst, which has the characteristics of simple separation, mild conditions, stable properties, and high methacrolein yield.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A heterogeneous catalyst for synthesizing methacrolein from formaldehyde and propionaldehyde. The heterogeneous phase is prepared by synthesizing an ionic liquid monomer in one step by neutralizing a secondary amine molecule with a polymerizable group with different types of acids (carboxylic acid, polycarboxylic acid, sulfonic acid, etc.) through acid-base neutralization. The unsaturated groups in the ionic liquid monomer react with a crosslinking agent under the action of an initiator.

[0007] The present invention provides a method for preparing a polymeric ionic liquid catalyst, comprising the following steps:

[0008] S1. Add allyl secondary amine into a flask, add organic acid at a certain reaction temperature, and react for a certain time to obtain an ionic liquid monomer.

[0009] S2. The obtained ionic liquid monomer is mixed with a crosslinking agent, and a certain amount of initiator is added, and the mixture is reacted at a certain temperature for a certain time. After separation, the solid matter is separated after the reaction is completed, and the impurities are removed by washing with a Soxhlet extractor.

[0010] Wherein, in step S1, the allylamine substance is N-methylallylamine or diallylamine.

[0011] Wherein, in the step S1, the molar ratio of the added organic acid to the allylamine substance is 0.1-10:1.

[0012] Wherein, in step S1, the organic acid is acetic acid, propionic acid, butyric acid, acrylic acid, methacrylic acid, oxalic acid, citric acid or benzenesulfonic acid.

[0013] Wherein, in step S2, the crosslinking agent is one or a combination of styrene, divinylbenzene or ethylene glycol dimethacrylate.

[0014] Wherein, in step S2, the initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile or benzoyl peroxide or a combination thereof.

[0015] Wherein, in step S2, the ratio of the cross-linking agent to the ionic liquid monomer is 0.01-5:1.

[0016] Wherein, in step S2, the reaction temperature is 60-100°C.

[0017] Wherein, in step S2, the reaction time is 4-12 hours. The present invention also provides the use of the above-mentioned polymeric ionic liquid heterogeneous catalyst in the preparation of methacrolein by aldol condensation of formaldehyde and propionaldehyde.

[0018] Based on the above technical solution, compared with the prior art, the technical effects achieved by the present invention are:

[0019] (1) The polymeric ionic liquid heterogeneous catalyst provided by the present invention has high catalytic activity and selectivity for the preparation of methacrolein by the aldol condensation of formaldehyde and propionaldehyde.

[0020] (2) Compared with traditional homogeneous catalysts, the polymerized ionic liquid heterogeneous catalyst prepared in the present invention is less corrosive to equipment and can be easily separated from the reaction system for recycling.

[0021] (3) The polymeric ionic liquid heterogeneous catalyst of the present invention has good thermal stability and catalytic stability in the process of preparing methacrolein by aldol condensation of formaldehyde and propionaldehyde. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the infrared spectrum of the polymer ionic liquid heterogeneous catalyst prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively in conjunction with the accompanying drawings and specific embodiments. The preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to understand the disclosure of the present invention more thoroughly and comprehensively.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0025] 1. Implementation Methods for Preparation of Polymeric Ionic Liquid Heterogeneous Catalysts

[0026] Implementation Case 1:

[0027] 0.1 mol of N-methylallylamine was added into the flask, and 0.1 mol of acetic acid was added at 40° C. and reacted for 6 hours to obtain an ionic liquid monomer.

[0028] Under stirring conditions, 0.05 mol of divinylbenzene and 0.005 mol of azobisisobutyronitrile were added to the ionic liquid monomer and reacted at 70°C for 6 hours. The obtained product was separated by filtration and washed with a Soxhlet extractor for 24 hours using methanol as the washing agent. After washing, the product was dried to obtain a polymerized ionic liquid heterogeneous catalyst A.

[0029] Implementation Case 2:

[0030] 0.1 mol of N-methylallylamine was added to the flask, and 0.05 mol of acrylic acid was added at -10°C and reacted for 6 hours to obtain an ionic liquid monomer.

[0031] Under stirring conditions, 0.2 mol of divinylbenzene and 0.01 mol of azobisisoheptanenitrile were added to the ionic liquid monomer and reacted at 80°C for 4 hours. The obtained product was separated by filtration and washed with a Soxhlet extractor for 6 hours using methanol as the washing agent. After washing, the product was dried to obtain a polymerized ionic liquid heterogeneous catalyst B.

[0032] Implementation Case 3:

[0033] 0.1 mol of diallylamine was added to a flask, and 0.08 mol of methacrylic acid was added at 0°C and reacted for 4 hours to obtain an ionic liquid monomer.

[0034] Under stirring conditions, 0.1 mol of ethylene glycol dimethacrylate and 0.008 mol of azobisisobutyronitrile were added to the ionic liquid monomer and reacted at 90°C for 8 hours. The obtained product was separated by filtration and washed with a Soxhlet extractor for 36 hours using methanol as the washing agent. After washing, the product was dried to obtain a polymerized ionic liquid heterogeneous catalyst C.

[0035] Implementation Case 4:

[0036] 0.1 mol of diallylamine was added into a flask, and 0.05 mol of oxalic acid was added at 10° C. and reacted for 9 hours to obtain an ionic liquid monomer.

[0037] Under stirring conditions, 0.3 mol of styrene and 0.015 mol of azobisisoheptanenitrile were added to the ionic liquid monomer and reacted at 100°C for 12 hours. The obtained product was separated by filtration and washed with a Soxhlet extractor for 48 hours using methanol as the washing agent. After washing, the product was dried to obtain a polymerized ionic liquid heterogeneous catalyst D.

[0038] 2. Preparation of Methacrolein by Aldol Condensation of Formaldehyde and Propionaldehyde Catalyzed by Heterogeneous Polymeric Ionic Liquids

[0039] Implementation Case 1:

[0040] In a flask equipped with a condenser, a thermometer and a magnetic stirrer, 0.06 mol of propionaldehyde and 0.06 mol of formaldehyde were added. After the temperature rose to 70°C under uniform stirring, 2 g of the polymerized ionic liquid heterogeneous catalyst A prepared in Example 1 was added and reacted for 10 min. After the reaction system was cooled to room temperature, the catalyst A was filtered out, and the yield of methacrolein was measured to be 72.5%.

[0041] Implementation Case 2:

[0042] In a flask equipped with a condenser, a thermometer and a magnetic stirrer, 0.06 mol of propionaldehyde and 0.06 mol of formaldehyde were added. After the temperature rose to 60°C under uniform stirring, 4 g of the polymerized ionic liquid heterogeneous catalyst B prepared in Example 2 was added and reacted for 20 min. After the reaction system was cooled to room temperature, the catalyst B was filtered out, and the yield of methacrolein was measured to be 60%.

[0043] Implementation Case 3:

[0044] In a flask equipped with a condenser, a thermometer and a magnetic stirrer, 0.06 mol of propionaldehyde and 0.06 mol of formaldehyde were added. After the temperature rose to 70°C under uniform stirring, 5 g of the polymerized ionic liquid heterogeneous catalyst C prepared in Example 3 was added and reacted for 10 min. After the reaction system was cooled to room temperature, the catalyst C was filtered out, and the yield of methacrolein was measured to be 80%.

[0045] Implementation Case 4:

[0046] In a flask equipped with a condenser, a thermometer and a magnetic stirrer, 0.06 mol of propionaldehyde and 0.06 mol of formaldehyde were added. After the temperature rose to 70°C under uniform stirring, 1 g of the polymerized ionic liquid heterogeneous catalyst D prepared in Example 4 was added and reacted for 30 min. After the reaction system was cooled to room temperature, the catalyst D was filtered out, and the yield of methacrolein was measured to be 55.1%.

[0047] The above contents are only examples and explanations of the present invention, and the descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and these obvious replacement forms all belong to the protection scope of the present invention.

Claims

1. A polymeric ionic liquid heterogeneous aldol condensation catalyst, characterized in that The polymerized ionic liquid heterogeneous catalyst is prepared by reacting a secondary amine having a polymerizable group with an organic acid through an acid-base reaction to prepare an ionic liquid monomer, and then synthesizing the monomer with a crosslinking agent under the action of an initiator. The preparation method is characterized in that it comprises the following steps: Step S1: a method for preparing an ionic liquid monomer, wherein an allyl secondary amine substance is added into a flask, an organic acid is added, and the mixture is reacted at a certain reaction temperature for a certain time to obtain an ionic liquid monomer, wherein the allyl secondary amine substance includes one of N-methylallylamine or diallylamine, and the organic acid includes one of acetic acid, propionic acid, butyric acid, acrylic acid, methacrylic acid, oxalic acid, citric acid or benzenesulfonic acid; Step S2: A method for preparing a polymerized ionic liquid heterogeneous catalyst, comprising mixing the obtained ionic liquid monomer with a crosslinking agent, adding a certain amount of initiator, and performing a polymerization reaction at a certain temperature. After the reaction is completed, the obtained solid material is separated and washed with a Soxhlet extractor to remove impurities, and finally the polymerized ionic liquid heterogeneous catalyst is obtained, wherein the crosslinking agent includes one of styrene, divinylbenzene or ethylene glycol dimethacrylate, and the initiator includes one of azobisisobutyronitrile, azobisisoheptylnitrile or benzoyl peroxide.

2. The method for preparing a polymeric ionic liquid heterogeneous aldol condensation catalyst according to claim 1, wherein: The molar ratio of the organic acid to the allylamine substance added in step S1 is 0.1-10:

1.

3. The method for preparing the heterogeneous aldol condensation catalyst of polymerized ionic liquid according to claim 1, characterized in that: In step S2, the ratio of the crosslinking agent to the ionic liquid monomer is 0.01-5:

1.

4. The method for preparing the heterogeneous aldol condensation catalyst of polymerized ionic liquid according to claim 1, characterized in that: In step S2, the reaction temperature is 60-100° C. and the reaction time is 4-12 hours.

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