阅读说明：本技术 煤基甲基丙烯醛制备过程中离子液体催化剂的回收方法 (Method for recovering ionic liquid catalyst in preparation process of coal-based methacrolein ) 是由 王蕾 陈洪楠 杨普 赵秋 李春山 杜利雄 张锁江 于 2020-06-23 设计创作，主要内容包括：本发明涉及的是煤基甲基丙烯醛制备过程中离子液体催化剂的回收方法,该方法利用多种手段从离子液体中去除有机杂质以及多余的水,方法是先将反应后甲基丙烯醛相和离子液体催化剂相分相,然后对离子液体催化剂相进行溶剂萃取,最后将萃取后的离子液体催化剂相加入薄膜蒸发装置进行薄膜蒸发,收集所得重组分即为回收后离子液体催化剂；本发明将分相,萃取和薄膜蒸发相结合,一方面可有效降低离子液体相中残留的有机物,另一方面可有效去除反应带来的过多水分等,使得到的离子液体纯度高、含水量合适,利于多次使用。本发明工艺简单、操作方便、能耗低、得到的催化剂纯度高,经过多次处理催化效果保持稳定。(The invention relates to a method for recovering an ionic liquid catalyst in a coal-based methacrolein preparation process, which utilizes a plurality of means to remove organic impurities and redundant water from ionic liquid, and comprises the steps of firstly separating a methacrolein phase and an ionic liquid catalyst phase after reaction, then carrying out solvent extraction on the ionic liquid catalyst phase, finally adding the extracted ionic liquid catalyst phase into a film evaporation device for film evaporation, and collecting the obtained heavy component, namely the recovered ionic liquid catalyst; the invention combines phase separation, extraction and thin film evaporation, on one hand, residual organic matters in the ionic liquid phase can be effectively reduced, on the other hand, excessive water and the like brought by reaction can be effectively removed, so that the obtained ionic liquid has high purity and proper water content, and is beneficial to multiple uses. The method has the advantages of simple process, convenient operation, low energy consumption, high purity of the obtained catalyst and stable catalytic effect after multiple treatments.)

1. The method for recovering the ionic liquid catalyst in the coal-based methacrolein preparation process is to recover the ionic liquid catalyst in the coal-based methacrolein preparation process by combining the standing phase splitting, the solvent extraction and the thin film evaporation, firstly, the phase splitting is carried out on the mixed solution after the reaction to obtain the ionic liquid catalyst phase, and then, the solvent extraction and the thin film evaporation are carried out on the ionic liquid catalyst phase in sequence, and the method comprises the following specific steps:

(1) quickly cooling the reacted mixed solution, standing at a certain temperature for phase splitting to respectively obtain a methacrolein phase and an ionic liquid catalyst phase;

(2) adding a certain amount of extractant into the ionic liquid catalyst phase obtained in the step (1), mixing and extracting at a certain temperature, and separating phases to obtain an extractant phase and an extracted ionic liquid catalyst phase;

(3) and (3) carrying out film evaporation on the extracted ionic liquid catalyst phase, and obtaining the recyclable ionic liquid catalyst aqueous solution after the film evaporation.

2. The method for recovering the ionic liquid catalyst in the preparation process of coal-based methacrolein according to claim 1, wherein: in the step (1), the phase separation temperature is 0-30 ℃, and the phase separation time is 0-3 h.

3. The method for recovering the ionic liquid catalyst in the preparation process of coal-based methacrolein according to claim 1, wherein: the extractant is at least one of benzene, toluene, diethyl ether, carbon tetrachloride, hexane and cyclohexane, the dosage of the extractant in the step (2) is 30-200% of the mass of the ionic liquid catalyst phase in the step (1), the extraction temperature is 20-80 ℃, the extraction time is 1-60 min, and the extraction times are not limited.

4. The method for recovering the ionic liquid catalyst in the preparation process of coal-based methacrolein according to claim 1, wherein: in the step (3), the evaporation pressure of the film is 5-35 bar, and the temperature is 50-100 ℃.

5. The process for preparing coal-based methacrolein according to claims 1 to 4, wherein the process is a process for preparing methacrolein by liquid phase condensation of formaldehyde and propionaldehyde.

6. The ionic liquid catalyst as claimed in claims 1 to 4, wherein the ionic liquid catalyst is amine organic acid salt or inorganic acid salt.

Technical Field

The invention relates to a method for recovering an ionic liquid catalyst, in particular to a method for recovering an ionic liquid catalyst in a coal-based methacrolein preparation process.

Technical Field

Methacrolein is an important chemical raw material, methacrylic acid can be prepared by oxygen molecular oxidation, and methyl methacrylate can be further prepared by esterification reaction of the methacrylic acid and methanol; the methyl allyl alcohol can be prepared by aldehyde group reduction; as a polymerization monomer, the product can be used for producing surface coatings, such as water-based coatings, solvent-based coatings, emulsion paints and the like, can be used as a raw material to generate impact modifiers ACR and MRS which can effectively improve the rigidity, toughness, dimensional stability, processing fluidity and color tone of polyvinyl chloride (PVC) products, and can also be used as an adhesive, a cross-linking agent, an additive and the like.

In the past, the synthesis of methacrolein mostly adopts an isobutene/tert-butyl alcohol high-temperature catalytic oxidation method, namely mixed raw material gas containing isobutene/tert-butyl alcohol and oxygen is subjected to catalytic oxidation reaction through a solid catalyst bed layer, the reaction temperature is 300-400 ℃, the retention time is about 2-5 s, the conversion rate of isobutene is more than 95%, and the yield of methacrolein and methacrylic acid is 82-88%. The method for preparing the methacrolein has low selectivity and high reaction energy consumption, and the solid catalyst is not beneficial to mass transfer.

In recent years, researchers at home and abroad increasingly study on the low-temperature synthesis of methacrolein by using a coal-based liquid phase, namely, methacrolein is obtained by taking formaldehyde and propionaldehyde as raw materials through aldol condensation. The reported catalysts are different from each other and are summarized to be mainly amine ionic liquid organic acid salts or inorganic acid salts and other ionic liquid salts. An ionic liquid catalyst is a new liquid which has been recently developed, and is more and more favored by scientists because of its advantages such as diversity, designability, low vapor pressure, and the like. In the process of preparing methyl methacrylate by ethylene carbonylation method initiated by BASF company, the preparation of methacrolein adopts Mannich reaction formaldehyde and propionaldehyde condensation method, the catalyst is secondary amine halogen salt or secondary amine organic acid salt, patent CN101074192A uses diethylamine hydrochloride as catalyst, US4408079 uses secondary amine and carboxylic acid as catalyst, US2639295 and other patents use organic amine and inorganic acid as catalyst, the literature reports on the catalyst are many, but the research on the recovery of ionic liquid catalyst after preparing methacrolein is less.

The ionic liquid catalyst is used as an excellent catalyst, has good catalytic effect, greatly improves the reaction and the reaction process, and has stable property, high efficiency, low corrosivity, mild reaction process, high yield of the methacrolein and high purity of the prepared methacrolein. But good economics can only be achieved with multiple uses of ionic liquid catalysts. The recovery and reuse of ionic liquids are of great significance both from an economic and environmental perspective.

In respect to the recovery of ionic liquid, a great deal of reports are provided, and in patent CN101219840A, a combined method of pretreatment, ultrafiltration, nanofiltration and reduced pressure distillation is adopted to recover an ionic liquid solvent from spinning wastewater; some patents have added inorganic salts to ionic liquids to recover ionic liquids, such as CN 1973943A; some employ ion exchange resins to recover ionic liquids, such as 200819200367.2; these patents are viable for the recovery of small amounts of ionic liquid, but are not applicable for the recovery of large amounts of ionic liquid and for ionic liquids with high water content. The patent reports mainly the recovery of ionic liquid solvent and little to no recovery of ionic liquid catalyst.

The thin film evaporation is a quick and efficient special liquid-liquid separation technology, the separation temperature can be far lower than the boiling point, meanwhile, the retention time of materials is short, and the thin film evaporation is favorable for separating materials with high boiling points, heat sensitivity and easy oxidation; the thin film evaporation is carried out under high vacuum, the materials are not easy to oxidize and damage, and the mass transfer efficiency and the heat transfer efficiency are high under the thin film state; the liquid boiling during the distillation process is weak and no bubbling occurs. As a mild and efficient liquid-liquid separation method, thin film evaporation is widely used for separating high molecular weight, high boiling point, high viscosity, heat sensitivity and easily oxidized substances in petrochemical, food, daily chemical, medicine and other industries.

Disclosure of Invention

Based on the existing recovery method of the ionic liquid catalyst, particularly aiming at the problems that the recovery method of the ionic liquid catalyst is few and is not applicable in the preparation process of the coal-based methacrolein, the invention particularly provides a novel recovery method of the ionic liquid catalyst in the preparation process of the coal-based methacrolein.

The ionic liquid catalyst phase in the preparation process of the coal-based methacrolein mainly has the following characteristics: 1) the mutual solubility of the methacrolein and the ionic liquid catalyst is not large, and the layering is easy; 2) the reaction is complex, and the organic substances after the reaction have more components and are partially dissolved in the ionic liquid phase; 3) the ionic liquid catalyst system contains water, the water content of the raw material formaldehyde is large, water is generated by reaction, and the like, so that the water content of the ionic liquid catalyst phase after the reaction is high; 4) the ionic liquid catalyst is easy to generate other reactions at high temperature and easy to denature after being heated for a long time.

Aiming at the characteristics of the ionic liquid catalyst phase in the preparation process of the coal-based methacrolein, the invention provides a novel method for recovering the ionic liquid catalyst. The method combines the phase separation, extraction and thin film evaporation technologies, on one hand, residual organic matters in the ionic liquid phase can be effectively reduced, on the other hand, excessive water and the like brought by reaction can be effectively removed, so that the obtained ionic liquid has high purity and proper water content, and is beneficial to multiple uses. The method has the advantages of simple process, convenient operation, low energy consumption, high purity of the obtained catalyst and repeated recycling.

The invention relates to a method for recovering an ionic liquid catalyst in a coal-based methacrolein preparation process, which is to recover the ionic liquid catalyst in the coal-based methacrolein preparation process by combining a standing phase splitting method, a solvent extraction method and a film evaporation method, wherein firstly, a product after reaction is subjected to phase splitting to obtain an ionic liquid catalyst phase, and then the ionic liquid catalyst phase is subjected to solvent extraction and film evaporation in sequence, and the method comprises the following specific steps:

(1) quickly cooling a product after reaction, standing and layering for a period of time at a certain temperature to respectively obtain a methacrolein phase and an ionic liquid catalyst phase;

(2) adding a certain amount of extraction solvent into the ionic liquid catalyst phase obtained in the first step at a certain temperature, stirring for a certain time, and then carrying out extraction phase splitting to obtain an extractant phase and an extracted ionic liquid catalyst phase;

(3) and adding the extracted ionic liquid catalyst phase into a thin film evaporator, and performing thin film evaporation by adjusting the feeding speed, the film scraping temperature, the film scraping pressure, the film scraping speed and the condensation temperature to obtain the recyclable ionic liquid catalyst aqueous solution.

In the invention, the phase separation temperature in the step (1) is 0-30 ℃, and the phase separation time is 0-3 h.

In the invention, the extractant is at least one of benzene, toluene, diethyl ether, carbon tetrachloride, hexane and cyclohexane, the dosage of the extractant is 30-200% of the mass of the ionic liquid catalyst phase in the step (1), the extraction temperature is 20-80 ℃, the extraction time is 1-60 min, and the extraction times are not limited.

In the invention, the evaporation pressure of the film is 5-35 bar, and the temperature is 50-100 ℃.

In the invention, the coal-based methacrolein preparation process is to prepare methacrolein by liquid phase condensation of formaldehyde and propionaldehyde.

In the invention, the ionic liquid catalyst system is an organic acid salt or inorganic acid salt aqueous solution of amines or alcohol amines.

Detailed Description

The present invention is described by the following examples, but the present invention is not limited to the following examples, and variations and implementations are included in the technical scope of the present invention without departing from the spirit of the invention described above and below.