Immobilized catalyst for preparing methylacrolein through Mannich condensation method and preparation method of immobilized catalyst

Abstract

The invention relates to the field of catalytic materials, in particular to an immobilized catalyst for preparing methylacrolein through a Mannich condensation method and a preparation method of the immobilized catalyst, and solves the problems that an existing catalyst is not easy to separate and poor in stability, and the catalytic performance needs to be improved. According to the method, organic amine is immobilized on the surface of silica gel through Si-O-Si bonds, and then the silica gel is acidified through organic acid. The catalyst is prepared by the method. The catalyst disclosed by the invention is good in catalytic performance, good in conversion rate and selectivity, easy to separate, recycle and reuse after being used, and stable in physical property after being recycled for multiple times; the method disclosed by the invention is extremely simple, low in cost and energy consumption and mild in reaction condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic materials, in particular to a solid supported catalyst for preparing methylacrolein by Mannich condensation and a preparation method thereof. BACKGROUND

[0002] Methylacrolein is an important organic synthesis intermediate, which can be used to synthesize basic chemical products such as methylacrylic acid, methyl methacrylate and methyl allyl alcohol, and further synthesize organic glass, cement water reducing agent, medicine and pesticide, and essence and flavor chemical products.

[0003] There are three main synthesis routes of methylacrolein: isobutene oxidation method, isobutane oxidation method and Mannich condensation method of formaldehyde and propionaldehyde. The isobutene oxidation method is currently widely used in industry, but the cost of raw material isobutene is high, which seriously restricts its development. The raw material isobutane of isobutane oxidation method is low in price, but the catalyst activity is not high at present, the yield of methylacrolein is low, and the industrialization prospect is not clear. The Mannich condensation method of formaldehyde and propionaldehyde has simple process route, mild reaction condition, wide raw material source and high yield, and does not have the problem of further oxidation into methylacrylic acid, which has good industrial application prospect.

[0004] The Mannich condensation method of formaldehyde and propionaldehyde mainly uses organic amine-organic base catalyst system, US4408079 and US4496770 disclose catalytic systems such as oxalic acid / diethanolamine and acetic acid / dimethylamine, and CN102659542 discloses a method for producing methylacrolein by using ionic liquid as catalyst. These catalyst systems can realize the water-oil phase separation of reaction products, but the catalyst and water are mutually soluble, which makes the catalyst recovery difficult and high in energy consumption. CN201811495101.5 develops Pickering emulsion and resin catalyst, which is beneficial to the separation of catalyst and reaction system, but may cause demulsification and catalyst loss in continuous production.

[0005] Therefore, it is an urgent problem for researchers to develop a catalyst suitable for Mannich condensation method and stable in physical properties and easy to separate. SUMMARY

[0006] The purpose of the present application is to solve the above technical problems, and provide a solid supported catalyst for preparing methylacrolein by Mannich condensation, which is stable in physical properties, high in performance, easy to separate, recover and reuse.

[0007] Another purpose of the present application is to provide a preparation method of the above solid supported catalyst, which is simple in method, low in cost and energy consumption, and mild in reaction condition.

[0008] The application relates to a preparation method of a supported catalyst for preparing methylpropyl aldehyde by a Mannich condensation method, which comprises the following steps of: I. Silica gel activation: after the silica gel particles are washed by alcohol, the silica gel particles are dried in an oven to obtain activated silica gel particles; II. Silica gel surface epoxy group supporting: under an inert atmosphere, silane coupling agent is dissolved into an organic reagent, then the activated silica gel particles obtained in step I are added, and refluxing is carried out under the action of a catalyst; after washing and drying, the silica gel particles with supported epoxy groups are obtained; III. Organic amine supporting: under an inert atmosphere, organic amine is dissolved into a solvent, and the silica gel particles with supported epoxy groups obtained in step II are added for organic amine supporting; after washing and drying, the silica gel particles with supported organic amine are obtained; IV. Acidification: an organic acid aqueous solution is used to acidify the silica gel particles with supported organic amine obtained in step III; after washing and drying, the supported catalyst is obtained.

[0009] In step I, the washing alcohol is methanol or ethanol, and methanol is preferred; the drying temperature is 80-150 DEG C, and 120-150 DEG C is preferred.

[0010] In step II, the silane coupling agent is 3-glycidyl ether oxypropyl trimethoxysilane (GPTMS) or 3-glycidyl ether oxypropyl triethoxysilane (GOTMS).

[0011] In step II, the mixing ratio of the silane coupling agent and the silica gel particles is 1-2 ml:1 g.

[0012] In step II, the catalyst is triethylamine or diisopropyl ethylamine, and triethylamine is preferred.

[0013] In step II, the catalyst is added in an amount of 5-10% of the volume of the silane coupling agent.

[0014] In step III, the organic amine is at least one of methylamine, ethylamine, propylamine, butylamine or ethanolamine, In step III, the mass ratio of the organic amine and the silica gel particles is 0.2-0.5:1.

[0015] In step III, the solvent is one of methanol, ethanol, isopropyl alcohol and acetonitrile, or a mixture of one of the solvents and water.

[0016] In step III, the supporting temperature is 30-50 DEG C.

[0017] In the fourth step, the organic acid is at least one of acetic acid, oxalic acid or glycolic acid, preferably acetic acid; and the concentration of the aqueous organic acid solution is 8-50 wt%.

[0018] In the fourth step, the acidification temperature is 10-40℃.

[0019] The supported catalyst for preparing methylacrolein by Mannich condensation method is prepared by the above preparation method.

[0020] In view of the problems in the background art, the inventors have made the following improvements: The silica gel particles are used as the carrier, and the organic amine-organic acid is supported on the surface of the silica gel by covalent bond to obtain the catalyst which is solid particles and is not soluble in water and is not easy to be lost. After the reaction, the catalyst can be separated from the liquid phase reaction system by filtration, and compared with the traditional liquid phase organic amine-organic acid catalyst system, the catalyst does not need to be heated to remove the formaldehyde aqueous solution and water produced in the reaction, thereby greatly saving the energy consumption.

[0021] The traditional liquid phase organic amine-organic acid catalyst generally uses heating distillation to remove the water, methanol and other light component substances introduced in the reaction to realize the reuse of the catalyst, but during the heating process, the decomposition of the catalyst, the secondary reaction of the aldehyde substances and the catalyst to generate inert substances, the accumulation of high-boiling point compounds in the catalyst solution and other problems occur, which makes it necessary to discard a part of the recovered catalyst solution and supplement fresh catalyst to maintain the activity of the catalyst during the production process. The catalyst of the present application only needs to be recovered by filtration, and the process does not need to heat the catalyst, which can effectively avoid the decomposition and denaturation of the catalyst, and in the case of need, the solvent washing method can be used to remove the reaction materials accumulated on the surface and in the pores of the catalyst, thereby eliminating the accumulation of impurities and heavy components in the secondary reaction, and greatly prolonging the number of cycles of the catalyst.

[0022] The primary amine and the coupling agent are used to produce the supported secondary amine, which not only has good catalytic activity and is not easy to fall off from the carrier, but also has the RCH-OH group generated after the reaction of the coupling reagent and the amine, the group has electron-withdrawing property, and has the adjusting effect on the alkalinity of the supported amine, so that the alkalinity of the supported amine is more moderate, the main reaction is facilitated, the self-polymerization of propyl aldehyde is reduced, and the yield of methylacrolein is improved.

[0023] The catalyst of the present application has good catalytic performance, good conversion rate and selectivity, is easy to separate and recycle after use, and has stable physical properties after multiple cycles; the method of the present application is extremely simple, has low cost and energy consumption, and has mild reaction conditions. DETAILED DESCRIPTION

[0024] Example 1 Take 5 g silica gel particles repeatedly washed with methanol for 3 times, then put into 80 °C oven for 12 h, cool in the desiccator. Take 5 ml of 3-glycidyloxypropyltrimethoxysilane dissolved into 100 ml of anhydrous toluene, disperse the activated silica gel particles into the toluene solution, drop 0.25 ml of triethylamine, heat to the boiling point of toluene under nitrogen atmosphere, react for 6 h. After the reaction is completed, filter out the silica gel particles, wash with toluene for 3 times, then wash with ethanol for 3 times, put into 80 °C oven for 12 h, cool in the desiccator. Take 2 g of ethylamine dissolved into 100 ml of methanol, disperse the silica gel particles with immobilized epoxy groups into the solution, protect under N2 atmosphere, react at 40 °C for 12 h, after the reaction is completed, filter out the silica gel particles, wash with methanol for 3 times, then wash with water for 3 times. Disperse the washed silica gel particles into 50 ml of 30 wt% concentration of acetic acid aqueous solution, acidify at 40 °C for 4 h, then filter, wash with water for 3 times, and place in a 50 °C vacuum oven for drying to obtain the catalyst SiO2-GPTMS-Ea-Ac.

[0025] Example 2 Take 5 g silica gel particles repeatedly washed with ethanol for 3 times, then put into 120 °C oven for 8 h, cool in the desiccator. Take 10 ml of 3-glycidyloxypropyltrimethoxysilane dissolved into 100 ml of anhydrous toluene, disperse the activated silica gel particles into the toluene solution, drop 1 ml of diisopropylethylamine, heat to the boiling point of toluene under nitrogen atmosphere, react for 12 h. After the reaction is completed, filter out the silica gel particles, wash with toluene for 3 times, then wash with ethanol for 3 times, put into 100 °C oven for 12 h, cool in the desiccator. Take 2.4 g of 40% methylamine aqueous solution dissolved into 50 ml of ethanol, disperse the silica gel particles with immobilized epoxy groups into the solution, protect under N2 atmosphere, react at 50 °C for 6 h, after the reaction is completed, filter out the silica gel particles, wash with ethanol for 3 times, then wash with water for 3 times. Disperse the washed silica gel particles into 50 ml of 40 wt% concentration of acetic acid aqueous solution, acidify at 30 °C for 6 h, then filter, wash with water for 3 times, and place in a 60 °C vacuum oven for drying to obtain the catalyst SiO2-GPTMS-Ma-Ac.

[0026] Example 3 Take 5 g silica gel particles and wash with methanol repeatedly for 3 times, then put into an oven at 140 °C for 8 h, cool in a desiccator. Dissolve 6 ml 3-glycidyloxypropyltriethoxysilane into 50 ml anhydrous xylene, disperse the cooled activated silica gel particles into the xylene solution, drop 0.5 ml diisopropylethylamine, heat to the boiling point of xylene under nitrogen atmosphere, reflux for 24 h. After the reaction is completed, filter out the silica gel particles, wash with xylene for 3 times, then wash with ethanol for 3 times, put into an oven at 130 °C for 12 h, cool in a desiccator. Dissolve 2.5 g propylamine into 50 ml acetonitrile, disperse the silica gel particles with immobilized epoxy groups into the solution, protect under N2 atmosphere, react at 40 °C for 24 h, after the reaction is completed, filter out the silica gel particles, wash with acetonitrile for 3 times, then wash with water for 3 times. Disperse the washed silica gel particles into 100 ml 9 wt% oxalic acid aqueous solution, acidify at 30 °C for 8 h, then filter, wash with water for 3 times, and dry in a vacuum oven at 70 °C to obtain the catalyst SiO2-GOTMS-Pa-Oc.

[0027] Example 4 Take 5 g silica gel particles and wash with ethanol repeatedly for 3 times, then put into an oven at 150 °C for 8 h, cool in a desiccator. Dissolve 8 ml 3-glycidyloxypropyltriethoxysilane into 50 ml anhydrous xylene, disperse the cooled activated silica gel particles into the xylene solution, drop 0.8 ml triethylamine, heat to the boiling point of xylene under nitrogen atmosphere, reflux for 24 h. After the reaction is completed, filter out the silica gel particles, wash with xylene for 3 times, then wash with ethanol for 3 times, put into an oven at 130 °C for 12 h, cool in a desiccator. Dissolve 1.5 g ethanolamine into 100 ml 90% ethanol aqueous solution, disperse the silica gel particles with immobilized epoxy groups into the solution, protect under N2 atmosphere, react at 30 °C for 48 h, after the reaction is completed, filter out the silica gel particles, wash with 90% ethanol aqueous solution for 3 times, then wash with water for 3 times. Disperse the washed silica gel particles into 50 ml 50 wt% acetic acid solution, acidify at 20 °C for 8 h, then filter, wash with water for 3 times, and dry in a vacuum oven at 90 °C to obtain the catalyst SiO2-GOTMS-Ae-Ac.

[0028] Example 5 Take 5 g silica gel particles and wash with methanol repeatedly for 3 times, then put into 130 °C oven for 12 h, cool in a desiccator. Take 6 ml 3-glycidyloxypropyltrimethoxysilane and dissolve into 50 ml anhydrous xylene, disperse the cooled activated silica gel particles into the xylene solution, drop 0.4 ml triethylamine, heat to xylene boiling point under nitrogen atmosphere, reflux for 24 h. After the reaction is completed, filter out the silica gel particles, wash with xylene for 3 times, then wash with ethanol for 3 times, put into 140 °C oven for 12 h, cool in a desiccator. Take 2 g butylamine and dissolve into 100 ml isopropanol, disperse the silica gel particles with immobilized epoxy groups into the solution, protect under N2 atmosphere, react at 40 °C for 36 h, after the reaction is completed, filter out the silica gel particles, wash with isopropanol for 3 times, then wash with water for 3 times. Disperse the washed silica gel particles into 50 ml acetic acid solution with a concentration of 40 wt%, acidify at 10 °C for 12 h, then filter, wash with water for 3 times, and dry in a vacuum oven at 80 °C, to obtain the catalyst SiO2-GPTMS-Ba-Ac.

[0029] Example 6 Take 5 g silica gel particles and wash with methanol repeatedly for 3 times, then put into 130 °C oven for 12 h, cool in a desiccator. Take 9 ml 3-glycidyloxypropyltrimethoxysilane and dissolve into 100 ml anhydrous toluene, disperse the cooled activated silica gel particles into the toluene solution, drop 0.5 ml triethylamine, heat to toluene boiling point under nitrogen atmosphere, reflux for 24 h. After the reaction is completed, filter out the silica gel particles, wash with toluene for 3 times, then wash with ethanol for 3 times, put into 140 °C oven for 12 h, cool in a desiccator. Take 2.5 g aniline and dissolve into 100 ml acetonitrile, disperse the silica gel particles with immobilized epoxy groups into the solution, protect under N2 atmosphere, react at 50 °C for 12 h, after the reaction is completed, filter out the silica gel particles, wash with acetonitrile for 3 times, then wash with water for 3 times. Disperse the washed silica gel particles into 50 ml acetic acid solution with a concentration of 40 wt%, acidify at 35 °C for 2 h, then filter, wash with water for 3 times, and dry in a vacuum oven at 80 °C, to obtain the catalyst SiO2-GPTMS-Ab-Ac.

[0030] Example 7 Take 5 g silica gel particles repeatedly washed with ethanol for 3 times, then to 130 °C oven for 12 h, in the dryer cooling. Take 5 ml 3-glycidyloxypropyl triethoxysilane dissolved in 50 ml anhydrous xylene, the cooled activated silica gel particles dispersed in the toluene solution, drop 0.25 ml triethylamine, in the nitrogen atmosphere to xylene boiling point reflux, reaction 16 h. After the reaction, filter out the silica gel particles, with toluene washed 3 times, again with ethanol washed 3 times, into the 140 °C oven for 12 h, in the dryer cooling. Take 1 g ethylamine dissolved in 50 ml ethanol, the silica gel particles after the immobilization of epoxy group dispersed in the solution, in N2 gas protection, at 40 °C reaction 12 h, after the reaction, filter out the silica gel particles, with ethanol washed 3 times after with water washed 3 times. The washed silica gel particles dispersed in 8 wt% concentration of 100 ml oxalic acid solution, 25 °C acidification 4 h after filtration, with water washed 3 times after placed in 60 °C vacuum oven drying, get catalyst SiO2-GOTMS-Ea-Oc.

[0031] Example 8 Take 5 g silica gel particles repeatedly washed with methanol for 3 times, then to 120 °C oven for 12 h, in the dryer cooling. Take 5 ml 3-glycidyloxypropyl trimethoxysilane dissolved in 50 ml anhydrous toluene, the cooled activated silica gel particles dispersed in the toluene solution, drop 0.25 ml triethylamine, in the nitrogen atmosphere to toluene boiling point reflux, reaction 12 h. After the reaction, filter out the silica gel particles, with toluene washed 3 times, again with ethanol washed 3 times, into the 130 °C oven for 12 h, in the dryer cooling. Take 2 g ethanolamine dissolved in 50 ml 80% ethanol aqueous solution, the silica gel particles after the immobilization of epoxy group dispersed in the solution, in N2 gas protection, at 30 °C reaction 16 h, after the reaction, filter out the silica gel particles, with 80% ethanol aqueous solution washed 3 times after with water washed 3 times. The washed silica gel particles dispersed in 40 wt% concentration of glycolic acid solution, 20 °C acidification 6 h after filtration, with water washed 3 times after placed in 60 °C vacuum oven drying, get catalyst SiO2-GPTMS-Ae-Ga.

[0032] Performance evaluation The performance evaluation of the catalyst was carried out in a tank reactor, and the reaction raw materials were 37% formaldehyde aqueous solution and 99% propyl aldehyde, and the molar ratio of formaldehyde to propyl aldehyde was 1.1:1.

[0033] The activity evaluation reaction conditions were that the mass of the catalyst was 5 wt% of the total mass of the reaction liquid, the reaction temperature was 80 °C, the reaction pressure was 1 MPa, and the reaction residence time was 30 min.

[0034] The catalyst performance data are as follows: Catalyst recycling reuse reaction conditions: the mass of catalyst is 5wt% of the total mass of reaction liquid, the reaction temperature is 80℃, the reaction pressure is 1 MPa, and the reaction residence time is 30 min. Catalyst treatment method: after the reaction is completed, the catalyst is filtered out and washed with acetonitrile and water for 3 times respectively. The performance data of each catalyst after 10 times of recycling use are as follows:

Claims

1. A method for preparing an immobilized catalyst for the Mannich condensation process to produce methacrolein, characterized in that, The organic amine is first immobilized on the surface of silica gel via Si-O-Si bonds, and then prepared by acidification with organic acid.

2. The method for preparing the supported catalyst for the Mannich condensation of methacrolein as described in claim 1, characterized in that, Includes the following steps:

1. Silica gel activation: After washing with alcohol, silica gel particles are dried in an oven to obtain activated silica gel particles; II. Epoxy groups immobilized on the surface of silica gel: Under an inert atmosphere, a silane coupling agent is dissolved in an organic reagent, and then the activated silica gel particles obtained in step one are added. The mixture is refluxed under the action of a catalyst, washed and dried to obtain silica gel particles with epoxy groups immobilized on the surface.

3. Organic amine immobilization: Under an inert atmosphere, organic amine is dissolved in a solvent, and silica gel particles with surface-immobilized epoxy groups obtained in step 2 are added for organic amine immobilization. After washing and drying, organic amine-immobilized silica gel particles are obtained. IV. Acidification: The organic amine-supported silica particles obtained in step 3 were acidified using an aqueous organic acid solution, and then washed and dried to obtain the supported catalyst.

3. The method for preparing the supported catalyst for the Mannich condensation of methacrolein as described in claim 2, characterized in that, In step two, the silane coupling agent is 3-glycidyl etheroxypropyltrimethoxysilane (GPTMS) or 3-glycidyl etheroxypropyltriethoxysilane (GOTMS), and its mixing ratio with silica gel particles is 1~2 ml: 1 g.

4. The supported catalyst for the Mannich condensation process to produce methacrolein as described in claim 2, characterized in that, In step two, the catalyst is triethylamine or diisopropylethylamine, and the amount added is 5-10% of the volume of the silane coupling agent.

5. The method for preparing the supported catalyst for the Mannich condensation of methacrolein as described in claim 2, characterized in that, In step three, the organic amine is at least one of methylamine, ethylamine, propylamine, butylamine, or ethanolamine, and the mass ratio of the organic amine to the silica gel particles is 0.2~0.5:

1.

6. The method for preparing the supported catalyst for the Mannich condensation of methacrolein as described in claim 2, characterized in that, In step three, the solvent is one of methanol, ethanol, isopropanol, acetonitrile, or a mixture of one of them and water.

7. The method for preparing the supported catalyst for the Mannich condensation of methacrolein as described in claim 2, characterized in that, In step three, the solidification temperature is 30~50℃.

8. The method for preparing the supported catalyst for the Mannich condensation of methacrolein as described in claim 2, characterized in that, In step four, the organic acid is at least one of acetic acid, oxalic acid, or glycolic acid, the concentration of the aqueous solution of the organic acid is 8-50 wt%, and the acidification temperature is 10-40℃.

9. A supported catalyst for the Mannich condensation process to produce methacrolein, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

Images