Catalyst coated with self-curing ionic liquid membrane as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst coated with a self-curing ionic liquid membrane as well as a preparation method and application of the catalyst, and the preparation process of the catalyst comprises the following steps: sulfonating polyethyleneimine to obtain self-curing acidic ionic liquid, namely sulfonated polyethyleneimine, and then coating the surface of a matrix with the sulfonated polyethyleneimine to prepare the catalyst coated with the self-curing acidic ionic liquid membrane. The prepared catalyst is respectively applied to a stirred tank, a membrane reactor and a fixed bed reactor to catalyze esterification reaction of oleic acid and methanol. The catalyst prepared by the invention not only has higher acid content, but also has large mass transfer area, and the diffusion resistance in a catalyst film layer is small, so that the catalyst has a better catalytic effect. When the solid acid catalyst is applied to a membrane reactor and a fixed bed reactor, the continuous esterification process of oleic acid and methanol is realized, the problems of large bed pressure drop and easy flooding when a conventional solid acid catalyst is applied to the fixed bed reactor are solved, and meanwhile, a novel filler which has a catalytic effect and can improve the mass transfer efficiency is provided for reactive distillation.

Description

Technical Field

[0001] The invention belongs to the field of membrane catalysis, and in particular relates to a catalyst coated with a self-curing ionic liquid membrane, and a preparation method and application thereof. Technical Background

[0002] Esterification is an important type of organic reaction that can synthesize various ester compounds. Esterification is widely used in the synthesis of products such as medicines, pesticides, dyes, surfactants, fragrances, and biofuels. Esterification reactions often use acids as catalysts, including liquid acid catalysts such as sulfuric acid and methanesulfonic acid, and solid acid catalysts such as strong acid ion exchange resins, molecular sieves, and sulfonated carbon. Liquid acid catalysts have problems such as strong corrosiveness, difficulty in recycling, and generation of large amounts of wastewater during washing and removal. Solid acid catalysts have problems such as large intra-particle mass transfer resistance, low catalytic efficiency, and long reaction time. In particular, when used in fixed bed reactors, there are problems such as large bed pressure drop and easy flooding. Summary of the invention

[0003] In view of the problems existing in the existing esterification reaction catalysts, the purpose of the present invention is to provide a catalyst coated with a self-curing ionic liquid membrane, and a preparation method and application thereof. The present invention uses high-viscosity polyethyleneimine as a raw material and 1,3-propane sultone as a sulfonating agent to synthesize a sulfonated polyethyleneimine ionic liquid with self-curing film-forming properties through a sulfonation reaction, and coats it on the surface of a base film or a filler to prepare a membrane catalyst. The prepared catalyst is implemented in a stirred tank, a membrane reactor, and a fixed bed reactor respectively to achieve catalysis of the esterification reaction of oleic acid and methanol.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A method for preparing a catalyst coated with a self-curing ionic liquid membrane comprises two steps: the first step is to sulfonate polyethyleneimine to obtain a self-curing acidic ionic liquid, namely sulfonated polyethyleneimine; the second step is to coat the self-curing ionic liquid on the surface of a substrate to prepare a catalyst with a surface coated with a self-curing acidic ionic liquid membrane.

[0006] The specific steps of preparing the catalyst of the present invention are as follows:

[0007] 1) heating and melting 1,3-propane sultone, dropping an ethanol solution of polyethyleneimine thereinto, stirring under heating to carry out a sulfonation reaction, cooling and filtering after the reaction, washing the filtered solid with ethanol to remove the incompletely reacted 1,3-propane sultone, and then drying to obtain an acidic self-curing ionic liquid containing a sulfonic acid group;

[0008] 2) The acidic self-curing ionic liquid obtained in step 1) is heated to above 70°C to make it a viscous liquid, and then evenly coated on the surface of the substrate, and the temperature is lowered to below 50°C to make it self-curing on the surface of the substrate to form an acidic ionic liquid film, thereby obtaining a catalyst with a self-curing ionic liquid film coated on the surface.

[0009] Furthermore, the molecular weight of the polyethyleneimine is 50,000-100,000, preferably 60,000-70,000, and the mass fraction of the polyethyleneimine ethanol solution is 30-70%.

[0010] Furthermore, the mass ratio of polyethyleneimine to 1,3-propane sultone is 1:1-5, preferably 1:3-5, the sulfonation temperature is 40-70°C, preferably 50-60°C, and the sulfonation time is 8-12h.

[0011] Furthermore, the substrate is a base film or a filler, the base film is a polypropylene film, a polyvinylidene fluoride film or a nylon film, the corresponding catalyst is a self-curing ionic liquid catalytic membrane, and the loading amount of the ionic liquid in the catalyst is 30-60%; the filler is a plastic filler or a metal filler, the corresponding catalyst is a self-curing ionic liquid catalytic membrane filler, and the loading amount of the ionic liquid in the catalyst is 20-50%.

[0012] The invention also discloses the use of the catalyst coated with the self-curing ionic liquid membrane in catalyzing esterification reaction of oleic acid. The reactor for catalyzing esterification reaction is a stirred tank, a membrane reactor or a fixed bed reactor.

[0013] Further, when the reactor is a stirred tank, the catalytic reaction steps are as follows:

[0014] 1) Add methanol and oleic acid into a stirred tank, the mass ratio of methanol to oleic acid is 1:0.8-1.2;

[0015] 2) adding a catalyst into a stirred tank, wherein the mass of the catalyst is 5%-16% of the mass of the oleic acid;

[0016] 3) Heat the material in the stirred tank to 60-70°C for reaction under stirring, and the reaction time is 2-4h;

[0017] 4) After the reaction is completed, the catalyst is filtered out and separated, and the reaction solution is distilled to remove methanol and water to obtain methyl oleate product.

[0018] Further, when the reactor is a membrane reactor, the catalytic reaction steps are as follows:

[0019] S1: The catalyst is a self-curing ionic liquid catalytic membrane, and the membrane reactor comprises the self-curing ionic liquid catalytic membrane and two reaction chambers, the self-curing ionic liquid catalytic membrane is sealed and arranged between the two reaction chambers, the liquid outlets of the two reaction chambers are connected to the liquid inlet of the storage tank through pipelines, and the liquid inlets of the two reaction chambers are connected to the liquid outlet of the storage tank through pipelines through delivery pumps;

[0020] S2: Methanol and oleic acid are added to the storage tank at a mass ratio of 1:0.8-1.2, and the reaction materials in the storage tank are heated to 60-70°C, and then the reaction materials are transported to the reaction chamber of the membrane reactor by a delivery pump, and the delivery flow rate of the delivery pump is 20-50mL / min. The reaction materials are in contact with the self-curing ionic liquid catalytic membrane for catalytic reaction. Under the operation of the delivery pump, the reaction materials circulate and react in the system formed by the storage tank, the delivery pump, the reaction chamber and the pipeline, and the reaction time is controlled to be 4-8h;

[0021] S3: After the reaction is completed, the liquid in the storage tank is released, and methanol and water are removed by distillation to obtain methyl oleate product.

[0022] Further, when the reactor is a fixed bed reactor, the catalytic reaction steps are as follows:

[0023] Step 1: The catalyst is a self-curing ionic liquid catalytic membrane filler, and the catalyst is filled in a fixed bed reactor. A heat preservation jacket is arranged outside the fixed bed reactor, and hot water at 60-70° C. is passed into the heat preservation jacket;

[0024] Step 2: Methanol and oleic acid are mixed in a mass ratio of 1:0.8-1.2, and the reaction mixture is heated to 60-70°C and then input from the bottom of the fixed bed reactor and overflowed from the top. The residence time of the reaction mixture in the fixed bed reactor is controlled to be 4-8h;

[0025] Step 3: The overflow material is evaporated to remove methanol and water to obtain methyl oleate product.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) After sulfonation of high-viscosity polyethyleneimine, an ionic liquid with both acidic catalytic sites and self-curing film-forming properties can be obtained.

[0028] (2) The ionic liquid catalytic membrane is prepared by coating the self-curing acidic ionic liquid on the surface of the base membrane, which has the following advantages: ① It can be directly applied to the membrane reactor to realize the continuous production of methyl oleate; ② After the self-curing acidic ionic liquid is coated on the surface of the base membrane, the mass transfer area is increased, the mass transfer path is shortened, and more catalytic sites are exposed on the catalyst surface, thereby overcoming the problem of large diffusion resistance in granular solid catalysts and the difficulty in solid-liquid separation of nano-powdered catalysts.

[0029] (3) The self-curing acidic ionic liquid is coated on the surface of the filler to prepare a self-curing ionic liquid catalytic membrane filler, which has the following advantages: ① The catalytic site is located in a very thin film layer on the inner and outer surfaces of the filler, which also overcomes the problem of large mass transfer resistance of conventional solid acid catalysts; ② The existing conventional solid acid catalysts are microporous particles with small particles. When conventional solid acid catalysts are used in fixed bed reactors, there are problems such as large bed pressure drop and easy liquid flooding. The present invention can directly apply the catalytic membrane filler to the fixed bed reactor, and utilize the characteristics of large filler particles, large pores, and large liquid holding capacity to avoid problems such as large bed pressure drop and easy liquid flooding; ③ It can be further applied to reactive distillation, providing a new type of filler for reactive distillation that has both catalytic effect and improved mass transfer efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the membrane reactor; wherein: 1-feed liquid inlet pipe, 2-PTFE plate; 3-reaction chamber; 4-ionic liquid catalytic membrane; 5-rubber gasket; 6-feed liquid outlet pipe.

[0031] Figure 2 This is a schematic flow chart of a reaction apparatus for continuously catalyzing the esterification reaction of oleic acid and methanol using an ionic liquid catalytic membrane in Example 11 of the present invention, wherein: 7-transport pump; 8-membrane reactor; 9-storage tank.

[0032] Figure 3 These are photos of the metal wire mesh and the wound cylindrical catalytic membrane filler in Example 9. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0034] Example 1 Preparation of self-curing ionic liquid

[0035] 10g of 1,3-propane sultone was added to a 50mL round-bottom flask and heated to about 35°C to melt it; 2g of polyethyleneimine with a molecular weight of 70,000 was mixed with 2g of ethanol to obtain an ethanol solution of polyethyleneimine, which was dropped into the 10g 1,3-propane sultone melt; the mixture was stirred and heated to 60°C, and the sulfonation reaction was carried out at 60°C for 8h. After the reaction was completed, the mixture was cooled to room temperature and filtered, and the filtered solid was washed with ethanol to remove the unreacted 1,3-propane sultone, and then placed in an oven at 70°C for 12h to obtain an acidic self-curing ionic liquid containing a sulfonic acid group. According to the method known in the prior art, the total acid content and strong acid content of the self-curing ionic liquid prepared were determined by NaOH titration and NaCl ion exchange, respectively, which were 4.83mmol / g and 3.70mmol / g, respectively.

[0036] Example 2-7 Preparation of self-curing ionic liquid

[0037] The preparation process of the self-curing ionic liquid of Example 2-7 is the same as that of Example 1, except that the following sulfonation conditions are changed: "adjusting the mass of 1,3-propane sultone to change the mass ratio of polyethyleneimine and 1,3-propane sultone", "changing the sulfonation temperature", and "changing the sulfonation time". The specific sulfonation conditions changed in Example 2-7, as well as the test results of the total acid content and strong acid content of the obtained self-curing ionic liquid are summarized in Table 1.

[0038] Table 1

[0039]

[0040] In the field of esterification of oleic acid and methanol, the amount of strong acid in the solid acid is positively correlated with the esterification effect.

[0041] Under the sulfonation conditions investigated in the examples of the present invention, self-curing acidic ionic liquids with a large acid content can be prepared. The self-curing ionic liquid obtained in Example 1 has a large acid content and a short sulfonation time. Therefore, the subsequent examples use the self-curing ionic liquid prepared in Example 1 as a raw material, coat it on the surface of the base film and the filler, and further prepare a catalyst coated with a self-curing acidic ionic liquid film, and apply it to the esterification reaction of oleic acid and methanol.

[0042] Example 8 Preparation of ionic liquid catalytic membrane

[0043] A polypropylene film with a diameter of 5 cm is used as the base membrane, the pore size of the base membrane is 0.45 um, and the mass of the base membrane is 0.37 g; the self-curing ionic liquid powder prepared in Example 1 is weighed, heated to 70°C to soften and melt it; it is evenly coated on both sides of the polypropylene film; it is allowed to stand at room temperature for 1 hour, and the coated ionic liquid layer self-cures on both sides of the polypropylene film and covers the surface of the base membrane to prepare an ionic liquid catalytic membrane, which is 0.5 g heavier than the base membrane, so the loading amount of ionic liquid in the catalytic membrane is 57.5%.

[0044] Example 9 Preparation of ionic liquid catalytic membrane filler

[0045] Using a metal wire mesh with a mesh size of 100 as the substrate and a metal wire mesh with a strip structure of 2.5 cm in length and 3 mm in width, refer to the coating method of the ionic liquid in Example 8, and evenly coat the molten ionic liquid in Example 1 on both sides of the metal wire mesh. Let it stand at room temperature for 1 hour to allow the ionic liquid to self-solidify to obtain an ionic liquid catalytic membrane. The coating amount of the ionic liquid is calculated by weighing to be 0.6 g / g substrate, that is, the loading amount of the ionic liquid in the catalytic membrane filler is 37.5%.

[0046] After the ionic liquid to be coated on the metal mesh is self-cured at room temperature to form a film, it is rolled into a column with a diameter of 3 mm and a height of 3 mm, which is the ionic liquid catalytic membrane filler. The bulk density of the catalytic membrane filler is measured to be 520 kg / m 3 , with a specific surface area of ​​2800m 2 / m 3 , the porosity is 93%.

[0047] The photos of the metal wire mesh and the wound cylindrical catalyst membrane filler in Example 9 are shown in FIG. Figure 3 shown.

[0048] Example 10 Application of ionic liquid catalytic membrane in stirred tank

[0049] The self-curing ionic liquid catalytic membrane prepared in Example 8 was cut into pieces of about 1 cm in size to facilitate stirring in the mixed solution in the stirred tank. 10 g of methanol and 10 g of oleic acid were added to a 100 mL stirred tank; 0.5 g of the above catalytic membrane fragments were weighed and added to the mixed solution of methanol and oleic acid; under stirring, the materials in the stirred tank were heated to 64°C and maintained for 3 hours to react; after the reaction was completed, the catalytic membrane was taken out, and the liquid was evaporated to remove methanol and water to obtain methyl oleate product, and the yield of methyl oleate was 91.2%.

[0050] Example 11 Application of ionic liquid catalytic membrane in membrane reactor

[0051] use Figure 1The membrane reactor shown in the figure comprises two square PTFE plates 2 of 100 mm×100 mm×30 mm, and a cylindrical cavity with an inner diameter of 50 mm and a depth of 20 mm is opened in the center of the PTFE plate 2, and the cylindrical cavity is recorded as a reaction chamber 3. An ionic liquid catalytic membrane 4 prepared in Example 8 is sealed between the two PTFE plates 2, and the ionic liquid catalytic membrane 4 is vertically aligned with the two reaction chambers 3, and a rubber gasket 5 is installed between the ionic liquid catalytic membrane 4 and the reaction chamber 3 to play a sealing role. Figure 1 It can be seen that bolt holes are arranged around the PTFE plate 2, and the two PTFE plates are fixed together by being pressed and installed by bolts.

[0052] according to Figure 2 The structural schematic diagram of the reaction device shown in the figure shows a constructed device. Two PTFE plates 2 and the ionic liquid catalytic membrane 4 therebetween constitute a membrane reactor 8. The left sides of the two reaction chambers of the membrane reactor are connected with a feed liquid inlet pipe 1, and the feed liquid inlet pipe 1 is connected to the liquid outlet of the storage tank 9 by a pipeline through a delivery pump 7; the right sides of the two reaction chambers are connected with a feed liquid outlet pipe 6, and the feed liquid outlet pipe 6 is connected to the liquid inlet of the storage tank 9.

[0053] 60g methanol and 60g oleic acid are added to the storage tank, the reaction mass in the storage tank is heated to 64°C, the reaction mass is transported to the reaction chamber of the membrane reactor by a delivery pump, the reaction mass is contacted with the self-curing ionic liquid catalytic membrane for catalytic reaction, the delivery pump flow is adjusted to 28mL / min, under the operation of the delivery pump, the reaction mass circulates and reacts in the system formed by the storage tank, the delivery pump, the reaction chamber and the pipeline, and the reaction time is controlled to be 6h; after the reaction is completed, the liquid in the storage tank is released, and the methanol and water are evaporated to obtain methyl oleate product, and the yield of methyl oleate is 75%. Due to the limited conditions of the laboratory test experiment, the size of the membrane reactor is small, and the amount of the reaction mass contacting the catalytic membrane is relatively small, so the experimental effect is relatively poor, but the experimental results of Example 10 verify the catalytic activity of the catalytic membrane.

[0054] Example 12 Application of ionic liquid catalytic membrane filler in stirred tank

[0055] 10 g of methanol and 10 g of oleic acid were added to a 100 mL stirring kettle; 1.6 g of the self-curing ionic liquid catalytic membrane filler prepared in Example 9 (1 g of filler surface is coated with 0.6 g of self-curing ionic liquid membrane) was weighed and added to the mixed solution of methanol and oleic acid; under stirring, the materials in the kettle were heated to 64°C and maintained for 3 hours to react; after the reaction was completed, the catalytic membrane filler was filtered out, and the liquid was evaporated to remove methanol and water to obtain methyl oleate product, and the yield of methyl oleate was 90.2%.

[0056] Example 13 Application of ionic liquid membrane filler in fixed bed reactor

[0057] Take a glass column with a jacket as a fixed bed reactor, the inner diameter of the glass column is 1cm, and the length is 15cm. 9.5g of the self-curing ionic liquid catalytic membrane filler prepared in Example 9 (1g of filler surface is coated with 0.6g of self-curing ionic liquid membrane) is filled into the glass column, and hot water at a temperature of 65°C is passed into the jacket of the glass column. When the filler temperature in the glass column rises to 60-64°C, a mixed solution of methanol and oleic acid heated to 64°C (the mass ratio of methanol and oleic acid is 1:1) is pumped from the bottom of the fixed bed reactor and overflows from the top. The pump delivery flow rate is adjusted to 0.03mL / min, that is, the mass flow rate of the material is 0.02518g / min, so that the residence time of the material in the fixed bed is 6h; after the overflowing material is evaporated to remove methanol and water, methyl oleate product is obtained, and the yield of methyl oleate is 95.6%.

Claims

1. A method for preparing a catalyst coated with a self-curing ionic liquid membrane, characterized in that Sulfonation of polyethyleneimine yields a self-curing acidic ionic liquid, namely sulfonated polyethyleneimine, which is then coated on the surface of a substrate. The specific steps are as follows: 1) 1,3-propane sultone is heated and melted, and an ethanol solution of polyethyleneimine is added dropwise thereto, and a sulfonation reaction is carried out under heating and stirring. After the reaction is completed, the temperature is lowered, filtered, and the filtered solid is washed with ethanol to remove the unreacted 1,3-propane sultone, and then dried to obtain an acidic self-curing ionic liquid containing a sulfonic acid group; 2) The acidic self-curing ionic liquid of step 1) is heated to above 70°C to make it a viscous liquid, and then evenly coated on the surface of the substrate, and the temperature is lowered to below 50°C to make it self-curing on the surface of the substrate to form an acidic ionic liquid film, thereby obtaining a catalyst with a self-curing ionic liquid film coated on the surface.

2. The method for preparing a catalyst coated with a self-curing ionic liquid membrane according to claim 1, characterized in that The molecular weight of the polyethyleneimine is 50000-100000, preferably 60000-70000, and the mass fraction of the polyethyleneimine ethanol solution is 30-70%.

3. The method for preparing a catalyst coated with a self-curing ionic liquid membrane according to claim 1, characterized in that The mass ratio of polyethyleneimine to 1,3-propane sultone is 1:1-5, preferably 1:3-5, the sulfonation temperature is 40-70°C, preferably 50-60°C, and the sulfonation time is 8-12h.

4. The method for preparing a catalyst coated with a self-curing ionic liquid membrane according to claim 1, characterized in that The substrate is a base film or a filler, the base film is a polypropylene film, a polyvinylidene fluoride film or a nylon film, the corresponding catalyst is a self-curing ionic liquid catalytic membrane, and the loading amount of the ionic liquid in the catalyst is 30-60%; the filler is a plastic filler or a metal filler, the corresponding catalyst is a self-curing ionic liquid catalytic membrane filler, and the loading amount of the ionic liquid in the catalyst is 20-50%.

5. A catalyst coated with a self-curing ionic liquid membrane prepared by the method according to any one of claims 1 to 4.

6. Use of a catalyst coated with a self-curing ionic liquid membrane as claimed in claim 5 in catalytic esterification of oleic acid, wherein the reactor for the catalytic esterification reaction is a stirred tank, a membrane reactor or a fixed bed reactor.

7. The use according to claim 6, characterized in that When the reactor is a stirred tank, the catalytic reaction steps are as follows: 1) Add methanol and oleic acid into a stirred tank, with the mass ratio of methanol to oleic acid being 1:0.8-1.2; 2) Add the catalyst into the stirred tank, the mass of the catalyst is 5%-16% of the mass of oleic acid; 3) Heat the materials in the stirring kettle to 60-70°C for reaction under stirring, and the reaction time is 2-4h; 4) After the reaction is completed, the catalyst is filtered out and separated, and the reaction liquid is distilled to remove methanol and water to obtain methyl oleate product.

8. The use according to claim 6, characterized in that When the reactor is a membrane reactor, the catalytic reaction steps are as follows: S1: The catalyst is a self-curing ionic liquid catalytic membrane, and the membrane reactor comprises the self-curing ionic liquid catalytic membrane and two reaction chambers, the self-curing ionic liquid catalytic membrane is sealed and arranged between the two reaction chambers, the liquid outlets of the two reaction chambers are connected to the liquid inlet of the storage tank through pipelines, and the liquid inlets of the two reaction chambers are connected to the liquid outlet of the storage tank through pipelines through delivery pumps; S2: Methanol and oleic acid are added to the storage tank at a mass ratio of 1:0.8-1.2, and the reaction materials in the storage tank are heated to 60-70°C, and then the reaction materials are transported to the reaction chamber of the membrane reactor by a delivery pump, and the delivery flow rate of the delivery pump is 20-50mL / min. The reaction materials are in contact with the self-curing ionic liquid catalytic membrane for catalytic reaction. Under the operation of the delivery pump, the reaction materials circulate and react in the system formed by the storage tank, the delivery pump, the reaction chamber and the pipeline, and the reaction time is controlled to be 4-8h; S3: After the reaction is completed, the liquid in the storage tank is released, and methanol and water are removed by distillation to obtain methyl oleate product.

9. The use according to claim 6, characterized in that When the reactor is a fixed bed reactor, the catalytic reaction steps are as follows: Step 1: The catalyst is a self-curing ionic liquid catalytic membrane filler, and the catalyst is filled in a fixed bed reactor. A heat preservation jacket is arranged outside the fixed bed reactor, and hot water at 60-70° C. is passed into the heat preservation jacket; Step 2: Methanol and oleic acid are mixed in a mass ratio of 1:0.8-1.2, and the reaction mixture is heated to 60-70°C and then input from the bottom of the fixed bed reactor and overflowed from the top. The residence time of the reaction mixture in the fixed bed reactor is controlled to be 4-8h; Step 3: The overflow material is evaporated to remove methanol and water to obtain methyl oleate product.

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