A method for preparing a self-microporous polymer acidic solid catalyst

Abstract

The application discloses a self-microporous polymer acidic solid catalyst, a preparation method thereof and application of the self-microporous polymer acidic solid catalyst in catalytic production of biodiesel in an esterification reaction, and belongs to the technical field of catalysts. The self-microporous polymer is used as a raw material, hydrazine hydrate is used to reduce nitrile groups of the self-microporous polymer, the self-microporous polymer with amino groups is prepared, and then a sulfonated reaction is carried out on the self-microporous polymer with amino groups by using a sulfonic acid lactone, so that the acidic solid catalyst with sulfonic acid groups and high specific surface area is prepared. The self-microporous polymer acidic solid catalyst prepared in the application has excellent catalytic performance in catalytic production of biodiesel in an esterification reaction, is easy to separate and recover, and has excellent reusability. Therefore, the self-microporous polymer acidic solid catalyst with sulfonic acid groups prepared in the application has important significance for promoting production of biodiesel.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and particularly relates to a self-microporous polymer acidic solid catalyst, a preparation method thereof and application thereof in the production of biodiesel by catalytic esterification reaction. BACKGROUND

[0002] Biodiesel is a green renewable energy and a main energy that can replace traditional petrochemical fuels. Acid-catalyzed esterification is an important way to produce biodiesel. At present, catalysts for esterification reaction to produce biodiesel are mostly inorganic acid and base catalysts such as concentrated sulfuric acid and sodium hydroxide. The use of such catalysts will cause equipment corrosion, recovery difficulty, environmental pollution and other problems, affecting the large-scale production of biodiesel. In recent years, ionic liquids as a new type of green and efficient catalyst can be used to replace traditional catalysts to catalyze the production of biodiesel. However, there are problems such as recovery difficulty. By loading ionic liquids on high molecular polymers, the problem of recovery difficulty is solved, but there are disadvantages such as small specific surface area and low catalytic activity. At the same time, the protonic acid for catalyzing biodiesel production by using solid-supported ionic liquids is mainly obtained by adding an external acid. During the reaction process, the protonic acid will be lost with the external acid in the reaction, thereby reducing the activity and poor reusability.

[0003] Fuel (2017, 188: 483-488) reported an acidic ionic liquid catalyst for catalyzing the transesterification reaction of rapeseed oil to produce biodiesel. First, an imidazole and 1,3-propanesulfonic acid lactone were used for sulfonation reaction, and then sulfuric acid was added for acidification, thereby preparing an imidazole ionic liquid catalyst, which was used for transesterification reaction. Under the conditions of a reaction temperature of 130℃, a mass fraction of 1-butylsulfonic acid-3-methylimidazole hydrogen sulfate ([BSO3HMIM][HSO4]) of 2%, a molar ratio of alcohol to oil of 12:1 and a reaction time of 3h, the yield of FAME was the highest. Under the optimal conditions, the yield of FAME was the highest and could reach 100% when [BSO3HMIM][HSO4] was used as the catalyst. However, the reaction conditions are harsh, the catalyst is difficult to recover and the repeatability is poor.

[0004] Energy Conversion and Management (2017, 231: 458-467) reported an ionic liquid catalyst, namely 3-(2,3-dihydroxypropyl)-1-methyl-1H-imidazole-3-hydroxide (DFImIL-OH - ) and poly(3-benzyl-1-(4-(sec-butyl)benzyl)-1H-benzimidazol-3-hydroxide) (PIL(OH - )). It was found that among all the synthesized catalysts, the benzimidazole-based The ionic liquid catalyst (BBAIL) is the best catalyst for catalyzing the ester exchange reaction of castor oil to prepare biodiesel. When the molar ratio of methanol to castor oil is 12:1, the reaction temperature is 40 DEG C, the reaction time is 14 h, and the catalyst dosage is 5 wt%, the biodiesel yield reaches 96%. The synthesized BBAIL catalyst in the study is difficult to recover, and the catalyst recycling performance is poor.

[0005] To solve the above problems, a self-porous polymer acidic solid catalyst with good catalytic performance, good stability and easy recovery and reuse is developed, which is of great significance for the production of biodiesel. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a self-porous polymer acidic solid catalyst, in order to overcome the technical defects of the existing catalysts for esterification reaction to produce biodiesel.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] A preparation method of a self-porous polymer acidic solid catalyst, comprising the following steps: dissolving a self-porous polymer PIM-1 in an organic solvent, then adding hydrazine hydrate into the PIM-1 solution to carry out a reduction reaction, synthesizing a self-porous polymer with amino groups (H-PIM-1), then reacting the H-PIM-1 with a sulfonic acid lactone to synthesize a self-porous polymer with sulfonic acid groups, and then precipitating, repeatedly washing and drying the reaction product to obtain a self-porous polymer acidic solid catalyst (H-PIM-PS).

[0009] The structural formula of the PIM-1 is as follows:

[0010]

[0011] The H-PIM-1 is composed of amino-containing repeating units and amino-free repeating units, and the structural formula is as follows:

[0012]

[0013] Wherein n=0.2%-100%, that is, the reduction degree of H-PIM-1.

[0014] The H-PIM-PS is composed of sulfonic acid group-containing repeating units and sulfonic acid group-free repeating units, and the structural formula is as follows:

[0015]

[0016] Wherein n=0-100%, that is, the sulfonation degree of H-PIM-PS.

[0017] The organic solvent used for dissolving H-PIM-1 is tetrahydrofuran, 1,4-dioxane or N,N-dimethylformamide.

[0018] The concentration of H-PIM-1 is 10wt%-60wt%.

[0019] The sulfolane is 1,3-propanesulfone or 1,4-butanesulfone.

[0020] The molar ratio of the repeat unit containing amino group in H-PIM-1 to the sulfolane is 1:1-20.

[0021] The reaction temperature of H-PIM-1 and the sulfolane is 30℃-70℃, and the reaction time is 4h-24h.

[0022] The self-porous polymer PIM-1 with high specific surface area is used as the starting material, hydrazine hydrate is used to reduce the nitrile group contained in PIM-1 to obtain the self-porous polymer (H-PIM-1) containing amino group, and then the sulfolane is used to modify H-PIM-1 to obtain the self-porous polymer acidic solid catalyst with sulfonic acid group. The self-porous polymer acidic solid catalyst provided by the application has the following advantages: (1) the self-porous polymer has ultra-high specific surface area to provide more contact area with reactants, thereby improving the catalytic activity; (2) the sulfonic acid group is introduced into the self-porous polymer through chemical reaction, and the stability is good; (3) the catalyst obtained by modification is a solid, which is easy to separate and recycle, and has excellent reusability; (4) the sulfonation degree can be controlled by adjusting the input amount of 1,3-propanesulfone, and the self-porous polymer acidic solid catalyst with the best performance can be selected for biodiesel production. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 FT-IR spectrum of PIM-1, H-PIM-1 and H-PIM-PS synthesized in Example 1 1 H NMR spectrum.

[0024] Figure 2 FT-IR spectrum of PIM-1, H-PIM-1 and H-PIM-PS synthesized in Example 1 1 H NMR spectrum.

[0025] Figure 3 FT-IR spectrum of PIM-1, H-PIM-1 and H-PIM-PS synthesized in Example 1 DETAILED DESCRIPTION

[0026] In order to make the content of the present application more convenient to understand, the technical solutions of the present application are further described below in combination with specific embodiments, but the present application is not limited to this.

[0027] The chemical reagents used in the embodiments of the present application are commercially available.

[0028] Example 1

[0029] Dissolve 19.86 g of catechol in a mixed solution of 44 mL of hydrobromic acid and 40 mL of glacial acetic acid, after complete dissolution, add 28 mL of acetone dropwise, and react at 120℃ for 12 h to obtain a red-brown reaction liquid. Pour the red-brown reaction liquid into a large amount of deionized water to precipitate brown solid, and wash with glacial acetic acid repeatedly to obtain white product, which is TTSBI, and place it in a 80℃ oven for drying. The synthesis reaction of PIM-1 uses a high-temperature method, sequentially add 10.212 g of dried TTSBI, 6.027 g of tetrafluoro-p-phenyldinitrile and 10.365 g of K2CO3 into a flask, then add 70 mL of anhydrous N-methylpyrrolidone to start stirring, and quickly place it in an oil bath at 155℃, then add 30 mL of anhydrous toluene, and react for 6 h under a nitrogen atmosphere. As the reaction time is prolonged, the viscosity of the reaction system gradually increases, and finally a bright yellow viscous mixture is obtained. After the reaction is completed, pour the mixture into methanol to obtain a bright yellow block solid, and wash with methanol and water repeatedly. After drying, dissolve the product in chloroform, filter using non-woven fabric, then precipitate the dissolved solution in methanol repeatedly for several times to obtain the final PIM-1, and place it in a 80℃ vacuum oven for drying for 16 h. Dissolve 2 g of PIM-1 in 100 mL of tetrahydrofuran, and place it in a 60℃ constant-temperature water bath, then add 40 mL of hydrazine hydrate and 0.2 g of palladium-carbon, and react for 24 h under a nitrogen atmosphere. After the reaction is completed, separate the palladium-carbon and the reaction liquid by filtration, pour the reaction liquid into methanol to precipitate yellow solid, and obtain a self-porous polymer with amino groups (H-PIM-1), then wash repeatedly with methanol until clean, and place it in a 80℃ oven for drying for 12 h.

[0030] Dissolve 1 g of dried self-porous polymer H-PIM-1 in 50 mL of tetrahydrofuran, and slowly add it dropwise to 0.2376 g of 1,3-propanesultone using a constant-pressure dropping funnel, and react for 24 h at 60℃. After the reaction is completed, pour the reaction liquid into methanol to precipitate brown solid. Wash repeatedly with methanol until clean, and place it in a 80℃ oven for drying for 12 h. After drying, soak it in 0.1 mol / L aqueous hydrochloric acid for 12 h to ensure that the sulfonic acid group is converted into H + type, then wash with deionized water until neutral, and finally place the prepared sulfonated self-porous polymer H-PIM-PS in a 60℃ constant-temperature drying oven for drying for 12 h. The acid exchange capacity of H-PIM-PS is measured to be 1.03 mmol / g.

[0031] The H-PIM-PS prepared in this example was used as catalyst to catalyze the esterification reaction of oleic acid and methanol to produce biodiesel, so as to evaluate the performance of the H-PIM-PS in catalyzing the production of biodiesel. Specifically, 3 g of oleic acid was mixed with 4.078 g of methanol (the molar ratio of methanol to oleic acid was 12:1), and then 0.35 g of the catalyst H-PIM-PS (the mass concentration was 5 wt%) was added. The reaction temperature was 70°C, and the reaction time was 2 h. Under the above conditions, biodiesel was produced. After the reaction was completed, the solid H-PIM-PS was recovered by filtration. The experimental results showed that the conversion rate of oleic acid was 72.5%, indicating that the catalyst H-PIM-PS-1 had excellent catalytic performance. The H-PIM-PS-1 was subjected to six repeated experiments of the above esterification reaction for the preparation of biodiesel. The results showed that after being used repeatedly for six times, the conversion rate of oleic acid remained unchanged, indicating that the H-PIM-PS had excellent stability. Moreover, the recovery rate of the H-PIM-PS after the reaction was >99%, indicating that the H-PIM-PS had excellent reusability.

[0032] Example 2

[0033] The H-PIM-PS was prepared from the same amino-containing microporous polymer H-PIM-1 as in Example 1. 1 g of H-PIM-1 was dissolved in 50 mL of tetrahydrofuran, and was slowly added dropwise to 1.1881 g of 1,3-propanesultone using a constant pressure dropping funnel, and was reacted at 30°C for 4 h. After the reaction was completed, it was poured into methanol to precipitate, and was repeatedly washed with methanol until it was clean. Then it was soaked in 0.1 mol / L hydrochloric acid aqueous solution for 12 h to ensure that the sulfonic acid group was H + The prepared catalyst H-PIM-PS was dried in a constant temperature drying box at 60°C for 12 h. Finally, the self-microporous polymer acidic solid catalyst H-PIM-PS was obtained. The acid exchange capacity of the H-PIM-PS was measured to be 0.76 mmol / g.

[0034] The catalyst H-PIM-PS prepared in this example was used to test its catalytic performance in the esterification reaction for the production of biodiesel under the same reaction conditions as in Example 1. The results showed that the conversion rate of oleic acid was 66.4%. Then the H-PIM-PS was subjected to six repeated experiments of the above esterification reaction for the preparation of biodiesel. The experimental results showed that the conversion rate of oleic acid remained unchanged, indicating that the H-PIM-PS had excellent stability. At the same time, the recovery rate of the H-PIM-PS after the reaction was >99%, indicating that the H-PIM-PS had excellent reusability.

[0035] Example 3

[0036] H-PIM-PS was prepared using the same amino-containing microporous polymer H-PIM-1 as in Example 1. 1 g of H-PIM-1 was dissolved in 50 mL of 1,4-dioxane, and was slowly added to 2.3762 g of 1,3-propanesultone using a constant pressure dropping funnel, and was reacted at 40 °C for 8 h. After the reaction was completed, it was poured into methanol to precipitate, and was repeatedly washed with methanol until clean. Then, it was soaked in 0.1 mol / L aqueous hydrochloric acid for 12 h to ensure that the sulfonic acid group was H + The H-PIM-PS was dried in a constant temperature drying oven at 60 °C for 12 h. Finally, the self-microporous polymer acidic solid catalyst H-PIM-PS was obtained. The acid exchange capacity of H-PIM-PS was measured to be 1.22 mmol / g.

[0037] The catalyst H-PIM-PS prepared in this example was tested for its catalytic performance in the esterification reaction for the production of biodiesel under the same reaction conditions as in Example 1. The results showed that the conversion rate of oleic acid was 86.4%. Then, the H-PIM-PS was subjected to 6 repeated experiments of the above-mentioned esterification reaction for the production of biodiesel, and the experimental results showed that the conversion rate of oleic acid remained unchanged, indicating that the H-PIM-PS had excellent stability. At the same time, the recovery rate of H-PIM-PS after the reaction was >99%, indicating that the H-PIM-PS had excellent reusability.

[0038] Example 4

[0039] H-PIM-PS was prepared using the same amino-containing microporous polymer H-PIM-1 as in Example 1. 1 g of H-PIM-1 was dissolved in 50 mL of tetrahydrofuran, and was slowly added to 4.7525 g of 1,3-propanesultone using a constant pressure dropping funnel, and was reacted at 50 °C for 24 h. After the reaction was completed, it was poured into methanol to precipitate, and was repeatedly washed with methanol until clean. Then, it was soaked in 0.1 mol / L aqueous hydrochloric acid for 12 h to ensure that the sulfonic acid group was H + The H-PIM-PS was dried in a constant temperature drying oven at 60 °C for 12 h. Finally, the self-microporous polymer acidic solid catalyst H-PIM-PS was obtained. The acid exchange capacity of H-PIM-PS was measured to be 1.59 mmol / g.

[0040] The catalyst H-PIM-PS prepared in this example was tested for its catalytic performance in the esterification reaction for the production of biodiesel under the same reaction conditions as in Example 1. The results showed that the conversion rate of oleic acid was 89.9%. Then the H-PIM-PS was subjected to 6 repeated experiments of the above-mentioned esterification reaction for the production of biodiesel, and the experimental results showed that the conversion rate of oleic acid remained unchanged, indicating that the H-PIM-PS had excellent stability. At the same time, the recovery rate of H-PIM-PS after the reaction was >99%, indicating that the H-PIM-PS had excellent reusability.

[0041] Example 5

[0042] The H-PIM-PS was prepared from the same amino-containing microporous polymer H-PIM-1 as in Example 1. The H-PIM-1 was dissolved in 50 mL of N,N-dimethylformamide and slowly added dropwise to 2.3762 g of 1,3-propanesultone using a constant pressure dropping funnel at 60°C for 24 h. After the reaction was completed, it was poured into methanol to precipitate and washed repeatedly with methanol until it was clean. Then it was soaked in 0.1 mol / L hydrochloric acid solution for 12 h to ensure that the sulfonic acid group was H + type, and repeatedly washed with deionized water until it was neutral. Finally, the prepared catalyst H-PIM-PS was placed in a constant temperature drying oven at 60°C for 12 h. Finally, the microporous polymer acidic solid catalyst H-PIM-PS was obtained. The acid exchange capacity of H-PIM-PS was measured to be 1.78 mmol / g.

[0043] The catalyst H-PIM-PS prepared in this example was tested for its catalytic performance in the esterification reaction for the production of biodiesel under the same reaction conditions as in Example 1. The results showed that the conversion rate of oleic acid was 89.9%. Then the H-PIM-PS was subjected to 6 repeated experiments of the above-mentioned esterification reaction for the production of biodiesel, and the experimental results showed that the conversion rate of oleic acid remained unchanged, indicating that the H-PIM-PS had excellent stability. At the same time, the recovery rate of H-PIM-PS after the reaction was >99%, indicating that the H-PIM-PS had excellent reusability.

[0044] Example 6

[0045] The microporous polymer acidic solid catalyst was prepared in a similar manner as in Example 1, except that the degree of amination was changed to 20%. The acid exchange capacity of the final microporous polymer acidic solid catalyst was 0.62 mmol / g, and under the same reaction conditions as in Example 1, the conversion rate of oleic acid was 63.8%. This indicates that the degree of amination of the amino-containing microporous polymer will affect the degree of sulfonation, thereby affecting the acid exchange capacity and catalytic performance of the microporous polymer acidic solid catalyst.

[0046] Example 7

[0047] The self-microporous polymer acidic solid catalyst was prepared by the similar method of Example 1, only the solvent of the reaction was changed to 1,4-dioxane. The acid exchange capacity of the prepared self-microporous polymer acidic solid catalyst was 1.10 mmol / g, and under the same reaction conditions as in Example 2, the conversion rate of oleic acid was 74.8%. It is illustrated that changing the reaction solvent does not affect the acid exchange capacity and catalytic performance of H-PIM-PS.

[0048] Example 8

[0049] The self-microporous polymer acidic solid catalyst was prepared by the similar method of Example 1, only the amount of tetrahydrofuran added was changed to 100 mL. The acid exchange capacity of the prepared self-microporous polymer acidic solid catalyst was 0.95 mmol / g, and under the same reaction conditions as in Example 1, the conversion rate of oleic acid was 69.3%. It is illustrated that the amount of solvent added does not affect the acid exchange capacity and catalytic performance of the prepared H-PIM-PS.

[0050] Example 9

[0051] The self-microporous polymer acidic solid catalyst was prepared by the similar method of Example 1, only the temperature was changed to 70°C. The acid exchange capacity of the prepared self-microporous polymer acidic solid catalyst was 1.26 mmol / g, which illustrates that changing the reaction temperature affects the modification degree, further affecting the acid exchange capacity and catalytic performance of the catalyst.

[0052] Example 10

[0053] The self-microporous polymer acidic solid catalyst was prepared by the similar method of Example 1, only 1,3-propane sulfonate was changed to 1,4-butane sulfonate. The acid exchange capacity of the prepared self-microporous polymer acidic solid catalyst was 1.22 mmol / g, which illustrates that the type of sulfonate has little effect on the modification degree.

[0054] The above example results show that the self-microporous polymer (H-PIM-1) with different amination degrees is selected as the raw material for modification and grafting of a large number of sulfonic acid groups. The self-microporous polymer acidic solid catalyst H-PIM-PS with excellent catalytic performance is prepared by utilizing the catalytic activity of sulfonic acid groups in esterification reaction of free fatty acids and short-chain alcohols. The catalyst is applied in the catalytic production of biodiesel, which can meet the requirements of actual industrial application and has important significance for large-scale production of biodiesel.

[0055] The above merely describes preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A process for the preparation of a self-microporous polymeric acidic solid catalyst, characterized by: The self-porous polymer PIM-1 is dissolved in an organic solvent to obtain a PIM-1 solution, hydrazine hydrate is added to perform a reduction reaction, and a self-porous polymer H-PIM-1 with amino groups is synthesized; the H-PIM-1 is reacted with a sulfonic acid lactone to synthesize a self-porous polymer with sulfonic acid groups, and the self-porous polymer acid solid catalyst H-PIM-PS is obtained through cleaning and drying treatment. The structural formula of the H-PIM-1 is as shown in the following formula: wherein n = 0.2%-100%; The concentration of the H-PIM-1 in the PIM-1 solution is 10-60wt%; The molar ratio of the amino-containing repeating units of the H-PIM-1 to the sulfonic acid lactone is 1:1-20.

2. The method of claim 1, wherein: The organic solvent is one of tetrahydrofuran, 1,4-dioxane and N,N-dimethylformamide.

3. The method of claim 1, wherein: The sulfonic acid lactone is 1,3-propanesulfonic acid lactone or 1,4-butanesulfonic acid lactone.

4. The method of claim 1, wherein: The reaction temperature of the H-PIM-1 and the sulfonic acid lactone is 30-70℃, and the reaction time is 4-24h. 5.A self-porous polymer acid solid catalyst prepared by the method according to any one of claims 1-4. 6.The application of a self-porous polymer acid solid catalyst prepared by the method according to any one of claims 1-4 in catalytic preparation of biodiesel in an esterification reaction.

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