Preparation method of a PPS fiber-supported acid-base bifunctional catalyst and its application in catalyzing the conversion of glucose into HMF

Abstract

The present invention discloses a method for preparing an acid-base bifunctional PPS fiber and its application in catalyzing the conversion of glucose into HMF, comprising the steps of reacting the cleaned PPS fiber with trimethylchlorosilane to obtain a chloromethylated PPS fiber, and then reacting the fiber with an acid-base bifunctional small molecule to prepare a PPS-supported acid-base bifunctional catalyst. The catalyst exhibits excellent catalytic activity in catalyzing the conversion of glucose into 5-hydroxymethylfurfural (HMF), with advantages such as a short reaction time, high reaction yield, a green solvent, and good recyclability. Furthermore, the PPS catalyst has high flexibility and can be woven into various shapes, making it convenient for filling an industrial fixed bed, thus having potential industrial application value.

Description

Technical Field

[0001] The invention belongs to the field of green catalytic biomass conversion and relates to a method for biomass conversion by catalyzing acid-base dual-functional PPS fibers. Background Art

[0002] 5-Hydroxymethylfurfural (HMF) is an important chemical platform compound that can be further transformed into a variety of high-value-added chemicals. Producing HMF from cellulose is the most promising route, where the isomerization of glucose to fructose is a crucial step influencing the efficiency of cellulose conversion to various compounds, including HMF.

[0003] Lewis bases are highly effective catalysts for the isomerization of glucose to fructose, while Bronsted acids are highly effective catalysts for the dehydration of fructose to HMF. Industrially, fructose is primarily produced by glucose isomerization. However, the isolation and purification of fructose is very expensive. Therefore, it is desirable to produce HMF from glucose in a single reactor for both the isomerization and fructose dehydration reactions. However, achieving high HMF selectivity using catalysts with a single active site is difficult. Therefore, developing catalysts with both acidic and base active sites is key to achieving the direct conversion of glucose to HMF.

[0004] Polyphenylene sulfide (PPS) fibers, as chemically synthesized fibers, possess high thermal stability, high strength, and excellent heat and chemical resistance. This study uses PPS fibers as carriers to prepare a series of PPS-based acid-base bifunctional catalysts through a two-step reaction process. These catalysts are then applied to catalyze the conversion of glucose to HMF. The catalysts are highly efficient, can meet a variety of complex reaction conditions, and exhibit excellent flexibility and stability, thus possessing significant potential for industrial application. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention proposes a method for preparing a PPS fiber-supported acid-base bifunctional catalyst and its application in catalyzing the conversion of glucose into HMF. Specifically, the present invention provides a method for synthesizing HMF catalyzed by an acid-base bifunctional PPS with a simple preparation process, high catalytic activity, and good recycling performance, thereby solving the problems of existing small molecule catalysts being non-recyclable, polluting the environment, and wasting resources in the HMF synthesis process.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing a PPS fiber-supported acid-base dual-function catalyst comprises the following steps:

[0008] (1) PPS fibers are placed in different solvents and heated under reflux, and then rinsed and dried to obtain pretreated PPS fibers;

[0009] (2) Chloromethylation of PPS fiber: pretreated PPS fiber, paraformaldehyde, tin tetrachloride, trimethylsilyl chloride and 1,2-dichloroethane were added to a hydrothermal reactor and placed in an oven for reaction. After the reaction was completed, the fiber was taken out and cleaned with ethanol, and dried to obtain chloromethylated PPS fiber PPS-Cl;

[0010] (3) Preparation of PPS-supported acid-base bifunctional catalyst: Chloromethylated PPS fiber PPS-Cl, acid-base bifunctional small molecules, base and distilled water were added to a hydrothermal reactor and reacted in an oven. The fiber was then removed and cleaned with ethanol and dried to obtain the PPS-supported acid-base bifunctional catalyst.

[0011] Furthermore, in step (1), the solvent is ethanol, cyclohexane, distilled water or acetone; the mass volume ratio of PPS fiber to solvent is 1:15-1:30 g / mL, and the reflux time is 4-10 h.

[0012] Furthermore, in step (2), the reaction solution consists of paraformaldehyde, tin tetrachloride, trimethylchlorosilane and 1,2-dichloroethane, the mass volume ratio of PPS fiber to the reaction solution is 1:20-1:80 g / mL, and the molar concentrations of paraformaldehyde, tin tetrachloride and trimethylchlorosilane in the reaction solution are 0.5-1.5 mol / L, 0.25-0.75 mol / L and 0.5-1.5 mol / L, respectively.

[0013] Furthermore, the reaction temperature in step (2) is 50-100° C., and the reaction time is 24-72 h.

[0014] Furthermore, in step (3), the acid-base bifunctional small molecule is one of glycine, taurine and p-aminobenzenesulfonic acid.

[0015] Furthermore, in step (3), the base is one of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

[0016] Furthermore, in step (3), the reaction solution is composed of an acid-base bifunctional small molecule, a base and distilled water, and the mass volume ratio of the chloromethylated PPS fiber PPS-Cl to the reaction solution is 1:15-1:50 g / mL; in the reaction solution, the molar concentration of the acid-base bifunctional molecule is 0.1-0.5 mol / L, and the molar ratio of the acid-base bifunctional molecule to the base is 1:1.

[0017] Furthermore, in step (3), the reaction temperature is 60-150° C., and the reaction time is 6-24 h.

[0018] Furthermore, the acid-base bifunctional PPS fiber catalyst prepared by the present invention is used to catalyze the conversion of glucose to prepare HMF.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] This invention prepares an acid-base bifunctional PPS fiber and uses it to catalyze the conversion of glucose into HMF. This catalyst features a simple preparation process, excellent catalytic effect, easy separation, and good recycling performance. This effectively addresses the issues of existing small molecule catalysts, such as the lack of recycling, environmental pollution, and high cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the preparation route of PPS fiber-supported acid-base bifunctional catalyst.

[0022] Figure 2 Schematic diagram of catalytic conversion of glucose to produce HMF. DETAILED DESCRIPTION

[0023] Below in conjunction with specific embodiment, the present invention will be further described.Should be understood that the following examples are only used to illustrate the present invention and are not used to limit the scope of the present invention, and those skilled in the art in this field can make some non-essential improvements and adjustments according to the content of the foregoing invention.Unindicated specific experimental steps or conditions in the embodiment, the operation or condition of the conventional experimental steps described in the document in this area can be carried out.Reagents used or instruments are not indicated by manufacturers, and are all conventional reagent products that can be obtained by commercial purchase.

[0024] In the following examples, the schematic diagram of the preparation route of the PPS fiber-supported acid-base dual-functional catalyst is as follows: Figure 1 shown.

[0025] Example 1

[0026] The preparation method of the acid-base dual-function PPS catalyst of this embodiment is as follows:

[0027] (1) 5 g of PPS fiber and 75 mL of cyclohexane were refluxed and stirred in a round-bottom flask for 4 h, then the fiber was taken out and placed in a round-bottom flask containing 75 mL of ethanol and refluxed and stirred for 4 h, and then the pretreated PPS fiber was rinsed and dried.

[0028] (2) Chloromethylation of PPS fiber: 1 g of PPS fiber was added to 20 mL of a 1,2-dichloroethane solution of paraformaldehyde, tin tetrachloride, and trimethylchlorosilane, where the molar concentrations of paraformaldehyde, tin tetrachloride, and trimethylchlorosilane were 0.5 mol / L, 0.25 mol / L, and 0.5 mol / L, respectively. The fiber and solution mixture was added to a hydrothermal kettle and reacted in an oven at 50°C for 24 h. The fiber was then removed and cleaned with ethanol and dried to obtain the chloromethylated PPS fiber PPS-Cl.

[0029] (3) Preparation of PPS-supported acid-base bifunctional catalyst: 1 g of PPS-Cl fiber was added to 15 mL of an aqueous solution of glycine and sodium bicarbonate, where the molar concentrations of glycine and sodium bicarbonate were 0.1 mol / L, respectively. The fiber-solution mixture was placed in a hydrothermal autoclave and reacted at 60°C for 6 h. The fiber catalyst was removed and washed with distilled water until neutral. After drying, the PPS fiber-supported acid-base bifunctional catalyst PPS-NCOOH was obtained.

[0030] Example 2

[0031] The preparation method of the acid-base dual-function PPS catalyst of this embodiment is as follows:

[0032] (1) 5 g of PPS fiber and 100 mL of cyclohexane were refluxed and stirred in a round-bottom flask for 6 h, then the fiber was taken out and placed in a round-bottom flask containing 100 mL of ethanol and refluxed and stirred for 6 h, and then the pretreated PPS fiber was rinsed and dried.

[0033] (2) Chloromethylation of PPS fiber: 1 g of PPS fiber was added to 40 mL of a 1,2-dichloroethane solution of paraformaldehyde, tin tetrachloride, and trimethylsilyl chloride, where the molar concentrations of paraformaldehyde, tin tetrachloride, and trimethylsilyl chloride were 0.8 mol / L, 0.4 mol / L, and 0.8 mol / L, respectively. The fiber-solution mixture was added to a hydrothermal autoclave and allowed to react in an oven at 60°C for 40 h. The fiber was then removed, cleaned with ethanol, and dried to obtain the chloromethylated PPS fiber PPS-Cl.

[0034] (3) Preparation of PPS-supported acid-base bifunctional catalyst: 1 g of PPS-Cl fiber was added to 30 mL of an aqueous solution of taurine and sodium hydroxide, where the molar concentrations of taurine and sodium hydroxide were 0.2 mol / L, respectively. The fiber-solution mixture was added to a hydrothermal reactor and reacted at 90°C for 12 h. The fiber catalyst was removed and washed with distilled water until neutral. After drying, the PPS fiber-supported acid-base bifunctional catalyst PPS-NSO3H was obtained.

[0035] Example 3

[0036] The preparation method of the acid-base dual-function PPS catalyst of this embodiment is as follows:

[0037] (1) 5 g of PPS fiber and 120 mL of cyclohexane were refluxed and stirred in a round-bottom flask for 8 h, then the fiber was taken out and placed in a round-bottom flask containing 120 mL of ethanol and refluxed and stirred for 8 h, and then the pretreated PPS fiber was rinsed and dried.

[0038] (2) Chloromethylation of PPS fiber: 1 g of PPS fiber was added to 60 mL of a 1,2-dichloroethane solution of paraformaldehyde, tin tetrachloride, and trimethylsilyl chloride, where the molar concentrations of paraformaldehyde, tin tetrachloride, and trimethylsilyl chloride were 1.2 mol / L, 0.6 mol / L, and 1.2 mol / L, respectively. The fiber-solution mixture was added to a hydrothermal autoclave and allowed to react in an 80°C oven for 56 h. The fiber was then removed, cleaned with ethanol, and dried to obtain the chloromethylated PPS fiber PPS-Cl.

[0039] (3) Preparation of PPS-supported acid-base bifunctional catalyst: 1 g of PPS-Cl fiber was added to 40 mL of an aqueous solution of taurine and potassium bicarbonate, where the molar concentrations of taurine and potassium bicarbonate were 0.35 mol / L, respectively. The fiber-solution mixture was placed in a hydrothermal autoclave and reacted at 120°C for 18 h. The fiber catalyst was removed and washed with distilled water until neutral. After drying, the PPS fiber-supported acid-base bifunctional catalyst PPS-NSO3H was obtained.

[0040] Example 4

[0041] The preparation method of the acid-base dual-function PPS catalyst of this embodiment is as follows:

[0042] (1) 5 g of PPS fiber and 150 mL of cyclohexane were refluxed and stirred in a round-bottom flask for 10 h, then the fiber was taken out and placed in a round-bottom flask containing 150 mL of ethanol and refluxed and stirred for 10 h, and then the pretreated PPS fiber was rinsed and dried.

[0043] (2) Chloromethylation of PPS fiber: 1 g of PPS fiber was added to 80 mL of a 1,2-dichloroethane solution of paraformaldehyde, tin tetrachloride, and trimethylchlorosilane, where the molar concentrations of paraformaldehyde, tin tetrachloride, and trimethylchlorosilane were 1.5 mol / L, 0.75 mol / L, and 1.5 mol / L, respectively. The fiber-solution mixture was added to a hydrothermal autoclave and reacted in an oven at 100°C for 72 h. The fiber was then removed, cleaned with ethanol, and dried to obtain the chloromethylated PPS fiber PPS-Cl.

[0044] (3) Preparation of PPS-supported acid-base bifunctional catalyst: 1 g of PPS-Cl fiber was added to 50 mL of an aqueous solution of p-aminobenzenesulfonic acid and potassium hydroxide, where the molar concentrations of p-aminobenzenesulfonic acid and potassium hydroxide were 0.5 mol / L, respectively. The fiber-solution mixture was added to a hydrothermal autoclave and reacted at 150°C for 24 h. The fiber catalyst was removed and washed with distilled water until neutral. After drying, the PPS fiber-supported acid-base bifunctional catalyst PPS-NPhSO3H was obtained.

[0045] Comparative Example 1

[0046] The preparation method of the monofunctional PPS catalyst of this comparative example is as follows:

[0047] (1) Same as Example 2.

[0048] (2) Same as Example 2.

[0049] (3) Preparation of PPS-supported alkali monofunctional catalyst: 1 g of PPS-Cl fiber was added to 30 mL of an aqueous solution of n-butylamine and sodium bicarbonate, where the molar concentrations of n-butylamine and potassium hydroxide were 0.2 mol / L, respectively. The fiber-solution mixture was placed in a hydrothermal autoclave and reacted at 90°C for 12 h. The fiber catalyst was removed and washed with distilled water until neutral. After drying, the PPS fiber-supported alkali monofunctional catalyst PPS-N containing only secondary amine groups was obtained.

[0050] Comparative Example 2

[0051] The preparation method of the acid monofunctional PPS catalyst of this comparative example is as follows:

[0052] (1) Same as Example 2.

[0053] (2) Same as Example 2.

[0054] (3) Preparation of PPS-supported alkali monofunctional catalyst: 1 g of PPS-Cl fiber was added to 30 mL of an aqueous solution of isethionic acid and sodium bicarbonate, where the molar concentrations of isethionic acid and potassium hydroxide were 0.2 mol / L, respectively. The fiber-solution mixture was placed in a hydrothermal autoclave and reacted at 90°C for 12 h. The fiber catalyst was removed and washed with distilled water until neutral. After drying, the PPS fiber-supported acid monofunctional catalyst PPS-SO3H containing only sulfonic acid groups was obtained.

[0055] Example 5

[0056] The PPS fiber catalysts prepared in the above examples and comparative examples were used to catalyze the conversion of glucose to produce HMF, as follows:

[0057] 50 mg of glucose, 50 mg of PPS catalyst and 5 mL of distilled water were mixed in a certain proportion and stirred at 120 ° C for 3 hours under nitrogen protection. After the reaction was completed, the reaction system was cooled to room temperature and the reaction yield was determined by high performance liquid chromatography. The experimental results are shown in Table 1 and Table 2. Figure 2 shown.

[0058] Table 1 Activity evaluation of acid-base bifunctional PPS fiber catalyst for glucose conversion reaction

[0059] catalyst Yield (%) Example 1 51 Example 2 69 Example 3 57 Example 4 45 Comparative Example 1 18 Comparative Example 2 40

[0060] Table 2 Example 2 Catalyst recycling results

[0061]

[0062]

[0063] According to the results of Table 1 and Table 2, the acid-base bifunctional PPS catalyst of Example 2 of the present invention can efficiently catalyze the conversion of glucose into HMF at a relatively low temperature with a yield of 69%. By comparing Example 2 with Comparative Examples 1 and 2, the alkali monofunctional PPS catalyst (Comparative Example 1) and the acid monofunctional PPS catalyst (Comparative Example 2) catalyze the production of HMF from glucose with yields of only 18% and 40%, respectively, which are much lower than the corresponding yield (69%) of the acid-base bifunctional PPS catalyst of Example 2, indicating that the catalyst of Example 2 does have an acid-base synergistic effect. In addition, the reaction yield of Example 2 catalyst does not significantly decrease after being recycled 8 times, indicating that its recycling effect is excellent, and that it can reduce pollution while reducing the cost of use, which is more in line with the requirements of green chemistry.

[0064] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a PPS fiber-supported acid-base dual-function catalyst, characterized in that: The following steps are involved: (1) PPS fibers are placed in different solvents and heated under reflux, and then rinsed and dried to obtain pretreated PPS fibers; the solvents are ethanol, cyclohexane, distilled water or acetone; (2) Chloromethylation of PPS fiber: pretreated PPS fiber, paraformaldehyde, tin tetrachloride, trimethylsilyl chloride and 1,2-dichloroethane were added to a hydrothermal reactor and placed in an oven for reaction. After the reaction was completed, the fiber was taken out and cleaned with ethanol, and then dried to obtain chloromethylated PPS fiber PPS-Cl; (3) Preparation of PPS-supported acid-base bifunctional catalyst: Chloromethylated PPS fiber PPS-Cl, acid-base bifunctional small molecule, base and distilled water were added to a hydrothermal reactor and reacted in an oven. The fiber was then taken out and cleaned with ethanol. After drying, the PPS-supported acid-base bifunctional catalyst was obtained. The acid-base bifunctional small molecule was one of glycine, taurine and p-aminobenzenesulfonic acid.

2. The method for preparing the PPS fiber-supported acid-base dual-function catalyst according to claim 1, characterized in that: The mass volume ratio of PPS fiber to solvent is 1:15-1:30 g / mL, and the reflux time is 4-10 h.

3. The method for preparing the PPS fiber-supported acid-base dual-function catalyst according to claim 1, characterized in that: In step (2), the reaction solution consists of paraformaldehyde, tin tetrachloride, trimethylchlorosilane and 1,2-dichloroethane, the mass volume ratio of PPS fiber to reaction solution is 1:20-1:80 g / mL, and the molar concentrations of paraformaldehyde, tin tetrachloride and trimethylchlorosilane in the reaction solution are 0.5-1.5 mol / L, 0.25-0.75 mol / L and 0.5-1.5 mol / L, respectively.

4. The method for preparing the PPS fiber-supported acid-base dual-function catalyst according to claim 1, characterized in that: The reaction temperature in step (2) is 50-100°C, and the reaction time is 24-72h.

5. The method for preparing the PPS fiber-supported acid-base dual-function catalyst according to claim 1, characterized in that: In step (3), the base is one of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

6. The method for preparing the PPS fiber-supported acid-base dual-function catalyst according to claim 1, characterized in that: In step (3), the reaction solution consists of an acid-base bifunctional small molecule, a base, and distilled water, and the mass volume ratio of the chloromethylated PPS fiber PPS-Cl to the reaction solution is 1:15-1:50 g / mL; in the reaction solution, the molar concentration of the acid-base bifunctional small molecule is 0.1-0.5 mol / L, and the molar ratio of the acid-base bifunctional small molecule to the base is 1:

1.

7. The method for preparing the PPS fiber-supported acid-base dual-function catalyst according to claim 1, characterized in that: In step (3), the reaction temperature is 60-150°C and the reaction time is 6-24 h.

8. Use of the acid-base bifunctional PPS fiber catalyst prepared by the preparation method according to any one of claims 1 to 7 in catalyzing the conversion of glucose into HMF.

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