Method for preparing 2, 5-dimethyloltetrahydrofuran from fructose through one-step method

Abstract

The invention relates to a method for preparing 2, 5-dimethyloltetrahydrofuran from fructose by a one-step method, which comprises the following steps: dissolving a fructose raw material in an ionic liquid, and carrying out contact reaction with a catalyst of a molecular sieve loaded noble metal in the presence of hydrogen. According to the method, the molecular sieve loaded noble metal is adopted as the catalyst, the solid acid center catalyzes fructose dehydration to generate 5-HMF, the loaded noble metal is beneficial to improving the dehydration efficiency and can also enable a 5-HMF intermediate product to be further hydrogenated to generate DHMTHF, the catalyst has the dual effects of catalytic dehydration and hydrogenation, DHMTHF prepared through a one-pot method is achieved, the method has the advantage of being simple in process, and the method is suitable for industrial production. The ionic liquid is selected as a solvent, so that the catalyst has the advantages of low volatility, good stability, low toxicity and the like, can inhibit the hydration reaction of an intermediate product 5-HMF and improve the conversion rate, has good stability under the condition that water is generated in a reaction system, and meanwhile, the hydrophobic property of the catalyst is beneficial to the stability of the acidic molecular sieve catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing 2,5-dihydroxymethyltetrahydrofuran (DHMTHF) from fructose in one step by utilizing a noble metal catalyst supported by a molecular sieve. Background Art

[0002] Fructose (C6H 12 Fructose (5-hydroxymethylfurfural) (5-HMF) is a common monosaccharide that is highly soluble in water and has the advantages of being cheap, widely available, and easy to obtain. It has great development potential and economic benefits to use it as a raw material to synthesize other substances. Among them, the acid-catalyzed fructose to obtain 5-hydroxymethylfurfural (5-HMF) is a catalytic reaction with high value. Because 5-HMF is one of the important synthetic raw materials, in the petroleum-based chemical industry and the biomass-based sugar chemistry research industry, 5-HMF plays a relatively important role as a high-value platform compound. As a platform compound, 5-HMF can be further transformed into downstream products. Now, 5-HMF has been used to prepare fine chemicals and a series of polymer materials required for production.

[0003] In the process of converting fructose to 5-HMF, an acid catalyst is needed to catalyze the dehydration reaction, so finding a suitable acid catalyst is one of the focuses of the research work. Traditional Bronsted acids include hydrochloric acid, phosphoric acid, sulfuric acid, etc. They have high dehydration reaction efficiency as homogeneous acid catalysts, but due to the disadvantage that homogeneous catalysts are difficult to recycle and reuse, they violate the concept of green chemistry.

[0004] 5-HMF obtained from fructose can be further converted to synthesize 2,5-dihydroxymethyltetrahydrofuran (DHMTHF). Since DHMTHF is easily degradable, has low toxicity, and is more stable than other unsaturated furan compounds, it can be used as a solvent for special reactions. Other reports clearly point out that DHMTHF can be used to convert into some linear polyols, such as 1,5-pentanediol, 1,6-hexanediol, etc., and then used to synthesize some polymers and special chemicals. DHMTHF can also be polymerized with acid to prepare new polyesters. It is a bio-based diol and a key monomer with high market potential.

[0005] CN112574142A discloses a method for preparing 2,5-furan dimethanol from biomass sugar, comprising: (1) a dehydration stage: the biomass sugar is hydrolyzed and converted into 5-hydroxymethylfurfural (HMF) in a water-organic two-phase solvent system under the action of a solid acid catalyst and a dehydration promoter; the HMF is extracted in situ and transferred from the aqueous phase to the organic phase; after oil-water separation, an organic solvent rich in HMF is obtained; and (2) a hydrogenation stage: H2 is introduced into the HMF-rich organic solvent to convert it into BHMF under the action of an efficient and stable hydrogenation catalyst.

[0006] CN103804329A discloses a method for directly synthesizing 2,5-dihydroxymethyltetrahydrofuran by sugar catalysis, wherein fructose and other hexose sugars are used as raw materials, 5-hydroxymethylfurfural is generated by dehydration under solid acid catalysis, the solid acid is separated, a hydrogenation catalyst is added, and hydrogen is introduced at room temperature and pressure to react and generate 2,5-dihydroxymethyltetrahydrofuran. This process also has the disadvantages of requiring intervals and separation of catalysts before and after the series reaction.

[0007] Wang Cong and others from Shanghai Normal University used the commercialized solid acid catalyst Amberlyst-15 and the metal catalyst Ru / NH2&CH3-MSNs in an aqueous phase and a two-phase system to prepare 2,5-dihydroxymethyltetrahydrofuran from fructose in a one-pot method. Compared with the multi-step organic phase and multi-step complex two-phase system reported in the literature, it has the advantages of easy catalyst availability and strong operational feasibility, but it still fails to significantly improve the current situation that the reaction is difficult to carry out efficiently in the aqueous phase and the waste liquid treatment in the organic phase is difficult.

[0008] In the synthesis method of the prior art, 2,5-dihydroxymethyltetrahydrofuran is generally prepared using 5-HMF, a dehydration product of sugars, as a raw material. The reaction of preparing 2,5-dihydroxymethyltetrahydrofuran from sugars (mainly glucose and fructose) is currently still mainly in the research stage of multi-step reaction system and two-phase system. Since the reaction is a multi-step cascade reaction, the reaction conditions are relatively high and it is difficult to achieve in one step. Although water is a cheap and environmentally friendly solvent, using pure water as a solvent will cause the generated HMF to hydrolyze into levulinic acid and formic acid, which is not conducive to the selectivity of the target product. If an organic solvent is used, it will involve more separation and purification steps, which will not only increase equipment investment and energy consumption, but also increase the difficulty of solvent treatment and the possibility of environmental pollution. Summary of the invention

[0009] In view of the shortcomings of the prior art, the present invention provides a method for preparing 2,5-dihydroxymethyltetrahydrofuran (DHMTHF) by one-step method using fructose as a raw material. The method of the present invention uses an ionic liquid as a solvent and a solid acid-supported metal as a catalyst to prepare DHMTHF by a one-pot method, and has the characteristics of simple process, environmental friendliness, and less by-products.

[0010] The technical purpose of the present invention is achieved through the following technical solutions:

[0011] A one-step method for preparing 2,5-dihydroxymethyltetrahydrofuran from fructose comprises: dissolving fructose raw material in ionic liquid, and contacting and reacting with a catalyst of a molecular sieve loaded with noble metal in the presence of hydrogen.

[0012] Furthermore, the ionic liquid is selected from the group consisting of anions [PF6] - or [BF4] -The ionic liquid is preferably at least one of [Bmim][PF6], [C4mim][PF6], [C8mim][PF6] and [Rpy][PF6].

[0013] Furthermore, the weight ratio of the ionic liquid to fructose is 5:1-15:1, preferably 5:1-10:1.

[0014] Furthermore, in the catalyst of the molecular sieve loaded with precious metal, the carrier is an acidic molecular sieve, selected from at least one of HZSM-5, HY and Hβ molecular sieves, preferably Hβ molecular sieve. The precious metal is selected from at least one of Pd, Pt and Ru, preferably Pd.

[0015] Furthermore, in the molecular sieve-loaded noble metal catalyst, the noble metal loading is 5%-30%, preferably 10%-20%, based on the weight of the metal.

[0016] Furthermore, the amount of the catalyst used is 10%-30% by weight of the fructose, preferably 10%-20%.

[0017] Furthermore, the reaction temperature is 120°C-200°C, preferably 160°C-180°C.

[0018] Furthermore, the reaction pressure is 3MPa-7MPa, preferably 4MPa-6MPa.

[0019] Furthermore, the reaction time is 5h-20h, preferably 8h-12h.

[0020] Furthermore, the reaction is carried out under stirring, and after the reaction is completed, it is rapidly cooled to 10° C.-30° C. to terminate the reaction, and a trace amount of nitrogen purge is maintained during the cooling process.

[0021] Furthermore, the reaction is carried out in an autoclave reactor, into which a solution of fructose and ionic liquid and a catalyst are first added, the reactor is sealed and then hydrogen is passed to replace the air in the reactor, and then a certain pressure of hydrogen is filled and the reactor is sealed, after which the autoclave is slowly heated to the reaction temperature, the reaction is carried out for a certain period of time under stirring to end the reaction, and then the reactor is quickly placed in an ice water bath to stop the reaction.

[0022] Furthermore, the reaction also includes a product post-treatment process, specifically, adding a mixed solution of methanol and water to the product to make the system into one phase, and then filtering to remove solid particles.

[0023] When the method of the invention is adopted to synthesize DHMTHF, the fructose conversion rate is greater than 45% and the DHMTHF yield is greater than 50%.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) The present invention uses a molecular sieve loaded with a noble metal as a catalyst, and a solid acid center catalyzes the dehydration of fructose to generate 5-HMF. The loaded noble metal is beneficial to improving the dehydration efficiency and can further hydrogenate the 5-HMF intermediate to generate DHMTHF. The catalyst has the dual functions of catalytic dehydration and hydrogenation, realizes a one-pot method for preparing DHMTHF, and has the advantage of a simple process.

[0026] (2) The present invention selects ionic liquid as a solvent, which has the advantages of low volatility, good stability, low toxicity, etc., can inhibit the hydration reaction of the intermediate product 5-HMF, improve the conversion rate, and has good stability under the condition that water is generated in the reaction system. At the same time, its hydrophobic property contributes to the stability of the acidic molecular sieve catalyst.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0028] The method of the present invention is further described in detail below by way of examples. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0029] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0030] In the embodiment of the present invention, the conversion rate and yield are detected by HPLC (Agilent 1200 Series), the chromatographic column is Shodex, Sugar, SC1011, the differential refractive index detector is used as the detector, the analysis conditions are 0.005mol / L H2SO4 as the mobile phase, the mobile phase flow rate is 0.5mL / min, the column temperature is 353K, the temperature of the detector is 313K, and the area external standard method is used to detect the conversion of fructose. Standard samples of different concentrations are prepared for sugar and 2,5-dihydroxymethyltetrahydrofuran, respectively, and a working line is made by liquid chromatography test, and the external standard method is used for quantification.

[0031] Fructose conversion rate = n (the amount of product converted into the amount of substance that consumes fructose) × 100% / n (the amount of product converted into the amount of substance that consumes fructose) + n (the amount of fructose substance remaining after the reaction).

[0032] DHMTHF yield = n (the amount of DHMTHF substance after the reaction) x 100% / n (theoretical yield of DHMTHF substance).

[0033] n is the molar molecular weight of the corresponding substance.

[0034] The catalysts in the following examples were prepared by impregnation method.

[0035] Example 1

[0036] Take 10g of fructose and dissolve it in 100g of [Bmim] [PF6], add 1g of 10wt% Pd / Hβ catalyst, stir and purge with hydrogen, and then fill with hydrogen at a pressure of 5.5MPa to seal. Slowly heat the autoclave to 180°C, control the stirring rate to 800r / min, react for 9h, then quickly put the reactor into an ice-water bath to stop the reaction, add a mixed solution of methanol and water to the product to make the system into one phase, then filter to remove solid particles for HPLC analysis. It was determined that the fructose conversion rate was 51.3% and the DHMTHF yield was 54.9%.

[0037] Example 2

[0038] Take 10g of fructose and dissolve it in 100g of [Bmim] [PF6], add 2g of 10wt% Pd / Hβ catalyst, stir and purge with hydrogen, and then fill with hydrogen at a pressure of 4MPa to seal. Slowly heat the autoclave to 160℃, control the stirring rate to 800r / min, react for 8h, then quickly put the reactor into an ice-water bath to stop the reaction, add a mixed solution of methanol and water to the product to make the system into one phase, then filter to remove solid particles for HPLC analysis. It was determined that the fructose conversion rate was 50.4% and the DHMTHF yield was 55.0%.

[0039] Example 3

[0040] Take 10g fructose and dissolve it in 80g [Bmim] [PF6], add 1.5g 15wt% Pd / Hβ catalyst, stir and purge with hydrogen, fill with 6MPa pressure hydrogen and seal it. Slowly heat the autoclave to 170℃, control the stirring rate to 700r / min, react for 8h, then quickly put the reactor into an ice-water bath to stop the reaction, add a mixed solution of methanol and water to the product to make the system into one phase, then filter to remove solid particles and perform HPLC analysis. It was determined that the fructose conversion rate was 51.6% and the DHMTHF yield was 55.3%.

[0041] Example 4

[0042] Take 10g fructose and dissolve it in 80g [Bmim] [PF6], add 1g 20wt% Pd / Hβ catalyst, stir and purge with hydrogen, fill with 7MPa pressure hydrogen and seal it. Slowly heat the autoclave to 150℃, control the stirring rate to 500r / min, react for 10h, then quickly put the reactor into an ice water bath to stop the reaction, add a mixed solution of methanol and water to the product to make the system into one phase, then filter to remove solid particles and perform HPLC analysis. It was determined that the fructose conversion rate was 48.9% and the DHMTHF yield was 53.7%.

[0043] Example 5

[0044] Take 20g fructose and dissolve it in 150g [Bmim] [PF6], add 3g 15wt% Pd / Hβ catalyst, stir and purge with hydrogen, fill with 6MPa pressure hydrogen and seal it. Slowly heat the autoclave to 170℃, control the stirring rate to 700r / min, react for 10h, then quickly put the reactor into an ice water bath to stop the reaction, add a mixed solution of methanol and water to the product to make the system into one phase, then filter to remove solid particles and perform HPLC analysis. It was determined that the fructose conversion rate was 54.9% and the DHMTHF yield was 55.8%.

[0045] Example 6

[0046] The preparation process and operating conditions were the same as those in Example 1, except that [C8mim][PF6] ionic liquid was used. The fructose conversion rate was 51.0% and the DHMTHF yield was 55.8%.

[0047] Example 7

[0048] The preparation process and operating conditions were the same as those in Example 1, except that [C4mim][PF6] ionic liquid was used instead of [Bmim][PF6]. The fructose conversion rate was 51.4% and the DHMTHF yield was 54.4%.

[0049] Example 8

[0050] The preparation process and operating conditions were the same as those in Example 1, except that [Rpy][BF4] ionic liquid was used instead of [Bmim][PF6]. The fructose conversion rate was 50.0% and the DHMTHF yield was 53.1%.

[0051] Example 9

[0052] The preparation process and operating conditions were the same as those in Example 1, except that 10 wt % Pd / HZSM-5 was used as the catalyst. The results showed that the fructose conversion rate was 49.6% and the DHMTHF yield was 52.7%.

[0053] Example 10

[0054] The preparation process and operating conditions were the same as those in Example 1, except that 10 wt% Pt / Hβ was used as the catalyst. The fructose conversion rate was 52.1% and the DHMTHF yield was 50.8%.

[0055] Comparative Example 1

[0056] The preparation process and operating conditions were the same as those in Example 1, except that water was used as the reaction solvent instead of the ionic liquid. The fructose conversion rate was 40.3%, and the DHMTHF yield was 35.0%.

[0057] Comparative Example 2

[0058] The preparation process and operating conditions were the same as those in Example 1, except that Al2O3 with substantially no B acid sites was used as a carrier, and a 10 wt% Pd / Al2O3 catalyst was prepared by impregnation for the reaction. The fructose conversion rate was 30.5%, and the DHMTHF yield was 32.7%.

[0059] Comparative Example 3

[0060] The preparation process and operating conditions are the same as those in Example 1, except that 10 wt% Ni / Hβ of non-noble metal is used as the catalyst. According to the measurement, the fructose conversion rate is 27.3%, and the DHMTHF yield is 23.2%.

Claims

1. A method for preparing 2,5-dihydroxymethyltetrahydrofuran from fructose in one step, comprising: The fructose raw material is dissolved in the ionic liquid, and is contacted with the catalyst of the molecular sieve loaded with the noble metal to react in the presence of hydrogen.

2. The method according to claim 1, characterized in that The ionic liquid is selected from the group consisting of anions [PF6] - or [BF4] - of ionic liquids.

3. The method according to claim 2, characterized in that The ionic liquid is selected from at least one of [Bmim][PF6], [C4mim][PF6], [C8mim][PF6] and [Rpy][PF6].

4. The method according to claim 1, characterized in that: The weight ratio of the ionic liquid to fructose is 5:1-15:

1.

5. The method according to claim 1, characterized in that In the molecular sieve-loaded noble metal catalyst, the carrier is an acidic molecular sieve selected from at least one of HZSM-5, HY and Hβ molecular sieves, and the noble metal is selected from at least one of Pd, Pt and Ru.

6. The method according to claim 1, characterized in that In the molecular sieve-loaded noble metal catalyst, the noble metal loading is 5%-30% by weight of the metal.

7. The method according to claim 1, characterized in that The dosage of the catalyst is 10%-30% of the weight of fructose.

8. The method according to claim 1, characterized in that The reaction temperature is 120°C-200°C.

9. The method according to claim 1, characterized in that: The reaction pressure is 3MPa-7MPa.

10. The method according to claim 1, characterized in that The reaction time is 5h-20h.

11. The method according to claim 1, characterized in that: The reaction is carried out in an autoclave reactor, wherein a solution of fructose and an ionic liquid and a catalyst are first added thereto, the reactor is sealed and then hydrogen is introduced to replace the air in the reactor, and then a certain pressure of hydrogen is filled in and the reactor is sealed, after which the autoclave is slowly heated to the reaction temperature, the reaction is carried out for a certain period of time under stirring to terminate the reaction, and then the reactor is quickly placed in an ice water bath to stop the reaction.