A method for synthesizing 2,5-dihydroxymethyltetrahydrofuran

Abstract

A synthesis method of 2,5-dihydroxymethyl tetrahydrofuran, comprising: 5-hydroxymethyl furfural is contacted with hydrogen after a plasma generator in the presence of a non-noble metal catalyst to generate 2,5-dihydroxymethyl tetrahydrofuran. The present application uses 5-hydroxymethyl furfural (5-HMF) as raw material, and synthesizes DHMTHF by hydrogen plasma coupling non-noble metal catalyst. The method of the present application does not need to use noble metal, utilizes the high reactivity of excited state particles in hydrogen plasma, reduces the reaction pressure and reaction temperature, and the plasma has the effect of dispersing the catalyst active metal again. The whole reaction process has the characteristics of relatively mild reaction conditions, low hydrogen consumption, high selectivity of target product, simple process, good stability of catalyst, low cost of catalyst, etc.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of organic synthesis, and particularly relates to a method for preparing 2,5-dihydroxymethyl tetrahydrofuran (DHMTHF) by combining plasma technology with a 5-hydroxymethylfurfural (5-HMF) hydrogenation reaction. BACKGROUND

[0002] Diols are commonly used monomers for the synthesis of high molecular polymer materials. From a global perspective, the existing diol monomer skeleton structure is composed of carbon and hydrogen, and no other element composed of cyclic diols has been used for industrial production. 2,5-dihydroxymethyl tetrahydrofuran (DHMTHF) is a high-value-added chemical substance that can be prepared from 5-HMF. Because DHMTHF is easily degradable, low-toxic, and more stable than other unsaturated furan compounds, it is often used as a special reaction solvent. It has also been reported 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. Therefore, 2,5-dihydroxymethyl tetrahydrofuran (DHMTHF) is a bio-based diol derived from 5-HMF downstream, and is a key monomer with market potential. It can also be polymerized with acids to prepare new polyesters. The preparation of DHMTHF from 5-HMF has a very broad research prospect.

[0003] Professor Schiavo used heterogeneous Ni, Cu, Pt, Pd, Ru catalysts in neutral solvents to obtain 80-100% DHMTHF selectivity. Secondly, Ru and Pt were used as catalysts for the hydrogenation of 5-HMF in acidic solvents to obtain 1-hexanol-2,5-diketone and 1,2,5-hexanetriol as two main products. LIMA et al. prepared DHMTHF by two-step hydrogenation of 5-HMF in aqueous solution at 9 MPa H2 pressure and 90℃. First, DHMF was prepared with Raney copper as catalyst, and then DHMTHF was prepared with Raney nickel as catalyst. KONG et al. realized the complete hydrogenation of 5-HMF to prepare DHMTHF in a solvent at 6 MPa H2 pressure and 60℃ with Ni / Al2O3 as catalyst.

[0004] CN111777578A discloses a method for preparing 2,5-dihydroxymethyl tetrahydrofuran from 5-hydroxymethylfurfural by reaction of a catalyst with excess tetrahydrofuran solvent and 5-hydroxymethylfurfural. The reaction conditions are as follows: 0.5-2.2 MPa of hydrogen is introduced, the stirring speed is 500 r / min, the reaction temperature is 80-140℃, and the reaction time is 14 h. The conversion rate is 100%, and the yield is >56%. ​

[0005] CN113061122A discloses a method for preparing 2,5-dihydroxymethyl tetrahydrofuran, which comprises the following steps: in a hydrogen-containing atmosphere, a material containing 5-hydroxymethyl furfural is reacted in the presence of a nickel-based catalyst at 70-130 DEG C under a pressure of 3-8 MPa for 3-12 hours, the conversion rate of the raw material is > 95%, and the selectivity of DHMTHF is > 69%.

[0006] Wang Cong et al. (Shanghai Normal University, 2017) prepared Ru / SiO2 Aerogel catalyst by using traditional impregnation method, and used it in the complete hydrogenation reaction of 5-hydroxymethyl furfural to 2,5-dihydroxymethyl tetrahydrofuran, under the conditions of metal loading 1.5%, reaction temperature 90 DEG C, pressure 5.5 MPa, rotation speed 600 r / min and 0.3 g catalyst, 5-HMF 100% conversion rate and DHMTHF 98.3% yield were achieved, but after four times of reuse, the ruthenium particles on the catalyst had obvious agglomeration phenomenon, and the stability of the catalyst was not good.

[0007] The 5-hydroxymethyl furfural hydrogenation conversion formula is:

[0008]

[0009] In the existing synthesis method, the complete hydrogenation of 5-HMF to produce high yield of DHMTHF is usually easy to generate incomplete hydrogenation product 2,5-dihydroxymethyl furan (DHMF), if better catalytic effect is wanted, harsh reaction conditions or a large amount of catalyst are needed, and often noble metal catalyst is used. However, under the conditions of high temperature and high pressure, on the one hand, too high temperature and pressure will cause the rupture of C-O bond outside the furan ring and cause dehydroxy side reaction, which is not conducive to the selectivity of the target product, on the other hand, the metal on the carrier is easy to agglomerate or fall off, which affects the catalytic effect and causes poor stability of the catalyst. SUMMARY

[0010] In view of the deficiencies of the prior art, the present application provides a synthesis method of 2,5-dihydroxymethyl tetrahydrofuran (DHMTHF) combined with plasma technology. As a kind of efficient molecular activation means, plasma technology can produce high-activity ions which can theoretically react directly with reactant molecules, such as electrons, free radicals, positive ions, negative ions, excited-state atoms or molecules, ground-state atoms or molecules, and molecules, particles, atoms and free radicals in the excited state in plasma have very high chemical activity. The present application utilizes plasma technology in the reaction of preparing and synthesizing DHMTHF from 5-hydroxymethyl furfural (5-HMF), which can make the chemical reaction which is difficult to carry out or has very slow reaction rate under normal conditions faster, so as to significantly reduce the reaction temperature and pressure and improve the reaction efficiency.

[0011] In order to achieve the above technical purposes, the technical scheme of the present application is as follows:

[0012] The synthesis method of 2,5-dihydroxymethyl tetrahydrofuran comprises: making 5-hydroxymethyl furfural (5-HMF) contact with hydrogen gas after a plasma generator in the presence of a non-noble metal catalyst to generate 2,5-dihydroxymethyl tetrahydrofuran (DHMTHF).

[0013] Further, the 5-HMF is dissolved in a solvent selected from at least one of methanol, ethanol, isopropanol, benzene, toluene and petroleum ether, and preferably ethanol. The volume fraction of 5-HMF is 1% to 20%, and preferably 5% to 10%.

[0014] Further, the plasma generator is selected from at least one of a dielectric barrier discharge plasma generator, a microwave discharge plasma generator, a radio frequency discharge plasma generator, a glow discharge plasma generator, a corona discharge plasma generator and a sliding arc discharge plasma generator, and preferably a dielectric barrier discharge plasma generator or a corona discharge plasma generator.

[0015] Further, the active component of the non-noble metal catalyst is a transition metal, and preferably metal nickel. Further, the non-noble metal catalyst is a supported catalyst or a bulk catalyst, and the weight content of the active component is 2% to 20% by weight of the metal, and preferably 5% to 20%.

[0016] Further, the carrier of the non-noble metal catalyst is selected from at least one of aluminum oxide, silicon oxide, magnesium oxide and zirconium oxide, and preferably aluminum oxide, and the aluminum oxide is selected from at least one of γ-Al2O3 and θ-Al2O3.

[0017] Further, the non-noble metal catalyst is prepared by one of an impregnation method, a coprecipitation method, a deposition precipitation method or an ion exchange method, which are well known to those skilled in the art.

[0018] Further, the temperature of the above reaction is 20 to 70°C, and preferably 30 to 50°C; and the reaction pressure is 0.1 to 2 MPa, and preferably 0.2 to 1 MPa.

[0019] Further, the liquid hourly space velocity of the entire reaction solution is 0.02 to 30 h -1 .

[0020] Further, the molar ratio of hydrogen gas to 5-HMF is 3:1 to 100:1, and preferably 10:1 to 20:1.

[0021] Further, the reaction is completed on a fixed bed reaction device, the fixed bed reaction device is filled with the non-noble metal catalyst, hydrogen is first introduced into the fixed bed reaction device for purging, then hydrogen after passing through the plasma generator is switched, and the raw material is introduced, so that complete hydrogenation reaction of 5-hydroxymethylfurfural is caused on the surface of the catalyst to produce DHMTHF.

[0022] The synthesis method of the present application has a 5-HMF conversion rate of ≥ 90%, and a product DHMTHF selectivity of ≥ 91%.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] (1) The present application uses 5-hydroxymethylfurfural (5-HMF) as a raw material, and synthesizes DHMTHF by using hydrogen plasma coupled with a non-noble metal catalyst. The method of the present application does not need to use noble metals, utilizes the high reactivity of excited state particles in hydrogen plasma, reduces the reaction pressure and the reaction temperature, and the plasma has the effect of re-dispersing the active metal of the catalyst, so that the entire reaction process has the characteristics of relatively mild reaction conditions, low hydrogen consumption, high selectivity of target product, simple process, good stability of catalyst, and low cost of catalyst.

[0025] (2) The present application uses the high activity species required for the reaction of hydrogen radicals, positive and negative ions, and high-energy electrons generated by ionization of hydrogen to hydrogenate the unsaturated bond in the 5-HMF molecule, and the reaction conditions are mild, which can avoid the occurrence of dehydroxy side reactions due to the rupture of the C-O bond outside the furan ring caused by excessively high temperature and pressure, and the catalyst can selectively activate the carbon-oxygen bond in the reactant molecule, further improving the selectivity of DHMTHF.

[0026] (3) The entire reaction process can avoid the deactivation of nickel-based catalysts due to coking, agglomeration, and falling off under high temperature and high pressure conditions, and the hydrogen plasma can further reduce the catalyst during the reaction process, thereby playing a role in re-dispersing the active metal and improving the stability of the catalyst.

[0027] Other features and advantages of the present application will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0028] The method of the present application will be further described in detail by the following examples. The examples are implemented on the premise of the technical solution of the present application, and detailed implementation methods and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

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

[0030] The present application adopts SPECTRO ARCOS II inductively coupled plasma optical emission spectrometer (ICP-OES) to quantitatively analyze the actual loading amount of elements in the catalyst.

[0031] The present application adopts TEM-100CX II type high-resolution transmission electron microscope to study the characteristics of nickel catalyst particles. The method is as follows: a small amount of catalyst sample is dispersed in anhydrous ethanol, ultrasonic dispersion is performed, a small amount of liquid is sucked and dropped on a copper net, and after the ethanol is volatilized, the size of the nickel particles in the catalyst is observed. Specifically, 10 places are randomly dispersed, and the average value of the size of all nickel particles in the field of view is taken.

[0032] The synthesis reaction of the present application is carried out on a fixed bed microreactor (purchased from Tianjin Pengxiang Technology Co., Ltd.).

[0033] The conversion rate of the reactant and the selectivity of the product of the present application are determined and calculated by a high performance liquid chromatograph (HPLC) of Agilent Technologies 1260 Infinity II type, which is equipped with an ultraviolet absorption light detector and an Extend-C18 USP L1 chromatographic column (4.6mm*250mm). The liquid chromatograph uses a mixed solution of methanol and ammonium formate aqueous solution as the mobile phase, the concentration of the ammonium formate aqueous solution is 5.0mM, the volume ratio of methanol to ammonium formate aqueous solution is 1:9, and the total flow rate of the mobile phase is 0.8mL / min.

[0034] The 5-HMF conversion rate is calculated according to the following formula:

[0035] 5-HMF conversion rate = 1-(5-HMF molar concentration after reaction / initial 5-HMF molar concentration)

[0036] DHMTHF selectivity = peak integral area of DHMTHF after reaction / total peak integral area*100%

[0037] The catalyst preparation method used in the embodiments of the present application is a conventional supported nickel-based catalyst, which is prepared by an impregnation method.

[0038] Example 1

[0039] Firstly, a supported Ni / gamma-Al2O3 catalyst is prepared by an impregnation method, and the actual loading amount of Ni on the catalyst is 10.2wt% determined by ICP-OES, and the loading amount of the catalyst in the reactor is 10mL.

[0040] An ethanol solution with a 5-HMF volume fraction of 10% is prepared and added to the raw material tank of the fixed bed reactor, and the raw material solution is fed into the reactor at a flow rate of 0.167mL / min (space velocity 1h -1) into the hydrogenation reactor. H2 entered the dielectric barrier discharge (DBD) plasma generator at a flow rate of 36.8 mL / min (H2 to 5-HMF molar ratio 10:1), the plasma generator power was turned on, the hydrogen plasma formed by ionization was then delivered into the hydrogenation reactor to react with the raw material, the reaction temperature in the reactor was 25°C, and the reaction pressure was 0.1 MPa. The product generated by the reaction was introduced into a fractionating tank from the bottom of the reactor, and then into a product tank after the gas was separated. The product after the reaction was sampled for composition analysis, and the conversion rate of 5-HMF was 95.3%, and the selectivity of DHMTHF was 96.1%.

[0041] Example 2

[0042] The same catalyst as in Example 1 was used, and the loading amount was the same.

[0043] An ethanol solution with a 5-HMF volume fraction of 10% was prepared and added to the raw material tank of the fixed bed reactor, and the raw material solution was input into the hydrogenation reactor at a flow rate of 0.083 mL / min (space velocity 0.5 h -1 ) into the hydrogenation reactor. H2 entered the dielectric barrier discharge (DBD) plasma generator at a flow rate of 36.8 mL / min (H2 to 5-HMF molar ratio 10:1), the plasma generator power was turned on, the hydrogen plasma formed by ionization was then delivered into the hydrogenation reactor to react with the raw material, the reaction temperature in the reactor was 25°C, and the reaction pressure was 0.1 MPa. The product generated by the reaction was introduced into a fractionating tank from the bottom of the reactor, and then into a product tank after the gas was separated. The product after the reaction was sampled for composition analysis, and the conversion rate of 5-HMF was 95.3%, and the selectivity of DHMTHF was 96.1%.

[0044] Example 3

[0045] A supported Ni / γ-Al2O3 catalyst was prepared by the impregnation method, and the actual loading amount of Ni was 15.3 wt% as determined by ICP-OES, and the loading amount was 15 mL.

[0046] An ethanol solution with a 5-HMF volume fraction of 10% was prepared and added to the raw material tank of the fixed bed reactor, and the raw material solution was input into the hydrogenation reactor at a flow rate of 0.083 mL / min (space velocity 0.5 h -1) into the hydrogenation reactor. H2 entered the dielectric barrier discharge (DBD) plasma generator at a flow rate of 1.38 mL / min (H2 to 5-HMF molar ratio 15:1), and the hydrogen plasma formed by ionization was delivered into the hydrogenation reactor to react with the raw material. The reaction temperature was 40°C, and the reaction pressure was 0.5 MPa. The product generated in the reaction was introduced into a fractionating tank from the bottom of the reactor, and after the gas was separated, it entered a product tank. After the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 96.8%, and the DHMTHF selectivity was 95.3%.

[0047] Example 4

[0048] A supported Ni / γ-Al2O3 catalyst was prepared by impregnation, and the actual Ni loading was 19.6wt% as determined by ICP-OES, and the loading amount was 5 mL.

[0049] An ethanol solution with a 5-HMF volume fraction of 10% was prepared and added to the raw material tank of the fixed bed reactor, and the raw material solution was input into the hydrogenation reactor at a flow rate of 0.004 mL / min (space velocity 0.05 h -1 ) into the hydrogenation reactor. H2 entered the dielectric barrier discharge (DBD) plasma generator at a flow rate of 1.38 mL / min (H2 to 5-HMF molar ratio 15:1), and the hydrogen plasma formed by ionization was delivered into the hydrogenation reactor to react with the raw material. The reaction temperature was 40°C, and the reaction pressure was 0.5 MPa. The product generated in the reaction was introduced into a fractionating tank from the bottom of the reactor, and after the gas was separated, it entered a product tank. After the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 96.8%, and the DHMTHF selectivity was 95.3%.

[0050] Example 5

[0051] A supported Ni / γ-Al2O3 catalyst was prepared by impregnation, and the actual Ni loading was 5.1wt% as determined by ICP-OES, and the loading amount was 20 mL.

[0052] An ethanol solution with a 5-HMF volume fraction of 10% was prepared and added to the raw material tank of the fixed bed reactor, and the raw material solution was input into the hydrogenation reactor at a flow rate of 0.004 mL / min (space velocity 0.05 h -1) was input into the hydrogenation reactor. H2 was input into a dielectric barrier discharge (DBD) plasma generator at a flow rate of 736.0 mL / min (H2 to 5-HMF molar ratio 10:1), the plasma generator power was turned on, and the hydrogen plasma formed by ionization was delivered into the hydrogenation reactor to react with the raw material, the reaction temperature was 35°C, and the reaction pressure was 0.6 MPa. The product generated in the reaction was introduced into a fractionating tank from the bottom of the reactor, and after the gas was separated, it was introduced into a product tank. After the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 94.8%, and the DHMTHF selectivity was 94.7%.

[0053] Example 6

[0054] A Ni / Al2O3 catalyst was prepared by a deposition precipitation method, and the actual Ni loading was 9.51% as determined by ICP-OES. Other reaction conditions were the same as in Example 1, and after the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 94.8%, and the DHMTHF selectivity was 95.5%.

[0055] Example 7

[0056] A Ni / Al2O3 catalyst was prepared by a co-precipitation method, and the actual Ni loading was 9.60% as determined by ICP-OES. Other reaction conditions were the same as in Example 1, and after the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 94.9%, and the DHMTHF selectivity was 95.6%.

[0057] Example 8

[0058] The catalyst preparation process and reaction operating conditions were the same as in Example 1, except that the hydrogen plasma was generated by a corona discharge plasma generator, and after the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 95.6%, and the DHMTHF selectivity was 95.9%.

[0059] Example 9

[0060] The catalyst preparation process and reaction operating conditions were the same as in Example 1, except that the volume concentration of 5-HMF in the reaction raw material solution was 5%, and after the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 96.2%, and the DHMTHF selectivity was 97.2%.

[0061] Example 10

[0062] The catalyst preparation process and reaction operating conditions were the same as in Example 1, except that methanol was used as the solvent for the reaction raw material solution, and after the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 94.3%, and the DHMTHF selectivity was 95.0%.

[0063] Example 11

[0064] The supported Ni / SiO2 catalyst was prepared by impregnation method, and the actual loading of Ni was 9.8wt% determined by ICP-OES. The other synthetic reaction conditions were the same as those in Example 1. The product after reaction was sampled for composition analysis, and the conversion of 5-HMF was 93.4% and the selectivity of DHMTHF was 92.3%.

[0065] Comparative Example 1

[0066] The catalyst used and the synthetic reaction conditions were the same as those in Example 1, except that H2 was not ionized by the plasma generator but was directly introduced into the reactor. The product after reaction was analyzed, and no conversion of 5-HMF was detected.

[0067] Comparative Example 2

[0068] The reactor was not loaded with any catalyst, and the synthetic reaction conditions were the same as those in Example 1. The product after reaction was sampled for composition analysis, and the conversion of 5-HMF was 86.0% and the selectivity of DHMTHF was 88.1%.

[0069] Comparative Example 3

[0070] The catalyst used was the same as that in Example 1, and H2 was not ionized by the plasma generator. The reaction temperature in the reactor was 200°C, the reaction pressure was 6 MPa, and the hydrogen liquid ratio was 300:1. The product after reaction was sampled for composition analysis, and the conversion of 5-HMF was 79.2% and the selectivity of DHMTHF was 80.2%.

[0071] In addition, the catalysts before reaction in Example 1, after reaction for 10 h in Example 1, and after reaction for 10 h in Comparative Example 3 were observed for nickel particle size by TEM-100CXII high-resolution transmission electron microscope, and the results are shown in Table 1.

[0072] Table 1

[0073]

Claims

1. A method of synthesizing 2,5-dihydroxymethyltetrahydrofuran, comprising: 5-hydroxymethylfurfural is reacted with hydrogen after a plasma generator in the presence of a non-noble metal catalyst to produce 2,5-dihydroxymethyltetrahydrofuran; the active component of the non-noble metal catalyst is nickel, and the carrier is at least one selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide and zirconium oxide.

2. The method of synthesis of claim 1, wherein, The 5-HMF is dissolved in a solvent selected from at least one of methanol, ethanol, isopropanol, benzene, toluene and petroleum ether, wherein the volume fraction of 5-HMF is 1%-20%.

3. The method of synthesis of claim 1, wherein, The plasma generator is at least one selected from the group consisting of a dielectric barrier discharge plasma generator, a microwave discharge plasma generator, a radio frequency discharge plasma generator, a glow discharge plasma generator, a corona discharge plasma generator and a sliding arc discharge plasma generator.

4. The method of synthesis of claim 1, wherein, The weight content of the active component of the non-noble metal catalyst is 2-20% by weight of the metal.

5. The method of synthesis of claim 1, wherein, The non-noble metal catalyst is prepared by one of impregnation, coprecipitation, deposition precipitation or ion exchange.

6. The method of synthesis of claim 1, wherein, The reaction temperature is 20-70°C, and the reaction pressure is 0.1-2 MPa.

7. The method of synthesis of claim 1, wherein, The liquid hourly space velocity in the reaction is 0.02-30 h -1 .

8. The method of synthesis of claim 1, wherein, The molar ratio of hydrogen to 5-HMF is 3:1-100:

1.

9. The method of synthesis of claim 1, wherein, The reaction is completed in a fixed bed reaction device filled with the non-noble metal catalyst, hydrogen is first introduced into the fixed bed reaction device for purging, then hydrogen after the plasma generator is switched in, and the raw material is introduced, so that 5-hydroxymethylfurfural is completely hydrogenated on the surface of the catalyst to produce DHMTHF.

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