Synthesis method of 2, 5-dihydroxymethyl tetrahydrofuran

Abstract

The invention relates to a synthesis method of 2, 5-dimethyloltetrahydrofuran, which comprises the following step: carrying out contact reaction on 5-hydroxymethylfurfural and hydrogen passing through a plasma generator in the presence of a non-noble metal catalyst to generate the 2, 5-dimethyloltetrahydrofuran. According to the method, 5-hydroxymethylfurfural (5-HMF) is used as a raw material, hydrogen plasma is coupled with a non-noble metal catalyst to synthesize DHMTHF, noble metal does not need to be used, high reaction activity of excited state particles in the hydrogen plasma is utilized, the reaction pressure and the reaction temperature are reduced, meanwhile, the plasma has the effect of re-dispersing active metal of the catalyst, and the yield of DHMTHF is increased. The whole reaction process has the characteristics of relatively mild reaction conditions, relatively low hydrogen consumption, high target product selectivity, simple process, good catalyst stability, low catalyst cost and the like.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis, and specifically relates to a method for preparing and synthesizing 2,5-dihydroxymethyltetrahydrofuran (DHMTHF) by combining plasma technology with 5-hydroxymethylfurfural (5-HMF) hydrogenation reaction. Background Art

[0002] Diols are commonly used monomers for the synthesis of polymer materials. From a global perspective, the skeleton structures of existing diol monomers are all composed of carbon and hydrogen, and there are no cyclic diols composed of other elements for industrial production. 2,5-Dihydroxymethyltetrahydrofuran (DHMTHF) is a high-value-added chemical that can be prepared from 5-HMF. Because DHMTHF is easily degradable, has low toxicity, and is more stable than other unsaturated furan compounds, it is often 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. Therefore, 2,5-dihydroxymethyltetrahydrofuran (DHMTHF) is a bio-based diol derived from the 5-HMF platform compound downstream, and is a key monomer with market potential. It can also be polymerized with acid to prepare new polyesters. The preparation of DHMTHF from 5-HMF has a very broad research prospect.

[0003] In the early stage, Professor Schiavo used heterogeneous Ni, Cu, Pt, Pd, and 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 two main products, 1-hexanol-2,5-dione and 1,2,5-hexanetriol. LIMA et al. hydrogenated 5-HMF in aqueous solution in two steps at 9MPa H2 pressure and 90℃ to produce DHMTHF. First, Raney copper 2,5-dihydroxymethylfuran (DHMF) was prepared with Raney nickel as catalyst Using nickel / alumina (Ni / Al2O3) as a catalyst, 5-HMF was completely hydrogenated to produce DHMTHF in a solvent at 6MPa H2 pressure and 60°C.

[0004] CN111777578A discloses a method for preparing 2,5-dihydroxymethyltetrahydrofuran by hydrogenating 5-hydroxymethylfurfural, wherein a catalyst is reacted with an excess of tetrahydrofuran solvent and 5-hydroxymethylfurfural, and the reaction conditions are: introducing 0.5-2.2 MPa of hydrogen, a stirring speed of 500 r / min, a reaction temperature of 80-140°C, a reaction time of 14 hours, a conversion rate of 100%, and a yield of >56%.

[0005] CN113061122A discloses a method for preparing 2,5-dihydroxymethyltetrahydrofuran. In a hydrogen-containing atmosphere, a material containing 5-hydroxymethylfurfural is reacted in the presence of a nickel-based catalyst at 70-130° C. and a pressure of 3-8 MPa for 3-12 hours. The raw material conversion rate is greater than 95%, and the DHMTHF selectivity is greater than 69%.

[0006] Wang Cong et al. (Shanghai Normal University, 2017) used the traditional impregnation method to prepare Ru / SiO2 Aerogel catalyst for the complete hydrogenation reaction of 5-hydroxymethylfurfural to 2,5-dihydroxymethyltetrahydrofuran. Under the conditions of metal loading of 1.5%, reaction temperature of 90°C, pressure of 5.5MPa, rotation speed of 600r / min, and 0.3g catalyst, a 100% conversion rate of 5-HMF and a 98.3% yield of DHMTHF were achieved. However, after four applications, the ruthenium particles on the catalyst showed obvious agglomeration and the catalyst stability was poor.

[0007] The hydrogenation conversion formula of 5-hydroxymethylfurfural is:

[0008]

[0009] In the existing synthesis method, the complete hydrogenation of 5-HMF to produce high-yield DHMTHF is usually easy to generate incomplete hydrogenation product 2,5-dihydroxymethylfuran (DHMF). If you want to achieve a good catalytic effect, you need more stringent reaction conditions or a large amount of catalysts, and often need to use precious metal catalysts. However, under high temperature and high pressure conditions, on the one hand, excessive temperature and pressure will cause the CO bond outside the furan ring to break and cause a dehydroxylation 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, affecting the catalytic effect and causing poor stability of the catalyst. Summary of the invention

[0010] In view of the deficiencies of the prior art, the present invention provides a method for synthesizing 2,5-dihydroxymethyltetrahydrofuran (DHMTHF) by combining plasma technology. As a highly efficient molecular activation means, plasma technology can produce highly active ions that can theoretically directly react with reactant molecules, such as electrons, free radicals, positive ions, negative ions, excited atoms or molecules, and ground-state atoms or molecules. Molecules, particles, atoms, and free radicals in the excited state in plasma have very high chemical activity. The present invention utilizes plasma technology in the reaction of preparing DHMTHF from 5-hydroxymethylfurfural (5-HMF), which can speed up chemical reactions that are difficult to carry out or have a very slow reaction rate under normal conditions, thereby significantly reducing the reaction temperature and pressure and improving the reaction efficiency.

[0011] In order to achieve the above technical objectives, the technical solution of the present invention is as follows:

[0012] A method for synthesizing 2,5-dihydroxymethyltetrahydrofuran comprises: making 5-hydroxymethylfurfural (5-HMF) contact and react with hydrogen after passing through a plasma generator in the presence of a non-noble metal catalyst to generate 2,5-dihydroxymethyltetrahydrofuran (DHMTHF).

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

[0014] Furthermore, 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, preferably a dielectric barrier discharge plasma generator or a corona discharge plasma generator.

[0015] Furthermore, the active component of the non-precious metal catalyst is a transition metal, preferably nickel. Furthermore, the non-precious metal catalyst is a supported catalyst or a bulk catalyst, and the weight content of the active component is 2-20%, preferably 5-20%, based on the weight of the metal.

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

[0017] Furthermore, the non-precious metal catalyst is prepared by an impregnation method, a co-precipitation method, a deposition precipitation method or an ion exchange method, and these preparation methods are well known to those skilled in the art.

[0018] Furthermore, the reaction temperature is 20-70°C, preferably 30-50°C; the reaction pressure is 0.1-2MPa, preferably 0.2-1MPa.

[0019] Furthermore, based on the volume of the entire reaction solution, the liquid hourly volume space velocity is 0.02-30h -1 .

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

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

[0022] According to the synthesis method of the invention, the conversion rate of the raw material 5-HMF is ≥90%, and the selectivity of the product DHMTHF is ≥91%.

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

[0024] (1) The present invention uses 5-hydroxymethylfurfural (5-HMF) as a raw material and adopts hydrogen plasma coupled with a non-precious metal catalyst to synthesize DHMTHF. The method of the present invention does not require the use of precious metals, utilizes the high reactivity of excited particles in hydrogen plasma, reduces the reaction pressure and reaction temperature, and at the same time, the plasma has the effect of redispersing the active metal of the catalyst. The entire reaction process has the characteristics of relatively mild reaction conditions, low hydrogen consumption, high selectivity of the target product, simple process, good catalyst stability, and low catalyst cost.

[0025] (2) The present invention utilizes highly active species required for the reaction, such as hydrogen free radicals, positive and negative ions, and high-energy electrons generated by the ionization of hydrogen, to hydrogenate the unsaturated bonds in the 5-HMF molecule. The reaction conditions are mild, and the dehydroxylation side reaction caused by the breakage of the CO bond outside the furan ring due to excessive temperature and pressure can be avoided. 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 shedding when operating under high temperature and high pressure conditions. Hydrogen plasma can also further reduce the catalyst during the reaction process and redisperse the active metal, thereby improving the stability of the 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] The present invention adopts the inductively coupled plasma optical emission spectrometer (ICP-OES) of SPECTRO ARCOSⅡ to quantitatively analyze the actual loading amount of elements in the catalyst.

[0031] The present invention uses a TEM-100CXⅡ high-resolution transmission electron microscope to study the characteristics of nickel catalyst particles. The method is: a small amount of catalyst sample is dispersed in anhydrous ethanol, and after ultrasonic uniform dispersion, a small amount of liquid is sucked and dripped onto a copper mesh, and the size of the nickel particles in the catalyst is observed after the ethanol evaporates. Specifically, 10 points are randomly dispersed and the average value of the sizes of all nickel particles in the field of view is taken.

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

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

[0034] The 5-HMF conversion rate was 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 = integrated area of ​​DHMTHF peak after reaction / integrated area of ​​all peaks × 100%

[0037] The catalyst preparation method used in the examples 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 / γ-Al2O3 catalyst was prepared by an impregnation method. The actual loading amount of Ni on the catalyst was 10.2wt% as determined by ICP-OES. The catalyst loading amount in the reactor was 10mL.

[0040] Prepare 10% 5-HMF ethanol solution and add it to the raw material tank of the fixed bed reactor. -1) is introduced into the hydrogenation reactor through a pipeline. H2 enters the dielectric barrier discharge (DBD) plasma generator at a flow rate of 36.8mL / min (molar ratio of H2 to 5-HMF is 10:1), the plasma generator power is turned on, and the hydrogen plasma formed by ionization is then transported to the hydrogenation reactor for hydrogenation reaction with the raw materials. The reaction temperature in the reactor is 25°C and the reaction pressure is 0.1MPa. The products generated by the reaction are introduced into the fractionation tank from the bottom of the reactor, and enter the product tank after the gas is separated. After the reaction, the product is sampled for composition analysis, and the conversion rate of 5-HMF is 95.3%, and the selectivity of DHMTHF is 96.1%.

[0041] Example 2

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

[0043] Prepare 10% 5-HMF ethanol solution and add it into the raw material tank of the fixed bed reactor. -1 ) is introduced into the hydrogenation reactor through a pipeline. H2 enters the dielectric barrier discharge (DBD) plasma generator at a flow rate of 36.8mL / min (molar ratio of H2 to 5-HMF 20:1), the plasma generator power is turned on, and the hydrogen plasma formed by ionization is then transported to the hydrogenation reactor for hydrogenation reaction with the raw materials. The reaction temperature is 30°C and the reaction pressure is 0.1MPa. The products generated by the reaction are introduced into the fractionation tank from the bottom of the reactor, and enter the product tank after the gas is separated. After the reaction, the product is sampled for composition analysis, and the 5-HMF conversion rate is 96.2% and the DHMTHF selectivity is 98.2%.

[0044] Example 3

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

[0046] Prepare 10% 5-HMF ethanol solution and add it to the raw material tank of the fixed bed reactor. -1) is introduced into the hydrogenation reactor through a pipeline. H2 enters the dielectric barrier discharge (DBD) plasma generator at a flow rate of 55.2mL / min (molar ratio of H2 to 5-HMF 5:1), the plasma generator power is turned on, and the hydrogen plasma formed by ionization is then transported to the hydrogenation reactor for hydrogenation reaction with the raw materials. The reaction temperature is 20°C and the reaction pressure is 0.2MPa. The products generated by the reaction are introduced into the fractionation tank from the bottom of the reactor, and enter the product tank after the gas is separated. After the reaction, the product is sampled for composition analysis, and the 5-HMF conversion rate is 95.7% and the DHMTHF selectivity is 98.2%.

[0047] Example 4

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

[0049] Prepare 10% 5-HMF ethanol solution and add it into the raw material tank of the fixed bed reactor. -1 ) is introduced into the hydrogenation reactor through a pipeline. H2 enters the dielectric barrier discharge (DBD) plasma generator at a flow rate of 1.38 mL / min (molar ratio of H2 to 5-HMF is 15:1), the plasma generator power is turned on, and the hydrogen plasma formed by ionization is then transported to the hydrogenation reactor for hydrogenation reaction with the raw materials. The reaction temperature is 40°C and the reaction pressure is 0.5 MPa. The products generated by the reaction are introduced into the fractionation tank from the bottom of the reactor, and enter the product tank after the gas is separated. After the reaction, the product is sampled for composition analysis, and the 5-HMF conversion rate is 96.8% and the DHMTHF selectivity is 95.3%.

[0050] Example 5

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

[0052] Prepare 10% 5-HMF ethanol solution and add it to the raw material tank of the fixed bed reactor. -1) is introduced into the hydrogenation reactor through a pipeline. H2 enters the dielectric barrier discharge (DBD) plasma generator at a flow rate of 736.0 mL / min (molar ratio of H2 to 5-HMF is 10:1), the plasma generator power is turned on, and the hydrogen plasma formed by ionization is then transported to the hydrogenation reactor for hydrogenation reaction with the raw materials. The reaction temperature is 35°C and the reaction pressure is 0.6 MPa. The products generated by the reaction are introduced into the fractionation tank from the bottom of the reactor, and enter the product tank after the gas is separated. After the reaction, the product is sampled for composition analysis, and the 5-HMF conversion rate is 94.8% and the DHMTHF selectivity is 94.7%.

[0053] Example 6

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

[0055] Example 7

[0056] The Ni / Al2O3 catalyst was prepared by coprecipitation method, and the actual Ni loading was 9.60% as determined by ICP-OES. The other reaction conditions were the same as those in Example 1, and the product was sampled for composition analysis, and the 5-HMF conversion 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 those in Example 1, except that a corona discharge plasma generator was used to generate hydrogen plasma. 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 those in Example 1, except that the volume concentration of 5-HMF in the reaction raw material solution was 5%. 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 those in Example 1, except that methanol was used as the solvent for the reaction raw material solution. 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] Embodiment 11

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

[0065] Comparative Example 1

[0066] The catalyst and the synthetic reaction operating conditions used 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. Analysis of the products after the reaction showed that no 5-HMF conversion was detected.

[0067] Comparative Example 2

[0068] No catalyst was loaded in the reactor. The synthetic reaction operating conditions were the same as those in Example 1. After the reaction, the product was sampled for composition analysis, and the conversion rate 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 in Example 1, the hydrogen 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. After the reaction, the product was sampled for composition analysis, and the 5-HMF conversion rate was 79.2%, and the DHMTHF selectivity was 80.2%.

[0071] In addition, the catalyst nickel particle size of the catalyst before reaction in Example 1, the catalyst after reaction for 10 hours, and the catalyst after reaction for 10 hours in Comparative Example 3 was observed using a TEM-100CXⅡ high-resolution transmission electron microscope. The results are shown in Table 1.

[0072] Table 1

[0073]

Claims

1. A method for synthesizing 2,5-dihydroxymethyltetrahydrofuran, comprising: 5-Hydroxymethylfurfural is contacted with hydrogen gas passed through a plasma generator in the presence of a non-precious metal catalyst to react and generate 2,5-dihydroxymethyltetrahydrofuran.

2. The synthesis method according to claim 1, characterized in that The 5-HMF is dissolved in a solvent, and the solvent is 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 synthesis method according to claim 1, characterized in that 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.

4. The synthesis method according to claim 1, characterized in that The active component of the non-precious metal catalyst is a transition metal, and the weight content of the active component is 2-20% based on the weight of the metal.

5. The synthesis method according to claim 4, characterized in that The active component of the non-precious metal catalyst is nickel.

6. The synthesis method according to claim 4, characterized in that The carrier of the non-precious metal catalyst is selected from at least one of aluminum oxide, silicon oxide, magnesium oxide and zirconium oxide.

7. The synthesis method according to claim 1, characterized in that The non-precious metal catalyst is prepared by an impregnation method, a co-precipitation method, a deposition precipitation method or an ion exchange method.

8. The synthesis method according to claim 1, characterized in that The reaction temperature is 20-70°C, and the reaction pressure is 0.1-2MPa.

9. The synthesis method according to claim 1, characterized in that In the reaction, the liquid hourly volume space velocity is 0.02-30h based on the volume of the entire reaction solution. -1 .

10. The synthesis method according to claim 1, characterized in that The molar ratio of hydrogen to 5-HMF is 3:1-100:

1.

11. The synthesis method according to claim 1, characterized in that: The reaction is completed in a fixed bed reaction device, the non-precious metal catalyst is loaded in the fixed bed reaction device, hydrogen is first introduced into the fixed bed reaction device for purging, then the hydrogen after passing through the plasma generator is switched, and the raw material is introduced, so that 5-hydroxymethylfurfural undergoes a complete hydrogenation reaction on the catalyst surface to produce DHMTHF.

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