Method for preparing monohydric alcohol through catalytic hydrogenation of bio-based micromolecular dihydric alcohol

Abstract

The invention discloses a method for preparing monohydric alcohol by catalytic hydrogenation of bio-based micromolecular dihydric alcohol, which comprises the following steps: putting a bio-based micromolecular dihydric alcohol aqueous solution into a high-pressure reaction kettle, adding an activated carbon supported metal catalyst and solid acid or liquid acid, then introducing hydrogen with certain pressure, and reacting at certain temperature for 2-4 hours to obtain the monohydric alcohol. Stirring and reacting for a period of time to obtain monohydric alcohol; the micromolecular dihydric alcohol is one of ethylene glycol, 1, 2-propylene glycol, 1, 4-butanediol, 1, 2-pentanediol, 1, 5-pentanediol and 1, 2-hexanediol; the active carbon is wide in raw material source, easy to prepare and recyclable. The catalyst is simple in preparation process, reusable, low in price, high in catalytic activity, mild in reaction condition and convenient to popularize.

Description

Technical field:

[0001] The invention relates to a method for preparing monohydric alcohol by catalytic hydrogenation of bio-based small molecule dihydric alcohol. Background technology:

[0002] Monohydric alcohols, i.e. alcohols containing only one hydroxyl group (R-OH) in the molecule, are an important class of organic compounds that can be used as organic solvents and fuels. They are also important platform compounds and are widely used in modern industrial production and life. At present, the main industrial production methods of monohydric alcohols include hydration, fermentation, and synthesis gas preparation technology. However, the hydration method consumes a large amount of concentrated sulfuric acid, and the sulfuric acid medium has a serious corrosive effect on the equipment. In addition, the separation and purification of the product is also difficult, which increases the production cost. The fermentation method has a long production cycle and the price of biological enzymes is high, and the enzyme activity is easily affected, making it difficult to recycle. The technology for preparing monohydric alcohols from synthesis gas is not yet mature, and the reaction conditions are relatively harsh, and the equipment requirements are high, making it difficult to promote on a large scale. In recent years, with the increasing consumption of fossil fuels, the deepening of the energy crisis, and multiple pressures such as environmental problems, countries around the world have accelerated the development and utilization of clean and renewable energy.

[0003] Biomass is a renewable carbon source with huge reserves on the earth. The development and utilization of biomass has the dual significance of alleviating the energy crisis and protecting the environment. Small molecule diols (Diols) refer to alcohols with two hydroxyl groups (-OH), such as ethylene glycol, propylene glycol, butanediol, etc. Bio-based small molecule diols are important polyester monomers and are widely used in food, medicine, and fine chemicals. Bio-based small molecule diols are of great significance for the sustainable development of society and the reduction of carbon emissions. Lignocellulosic biomass is widely distributed in nature and has huge reserves. Cellulose, hemicellulose and other components can be obtained through depolymerization, and then hydrogenolysis can be used to prepare small molecule diols, which can be used as raw materials for the production of corresponding monohydric alcohols. At present, the preparation process of bio-based small molecule diols is becoming more and more mature, so the development of a method for preparing monohydric alcohols from bio-based small molecule diols has a distinct significance and practical value.

[0004] Studies have shown that bio-based small molecule diols can generate aldehyde intermediates through catalytic dehydration, and then hydrogenate to generate monohydric alcohols. However, due to the relatively stable properties of bio-based small molecule diols, it is difficult to directly convert and utilize them. Currently, there are few reports on the preparation of monohydric alcohols from bio-based small molecule diols. Li et al. reported the use of Ru-WO x / HZSM-5 catalyzes the preparation of ethanol from cellulose and ethylene glycol as substrates (Green Chemistry, 2019.21(9):p.2234-2239), and the ethanol yields can reach 59% and 77.6% respectively, but the catalyst preparation used in this method is relatively complicated, the reaction time is long, and the overall cost is high. Chu et al. reported a method for preparing ethanol from ethylene glycol using 1% Au-(20% Cu-2% Ni) / SiO2 catalyst (Chinese Journal of Catalysis, 2021.42(5):p.844-854), and the ethanol yield of this method can reach 62.2%, but the catalyst structure used in this method is relatively complex and the preparation is difficult. In addition, the reaction temperature of this method is high, which is not conducive to promotion and application. Schlaf et al. reported a method for preparing n-propanol from 1,2-propylene glycol (Adv.Synth.Catal.2009,351,789–800), but the catalyst preparation process of this method is complicated, the product is not easy to separate, and it is difficult to promote. Japanese scholars Amada and Liu et al. reported a method for preparing monohydric alcohols from 1,2-propylene glycol using a bimetallic supported catalyst (ChemSusChem 2010, 3, 728–736; ACS Sustainable Chem. Eng. 2022, 10, 1220-1231). The yields of n-propanol and isopropanol were 66% and 19%, respectively, but the reaction took a long time and had low efficiency. Liu et al. studied the process of preparing n-butanol and isobutanol from 1,2-butanediol (ACS Catal. 2022, 12, 15431-15450). The product selectivity could reach 78% and 64%, respectively, but the hydrogen pressure used in the reaction was high, the reaction time was long, and the conditions were harsh. Patent CN 102731247 A discloses a method for preparing n-propanol from bio-based small molecule diols, wherein 1,2-propylene glycol, a product of glycerol hydrogenolysis, and a catalyst loaded with a transition metal element carrier are subjected to high-temperature dehydration coupled with hydrogen transfer continuous reaction in a fixed bed reactor to prepare n-propanol. The single-pass conversion rate of the reaction using this method reaches 86.01%, and the selectivity of n-propanol in the product reaches 45.01%. However, the reaction temperature of this method is relatively high, the required equipment is relatively complex, and the selectivity of the obtained product is low, which is not conducive to large-scale production. Beeck et al. reported the process of preparing monohydric alcohols from biomass derivatives 1,2-hexanediol and 2,5-hexanediol (Energy Environ. Sci., 2015, 8, 230–240). The reaction time of this method is short, but the yield of the target product is less than 10%, and the overall benefit is not high.Nakagawa et al. reported a method for preparing monohydric alcohols using biomass derivatives 1,2-pentanediol and 1,5-pentanediol (ACS Catal. 2013, 3, 2655-2668). The reaction conditions of this method are relatively mild, but the reaction time required is long and the product selectivity is low (16%), which is not suitable for promotion and application.

[0005] In summary, the hydrogenation of bio-based small molecule diols to prepare monohydric alcohols is a feasible process route. However, most of the methods currently used are complex and have harsh reaction conditions, which hinders the development of industrial preparation of monohydric alcohols from bio-based small molecule dihydric alcohols. It is urgent to develop a low-cost and high-efficiency method for preparing monohydric alcohols. Summary of the invention:

[0006] The purpose of the present invention is to provide a method for preparing monohydric alcohol by catalytic hydrogenation of bio-based small molecule dihydric alcohol.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing monohydric alcohol by catalytic hydrogenation of bio-based small molecule diols, the method comprising the following steps: placing an aqueous solution of the bio-based small molecule diol in a high-pressure reactor, adding an activated carbon-supported metal catalyst and a solid acid or a liquid acid, then introducing hydrogen gas at a certain pressure, stirring and reacting for a period of time at a certain temperature to obtain a monohydric alcohol; the small molecule diol is one of ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol and 1,2-hexanediol, and the monohydric alcohol It is one of ethanol, n-propanol, isopropanol, n-butanol, n-pentanol and n-hexanol; the metal in the activated carbon-loaded metal salt is one of Ru, Pd, Pt, Ir, Ni, Co and Rh, and the metal loading amount is 1-5%; the solid acid is any one of phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, zirconium oxide and tungsten oxide; the liquid acid is any one of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid; the hydrogen pressure is 1-6Mpa, the reaction temperature is 150-220°C and the reaction time is 0.5-30h.

[0009] The preparation method of the activated carbon-supported metal catalyst is as follows: first, the activated carbon is washed with a 1M nitric acid solution for 8 hours, then washed with water until neutral, and dried at 100°C to obtain an activated carbon carrier, and then the prepared metal salt solution is evenly impregnated on the surface of the activated carbon in a certain proportion, and then reduced with hydrogen to obtain the desired activated carbon-supported catalyst.

[0010] Preferably, the concentration of the bio-based small molecule diol is 10-60 g / L, the mass ratio of the metal catalyst to the solid / liquid acid is 1:10-1:2, more preferably 1:5-1:2, and the mass ratio of the total amount of the metal catalyst and the solid / liquid acid to the bio-based small molecule diol is 1:10-4:1, more preferably 1:10-2:1.

[0011] Preferably, the hydrogen pressure is 3-6 MPa, the reaction temperature is 180-220° C., and the reaction time is 0.5-12 h.

[0012] The beneficial effects of the present invention are as follows: the activated carbon raw material has a wide range of sources, is easy to prepare, and can be recycled. The catalyst preparation process is simple, can be reused, is low in price, has high catalytic activity, and has relatively mild reaction conditions, which is easy to promote. Description of the drawings:

[0013] Figure 1 Schematic diagram of the catalytic conversion pathway of diols;

[0014] Figure 2 This is the HPLC test spectrum of the ethylene glycol reaction product in Example 1;

[0015] Figure 3 This is the GC test spectrum of the 1,2-propylene glycol reaction product in Example 19;

[0016] Figure 4 This is the GC test spectrum of the 1,4-butanediol reaction product in Example 27;

[0017] Figure 5 This is the GC test spectrum of the 1,2-pentanediol reaction product in Example 34;

[0018] Figure 6 This is the GC test spectrum of the 1,2-hexanediol reaction product in Example 42;

[0019] Figure 7 The XRD characterization results of the Pd / C catalyst in Example 1;

[0020] Figure 8 These are the TEM characterization results of the tungsten oxide catalyst in Example 58. Specific implementation method:

[0021] The following is a further description of the present invention, rather than a limitation of the present invention.

[0022] Embodiment 1:

[0023] One gram of activated carbon was washed with a 1M nitric acid solution for 8 hours, then washed with water until neutral, and dried at 100°C to obtain an activated carbon carrier. Then, a 1% PdCl3 (w / w) metal chloride solution was mixed with the activated carbon in a ratio of 5:1 (w / w), and the mixture was evenly impregnated on the surface of the activated carbon. The catalyst was then reduced with hydrogen at 500°C under normal pressure for 2 hours to obtain a 5% Pd / C catalyst.

[0024] 20 mL of 10 g / L ethylene glycol solution was placed in a high pressure reactor, 0.2 g of the prepared 5% Pd / C catalyst and 0.6 g of phosphotungstic acid were added, and the air in the reactor was replaced with hydrogen for 3 times, and then 6 MPa of hydrogen was introduced, and the reaction was stirred at 220 ° C and 800 rpm for 2 hours. The obtained product was detected by HPLC, and the ethanol yield was 80.6%.

[0025] Embodiment 2-8:

[0026] Refer to Example 1, the difference is that the ratio of the supported catalyst to the solid acid and the reaction time are different. The specific examples are shown in Table 1.

[0027] Table 1:

[0028] Example Ratio of metal catalyst to solid acid Reaction time (h) Ethanol yield (%) 2 1:5 5 71.9 3 1:5 10 61.2 4 1:4 12 63.3 5 1:3 10 65.8 6 1:2.5 6 70.6 7 1:2.5 8 72.3 8 1:2.5 12 78.5

[0029] Embodiment 9-18:

[0030] Refer to Example 1, the difference is that the amount of catalyst used, the mass ratio of bio-based small molecule diols, the reaction time and the hydrogen pressure are different. The specific examples are shown in Table 2.

[0031] Table 2:

[0032] Example Catalyst to substrate ratio Reaction time (h) Hydrogen pressure(Mpa) Ethanol yield (%) 9 1:10 10 6 39.5 10 1:8 10 5 40.3 11 1:8 12 5 44.6 12 1:6 10 5 45.2 13 1:5 10 4 50.1 14 1:4 8 5 52.6 15 1:2 10 3 61.8 16 1:1 2 5 75.6 17 2:1 1 6 85.6 18 2:1 0.5 6 82.5

[0033] Embodiment 19:

[0034] Take 20mL of 10g / L 1,2-propylene glycol solution, place it in a high-pressure reactor, add 0.2g of the prepared 5% Pt / C catalyst and 0.4g of phosphoric acid, then pass 3Mpa hydrogen, react at 220°C, 800rpm stirring for 3h, and the yield of n-propanol is 88.5%.

[0035] Embodiment 20-26:

[0036] Refer to Example 19, the difference is that the reaction time and hydrogen pressure are different. The specific example is shown in Table 3.

[0037] Table 3:

[0038]

[0039]

[0040] Embodiment 27:

[0041] The preparation of the catalyst is based on Example 1, except that the metal salt is 1% IrCl3 (w / w), and finally a 5% Ir / C catalyst is obtained.

[0042] Take 20mL of 10g / L 1,4-butanediol solution, place it in a high-pressure reactor, add 0.1g of the prepared 5% Ir / C catalyst and 0.2g of hydrochloric acid, then pass 3Mpa hydrogen, react at 220°C, 800rpm stirring for 6h, and the yield of n-butanol is 86.02%.

[0043] Embodiment 28-33:

[0044] Refer to Example 27, the difference is that the reaction time and hydrogen pressure are different. The specific example is shown in Table 4.

[0045] Table 4:

[0046]

[0047]

[0048] Embodiment 34:

[0049] The preparation of the catalyst is based on Example 1, except that the metal salt is 1% Co(NO3)2 (w / w), and a 5% Co / C catalyst is finally obtained.

[0050] Take 20mL of 10g / L 1,2-pentanediol solution, place it in a high-pressure reactor, add 0.02g of the prepared 5% Co / C catalyst and 0.05g of sulfuric acid, then pass 3Mpa hydrogen, react at 200°C, 800rpm stirring for 6h, and the yield of n-pentanol is 72.5%.

[0051] Examples 35-41:

[0052] Refer to Example 34, the difference is that the reaction time and hydrogen pressure are different. The specific example is shown in Table 5.

[0053] Table 5:

[0054]

[0055]

[0056] Embodiment 42:

[0057] The preparation of the catalyst is based on Example 1, except that the metal salt is 1% RhCl3 (w / w), and finally a 5% Rh / C catalyst is obtained.

[0058] Take 20mL of 10g / L 1,2-hexanediol solution, place it in a high-pressure reactor, add 0.01g of the prepared 5% Rh / C catalyst and 0.02g of silicotungstic acid, then pass 3Mpa hydrogen, react at 180°C, 800rpm stirring for 2h, and the yield of n-hexanol is 60.5%.

[0059] Examples 43-49:

[0060] Refer to Example 42, the difference is that the reaction time and hydrogen pressure are different. The specific example is shown in Table 6.

[0061] Table 6:

[0062] Example Reaction time (h) Hydrogen pressure(Mpa) Yield of n-hexanol (%) 43 12 5 50.2 44 10 3 52.3 45 8 3 56.1 46 5 4 62.5 47 2 6 58.6 48 1 5 43.3 49 0.5 5 39.6

[0063] Embodiment 50:

[0064] Take 20mL of a 10g / L mixed solution of ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,2-pentanediol and 1,2-hexanediol, in which the mass proportions of different types of diols are equal, place it in a high-pressure reactor, add 0.02g of the prepared 5% Pd / C catalyst and 0.05g of phosphotungstic acid, then pass 3Mpa hydrogen, react at 200°C, 800rpm stirring for 6h, and the yield of monohydric alcohol is 72.5%.

[0065] Examples 51-58:

[0066] Refer to Example 50, the difference is that the type of acid used, the reaction time and the hydrogen pressure are different. The specific example is shown in Table 7.

[0067] Table 7:

[0068] Example Solid / Liquid Acid Reaction time (h) Hydrogen pressure(Mpa) Monohydric alcohol yield (%) 51 Phosphoric acid 12 5 82.6 52 hydrochloric acid 10 5 83.5 53 Nitric acid 8 6 80.2 54 sulfuric acid 5 6 75.6 55 Silicotungstic acid 3 4 68.1 56 Phosphomolybdic acid 8 5 65.4 57 Zirconia 12 6 58.9 58 Tungsten Oxide 10 5 61.7

Claims

1. A method for preparing monohydric alcohol by catalytic hydrogenation of bio-based small molecule diols, characterized in that: The method comprises the following steps: placing a bio-based small molecule diol aqueous solution in a high pressure reactor, adding an activated carbon-supported metal catalyst and a solid acid or a liquid acid, then introducing a certain pressure of hydrogen, stirring and reacting at a certain temperature for a period of time to obtain a monohydric alcohol; the small molecule dihydric alcohol is one of ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol and 1,2-hexanediol; the monohydric alcohol is one of ethanol, n-propanol, isopropanol, One of n-butanol, n-pentanol and n-hexanol; the metal in the activated carbon-loaded metal salt is one of Ru, Pd, Pt, Ir, Ni, Co and Rh, and the metal loading amount is 1-5%; the solid acid is any one of phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, zirconium oxide and tungsten oxide; the liquid acid is any one of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid; the hydrogen pressure is 1-6Mpa, the reaction temperature is 150-220℃ and the reaction time is 0.5-30h.

2. The method according to claim 1, characterized in that The preparation method of the activated carbon-supported metal catalyst is as follows: first, the activated carbon is washed with a 1M nitric acid solution for 8 hours, then washed with water until neutral, and dried at 100°C to obtain an activated carbon carrier, and then the prepared metal salt solution is evenly impregnated on the surface of the activated carbon, and then reduced with hydrogen to obtain the desired activated carbon-supported catalyst.

3. The method according to claim 1, characterized in that The concentration of the bio-based small molecule diol is 10-60 g / L, and the mass ratio of the metal catalyst to the solid / liquid acid is 1:10-1:

2.

4. The method according to claim 1, characterized in that The mass ratio of the metal catalyst to the solid / liquid acid is 1:5-1:

2.

5. The method according to claim 1, characterized in that The mass ratio of the total amount of the metal catalyst and the solid / liquid acid to the bio-based small molecule diol is 1:10-4:

1.

6. The method according to claim 1, characterized in that The mass ratio of the total amount of the metal catalyst and the solid / liquid acid to the bio-based small molecule diol is 1:10-2:

1.

7. The method according to claim 1, characterized in that The hydrogen pressure is 3-6Mpa, the reaction temperature is 180-220°C, and the reaction time is 0.5-12h.

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