Method for preparing 1, 2-propylene glycol from enteromorpha and rhamnose derived from enteromorpha

Abstract

The invention discloses a method for preparing 1, 2-propylene glycol from enteromorpha and rhamnose derived from enteromorpha, which comprises the following steps: adding 100 parts of substrate, 50-200 parts of catalyst and a proper amount of deionized water into a reaction kettle under the conditions that the pressure of the reaction kettle is 3 MPa, the temperature is 180 DEG C and the reaction time is 120 minutes; then cooling and decompressing the reaction kettle, carrying out suction filtration to remove the solid catalyst, and detecting and filtering reaction liquid by using HPLC (High Performance Liquid Chromatography) to obtain small molecules which are the product 1, 2-propylene glycol; the substrate is enteromorpha prolifera and rhamnose derived from the enteromorpha prolifera; the catalyst is a W or Mo doped Pt / CeO2 based catalyst. The solid catalyst is easy to prepare, low in cost and high in catalytic efficiency, and the yield of the obtained 1, 2-propylene glycol is high. Meanwhile, after the reaction, the solid catalyst can be simply filtered and recycled, and the repeated utilization rate is high. According to the method, the blank of directionally preparing 1, 2-propylene glycol by catalyzing enteromorpha and derivative rhamnose thereof through a chemical catalysis method is filled, and the defects of low production efficiency and long reaction period of a traditional synthesis method and a microbiological method are overcome.

Description

Technical Field

[0001] The invention relates to the field of biochemistry, and in particular to a method for preparing 1,2-propylene glycol from Enteromorpha and rhamnose derived therefrom. Background Art

[0002] Developing chemical processes for converting biomass solid waste resources into high-value chemicals is conducive to the sustainable development of society. Enteromorpha is a common large algae that is rich in carbohydrates (such as rhamnose, glucose and xylose). Converting Enteromorpha resources into high-value chemicals (such as 1,2-propylene glycol) required for human life is conducive to the realization of "turning waste into treasure" of solid waste resources and improving the aquatic environment.

[0003] 1,2-propanediol is an important chemical raw material and pharmaceutical intermediate, widely used in polyester resins, surface coatings, medicines, cosmetics, tobacco, antifreeze and other fields. With the increasing global attention to sustainable development and environmental protection, the use of renewable resources to replace traditional petroleum-based raw materials to produce high-value chemicals has become an important development goal. Therefore, the development of a chemical process for the selective preparation of 1,2-propanediol from Enteromorpha-derived sugar compounds with high efficiency has important economic and social significance.

[0004] The traditional method for producing 1,2-propylene glycol is mainly the propylene oxide hydration method. However, the raw materials for the reaction are non-renewable petroleum-based chemicals, and a large amount of strong alkali (NaOH) is required in the reaction process, which generates a large amount of waste salt and wastewater, which is not conducive to the sustainable development of society. In existing reports, the substrate for preparing 1,2-propylene glycol from biomass resources is usually glucose, and the catalyst is a supported multifunctional catalyst. However, the yield of 1,2-propylene glycol prepared from glucose is generally <50%, and the concentration of the obtained 1,2-propylene glycol product is generally less than 5 mg / mL, resulting in low energy efficiency and other unfavorable situations.

[0005] There has been no report on the direct catalytic conversion of Enteromorpha and its derived rhamnose to produce high-concentration and high-yield 1,2-propylene glycol. Summary of the invention

[0006] The object of the present invention is to overcome the above-mentioned background technical difficulties and provide a method for preparing high-concentration and high-yield 1,2-propylene glycol from Enteromorpha or rhamnose.

[0007] In order to achieve the above object, the technical scheme adopted is: a method for preparing 1,2-propylene glycol from Enteromorpha and its derivative rhamnose, According to the mass ratio, 100 parts of substrate, 50-200 parts of catalyst and appropriate amount of deionized water are added into a reactor, the pressure of the reactor is 0.5-5 MPa, the temperature is 100-200 °C under the initial hydrogen atmosphere, and the reaction time is 1-180 min; then the reactor is cooled and depressurized, the solid catalyst is filtered out, and the filtered reaction liquid is detected by HPLC, and the obtained small molecule is the product 1,2-propylene glycol; the substrate is Enteromorpha and its derivative rhamnose; the catalyst is a W or Mo doped Pt / CeO2-based catalyst, the loading amount of Pt is 1 wt%, and the loading amounts of W and Mo are 1-7 wt%.

[0008] Furthermore, the CeO2 carrier in the catalyst has a fishing rod-like (rod-like) shape.

[0009] Further, the catalyst is Pt1Mo5 / CeO 2。

[0010] Further, the preparation method of the catalyst is: A certain amount of Ce precursor Ce(NO3)3·6H2O was dissolved in 100 mL of water and ultrasonically stirred for 10 min to facilitate the dissolution and dispersion of the Ce component. Then, 24 g of NaOH was quickly added and the mixture was transferred to a hydrothermal reactor. The speed was set to 200 rpm, the reaction temperature was set to 100 °C, and the reaction time was set to 24 h. After the reaction, the obtained solid was filtered, washed, and dried. It was calcined in a tubular furnace in an air atmosphere at 450 °C with a heating rate of 5 °C / min for 3 h to obtain a fish rod-shaped CeO2 carrier. The precursor chloroplatinic acid aqueous solution of Pt, the precursor of Sn / W / Mo and the surfactant PVP-K30 were added to 5 mL of water and ultrasonically stirred for 15 min to facilitate the dissolution and dispersion of the active components. Then, the CeO2 carrier was added and stirred for 4 hours. After immersion for 24 hours, the moisture was removed by freeze-drying and dried at 80°C for 10 h. The dried solid was ground and placed in a tubular furnace, calcined at 450°C for 3 h with a heating rate of 5°C / min. The obtained solid was reduced at 350°C, H2 atmosphere, 40 mL / min, for 2 h to obtain Pt / CeO2-based catalysts doped with different components.

[0011] Furthermore, the solid catalyst obtained by filtration was placed in an oven and dried at 80 °C for 10 h, then placed in a tubular furnace in an air atmosphere and calcined at 450 °C for 3 h, and then reduced at 350 °C for 2 h in a H2 atmosphere at 40 mL / min, and can be reused.

[0012] Furthermore, the reaction temperature is 180°C.

[0013] Furthermore, the reaction time is 120 min.

[0014] Furthermore, the catalyst is 100 parts.

[0015] Furthermore, the reactor and H2 pressure are 3 MPa.

[0016] Furthermore, the reaction substrates may be glucose and xylose, saccharide compounds derived from Enteromorpha.

[0017] The beneficial effects of adopting the above scheme are: The present invention designs and prepares a Pt / CeO2-based catalyst doped with different components (Sn, W, Mo) for catalytic conversion of Enteromorpha and its derivative rhamnose to prepare 1,2-propylene glycol, wherein Pt1Mo5 / CeO2 exhibits the best catalytic activity. The solid catalyst is easy to prepare, has low cost, and has high catalytic efficiency, and the yield of the obtained 1,2-propylene glycol is high. At the same time, after the reaction, the solid catalyst can be recovered by simple filtration, and has a high reuse rate. This method fills the gap in the directional preparation of 1,2-propylene glycol by Enteromorpha and its derivative rhamnose by chemical catalysis, and also overcomes the shortcomings of low production efficiency and long reaction cycle of traditional synthesis methods and microbial methods.

[0018] The present invention uses Enteromorpha and its derivative rhamnose as raw materials to prepare 1,2-propylene glycol, which has the advantage of renewable raw materials compared to the existing industrial synthesis method-propylene oxide method.

[0019] The present invention establishes for the first time a reaction system for preparing 1,2-propylene glycol from Enteromorpha and its derivative rhamnose, thus expanding the application of Enteromorpha and realizing the value-added of solid waste resources such as Enteromorpha. The catalyst of the invention has a simple preparation process and good stability, and the maximum yield of 1,2-propylene glycol is over 55%, and has good application prospects. DETAILED DESCRIPTION

[0020] The technical scheme of the present invention is clearly and completely described below in conjunction with the specific embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0021] It should be understood that the following terms included in the text may be for the convenience of description and simplification of description, or are merely based on the relationship shown in the legend, rather than indicating or implying a specific relationship that is required. Technical personnel in this field need to make a broad understanding in conjunction with the full text, and it cannot be interpreted as a limitation on the present technical solution.

[0022] The applicant has for the first time achieved the conversion of rhamnose derived from Enteromorpha to produce hydroxyacetone, with a yield of 62.2 C-mol%. Analysis of the structures of rhamnose and hydroxyacetone shows that the carbonyl group (-C=O) in hydroxyacetone can be further hydrogenated to produce 1,2-propylene glycol.

[0023] The present invention designs and prepares a Pt / CeO2-based catalyst doped with different components (Sn, W, Mo) for catalytic conversion of Enteromorpha and its derivative rhamnose to prepare 1,2-propylene glycol, wherein Pt1Mo5 / CeO2 exhibits the best catalytic activity. The solid catalyst is easy to prepare, has low cost, and has high catalytic efficiency, and the yield of the obtained 1,2-propylene glycol is high. At the same time, after the reaction, the solid catalyst can be recovered by simple filtration, and has a high reuse rate. This method fills the gap in the directional preparation of 1,2-propylene glycol by Enteromorpha and its derivative rhamnose by chemical catalysis, and also overcomes the shortcomings of low production efficiency and long reaction cycle of traditional synthesis methods and microbial methods.

[0024] A certain amount of Ce precursor (Ce(NO3)3·6H2O) was dissolved in 100 mL of water and ultrasonically stirred for 10 min to facilitate the dissolution and dispersion of the Ce component. Then 24 g of NaOH was quickly added and transferred to a hydrothermal reactor. The speed was set to 200 rpm, the reaction temperature was 100 ℃, and the reaction time was 24 h. After the reaction, the obtained solid was filtered, washed, and dried, and calcined at 450 ℃ (heating rate of 5 ℃ / min) for 3 h in a tube furnace in an air atmosphere to obtain a fish rod-shaped (rod-shaped) CeO2 carrier.

[0025] The precursor of Pt (chloroplatinic acid aqueous solution), the precursor of Sn / W / Mo and the surfactant PVP (K30) were added to 5 mL of water, and ultrasonic stirring was performed for 15 min to facilitate the dissolution and dispersion of the active components. Then, the CeO2 carrier was added and stirred for 4 hours. After immersion for 24 hours, the water was removed by freeze-drying and dried at 80 °C for 10 h. The dried solid was ground and placed in a tube furnace, calcined at 450 °C for 3 h (heating rate 5 °C / min), and the obtained solid was reduced at 350 °C in H2 atmosphere (40 mL / min) for 2 h to obtain Pt / CeO2-based catalysts doped with different components.

[0026] Embodiment 1-4: 1) Add 100 mg rhamnose, 100 mg Pt / CeO2-based catalyst (the loading amount of Pt in the catalyst is 1 wt%, and the loading amount of Sn, W, and Mo is 5 wt%), and then add 50 mL of deionized water to a 100 mL autoclave. After sealing the autoclave, introduce hydrogen into the autoclave to maintain its pressure at 3 MPa. After stirring and heating to 180 °C, react for 120 minutes, lift the autoclave out of the heating device and quickly cool it to room temperature. Open the autoclave, separate the solid-liquid mixture in the autoclave by vacuum filtration, and obtain a solid residue and a product mixture.

[0027] ) The collected solid residue was washed with deionized water for 3 times, placed in an oven, dried, and then placed in a tube furnace in an air atmosphere and calcined at 450 °C for 3 h. It was then reduced in a H2 atmosphere (40 mL / min) at 350 °C for 2 h and used for the next catalytic reaction. The small molecule products in the reaction solution were detected by HPLC, and the results are shown in Table 1 (the yield in the table is the carbon molar yield, product yield = carbon molar amount of the obtained product / carbon molar amount of the added raw material × 100%).

[0028] Table 1 Implementation Cases catalyst Conversion rate Rhamnitol lactic acid glycerin Ethylene glycol 1,2-Propanediol Hydroxyacetone 1 <![CDATA[Pt1 / CeO2]]> 99.8% 11.7 % 5.0 % 8.6% 15.1 % 42.6% <0.2% 2 <![CDATA[Pt1Sn5 / CeO2]]> 99.8% 1.4% 13.0% 2.7% 3.8% <0.2% 52.6% 3 <![CDATA[Pt1W5 / CeO2]]> 99.8% 8.7% 3.3% 6.6% 14.4% 53.6% <0.2% 4 <![CDATA[Pt1Mo5 / CeO2]]> 99.8% 4.7% 3.6% 3.4% 12.4% 55.8% <0.2% From the results in Table 1, it can be seen that after doping with W / Mo elements, the yield of 1,2-propylene glycol is significantly improved, and the catalytic activity of Pt1Mo5 / CeO2 catalyst is the best. When doped with Sn element, the main product changes from 1,2-propylene glycol to hydroxyacetone.

[0029] Embodiment 5-7: The experimental steps are the same as those in Example 4, except that the Mo loading amount in the selected Pt1Mo / CeO2 catalyst is different, and other conditions remain unchanged. The specific results are listed in Table 2 (the yield in the table is the carbon molar yield).

[0030] Table 2 Implementation Cases Mo loading Conversion rate Rhamnitol lactic acid glycerin Ethylene glycol 1,2-Propanediol Hydroxyacetone 5 1 wt% 99.8% 9.4 % 4.8 % 7.2% 14.5 % 44.7% <0.2% 6 3 wt% 99.8% 6.2% 4.1% 4.7% 13.8% 49.1% <0.2% 7 7 wt% 99.8% 3.5% 2.6% 2.5% 10.7% 47.4% <0.2% Combining the results of Example 4 and Table 2, it can be seen that different Mo doping amounts greatly affect the formation of 1,2-propylene glycol. However, excessive Mo doping is not conducive to the formation of 1,2-propylene glycol. When the Mo doping amount is 5 wt%, the catalytic activity is the highest.

[0031] Embodiment 8-11: The experimental steps are the same as those in Example 4, except that the reaction temperature is different and other conditions remain unchanged. The specific results are listed in Table 3 (the yield in the table is the carbon molar yield).

[0032] Table 3 Implementation Cases Reaction temperature Conversion rate Rhamnitol lactic acid glycerin Ethylene glycol 1,2-Propanediol Hydroxyacetone 8 160 ℃ 99.8% 7.7 % 1.1 % 1.4% 5.5 % 38.9% <0.2% 9 170 ℃ 99.8% 6.2% 2.3% 1.8% 7.9% 47.1% <0.2% 10 190 ℃ 99.8% 4.0% 3.3% 2.6% 11.0% 57.7% <0.2% 11 200 ℃ 99.8% 3.0% 2.8% 2.9% 11.4% 57.5% <0.2% Combining the results of Example 4 and Table 3, it can be seen that when the temperature is low, more rhamnitol is generated by the competitive reaction. As the reaction temperature increases, the CC bond cleavage products, especially 1,2-propylene glycol, increase. After >100 °C, the yield of 1,2-propylene glycol is significantly improved. After >180 °C, the yield of 1,2-propylene glycol does not change significantly when the reaction temperature continues to increase.

[0033] Embodiment 12-16: The experimental steps are the same as those in Example 4, except that the reaction time is different and other conditions remain unchanged. The specific results are listed in Table 4 (the yield in the table is the carbon molar yield).

[0034] Table 4 Implementation Cases Reaction time Conversion rate Rhamnitol lactic acid glycerin Ethylene glycol 1,2-Propanediol Hydroxyacetone 12 1 min 50.8% 1.0 % <0.2% <0.2% 0.4 % 12.1% <0.2% 13 30 min 82.7% 2.2% 0.4% 0.3% 2.2% 35.6% <0.2% 14 60 min 99.8% 3.6% 1.1% 1.1% 7.9% 42.4% <0.2% 15 90 min 99.8% 4.1% 2.6% 1.7% 9.1% 49.7% <0.2% 16 150 min 99.8% 4.0% 3.3% 2.3% 9.6% 55.5% <0.2% Combining the results of Example 4 and Table 4, it can be seen that the yield of 1,2-propylene glycol increases continuously with increasing reaction time. After exceeding 120 min, the yield of 1,2-propylene glycol does not change significantly with further increasing reaction time. After exceeding 180 min, the yield of 1,2-propylene glycol no longer increases.

[0035] Embodiment 17-20: The experimental steps are the same as those in Example 4, except that the amount of catalyst used is different. Other conditions remain unchanged. The specific results are listed in Table 5 (the yield in the table is the carbon molar yield).

[0036] Table 5 Implementation Cases Catalyst dosage Conversion rate Rhamnitol lactic acid glycerin Ethylene glycol 1,2-Propanediol Hydroxyacetone 17 50 mg 99.8% 2.0 % 2.4 % 1.2% 4.7 % 40.3% <0.2% 18 75 mg 99.8% 3.6% 3.1% 2.2% 8.6% 46.7% <0.2% 19 125 mg 99.8% 5.9% 4.1% 3.5% 11.3% 54.5% <0.2% 20 150 mg 99.8% 7.1% 4.3% 3.8% 10.1% 53.2% <0.2% Combining the results of Example 4 and Table 5, it can be seen that the yield of 1,2-propylene glycol increases continuously with increasing the amount of catalyst used. When the amount of catalyst used exceeds 100 mg, the yield of 1,2-propylene glycol decreases slightly.

[0037] Embodiment 21-25: The experimental steps are the same as those in Example 4, except that the hydrogen pressure is different (when the hydrogen pressure is 0, 3 MPa N2 is used instead), and other conditions remain unchanged. The specific results are listed in Table 6 (the yield in the table is the molar yield of carbon).

[0038] Table 6 Implementation Cases <![CDATA[H2 pressure]]> Conversion rate Rhamnitol lactic acid glycerin Ethylene glycol 1,2-Propanediol Hydroxyacetone 21 0 99.8% <0.2% 22.2 % <0.2% <0.2% <0.2% 46.6% 22 1 MPa 99.8% 2.2% 8.5% 1.1% 3.5% 41.6% <0.2% 23 2 MPa 99.8% 3.4% 6.2% 1.9% 7.8% 48.5% <0.2% 24 4 MPa 99.8% 5.5% 3.4% 2.8% 12.4% 53.1% <0.2% 25 5 MPa 99.8% 6.3% 3.2% 3.3% 13.9% 50.2% <0.2% Combining the results of Example 4 and Table 6, it can be seen that when there is no H2 (N2 atmosphere), the main product of the reaction is hydroxyacetone, and the main product is 1,2-propylene glycol after adding 1 MPa H2. As the H2 pressure continues to increase, the yield of 1,2-propylene glycol continues to increase. When the H2 pressure is >3 MPa, the H2 pressure continues to increase, the yield of 1,2-propylene glycol decreases, and the yield of rhamnitol increases significantly.

[0039] Embodiment 26-29: The experimental steps are the same as those in Example 4, except that the catalyst is reused for different times and other conditions remain unchanged. The specific results are listed in Table 7 (the yield in the table is the carbon molar yield).

[0040] Table 7 Implementation Cases Cycle times Conversion rate Rhamnitol lactic acid glycerin Ethylene glycol 1,2-Propanediol Hydroxyacetone 26 1 97.9% 4.5% 3.4 % 3.2% 11.8 % 53.4% <0.2% 27 2 96.2% 4.1% 3.3% 3.0% 11.5% 52.8% <0.2% 28 3 95.8% 4.0% 3.3% 2.9% 11.1% 52.0% <0.2% 29 4 94.0% 3.7% 2.6% 2.4% 10.4% 50.3% <0.2% From the results in Table 7, it can be seen that the prepared Pt1Mo5 / CeO2 catalyst exhibits good stability in the process of catalytic conversion of rhamnose to prepare 1,2-propylene glycol.

[0041] Embodiment 30-32: The experimental steps are the same as those in Example 4, except that different reaction substrates are used, wherein Enteromorpha enteromorpha is hydrolyzed with oxalic acid and then purified for the reaction, and other conditions remain unchanged. The specific results are listed in Table 8 (the yield in the table is the carbon molar yield).

[0042] Table 8 Implementation Cases Reaction substrate Conversion rate 1,2-Propanediol 30 glucose 99.8% 48.8% 31 Xylose 99.8% 36.2% 32 Enteromorpha - 40.1% From the results in Table 8, it can be seen that the above-mentioned catalytic system can be used to catalyze other sugar compounds (glucose, xylose) derived from Enteromorpha, or even directly generate 1,2-propylene glycol from Enteromorpha.

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0044] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing 1,2-propylene glycol from Enteromorpha and its derivative rhamnose, characterized in that: According to the mass ratio, 100 parts of substrate, 50-200 parts of catalyst and appropriate amount of deionized water are added into a reactor, the pressure of the reactor is 0.5-5 MPa, the temperature is 100-200 °C under the initial hydrogen atmosphere, and the reaction time is 1-180 min; then the reactor is cooled and depressurized, the solid catalyst is filtered out, and the filtered reaction liquid is detected by HPLC, and the obtained small molecule is the product 1,2-propylene glycol; the substrate is Enteromorpha and its derivative rhamnose; the catalyst is a W or Mo doped Pt / CeO2-based catalyst, the loading amount of Pt is 1 wt%, and the loading amounts of W and Mo are 1-7 wt%.

2. The method for preparing 1,2-propylene glycol from Enteromorpha and its derivative rhamnose according to claim 1, characterized in that: The CeO2 carrier in the catalyst has a fish rod shape.

3. The method for preparing 1,2-propylene glycol from Enteromorpha and its derivative rhamnose according to claim 1, characterized in that: The catalyst is Pt1Mo5 / CeO2.

4. The method for preparing 1,2-propylene glycol from Enteromorpha and its derived rhamnose according to claim 2, characterized in that: The preparation method of the catalyst is: A certain amount of Ce precursor Ce(NO3)3·6H2O was dissolved in 100 mL of water and ultrasonically stirred for 10 min to facilitate the dissolution and dispersion of the Ce component. Then, 24 g of NaOH was quickly added and the mixture was transferred to a hydrothermal reactor. The speed was set to 200 rpm, the reaction temperature was set to 100 °C, and the reaction time was set to 24 h. After the reaction, the obtained solid was filtered, washed, and dried. It was calcined in a tubular furnace in an air atmosphere at 450 °C with a heating rate of 5 °C / min for 3 h to obtain a fish rod-shaped CeO2 carrier. The precursor chloroplatinic acid aqueous solution of Pt, the precursor of Sn / W / Mo and the surfactant PVP-K30 were added to 5 mL of water and ultrasonically stirred for 15 min to facilitate the dissolution and dispersion of the active components. Then, the CeO2 carrier was added and stirred for 4 hours. After immersion for 24 hours, the moisture was removed by freeze-drying and dried at 80°C for 10 h. The dried solid was ground and placed in a tubular furnace, calcined at 450°C for 3 h with a heating rate of 5°C / min. The obtained solid was reduced at 350°C, H2 atmosphere, 40 mL / min, for 2 h to obtain Pt / CeO2-based catalysts doped with different components.

5. The method for preparing 1,2-propylene glycol from Enteromorpha and its derivative rhamnose according to claim 1, characterized in that: The solid catalyst obtained by filtration was placed in an oven and dried at 80 °C for 10 h, then placed in a tubular furnace in an air atmosphere and calcined at 450 °C for 3 h, and then reduced at 350 °C for 2 h in a H2 atmosphere at 40 mL / min, and can be reused.

6. The method for preparing 1,2-propylene glycol from Enteromorpha and its derived rhamnose according to claim 1, characterized in that: The reaction temperature is 180°C.

7. The method for preparing 1,2-propylene glycol from Enteromorpha and its derived rhamnose according to claim 1, characterized in that: The reaction time is 120 min.

8. The method for preparing 1,2-propylene glycol from Enteromorpha and its derivative rhamnose according to claim 1, characterized in that: The catalyst is 100 parts.

9. The method for preparing 1,2-propylene glycol from Enteromorpha and its derivative rhamnose according to claim 1, characterized in that: The reactor and H2 pressure are 3 MPa.

10. The method for preparing 1,2-propylene glycol from Enteromorpha and its derived rhamnose according to claim 1, characterized in that: The reaction substrates may be glucose and xylose, saccharide compounds derived from Enteromorpha.