Method for separating and purifying levoglucosenone from bio-oil

Abstract

The invention belongs to the field of separation and purification of bio-based chemicals, and particularly relates to a method for separating and purifying levoglucosenone from bio-oil. According to the method, the bio-oil obtained in the process of preparing levoglucosenone (LGO) through selective pyrolysis of biomass is used as a raw material, organic acid in the bio-oil is removed through a supersaturated carbonate solution, and then an oil phase is obtained through step-by-step extraction. And then adjusting working conditions, carrying out echelon reduced pressure distillation on the oil phase, and sequentially removing the extracting agent, low-boiling-point impurities and high-boiling-point oligomers, so as to obtain high-purity LGO. The pyrolysis bio-oil is subjected to coupling treatment of deacidification, step-by-step extraction and echelon reduced pressure distillation, so that the aim of separating and purifying high-added-value chemicals from low-value and complex-component bio-oil is fulfilled. The raw materials are cheap and easy to obtain, the process is simple, and the method is a biomass resource utilization method with great prospects.

Description

Technical Field

[0001] The present invention belongs to the field of separation and purification of bio - based chemicals, and particularly relates to a method for separating and purifying levoglucosenone from bio - oil. Background Art

[0002] As a carbon - rich resource with abundant reserves, biomass can be converted into fuels, new materials, and chemical products through different technologies. Fast pyrolysis is a promising biomass utilization technology that can rapidly and efficiently convert biomass into bio - oil containing high - value compounds such as phenols, ketones, and sugars.

[0003] Among the numerous components of bio - oil, levoglucosenone (1,6 - anhydro - 3,4 - dideoxy - β - D - glucopyranos - 2 - one, LGO) is an important dehydrated sugar compound with a special chiral structure and multiple active centers, and has broad application prospects in the synthesis of chiral auxiliaries, anticancer drugs, and highly efficient targeted drugs such as tetrodotoxin. At present, at home and abroad, LGO is mainly synthesized by chemical methods using galactomannan, D - galactose, and mannitol as raw materials. Although the LGO obtained by chemical synthesis has a high purity, due to the high cost of the initial raw materials, its production is small, making it difficult to achieve large - scale application. In recent years, research on the preparation of LGO by pyrolysis of biomass as raw materials has been widely reported. Due to the low cost and easy availability of the initial raw materials and the simple process, it has received extensive attention. Chinese patent applications CN202210670823.X, CN202210670822.5, and CN201910962271.8 disclose various methods for the selective preparation of LGO by catalytic pyrolysis of biomass, effectively improving the yield of LGO and making the large - scale production of LGO promising. However, the bio - oil obtained by selective pyrolysis is still a complex mixture of components. In addition to the main product LGO, it also contains dozens of organic compounds such as organic acids, phenols, ketones, and aldehydes, making it very difficult to separate and purify LGO, seriously affecting its economic benefits. How to separate high - purity LGO from the bio - oil obtained by selective pyrolysis is the key problem to be solved.

[0004] At present, there are few reports on the separation and purification of LGO from bio - oil, and only column chromatography separation methods on a laboratory scale are available, which cannot form large - scale process technologies. Therefore, developing an efficient separation and purification process to separate LGO from bio - oil and obtaining high - purity LGO with commercial value is the key to realizing the industrial application of LGO. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for separating and purifying levoglucosenone from bio - oil.

[0006] The present invention provides a method for separating and purifying levoglucosenone from bio - oil, comprising the following steps:

[0007] (1) Add solid carbonate to water and stir to dissolve at room temperature to obtain a supersaturated alkaline solution.

[0008] Preferably, the carbonate is one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.

[0009] Preferably, the supersaturated alkaline solution is prepared according to a solid-liquid ratio of carbonate to water of (1:10) to (2:1) (g / mL).

[0010] (2) Using the bio-oil obtained from the selective pyrolysis of biomass as the raw material, uniformly add the supersaturated alkaline solution obtained in step (1) to the bio-oil and stir until no bubbles are generated on the liquid surface to obtain a mixed solution.

[0011] Preferably, the bio-oil obtained from the selective pyrolysis of biomass includes: after impregnating biomass with an aqueous phosphoric acid solution, rapidly pyrolyzing under inert and anaerobic conditions, and condensing the generated pyrolysis gas to obtain a liquid product (bio-oil) rich in LGO.

[0012] More preferably, the aqueous phosphoric acid solution refers to a solution prepared by mixing concentrated phosphoric acid (concentration 85%) with water, and the mass concentration of the aqueous phosphoric acid solution is 1 to 5%.

[0013] More preferably, the biomass is impregnated with the aqueous phosphoric acid solution according to a solid-liquid ratio of (1:10) (g / mL), then dried to a constant weight, and pyrolyzed at a temperature of 270 to 420 °C.

[0014] More preferably, the biomass includes all lignocellulosic biomasses with a cellulose content exceeding 35%, such as poplar, corn stover, rice straw, corn cob, etc.

[0015] Preferably, the mass ratio of the supersaturated alkaline solution to the bio-oil is (1:1) to (4:1).

[0016] Preferably, the non-generation of bubbles means that no bubbles are generated due to the acid-base neutralization reaction between the bio-oil and the supersaturated alkaline solution.

[0017] (3) Add the extractant step by step and multiple times to the mixed solution obtained in step (2), shake and let stand. After obvious stratification occurs between the water and oil phases, separate to obtain the oil phase.

[0018] Preferably, the extractant is one of dichloromethane, ethyl acetate, and chloroform, and the mass ratio of the extractant to the bio-oil is (2:1) to (5:1).

[0019] Preferably, the separation refers to obtaining the oil phase by liquid separation.

[0020] More preferably, the oil phase means that when the density of the extractant is greater than that of water, the lower layer is the oil phase; when the density of the extractant is less than that of water, the upper layer is the oil phase.

[0021] (4) Use a rotary evaporator to carry out vacuum distillation on the oil phase obtained in step (3) under low temperature and low pressure conditions to remove the extractant, and obtain an LGO mixture sample.

[0022] A rotary evaporator is a conventional vacuum distillation device and can be obtained through commercial purchase, for example, purchased from Shanghai Yarong Biochemical Instrument Factory.

[0023] Preferably, the low temperature and low pressure conditions refer to a distillation temperature of 20 - 50 °C and a distillation pressure of 40 - 60 mmHg.

[0024] Preferably, the removal of the extractant means that no condensate droplets are formed on the condenser tube of the rotary evaporator within 5 minutes, and it is considered that the extractant has been completely removed.

[0025] (5) Use a Claisen distillation apparatus to carry out vacuum distillation on the LGO mixture sample obtained in step (4) under medium temperature and medium pressure conditions to remove low-boiling impurities, and obtain a residue.

[0026] A Claisen distillation apparatus is a standardized vacuum distillation device and can be obtained through commercial purchase, for example, purchased from Shanghai Yarong Biochemical Instrument Factory.

[0027] Preferably, the medium temperature and medium pressure conditions refer to a distillation temperature of 80 - 110 °C and a distillation pressure of 25 - 35 mmHg.

[0028] Preferably, the removal of low-boiling impurities means that no condensate droplets are formed on the condenser tube of the Claisen distillation apparatus within 5 minutes, and it is considered that the low-boiling impurities have been completely evaporated into the distillate, and LGO remains in the residue, so as to achieve the purpose of removing low-boiling impurities.

[0029] (6) Use a Claisen distillation apparatus to carry out vacuum distillation on the residue obtained in step (5) under high temperature and high pressure conditions to remove high-boiling oligomers, and obtain an LGO-rich fraction.

[0030] Preferably, the high temperature and high pressure conditions refer to a distillation temperature of 120 - 150 °C and a distillation pressure of 15 - 25 mmHg.

[0031] Preferably, the removal of high-boiling oligomers means that no condensate droplets are formed on the condenser tube of the Claisen distillation apparatus within 5 minutes, and it is considered that LGO has been completely evaporated into the distillate, and the high-boiling oligomers remain in the residue, so as to achieve the purpose of removing high-boiling oligomers.

[0032] (7) Use a molecular distillation device to perform 3 to 9 stages of molecular distillation on the LGO-rich fraction obtained in step (6) under suitable distillation temperature, distillation pressure, feed rate, and scraper rotation speed conditions to obtain high-purity LGO.

[0033] The molecular distillation device is a standardized vacuum distillation equipment and can be obtained through commercial purchase, for example, purchased from Beijing Kangbaite Technology Co., Ltd.

[0034] Preferably, the suitable conditions refer to a distillation temperature of 60 to 100 °C, a distillation pressure of 3 to 8 mmHg, a feed rate of 0.2 to 0.7 ml / min, and a scraper rotation speed of 90 to 200 r / min.

[0035] Preferably, the high-purity LGO means that the purity of LGO is not less than 90%. Preferably, the 3 to 9 stages of molecular distillation refer to using the LGO-rich component obtained from the previous molecular distillation as the raw material for the next molecular distillation, and then performing multiple repeated molecular distillations under the same conditions. For example, 3 repeated molecular distillations are 3-stage molecular distillation.

[0036] The beneficial effects of the present invention are as follows:

[0037] The present invention performs a coupling treatment on bio-oil, greatly increasing the purity of LGO in bio-oil from 20% to over 90%. At present, there are many problems in separating and purifying LGO from bio-oil. First, LGO has multiple active centers and is prone to acidification reactions at elevated temperatures, so it cannot be directly separated by one-step distillation. Second, the normal boiling point of LGO is as high as 270 °C, and LGO is easily decomposed at high temperatures, resulting in the inability to use normal pressure distillation technology for separation. Finally, bio-oil contains various organic compounds such as acids, phenols, ketones, aldehydes, sugars, and oligomers. Not only is the composition complex, but a slightly higher temperature will induce the reaction between LGO and acids, making it difficult to separate LGO from numerous components using a single distillation method. The present invention adopts a coupling treatment of deacidification-stepwise extraction-stepwise vacuum distillation. First, use an alkaline solution to remove small-molecule organic acids to avoid the reaction between LGO and organic acids in the vacuum distillation stage. Then, extract LGO in bio-oil with an extractant while removing water and water-soluble organic compounds in bio-oil to achieve the effects of deacidification and dewatering. Then, utilize the boiling point difference of different compounds to sequentially remove phenols, ketones, aldehydes, and oligomers in bio-oil through stepwise vacuum distillation, effectively solving the difficulty of complex bio-oil components and difficult separation of single compounds, and successfully achieving the high-purity separation of LGO. In addition, the process of the present invention is simple, has a low cost, and is applicable to the separation of bio-oil with low LGO purity. This not only accelerates the research on the preparation of high-value-added chemicals from biomass but also can improve the economic, ecological, and social benefits in the bioenergy utilization and refining industry, and has great potential in promoting the resource utilization of biomass.

[0038] The present invention has been described in detail above. However, the above embodiments are essentially illustrative only and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the foregoing prior art, summary of the invention, or the following examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The present invention will be further described below in conjunction with the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of the present invention claimed.

[0041] The test materials, reagents, etc. used in the following embodiments can be obtained from commercial sources without special instructions.

[0042] The calculation method of LGO purity in the following embodiments is as follows:

[0043] LGO purity = (mass of LGO ÷ mass of bio - oil) × 100%.

[0044] In the following embodiments, the content of LGO in the sample is quantified by gas chromatography / mass spectrometry using the external standard method.

[0045] Unless otherwise specified, the percentages in the following embodiments are all mass percentages.

[0046] Example 1

[0047] Take 50 g of sodium carbonate and put it into 100 mL of water, stir to prepare a supersaturated sodium carbonate solution; dry 150 g of poplar wood impregnated with a 2% phosphoric acid aqueous solution and perform rapid pyrolysis at 270 °C to obtain 50 mL of bio-oil rich in LGO; take the above 100 mL of supersaturated sodium carbonate solution and uniformly add it to 50 mL of bio-oil, stir until no bubbles are generated to obtain a mixed solution; take 100 mL of dichloromethane and add it to the mixed solution step by step and multiple times, shake and let stand. After obvious stratification of the water and oil phases, separate to obtain the lower oil phase; place the oil phase in a rotary evaporator and perform vacuum distillation at 20 °C and 40 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 80 °C and 25 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 120 °C and 15 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 5-stage molecular distillation at 60 °C, 3 mmHg, 0.2 ml / min, and 100 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 90.14%.

[0048] Example 2

[0049] Take 15 g of sodium bicarbonate and put it into 130 mL of water, stir to prepare a supersaturated sodium bicarbonate solution; dry 120 g of corn straw impregnated with a 2% phosphoric acid aqueous solution and perform rapid pyrolysis at 300 °C to obtain 40 mL of bio-oil rich in LGO; take the above 130 mL of supersaturated sodium bicarbonate solution and uniformly add it to 40 mL of bio-oil, stir until no bubbles are generated to obtain a mixed solution; take 80 mL of ethyl acetate and add it to the mixed solution step by step and multiple times, shake and let stand. After obvious stratification of the water and oil phases, separate to obtain the upper oil phase; place the oil phase in a rotary evaporator and perform vacuum distillation at 25 °C and 45 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 90 °C and 30 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 125 °C and 20 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 6-stage molecular distillation at 65 °C, 4 mmHg, 0.3 ml / min, and 150 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 91.43%.

[0050] Example 3

[0051] Take 18 g of sodium bicarbonate and place it in 150 mL of water, stir to prepare a supersaturated sodium bicarbonate solution; dry 320 g of corn straw impregnated with a 3% phosphoric acid aqueous solution and perform rapid pyrolysis at 370 °C to obtain 100 mL of bio-oil rich in LGO; take the above 150 mL of supersaturated sodium bicarbonate solution and uniformly add it to 100 mL of bio-oil and stir until no bubbles are generated to obtain a mixed solution; take 300 mL of dichloromethane and add it to the mixed solution step by step and multiple times, shake and let stand, and separate to obtain the lower oil phase when obvious stratification occurs between the water and oil phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 30 °C and 40 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation apparatus and perform vacuum distillation at 95 °C and 28 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation apparatus at 150 °C and 25 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation apparatus and perform 3-stage molecular distillation at 70 °C, 6 mmHg, 0.5 ml / min, and 130 r / min to obtain high-purity LGO. Analyze the content of LGO therein by gas chromatography, and calculate that the purity of LGO is 90.67%.

[0052] Example 4

[0053] Take 110 g of potassium carbonate and place it in 100 mL of water, stir to prepare a supersaturated potassium carbonate solution; dry 150 g of rice straw impregnated with a 3% phosphoric acid aqueous solution and perform rapid pyrolysis at 420 °C to obtain 50 mL of bio-oil rich in LGO; take the above 100 mL of supersaturated potassium carbonate solution and uniformly add it to 50 mL of bio-oil and stir until no bubbles are generated to obtain a mixed solution; take 250 mL of dichloromethane and add it to the mixed solution step by step and multiple times, shake and let stand, and separate to obtain the lower oil phase when obvious stratification occurs between the water and oil phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 40 °C and 55 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation apparatus and perform vacuum distillation at 90 °C and 30 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation apparatus at 130 °C and 25 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation apparatus and perform 4-stage molecular distillation at 70 °C, 8 mmHg, 0.6 ml / min, and 200 r / min to obtain high-purity LGO. Analyze the content of LGO therein by gas chromatography, and calculate that the purity of LGO is 92.33%.

[0054] Example 5

[0055] Take 90 g of sodium carbonate and put it into 180 mL of water, stir to prepare a supersaturated sodium carbonate solution; dry 150 g of rice straw impregnated with a 5% phosphoric acid aqueous solution and perform rapid pyrolysis at 420 °C to obtain 45 mL of bio-oil rich in LGO; take the above 180 mL of supersaturated sodium carbonate solution and uniformly add it to 45 mL of bio-oil, stir until no bubbles are generated to obtain a mixed solution; take 180 mL of chloroform and add it to the mixed solution step by step and in multiple times, shake and let it stand, and separate to obtain the lower oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 40 °C and 50 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 100 °C and 35 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 130 °C and 18 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 8-stage molecular distillation at 70 °C, 3 mmHg, 0.3 ml / min, and 140 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 95.23%.

[0056] Example 6

[0057] Take 55 g of potassium bicarbonate and put it into 160 mL of water, stir to prepare a supersaturated potassium bicarbonate solution; dry 180 g of corncobs impregnated with a 4% phosphoric acid aqueous solution and perform rapid pyrolysis at 400 °C to obtain 60 mL of bio-oil rich in LGO; take the above 160 mL of supersaturated potassium bicarbonate solution and uniformly add it to 60 mL of bio-oil, stir until no bubbles are generated to obtain a mixed solution; take 120 mL of ethyl acetate and add it to the mixed solution step by step and in multiple times, shake and let it stand, and separate to obtain the upper oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 50 °C and 40 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 90 °C and 25 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 120 °C and 22 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 5-stage molecular distillation at 75 °C, 5 mmHg, 0.6 ml / min, and 190 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 92.04%.

[0058] Example 7

[0059] Take 20 g of sodium bicarbonate and put it into 200 mL of water, stir to prepare a supersaturated sodium bicarbonate solution; dry 370 g of poplar wood impregnated with a 3% phosphoric acid aqueous solution and then perform rapid pyrolysis at 330 °C to obtain 120 mL of bio-oil rich in LGO; take the above 200 mL of supersaturated sodium bicarbonate solution and uniformly add it to 120 mL of bio-oil and stir until no bubbles are generated to obtain a mixed solution; take 360 mL of dichloromethane and add it to the mixed solution step by step and multiple times, shake and let it stand, and separate the lower oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 45 °C and 45 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 100 °C and 33 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 145 °C and 16 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 9-stage molecular distillation at 80 °C, 7 mmHg, 0.2 ml / min, and 190 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 97.21%.

[0060] Example 8

[0061] Take 35 g of potassium bicarbonate and put it into 110 mL of water, stir to prepare a supersaturated potassium bicarbonate solution; dry 100 g of poplar wood impregnated with a 5% phosphoric acid aqueous solution and then perform rapid pyrolysis at 280 °C to obtain 35 mL of bio-oil rich in LGO; take the above 110 mL of supersaturated potassium bicarbonate solution and uniformly add it to 35 mL of bio-oil and stir until no bubbles are generated to obtain a mixed solution; take 140 mL of ethyl acetate and add it to the mixed solution step by step and multiple times, shake and let it stand, and separate the upper oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 40 °C and 55 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 105 °C and 28 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 130 °C and 20 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 4-stage molecular distillation at 70 °C, 8 mmHg, 0.4 ml / min, and 130 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 93.46%.

[0062] Example 9

[0063] Take 70 g of sodium carbonate and put it into 130 mL of water, stir to prepare a supersaturated sodium carbonate solution; dry 130 g of rice straw impregnated with a 2% phosphoric acid aqueous solution and perform rapid pyrolysis at 360 °C to obtain 40 mL of bio-oil rich in LGO; take the above 130 mL of supersaturated sodium carbonate solution and evenly add it to 40 mL of bio-oil and stir until no bubbles are generated to obtain a mixed solution; take 80 mL of chloroform and add it to the mixed solution step by step and multiple times, shake and let stand, and separate to obtain the lower oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 25 °C and 35 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 110 °C and 25 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 150 °C and 22 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 6-stage molecular distillation at 85 °C, 4 mmHg, 0.4 ml / min, and 180 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 95.31%.

[0064] Example 10

[0065] Take 20 g of sodium bicarbonate and put it into 180 mL of water, stir to prepare a supersaturated sodium bicarbonate solution; dry 300 g of corncob impregnated with a 2% phosphoric acid aqueous solution and perform rapid pyrolysis at 350 °C to obtain 90 mL of bio-oil rich in LGO; take the above 180 mL of supersaturated sodium bicarbonate solution and evenly add it to 90 mL of bio-oil and stir until no bubbles are generated to obtain a mixed solution; take 180 mL of chloroform and add it to the mixed solution step by step and multiple times, shake and let stand, and separate to obtain the lower oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 50 °C and 20 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 85 °C and 25 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 135 °C and 23 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 4-stage molecular distillation at 90 °C, 6 mmHg, 0.7 ml / min, and 170 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 94.32%.

[0066] Example 11

[0067] Take 10 g of sodium bicarbonate and put it into 100 mL of water, stir to prepare a supersaturated sodium bicarbonate solution; dry 100 g of poplar wood impregnated with a 3% phosphoric acid aqueous solution and then carry out rapid pyrolysis at 350 °C to obtain 30 mL of bio-oil rich in LGO; take the above 100 mL of supersaturated sodium bicarbonate solution and uniformly add it to 30 mL of bio-oil, stir until no bubbles are generated to obtain a mixed solution; take 90 mL of dichloromethane and add it to the mixed solution step by step and multiple times, shake and let stand, and separate the lower oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and carry out vacuum distillation at 30 °C and 40 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and carry out vacuum distillation at 90 °C and 27 mmHg to obtain a residue; carry out vacuum distillation on the residue in the Kjeldahl distillation device at 145 °C and 15 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and carry out 4-stage molecular distillation at 95 °C, 3 mmHg, 0.5 ml / min, and 130 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 91.11%.

[0068] Example 12

[0069] Take 15 g of sodium bicarbonate and put it into 140 mL of water, stir to prepare a supersaturated sodium bicarbonate solution; dry 110 g of poplar wood impregnated with a 3% phosphoric acid aqueous solution and then carry out rapid pyrolysis at 350 °C to obtain 35 mL of bio-oil rich in LGO; take the above 140 mL of supersaturated sodium bicarbonate solution and uniformly add it to 35 mL of bio-oil, stir until no bubbles are generated to obtain a mixed solution; take 140 mL of ethyl acetate and add it to the mixed solution step by step and multiple times, shake and let stand, and separate the upper oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and carry out vacuum distillation at 35 °C and 55 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and carry out vacuum distillation at 100 °C and 31 mmHg to obtain a residue; carry out vacuum distillation on the residue in the Kjeldahl distillation device at 150 °C and 22 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and carry out 7-stage molecular distillation at 85 °C, 6 mmHg, 0.3 ml / min, and 200 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 96.64%.

[0070] Example 13

[0071] Take 15 g of sodium bicarbonate and put it into 130 mL of water, stir to prepare a supersaturated sodium bicarbonate solution; dry 320 g of poplar wood impregnated with 3% phosphoric acid aqueous solution and perform rapid pyrolysis at 350 °C to obtain 100 mL of bio-oil rich in LGO; take the above 130 mL of supersaturated sodium bicarbonate solution and evenly add it to 100 mL of bio-oil and stir until no bubbles are generated to obtain a mixed solution; take 300 mL of chloroform and add it to the mixed solution step by step and multiple times, shake and let stand, and separate the lower oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 45 °C and 40 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 80 °C and 28 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 125 °C and 17 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 5-stage molecular distillation at 90 °C, 7 mmHg, 0.2 ml / min, and 90 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 93.82%.

[0072] Example 14

[0073] Take 15 g of sodium bicarbonate and put it into 150 mL of water, stir to prepare a supersaturated sodium bicarbonate solution; dry 220 g of poplar wood impregnated with 3% phosphoric acid aqueous solution and perform rapid pyrolysis at 350 °C to obtain 75 mL of bio-oil rich in LGO; take the above 150 mL of supersaturated sodium bicarbonate solution and evenly add it to 75 mL of bio-oil and stir until no bubbles are generated to obtain a mixed solution; take 150 mL of dichloromethane and add it to the mixed solution step by step and multiple times, shake and let stand, and separate the lower oil phase after obvious stratification of the water-oil two phases; place the oil phase in a rotary evaporator and perform vacuum distillation at 30 °C and 60 mmHg to obtain an LGO mixture sample; place the LGO mixture sample in a Kjeldahl distillation device and perform vacuum distillation at 105 °C and 33 mmHg to obtain a residue; perform vacuum distillation on the residue in the Kjeldahl distillation device at 135 °C and 21 mmHg to obtain a fraction rich in LGO; place the fraction rich in LGO in a molecular distillation device and perform 6-stage molecular distillation at 100 °C, 8 mmHg, 0.4 ml / min, and 160 r / min to obtain high-purity LGO. Analyze the content of LGO in it by gas chromatography, and calculate that the purity of LGO is 94.57%.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that the molecular distillation temperature is changed to 50 °C and the pressure is changed to 2 mmHg. The content of LGO in the obtained product is analyzed by gas chromatography, and it is calculated that the purity of LGO is 71.08%.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 8 is that the molecular distillation pressure is changed to 10 mmHg and the 4-stage molecular distillation is changed to 1-stage molecular distillation. The content of LGO in the obtained product is analyzed by gas chromatography, and it is calculated that the purity of LGO is 77.52%.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 14 is that the molecular distillation temperature is changed to 120 °C and the 6-stage molecular distillation is changed to 3-stage molecular distillation. The content of LGO in the obtained product is analyzed by gas chromatography, and it is calculated that the purity of LGO is 80.33%.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separating and purifying levoglucosenone from bio-oil, characterized in that, It includes the following steps: (1) Add solid carbonate to water and stir to dissolve at room temperature to obtain a supersaturated alkaline solution; (2) Use the bio-oil obtained by selective pyrolysis of biomass as the raw material, add the supersaturated alkaline solution obtained in step (1) to the bio-oil and stir until no bubbles are generated on the liquid surface to obtain a mixture; (3) Add the extractant to the mixture obtained in step (2) step by step and multiple times, shake and let stand. After obvious stratification occurs between the water and oil phases, separate to obtain the oil phase; (4) Use a rotary evaporator to carry out vacuum distillation on the oil phase obtained in step (3) under low temperature and low pressure conditions to remove the extractant and obtain an LGO mixture sample; (5) Use a Claisen distillation device to carry out vacuum distillation on the LGO mixture sample obtained in step (4) under medium temperature and medium pressure conditions to remove low-boiling impurities and obtain a residue; (6) Use a Claisen distillation device to carry out vacuum distillation on the residue obtained in step (5) under high temperature and high pressure conditions to remove high-boiling oligomers and obtain an LGO-rich fraction; (7) Use a molecular distillation device to carry out 3-9 stages of molecular distillation on the LGO-rich fraction obtained in step (6) at appropriate distillation temperature, distillation pressure, feed rate and scraper speed to obtain high-purity LGO.

2. The method according to claim 1, wherein The carbonate in step (1) is one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate, and the supersaturated alkaline solution is prepared according to the solid-liquid ratio of carbonate to water of 1:10 g / mL to 2:1 g / mL.

3. The method according to claim 1, characterized in that, The bio-oil obtained by selective pyrolysis of biomass in step (2) includes: biomass impregnated with an aqueous phosphoric acid solution with a mass concentration of 1-5%, dried and rapidly pyrolyzed at 270-420 °C under inert and oxygen-free conditions, and the generated pyrolysis gas is condensed to obtain a liquid product rich in LGO. Among them, the biomass includes lignocellulosic biomass with a cellulose content exceeding 35%.

4. The method according to claim 1, wherein The mass ratio of the supersaturated alkaline solution to the bio-oil in step (2) is 1:1 to 4:

1.

5. The method according to claim 1, characterized in that, The extractant in step (3) is one of dichloromethane, ethyl acetate, and chloroform, and the mass ratio of the extractant to the bio-oil is 2:1 to 5:

1.

6. The method according to claim 1, wherein The low temperature and low pressure conditions in step (4) refer to a distillation temperature of 20-50 °C and a distillation pressure of 40-60 mmHg.

7. The method according to claim 1, wherein The medium temperature and medium pressure conditions in step (5) refer to a distillation temperature of 80-110 °C and a distillation pressure of 25-35 mmHg.

8. The method according to claim 1, wherein The high temperature and high pressure conditions in step (6) refer to a distillation temperature of 120-150 °C and a distillation pressure of 15-25 mmHg.

9. The method according to claim 1, wherein The distillation temperature in step (7) is 60-100 °C, the distillation pressure is 3-8 mmHg, the feed rate is 0.2-0.7 ml / min, and the scraper speed is 90-200 r / min.

10. The method according to claim 1, wherein The high-purity LGO obtained in step (7) has a purity of LGO not less than 90%.

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