Method for producing liquid fuel by co-liquefaction of lignin and polyethylene

Abstract

The invention discloses a method for producing liquid fuel by co-liquefaction of lignin and polyethylene, which belongs to the field of waste resource recycling, and utilizes a two-phase solvent system to efficiently catalyze and convert a mixture of lignin and polyethylene into liquid fuel. The method comprises the following steps: placing a mixed solvent, lignin, polyethylene and a catalyst in a reactor together, flushing and sealing with nitrogen, reacting for a preset time at a certain temperature, and separating gas, liquid and solid three-phase products after the reaction is finished, so as to obtain a liquid product with the highest content of 59.5%. The two-phase solvent is used, the lignin and the polyethylene are efficiently converted into the liquid fuel under the mild condition, and a new method is provided for high-value synergistic utilization of the lignin and the polyethylene.

Description

Technical Field

[0001] The present invention belongs to the field of energy conservation, environmental protection and waste resource recycling, and relates to a co-liquefaction technology of lignin and polyethylene, and particularly to a method for co-liquefying lignin and polyethylene to produce liquid fuel. Background Art

[0002] Lignin is the second largest biomass resource in nature after cellulose and is also the largest renewable aromatic polymer in terms of reserves. As the main by-product in the pulp and paper making process, the annual output of lignin is about 70 million tons, which has great potential to be converted into high-quality bio-oil. Due to a series of C-O and C-C bonds with relatively high bond energies in lignin, it has extremely high thermal stability, which severely limits subsequent recycling and utilization. At the same time, the high oxygen content of lignin itself results in high oxygen content and low calorific value of the bio-oil after depolymerization, and further hydrodeoxygenation is required. Polyethylene (PE), as a hydrogen-rich plastic, accounts for about 40% of global plastic waste and is an economically viable and environmentally sustainable hydrogen source.

[0003] Pyrolysis is widely used for the co-depolymerization of lignin and polyethylene due to its fast and efficient characteristics. During the pyrolysis process, various types of catalysts are usually used to accelerate the reaction process. For example, Patent CN 117247789A discloses a technology for catalytic pyrolysis of lignin and low-density polyethylene to prepare aromatic hydrocarbons. Using ZSM-5 molecular sieve as a catalyst, lignin and polyethylene are pyrolyzed into pyrolysis oil containing aromatic hydrocarbons, and finally, the highest oil yield of 39.1% is obtained at 500°C. The literature (International Journal of Energy Research, 2022, 46, 13, 18529-18539) uses activated carbon to catalyze the depolymerization of lignin and polyethylene at 550°C, increasing the yield of pyrolysis oil from 36% obtained by lignin pyrolysis alone to 52%, and improving the selectivity of aromatic hydrocarbons and short-chain alkanes. In addition, some studies strengthen the pyrolysis process of raw materials by microwave irradiation. For example, Patent CN 109370632A discloses a microwave pyrolysis-fixed bed catalytic upgrading technology for lignin and polyethylene. Using zinc-modified ZSM-5 / MCM-41 composite molecular sieve as a catalyst, the highest pyrolysis oil yield of 34.7% is obtained at 650°C, and the proportion of hydrocarbons in the pyrolysis oil is 87.22%. Although the co-pyrolysis technology can obtain a pyrolysis oil yield of nearly 40-50%, its pyrolysis temperature requirement is relatively high and the reaction conditions are harsh.

[0004] Compared with co-pyrolysis, the co-liquefaction technology strengthens the heat and mass transfer during the reaction process by adding solvents, so it can achieve a higher liquid yield at a relatively mild temperature. The literature (Chemical Engineering Journal, 2024, 502, 157845 - 157857) achieved the co-liquefaction of lignin and polyethylene using a water-ethanol mixed solvent at 320 °C, but the liquid yield was only 38%. This study pointed out that there was no synergistic effect of the water-ethanol mixed solvent on the co-liquefaction of lignin and polyethylene, and the quality of its liquid products did not change compared with the depolymerization of lignin alone.

[0005] In summary, although the current co-pyrolysis technology can produce pyrolysis oil with a high yield, the reaction temperature is too high and the energy consumption is serious. The existing co-liquefaction technology has a lower liquid yield than the co-pyrolysis technology under mild conditions, and lignin and polyethylene do not show a synergistic effect in the current solvent system. Therefore, it is urgent to develop an efficient co-liquefaction technology for lignin and polyethylene under mild conditions to obtain liquid fuels with a high yield. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a method for efficiently co-liquefying lignin and polyethylene raw materials into liquid fuels using a non-polar solvent and a polar solvent - water as a mixed solvent. The purpose of the present invention is to co-liquefy lignin and polyethylene under relatively mild conditions to obtain a liquid product with a high yield.

[0007] The technical solution adopted by the present invention is as follows:

[0008] In the first aspect, the present invention provides a method for co-liquefying lignin and polyethylene to produce liquid fuels, comprising the following steps:

[0009] Add lignin, polyethylene, and a catalyst into a reaction vessel;

[0010] Add a biphasic mixed solvent into the reaction vessel;

[0011] Under an inert gas atmosphere, heat the reaction to completion;

[0012] After the reaction is completed, cool the reaction vessel;

[0013] Wash the reactants with an organic solvent and centrifuge to separate the solid residue and the liquid product;

[0014] Separate the upper layer solution and the lower layer solution from the liquid product, combine the upper layer solution after extraction with the lower layer solution; separate and recover the organic solvent to obtain liquid fuels.

[0015] In a possible implementation, the catalyst is activated carbon loaded with metal, and the loading amount is 0.5-10 wt.%; the metal includes one or a combination of two of copper, nickel, palladium, ruthenium, and platinum.

[0016] In a possible implementation, the mass ratio of the lignin to the polyethylene is (0.3-3):1. Preferably, the mass ratio of the lignin to the polyethylene is 1:1.

[0017] In a possible implementation, the average molecular weight of the polyethylene is 5×10 4 ~1×10 5 。

[0018] In a possible implementation, the addition amount of the catalyst is 25%-75% of the sum of the masses of the lignin and the polyethylene mixture. Preferably, the addition amount of the catalyst is 50% of the sum of the masses of the lignin and the polyethylene mixture.

[0019] In a possible implementation, the biphasic mixed solvent includes a non-polar solvent and a polar solvent; wherein, the non-polar solvent includes one of n-pentane, n-hexane, cyclohexane, benzene, and methylcyclohexane, and the polar solvent includes water.

[0020] Further, the total addition amount of the biphasic mixed solvent is 30-70 mL g -1 ; the volume ratio of the non-polar solvent to the polar solvent in the biphasic mixed solvent is (0.25-4):1. Preferably, the volume ratio of the non-polar solvent to the polar solvent in the biphasic mixed solvent is 4:1.

[0021] In a possible implementation, the inert gas is selected from one of nitrogen, argon, or helium.

[0022] In a possible implementation, the pressure of the inert gas atmosphere is 0.1-3 Mpa; the heating reaction temperature is 200-360 °C, and the reaction time is 1-12 h.

[0023] Further, the heating reaction temperature is 260-360 °C, and the reaction time is 2-8 h.

[0024] In a possible implementation, the organic solvent includes dichloromethane.

[0025] In a possible implementation, the extraction is multiple extractions.

[0026] In a possible implementation, in the method, the catalyst in the gas and the solid residue in the reaction vessel is recovered.

[0027] In a possible implementation, the method for separating and recovering the organic solvent includes heating or distillation separation.

[0028] In a second aspect, the present invention provides a liquid fuel prepared by the method described in the first aspect.

[0029] The beneficial effects of the present invention are as follows:

[0030] (1) In the method of the present invention, waste carbon resource lignin is used as a reaction raw material, and waste plastic polyethylene is used as an initial hydrogen source, realizing the recycling of waste, reducing costs while improving the quality of liquid products.

[0031] (2) The method of the present invention constructs a polar-nonpolar two-phase solvent system. Polyethylene is easily soluble in nonpolar solvents at high temperatures, increasing its contact with the catalyst, promoting the dehydrogenation of polyethylene and thus initiating the subsequent reaction process.

[0032] (3) The method of the present invention realizes the synergistic depolymerization of lignin and polyethylene under mild conditions, reducing the reaction energy consumption and having good economic feasibility.

[0033] (4) The present invention also provides a liquid fuel, which can be mixed and used with vehicle fuel and aviation kerosene respectively. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the operation process of a method for co-liquefying lignin and polyethylene to produce liquid fuel according to the present invention.

[0035] Figure 2 It is the distribution of co-liquefied liquid products of lignin (a) and polyethylene (b) under different nonpolar solvents in Examples 2-5 of a method for co-liquefying lignin and polyethylene to produce liquid fuel according to the present invention.

[0036] Figure 3 It is the distribution of co-liquefied liquid products of lignin (a) and polyethylene (b) under different n-pentane and water ratio conditions in Examples 6-7 of a method for co-liquefying lignin and polyethylene to produce liquid fuel according to the present invention.

[0037] Figure 4 It is the distribution of co-liquefied liquid products of lignin (a) and polyethylene (b) at different reaction temperatures in Examples 8-12 of a method for co-liquefying lignin and polyethylene to produce liquid fuel according to the present invention.

[0038] Figure 5 It is the distribution of co-liquefied liquid products of lignin (a) and polyethylene (b) at different reaction times in Examples 13-16 of a method for co-liquefying lignin and polyethylene to produce liquid fuel according to the present invention.

[0039] Figure 6Product distribution of the co-liquefaction of lignin (a) and polyethylene (b) under different catalysts in Example 17-20 of the method for co-liquefying lignin and polyethylene to produce liquid fuel according to the present invention. Detailed implementation mode

[0040] To better understand the present invention, the present invention will be further described below in conjunction with embodiments.

[0041] The existing co-liquefaction technology has a lower liquid yield than the co-pyrolysis technology under mild conditions, and lignin and polyethylene do not show a synergistic effect in the current solvent system, resulting in a low liquid yield.

[0042] In view of this, the present invention provides a method for co-liquefying lignin and polyethylene to produce liquid fuel. This method can co-liquefy lignin and polyethylene to obtain a liquid product with a high yield under relatively mild conditions.

[0043] The following will be described in more specific embodiments.

[0044] In the following examples, lignin was purchased from Shandong Longli Biotechnology Co., Ltd., and the average molecular weight of polyethylene was 5×10 4 ~1×10 5 .

[0045] Example 1

[0046] Refer to Figure 1 , the method for co-liquefying lignin and polyethylene to produce liquid fuel includes the following steps:

[0047] Weigh 100 mg of lignin, 100 mg of polyethylene, 100 mg of catalyst Ru 5％ C (indicating that the metal ruthenium loading is 5% of the total mass of the catalyst), 2 mL of deionized water, and 8 mL of n-pentane solvent are added to the reactor.

[0048] The reactor is repeatedly cleaned and filled with normal pressure nitrogen 5 times. React at 280 °C for 4 hours. After the reaction, place the reactor in an ice-water mixture to cool down. Record the internal pressure of the reactor after cooling, collect the gas generated by the reaction with an aluminum foil gas collection bag, and conduct qualitative and quantitative analysis.

[0049] Rinse the reaction kettle with 5 mL of dichloromethane to collect all the solid and liquid products into a test tube. Then, centrifuge to separate the solid. After the liquid is layered, separate the upper layer solution and the lower layer solution. Add 10 mL of dichloromethane to the upper layer solution in five portions for extraction. After mixing the extraction solution with the lower layer solution, add 1 mg of internal standard ethylbenzene to obtain the test solution. Take 1 mL of the test solution for qualitative and quantitative analysis by GC-MS (FID).

[0050] The separated solid mixture was washed with tetrahydrofuran to separate Ru 5％ The C catalyst was then dried overnight in a vacuum drying oven at 50 °C and used as the catalyst for subsequent cycle experiments. The remaining reactant residue after washing was also dried overnight in a vacuum drying oven at 50 °C and weighed separately. The test solution was distilled to separate dichloromethane at 50 °C and weighed.

[0051] The liquid product components of the co-liquefaction of lignin and polyethylene were identified by a GC-MS instrument (Agilent 7890B-5977B) equipped with an Agilent J&W HP-5 chromatographic column (0.25 mm × 30 m, 0.25 μm). The gas chromatograph was initially held at 50 °C for 2 minutes, then heated at a rate of 5 °C min -1 to 280 °C, and finally held at 280 °C for 30 minutes, with a total running time of 78 minutes.

[0052] The phenolic monomers in the lignin product were quantified by the external standard method and the effective carbon number method. Using ethylbenzene, phenol, guaiacol, and eugenol as standard samples, their effective carbon numbers were calculated (Table 1). The effective carbon numbers of other monomer products were calculated according to the effective carbon number rules established using these standards. The C9-C 29 alkanes and ketone products derived from polyethylene were quantified by the mixed external standard method, and the influence factors of other polyethylene products were evaluated with the influence factor of n-octacosane as 1 (Table 2).

[0053] Table 1 Effective carbon numbers of standard samples ethylbenzene, phenol, guaiacol, and eugenol

[0054]

[0055] Table 2 Influence factors of C9-C 29 alkanes and ketone products derived from polyethylene

[0056]

[0057]

[0058] The specific calculation methods for the yields of lignin and polyethylene products are as follows:

[0059]

[0060] W monomer =n monomer *Mw monomer (3)

[0061]

[0062] In these formulas:

[0063] Wethylbenzeneinsample (mg): Mass of ethylbenzene, the internal standard used in each sample, 1 mg;

[0064] Mw ethylbenzene (mg*mmol -1 ): Relative molecular mass of ethylbenzene, 106 mg mmol -1 ;

[0065] n ethylbenzene (mmol): Amount of substance of ethylbenzene in each sample, 9.43*10 -3 mmol;

[0066] n monomer (mmol): Amount of substance of each lignin monomer product in each sample;

[0067] A monomerinsample : Peak area corresponding to each monomer product in GC FID;

[0068] A ethylbenzeneinsample : Peak area corresponding to the internal standard ethylbenzene in GC FID;

[0069] ECN ethylbenzene : Effective carbon number of ethylbenzene, ECN ethylbenzene = 7.6;

[0070] ECN monomer : Effective carbon number of each lignin monomer product in the sample;

[0071] W monomer (mg): Mass of each lignin monomer product in each sample;

[0072] Lignin monomer yield(%): Mass yield of all lignin monomer products in the sample;

[0073] Yield of alkanes in polyethylene(%): Mass yield of polyethylene alkane products in the sample;

[0074] Yield of ketones in polyethylene(%): Mass yield of polyethylene ketone products in the sample;

[0075] The sum ofW ligninmonomer (mg): Total mass of lignin monomer products in each sample;

[0076] mass of lignin(mg): Total mass of lignin;

[0077] The sum of W polyethylene alkane (mg): The total mass of polyethylene product alkane in each sample;

[0078] mass of polyethylene (mg): The total mass of polyethylene;

[0079] W polyethylene ketone (mg): The total mass of polyethylene product ketones in each sample.

[0080] The liquid product yield was calculated to be 59.5%, the gas yield was 10.3%, and the solid yield was 30.2%. Under these conditions, the lignin monomer yield was 6.25%, and the total yield of polyethylene product alkane and ketones was 61%.

[0081] Examples 2 - 5

[0082] On the basis of Example 1, n - hexane, cyclohexane, benzene, and methylcyclohexane were used to replace n - pentane as non - polar solvents respectively. The same operation steps as in Example 1 were carried out, and the test results are shown in Table 3, Figure 2 as shown.

[0083] Table 3 Effects of different non - polar solvents on the distribution of three - phase products in the co - liquefaction of lignin and polyethylene

[0084]

[0085] According to Table 3, using different non - polar solvents has little effect on the liquid product yield in the co - liquefaction process. The liquid product yields of Examples 2, 3, and 5 are almost the same, and the liquid product yield of Example 4 is slightly lower, at 41.4%. From Examples 2 - 5, the gas yield decreases from 9.3% to 4.0%. According to Figure 2 , using different non - polar solvents, the lignin monomer yield changes little overall, while the yields of alkane and ketone products in polyethylene change significantly, and no olefins are produced under the solvent conditions of cyclohexane and methylcyclohexane.

[0086] In the following examples, n - pentane was continued to be used as the non - polar solvent to explore the effect of the ratio of non - polar solvent to polar solvent water on the co - liquefaction of lignin and polyethylene.

[0087] Examples 6 - 7

[0088] On the basis of Example 1, the ratio of n - pentane to water was changed while keeping the total volume of the solvent unchanged. The same operation steps as in Example 1 were carried out, with a reaction temperature of 280 °C and a reaction time of 4 h. The results obtained are shown in Table 4, Figure 3 as shown.

[0089] Table 4 Effects of different mixed solvent ratios on the distribution of three - phase products in the co - liquefaction of lignin and polyethylene

[0090]

[0091]

[0092] Comparing Table 4 and Example 1, the liquid yield increases with the increase in the volume of n-pentane added, increasing from 34.6% in Example 6 to 59.5% in Example 1. The gas yield decreases from 20.2% to 10.3%, and the solid yield decreases from 45.2% to 30.2%. According to Figure 3 , using mixed solvents with different ratios, the yield of lignin monomers changes significantly, and the highest yield of lignin monomers is also obtained under the conditions of Example 1.

[0093] In the following examples, the mixed solvent ratio of 4:1 is continued to explore the effects of reaction temperature and reaction time on the liquid yield.

[0094] Examples 8 - 12

[0095] On the basis of Example 1, the co-liquefaction reaction temperature is changed, and after the reaction is completed, the same operation steps as in Example 1 are carried out, and the results obtained are shown in Table 5, Figure 4 as shown.

[0096] Table 5 Influence of reaction temperature on the distribution of three-phase products of co-liquefaction of lignin and polyethylene

[0097]

[0098] According to the results in Table 5, with the increase in temperature, both the liquid yield and the gas yield increase significantly, increasing from 19.8% in Example 8 to 72.2% in Example 12. According to Figure 4 , at 260 - 300 °C, the yields of the lignin monomer products phenol and guaiacol increase significantly, while the selectivity of alkanes in the polyethylene product increases rapidly with the increase in temperature and reaches 79% at 300 °C, indicating that too high a temperature inhibits the production of ketones.

[0099] Examples 13 - 16

[0100] On the basis of Example 1, the co-liquefaction reaction time of lignin and polyethylene is changed to 1, 2, 8, 12 hours, and then the same operation steps as in Example 1 are carried out, and the results obtained are shown in Table 6, Figure 5 as shown.

[0101] Table 6 Influence of reaction time on the distribution of three-phase products of co-liquefaction of lignin and polyethylene

[0102]

[0103]

[0104] According to Table 6 and Example 1, when the co-liquefaction reaction time exceeds 4 hours, the liquid yield gradually decreases, from 59.5% to 20.8%. With the extension of the reaction time, the gas yield increases from 4.2% to 40.8%. This indicates that too long reaction time causes excessive depolymerization of the product, and the liquid product is converted into gas product. According to Figure 5 , too short (1 h) or too long (12 h) reaction time is beneficial to the formation of ketones.

[0105] Examples 17 - 20

[0106] On the basis of Example 1, the Ru 5％ C catalyst was replaced with Pd 5％ C, Pt 5％ C, Cu 5％ C, Ni 5％ C respectively, and the same operation steps as in Example 1 were carried out. The reaction temperature was 280 °C and the reaction time was 4 h. The results obtained are shown in Table 7, Figure 6 as shown.

[0107] Table 7 Effects of different catalysts on the distribution of three-phase products of lignin and polyethylene co-liquefaction

[0108]

[0109] According to Table 7, when using noble metal (palladium, platinum) catalysts, the liquid product yield is significantly higher than that when using non-noble metal (copper, nickel) catalysts. According to Figure 6 , the Pd 5％ C catalyst also has a good effect on the formation of lignin monomers. When using Ru 5％ C as the catalyst, the polyethylene product yield is significantly higher than that of other catalysts.

[0110] Comparative Examples 1 - 2

[0111] To prove the necessity of the mixed solvent in the present invention, water and n-pentane were used as solvents respectively. The specific implementation method was the same as that of Example 1. The reaction temperature was 280 °C and the reaction time was 4 h. The catalyst was Ru 5％ C. The results are shown in Table 8, Figure 3 as shown.

[0112] Table 8 Distribution of three-phase products of lignin and polyethylene co-liquefaction when n-pentane and water are used as solvents alone

[0113]

[0114] According to Figure 3, when using a single solvent (n-pentane or water), the yields of lignin and polyethylene products are relatively low. Comparing Table 8 with Example 1, the liquid yield under the n-pentane solvent is 41.4%, and the liquid yield under water as the solvent is 21.7%, both of which are much lower than the liquid yield under the two-phase solvent. This indicates that the two-phase solvent has a good promoting effect on the co-liquefaction conversion of lignin and polyethylene into liquid products.

[0115] Comparative Example 3

[0116] To prove the necessity of the catalyst in the present invention, this comparative example repeated Example 1 with a blank experiment without a catalyst at a reaction temperature of 280 °C and a reaction time of 4 h. The results are shown in Table 9.

[0117] Table 9 Distribution of the three-phase products of the co-liquefaction of lignin and polyethylene in the blank experiment without adding a catalyst

[0118]

[0119] According to Table 9 and Figure 6 , under non-catalytic conditions, the liquid oil yield is only 35.4%, much lower than 59.5% of the liquid oil yield under the Ru 5％ C catalyst, and the yield of the polyethylene product is extremely low. This indicates that the catalyst plays an irreplaceable role in the co-liquefaction process of lignin and polyethylene.

[0120] The catalytic co-liquefaction reaction mechanism of lignin and polyethylene in the method of the present invention is as follows:

[0121] Due to the miscibility of polyethylene with non-polar solvents, polyethylene is easily dissolved in non-polar solvents at high temperatures, thereby enhancing the contact between polyethylene and the catalyst and promoting polyethylene dehydrogenation. Under the combined action of a hydrogen source and a metal catalyst, polyethylene and lignin start to undergo hydrogenolysis. During this process, lignin containing carbonyl functional groups undergoes decarbonylation to generate carbon monoxide, thereby triggering the water-gas shift reaction, and the reaction of carbon monoxide with water generates two equivalents of hydrogen. This further promotes the hydrogenolysis of lignin to form monomers and oligomers, while polyethylene is hydrogenolyzed into low-molecular-weight alkanes. The key to this invention is to introduce a non-polar solvent to enhance the contact between polyethylene and the catalyst for dehydrogenation, and water acts as a substrate to trigger the water-gas shift reaction, providing an abundant hydrogen source for the subsequent hydrogenolysis of lignin and polyethylene.

[0122] The method of the present invention realizes the synergistic depolymerization of lignin and polyethylene under mild conditions, reducing energy consumption and costs while increasing the liquid product yield.

[0123] As described above, it is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the technical scope disclosed by the present invention shall be included within the scope of protection of the invention.

Claims

1. A method for producing liquid fuel by co-liquefaction of lignin and polyethylene, characterized in that: The following steps are involved: adding lignin, polyethylene and a catalyst into a reaction vessel; adding a biphasic mixed solvent into a reaction vessel; Under an inert gas atmosphere, heat the reaction until completion; After the reaction is completed, the reaction vessel is cooled; The reactants are washed with an organic solvent and the solid residue and the liquid product are separated by centrifugation; An upper solution and a lower solution are separated from the liquid product, the upper solution is extracted and combined with the lower solution, and the organic solvent is separated and recovered to obtain a liquid fuel.

2. The method for producing liquid fuel by co-liquefaction of lignin and polyethylene according to claim 1, characterized in that: The catalyst is activated carbon loaded with metal, and the loading amount is 0.5-10wt.%; the metal includes one or a combination of two of copper, nickel, palladium, ruthenium and platinum.

3. The method for producing liquid fuel by co-liquefaction of lignin and polyethylene according to claim 1, characterized in that: The mass ratio of lignin to polyethylene is (0.3-3):

1.

4. The method for producing liquid fuel by co-liquefaction of lignin and polyethylene according to claim 1, characterized in that: The added amount of the catalyst is 25%-75% of the total mass of the mixture of lignin and polyethylene.

5. The method for producing liquid fuel by co-liquefaction of lignin and polyethylene according to claim 1, characterized in that: The two-phase mixed solvent includes a non-polar solvent and a polar solvent; wherein the non-polar solvent includes one of n-pentane, n-hexane, cyclohexane, benzene and methylcyclohexane, and the polar solvent includes water.

6. The method for producing liquid fuel by co-liquefaction of lignin and polyethylene according to claim 5, characterized in that: The total amount of the two-phase mixed solvent added is 30-70 mL g -1 ; The volume ratio of non-polar solvent to polar solvent in the two-phase mixed solvent is (0.25-4):

1.

7. The method for producing liquid fuel by co-liquefaction of lignin and polyethylene according to claim 1, characterized in that: The pressure of the inert gas atmosphere is 0.1-3Mpa; the heating reaction temperature is 200-360°C, and the reaction time is 1-12h.

8. The method for producing liquid fuel by co-liquefaction of lignin and polyethylene according to claim 1, characterized in that: The organic solvent includes dichloromethane.

9. The method for producing liquid fuel by co-liquefaction of lignin and polyethylene according to claim 1, characterized in that: In the process, the catalyst is recovered from the gas and solid residue in the reaction vessel.

10. A liquid fuel, characterized in that: The method is prepared by any one of claims 1 to 9.

Images