Method for preparing fuel precursor by deconstructing biomass through choline-based deep eutectic solvent

Abstract

The invention discloses a method for preparing a fuel precursor by deconstructing biomass through a choline-based deep eutectic solvent, and belongs to the technical field of biomass thermal conversion. The method comprises the following steps: under certain temperature and pressure conditions, pretreating oriented deconstruction biomass by using a choline-based deep eutectic solvent to obtain a reactant; performing solid-liquid separation on reactants, washing a solid substrate to be neutral, and obtaining a cellulose-rich sample deconstructed by the choline-based deep eutectic solvent after the solid substrate is absolutely dry; the cellulose-rich sample is pyrolyzed, and the obtained pyrolysis product is condensed to obtain liquid fuel precursor pyrolysis sugar. The method has the advantages of effectively enriching cellulose and efficiently preparing liquid fuel precursor pyrolytic sugar, a green and recyclable biomass pretreatment system is formed, and sustainable development from biomass to high-quality liquid fuel is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass thermal conversion, and particularly relates to a method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents. Background Art

[0002] Lignocellulose has the advantages of large reserves, short production cycle, rich resources, etc., and is a natural raw material for preparing liquid fuels. However, due to the inherent biological resistance and complex chemical components of biomass, its direct thermal conversion to produce liquid fuel precursors is inhibited. The main reasons include the inhibitory effect of the inherent resistance of biomass, the interaction between the three chemical components of cellulose, hemicellulose and lignin, and the negative effect of alkali and alkaline earth metals in biomass. In order to effectively solve the above problems, different pretreatment technologies (such as physical method, chemical method, biochemical method, coupling method, etc.) coupled with thermal conversion or enzyme conversion to prepare liquid fuel precursors have been widely applied and studied, and certain research progress has been made.

[0003] Based on the problems of traditional pretreatment technologies (such as acids, alkalis, etc.) such as difficult recovery and easy environmental pollution, combined with the concept of high-value utilization of biomass for green environmental protection and sustainable development, some patents or papers have currently carried out research on the use of recyclable organic solvents or green environmental protection ozone, hydrogen peroxide, Fenton, etc. for oxidative pretreatment of biomass coupled with enzyme conversion or thermal conversion to prepare liquid fuel precursors. Although some breakthroughs have been made, the above pretreatment technologies are mainly aimed at weakly resistant biomass (such as straw, rice husk, corn cob, etc.), and the technology for effectively pretreating strongly resistant biomass (such as pine wood, bamboo, etc.) still needs further research. Due to the complex chemical structure and strong biological resistance of biomass such as pine wood and bamboo, a single pretreatment technology is difficult to break the chemical bond of its chemical structure, achieve effective enrichment of cellulose components, and inhibit the subsequent enzyme conversion or thermal conversion to prepare liquid fuel precursors in a targeted manner.

[0004] Based on this, the present invention proposes a new method for deconstructing high-resistant biomass such as bamboo with choline-based deep eutectic solvents and coupling thermochemical conversion to prepare liquid fuel precursors. The choline-based deep eutectic solvents are used to synergistically weaken and break the chemical bonds of the complex chemical structure of high-resistant bamboo biomass, realizing the efficient enrichment and separation of cellulose components, and providing favorable conditions for the subsequent thermal conversion to prepare liquid fuel precursors. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents, which includes the following steps: Under certain temperature and pressure conditions, use choline-based deep eutectic solvents to pretreat and deconstruct biomass in a targeted manner to obtain reactants; The reactants are subjected to solid-liquid separation, and the solid substrate is washed to neutrality and then dried to obtain a cellulose-rich sample deconstructed by a choline-based deep eutectic solvent; The cellulose-rich sample is pyrolyzed, and the pyrolysis products are condensed to obtain pyrolytic sugars as liquid fuel precursors.

[0006] Preferably, the choline-based deep eutectic solvent includes choline chloride and its compositions, and the compositions include one of formic acid, lactic acid, propylene glycol, glycerol, ethanolamine, and diethanolamine.

[0007] More preferably, in the choline-based deep eutectic solvent, the molar ratio of choline chloride to the composition is 1:1 - 6.

[0008] Preferably, the temperature of the pretreatment is 70 - 130 °C.

[0009] Preferably, the pressure of the pretreatment is 0.5 - 2.0 Mpa.

[0010] Preferably, the time of the pretreatment is 1 - 12 h.

[0011] Preferably, the solid substrate is washed to neutrality with deionized water.

[0012] Preferably, the temperature of the absolute drying is 105 °C.

[0013] Preferably, the temperature of the pyrolysis is 450 - 550 °C.

[0014] Preferably, the time of the rapid pyrolysis is 5 - 10 min.

[0015] Based on the above technical solutions, the present invention provides a method for deconstructing biomass by a recyclable green deep eutectic solvent pretreatment to improve the thermal conversion efficiency of lignocellulose and the yield of liquid fuel precursors. By using a base deep eutectic solvent composed of acids, alcohols, etc. combined with basic amines for biomass pretreatment and deconstruction, it is easier to break the ether bonds and ester bonds between lignin and holocellulose, forming a cellulose-rich component to achieve the purpose of coupling rapid pyrolysis. The content of levoglucosan in the rapid pyrolysis of the cellulose-rich component is greater than 198 mg / g, realizing the directional preparation of pyrolytic sugars as liquid fuel precursors.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention provides a method for preparing fuel precursors by deconstructing biomass with a choline-based deep eutectic solvent, which has the advantages of effectively enriching cellulose and efficiently preparing pyrolytic sugars as liquid fuel precursors, forming a green and recyclable biomass pretreatment system, and promoting the sustainable development of biomass into high-quality liquid fuels. Description of the Drawings

[0017] Figure 1Recovery of cellulose-rich substrates by deconstructing biomass with different combinations of choline-based deep eutectic solvents; Figure 2 Yield of levoglucosan from deconstructing biomass with raw materials and choline-based deep eutectic solvents; Figure 3 Pyrolysis product distribution (a) and levoglucosan yield (b) of choline chloride / formic acid deconstructing biomass at different times. Detailed implementation manners

[0018] The present invention will be further illustrated by the following examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0019] In the following examples, the biomass sample is bamboo.

[0020] Example 1 Method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents, the steps are as follows: The choline-based deep eutectic solvent in this example is choline chloride / formic acid (CF), and the molar ratio is 1:2; Accurately weigh 3.0 g of biomass sample, add 30 mL of choline-based deep eutectic solvent, the solid-liquid ratio is 1:10 g / mL, and perform pretreatment at 110 °C in a hydrothermal reaction kettle for 3 h to deconstruct biomass directionally to obtain reactants; After the pretreatment, solid-liquid separation is achieved through a suction filtration device, and the solid substrate is washed with deionized water until neutral, and then placed in an oven at 105 °C for absolute drying to obtain a cellulose-rich sample deconstructed by choline-based deep eutectic solvents. The recovery rate of the obtained cellulose-rich sample is counted as 58.1 wt.%; Take 0.5 g of the cellulose-rich sample and load it into a pyrolysis basket, perform rapid pyrolysis at 500 °C in a fixed bed, and the pyrolysis liquid is collected through a condensation device and methanol solution to obtain pyrolysis sugars of liquid fuel precursors. The pyrolysis sugars (mainly levoglucosan) are qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry (GC-MS). The pyrolysis sugar yield of the cellulose-rich component is 114.9 mg / g.

[0021] Example 2 Method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents, the steps are as follows: The choline-based deep eutectic solvent in this example is choline chloride / lactic acid (CL), and the molar ratio is 1:2; Accurately weigh 3.0 g of biomass sample, add 30 mL of choline-based deep eutectic solvent, the solid-liquid ratio is 1:10 g / mL, and perform pretreatment at 110 °C in a hydrothermal reaction kettle for 3 h to deconstruct biomass directionally to obtain reactants; After the pretreatment was completed, solid-liquid separation was achieved through a suction filtration device. The solid substrate was washed with deionized water until neutral, and then placed in an oven at 105 °C for absolute drying to obtain a cellulose-rich sample deconstructed by the choline-based deep eutectic solvent. The recovery rate of the obtained cellulose-rich sample was statistically 73.1 wt.%. Take 0.5 g of the cellulose-rich sample and place it in a pyrolysis basket. Rapid pyrolysis was carried out at 500 °C in a fixed bed. The pyrolysis liquid was collected through a condensation device and a methanol solution to obtain pyrolysis sugars, the liquid fuel precursors. The pyrolysis sugars (mainly levoglucosan) were qualitatively and quantitatively analyzed by GC-MS. The pyrolysis sugar yield of the cellulose-rich component was 78.3 mg / g.

[0022] Example 3 The method for preparing fuel precursors by deconstructing biomass with a choline-based deep eutectic solvent is as follows: The choline-based deep eutectic solvent in this example was choline chloride / propylene glycol (CP) with a molar ratio of 1:2; Accurately weigh 3.0 g of the biomass sample, add 30 mL of the choline-based deep eutectic solvent, with a solid-liquid ratio of 1:10 g / mL. Pretreatment was carried out in a hydrothermal reaction kettle at 110 °C for 3 h to directionally deconstruct the biomass to obtain the reactants; After the pretreatment was completed, solid-liquid separation was achieved through a suction filtration device. The solid substrate was washed with deionized water until neutral, and then placed in an oven at 105 °C for absolute drying to obtain a cellulose-rich sample deconstructed by the choline-based deep eutectic solvent. The recovery rate of the obtained cellulose-rich sample was statistically 92.0 wt.%; Take 0.5 g of the cellulose-rich sample and place it in a pyrolysis basket. Rapid pyrolysis was carried out at 500 °C in a fixed bed. The pyrolysis liquid was collected through a condensation device and a methanol solution to obtain pyrolysis sugars, the liquid fuel precursors. The pyrolysis sugars (mainly levoglucosan) were qualitatively and quantitatively analyzed by GC-MS. The pyrolysis sugar yield of the cellulose-rich component was 20.2 mg / g.

[0023] Example 4 The method for preparing fuel precursors by deconstructing biomass with a choline-based deep eutectic solvent is as follows: The choline-based deep eutectic solvent in this example was choline chloride / glycerol (CG) with a molar ratio of 1:2; Accurately weigh 3.0 g of the biomass sample, add 30 mL of the choline-based deep eutectic solvent, with a solid-liquid ratio of 1:10 g / mL. Pretreatment was carried out in a hydrothermal reaction kettle at 110 °C for 3 h to directionally deconstruct the biomass to obtain the reactants; After the pretreatment was completed, solid-liquid separation was achieved through a suction filtration device. The solid substrate was washed with deionized water until neutral, and then placed in an oven at 105 °C for absolute drying to obtain a cellulose-rich sample deconstructed by the choline-based deep eutectic solvent. The recovery rate of the obtained cellulose-rich sample was statistically 95.1 wt.%; Take 0.5 g of the cellulose-rich sample and place it in a pyrolysis basket. Rapid pyrolysis is carried out at 500 °C in a fixed bed. The pyrolysis liquid is collected through a condensation device and a methanol solution to obtain pyrolysis sugars, which are the precursors of liquid fuel. The pyrolysis sugars (mainly levoglucosan) are qualitatively and quantitatively analyzed by GC-MS. The pyrolysis sugar yield of the cellulose-rich component is 16.3 mg / g.

[0024] Example 5 Method for deconstructing biomass with choline-based deep eutectic solvents to prepare fuel precursors, the steps are as follows: The choline-based deep eutectic solvent in this example is choline chloride / ethanolamine (CM), and the molar ratio is 1:6; Accurately weigh 3.0 g of the biomass sample, add 30 mL of the choline-based deep eutectic solvent, with a solid-liquid ratio of 1:10 g / mL. Pretreat it at 110 °C for 3 h in a hydrothermal reaction kettle to directionally deconstruct the biomass and obtain the reactants; After the pretreatment, solid-liquid separation is achieved through a suction filtration device. The solid substrate is washed with deionized water until neutral, and then placed in an oven at 105 °C for absolute drying to obtain a cellulose-rich sample deconstructed by the choline-based deep eutectic solvent. The recovery rate of the obtained cellulose-rich sample is statistically 61.6 wt.%. Take 0.5 g of the cellulose-rich sample and place it in a pyrolysis basket. Rapid pyrolysis is carried out at 500 °C in a fixed bed. The pyrolysis liquid is collected through a condensation device and a methanol solution to obtain pyrolysis sugars, which are the precursors of liquid fuel. The pyrolysis sugars (mainly levoglucosan) are qualitatively and quantitatively analyzed by GC-MS. The pyrolysis sugar yield of the cellulose-rich component is 68.5 mg / g.

[0025] Example 6 Method for deconstructing biomass with choline-based deep eutectic solvents to prepare fuel precursors, the steps are as follows: The choline-based deep eutectic solvent in this example is choline chloride / diethanolamine (CD), and the molar ratio is 1:6; Accurately weigh 3.0 g of the biomass sample, add 30 mL of the choline-based deep eutectic solvent, with a solid-liquid ratio of 1:10 g / mL. Pretreat it at 110 °C for 3 h in a hydrothermal reaction kettle to directionally deconstruct the biomass and obtain the reactants; After the pretreatment, solid-liquid separation is achieved through a suction filtration device. The solid substrate is washed with deionized water until neutral, and then placed in an oven at 105 °C for absolute drying to obtain a cellulose-rich sample deconstructed by the choline-based deep eutectic solvent. The recovery rate of the obtained cellulose-rich sample is statistically 83.6 wt.%. Take 0.5 g of the cellulose-rich sample and place it in a pyrolysis basket. Perform rapid pyrolysis at 500 °C in a fixed bed. The pyrolysis liquid is collected through a condensation device and a methanol solution to obtain pyrolysis sugars, which are the precursors of liquid fuel. Qualitative and quantitative analysis of the pyrolysis sugars (mainly levoglucosan) is carried out by GC-MS. The pyrolysis sugar yield of the cellulose-rich component is 8.6 mg / g.

[0026] Example 7 In this example, the untreated raw material (UB) was used as a comparison. The pyrolysis sugars, which are the precursors of liquid fuel, obtained by rapid pyrolysis are as follows: Take 0.5 g of the untreated raw material and place it in a pyrolysis basket. Perform rapid pyrolysis at 500 °C in a fixed bed. The pyrolysis liquid is collected through a condensation device and a methanol solution to obtain pyrolysis sugars, which are the precursors of liquid fuel. Qualitative and quantitative analysis of the pyrolysis sugars (mainly levoglucosan) is carried out by GC-MS. The pyrolysis sugar yield of the untreated raw material is 4.5 mg / g.

[0027] Combined with the statistical results of Examples 1-6, the recovery rates of cellulose-rich substrates by different combinations of choline-based deep eutectic solvents for biomass deconstruction are as Figure 1 shown; the levoglucosan yields of raw materials and biomass deconstruction by choline-based deep eutectic solvents are as Figure 2 shown.

[0028] Using the choline-based deep eutectic solvents of the present invention for biomass deconstruction can more easily break the ether bonds and ester bonds between lignin and holocellulose, forming cellulose-rich components.

[0029] Example 8 The process of this example is basically the same as that of Example 1. The influence of different reaction times of biomass deconstruction by pretreatment under the same pyrolysis conditions was studied. The pyrolysis sugar yields under the conditions of pretreatment times of 1.5 h (CF 1.5h), 6 h (CF 6h), and 12 h (CF 12h) were respectively tested and statistically analyzed, and were plotted and compared with the results of the untreated raw material and Example 1 (CF 3h). The results are as Figure 3 shown.

[0030] Figure 3 (a) shows the pyrolysis product distribution of biomass deconstruction by choline chloride / formic acid at different times, Figure 3 (b) shows the levoglucosan yield. With the increase of the reaction time of biomass deconstruction by pretreatment with choline chloride / formic acid (CF), the pyrolysis sugar yield increased from 4.5 mg / g of untreated bamboo to 88.1 mg / g (CF1.5h), 114.9 mg / g (CF 3h), 177.0 mg / g (CF 6h), and 198.6 mg / g (CF 12h) respectively In summary, the present invention utilizes a deep eutectic solvent of bases combined with acids, alcohols, etc. for the pretreatment and deconstruction characteristics of biomass, which is more likely to break the ether bonds and ester bonds between lignin and holocellulose, forming a cellulose-rich component to achieve the purpose of coupling with fast pyrolysis. Under the optimal conditions, the content of levoglucosan in the fast pyrolysis of the cellulose-rich component is greater than 198 mg / g, realizing the directional preparation of pyrolytic sugars as liquid fuel precursors.

[0031] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. A method for deconstructing biomass with choline-based deep eutectic solvents to prepare fuel precursors, characterized in that, It includes the following steps: Under certain temperature and pressure conditions, choline-based deep eutectic solvents are used for pretreatment to directionally decompose biomass to obtain reactants; The reactants are subjected to solid-liquid separation, and the solid substrate is washed to neutrality and then dried to obtain a cellulose-rich sample decomposed by choline-based deep eutectic solvents; The cellulose-rich sample is pyrolyzed, and the obtained pyrolysis products are condensed to obtain pyrolysis sugars as liquid fuel precursors.

2. The method for preparing fuel precursors by deconstructing biomass with choline base deep eutectic solvents according to claim 1, wherein: The choline-based deep eutectic solvents include choline chloride and its compositions, and the compositions include one of formic acid, lactic acid, propylene glycol, glycerol, ethanolamine, and diethanolamine.

3. The method for preparing fuel precursors by deconstructing biomass with choline base deep eutectic solvents according to claim 2, wherein: In the choline-based deep eutectic solvents, the molar ratio of choline chloride to the composition is 1:1 - 6.

4. The method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents according to claim 1, characterized in that: The temperature of the pretreatment is 70 - 130 °C.

5. The method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents according to claim 1, characterized in that: The pressure of the pretreatment is 0.5 - 2.0 Mpa.

6. The method for preparing fuel precursors by deconstructing biomass with choline base deep eutectic solvents according to claim 1, wherein: The time of the pretreatment is 1 - 12 h.

7. The method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents according to claim 1, characterized in that: The solid substrate is washed to neutrality with deionized water.

8. The method for preparing fuel precursors by deconstructing biomass with choline base deep eutectic solvents according to claim 1, wherein: The temperature of the absolute dryness is 105 °C.

9. The method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents according to claim 1, wherein: The temperature of the pyrolysis is 450 - 550 °C.

10. The method for preparing fuel precursors by deconstructing biomass with choline-based deep eutectic solvents according to claim 1, characterized in that: The rapid pyrolysis time is 5 - 10 min.

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