WO2023083029A1 - Green alkali lignin micromolecule separation method and product - Google Patents

Abstract

Disclosed in the present invention are a green alkali lignin micromolecule separation method and a product. The method of the present invention comprises: adding water or ethanol/water into black liquor for dilution, performing centrifugal treatment, and performing self-hydrolysis reaction on supernate to obtain hydrolysate; and after cooling the hydrolysate, performing acidifying, standing and centrifuging, extracting an obtained filtrate by using a green organic solvent, and drying to obtain a soluble micromolecule fraction, namely an alkali lignin micromolecule. According to the present invention, lignin in alkaline pulping black liquor obtained by an alkaline process, a sulfate process and the like is extracted and utilized, and the method has the characteristics such as waste utilization, environmental protection, high economic benefit; according to the method, lignin fractions with different molecular weights can be obtained, the polydispersity of each fraction is reduced, and small molecular fractions can be selectively dissolved out; the separation method of the present invention is green and environmentally-friendly, the solvent is non-toxic, the content of micromolecule fractions is rich, the whole process is relatively environmentally-friendly, and the method has a relatively good industrial production prospect.

Description

A kind of green alkali lignin small molecule separation method and product technical field

The invention relates to the technical field of lignin pretreatment and the technical field of lignin recovery and reuse, in particular to a green alkali lignin small molecule separation method and a product.

Background technique

Industrial alkali lignin is an important industrial raw material with good flame retardancy, oxidation resistance and thermal stability. It has good application potential in the field of water agent and so on. At present, industrial alkali lignin is mainly extracted from the black liquor produced in the cooking process of the pulp and paper industry, which contains a large amount of degradation products of small lignin molecules. It has been reported that using dichloromethane to classify crude lignin extracted from black liquor can obtain high-yield small lignin fractions, which contain a large number of monomers and dimers. The development and utilization of new materials and chemicals is of great significance. Although dichloromethane has better selectivity to small molecular fractions, it is more toxic and unfavorable for subsequent production (C. Zhao, Z. Hu, L. Shi, C. Wang, F. Yue, S. Li, H. Zhang, F. Lu, Green Chem 2020, 22, 7366-7375.).

technical solution

In view of the deficiencies in the prior art, the purpose of the present invention is to adopt a green and efficient self-hydrolysis classification method combined with a green solvent system to achieve direct fractionation from black liquor to obtain small lignin fractions with considerable content, to replace the traditional A solvent system with high selectivity but high toxicity to realize efficient utilization of lignin.

There will be a large amount of lye remaining in the black liquor of alkaline method and kraft pulping, so the residual lye can be used to cause self-hydrolysis reaction at high temperature to achieve classification. In this process, the unbroken and complete lignin The bond is further broken to form low-molecular-weight fragment products, and then extracted with a green organic solvent to obtain a relatively high-yield small-molecule fraction of lignin. The whole process is green and non-toxic, and it is expected to replace the more toxic dichloromethane, and directly extract the small molecular fraction of lignin from black liquor to realize the effective utilization of lignin, which is of great significance both from the perspective of environmental protection and economics.

In order to achieve the above object, the present invention adopts following technical scheme:

A green alkali lignin small molecule separation method and product, comprising the following steps:

(1) Self-hydrolysis reaction: add water or ethanol/water to the black liquor to dilute, centrifuge, and perform self-hydrolysis on the supernatant to obtain a hydrolyzate;

(2) Separation of small molecules of alkali lignin: after cooling the hydrolyzate obtained in step (1), acidify, stand still, and centrifuge, extract the obtained filtrate with a green organic solvent, and dry to obtain the soluble small molecule fraction, namely alkali lignin Small molecule.

Further, the black liquor in step (1) is the black liquor produced in the cooking stage in the alkaline pulping process.

Further preferably, the alkaline pulping process is an alkaline or kraft pulping process.

Further, the mass multiple of the dilution in step (1) is 5-15 times that of the black liquor.

Further, the volume ratio of ethanol/water to ethanol in step (1) is 0-5:1, and not 0; further preferably, the volume ratio of ethanol/water to water in step (1) is 1:5, 1:1, 5:1.

Further, the reaction in step (1) is carried out in a high-pressure reactor.

Further, the temperature of the reaction in step (1) is 90-140°C.

Further, the reaction time in step (1) is 1-4 h.

Further, the acidification in step (2) uses hydrochloric acid with an acid concentration of 0.1-6 mol/L; the acidification is to pH<3.

Further, the standing time in step (2) is 4-16 h. Further preferably, the standing time is 12 h.

Further, the organic solvent in step (2) is ethyl acetate.

Further, the number of extractions in step (2) is 1-5 times.

Further, the condition for removing the solvent in step (2) is to evaporate to dryness under reduced pressure at 30-60°C.

The small alkali lignin molecules separated by the above-mentioned green alkali lignin small molecule separation method.

Beneficial effect

Compared with the prior art, the present invention has the following advantages:

(1) The present invention utilizes the characteristics of a large amount of lye remaining in the alkaline pulping black liquor such as the alkali method and the sulfate method, and adopts a simple, green and low-cost self-hydrolysis method combined with a green organic solvent extraction method to reduce lignin heterogeneity properties, thereby improving the utilization of lignin-rich waste.

(2) The present invention utilizes the self-hydrolysis reaction to further break the connecting bonds in the lignin, forming fragments with lower molecular weights, and improving the yield of small molecular fractions.

(3) The solvent selected in the present invention is green and non-toxic, and is expected to replace the traditional toxic solvent with high selectivity to small molecule fractions, and is an economically sustainable method.

Description of drawings

Fig. 1 is the GC-MS diagram of the small molecular fraction of eucalyptus kraft lignin in Example 1.

Fig. 2 is the GC-MS chart of the small molecular fraction of eucalyptus kraft lignin in Example 2.

Fig. 3 is the GC-MS chart of the small molecular fraction of eucalyptus kraft lignin in Example 3.

Fig. 4 is the GC-MS chart of the small molecular fraction of eucalyptus kraft lignin in Example 4.

Fig. 5 is a GC-MS diagram of the small molecule fraction of eucalyptus kraft lignin in Example 5 (blank sample).

Fig. 6 is a structural diagram of each substance in each embodiment.

Embodiments of the present invention

In order to better understand the technical characteristics of the present invention, the present invention will be described in further detail below based on examples, but the scope of protection claimed by the present invention is not limited thereto.

Example 1

A green alkali lignin small molecule separation method, comprising the steps of:

(1) Take 10 g of black liquor sample produced in the cooking stage of eucalyptus kraft pulping process, add 60 mL of distilled water to dilute, and centrifuge (8000 r/min, 15 min), the supernatant was subjected to autohydrolysis in a reactor at 120 °C for 3 h to obtain a hydrolyzate;

(2) After cooling the above hydrolyzate, acidify it with 1 mol/L hydrochloric acid to pH<3, let it stand for 12 h, centrifuge (8000 r/min, 15 min) to separate the filter residue from the filtrate, and wash the filter residue with deionized water 2 times;

(3) The filtrates obtained in step (2) were combined, extracted three times with ethyl acetate, and the organic phase was evaporated under reduced pressure at 40 °C to remove ethyl acetate, and then vacuum-dried at 40 °C (overnight) to obtain Soluble fraction (small molecular fraction of eucalyptus kraft lignin); the filter residue was vacuum-dried (overnight) at 40 °C to obtain the insoluble fraction.

The GC-MS diagram of the small molecular fraction of eucalyptus kraft lignin obtained is shown in Figure 1.

The yield of small molecule fraction of eucalyptus kraft lignin was 20.7%.

the

Example 2

A green alkali lignin small molecule separation method, comprising the steps of:

(1) Take 10 g of the black liquor sample produced in the cooking stage of the kraft pulping process of eucalyptus, add 50 mL of distilled water and 10 mL of ethanol to dilute, and centrifuge (8000 r/min, 15 min), and the supernatant is at 120 Under the condition of ℃, the autohydrolysis reaction was carried out in the reactor for 3 h to obtain the hydrolyzate;

(2) After cooling the above hydrolyzate, acidify it with 1 mol/L hydrochloric acid to pH<3, let it stand for 12 h, centrifuge (8000 r/min, 15 min) to separate the filter residue from the filtrate, and wash the filter residue with deionized water 2 times;

(3) The filtrates obtained in step (2) were combined, extracted three times with ethyl acetate, and the organic phase was evaporated under reduced pressure at 40 °C to remove ethyl acetate, and then vacuum-dried at 40 °C (overnight) to obtain Soluble fraction (small molecular fraction of eucalyptus kraft lignin); the filter residue was vacuum-dried (overnight) at 40 °C to obtain the insoluble fraction.

The GC-MS diagram of the obtained eucalyptus kraft lignin small molecule fraction is shown in Figure 2.

The yield of small molecule fraction of eucalyptus kraft lignin was 29.8%.

the

Example 3

A green alkali lignin small molecule separation method, comprising the steps of:

(1) Take 10 g of the black liquor sample produced in the cooking stage of eucalyptus kraft pulping process, add 30 mL of distilled water and 30 mL of ethanol to dilute, and centrifuge (8000 r/min, 15 min). Under the condition of ℃, the autohydrolysis reaction was carried out in the reactor for 3 h to obtain the hydrolyzate;

(2) After cooling the above hydrolyzate, acidify it with 1 mol/L hydrochloric acid to pH<3, let it stand for 12 h, centrifuge (8000 r/min, 15 min) to separate the filter residue from the filtrate, and wash the filter residue with deionized water 2 times;

(3) The filtrates obtained in step (2) were combined, extracted three times with ethyl acetate, and the organic phase was evaporated under reduced pressure at 40 °C to remove ethyl acetate, and then vacuum-dried at 40 °C (overnight) to obtain Soluble fraction (small molecular fraction of eucalyptus kraft lignin); the filter residue was vacuum-dried (overnight) at 40 °C to obtain the insoluble fraction.

The obtained eucalyptus kraft lignin small molecular fraction GC-MS diagram is shown in Figure 3.

The yield of small molecule fraction of eucalyptus kraft lignin was 41.1%.

the

Example 4

A green alkali lignin small molecule separation method, comprising the steps of:

(1) Take 10 g of black liquor sample produced in the cooking stage of eucalyptus kraft pulping process, add 10 mL of distilled water and 50 mL of ethanol to dilute, and centrifuge (8000 r/min, 15 min). Under the condition of ℃, the autohydrolysis reaction was carried out in the reactor for 3 h to obtain the hydrolyzate;

(2) After cooling the above hydrolyzate, acidify it with 1 mol/L hydrochloric acid to pH<3, let it stand for 12 h, centrifuge (8000 r/min, 15 min) to separate the filter residue from the filtrate, and wash the filter residue with deionized water 2 times;

(3) The filtrates obtained in step (2) were combined, extracted three times with ethyl acetate, and the organic phase was evaporated under reduced pressure at 40 °C to remove ethyl acetate, and then vacuum-dried at 40 °C (overnight) to obtain Soluble fraction (small molecular fraction of eucalyptus kraft lignin); the filter residue was vacuum-dried (overnight) at 40 °C to obtain the insoluble fraction.

The obtained eucalyptus kraft lignin small molecular fraction GC-MS diagram is shown in Figure 4.

The yield of small molecule fraction of eucalyptus kraft lignin was 52.5%.

the

Example 5

A green alkali lignin small molecule separation method, comprising the steps of:

(1) Take 10 g of black liquor sample produced in the cooking stage of eucalyptus kraft pulping process, add 60 mL of distilled water to dilute, and centrifuge (8000 r/min, 15 min), the supernatant was acidified with 1 mol/L hydrochloric acid to pH<3, allowed to stand for 12 h, centrifuged (8000 r/min, 15 min) to separate the filter residue from the filtrate, and washed the filter residue twice with deionized water;

(2) The filtrates obtained in step (1) were combined, extracted three times with ethyl acetate, the organic phase was evaporated under reduced pressure at 40 °C to remove ethyl acetate, and then vacuum dried (overnight) at 40 °C to obtain Soluble fraction (small molecular fraction of eucalyptus kraft lignin); the filter residue was vacuum-dried (overnight) at 40 °C to obtain the insoluble fraction.

The GC-MS diagram of the obtained eucalyptus kraft lignin small molecule fraction is shown in Figure 5.

The yield of small molecule fraction of eucalyptus kraft lignin was 14.6%.

The structure diagram of each substance is shown in Figure 6. These substances play an important role in the development of new materials and chemicals, and have important guiding significance for the identification of the structure of industrial lignin.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. A green alkali lignin small molecule separation method is characterized in that it comprises the following steps:

   (1) Self-hydrolysis reaction: add water or ethanol/water to the black liquor to dilute, centrifuge, and perform self-hydrolysis on the supernatant to obtain a hydrolyzate;

   (2) Separation of small molecules of alkali lignin: after cooling the hydrolyzate obtained in step (1), acidify, stand still, and centrifuge, and extract the obtained filtrate with a green organic solvent. After removing the solvent, the soluble small molecule fraction is obtained. Lignin small molecule.
2. A green method for separating small molecules of alkali lignin according to claim 1, characterized in that: the black liquor in step (1) is the black liquor produced in the cooking stage in the alkaline pulping process.
3. A green method for separating small molecules of alkali lignin according to claim 2, characterized in that: the alkaline pulping process is an alkaline pulping process or a kraft pulping process.
4. A green alkali lignin small molecule separation method according to claim 1, characterized in that: the mass multiple of the dilution in step (1) is 5-15 times that of the black liquor; the ethanol/water ethanol and water The volume ratio is 0~5:1, and not 0.
5. A green method for separating small alkali lignin molecules according to claim 1, characterized in that: the reaction temperature in step (1) is 90-140°C.
6. The green small-molecule separation method of alkali lignin according to claim 1, characterized in that: the reaction time in step (1) is 1-4 h; the reaction is carried out in a high-pressure reactor.
7. A green small molecule separation method of alkali lignin according to claim 1, characterized in that: the acidification in step (2) uses hydrochloric acid with an acid concentration of 0.1-6 mol/L; the acidification is to pH<3 .
8. A green alkali lignin small molecule separation method according to claim 1, characterized in that: the standing time in step (2) is 4-16 h.
9. A green alkali lignin small molecule separation method according to claim 1, characterized in that: the number of extractions in step (2) is 1-5 times; the organic solvent is ethyl acetate; step (2) ) The condition for removing the solvent is to evaporate to dryness under reduced pressure at 30-60 °C.
10. The small alkali lignin molecules separated by the green alkali lignin small molecule separation method according to any one of claims 1-9.

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