CN109970991A - It is classified the modified method of comprehensive utilization of the small fraction demethoxylation of lignin - Google Patents
It is classified the modified method of comprehensive utilization of the small fraction demethoxylation of lignin Download PDFInfo
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- CN109970991A CN109970991A CN201910211072.3A CN201910211072A CN109970991A CN 109970991 A CN109970991 A CN 109970991A CN 201910211072 A CN201910211072 A CN 201910211072A CN 109970991 A CN109970991 A CN 109970991A
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Abstract
The invention discloses the modified method of comprehensive utilization of the small fraction demethoxylation of classification lignin.Steps of the method are: classification processing is carried out to lignin by ethanol-water, its dispersibility is reduced, obtains the lignin of different molecular weight, lignin small molecule is then subjected to demethoxylation study on the modification.Lignin has high polymerization degree, polydispersity, and wherein contains a large amount of methoxyl group, and hydroxy radical content is low, keeps steric hindrance on phenyl ring big, causes reactivity site low, therefore de-methoxy is to improve the active basis of lignin reaction.And lignin is classified by ethanol-water, obtain the lignin of different fractions, and the small molecule grade lignin obtained by the method remains most methoxyl group, the fraction more than methoxyl content can be concentrated in together by way of classification in this way, then it is modified to carry out demethoxylation, to effectively improve the reactivity site of lignin, lignin is made effective use of.
Description
Technical field
The invention belongs to biomass resource lignin field of comprehensive utilization, and in particular to the classification small fraction demethoxy of lignin
The modified method of comprehensive utilization of base.
Background technique
Lignin is the second largest renewable plant resources for being only second to cellulose, and being known as 21 century can be by human use's
One of the most abundant green resource, annual output is very big, industrial pulping waste liquor is mainly derived from, to environment if direct emission
It adversely affects, but due to the difference of the degree of polymerization, the molecular weight of lignin shows certain polydispersity, and leads to its knot
Structure performance is inhomogenous.The reactivity and performance being classified using molecular weight as scale can be prepared in such a way that solvent is classified
Similar lignin is used respectively according to its different characteristics.
Lignin is by para hydroxybenzene propane (H-type), lilac base (S type) and guaiacyl (G type) three basic structures list
Member composition.Connection type between main structure body is mainly ehter bond and carbon-carbon bond, and wherein methoxyl content is high, and hydroxy radical content is low,
Steric hindrance is big on phenyl ring, causes lignin reaction's activity low, therefore improves the basis that lignin reaction's activity is lignin application,
So carrying out demethoxylation to lignin is to improve a kind of active means of lignin reaction.
The phenolic acid for the small molecule grade lignin being classified by solvent and the content of S type lignin structure unit
It is higher than middle molecular level and macromolecular grade lignin, and the content of G type lignin structure unit is lower than other two kinds of fractions.Thus
Know that methoxyl content is relatively more in small molecule fraction lignin, it in this way can be more by methoxyl content by way of classification
Fraction concentrate in together, it is modified then to carry out demethoxylation, to effectively improve the reactivity site of lignin, sufficiently has
Effect utilizes lignin.
Summary of the invention
The main object of the present invention is that lignin is rich in the small classification lignin separation of methoxyl group by ethanol-water solution
Out, microwave-assisted method is then used, the methoxyl group on phenyl ring is attacked by nucleopilic reagent, becomes phenolic hydroxyl group, to mention
The activity of high lignin.
Technical solution of the present invention is as follows.
It is classified the modified comprehensive utilization of the small fraction demethoxylation of lignin, is included the following steps:
It is classified the modified method of comprehensive utilization of the small fraction demethoxylation of lignin, which comprises the following steps:
(1) ethanol-water method prepares different fractions lignin: it is 85% ~ 95% ethyl alcohol that lignin addition, which is filled volumetric concentration,
It is dissolved in the round-bottomed flask of solution, solid-to-liquid ratio is 1:10 ~ 1:50g/mL, and 5 ~ 20min is sufficiently stirred, then carries out solid-liquid
Separation, obtains solid and lignin small molecule fraction solution, and it is 70% that isolated solid, which is and then added to volumetric concentration,
It is dissolved in ~ 80% ethanol solution, solid-to-liquid ratio is 1:10 ~ 1:50g/mL, after being sufficiently stirred, is separated by solid-liquid separation, obtains lignin
Molecular level liquid separation body in macromolecular fraction solid and lignin, by molecular level in obtained lignin small molecule fraction and lignin
Liquid separation body, the method that rotary evaporation is respectively adopted are handled, by obtained concentrate and lignin macromolecular fraction solid into
Row drying grinding, respectively obtains lignin small molecule fraction, molecule fraction and lignin macromolecular fraction in lignin；
(2) small fraction lignin demethoxylation is modified: nucleopilic reagent and catalyst being added to round bottom with the ratio of 1:1 ~ 1:3 and burnt
In bottle, 5 ~ 10min is sufficiently stirred, takes lignin small molecule fraction obtained in solvent dissolving step (1), with nucleopilic reagent: wood
Quality small molecule fraction mass ratio is that lignin liquor is slowly added into said mixture by the ratio of 1:2 ~ 1:4, side edged
Stirring finishes and flask is put into normal pressure microwave reactor to the reaction was continued, and adjusting reaction temperature is 70 DEG C ~ 110 DEG C, when reaction
Between be 40min ~ 90min, after reaction, take out flask be put into ice bath, add water terminate reaction, then plus 0.5M ~ 1M HCl tune
PH to 2 ~ 3, settle out lignin, is then separated by solid-liquid separation, then the solid that drying at room temperature is centrifuged out cleans wood with n-hexane dissolution
Dimethyl sulfide in quality obtains the shallower demethylation modified lignin resin of color.
In the above method, the lignin is alkali lignin, sulfate-reducing conditions or organic solvent lignin.
In the above method, the nucleopilic reagent is n- dodecyl mereaptan or hydrobromic acid
In the above method, the catalyst is organic base sodium methoxide or inorganic base sodium hydroxide.
In the above method, dissolved lignin's solvent is DMSO or DMF.
Various characterizations prove that the lignin and raw material for the different fractions that alcohol-water is classified compare, only molecular weight
Changed, chemical structure does not occur significantly to change, and small component lignin phenol acid and S type lignin knot
The content of structure unit is higher than intermediate molecular weight and macromolecule, and the content of G type lignin structure unit is lower than intermediate molecular weight
And macromolecule, it can thus be appreciated that the methoxyl group in lignin is concentrated mainly in small molecule fraction.In the most of anti-of lignin
Ying Zhong, since 3,5 methoxyl groups reduce the activity of lignin reaction, so that the field of lignin application is reduced, it can be with
Lignin is modified by demethoxylation reaction, improves the reactivity of lignin.Ethanol-water can be passed through in this way
The mode of classification concentrates in together the lignin more than methoxyl content, is then focused on, to effectively improve wooden
The utility value of element, and lignin abundance have renewable, nontoxic, pollution-free degradable performance, therefore prepare
Modified sample also has the characteristics that green safe.
Compared with prior art, present invention has an advantage that
Lignin has high polymerization degree, polydispersity, and wherein contains a large amount of methoxyl group, and hydroxy radical content is low, keeps phenyl ring upper
Resistance is big, causes reactivity site low, therefore de-methoxy is to improve the active basis of lignin reaction.And pass through alcohol-water
Solvent is classified lignin, obtains the lignin of different fractions, and protect by the small molecule grade lignin that the method obtains
It has stayed most methoxyl group, can have been concentrated in together the fraction more than methoxyl content by way of classification in this way, then
It is modified to carry out demethoxylation, to effectively improve the reactivity site of lignin, makes effective use of lignin.
Detailed description of the invention
Fig. 1 is the infrared spectroscopy of three fraction of lignin raw material and lignin.
Specific embodiment
The present invention will be further specifically described in detail with reference to specific embodiments, but embodiments of the present invention are not
It is limited to this, for not specifically specified technological parameter, can refer to routine techniques progress.
Embodiment 1
(1) ethanol-water method prepares different fractions lignin: it is 85% ethyl alcohol that the addition of 20g alkali lignin, which is filled volumetric concentration,
It is dissolved in the round-bottomed flask of solution, solid-to-liquid ratio (w/v, g/mL) is 1:10, and 10min is sufficiently stirred, then carries out solid-liquid
Separation, obtains solid and lignin small molecule fraction solution, and it is 70% that isolated solid, which is and then added to volumetric concentration,
Ethanol solution in dissolved, solid-to-liquid ratio (w/v, g/mL) be 1:10, after being sufficiently stirred, be separated by solid-liquid separation, it is big to obtain lignin
Molecular level liquid separation body in molecule fraction solid and lignin, molecular level liquid separation in obtained lignin small molecule fraction and lignin
Body, the method that rotary evaporation is respectively adopted are handled, and obtained concentrate and lignin macromolecular fraction solid are dried
Dry grinding respectively obtains lignin small molecule fraction, molecule fraction and lignin macromolecular fraction in lignin；
(2) small fraction lignin demethoxylation is modified: by 5g nucleopilic reagent n- dodecyl mereaptan and 5g catalyst sodium methoxide with quality
Than being added in round-bottomed flask for the ratio of 1:1,5min is sufficiently stirred, the alkali lignin obtained in DMSO dissolving step (1)
Small molecule fraction is 1:2(nucleopilic reagent: alkali lignin with mass ratio) ratio be 50% by 20g mass fraction DMSO alkali wood
Quality solution is slowly added into said mixture, stirring while adding, finishes flask being put into normal pressure microwave reactor relaying
Continuous reaction, adjusting reaction temperature is 70 DEG C, reaction time 80min, after reaction, takes out flask and is put into ice bath, adds few
Measure water terminate reaction, then plus 1M HCl tune pH to 2 ~ 3, settle out lignin, be then separated by solid-liquid separation, what drying at room temperature was centrifuged out
Then solid cleans the Dimethyl sulfide in lignin with n-hexane dissolution, it is wooden to obtain the shallower demethylation modification of color
Element.
Examination of infrared spectrum is carried out using the present embodiment products obtained therefrom, as shown in Figure 1, passing through comparison lignin raw material and wood
The infrared spectroscopy of three fraction of quality is it can be found that substantially absorption peak is the same, and only there are slight changes for some characteristic absorption peaks.First
Observation is in 1700 cm-1Absorption peak caused by the non-conjugated carbonyl at place and the ester bond of conjugation, it can be found that the peak intensity of raw material here
Degree is maximum, followed by small molecule fraction, and absorption peak strength is greater than middle molecule fraction and macromolecular fraction, which is by phenol
Caused by acid, illustrate that the content of phenolic acid in small molecule fraction is higher than middle molecule fraction and macromolecular fraction.
Middle molecule fraction and macromolecular fraction are in 1120 cm-1The absorption peak strength at place will be weaker than absorption peak of the small molecule fraction at this,
1120 cm-1The absorption peak at place is corresponding with lilac base (S) structural unit, illustrates the S type structural unit in small molecule fraction
Content is higher than middle molecule fraction and macromolecular fraction；1060 cm of another observation-1Place represents guaiaci lignum fundamental mode (G) structural unit
Characteristic absorption peak discovery, peak intensity is gradually increased from small molecule fraction to macromolecular fraction, this demonstrate with
Polymer wood quality compares, its S type structural content of the lower lignin of molecular weight is higher, and the content of G type structural unit is lower.
Embodiment 2
(1) ethanol-water method prepares different fractions lignin: it is 90% ethyl alcohol that the addition of 20g alkali lignin, which is filled volumetric concentration,
It is dissolved in the round-bottomed flask of solution, solid-to-liquid ratio (w/v, g/mL) is 1:25, and 15min is sufficiently stirred, then carries out solid-liquid
Separation, obtains solid and lignin small molecule fraction solution, and it is 75% that isolated solid, which is and then added to volumetric concentration,
Ethanol solution in dissolved, solid-to-liquid ratio (w/v, g/mL) be 1:25, after being sufficiently stirred, be separated by solid-liquid separation, it is big to obtain lignin
Molecular level liquid separation body in molecule fraction solid and lignin, molecular level liquid separation in obtained lignin small molecule fraction and lignin
Body, the method that rotary evaporation is respectively adopted are handled, and obtained concentrate and lignin macromolecular fraction solid are dried
Dry grinding respectively obtains lignin small molecule fraction, molecule fraction and lignin macromolecular fraction in lignin；
(2) small fraction lignin demethoxylation is modified: by 5g nucleopilic reagent n- dodecyl mereaptan and 10g catalyst sodium methoxide with quality
Than being added in round-bottomed flask for the ratio of 1:2,8min is sufficiently stirred, the alkali lignin obtained in DMSO dissolving step (1)
Small molecule fraction is 1:3(nucleopilic reagent: alkali lignin with mass ratio) ratio be 50% by 30g mass fraction DMSO alkali wood
Quality solution is slowly added into said mixture, stirring while adding, finishes flask being put into normal pressure microwave reactor relaying
Continuous reaction, adjusting reaction temperature is 90 DEG C, reaction time 60min, after reaction, takes out flask and is put into ice bath, adds few
Measure water terminate reaction, then plus 1M HCl tune pH to 2 ~ 3, settle out lignin, be then separated by solid-liquid separation, what drying at room temperature was centrifuged out
Then solid cleans the Dimethyl sulfide in lignin with n-hexane dissolution, it is wooden to obtain the shallower demethylation modification of color
Element.
Embodiment 3
(1) ethanol-water method prepares different fractions lignin: it is 95% ethyl alcohol that the addition of 20g alkali lignin, which is filled volumetric concentration,
It is dissolved in the round-bottomed flask of solution, solid-to-liquid ratio (w/v, g/mL) is 1:50, and 20min is sufficiently stirred, then carries out solid-liquid
Separation, obtains solid and lignin small molecule fraction solution, and it is 80% that isolated solid, which is and then added to volumetric concentration,
Ethanol solution in dissolved, solid-to-liquid ratio (w/v, g/mL) be 1:50, after being sufficiently stirred, be separated by solid-liquid separation, it is big to obtain lignin
Molecular level liquid separation body in molecule fraction solid and lignin, molecular level liquid separation in obtained lignin small molecule fraction and lignin
Body, the method that rotary evaporation is respectively adopted are handled, and obtained concentrate and lignin macromolecular fraction solid are dried
Dry grinding respectively obtains lignin small molecule fraction, molecule fraction and lignin macromolecular fraction in lignin；
(2) small fraction lignin demethoxylation is modified: by 5g nucleopilic reagent n- dodecyl mereaptan and 15g catalyst sodium methoxide with quality
Than being added in round-bottomed flask for the ratio of 1:3,10min is sufficiently stirred, the alkali lignin obtained in DMSO dissolving step (1)
Small molecule fraction is 1:4(nucleopilic reagent: alkali lignin with mass ratio) ratio be 50% by 40g mass fraction DMSO alkali wood
Quality solution is slowly added into said mixture, stirring while adding, finishes flask being put into normal pressure microwave reactor relaying
Continuous reaction, adjusting reaction temperature is 110 DEG C, reaction time 40min, after reaction, takes out flask and is put into ice bath, adds few
Measure water terminate reaction, then plus 1M HCl tune pH to 2 ~ 3, settle out lignin, be then separated by solid-liquid separation, what drying at room temperature was centrifuged out
Then solid cleans the Dimethyl sulfide in lignin with n-hexane dissolution, it is wooden to obtain the shallower demethylation modification of color
Element.
The above embodiment of the present invention be only to clearly illustrate example of the present invention, and not be to the present invention
Embodiment restriction.For those of ordinary skill in the art, it can also make on the basis of the above description
Other various forms of variations or variation.There is no necessity and possibility to exhaust all the enbodiments.It is all of the invention
Made any modifications, equivalent replacements, and improvements etc., should be included in the protection of the claims in the present invention within spirit and principle
Within the scope of.
Claims (5)
1. being classified the modified method of comprehensive utilization of the small fraction demethoxylation of lignin, which comprises the following steps:
(1) ethanol-water method prepares different fractions lignin: it is 85% ~ 95% ethyl alcohol that lignin addition, which is filled volumetric concentration,
It is dissolved in the round-bottomed flask of solution, solid-to-liquid ratio is 1:10 ~ 1:50g/mL, and 5 ~ 20min is sufficiently stirred, then carries out solid-liquid
Separation, obtains solid and lignin small molecule fraction liquid, and it is 70% that isolated solid, which is and then added to volumetric concentration,
It is dissolved in ~ 80% ethanol solution, solid-to-liquid ratio is 1:10 ~ 1:50g/mL, after being sufficiently stirred, is separated by solid-liquid separation, obtains lignin
Molecular level liquid separation body in macromolecular fraction solid and lignin, by molecular level in obtained lignin small molecule fraction and lignin
Liquid separation body, the method that rotary evaporation is respectively adopted are handled, by obtained concentrate and lignin macromolecular fraction solid into
Row drying grinding, respectively obtains lignin small molecule fraction, molecule fraction and lignin macromolecular fraction in lignin；
(2) small fraction lignin demethoxylation is modified: nucleopilic reagent and catalyst being added to round bottom with the ratio of 1:1 ~ 1:3 and burnt
In bottle, 5 ~ 10min is sufficiently stirred, takes lignin small molecule fraction obtained in solvent dissolving step (1), with nucleopilic reagent: wood
Quality small molecule fraction mass ratio is that lignin liquor is added in said mixture by the ratio of 1:2 ~ 1:4, stirring while adding,
It finishes and flask is put into normal pressure microwave reactor to the reaction was continued, adjusting reaction temperature is 70 DEG C ~ 110 DEG C, and the reaction time is
40min ~ 90min, after reaction, take out flask be put into ice bath, add water terminate reaction, then plus 0.5M ~ 1M HCl tune pH extremely
2 ~ 3, settle out lignin, is then separated by solid-liquid separation, then the solid that drying at room temperature is centrifuged out cleans lignin with n-hexane dissolution
In Dimethyl sulfide, obtain the shallower demethylation modified lignin resin of color.
2. the modified method of comprehensive utilization of the small fraction demethoxylation of classification lignin according to claim 1, which is characterized in that
The lignin is one of alkali lignin, sulfate-reducing conditions and organic solvent lignin.
3. the modified method of comprehensive utilization of the small fraction demethoxylation of classification lignin according to claim 1, which is characterized in that
The nucleopilic reagent is n- dodecyl mereaptan or hydrobromic acid.
4. the modified method of comprehensive utilization of the small fraction demethoxylation of classification lignin according to claim 1, which is characterized in that
The catalyst is organic base sodium methoxide or inorganic base sodium hydroxide.
5. the modified method of comprehensive utilization of the small fraction demethoxylation of classification lignin according to claim 1, which is characterized in that
In step (2), solvent is DMSO or DMF.
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Cited By (2)
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| CN111607202A (en) * | 2020-07-08 | 2020-09-01 | 浙江晟祺实业有限公司 | Methylated lignin PBAT biodegradable plastic and preparation method thereof |
| CN114105739A (en) * | 2021-11-10 | 2022-03-01 | 华南理工大学 | Green alkali lignin micromolecule separation method and product |
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| CN111607202A (en) * | 2020-07-08 | 2020-09-01 | 浙江晟祺实业有限公司 | Methylated lignin PBAT biodegradable plastic and preparation method thereof |
| CN114105739A (en) * | 2021-11-10 | 2022-03-01 | 华南理工大学 | Green alkali lignin micromolecule separation method and product |
| WO2023083029A1 (en) * | 2021-11-10 | 2023-05-19 | 华南理工大学 | Green alkali lignin micromolecule separation method and product |
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Application publication date: 20190705 |