CN101957315B - Method for measuring lignin content in black liquor - Google Patents
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- 238000002835 absorbance Methods 0.000 claims abstract description 45
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- 239000000284 extract Substances 0.000 claims description 6
- VZOPRCCTKLAGPN-ZFJVMAEJSA-L potassium;sodium;(2r,3r)-2,3-dihydroxybutanedioate;tetrahydrate Chemical compound O.O.O.O.[Na+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O VZOPRCCTKLAGPN-ZFJVMAEJSA-L 0.000 claims description 6
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- VUEOQWDVOXEFDJ-UHFFFAOYSA-N 2-pyridin-2-ylacetic acid;hydrate Chemical compound O.OC(=O)CC1=CC=CC=N1 VUEOQWDVOXEFDJ-UHFFFAOYSA-N 0.000 claims description 4
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims description 4
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- 239000000047 product Substances 0.000 claims 4
- LWFUFLREGJMOIZ-UHFFFAOYSA-N 3,5-dinitrosalicylic acid Chemical compound OC(=O)C1=CC([N+]([O-])=O)=CC([N+]([O-])=O)=C1O LWFUFLREGJMOIZ-UHFFFAOYSA-N 0.000 claims 3
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- 239000012086 standard solution Substances 0.000 claims 2
- XVMSFILGAMDHEY-UHFFFAOYSA-N 6-(4-aminophenyl)sulfonylpyridin-3-amine Chemical compound C1=CC(N)=CC=C1S(=O)(=O)C1=CC=C(N)C=N1 XVMSFILGAMDHEY-UHFFFAOYSA-N 0.000 claims 1
- LJCNRYVRMXRIQR-OLXYHTOASA-L potassium sodium L-tartrate Chemical compound [Na+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O LJCNRYVRMXRIQR-OLXYHTOASA-L 0.000 claims 1
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- 239000010902 straw Substances 0.000 abstract description 21
- YGSDEFSMJLZEOE-UHFFFAOYSA-N salicylic acid Chemical compound OC(=O)C1=CC=CC=C1O YGSDEFSMJLZEOE-UHFFFAOYSA-N 0.000 abstract description 8
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- FJKROLUGYXJWQN-UHFFFAOYSA-N papa-hydroxy-benzoic acid Natural products OC(=O)C1=CC=C(O)C=C1 FJKROLUGYXJWQN-UHFFFAOYSA-N 0.000 abstract description 4
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Abstract
The invention provides a method for measuring lignin content in black liquor based on the linear relation between the absorbance value of salicylic acid solution and dissolved quantity of lignin in case of the lignin in straw pulp black liquor at 520nm. The method can quickly, conveniently and accurately measure the lignin content in the black liquor and can remove interference from reducing sugar and sodium sulfite in the straw pulp black liquor during the measuring process. The method can measure the lignin content in the alkali straw pulp black liquor and the lignin content in the alkaline sulphite straw pulp black liquor. The method for measuring the relative content of the lignin in the straw pulp black liquor is accurate and reliable.
Description
Technical field
The present invention relates to technological process of treating papermaking and black liquor comprehensive utilization of resources technical field, specifically is to utilize lignin technology in the spectrophotometry black liquor, be mainly used in that paper waste is handled and the black liquid comprehensive utilization process in lignin quantitatively.
Background technology
Lignin is that nature synthetic quantity and amount are only second to cellulosic natural polymer.The annual industrial lignin about 5 * 10 that produces of whole world paper industry
7Ton is only effectively utilized less than 10%.Industrial lignin mainly obtains from pulping back liquor.According to the difference of pulping process, industrial lignin mainly contains alkali lignin and lignin sulfonate etc., and wherein alkali lignin accounts for the overwhelming majority.Lignin structure is complicated, and molecular weight distribution is wide, contains ehter bond in the molecule, carbon-carbon double bond, benzyloxy, alcoholic extract hydroxyl group, phenolic hydroxyl group, carbonyl and phenyl ring etc.
Because the lignin structure more complicated, and be difficult to separate and extract, lot of domestic and international scholar is devoted to lignin separation means and Research on Structural Analysis, but for how measuring in the black liquor lignin content research seldom.Being used for the lignin assay method mainly is to measure raw material and paper pulp lignin, and the lignin method generally has gravimetric method and AAS in the mensuration raw material, and gravimetric method has GB to measure the content of Klason lignin, also has acid detergent fiber method and TGA method in addition; AAS mainly contains acid soluble lignin method and acetyl bromide method.Survey lignin in the raw material, also have the content report of infra-red sepectrometry fast measuring mao bamboon Klason lignin recently.Lignin content utilizes Kappa number to come the indirect reaction height in the paper pulp.
Most of lignin and a part of carbohydrates are degraded in pulping digestion process, are dissolved among the black liquor, and great changes will take place to make in the black liquor in the lignin and raw material lignin form and structure.And the solid content in the black liquor is formed more complicated, and dispersed system is colloidal property.In measuring black liquor during lignin content, all inapplicable when measuring in the black liquor lignin with the assay method of raw material and paper pulp lignin content.Have direct absorption value to measure lignin content in the black liquor, but this method error is big, be difficult to get rid of the interference of some other component with ultraviolet spectrum 280nm place phenyl ring.Lignin content mensuration is different with raw material lignin content assay method in the black liquor, sets up and measures lignin content experimental technique in the black liquor simply, fast and accurately, has bigger using value for lignin in the development and use pulping back liquor.
Summary of the invention
The present invention adopts lignin content in the salicylic acid dissolving spectrophotometry black liquor, and purpose is to set up a kind of quick, easy, lignin content assay method in the black liquor accurately.Result of study shows, the two has higher linear relationship to black liquor lignin at the DNS of 520nm place solution absorbance value and lignin meltage.This method can be got rid of the interference of reducing sugar and sodium sulphite in the black liquor when measuring.Not only lignin content in the alkaline straw-pulp black liquid can be measured, lignin content in the alkali sulfite process straw pulp black liquor can also be measured.Accompanying drawing 1 is for being reference with the deionized water; The ultraviolet-visible light spectrogram of DNS solution and straw, reed and maize straw DNS dissolved lignin, accompanying drawing 2 is for being three types of grass as raw material DNS lignin solution ultraviolet-visible light 450～600nm place spectrograms that reference records with DNS.Two figure horizontal ordinates all are wavelength, and ordinate is an absorbance.Can find out that from two figure selecting this method to measure lignin content has certain practical basis.
Concrete operation method is following:
The preparation of the first step, DNS solution takes by weighing 6.3gDNS and 262ml 2moll
-1Sodium hydroxide solution adds in the sodium potassium tartrate tetrahydrate hot solution (the 182g sodium potassium tartrate tetrahydrate is dissolved in the 500ml deionized water), adds 5g crystalline phenol and 5g sodium sulphite stirring and dissolving again.Be settled to 1000ml after the cooling, be stored in brown bottle, use behind the placement 72h.
Second the step, lignin extraction, get a certain amount of alkaline cooking black liquor, with the dilute sulfuric acid regulator solution to pH6, centrifuging; Get supernatant liquid, transfer to pH 3 with dilute sulfuric acid again, sediment is taken out in centrifuging again; And with the dilute sulfuric acid washing, centrifugal then, repetitive operation 2～3 times; Get the centrifuged deposit thing and place 80 ℃ of vacuum drying chamber oven dry, grind, make thick lignin with mortar.
The purification of the 3rd step, lignin is dissolved in thick lignin in 140ml pyridine-acetic acid-water (volume ratio 9: 1: 4) system, uses the 180ml chloroform extraction, sways after leaving standstill the 4h layering; After the layering, tell the organic layer that lower floor is dissolved with lignin once more, add the 150ml chloroform in the upper solution and extract once more; Leave standstill after swaying, treat to isolate after the layering organic layer of lower floor, merge extract twice; In rotary vacuum evaporator, be concentrated into about 100ml, move in the 1000ml absolute ether, go out lignin in the stirring settle; The lignin that is settled out is washed with ether, till the non-pyridine flavor, place P
2O
5Vacuum dryer in dry, obtain light grey refining lignin.
The 4th step, lignin absorbance curve plotting, accurately the refining lignin 1.000g of weighing is dissolved in normal temperature 50mlDNS solution, is settled to 500ml with deionized water, makes the lignin titer.Press table 1 and in color comparison tube, add quantitative lignin; Surely dissolve 10ml with DNS solution after diluting 10 times; At wavelength 520nm place, use 10 times of DNS of dilution to measure absorbance as reference, with the lignin concentration horizontal ordinate; Absorbance is the ordinate mapping, obtains linear relationship curve between lignin content and the absorbance.
The 5th step, lignin content is measured in the black liquor, according to the standard curve making process, lignin is dissolved in the DNS solution, through the dilution rear side fixed its at the 520nm place absorbance, calculate wherein lignin content according to typical curve then.
The present invention can be used for measuring the content of lignin in the black liquor, also can measure in the black liquor content of lignin in the solid content.
When measuring in the black liquor solution lignin content; Get black liquor dilution suitable multiple, get dilution 5ml then to color comparison tube, add 2ml DNS solution; Add deionized water and be settled to 20ml; Sampling is a reference to dilute 10 times of DNS solution, measures absorbance in the 520nm place, calculates lignin content in the black liquor according to the lignin typical curve.
When measuring in the black liquor in the solid content lignin content, its concrete grammar is following:
The first step, get a certain amount of alkaline cooking black liquor, with the dilute sulfuric acid regulator solution to pH 6, centrifuging; Get supernatant liquid, transfer to pH 3, centrifuging again with dilute sulfuric acid again; Take out sediment, and with the dilute sulfuric acid washing, centrifugal then; Repetitive operation 2～3 times is got the centrifuged deposit solid content and is placed 80 ℃ of vacuum drying chamber oven dry, grinds;
Second step, from dry postprecipitation solid content, get 0.100g and place color comparison tube, add suitable quantity of water, add 2ml 3 again; 5-dinitrosalicylic acid solution dissolves it, adds deionized water then and is settled to 20ml, gets that solution 4ml places another color comparison tube in the color comparison tube again; Add 10 times of DNS solution of dilution to 20ml; Sampling is a reference to dilute 10 times of DNS solution, measures absorbance in the 520nm place, calculates lignin ratio in the solid content according to the lignin typical curve.
The present invention is applicable to the assay of lignin in the grass as raw material gained black liquor.
The present invention measures lignin content in the black liquor with salicylic acid dissolving UV-VIS spectrophotometry; Set up a kind of experimental technique of measuring lignin content in the black liquor simply, fast and accurately, have bigger using value for lignin resource in the development and use pulping back liquor.
Description of drawings
Fig. 1, be reference with the deionized water, the ultraviolet-visible light spectrogram of DNS solution and straw, reed and maize straw DNS dissolved lignin.
Fig. 2, for being three types of grass as raw material DNS lignin solution ultraviolet-visible light 450～600nm place spectrograms that reference records with DNS.
Fig. 3, be linear relationship curve between three kinds of grass as raw material lignin contents and the absorbance.
Fig. 4, glucose solution are at 350～600nm wave band absorbance scanning curve.
Fig. 5, Na
2SO
3Solution is at 350～600nm wave band absorbance scanning curve.
Embodiment
Below in conjunction with embodiment the present invention is described further.
With this method lignin content in straw, reed and the maize straw alkaline sodium sulfite black liquor is measured.
The first step, the preparation of DNS solution:
Take by weighing 6.3g DNS and 262ml 2moll
-1NaOH solution adds in the sodium potassium tartrate tetrahydrate hot solution (the 182g sodium potassium tartrate tetrahydrate is dissolved in the 500ml deionized water), adds 5g crystalline phenol and 5g sodium sulphite stirring and dissolving again.Be settled to 1000ml after the cooling, be stored in brown bottle, use behind the placement 72h;
The extraction of second step, lignin:
Get a certain amount of alkaline cooking black liquor, to pH 6, supernatant liquid is got in centrifuging with the dilute sulfuric acid regulator solution; Transfer to pH 3 with dilute sulfuric acid again, sediment is taken out in centrifuging again; And with the dilute sulfuric acid washing, centrifugal then, repetitive operation 2～3 times; Get the centrifuged deposit thing and place 80 ℃ of vacuum drying chamber oven dry, grind, make thick lignin with mortar;
The purification of the 3rd step, lignin:
Thick lignin is dissolved in 140ml pyridine-acetic acid-water (volume ratio 9: 1: 4) system, uses 180ml CHCl
3Extraction is swayed after leaving standstill the 4h layering, after the layering, tells the organic layer that lower floor is dissolved with lignin once more.Add 150ml CHCl in the upper solution
3Extraction is left standstill after swaying once more, treats to isolate after the layering organic layer of lower floor.Merge extract twice, in rotary vacuum evaporator, be concentrated into about 100ml, move in the 1000ml absolute ether, go out lignin, the lignin that is settled out is washed with ether, till the non-pyridine flavor in the stirring settle.Place P
2O
5Vacuum dryer in dry, obtain light grey refining lignin;
The 4th step, lignin absorbance curve plotting:
Accurately the refining lignin 1.000g of weighing is dissolved in normal temperature 50ml DNS solution, is settled to 500ml with deionized water, makes the lignin titer.Press table 1 and in color comparison tube, add quantitative lignin; Surely dissolve 10ml with DNS solution after diluting 10 times,, use 10 times of DNS of dilution to measure absorbance as reference at wavelength 520nm place; With the lignin concentration is horizontal ordinate; Absorbance is ordinate mapping, obtains between lignin content and the absorbance linear relationship curve and sees Fig. 3, can obtain computing formula between lignin content and absorbance according to curve among the figure.
The DNS solution absorbance value of table 1, different lignin contents:
Fig. 3 semilate rice vegetation cellulose content and absorbance relation curve are y
1=1.2225x
1+ 0.0046, R
1 2=0.9991; Maize straw is y
2=1.0065x
2+ 0.0041, R
2 2=0.9991; Reed is y
3=0.7485x
3+ 0.0035, R
3 2=0.9998.
According to typical curve linear regression formula, can obtain lignin content c (gl
-1) and absorbance A between concern.
Straw:
Straw:
Reed:
Wherein, c
1, c
2, c
3Be respectively lignin concentration in straw to be measured, maize straw, the reed black liquor; A
1, A
2, A
3Be respectively straw, maize straw, reed black liquor absorbance when measuring.N
1, N
2, N
3Be solution dilution multiple to be measured, N should get appropriate value, makes A between 0.3～0.7.
Lignin content is measured in the 5th step, the black liquor
The lignin of measuring in the alkali sulfite process black digestion liquid is the comparison difficulty.Because lignin can not be precipitated out fully, is unmeasured with conventional method.Measure lignin content in straw, maize straw, reed alkaline sodium sulfite black liquor acid out gained sediment and the supernatant liquid, the feasibility of checking this method.
Get black liquor 100ml and place the 500ml beaker, add the 1moll of certain volume then
-1Hydrochloric acid solution is about about 5 black liquor pH value, and centrifuged deposit is weighed after placing the baking oven drying, is acid out one-level sediment.Because pH is about 5 behind the adding hydrochloric acid solution, the following acid out of this pH value goes out lignin and contains more impurity, so will survey its purity.With lignin content in lignin content method mensuration and the deposition in the mensuration solid content, promptly from dry postprecipitation solid content, get 0.100g and place color comparison tube, add suitable quantity of water, add 2ml DNS again it is dissolved, add deionized water then and be settled to 20ml.Get that solution 4ml places another color comparison tube in the color comparison tube again, add 10 times of DNS solution of dilution to 20ml, sampling is a reference to dilute 10 times of DNS solution, and the mensuration absorbance calculates lignin ratio in the solid content according to the lignin typical curve in 520nm place.
Get upper strata, centrifugal back liquid and add certain volume 1moll again
-1About hydrochloric acid solution, adjust pH to 2, centrifugal then.Take out deposition, and with watery hydrochloric acid washing precipitation, centrifugal, repetitive operation 2～3 times will obtain sediment at last and place baking oven, be dried to constant weight, and the record sediment is heavy.Gained is precipitated as the two-stage precipitation thing, because after adding hydrochloric acid again, pH value of solution is less than 3, these other materials of pH section settle are fewer, and again through repeatedly pickling, it is higher to obtain lignin purity, thinks that the two-stage precipitation thing is lignin entirely.
Top each centrifugal back supernatant liquid is all inserted in the same 500ml beaker; And lignin content in the mensuration centrifugate: get black liquor dilution suitable multiple, get dilution 5ml then to color comparison tube, add 2ml DNS solution; Add deionized water and be settled to 20ml; Sampling is a reference to dilute 10 times of DNS solution, measures absorbance in the 520nm place, calculates lignin content in the black liquor according to the lignin typical curve.
Measure lignin content in the raw black liquid, and with deposition lignin and lignin content sum comparison in the stillness of night, the result sees table 2.
Table 2, black liquor lignin acidizing separation assay and comparison:
From table 2, can find out; Residual lignin and be more or less the same with original black liquor 100ml lignin content in acid out postprecipitation lignin and the upper strata liquid in three types of grass as raw material black liquor of 100ml explains that to adopt the salicylic acid UV-VIS spectrophotometry to measure in the black liquor lignin content accuracy higher.
The analysis of the influence that interfering material is measured lignin:
DNS is a kind of developer of measuring reducing sugar in the solution, when temperature is higher, can react with reducing sugar in the solution, generates the darker material of color, and there is the mensuration that will disturb lignin content in reducing sugar.When measuring in the solution content of reducing sugar, generally selecting wavelength is 485～540nm.To D/W 10gl
-1(get 2ml DNS, use 10gl with glucose DNS solution
-1D/W is settled to 20ml) carry out test scan at 350～600nm wave band absorbance, scanning result is as shown in Figure 4.As can beappreciated from fig. 4; Glucose does not have absorption peak in this wave band; And absorbance curve and DNS absorbance curve differ very few behind the DNS dissolving glucose; This explains that at normal temperatures glucose reducing end group and DNS do not produce new extinction material, can get rid of the interference of carbohydrate during the test lignin content.
In measuring the alkaline sulfite black digestion liquid, during lignin content, get rid of Na
2SO
3Interference.To 10gl
-1Na
2SO
3Solution and Na
2SO
3DNS solution (is got 2ml DNS, is used Na
2SO
310gl
-1The WS is settled to 20ml) carry out the scanning of 400～600nm wave band absorbance, the result sees Fig. 5.
Can find out by Fig. 5: Na
2SO
3Do not absorb at 400～600nm wave band, absorption curve linearly.Na
2SO
3-DNS solution slightly improves than former DNS solution absorbance value, when wavelength during greater than 500nm absorbance go to zero Na
2SO
3The interference meeting smaller.
At the DNS dilute solution is reference with water, and other solution are reference with the DNS dilute solution, and the DNS solution concentration of lignin is 0.5gl
-1Condition under, measure each sample at the 520nm place absorbance as shown in table 3.Can find out that by table 3 absorbance of interfering material is all smaller, glucose solution measured concentration 9gl
-1The time absorbance 0.086, sodium sulphite measured concentration 9gl
-1The time absorbance 0.048, and lignin concentration 0.5gl
-1The time absorbance reach 0.526, it is little to explain that chaff interference is measured influence to lignin.
Table 3, each sample be absorbance at the 520nm place:
Annotate: the DNS dilute solution is to be reference with water, and other solution are reference with the DNS dilute solution all.The DNS solution concentration of lignin is 0.5gl
-1
Claims (4)
1. method of measuring lignin content in the black liquor is characterized in that operating according to the following steps:
The first step, preparation 3,5-dinitrosalicylic acid solution takes by weighing 6.3g 3,5-dinitrosalicylic acid and 262ml 2moll
-1Sodium hydroxide solution adds in the sodium potassium tartrate tetrahydrate hot solution, adds 5g crystalline phenol and 5g sodium sulphite stirring and dissolving again, is settled to 1000ml after the cooling, is stored in brown bottle, uses behind the placement 72h;
Second the step, lignin extraction, get a certain amount of alkaline cooking black liquor, with the dilute sulfuric acid regulator solution to pH6, centrifuging; Get supernatant liquid, transfer to pH 3 with dilute sulfuric acid again, sediment is taken out in centrifuging again; And with the dilute sulfuric acid washing, centrifugal then, repetitive operation 2～3 times; Get the centrifuged deposit thing and place 80 ℃ of vacuum drying chamber oven dry, grind, make thick lignin with mortar;
The purification of the 3rd step, lignin is dissolved in thick lignin in 140ml pyridine-acetic acid-water system, uses the 180ml chloroform extraction; Sway after leaving standstill the 4h layering, after the layering, tell the organic layer that lower floor is dissolved with lignin once more; Add the 150ml chloroform in the upper solution and extract once more, leave standstill after swaying, treat to isolate after the layering organic layer of lower floor; Merge the organic layer extract twice, in rotary vacuum evaporator, be concentrated into 95～105ml, move to 1000
In the ml absolute ether, stir to make and separate out deposition, will precipitate, till the non-pyridine flavor, place P with the ether washing
2O
5Vacuum dryer in dry, obtain light grey refining lignin;
The 4th step, lignin absorbance curve plotting, the lignin standard solution of preparation 0.2g/ml is got quantitative lignin standard solution and is added in the color comparison tube; With 3 of 10 times of dilutions, 5-dinitrosalicylic acid solution dissolves 10ml surely, at wavelength 520nm place; With 3 of 10 times of dilutions, 5-dinitrosalicylic acid solution is that reference is measured absorbance, is horizontal ordinate with the lignin concentration; Absorbance is the ordinate mapping, obtains linear relationship curve between lignin content and the absorbance;
Lignin content is measured in the 5th step, the black liquor; According to the standard curve making process; Product to be tested is dissolved in 3, in the 5-dinitrosalicylic acid solution, through dilution back mensuration its at the 520nm place absorbance; Calculate wherein lignin content according to typical curve then, product to be tested is a solid content in black liquor solution or the black liquor;
Wherein, potassium sodium tartrate solution is the 182g sodium potassium tartrate tetrahydrate to be dissolved in the 500ml deionized water process pyridine in pyridine-acetic acid-water system: acetic acid: the volume ratio of water is 9: 1: 4.
2. a kind of method of measuring lignin content in the black liquor according to claim 1 is characterized in that product to be tested is a black liquor solution, at first makes linear relationship curve between lignin content and the absorbance; Next measures the content of lignin in the black liquor solution, and concrete assay method is: get black liquor dilution suitable multiple, get dilution 5ml then to color comparison tube; Add 2ml 3,5-dinitrosalicylic acid solution adds deionized water and is settled to 20ml; Sampling is to dilute 10 times 3; 5-dinitrosalicylic acid solution is reference, measures absorbance in the 520nm place, calculates lignin content in the black liquor according to the lignin typical curve.
3. a kind of method of measuring lignin content in the black liquor according to claim 1; It is characterized in that product to be tested is a solid content in the black liquor; At first make linear relationship curve between lignin content and the absorbance, next measures the lignin content in the solid content in the black liquor, and concrete assay method is following:
The first step, get a certain amount of alkaline cooking black liquor, with the dilute sulfuric acid regulator solution to pH 6, centrifuging; Get supernatant liquid, transfer to pH 3, centrifuging again with dilute sulfuric acid again; Take out sediment, and with the dilute sulfuric acid washing, centrifugal then; Repetitive operation 2～3 times is got the centrifuged deposit solid content and is placed 80 ℃ of vacuum drying chamber oven dry, grinds;
Second step, from dry postprecipitation solid content, get 0.100g and place color comparison tube, add suitable quantity of water, add 2ml 3 again; 5-dinitrosalicylic acid solution dissolves it, adds deionized water then and is settled to 20ml, gets that solution 4ml places another color comparison tube in the color comparison tube again; Add 10 times 3 of dilution, 5-dinitrosalicylic acid solution is to 20ml, sampling with dilute 10 times 3; 5-dinitrosalicylic acid solution is reference, measures absorbance in the 520nm place, calculates lignin ratio in the solid content according to the lignin typical curve.
4. a kind of method of measuring lignin content in the black liquor according to claim 1 is characterized in that being applicable to the assay of lignin in the grass as raw material gained black liquor.
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