JPH07145581A - Digestion of lignocellulose material - Google Patents

Abstract

PURPOSE:To provide a digestion method improved in oxidation-reduction cycle of a quinone-hydroquinone-based compound used as a digesting assistant and efficiency of the digesting assistant and capable of improving the yield and reducing active alkalis in comparison with the conventional method. CONSTITUTION:This is related to a method for digesting a lignocellulose material in an alkaline digesting solution containing a quinone-hydroquinone-based compound. In this method, a reducing agent is added to this digesting system during a period from temperature rise to a prescribed digestion temperature to the first half of the prescribed digestion temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for cooking lignocellulosic material in an alkaline cooking liquor containing a quinone compound.

[0002]

2. Description of the Related Art Alkaline cooking is known as one of the methods for pulping various lignocellulosic materials such as wood, straw, bagasse, hemp, kenaf, etc., in which a quinone compound is added. This method includes anthraquinone, tetrahydroanthraquinone, 1,4-dihydro-9 in so-called alkaline cooking liquor, such as soda cooking liquor, kraft cooking liquor, polysulfide cooking liquor, sulfite cooking liquor, sulfite cooking liquor using sodium carbonate and caustic soda together. The pulping method is carried out by adding a quinone compound such as sodium salt of 10-dihydroxyanthracene. Since the effect produced by the addition of a quinone compound can be applied in various fields, the cooking method with the addition of a quinone compound is now widely used in the pulp industry around the world.

Regarding this quinone cooking method, conventionally,
Kraft cooking method, a method using anthraquinone sulfonate as a quinone-based cooking aid in a cooking method such as sulfite cooking method (East German Patent No. 98549), a method using anthraquinone (Japanese Patent Publication No. 55-1398), A method using dihydrodihydroxyanthracene or a sodium salt thereof (Japanese Patent Publication No. 53-13002), a method using a cyclic keto compound such as naphthoquinone, anthraquinone, anthrone (JP-A No. 52-378003),
Method using Diels-Alder adduct of naphthoquinone such as tetrahydroanthraquinone and 2-ethyltetrahydroanthraquinone (Japanese Patent Publication No. 53-45404)
In addition, many methods such as a method using anthraquinone, phenanthrenequinone, naphthoquinone, anthrone, anthrahydroquinone, naphthohydroquinone or a tautomer of the above quinone (JP-A-52-155202) are disclosed.

Many publications have been made on the mechanism of action of quinone compounds in cooking when these quinone compounds are used as cooking aids. For example, Loewen
dahl, Tappi, 61 (No. 2), p. 19 (1
978) shows the following formula [Formula 01].

[0005]

[Chemical 01]

That is, since the terminal aldehyde groups of cellulose and hemicellulose are oxidized by anthraquinone (oxidized quinone) to stabilize the sugar chain, the pulp yield and pulp strength are improved. On the other hand, this reaction The anthrahydroquinone (reduced quinone) produced by the reduction by the reaction with β-phenyl ether bond in the lignin structure, which is difficult to decompose with caustic soda, is easily cleaved to promote the delignification reaction. To be done. As a result, when the quinone compound is added, the cooking conditions are alleviated as compared with the case where no quinone compound is added. In other words, anthraquinone functions as a redox catalyst that intervenes in the lignocellulosic structure to stabilize the sugar and promote the delignification reaction. Therefore, even if an extremely small amount of anthraquinone is added, a great auxiliary effect is exhibited. That is, the cooking of quinone compounds can be summarized in the following two basic actions. 1. Acceleration of delignification reaction (acceleration of cleavage of β-phenyl ether bond etc.) 1. Stabilizing action of cellulose and hemicellulose (oxidation of sugar chain terminal aldehyde group) There are various effects obtained by these two actions,
For example, from (1) promotion of delignification reaction, (a) reduction of cooking temperature ... energy saving, (b) reduction of cooking time ... increase of production, (c) saving of active alkali ... chemical agent (D) It is possible to produce low kappa number pulp ... Reduce the burden of the bleaching process, and (e) Allow low-sulphurity cooking ... Reduce odor. From the stabilization of celluloses,
(F) Improving pulp yield ... saving chips and increasing pulp, (g) improving paper strength ... improving paper quality. The common effect of this basic action is to ease cooking conditions. Is to be done. There have been proposed some methods for more effectively exhibiting the action of the quinone compound in the alkaline cooking method in which the quinone compound is added. For example, alkali sulfide pulping method,
In the so-called kraft cooking method, anthraquinone, a quinone compound such as tetrahydroanthraquinone or a hydroquinone compound such as anthrahydroquinone, and a reducing aid such as sulfite, bisulfite, thiosulfate and formate are added to the cooking liquor to produce a lignocellulosic material. A method of digesting soybeans in a so-called craft cooking liquor (for example, Japanese Patent Publication 6
0-29794, JP-B-62-274, JP-A-55
-142785) has been proposed.

[0007]

However, as disclosed in the examples of these methods, the reducing agent is added in advance to the cooking liquor together with the quinone compound in the cooking liquor before the temperature is raised to the predetermined cooking temperature. After that, it is a method in which the temperature is raised to a predetermined cooking temperature to carry out the cooking. The present inventors were able to confirm the following facts, when they made earnest studies for the purpose of further enhancing the effect of the quinone compound-added cooking method. That is, a kraft cooking liquor or an active alkali 2 having a sulfidity of 25%, an active alkali addition rate of 18% and a liquid ratio of 5
1,4 as a cooking aid in 0% caustic soda cooking liquor
-Dihydro-9,10-dihydroxyanthracene disodium salt (hereinafter, 1,4-dihydro-9,10-dihydroxyanthracene is abbreviated as DDA and its sodium salt as DDANa) and powdery anthraquinone having an average particle diameter of 24μ. When wood chips were used for test cooking at a cooking temperature of 160 ° C and the cooking process was examined, it was found that this quinone compound exerts an auxiliary effect from a fairly early stage of cooking to stabilize sugar. It was Also,
One of the characteristics of quinone compounds [oxidized type ← → reduced type]
It was revealed that the equilibrium of ss was strongly biased toward the oxidative form in the early stages of cooking.

In this test, the oxidized form (anthraquinone) and reduced form (anthrahydroquinone or DDA or 1,4-dihydro-anthrahydroquinone) of the quinone compound corresponding to the temperature rising process and each temperature after reaching the predetermined cooking temperature are used. The results of analyzing and graphing the compound of the above are shown in FIG. 1 for kraft cooking and FIG. 2 for soda cooking. As is clear from [FIG. 1] and [FIG. 2], most of the anthraquinone and DDANa oxidize most of the quinone compounds at a cooking temperature of 120 ° C. or higher, particularly 140 ° C. or higher, and even 160 ° C. It is a mold.

The cooking aid effect of quinone compounds is as follows:
As shown in Fig. 2, it occurs as a result of redox reaction between anthraquinone (oxidized type) and anthrahydroquinone (reduced type). It is considered that the effect is positively influenced. Therefore, as is apparent from [Fig. 1] and [Fig. 2], it is difficult to exert the effect of the cooking aid because the quinone is largely biased to the oxidized form during the heating process and during the heating process after the heating process. Therefore, it is necessary to return this equilibrium to the reduced form. Therefore, if it is possible to return the oxidized form to the reduced form, it is considered that the redox cycle is restored by this and the effect of the cooking aid by the quinone compound is further increased. Therefore, the object of the present invention is to effectively exhibit the cooking aid effect of quinone.

[0010]

[Means for Solving the Problem] Specifically, various reducing agents are added to the digestion system at the time when the abundance ratio of the quinone oxidized form becomes high, that is, at the relatively early stage of cooking from the temperature rising process,
It was found that the delignification reaction can be promoted by returning the oxidized quinone compound to the reduced quinone compound, and at the same time, the number of redox cycles can be improved, and as a result, the cooking aid effect of the quinone compound can be increased. Came to.

Therefore, the present invention is a method for cooking a lignocellulosic material in an alkaline cooking liquor in which a quinone-hydroquinone compound and its precursor are present, from the time of heating up to a predetermined cooking temperature to the first half of a predetermined cooking temperature. In between, there is a method for cooking lignocellulosic material, characterized in that a reducing agent is added to this cooking system.

In the present invention, examples of the quinone-hydroquinone compound include the following compounds. Examples of the quinone compound include anthraquinone and 1
-Methyl anthraquinone, 2-methyl anthraquinone,
Alkylanthraquinones such as 1-ethylanthraquinone, 2-ethylanthraquinone and 2-t-butylanthraquinone, aminoanthraquinones such as 2-aminoanthraquinone, and nitroanthraquinones such as 2-nitroanthraquinone and anthraquinone-2-sulfonates and 1,4 -Anthraquinone represented by hydrogenated atraquinone such as dihydroanthraquinone, 2-methyl-1,4-dihydroanthraquinone, 1,4,4a, 9a-tetrahydroanthraquinone and 2-methyl-1,4,4a, 9a-tetrahydroanthraquinone Examples of the compound include naphthoquinone and the like. Examples of the hydroquinone compound include hydroquinone of the above quinone compounds and alkali metal salts thereof. For example, anthrahydroquinone, DDA (1,4-dihydro-9,10-dihydroxyanthracene), DD
ANa (disodium salt of 1,4-dihydro-9,10-dihydroxyanthracene), 2-methylanthrahydroquinone, 2-methyl-1,4-dihydro-9,10
-Anthrahydroquinone compounds such as the disodium salt of dihydroxyanthracene. In the present invention, the precursor of a quinone-hydroquinone compound refers to a compound whose precursor may be converted into quinone or hydroquinone under cooking conditions, and examples thereof include anthrone, anthranol, and an alkali metal salt of anthranol. 10-hydroxyanthrone and the like can be mentioned.
Alternatively, if necessary, these quinone compounds can be used together. However, in general, anthrahydroquinone compounds are preferable as the anthraquinone compound, and particularly, anthraquinone, DDA and DDANa which are industrially manufactured at low cost are advantageously used.

The amount of these quinone compounds used varies depending on the cooking conditions, the desired Kappa number, etc., but generally the addition rate to the lignocellulosic material is 0.00
5 to 3% by weight, preferably 0.01 to 1.2% by weight,
More preferably, 0.01 to 0.5% by weight is sufficient.

In the present invention, as the reducing agent, low polymers such as cellulose and hemicellulose, starch and its low polymers, oligosaccharides and monosaccharides constituting these sugars and reducing sugars such as molasses; formaldehyde And formaldehydes such as paraformaldehyde,
Organic reducing agents such as urea and thiourea; and one or more reducing agents selected from reducing black liquors and reducing substances derived from lignocellulosic substances such as extracts of wood and herbs with aqueous or alkaline aqueous solutions. Examples include reducing substances.

The amount of these reducing agents used is 0.05 to 6% by weight, preferably 0.1 to 5% by weight, more preferably 0.3 to 5% by weight, based on the pair of lignocellulosic materials. Is. There is no effect if the amount of reducing agent used is too small,
Too much is not economical for its effect. As a method of adding the reducing agent to the digestion system, generally known feeding methods such as a method of dissolving a necessary amount in an aqueous medium such as water or white liquor or a method of pressurizing as a slurry by a pump or the like are adopted.

The cooking method can be applied to a wide range of cooking methods such as soda cooking method, kraft cooking method, polysulfide cooking method, alkaline sulfite cooking method and cooking method using sodium carbonate. As the cooking conditions, the conditions generally practiced are applied. For example, in the soda cooking method, an active alkali (hereinafter, all weight% of Na ₂ O based on the absolutely dried chips) 8 to 20% by weight, a cooking temperature of 160 to 200 ° C.,
In the Kraft cooking method, the active alkali is 13 to 25% by weight, the sulfidity is 10 to 30% by weight, the cooking temperature is 140 to 200 ° C, and the polysulfide amount is 0.3 in the polysulfide cooking method.
~ 2.2% by weight (against chips) and other cooking conditions according to the Kraft cooking method are applied. In the alkaline sulfite cooking method, the caustic soda addition rate is 0.5 to 7%, the sodium sulfite addition rate is 2 to 25% (vs. chips). ), Cooking temperature 130-200 ℃
And the liquid ratio is generally 2 to 6.

In the present invention, the reducing agent is added to the cooking liquor from the beginning together with the cooking aid as in the conventional method.
Instead of raising the temperature, the temperature of the cooking liquor containing the lignocellulosic material and the cooking aid, that is, the quinone-hydroquinone compound and its precursor, is raised to about 120 ° C.
Above all, it is most effective to add at the time when the temperature is raised to 140 ° C. or higher, more preferably to 160 ° C. or higher, or when the predetermined cooking temperature is reached. Further, it is still effective from the beginning of the cooking to the first half, generally within 20 minutes after reaching the predetermined cooking temperature. Since this quinone compound reacts with lignin fragments and the like with the lapse of cooking time, the amount of quinone compound present in the cooking system decreases, and at the end of cooking, only 10-20% of the amount of the quinone compound initially added is present. Since the amount of the remaining quinone compound is small in the middle or second half of the cooking, the addition of the reducing agent at that time is not effective.

In the cooking of the present invention, either a batch cooking method or a known continuous cooking method can be used. In the batch cooking method, the reducing agent can be added through the cooking liquor circulation line from the latter half of the heating or when the cooking temperature is reached. Further, in the Kamyr type continuous digester, a reducing agent can be introduced into the cooking liquor circulation line of the first heater from the top of the tower.

[0019]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. .

[Examples 1 and 2 and Comparative Examples 1 to 1]
A 6-liter mangrove chip (700 g (absolutely dry)) was charged into a 41-Oken type autoclave, and cooking was performed at a sulfidity of 30%, a liquid ratio of 3, a heating time of 40 minutes, a cooking temperature of 168 ° C., and a holding time of 60 minutes.

A curve having an X-axis and a Y-axis representing the amount of active alkali and the Kappa number for each experiment number shown in Table 1 was drawn to determine the amount of active alkali having a Kappa number of 17. At the same time, a curve was drawn with the Kappa number and pulp yield on the X and Y axes, and the pulp yield at a Kappa number of 17 was determined.

In Comparative Examples 1 to 6, no cooking aid was added, or a quinone compound and a reducing agent as a cooking aid were added to the cooking liquor in advance before the temperature was raised to the cooking temperature, and the autoclave was filled with the above. Is a comparative example of cooking under the conditions of, and in Examples 1 and 2, when the cooking temperature reached 165 ° C., a solution prepared by dissolving 28 g of starch as a reducing agent in 40 ml of water was pressed into the autoclave to continue the cooking. It was The pulp yield and the amount of active alkali required under each cooking condition thus obtained are shown in [Table 1].

[0023]

[Table 1]

[Examples 3 and 4 and Comparative Examples 7-1]
2 ”Chip 500 made from Douglas Fir-based softwood mixture
4 g (absolutely dry) was charged into an Oken type autoclave, the sulfidity was 30%, the liquid ratio was 5, the heating time was 60 minutes, and the cooking temperature was 174.
Cooking was carried out under conditions of ℃ and holding time of 70 minutes. However, for the pulp yield and the amount of active alkali, values at a Kappa number of 25 were obtained. Comparative Examples 7 to 12 are Comparative Examples carried out in the same manner as in "Examples 1 and 2" except for the above cooking conditions, and Examples 3 and 4 are examples according to the present invention. The method for determining the amount of active alkali and the yield of pulp is described in Example 1.
And the same as 2. The results are shown in [Table 2].

[0025]

[Table 2]

"Examples 5 and 6" In Examples 1 and 2, the temperature at the time of addition of the reducing agent was raised to 15
The same operation as in Examples 1 and 2 was carried out except that the temperature was changed to 0 ° C, and the results shown in Table 3 were obtained.

[0027]

[Table 3]

[Examples 7 and 8] In Examples 3 and 4, the temperature at the time of addition of the reducing agent was raised to 15
The same operation as in Examples 3 and 4 was carried out except that the temperature was changed to 0 ° C., and the results shown in [Table 4] were obtained.

[0029]

[Table 4]

[Examples 9 to 12] The same procedure as in Examples 1 and 2 was repeated except that the types of the reducing agent were changed to the compounds shown in [Table 5]. The results of Table 5] were obtained.

[0031]

[Table 5]

[0032]

INDUSTRIAL APPLICABILITY According to the method of the present invention, when a quinone compound is used as a cooking aid, the action of the quinone compound is more effectively exhibited than in the conventional method in which a quinone compound and a reducing agent are simultaneously added. As a result, it is possible to improve the pulp yield and save the active alkali.

[Brief description of drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the results of kraft cooking using anthraquinone and DDANa (a disodium salt of 1,4-dihydro-9,10-dihydroxyanthracene) as cooking aids. FIG. 3 is a graph showing the analysis results of oxidized quinone and reduced quinone of the quinone compound present in the cooking liquor at temperature as the recovery rate (%) with respect to the amount of quinone compound added first.

FIG. 2 is a graph showing results of soda cooking instead of kraft cooking in FIG.

[Explanation of symbols]

 A1 When anthraquinone is used as a cooking aid B1 When DDANa is used as a cooking aid A2 When anthraquinone is used as a cooking aid B2 When DDANa is used as a cooking aid C1 10 minutes after reaching the predetermined cooking temperature After cooking C2 After 10 minutes after reaching the specified cooking temperature

Claims (4)

[Claims] 1. A method for digesting a lignocellulosic material in an alkaline cooking liquor in which a quinone-hydroquinone compound and a precursor thereof are present, wherein the lignocellulosic material is heated at a predetermined temperature up to the first half of the predetermined temperature. A method for cooking lignocellulosic material, which comprises adding a reducing agent to the cooking system. 2. The reducing agent is a low polymer such as cellulose or hemicellulose, starch or a low polymer thereof and oligosaccharides, monosaccharides constituting these sugars and reducing sugars such as molasses, formaldehyde, urea, One or more selected from organic reducing substances such as thiourea, and reducing substances obtained from lignocellulosic substances such as reducing black liquor, wood extract of wood and herbs with water or alkaline aqueous solution The reducing substance according to claim 1.
The cooking method described. 3. The cooking method according to claim 1, wherein the quinone-hydroquinone compound is an anthraquinone compound and an anthrahydroquinone compound. 4. The temperature at the time of temperature increase when the reducing agent is added is 12
The cooking method according to claim 1, which has a temperature of 0 ° C or higher.