Method for digesting lignocellulosic material

Abstract

A method of digesting lignocellulosic material includes mixing lignocellulosic material comprising lignocellulosic biomass, a polymeric naphthalene sulfonate, sodium xylene sulfonate, and a white liquor comprising sodium hydroxide and sodium sulfide to form a mixture. In addition, the method further includes heating the mixture to digest at least a portion of the lignocellulosic material.

Description

TECHNICAL FIELD

[0001] The embodiments described herein relate to compositions and methods for digesting lignocellulosic materials, such as in the Kraft pulping process. More specifically, the present disclosure relates to a combination of polymeric naphthalenesulfonates and sodium xylenesulfonate, which synergistically improves digestion efficiency compared to methods that do not utilize the combination of polymeric naphthalenesulfonates and sodium xylenesulfonate. BACKGROUND ART

[0002] The Kraft pulping process is one of the main pulping processes in the pulp and paper industry. This process utilizes sodium hydroxide and sodium sulfide added to the medium used to cook wood chips and produce pulp. When this technology was introduced over a century ago, the addition of sodium sulfide significantly improved pulp strength, pulp yield, and the durability of the paper produced therefrom.

[0003] In a typical Kraft digestion process, wood chips are added to an aqueous medium mainly containing white liquor, which turns into dark "black liquor" as lignin and wood components dissolve and disintegrate during the cooking process. Typical white liquor includes a solution of sodium hydroxide, sodium carbonate, sodium sulfate, sodium sulfide, and various other inorganic substances. The white liquor dissolves the wood components and removes most of the lignin from the wood chips, thereby obtaining released fibers or "pulp" in the "black liquor" solution. In fact, the liquid (or cooking liquor) in which the wood chips are cooked contains a mixture of black liquor and white liquor. Specifically, the black liquor can be recycled from a previous batch of wood chips into the cooking vessel or digester, while the white liquor is freshly prepared alkaline solution. The composition of the black liquor can vary from one mill to another depending on the white liquor, the type of wood, and the cooking method.

[0004] Ideally, all wood chips would be evenly cooked during the digestion process. However, in practice, not all of the fibers in the wood chips are separated. Any unseparated fiber bundles are classified as "rejects". The more rejects are screened out during the pulping process, the lower the yield (defined as the dry weight of pulp produced per unit dry weight of wood consumed).

[0005] In addition to cellulose and hemicellulose, lignin is also one of the main components of wood. Lignin is a natural, highly aromatic, and hydrophobic polymer. To produce bleachable pulp, most of the lignin is decomposed and removed from the cellulose by the kraft pulping process, while additional amounts of lignin are further reduced through a series of bleaching and extraction stages. There is a continuing need for improvement in lignin removal, savings in cooking and bleaching chemicals, and shortening of the cooking time.

[0006] During the cooking process, various additives can be used to impart desired characteristics and properties to the pulp and / or the resulting paper product. Additionally, various additives can be used to control or enhance the digestion process. For example, additives can be used to increase pulp yield and / or reduce the amount of extractives. Although various reagents and processes have been employed to enhance the cooking of wood pulp, many compositions and methods are deficient in reducing pulp rejects and increasing pulp yield.

[0007] Accordingly, despite the various compositions and methods currently available, we desire to provide a composition and method for improving the performance of kraft pulping processes. Additionally, we desire to provide a composition and method for increasing digester efficiency. More specifically, the pulping industry needs a more effective combination of digester additives to replace anthraquinone, which was widely used but has recently been phased out by most pulp manufacturing associations due to concerns about potential toxicity. Other desired features and characteristics of the present disclosure will become apparent from the following detailed description and the appended claims in conjunction with the accompanying drawings and this background art. Summary of the Invention

[0008] The present disclosure provides a method for digesting lignocellulosic materials. The method includes mixing a lignocellulosic material comprising lignocellulosic biomass, a polymeric naphthalenesulfonate, sodium xylenesulfonate, and white liquor comprising sodium hydroxide and sodium sulfide to form a mixture. Additionally, the method includes heating the mixture to digest at least a portion of the lignocellulosic material.

[0009] In an exemplary embodiment of the method, the lignocellulosic material is present in an amount of 10 to 30 weight percent based on the total weight of the mixture.

[0010] In an exemplary embodiment of the method, the weight ratio of the polymeric naphthalenesulfonate to the sodium xylenesulfonate is from 10:90 to 90:10.

[0011] In an exemplary embodiment of the method, the weight ratio of the polymeric naphthalenesulfonate to the sodium xylenesulfonate is from 40:60 to 60:40.

[0012] In an exemplary embodiment of the method, the combination of the polymeric naphthalenesulfonate and the sodium xylenesulfonate is present in an amount of 0.1 to 10 kg per metric ton of dry lignocellulosic material.

[0013] In an exemplary embodiment of the method, the white liquor is present in an amount of 70 to 90 weight percent based on the total weight of the mixture.

[0014] In an exemplary embodiment of the method, the mixture is free of added surfactants that are not polymeric naphthalenesulfonates and / or sodium xylenesulfonates.

[0015] In an exemplary embodiment of the method, the method has improved digestion efficiency compared to a method that does not utilize the combination of polymeric naphthalene sulfonate and sodium xylene sulfonate.

[0016] In an exemplary embodiment of the method, heating the mixture includes heating the mixture to a temperature of 125°C to 185°C.

[0017] In an exemplary embodiment of the method, based on the total weight of the mixture, the lignocellulosic material is present in an amount of 10 to 30 wt%; the weight ratio of polymeric naphthalene sulfonate to sodium xylene sulfonate is 10:90 to 90:10; the combination of polymeric naphthalene sulfonate and sodium xylene sulfonate is present in an amount of 0.1 to 10 kg per metric ton of dry lignocellulosic material; based on the total weight of the mixture, white liquor is present in an amount of 70 to 90 wt%; the mixture does not contain added surfactant that is not polymeric naphthalene sulfonate and / or sodium xylene sulfonate; and the method has improved digestion efficiency compared to a method that does not utilize the combination of polymeric naphthalene sulfonate and sodium xylene sulfonate.

[0018] In an exemplary embodiment of the method, the mixture consists essentially of a lignocellulosic material, a polymeric naphthalene sulfonate, sodium xylene sulfonate, white liquor, and a recycle water stream from a pulping process.

[0019] In another embodiment, a method of digesting a lignocellulosic material is disclosed, the method comprising: mixing a lignocellulosic material comprising lignocellulosic biomass, a dispersant, a penetrant, and white liquor comprising sodium hydroxide and sodium sulfide to form a mixture; and heating the mixture to digest at least a portion of the lignocellulosic material. In the method, the ratio of the dispersant to the penetrant in the mixture is 10:90 to 90:10, and the combined total content of the dispersant and the penetrant in the mixture is 0.1 to 10 kg per metric ton of dry lignocellulosic material.

[0020] In an exemplary embodiment of the method, the ratio of the dispersant to the penetrant in the mixture is 40:60 to 60:40.

[0021] In an exemplary embodiment of the method, the dispersant comprises a polymeric naphthalene sulfonate and the penetrant comprises sodium xylene sulfonate.

[0022] In an exemplary embodiment of the method, the dispersant consists of a polymeric naphthalene sulfonate and the penetrant consists of sodium xylene sulfonate.

[0023] In another embodiment, a mixture is provided and the mixture comprises: a lignocellulosic material comprising lignocellulosic biomass, present in an amount of 10 to 30% by weight based on the total weight of the mixture; white liquor comprising sodium hydroxide and sodium sulfide, present in an amount of 70 to 90% by weight based on the total weight of the mixture; a dispersant; and a penetrant. In an exemplary embodiment, the dispersant and the penetrant are present in the mixture at a weight ratio of 10:90 to 90:10, respectively, and the combination of the dispersant and the penetrant is present in an amount of 0.1 to 10 kg of active substance per metric ton of dry lignocellulosic material.

[0024] In an exemplary embodiment, the mixture is free of added surfactants that are not dispersants and / or penetrants.

[0025] In an exemplary embodiment of the mixture, the dispersant consists of a polymeric naphthalenesulfonate and the penetrant consists of sodium xylene sulfonate.

[0026] In an exemplary embodiment of the mixture, the mixture consists essentially of a lignocellulosic material, a polymeric naphthalenesulfonate, sodium xylene sulfonate, white liquor, and a recycle water stream from a pulping process.

[0027] In an exemplary embodiment of the mixture, the mixture consists essentially of a lignocellulosic material, a dispersant, a penetrant, white liquor, and a recycle water stream from a pulping process.

[0028] This summary is intended to introduce, in simplified form, some concepts that will be further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to assist in determining the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present disclosure will be described in conjunction with the following drawings, where like numerals represent like elements, and

[0030] Figure 1 is a bar graph showing the percentage of waste fiber bundles produced by treating lignocellulosic material according to an exemplary method herein and according to a comparative method;

[0031] Figure 2 is a bar graph showing the residual alkali present in black liquor after treating lignocellulosic material according to an exemplary method herein and according to a comparative method;

[0032] Figure 3 is a bar graph showing the measurement results (Kappa value) of the amount of residual lignin in lignocellulosic material after treating according to an exemplary method herein and according to a comparative method. DETAILED DESCRIPTION

[0033] The following specific embodiments are merely illustrative and are not intended to limit the embodiments of the present subject matter or the application and use of such embodiments. The word "exemplary" as used herein means "used as an example, instance or illustration". It is not necessary to understand any embodiment described herein as an example as being preferred or superior to other embodiments. In addition, this article is not intended to be bound by any express or implied theory proposed in the aforementioned technical field, background technology, invention summary or the following specific embodiments.

[0034] Unless otherwise indicated, "a / a kind of" or "the" as used herein refers to one or more. The term "or" can be conjunction or disjunction. Open-ended terms such as "include", "comprise", "contain", etc. mean "comprising". In the present disclosure, the term "about" can describe a value ± 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% in various embodiments. In addition, in various non-limiting embodiments, it should be understood that all numerical values listed herein can be alternatively expressed as approximations or "about".

[0035] Embodiments of the present disclosure generally relate to lignocellulosic mixtures and methods for digesting the same. For the sake of brevity, conventional techniques associated with the development and treatment of lignocellulosic materials may not be described in detail herein. In addition, the various tasks and process steps described herein may be incorporated into a more comprehensive program or process with additional steps or functions not described in detail herein. Specifically, the various steps in the treatment of lignocellulosic materials are well known, and therefore, for the sake of brevity, many conventional steps will only be briefly mentioned herein, or will be omitted entirely, without providing well-known process details.

[0036] The present disclosure provides a method for digesting lignocellulosic materials, such as improving the digestion efficiency of lignocellulosic materials. In an exemplary embodiment, the method comprises, consists essentially of, or consists of the following steps: mixing lignocellulosic materials comprising lignocellulosic biomass, polymeric naphthalenesulfonate, sodium xylenesulfonate, and white liquor comprising sodium hydroxide and sodium sulfide to form a mixture; and heating the mixture to digest at least a portion of the lignocellulosic materials; wherein the lignocellulosic materials are present in an amount of 10 to 30 weight percent based on the total weight of the mixture; the weight ratio of polymeric naphthalenesulfonate to sodium xylenesulfonate is 10:90 to 90:10; the combination of polymeric naphthalenesulfonate and sodium xylenesulfonate is present in an amount of 0.1 to 10 kg per metric ton of dry lignocellulosic materials; the white liquor is present in an amount of 70 to 90 weight percent based on the total weight of the mixture; the mixture does not contain added surfactants other than polymeric naphthalenesulfonate and / or sodium xylenesulfonate; and / or the method has improved digestion efficiency compared to a method that does not utilize the combination of polymeric naphthalenesulfonate and sodium xylenesulfonate.

[0037] The present disclosure also provides another method for digesting lignocellulosic materials, such as improving the digestion efficiency of lignocellulosic materials. In an exemplary embodiment, the method comprises the steps consisting essentially of or consisting of: mixing a lignocellulosic material containing lignocellulosic biomass, a dispersant, a penetrant, and white liquor containing sodium hydroxide and sodium sulfide to form a mixture; and heating the mixture to digest at least a portion of the lignocellulosic material; wherein the lignocellulosic material is present in an amount of 10 to 30% by weight based on the total weight of the mixture; the weight ratio of the dispersant to the penetrant is 10:90 to 90:10; the combination of the dispersant and the penetrant is present in an amount of 0.1 to 10 kg per metric ton of dry lignocellulosic material; the white liquor is present in an amount of 70 to 90% by weight based on the total weight of the mixture; the mixture does not contain added surfactants that are not dispersants and / or penetrants; the method has improved digestion efficiency compared to a method that does not utilize the combination of the dispersant and the penetrant; the dispersant comprises a polymeric naphthalene sulfonate; the penetrant comprises sodium xylene sulfonate; the dispersant consists essentially of a polymeric naphthalene sulfonate; the penetrant consists essentially of sodium xylene sulfonate; the dispersant consists of a polymeric naphthalene sulfonate; and / or the penetrant consists of sodium xylene sulfonate.

[0038] The present disclosure also provides a mixture comprising, consisting essentially of, or consisting of: a lignocellulosic material containing lignocellulosic biomass, which is present in an amount of 10 to 30% by weight based on the total weight of the mixture; white liquor containing sodium hydroxide and sodium sulfide, which is present in an amount of 70 to 90% by weight based on the total weight of the mixture; a dispersant; and a penetrant; wherein: the dispersant and the penetrant are present in the mixture at an active substance weight ratio of 10:90 to 90:10; the combination of the dispersant and the penetrant is present in an amount of 0.1 to 10 kg of active substance per metric ton of dry lignocellulosic material; the mixture does not contain added surfactants that are not dispersants and / or penetrants; the dispersant comprises a polymeric naphthalene sulfonate; the penetrant comprises sodium xylene sulfonate; the dispersant consists mainly of a polymeric naphthalene sulfonate; the penetrant consists mainly of sodium xylene sulfonate; the dispersant consists of a polymeric naphthalene sulfonate; and / or the penetrant consists of sodium xylene sulfonate.

[0039] An exemplary embodiment of the method comprises mixing a lignocellulosic material, a polymeric naphthalene sulfonate, sodium xylene sulfonate, and white liquor to form a mixture, or alternatively, to form an assembly or pulp composition. It should be understood that the mixture of the present disclosure can also be alternatively described as an assembly or pulp composition.

[0040] Generally, the mixture is charged into a processing vessel (such as a digester) and cooked with a cooking liquor (such as the white liquor described herein) for a predetermined time. The processing vessel (such as a digester) is not particularly limited and can be any known vessel in the art. The mixture can be formed in the processing vessel, or can be formed outside the processing vessel and then added to the processing vessel, or can be formed both in and outside the processing vessel.

[0041] The polynaphthalene sulfonate, sodium xylene sulfonate, and white liquor can be transported or conveyed by any method known in the art to contact the lignocellulosic material and form a mixture. For example, the one or more components can be directly added to a processing vessel (such as a digester). Alternatively, one or more components can be added to an input feed stream (such as an input feed stream of the cooking liquor) and then transported to contact the lignocellulosic material. For example, in a batch digester, a mixture of lignocellulosic material, recycled "black liquor" (i.e., the waste liquor recovered from a previous digester cook, such as used as a diluent), white liquor, and various inorganic materials is pumped into the digester. During the cooking process, the lignin that binds the lignocellulosic material together is dissolved in the white liquor, forming pulp and black liquor. Other suitable additives can also be added to the white liquor.

[0042] Compared with a process or mixture without the combination of the dispersant and penetrant described herein, the methods and mixtures described herein can reduce the amount of white liquor required to achieve the desired digestion efficiency. For example, the required white liquor can be reduced by 0.1% or more (such as 0.5% or more, such as 1% or more, such as 1.5% or more, such as 2% or more, such as 2.5% or more, such as 3% or more, such as 3.5% or more, such as 5% or more) to 15% or less (such as 10% or less, such as 7% or less, such as 5% or less, such as 4% or less, such as 3% or less).

[0043] Compared with a process or mixture without the combination of the dispersant and penetrant described herein, the methods and mixtures described herein can reduce the amount of sodium hydroxide required to achieve the desired digestion efficiency. For example, the required sodium hydroxide can be reduced by 0.1% or more (such as 0.5% or more, such as 1% or more, such as 1.5% or more, such as 2% or more, such as 2.5% or more, such as 3% or more, such as 3.5% or more, such as 5% or more) to 15% or less (such as 10% or less, such as 7% or less, such as 5% or less, such as 4% or less, such as 3% or less).

[0044] Compared with processes or mixtures without the combination of dispersants and penetrants described herein, the methods and mixtures described herein can reduce the amount of sodium sulfide required to achieve the desired digestion efficiency. For example, the required sodium sulfide can be reduced by 0.1% or more (such as 0.5% or more, such as 1% or more, such as 1.5% or more, such as 2% or more, such as 2.5% or more, such as 3% or more, such as 3.5% or more, such as 5% or more) to 15% or less (such as 10% or less, such as 7% or less, such as 5% or less, such as 4% or less, such as 3% or less).

[0045] Typically, after placing the mixture in a processing vessel, the processing vessel is sealed and heated under high pressure to a suitable cooking temperature to at least partially digest the lignocellulosic material and form pulp. For example, in various embodiments, the method further includes the step of heating the mixture in the processing vessel to a temperature of 125 to 185 °C to digest at least a portion of the lignocellulosic material. In various embodiments, the temperature is at least 125 °C, at least 130 °C, at least 135 °C, at least 140 °C, at least 145 °C, at least 150 °C, at least 155 °C, at least 160 °C, at least 165 °C, at least 170 °C, at least 175 °C or at least 180 °C. In various embodiments, the temperature does not exceed 185 °C, does not exceed 180 °C, does not exceed 175 °C, does not exceed 170 °C, does not exceed 165 °C, does not exceed 160 °C, does not exceed 155 °C, does not exceed 150 °C, does not exceed 145 °C, does not exceed 140 °C, does not exceed 135 °C or does not exceed 130 °C. In other non-limiting embodiments, it should be understood that the temperature can be higher or lower than the above range, as long as those skilled in the art consider the temperature sufficient to digest at least a portion of the lignocellulosic material.

[0046] In various embodiments, the lignocellulosic material is treated with an alkaline reagent in a processing vessel (such as a digester) under high temperature and high pressure to prepare pulp. In some embodiments, the temperature is from about 93 °C (200 °F) to about 260 °C (500 °F), such as from about 121 °C (250 °F) to about 177 °C (350 °F), and the pressure is 60 psi / g to 130 psi / g. The cooking time can be from 30 minutes to 10 hours, depending on the process conditions and the desired pulp / paper properties. In various non-limiting embodiments, all values and value ranges, whether integers or fractions, including the above values and values between the above values, are explicitly contemplated herein.

[0047] Reaction conditions during cooking or digestion result in the hydrolysis of lignin, an amorphous polymer binder present in woody biomass. Ideally, the digestion time of lignocellulosic material should be long enough to dissolve enough lignin and release the fibers, thereby minimizing overcooking and yield loss. Pulping processes generally attempt to maximize pulp yield, which is defined as the dry weight of pulp produced per unit dry weight of wood consumed.

[0048] After cooking, the lignocellulosic material can usually be blown from the processing vessel into a blowing tank and broken into individual lignocellulosic fibers. In other words, the fibers originally present in the lignocellulosic material are usually broken and separated from each other. However, in practice, some fibers cannot be separated, partly due to the undissolved lignin remaining in the pulp. These unseparated fibers are usually removed by passing the pulp through a screen with a predetermined size opening. In the pulping industry, the standard test screen used is flat with 0.01 inch slits.

[0049] The material that cannot pass through the screen and is separated by the screening process is called "residues". These rejects include fibers that can be used for papermaking. Therefore, it is very desirable to reduce the amount of rejects. One method of reducing the amount of rejects includes extending the digestion time or creating more severe hydrolysis conditions. However, these conditions will increase the costs involved and cause some cellulose to be hydrolyzed and unusable. As described herein, the present disclosure surprisingly and unexpectedly reduces the amount of rejects present without extending the digestion time or creating more severe hydrolysis conditions.

[0050] As is known in the art, the Kappa number is directly related to the amount of residual lignin in the pulp. Generally, the higher the Kappa number, the more lignin is present in the pulp. Generally, the Kappa number decreases with increasing digestion time or increasing cooking liquor alkalinity. Generally, the Kappa number is determined using TAPPI STANDARD T236 (Kappa Number of Pulp). As described herein, the present disclosure unexpectedly and unexpectedly reduces the Kappa number without extending the cooking time or creating more severe hydrolysis conditions.

[0051] When the amount of rejects in the pulp has been reduced to an acceptable level, cooking or digestion can be terminated.If the lignocellulosic material is cooked to an acceptable lignin content while maintaining an acceptable level of rejects, an appreciable yield can be obtained.

[0052] The efficiency of the cooking or digestion process can also be evaluated by determining the amount of alkali remaining in the black liquor after the process is completed. When comparing processes with the same process conditions, different mixtures, and the same digestion efficiency, the higher the amount of residual alkali, the higher the efficiency of the delignification process. Specifically, the higher the amount of residual alkali, the less alkali is used to obtain the same result. Due to the increased permeability to lignocellulosic materials, a higher yield can be obtained when using the same amount of alkali. For example, when the mixture can rapidly penetrate the lignocellulosic material, the alkali can be uniformly introduced into the entire biomass matrix and contact the lignin for a longer process time. In processes that penetrate the biomass slowly or incompletely, although the process duration is longer, the contact time between the alkali and the lignin is shorter. As described herein, the present disclosure unexpectedly and unexpectedly increases the residual alkali without extending the digestion time or creating more severe hydrolysis conditions.

[0053] Lignocellulosic material:

[0054] In an exemplary embodiment, the lignocellulosic material includes biomass. The use of biomass is not limited and can include annual plants and agricultural residues, perennial woody plants, forestry residues, and trees.

[0055] In various embodiments, the lignocellulosic material / biomass can be wood or wood chips. For example, the wood can be any wood known in the art for pulping processes. For example, the wood can include hardwood, softwood, or a mixture thereof. In one embodiment, the wood can mainly include coniferous wood (e.g., spruce, fir, pine, etc.) or mainly include deciduous wood (e.g., eucalyptus, poplar, maple, etc.). Generally, the terms "lignocellulosic material" and / or "biomass" are different from "pulp" herein, as pulp refers to at least partially digested lignocellulosic material / biomass.

[0056] Dispersant

[0057] A dispersant is a substance that improves the separation of colloidal particles suspended in a solution to prevent agglomeration and deposition. In the embodiments herein, the colloidal particles can be organic wood degradation components or inorganic crystalline salts or a mixture thereof. It is expected that the formulations of the present invention can use dispersants to prevent particle agglomeration and sedimentation.

[0058] In an exemplary embodiment, the dispersant is an anionic surfactant or a strong anionic surfactant. Exemplary anionic surfactants include carboxylates, sulfonates, phosphates, polyphosphates, polymeric alkylaryl sulfonates, and polymeric naphthalenes. Polymeric naphthalene / formaldehyde condensates, etc. can be used, and sulfonates can also be used. In an exemplary embodiment, the dispersant is a dispersant polymer.

[0059] In certain embodiments, the dispersant is an anionic sulfate or sulfonate dispersant. In an exemplary embodiment, the anionic dispersant is an anionic sulfonate dispersant. In certain embodiments, the anionic dispersant is a sulfated / sulfonated polyaromatic compound. In certain embodiments, the anionic dispersant is sodium lignosulfonate.

[0060] In one exemplary embodiment, the anionic dispersant is a condensate, such as a naphthalene sulfonate condensate. Generally, condensates can be classified according to the degree of condensation and the content of residual dissolved salts. In one exemplary embodiment, the anionic dispersant is a low-degree condensation polymer.

[0061] Suitable anionic dispersants include condensation products of aromatic sulfonic acids with formaldehyde, such as condensation products of formaldehyde with alkyl naphthalene sulfonic acids, or condensation products of formaldehyde, naphthalene sulfonic acid, and / or benzenesulfonic acid, as well as condensation products of optionally substituted phenols with formaldehyde and sodium bisulfite. Dispersants selected from sulfosuccinates and alkylbenzene sulfonates are also suitable. Lignosulfonates, such as those obtained by the sulfite process or the kraft process, may also be suitable. Such compounds can be products that have been partially hydrolyzed, oxidized, propoxylated, sulfonated, sulfomethylated, or desulfonated and classified by known methods (e.g., according to molecular weight or degree of sulfonation).

[0062] Exemplary anionic dispersants can be selected from formaldehyde condensation products of alkyl naphthalene sulfonates, formaldehyde condensation products of β-naphthalene sulfonic acid, sodium polymethylene naphthalene sulfonate, etc.

[0063] An exemplary anionic dispersant is a formaldehyde / sodium naphthalene sulfonate condensation product.

[0064] In one exemplary embodiment, the anionic dispersant is a low molecular weight condensate. For example, the molecular weight of the anionic dispersant can be less than 20,000 g / mol; such as less than 10,000 g / mol; less than 8,000 g / mol; less than 7,000 g / mol; or about 6,500 g / mol. The molecular weight can be an indicator of the degree of condensation of these polymer types.

[0065] An exemplary anionic dispersant is a naphthalene sulfonic acid condensate, such as those available from BASF Corporation under the trade name TAMOL SN.

[0066] In certain embodiments, the treatment composition can contain a single dispersant. In other embodiments, the anionic dispersant can comprise a combination of more than one dispersant.

[0067] In an exemplary embodiment, based on the total weight of the active composition, the active composition comprising a dispersant and a penetrant comprises at least 1% of the dispersant, such as at least 2%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, at least 30%, at least 31%, at least 32%, at least 33%, at least 34%, at least 35%, at least 36%, at least 37%, at least 38%, at least 39%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85% or at least 90% of the dispersant.

[0068] In an exemplary embodiment, based on the total weight of the active composition, the active composition comprises no more than 99% of the dispersant, such as no more than 98%, no more than 97%, no more than 96%, no more than 95%, no more than 90%, no more than 85%, no more than 80%, no more than 75%, no more than 70%, no more than 65%, no more than 60%, no more than 55%, no more than 50%, no more than 45%, no more than 40%, no more than 39%, no more than 38%, no more than 37%, no more than 36%, no more than 35%, no more than 34%, no more than 33%, no more than 32%, no more than 31%, no more than 30%, no more than 29%, no more than 28%, no more than 27%, no more than 26%, no more than 25%, no more than 24%, no more than, no more than 23%, no more than 22%, no more than 21%, no more than 20%, no more than 19%, no more than 18%, no more than 17%, no more than 16%, no more than 15%, no more than 14%, no more than 13%, no more than 12%, no more than 11%, no more than 10%, no more than 9%, no more than 8%, no more than 7%, no more than 6%, no more than 5%, no more than 4%, no more than 3%, no more than 2% or no more than 1%.

[0069] In various embodiments, the dispersant is present in the mixture at an active weight ratio (dispersant to penetrant) of at least 1:99, at least 5:95, at least 10:90, at least 15:85, at least 20:80, at least 25:75, at least 30:70, at least 35:65, at least 40:60, at least 45:55, at least 50:50, at least 55:45, at least 60:40, at least 65:35, at least 70:30, at least 75:25, at least 80:20, at least 85:15, at least 90:10, or at least 95:5. In various non-limiting embodiments, all values and value ranges, whether integers or fractions, including the above values and values between the above values, are specifically contemplated herein for use herein.

[0070] Penetrant:

[0071] The penetrant can be a strong anionic surfactant. The anionic surfactant can have a hydrophobic chain composed of an alkane and be covalently bonded to an atom or group containing a formal negative charge. In certain embodiments, the strong anionic surfactant is an anionic sulfonate surfactant. Exemplary anionic surfactants are sodium sulfate or sodium sulfonate surfactants. Exemplary sodium surfactants include, but are not limited to: sodium alkyl sulfate, sodium polyoxyethylene sulfate, sodium lauryl ether sulfate, sodium polyoxyethylene lauryl ether sulfate, sodium lauryl sulfate, sodium alkyl sulfonate, sodium alkyl ether sulfonate, sodium alkyl benzene sulfonate, linear alkyl benzene sulfonate, sodium α-olefin sulfonate, sodium alcohol polyoxyethylene ether sulfonate, sodium dioctyl sulfosuccinate, and sodium dioctyl sulfosuccinate.

[0072] In certain embodiments, the anionic surfactant can be an alkylaryl sulfonate surfactant, an alkyl sulfonate surfactant, an alkyl ether sulfonate surfactant, an α-olefin sulfonate surfactant, a paraffin sulfonate surfactant, or an alkenyl sulfonate surfactant, such as sodium octadecyl phenyl sulfonate, sodium xylene sulfonate, sodium (C14-C16) α-olefin sulfonate, sodium tridecyl benzene sulfonate, sodium dodecyl benzene sulfonate, or disodium alkyl diphenyl ether disulfonate. An exemplary anionic surfactant is sodium xylene sulfonate.

[0073] In certain embodiments, the treatment composition can contain a single penetrant. In other embodiments, the penetrant can comprise a combination of more than one penetrant.

[0074] In an exemplary embodiment, based on the total weight of the active composition, the treatment composition comprises at least 1% of a penetrant, such as at least 2%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least 11%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, at least 30%, at least 31%, at least 32%, at least 33%, at least 34%, at least 35%, at least 36%, at least 37%, at least 38%, at least 39%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85% or at least 90% of a penetrant.

[0075] In an exemplary embodiment, based on the total weight of the active composition, the treatment composition comprises no more than 95% of a penetrant, such as no more than 98%, no more than 97%, no more than 96%, no more than 95%, no more than 90%, no more than 85%, no more than 80%, no more than 75%, no more than 70%, no more than 65%, no more than 60%, no more than 55%, no more than 50%, no more than 45%, no more than 40%, no more than 39%, no more than 38%, no more than 37%, no more than 36%, no more than 35%, no more than 34%, no more than 33%, no more than 32%, no more than 31%, no more than 30%, no more than 29%, no more than 28%, no more than 27%, no more than 26%, no more than 25%, no more than 24%, no more than 23%, no more than 22%, no more than 21%, no more than 20%, no more than 19%, no more than 18%, no more than 17%, no more than 16%, no more than 15%, no more than 14%, no more than 13%, no more than 12%, no more than 11%, no more than 10%, no more than 9%, no more than 8%, no more than 7%, no more than 6%, no more than 5%, no more than 4%, no more than 3%, no more than 2% or no more than 1% of a penetrant.

[0076] In various embodiments, the penetrant is present in the mixture at an active weight ratio (ratio of penetrant to dispersant) of at least 1:99, at least 5:95, at least 10:90, at least 15:85, at least 20:80, at least 25:75, at least 30:70, at least 35:65, at least 40:60, at least 45:55, at least 50:50, at least 55:45, at least 60:40, at least 65:35, at least 70:30, at least 75:25, at least 80:20, at least 85:15, at least 90:10, or at least 95:5. In various non-limiting embodiments, all values and ranges of values, whether integers or fractions, including the above values and values in between the above values, are expressly contemplated herein for the present disclosure.

[0077] In other embodiments, based on the total weight of the mixture, the polymeric naphthalene sulfonate and sodium xylene sulfonate are present in the mixture in an amount of 0.1 to 99 wt% active matter. In various embodiments, the combination of the polymeric naphthalene sulfonate and sodium xylene sulfonate is present in an amount of 0.1 to 10 kg active matter per metric ton of dry lignocellulosic material, or in an amount of 0.5 to 2 kg, 1 to 1.5 kg, 0.5 to 1 kg, 0.5 to 1.5 kg, or 0.1 kg, 0.2 kg, 0.3 kg... 1 kg, 2 kg, 3 kg... up to 10 kg active matter per metric ton of dry lignocellulosic material. In various non-limiting embodiments, all values and ranges of values, whether integers or fractions, including the above values and values in between the above values, are expressly contemplated herein for the present disclosure.

[0078] White liquor

[0079] In other embodiments, based on the total weight of the mixture, the white liquor is present in an amount of 0.1 to 99 wt%. In various embodiments, based on the total weight of the mixture, the white liquor is present in an amount of 70 to 90 wt%, 75 to 85 wt%, or 75 to 80 wt% active matter. In various non-limiting embodiments, all values and ranges of values, whether integers or fractions, including the above values and values in between the above values, are expressly contemplated herein for the present disclosure.

[0080] Mixture

[0081] Typically, the mixture does not contain added surfactants that are non-dispersants (such as polymeric naphthalene sulfonates) and / or penetrants (such as sodium xylene sulfonate). The term "added" surfactant differentiates those surfactants added to the pulping process from any surfactants generated in situ during the pulping process (such as tall oil soap). Thus, in various embodiments, the mixture does not contain added surfactants, but may contain surfactants generated in situ (such as tall oil soap, etc.), which should be understood by those skilled in the art.

[0082] In various embodiments, the term "free of" describes a mixture that contains less than 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5% or 0.1% by weight of surfactant actives of a non-dispersant (such as a polymeric naphthalene sulfonate) and / or a penetrant (such as sodium xylene sulfonate). Alternatively, the term "free of" can also describe a mixture that contains zero weight % of surfactant actives of a non-dispersant (such as a polymeric naphthalene sulfonate) and / or a penetrant (such as sodium xylene sulfonate). In various non-limiting embodiments, all values and value ranges, whether integers or fractions, including the above values and values in between the above values, are expressly contemplated herein for this application.

[0083] In various embodiments described in the present disclosure, the term "consisting essentially of" can describe one or more embodiments of surfactants free of added non-dispersants (such as polymeric naphthalene sulfonates) and / or penetrants (such as sodium xylene sulfonate); embodiments free of one or more additives not described herein and / or additives described herein as optional; embodiments free of one or more pulps not described herein and / or described herein as optional; embodiments free of one or more white liquor and / or black liquor and / or cooking liquor not described herein and / or described herein as optional, and so on.

[0084] In various embodiments, the mixtures described herein consist of, include, consist essentially of, or consist of: a lignocellulosic material, a dispersant, a penetrant, white liquor, and optionally a recycle water stream from a pulping process.

[0085] In various embodiments, the mixtures described herein consist of, include, consist essentially of, or consist of: a lignocellulosic material, a polymeric naphthalene sulfonate, sodium xylene sulfonate, white liquor, and optionally a recycle water stream from a pulping process.

[0086] In various embodiments, the present disclosure (e.g., methods, mixtures, compositions, etc.) may be free of or may include one or more other anionic surfactants, derivatives thereof, salts thereof, or any combination thereof having less than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 weight % active ingredient. For example, such other anionic surfactants may include, but are not limited to, sulfonic acids, sulfates, carboxylates or carboxylic acids, phosphates, polyoxyalkylene glycols, polyalkylene glycol-polyalkylene glycol copolymers, or derivatives thereof, or copolymers thereof, or salts thereof, or any combination thereof. In other embodiments, the present disclosure (e.g., methods, mixtures, compositions, etc.) may be free of or may include one or more unrefined fatty acids having less than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 weight % active ingredient, the unrefined fatty acids including, but not limited to, coconut oil, cocoa butter, corn oil, cottonseed oil, linseed oil, olive oil, palm oil, palm kernel oil, peanut oil, soybean oil, sunflower oil, tall oil, tallow, lesquerella oil, tung oil, whale oil, tea seed oil, sesame oil, safflower oil, rapeseed oil, fish oil, avocado oil, mustard oil, rice bran oil, almond oil, walnut oil, derivatives thereof, and combinations thereof.

[0087] In various embodiments, the present disclosure (e.g., methods, mixtures, compositions, etc.) may include, may be free of, or may include less than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 weight % active ingredient of one or more carriers, e.g., the carriers may be used to convey or transport any of the components described herein. Generally, the present disclosure relates to aqueous pulping rather than solvent pulping. For example, the carrier may be water, an organic solvent, an alcohol, etc. In various embodiments, based on the weight of the mixture, the amount of the carrier is 20 weight % or more, such as 30 weight % or more, such as 40 weight % or more, such as 50 weight % or more, such as 60 weight % or more, such as 70 weight % or more, such as 80 weight % or more up to less than 100 weight %, such as 99 weight % or less, such as 95 weight % or less, such as 90 weight % or less, such as 80 weight % or less.

[0088] In various embodiments, the processes of the present disclosure exhibit higher digestion efficiency as compared to processes that do not utilize a combination of a dispersant (such as a polymeric naphthalene sulfonate) and a penetrant (such as sodium xylene sulfonate). This increased digestion efficiency can be manifested in various ways.

[0089] For example, as previously introduced above, it is well known that in various types of pulping processes, lignocellulosic materials are blown from a treatment vessel into a blow tank and then broken into individual wood fibers. However, in practice, due in part to undissolved lignin, some lignocellulosic materials cannot be fully separated. These unseparated materials are removed by passing through a screen having openings of a predetermined size. In the pulping industry, the standard test screen used is flat and has slits of 0.01 inches. The materials recovered through this screening process are referred to as "screenings". These screenings include fibers that can be used to achieve the desired result. Therefore, it is highly desirable to reduce the amount of screenings. One way to reduce the amount of screenings is by extending the digestion time or creating more severe hydrolysis conditions. However, these conditions increase the costs involved and cause some of the cellulose in the wood chips to hydrolyze and become unusable. Accordingly, the method of the present disclosure can unexpectedly, unexpectedly and efficiently reduce the amount of screenings as described above without extending the digestion time or creating more severe hydrolysis conditions, thus indicating an increase in digestion efficiency. In various embodiments, based on the total initial weight % of the lignocellulosic material added to the treatment vessel, the screenings percentage is less than 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0.5 weight %. In various non-limiting embodiments, all values and ranges of values, whether integers or fractions, including the above values and values between the above values, are specifically contemplated herein for use herein.

[0090] In other embodiments, the method can increase the pulp yield by 0.01% to 5%, which is calculated based on the weight of the available fibers produced by the method divided by the initial oven-dried wood weight. In various non-limiting embodiments, all values and ranges of values, whether integers or fractions, including the above values and values between the above values, are specifically contemplated herein for use herein.

[0091] In other embodiments, the method can reduce the amount of white liquor required. For example, the white liquor required can be reduced by 0.1% or more (such as 0.5% or more, such as 1% or more, such as 1.5% or more, such as 2% or more, such as 2.5% or more, such as 3% or more, such as 3.5% or more, such as 5% or more) to 15% or less (such as 10% or less, such as 7% or less, such as 5% or less, such as 4% or less, such as 3% or less). In various non-limiting embodiments, all values and ranges of values, whether integers or fractions, including the above values and values between the above values, are specifically contemplated herein for use herein.

[0092] In other embodiments, the method can reduce the kappa number, which indicates the amount of residual lignin on the fibers. Generally, the kappa number is determined using TAPPI STANDARD T236 (Kappa Number of Pulp). In various non-limiting embodiments, all values and value ranges, whether integers or fractions, including the above values and values between the above values, are expressly contemplated herein for this purpose.

[0093] In other embodiments, the method can increase the residual active alkali (also known as RA). Generally, RA is determined using SCAN-N33:94. In various embodiments, the RA is from 5 to 20, such as at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, or at least 12 g / L. In various non-limiting embodiments, all values and value ranges, whether integers or fractions, including the above values and values between the above values, are expressly contemplated herein for this purpose.

[0094] In other embodiments, it has been observed that the synergistic mixture provides pulp having a lower reject count and a lower lignin content (corresponding to ~ kappa number units), while increasing the yield.

[0095] Examples

[0096] Hardwood and / or softwood wood chips were added to a circulating laboratory digester (M / K Systems) with white liquor at a ratio of 1:4.5.

[0097] No active composition treatment agent was added to the control sample. In other words, no dispersant (such as polymeric naphthalene sulfonate) and no penetrant (such as sodium xylene sulfonate) were added. This is labeled herein as "No Treatment" (NT).

[0098] In comparative sample A, a dispersant, namely polymeric naphthalene sulfonate, was added, but no penetrant was added.

[0099] In comparative sample B, a penetrant, namely sodium xylene sulfonate, was added, but no dispersant was added.

[0100] In the sample of the present invention, both a dispersant in the form of polymeric naphthalene sulfonate and a penetrant in the form of sodium xylene sulfonate were added. The weight ratio of the dispersant to the penetrant was 50:50. This is hereinafter labeled as mixture 1.

[0101] After forming the above samples, the digester was sealed and the mixture was heated to reach a certain H-factor. The H-factor is a single value that represents the combined value of two values: cooking time and pulping temperature. All comparative tests were carried out using the same H-factor, i.e., (GD H = 165), depending on the type of wood chips used. The wood chips were deliberately undercooked using the same H-factor. This helped to determine the distinguishable differences after each digestion, especially the amount of rejects screened out during the pulping process (% reject rate), the Kappa number indicating the amount of lignin remaining in the lignocellulosic material after treatment, and the residual alkali indicating the efficiency of the delignification process.

[0102] The test results are given in Table 1 below and shown in Figures 1-3 as follows:

[0103] Table 1

[0104] In the above, the lignocellulosic material was pine wood chips.

[0105] The weight fraction of the lignocellulosic material expressed as dry lignocellulosic material was 1 / 5.5 (i.e., 1 part of lignocellulosic material in a total of 5.5 parts of the mixture).

[0106] Based on the total weight of the dry lignocellulosic material, the total weight of the active substances of the polynaphthalene sulfonate and sodium xylene sulfonate was 0.1% by weight.

[0107] The white liquor was an aqueous solution of 1.29% by weight of Na2S and 3.98% by weight of NaOH, and based on the total weight of the mixture, the white liquor was present in the mixture in an amount of 81.82% by weight.

[0108] The control example did not contain an added active composition, had a high % reject rate; a high Kappa number, indicating the presence of a large amount of undissolved lignin; and a low residual alkali amount, indicating low efficiency of the delignification process.

[0109] Comparative example A contained only a dispersant in the added active composition, with a reduced reject rate, a reduced Kappa number, and an increased residual alkali amount.

[0110] Comparative example B included only a penetrant in the added active composition, with a smaller decrease in the reject rate, a smaller decrease in the Kappa number, and the lowest residual alkali amount.

[0111] Mixture 1 had the lowest % reject rate, the lowest Kappa number, and the highest residual alkali amount. Compared with the embodiments using only a dispersant or a penetrant alone, Mixture 1 also exhibited excellent and unexpected synergistic effects.

[0112] The data generated by the above tests indicate that the mixture of polymeric naphthalene sulfonate and sodium xylene sulfonate is a superior digester additive compared to the individual polymeric naphthalene sulfonate or sodium xylene sulfonate.

[0113] These results were unexpected and demonstrate a beneficial synergistic effect, resulting in a lower reject rate and lower lignin content (corresponding to lower kappa number units) of the pulp. The residual alkali amount was also increased. This represents a significant improvement in delignification efficiency.

[0114] Figure 1 The % reject rate of the control example (NT), comparative example A (TSN), comparative example B (XS), mixture 1 (50:50) with a blend ratio of 50:50 (weight ratio) of the dispersant and penetrant, mixture 2 (75:25) with a blend ratio of 75:25 (weight ratio) of the dispersant and penetrant in the added active composition, and mixture 3 (66:33) with a blend ratio of 66:33 (weight ratio) of the dispersant and penetrant in the added active composition is shown. As shown, the performance of each of mixtures 1 - 3 is superior to the control example and comparative examples, with the best performance at a blend ratio of 50:50.

[0115] Figure 2 The residual alkali of the control example (NT), comparative example A (TSN), comparative example B (XS), mixture 1 (50:50), mixture 2 (75:25), and mixture 3 (66:33) is shown. As shown, the performance of each of mixtures 1 - 3 is superior to the control example and comparative examples, with the best performance at a blend ratio of 50:50.

[0116] Figure 3 The kappa number of the control example (NT), comparative example A (TSN), comparative example B (XS), mixture 1 (50:50), mixture 2 (75:25), and mixture 3 (66:33) is shown. As shown, the performance of each of mixtures 1 - 3 is superior to the control example and comparative examples, with the best performance at a blend ratio of 50:50.

[0117] Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that there are numerous variations. It should also be understood that the at least one exemplary embodiment described herein is not intended to limit in any way the scope, applicability, or configuration of the claimed subject matter. Instead, the foregoing detailed description will provide those skilled in the art with a convenient roadmap for implementing one or more of the described embodiments. It should be understood that various changes can be made to the functions and arrangements of the elements described in the exemplary embodiments without departing from the scope defined in the appended claims.

Claims

1. A method for digesting lignocellulosic materials, the method comprising: mixing a lignocellulosic material comprising lignocellulosic biomass, a polymeric naphthalenesulfonate, sodium xylene sulfonate, and white liquor comprising sodium hydroxide and sodium sulfide to form a mixture; and heating the mixture to digest at least a portion of the lignocellulosic material.

2. The method according to claim 1, wherein the lignocellulosic material is present in an amount of 10 to 30% by weight based on the total weight of the mixture.

3. The method according to claim 1, wherein the weight ratio of the polymeric naphthalenesulfonate to the sodium xylene sulfonate is 10:90 to 90:

10.

4. The method according to claim 1, wherein the weight ratio of the polymeric naphthalenesulfonate to the sodium xylene sulfonate is 40:60 to 60:

40.

5. The method according to claim 1, wherein the combination of the polymeric naphthalenesulfonate and the sodium xylene sulfonate is present in an amount of 0.1 to 10 kg per metric ton of dry lignocellulosic material.

6. The method according to claim 1, wherein the white liquor is present in an amount of 70 to 90% by weight based on the total weight of the mixture.

7. The method according to any one of claims 1 to 6, wherein the mixture does not contain an added surfactant that is not a polymeric naphthalenesulfonate and / or sodium xylene sulfonate.

8. The method according to any one of claims 1 to 6, wherein the method has improved digestion efficiency compared to a method that does not utilize the combination of the polymeric naphthalenesulfonate and the sodium xylene sulfonate.

9. The method according to any one of claims 1 to 6, wherein heating the mixture comprises heating the mixture to a temperature of 125°C to 185°C.

10. The method according to claim 1, wherein: the lignocellulosic material is present in an amount of 10 to 30% by weight based on the total weight of the mixture; the weight ratio of the polymeric naphthalenesulfonate to the sodium xylene sulfonate is 10:90 to 90:10; the combination of the polymeric naphthalenesulfonate and the sodium xylene sulfonate is present in an amount of 0.1 to 10 kg per metric ton of dry lignocellulosic material; the white liquor is present in an amount of 70 to 90% by weight based on the total weight of the mixture; the mixture does not contain an added surfactant that is not a polymeric naphthalenesulfonate and / or sodium xylene sulfonate; and the method has improved digestion efficiency compared to a method that does not utilize the combination of the polymeric naphthalenesulfonate and the sodium xylene sulfonate.

11. The method according to any one of claims 1 to 6, wherein the mixture consists essentially of a lignocellulosic material, a polymeric naphthalenesulfonate, sodium xylene sulfonate, white liquor, and recycled water stream from a pulping process.

12. A method for digesting lignocellulosic materials, the method comprising: mixing a lignocellulosic material comprising lignocellulosic biomass, a dispersant, a penetrant, and white liquor comprising sodium hydroxide and sodium sulfide to form a mixture; and heating the mixture to digest at least a portion of the lignocellulosic material, wherein the ratio of the dispersant to the penetrant in the mixture is 10:90 to 90:10, and the combined total content of the dispersant and the penetrant in the mixture is 0.1 to 10 kg per metric ton of dry lignocellulosic material.

13. The method according to claim 12, wherein the ratio of the dispersant to the penetrant in the mixture is from 40:60 to 60:

40.

14. The method according to any one of claims 12 or 13, wherein the dispersant comprises a polymeric naphthalene sulfonate and the penetrant comprises sodium xylene sulfonate.

15. The method according to any one of claims 12 or 13, wherein the dispersant consists of a polymeric naphthalene sulfonate and the penetrant consists of sodium xylene sulfonate.

16. A mixture comprising: a lignocellulosic material comprising lignocellulosic biomass, which is present in an amount of 10 to 30% by weight based on the total weight of the mixture; white liquor comprising sodium hydroxide and sodium sulfide, which is present in an amount of 70 to 90% by weight based on the total weight of the mixture; a dispersant; and a penetrant; wherein the dispersant and the penetrant are present in the mixture at an active substance weight ratio of from 10:90 to 90:10, respectively; and wherein the combination of the dispersant and the penetrant is present in an amount of 0.1 to 10 kg of active substance per metric ton of dry lignocellulosic material.

17. The mixture according to claim 16, wherein the mixture does not contain added surfactants that are not dispersants and / or penetrants.

18. The mixture according to claim 16, wherein the dispersant consists of a polymeric naphthalene sulfonate and the penetrant consists of sodium xylene sulfonate.

19. The mixture according to claim 18, wherein the mixture consists essentially of a lignocellulosic material, a polymeric naphthalene sulfonate, sodium xylene sulfonate, white liquor, and a recycle water stream from a pulping process.

20. The mixture according to claim 16, wherein the mixture consists essentially of a lignocellulosic material, a dispersant, a penetrant, white liquor, and a recycle water stream from a pulping process.

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