Fertilizer manufacturing method

Abstract

The present invention provides a method for efficiently obtaining a fertilizer containing polysaccharide hydrolysates and nutrients such as calcium, phosphoric acid, and nitrogen. The present invention is a method for manufacturing a fertilizer, characterized by comprising: a hydrolysis step for obtaining a mixture including polysaccharide hydrolysates through hydrolysis of polysaccharides using an acid catalyst; and a neutralizing step after the hydrolysis step for adding at least one basic compound selected from the group consisting of potassium salt, phosphate, ammonium salt, and ammonia.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a fertilizer containing a polysaccharide hydrolysate. [Background technology]

[0002] In recent years, it has been reported in the agricultural field that xylooligosaccharides, cellooligosaccharides, and other oligosaccharides can be used to promote plant growth, as in Patent Document 1. Furthermore, Patent Document 2 reports that the phytoalexin-inducing activity (elicitor activity) of chitin oligosaccharides and the antibacterial activity against plant pathogens of at least one selected from chitosan, chitosan oligosaccharides, and salts thereof act synergistically to provide excellent disease resistance and growth-promoting effects, and the use of polysaccharide hydrolysates such as these oligosaccharides as plant growth promoters is a very useful method.

[0003] As a method for synthesizing these polysaccharide hydrolysates, Patent Document 3 discloses the hydrolysis of chitin using a hydrochloric acid catalyst, but requires a step of neutralizing with an alkali to separate the hydrochloric acid and desalting the by-product salt using ion exchange membrane electrodialysis. Patent Document 4 discloses a method for hydrolyzing cellulose with concentrated hydrochloric acid or concentrated sulfuric acid, but this is a treatment as a preliminary step to enzymatic decomposition, and does not disclose separation of the acid from the hydrolysate.

[0004] Patent Documents 5 and 6 disclose the hydrolysis of chitin using a ball mill in the presence of an acid catalyst such as sulfuric acid, nitric acid, hydrochloric acid, perchloric acid, phosphoric acid, nitrous acid, or an organic acid. Although this is an excellent method for hydrolysis, it does not disclose a method for separating the acid from the polysaccharide hydrolysate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 63-215606 [Patent Document 2] Japanese Patent Application Publication No. 9-143013 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-281648 [Patent Document 4] Special Publication No. 57-53801 [Patent Document 5] Japanese Patent Application Laid-Open No. 2017-197468 [Patent Document 6] International Publication No. 2017 / 187672 Summary of the Invention [Problem to be solved by the invention]

[0006] Although there are methods for hydrolyzing sugars using enzymes or the like, these are costly and do not necessarily provide a high yield of polysaccharide hydrolysate.

[0007] Although polysaccharide hydrolysates can be produced by hydrolysis using a protonic acid as a catalyst, the hydrolysis rate is slow unless the acid has a certain degree of acid strength, such as sulfuric acid, hydrochloric acid, or phosphoric acid. The presence of such strong acids in polysaccharide hydrolysates raises concerns about adverse effects on plants. Furthermore, the presence of strong acids in polysaccharide hydrolysates can cause unexpected side reactions when mixed with other fertilizers or pesticides, or can lead to precipitation when the pH changes from acidic to neutral. Therefore, it is necessary to separate the acid, but this requires special methods, such as ion-exchange membrane electrodialysis, making industrial production inexpensive.

[0008] The present invention provides a method for efficiently obtaining a fertilizer containing polysaccharide hydrolysate and nutrients such as potassium, phosphate, and nitrogen. [Means for solving the problem]

[0009] The present invention was made in consideration of the above circumstances, and the inventors have made a completely different approach from conventional approaches, by using a basic compound containing potassium, phosphoric acid, nitrogen, etc., which are nutrients necessary for plants, as a neutralizer for an acid catalyst, and have investigated the use of the resulting polysaccharide hydrolysate and neutralized salt as fertilizers as they are.

[0010] As a result, the present inventors discovered a method in which polysaccharides are hydrolyzed using an acid catalyst, and then neutralized by adding at least one basic compound selected from the group consisting of potassium salts, phosphate salts, ammonium salts, and ammonia.

[0011] That is, the present invention includes the following [1] to

[14] .

[0012] [1] A method for producing a fertilizer, comprising: a hydrolysis step of hydrolyzing polysaccharides with an acid catalyst to obtain a mixture containing a polysaccharide hydrolysate; and a neutralization step of adding, after the hydrolysis step, at least one basic compound selected from the group consisting of potassium salts, phosphate salts, ammonium salts, and ammonia. [2] The method for producing a fertilizer according to [1], further comprising a pH adjustment step of adjusting the pH to a range of 4 to 10 after the neutralization step. [3] The method for producing a fertilizer according to either [1] or [2], further comprising a filtration step of separating solids by filtration after the neutralization step. [4] The method for producing a fertilizer according to any one of [1] to [3], wherein the basic compound is at least one selected from the group consisting of potassium hydroxide, potassium carbonate, and potassium hydrogen carbonate. [5] The method for producing a fertilizer according to any one of [1] to [3], wherein the basic compound is at least one selected from the group consisting of dipotassium monohydrogen phosphate, tripotassium phosphate, and diammonium hydrogen phosphate. [6] The method for producing a fertilizer according to any one of [1] to [5], wherein the acid catalyst is at least one acid selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, perchloric acid, nitric acid, nitrous acid, and phosphoric acid, or a partially neutralized salt thereof. [7] The method for producing a fertilizer according to [6], wherein the acid catalyst is phosphoric acid or a partially neutralized salt thereof. [8] The method for producing a fertilizer according to [7], wherein the acid catalyst is phosphoric acid. [9] The method for producing a fertilizer according to either [7] or [8], further comprising, after the hydrolysis step, an extraction step of adding water to the mixture to extract water-soluble components.

[10] The method for producing a fertilizer according to any one of [1] to [9], wherein the hydrolysis step is carried out by a mechanochemical method.

[11] The method for producing a fertilizer according to

[10] , wherein the mechanochemical method includes a grinding treatment using a planetary ball mill or a vibrating mill.

[12] The method for producing a fertilizer according to either

[10] or

[11] , wherein the amount of water in the hydrolysis step is 0.1 to 10 parts by mass per 100 parts by mass of the polysaccharide.

[13] The method for producing a fertilizer according to any one of [1] to

[12] , wherein the polysaccharide contains at least one selected from chitin and cellulose.

[14] The method for producing a fertilizer according to

[13] , wherein the polysaccharide contains both chitin and cellulose. [Effects of the Invention]

[0013] The method for producing a fertilizer of the present invention includes a hydrolysis step in which a polysaccharide is hydrolyzed with an acid catalyst to obtain a mixture containing a polysaccharide hydrolysate, and a neutralization step in which, after the hydrolysis step, at least one basic compound selected from the group consisting of potassium salts, phosphate salts, ammonium salts, and ammonia is added, and this method makes it possible to efficiently produce a fertilizer containing a polysaccharide hydrolysate and nutrients such as potassium, phosphate, and nitrogen. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described. Note that the embodiments described below are representative examples of the present invention, and the present invention is not limited thereto.

[0015] In one embodiment, a method for producing a fertilizer includes a hydrolysis step of hydrolyzing a polysaccharide with an acid catalyst to obtain a mixture containing a polysaccharide hydrolysate, and a neutralization step of adding, after the hydrolysis step, at least one basic compound selected from the group consisting of potassium salts, phosphate salts, ammonium salts, and ammonia.

[0016] <Hydrolysis process> The hydrolysis step is a step in which a polysaccharide is hydrolyzed with an acid catalyst to obtain a mixture containing a polysaccharide hydrolysate.

[0017] [Polysaccharide] The polysaccharide is not particularly limited as long as it is a polysaccharide that can be hydrolyzed by acid, and examples thereof include cellulose, xylan, xyloglucan, glucomannan, chitin, etc. The polysaccharide preferably contains at least one selected from chitin, xylan, and cellulose, and more preferably contains at least one selected from chitin and cellulose. Only one polysaccharide may be used, or two or more polysaccharides may be used in combination. When two or more polysaccharides are combined, the polysaccharide preferably contains both chitin and cellulose.

[0018] Cellulose and xylan are known as biomass, which is an organic resource derived from plants rather than fossil fuels.

[0019] Examples of cellulosic biomass include woody biomass such as cotton, wood pulp, kenaf, hemp, small diameter trees, thinned wood, sawdust, wood chips, defatted wood flour, waste paper, newspaper, wrapping paper, tissue paper, toilet paper, and cardboard; and herbaceous biomass such as bagasse, switchgrass, elephant grass, corn cobs, rice straw, and wheat straw. These biomass can be used alone or in combination of two or more. For example, water-insoluble cellulose can be obtained by further alkali-treating chemical pulp (holocellulose) obtained by bleaching defatted wood flour with chlorine treatment to remove hemicellulose. Cellulosic biomass may also contain xylan in addition to cellulose.

[0020] Generally, cellulose exhibits crystallinity due to the bonding of two or more cellulose molecules through hydrogen bonds. In one embodiment, cellulose having such crystallinity can also be used as a raw material. In this embodiment, it is preferable to use cellulose after reducing its crystallinity by performing a treatment for reducing crystallinity, such as pre-crushing, in order to increase the hydrolysis rate. Cellulose with reduced crystallinity may be cellulose whose crystallinity has been partially reduced or whose crystallinity has been completely or almost completely eliminated. There are no particular limitations on the method of crystallinity reduction treatment, but a crystallinity reduction treatment that can break the hydrogen bonds and at least partially produce single-chain cellulose molecules is preferred. Using cellulose containing at least partially single-chain cellulose molecules as a raw material can significantly improve the efficiency of hydrolysis.

[0021] Examples of treatments for reducing the crystallinity of the raw cellulose include methods such as ball milling as a preliminary disintegration method, which physically breaks the hydrogen bonds between cellulose molecules to obtain single-chain cellulose molecules (see Zhao et al., Energy & Fuels, 20, 807 (2006)), and methods such as phosphoric acid treatment, which chemically breaks the hydrogen bonds between cellulose molecules to obtain single-chain cellulose without applying compressive shear stress (see Zhang et al., Biomacromolecules, 7, 644 (2006)). The treatment for reducing the crystallinity of cellulose does not necessarily have to completely eliminate the crystallinity of cellulose, but may also be a treatment that only partially reduces the crystallinity of the cellulose before treatment. Using cellulose that has been subjected to these treatments as a raw material can significantly improve the efficiency of hydrolysis.

[0022] Furthermore, examples of treatments for reducing the crystallinity of the raw cellulose include treatment with compressed hot water (see, for example, Hayashi et al., J. Jpn. Inst. Energy, 83, 805 (2004); Sasaki et al., Ind. Eng. Chem. Res., 39, 2883 (2000)).

[0023] Xylan is a polysaccharide in which D-xylose residues are linked by β-1,4 or β-1,3 bonds. The sugars that make up xylan may include arabinose, glucuronic acid, 4-O-methylglucuronic acid, glucose, galactose, etc. in addition to xylose.

[0024] The xylan-containing raw material is preferably pre-crushed by applying compressive shear stress before the hydrolysis step. A compressive shear crusher can be used to crush the xylan-containing raw material by applying compressive shear stress. A compressive shear crusher is a machine capable of applying both compressive stress and shear stress, and examples thereof include a vibrating rod mill and a vibrating ball mill. Of these, a vibrating rod mill is preferred from the viewpoint of production efficiency. The rods are not particularly limited, but preferably have an outer diameter of 0.1 to 100 mm, more preferably 0.5 to 50 mm. The rod filling rate (apparent volume of the rod relative to the volume of the stirring section of the vibration mill) varies depending on the model, but is preferably 10 to 97%, more preferably 15 to 95%.

[0025] The crushing conditions, such as the crushing time and the number of revolutions of the crusher, may be appropriately set to form the desired crushed material. From the viewpoint of obtaining a high hydrolysis rate, it is preferable that the crystallinity of the xylan-containing crushed material is low.

[0026] The xylan-containing raw material may be coarsely pulverized before being crushed by applying compressive shear stress. The method for coarsely pulverizing is not particularly limited, and for example, a cutter-type pulverizer such as a grinder or roll cutter, an impact pulverizer such as a hammer mill, or a grinding pulverizer such as a colloid mill can be used as the pulverizer.

[0027] Chitin is a substance contained in biomass, for example, the shells or epidermis of crustaceans such as shrimp and crab, arthropods, insects, squid, shellfish, krill, and the like, and the cell walls of fungi such as mushrooms.

[0028] Chitin may be purified or unpurified, but purified chitin is preferred. For example, purified chitin can be obtained from crab shells by dissolving proteins with alkali or calcium with acid, followed by neutralization, solid-liquid separation, washing with water, and other processes. Industrially prepared purified chitin is readily available. Unpurified chitin can be used as long as it is obtained from natural sources and substances that inhibit the hydrolysis of chitin have been removed.

[0029] Chitin may be dry or wet, and may be crystalline or non-crystalline. It is preferable that chitin be pre-crushed prior to the hydrolysis step. Pre-crushing increases contact with the acid catalyst, accelerating decomposition. Therefore, the shape and size of chitin used for pre-crushing are preferably suitable for crushing. Examples of such shapes and sizes include powder with particle sizes of 20 to 1000 μm.

[0030] When pre-crushing chitin, pre-crushing machines such as shredders, jaw crushers, gyratory crushers, cone crushers, hammer crushers, roll crushers, and roll mills can be used, as well as medium-sized crushers such as stamp mills, edge runners, cutting and shear mills, rod mills, autogenous crushers, and roller mills. The pre-crushing time is not particularly limited as long as the chitin is uniformly pulverized after the treatment. Furthermore, a low degree of crystallinity of chitin is preferable to achieve a high hydrolysis rate.

[0031] [Acid catalyst] As the acid catalyst used for the hydrolysis of polysaccharides, conventionally known acids such as those described in Patent Documents 3 to 6 can be used. Specifically, at least one acid selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, perchloric acid, nitric acid, nitrous acid, and phosphoric acid, or a partially neutralized salt thereof can be used. Examples of the partially neutralized salt of the acid include monopotassium dihydrogen phosphate, monoammonium dihydrogen phosphate, and potassium hydrogen sulfate. The acid catalyst is preferably phosphoric acid or a partially neutralized salt thereof, and more preferably phosphoric acid.

[0032] [Hydrolysis reaction] The amount of acid catalyst used in the hydrolysis step varies depending on the type of hydrolysis. For example, when hydrolysis is performed using hydrochloric acid with a concentration of 30% or higher at around room temperature, it is preferable to use a large excess of acid, at least 10 times the molar equivalent of the polysaccharide. When hydrolysis is performed by a mechanochemical method at 110°C or lower, the mass ratio of polysaccharide to acid catalyst is preferably polysaccharide / acid catalyst = 2 to 100, more preferably polysaccharide / acid catalyst = 4 to 20, and even more preferably polysaccharide / acid catalyst = 3 to 10. When the mass ratio of polysaccharide to acid catalyst is 100 or less, hydrolysis proceeds at a rate that is practically acceptable. When the mass ratio of polysaccharide to acid catalyst is 2 or more, side reactions such as dehydration reactions and carbon-carbon bond cleavage can be suppressed during hydrolysis.

[0033] The mass of polysaccharides referred to here is the true mass (dry mass) of polysaccharides, excluding the water content of the raw material. Polysaccharides typically contain physically adsorbed water, so the amount of attached water is analyzed, and the mass ratio of polysaccharide to acid catalyst is determined from the mass of the polysaccharide excluding the water content. One method for analyzing the amount of attached water is to place the raw polysaccharide in a thermostatic oven at 100 to 150°C, dry it until no mass loss occurs, and then quantify it. To prevent the effects of side reactions such as dehydration during drying, it is more desirable to dry it at a lower temperature using a vacuum dryer and then quantify it. The mass of the acid catalyst is also the true mass (dry mass) of the acid catalyst.

[0034] As mentioned above, polysaccharides before hydrolysis already contain approximately 1 to 3% by mass of physically adsorbed water. Furthermore, many commercially available acid catalysts, such as hydrochloric acid and phosphoric acid, contain water. Therefore, the hydrolysis of polysaccharides can be carried out using the water physically adsorbed on the polysaccharides and the water contained in the acid catalyst. While the amount of water is usually sufficient without adding water, hydrolysis can be carried out with the addition of water for polysaccharides that are very dry.

[0035] Whether or not water is added, polysaccharides contain approximately 1 to 3% by mass of physically adsorbed water. Therefore, the amount of water in the hydrolysis step, including the water physically adsorbed on the polysaccharide, the water contained in the acid catalyst, and, if water is added, the amount of water added, is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 8 parts by mass, per 100 parts by mass of the actual polysaccharide (dry mass). An amount of 10 parts by mass or less ensures a sufficient hydrolysis rate and prevents inoperability due to adhesion to the apparatus. Furthermore, an amount of 0.1 part by mass or more can suppress side reactions such as dehydration or branching reactions of the polysaccharide.

[0036] The hydrolysis method is not particularly limited, and examples include a method using hydrochloric acid with a concentration of 30% or more at a reaction temperature of 5°C to 30°C, a method using a catalytic amount of sulfuric acid and water at a mass ratio of 10 times or more to the polysaccharide, under subcritical conditions (150 to 350°C, 0.5 to 25 MPa), and a mechanochemical method. Among these, the mechanochemical method is preferred. The mechanochemical method is a method of hydrolyzing polysaccharides by applying mechanical external force through a pulverization process. When chitin is used as the polysaccharide, methods described in Patent Documents 5 and 6 can be used. When cellulose is used as the polysaccharide, methods described in Kuga et al., Cellulose, 26, 215 (2019), for example, can be used.

[0037] Examples of grinding equipment used in the grinding process include tumbling ball mills such as pot mills, tube mills, and conical mills; jet grinders such as swirling flow jet mills, collision type jet mills, fluidized bed jet mills, and wet type jet mills; shear mills such as mortars and ong mills; colloid mills such as mortars and stone mortars; impact grinders such as hammer mills, cage mills, pin mills, disintegrators, screen mills, turbo mills, and centrifugal classifying mills; vibration mills that grind by vibrating a drum to move the medium inside; and planetary ball mills, which are grinders that use rotational and revolutionary motions.

[0038] The grinding device is preferably a ball mill or a vibration mill, which applies a strong compressive force to the polysaccharide and a tensile stress in both directions of the main chain, more preferably a planetary ball mill, a tumbling ball mill, or a vibration mill, and even more preferably a planetary ball mill or a vibration mill.

[0039] At the laboratory level, it is preferable to use a planetary ball mill. Industrially, it is preferable to use a vibrating mill. A vibrating mill does not rotate a drum (grinding cylinder) into which the grinding media is inserted, but rather vibrates the drum to move the media inside, making it possible to grind materials in about 1 / 10 to 1 / 20 of the time required by a drum-rotating ball mill.

[0040] The pulverization treatment can be carried out continuously or intermittently. In order to suppress the temperature rise of the material to be treated that accompanies the pulverization treatment, it is preferable to carry out the pulverization treatment intermittently. When the pulverization treatment is carried out intermittently, the optimum value varies greatly depending on the pulverization device. For example, in the case of a planetary ball mill, the pulverization treatment can be carried out by repeating a cycle in which a 5-15 minute interval is inserted between each 5-15 minute pulverization treatment. When the pulverization treatment is carried out continuously, it is preferable to carry out the pulverization treatment while maintaining an appropriate temperature by installing a jacket or the like on the pulverization device for cooling.

[0041] When polysaccharides are hydrolyzed using a grinding device such as a ball mill, the polysaccharides can be hydrolyzed while their crystallinity is reduced by grinding, or the polysaccharides can be hydrolyzed by adding an acid catalyst after being pre-treated to reduce their crystallinity as described above. When polysaccharides are pre-ground using a Henschel mixer and then ground using a ball mill or the like, the acid catalyst may be added from the pre-ground stage.

[0042] The hydrolysis temperature is preferably room temperature to 110°C, and more preferably 50°C to 100°C. At room temperature or higher, the decomposition process does not slow down and the time required for decomposition does not become too long. To further accelerate the decomposition rate, hydrolysis can be performed at a high temperature. If the hydrolysis temperature is 110°C or lower, side reactions such as dehydration reactions can be suppressed. If the hydrolysis temperature is higher than 110°C, dehydration reactions are more likely to occur and water evaporation may also be promoted. When hydrolysis is performed by the mechanochemical method, shear heat is generated, so it is preferable to control the hydrolysis temperature by repeating cycles with intervals as described above, or by running cooling water through the jacket of the grinding device.

[0043] The hydrolysis time is preferably 10 to 100 hours, more preferably 15 to 70 hours, even more preferably 20 to 60 hours, and particularly preferably 30 to 50 hours. When the hydrolysis time is 10 hours or longer, the decomposition of the polysaccharides is promoted. When the hydrolysis time is 100 hours or shorter, the polysaccharide hydrolyzate can be obtained more efficiently. When hydrolysis is performed by the above-mentioned mechanochemical method and the pulverization treatment is performed intermittently, the hydrolysis time refers to the net pulverization treatment time excluding the intervals.

[0044] The progress of hydrolysis of polysaccharides can be confirmed by sampling small amounts of the material to be treated over time and measuring the amount of water-soluble components contained in the samples.

[0045] After the hydrolysis step, a mixture containing a polysaccharide hydrolysate is obtained. This mixture may contain, in addition to the polysaccharide hydrolysate, undecomposed polysaccharides, an acid catalyst, etc. Furthermore, the polysaccharide hydrolysate may contain, in addition to oligosaccharides, monosaccharides, dehydrated products in which the sugar terminals have undergone dehydration reactions, branched products in which the hydroxyl group at the 6-position has reacted with a β-1,4-glycosidic bond to form an α-1,6-glycosidic bond, or other by-products.

[0046] The mixture containing the polysaccharide hydrolysate obtained in the hydrolysis step may be used in the neutralization step as is, or may be subjected to the extraction step described below followed by the neutralization step. The mixture obtained in the hydrolysis step contains by-products other than oligosaccharides as polysaccharide hydrolysates, and these by-products also have some plant growth effect or elicitor activity. Therefore, it is efficient to use the mixture containing these by-products in the neutralization step.

[0047] <Neutralization process> The neutralization step is a step of neutralizing the solution after the hydrolysis step by adding at least one basic compound selected from the group consisting of potassium salts, phosphates, ammonium salts, and ammonia. In a system in which an excess amount of concentrated hydrochloric acid is used as an acid catalyst in the hydrolysis step, the neutralization step generates significant heat, so the neutralization step and the extraction step described below may be carried out simultaneously by adding ice instead of water and stirring while cooling.

[0048] The mixture containing the polysaccharide hydrolysate obtained by the hydrolysis step contains residual acid catalyst used in the hydrolysis. Therefore, by adding at least one basic compound selected from the group consisting of potassium salts, phosphate salts, ammonium salts, and ammonia, the acid catalyst can be neutralized and a fertilizer containing the polysaccharide hydrolysate and nutrients such as potassium, phosphate, and nitrogen can be efficiently produced.

[0049] [Basic compounds] When a potassium salt is used as the basic compound, for example, potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium formate, potassium acetate, potassium ethoxide, monopotassium dihydrogen phosphate, dipotassium monohydrogen phosphate, tripotassium phosphate, potassium amide, etc. can be used. Among these, potassium hydroxide, potassium carbonate, potassium bicarbonate, dipotassium monohydrogen phosphate, and tripotassium phosphate are preferred, and at least one selected from the group consisting of potassium hydroxide, potassium carbonate, and potassium bicarbonate is more preferred. Only one potassium salt may be used, or two or more potassium salts may be used in combination.

[0050] When a phosphate is used as the basic compound, monopotassium dihydrogen phosphate, dipotassium monohydrogen phosphate, tripotassium phosphate, diammonium hydrogen phosphate, triammonium phosphate, etc. can be used. Among these, at least one selected from the group consisting of dipotassium monohydrogen phosphate, tripotassium phosphate, and diammonium hydrogen phosphate is preferred. Thus, the phosphate may simultaneously be a potassium salt or an ammonium salt. Only one type of phosphate may be used, or two or more types may be used in combination.

[0051] When an ammonium salt is used as the basic compound, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, triammonium phosphate, ammonium nitrate, ammonium sulfate, etc. can be used. Among these, diammonium hydrogen phosphate and ammonium sulfate are preferred. The ammonium salt may be used alone or in combination of two or more.

[0052] When ammonia is used as the basic compound, it is preferable to use aqueous ammonia.

[0053] By using only potassium salts as the basic compound, potash fertilizers can be produced. By using only phosphate salts as the basic compound, phosphate fertilizers can be produced. By using only ammonium salts or ammonia as the basic compound, nitrogen fertilizers can be produced.

[0054] Furthermore, by using potassium salts, phosphates, ammonium salts or ammonia in combination, a compound fertilizer can be produced.

[0055] The amount of basic compound added does not necessarily have to be equimolar to the acid, but can be set appropriately taking into consideration its use as a fertilizer. In other words, since the amount of nitrogen (N), phosphorus (PO), and potassium (KO) components required for fertilizer is a minimum guaranteed value, it is preferable to add an amount that is sufficient to ensure that amount.

[0056] Fertilizer ingredient labeling displays the total nitrogen, total phosphorus, and total potassium as percentages. Therefore, the amount of basic compounds added is adjusted so that the total nitrogen, total phosphorus, or total potassium is 2-5% greater than the amount of the ingredient being labeled. The definitions of total nitrogen, total phosphorus, and total potassium for fertilizer ingredient labeling (from Ministry of Agriculture, Forestry and Fisheries Notification No. 1,163, August 31, 2000) are shown below. 1 Total nitrogen The amount of nitrogen in the test sample is determined by the Kjeldahl method, and the percentage (%) of this amount relative to the weight of the test sample is taken as the total amount of nitrogen. However, if nitrate nitrogen is contained, the nitrate nitrogen shall be reduced to ammonia nitrogen as a pretreatment. 2 Total Phosphate After the test sample is incinerated, it is dissolved in hydrochloric acid, and the amount of phosphoric acid (P2O5) in the solution is determined by the ammonium vanadomolybdate method, etc., and the percentage (%) of this to the weight of the test sample is taken as the total amount of phosphoric acid. 3 total potassium After carbonizing the test sample, dissolve it in hydrochloric acid, and quantify the amount of potassium (KO) in the solution using atomic absorption spectrometry or other methods. The percentage (%) of this amount relative to the weight of the test sample is taken as the total amount of potassium.

[0057] Fertilizer components are managed based on the elemental content of nitrogen (N), phosphorus (P), and potassium (K), but in the case of P and K, the fertilizer is displayed as the total amount of phosphate and total amount of potassium, respectively, so the management value must be determined taking this into consideration.

[0058] [Neutralization reaction] The temperature for the neutralization reaction is preferably within the range of 0°C to 50°C, more preferably 5°C to 40°C, and even more preferably 20°C to 30°C to prevent excessive reaction of the polysaccharide hydrolyzate. Although the neutralization reaction itself is rapid, if insoluble matter derived from the raw polysaccharide is present, sufficient diffusion of the acid is required. Therefore, the neutralization reaction time is preferably 0.1 to 10 hours, more preferably 0.5 to 5 hours, and even more preferably 1 to 3 hours. No special equipment is required for the neutralization reaction; an ordinary stirring tank can be used. When hydrochloric acid or sulfuric acid is used as the acid, a stirring tank with a corrosion-resistant lining such as glass is preferred.

[0059] When the produced fertilizer is used as a soil-spreading fertilizer, the mixture obtained in the hydrolysis step may be used in the neutralization step while still containing solids. When the neutralization step is performed while containing solids, the apparatus used in the hydrolysis step (e.g., a grinding apparatus) can be used directly in the neutralization step, and the mixture containing the polysaccharide hydrolyzate and the basic compound can be mixed. Alternatively, after removing the mixture from the apparatus used in the hydrolysis step, the neutralization step can be performed separately in a Henschel mixer or the like, and the mixture containing the polysaccharide hydrolyzate and the basic compound can be mixed.

[0060] When two or more polysaccharides are used as the polysaccharide, the hydrolysis step may be carried out separately for each polysaccharide, and then the resulting hydrolysates may be mixed and subjected to the neutralization step. Alternatively, the hydrolysis step may be carried out in a state where two or more polysaccharides are mixed from the beginning, to obtain a mixture of multiple polysaccharide hydrolysates, which may then be subjected to the neutralization step.

[0061] <Other processes> In addition to the above hydrolysis step and neutralization step, the following steps may be optionally carried out as necessary.

[0062] [Extraction process] The method for producing a fertilizer according to one embodiment may include, after the hydrolysis step, an extraction step of adding water to a mixture containing the polysaccharide hydrolysate obtained in the hydrolysis step (hereinafter, sometimes simply referred to as "mixture") to extract water-soluble components. In particular, when hydrolysis is performed by a mechanochemical method, the mixture is in a solid form containing the polysaccharide hydrolysate because only a small amount of water is used, and therefore, it is preferable to perform this extraction step.

[0063] The extraction step may be carried out after the hydrolysis step and before the neutralization step, or may be carried out simultaneously with the neutralization step. When concentrated hydrochloric acid is used as the acid catalyst in the hydrolysis step, it is preferable to add ice to the mixture and stir it while cooling it to suppress heat generation in the neutralization step, which allows the neutralization step and the extraction step to be carried out simultaneously.

[0064] When the produced fertilizer is used as a liquid fertilizer, it is difficult to use if it contains undissolved components. In such cases, it is preferable to add water to the mixture obtained in the hydrolysis step to extract the water-soluble components, and then filter or otherwise remove the solids as necessary, followed by a neutralization step.

[0065] The mass ratio of the amount of water added to the mixture is preferably (amount of water added) / (mixture)=0.5 to 100, more preferably 1 to 20, and even more preferably 2 to 10. When the mass ratio of the amount of water added to the mixture is 0.5 or more, the water-soluble components (e.g., oligosaccharides) in the polysaccharide hydrolysate can be efficiently dissolved, and when it is 100 or less, the container for dissolution does not need to be too large, which is efficient.

[0066] The water to be added to the mixture is not particularly limited, but ion-exchanged water or distilled water is usually used. In addition to ion-exchanged water or distilled water, a solution containing a salt or a buffer solution may also be used. A water-miscible organic solvent may also be added to the mixture as long as it does not affect the dissolution of the water-soluble components in the polysaccharide hydrolysate.

[0067] The separation of the water-soluble component and the solid component can be carried out by a commonly used method for removing solids from a suspension, such as filtration using filter paper, filter cloth, membrane filter, filter press, cross-flow filtration, or natural sedimentation or centrifugal sedimentation.

[0068] In order to obtain oligosaccharides of relatively high purity as polysaccharide hydrolysates, a purification procedure may be carried out, such as removing solids from the mixture, adding ethanol or the like to an aqueous solution containing water-soluble components to reprecipitate the oligosaccharides, dissolving the resulting precipitate in water again, and repeating the ethanol reprecipitation.

[0069] [pH adjustment process] The method for producing a fertilizer according to one embodiment may include, after the neutralization step, a pH adjustment step of adjusting the pH to between 4 and 10. When producing an acidic fertilizer, the fertilizer is dissolved in water and then adjusted to be acidic, and when producing an alkaline fertilizer, the fertilizer is dissolved in water and then adjusted to be alkaline.

[0070] As the pH adjuster, those that are also used as fertilizers are preferred. Examples of such pH adjusters include acidic pH adjusters such as potassium dihydrogen phosphate and ammonium sulfate, and alkaline pH adjusters such as tripotassium phosphate, triammonium phosphate, lime, and calcium hydroxide.

[0071] When used as a liquid fertilizer, taking into consideration storage stability or stability when blended with other agricultural materials, the pH is preferably adjusted to 4 to 10, and more preferably adjusted to 5 to 9. If the pH is 4 or higher, problems such as precipitation are unlikely to occur when blended with other agricultural materials, and if the pH is 10 or lower, storage stability is good.

[0072] [Filtration process] The fertilizer production method according to one embodiment may include a filtration step of separating solids by filtration after the neutralization step. In the neutralization step, a precipitate may be formed by bringing the pH to the neutral side. The precipitation of precipitates is particularly pronounced when the polysaccharide is chitin. When the produced fertilizer is to be used as a liquid fertilizer, the presence of precipitates is undesirable, and therefore, it is desirable to separate the solids by filtration.

[0073] The solid content can be separated by a commonly used method for removing solid content from a suspension, such as filtration using filter paper, filter cloth, membrane filter, filter press, cross-flow filtration, or natural sedimentation or centrifugal sedimentation.

[0074] When this filtration step is carried out, the operation of separating (filtering) the water-soluble components from the solid components after extracting the water-soluble components in the extraction step can be omitted.

[0075] [Step of adding other ingredients] The method for producing a fertilizer according to one embodiment may further include a step of adding other components that are effective as a fertilizer, such as essential elements such as calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), boron (B), zinc (Zn), nickel (Ni), molybdenum (Mo), copper (Cu), and chlorine (Cl), as well as useful elements that support plant growth, such as sodium (Na), silicon (Si), selenium (Se), cobalt (Co), aluminum (Al), and vanadium (V). [Example]

[0076] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. [Filtrate analysis method]

[0077] Polysaccharide Hydrolysate Content: The content of polysaccharide hydrolysate was determined by subtracting the phosphoric acid content calculated from the P content and the KOH content calculated from the K content from the evaporation residue ratio of the filtrate analyzed at 105°C using a Kett moisture meter (A&D Co., Ltd., heat-drying moisture meter ML-50).

[0078] Polysaccharide Hydrolysate Content: The polysaccharide hydrolysate content was calculated from the evaporation residue ratio of the filtrate analyzed at 105°C using a Kett moisture meter (A&D Co., Ltd., heat-drying moisture meter, ML-50), and the solids content was calculated from this value. The polysaccharide hydrolysate content was determined by subtracting the P content calculated from the phosphate content and the K content calculated from the potassium (KO) content from this solids content.

[0079] P content: In accordance with 4.2.4.a of the Fertilizer Testing Methods (2019) established by the Food and Agriculture Organization of the United Nations, the water-soluble phosphate concentration (equivalent to diphosphorus pentoxide) measured using ammonium vanadomolybdate spectrophotometry was divided by a coefficient of 2.291 to calculate the phosphate (P2O5) content, and the P content was calculated from this value.

[0080] K content: In accordance with 4.3.3.d of the Fertilizer Testing Methods (2019) established by the Food and Agriculture Organization of the United Nations, the potassium (KO) content was calculated by dividing the water-soluble potassium (equivalent to potassium oxide) concentration measured by ICP atomic emission spectrometry by a coefficient of 1.2046, and the K content was then calculated from this value.

[0081] N content: The ammoniacal nitrogen (N) content was calculated using the formaldehyde method in accordance with 4.1.2.b of the Fertilizer Testing Methods (2019) established by the Food and Agriculture Organization of the United Nations (FAO). The N content was then calculated from this value.

[0082] [Example 1] Method for producing a fertilizer containing cellulose hydrolysate 3.91 kg of Avicel (Merck crystalline fine powder cellulose) (moisture content 3.1%, dry mass 3.79 kg) was mixed with 0.53 kg of 85% by mass phosphoric acid (special grade reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) using a Henschel mixer (apparatus name: FM20C / I, Nippon Coke & Engineering Co., Ltd.). The mixing conditions were a rotation speed of 1400 rpm and an aeration of 0.4 m. 3 Based on the moisture content of the raw material (cellulose) and phosphoric acid, 5.3 parts by mass of moisture was contained per 100 parts by mass of dry cellulose.

[0083] 350 g of this mixture was transferred to a vibration mill (model MB-1, manufactured by Chuo Kakoki Co., Ltd.) and pulverized to carry out a hydrolysis step using a mechanochemical method. The pulverization conditions were a total amplitude of 8 mm, a vibration frequency of 16.2 Hz, and a φ3 / 4 inch carbon steel ball. The temperature of the cooling water flowing through the jacket was set to 80°C, and hydrolysis was carried out for 24 hours.

[0084] The pulverized material was separated from the balls in the vibration mill, and 186 g of the pulverized material was transferred to a dissolving apparatus (2 L beaker). 721 g of ion-exchanged water was added, and the mixture was stirred at 25°C for 1 hour using a Three-One Motor (registered trademark). This dissolved the water-soluble components, and an extract of the cellulose hydrolysate was obtained.

[0085] To this extract, 154.4 g of a 15% by mass aqueous potassium hydroxide solution was added, and the mixture was stirred using a Three-One Motor (registered trademark) for 1 hour at 25° C. 42 g of perlite #31 (manufactured by Showa Chemical Industry Co., Ltd.) was added as a filter aid, and the mixture was filtered using a pressure filter (KST-293-20, manufactured by Advantec Toyo Co., Ltd.) to obtain 674 g of filtrate.

[0086] Analysis of the filtrate revealed that the pH was 6.8, the cellulose hydrolysate content was 47.8 g, and it contained 1.8 g of P and 6.8 g of K. The composition containing the cellulose hydrolysate thus obtained can be used favorably as a fertilizer.

[0087] [Example 2] Method for producing fertilizer containing chitin hydrolysate Purified chitin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the raw material.

[0088] 3.96 kg of the raw material (moisture content 3.3%, dry mass 3.83 kg) was mixed with 0.54 kg of 85% by mass phosphoric acid (special grade reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) using a Henschel mixer (apparatus name: FM20C / I, manufactured by Nippon Coke & Engineering Co., Ltd.). The mixing conditions were a rotation speed of 1400 rpm and aeration of 0.4 m. 3 Based on the moisture content of the raw material (chitin) and phosphoric acid, 100 parts by mass of dry chitin contains 5.5 parts by mass of moisture.

[0089] This mixture was transferred to a vibration mill (model MB-1, manufactured by Chuo Kakoki Co., Ltd.) and pulverized to carry out a hydrolysis process using a mechanochemical method. The pulverization conditions were a total amplitude of 8 mm, a vibration frequency of 16.2 Hz, and a φ3 / 4 inch carbon steel ball. The temperature of the cooling water flowing through the jacket was set to 80°C, and hydrolysis was carried out for 24 hours.

[0090] The pulverized material was separated from the balls and transferred to a dissolving apparatus (2 L beaker) (101.6 g). 431 g of ion-exchanged water was added, and the mixture was stirred at 25°C for 1 hour using a Three-One Motor (registered trademark). This dissolved the water-soluble components, yielding a chitin hydrolyzate extract.

[0091] To this extract, 71.7 g of a 15% by mass aqueous potassium hydroxide solution was added, and the mixture was stirred for 1 hour at 25° C. using a Three-One Motor (registered trademark). 24.3 g of perlite #31 (manufactured by Showa Chemical Industry Co., Ltd.) was added as a filter aid, and the mixture was filtered using a pressure filter (KST-293-20, manufactured by Advantec Toyo Co., Ltd.) to obtain 257 g of filtrate.

[0092] Analysis of the filtrate revealed that the pH was 6.8, the chitin hydrolysate content was 19.7 g, and it contained 0.61 g of P, 2.2 g of K, and 1.3 g of N. The composition containing the chitin hydrolysate thus obtained can be used well as a fertilizer.

[0093] [Example 3] Method for producing fertilizer containing chitin hydrolysate 11.7 g of 28% by mass aqueous ammonia (Tokyo Chemical Industry Co., Ltd.) was added to the chitin hydrolyzate extract obtained by the same treatment as in Example 2, and the mixture was stirred for 1 hour at 25°C using a Three-One Motor (registered trademark). 24.3 g of perlite #31 (Showa Chemical Industry Co., Ltd.) was added as a filter aid, and the mixture was filtered using a pressure filter (KST-293-20, Advantec Toyo Co., Ltd.) to obtain 242 g of filtrate.

[0094] Analysis of the filtrate revealed that the pH was 6.8, the chitin hydrolysate content was 19.7 g, and it contained 1.4 g of P and 4.0 g of N. The composition containing the chitin hydrolysate thus obtained can be used favorably as a fertilizer.

[0095] [Example 4] Method for producing fertilizer containing chitin hydrolysate The raw material used was 5 g of chitin (manufactured by Koyo Chemical Co., Ltd.) (moisture content: 1.9%, dry mass: 4.91 g). This chitin had a deacetylation degree of 5% or less, a viscosity of several tens of cps, and was crushed to a size of 5 mm or less.

[0096] 5 g of the above raw material was placed in a 200 mL Erlenmeyer flask, dispersed and dissolved in 50 mL of 35% concentrated hydrochloric acid, and a hydrolysis step was carried out for 24 hours while maintaining the reaction temperature at 25°C by heating a water bath.

[0097] After the hydrolysis step, about 300 g of ice was added to each reaction solution to rapidly cool the reaction solution, and a neutralization step was carried out using 48% by mass KOH to neutralize the solution to a pH of 5 to 6. After the neutralization step, the solution was decolorized overnight with activated carbon and filtered with Celite to obtain 311 g of filtrate.

[0098] Analysis of the filtrate revealed that the chitin hydrolyzate contained 2.2 g and 25 g of K. The composition containing the chitin hydrolyzate thus obtained can be used favorably as a fertilizer.

[0099] [Example 5] Method for producing a fertilizer containing cellulose hydrolysate and chitin hydrolysate 349 g of a cellulose hydrolyzate extract obtained by the same treatment as in Example 1 and 103 g of a chitin hydrolyzate extract obtained by the same treatment as in Example 2 were mixed, 226.1 g of a 15% by mass aqueous potassium hydroxide solution was added, and the mixture was stirred for 1 hour at 25° C. using a Three-One Motor (registered trademark). 70 g of perlite #31 (Showa Chemical Industry Co., Ltd.) was added as a filter aid, and the mixture was filtered using a pressure filter (KST-293-20, Advantec Toyo Co., Ltd.) to obtain 935 g of filtrate.

[0100] Analysis of the filtrate revealed that it had a pH of 6.8, contained 48.5 g of cellulose hydrolysate, and 20.1 g of chitin hydrolysate, and contained 2.5 g of P, 9.3 g of K, and 1.4 g of N. The composition containing the cellulose hydrolysate and chitin hydrolysate thus obtained can be used favorably as a fertilizer.

[0101] As shown in Examples 1 to 5, a polysaccharide hydrolyzate and a fertilizer containing nutrients such as potassium, phosphoric acid, and nitrogen can be easily obtained by hydrolyzing a polysaccharide with an acid catalyst and then carrying out a neutralization step in which at least one basic compound selected from the group consisting of potassium salts, phosphate salts, ammonium salts, and ammonia is added.

[0102] [Reference example 1] 10 g of purified chitin (Fujifilm Wako Pure Chemical Industries, Ltd.) was dispersed in 30 mL of water containing 1.2 g of 85% by mass phosphoric acid (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent). The powder was then dried under reduced pressure and placed in a 250 mL alumina pot along with 100 g of 5 mm diameter alumina balls. The pot was then placed in a planetary ball mill (Fritsch, Pulverisette 6) and milled at 500 rpm for 6 hours to obtain chitin hydrolysate. The temperature was started at room temperature, and the temperature increase due to shear heating was allowed to proceed.

[0103] Next, the chitin hydrolyzate was suspended in water and neutralized with calcium hydroxide to form a slurry, which was then filtered through a Nutsche filter using 5B filter paper. The collected filtrate was freeze-dried to obtain chitin oligosaccharide powder.

[0104] A fertilizer solution containing chitin hydrolysate with a composition almost equivalent to that of Example 2 was obtained by dissolving 1.0 g of the obtained chitin hydrolysate, 0.011 g of potassium dihydrogen phosphate (first grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.193 g of potassium tripotassium phosphate (first grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (totaling 0.031 g of P and 0.11 g of K) in 11.5 g of water.

[0105] [Tomato cultivation test] The fertilizer solutions prepared in Example 2 and Reference Example 1 were sterilized with a 0.45 μm filter to prepare stock solutions, which were then diluted 1000 times with water and used in the following cultivation tests.

[0106] Tomato seeds were soaked in distilled water for 6 hours, after which the stratum corneum was removed and then dried in an aerated area for 30 minutes. Ten seeds were then placed on each culture dish lined with absorbent paper. Each dish was then filled with a 1:1000 diluted fertilizer solution or water and soaked for 6 hours. Three uniformly sized seeds were then selected from each culture dish and potted. The 1:1000 diluted fertilizer solution or water was added every two days for a total of five times, and the seeds were grown for 11 days. The dry weights of the germinated seeds were measured and compared. The roots were cut off, and the remaining tops were dried in a constant temperature oven at 50°C for 12 hours before being measured. The results are shown in Table 1.

[0107] [Table 1]

[0108] The results in Table 1 show that the dry weight of the plants was similar when the fertilizer solution of Example 2 was applied to the plants when the fertilizer solution of Reference Example 1 was applied, and that the dry weight of the plants was greater than when only water was applied. This indicates that the composition containing the chitin hydrolysate obtained by the method of Example 2 is effective as a fertilizer and can be produced more efficiently than the method of Reference Example 1. [Industrial Applicability]

[0109] According to the method for producing a fertilizer of the present invention, a fertilizer containing a polysaccharide hydrolysate and nutrients such as potassium, phosphoric acid, and nitrogen can be efficiently produced.

Claims

1. a hydrolysis step of hydrolyzing polysaccharides with an acid catalyst to obtain a mixture containing a polysaccharide hydrolysate; an extraction step of adding water to the mixture after the hydrolysis step to extract water-soluble components; a neutralization step of adding at least one basic compound selected from the group consisting of potassium salts, phosphate salts, ammonium salts, and ammonia after the hydrolysis step; a filtration step of separating solids by filtration after the extraction step and the neutralization step; A method for producing a liquid fertilizer, comprising: the polysaccharide comprises at least one selected from chitin and cellulose, the acid catalyst is phosphoric acid or a partially neutralized salt thereof, A method for producing a liquid fertilizer, wherein the liquid fertilizer contains a neutralized salt produced in the neutralization step.

2. The method for producing a liquid fertilizer according to claim 1, further comprising a pH adjustment step of adjusting the pH to between 4 and 10 after the neutralization step.

3. 3. The method for producing a liquid fertilizer according to claim 1, wherein the basic compound is at least one selected from the group consisting of potassium hydroxide, potassium carbonate, and potassium bicarbonate.

4. 3. The method for producing a liquid fertilizer according to claim 1, wherein the basic compound is at least one selected from the group consisting of dipotassium monohydrogen phosphate, tripotassium phosphate, and diammonium hydrogen phosphate.

5. The method for producing a liquid fertilizer according to any one of claims 1 to 4, wherein the acid catalyst is phosphoric acid.

6. The method for producing a liquid fertilizer according to any one of claims 1 to 5, wherein the hydrolysis step is carried out by a mechanochemical method.

7. The method for producing a liquid fertilizer according to claim 6, wherein the mechanochemical method includes a grinding treatment using a planetary ball mill or a vibrating mill.

8. The method for producing a liquid fertilizer according to claim 6 or 7, wherein the amount of water in the hydrolysis step is 0.1 to 10 parts by mass per 100 parts by mass of the polysaccharide.

9. The method for producing a liquid fertilizer according to any one of claims 1 to 8, wherein the polysaccharides include both chitin and cellulose.

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