FI67565C - FOER FARING FRAMSTAELLNING AV METAL CHELATER PAO LIGNOCELLULOSABAS MED SALPETERSYRAOXIDATION - Google Patents

Description

67565

Process for the preparation of metal chelates from ligno-cellulose-based lean nitrogen nitrogen apoh ape tuk s e11a

The invention relates to a process for the preparation of metal chelates based on lignocellulose by nitric acid oxidation. The metal chelates prepared by the method according to the invention can be used in agriculture, on the one hand in the cultivation of plants, to compensate for the need for meso and microelements in the soil, and on the other hand in the care of livestock. for the administration of the essential elements, which will be described in more detail below.

It is known that due to intensive tillage and NPK / nitrogen-phosphorus-potassium fertilization, some meso- and micro-nutrients, such as iron, zinc, manganese, copper, boron, molybdenum, cobalt and / or chromium, are increasingly present in soils worldwide. shortage. Micronutrient deficiencies can also be caused by the addition of lime and gypsum to the soil, which causes too much calcium and magnesium, as well as excessive soil temperature and humidity, soil humic substances, cation-imbalance, and excess heavy metal ions (e.g. copper, zinc or nickel). Jones, JN: "Iron deficiency in plants and its correction." Com. Soil .Sei .Plant Anal. 7 (1 /.

i (1976 / 7-

Plant digestion disease due to lack of meso- and micro-element or elements can be treated by adding meso- and micro-elements to the soil. The two main preconditions for this measure are the effectiveness of the treatment provided and its economy. The treatment can take place on the leaves of plants so-called. as foliar fertilization or root fertilization in the soil (for example by spreading, applying liquid fertilizer or artificial fertilizer applied with irrigation water) as well, although less frequently by treating seeds or spraying them on the trunk. Foliage spraying is generally less efficient and more expensive than root fertilization / Wallace, A .: "Regulation of the micronutrient status of plants by chelating agents and other factors", UCLA 34P51-53 Los Angeles, California, pp. 267-272 (1971) _7 / because in severe deficiency diseases, on the one hand, plants do not get enough nutrients through the leaves and on the other hand too concentrated solutions destroy the leaves, and when the solutions are too weak, they have to be sprayed frequently, which is not economical. , but does not migrate to new top tumors in a physiologically acceptable form.Especially in the treatment of perennial glanders, only root fertilization is a satisfactory solution.

Meso- and micronutrient metal ions that can be utilized by plants are in the form of hydrated ions in soil solutions or soil clay minerals or in the form of ions associated with pectins corresponding to the cation exchange capacity of root systems, or are weakly bound to complexes with water or hydroxy. -ulkokehä; / For extensive professional literature, see, for example, Lakatos, B. and keel. "Biopolymer-Metall-Complex System IV", Agrokem. Talajtan, 25. 305-326 (1976/7 · Previously there was the use of highly soluble, readily available and inexpensive inorganic metal salts such as iron / II / sulphate in the form of hydrated ions in water / Seuchelli, V .: "Trace Elements in Agriculture ", pp. 39-57 and 151-171 (1976), published by Van Nostrand Reinhold Co., New York7, and iron lignosulfonates derived from poorly stable metal complexes, e.g., papermaking waste solutions (Iron / II / lignosulfonates) are described in U.S. Patent 2,929,700. ), or the use of iron polyflavonoids, is very common, however, humic substances in soil, peat, bog and fresh tallow, such as humic acids, form a water-insoluble form with meso- and micronutrient metal ions dosed in the above form.

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67565 with a so-called inner circumference and which is of the chelate type (see Lakatos, B, supra study). Thus, divalent and trivalent micronutrients are in the soil in a form that can hardly be used by plants / Szalay, A. and Szilägyi, M .: "Laboratory experiments on the retention of micronutrients by Pest humic acids" Plant Soil., 29, 219 (1968 / In order to achieve a clearly detectable effect, it is therefore necessary to add inorganic metal salts, for example ferrous sulphate, in an amount of about a thousand times the actual need, which is, of course, extremely uneconomical. nor is it economical due to the movement of the necessary abundant material.

A whole new chapter in the transport of meso- and micronutrient elements to the plant organism was opened by the use of water-soluble, highly stable metal chelates, such as zinc ethylenediamine tetraacetate / Halverson, A.D. and 2+

Lindsay, W.L .: "Theoretical Zn -concentration for corn and the nonabsorption of chelated zinc", Soil.Sci, Soc.Am.J. 41 (3), 531-534 (1977 //, chelates of various derivatives of ethylenediaminephenylacetic acid (U.S. Pat. Nos. 2,921,847, 3,038,793 and 3,248,207), iron potassium methylaminobis- (2-hydroxyphenyl) sulfonate (Hungarian Pat. ), or the metal chelates described in Hungarian Patent Publication No. 162,649, because these chelates, when applied through the soil, protect the cations of meso- and micronutrient elements from precipitation over a wide pH range and thus allow them to migrate to plant roots, even over long distances. , on the one hand, because of their uneconomical nature (their preparation is also very complex and therefore expensive) and, on the other hand, because, as physiological studies have shown, their absorption through the plant roots does not take place in the form of an indestructible complex but dissociates first into ions, therefore is obliged, the equivalent in order to be effective in itself from very expensive metal chelates, use an even greater surplus compared to the actual need for trace elements in plants (see for example, Halverson and Lindsay, supra). The stability of the metal chelates mentioned in Hungarian Patents 154,287 and 162,649 is also unsatisfactory, especially on alkaline and calcareous soils.

There is a very high demand in agricultural production units for metal chelates, the metal of which can be used efficiently by plants, while at the same time being simple to manufacture and therefore economically viable.

It is further known that certain trace elements such as iron, copper, cobalt, manganese, zinc and chromium are essential for the animal organism. These elements are generally referred to in the professional literature as essential elements. In the context of the efficiency of large livestock farms, it is now necessary to provide livestock with premixtures containing macro-elements and vitamins, as well as essential amino acids and fatty acids, as these substances are essential for the optimal development of the animals. In the absence of these essential elements, animals may experience loss of appetite, deterioration in health and meat quality, anemia, trace element deficiency diseases, impaired resistance to external stresses, such as infectious diseases, and not least death. These elements are now supplemented in most cases by readily available, inexpensive inorganic salts or salts formed with simple organic acids, for example acetic acid, fumaric acid or oxalic acid (log k = 3) (HorvSth, Z. and Nacsev, B .: "Futterschäden, Mangelkrankheiten" f the book was published in 1972 in Budapest, published by Landwirtschaft-Verlag). However, the absorption of essential metal ions cannot be ensured by means of said metal salts and

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5,67565 because these metal salts form very sparingly soluble compounds (e.g., sulfides, oxyhydroxides, or phytates) in the body with the individual components of the feed or the substances formed when the feed melts, and thus are eliminated in a poorly soluble form without significant bioavailability from the organism. A further disadvantage of said metal salts is that they catalytically degrade a large proportion of the vitamins in the nutrients, which are easily oxidized, pollute by oxidizing the fat they contain, so that these foods have an unpleasant taste and are no longer suitable for human consumption.

Although organic chelate complexes of essential elements, such as citrates or ethylenediaminetetraacetates, are better absorbed, these complexes, which have high thermodynamic stability, release only a small proportion of important trace elements in the animal and can even remove important HIV from the body. Thus, for example, increased use of citrate can lead to anemia, as it removes iron from the body in the form of a stable complex and prevents the absorption of copper, which is a very important element in the treatment of anemia in addition to iron.

Metal complexes with average stability are also known; they are used orally in livestock to replace hi-venous elements. According to Hungarian Patent Publication 152,252, the essential metal complexes formed with humic acids are known. Metal humates are well absorbed in the animal when administered orally and are useful, but their use is hampered by the fact that humic acids are chemically undefined substances with very different compositions and thus cannot be prepared into any metal complexes of the same quality. Therefore, no uniform and predetermined biological effect can be achieved with metal humates. Hungarian Patent Publication 172,831 discloses highly reproducible and chemically well-defined complexes of oligo- and polygalacturonic acids formed with essential metal ions with constant composition, average stability and relatively low molecular weight. These complexes are highly absorbable and useful, but their downside is that the preparation of the pectin used as a starting material is cumbersome and quite expensive; therefore, these complexes will not be widely used due to their uneconomical nature.

It has been found that oxidation of lignocellulosic plant wastes with nitric acid yields chelating compounds which form essential meso and micronutrient metal salts or complexes which are less stable than the stability of the chelates of the invention. with good yield and economy and which release the metal they contain even more efficiently in a living organism than many other metal complexes used so far.

The invention therefore relates to a process for the preparation of metal chelates based on lignocellulose. The metal chelates according to the invention are prepared by oxidizing the lignocellulosic starting material, optionally in a comminuted and / or hydrolysed and / or dried state, at a temperature of 30-100 ° C for 0.5-12 h with 4-12 volumes of an aqueous solution of 6-65% by weight nitric acid. per part of the dry matter of the starting material, and the chelating mixture thus obtained is reacted, preferably in situ, with alkali, boron, ammonium or alkaline earth metal salts, salts of 3d and 4d transition metals and / or complexes thereof with 7 67565 has a lower stability than the corresponding chelate complexes, or mixtures thereof, or oxidation is carried out in the presence of said salts and / or complexes, and, if desired, the chelate or chelate mixture formed is isolated in a manner known per se.

In the process according to the invention, agricultural or forestry waste materials can be used as starting material, for example straw, rice husks, corn cobs, corn cobs, straw, pieces of straw, bran, pieces of wood or sawdust. Of particular interest are, for example, the lignocellulosic by-product remaining in the preparation of furfural in the Hungarian patent publication 164 886, the so-called furfural bran (their composition and properties are disclosed in Hungarian Patent Publication 170,617).

The nitric acid oxidation carried out in the process according to the invention produces, as chelating agent, primarily oxidized lignin derivatives from plant waste.

In general, quite a number of chelating compounds are formed, so determining their exact chemical nature would be too complex an analytical task, but in practice it is also completely unnecessary.

As already mentioned above, the nitric acid oxidation can be carried out using nitric acid at a concentration of between 6% (rather dilute) and 65%, at any temperature between 30 and 100 ° C, but 96 ° C and a 12% nitric acid solution are most preferred. When these parameters are maintained, the reaction time is 1.5 h.

It has also been mentioned above that the starting material used in the process according to the invention may optionally be hydrolysed and / or comminuted and / or dried. The hydrolysis can be carried out as intended as indicated in the aforementioned Hungarian patent publication 164,886, i.e. at a temperature of about 180 ° C and steam at 67565 at 12 atmospheres. Drying and grinding take place in a manner known per se. As a starting material for the above purpose, said furfural broth is a substance hydrolyzed as described above; for hydrolysis, corn cob or sawdust is most often used as a starting material. The dried starting material has proved to be suitable in the process according to the invention.

Nitric acid - after oxidation is separated - if desired, the chelating agents of the reaction system in the form of their aqueous solution are filtered or centrifuged as appropriate. The chelating agents are then reacted with one or more metal salts or metal complexes to give the metal chelates of the invention. When metal chelates are to be used in the cultivation of plants, in view of the sensitivity of several crops, it is expedient to use metal salts other than chlorides, for example sulphates or nitrates, to form chelates. In the formation of chelates from the metal complexes in question, mention may be made, for example, of acetates which cannot be regarded as salts because they do not have a complete ionic nature.

As already mentioned above, the addition of metal salts or metal complexes to the reaction system by chelating and forming agents cannot be by oxidation, but the possible self-oxidation and catalytic effect of some metal salts, such as iron (II) salts, must also be taken into account. much cheaper.

The main advantages of the process according to the invention are the following: 1) By means of the process according to the invention, metal chelates can be prepared with excellent economy and can be

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9,67565 uses both plant and animal organisms very efficiently and are very suitable for introducing essential metals into the organism.

2) The starting material for the process according to the invention is plant waste, the use of which is also important for the protection of the environment.

3) Of the metal chelates prepared by the process of the invention, the plants utilize the iron of the iron chelates more efficiently than, for example, the iron chelated with ethylenediaminotetraacetic acid.

The invention is further illustrated by the following embodiments.

Example 1

Poor Nitric Acid Oxidation of Granulated Corn Cob-Furfural Bran (Experiments I-V) A 3 d dm four-necked flask is equipped with a paddle stirrer, thermometer, feeder, and condenser.

The nitrous gases produced by the oxidation are passed to washing columns filled with 25% by weight potassium hydroxide solution and acidic potassium permanganate solution, through a vertical condenser and absorbed while being sucked in a light vacuum. Place the flask in an electrically heated water bath heated to the temperature indicated in Table 1 (30, 40 or 50 ° C).

3

1500 cm of 56% by weight nitric acid with a specific gravity of 1,350 and of technical quality are placed in the hob described above? within about 30 min, it is heated to the temperature indicated in Table 1. When the desired temperature is reached, 250 g of granulated furfural bran (having a dry content I; 10 67565 is 91% by weight) derived from corn cobs are added over a period of 30 minutes with constant stirring. The system is then kept continuously for the time specified in Table 1 (2, 4 or 6 h) with constant agitation at the temperature specified in Table 1 (30, 40 or 50 ° C). After the time indicated in Table 1, the contents of the flask are cooled to room temperature with tap water and then neutralized using saturated aqueous potassium hydroxide solution (900 g) and 1700 cm or 1050 cm · 3 25% strength by weight ammonium hydroxide solution (specific gravity 0.906). After neutralization, the reaction mixture is diluted with 3 distilled water to 6 dm and the insoluble residue containing mainly cellulose is separated off by centrifugation. (The centrifuge is of the Janetzky K-70 type, 3000 rpm). The residue is suspended in distilled water and centrifuged again. Washing and spinning are repeated three times. The washed insoluble precipitate is dried at 105 ° C in an oven. As can be seen from the data in Table 1, 36-46% by weight of precipitate is obtained. Carefully evaporate 6 dm of the solution (100 ° C or 40 ° C) to dryness. After deducting the amount of potassium or ammonium nitrate calculated on the basis of the reduced amount of potassium hydroxide or ammonium hydroxide in the neutralization from the weight of the product obtained, 90 to 110 g of potassium or ammonium chelate are obtained, corresponding to a yield of 40 to 50% by weight. The acid capacity is 3.7-4.6 milliequivalents / g, henceforth denoted by meq / g, the capacity of iron (III) ions is 4.0-6.7 meq / g, and gram (g) in both cases indicates the amount of starting furfural residues. Thus, the product has a calculated acid capacity of about 10 meq / g and an iron (III) ion capacity of 12 meq / g.

Example 2

Medium-strong nitric acid oxidation of granulated maize cob furfural bran (Experiments VI-XI) 3

A four-necked flask with a capacity of 6 dm is equipped with a vane stirrer, a feed member and a vertical condenser and then placed in an electrically heated water bath.

11 67565 3

Add 1500 cm of 12% strength by weight nitric acid to the flask, then start heating the water bath. After about 30 minutes, as the water bath begins to boil, the temperature of the solution in the flask rises to 85 ° C. Thereafter, the addition of furfural bran made from granulated corn cobs (250 g, dry matter content 91%) begins with constant stirring.

The addition, the rate of which depends on the amount of foam formed due to the gases generated in the oxidation, continues for about 45 min. Due to the exothermic reaction, the temperature of the mixture rises rapidly (within about 10 minutes) to 96 ° C and remains at this temperature after the addition for as long as indicated in Table 1 (0.5, 1, 1.5, 3 and 6 h).

The nitrous gases formed in the reaction are absorbed by washing under light vacuum with columns filled with a 25% by weight potassium hydroxide solution and an acidic potassium permanganate solution connected to a condenser. After completion of the reaction, the reaction mixture is cooled with tap water to room temperature and then neutralized with saturated aqueous potassium hydroxide solution (72 g) (or 200 cm 2 of 25% strength by weight ammonium hydroxide solution), specific gravity 0.906. The neutralized mixture is diluted with distilled water to 3 6 dm and the cellulosic insoluble precipitate is separated by centrifugation (Janetzky K-70, 3000 rpm). The centrifuged precipitate is suspended in distilled water three times and centrifuged again. The washed material is dried at 105 ° C in an oven. As shown in Table 1, 36-58% by weight of precipitate is obtained. The solution is carefully evaporated to dryness (100 ° C or 40 ° C). After subtracting the amount of potassium or ammonium nitrate calculated from the amount of potassium or ammonium hydroxide required for neutralization by weight of the substance obtained, 90-100 g of potassium or ammonium chelate are obtained (yield: 40-45%). The acid capacity is 3.1-3.4 meq / g and the iron (III) ion binding capacity is 6-8 meq / g, and gram (g) in each case means the starting amount of furfural bran.

12 67565

Example 3

Strong nitric acid oxidation of granulated maize cob furfural bran (Experiments XI-XV) 3. .

A 6 dm four-necked flask is equipped with a snake stirrer, thermometer, feeder and condenser and then placed in an electrically heated water bath. Place 1500 cm of 56% by weight nitric acid with a specific gravity of 1,350 in the flask and then heat in a water bath. After about 60 minutes (when the acid is in the flask at 80 degrees), 250 g (dry matter content 91% by weight, made from granulated corn cobs) of furfural bran are introduced. The addition, the rate of which depends on the amount of foam formation caused by the gases evolved in the reaction, takes about 60 minutes. Due to the exothermic reaction, the temperature of the oxidation mixture rises to 90 ° C in about 10 minutes. At this temperature, the system is maintained during the reaction after the addition for 0.5, 1, 1.5, 3 and 10 h (see Table 1). After completion of the reaction, the reaction mixture is cooled with tap water to room temperature, and then neutralized using 640 g of saturated aqueous potassium hydroxide solution 3 or 800 cm 2 of 25% strength by weight ammonium hydroxide solution (specific gravity: 0.906). The neutralized mixture is diluted with distilled water to 6 dm ^ and then the cellulose-containing insoluble precipitate is separated by centrifugation (Janetzky K-70; 3000 rpm). Finally, the precipitate formed is suspended three times in distilled water, washed and centrifuged. The washed material is dried at 105 ° C in an oven. As shown in Table 1, 24-34% of precipitate is obtained.

The solution is carefully evaporated (100 ° C or 40 ° C) to dryness. After subtracting the amount of potassium or ammonium nitrate, calculated on the basis of the amount of potassium or ammonium hydroxide required for neutralization, from the weight of the product obtained, 100 to 110 g of potassium or ammonium chelate are obtained, i.e. a yield of 45 to 50% by weight. The acid capacity is 4.8-5.6 meq / g, the iron (III) ion formation capacity is 8-10 meq / g, and the gram (g) in each case means the starting amount of furfural broths.

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Example 4

Preparation of iron (III) complexes from substances obtained by nitric acid oxidation (weak, medium, strong) from granulated maize cob furfural bran to 3 750 cm, by nitric acid oxidation from granulated corn cob furfural halide oxide (or from sodium hydroxide and ammonium hydroxide) and ammonium hydroxide 3) an amount of 1 M ferric chloride solution equivalent to the acid capacity is added. In addition to the decrease in pH, a precipitate can be observed in the solution. The precipitate is dissolved using a glass electrode by restoring the pH of the solution to 7 with 25% ammonium hydroxide solution or 1 N potassium hydroxide solution. Any precipitate that has not yet dissolved is centrifuged off after 24 h. The iron content of the soluble iron complex is determined by a calorimetric method using O-fenatroline.

In this example, the oxidation products obtained in Experiments V, VII and XI are first charged with 1 mol of ferric chloride solution corresponding to the simple, double and triple acid capacities of these substances and then with one equivalent of 0.5 M ferrous sulphate solution complexes are prepared the iron (II) (III) ion content is of different magnitudes and has different valences (see Table II). Their repetitions are shown in Table III, with the difference that instead of ferric chloride corresponding to a simple acid capacity, ferric chloride corresponding to 0.9 times the acid capacity is added. Adjust the pH of the solution to 7 with 1 N potassium hydroxide. Any insoluble matter is removed after 24 h by centrifugation. The total iron content of the solution, iron (II) and iron (III), is determined after decomposition with a basic hydrogen peroxide solution and reduction with ascorbic acid using the O-phenanthroline method. The amount of iron (II) in the solution is likewise measured using the O-phenanthroline method. Tables II and III show the total amount of iron in solution, its distribution into iron (II) and iron (III) forms and the ratios of iron (III) to iron (II) or iron (II)

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67565 iron (III). It is observed that with substances obtained in oxidation experiments V, VII and XI from maize cob furfural bran, the reaction with both iron (III) chloride and iron (II) sulphate results in iron (III) - II) having virtually the same composition. complexes. In these complexes, the repetition of iron (II) -iron (III) ratios can be considered satisfactory.

Table IV contains basic analytical data on potassium ammonium chelates and iron (III) (II) complexes obtained in oxidation experiments V, VII and XI.

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Example 5

Medium-strong nitric acid oxidation (type VIII) of coarse furfural slurries obtained from wood chips 3 750 cm of dilute (12% by weight) nitric acid are weighed into a four-necked flask of capacity 6 3 dm, 3a equipped with a stirrer, a condenser and a thermometer. Dilute nitric acid is heated to about 80 ° C in a reaction flask using a hot water bath. After suspending 250 g wet (162 g dry) coarse obtained wood chips furfural-3 bran with 750 cm of dilute (12 weight percent) nitric acid and this suspension is added to a strong and evenly, stirring in about a half hour in hot nitric acid, at a temperature rises to about 96 ° C after about 10 minutes after the addition - because the reaction is somewhat exothermic - and remains here throughout the one and a half hour reaction time after the addition is complete. When the reaction is complete, the mixture is cooled to about 30 ° C with tap water, poured into a graduated cylinder and made up to 3 cm 3 with distilled water up to 1730 cm 3. This 1800 cm mixture is divided into two parts.

3

One half is neutralized using 118 cm of 30% by weight potassium hydroxide solution, the other half using 46 3 cm of 25% by weight ammonium hydroxide solution (specific gravity: 0.905). The solution is separated from the reaction mixture by centrifugation of the unreacted cellulose oxycellulose residue. The yield is 80 g (50%), the residue 79.5 g (49%) r has an acid capacity of 3.0 meq / g and an iron (III) ion formation capacity of 6 meq / g, and gram (g) represents the starting amount of furfural slurries. Oxidation can be performed in the same way for coarse furfural bran obtained from corn cob.

Example 6

Preparation of iron (III) (II) complexes with complexing agents derived from furfural bran obtained from wood chips by nitric acid oxidation (type VIII) 3

To the solutions obtained according to Example 5 (900 cm each) is added 1 M ferric chloride solution with slow stirring and vigorous. The amount of this solution is chosen so that it must contain 18.6 mg of iron per unit of acid capacity. During the separation of the precipitate, the pH of the solutions gradually decreases from neutral and therefore the system is adjusted to neutral (pH = 7) again with 2 N potassium hydroxide solution or 25% ammonium hydroxide solution in a sauna when the precipitate dissolves vigorously with stirring. Solutions containing iron chelate are carefully evaporated to dryness (100 ° C or 40 ° C). Thus 44-45 g of iron chelate are obtained, i.e. an almost quantitative catch.

Example 7

Copper (II), cobalt (II), manganese (II) and zinc (II) complexes and iron (II), copper (II), cobalt (II), manganese (II) and preparation of zinc (II)) complexes To 3,200 cm of the neutralized solution prepared according to Example 5 (pH = 7) an amount of 0.5 M metal (II) sulphate solution (47.5 cm) equivalent to the acid capacity is added. .

This forms a precipitate. The precipitate of this solution is dissolved 3 by adding about 3 cm 1 of aqueous potassium hydroxide solution (pH = 9-10). The resulting solution is then carefully evaporated to dryness at 70 ° C. An almost quantitative catch is obtained. The results of the analysis are shown in Table V. Multimetal complexes, so-called mixed complexes, for example corresponding to the following micronutrient ratio: 7.6% iron, 0.79% copper, 1.48% manganese, 0.83% zinc and 0.015% cobalt.

21 67565

Table V

Analytical data for chelates prepared according to Example 7

Formula Acid capacity _ (meq / g) C H 0_N_K Metal_ 34.50 2.70 40.59 7.51 16.6

Independent 35.79 2.61 38.69 4.21 5.7 11.1 (Fe) complexes 34.09 2.37 39.25 2.79 4.4 17.1 (Cu) 39.06 2.99 39.06 4.17 3.7 11.0 (Co) 42.26 3.23 40.29 3.17 3.8 7.25 (Ma) 3.3 37.56 2.73 40.19 2, 78 12.9 3.9 (Zn) ~ 5X78

Mixed Kanplex 35.2 3 2.37 39.55 3.7 5 5.4 1.0 (Cu) 0.5 (Mn) 0.4 (Zn) 0.005 (Co)

Example 8

Dilute nitric acid oxidation of coarse furfural bran (type VIII) with ferrous sulphate

In a three-necked flask equipped with a condenser, a thermometer, a feed member and a capacity of 6 dm, 85 g of 12% nitric acid are dissolved in 250 g of ferric sulphate at room temperature and the solution is heated in a boiling water bath to about 80 ° C. :in. 250 g (dried at 105 ° C) of wood chips and furfural bran are then suspended separately in 1250 cm of 12% nitric acid at room temperature and this suspension is added over a period of about 1/2 hour with slow and even stirring to an iron sulphate-nitric acid system 80 degrees. The rate of addition is determined - as in the previous case - by the formation of foam during the reaction; care must be taken not to create too much foam during rapid addition and to overflow the system. The temperature of the reaction mixture rises slightly to 92-96 ° C in about a quarter hour due to the exothermic oxidation reaction and also remains there for 1 1/2 h until the reaction is practically complete, as observed by 22 67565 of the cessation of nitrogen oxides and a few degrees of temperature drop. The jacket is then cooled to 40 ° C with tap water over a period of about 10 minutes. This is followed by neutralization of the oxidation mixture during cooling of the jacket with tap water 3 using 200 cm of 25% by weight ammonium hydroxide solution (specific gravity: 0.906) to pH = 7.0-7.4, and then separated from the solution using an artificial filter cloth 519-15 (Csillaghegy product) and a centrifuge of the Janetzky K-70 type (filter rotor radius 12 cm, 2400 rpm, i.e. 720 g) and centrifuging the insoluble cellulose oxycellulose residue for 10 min. The centrifuged residue weighs - dried at 105 ° C - 145 g, which corresponds to 58% of the yield calculated on the furfural bran used as starting material.

From a part of the neutralized solution obtained by centrifugation, which was 3 2360 cm, the spectrophotometric iron determination using o-phenanthroline shows that the iron content is 6.00 mg / cm. When half of the solution is dried at 45 ° C 3 3 (1180 cm), 93.4 mg / cm 3 of a dry matter with an iron content of 6.46% are obtained. This solid dissolves easily in distilled water. The total yield is 109.56 g and thus 82.8% of the amount of iron present in the reacted ferrous sulfate enters the solution.

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Claims (2)

23 67565 Process for the preparation of metal chelates on a lignocellulosic base, characterized in that the lignocellulosic feedstock is oxidized in an optionally comminuted and / or hydrolysed and / or dried state at a temperature of 30-100 ° C for 0.5-12 h with 4-12 volumes. -65% by weight of an aqueous solution of nitric acid, based on one part of the dry matter of the starting material, and the mixture of chelating agents thus formed is reacted, preferably in situ, with alkali, boron, ammonium or alkaline earth metal salts, 3d and 4d transition metal salts and / or with their less stable stability than the corresponding chelate complexes or mixtures thereof, or oxidation is carried out in the presence of said salts and / or complexes and, if desired, the chelate or chelate mixture formed is isolated in a manner known per se. 2. Lignocellulose-based metal chelates, characterized in that they have been prepared by oxidizing the lignocellulosic feedstock in an optionally comminuted and / or hydrolysed and / or dried state at a temperature of 30-100 ° C for 0.5-12 h with 4-12 parts by volume 6 -65% by weight of an aqueous solution of nitric acid, based on one part of the dry matter of the starting material, and reacting the mixture of chelating agents thus formed, preferably in situ, with alkali, boron, ammonium or alkaline earth metal salts, 3d- and 4d-transition metal salts and / or with complexes or mixtures thereof having a lower stability than the corresponding chelate complex, or by carrying out oxidation in the presence of said salts and / or complexes, and isolating the chelate or chelate mixture formed in a manner known per se.