JPH0264009A - Production of cyanamide - Google Patents

Abstract

PURPOSE:To industrially obtain high-purity cyanamide in high yield by using a nonaqueous organic liquid containing a specific aliphatic alcohol as a medium in a method for reacting lime nitrogen dispersed in the above-mentioned medium with gaseous carbon dioxide. CONSTITUTION:Lime nitrogen is dispersed in an organic liquid containing a 1-3C aliphatic alcohol and gaseous carbon dioxide is then blown into the resultant dispersion. Although the organic liquid which is a dispersion medium used in the above-mentioned method for production may substantially consists of a 1-3C aliphatic alcohol, an organic solvent, as necessary, may be further contained so as not to impair purity and yield of the cyanamide. Acetonitrile, dimethylformamide, ethyl acetate, acetone, etc., are used as the organic solvent. Formation of dicyandiamide which is a by-product and hardly separable from the cyanamide in carrying out the reaction in an aqueous medium can be effectively suppressed by the afore-mentioned method for production.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing cyanamide, which is useful as an intermediate for pharmaceuticals, agricultural chemicals, and industrial chemicals.

Prior Art: Various methods for producing cyanamide from lime nitrogen have been proposed so far. For example, “InorganicSy
Chimie & 1st, pp. 39-43 discloses a manufacturing method in which lime nitrogen is dispersed in an aqueous medium and sulfuric acid is added thereto.
ustrie"58. pp. 545-547 (1947)
discloses a method in which lime nitrogen is dispersed in an aqueous medium, hydrochloric acid or nitric acid is added thereto, and the produced cyanamide is extracted with a water-immiscible solvent, such as ethyl acetate.

Also, J, Chem, Soc, l 958, No. 290
Page 3 discloses a method for producing cyanamide, in which lime nitrogen is dispersed in a two-phase water-ether solvent system, and oxalic acid is added to the dispersion, whereby the cyanamide formed is dissolved in the ether phase.

In the conventional manufacturing method exemplified above, the presence of water was essential.

Conventionally, industrially, a method has been adopted in which lime nitrogen dispersed in the form of a slurry in water is reacted with carbon dioxide gas.

In this method, lime nitrogen reacts with water as shown in the following formula (1), 2CaCNt+2HzO-Ca(HNCN), +C
a(OH)*”(1) Then, the generated Ca(HNCN
) 2 or Ca(OH) and carbon dioxide gas are each expressed by the following formula (
It is thought that reactions occur as shown in 2) and (3).

Ca(OH)z+CO2= H20+CaCOx""
...(2) Ca (HNCN) t + Co!
＋H! O→2Ht NCN + CaC0s ・・
・(3) When these reaction formulas (1) to (3) are combined, the above production method ends up being the following formula (4): CaCN2+CO2+H,O-” Ca in H2NCN
C0n...It can be considered that (4) is followed.

As is clear from the above reaction formula, in the method for producing anamide by dispersing lime nitrogen in water, the reaction is generally carried out in an alkaline aqueous medium, so cyanamide dimerizes to form dicyandiamide as a by-product. easy. Since it is generally not easy to separate the by-product dicyandiamide from cyanamide, cyanamide obtained by the above-mentioned manufacturing method using an aqueous medium as a dispersion medium is inevitably contaminated with dicyancyanamide, and has a high purity of over 92%. It has been extremely difficult to industrially produce cyanamide of high purity.

An object of the present invention is to provide a new method that overcomes the above-mentioned drawbacks of the prior art and can industrially produce high-purity cyanamide at a higher yield than lime nitrogen.

The present invention: According to the present invention, lime nitrogen is dispersed in an organic liquid containing an aliphatic alcohol having 1 to 3 carbon atoms,
A method for producing cyanamide from lime nitrogen is provided, which comprises blowing carbon dioxide gas into the resulting dispersion.

The present invention will be explained in detail below.

The raw material lime nitrogen of the present invention is industrially produced by nitriding calcium carbide in a nitriding furnace. In addition to calcium cyanamide, lime nitrogen contains impurities such as graphitic carbon and quicklime, which are produced as by-products during nitriding. Generally, commercially available lime nitrogen has a nitrogen content of 20 to 27% by weight, and a cyanamide nitrogen content of 19 to 26% by weight.
It is.

In the production method of the present invention, lime nitrogen is pulverized if necessary so that the amount of particles passing through a 200 mesh of Tyler mark 4ill&ill becomes 50% by weight or more.

According to the invention, lime nitrogen is dispersed in an organic liquid containing an aliphatic alcohol having 1 to 3, preferably 1 to 2, most preferably 11 carbon atoms, and in the resulting dispersion By blowing carbon dioxide gas, cyanamide, which is purer than lime nitrogen, is produced in an innovative process and in high yields.

Examples of the aliphatic alcohol having 1 to 3 carbon atoms include monohydric alcohols such as methanol, ethanol, impropatol, and normal propatool, and polyhydric alcohols such as hyethylene glycol, propylene glycols, and glycerin. In the production method of the present invention, a mixture of two or more of these aliphatic alcohols can also be used.

Among the aliphatic alcohols having 1 to 3 carbon atoms, methanol and ethylene glycol are preferred, and methanol is particularly preferred.

The organic liquid that is the dispersion medium used in the production method of the present invention contains the above-mentioned aliphatic alcohol having 1 to 3 carbon atoms. The organic liquid may consist essentially of an aliphatic alcohol having 1 to 3 carbon atoms, but if necessary, a further organic solvent may be added to the extent that the purity and yield of the cyanamide obtained are not impaired. May contain.

Examples of the above-mentioned further organic solvents include acetonitrile, dimethylformamide, ethyl acetate, acetone, and tetrahydro-7rane.

In the present invention, the concentration of lime nitrogen in the lime nitrogen dispersion in the organic liquid that is the dispersion medium is preferably 5 to 25% by weight, more preferably 15 to 20% by weight at the time of delivery. ! amount%
It is.

In the method for producing cyanamide according to the present invention, cyanamide is produced as a cyanamide solution in an organic liquid by blowing carbon dioxide into the dispersion of lime nitrogen. The carbon dioxide gas used in the present invention does not necessarily have to be highly pure, and may be diluted with an inert gas for this reaction system, such as nitrogen, oxygen, or air. However, if the concentration of carbon dioxide in the gas is too low, problems such as aliphatic alcohol being lost along with the gas will occur. The amount of water in the gas is preferably 40% by weight or more, and the water content in the gas is also 20% by weight or less, preferably 2% by weight or less, particularly 0.2% by weight or less.

The reaction by blowing carbon dioxide gas is 0.1-10kg/m2
, preferably atmospheric pressure, and at a temperature of 0 to 40°C, preferably 0 to 30°C. If the temperature is too high, exceeding 40°C, the purity of cyanamide tends to decrease, which is undesirable, while if it is too low, below 0°C, there is no particular advantage.

After the reaction is completed by blowing carbon dioxide gas, the muddy reaction dispersion is filtered by a conventional method to easily obtain a solution of 7-anamide in an organic liquid.

The water content of the reaction system in the production method 8 of the present invention (the content of water in the organic liquid as a dispersion medium) is generally 20% by weight or less,
Preferably 5% by weight or less, more preferably 3.5% by weight
The content is more preferably 2.5% by weight or less, most preferably 1% by weight or less. As the water content of the reaction system decreases to 20% by weight or less, the reaction dispersion after the reaction does not undergo gelation (if gelation occurs, filtration becomes impossible), and dimerization of cyanamide occurs. The by-product of dicyandiamide is suppressed.

The water content of the reaction system in this specification refers to the water content of the reaction system at the end of the carbon dioxide gas blowing reaction. The water content of the reaction system was measured by the following method. First, the reaction dispersion liquid collected from the reaction system is centrifugally filtered to remove organic liquid insoluble components, and the obtained filtrate (organic liquid solution) is subjected to gas chromatography analysis (hereinafter abbreviated as GC analysis (TCD method)). ] The water content in the filtrate was measured and taken as the water content of the reaction system.

A novel method for producing cyanamide from lime nitrogen according to the present invention! :8, it is not clear what kind of chemical reaction is occurring. However, as shown in Example 1 using methanol as the aliphatic alcohol, when water is added to the filtration residue produced as a by-product when a cyanamide solution is obtained by filtering the reaction dispersion and stirred, carbon dioxide gas is released. methanol and calcium carbonate are generated, and as shown in Example 1, the total number of moles of carbonate radicals in the carbon dioxide gas and the calcium carbonate and the number of moles of the methanol are equal to the amount of Ca in the carbonate. The filtration residue contains graphitic carbon in lime nitrogen and the formula [A]Ca(0-C-OCHx)z ++
+++++++++ Compound [A] (French patent No. 1
, 513.416) as a main component.

For the above reasons, it is presumed that in Example 1 of the present invention, carunium cyanamide, methanol, and carbon dioxide gas in lime nitrogen react to produce cyanamide and the compound of the above formula [A].

In the process of the invention, the /anamide is obtained as a solution in an organic liquid. Since this cyanamide solution may undergo gelation during storage, an acid can be added to the solution to stabilize the solution, if necessary. Examples of acids used for stabilization include inorganic acids such as phosphoric acid, sulfuric acid, nitric acid, and hydrochloric acid, organic acids such as acetic acid and oxalic acid, and cation exchange resins such as sulfonic acid type cation exchange resins.

Among them, phosphoric acid is preferably used.

The amount of the acid added to the cyanamide solution is about 1 per Cal equivalent of a trace amount of Ca compound dissolved in the solution.
Equivalent amounts are preferred.

The cyanamide solution obtained according to the present invention can be concentrated, preferably under reduced pressure, if necessary, to remove the organic liquid and easily obtain high-purity crystalline cyanamide.

Effects of the present invention: According to the production method of the present invention, the by-formation of dicyandiamide is extremely effectively suppressed, so that a solution or crystal of cyanamide with a high purity of, for example, 96% can be produced in a high yield and in an industrially simple method. You can get it at

The present invention will be explained in more detail below using Examples.

Sorrow Man: Example 1 Methanol 3751C297 (9) (purity 99.5% by weight, water content 0.5% by weight) and lime nitrogen 6 were placed in a stainless steel reaction tank with a 500p cooling jacket and reflux condenser.
3 kg [nitrogen content 24.6% by weight (nitrogen content as calcium cyanamide 23°6% by weight); particle size 200
65% by weight of 1 was added through the mesh and dispersed into a slurry by stirring. Then, while stirring and maintaining the temperature at about 15°C, it was heated to 62.1 kt for about 8 hours. of carbon dioxide gas (purity 99.99
% by weight) to cause a reaction, and after the reaction was completed, methanol-insoluble matter was separated using a centrifugal filter. The obtained furnace liquid (
Water content in methanol solution) is determined by GC analysis (TCD method)
It was 1.8% by weight. The methanol-insoluble matter was washed with methanol 63j (50 kg) similar to that used in the reaction, and the washing liquid was combined with the filtrate to obtain a total of 290 kg of a methanol solution of cyanamide. The content of cyanamide and by-product dicyandiamide in the methanol solution is determined by liquid chromatography (hereinafter sometimes abbreviated as LC).
According to analysis, they were 6.9% by weight and 0.02% by weight, respectively, and the production yield of cyanamide was 90% and the production rate of dicyandiamide was 0.3% with respect to calcium cyanamide in the raw lime nitrogen.

To the methanol solution, 3.3 kg of 85% by weight phosphoric acid was added and stirred, and the resulting insoluble matter was filtered off.

The methanol solution thus obtained remained stable without gelation even after one month.

A portion of the methanol solution before adding phosphoric acid was taken and left to stand in a tightly sealed container. However, after 7 days, the entire solution turned into an agar-like gel.

Further, after drying a portion of the methanol-insoluble matter under reduced pressure, approximately 12% of it was accurately weighed and placed in a flask equipped with a reflux condenser, and 10% of the methanol-insoluble matter was dried with deionized water. ? After stirring at room temperature for about 3 hours, insoluble matter was filtered off, and the resulting filtrate was analyzed by GC to quantify methanol, which was about 8.5 mmol/2. On the other hand, 1 l of the same dry methanol-insoluble compound was accurately weighed and placed in a kill pool type decomposition flask, and 50 cc of IN hydrochloric acid was added.
The amount of carbonate radicals in the insoluble matter is determined by adding and slowly heating to about 100 ° C., introducing the generated gas into a saturated barium hydroxide aqueous solution, and quantifying the precipitated barium carbonate. . The amount of carbonate radicals is approximately 8.6 mmol/2. Next, the contents in the Kirdahl-type digestion 7 flask were filtered, the filtrate was diluted with deionized water to make 50 cc, and 10 cc of the filtrate was used to quantify calcium using ethylenediaminetetraacetic acid with the TB reagent as an indicator. Ta. The amount of calcium was approximately 5.0 mmol/9. From the above quantitative results, approximately 1.7 mol each of methanol and carbonate radicals were detected per 1 mol of calcium from the methanol-insoluble matter.

Example 2 Methanol loj! in a 201 glass reaction tank equipped with a stirring device and a reflux condenser. (7,93kg) (purity 98.3
(wt% water content: 1.7 wt%) and 2 kg of lime nitrogen similar to Example 1 were charged and dispersed into a slurry by stirring. Cool from the outside in a water bath and keep at about 20°C until about 8 ℃.
1.98 kg of carbon dioxide similar to that used in Example 1
was introduced and reacted. After the reaction was completed, methanol-insoluble components were separated using a centrifugal filter. When measured in the same manner as in Example 1, the water content of the filtrate was 3.3% by weight.

The insoluble matter was further removed by methanol 21 (1,586 kg
(purity 99.5% by weight), combine the washing liquid with the filtrate,
Next, 85% by weight phosphoric acid 1292 was added and stirred, and the resulting insoluble matter was filtered off to obtain 9.40 kg of a stabilized methanol solution of cyanamide. The contents of cyanamide and by-product dicyandiamide in the methanol solution were determined to be 6.8% by weight and 0.02% by weight, respectively, by LC analysis as in Example 1.
% by weight, and the production yields for calcium cyanamide in the raw lime nitrogen are 9(]% and 0.3%, respectively)
Deatsu Iko.

When a portion of the methanol solution before addition of phosphoric acid was taken and left to stand in a tightly sealed container, the entire solution gelled into agar-like gel after 24 hours. Furthermore, the □ methanol solution to which phosphoric acid was added remained stable without gelation even after one sunset, as in Example 1.

Methanol solution of cyanamide added with phosphoric acid (large size)
Using an evaporator, it was concentrated under reduced pressure (20 Torr) at a temperature below 30°C, and then dried to give a white crystal of 0.63
I got 7kg.

The analysis revealed the following.

Purity 99.2% by weight Dicyandiamide 0.4% by weight Elements 0.01% by weight Water 0.3% by weight Example 3 In Example 2, the reaction temperature was about lθ°C, and the purity of methanol used was 96.3%. The reaction was carried out in the same manner except that the water content was 3.7% by weight. After the reaction was completed, methanol-insoluble matter was filtered off in the same manner as in Example 1. When measured in the same manner as in Example 1, the water content in the filtrate was 4.
It was 3% by weight.

Hereinafter, in the same manner as in Example 2, the insoluble matter was washed with methanol,
The washing liquid was combined with liquid d, 85% by weight phosphoric acid was added to this solution, stirred, and the resulting insoluble matter was filtered off to obtain 9.40 kg of a methanol solution of cyanamide. The content of cyanamide and by-product dicyandiamide in the methanol solution was determined to be 6.8% by weight and 0.03% by weight, respectively, by LC analysis as in Example 1, and the production yield relative to calcium cyanamide in the raw lime nitrogen were 90% and 0.4%, respectively.

Note that when a portion of the methanol solution before addition of phosphoric acid was taken and left to stand in a tightly sealed container, the gold body gelled into an agar-like state after 4 hours.

Further, the methanol solution to which phosphoric acid was added remained stable without gelation even after one month, as in Example 1.

Thereafter, it was concentrated to dryness using the same apparatus and under the same conditions as in Example 2 to obtain 0.640 kg of white cyanamide crystals.

The analysis revealed the following.

Purity 98.6% by weight Dicyandiamide 0.8% by weight Urea 0.1% by weight Water 0.4% by weight Comparative Example In a reaction tank similar to Example 1, 150j of water was added! (150kg
) was charged, and carbon dioxide gas similar to that used in Example 1 was introduced while stirring. The reaction temperature was kept at 15°C and the pH was 7.5.
63 kg of lime nitrogen, which was the same as that used in the example, was added little by little while making adjustments so as not to exceed the above amount. The addition of lime nitrogen was completed in 7 hours, and after keeping the condition as it was for another 1 hour, the introduction of carbon dioxide gas was stopped and the insoluble matter was separated using a centrifuge, and the insoluble matter was washed with approximately 30% water and combined with the filtrate. Ta.

The cyanamide aqueous solution obtained was 164.3 kg, the content of cyanamide was 10.8% by weight, the content of by-product dicyandiamide was 0.74% by weight, and the production yield of calcium cyanamide in the raw lime nitrogen was 80%. %, 5
%Met.

(procedural amendment) June 8, 1999 Director General of the Japan Patent Office Yoshi 1) Takeshi Moon 1, Indication of the case 1999 Patent Application No. 98775 2, Title of invention Process for manufacturing cyanamide 3, Person making the amendment Case Relationship with Patent applicant name (459) Nippon Carbide Kogyo Co., Ltd. 5 Date of amendment order None 6 Column 7 for detailed explanation of the invention in the specification subject to amendment 7 Contents of the amendment As shown in the attached sheet (1) Description In the 8th line from the bottom of page 2, r J , Chem,
Soc, ”, r″J, Chem, Soc
, corrected to J.

(2) On page 3, line 6 of the same page, replace “rCa(OH)” with rca
(OH) Corrected to 2J.

(3) On page 9, lines 1 to 11, the phrase [However, aliphatic... and formula [A]'' has been changed. r However, when methanol is used as the aliphatic alcohol, the reaction dispersion liquid is less By adding water to the methanol-insoluble matter, which is a filtration residue when obtaining a cyanamide solution, and stirring it, the generation of carbon dioxide gas and the production of methanol and lucium carbonate were confirmed.
When the composition of the insoluble matter is analyzed as described in , it contains about 1.7 mol of carbonate radicals per mol of Ca in the insoluble matter, and about 1.7 mol of methanol is generated by adding water. I understand that. From these facts, the methanol-insoluble matter is the graphite in lime nitrogen and the formula [A]
Correct to 1.

(4) On page 13, line 11 of the same page, replace “rTB reagent” with rBT.
Correct to reagent 1.

Claims (1)

[Claims] 1. Lime nitrogen is dispersed in an organic liquid containing an aliphatic alcohol having 1 to 3 carbon atoms, and carbon dioxide gas is blown into the resulting dispersion. A method for producing cyanamide from lime nitrogen. 2. The method according to claim 1, wherein the aliphatic alcohol having 1 to 3 carbon atoms is methanol. 3. The method according to claim 1 or 2, wherein the water content of the reaction system is 5% by weight or less. 4. The method according to claim 3, wherein the water content of the reaction system is 3.5% by weight or less. 5. The method according to claim 4, wherein the water content of the reaction system is 2.5% by weight or less.