KR790001016B1 - Method for oxidation of cyanic acid - Google Patents

Abstract

(CN)2 was manufd. by reaction of HCN with O2 (optionally air) in an aq. soln. contg. Cu(NO3)2 catalyst at 20-60≰C and PH-0.5 to+1.5. Thus, 150ml soln. contg. 1.5 mole Cu(NO3)2/1. was circulated downward through a packed tower at 120 ml/min and 0.5 mole HCN/hr and 0.14 mole O2/hr were passed upward to give 92% (CN)2 at HCN conversion 98%. The pH of the soln. was kept at O±0.1 during the reaction by addn. of 70% HNO3. The product gas contained 82% (CN)2 and 4% NO2.

Description

Oxidation Method

The figure shows the experimental apparatus of the present invention.

1 and 1 'are reactors, 2 and 2' are packed towers,

3 'and 3' and 4 are metering pump, 5 is clearing injection pipe,

6 is oxygen injection tube, 7 is glass electrode, 8 is nitrate injection tube equipped with solenoid valve, 9 and 9 'control coke, 10 and 10' collection bag.

The present invention relates to a process for producing dicyne by oxidizing cyanide with oxygen in a nitrate solution.

More specifically, the present invention relates to a method for producing a high concentration of dicyan containing almost no nitrogen oxides with good efficiency by simultaneously concentrating and oxidizing cyanide and oxygen in an nitrate aqueous solution.

Dicyane is a compound useful for the preparation of organic synthesis, for example oxamide, diimino succinonitrile and the like. There are two methods for preparing dicyne: a method of reacting cyanide and oxidant in a gaseous phase at a high temperature in the presence of a catalyst and a method of reacting cyanate and oxidant in a second copper salt aqueous solution. It is a potent but has many flaws. Herein, as a method of preparing dicyne by reacting cyanide and an oxidizing agent in a second copper salt aqueous solution, a method of reacting cyanide and nitrogen dioxide in a solution of a second copper salt is known (see Japanese Patent Publication No. 43-17289). In order to prevent the incorporation of dicyanate with almost equal molar nitrogen monoxide in the product gas obtained by this method and to obtain a high concentration of dicyanate, it is necessary to absorb dicyanate in a suitable solvent such as acetonitrile to separate nitrogen monoxide. There is a drawback to doing such complicated operations.

It is an object of the present invention to produce high concentrations of dicyanus directly in clearing without the use of nitrogen dioxide. According to the present invention, dicyne is prepared by reacting cyanide with a coral or oxygen-containing inert gas at pH-0.5 to 1.5 in an aqueous copper nitrate solution or an aqueous solution of copper nitrate and at least one alkali metal, alkaline earth metal or nitrate solution of aluminum.

The method of the present invention has the following advantages.

Dicyne can be produced in concentrations of more than 82% in the product gases, and no special separation methods such as using acetonitrile are necessary. The values in Table 1 indicate that the method of the present invention is superior to conventional methods (Japanese Patent Laid-Open No. 43-17289). This reaction is as follows.

Method of the invention

The method of Japanese Patent Laid-Open No. 43-17289

2HCN + NO _2- (CN) ₂ ↑ + H ₂ O + NO ↑

TABLE 1

Second, by adding a small amount of nitric acid, the nitrate roots during the reaction to obtain a high concentration of cyanine from the clearing and oxygen are sufficiently replenished. A low concentration of oxygen-containing inert gas, such as air, can be used as the oxidant to obtain a low concentration of dicyan. This method is very economically beneficial.

Moreover, the reaction can be carried out more stably for a long time, for example, more than 30 hours, without forming an oxamide when the reaction is carried out in a low concentration of copper nitrate to which calcium nitrate is applied. The results in Table 2 show the effect of adding calcium nitrate to the catalyst solution.

TABLE 2

In addition, since a small amount of nitric oxide to be produced is removed by adsorbing copper nitrate or a mixture of copper nitrate and at least one alkali metal, alkaline earth metal or aluminum nitrate mixture, diancia containing little nitrogen oxide is removed at reaction temperature 45 It can manufacture uniformly at 60 degreeC inside. This effect is very beneficial for the industrial manufacture of dicynes. Furthermore, the resulting dicyan can be used to prepare oxamide without purification.

Excellent effects of the present invention are achieved by reacting under the following conditions.

In order to carry out the present reaction continuously and stably at a constant rate, it is necessary to control the pH of the copper nitrate aqueous solution in the range of -0.5 to 1.5. If the pH is lower than -0.5, the unreacted clearing is increased, and if it is higher than 1.5, it forms a precipitate to inhibit the reaction. Adding one or more alkali metal nitrates to the copper nitrate solution makes it easy to adjust the pH of the solution to 0.5 to 0.8. Adding one or more nitrates of alkaline earth metal or aluminum to copper nitrate makes it easy to adjust the pH of the solution from 0 to 0.6. The pH can be adjusted by adding nitrate to the original pH solution.

As to the concentration of the catalyst solution, it is effective to use a solution containing 0.5 to 3 mol per liter of the solution. When the concentration is 0.5 mol or less per liter, the reaction tends to become unstable, and when it is 3 mol or more per liter, adsorption of oxygen starts to decrease.

If the reaction persists for a long time, it is preferable to add one or more nitrates to the copper nitrate solution. As nitrates, nitrates of alkali metals, alkaline earth metals and aluminum are used. Examples of nitrates are sodium nitrate, potassium nitrate, lithium nitrate, magnesium nitrate, potassium nitrate and aluminum nitrate. The use of ammonium nitrate is undesirable because nitrogen is generated. Large amounts of nitrates of transition metals such as iron, nickel, cobalt, and chromium are undesirable because these metal ions increase the formation of oxides during the reaction. The higher the concentration of nitrate solution added to increase the concentration of nitrate roots in the catalyst solution, the higher the catalytic action and the shorter the induction period of the reaction. Thus, this reaction can be carried out in a low concentration of copper ions which do not affect the rate of reaction of the clearing. However, the solubility of nitrates should be considered. For example, precipitation of copper cyanide occurs when the reaction is carried out in an extremely low concentration of copper nitrate (eg 0.2 mol / l).

However, the addition of the nitrates or nitrates can prevent precipitation in the solution and the reaction is performed smoothly. Thus, the concentration of the nitrate root is preferably from 2 mol / l up to the upper limit of the solubility of the nitrate used. In this case, it is preferable to use 0.15-1 mol / l of copper nitrate. When the concentration of copper nitrate is extremely high, oxamido occurs.

The amount of the catalyst solution relative to the starting material is not particularly limited, but for example, 5 to 50 g / hour of starting material is used for 500 ml of the catalyst solution in order to sustain the reaction at a constant rate.

Clearing can be used in liquid or gaseous form.

As the oxidizing agent, an oxygen-containing inert gas such as air or a mixture of air and oxygen may be used. When air is used as an oxidant, the concentration of dicyan produced is reduced by about 30%, but the concentration of nitric oxide (about 1%) and the conversion of clearing are hardly changed. Therefore, the use of oxygen, air or a mixture of air and oxygen as the oxidant can be freely selected according to the reaction purpose.

The amount of clearing and oxygen used uses more than stoichiometric amount of oxygen. From an economic point of view, it is preferable to use 5 to 10% excess oxygen.

The reaction is preferably carried out at 10 to 75 ° C, in particular at 20 to 60 ° C. In any case, the copper nitrate solution must remain liquid. If the reaction is carried out at unnecessarily high temperatures, nitrogen and carbon dioxide are generated and the consumption of nitric acid is disadvantageously increased.

The reaction pressure is not limited, but the reaction may be carried out under atmospheric pressure, pressure, or reduced pressure.

When the crude reaction product is brought into contact with the catalyst solution when the reaction is finished or delayed, most of the nitrogen oxides produced can be recycled and adsorbed to the reusable catalyst solution and the desired product does not use any separation process. It can be obtained easily without.

The method of the present invention used two reactors in the figure. Reactor I consists of reactor 1 and packed tower 2, and reactor II consists of reactor 1 'and packed tower 2'. In order to adsorb and remove the produced nitric oxide in the catalyst solution, two reactors are used as shown in the figure. The catalyst solution is filled in reactors 1 and 1 'which are circulated in packed towers 2 and 2' by metering pumps 3 and 3 '. At the same time the catalyst solution in reactors 1 and 1 'is circulated by metering pump 4 between the two reactors. Clearing is injected through line 5 and oxygen is injected through line 6 (1.1 times the theoretical amount) and simultaneously enters reactor 1 and the reaction is carried out.

The pH of the catalyst solution in reactor 1 is controlled by adding nitric acid from line 8 equipped with a solenoid valve connected to glass electrode 7. The resulting gas is passed through packed column 2 in contact with the catalyst solution and then through reactor 1 'and packed column 2'. At this time, the gas is brought into contact with the catalyst solution again and collected in the collecting bags 10 and 10 'through the control cocks 9 and 9'. Nitrogen oxide, a byproduct, is absorbed into the catalyst solution as follows. An appropriate amount of catalyst solution circulates through reactors 1 and 1 'of reactors I and II and the reaction is almost terminated in the catalyst solution in the reactor. The gas produced in reactor I containing several% of nitrogen oxide is brought into contact with the catalyst solution in packed column 2 'of reactor II and the nitrogen oxide is absorbed and removed by the catalyst solution. By the absorption of nitrogen oxides, the pH of the catalyst solution in the reactor is lower than the pH of the catalyst solution in the reactor II, and the catalyst solution in the reactor II reaches a stationary state and continues to absorb nitrogen oxides again. This process is based on the principle that dilute nitric acid (several%) continues to remove nitric oxide. This process yields a high concentration of dicyne and the nitrogen oxides are always absorbed and removed by the same catalyst solution. Furthermore, a portion of the catalyst solution in the reactor 1 that is not terminated in reactor 1 is sent to reactor 2 and the pH of the catalyst solution in reactor II is lower than the pH of the catalyst solution in reactor I. The reaction is terminated by contact mixing at. On the other hand, a part of the catalyst solution in the reactor II absorbs and circulates the nitric acid that has not reacted with nitrogen oxide, is sent to the reactor 1, the pH is raised, and the liquid acid starts to oxidize again. The data in Table 2 was obtained by reaction at 45 ° C. for 100 hours.

When by-product nitric oxide is not absorbed and removed from the catalyst solution, the reaction is carried out using only reactor I. In this case, the catalyst solution is transferred to the reactor, which is circulated through packed column 2 by metering pump 3. The reaction is carried out continuously by supplying clearing and oxygen or air via lines 5 and 6, respectively, and the produced gas from the outlet of packed column 2 is discharged and sent to coke 9 connected to the collection bag 10. If desired, two or more reactors similar to reactor I may be connected in parallel.

Example 1

Reactors I and II used the same diagrams, but with a slight change in the connection lines as follows. Reactors 1 and 1 'were connected to one line, and reactor 2 and packed tower 2 through pump 3 were omitted. The line was connected to the filling tower 2 'and to the tower top of the filling tower 2. Each control coke was installed under the tops of the filling towers 2 and 2 'and the outlet of tower 2 was connected to the reactor 1' and the top of the filling tower 2 'by the T-shaped line. It is connected to the collection bags 10 and 10 'through 9'. As reactors 1 and 1 ', a 200 ml separation flask (Separable Flask) was used. Each flask was charged with 150 ml of catalyst solution containing 1.5 mol of copper nitrate per liter of water. The catalyst solution is circulated by the pump 3 'at a rate of 120 ml / min through the packed towers 2 and 2' (20 mm? X 600 mm), respectively. The gaseous clearing is introduced in line 5 at a rate of 0.5 moles (13.5 g) / hour, oxygen is introduced in line 6 at a rate of 0.14 moles (4.48 g) / hour (1.1 times the theoretical amount) and the reaction is 30 ° C. For 10 hours. During the reaction, 70% nitric acid is added via line 8, equipped with a solenoid valve connected to glass electrode 7, to maintain the pH of the catalyst solution at 0 + 0.1. The resulting gas was analyzed by gas chromatography in a collection bag. The result is as follows. 2.30 mol (119.6 g) of dicyne 0.10 mol (2.7 g) unreacted, 0.18 mol (5.8%) oxygen, CO _2, etc .: 0.10 mol, 0.11 mol (5.1 g) of nitrogen dioxide, the conversion rate of % Of cleared converted) is 98% and the yield of dicyan (% of dicyan obtained relative to the theoretical amount) is 92%. The concentration of dicyan in the collected gas was 82% and nitrogen dioxide was 4%. 7 ml of 70% nitric acid was added for 10 hours to adjust the pH of the catalyst solution.

Example 2

The reaction was carried out in the same manner as in Example 1, by changing the reaction temperature (20, 30, or 60 ° C), and the pH (-0.5, or 1.5) concentration of copper nitrate solution (0.5, 1.5, or 3.0 mol / l) as shown in Table 3. It was carried out for 10 hours. The results are shown in Table 3.

TABLE 3

Example 3

A similar process as in Example 1 or by replacing with 0.67 mol / hour of air instead of 0.14 mol / hour of oxygen. The collected gas was 2.29 mol (119.0 g) of dicyne, 0.19 mol (2.7 g) of unreacted cyanide, 0.20 mol (6.2 g) of oxygen, 5.3 mol (148.0 g) of nitrogen, 0.11 mol of carbon dioxide, 0.19 mol (8.74 g of nitrogen dioxide). ), The conversion of liquidation is 98% and the yield of dicyne is 92%.

The concentration of dicyan in the collected gas is 28% and the concentration of nitrogen dioxide is 2.3%. 12 ml of 70% nitric acid was consumed for 10 hours to adjust the pH of the catalyst solution.

Example 4

Only reactor I in the figure was used. 250 ml of mixed catalyst solution containing 2 mol of calcium nitrate and 0.5 mol of copper nitrate per liter of water in a 500 ml separation flask (reactor 1) was charged at a rate of 150 ml / min via packed column 2 (30 mmφ × 600 mm) by metering pump 3 Circulated. Cyanide and oxygen were introduced into Reactor 1 at a rate of 0.8 mol / hour and 0.22 mol / hour, respectively (the amount of oxygen was 1.1 times the theoretical amount) and reacted at 45 ° C. for 20 hours. The gas produced is discharged from packed column 2 and passes through control cokes 9 and 9 'to collection bags 10 and 10'. The pH of the catalyst solution mixed during the reaction was maintained at 0.5 by adding 70% nitric acid to line 8 with the solenoid valve connected to the glass electrode 7. The collected gas was chemically analyzed by gas chromatography. The results were as follows: conversion of clearing: 97%, yield of dicyan 91%, concentration of dicyan in collected gas 77%, nitrogen oxide 5.5% 0.075 mol / h of 70% nitric acid was used to adjust the pH of the catalyst solution. .

Example 5

The apparatus in the figure was used. Reactors 1 and 1 'were each used with 500 ml separation flask. Packed columns 2 and 2 'were each 30 mm in diameter and 600 mm in length. Each reactor 1 and 1 'contains 250 ml of a mixed catalyst solution containing 0.5 mol of copper nitrate and 2 mol of calcium nitrate per liter of water, and the metering pumps 3 and 3' at 150 ml / min. Purified. At the same time the catalyst solution in reactors 1 and 1 'was circulated at a rate of 200 ml / hour with a pump 4 between the two reactors. The reaction was carried out at 45 ° C. for 400 hours at a rate of 0.8 mol / hour on the line 5 and oxygen at a rate of 0.22 mol / hour on the line 6 (1.1 times the theoretical amount). . During the reaction, the pH of the catalyst solution in reactor 1 was maintained at 0.5 by adding 70% nitric acid through line 8 with a solenoid valve connected to glass electrode 7. The generated gas was collected in collection bags 10 and 10 'and analyzed by gas chromatography. The analysis results are as follows: conversion of cyanide, 97%, yield of dicyan 91%, concentration of dicyan in collected gas 82% concentration of acid nitrogen 1.1%.

No precipitation, such as oxamide, occurred. 0.035 mol / hour of 70% nitric acid was consumed to adjust the pH of the catalyst solution. The pH of the catalyst solution in the reactor port II was -0.8.

Example 6

Using a process similar to Example 5 and as described in Table 4, the reaction was carried out for 400 hours by changing the reaction temperature (20, 45 or 60 ℃) and the type and concentration of nitrate added and the oxidizing agent. The results are shown in Table 4. In Table 4, Experiment No. 1 is the result of Example 5. Experiments 11 and 12 used only copper nitrate for comparison.

There was no precipitation of oxamide in all reactions.

TABLE 4

Claims (1)

Process for producing cyanide characterized in that cyanide is reacted with oxygen or an oxygen-containing inert gas at pH-0.5 to 1.5 in an aqueous copper nitrate solution or an aqueous solution of copper nitrate containing at least one alkali metal, alkaline earth metal or nitrate of aluminum .

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