JPS6050726B2 - Production method of cyanogen chloride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing cyanogen chloride from hydrogen cyanide (cyanic acid) and chlorine in an aqueous medium.

The use of hydrocyanic acid and chlorine is a method often used to produce cyanogen chloride, which has the formula (1) ■ HCN+Cl2
→Proceed according to ClCNfHCl (1). The reaction can be carried out in the gas phase (see DE 21 54 721), in the condensed phase (see US Pat. No. 3,666,427) or in a liquid. The liquid used is an organic medium (see German Patent Application No. 1801311) or water. The reaction is advantageously carried out in an aqueous medium, since it can be carried out at or near normal temperature and, moreover, requires the use of relatively expensive organic liquids, which are technically more difficult to handle than water. This is because there is no.

The production of cyanogen chloride in aqueous media is described, for example, in West German Patent No. 827,358 or in US Pat. No. 3,197,27.
It is described in the specification of No. 3.

In principle, hydrogen cyanide (as gas, liquid, aqueous solution or made in situ from cyanide and acid) is supplied in water or in dilute hydrochloric acid. Then chlorine gas is supplied. The reaction proceeds according to Equation 1, and the resulting hydrogen chloride dissolves in the aqueous medium to form hydrochloric acid. The production of cyanogen chloride is preferably carried out in an aqueous medium, the cyanogen chloride formed undergoing side reactions with increasing temperatures and/or simultaneously increasing concentrations of hydrochloric acid formed, namely elimination of chlorine and saponification of the nitrile groups. This ultimately results in the formation of ammonium chloride: C
lCN+2H20-+CO2+NH4Ce (2) Hydrogen cyanide contained in the reaction medium is also saponified by aqueous hydrochloric acid with a similar reaction rate and a similar dependence of the rate on temperature and hydrogen ion activity: HCN+2H20+HC
e-) HCOOH + NH4ce (3) The two reactions imply not only a reduction in yield, but also a risk of the formation of explosive nitrogen chloride under certain conditions: NH4Ce + 3Ce2-Nc
e3+4Hc' (4) Therefore, the production of ammonium chloride must be suppressed as much as possible.

The object of the present invention is to suppress hydrolysis by reducing the reaction space and thus improving the space-time yield of cyanogen chloride.

It has now been found that the space-time yield can be significantly improved in constant-volume cyanogen chloride reactions if, by the use of pressure, the entire amount of chlorine present in the reaction medium, which is present in the reaction proceeding in an aqueous medium, is completely dissolved. did.

In a mixed phase, that is, gaseous and liquid phase, and in large quantities. It has been found that for the previously known process, which operates with poor space-time yields in the presence of water, only dissolved chlorine reacts with hydrogen cyanide to form cyanogen chloride. Advantageously, the pressure is chosen so high that the cyanogen chloride formed is also in solution, so that it is operated in a homogeneous liquid phase.

In this case, it is possible to operate under pressure in the entire system or only in the reactor. Pressure is 1.5×1Cf'~16×1σ
Pal preferably uses 2×1CP to 4×1σPa. The pressure used in each case depends on the desired amount of cyanogen chloride or the desired concentration of hydrochloric acid produced at the same time. It has been found that as the pressure increases, a large amount of chlorine and hydrogen cyanide reacts per unit volume of water. In other words, a large amount of cyanogen chloride and at the same time a high concentration of hydrochloric acid are produced. The amount of water is selected to be sufficient to dissolve the chlorine and any cyanogen chloride formed at the temperature and pressure applied.

This can be determined by simple manipulation experiments. Instead of water, aqueous hydrochloric acid (such as occurs in circulation) can also be used. The invention therefore operates at high chlorine and cyanogen chloride concentrations in the aqueous medium.

For example, it is possible to operate with a cyanogen chloride concentration of more than 100 q cyanogen chloride per e of aqueous medium. In the past, only about 30 y of cyanogen chloride per 1' of aqueous medium was usual. However, high concentrations of cyanogen chloride have heretofore been consciously avoided, as the industry believed that this would accelerate the hydrolysis reactions according to Equations 2 and 3.

However, in contrast to this idea, it has become clear that if the reaction is allowed to proceed under the above-mentioned pressure, hydrolysis is not only not accelerated but also significantly reduced.

The reason for this is the extremely short residence time of the reaction mixture in the reactor, which time is so shortened that it is even possible to use higher temperatures than hitherto. Temperatures up to the boiling point of water have been shown to be possible, but temperatures up to about 70'C can be safely used.

The lower limit of the temperature range is the boiling temperature of cyanogen chloride, and the preferred temperature range is 20-60°C. Previously, the reaction section was operated only at approximately 30°C, with the temperature being kept low, for example by direct water supply (US Pat. No. 31,972).
(See specification No. 73). The high temperature in the process of the invention saves cooling energy for the solution carried in circulation, since the heat of reaction can be derived from a higher temperature level. It is therefore possible to use coolers with warmer cooling water or smaller cooling surfaces than before. The temperature of the part stream (or the total liquid volume in the case of simple flow-down) of the circulating solution to be removed is also higher than in the pressureless process, so that the temperature of the part stream for the recovery of cyanogen chloride and hydrogen cyanide is also higher. Less heating energy is required for boiling.

The hydrochloric acid resulting as the second end product can also be obtained in a more concentrated form than before. This hydrochloric acid is therefore more suitable for post-treatment than extremely dilute hydrochloric acid.

That is, according to the method of the present invention, it is possible to obtain, for example, 25% by weight monohydrochloric acid. For example, it is advantageous to operate at a pressure of 2.5.times.10@5 Pa and a temperature of 55.degree. C., obtaining 15% by weight of hydrochloric acid.

The raw materials hydrogen cyanide and chlorine can be used in gaseous or liquid form, but are preferably in liquid form. Hydrogen cyanide can also be used as a 2% by volume aqueous solution or as liberated from cyanide.

The process is carried out using stoichiometric amounts of the reactants, with only a slight excess of hydrogen cyanide being charged at the beginning, preferably from 0.1 to about 0.5% by weight or more, based on the aqueous medium. (see West German Patent No. 827,358 or US Pat. No. 2,672,398). The stoichiometric amounts of chlorine and hydrocyanic acid supplied during the process react virtually quantitatively in solution. Therefore, it is not necessary to have a high concentration of hydrogen cyanide in the aqueous solution to obtain cyanogen chloride gas that does not contain excess chlorine, and it is necessary to use an amount of chlorine in excess of the stoichiometric amount to obtain cyanogen chloride gas that does not actually contain hydrogen cyanide. is not necessary either. This is the case when the known low hydrogen cyanide concentration in the aqueous medium is to be maintained, as mentioned above. This also applies. If, however, the reaction according to equation 1 shifts completely to the right at correspondingly high pressures, cyanogen chloride is formed which does not contain any chlorine gas, as is necessary, for example, with regard to the storage capacity of cyanogen chloride in cylinders.

It is also possible to adjust the pressure in the reaction chamber slightly lower than mentioned above.

At this low pressure, the reaction does not reach 100% conversion. When using liquefied chlorine, it is advantageous to maintain a pressure corresponding to the vapor pressure of the chlorine, for example 9 bar, at least at least at the inlet of the chlorine to the chlorination process during the chlorination process.

This avoids sudden pressure drops with the known aftereffects of undesired gas outflow. The direct use of liquid chlorine in the cyanogen chloride process is made possible by pressure chlorination without technical difficulties and is therefore an element of the invention.
In the industrial implementation of the production of cyanogen chloride, an aqueous reaction medium is added to the apparatus, as was also customary in the conventional processes.
It can be conducted several times in degrees or cycles. The reaction is carried out in conventional chilled or uncooled reaction tubes. The pressure on the cyanogen chloride production unit is partially reduced by the subsequent post-reactions which proceed with reduced volume, for example 3CeCNd(
CeCN)3 (5) can be used to facilitate trimerization of cyanuric chloride to cyanuric chloride via activated carbon.

Another embodiment according to the invention is to release the pressure through a suitable throttling mechanism in the cyanogen chloride production equipment.

The present invention will now be described in detail with reference to FIGS. 1 and 2 of the accompanying drawings.

Alternatively, aqueous hydrochloric acid is fed together with hydrocyanic acid via line 1 by means of pump b to cooling device a (see FIG. 1), the given pressure being maintained by control valve c.

Chlorine enters via conduit 2.

The reaction according to Equation 1 is completed in the cooling device.

The pressure in the cooling device can be adjusted so that the chlorine supplied or the cyanogen chloride produced also dissolves in the hydrochloric acid. After the pressure-holding valve c, the solution is depressurized and passes via line 3 into a subseparator d, during which phase separation takes place with subsequent cooling.

The liquid phase returns to pump b via conduits 4a and 4b or flows directly to column f via conduit 5. The liberated gas enters the washing column e via line 6 and is washed there in a known manner with water supplied via line 7a.

In the washing tower, washing water circulates A, c, d, b or flows down A, c.
. The amount of hydrocyanic acid required for the formation of cyanogen chloride according to equation 1 is added to the dilute water stream entering in line 7a and leaving column e via line 7b as described above in line 8.
Supply via.

Flow A, c, d or A, c with an amount of hydrochloric acid corresponding to the dilution water.
, d, b, and a, and the dissolved gas is taken out from conduit 5.
in a column f equipped with a heating device g in a known manner. This gas is supplied to the process via conduit 9. 11
and 12 represents the coolant inlet and outlet.

The so-called "internally cooled chlorination" can be carried out using a fluid cooling system (see FIG. 1) or, however, in a thin film cooling system.

The advantage of this method of operation is that the heat of reaction can be derived at the generating station and from the highest possible temperature level.

This method of operation is advantageously applied in places where relatively hot cooling water has to be used. After the pressure of the flowing solution is released, the temperature decreases again. FIG. 2 shows a second embodiment of the method of the invention.

Water or aqueous hydrochloric acid is fed together with hydrocyanic acid via line 8 via line 1 by means of pump b to pressure line a1, the given pressure being maintained by control valve c. The reaction according to equation 1 is completed in pressure tube a1. The pressure can be adjusted so that the chlorine supplied and/or the cyanogen chloride produced dissolves in the hydrochloric acid. After the pressure-holding valve c, the solution is depressurized and passed via line 3 and possibly an intermediate separator to the cooler A.
2, during which phase separation occurs. The liquid phase is either cooled and returned to pump b via line 4 or sent without cooling via line 5 to a degassing column (not shown). The degassing column corresponds to column f in FIG. The liberated gas exits via conduit 10 as in FIG.

Water adjustment is also the same as in FIG. The advantage of this method of operation is that the residence time of the molten cyanogen chloride at elevated temperatures is even shorter. Moreover, there is no need to design the cooling device to be pressure resistant, which allows for greater selectivity of materials.
Next, the present invention will be explained in detail with reference to examples. Example 1 (no pressure) Hydrocyanic acid and chlorine were cooled by direct current flow together with aqueous hydrochloric acid and then introduced into a group of tubes.

HCNO. 45k9lhl chlorine 1.2k91h and 10
Hydrocyanic acid reacted quantitatively at 20° C. at a flow rate of 60 e1 h of monoaqueous hydrochloric acid (wt%). The concentration of hydrolysis products in the form of NH4Ce in hydrochloric acid was 0.09% by weight. Therefore, 0.05 kg of ammonium chloride is produced per hour, which is 11 kg of ammonium chloride per 100 kg of hydrogen cyanide.
It is. Example 2 Circulating flow of 15% by weight monohydrochloric acid containing hydrocyanic acid at 9.5 i/h with an effective width of 80T! It was connected to the Un tube and chlorine was supplied in parallel flow.

The stoichiometric amounts of chlorine and hydrocyanic acid were gradually increased in equal proportions and the mixture was separated into gas and liquid via a reaction tube.
0.3×1 (1f'Pa, l.5×1
(When the overpressure of 11'Pa and 2.0 x 10'Pa is maintained by the throttling mechanism, hydrocyanic acid is 39k91h and 80k91h.
h and 112 kg1h could be reacted. Therefore, there is a slight damming pressure (4) on the subsequent equipment. 3×1σP
Changing from a) to an overpressure of 2×10'Pa enabled a three times higher throughput. CeCN produced in this way
- It was advantageous for the gas to contain a free chlorine content of less than 0.1%. Therefore, the conversion of chlorine was practically 100% and the hydrocyanic acid was reacted quantitatively. The temperature is 45
It was warm at ℃. The hydrolysis product from cyanogen chloride is NH4CeO. O2% was observed. NH4Cfl. per hour. 9kg is produced, which is about 5k9, 2.5kg of Nll4Cf per 100kg of hydrogen cyanide.
It is 2 kg.

Example 3 Hydrochloric acid containing hydrocyanic acid (Example 2)
) was reacted with chlorine as described in .

The pressure applied to the reaction tube was maintained at 2×1σPa. When passed through 20% by weight of diluted hydrochloric acid 7.5, 9.5, 11.3d1h, hydrocyanic acid 103kgIh, 112kgIh, 144k9
1 h reacted.

The cyanogen chloride was chlorine-free and the conversion was quantitative in nature. Example 4 A large test was carried out with a work load of 580 k91 h of hydrocyanic acid under pressure (2.4 x 1 σPa) and cooling.

At this time, the temperature of the hydrochloric acid was 37C, and the pressure was released to further increase the temperature to 6.
We were able to lower the temperature by 5℃. The acid is NH4CeO. Ol
It contained 6%. Cyanogen chloride contained no free chlorine. The hydrochloric acid concentration was 1% by volume. Example 5 In a test similar to Example 4, operation was carried out at a hydrochloric acid concentration of 15% by weight and a temperature of 50° C., with the hydrochloric acid being circulated and
Only 0% was continuously replaced with fresh water.

Mr. N's Ce concentration was 0.01 to 0.03%. Example 6
To produce 1 kgIh of cyanogen chloride gas, chlorine and hydrocyanic acid were metered in stoichiometric proportions of 2.5×1 (f'Pa) to 9e1h of water at 20°C.

The temperature in the pressure tube rose to 100°C. CeCN escaped after the pressure was released to normal pressure, while the obtained hydrochloric acid of slightly less than 7% was supplied for detoxification. The feed water was used to wash and simultaneously cool the steam-containing C'CN produced.

[Brief explanation of drawings]

1 and 2 are flow sheets for carrying out the method of the present invention. a...Cooling device, a1...Pressure pipe, A2...Cooling device, b...Pump, c...Pressure holding valve, d...
Separation device, e... washing tower.

Claims (1)

[Claims] 1. A process for producing cyanogen chloride from hydrocyanic acid and chlorine in an aqueous medium, characterized in that the entire amount of chlorine present in the reaction medium is completely dissolved by the use of pressure. . 2. The method for producing cyanogen chloride according to claim 1, which uses a pressure of 1.5 x 10^5 to 16 x 10^5 pa. 3. A method for producing cyanogen chloride according to claim 1 or 2, wherein the pressure reaction is carried out in a heat exchanger. 4 Claim 1 operating at a temperature of 12 to 100°C
A method for producing cyanogen chloride according to any one of Items 3 to 3. 5. A method for producing cyanogen chloride according to any one of claims 1 to 4, wherein the chlorine used is supplied in liquid form.