DE1667779A1 - Process and device for the continuous production of cyanogen chloride from hydrocyanic acid and chlorine - Google Patents

Description

Patent attorneys

Munich 2, Bräuhaussfrafje 4 / I1I

Process and device for the continuous production of cyanogen chloride from hydrocyanic acid and chlorine

The invention relates to a method and a device for the continuous production of cyanogen chloride, in particular in the liquid phase, from hydrocyanic acid and chlorine in a reactor column with external cooling, using a corresponding Inlet arrangement conducts finely divided gaseous chlorine into the reactor column -and in the presence of concentrated Hydrochloric acid works, which according to the previous state of the art did not appear to be feasible.

Cyanogen chloride is a valuable intermediate for the production of cyanuric chloride, which itself is an intermediate for the manufacture of numerous products such as pharmaceuticals, herbicides, dyes, brighteners, synthetic resins, plastics, Rubber, explosives, etc. is used.

A currently used fabrication method is shown in U.S. Patent No. 3,197,273 (Elwood Bruce Trickey) for the production of cyanogen chloride for the purpose of converting it into cyanuric chloride. In this process, chlorine and Hydrocyanic acid passed into the reactor part of a packed column, which consists of a fractionation part, a gas scrubber part, a

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Reactor part and a gas separation part. At the upper end of the gas scrubber part, water is introduced, the sump at the The lower end of the gas separation part is heated with steam. By choosing the right load with the various Reaction components, the temperature in the column can be controlled so that gaseous cyanogen chloride can be withdrawn in high yield at the top of the column.

That described in the patent mentioned above Although the process is entirely satisfactory with regard to the quality and quantity of the desired process product, however, a dilute, i.e. 2-3% aqueous hydrochloric acid obtained. This by-product can be disposed of relatively easily, if only in small amounts Quantities accumulate; in practice, however, the quantities produced are so significant that they cannot be used without Violation of the water protection regulations simply into the wastewater could be directed. On the other hand, the diluted hydrochloric acid would be concentrated so that it can be used again or to be able to sell is not economically feasible, since the costs would be greater than the market price for technically pure concentrated hydrochloric acid.

Solving the problem of reusing or selling hydrochloric acid as a by-product by that the production of the cyanogen chloride takes place under conditions which 'lead directly to a higher concentrated hydrochloric acid, again did not seem feasible until now, namely because of the economically unacceptable losses of the cyanogen chloride obtained as the reaction product by hydrolysis or

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in the sump phase together with the hydrochloric acid produced there. With a superior technical manufacturing process for cyanogen chloride, hydrolysis losses must therefore be kept low, or the losses of cyanogen chloride must be practically excluded will. Another important aspect concerns the suppression of a possible side reaction to the very explosive nitrogen trichloride, its formation is undesirable not only because of the loss in yield of the main product, but also for safety reasons.

The present invention relates to a method and an apparatus for solving the above mentioned Problems posed task and is characterized in that one is the implementation of chlorine with hydrocyanic acid for the production of cyanogen chloride in a combined reactor-gas scrubber column executes, and thereby in the liquid Phase in the reactor part of the column introduces hydrocyanic acid from above and from below through a corresponding introduction arrangement of finely distributed chlorine gas. The ones released in the liquid reaction medium in the column Heat of reaction is with the help of a liquid circulation cooling discharged. If the reaction conditions in the column are carefully controlled, hydrolysis losses can be low A very high conversion rate to cyanogen chloride is achieved and at the same time an aqueous, approx. 20% hydrochloric acid can be obtained as a usable by-product. The present invention also enables an excellent continuous operation, with a higher throughput of the reaction ^ artner than in the usual packing-—

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columns can be achieved with smooth heat exchange.

The invention is described with reference to the accompanying drawing, wherein

1 shows a schematic view of the device for carrying out the method according to the invention, consisting of a reactor column with a liquid phase reactor and an arrangement for introducing it attached to the bottom of the reactor represents of finely divided gas.

According to a preferred embodiment, the device according to the invention consists of a combined reactor-gas scrubber column 13 with a reactor part 14, composed of at least one inner pipe 15, which extends from the charging chamber 16 to the discharge chamber 16a, the whole being surrounded by a pipe jacket 17 _/ the with The cooler 18 forms the inlet and outlet connections 20 and 21 for cooling liquid. A hydrocyanic acid inlet 22 leads into the charging chamber 16. Above the reactor part is the gas scrubber part 23, which consists of a column section with packing, and the head of which is provided with a water inlet 24 and a gas outlet 25, whereby water is introduced into the gas scrubber part 23 or the gas originating from the reactor is withdrawn from the column after passing through the gas scrubber.

With the bottom of the 'drainage chamber 16a is a hydrochloric acid drain 26 connected to a gas separator

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BATH ORIGINAL

can be concluded as described in patent application no

same filing date with the title "Process and device for separating cyanogen chloride from a cyanogen chloride synthesis Strongly acidic reaction mixture obtained from chlorine and hydrogen cyanide "is described. The reactor part 14 of the Column 13 is constructed in such a way that a flow gradient from top to bottom occurs for the liquid reaction phase. The discharge chamber 16a is provided with a chlorine inlet 27, through which chlorine gas is passed into the reactor part of the column. The chlorine inlet 27 opens into an inlet arrangement 28, through which the chlorine gas, distributed in fine bubbles, flows into the liquid phase of the reactor part 14.

During the operation of the device for carrying out the process, the reactor part of the column is constantly with filled with the liquid reaction mixture, which consists of aqueous hydrochloric acid, in the hydrocyanic acid, chlorine and cyanogen chloride are present in dissolved form or in the form of fine bubbles. The reactor part is filled with chlorine gas through the chlorine inlet 27 and fed through the hydrocyanic acid feed 22 with gaseous or liquid hydrocyanic acid. To achieve a smooth implementation from hydrogen cyanide to cyanogen chloride, there is excess chlorine used beyond the theoretically necessary amount. For gas scrubbing, water is used through the water inlet 24 at the head of the combined Reactor gas scrubber column initiated. The cooler 18 is flushed through the inlet and outlet connections 20 and 21 with a cooling liquid, e.g. with water. This coolant removes the heat of reaction from the reactor part 14 in which the reaction mainly takes place.

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The chlorine introduced through the discharge chamber 16a into the sump of the reactor part 14 is converted into very fine bubbles distributed, which rise up through the inner tube 15, so that in the ideal case, the entire liquid phase in the tube 15 with is interspersed with fine vesicles. Because of the flow gradient of the liquid phase through the reactor part, the chlorine gas flows in countercurrent to the hydrocyanic acid flowing into the hydrochloric acid solution from above. The continuous blistering fe constantly guarantees a large surface for an effective gas / liquid exchange. Simultaneously leads the fine distribution of the chlorine gas to a vigorous mixing and thus to a good heat transfer, whereby the dissipation of heat from the reactor part is promoted.

The gaseous cyanogen chloride formed flows upwards through the gas scrubber 23, in which hydrogen cyanide is still present is washed out by the trickling water. Cyanogen chloride gas and excess chlorine are withdrawn together as overhead product through the gas outlet. Aqueous, with cyanogen chloride Saturated hydrochloric acid with a very low content of hydrogen cyanide and chlorine is at the bottom of the discharge chamber 16a pumped out and passed to a separation device for separating the cyanogen chloride and chlorine contained. That through the Gas inlet arrangement 28 introduced chlorine can come from a separation plant for cyanogen chloride and chlorine, where it has been used to separate the cyanogen chloride.

The reaction temperatures in the inventive combined reactor-gas scrubber column are lower than those of the previously known method according to the above

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Patent specification. The air flowing through the radiator 18 cooling liquid is dosed, the temperatures that can be kept in the reactor section 14 between 25 and 60 ⁰ C. A further rise in temperature can be observed in the column at the point between the reactor part 14 and the gas scrubber part 23, since there the formation of cyanogen chloride also takes place to a small extent. Preferably, the reaction conditions are, however, selected so that the temperature in the lower part of the scrubber is not substantially more than 65 - 70 ⁰ C increases. The amount of heat dissipated from the reactor part 14 is generally so great that due to the heat radiation in the gas scrubber part 23 of the column and the cooling effect of the water introduced at the top of the column, the temperature in the gas scrubber part falls fairly rapidly upwards and about 25 ^° C. at the top of the column amounts to. The temperature at the top of the column should therefore not be more than 25 ^° C., because at higher temperatures the hydrogen cyanide is no longer completely washed out of the cyanogen chloride. To avoid this, the procedure initiated on top of the column wash water should have a temperature of 13 - 25 ^0C, preferably 15 - have 20 ⁰ C. Lower temperatures could lead to a liquefaction of the cyanogen chloride.

The charging of the reactor part 14 with the reaction components Hydrocyanic acid and chlorine and the gas scrubber with the washing water are controlled in such a way that the course of the reaction leads to 17-20% hydrochloric acid in the bottom product. In terms of quantity, the throughput depends mainly on the dimensions of the device, whereby temperature drops

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differ only in the washing water supplied through the gas scrubber 23 cause little impact. In practice, the reaction temperature is set with the aid of the cooling liquid, i.e. by variation controlled by temperature and flow rate of the coolant.

As a specific gas inlet arrangement 28 for finely divided chlorine gas, one of the usual arrangements that distribute a gas stream in fine bubbles and function in the strongly acidic environment of the reactor part 14 is used 'Will. In the following examples, a gas inlet glass frit was used used; however, larger dimensions will be used Columns, instead of a glass frit, have a gas inlet arrangement with a random packing of Intalox saddles or in particular Raschig rings are preferred.

The examples to illustrate the invention were carried out with a reactor of a specific size and shape. The gas scrubber part 23, which is used in practice to remove residual amounts of hydrocyanic acid, was missing to wash off the top product.

The operating data and results are listed in Table I at the end of the examples.

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Examples 1 to 5

The reactor part 14 consisted of a column 80-120 cm in height and 2 cm in diameter with a radiator jacket. The column was filled to the desired height with 20% hydrochloric acid, and a 15 sequence aqueous hydrocyanic acid solution was pumped into the column from above just below the surface of the standing liquid during the reaction. The sump outflow was matched to the hydrocyanic acid-water inflow. The feed rates for hydrocyanic acid and chlorine were chosen so that cyanogen chloride to a 20 follow hydrochloric acid is accumulated in complete reaction of the hydrocyanic acid in the bottoms. An operating time of 1 to 4 hours was necessary to achieve equilibrium conditions in the column.

In summary, based on the data for these test examples 1-5, the following can be said;

With a large excess of chlorine high, were in fact 89 - achieved 100 follow conversion rates; the hydrolysis losses were acceptable; the chlorine content in the top product was high; the gas inlet arrangement was not always fully effective; the throughput rates were generally quite low.

Examples 6 to 9

The device was the same as in Examples 1-5, but with a 2.5 cm column diameter. The level of liquid heaktionsphase in the column was increased, and in Test Examples 8 and 9, the excess chlorine was comparable

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The results of Examples 6-9 show that larger amounts of material can also be handled, and that even with a small excess of chlorine, which also contains the chlorine content reduced in the top product, good conversion rates are still achieved. It was also found that with an increased Hydrocyanic acid supply considerably lower hydrolysis losses occur; but this also increases the proportion of hydrocyanic acid in the overhead, demonstrating the practical need for a scrubber column.

Examples 10 and 11

The device was again the same as in Examples 1-5, but with a column diameter of 5 cm. Of The level of the liquid reaction phase was increased and the excess chlorine decreased.

As with Examples 6-9, the results for Examples 10 and 11 show that with larger throughputs can be operated on, and that even with a small excess of chlorine, very good conversion rates are affordable Hydrolysis losses can be achieved.

It must be mentioned that the hydrolysis losses given in Table I boil off that drawn off at the bottom Reaction mixture were determined, and that therefore these values are due to the hydrolysis of the in this mixture dissolved cyanogen chloride are excessive. In practice, however, there are only the far lower hydrolysis losses that occur in the column occur even during the reaction. So was in a side experiment to the test examples 6 and

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from samples of the bottom product the cyanogen chloride first by one hour Passing in nitrogen, driven out at room temperature and then the loss of hydrolysis is determined. The ones found in this way Values were 0.08 and 0.12%, respectively, instead of those in the table I specified values according to the boiling-out method. The partly high numerical values for the hydrolysis losses in the table I are also partly determined by the higher solubility of the cyanogen chloride and the sump phase in the lower Reaction temperatures of the process according to the invention, so that compared to previously known procedures more cyanogen chloride is dissolved in the bottom product and is hydrolyzed during boiling.

The invention was made in the context of a particular Described reactor column, but it should not be limited to such a reactor column. The present Rather, the invention also relates to other types of devices in which chlorine is introduced into a liquid reaction mixture has good gas / liquid contact with high throughput rates and good heat transfer is achieved.

The above description shows the superiority of the measures according to the invention over the prior art Technology. The form of the device according to the invention described and sketched here represents only one preferred embodiment. Deviations in shape, • construction and arrangement of parts according to the invention Apparatus are obviously possible within the scope of the present invention.

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Tabel !

test
example Columns
diameter
[cm] Gas bubbles
distribution ί chlorine
excess HCN ) throughput g / min H ₂ O Suinpfprodukt HCN - analysis % Hydro
lysenver
rush through
Boil out % Conversion
si on [be
pulled up
HCN] - 100 Head product analysis ^C1 2 CNCl. liquid
level in the
Column [cm] 1. 2.0 Well 39 0.462 ^C1 2 2.92 HCl 0.38 N -Best,
by
Boil out 4.5 97.1 100 HCN 22nd 78.0 34 2. 2.0 Well 30th O ", 508 1.70 2.81 17.4 0.29 0.35 97.9 88.5 0.03 8.0 91.1 34 -1 3.
4th 2.0
2.0 Well
Well 34
30th 0.485
0.495 1.70 2.84
2.83 19.1 1.40
0.05 0.37 6.3
4.0 88.7
99.6 92.6
97.1 0.91 41.5
24.7 55.8
74.6 31
33 09828 5. 2.0 emerged 30th 0.465 1.73
1.73 2.86 15.9
18.7 0.01 0, «6
0.30 2.6 100 86.9 2.7
0.6 26.4 73.2 : 3i outstanding 1.75 19.0 0.20 0.5 6th 2.5 emerged
outstanding 60 0.797 4.12 Neg, 0.80 31.8 67.7 54 - * 7th 2.5 emerged
outstanding 44 1.08 3.35 6.03 18.1 Neg. 0.06 0.53 0.44 35.9 63.9 54 8th. 2.5 emerged
outstanding 20th 1.17 4.10 6.66 19.4 Neg. 0.04 0.44 0.21 11.9 87.9 67 9.
10. 2.5
5.0 emerged
outstanding
'emerged
outstanding 0
5 1.17
1.19 3.65 6.60
6.58 18.3 Neg.
Neg. 0.03 0.30 1.03 4.31
5.2 96.8
94.5 67
75 η. 5.0 emerged
outstanding 5 1.64 3.10
3.25 9.06 18.3
19.4 0.01 0.031 6.3 2.92
0.31 8.06 91.6 71 4.52 18.8 0.49 0.34

Claims (3)

- 13 claims 1. Process for the continuous production of cyanogen chloride from hydrogen cyanide and chlorine in a strongly acidic liquid Reaction mixture, characterized in that the chlorine is introduced into the reaction mixture in the form of finely divided gas bubbles initiates. 2. The method according to claim 1, wherein the reaction of hydrocyanic acid and chlorine in a liquid column of the aqueous reaction mixture makes up to 20 $ hydrochloric acid contains, and from which a large part of the heat of reaction is dissipated during the reaction, characterized in that, that the chlorine is introduced into the reaction mixture from below in the form of finely divided gas bubbles. 3. Device for the continuous production of cyanogen chloride from hydrogen cyanide and chlorine, which consists of a reactor part consists of at least one column which can be filled with a reaction mixture, characterized in that that an inlet arrangement through which chlorine distributed in fine gas bubbles is introduced into the reaction mixture, is attached at the foot of this column. 109828 / H71 Blank page