DE1934856C - Continuous process for the recovery of chlorine and cyanogen chloride from the gas mixture resulting from the catalytic production of cyanogen chloride from hydrogen cyanide and chlorine and the subsequent polymerization of the cyanogen chloride to cyanuric chloride - Google Patents

Description

i 934

rkv'hlenstefF or perchlorine> len. treated, remove chlorine / u, and that the s> -. ■ η '---- de ^. ■ mi-ch, which reveals the vapors of this solvent, is treated with a second, higher-polluting un- ^ mif-ol, which the Vapors de, urasmiuels dissolves. As the second, higher boiling point, the first one to be considered is Lime He \ achk> rdien and trichlorobenzene. The application of this relatively complicated process is therefore not mottled because bel ^ n-.lich cyanogen chloride in such Î ungsmüteln in (j _Ci. '.. art v% polymerized hydrochloric Sun (, .treibt Canadian Patent ^ 4M Hi ^ P, iV ^ sation of cyanogen chloride to C \ am.rchlorid in T -'- · --lorkohlenstoff in Geeenwart -.on Chlorwasser- JX "\ n Chem. Abstr .. 61? S. 9160, WMi. is a p _u hi.K.ition K ο dama et al. refer.ert (J Soc o _r . s> n Chcm., Japan), in which it is mentioned that "ro'rated hydrocarbons w _U - chloroform. vr tetrachloroethane, in the presence of chlorine-. toff at higher temperatures e.ne Po ^1. , - tH.n of cyanogen chloride «, to the Tn and tetranerene κ si

^It has now been found, surprisingly, that the use of pentachloride as the solution _m , M for the selective separation of chlorine

1, on the one hand, and chlorine and chlorine on the other -

_au , ^ n ₁ ternary mixture of hydrogen chloride -Chlor-Ch '.-'. Aan no polymerization of the C hlorcvans en-

U and that d.eses solvents hafien still e.ne Re.he _"c" .rer valuable and essential h.gcn ^

bev - I s has the necessary higher. Boiling point (ItO C). at least

t, --htin too large quantities with the 35 »e to be generated, is em

Ga-η to go away. Hs is relative chlorfev. and the SC betneben w

_m \ -nngen amounts by chlorination s _lt | Fine,

¹ H, - .hloräthanlt firmly and can le, _t h: from the

G,. ", Are deposited.

; ,, - nsLd of the invention is therefore e, n kon, .- "uicrUches process for the recovery of Ci ,, .. _uni , cyanogen chloride from the be, the catalytic her-" oning of cyanogen chloride from hydrogen cyanide and chlorine, V: the subsequent ο chloro-.eßenden Tnmensierung of,:;. / u cyanuric chloride in the vapor phase, after condensation of the latter resulting Ciasge _{ml> l} h which consists essentially of chlorine cyanogen chloride and hydrogen chloride, by selective Xb .orption of chlorine and cyanogen chloride in.. a halogenated solvent and removal from the latter · ,, so withdrawn Ls is characterized in that the ha ", emitted * solvent pentachloroethane -.used and the solution of chlorine and cyanogen chloride formed in an absorber at 3C. to 80C is continuously fed to an evaporator and the middle of the solution from the vapors, which measures it back into the absorber «.

present in chlorine and chlordane; ^d Ji'ji ^ P ^. "^ a ZtmabcÄsc lvmdigkeit of - · '. ^'^"""'V, r chlorine per hour a Peniachlorainan-KULK. from 230 to 240 parts by weight per btunch. n <- : liv small Return quantities (concentrated losu ,,

the separation is improved. At the prJMi.l. Carrying out the procedure can be the \ ^ l -

returning solvent but net.a ^. v. ·

be higher. . ^ ₁ ,

o The separation process according to the invention ne. γ ^ on the different solubility of the r> ei u, ... production of cyanogen chloride from chlorination *, tot uuo excess chlorine or after the ^^^ j Trimerization of cyanogen chloride to> j , - resulting gases in Pentachloratnan. U ^ Mix is in one with Peniachlorathan be Absorber under stirrer, initiated, l.arx.i ^

Chlorine and cyanogen chloride in the solvent aut. W-nrt. only traces of hydrogen chloride in the solution are included in the absorber. > i vaporizer ^durtn '

outlet in such a way that ^{there is always a} _U1 r

Solution can fall into the evaporator, see the Principle of communicating Oetatie iwtr ^ Pumping into the evaporator IJic r- ^. quantities in the two vessels (absorber and ^ steam,) should be about the same but can that. cim. Vessel a little more liquid than uj. . contain. Vorzueswe.se Absiuner u damper z. B. by means of aluminum foil «ttn li ^. 3 »cut off. about the chlorination ^ doethans / u hexachloroethar. if possible / u_ above the absorber, we ^ r still open ^ ^ die (, as / ufuhr. Thermometer. Ruhrwerk unü ge.

otherwise for hintauch-He./- or ^Kuhlsyste J; ^e _{0 hs}

SC is used f ^, "ieTo

Lnteneinlauf carries a recoverable fraction erko over which em Ruckrlußkuhler is applied. the one with a cooling medium. Ns about 30 ι £ 'next is the ^ rda pfer w _r d d over «« £ _ temperature of pentachlorophenol ^ hans gheirt sungsm.tlel evaporates and, JJ ¹ _{flllßküh he} hlorcyan C-gas mixture mU located in "" «

C hlorocyanine gas gas
\ ^onoe ™ ^et \ ^ t ° 27 SS

from chlorine and ^
Hydrogen chloride and '
steam up on

ν a KuMeV des the mixture

_Well , through there

xachlorethane

Κ ^^ Ausfneryie «Sieving gases (Chl-r. Chlor ^ ™ ^ w, then in

The preferred temperature in the absorber is cyanogen chloride * about 70 ° C, while the evaporator at reflux · Aus de «?

temperature of the pentachloroethane (S.edebere.ch 159 6o (optimal up to 164 ⁰ C). With these temperature ^.% values, the best results with regard to separation ele. e ^ g ^

sharpness, quality and yields achieved. The solubility weight ^{zwlSthe a} "Feit of chlorine in Pentachlorathan at 70 C is ^<rennend% _t ^^ _t ^ _{n |} j £ g 2.3 ⁰ ₀ Z, the solubility of cyanogen chloride 8.6." _0, while 6 ₅ solvent andI the f ^ "" ¹ J ^ _un ^b _{d cyanogen} de L & Hchkeit of hydrochloric only about 0.1 * ,. (Hydrogen chloride emerse.ts ^, n Chto un >

amounts to. The return should be chosen so that «^^^^^ ^d " ^?

If possible, place a saturated solution in the absorption vessel after 24 to 48 hours.

_{on WC}

gde? Absorbers η, ο, hydrogen

£% n a Gbich-

£ ^ _ufunramins (to

5 6

The solvent losses due to the partial pressure produce economically readily usable hydrogen chloride to ^{obtain pentachloroethane (4 mm Hg at 20 °} C., 1 mm Hg.

at 0 ⁰ C) are low and after an operating The gas mixture to be separated can sometimes still

only contain 1.16 percent by weight of traces of carbon dioxide and phosgene over a period of 236 hours, solvent used; these losses can 5 which, however, are of no consequence for the feasibility of the inventive chlorination of the gaseous entrained pentagonal separation process, chlorf.thans to Hcxachloräthan in UV chlorination- The recovered practically pure chlorinated water-

rcakior can be significantly reduced (partial pressure of the substance is usable by introducing it into water Hexachloroethane at 30 ° C 0.4 mm Hg). transferred to aqueous hydrochloric acid. That on the other

The undesired chlorination of the penlachloro side resulting mixture of chlorine and cyanogen chloride in the liquid phase (as a solvent in the exhaust becomes gaseous with the starting materials of the Fabrisorber and evaporator) can be mixed and shielded the apparatus except by abrasion (hydrogen cyanide and chlorine) Before light, the cyanogen chloride and cyanuric acid can be reduced considerably by adding a little iodine to the reactor (about chloride production initiated. 0.3 g of iodine per liter of pentachloroethane). The not quite ts The nir implementation of the avoidable chlorination according to the invention to hexachloroethane, the system used in driving, for example, is enriched on hand pentachloroethane, is explained in more detail after the schematic drawing. Operating time (236 hours) 18 to 20 · /, and does not exceed Ein with one driven by the motor M any longer. Agitator and absorber equipped with a heating jacket

Comparative experiments with the non-chlorinable μ over 1 has a supply line 9 for the carbon tetrachloride to be separated because of the low gas levels and is at the bottom through a line 3 Boiling point of this solvent no fricdi- the heatable evaporator 4 connected. The protective separation of the gases and high solvent occurs from the liquid from the absorber 1 in the losses along with the polymerisation of the cyanogen chloride. damper 4 takes place through this line 3, in which

Experiments with aromatic solvents showed 45 a feed pump can be connected in between probably a good separation, but already after the absorber 1 a cooler 2 is attached, short time a complete chlorination to solid at the upper end of the outlet line 10 for Hexachlorobenzene (m.p. 227 ° C). the separated hydrogen chloride is located.

Of all the solvents searched for, one is preferably with over the evaporator 4 only pentachloroethane for economical implementation of the gas separation process. lonne 5 arranged, from which the vapors in a

The feasibility of the present invention reflux cooler will be guided. The refluxing process according to the present invention, namely the separation of solvent, runs back through line 13 and the hydrogen chloride from the other two existing coolers 2 back to absorber 1. A line dividing chlorine and cyanogen chloride by selective absorption ₃₅ connects the upper part of the reflux agent pentachloroethane, must for the expert cooler 6 with a UV chlorination reactor 7, and because of the non-occurrence of polymerisation of the latter connects the latter with the separator 8 cyanogen chloride * to form cyanuric chloride Extremely surprising (freeze trap) for the solid hexachloroethane. They apply. The invention thus overcomes a large chlorine-cyanogen chloride phase occurs through the derivation U prejudice. 40 and can from there back into the reactor for

The production of cyanogen chloride and cyanuric chloride must be derived from the literature references cited earlier be concluded that a separation of chlorine will be.

Hydrogen from mixtures of cyanogen chloride, chlorine- the following example serves to explain the

Hydrogen and chlorine by selective absorption process according to the invention: in halogenated hydrocarbons as a result of the 45

long dwell would be impossible as an example

practically quantitative polymerization of cyanogen chloride In the absorber 1 1000 parts by volume ( 1 677 parts

to cyanuric chloride and letramercm cyanogen chloride to weight) pentachloroethane and 0.3 parts by weight was expected. Filled with iodine and with the line 3 open

A trimerization of the cyanogen chloride to cyanuric so a stirrer M with about STJO revolutions per chloride during the separation of the residual gases is stirred for one minute. The pentachloroethane quantity is not desired in this way. On the one hand, the separation between absorber 1 and vaporizer 4 would be so complicated that the cyanuric chloride formed would require 592 parts by volume (992 parts by weight) and equipment in the absorber, which in view of the vaporizer 408 parts by volume (685 parts by weight) of the low expected amounts of cyanuric chloride 55 pentachloroethane condition. The following (1 to 2 ^e /, of the residual gas) are now set and maintained economically unacceptable temperatures: would be; on the other hand, when polymerizing in Kühler2, Obis S ⁰ C is ordered

liquid phase the strong tendency to form large coolers 6 '".". 30 ⁰ C

rer amounts of undesirable tetrameric cyanogen chloride absorber 1 70 ^c C

instead of cyanuric chloride. It must therefore be extracted 6 »Ventannfer 4 ". '.'. '.'. '.'. '.'. '. " 160 Ws 165 ° C for economic reasons a polymerisation of the chlorine column 5 160 to 165 ° C

cyans avoided when separating the residual gases

will. The return control in line 13 is so

According to the invention, it is made possible in a simple and simple manner that 400 parts by weight of pentatechnically easily feasible per hour are possible for the 65 chloroethane to flow back into the absorber 1. Cyanogen chloride and chlorine of the residual gases back into the circuit- Then the residual gases from the catalytic!

The course of the chlo ^ cyan production fluid and trimerization production of cyanuric chloride according to the French and at the same time practically pure, see patent specification 311400, consisting of 48.8 parts

percent by weight of hydrogen chloride, 47.5 percent by weight of chlorine and 3.7 percent by weight of cyanogen chloride by the Line 9 at a rate of 11.96 parts by weight per hour (i.e. 5.84 parts by weight Hydrogen chloride. 5.68 parts by weight of chlorine and 0.44 parts by weight of cyanogen chloride per hour) into absorber 1 initiated. The plant is operated continuously for 236 hours. The optimum in gas separation occurs after about 24 hours. The gases leaving the evaporator 4 above the cooler 6 are contaminated with entrained pentachloroethane. To separate the entrained solvent this is practically completely chlorinated in reactor 7 by UV irradiation at room temperature, and the hexachloroethane formed is deposited in the cold trap S in solid form.

After equilibrium was reached, the following yields in percent by weight were achieved:

Share of total chlorinated water

substance on exit 10 85.7 · '"

Share of total chlorine in

Exit U 98.9%,

Share of total cyanogen chloride in

Exit 11 100.0 ° /,

The composition of the escaping gases was as follows:

Exit 10 ... HCI 98.4, Cl, 1.6 · / ,;

▲ ». Enter 1! Hfl UI Cl. 81.7. CICN 7.2 ¹ V ₀ .

After 236 hours of operation, the solvent showed the following compositions (gas chromatographic Determination):

5 Pcnta-
chloroethane Hexa
chloroethane other substances In the absorber 1
In the evaporation
10 fer 4 67 ° / e
76 ° / o "° / o
20 ° / _ft 16 ° / "
4 ° / "

The numerical values given above for hydrogen chloride, chlorine and cyanogen chloride were determined analytically. The gases from line 10 were during is absorbed in water for 24 hours and the hydrochloric acid and the chlorine is then determined titrimetrically.

The gases from line 11 became aqueous Potassium iodide solution absorbed and hydrochloric acid and Chlorine determined by titration. The cyanogen chloride

ao mood was carried out by analytical determination of the

Nitrogen in the solution.

At 70 ⁰ C, the quality and yield of the separated gases is better than at 30 ° C. On the other hand, more solvent is aufchloriert to hexachloroethane is at 70 ° C.

By adding iodine as a chlorination inhibitor

and shielding the apparatus from light

the chlorination of pentachloroethane during the

first 100 hours of operation practically prevented anyone the.

1 sheet of drawings

309631V

Claims (3)

1 2 economically extremely important problem from this patent claims: residual gas mixture the volume of the main constituent part of hydrogen chloride as completely as possible and in 1. Continuous process / for return as pure and'or highly concentrated form as possible recovery of chlorine and cyanogen chloride from the hot 5 / u remove the other two constituents the kaiaK table production of cyanogen chloride from chlorine and cyanogen chloride, preferably continuously Hydrogen cyanide and chlorine and the subsequent in the cycle of the catalytic production trimerization from cyanogen chloride to cyanuric chloride driving back for cyanuric chloride; -u can. in the vapor phase - after condensation of the previous one went by one of the following methods the latter occurring gas mixture, which in: o before: essentially composed of chlorine, cyanogen chloride and chlorine:. The residual gas mixture is blown off or through hydrogen is destroyed quantitatively by selective absorption introduction into lye. In addition to the of chlorine and cyanogen chloride consists in halogenating this procedure, which is great inefficiency Solvent and removal from the latter, there is a great risk of air and sewage pollution marked that one as 15 tongue. halogenated solvent! Peniachlorethane \ er 2. The hydrogen chloride is removed by means of water turns and washed out in an absorber at 3ö to the residual gas mixture (French Pa- Solution of chlorine and cyanogen chloride formed at 80 C ( 231 189 and 1 31 \ AOOi). This method continuousILi an evaporator? ufühi: and from has the great disadvantage of being practically worthless the vapors, the solvent that accumulates in the 30 strongly diluted hydrochloric acid and the remaining Absorber flows back, condenses. Gases - chlorine and cyanogen chloride - before recirculation 2. The method according to claim 1, thereby having to be dried again in the circuit The key feature is that the pentachlo athan is saponified to the one that falls into the aqueous hydrochloric acid Iodine is added to make its chlorination difficult. more or less large proportion of the valuable chlorine 3. The method according to claim 1, characterized in that 25-cyan, the more the higher the concentration, that the tration of the waste hydrochloric acid from the distillation is chosen. For this of the pentachloroethane after the ground has condensed, it is not possible to do so on the latter Gas mixture obtained from mainly fraction of hydrogen chloride with water-based To operate chlorine and cyanogen chloride with ultraviolet light be so economical that radiates to quantitatively remove entrained pentachloroethane vapor and the unconverted cyanogen chloride chlorine to solid Hexachioräihan ζ · _, which is recovered and at the same time a technical one then usable hydrochloric acid of the country's usual concentration is deposited is obtained as a by-product. Either must concentrated aqueous hydrochloric acid or else on one 35 large part of the valuable cyanogen chloride can be dispensed with. Various processes are known, Cyanur-Fs is also known that the slightest traces Chloride in the vapor phase by trimerization of water by the mechanism of trimerization Cyanogen chloride irreversibly interfere with the catalytic route at increased temperature poisoning of the contact, so that to establish temperature. The cyanogen chloride 40 to be trimerized inevitably results in the separation with water is made from dry mixtures of hydrogen cyanide gas mixture, consisting of chlorine and cyanogen chloride, (HCN) and chlorine (CIj) also at higher temperatures before they are returned to the manufacturing process temperature obtained catalytically in the gas phase. That of a sharp and therefore time-consuming drying so formed cyanogen chloride (CICN) can be subjected to the co-formed must. Liberated hydrogen chloride and in a further opera- 45 j. The gases are by adsorption, in particular tion stage to be trimeiisiert to cyanuric chloride. Be by means of activated carbon, from the hydrogen chloride, which does not However, preference is given to direct processes, which are withheld without iso, separated (French patenting the intermediate formed from hydrogen cyanide and chlorine 1 231 189, USA.-Patent 3 338 898). It cyanogen chloride product under the direct contact is now easy to remove from admixtures subsequent trimerization to cyanuric chloride renders hydrogen chloride anhydrous or as highly concentrated (See French patents 1 231 189, 'trated hydrochloric acid to win; for this is the Rück-1311400, U.S. Patent 2,762,798). management of the residual gases absorbed by the coal in In all of these processes, ternary gas circulation is associated with difficulties that arise mixtures, which consist practically exclusively of chlorine, result from the need to manipulate Cyanogen chloride and hydrogen chloride exist. Depending on the 55 solids in a poison gas atmosphere. Also Depending on the process used, the quantities are, in this procedure, the yields of reverse ratios of these three components in gases that can be carried by residual gas. mixed considerably. Will not be used directly It is already known that mixtures of chlorine, Subsequent to the cyanogen chloride production trimeric hydrogen chloride and organic vapors , the cyanogen chloride content in the gas, in addition to chlorine from halogenated solvents, can be separated by selective hydrogen and unreacted chlorine relative absorption (Ulimann, Enzyclopadie high however the trimerization to cyanuric der teihnischen Chemie, 3rd edition, vol. 15, p. 81; chloride immediately following the formation of the German patent 1 104 517, British patent cyanogen chloride in the direct process, the residual gas is written 983 694 and U.S. Patent 2,841,243). Thus, according to the desublimation of the cyanuric 65 formed USA. Patent 2,841,243 pure chlorine mainly hydrogen chloride from chlorine and Chlorwasser- is obtained in accordance with, that a mixture material together with a little non-trimerized cyanogen chloride. of hydrogen chloride * and chlorine with a low It is therefore in all these processes the boiling halogenated solvent, such as tetra-