DE2026671C - Process for the production of 1,1,1-trichloroethane by photochlorination of 1,1-dichloroethane - Google Patents

Description

liquid directly into the photoreactors The chlorination of 1,1-dichloroethane to 1,1,1-

sprays, trichloroethane is the last stage of one of several

(2) the process consisting of the respective photoreactors grain steps for the representation of Mende gaseous reaction mixture in 1,1,1-trichloroethane, the formula-based z. B. the following between the reactors arranged dimensions can run:

Stage I: CH ₂ Cl - CH ₂ CI _{QHa =} ^ ₊

Grade II: CHCl = CHj + HCl> CHClj-CH ₃

Stage HI: CHCI ₂ - CH ₃ + Cl ₂ > CCI ₃ -CH ₃ + HCl

The III. Stage is preferably in the gas phase 40 this process is only about per photoreactor

using high-energy rays through 1 t / month 1,1,1-trichloroethane. To the achievement of a

performed (see French patent specification 1 436 453). In order to increase the system, example 2 of this

such a procedure, the yields are higher, each new photoreactors with a patent

than when working in the liquid phase. Output of 1 t / month each switched on in parallel

The known processes of gas-phase chlorination 45 are used. According to Example 2, this is about 60 t / month

from 1,1-dichloroethane to 1,1,1-trichloroethane, 1,1,1-trichloroethane have already required 32 photoreactors

however, disadvantages that their transmission in the major.

affect the technical scale. In another procedure (French patent

Since the chlorination reaction is strongly exothermic and writing 1 436 453) the disadvantages mentioned are

at temperatures above 250 "C intensified formation 50 bypassed that the heat of reaction through

of more highly chlorinated products and also an injection of liquid 1,1-dichloroethane into the

If the chlorinated ethane decomposes, it must be removed from the photoreactor.

Use of gas-phase chlorination the reaction The heating carried out in a laboratory apparatus is dissipated as far as possible. However, this search does not reveal the chlorine conversion and this is done in accordance with the French 55 capacity per reactor method. Furthermore, by the fact that the reaction rate in the process of this patent is _{cooled by a heat exchange surface for about 20 ° / 0} , by-products with higher chlorine levels arise. Since the 1,1,1-trichloroethane isomeric and 1,1,2-trichloroethane byproduct formed as a usable surface, 1,1,2-trichloroethane, is used as the cooling liquid for this heat exchange. It is obvious that the cooling effect has the same degree of chlorination; the heat exchange surface with increasing reactor throughput can only be tetra- and pentachloroethanes. This knife keeps getting worse. are in contrast to 1,1,2-trichloroethane

Furthermore, in the method according to this, it appears practically worthless.

Patent specification disadvantageous from the fact that the chlorination has a disadvantageous effect in the process of the French

leaving hydrogen chloride still 2 to 4% of the French patent 1436 453 also still from that

contains set chlorine; this means that less one is the radiation source when transmitting the

HCI is free, so that after stage II, the yield of the process on an industrial scale is not in the

entire process is reduced. The discharge can be arranged inside the reactor. Due to the

3 _ ^ ₁ a

thermal instability of 1,1,1-trichloroethane would in den AbjdjjdgJ ^ finJrtene

In such a case the hot surface of the a «s Je» ναrai «^ _the j _{R ktor}

Cover UV lamps with a layer of soot, which after ^^^ Scai ^ ca and cooled R ^ ions-

short period of operation of the reactor the effective * ™™ ^ _o ^K _KUgsweise be doing d.eKuhlgase

Light deny entry into the reaction space 5 ° ^^ ^ _bs ^g _chreckt ürme ^ f ^ Zf ^ ti ^ l

has now been a process for the production of
by photochlorination of a
_JÜCl ^ .. u _M > is of 1,1-dichloroethane in the
found, which is characterized by io

the

aaaa: a »^ ^e = ^l5

aaaa: a »^ = SSSSStsÄÄÄ ΐ

carries out, whereby the temperature of the mixture of CMor and. _Mo | verhHtn.s vorwendeten coolant adjusts that the tem- neither initiated advise in r orae. The nature of the cooling jacket mixed under the respective, Β ™haben ^{τ {ηι} Ζ. ™ _η °? ⁿ ™ L partially in liquid Sltempcralur (boiling point of U-dich.or- _ao dicyan £ nn J ^^ «£ photoreactor athansbis ^ CHegt.undwobe.man SS ^^

a) either the entire U-D chlor-

b) only a part of the 1,1-Dwhlor-guided _{tour used} unhealthily individual photo-

ethane head of the said Destinations- _{The reaction} ture in the ^{e 'n'} ™ ^s _DicWor.

column and the rest of the liquid unm.tiel- _{reactors is Z9lisaKn} the boiling point of the wc

sprayed bar into the photoreactors, _{ethans and} 220 ⁰ C, preferably between

^{(2) the 2} ^, ^ the SfraK- effective _{for the} photochlorination coming from the respective photoreactors

UCN gaseous reaction mixture in between to _{take advantage of} that in StiahlenquelIe must

_Quenching towers arranged in reactors in 35 ^ g P _{k | ore} "angeor dnet ^ ^β " _ββ \ ^ £

Countercurrent with condensed _technical scale have shown that the

setzingsmischung under material and Warmeaus- gjj "^ _{from unge-cooled} UV lamps. info ge de

cools exchange and instability of the 1,1 ^ - ^Tric J ^ll ° ^^ f _t ^{n S} * _wi th a soot

J ^^ f _tmi t one

(3) the reaction mixture condenses after leaving the 4 ° f ^^^^ Tm'LenV "um ^ er Vhotoreactors let / th reactor, then through ™ ^ £ UV lamps could only then long countercurrent 1,1-dichloroate vapor from ^^ _en ^U _au, are _ese Tzt as according vorResten of chlorine and hydrogen chloride liberated in tmbszeUen ^ ag _{u with EMCM Lich,} -this column 1.1 Dichlorathar, 1,1,1-tri- ^ f ^ i ^ ^ Kühf surrounded ssermantel were chloroethane and higher Chlorierungspro- 45 ~ ³ ^ _{the Strah} ienquelle is separated by distillation Dukten that still unver- _n. ^{A 'S} _n ""was'er in question, but also all other needed 1,1-dichloroethane in vapor form in de ^^^ "ο ^ ώβη. provided that such light-photo-chlorination returns and not dec preserved from the ER tekannten KuB g ^ ^^ raw ground product is 1,1.1-Tnchlor- ^ ⁸ ^ ⁵¹ ^ 'n _{gases could} in principle ethane as a coolant is separated as final product. be used. _ and arrangement

With the help of this photochlorination process it becomes ^ J ^^ to a

possible, the mentioned disadvantages of the known ver ■ pnotorea ^^ _{but h}

were able to exclude walking and a quanU- ^^ ₍ ^ _to use uncooled

to achieve a relative conversion of the chlorine (stage III), 55 a ^ im g _{runtime def} photoreac-

without mentioning more highly chlorinated by-products> -, ^ "^ yi ,, cleaning of the lamp surface

worth a lot. On the one hand, this will be fatal without the above

obtained in that "in the present invention ma, el ^^^" ,,, ^^ turnover of chlorine, "t it used to be cooled UV lamps _ie inside JJGJ ^ J _pholoreakt Oren leaving Ch order reactors are arranged" «« srstoff further processed directly, for. example, for one other hand, causes the series connection ™ ^st ° R ure _"to! ^. Dichioräthan

, 6 _{5 of} an excess of U-dichloroethane | "good ⁵ A ... U -....".> W3 "ft contains the rhotoreactor after the chlorination, which enables it to leave the photoreactor
Gases are chlorine-free.

which must be returned to the photochlorination. Before the repatriation is therefore a good separation of 1,1-dichloroethane from 1,1,1-trichloroethane necessary because otherwise from the 1,1,1-trichloroethane fed into the photochlorination Tetra- and pentachloroethanes were created. The economic separation of 1,1-dichloroethane in a distillation column and its return from this column to the chlorination process achieved by the present process in that the photoreactors are directly connected to the separating column connected and fed from this directly with vaporous 1,1-dichloroethane. The setting a constant amount of 1,1-dichloroethane vapor for the photochlorination is expediently carried out via a partial capacitor, which is located between Distillation column and photoreactor is located. The fresh 1,1-dichloroethane fed to the overall process is fed to the top of the same distillation column in which the separation of 1,1-dichloroethane of 1,1,1 -Trichloräthan and the higher chlorination products takes place and generates there the necessary return.

The reaction mixture fed to the distillation column from 1,1-dichloroethane, 1,1,1-trichloroethane and higher radiation products must be free of chlorine and hydrogen chloride, as these would lead to corrosion in the downstream equipment. In order to achieve this, according to the present invention, the chlorination products are carried out before they enter the separating column arrive in a tower charged with random packings or floors through countercurrent flows 1,1-dichloroate vapor of chlorine and hydrogen chloride freed.

Using the sketch, the method according to the present invention is described below (dashed lines Lines mean gas or steam lines, solid lines mean liquid lines). 1,1-dichloroethane is added to the top of a distillation column 2 via 1. The vaporous one 1,1-dichloroethane enters a partial condenser 3. This enables the variable cooling effect it is necessary to supply a constant amount of 1,1-dichloroate vapor to the photoreactor 8 via line 4. The condensed Excess is returned to column 2 via 5. In a tower 11 loaded with random packings the 1,1-dichloroate hand vapors arrive before they are mixed with chlorine at 6 with the chlorination products coming from the condenser 12 via 13 and quenching tower 9 for an exchange. Chlorine and hydrogen chloride produced in particular in 9 are thereby used blown out so that the chlorination products flowing off from 11 through 7 to column 2 do not corrode in the column 2 and the partial condenser 3 can cause.

After the 1,1-dichloroate vapor has been mixed with chlorine at 6, the reactants enter the photoreactor 8. This has a volume of 0.25 m ³ and is equipped with a 2 kW lamp 18 which is surrounded by a coolant 14. If necessary, some of the freshly used 1,1-dichloroethane can be fed directly to the photoreactors via a line 15 and sprayed there. After the first reactor 8, the gaseous chlorination products reach the quenching tower 9. Here they come to exchange heat and substances with the cold, condensable reaction products flowing back from the condenser 12 via 13. The gases cooled in 9 then enter the second photo reactor 10, which is analogous to reactor 8. In the condenser 12, with the exception of hydrogen chloride 19, all chlorination products are liquefied. These pass through line 13, quenching tower 9, blow-out tower 11 and line 7 to column 2. In this column the unreacted 1,1-dichloroethane is returned to the process in vapor form overhead. All liquid chlorination products leave the bottom of column 2 via line 16 for the final distillation.

example 1

(The stated amounts in kg are throughputs / hour.) At 1 84.04 kg of 1,1-dichloroethane are pumped to the top of column 2. The circulation evaporator 17 of this distillation is fed so much heating steam that 252 kg of 1,1-dichloroethane leave the partial condenser 3 in vapor form and thus enter the photochlorination. 60.5 kg of chlorine are mixed into this 1,1-dichloroethane vapor at 6. This corresponds approximately to a molar ratio of 1,1-dichloroethane to chlorine = 3: 1. The temperature in the first photoreactor rises rapidly to 170 ^° C. The temperature of the water serving as cooling liquid for the UV lamp in the cooling jacket 14 is 16 ^° C. at the inlet and 42 ^° C. at the outlet.

After leaving the first photoreactor, the gas contains only 6 kg of chlorine, ie 90% of the chlorine has already reacted in the first reactor. The 170 "C hot gases then enter the quenching tower 9, where they are cooled to 90" C by counter-flowing condensate. The temperature rise in the second photo-reactor 10 is 6O ⁰ C. With 150 ° C reach the vapors in the condenser 12. The don escaping hydrogen chloride is chlorine-free. The distillation column 2 flows in via 7,281 kg of chlorination products, of which the unconverted 1,1-dichloroethane is returned to the photochlorination via the top of column 2. 113.3 kg are collected from the bottom of column 2.

Composition of the bottom product:

79.5 percent by weight 1,1,1-trichloroethane, 17.0 percent by weight 1,1,2-trichloroethane 3.5 weight percent higher chlorinated, predominantly! Tetra- and pentachloroethanes

The output of the apparatus described with only two photoreactors is 90 kg / h of 1,1,1-Trichloi ethane. With continuous operation, it was in operation for 14 months.

The same system had to be used approximately every 4 weeks when using non-cooled lamps to remove the soot from the surface of the lamp.

Example 2

In the same apparatus, the amount used as described in Example 1 is retained of chlorine and 1,1-dichloroethane fed in at 1 64 kg of 1,1-D chloiäthan, while 20.04 kg of liquid 1,1-dichloroethane is fed directly to the first photoreactor 8 via line 15 and atomized there

^{A temperature of 130 °} C. is established in this reactor. After quenching, the chlorination "whose temperature ungsprodukte 9 is in prior to entering the second reactor 10 8O ⁰ C. When Verassen of the second reactor 10, the Reakionsprodukte to 125 ° C are heated. The off at 16

Pulled bottom product has the following composition:

81.5 percent by weight 1,1,1-trichloroethane 15.5 percent by weight 1,1,2-trichloroethane 3.0 percent by weight of higher chlorinated ethanes.

For this 1 sheet of drawings

209683/412

Claims (2)

1 2 shock tower in countercurrent with patent claims already: condensed uraseizungsmixture with mass and heat exchange cools and 1. Process for the preparation of 1,1,1-trichloro- (3) the reaction mixture after leaving the Ethane condensed by photochlorination of a molar over- S last reactor, then Shot of 1,1-dichloroethane in the gas phase, through counter-flowing 1,1-dichloroethane characterized in that steam of residues of chlorine and chlorine water (1) the photochlorination freed in at least two substances, in a column 1,1-dichloro series-connected photoreactors with ethane of 1,1,1-trichloroethane and the higher interior arranged UV lamps, which are surrounded by io ren chlorination products by distillation and separates from a translucent cooling jacket , the still unused 1,1-dichloro, is carried out, setting the temperature in vapor form in the photochlorination of the coolant used so that the temperature of the cooling jacket under the bottom product returns the 1,1,1-trichloroethane as from the raw material obtained respective reactor temperature {boiling point of the end product separates
1,1-dichloroethane to 220 ⁰ C) is, and where 2. The method according to claim 1, characterized geman indicates that the constant amount of a) either all of the 1,1-diene used is supplied in vapor form to the photochlorination chloroethane below the head of the 1,1-dichloroethane below by means of a partial condenser (3) said distillation column »0 sator regulates. and from this column from the first
Photoreactor supplies gaseous or b) only part of the 1,1-di- chloräthans the head of the named Distillation column feeds and the remainder 25