DE720079C - Process for the substitutional chlorination of hydrocarbons - Google Patents

Description

Process for the substitutional chlorination of hydrocarbons It is known to use fixed gaseous hydrocarbons in the dark Catalysts at elevated temperatures with chlorine with the formation of chlorine substitution products - When working in continuous operation, however, this often results in considerable Difficulties in that by separating coal or other by-products the catalysts are smeared, the inlets and outlets are clogged or the effectiveness the mixing elements is reduced. Already when the implementation participants are heated up or mixtures of these occur as a result of the frequent overheating of the heat exchangers Secondary reactions, which also give rise to undesirable deposits. It has now been found that the substitute chlorination of hydrocarbons largely avoid these difficulties at high temperatures in the gas phase and the implementation can also be carried out trouble-free in continuous operation, if you are fixed Used catalysts that are in suspension.

The implementation is expediently designed so that the by the Starting gases formed gas stream used to move the solid catalyst particles. The procedure here is that the reaction participants mixed in a conventional device, one or all of which can be preheated, by a vertical, upwards The extended pipe leads and the catalyst into this pipe brings in which is then held in suspension by the gas flow. " It is not necessary, that all particles of the catalyst are constantly in suspension. are located, but the method can also: be carried out in such a way that the solid catalyzer particles in a flowing movement caused by the gas flow on the solid Underlay.

If you work in such a way that the catalyst is permanently suspended is located, it is very easy to determine the conversion conditions, such as gas velocity, Apparatus dimensions, grain size and / or the specific weight of the catalyst, to be coordinated so that the catalyst neither on the bottom of the reaction vessel falls is still carried too far by the gas flow. Even if this is still minor If quantities of soot are deposited on the catalytic converter, this interferes with the proper process the implementation no longer, because the soot by the movement of the catalyst particles is rubbed against each other. The ones present in the conversion vessel with an axial gas flow Lively movement can be intensified by adding the catalyst mass through suitable guidance of the gases or special shaping of the reaction vessel lively whirled around. So you can, for example, the gas flow tangentially in the Introduce implementation space or design the mixing device so that the Gas mixture enters the reaction vessel in a vortex shape.

It is not necessary to @ of a uniform catalyst or to use nearly uniform particle size; for example, can even increase throughput by increasing the catalyst suspension zone, by using catalyst masses consisting of particles of different sizes. The permissible fluctuations in the particle size are again dependent on the other implementation conditions already mentioned above. So you can, for example Pour a previously sieved catalyst into the reaction vessel, which then passes through the Gas stream is sifted out, so to speak: The excessively heavy components quickly fall on the Bottom of the conversion room, while the too light parts are carried away by the bass current and can be deposited in a downstream device.

The present process is suitable for substituting chlorination of hydrocarbons of saturated and unsaturated type, which under the reaction conditions are gaseous, especially of aliphatic hydrocarbons. As solid catalysts '' -L., 11r? »R acceleration of the substituting chlorination of hydrocarbons used catalysts, especially active coal, coke, pumice stone or grains of clay, which may be impregnated with halogen carriers, such as metal halides can.

In general, in the substitutional chlorination of hydrocarbons, the reaction must be initiated or kept going by bringing the starting materials to a certain temperature, usually between about 250 and 300 °, and feeding the heated mixture to the actual reaction vessel. The reaction itself is very rapid and highly exothermic and thus causes a sharp increase in the temperature of the starting mixture. There is an upper temperature limit which the end products must not exceed without the risk of decomposition and which depends on the chain length of the starting hydrocarbon. In general, the lower the carbon number, the higher the reaction temperature that can be chosen. It is therefore necessary to maintain certain temperatures which, on the one hand, must be high enough to initiate the reaction, but which, on the other hand, must not be so high that the decomposition temperature is exceeded by the development of the heat of reaction.

The present process now offers the particular advantage that the starting materials do not need to be heated to the initial temperature required to initiate and maintain the reaction, since continuous operation occurs. the lively movement of the floating or flowing catalyst immediately results in an intimate mixing and an effective heat exchange between the incoming fresh gas mixture and the hotter reaction gases, so that the fresh gas mixture is sufficiently heated. As a result, one does not have to rely on painstakingly adhering to certain temperature limits in the present process; in particular can. the ratio of the amount of hydrocarbons to the amount of chlorine can also be increased in favor of the chlorine in view of the larger temperature range available. In general, the reaction between chlorine and hydrocarbon is allowed to proceed between about 300 and 600 ° here.

It has been known already from the American patent specifications 1I57.155, 1,355,105 and r 557,687, applicable to reactions in the gas phase finely dispersed catalysts are not fixedly arranged, but suspended in the gas stream. The possibility of a substituting chlorination of hydrocarbons is not mentioned in the patents. It was also not obvious to use suspended catalysts in the substitutional chlorination of hydrocarbons in the gas phase, since in this reaction there was no need to fear the deposition of soot on the catalysts. Since, according to the information in the above-mentioned patents, the suspension catalyst, if it has coated deposits from the conversion mixture for a period of time, has to be removed and replaced by a new catalyst, it was therefore in continuous operation in the substitutional chlorination of hydrocarbons when using suspension catalysts reckon with the necessity of frequent replacement of the contaminated catalyst. Surprisingly, however,. this implementation of the soot that separates out, rubbed off by the movement of the catalyst, so the catalyst is constantly reactivated without any special measures.

The implementation can, for example, with one of the in the enclosed Illustrations explained devices are carried out.

In Fig. I, a conical iron pipe i serves as the catalyst space, which can be covered with an insulating or cooling jacket 6. For filling the catalyst a gas-tight filling device 5 is used. The hydrocarbon enters the annulus 3 and then passes through four tangential slots into the mixing chamber 2, into the the chlorine is also passed through two tubes 4 with side openings. It a swirling gas flow is then created, which enters the catalyst chamber and passes through it that the catalyst is made to float. The tube i can also only be in his lower part be conical, while the upper part is cylindrical.

Fig.2 shows a conversion vessel, the lower part of which is different is designed as in the case of the vessel according to Fig. i, that in place of the one inlet opening a plurality of inlet openings is also used. The hydrocarbon kicks in through the line 12 into the distribution space 13, which has a number of openings 14 at the top possesses, which are dimensioned so that the gas flow is a fall in the reaction space i i prevented filled catalyst in the openings. Before desolate in these openings the supply lines 15 are arranged for the chlorine, which through the line 16 and the Distribution space i 7 is supplied.

Example i Chlorine at normal temperature and butane at 80 ° are conducted separately in a volume ratio of 1: 3 through lines 4 and 3 in Fig. 1 and brought together in mixing chamber 2. The speed of the gas mixture on entry into the catalyst chamber is 6.7 m / sec. In the catalyst space, which is heated to 450 °, there is activated carbon with a grain size of 0.5 to 2 mm, which has been added through the filling device 5 before the start of the reaction. The chlorine reacts completely with the butane. * 90% of monobutyl chlorides are obtained; the rest consists of dichlorides and very small amounts of trichlorides. _ The mixing device remains free of deposits even during continuous operation; only a thin layer of coal is deposited on the wall of the iron pipe.

If one has the same volume parts under the conditions described above of isobutylene and chlorine, of which the isobutylene, preheated to '"about' 35o ° is introduced into the reaction vessel, it is obtained at one reaction temperature of about 550 ° isobutenyl chloride in 8oo! oiger yield, based on the amount of used isobutylene.

Example 2 In the manner described in Example i, ethane, the Is 16o °, treated with the same amount of room chlorine at normal temperature, keeping the temperature in the catalyst chamber at 46o °. The speed of entry is 6.7 m / sec. This gives ethyl chloride in a 93% yield, based on the converted ethane.

Example 3 In a device as described in Fig. 2, if chlorine at ordinary temperature is added to twice the amount of propylene is heated to 22o °. Fine-grained activated charcoal is used as a catalyst the incoming gas stream is kept in flowing motion. The temperature in Catalyst space is 600 °, the entry speed 6.7 m / sec. You get Allyl chloride in a yield of 80% of the propylene used, while the rest of the set is converted into higher chlorides, especially dichlorides will.

EXAMPLE In the device described in Example i, methane, which has been preheated to 300 °, is reacted with non-preheated chlorine in a volume ratio of 3.5: 1 using activated carbon as a catalyst. The gas velocity at the inlet is 6.7 m / sec., The reaction temperature at the catalyst is about 50 °. The chlorination products are composed of 86 percent by weight methyl chloride, 12 percent by weight methylene chloride and 2 percent by weight chloroform and carbon tetrachloride.

Example 5 Vaporous benzene of 25o ° is with half its Volume of chlorine mixed in the manner described in Example i. The mix will in a vessel according to Fig. i, which is charged with active charcoal as a catalyst a speed of 5 m / sec. introduced. The temperature inside the decomposition vessel is held at .f5o '. : Ulan thus receives monochlorobenzene in S7% yield, based on the amount of benzene reacted.

Claims (1)

"PATENT CLAIM: Process for the substitutional chlorination of hydrocarbons at high temperatures in the presence of catalysts, characterized in that that one uses solid catalysts which are in suspension.