SE190888C1 - - Google Patents

Description

Inventor: H J Vogt Priority Application, September 19, 1960 (USA) The present invention relates to the production of methyl chloroform (1,1,1-trichloroethane) from ethylene and chlorine.

The preparation of methyl chloroform from ethylene and elemental chlorine is carried out according to the present invention by a special sequence of steps adapted to each other, which comprise a) substituting chlorination of ethylene (or 1,2-oligloroethane) with elemental chlorine to form 1,1,2 trichloroctane and remove chlorvate, b) evaporation of chlorvate frail donna 1,1,2-trichloroethane to form vinylidene chloride (1,1-dichloroethene) and c) reaction Indian yinylidene chloride and the chlorovate selected in step a) for preparation of methyl chloroform. With chemical equations, these steps and their inboard ratios can be expressed as follows: 2C1 2 + C2H4HCl + Cz1-13C13 (1,1,2-trichloroethane) C21-13C13 HCl + C, H2C12 (1,1,1-trichloroethane) (1 , 1-dichloroethene) Chloride and vinylidene chloride, which are necessary for the production of methyl chloroform, are obtained from the intermediate steps of the intended process.

In this process, the consumption of chlorine is measured at a minimum value. About 75 percent of the chlorine needed for the process is theoretically recovered as a product, such as methyl chloroform. Since the yield in each step of the process is high and often approaches the theoretical value, methyl chloroform is recovered extremely efficiently from elemental chlorine. An inconvenient by-production of mostly undesirable chlorinated hydrocarbons, which is a by-product in the production of many chlorinated hydrocarbons, avoids liters or less completely. 1,1,2-Trichloroethane for the production kit of the present invention is most conveniently obtained by reacting ethylene or 1,2-dichloroethane and elemental chlorine in a liquid reaction medium of dichloroethane, which contains a reasonable concentration of a candle catalyst such as, for example, 3-yard yam chloride. A complete process involves feeding the chlorine and ethylene to a substantially anhydrous catalyst, which is enclosed in a yat mass of chlorinated ethanes, essentially 1,2-dichloroethane, while this 1,2-dichloroethane is co-evaporated to the lathate solution. Thus, trichloroethane is formed during the use of chlorine and ethylene in the liquid under such conditions that gaseous dichloroethane is evolved. Iron side with dichloroethane atyecklas chlorvate, compounds with lower boiling point and flake trichloroethane.

Depending on, among other things, the specific composition of the yat solution, these conditions vary. With a liquid solution having a low concentration of 1,1,2-trichloroethane (for example about 5% by weight or less), the temperature of the liquid is measured approximately at the boiling point (under radiating pressure) of 1,2-chlorochloroethane, which meant about 83 ° C under atmospheric pressure.

The heat of evaporation, especially of the dichloroethane, enables temperature control, since the chlorination is exothermic and the evolved gases are withdrawn from the reaction zone and cooled so that the organic gases, preferably the 1,2-dichloroethane, condense. 2— - Usually chlorine levels remain uncondensed. Some or all of the 1,2-dichloroethane may be returned to the liquid to facilitate further temperature control of the reaction medium. When the chlorination is carried out, mainly for the purpose of obtaining trichloroethane, substantially all of this dichloroethane is returned to the liquid. Om sa. If desired, freely selected amounts of evolved trichloroethane can be separated and used as such or all trichloroethane is finally converted to methyl chloroform by means of further treatment steps, which will be described in more detail below.

As an example, in order to produce 1,1,2-trichloroethane, about 2 moles of chlorine gas (between 1.8 to 2.05 moles) per mole of ethylene are fed to a liquid mass consisting of 1,2-dichloroethane, in which a considerable concentration of 1,1,2-trichloroethane is maintained. Substantially all of the organic substances which emit in vapor form from the liquid mass are usually recycled to liquid form and trichloroethane is recovered by a roller stream from which the trichloroethane is separated periodically or continuously removed. The dichloroethane in this reflux is returned to the reaction vessel.

If desired, the chlorination can be advantageously used for the simultaneous production of 1,2-dichloroethane and 1,1,2-trichloroethane from ethylene. For such a common production of chlorinated ethanes, the liquid reaction medium is fed in a proportion exceeding one mole (usually from 1.2 to 1.5 moles) of chlorine but less than 1.8 moles of chlorine per mole of ethylene. The liquid mass Mlles boiling by the exothermic nature of the reaction or reactions. At pressure Above atmospheric pressure, the temperature rises. As a result of the exothermic nature of the reactions in the liquid, 1,2-dichloroethane and other but boiling ingredients of the reaction medium are evolved in the form of a gas mixture. Salunda is developed in the continuous reaction of chlorine and ethylene, which are to form both 1,2-dichloroethane and trichloroethane, a gas mixture consisting of ethylene dichloride, trichloroethane and low-boiling constituents such as chlorine water continuously from the liquid reaction medium. The heat, which: Agar to the steam formation, helps to dissipate heat from the reaction medium and thus maintains the liquid mass at a suitable reaction temperature. The gas mixture is kept away from direct contact with the volatile reaction medium and cooled so that organic constituents (for example chlorinated hydrocarbons) condense and thereby separate the chlorine water from the chlorinated hydrocarbons. Some but not all of the 1,2-dichloroethane is returned to the reaction vessel in liquid form. According to an embodiment of the invention, the & Isom gas-evolved trichloroethane can be returned to the roller body. According to another embodiment, this trichloroethane is also separated and used later for the preparation of methyl chloroform.

Trichloroethane and other constituents which boil substantially over the temperature of the liquid reaction medium show a tendency to accumulate in the liquid reaction medium if evolved trichloroethane Ater-Hires. In this case it is advantageous to deposit a portion of the liquid periodically or continuously, usually from a lb. 'level in the liquid reaction medium as the simplest way to remove formed trichloroethane from the reaction medium. Alternatively to or in conjunction with this treatment step, trichloroethane may be developed with and separated from dichloroethane.

The ratio in which dichloroethane and trichloroethane are formed can be controlled by 1) the ratio in which ethylene and chlorine are fed to the reaction zone and 2) the concentration. of the metal chloride catalyst, in the anterior space anhydrous jam chloride, which retains the reaction medium. Usually chlorine and ethylene are fed in the above molar ratio, but below two moles of chlorine per mole of ethylene and Maradeswise between about 1.2 to 1.8 moles of chlorine per mole of ethylene. The concentrations of the 3-valent jam chloride can range upwards of 0.005% by weight, the lower concentrations of ferric chloride having a beneficial effect on the production of trichloroethane.

The node of evolved trichloroethane, which is separated from the reaction medium, may contain higher chlorinated ethanes such as tetrachloroethane and usually contains significant amounts of dichloroethane.

The present invention seeks primarily to obtain pure 1,1,2-trichloroethane. Thus, the 1,1,2-trichloroethane must be substantially free of 1,2-dichloroethane and in most cases contain only insignificant amounts of other chlorinated constituents. It is therefore appropriate to resort to fractionation according to per se known methods.

However, while in the foregoing the simultaneous preparation of 1,2-dichloroethane and 1,1,2-trichloroethane has been described with ethylene and chlorine as starting materials, 1,2-dichloroethane can be used instead of ethylene.

This 1,1,2-trichloroethane is liberated from chlorvale to form vinylidene chloride. In order to obtain the best possible results, trichloroethane is liberated from the chlorohydrate with a small amount of Alp by a water-soluble inorganic alkali oxide or hydroxide, preferably a strong alkali of the alkali metal hydroxide type such as sodium hydroxide, potassium hydroxide and alkaline earth metal hydroxide, e.g. calcium hydroxide. Theoretically, one equivalent mole of alkali metal hydroxide is required to convert it to vinylidene chloride by liberating trichloroethane from the chloroate. Sales, in the chlorine-hydrogen stripping step, are about one mole of sodium hydroxide per mole of vinylidene chloride formed. The reactants are added in quantities depending on the stoichiometric process, with some excess (for example from 2 to 10 hundredths) of the alkali metal hydroxide being beneficial.

The temperatures for the chlorate-water evaporation are usually moderate, for example in the order of 10 ° C to 85 ° C, and enable its implementation in an aqueous alkali solution.

After the vinylidene chloride is separated from the reaction medium in which it is formed, it is suitable to react with the chlorine water which developed in the production of trichloroethane by chlorination.

The reaction of hydrogen chloride and vinylidene chloride to form methyl chloroform is most conveniently carried out in a liquid phase reaction in a medium consisting of an inert organic solvent, usually methyl chloroform. Narvaron air a catalyst in appropriate concentration in the water reaction medium is onskvd.rt. As a rule, the conventional catalysts suitable for reaction with chlorine (hydrochlorination) catalysts, preferably metal chlorides such as 3-yard iron chloride, are used in a typical catalytic concentration between 0.01 and 1.0% by weight in the reaction medium.

As a rule, equimolar amounts of vinylidene chloride and hydrochlorate (preferably preferably anhydrous) are fed into a substantially anhydrous liquid mass, which is mainly formed of methyl methyl chloroform containing catalytic concentrations of a hydrochloride lamp-hg catalyst, preferably 3-yard iron chloride. The temperature of the reaction medium is preferably between 10 ° C and 80 ° C, if operating at atmospheric pressure. Pressures below atmospheric pressure are particularly advantageous when it is desired to carry out the reactions with carbonate below the normal boiling point of the methyl chloroform.

Hydrochlorination of vinylidene chloride can be carried out in a liquid mass containing methyl chloroform, Iran which methyl chloroform gives off in angular form. Condensation of such an agent serves to deposit the product from the reaction zone.

When the liquid mass consists mainly of the methyl chloroform, the reaction is carried out in a liquid mass of boiling methyl chloroform f5 - respectively at lower atmospheric pressure, so that the temperature of the boiling white is below 60 ° C. By removing the methyl chloroform from the reactor high purity grade and is substantially free of the metal chloride catalyst.

As soon as the methyl chloroform in gaseous form is removed from the reaction zone, it is condensed by cooling below the normal boiling point of the methyl chloroform to 25 ° G. If desired, some of this condensed chloroform can be returned to the reactor to increase the volume of the liquid reaction medium. essentially constant. The residue of or all of the methyl chloroform can be further purified, for example, by precipitating lost chlorovalence and further transporting it for further treatment, including drying and stabilization.

The invention will be described in more detail below with reference to a flow chart shown in the accompanying appendix A, in which case the characteristics of the invention may also be stated.

Elemental kkr in gaseous or liquid form and ethylene is fed into a reactor 2 below the upper level of a substantially anhydrous liquid mass 1, which for the most part (usually at least 75% by weight) is ay. 1,2-dichloroethane and which contains at least 0.06% by weight of 3-yard iron chloride. The liquid is kept at a temperature corresponding to the normal boiling point of ethylene dichloride or the boiling point of the mixture of predominant ethylene dichrid and trichloroethane at atmospheric pressure. Under these conditions the process is exothermic, so that the liquid 1 continues to boil. Chlorine is added in such an amount that a part of the ethylene dichloride formed by the additive chlorination is further chlorinated to 1,1,2-trichloroethane by substituting chlorine. rering. As a rule, 1.1 to 2.0 moles of chlorine were added per mole of ethylene. Some higher chlorinated ethanes such as tetrachloroethane and possibly also pentachloroethane are formed in excess but usually in smaller concentrations, especially if the concentration of 1,1,24-chloroethane in the water mass is below 25% by weight.

A gas mixture consisting mainly of 1,2-dichloroethane, 1,1,2-trichloroethane and chlorovale is taken from the reaction zone of reactor 2.

The amount of chlorine in the reactor 2 developed and the amount of chlorine removed is approximately equal to the amount of trichloroethane formed, with a small excess of air chlorine being formed as the MA air formation in the smaller amounts of higher trichloroethane chlorinated ethanes. The gas stream is cooled in a condenser 3 to about 25 ° C to thereby condense substantially all of the dichloroethane, while the hydrogen chloride remains as gas.

A portion of the condensed dichloroethane is returned to the reactor 2 in order to maintain a substantially constant volume of the liquid reaction medium and in order to facilitate the temperature control. The residue is purified in a distiller column 7 to produce a stream of substantially pure dichloroethane.

From the bottom of the distiller column a stream of organic substances is discharged with a high concentration of 1,1,2-trichloroethane to be fed into a column 4. Alternatively, trichloroethane can be obtained by removing a part of the liquid mass and separating it from its trichloroethane content, which content normally 4— - does not exceed 25% by weight. In column 4, constituents with a boiling point lower than the normal boiling point of trichloroethane (mainly 1,2-dichloroethane) are separated from the top of the column. They can be returned to which stream of dichloroethane is raised in the process, but they are usually returned to the reactor, as indicated in the drawing. From the bottom of column 4 a stream of trichloroethane, which is substantially free of constituents with a boiling point below 1,1,2-trichloroethane, is passed to the column 5. In this column the trichloroethane undergoes a high degree of purification from constituents with a higher boiling point & Isom tetrachloroethane. The residual flood from column 5, which consists mainly of tetrachloroethane and possibly also some pentachloroethane and hexachloroethane, is separated.

The stream from the top of the column of purified 1,1,2-trichloroethane is led to a column 6 to evaporate the chlorine water. There the top flood is mixed with an aqueous solution of sodium hydroxide. In order to avoid the occurrence of illegal polymerization of the vinylidene chloride in column 6, the Mies system is essentially free of oxygen, and small amounts of stabilizers & Oman phenol are added to the vinylidene chloride, especially if it is stored for a long time. Typically, from 0.1 to 1.0 percent phenol based on the weight of vinylidene chloride was added. Temperature and pressure are installed in the column 6 for the evaporation of the chlorine water so that the gas flow from the upper part of the column 6 consists of a gas mixture of vinylidene chloride and water vapor which is substantially free of organic contaminants. This gas mixture is cooled after discharge from column 6 in a condenser 8. In order to make this discharge fully toothed, fresh air is introduced into a lower part of column 6, which thus serves as a stripping section, while the upper part emits the return flow. Sodium chloride, water and boiling organic chlorides (tar) released from the bottom of the stripping section.

The vapor stream from the top of column 6 is liquefied by cooling in condenser 8, separating any water present from the phase and returning to column 6. The organic phase is further cooled to between and 10 ° C by means of supplied water, which is again separated in a separator 10. A further drying of the vinylidene chloride is obtained by means of molecular filters 11 or other solid dryers in order to obtain vinylidene chloride, which contains less than 400 parts by weight and often less than 100 parts by weight of water per million parts by weight of vinylidene chloride.

The dried vinylidene chloride is then passed on to a reaction vessel 16 to react with the hydrochloric acid which evolved during the sewerage in the reactor 2.

As a rule, the stream is subjected to chlorvate, cras, which differs from the dichloroethane in condenser 3, in a compressor 12 a pressure increase to superatmospheric pressure of about 1.1 kplcm2 and in a cooler 13 a temperature drop to between 1 ° C and 5 ° C. Nastan all dichloroethane which accompanies the hydrochlorate is condensed and separated. This dichloroethane can be combined with any stream of crude dichloroethane in the system, either to be returned to the reaction vessel 2 or to a stream of crude dichloroethane which is drained to undergo. the purification which is necessary.

If required, the chlorate water drum can be further freed after exiting the cooler 13. My savings of organic pollutants such as dichloroethane by washing at superatmospheric pressure as 1.4 kp per cm 2. me-deist polychlorinated ethanes, which contain the residual flood from column 5.

The thus purified chlorvate gas is then passed on to the reaction vessel 16 for reaction with the vinylidene chloride. As a rule, both the vinylidene chloride and the chlorine water are fed in substantially equivalent molar ratios to the vessel 16 below the spruce surface between the liquid and the gas therein. The liquid mass 14 consists mainly of only methyl chloroform or methyl chloroform mixed with vinylidene chloride in the form of boiling liquid. A small amount of a suitable catalyst such as 3-yard ferric chloride is present. A normally appropriate concentration of the catalyst ranges from 0.1 to 2.0 percent 3-yard ferric chloride, based on the weight of the liquid. While the liquid 11 is kept boiling, usually at a temperature around the normal boiling point of methyl chloroform or the boiling point of a mixture of methyl chloroform and vinylidene chloride under approximately atmospheric pressure, formed methyl chloroform is recovered as an Angnode from the top of the vessel and passed to a condenser 15 to be completely brought to liquid form by cooling to 25 ° C. This condensate can then be further purified, if necessary, or a part of it can be returned to the reaction vessel 16 to maintain a substantially constant liquid volume therein.

A number of auxiliaries can be used to further purify the methyl chloroform obtained in the form of condensate & An condenser 15. This condensed methyl chloroform may contain dissolved chlorate and often even some vinylidene chloride. These compounds can be driven from the methyl chloroform and returned to the system. Such evaporation can be accomplished by removing the methyl chloroform in angular form. Smaller or residual traces of hydrogen chloride can be removed by treating the methyl chloroform with an inorganic alkali such as ammonia and water. The purified methyl chloroform is then preferably subjected to a stabilization treatment, stored and packaged for sale or use.

The following examples set forth a specific method in which the present invention is employed.

ExampleI. The process schematically shown in the drawing shows the process for the preparation of methyl chloroform being carried out in a first step, in which 87.6 kg of elemental chlorine in gaseous form and 32.6 kg of ethylene (with a purity of 98 mol%) per hour are fed into liquid mass 1 in the reactor 2, temperature Mlles at about 84 ° C. This liquid mass consists of 1,2-dichloroethane with about 8.1% by weight of trichloroethane and 0.06% by weight of 3-yard iron chloride. While the liquid mass of Mlles is boiling and consequently develops anga, which consists mainly of 1,2-dichloroethane and chlorvate, both dichloroethane and trichloroethane are produced, their reaction heaters maintaining the reaction temperature of the liquid.

These gases are cooled so that their organic constituents are condensed in the condenser 3, whereby a part of the liquid organic content is returned to the reaction vessel 2. The residue is passed to the distillator column 7, where 1,2-dichloroethane is taken out as an impact at 107.2 kg per hour, condensed and stored for further use. A river of water, which transports 0.5 kg of 1,2-dichloroethane, 8.9 kg of 1,1,2-trichloroethane, 0.8 kg of tetrachloroethane and 0.23 kg of pentachloroethane per hour, is withdrawn from the Iran bottom zone in column 7 and fed to distiller columns 4.

Essentially all of the 1,2-dichloroethane fed to column 4 is separated, together with about 27 g of trichloroethane per Hume, in the stream which is fed to reactor 1. The residue is taken out as liquid from the bottom of column 4 and passed on to column 5, where substantially pure 1,1,2-dichloroethane in an amount of 8.7 kg per hour and traces of tetrachloroethane are separated as peak flow and further passed to the chlorohydrogen stripper 6 together with an aqueous solution containing 10.5% by weight NaOH and 14.5% by weight NaCl and feed in an amount of 2.9 kg of NaOH per hour. Aliga inf5res in the colon, the lower part of the nen. The temperatures in the stripper 6 vary from 115 ° C in the bottom zone to about 33 ° C in the top zone. Sodium chloride, water and some tar are removed from the bottom of the stripper column 6.

The vinylidene chloride is separated in the peat, over-formed into liquid form by cooling and dried, whereby about 6 kg of substantially pure vinylidene chloride is obtained per hour to be fed to the reaction vessel 16.

A part of the chlorine water formed in the reactor 2 is also fed to the reaction vessel 16, namely 3.8 kg in [Unmet '. After the gaseous chlorine water is removed from the Iran reactor 2, it is simultaneously cooled to -35 ° C and compressed to 1.4 kp / cm 2. As a result, about 95% by weight of the 1,2-dichloroethane and almost all of the trichloroethane in the chloroquart are condensed and phased.

A portion of the hydrogen chloride is then aerated and further purified by washing with the organic substances in liquid form, taken from the bottom of the column 5, whereby a strain of hydrogen chloride, which is substantially free of 1,2-dichloroethane, is provided. In such a renal state, approximately 2.4 kg of chlorine is fed per hour to the reaction vessel 16, where it reacts with vinylidene chloride to form methyl chloroform.

The reaction Hied chlorvate is carried out in liquid methyl chloroform, which contains 0.3% by weight of 3-yard iron chloride. About 40 g of 3-yard iron chloride bar is added per hour to maintain the steering wheel concentration of the catalyst. The temperature of the liquid 14 Mlls is constant at about 74 ° C at the spruce surface between liquid and gas, which means that the temperature is approximately at the normal boiling point of methyl chloroform. Thus, the methyl chloroform is drained in the form of a gas stream, condensed and separated in part, namely in an amount of about 8 kg of chloroform per hour, as a node of aspirated product, which can be further purified and stabilized if necessary. The residue of the condensate is returned to the reactor 2.

The invention is, of course, limited to the example described, but can be varied in many respects within the scope of the underlying idea.

Claims (6)

Patent claim: 1. Prepared to produce methyl chloroform, it may be clarified that 1,1,2-trichloroethane is generated by a substituting chlorination of ethylene which develops chlorvate, separates the trichloroethane and the chlorohydrate from each other, evaporates the chlorovat from the separated trichloroethane to form vinylchloridyl vinyl chloride. react with the hydrochloric acid obtained during the chlorination to thereby form methyl chloroform. 2. A seed according to claim 1, characterized in that the trichloroethane is liberated from the chlorine water by means of an aqueous solution of an inorganic alkali oxide or hydroxide to form the vinylidene chloride. Wear according to claim 1 or 2, characterized in that the chlorination is carried out with elemental chlorine. 4. San according to claim 2 or 3, characterized in that the ethylene is chlorinated in the presence of 1,2-dichloroethane to form the chloroate and the 1,1,2-trichloroethane, which after the separation from the chlorovat is freed from substantially all 1,2-dichloroethane , before it is converted to vinylidene chloride by the evaporation of the chlorine water. 5. A claim according to claim 4, characterized in that the ethylene is chlorinated in a liquid mass consisting of 1,2-dichloroethane and that the 6 - - after the separation of the chloroform formed by the chlorination and the liberation from substantially all of the 1,2-dichloroethane present is purified by the evaporation of the chlorohydrate is converted into the vinylidene chloride, which is fed with the chlorovat formed in said chlorination, which is also substantially freed from all dichloroethane, before the same is used for the formation of the methyl chloroform. Anfarda Publications: Patent Papers from Sweden 124,024; France 1,211,593; Germany 523 43 6.