JPS6215534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing chlorinated organic compounds, and more particularly to an improved method for producing reactive alkyl halides by the reaction of an alcohol with hydrogen chloride. In particular, the present invention includes a novel series of steps for the treatment of crude alkyl chloride product streams, namely a distillation step for acid removal and a distillation step for the recovery of cooled alcohol, thereby substantially removing the alkyl chloride. It is recovered in pure and dry form.

US Pat. No. 2,421,441 to EAThronson et al. describes a method for producing methyl chloride by the reaction of methanol and hydrogen chloride. The gaseous crude product obtained contains, in addition to methyl chloride, unreacted hydrochloric acid, unreacted methanol, water and dimethyl ether. Removal of these by-products and reactants is accomplished according to the method described in that patent by sequentially washing this gaseous crude product stream with water, dilute sodium hydroxide solution and concentrated sulfuric acid. There is. However, operation of such a process requires large amounts of water in the absorption and distillation equipment, and the effluent from the water gas scrubbing tower carries organic matter, primarily methanol, with it when it is sent to the waste treatment facility. However, they were economically expensive and tended to cause significant environmental pollution problems. J.
Another method for preparing ethyl chloride, n-propyl chloride and isopropyl chloride from the corresponding alcohols is proposed in US Pat. No. 2,516,638 to L. McCurdy. According to this method, the reaction is carried out in the presence of an azeotrope-forming liquid that is used to aid in the separation of the alkyl halide from the alcohol after cooling in a decanter and removing the resulting layer. Although this method allows recycling of unreacted alcohol to the reactor, it requires the addition of an azeotrope-forming liquid, which requires extra cost and furthermore the azeotrope-forming liquid This is disadvantageous because some, such as carbon tetrachloride, are toxic, and others, such as benzene, are easily flammable. Also G.
W.Mattsen's U.S. Patent No. 2,622,107 states:
Alkyl chloride, unreacted alcohol and by-product HCl
A method has been proposed in which a vaporized mixture of and is first supplied to a refrigeration cooler and then sent to a compressor and an alkaline scrubber.

The disadvantages of typical alkyl chloride production methods proposed to date are summarized as follows.

(i) during the purification of alkyl chlorides, it is necessary to discharge organic materials, primarily alcohol, into the effluent stream from the equipment; (ii) to remove alcohol and other organic materials from the effluent stream from the equipment; (iii) the difficulty of disposing of the used alkaline solution containing unreacted alcohol; (iv) the difficulty of recovering alcohol from the waste stream from the equipment at a purity suitable for reuse in the reactor; Requires large amounts of steam and water in the absorption and distillation steps; and (v) also requires large amounts of water to remove alcohol from the gaseous alkyl chloride stream by air washing.

The inventors have now developed a new process that combines steam distillation for acid removal followed by distillation for recovery of the cooled alcohol. This method eliminates all of the above-mentioned drawbacks of conventional alkyl chloride production methods and also eliminates the contamination of environmental waters such as rivers by removing organic materials before they are discharged into the effluent from the equipment. This effectively avoids the In the case of high acid contents, it is very advantageous to incorporate a gas scrubbing step with an alkali between the distillation step for removing the acid and the recovery step of the cooled alcohol.

The advantages of the method of the present invention are summarized as follows.

(i) the ability to recover residual alcohol in the product of the alkyl halide production reactor in such a high degree of purity that it is suitable for recycling to the reactor; (ii) the discharge of organic matter from the unit into the waste stream; (iii) When performing gas scrubbing with alkali, the effluent from the gas scrubbing tower should be stripped by stripping without being directly discharged into the equipment waste stream. (iv) Direct distillation of the superheated vapor feed requires the use of a relatively small amount of steam, thus reducing the heat burden and reducing the (v) The aqueous hydrochloric acid solution produced as a by-product and discharged in this method has a low content of organic substances and can therefore be used for alkali neutralization and various other methods;
and (vi) in another embodiment, cooling for distillation for alcohol recovery can be accomplished economically by recycling methyl chloride from the product compressor.

According to the invention, alkyl chloride having 1 to 3 carbon atoms in the alkyl group (hereinafter referred to as C ₁ -C ₃ chloride) is prepared by reacting a C ₁ -C ₃ alcohol with hydrogen chloride in a reactor. (a) A superheated vapor reaction mixture consisting of the obtained C ₁ -C ₃ alkyl chloride, by-product water, unreacted hydrogen chloride and unreacted C ₁ -C ₃ alcohol, and steam are (b) gaseous chloride C ₁ -C from the acid removal still to form an acid byproduct solution containing substantially all hydrogen chloride; ₃ The alkyl is removed and sent to a still for cooling and recovery of alcohol, where unreacted
Liquefied _C1 - _C3 alcohol and liquefied _C1
~ _C3 alcohol is removed from the still; and
(c) An improved process is provided comprising removing and recovering gaseous _C1 - _C3 alkyl chloride from the chilled recovery still.

When the hydrochloric acid content is relatively high, a variant of the invention includes (a) superheating of the C ₁ -C ₃ alkyl chloride, by-product water, unreacted hydrogen chloride and unreacted C ₁ -C ₃ alcohol; (b) supplying the vaporized reaction mixture and the spent recycled aqueous alkaline solution to an acid removal still to form an acid byproduct solution containing a major proportion of hydrogen chloride and removing it from the still; The gaseous _C1 - _C3 alkyl chloride is removed from the industrial distiller and fed into a gas scrubber where it is brought into intimate contact with an aqueous alkaline solution to remove residual hydrogen chloride and remove the used alcohol-containing waste. (c) obtaining a recirculating aqueous alkaline solution and recycling the aqueous solution from the gas scrubber to the acid removal distiller of step (a);
The gaseous C ₁ -C ₃ alkyl chloride is removed from the gas scrubber and sent to a still for cold recovery of alcohol, where the unreacted C ₁ -C 3 alcohol is liquefied and the liquefied C ₁ -C ₃ alcohol is liquefied. C ₃ alcohol is removed from the still; and (d) gaseous chloride C ₁ -C ₃ is removed from the still.
An improved process is provided comprising removing and recovering alkyl from the chilled recovery still.

In a preferred embodiment of the invention, the step
Liquefied unreacted C ₁ recovered from the cooler in (c)
The ~ _C3 alcohol is recycled to the _C1 - _C3 alkyl chloride production reactor. In another preferred embodiment, methyl chloride is used as the coolant in the recovery distillation unit.

The alkyl chloride produced in this invention can be methyl chloride as described in U.S. Pat. No. 2,421,441, or
It can also be a crude gas stream of ethyl chloride, n-propyl chloride or i-propyl chloride, as in 2516638. These are respectively produced from methanol, ethanol, n-propanol and i-propanol.
The process of the invention is particularly advantageously applicable to the production of methyl chloride because it has a wide range of uses as a chemical intermediate and can advantageously be used as a coolant in the process of the invention.

In the method of the present invention, C1 _{- C3} alkyl chloride is prepared by reacting _{a 1} -C3 alcohol corresponding to _the desired alkyl chloride with hydrochloric acid in the presence of a conventional catalyst, such as zinc chloride. Formed with small amounts of the corresponding _C1 - _C3 dialkyl ether. The crude gaseous product obtained in this manner contains, in addition to the desired alkyl chloride and the corresponding ether, unreacted hydrogen chloride, unreacted C ₁ -C ₃ alcohols and by-product water.

Next, the basic method of the present invention will be explained with reference to FIG. The gas leaving the reactor 2, usually in superheated conditions, e.g. 130° to 150° C., is fed to a suitable distiller 4, e.g. a packed column, where by selective extraction-condensation hydrogen chloride is also fed to said distiller. It is removed as an aqueous stream resulting from condensation in a steamer.
The hydrogen chloride forms a solution with a concentration of, for example, 5 to 20% and is then discharged from the system via conduit 20. This hydrogen chloride has a low content of organic by-products and is suitable for reuse, for example, in alkali neutralization or other equipment operations.

The vapor stream of alkyl chloride from which substantially all of the hydrogen chloride has been removed in the acid removal distiller 4 is then sent to a cooling vessel 8 of any conventional type where unreacted C ₁ -
The _C3 alcohol is liquefied and removed from the gas stream. Any conventional coolant may be used, but methyl chloride is particularly preferred from the standpoint of economy and effectiveness. The liquid alcohol removed from the cooling container 8 (accompanied by some amount of alkyl chloride and water) is stored,
Can be reused. Surprisingly, however, its purity is sufficient as such to allow it to be recycled to the reactor for reuse in the process.

Finally, the gaseous _C1 - _C3 alkyl chloride from the previous stage is removed via conduit 32 and recovered. Although any conventional means for recovery may be used, it is advantageous to carry out the final drying and then liquefy it, for example by compression.

If the product stream contains relatively large amounts of hydrogen chloride, a system incorporating an alkali gas scrubbing step as shown in FIG. 2 is employed.

The first part of this variant is similar to that described in FIG. It is also sent to a column or of other suitable type - where it is treated with an aqueous alkaline solution, such as potassium hydroxide or sodium hydroxide solution. The concentration of alkali may vary, but is preferably in the range of 3 to 25% by weight, and the temperature may also vary, but will usually be in the range of 10 to 50°C. In this step, the so-called final cleaning step, all remaining hydrogen chloride is converted to the corresponding alkali metal salt and water, and the effluent, i.e. the spent alkaline solution - containing unreacted alcohol, is discharged to the environmental water system. conduit 18 instead of
is recycled to the acid removal distiller 4.

The alkyl chloride vapor, from which substantially all hydrogen chloride has been removed in gas scrubber 6, is then passed via conduit 24 to cooler 8 and treated as described above with respect to FIG.

Next, the present invention will be further explained with reference to Examples, but the present invention is not limited by these in any way.

Example 1 Crude methyl chloride is produced by mixing methanol and hydrogen chloride in reactor 2 in the presence of zinc chloride or other catalyst in a conventional manner using the apparatus schematically shown in FIG. Then, the resulting reaction mixture vapor was passed to a distillation device 4 for acid removal, then sent to a distillation device 8 for cooling and recovery, and finally recovered. Methanol and hydrogen chloride were introduced into reactor 2 via line 10 and immersion line 12, respectively. The crude gaseous product contains about 3-10% unreacted methanol and about 3% unreacted hydrogen chloride and varying amounts of water vapor, dimethyether, and
It was removed from the reactor at a temperature of 220°C, usually between 130° and 150°C. The steam was fed to distiller 4 via conduit 16 at such a rate as to maintain the methyl chloride and other components in vapor form and cause them to flow upwardly and be removed from distiller 4. The methyl chloride vapor leaving the distiller 4 is then passed via conduit 22 to the chilled recovery distiller 8 where it is passed to the circuit 26.
The liquid is liquefied by contacting it with a coolant inside. The liquefied methanol is taken out via conduit 28, recovered and reused. Optionally and preferably, the liquefied alcohol from still 8 is transferred to conduit 30.
can be returned to reactor 2 via . Methyl chloride (and some dimethyl ether) is removed from distiller 8 via line 32. Recovery of the methyl chloride is carried out in customary manner, for example by condensation or compression liquefaction. For some purposes it may be desirable to remove the last traces of water as part of this recovery operation.

In one preferred embodiment, a portion of the liquefied methyl chloride is used as a coolant. That is, a portion of the liquefied methyl chloride is introduced via conduit 34 into condenser circuit 26, and the evaporated liquid is removed via conduit 36 and recompressed.

Example 2 Crude methyl chloride is produced by mixing methanol and hydrogen chloride in reactor 2 in the presence of zinc chloride or other catalyst in a conventional manner using the apparatus schematically shown in FIG. Then, the resulting reaction mixture vapor was sequentially passed to a distillation device 4 for acid removal, a gas scrubbing device 6 with alkali, and a distillation device 8 for cooling and recovery, and finally recovered. Methanol was charged to the reactor via line 10 and hydrogen chloride via dip tube 12. The crude gaseous products each contain about 3 to 10% unreacted methanol and unreacted hydrogen chloride and varying amounts of steam and dimethyl ether and are heated at temperatures of 50° to 200°C, usually 130° to 150°C. It was taken out from the reactor. A dilute alkaline solution, such as a 5-25% aqueous sodium hydroxide or potassium hydroxide solution, is added to the gas scrubber 6.
conduit 1 at such a rate as to maintain the volume of the contents therein.
7 to the gas scrubber 6, and the spent aqueous alkaline solution is returned to the distiller 4 via conduit 18 in order to recycle the methanol into a vapor stream and prevent it from entering the discharged effluent. did. The steamer was added via line 16 and the methyl chloride vapor leaving the still 4 was passed via line 22 to the gas scrubber 6 where it was intimately mixed with the aqueous alkaline solution to remove any remaining hydrogen chloride. These vapors were then passed via conduit 24 to the chilled recovery distiller 8 where the methanol was liquefied by contacting these vapors with a refrigerant in circuit 26. The liquefied methanol is taken out via conduit 28 and is recovered and reused. Optionally and preferably, the liquefied alcohol from still 8 can be returned to reactor 2 via conduit 30. Methyl chloride (and some dimethyl ether) was removed from distiller 8 via line 32. Recovery of methyl chloride was carried out by conventional methods, such as condensation or compression liquefaction. For certain purposes, it may be desirable to remove the last traces of water as part of the recovery operation.

In one representative implementation, the feed to the acid removal distillation column consisted of approximately 1.0% dimethyl ether, 62% methyl chloride, 6.5% methanol, 7.3% hydrogen chloride, and 23% water. External steam is typically fed to the bottom of the distillation column in an amount of 0.2 to 0.3 pounds (0.09 to 0.14 Kg) per pound (0.45 Kg) of methyl chloride, and feed vapor is fed to the center of the column to form steam. Take it out from the top. The recycled used alkaline aqueous solution is introduced near the center of the column and is passed downward through the column, during which hydrogen chloride is absorbed and taken out from the bottom of the column.

The steam supplied to the bottom of the alkali gas scrubbing tower contains approximately 1.6% dimethyl ether and approximately 1.6% methyl chloride.
97%, about 0.0006% hydrogen chloride and about 0.012% water. An alkaline aqueous solution with a concentration of 20% has a temperature of
It was introduced near the top of the column at 40°C and allowed to flow down the column. The spent alkali taken out from the gas scrubbing tower and recycled to the acid removal distillation tower contains approximately 58% methanol and water.
24.4%, alkali 6.7% and sodium chloride 11
%.

The vapor leaving the gas scrubbing tower was sent to a cooling recovery device (the middle part of the packed tower through which cooled liquid methyl chloride was flowing downward). The feed steam consisted of approximately 1.3% dimethyl ether, 84% methyl chloride, 14% methanol, 1.3% water, and contained no hydrogen chloride. The liquefied condensate taken out from the bottom of this packed column contains approximately 90% methanol and methyl chloride.
It consisted of 0.6% and water 9.4%. This is of sufficient purity to be returned to the reactor.

The product removed from the top of the alcohol cooling recovery unit consisted of approximately 1.6% dimethyl ether and 98.4% methyl chloride, free of water and hydrogen chloride.

In a manner similar to that described above, ethanol, n-propanol and i-propanol are converted to ethyl chloride, n-propyl chloride and i-propyl chloride, respectively, and the desired products free of hydrogen chloride, alcohol and water are economically produced. Moreover, it was recovered without risk of environmental pollution.

[Brief explanation of the drawing]

The drawings are schematic diagrams illustrating in the form of a flow sheet an apparatus suitable for carrying out the process of the invention; FIG. FIG. 2 illustrates a modified method in which an alkali gas scrubbing device is disposed between the acid removal distillation device and the cooling recovery device. 2: Reactor for producing alkyl chloride; 4: Distillation device for acid removal; 6: Gas cleaning device with alkali;
8: Distillation device for cooling recovery.

Claims (1)

[Claims] When producing C ₁ - C ₃ alkyl chloride by reacting 1 C ₁ - C ₃ alcohol and hydrogen chloride in a reactor, (a) the obtained C ₁ - C ₃ alkyl chloride, A superheated vapor reaction mixture consisting of by-product water, unreacted hydrogen chloride, and unreacted C ₁ to C ₃ alcohol and steam are supplied to an acid removal distiller, and the steam is condensed to contain substantially the entire amount of hydrogen chloride. forming and removing an acid byproduct solution from the still; (b) removing gaseous C1 _{- C3} alkyl chloride and unreacted gaseous _C1 - _C3 alcohol from the acid removal still; _and ( _{c )} gaseous C _chloride . A method for recovering _C1 - _C3 alkyl chloride, comprising: taking out and recovering the _C1 - _C3 alkyl from the cooling recovery distiller. 2. The method of claim 1, wherein the _C1 - _C3 alcohol is methanol and the _C1 - _C3 alkyl chloride is methyl chloride. 3. When producing _C1 - _C3 alkyl chloride by reacting _C1 - _{C3 alcohol and hydrogen chloride in a reactor, (a) the resulting C1-C3 alkyl chloride} , by-produced water, and The superheated vapor reaction mixture consisting of reacted hydrogen chloride and unreacted _C1 - _C3 alcohol, steam and spent recycled alkaline aqueous solution are fed to an acid removal distiller to form an acid containing a major proportion of hydrogen chloride by condensation of the steam. forming a by-product solution and removing it from the still; (b) removing gaseous _C1 - _C3 alkyl chloride and unreacted gaseous _C1 - _C3 alcohol from the acid removal still; It is fed into a gas scrubber where it is brought into intimate contact with an aqueous alkaline solution to remove residual hydrogen chloride and obtain a spent recycled aqueous alkali solution, and this aqueous solution is transferred from the gas scrubber to step (a). (c) removing the gaseous _C1 - _C3 alkyl chloride and unreacted gaseous _C1 - _C3 alcohol from the gas scrubber and transferring it to the cooled recovery distiller; send it to
the unreacted _C1 - _C3 alcohol is then liquefied and the liquefied _C1 - _C3 alcohol is removed from the still; and (d) the gaseous _C1 - _C3 alkyl chloride is removed from the cooled recovery still. A method for recovering _C1 - _C3 alkyl chloride, which comprises: taking out and recovering; 4. Claim 3 comprising the step of recycling the liquefied unreacted _C1 - _C3 alcohol recovered from the cooled recovery distiller of step (c) to the _C1 - _C3 alkyl chloride production reactor. Method described. 5. The method of claim 3, comprising the step of using methyl chloride as a coolant for the cooled recovery distiller of step (c). 6 _C1 - _C3 alkyl chloride is methyl chloride, ethyl chloride, n-propyl chloride or i-propyl chloride, and C1 _{- C3} alcohol is correspondingly methanol, ethanol, n-propanol or i-propanol. A method according to claim 3. 7 C1 _{- C3} alkyl chloride is methyl chloride,
4. The method of claim 3, wherein the _C1 - _C3 alcohol is methanol. 8 C1 _{- C3} alkyl chloride is methyl chloride;
5. The method of claim 4, wherein the _C1 - _C3 alcohol is methanol. 9 C1 _{- C3} alkyl chloride is methyl chloride;
6. The method of claim 5, wherein the _C1 - _C3 alcohol is methanol. 10. The method of claim 9, wherein the methyl chloride coolant is part of the product recovered from step (d). 11. The method according to claim 3, wherein the alkali is sodium hydroxide or potassium hydroxide.