JPS6023649B2 - Method for producing methyl bromide using hydrobromic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an aqueous solution of hydrogen bromide (hereinafter referred to as hydrobromic acid).

) with methanol, and more specifically, it relates to a method for producing methyl bromide in a high yield by reacting hydrobromic acid and methanol in the presence of an aqueous sulfuric acid catalyst. It relates to an industrial method for manufacturing. The present invention can be carried out by either a batch method or a continuous method, but from an industrial perspective, a continuous method is preferable. In general, in the industrial production of methyl bromide, unlike the case of other alkyl halides, such as methyl chloride, the price of the bromine compound that is the raw material is extremely expensive, so it is necessary to make it as cheap as possible. The most important things are to use a bromide as the bromine source and to increase the reaction conversion rate of the raw material bromide to methyl bromide as high as possible.

In this regard, in the production of methyl bromide using hydrobromic acid, the maximum hydrobromic acid can contain is only about 40% by weight of hydrogen bromide, which is equivalent to 1 mole of hydrogen bromide. On the other hand, water is 5
．． As is clear from the reaction formula for producing methyl bromide shown in equation '1}, such a composition can produce HBr+CH30H→CH3Br+ in a sufficiently good yield.
Day 20...'1'〈It was previously considered impossible to produce methyl bromide.

For this reason, as an industrial method for producing methyl bromide using hydrogen bromide and methanol, as shown in equation m, conventionally the method was to introduce hydrogen bromide gas of good purity into a liquid layer containing methanol (Japanese Patent Publication No. 4269), a method of bringing hydrogen bromide gas into direct gas phase contact with methanol (Special Publication No. 46-5682),
However, although these methods are suitable for producing methyl chloride using inexpensive hydrogen chloride and methanol, as an industrial method for producing methyl bromide, they are not suitable for producing methyl bromide using hydrogen bromide gas. Since the price is much higher than that of hydrobromic acid and it is currently impossible to obtain it in large quantities, it is considered an unappealing method from an industrial perspective and is not implemented. It's not as familiar as it should be.

Another method for producing methyl bromide is to use an alkali bromide such as sodium bromide or ammonium bromide as a bromine source and decompose it with a mixture of sulfuric acid, phosphoric acid, etc. (C.A. (Chemical Abstracts) 504193). (1956))
However, with this method, it is possible to increase the concentration of bromide per unit volume in the reaction zone, and it seems to be an advantageous method. When introduced into the reaction zone, it is necessary to conduct it in a solid or slurry state, and furthermore, this alkali bromide itself is produced from hydrogen bromide or hydrobromic acid, and as its raw material. The price of this method cannot be low, and it cannot necessarily be said that it is a good method from an industrial point of view.

Instead of these methods, sulfur is now used as a reducing agent,
A method for producing methyl bromide from bromine and methanol (hereinafter referred to as the sulfur method).

) are widely practiced industrially. However, even in this sulfur method, [1] Since bromine is an extremely corrosive substance, it is impossible to accurately measure and transport it industrially.

{2- For this reason, the composition of the reaction components in the reaction zone cannot be arbitrarily and precisely controlled, and if methyl bromide is to be produced continuously, unreacted sulfur or this may be present in the reaction waste liquid. Since it contains substances such as thioic acid, which is produced by partial oxidation, it causes environmental pollution.

{3} Under normal pressure, the boiling point of bromine is 58 points, so the reaction temperature cannot be raised any higher. In such a low-temperature castle reaction, the reaction of the sulfur method becomes complicated,
It has drawbacks such as the inability to maintain a stable production rate of methyl bromide. The main drawback of this sulfur method can be avoided by increasing the reaction pressure, but since this method uses bromine, which is highly corrosive, as a raw material, the manufacturing equipment is made of glass. It is necessary to provide a lining, and in addition to this, it must be made pressure resistant, and producing methyl bromide, which is harmful to living organisms, involves considerable difficulty and danger. Therefore, the present inventors have conducted intensive and detailed research on the industrial production method of methyl bromide using hydrobromic acid, which was previously thought to be difficult to establish as an industrial production method. This led to the completion of an industrial production method that can solve all the problems in methyl bromide production at once. Generally, in the reaction of methyl bromide by the reaction of hydrobromic acid and methanol, the concentration of unreacted hydrogen bromide contained in the reaction completed liquid is
The hydrogen bromide concentration is considerably lower than that in the hydrobromic acid used as a raw material, so even if it is recovered and used again in the reaction, the hydrogen bromide concentration from such a concentration of hydrobromic acid is very low. It is now extremely difficult to produce methyl, and for this reason, the industrial production method of methyl bromide using this reaction requires hydrobromic acid, which is extremely expensive compared to other raw materials. As much as possible, at least 97% to 98%,
Desirably, nearly 100% reaction conversion to methyl bromide is required.

Conventionally, in production methods utilizing this reaction, it has been impossible to achieve such a high reaction conversion D rate of raw material hydrobromic acid, even if sulfuric acid is used as a catalyst.

The main reason for this is that, as mentioned above, hydrobromic acid, which is the bromine source in the reaction, contains a minimum of about 5% by weight of water, so the sulfuric acid concentration of the catalyst cannot be high. If this is unreasonably high, for example, 75% by weight or more, the hydrogen bromide in the raw material hydrobromic acid will vaporize and escape from the reaction zone, and further, This is because some of it decomposes into bromine and does not take part in the reaction. However, the most noteworthy point of the present invention is that although the reaction is an equimolecular reaction of hydrogen bromide and methanol, as is clear from reaction formula '1', sulfuric acid is present in the reaction zone. The present inventors have discovered that when an aqueous solution is present, the reaction is accelerated to a greater extent by methanol than by hydrogen bromide.

Such a phenomenon occurs when no sulfuric acid is present in the reaction zone.
That is, this phenomenon is not observed when 47% hydrobromic acid and methanol are simply reacted, and in such a case, the reaction is caused by bromide rather than by the methanol concentration in the reaction zone. Since the reaction is greatly accelerated by the hydrogen concentration, no matter what you do, it is impossible to increase the reaction conversion rate of raw material hydrobromic acid to methyl bromide to 50% or more.

That is, in the method of the present invention, a sulfuric acid aqueous solution is present in the reaction zone, and hydrobromic acid and sulfuric acid are added to this in a molar ratio of CH30H/HBr>1.0, industrially preferably 1. By feeding the reaction at a ratio of .05 to 2.0, under conditions where the reaction has sufficiently progressed, the ratio of methanol in the reaction zone to hydrogen bromide is greater than the theoretical reaction equivalent, and is in large excess. The purpose is to further accelerate the reaction by adjusting the sulfuric acid concentration of the sulfuric acid aqueous solution that is the catalyst in the reaction zone to 50 to 75% by weight.
Industrially desirable is one that can further accelerate the reaction by maintaining the concentration between 65% and 65% by weight, and can achieve a sufficiently high reaction conversion rate of raw material hydrobromic acid to methyl bromide of 97% or more. It is.

More preferably, the sulfuric acid supplied to the reaction zone is at least 9% by weight concentrated sulfuric acid or fuming sulfuric acid, industrially preferably 9% by weight sulfuric acid, and the reaction in the reaction zone is By increasing the concentration of the components per unit volume as much as possible and easily maintaining the reaction temperature above 95 qo even when a large amount of methanol is present in the reaction zone, the reaction can be further promoted and reduced. In both cases, the reaction conversion rate of raw material hydrobromic acid to methyl bromide was 98% or more, approximately 1
00%.

As mentioned above, the method of the present invention is an industrially extremely advantageous method for producing methyl bromide, which will be explained in more detail with reference to the attached drawings. When introducing, the molar ratio of C is OH/HBr
>1. More preferably, the reaction is carried out by continuously feeding at a temperature of 1.05 to 1.40.

At the same time, concentrated sulfuric acid or fuming sulfuric acid, industrially preferably 9% by weight sulfuric acid 3, is introduced into the reactor in an amount equal to the amount of water brought into the reactor by the above raw materials. Assuming that these raw materials are completely opposite, the sulfuric acid concentration of the sulfuric acid solution present in the reactor is made to be 50 to 75% by weight, including the produced water. Furthermore,
The reaction temperature is 95°C or higher, preferably 105-130°C
to be maintained. The produced methyl bromide is generated in gaseous form from the reactor, but at this time, it is accompanied by methanol hydrobromic acid, so most of it is returned to the reactor using a cooler 6 installed at the top of the reactor. Furthermore, hydrobromic acid contained in methyl bromide is removed by absorption into an alkaline solution or water 4 in an absorption tower 7. However, if appropriate conditions of the present invention are selected, this absorption tower 7 is not necessarily essential. Then, dimethyl ether, the only by-product of the reaction contained in methyl bromide, and
By absorbing water, methanol, etc. into concentrated sulfuric acid 3 in the purification tower 8, the purified methyl bromide is produced with a purity of at least 99. % or more of the string volume. In the method of the present invention, the amount of dimethyl ether by-produced by this reaction is approximately 1/100 of methyl bromide in terms of molar ratio as long as hydrogen bromide is present in the reaction zone. This proportion remains unchanged.

In addition to the effect on the reaction when carrying out the method of the present invention, the industrial advantage is that the concentrated sulfuric acid that has absorbed dimethyl ether in the purification column 8 can be used as it is as a catalyst for the reaction. However, it does not lead to any accumulation of dimethyl ether. If anything, the reaction formula [
This is because, like methanol, this dimethyl ether quickly reacts with hydrobromic acid to produce methyl bromide, as shown in 21.

C ratio OCH 312 HBr → Today 3Br + Day 20
......'2) On the other hand, the reaction-completed liquid extracted from the reactor 5 contains almost no hydrogen bromide and consists mostly of methanol and an aqueous sulfuric acid solution. After combining the aqueous solutions, the mixture is passed through a distillation column to recover unreacted methanol, dissolved methyl bromide, dimethyl ether, etc. present in the mixture, and these recovered substances are circulated to the reactor 5.

Therefore, only a simple aqueous sulfuric acid solution is discharged from the bottom of the distillation column 10, and the chemical oxygen demand of the discharged liquid is approximately 1 kg, so that it can be reused for other uses of sulfuric acid. However, even if the material is simply neutralized with alkali and then disposed of, there is no risk of causing any environmental pollution. As described above, the method of the present invention converts the hydrobromic acid used as a raw material almost completely into methyl bromide by simply converting concentrated sulfuric acid or fuming sulfuric acid used as a catalyst into a diluted sulfuric acid aqueous solution. Furthermore, it is a continuous production method that completely converts methanol, one of the raw materials, into methyl bromide.Furthermore, unlike the sulfur method, the process is simple and its normal operation is easy. It's something you get.

The present invention will be specifically illustrated below using specific examples. In these specific examples, all parts and percentages are by weight. Example 1 97 parts of an aqueous sulfuric acid solution with a concentration of 60% was placed in a four-bottle flask with an internal volume of approximately 1, and the mixture was electromagnetically concentrated to bring the internal temperature of the flask to 9,000.

Add 173 parts of 47% hydrobromic acid to the above sulfuric acid aqueous solution, and add 99 parts of 47% hydrobromic acid.
5% methanol65. The methyl bromide generated from the reactor was quantitatively introduced over a period of 60 minutes, and the methyl bromide generated from the reactor was cooled at 4 to 5°C by flowing cooling water into a double condenser tube type cooler attached to the upper reactor. The mixture was cooled and then absorbed into a glass trap (hereinafter referred to as ethanol trap) containing a predetermined amount of ethanol immersed in a liquid cooled to 170 qo.

The weight increase of the ethanol trap was determined by weighing, and a portion of it was subjected to gas chromatography to analyze organic substances such as methyl bromide, dimethyl ether, and methanol.

A portion of the solution was diluted with a large amount of water, brought to room temperature, made alkaline with an aqueous solution of caustic soda, and removed low-boiling components on a sand bath. After that, bromides were analyzed by Holhardt's method. Furthermore, the reaction completed liquid was also analyzed in the same manner as the ethanol trap.

As a result, from the end of the introduction of hydrobromic acid and methanol,
Methyl bromide and dimethyl ether collected in the eta/l trap after 30 minutes, 6 whiskers, and 120 minutes were methyl bromide = 84.7 parts and dimethyl ether = 0.4 parts, respectively.
1 part: methyl bromide = 91.3 parts, dimethyl ether = 0
．． 51 parts: methyl bromide = 93.9 parts, dimethyl ether = 0.52 parts, no hydrogen bromide was observed, and methanol was also 0.01 part or less. On the other hand, 120 minutes after the end of the monkey feed supply, the internal temperature of the reactor was immediately set to about 1000 below room temperature, the weight of the liquid in the reactor was measured, and a part of it was analyzed by gas chromatography. Weight = 1 female, 1 part, which contains 0.15% and 0.0% of methyl bromide and dimethyl ether, respectively.
It contained 7%. Example 2 An experiment was carried out under the same conditions as in Example 1 except that the reaction temperature was 180 qo.

The amounts of methyl bromide and dimethyl ether produced after 3 minutes, 6 minutes, and 90 pieces after the end of raw material supply were methyl bromide = 91.1 parts, and dimethyl ether = 0.4 parts, respectively.
4 parts; methyl bromide = 94.2 parts, dimethyl ether = 0
．． 46 parts; methyl bromide = 94. $ part, dimethyl ether = 0.46 part, and on the other hand, the reaction completed liquid was 108 parts, which contained methyl bromide and dimethyl ether at 0.0 total% and 0.04%, respectively. .

Example 3 In the same manner as in Example 1, 63% sulfuric acid aqueous solution 4
50 parts were placed in a reactor, the internal temperature of the reactor was set to 120°C, and 17 parts of 47% hydrobromic acid and 41.5 parts of 99.5% methanol were introduced in 1 hour. After a 30 minute delay from the start, 20 parts of a 90% sulfuric acid aqueous solution was further introduced into the reactor over a period of 30 minutes.

The methyl bromide and dimethyl ether captured by the ethanol trap at the end of the introduction of hydrobromic acid, methanol, and sulfuric acid aqueous solution and 30 minutes after the above point were as follows:
Methyl bromide = 88. Akuto, dimethyl ether = 0
．． 19 parts; methyl bromide = 94.6 parts, dimethyl ether: 0.25 parts.

Furthermore, the reaction-completed solution contained 0.07% and 0.01% of methyl bromide and dimethyltable, respectively. Reference Example 1 In the same manner as in Example 1, 970 parts of a 49% sulfuric acid aqueous solution was placed in a reactor, and the reaction temperature was kept constant at 95 qC.

To this, 173 parts of 47% hydrobromic acid and 31.5 parts of 99.5% methanol were introduced over 60 minutes, and the odor generated 60 minutes, 12 minutes, and 240 minutes after the end of introduction of these raw materials. When the amounts of methyl chloride and dimethyl ether produced were determined, methyl bromide = 26.7 parts, dimethyl ether = 0.06 parts, and methyl bromide = 44. $ part, dimethyl ether = 0.12 part: methyl bromide = 56.2 part, dimethyl ether = 0.14 part. On the other hand, the amounts of methyl bromide and dimethyl ether dissolved in the reaction-completed solution were 0.07% and 0.006%, respectively. Reference Example 2 In the same manner as in Example 1, 970 parts of a 60% sulfuric acid aqueous solution was placed in a reactor in advance, the reaction temperature was kept constant at 95°C, and 173 parts of 47% hydrobromic acid and 99.5% methanol were added. 32.5 parts were introduced over 1 hour.

From the end of the introduction of these raw materials, 6 generations, 12 generations, 240
Methyl bromide and dimethyl ether generated up to the minute point were 50.5 parts of methyl bromide and 0 parts of dimethyl ether, respectively.
．． 04 parts: methyl bromide = 64.8 parts, dimethyl ether = 0.057 parts; methyl bromide = 72. Ikarito, dimethyl ether = 0.061 part. On the other hand, the content of methyl bromide and dimethyl ether in the reaction completed liquid is approximately 0.06%.
, 0.005%.

As is clear from the results of Reference Examples 1 and 2, C horse OH/H
When Br<1, the production rate of methyl bromide is slow.

Example 4 A four-necked flask with arms having an effective volume of about 1 was used as a reactor,
Approximately 63% sulfuric acid aqueous solution is poured into this, immersed in an oil bath, heated from the outside, and the inside of the reactor is kept at a constant temperature of 120°C by using an electromagnetic lamp and stirring the inside of the reactor. And so.

To this, 47% hydrobromic acid, 99.5% methanol, and fuming sulfuric acid containing 30% free sulfuric anhydride were continuously introduced in amounts of 16 parts, 30 parts, and 146 parts per hour, respectively.

The product gas continuously generated from the reactor was passed through a condenser and absorbed into ethanol traps in the same manner as in the example, and the ethanol traps were replaced every 30 minutes and the weight of each trap was measured. and conducted an analysis. In addition, the reaction finished liquid overflowing from the reactor was received in a glass receiver, which was also replaced every third batch, and its weight was measured and analyzed by gas chromatography. About 15 to 2 feeding hours after the start of the reaction, methyl bromide absorbed into the ethanol trap,
and dimethyl ether, each 43.9±0.2 parts/
3 minutes, 0.225±0.023 parts/30 minutes, and methanol and bromine ions were hardly contained at 0.001 parts or less.

On the other hand, the overflow liquid was 128±0.3 parts/3 parts, which contained approximately 0.13% each of methyl bromide and dimethyl ether.
, 0.0007%. Reference Example 3 In the same manner as in Example 4, a side flask with an effective volume of approximately 1 was filled with approximately 77% sulfuric acid solution, and the internal temperature was set to 120%.
00 constant, and 47% hydrobromic acid, 99.5% methanol, and 90% sulfuric acid aqueous solution were each added at 10% per hour.
When hydrogen bromide was introduced at feed rates of 0 parts, 187 parts, and 376 parts, the liquid inside the reactor was colored reddish brown at the same time as the supply of hydrogen bromide started, and the ethanol trap absorption liquid and overflow liquid from the reactor were also colored. It also turned reddish brown.

Analysis of the liquid in the ethanol trap between 15 and 2 hours after the start of the reaction revealed that methyl bromide was 23.0 parts/30 minutes, and dimethyl ether was 0.115 parts/30 minutes.
The amount was 0.02 parts/3 minutes, and in addition, bromine ions were present in the amount of 0.3 parts/30 minutes in terms of hydrogen bromide.

Furthermore, the overflow from the reactor was 220±0.5 parts/30 minutes, which contained 0.03% and 0.007% of methyl bromide and dimethyl ether, respectively.

As is clear from the above results, the concentration of sulfuric acid aqueous solution is 75
Above % by weight, hydrogen bromide escape and decomposition of hydrogen bromide to bromine occur.

[Brief explanation of the drawing]

The accompanying drawing (FIG. 1) is a flow sheet for implementing one example of the present invention. In the figure, 1 indicates the supply of hydrobromic acid, 2 indicates methanol, 3 indicates concentrated sulfuric acid for catalyst, and 4 indicates diluted caustic soda water for absorbing the hydrogen bromide component accompanying the generation of methyl bromide. This shows the supply of liquid. Reference numeral 5 indicates a reactor equipped with rope blades, the reactor is a jacket, and is heated by steam or the like. 6 is a cooler for returning unreacted components accompanying the produced methyl bromide to the reactor. Reference numeral 7 indicates an absorption tower for absorbing the collected hydrogen bromide component accompanying the produced methyl bromide, and 8 is an absorption tower for removing by-produced dimethyl ether from the methyl bromide. The concentrated sulfuric acid that has absorbed dimethyl ether in step 8 is supplied to reactor 5 as it is. 9 shows purified methyl bromide from which impurities have been removed. Reference numeral 10 denotes a distillation column for recovering reaction methanol and the like in the reaction-finished liquid and rendering the reaction-finished liquid harmless. Reference numeral 11 indicates a cooler for increasing the purity of the unreacted methanol, dissolved methyl bromide, dimethyl ether, etc. recovered in step 10 and returning them to the reactor. Reference numeral 12 indicates an aqueous sulfuric acid solution from which low-boiling point organic substances have been removed in the distillation column 10 and which contains a certain amount of odorous substances. Figure 1

Claims (1)

[Claims] 1. In producing methyl bromide from hydrobromic acid and methanol, using an aqueous sulfuric acid solution as a catalyst, the molar ratio of hydrobromic acid and methanol is CH_3OH/HBr>1.
A method for producing methyl bromide, which comprises introducing methyl bromide into a reaction zone and allowing the reaction to occur so that the amount of methyl bromide becomes 0. 2. The sulfuric acid concentration of the catalytic sulfuric acid aqueous solution in the reaction zone is equal to the water produced by the reaction of the raw material hydrobromic acid and methanol,
Including the water that these raw materials bring into the reaction zone,
A method according to claim 1, wherein the amount is 50 to 75% by weight. 3. The method according to claim 1 or 2, wherein sulfuric acid with a concentration of 90% by weight or more is introduced into the reaction zone as a sulfuric acid source for the catalytic sulfuric acid aqueous solution. 4. The method according to claim 3, in which concentrated sulfuric acid or fuming sulfuric acid is used as the sulfuric acid with a concentration of 90% by weight or more.