JPH0564945B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing alkanesulfonic acids, and in particular, in a reaction system substantially free of water, saturated hydrocarbons are treated with sulfur dioxide and oxygen under irradiation with light. The present invention relates to a method for producing alkanesulfonic acid. Prior Art A method of photo-sulfoxidizing saturated hydrocarbons using sulfur dioxide and oxygen in a reaction system substantially free of water causes colored substances to adhere to the side wall of the light source.
Interfering with light irradiation, the photo-sulfoxylation reaction is significantly reduced. Therefore, when a predetermined amount of this colored substance adheres to the side wall surface of the light source, it is necessary to stop the operation of the reaction apparatus and remove the colored substance, which is inefficient and makes continuous operation impossible. For this reason, in the industrial production of alkanesulfonic acids, a method of photo-sulfoxylation in the presence of water is exclusively employed. However, in this method, water interferes with the radical chain reaction, resulting in poor reaction efficiency, and in addition to the alkanesulfonic acid, almost equimolar sulfuric acid is produced as a by-product. It is necessary to remove the alkanesulfonic acid by distillation at a temperature of about 100 ml, which causes problems such as odor and coloration of the alkanesulfonic acid. On the other hand, even in this method of photo-sulfoxylation in the presence of water, some colored substances are produced. In order to suppress the formation of this colored substance, there is a method in which saturated hydrocarbons are first irradiated with ultraviolet rays in the presence of sulfur dioxide in the substantial absence of oxygen, and then oxygen is introduced into the irradiated saturated hydrocarbons. It has been proposed (Special Publication No. 47-28973). In addition, in order to suppress the adhesion of the generated colored substances to the side wall surface of the light source,
A method has been proposed in which a predetermined amount of nitrogen or air is circulated near the side wall of the light source (Japanese Patent Publication No. 1973-
Publication No. 11740). Problems to be Solved by the Invention In the method of irradiating ultraviolet rays in the substantially absence of oxygen, the reaction rate is extremely slow because oxygen radicals, which are an important promoter of the photo-sulfoxylation reaction, are not sufficiently present. , not economical. Furthermore, with the method of circulating nitrogen or the like near the light source side wall surface, it is not possible to completely prevent liquid from coming into contact with the wall surface, and staining of the light source side wall surface is unavoidable. Since the sulfur dioxide dissolved in the reaction solution is expelled out of the reaction system, the concentration of sulfur dioxide in the reaction solution does not increase and the reaction rate becomes slow. It should be noted that no proposal has been found regarding a method for suppressing the production of colored substances and preventing their adhesion to the side wall surface of the light source in a system substantially free of water. As a result of intensive studies to solve these problems, the inventors of the present invention found that by bringing the reaction solution into contact with a sodium salt, it is possible to suppress the production of colored substances without reducing the reaction rate of photo-sulfoxylation, and moreover, the reaction We have discovered the surprising fact that some sulfuric acid produced during the process can be removed as sodium hydrogen sulfate by solid-liquid separation. The present invention was made based on this knowledge,
When photo-sulfoxidizing saturated hydrocarbons in a system substantially free of water, it prevents colored substances from adhering to the side wall of the light source without reducing the reaction rate, and also continuously removes sulfuric acid. The purpose is to propose a method for producing alkanesulfonic acids. Means for Solving the Problems The present invention provides a reaction system substantially free of water,
In a method for producing alkanesulfonic acid by reacting sulfur dioxide and oxygen on a saturated hydrocarbon under irradiation with light, a photo-sulfoxylation reaction is carried out while the reaction solution of the reaction system is brought into contact with a sodium salt, and then the After degassing the reaction solution, the precipitate is separated. In particular, the sodium salt is sodium sulfite or sodium carbonate, and the contact with the sodium salt adds sodium salt to the reaction system. This is a method for producing alkanesulfonic acid, which is carried out by extracting a part of the reaction liquid from the reaction system, bringing it into contact with a sodium salt, and then returning it to the reaction system. The saturated hydrocarbon that can be used in the present invention may be any saturated hydrocarbon as long as it exists as a liquid in the reaction system, but if it is used for production as a raw material for surfactants such as synthetic detergents, carbon atoms 8 to 24 normal paraffins are preferred. As a light source for irradiation, one that can irradiate light with a wavelength of 500 nm or less can be used. The reaction temperature is appropriately selected in the range of -20 to 200°C, taking into account the melting point or boiling point of the saturated hydrocarbon, but when using a saturated hydrocarbon that is liquid at room temperature, there is no particular need for heating. The higher the reaction pressure, the higher the reaction rate, which is preferable, but a range of 0 to 50 atmospheres is sufficient. Sulfur dioxide and oxygen can be used as a gas mixture, and this gas mixture may be left in the reactor only to replenish the consumed amount, or it may be allowed to flow through the reactor. This mixed gas may have a molar ratio of sulfur dioxide to oxygen of 1 to 1000, preferably 2 to 100. Generally, for the photo-sulfoxylation reaction, it is preferable to use a cylindrical reactor that is equipped with a cylindrical light source in the center and can retain a saturated hydrocarbon liquid around the light source. It is preferred that sulfur dioxide and oxygen gases are introduced into the saturated hydrocarbon liquid via the saturated hydrocarbon liquid, and that the gases after contact can be partly recycled. As the sodium salt, sodium sulfite, sodium carbonate, sodium hydrogen sulfite, sodium sulfide, etc. can be used, but especially sodium sulfite is used because the gas generated by decomposition does not interfere with the reaction and does not have a bad odor. Alternatively, sodium carbonate is preferred. These sodium salts may be used either anhydrous or containing water of crystallization without any particular problem. This sodium salt may be used in the form of powder, pellets, or flakes, but
When it is added to the reaction system, it is preferably in the form of a powder, and when it is used in a column, it is preferably in the form of pellets or flakes. When adding a sodium salt to the reaction system, the sodium salt may be added to the saturated hydrocarbon in advance before introducing the saturated hydrocarbon into the reactor, or it may be added directly to the reaction liquid in the reactor. good. The amount added at this time is 0.1% by weight based on the saturated hydrocarbon.
The content is preferably from 10% by weight. 0.1% by weight
Below this, it is not possible to sufficiently suppress the adhesion of the colored substance to the wall surface of the light source, and the photo-sulfoxylation reaction cannot be carried out continuously for a long time, which is not preferable. The larger the amount of sodium salt added, the longer the adhesion of colored substances can be inhibited, but even if it exceeds 10% by weight based on the saturated hydrocarbon, no significant increase in the inhibitory effect is observed. for 10% by weight
It is economical to do the following. Incidentally, the reaction solution in which the sodium salt is dispersed becomes a suspension in the reactor, but when the addition amount is below 10% by weight, no particular reduction in the reaction rate due to light scattering etc. is observed. Further, in the present invention, a method is adopted in which a column is filled with a sodium salt, a part of the reaction solution is extracted from the reactor, and the reaction solution is brought into contact with the sodium salt by flowing it through the column. Good too. In this case, the contact time between the sodium salt and the reaction solution is such that the sodium salt dissolves in the reaction solution and decomposes and removes the substance that causes the formation of colored substances, and the dissolution rate in this case is determined by , is extremely fast, so the contact time is not particularly rate-limiting, and a short time is sufficient. On the other hand, the amount of reaction liquid withdrawn from the reactor is preferably 0.01 to 1 vol%/sec of the reaction liquid in the reactor, although it depends on the reaction speed. If it is less than 0.01vol%/sec, it will not be possible to effectively prevent the formation of colored substances;
%/sec or more is meaningless and uneconomical. Note that as the reaction progresses, the sodium salt dissolves in the reaction solution and flows out of the column, so it can be handled by appropriately replenishing the column. Degassing can be performed by blowing a degassing gas into the reaction solution. The purpose of this degassing gas is to remove SO ₂ from the reaction solution, so any gas that is inert to the reaction solution can be used, but if oxygen gas is used, This is particularly preferred because the gas after degassing can be recycled and reused in the reaction system. The amount of degassing gas to be blown cannot be determined unconditionally because it varies depending on the size and shape of the container, but it is usually 0.5 per reaction liquid.
It is appropriately selected from the range of cc/sec to 100c.c./sec. Through this degassing operation, sulfuric acid reacts with sodium ions dissolved in the reaction solution and precipitates as sodium hydrogen sulfate. In this case, sodium hydroxide or the like may be added to completely remove remaining sulfuric acid. This precipitated sodium hydrogen sulfate can be separated and removed by methods such as decantation, filtration, and centrifugation. Next, one embodiment of the present invention will be described based on the drawings. In the figure, 1 is a reactor, and a light source 2 is installed in the center of the reactor. A mixed gas of sulfur dioxide and oxygen is supplied from the lower part of the reactor 1, and saturated hydrocarbons are supplied from the upper part. Unreacted gas is extracted from the upper part of the reactor 1, fresh sulfur dioxide and oxygen are added, and the gas is recycled. A portion of the reaction liquid is extracted from the reactor 1 and supplied to a packed column 3 filled with sodium salt. In this packed column 3, the sodium salt and the reaction solution come into contact, and the causative agent (estimated to be peroxide of saturated hydrocarbon) that generates the colored substance is decomposed and removed. The reaction liquid flowing out from the packed column 3 is returned to the reactor 1 with new saturated hydrocarbon added thereto. The reaction liquid in the reactor 1 has a saturated hydrocarbon reaction rate of 0.1 to 60%,
In particular, the reaction time is preferably adjusted to 2 to 30%. In this case, if the reaction rate is too low, the economic efficiency will be poor, and if the reaction rate is too high, alkanedisulfonic acid or alkane trisulfonic acid will be produced, and the selectivity for alkane monosulfonic acid will decrease. Alkane monosulfonates have excellent properties as surfactants.
It is preferable to control the reaction so as to reduce the production of di- or trisulfonic acid. However, if a small amount of di- or trisulfonic acid is mixed in, the quality of the alkanesulfonic acid product will not be particularly degraded. The amount of sulfuric acid produced in the photo-sulfoxylation of the present invention is approximately equimolar to the alkanesulfonic acid, but this sulfuric acid is converted into sodium hydrogen sulfate by degassing the sulfur dioxide in the reaction solution. It precipitates and suspends in the reaction solution. The reaction liquid extracted from the reactor 1 is sent to the degassing tower 4.
The dissolved sulfur dioxide is degassed by blowing oxygen into the reactor, and the degassed gas is recycled to the reactor 1 for reuse. On the other hand, the reaction solution in which sodium hydrogen sulfate has been precipitated by deaeration is further added with sodium hydroxide if necessary to precipitate the remaining sulfuric acid as sodium hydrogen sulfate, and then transferred to a filter, a standing tank,
Alternatively, it is supplied to a solid-liquid separator 5 such as a centrifuge to separate the sodium hydrogen sulfate. The reaction solution after this separation is introduced into an extraction device 6 such as a centrifugal extractor or a rotating disk extractor, and extracted with an extraction solvent such as water, alcohol, or a mixed solvent thereof. The extract containing alkanesulfonic acid is introduced into the neutralization tank 7, neutralized with an alkali such as sodium hydroxide, potassium hydroxide, calcium hydroxide, etc., and recovered as an alkanesulfonic acid salt. On the other hand, the extraction solvent is recovered from the roughinate liquid from the extraction device 6 by a distillation device 8 or the like.
It is combined with the extraction solvent (not shown) recovered after the neutralization and recycled in the extraction device 6 for reuse. The unreacted saturated hydrocarbons recovered in the distillation device 8 etc.
It is recycled to reactor 1 and reused. Example (Example) A reactor consisting of a cylindrical shape made of glass with an inner diameter of 50 mmφ and a height of 1000 mm, and a reactor equipped with a mercury lamp protected by quartz glass at the axis of the reactor, and a reactor with an inner diameter of 50 mmφ and a height of 200 mm.
A photo-sulfoxylation reaction was carried out using a glass column filled with 400 g of sodium sulfite while circulating the reaction solution between the reactor and the packed column at a rate of 5 c.c./sec. First, 1.2% of normal paraffin with 14 to 16 carbon atoms is put into a reactor as a raw material, and 150% of sulfur dioxide is added from the bottom of the reactor.
/hr.Oxygen was introduced at a rate of 50/hr, and the photo-sulfoxylation reaction was carried out for 40 minutes. Subsequently, the reaction liquid in the reactor was drawn out of the system at a rate of 30c.c./min.
The reaction was carried out continuously while supplying the same amount of new normal paraffin as above. When 1.8 of the reaction solution extracted from the system was degassed with oxygen at 5 c.c./sec for 60 minutes, white powdery sodium hydrogen sulfate was precipitated. Further, 2 g of sodium hydroxide powder was added to this liquid, and the sulfuric acid was almost completely converted into sodium hydrogen sulfate, and the mixture was filtered through paper. This filtered liquid was extracted with a water-methanol solution (vol ratio 50/50).
The yield of alkanesulfonic acid was determined by the method specified in JISK3362, "5.3.3 Determination of anionic surfactant." Moreover, this extract contained almost no sulfuric acid. The photo-sulfoxylation reaction was carried out continuously for more than 10 hours, but no colored substances were observed to adhere, and as shown in Table 1, there was no decrease in yield. (Comparative Example) When a photo-sulfoxylation reaction was carried out in the same manner as in the example except that the sodium sulfite packed column was not used, colored substances were observed to adhere to the reactor wall after 1 hour. Approximately 1% by weight of sulfuric acid was also mixed into the reaction solution, and was extracted together with the alkanesulfonic acid into the extract. Furthermore, as shown in Table 1, the yield of alkanesulfonic acid decreased over time.

[Table] Effects The method of the present invention as described above suppresses the production of colored substances and performs the photo-sulfoxylation reaction continuously and efficiently even when the photo-sulfoxylation reaction is carried out in a water-free system. Moreover, the produced sulfuric acid can be removed as sodium hydrogen sulfate, and the product has the special effect of eliminating the coloration of the alkanesulfonate product that is caused by the removal of sulfuric acid.

[Brief explanation of drawings]

The figure shows a schematic flow for explaining one embodiment of the present invention. 1... Reactor, 2... Light source, 3... Packed column.

Claims (1)

[Scope of Claims] 1. A method for producing alkanesulfonic acid by causing sulfur dioxide and oxygen to act on a saturated hydrocarbon under irradiation of light in a reaction system substantially free of water, wherein the reaction in the reaction system is A method for producing an alkanesulfonic acid, which comprises carrying out a photo-sulfoxylation reaction while bringing a liquid into contact with a sodium salt, then degassing the reaction liquid, and then separating a precipitate. 2. The method for producing alkanesulfonic acid according to claim 1, wherein the sodium salt is sodium sulfite or sodium carbonate. 3. The method for producing an alkanesulfonic acid according to claim 1, wherein the contact with the sodium salt is carried out by adding the sodium salt to the reaction system. 4. The alkane according to claim 1, wherein the contact with the sodium salt is carried out by extracting a part of the reaction liquid from the reaction system, bringing it into contact with the sodium salt, and then returning it to the reaction system. Method for producing sulfonic acid.