JPH0571586B2 - - 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 in the presence of sodium sulfite, 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, for the industrial production of alkanesulfonic acids by photo-sulfoxylation, a method is employed in which the process is carried out exclusively in the presence of water. 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 it by distillation at a temperature of 0.degree. C., which causes problems such as odor and coloration of the alkanesulfonic acid. Therefore, the present inventor proposed that the photo-sulfoxylation reaction be carried out by adding sodium sulfite to the reaction system in which water is substantially absent (Japanese Patent Application Laid-Open No. 193961/1982). [Problems to be Solved by the Invention] The method of carrying out the photo-sulfoxylation reaction by adding sodium sulfite to the reaction system that is substantially free of water has the disadvantage that the reaction solution is colored pale yellow and the alkane that becomes the final product is There was a problem in that the sulfonate was colored yellow. As a result of intensive studies to solve this problem, the present inventor found that by coexisting sodium sulfite and a small amount of water in the reaction system, the reaction solution did not turn pale yellow, and thus the alkanesulfonic acid We have discovered the surprising fact that the reaction rate of photo-sulfoxylation can be increased without coloring the salt. The present invention was made based on this knowledge,
An object of the present invention is to propose a method for efficiently carrying out a photo-sulfoxylation reaction and producing a colorless alkanesulfonate. [Means for Solving the Problems] The present invention provides a method for producing alkanesulfonic acid by causing sulfur dioxide and oxygen to act on a saturated hydrocarbon under light irradiation in a reaction system in the presence of sodium sulfite. This method consists of adding water to the reaction system corresponding to 0.1 to 1% by weight of the saturated hydrocarbons newly supplied to the reaction system. is a method for producing alkanesulfonic acid containing an alkanesulfonic acid salt. The reaction system in which sodium sulfite exists as used in the present invention refers to a method in which sodium sulfite is added to the reaction system, a column is filled with sodium sulfite, and a part of the reaction liquid is extracted from the reactor and distributed to the column. This can be accomplished by a method in which the reaction solution is brought into contact with sodium sulfite and returned to the reaction system. In this case, the sodium sulfite may be either anhydrous or one having water of crystallization in the form of heptahydrate without any particular problem. This sodium sulfite may be used in the form of powder, pellets, or flames, but when it is added to the reaction system, it is used as a powder, and when it is used packed in a column, it is used as a pellet or flake. Preferably. When adding sodium sulfite to the reaction system, sodium sulfite 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 preferably 0.1% to 10% by weight based on the saturated hydrocarbon. The reaction solution in which sodium sulfite 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. Furthermore, in a method in which a column is filled with sodium sulfite and a portion of the reaction solution is brought into contact with the sodium sulfite, a short time period for the contact between the sodium sulfite and the reaction solution is sufficient. This is because once the sodium sulfite is dissolved in the reaction solution, it decomposes and removes the substances that cause the formation of colored substances.The dissolution rate in this case is extremely fast, so the contact time is particularly rate-limiting. This is to prevent this from happening. The saturated hydrocarbon used in the present invention may be any 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, the saturated hydrocarbon has a carbon number of 8 to 8. 24 normal paraffin is preferred. As the light source for irradiation in the present invention, the wavelength
A device that can emit light of 500 nm or less can be used. In addition, 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 need to heat it. . The reaction pressure is
The higher the reaction rate, the higher the reaction rate, which is preferable, but from 0 to
A range of 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 reactor that is equipped with a cylindrical light source in the center and is capable of retaining a saturated hydrocarbon liquid around the cylindrical light source. Suitably, sulfur dioxide and oxygen gases are introduced into the saturated hydrocarbon liquid, and the gases after contact can be partially recycled. The amount of water added to the reaction system must be 0.1 to 1% by weight of the saturated hydrocarbon newly supplied to the reaction system. If it is less than 0.1% by weight, the reaction rate cannot be expected to improve much, and the reaction solution becomes pale yellow.
This results in a yellow coloration of the alkanesulfonate in the final product. Adding water in an amount of 1% by weight or more lowers the reaction rate and increases the loss of sodium sulfite, making it uneconomical. The water may be added directly to the reaction liquid in the reaction system, or may be added to the newly supplied saturated hydrocarbon. This water forms sulfuric acid in the reaction system, but immediately reacts with sodium sulfite present in the reaction system to generate sodium hydrogen sulfate. In addition, an alkanesulfonate salt, for example, is added to the water.
It is preferable to add a sodium salt or the like, since the reaction rate can be accelerated, especially in the initial stage of the photo-sulfoxylation reaction. By adding a predetermined amount of sodium hydroxide to the reaction solution reacted in the above method to partially neutralize the remaining sulfuric acid, the entire amount of the produced sulfuric acid radical is precipitated as sodium hydrogen sulfate monohydrate. Solid-liquid separation of sodium hydrogen. The reaction solution after this separation is, for example, water, alcohol, or
It is extracted with an extraction solvent such as a mixed solvent of these. The extract containing alkanesulfonic acid is alkali,
For example, it is neutralized with sodium hydroxide, potassium hydroxide, calcium hydroxide, etc., and becomes the final product in the form of an alkanesulfonate. [Action] The action of the present invention is that by adding a small amount of water to a reaction system in which sodium sulfite is present, the peroxide sulfonic acid produced in the photo-sulfoxylation reaction is converted to sulfuric acid by the action of the water, and this produced Sulfuric acid becomes sodium hydrogen sulfate with sodium sulfite, and the equilibrium is shifted, which accelerates the decomposition rate of peroxide sulfonic acid and prevents the peroxide sulfonic acid, which is thought to be the cause of coloring, from remaining at a high concentration. is not colored, and it is estimated that the final product, the alkanesulfonate, will not be colored. Furthermore, the addition of water has the effect of increasing the speed of the photo-sulfoxylation reaction by preventing coloring of the reaction solution and eliminating the absorption of light effective for the reaction by the colored substance in the reaction solution. This effect is further enhanced by adding the alkanesulfonate at an early stage of the initiation of the photosulfoxylation reaction. [Example] (Example 1, Comparative Example 1) A reactor consisting of a cylindrical glass reactor with an inner diameter of 50 mmφ and a height of 1000 mm was equipped with a mercury lamp protected by quartz glass at the axial center of the reactor, and a reactor with an inner diameter of 50 mmφ and a high length 200mm
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 having 14 to 16 carbon atoms and water in the proportions shown in Table 1 to this normal paraffin as raw materials were put into a reactor, and 150c.c./hr of sulfur dioxide and 50c of oxygen were added from the bottom of the reactor. The photo-sulfoxylation reaction was carried out for 40 minutes by introducing at a rate of .c./hr. Next, the reaction liquid in the reactor was drawn out of the system at a rate of 30 c.c./min, and in order to keep the liquid level constant, the same new normal paraffin as above and the newly supplied normal paraffin were added as shown in Table 1. The reaction was carried out continuously while supplying water in the proportions shown. After filtering the reaction solution taken out of the system, it was extracted with a water-methanol solution (VO1 ratio 50/50) and extracted according to JISK3362.
The yield of alkanesulfonic acid was determined by the method specified in "5.3.3 Determination of anionic surfactant."
The photo-sulfoxylation reaction was carried out continuously for more than 10 hours, but no coloration was observed in the reaction solution, and the yields shown in Table 1 were obtained. Further, the obtained alkanesulfonic acid was neutralized with sodium hydroxide to obtain sodium alkanesulfonate, but no coloration was observed in this salt either. However, in Comparative Example 1 in which a large amount of water was added, the reaction yield was poor as shown in Table 1. (Comparative Example 2) When a photo-sulfoxylation reaction was carried out in exactly the same manner as in Example 1 except that water was not added, pale yellow coloring was observed in the reaction solution after 1 hour, and Table 1 shows that As shown in Figure 2, the yield of alkanesulfonic acid was slightly lower than that in Examples. Moreover, yellow coloration was also observed in sodium alkanesulfonate obtained by neutralizing the obtained alkanesulfonic acid with sodium hydroxide. (Example 2) In the method of Example 1 in which the amount of water added was 0.3 wt%, except that 1 g of alkanesulfonic acid sodium salt was added to the water added at the start of the reaction.
When the photo-sulfoxylation reaction was carried out in the same manner as above, the yields shown in Table 1 were obtained.

[Table] [Effects of the Invention] The method of the present invention as described above can color the reaction solution,
As a result, the final product, the alkanesulfonate salt, is not colored, and the photo-sulfoxylation reaction can be carried out efficiently, which is a special effect.

Claims (1)

[Scope of Claims] 1. In a method for producing alkanesulfonic acid by causing sulfur dioxide and oxygen to act on a saturated hydrocarbon under light irradiation in a reaction system in which sodium sulfite is present, a method for producing alkanesulfonic acid, in which a new supply of sodium sulfite to the reaction system is provided. A method for producing an alkanesulfonic acid, which comprises adding water corresponding to 0.1 to 1% by weight of the saturated hydrocarbon to the reaction system. 2. The method for producing alkanesulfonic acid according to claim 1, wherein the water added contains an alkanesulfonic acid salt at an early stage of the reaction.