JPS6366827B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing alkanesulfonic acid, which is a raw material for alkanesulfonate having excellent performance as a surfactant for synthetic detergents, etc.
In particular, the present invention relates to a method for producing alkanesulfonic acids by causing sulfur dioxide and oxygen to act on saturated hydrocarbons under irradiation with light in a system substantially free of water. Compared to soaps, alkylbenzene sulfonates, etc. whose cleaning power is significantly reduced in hard water, alkanesulfonates can maintain their cleaning power even in the absence of cleaning aids such as phosphates, and Compared to alkylbenzene sulfonates, it has excellent biodegradability and is preferable from an environmental conservation standpoint, and demand is expected to increase in the future. Prior Art In the method of photo-sulfoxylating saturated hydrocarbons using sulfur dioxide and oxygen in a system substantially free of water, a colored substance adheres to the side wall of the light source, significantly interfering with light irradiation, and causing photo-sulfoxylation. The drawback is that the chemical reaction is reduced. For this reason, when a predetermined amount of the 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. Therefore, in the industrial production of alkanesulfonic acids, a method of photo-sulfoxylation in the presence of water is employed. However, in this method, water interferes with the radical chain reaction, resulting in poor reaction efficiency.In addition to the alkanesulfonic acid, almost equimolar sulfuric acid is produced as a by-product, and in order to separate the sulfuric acid, water is When removed by distillation at a temperature of 140°C, alkanesulfonic acid has problems such as odor and coloration. 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. has been proposed (Special Publication No. 47-28973). However, this method is not economical because there is not enough oxygen radical, which is an important promoter of the photo-sulfoxylation reaction, and the reaction rate is extremely slow. Furthermore, 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 surface of the light source (Japanese Patent Publication No. 11740/1983). However, with this method, it is not possible to completely prevent the liquid from coming into contact with the wall surface, staining of the wall surface on the side of the light source is unavoidable, and furthermore, the nitrogen or air that is being circulated is not able to completely prevent the liquid from coming into contact with the reaction liquid. Since the sulfur 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. Purpose of the Invention As a result of intensive studies to solve the above-mentioned problems, the present inventor discovered that adding and dispersing sodium sulfite to saturated hydrocarbons to carry out a photo-sulfoxylation reaction can reduce the amount of colored substances without reducing the reaction rate. We have discovered the surprising fact that it is possible to suppress the formation of The present invention was made based on this knowledge, and it is possible to reduce the adhesion of colored substances to the side wall surface of the light source without reducing the reaction rate when photo-sulfoxidizing saturated hydrocarbons in a system substantially free of water. The purpose of the present invention is to propose a method that can continuously produce alkanesulfonic acid while preventing the above. Structure of the Invention The present invention provides a method for producing alkanesulfonic acid by causing sulfur dioxide and oxygen to act on a saturated hydrocarbon under irradiation of light in a system substantially free of water. This is a method for producing alkanesulfonic acid in which sodium sulfite is added to cause sulfur dioxide and oxygen to interact, and in particular, the sodium sulfite is added in an amount of 0.1% to 10% by weight based on the saturated hydrocarbon. The present invention will be described in detail below. 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, such as a high-pressure mercury lamp, a low-pressure mercury lamp, and a low-pressure mercury fluorescent lamp. 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, more preferably 2 to 100. Furthermore, it is dissolved in saturated hydrocarbons.
The higher the concentration of SO ₂ , the greater the polarity of the saturated hydrocarbon solution, which increases the solubility of colored substances and reduces the amount of adhesion to the side wall of the light source, so the molar ratio of sulfur dioxide to oxygen is large. is preferable. Generally, for photo-sulfoxylation reactions, 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 it, and a dispersion plate is inserted from the bottom of the reactor. Preferably, sulfur dioxide and oxygen gases are introduced into the saturated hydrocarbon liquid via the saturated hydrocarbon liquid, such that the liquid and the gas after contact can be partially recycled. Sodium sulfite added to saturated hydrocarbons is
Even if it is anhydrous, it may be used that has water of crystallization such as heptahydrate, but anhydrous is particularly preferable because it does not generate sulfuric acid, and it is preferable to use these in the form of powder. When used as an aqueous solution, water is present in the reaction system and the amount of sulfuric acid produced increases, which is not preferable. This addition of sodium sulfite may be carried out before introducing the saturated hydrocarbon into the reactor, or it may be added directly to the saturated hydrocarbon in the reactor. On the other hand, if the amount added is less than 0.1% by weight based on the saturated hydrocarbon, it will not be possible to sufficiently suppress the adhesion of colored substances to the side wall surface of the light source, making it impossible to carry out the photo-sulfoxylation reaction continuously, which is not preferable. . On the other hand, the larger the amount of sodium sulfite added, the longer the adhesion of colored substances can be suppressed, but when the amount exceeds 10% by weight based on the saturated hydrocarbon, no significant increase in the suppressing effect is observed. Therefore, it is economical to keep the content to 10% by weight or less. Note that the saturated hydrocarbon liquid in which sodium sulfite is dispersed becomes a suspension in the reactor, but when the amount added is below 10% by weight, no particular reduction in the reaction rate due to light scattering etc. is observed. In the above photo-sulfoxylation reaction,
The reaction solution is taken out when the reaction rate of the saturated hydrocarbon reaches 0.1 to 60%, more preferably 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 and alkane trisulfonic acid will also be produced, resulting in a decrease in the selectivity of the alkane monosulfonic acid. Alkane monosulfonic acid salts have excellent properties as surfactants, and it is preferable to control the reaction so as to reduce the production of alkanedisulfonic acids and alkane trisulfonic acids. Even if a small amount of alkanedisulfonic acid or alkanetrisulfonic acid is produced, the quality of the alkanesulfonate product will not be particularly deteriorated. Since almost no water coexists in the photo-sulfoxylation of saturated hydrocarbons as described above, the amount of sulfuric acid produced is at most about 15% by weight based on the alkanesulfonic acid. The reaction liquid taken out from the reactor is separated from sodium sulfite by solid-liquid separation means such as filtration or centrifugation, and then the alkanesulfonic acid is neutralized by the addition of alkali to form an alkanesulfonic acid salt. can be precipitated, and unreacted saturated hydrocarbons can be recycled to the reaction system. In addition to this method, the liquid extracted from the reactor is extracted with an extraction solvent such as water, alcohol, amine, alkanolamine, etc., and the alkanesulfonic acid in the reaction liquid is extracted and recovered. The unreacted saturated hydrocarbon in which sodium sulfite is dispersed as a residual liquid can be recycled as it is, or with new sodium sulfite added thereto, and recycled to the reactor for reuse. The method of the present invention as described above prevents the adhesion of colored substances to the side wall surface of the light source without reducing the reaction rate of photosulfoxylation, and continuously performs the photosulfoxylation reaction in a system substantially free of water. This provides a special effect in that alkanesulfonic acid can be efficiently produced. Examples and comparative examples will be shown below to specifically describe the effects of the present invention. Example 1 Photo-sulfoxidation was carried out using a cylindrical glass reactor with an inner diameter of 50 mmφ and a height of 1000 mm, and a mercury fluorescent lamp protected by quartz glass was installed at the core of the reactor. 1.2% of normal paraffin having 14 to 16 carbon atoms was put into a reactor as a raw material, 9 g of anhydrous sodium sulfite (1% by weight of normal paraffin) was added, and sulfur dioxide was added from the bottom of the reactor.
The photo-sulfoxy reaction was carried out for 1 hour by introducing oxygen at a flow rate of 60/hr and oxygen at a flow rate of 6/hr. After the reaction was completed, the alkanesulfonic acid in the reaction product was extracted with monoethanolamine, and the yield of the alkanesulfonic acid was determined. Next, new normal paraffin was added to the normal paraffin remaining after the extraction, the total amount was 1.2, and the mixture was put into a reactor, and anhydrous sodium sulfite 9
g was added and the same operation as above was performed again. This was repeated 10 times. As a result, no colored substances adhered to the quartz glass protective tube in the reactor, and as shown in Table 1, no decrease in the yield of alkanesulfonic acid was observed. Example 2 The same procedure as in Example 1 was carried out except that 0.9 g of anhydrous sodium sulfite (0.1% by weight relative to normal paraffin) was added. As a result,
Some colored substances were observed on the quartz glass protective tube, and as shown in Table 1, the yield of alkanesulfonic acid decreased as the number of repetitions increased, but compared to the comparative example, the yield of sodium sulfite The additive effect is clearly visible. Comparative Example The other operations were performed in exactly the same manner as in Example 1 without adding sodium sulfite. As a result, adhesion of colored substances to the quartz glass protective tube was observed from the third repetition, and as shown in Table 1, the yield of alkanesulfonic acid sharply decreased as the repetition progressed. 【table】

Claims (1)

[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 system substantially free of water, comprising:
A method for producing alkanesulfonic acid, which comprises adding sodium sulfite to the saturated hydrocarbon to cause sulfur dioxide and oxygen to interact with each other. 2. The method for producing alkanesulfonic acid according to claim 1, wherein the sodium sulfite is added in an amount of 0.1% to 10% by weight based on the saturated hydrocarbon.