JPS5955877A - Preparation of saccharin - Google Patents

Abstract

PURPOSE:To prepare a high-quality titled substance, at a low cost, without using expensive compounds, by oxidizing o-toluenesulfonamide with an O2-containing gas in the presence of an oxidization catalyst and further a zirconium compound, thereby increasing the rate of reaction. CONSTITUTION:The titled compound is prepared by using o-toluenesulfonamide as a raw material, and oxidizing the raw material with an O2-containing gas in about 2-20 times weight (based on the material) of acetic acid using a catalyst system composed of cobalt, manganese and bromine, in the presence of a zirconium compound. The amount of the cobalt compound is 0.04-2wt%, based on the acetic acid used as the solvent, in terms of metallic cobalt, and that of the manganese compound is 0.01-50wt%, based on th metallic cobalt. The weight ratios of the bromine compound and the zirconium compound to the metallic cobalt are 0.01-5 and 0.001-2, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing saccharin (0-sulfobenzoic acid imide), which is useful as a food additive (sugar substitute sweetener), medicine, agricultural chemical intermediate, etc.

Conventionally, saccharin has been produced by oxidizing 0-toluenesulfonamide with dichromic acid in sulfuric acid (for example, Japanese Patent Publication No. 49-40232), but by-product chromium sulfate is recovered and reused. In addition to requiring a large-scale electrolyzer, a large amount of waste liquid and waste liquid containing chromium had to be treated, and this was not an industrially preferable method.

Therefore, the present inventors have developed a method for oxidizing molecular oxygen-containing gas, which does not require recovery and is easy to handle, in place of dichromic acid.
The present invention was achieved through extensive research into a method for producing saccharin from 0-toluene sulfonamide.

That is, the present invention provides a method for producing saccharin by oxidizing 0-toluenesulfonamide in an acetic acid solvent with a molecular oxygen-containing gas in the presence of a catalyst composed of cobalt, manganese, and bromine. This is a method for producing saccharin characterized by the presence of a reaction system.

The method of the present invention will be specifically explained below.

In the present invention, 0-toluenesulfonamide, which is obtained by converting toluene into chlorsulfurophonate, separating 9 compounds, and reacting 0-toluenesulfochloride with ammonia, is used as a raw material. Then, about 2 to 20 tons of acetic acid is used as a solvent to 0-toluenesulfonamide. Although there is no particular problem even if water is present in the acetic acid in an amount of more than 5% by weight or less, it is preferable that the amount of water in the acetic acid is as small as possible.

As an oxidation catalyst, we use a catalyst system consisting of carbon dioxide, manganese, and bromine, and use it as an oxidation catalyst. A reconium compound is present in the reaction system.

These catalyst components are then added in the form of the compounds shown below.

That is, cobalt compounds and manganese compounds can be used as long as they are soluble in acetic acid, but acetates, carbonates, hydroxides, bromides, etc. are particularly preferred.

Examples of bromine compounds include inorganic bromine compounds such as bromine, hydrogen bromide, ammonium bromide, alkali gold M bromide, bromide, manganese bromide, and organic bromine compounds such as del-l-bromoethane and bromoacetic acid. Although available, cobalt bromide, manganese bromide, sodium bromide, and the like are particularly preferred.

The amount of the cobalt compound to be used is preferably such that the amount of cobalt metal used is in the range of 0.04 to 2% by weight based on the amount of acetic acid used as the solvent. (Koba) of V l/compound,
If the amount used is less than 0.04% by weight, a sufficient reaction rate cannot be obtained, and if it exceeds 2% by weight, separation of the catalyst and products becomes laborious and the cost of the catalyst increases.

The amount of the manganese compound to be used is preferably 0.01 to 50 parts by weight, especially 0.1 to 10 parts by weight, relative to the cobalt metal. If the amount used is less than 0.01% by weight, sufficient catalytic activity will not be obtained, while if it exceeds 50% by weight, the catalytic activity will tend to decrease, resulting in increased labor and catalyst cost for separation from the product. The burden increases.

The amount of the bromine compound to be used is in the range of 0.01 to 5 times the weight of cobalt metal, especially 0.01 to 5 times the weight of cobalt metal.
A range of 0.05 to 3 times the weight is appropriate. If the amount of bromine compound used is less than 0.01 times by weight, sufficient catalytic activity will not be obtained, and if it exceeds 5 times iW, This is not desirable.

In the present invention, the reaction rate can be further increased by coexisting a zirconium compound in the reaction system in addition to cobalt, manganese, and bromine, which are catalyst components.

Suitable zirconium compounds used for this purpose include +4-valent zirconium compounds that are soluble in acetic acid and do not contain counterions that interfere with the reaction, such as schiffleconium bromide and silconium acetate/'s zirconium acetate. The use of a zirconium compound [,1 means that the amount of zirconium metal used is o, ooi to 2 times h1 times the amount of cobalt metal used as a catalyst component.Specially 0.005
- 1 fold: 1; a range of 1 fold is appropriate. Use of zirconium compounds 1. If the number is less than this range, then
The i+11B media activity is 41t, and if the amount exceeds this range, it will be difficult to separate it from the raw material.

Although pure oxygen or industrial exhaust gas can be used as the molecular oxygen-containing gas used as the oxidizing agent, normal air is most suitable from an industrial standpoint.

Reaction l blackness is 80~200℃, especially 1,00~160i
A range of is preferred. The reaction pressure is set so as to maintain the solvent acetic acid in a liquid phase at this temperature, and is suitably in the range of 5 to 30 atm. From the viewpoint of safety, it is desirable to adjust the rate at which molecular oxygen-containing gas (usually air) is blown into the reactor so that the oxygen concentration of the exhaust gas from the reactor is in the range of 1 to 8 volume Ml%.

The reactor used in the present invention is preferably of a forced mixing type rather than a simple bubble column type. That is, in order to achieve good gas-liquid mixing of the molecular oxygen-containing gas and the reaction liquid, to promote dissolution of molecular oxygen into the reaction liquid, and to ensure smooth contact between the reactants in the reactor, The reactor is equipped with a gas inlet consisting of a large number of pores at the bottom of the reactor, and forced stirring by a rotating stirring blade or forced circulation by a circulation pump outside the reactor is performed.
Preferably, rt is used.

A reflux condenser is installed in the reactor Lt7 and vessel 11, and the exhaust gas is discharged through the reflux condenser, and the solvent acetic acid and the like contained in the IJI gas E are condensed and circulated to the reaction system.

In the anti-single-core method, the entire rust of the raw material mixture consisting of the substance to be oxidized, the solvent, and the catalyst is charged into the reactor in advance, and the reaction product is not taken out until the reaction is completed, and the oxygen-containing gas is released in the form of a fraction. There is a batch system in which the raw material mixture or the oxidized substance dissolved in a solvent is continuously fed into the reactor until the reaction is completed. It is possible to use any continuous method in which the reaction product is continuously supplied and the reaction product is continuously taken out.

When the oxidation reaction is carried out for several hours until the raw material is almost completely consumed in the previous hE process f1, the target product Isu-tucarin is produced by hydrolysis of → J-laccan as the main by-product. ○-Sulpobenzoic acid 1) Tamonoammonium, cobalt O-sulfobenzoic acid heptanoammonium produced by forming a salt with cobalt ion of the oxidation catalyst, and O-formylbenzenesulfonamide, which is an oxidation intermediate, or this in the molecule A compound presumed to be a dehydrated ring-closed Nuch base is produced.

The reaction product and acetic acid can be separated by cooling the reaction product liquid as it is, by concentrating it and then cooling it, crystallizing the reaction product, and separating the acetic acid from solid-liquid, or by completely removing the acetic acid in the reaction product liquid. A suitable method is to obtain a reaction product containing an oxidation catalyst as a residue by distilling off the oxidation catalyst.

Thus, the reaction product from which acetic acid has been removed is washed with water of about 1 to 10 times the weight of the reaction product.
The metal catalyst and by-products are separated from saccharin by recrystallization using approximately 60 times the weight of water, or by dissolving in an aqueous solution of saccharin to remove insoluble matter and precipitating with acid. Remove. In order to further improve the purity and color tone of saccharin, these treatments are carried out in combination,
It is also a preferred embodiment to carry out activated carbon treatment at the time of recrystallization.

In addition, the metal catalyst dissolved in the washing liquid or the ILT crystal mother liquor can be precipitated as a carbonate by adding charcoal or resodium, or concentrated and left in the coexistence of saccharin to precipitate as a saccharin salt, and then recovered and oxidized. It is also possible to recycle it as a catalyst.In addition, when the reaction product is crystallized and separated from the product solution, the mother liquor (acetic acid solution) contains saccharin, intermediates, by-products, oxidation catalyst, etc. in proportion to its solubility. Therefore, after the by-product water is distilled and separated, it can be recycled to the reaction system as it is or after being subjected to an appropriate purification treatment.

According to the method of the present invention detailed above, saccharin of good quality can be produced economically by using molecular oxygen-containing gas, which is inexpensive and easy to handle, as an oxidizing agent instead of dichromic acid, which is expensive and difficult to handle. It became possible.

The present invention will be specifically explained below with reference to Examples.

Example 1 40 parts of O-)/renineurponamide, vinegar + i! 400 parts, cobalt acetate ion 6.81 parts, vinegar [1 cumanganese tetrahydrate 0.11 parts, cobalt bromide large water L
! 1.67 parts, Vinegar Km Citreconil 0.60 parts,
(0.3% by weight of cobalt metal relative to acetic acid, 2% by weight of manganese metal relative to cobalt metal, 68 weight% of bromine atoms relative to cobalt metal, 10% by weight of dil-reconium metal relative to cobalt metal) Prepared, reaction power 18
At a pressure gauge and a reaction temperature of 120° C., the reactor was brought into contact with air blown from the reaction chamber at a flow rate such that the oxygen concentration in the exhaust gas became 8% or less for 2.5 hours.

A cake obtained by concentrating the reaction product and separating it into solid and liquid (dry weight: 40.0 parts, composition of the dry product: saccharinf 2.3
%, monoammonium cobalt O-nulphobenzoate 20.7 ftN=%, O-formylbenzenesulfonamide or its dehydrated closed product 5.0% by weight) was washed twice with 50 parts of water at room temperature and dried. te23.6
The white crystals (saccharin) (!
/ill'L degrees and contacted with air for 5 hours at 120°C.

Cake 20.4 obtained by concentrating the reaction product and separating it into solid and liquid
The composition of 62.6 parts by weight of saccharin, 2.2 iilφ of monoammonium O-nulpobenzoate, and the remainder was intermediates such as O-formylbenzene nulphonamide or its dehydrated ring product.

Patent applicant: Toshi Co., Ltd.

Claims (1)

[Claims] 0-Toluenesulfonamide was dissolved in an acetic acid solvent and 1
A method for producing saccharin, characterized in that a sil p=um compound is present in the reaction system when saccharin is produced by oxidation with a molecular oxygen-containing gas in the presence of a catalyst consisting of manganese and bromine.