RU2316543C1 - Method for preparing trifluoromethane sulfoacid - Google Patents

Abstract

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for synthesis of trifluoromethane sulfoacid (TFMSA) used in fine organic synthesis. Trifluoromethane sulfoacid is synthesized by treatment of mixture of dehydrated TFMSA salt and silicon dioxide with concentrated sulfuric acid at heating and distillation of crude trifluoromethane sulfoacid from reaction mixture followed by distillation of crude trifluoromethane sulfoacid and utilization of by-side fractions of distillation. Synthesis and distillation of crude trifluoromethane sulfoacid is carried out in continuous operation reactor under vacuum and with separate continuous feeding solid and liquid reagents to reaction zone and in continuous removal of depleted solid reaction mixture and continuous condensation of crude trifluoromethane sulfoacid vapors. The following distillation of crude trifluoromethane sulfoacid is carried out in bubbling of inert gas. Method provides enhancing yield of the end product and its quality.

EFFECT: improved method of synthesis.

2 tbl, 1 dwg

Description

The invention relates to an improved method for producing organofluorine compounds, in particular to a technology for producing trifluoromethanesulfonic acid.

Trifluoromethanesulfonic acid (hereinafter TFMSK) is used in fine organic synthesis, in the production of pharmaceuticals, fungicides, insecticides, surfactants, motor fuels, etc.

A known method of producing TFMSC by the interaction of its dehydrated salts of alkali or alkaline earth metals with an excess of 100% sulfuric acid, followed by distillation of TFMSK (US Patent 2732398, 1956). In this method, the TFMSC salt is treated with sulfuric acid at a weight ratio of salt to H ₂ SO _{4 of} 1: 1, TFMSC is distilled from the reaction mixture. The disadvantage of this method is the increased consumption of reagents, the increased content of impurities in the synthesized TFMSK, the formation of difficult to remove sintered waste from the synthesis reactor TFMSK.

There is also an industrial method for producing TFMSK according to the patent of the Russian Federation No. 2203271, 2003 (prototype). The method is as follows. The TFMSC salt is charged into the reactor, the mixer is turned on, and 99.5-100.5% sulfuric acid is added in an amount exceeding 1.5-2.1 times the stoichiometry, the reactor is heated, the nitrogen supply to the reaction space is opened and the crude TFMSC is distilled off at atmospheric pressure with its selection to a temperature of the vapor of the distilled mixture of 180-190 ° C. The distilled vapors are condensed in a refrigerator cooled by water, the raw TFMSK is collected in a receiving tank. When the vapor temperature reaches 190 ° C, the reactor heating is turned off, the waste is unloaded, neutralized and sent for burial.

Then, the crude TFMSC is pumped with compressed nitrogen from a receiving tank into a distillation cube equipped with a reflux condenser, silicon dioxide is added, a cold water supply is opened into the jacket of the reflux condenser, and heating is turned on. An inert gas is supplied to the system and placed under vacuum, the mixture is kept at boiling for 2 hours, after which the selection of side and main distillation fractions begins. The method allows to obtain commodity TFMSC with a fluorine content of not more than 10 ppm. The disadvantages of the method include: the lack of stable quality indicators of marketable products and low productivity, due primarily to the frequency of the process of obtaining raw TFMSK, a large amount of manual labor, an increased content of sulfate ion in the finished product (at 100 ppm).

An object of the invention is to increase productivity, stabilize and improve the quality of TFMSK, improve working conditions for staff.

The problem is solved in that when receiving TFMSC by processing a mixture of dehydrated salt with silicon dioxide with concentrated sulfuric acid when heating and distillation of crude TFMSK from the reaction mixture when inert gas is fed into the reaction mixture, followed by distillation of crude TFMSK and recycling distillation by-products, synthesis and distillation crude TFMSK is carried out continuously under vacuum, with separate continuous supply of solid and liquid reagents to the reaction zone with continuous removal of spent solid of the reaction mixture and condensation of vapors of crude TFMSK, and the subsequent distillation of crude TFMSK is carried out by bubbling an inert gas into crude TFMSK. The process is carried out in a device, which is a horizontal tubular screw reactor equipped with heating and equipped with units for supplying solid and liquid reagents, an inert gas blowing nozzle, a discharge pipe for unloading the spent reaction mixture into a heated receiving container, a reaction gas outlet pipe and a crude TFMSK vapor condensation unit.

The rationale for the proposed invention is as follows:

1. We have established the optimal composition of the mixture obtained in the reaction zone, which does not crumple, does not vitrify, is well transported in the reaction zone. This mixture corresponds to a molar ratio of salt (barium) of TFMSC to sulfuric acid monohydrate 1: (2.6-3.1). The consumption of sulfuric acid monohydrate in this method is higher than that described in the prototype, but with this ratio, the reaction mass is well poured, agitated, the solid residue (dump) does not vitrify at the end of the reaction. With a lower ratio, the yield of TFMSC raw is reduced, with a large excess of acid, either a glassy or pasty state of the mixture occurs. Transportation of such mixtures is difficult. Excess sulfuric acid monohydrate is dumped into a container with a dump, after which it is sent for neutralization and disposal.

2. Vapor distillation of crude TFMSK with inert gas injection into the reaction zone at an absolute pressure of 500-600 mm Hg (in the prototype 550-600 mm Hg) promotes the accelerated removal of vapors of crude TFMSK from the reaction zone and stabilization of the quality of crude TFMSK. With a larger vacuum, there is an increased ablation of sulfuric acid vapor.

3. We have established empirically: bubbling an inert gas into crude TFMSC during its distillation provides a decrease in the content of sulfate ion in commodity acid. The inert gas (nitrogen) consumption in this case is 15-17% of the volume of distilled vapors of the reaction mixture. With a larger flow rate, the yield of the target fraction — commodity TFMSC — decreases, while lower consumption in the commodity TFMSC increases the content of sulfate ion.

Based on the foregoing, the new process is as follows. A device for the continuous synthesis of raw trifluoromethanesulfonic acid, consisting of (see drawing): an electric motor (1), a synthesis reactor (2) equipped with three electric heating zones, a loading hopper (3), a loading screw (4), a metering pump (5), a measuring device (6), a column (7) filled with silica gel and equipped with electric heating, condensers-refrigerators (8), a receiving hopper (9) equipped with electric heating, a receiving tank of crude TFMSK (10), weights (11), a rotameter (12), an adsorber (13), a sampling pipe (14) and a sampling container (15), are prepared for OTE. The heating of the reactor (2), the receiving hopper (9), the column (7) is turned on and the following temperatures are set in the zones of the reactor 230-260 ° C (the maximum temperature is set in the middle zone), the column (7) is 150-180 ° C, the receiving hopper (9) 240-250 ° C. The pre-dried and ground barium triflate and silica gel are loaded into the loading hopper (3). Sulfuric acid monohydrate with a basic substance content of at least 99.6% of the mass is poured into a mernik (6). The electric motor (1) is turned on, the rotary auger of the reactor (2) rotating through the gearbox, and the set frequency of rotation of the auger shaft is set. Compressed nitrogen is supplied to the reactor (2) through a rotameter (12) and an adsorber with aluminum gel (13) with a flow rate of 10-100 l / h. Using a vacuum pump in the reactor (2), a receiving hopper (9), a column (7), condenser-heat exchangers (8) and a receiving tank (10) create an absolute pressure of 550-600 mm Hg Cold water is supplied to the duct in condenser-heat exchangers (8). Turn on the loading auger (4) and set the desired flow rate of barium triflate in the reactor (2). Turn on the metering pump (5) and set the desired flow rate of sulfuric acid monohydrate.

In the reactor (2), barium triflate and sulfuric acid are mixed. This mixture is transported through the reactor (2) from the loading hopper (3) to the receiving hopper (9) with a blade screw, passing through the temperature zones T1, T2 and T3.

The resulting trifluoromethanesulfonic acid vapors, through a heated column (7) filled with silica gel, are transferred from the 2nd heated zone of the reactor to condenser-heat exchangers (8). Condensed crude TFMSK accumulates in the receiving tank (10) and is controlled by weights (11). During the process, raw TFMSC is sampled through the sampling pipe (14) into a container (15) connected to the vacuum line. The process is carried out with constant monitoring of the temperature in the zones of the reactor (2): T1, T2 and T3, vapor temperature T4 and dump temperature T5. The obtained crude TFMSC from the receiving tank (10) is transferred with an inert gas to a distillation cube of periodic operation and the commodity TFMSC is distilled off with the addition of silicon oxide and bubbling of inert gas. The blade from the receiving hopper is sent to neutralization and disposal.

The results of industrial experiments on testing a new method and device are presented in tables 1 and 2.

Table 1 Synthesis of crude TFMSK The results of the analysis of crude TFMSK E / N SO ₄ ^2- ,% of the mass. F ^- ,% of the mass. Basic method 143.0-148.0 0.01-1.5 0.03-0.45 New way 146.0-149.7 0.01-0.1 0.01-0.1

From table 1 it is seen that the obtained crude TFMSK according to the new method has a better and more stable quality.

Table 2 Distillation of crude TFMSK The results of analyzes of commodity TFMSK The content of the main substance (equivalent to neutralization),% of the mass. SO ₄ ^2- ,% of the mass. F ^- ,% of the mass. Basic method with nitrogen injection No less than 99.5 0.009-0.01 0,0008-0,001 New way with bubbling N ₂ No less than 99.5 No more than 0,005 0.0005-0.001

From table 2 it can be seen that the obtained commodity TFMSC according to the new method is superior in quality (content of sulfate and fluoride ion) to the product synthesized by the basic method (prototype), and more importantly for large-tonnage production - the quality of commodity TFMSC is more stable.

Claims (1)

A method of producing trifluoromethanesulfonic acid, comprising treating a mixture of a salt of trifluoromethanesulfonic acid and silicon dioxide with sulfuric acid monohydrate while heating the reaction mixture with stirring while supplying an inert gas to the reaction zone and distilling off crude trifluoromethanesulfonic acid vapors, distilling the crude trifluoromethanesulfonic acid in the presence of silicon dioxide, at an absolute pressure of 500-600 mm Hg, at a temperature of the reaction zone of 230-260 ° C and with molar s the ratio of trifluoromethanesulfonic acid salt to sulfuric acid monohydrate 1: (2.6-3.1) with continuous separate supply of solid and liquid reagents to the reaction zone, continuous removal of the spent solid mixture from the reaction zone, and continuous condensation of the crude trifluoromethanesulfonic acid vapor, and distillation of crude trifluoromethanesulfonic acid when bubbling inert gas under a layer of liquid with a flow rate of 2-20% of the volume of distilled vapors of the reaction mixture.