RU2150459C1 - Method of synthesis of polyfluorinated alcohols - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: invention relates to method of synthesis of polyfluorinated alcohols of the formula: R-OH where R is HCF₂CF₂CH₂-, CF₃CFHCF₂CH₂- by heating peroxide initiator solution (concentration is 3.5-15.4 wt.%) in aliphatic alcohol under pressure 3.4-6.5 kg/cm² to fixing temperature 110-120 C followed by controlled feeding fluoro-containing olefin to excess of this alcohol and increase of pressure to 9-15 kg/cm² and temperature to 150 C. Process is carried out expediently at mole ratio fluoroolefin : initiator = (7.2-28.2):1 and heating is carried out in the presence of polyfluorinated alcohol taken in the amount 0.2-1.2% of loaded alcohol mass. EFFECT: increased yield of end product. 3 cl, 2 tbl, 9 ex

Description

The invention relates to the field of organic chemistry, in particular, to the production of polyfluorinated alcohols of the general formula
R _f -OH, where R _f = HCF ₂ CF ₂ CH ₂ - CF ₃ CFHCF ₂ CH ₂ -
which are the product of monoaddition of aliphatic alcohols (methanol) to fluoroolefins (tetrafluoroethylene, hexafluoropropylene) in the presence of a source of free radicals (for example, di-tert-butyl peroxide).

The methods for preparing these compounds described in the literature are based on the reaction of free radical addition of aliphatic alcohols to fluorine-containing olefins at elevated temperature and pressure. When using easily polymerizable fluoroolefins, for example tetrafluoroethylene, the monoaddition reaction is accompanied by the formation of telomeric alcohols of the general formula H (CF ₂ CF ₂ ) _n CH ₂ OH, where n = 1-8 when methanol is used as an aliphatic alcohol.

So, the process at a temperature of 80-150 ^o C and a self-developing pressure (up to 100 at) with a molar ratio of methanol-tetrafluoroethylene from 1: 1 to 10: 1 in the presence of peroxide catalysts [Pat. U.S. N 2559628, CA. 46.3063 (1952)] leads to the practical absence of the monoaddition product and is accompanied by the formation of secondary alcohols H (CF ₂ CF ₂ ) _n CHOH (CF ₂ CF ₂ ) _m H, where n and m are integers 1-5. Similar results are described in [Pat. USA N 3022356, Rzhkh, 13H26P (1963)].

To increase the selectivity of the process of addition of aliphatic alcohols to fluoroolefins, a number of publications have proposed changing the molar ratio of methanol-tetrafluoroethylene and carrying out the process under less severe conditions. So, the process at a temperature of 20-70 ^o C and a pressure of tetrafluoroethylene of 2-10 bar in the presence of 1.5% acyloyl peroxide of the formula R ¹ (Me) ₂ COOC (O) C (R ² ) (R ³ ) R ⁴ , where R ¹ = Me, Et or Pr, R ² - R ⁴ - alkyl C ₁ - C ₆ allows you to vary the composition of the obtained polyfluorinated alcohols in a relatively wide range [Application Germany 3915759, MKI, C 07 C 31/38, C 07 C 20/44 , op. 11/15/90]. On the increase of selectivity is discussed in [Pat. U.S. N 4346250, op. 08.24.82. prior. 08.21.78, N 43-48045, Japan, MKI C 07 C 31/38, NKI 568/842.], Where the process is carried out at 25-150 ^o C and a pressure of 1-12 atm in the presence of acceptors.

 The main disadvantages of the above patents are insufficiently high productivity and the fact that the use of peroxydicarbonate acyloyl peroxides as initiators leads to the formation of acidic decomposition products and the need to introduce acid-removing agents (oxides, hydroxides, alkaline earth metal carbonates) into the reaction mixture.

 In addition, the use of peroxydicarbonates as initiators due to their thermal instability (in their pure form they quickly decompose even at room temperature) and the danger in handling, requires special precautions.

The closest in technical essence and combination of essential features is a method for producing polyfluorinated alcohols of type H (CF ₂ CF ₂ ) _n with CH ₂ OH n ≤ 4 by telomerization of tetrafluoroethylene with methanol by continuous or periodic supply of tetrafluoroethylene to a mixture of methanol and initiator in the presence of an acceptor at a temperature of 25 -150 ^o C and a pressure of 1-12 kg / cm ² while supporting the partial pressure of tetrafluoroethylene and methanol 30 / 1-1 / 5 [US Pat. USA N 4346250 from 08.24.82].

 The main disadvantages of this method are the low yield of the target product per unit reaction volume, the possibility of induced decomposition of the initiator during heating of the reaction mixture to operating temperature, which reduces the efficiency of the process as a whole.

 The task of the invention is to remedy these disadvantages and to develop a method for producing polyfluorinated alcohols, which provides an increase in the unit power of the reaction apparatus used by increasing the reaction rate and high selectivity for the target product. In the process of developing the production technology of polyfluorinated alcohols, we obtained experimental data that led to the conclusion that the molar ratio of fluoroolefin: peroxide initiator, and the rate its formation is determined by the concentration of the initiator per unit reaction volume and temperature.

The possibility of the practical use of sufficiently high concentrations to initiate the process to date has been limited by the known tendency of peroxide initiators (at elevated concentration and temperature, especially in the environment of "active" solvents, which include methanol) to induced (chain) decomposition. Thus, benzoyl peroxide (PB), which was used as an initiator in the form of a 3% solution for the production of hexafluorobutanol from methanol and hexafluoropropylene, has a half-life of less than 15 minutes in a 0.2 M solution in methanol at 80 ^o C (in inert solvents, the half-life is 4-6 hours). Similar results are described for di-tert-butyl peroxide (PTB), which was used in the prototype (along with others) and we as an initiator. The task of eliminating the disadvantages of the method taken as a prototype is solved by the method of obtaining polyfluorinated alcohols of the formula R-OH, where R = HCF ₂ CF ₂ GH ₂ , CF ₃ CFHCF ₂ CH ₂ , by heating a solution of 3.5-15.4 wt.% peroxide initiator with a decomposition temperature above 100 ^o C in aliphatic alcohol at a pressure of 3.4-6.5 kg / cm ² until a temperature of 110-120 ^o C is established, followed by a controlled supply of an excess of fluorine-containing olefin in excess of this alcohol with an increase in pressure to 9-15 kg / cm ² and temperatures up to 150 ^o C.

 The process is expediently carried out at a molar ratio of fluoroolefin: initiator equal to 7.2-28.2: 1. Heating is preferably carried out in the presence of polyfluorinated alcohol, taken in an amount of 0.2-1.2% by weight of the loaded alcohol.

All experiments on the development of optimal synthesis conditions were carried out on autoclaves from the station. X18N10T with a capacity of 0.25 L and 1000 L (1 m ³ ), equipped with a mixing device, feed systems for the starting components and temperature and pressure control devices.

 The essence of the invention is illustrated by the following examples.

 Example 1

Before the start of each experiment, approximately 100 g of methanol mixed with 6-15 g of initiator (di-tert-butyl peroxide) and 0.5-0.8 g of calcium oxide were charged into an autoclave V = 0.25 L. The apparatus was closed, checked for leaks, after removing oxygen from the reaction volume, the tetrafluoroethylene supply system was turned on and a pressure of 3.4-6.5 kg / cm ^{2 was} set in the reactor, then the heating was turned ^on , and at a self-developing pressure it was heated to 110-120 ^o C ( 40-50 minutes). If during the heating process a noticeable pressure drop began, the heating was turned off and the supply of tetrafluoroethylene was started, maintaining the pressure at the level of 10-12 kg / cm ² and the temperature in the reactor 120-150 ^o C.

 The conditions for conducting typical experiments N 1-6 of example 1 and the resulting results are presented in table 1.

The reaction products were unloaded at room temperature, subjected to rectification, and analyzed by GLC (gas-liquid chromatography). The yield of trihydrotetrafluoropropanol (TFP) HCF ₂ CF ₂ CH ₂ OH is shown in column 13 of Table 1. A product with a HCF content of ₂ CF ₂ CH ₂ OH 99.8 wt.% Was obtained.
Example 2
390-440 kg of methanol, calcium oxide (experiment 1–4 kg, experiments. 2, 3, 2.8 kg each) were loaded into the reactor V = 1000 L (1 m ³ ); initiator loading was carried out from a measuring device in the form of solutions in methanol, which in experiments 2 and 3 contained an addition of trihydrotetrafluoropropanol (0.8 and 4.2 kg, respectively). The measuring device design allows initiator solutions to be fed in portions throughout the process. After removal of oxygen from the reaction mass, tetrafluoroethylene was fed into the reactor to 3.4-6.5 kg / cm ² and heating to a temperature of 120 ^° C was started. After the start of the pressure drop, a constant feed rate of tetrafluoroethylene was established, and the technological parameters were adjusted by temperature.

Пример 3
В 0,25 л автоклав помещали смесь 100 г метанола, 10 г перекиси ди-трет-бутила (ПТБ), 0,8 г окиси кальция и при перемешивании нагнетали до 6,5 кг/см² гексафторпропилен, после чего нагревали до 120^oC. По достижении этой температуры возобновляли подачу гексафторпропилена, поддерживая его на уровне 13-14 кг/см² (мольное соотношение C₂F₆ : ПТБ равно 11,6:1) при температуре 130-140^oC в течение 4,5 часа. После этого реактор охлаждали до комнатной температуры и из полученной реакционной массы весом 289,5 г выделяли 143,6 г гексафторбутанола, CF₃CFHCF₂CH₂OH. В опыте без добавки окиси кальция вес реакционной массы составил 287,2 г.At the end of the synthesis, the reactor was cooled, the reaction products were pushed into the collector and subjected to rectification. The conditions of the experiments 1-3 of example 2 and the results are presented in table. 2. The resulting product contained 99.5 wt.% Trihydrotetrafluoropropanol HCF ₂ CF ₂ CH ₂ OH
In the conditions of example 1 was carried out and the synthesis of hexafluorobutanol by the reaction of hexafluoropropylene with methanol

Example 3
A mixture of 100 g of methanol, 10 g of di-tert-butyl peroxide (PTB), 0.8 g of calcium oxide was placed in a 0.25 L autoclave, and hexafluoropropylene was pumped to 6.5 kg / cm ² with stirring, and then heated to 120 ^° C. Upon reaching this temperature, the flow of hexafluoropropylene was resumed, maintaining it at a level of 13-14 kg / cm ² (molar ratio C ₂ F ₆ : PTB equal to 11.6: 1) at a temperature of 130-140 ^o C for 4.5 hours . After that, the reactor was cooled to room temperature and 143.6 g of hexafluorobutanol, CF ₃ CFHCF ₂ CH ₂ OH were isolated from the resulting reaction mass weighing 289.5 g. In the experiment without the addition of calcium oxide, the weight of the reaction mass was 287.2 g.

In an alternative method of producing hexafluorobutanol by heating 1 kg of methanol with 1 kg of hexafluoropropylene in the presence of 30 g of benzoyl peroxide (3 wt.%) As an initiator for 4 hours at 100 ^° C and self-developing pressure, 675.6 g of hexafluorobutanol CF ₃ CFHCF ₂ CH are obtained ₂ OH content of the isomer CF ₃ CF (CF ₂ H) CH ₂ OH ~ 5%), i.e. the yield of the target product (calculated on the starting components) is 2.1 times lower than by the proposed method.

The consideration presented in table. 1, 2 of the data allows us to establish certain patterns and draw conclusions about ways to optimize the process as a whole. For convenience, comparing the results obtained at reactors of different capacities in the table. 1 (columns 15, 16) shows the calculated data on the yield of tetrafluoropropanol in 1 m ³ reactor.

 In column 17 of the table. Table 1 and column 16 of Table 2 show the pressure of tetrafluoroethylene recommended by us to reduce the induced decomposition of the initiator (PTB) during heating of the reaction mixture to operating temperature. Limitations on the upper limit are due to a possible excess of working pressure due to thermal expansion.

From the table. 1 (columns 1, 10, 11) it can be seen that an increase in the temperature and concentration of the initiator leads to an increase in the rate of consumption of tetrafluoroethylene (column 14) and the optimal parameters for these indicators are in the range of 8.3-12.1 wt.% At a temperature of 130- 150 ^o C.

At the same time, the yield of tetrafluoropropanol (TFP) column 13, table. 1, 2 is determined, as follows from the data obtained, with a molar ratio of tetrafluoroethylene: initiator - column 12, table. 1, 2, i.e. at practically the same rate of tetrafluoroethylene consumption, the selectivity for the formation of tetrafluoropropanol is optimal with a molar ratio of C ₂ F ₄ : PTB equal to 8.8-15.2: 1.

 This conclusion is confirmed by comparing the best technological parameters of examples 18 and 21 of the prototype, calculated on the reactors V = 0.25 and V = 1000 l and are given in table. 1 under N 7 and table. 2 under N 4.

 Thus, carrying out the process under the conditions we offer allows us to increase the yield of the target product from a unit of the reaction volume per unit time by 1.3-1.8 times.

 Similar results, as shown above (example 3), were obtained in the synthesis of hexafluorobutanol.

Claims (3)

1. The method of producing polyfluorinated alcohols of the formula R-OH, where R = HCF ₂ CF ₂ CH ₂ -, CF ₃ CFHCF ₂ CH ₂ -, by heating a solution of peroxide initiator with a decomposition temperature above 100 ^o C in aliphatic alcohol, followed by controlled supply in excess this aliphatic alcohol fluorine-containing olefin at elevated temperature and pressure, characterized in that the heating is carried out at a concentration of initiator equal to 3.5 - 15.4% by weight of the loaded alcohol, at a pressure of 3.4 - 6.5 kg / cm ² until established temperature 110 - 120 ^o With the subsequent increase in pressure to 9 - 15 kg / cm ² and temperatures up to 150 ^o C.  2. The method according to claim 1, characterized in that the molar ratio of fluoroolefin: initiator is 7.2 - 28.2: 1.  3. The method according to PP. 1 and 2, characterized in that the heating is carried out in the presence of polyfluorinated alcohol, taken in an amount of 0.2 - 1.2% by weight of the loaded alcohol.

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