BE893357A - PROCESS FOR THE PREPARATION OF FORMIC ACID AND PRODUCT THUS OBTAINED - Google Patents

Description

       

  "Process for the preparation of formic acid and product thus obtained" "Process for the preparation of formic acid and product

  
 <EMI ID = 1.1>

  
The present invention relates to the field of the synthesis of main organic products, and more specifically, to processes for the preparation of formic acid. Formic acid is widely used as a raw material in the production of pharmaceutical preparations, dimethylformamide, oxamide, fungicides, herbicides, insecticides as well as in the leather industry and for the preservation of products. The most important current use of formic acid is the preservation of farmed green foods.

  
A process for the preparation of formic acid is known by hydrolysis of methylformate with water in the presence of an acid type catalyst, in particular of a mineral acid, at a temperature of 150 to 400 [deg.] C and at high pressures; sulfuric acid is then used as the catalyst. Hydrolysis is carried out continuously (patent of the United States of America

  
 <EMI ID = 2.1>

  
The disadvantage of the process indicated is the use of an inorganic catalyst in the homogeneous phase, this fact making it difficult to isolate it from the catalysis product and, consequently, the targeted product, formic acid, is polluted. In addition, another drawback of said process is the need to create severe conditions under which the process is carried out (high temperature and pressure), given the insufficient activity of the catalyst.

  
There is also known a process for the preparation of formic acid by hydrolysis of methylformate to a

  
 <EMI ID = 3.1>

  
acid type, namely very acid sulfocationite based on styrene copolymer and 8% by weight of divinylbenzene. The process is carried out in a reactor filled with the indicated cationite, by continuous admission with direct flow of water and methylformate in a mole ratio of 14/1 respectively. According to the process indicated, a conversion rate of
90% methylformiate (M.I. Vysotsky, M.M.Ketslakh, A.I.Rotanova "Revue de la chimie appliqué", 1967, v.40

  
 <EMI ID = 4.1>

  
The main drawback of the abovementioned process is a high consumption of water for the hydrolysis of methylformate in order to achieve a high degree of conversion of methylformate.

  
The excess water dilutes the hydrolysis products, which reduces the yield of the targeted product according to the reaction volume. By carrying out the process by the process indicated, a hydrolysis product containing at most 15% formic acid is obtained, which corresponds to the equal-weighting composition. Isolation

  
formic acid in the indicated hydrolysis product is economically disadvantageous and technologically complicated.

  
The closest process in the technical sense is the process for the preparation of formic acid by hydrolysis of methylformate with water, in a molar ratio of 1/0, 3-3 respectively, at a temperature of 60 to 150 [deg.] C and at a pressure of 3 to 8 bar
(United States patent N [deg.] 3907884 published

  
on 23.09.1975, cl. 260-542). The process is carried out continuously or periodically by adding a catalytic amount of formic acid to the starting mixture. Is introduced into the mixture, for the homogenization of the starting mixture of methylformate and water, 3 to 30% by weight of methanol (the latter, like formic acid, is also a product of the hydrolysis of methylformate). According to this process, the hydrolysis of the methylformate is carried out in a reactor in which an ideal mixing takes place with the obtaining of the hydrolysis product which is a mixture of formic acid, of methylformate,

  
of methanol and water in concentrations close to the weighting concentrations.

  
As is known, the equilibrium of the reaction of the hydrolysis of methylformate is shifted in the direction of formation of the initial bodies:

  

 <EMI ID = 5.1>


  
 <EMI ID = 6.1>

  
Therefore, in the hydrolysis product, the composition of which is close to the equal-weighting composition, the formic acid content does not exceed
15% by weight which makes it difficult to isolate it.

  
The drawbacks of the process indicated are a low conversion rate of the initial methylformate (not more than 60%) with the water / methylformate ratio in the starting mixture of 3/1 respectively, a low yield of formic acid not exceeding 55 g / h for 1 liter of the reaction volume, a low yield of formic acid equal to 169.1 g per kg of the reaction mixture

  
flow, as well as a high pressure application (3-8 bar).

  
The object of the invention is to eliminate the drawbacks indicated.

  
It has been proposed in the process for the preparation of formic acid consisting of a hydrolysis of methylformate with water, their mole ratio being 1 / 1-3 respectively, under heating and in the presence of a type catalyst. acid, the process being carried out continuously, to modify the conditions of the process so as to make it possible to increase the content of the hydrolysis product in formic acid, to increase the rate of conversion of methylformate into formic acid and to raise the productivity of the process.

  
The solution according to the invention consists

  
in that the hydrolysis is carried out in a vertical reactor of the column type with two zones, at atmospheric pressure and by admission against the current of water in the upper zone of the reactor, filled with very acid sulfocationite based on copolymer of styrene and

  
2 to 8% by weight of divinylbenzene as catalyst, and methylformate in the lower region of the. reactor; in the upper zone of the reactor, the hydrolysis is then carried out at a temperature of 60 to 100 [deg.] C with a simultaneous evacuation from the upper zone of a mixture of methylformiate not entered into reaction and of methanol formed, and in the lower zone of the reactor the hydrolysis is carried out by autocatalysis, in the presence of formic acid arriving from the zone above

  
 <EMI ID = 7.1>

  
107 [deg.] C, with a simultaneous evacuation from the lower zone of a mixture of water, formic acid and methanol in which the formic acid is isolated; then evacuated from the upper zone of the reactor 70 to

  
99% of methanol of the total amount of methanol formed in the reactor and, from the lower zone, 1 to 30% of methanol is removed.

  
The process according to the invention makes it possible to combine the chemical process (hydrolysis of methylformate) and the mass exchange process in the reactor and to separate a mixture of methylformiate and methanol and a mixture of formic acid from the reactor, methanol and water. This makes it possible to shift the balance of the hydrolysis reaction in the direction of the formation of the targeted product and to reach a conversion rate of 56.3 to 98% of the methylformate under controlled conditions (temperature not higher than 107 [ deg.] C, atmospheric pressure) with a methylformate / water mole ratio of 1 / 1-3 respectively.

  
It is very important in the process for the preparation of formic acid according to the invention to divide the reactor into zones according to the temperature.

  
The temperature regime in the upper zone of the reactor is chosen so that, in this zone, the following processes take place simultaneously:

  
1) hydrolysis with the formation of a liquid hydrolysis product consisting of formic acid,

  
methanol, methylformate not entered into reaction

  
and water;

  
2) separation by distillation, from the indicated hydrolysis product, of the mixture of methylformate which has not entered into reaction and of methanol (70 to 99% of the total amount of methanol formed in the reactor) and evacuation of this mixture from reactor;

  
3) flow of the liquid mixture of formic acid, water and methanol residue not removed by distillation in the lower zone of the reactor.

  
A lowering of the temperature in the upper part of the reactor below 60 [deg.] C results

  
an alteration of the distillation conditions of the mixture of methanol and methylformate, and therefore a reduction in the conversion rate of methylformate and in the productivity of the process. In addition, at a temperature below 60 [deg.] C, the rate of hydrolysis of methylformate is suddenly reduced which likewise reduces the productivity of the process.

  
An increase in temperature in the

  
 <EMI ID = 8.1>

  
the alteration of the distillation conditions of the mixture of methanol and methylformate in the upper zone of the reactor due to the increase, at these temperatures, in the volatility of water and of formic acid, which results in a reduced methylformate conversion rate and process productivity.

  
The temperature regime of the lower zone of the reactor is chosen so as to ensure at atmospheric pressure a sufficiently high rate of hydrolysis of methylformate in this zone and to obtain at the outlet of the reactor a mixture of formic acid, of methanol and water, preferably at a concentration of not less than 50% by weight. Since the hydrolysis in the lower zone of the reactor is carried out by autocatalysis, lowering the temperature below 100 [deg.] C is not advantageous, given the reduction in the rate of hydrolysis .

   An increase in the temperature in the lower zone of the reactor to more than 107 [deg.] C is not desirable, since in this case all the constituents of the reaction mixture, including formic acid, are in vapor phase which suddenly reduces the productivity of the process (the speed of hydrolysis in vapor phase is significantly lower than that of hydrolysis in liquid phase).

  
It is no less important in the process according to the invention for the hydrolysis of methylformate to use, in the upper zone of the reactor, a heterogeneous catalyst, in particular sulfocationite

  
very acid based on styrene copolymer and 2-8% by weight of divinylbenzene. This eliminates the need for intake with water of either formic acid or a mineral acid and thereby the technological process is simplified and the productivity of the process increased.

  
The advantages of using highly acid sulfocationite as a catalyst are its easy isolation in the reaction mass and its high activity in ionic type reactions to which the hydrolysis of methylformate also belongs.

  
The essential requirements to be met

  
the cationite used in the process according to the invention are sufficient mechanical strength and chemical resistance as well as good kinetic properties and a high activity in the hydrolysis of methylformate. A divinylbenzene content of the sulfocationite copolymer base of less than 2% by weight greatly alters the mechanical strength and the chemical resistance of the cationite, which reduces its ability to function. If the copolymer base of the cationite contains more than 8% by weight of divinylbenzene, its mass exchange activity and the kinetic properties deteriorate, this fact also reducing its productivity.

  
As mentioned above, the hydrolysis of methylformate in the lower zone of the reactor is carried out by autocatalysis, in the presence of formulated acid.

  
 <EMI ID = 9.1>

  
When the pH is equal to or greater than 1, 9,

  
the concentration of protons in the reaction mixture in the lower zone of the reactor is insufficient for carrying out the hydrolysis of methylformate.

  
By carrying out the process by the process according to the invention, a concentration of formic acid is obtained in the mixture, at the outlet of the lower zone of the reactor, equal to 56-86% by weight and a yield of formic acid per liter. reaction volume of 395.7-735.0 g / h. The yield of formic acid is 254.8 to 470.2 g per kg of starting raw material.

  
The process for the preparation of formic acid by hydrolysis of methylf ormiate is carried out in a vertical reactor with two column type zones, at atmospheric pressure.

  
In the upper zone of the reactor fitted with a thermostatic jacket, the highly activated sulfocationite is previously activated and the temperature in this zone is brought to 60-100 [deg.] C. In the lower zone of the reactor also equipped with a thermostatic jacket, a temperature of 100 to

  
 <EMI ID = 10.1>

  
the cationite layer of water and in the lower zone of the reactor is introduced continuously, countercurrently, methylformate, the mol / water / methylformate ratio being equal to 1-3 / 1 respectively. The water flowing from top to bottom through the cationite layer comes into contact with methyl form vapors, forming a liquid hydrolysis product composed of formic acid, methanol, methylformate which has not reacted and water. Methanol at <EMI ID = 11.1>

  
reactor (70-99% of the total amount of methanol formed in the reactor) mixed with the methylformate which has not entered the reaction is distilled off from the hydrolysis product and is continuously evacuated, in the form of vapor, from the upper reactor area. The methylformate and methanol vapors are condensed in a de-phlegmator and the condensation product is collected in a collector for the methanol-methylformate mixture.

  
The liquid mixture of formic acid, water and methanol residue not removed by distillation flows from the upper zone of the reactor into the zone

  
 <EMI ID = 12.1>

  
methyl formate vapors admitted from below. Hydrolysis of the methylformate is then carried out by autocatalysis. From the lower zone of the reactor is continuously discharged an aqueous solution of highly concentrated formic acid (1 to 30% of the total amount of methanol formed in the reactor), which is collected in a collector. The formic acid is isolated from the indicated solution by known methods, for example by rectification.

  
The very acid sulfocationite used as catalyst in the process according to the invention is activated by the following known process.

  
To purify the technical sulfocationite of organic and mineral impurities of low molecular weight, it is washed several times with water, then with a 3N aqueous solution of hydrochloric acid until complete elimination of the impurity.

  
iron (control carried out using ammonium rhodianite). Then the cationite undergoes washing with distilled water to a constant pH of the washing water, with a 10% aqueous solution of chloride.

  
sodium, with water and again with a 3N aqueous solution of hydrochloric acid. This treatment ensures "training" of the reticular three-dimensional network of the polymer. A reliable criterion for the completion of the preparation of the H form of the sulfocationite is the obtaining of a hydrochloric acid concentration in the solution, after the cationite has been washed,

  
 <EMI ID = 13.1>

  
tion the sulfocationite is washed with water until a neutral reaction in the presence of methyl orange and it is dried.

  
The process according to the invention is of simple technological realization with the use of an accessible catalyst (cf. KMSoldadze "Compounds exchangers of macromolecular ions" Moscow, Edt. Goskhimizdat, 1960) and it makes it possible to carry out a hydrolysis with a rate of high methylformate conversion and high productivity of technical material
(395.7-735.0 g / h per liter of the reaction volume, calculated relative to formic acid).

  
Other advantages and characteristics of the invention will be better understood on reading the description which will follow of concrete embodiments. not limiting.

Example 1.

  
For a continuous production of formic acid by hydrolysis of methylformiate, a vertical cylindrical glass reactor is used, of the type of a column 650 mm high and 20 mm in diameter.

  
The highly acid activated sulfocationite based on styrene copolymer and 3% by weight of div inylbenzene is charged in the upper zone of the reactor, fitted with a dynamic type thermostatic jacket. The height of the cationite layer is
150 mm. The weight of the cationite loaded into the reactor is 57 g. In the lower zone of the reactor, provided with a dynamic type thermostatic jacket, a packing is loaded, namely 5 × 5 mm Raschig rings. The upper area of the reactor is

  
 <EMI ID = 14.1>

  
less than 107 [deg.] C. The pressure in the reactor is atmospheric pressure. 120 g / h (6.66 mol / h) is continuously admitted into the reactor (in the upper zone)

  
h) water and in the lower zone 199.2 g / h (3.32 moles / h) of methylformate. The mol / water / methylformate ratio is equal to 2/1 respectively.

  
The hydrolysis of methylformate in the upper zone of the reactor takes place at the temperature of

  
 <EMI ID = 15.1> and in the lower zone of the reactor the hydrolysis is carried out by autocatalysis, in the presence of formic acid which comes from the upper zone and which has a pH. = 1, 3 and a temperature of 107 [ deg.] C.

  
108.3 g / h are continuously discharged from the upper zone of the reactor of a mixture composed of
85.2% by weight of methanol (which corresponds to

  
94.4% of the total amount of methanol formed in the

  
 <EMI ID = 16.1>

  
entered into reaction. 210.9 g / h of a mixture are continuously discharged from the lower zone of the reactor

  
 <EMI ID = 17.1>

  
by weight of water and 2.6% by weight of methanol (this

  
which corresponds to 5.6% of the total amount of methanol formed in the reactor). Is isolated from the indicated mixture (discharged from the lower zone of the reactor) 140.5 g / h of formic acid by rectification in two stages, with the formation of an intermediate azeotrope.

  
The composition of the products removed from the reactor is determined by chromatography. The conversion rate of the starting methylformate is 92%. The yield of formic acid is 440.0 g per kg of initial bodies. The yield of formic acid per liter of reaction volume is equal to 687.8 g / h.

Example 2.

  
The process is carried out as in Example 1, except that the upper zone of the reactor is thermostatically adjusted to

  
 <EMI ID = 18.1>

  
We admit continuously, in the upper zone

  
from the reactor, 120 g / h of water and, in the lower zone,
199.2 g / h of methylformate. The ratio in mole water / <EMI ID = 19.1>

  
The hydrolysis of methylformate in the lower zone is carried out by autocatalysis, in the presence

  
formic acid arriving from the upper zone, at a pH of 1.5 and at a temperature of 100 [deg.] C.

  
96.6 g / h of a mixture composed of 63.6% by weight of methanol (which corresponds to 70.6% of the total amount of methanol formed in the reactor) are continuously removed from the upper zone of the reactor. and 36.4% by weight of methylformate which has not entered into reaction. Evacuated continuously from the lower zone of the reactor
222.6 g / h of a mixture consisting of 56.5% by weight of formic acid, 31.8% by weight of water and 11.7% by weight of methanol (which corresponds to 29, 4% of the total amount of methanol formed in the reactor).

  
The conversion rate of the starting methylformate is 82.3%. The yield of formic acid is 394 g per kg of starting substances. The productivity per liter of the reaction volume, calculated with respect to formic acid, is 615.9 g / h.

Example 3.

  
The process is carried out as in Example 1, except that the upper zone of the reactor is thermostatically adjusted to the temperature of 100 [deg.] C and the zone below 107 [deg.] C.

  
120 g / h of water are admitted continuously into the upper zone of the reactor and, in the lower zone, 199.2 g / h of methylformate are continuously introduced.

  
The molar ratio of water / methylformate is 2/1 re spectrally.

  
Hydrolysis of methylformate in the lower zone is carried out by autocatalysis, in the presence of formic acid from the upper zone

  
 <EMI ID = 20.1>

  
Evacuated continuously from the upper zone of the reactor 143.7 g / h of a mixture composed of 35.8% by weight of methanol (which corresponds to
91.7% of the total amount of methanol formed in the reactor) and 64.2% by weight of methylformate which has not entered into reaction. From the lower reactor area

  
173.4 g / h of a compound mixture are continuously discharged

  
46.6% by weight of formic acid, 50.7% by weight of water and 2.7% by weight of methanol (this corresponds to 8.3% of the total amount of methanol formed in the reactor ).

  
The conversion rate of the starting methylformate is 56.3%. The yield of formic acid is 254.8 g per kg of starting reagents. The productivity of 1 liter of the reaction volume calculated relative to the formic acid is 395.7 g / h.

Example 4.

  
The hydrolysis of methylformate is carried out as in Example 1, with the difference that water and methylformate are admitted into the reactor in a molar ratio of 1/1 and that a very acid sulfocationite is used based on styrene copolymer and 2% by weight of ivinylbenzene. The upper zone of the reactor is thermostatically adjusted to the temperature of 80 [deg.] C and the lower zone to the temperature of 103 [deg.] C.

  
We admit continuously, in the upper zone,
60 g / h (3.33 moles / h) of water and, in the lower zone,
199.2 g / h (3.32 moles / h) of methylformate.

  
The hydrolysis of methylformate in the lower zone is carried out by autocatalysis, in the presence

  
formic acid arriving from the upper zone at pH = 1.2 and at a temperature of 103 [deg.] C.

  
127.1 g / h are continuously discharged from the upper zone of the reactor of a mixture consisting of 60.8% by weight of methanol (which corresponds to 97% of the total amount of methanol formed in the reactor) and 39.2% by weight of methylformate which has not entered into reaction. 132.1 g / h of a mixture composed of 86.7% by weight of acid are continuously removed from the lower zone.

  
 <EMI ID = 21.1>

  
methanol (which corresponds to 3% of the total amount of methanol formed in the reactor).

  
The conversion rate of the starting methylformate is equal to 75.0%. The yield of formic acid is 441.9 g per kg of starting reagents. The productivity of 1 liter of the reaction volume calculated relative to formic acid is 560.9 g / h.

Example 5.

  
The process is carried out as in Example 1, except that water is introduced

  
and methylformate in the reactor in a mole ratio of 3/1 respectively and using very acid sulfocationite based on styrene copolymer and 2% by weight of divinylbenzene. The upper zone of the reactor is thermostatically adjusted to the temperature of 80 [deg.] C. and the zone lower than 103 [deg.] C.

  
180 g / h (10 mol / h) of water are admitted continuously into the upper zone of the reactor and 199.2 g / h (3.32 mol / h) of methylformate into the lower zone.

  
The hydrolysis of methylformate in the lower zone of the reactor is carried out by autocatalysis, in the presence of formic acid arriving from the upper zone.

  
 <EMI ID = 22.1>

  
We evacuate from the upper zone, continuously,
104.6 g / h of a mixture composed of 91.0% by weight of methanol (which corresponds to 94% of the total amount

  
 <EMI ID = 23.1>

  
of methylformate not entered in reaction. 274.6 g / h of a mixture of 53.0% by weight of formic acid,
44.8% by weight of water and 2.2% by weight of methanol
(which corresponds to 6% of the total amount of methanol formed in the reactor).

  
The conversion rate of the starting methylformate is equal to 95.3%. The yield of formic acid is 383.7 g per kg of starting reagents. The productivity of 1 liter of the reaction volume calculated relative to the formic acid is 712.5 g / h.

Example 6

  
The hydrolysis of methylformate is carried out as in Example 1, with the difference that a very acid sulfocationite is used based on a styrene copolymer and 8% by weight of divinylbenzene. The upper zone of the reactor is adjusted so

  
 <EMI ID = 24.1>

  
In the upper zone of the reactor 120 g / h (6.66 moles / h) of water are continuously admitted and in the lower zone 199.2 g / h (3.32 moles / h) of methylformate. The mol / water / methylformate ratio is equal to 2/1 respectively.

  
The hydrolysis of methylformate in the lower zone of the reactor is carried out by autocatalysis, in the presence of formic acid arriving from the upper zone <EMI ID = 25.1>

  
Evacuated continuously from the upper zone of the reactor 124.9 g / h of a mixture composed of 60.9% by weight of methanol (which corresponds to 94.7% of the total amount of methanol formed in the reactor) and 39.1% by weight of unreacted methylformate. 194.3 g / h of a mixture composed of 59.3% by weight of formic acid, 38.5% by weight of water and

  
2.2% by weight of methanol (which corresponds to

  
5.3% of the total amount of methanol formed in the reactor).

  
The conversion rate of the starting methylformate is 75.4%. The yield of formic acid is 361.0 g per kg of starting reagents. The productivity of 1 liter of the reaction volume calculated by

  
 <EMI ID = 26.1>

Example 7

  
The hydrolysis of methylformate is carried out as in Example 1, except that a temperature of 90 [deg.] C is maintained in the upper zone.

  
 <EMI ID = 27.1>

  
the lower area.

  
120 g / h (6.66 moles / h) of water and are continuously admitted into the upper zone of the reactor. in the

  
 <EMI ID = 28.1>

  
is 2/1 respectively.

  
The hydrolysis of methylformate in the lower zone of the reactor is carried out by autocatalysis, in the presence of formic acid which arrives from the zone

  
 <EMI ID = 29.1>

  
107 [deg.] C.

  
106.9 g / h are continuously discharged from the upper zone of the reactor of a mixture consisting of 96.6% by weight of methanol (which corresponds to 99% of the total amount of methanol formed in the reactor) and 3.4% by weight of non-reacted methylformate. 212.3 g / h of a mixture composed of 70.7% by weight of formic acid, 28.8% by weight of water are continuously removed from the lower zone.

  
and 0.5% by weight of methanol (which corresponds

  
1% of the total amount of methanol formed in the reactor).

  
 <EMI ID = 30.1>

  
departure is 98.2%. The yield of formic acid is 470.2 g per kg of starting reagents. The productivity of 1 liter of the reaction volume calculated relative to the formic acid is 735.0 g / h.

  
It should be understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made without departing from the scope of this patent.


    

Claims (3)

1. Process for the preparation of formic acid by hydrolysis of methylformate with water, in a mole ratio of 1/3 respectively, under heating, in the presence of an acid type catalyst and in continuous regime, characterized in that hydrolysis is carried out in a vertical reactor with two zones of column type, at atmospheric pressure and by counter ion admission of water in the upper zone of the reactor, filled with very sulphocationite acid based on styrene copolymer and 2 to 8% by weight of divinylbenzene as catalyst, and of methylformate in the lower zone of the reactor, the hydrolysis in the upper zone of the reactor then being carried out at a temperature of 60 to 100 [deg.] C with a simultaneous evacuation from the upper zone of a mixture of methylformate which has not reacted and methanol formed, the hydrolysis in the lower zone of the reactor being carried out by autocatalysis, in the presence of formic acid which arrives from the upper zone <EMI ID = 31.1> with a simultaneous evacuation from the lower zone of a mixture of water, formic acid and methanol from which the formic acid is then isolated, and in that evacuation, from the upper zone of the reactor , 70 to 99% of the total amount of methanol formed in the reactor and, from the lower zone of the reactor, 1 to 30% of said methanol. 2. Process for the preparation of formic acid, as described above, in particular in the examples given. 3. Formic acid, as obtained according to the preparation process according to either of Claims 1 and 2.