RU2291856C1 - Method of production of iron formate (ii) - Google Patents

Abstract

FIELD: production of salts of organic acids, salt of ferrous iron and formic acid in particular.

SUBSTANCE: proposed method consists in loading preliminarily prepared aqueous solution of formic acid at concentration of 4.5-10 mole/kg into reactor provided with bladed mixer, back-flow condenser-cooler and air bubbler. Then, powder of reduced iron and/or broken iron and/or steel chips at any mass ratio in total amount of 20.0-30.6% of mass of liquid phase and stimulating iodine additive in the amount of 0.016-0.164 mole/kg of liquid phase are introduced. Reactor may be provided with steel or cast iron ferrule over entire height. At mechanical mixing, consumption of air for bubbling is maintained between 1.2 and 2.0 l/(min·kg of liquid phase). Working temperature range is 45-65°C which is maintained by external cooling. Process is discontinued when content of iron salts (II) in reaction mixture reaches 1.8-2.0 mole/kg. Suspension of salt in liquid phase is separated from unreacted iron particles and is filtered afterwards. Filtrate is directed for repeated process and salt sediment is re-crystallized from aqueous solution saturated with iron formate by formic acid at concentration of 1-2 mole/kg at heating to temperature of 95°C followed by natural cooling.

EFFECT: enhanced efficiency.

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Description

The invention relates to a technology for the production and isolation of ferrous salt and formic acid in aqueous media and can be used in various fields of industrial and laboratory chemistry, in analytical control methods and studies in different directions.

A known method of producing iron (II) formate by reacting iron (II) sulfate with sodium formate in an aqueous solution in an inert medium. The resulting product is slightly soluble in water and resistant to oxidation in air (US Pat. US No. 2688032, publ. 1952, serial No. 311733).

The disadvantages of this method are the use of water-soluble salts of iron (II) and sodium formate as reagents, which must first be obtained through chains of numerous successive transformations, as well as the creation and maintenance of an inert medium.

Closest to the claimed is a method for producing iron (II) acetate (application No. 2004108557/04 (009022) op. 20.09.05), in accordance with which the iron powder is oxidized first with oxygen in the air in the mode of bubbling in an acetic acid medium in the presence of acetic anhydride with vigorous mechanical stirring until 0.75-0.96 mol / kg of iron (III) salt is accumulated, and then the air is replaced by nitrogen, the content of acetic anhydride in the reaction mixture is increased and the temperature is increased, and in this mode, iron is oxidized with the iron (III) salt until fully spent I was the last to the accumulation of salts of iron (II).

The disadvantages of this method are:

1. Obtaining an iron (II) salt is actually only in the second stage by oxidation of iron with an iron (III) salt. This is predetermined by the fact that the iron (III) salt is more stable under ordinary conditions, i.e. in contact with air in solution, in suspension, and in the precipitate moistened with the reaction mixture during filtration and drying in comparison with the iron (II) salt. It is not necessary that this situation be maintained when replacing the anion of acetic acid with formic.

2. The use of nitrogen medium during the second stage of the process, which presents certain inconveniences and complicates the hardware design of the process.

3. The process is carried out in a practically anhydrous environment, achieved by introducing acetic anhydride into the reaction mixture to eliminate the reaction water and stimulate the redox process as a whole.

4. The absence of formic acid anhydride per se makes it practically impossible to reproduce the model under consideration when replacing acetic acid with formic acid.

The objective of this solution is to obtain iron (II) formate in a process where iron, formic acid and atmospheric oxygen are used as initial reagents, and the process itself should be carried out in one stage and in an aqueous medium.

The task is achieved in that the liquid phase of the load in the form of 4.5-10 mol / kg of an aqueous solution of formic acid is introduced into intensive and updated with high frequency contact with iron and (or) its alloys in the form of a steel or cast iron shell over the entire height of the reactor or (and additionally) with 20.0-30.6% by weight of the liquid phase of the reduced iron powder, or (and) pieces of beaten iron, and (or) steel chips in any mass ratio between each other in the presence of a stimulating additive of iodine in an amount of 0.016 -0.164 mol / kg liquid phase and bubbling air with a flow rate of 1.2-2.0 l / (min · kg of the liquid phase), and the process starts at room temperature, is conducted in the temperature range 45-65 ° C as a result of restraint of spontaneous growth using external forced cooling and is stopped when the content of iron salts in the reaction mixture is 1.8-2.0 mol / kg, after which the suspension of salt in the liquid phase of the final reaction mixture is separated from the heavy particles of iron and (or) its alloys (a) and sent for filtration, the filtrate is returned for repeated process, and the precipitate is dissolved by alternating Shivani and heated in a saturated iron formate (II) aqueous solution with formic acid content 1.2 mol / kg, the resulting solution purified from the undissolved solid impurities by hot filtration, and left for crystallization of salts with natural cooling which subsequently is separated by filtration and dried.

Characteristics of the raw materials used.

Reduced reactive iron according to TU 6-09-2227-81

Steel 3 according to ChMTU 1-84-67

Steel 45 according to GOST 1050-74

Gray cast iron SCH 15-32 according to GOST 1412-70

Crystalline iodine according to GOST 4159-79

Formic acid according to GOST 5848-73

The process of the claimed method is as follows. Into a reactor with a glass case in the absence or with a cast-iron (steel) shell along the entire height, as well as with a high-speed paddle mixer that repeats the bottom profile well and is no more than 0.3 mm apart, with a reflux condenser and bubbler for 4.5 to 10 mol / kg aqueous solution of formic acid, pre-prepared (or component-wise), loaded; reduced iron powder is introduced individually or together with fractions of beaten cast iron and (or) steel shavings in any mass the ratio of each other, but in the calculated total amount and the stimulating additive of iodine in the amount of 0.016-0.164 mol / kg of the liquid phase. Upon completion of loading, the reactor is placed in its place in the installation, cooling water is supplied to the reflux condenser, mechanical stirring is switched on, and the air flow rate is set for bubbled. This moment is considered the beginning of the process. Observe the temperature change. As soon as the latter begins to rise, forced cooling is introduced through a liquid bath and the temperature is stabilized in the range of 45-65 ° C. In this mode, the process is continued until the accumulation of the iron salt in the reaction mixture is 1.8-2.0 mol / kg. Control is carried out by sampling the reaction mixture and determining the content of iron (II) and (III) salts in them.

Upon reaching the indicated salt content in the reaction mixture, the process is stopped (stirring and air bubbling are stopped, the cooling of the reflux condenser is removed and with the help of a liquid bath). The reaction mixture is separated from the heavy particles of unreacted iron and sent for filtration. The filtrate is recycled. And the precipitate is dissolved by heating in an aqueous solution of formic acid saturated with iron formate with a concentration of 1-2 mol / kg, followed by hot filtration and crystallization of the product under natural cooling.

Example No. 1

A thick-walled glass reactor with an inner diameter of 71.3 mm and a height of 117 mm, placed in a protective casing, with a high-speed (1440 rpm) paddle mixer that repeats the bottom profile well and is 0.3 mm apart from it, with a reflux condenser and bubbler 180 g of an aqueous solution of formic acid with a concentration of 6.1 mol / kg, 1.27 g of iodine and 55.08 g of reduced iron powder are charged with air. Cooling water is supplied to the refrigerator-condenser, mechanical stirring is switched on, and the air flow rate for bubbling is set at 1.5 l / (min · kg of the liquid phase). The temperature at this moment was 24 ° C. After 31 minutes, it rose to 39 ° C. The reactor is placed in a cooling liquid bath and the temperature is stabilized at 45 ° C. After 110 minutes of stirring at this temperature, the salt content of the suspension became 1.80 mol / kg. Stirring is stopped and given 3 minutes to settle heavy particles of unreacted iron. The salt suspension in the liquid phase of the system is carefully drained so that the iron particles with the remaining reaction mixture remain in the dead zone of the reactor. 184 g of suspension were unloaded. It is sent for filtering. The filtrate is returned to the repeated process.

The precipitate is dissolved in 300 g of a solution of formic acid saturated with iron (II) formate with a concentration of 1.54 mol / kg with stirring and heating to 93 ° C for 95 minutes. The resulting mass is immediately filtered at about the same temperature. The resulting filtrate was allowed to cool naturally and crystallize the salt for 12 hours. The crystallized salt was filtered and dried. Yield 49.4 g.

Examples No. 2-9

The reactor used, the amount of the liquid phase and the sequence of operations are similar to those described in Example 1. They are distinguished by separate loading of water and formic acid, the presence of a shell along the entire height of the reactor, the nature of the shell material, and the concentrations of formic acid and iodine in the liquid phase of the initial reaction mixture, using in addition to iron powder of fractions of broken cast iron and broken steel chips and their mass ratio, dosage of crushed iron-containing materials, process temperature, the time of termination of the process, the mass of the solution for recrystallization, and the concentration of formic acid in it. The results are summarized in table.

Table Download and process specifications Example No. 2 3 four 5 6 7 8 9 Shell no no no cast iron cast iron cast iron steel steel The concentration of acid in the liquid phase, mol / kg 7.9 8.3 10.0 4,5 5,4 5.7 6.1 6.3 The concentration of iodine in the liquid phase, mol / kg 0,053 0,071 0.016 0.164 0,048 0,048 0,073 0,081 Loading: reduced iron, g 0 0 10.00 0 0 0 36.00 4,59 broken cast iron, g 55.08 0 20,13 25.27 10.48 35.42 0 20.11 broken steel shavings, g 0 55.08 20.17 25.39 35.63 10.87 0 20.47 in total,% of the liquid phase 30.6 30.6 22.4 28.1 25.6 25.7 20,0 25.1 Temperature, ° С at the start of the process 23 21 19 25 23 24 twenty eighteen in the working range 51 58 45 57 49 55 63 65 Air consumption, l / (min · kg of liquid phase) 1,2 1.7 1.4 1,5 1,6 1,2 2.0 1.9 The duration of the process, min 89 75 183 84 105 97 103 111 The concentration of iron salts in the reaction mixture at the time of termination 1.90 1.95 1.86 2.00 1.87 1.93 1.84 1.97 The amount taken for recrystallization solution, g 350 330 340 283 290 290 300 300 Concentration of formic acid on recrystallization, mol / kg 1.00 1.40 1.27 2.00 1.84 1.84 1.75 1.75 The yield of dried iron (II) formate after recrystallization, g 52.8 53.1 50,2 55.1 54.3 53,2 54.8 56.2

The positive effect of the proposed solution is as follows.

1. There is no need to use organic solvents and an inert medium.

2. For the preparation of the liquid phase, aqueous solutions of formic acid can be used instead of practically anhydrous acid.

3. When cleaning the product by recrystallization, only the components of the reaction mixture of the main process are used.

4. The process proceeds at low operating temperatures, which may well be supported by the use of heat exothermic stages.

5. Cast iron and steel wastes may well be used as raw materials. The carbon formed from them is not an inhibitor of the process and is easily removed by recrystallization.

6. The process can be repeated many times without intermediate purification of the reactor and emptying of the dead zones, which significantly reduces the loss of the reaction mixture and favors the yield of the product and the reduction of waste-pollution.

Claims (1)

A method of producing iron (II) formate by direct interaction of crushed iron with acid in the presence of atmospheric oxygen as an oxidizing agent under conditions of intense mechanical stirring, characterized in that the liquid phase of the charge in the form of 4.5-10 mol / kg of an aqueous solution of formic acid is introduced into intensive and updated with high frequency contact with iron and (or) its alloys in the form of a steel or cast iron shell over the entire height of the reactor or (and additionally) with 20.0-30.6% of the mass of the liquid phase of the reduced powder about iron or (and) pieces of beaten cast iron and (or) steel chips in any mass ratio to each other in the presence of a stimulating additive of iodine in an amount of 0.016-0.164 mol / kg of liquid phase and air sparging with a flow rate of 1.2-2.0 l / min-kg of the liquid phase, and the process starts at room temperature and is carried out in the temperature range of 45-65 ° C as a result of restraint of spontaneous growth using external forced cooling and is stopped when the content of iron salts in the reaction mixture reaches 1.8-2.0 mol / kg, followed by a suspension of salt in rye In this phase, the final reaction mixture is separated from heavy particles of iron and (or) its alloys (a) and sent for filtration, the filtrate is returned to the repeated process, and the precipitate is dissolved with stirring and heating in an aqueous solution of iron (II) saturated with formic acid 1.2-2.0 mol / kg, the resulting solution is purified from insoluble solid impurities by hot filtration and left to crystallize the salt under natural cooling, which is subsequently separated by filtration and dried.