RU2511388C1 - Method of obtaining sodium hydrocarbonate, containing stable isotope 13c - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in inorganic chemistry, medicine and microbiology. Method of obtaining sodium hydrocarbonate, which contains stable isotope ¹³C, includes interaction of sodium hydroxide with ¹³CO₂ in solution with heating at excessive pressure. Process from the beginning to the end is carried out in water medium under pressure not more than 1 atm at temperature 70-80°C.

EFFECT: invention makes it possible to obtain target product with output up to 97,8%, with isotope purity not less than 98%, and reduce loss of initial ¹³CO₂.

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Description

The invention relates to inorganic chemistry, in particular to a method for producing sodium bicarbonate containing a stable carbon isotope ¹³ C.

This compound is used for non-invasive diagnosis of acidity in the stomach, for determining the value of the body’s main energy metabolism for the reasonable calculation of caloric intake ( ¹³ C-bicarbonate breath test), and also as a culture medium for growing ¹³ C-microorganisms used in microbiological synthesis polymerized ¹³ C-compounds (unsaturated acids, carbohydrates, amino acids and others).

An analysis of the scientific and technical literature shows that the only way to obtain sodium bicarbonate of high (food) purity (I. Kolmanovsky. Production of sodium bicarbonate (bicarbonate). M: Publishing House "Chemistry", 1964, 166 pp .; Krasheninnikov S.A. The technology of soda ash and purified sodium bicarbonate. M .: Publishing house "Higher School", 1985, 287 pp .; Zaitsev ID, Tkach GA, Stoev ND Production of soda. M: Publishing House. "Chemistry", 1986, 311 pp.) Is the carbonization of a soda solution by passing carbon dioxide under pressure into a saturated solution of sodium carbonate I at a temperature of about 75 ° C by the reaction:

Na ₂ CO ₃ (p.) + CO ₂ (g.) + H ₂ O (f) ↔2NaHCO ₃ (tv)

The carbonization method allows you to use a small amount of liquid necessary to obtain a unit of sodium bicarbonate, since the solubility of soda ash is several times higher than the solubility of sodium bicarbonate.

For the production of pure (food) sodium bicarbonate, the carbonation of the soda solution is carried out in carbonization columns on the principle of countercurrent flow of liquid and gas: soda solution enters the upper part of the column, and gas containing 33-40% vol. carbon dioxide. As carbon dioxide is absorbed, the gas is depleted and released into the atmosphere with a CO ₂ content _of 14–16%, which is completely unacceptable from an economic point of view if ¹³ CO _{2 is used} .

Pure baking soda, precipitated upon saturation of the soda solution with carbon dioxide, is separated on the filter, and the mother liquor containing a mixture of sodium carbonate and bicarbonate, as well as dissolved impurities, is returned to the beginning of the process to obtain the initial solution. The output of sodium bicarbonate in an industrial process usually does not exceed 65-75%.

Since the objective of this invention is to develop a method for the synthesis of labeled sodium bicarbonate, the above industrial methods are unacceptable from the point of view of technological implementation of the process.

One of the main requirements for sodium bicarbonate containing a stable carbon isotope ¹³ C is a low content of sodium carbonate (intermediate), it should not exceed 0.4-0.7%, similar to the requirements of GOST 2156-76 for sodium bicarbonate.

A known method of producing sodium bicarbonate labeled with a stable isotope ¹³ C - Japanese application JP 2004339017 - prototype. The process described in this application is carried out by reacting sodium hydroxide with ¹³ CO ₂ at a temperature of 60 ° C and a pressure of 1 MPa (10 atm).

The beginning of the process is carried out in an aqueous medium, and after the reaction mass is cloudy, ethanol is added and then the process is carried out in 67% ethanol. The yield of the target product is 78%. And during the process in a minimum amount of water - 56% (a comparative example without the addition of ethyl alcohol).

The disadvantage of the process is that the addition of ethanol during the detection of turbidity of the reaction mass significantly complicates the hardware design of the process, because a special autoclave design will be required; in addition, the yield of the target product - 78% - is not high enough, and the loss of the initial expensive ¹³ CO ₂ is more than 20%, which indicates a low efficiency of the process.

The objective of the invention is to develop a method for producing sodium bicarbonate labeled with a stable isotope ¹³ C, which would be technologically advanced, provide a sufficiently high yield of the target product and minimal loss of expensive source ¹³ CO ₂ .

The problem is solved by carrying out the process of interaction of sodium hydroxide with ¹³ CO ₂ in an aqueous medium from the beginning to the end of the reaction at a temperature of 70-80 ° C and a pressure of no higher than 1 atm.

It is the combination of these conditions that allows to obtain the yield of the target product (calculated on ¹³ CO ₂ ) up to 97.8% with a significant increase in the processability, minimal loss of the initial ¹³ CO ₂ and with an isotopic purity of the target product of at least 98%.

The following examples illustrate the invention.

Example 1

2 g (50 mmol) of sodium hydroxide and 20 ml of distilled water are charged to the reactor. Then, after sealing and evacuation, the reactor is filled with carbon dioxide ¹³ CO ₂ (with an isotopic purity of at least 99%) in a molar excess with respect to NaOH equal to 15-20%, stirring is switched on and heated to a temperature of 75 ° C. As the gas is absorbed, ¹³ CO _{2 is} added, maintaining a slight excess pressure (not more than 1 atm) in the reactor. The reaction is carried out until the termination of the absorption of ¹³ CO ₂ , then turn off the mixing and flow of coolant. After cooling the reactor to room temperature, unreacted gas is collected in a special container. The reactor is unloaded, the reaction mass is cooled in the refrigerator. The precipitate was separated on a Schott filter. 30 ml of 95% alcohol are poured into the obtained filtrate, and after cooling, the precipitate is separated on the same filter. Then the obtained NaH ¹³ CO ₃ on the filter is washed with a small amount of alcohol, dried first in air and then in a desiccator over calcined silica gel to a constant weight.

The yield of NaH ¹³ CO ₃ based on ¹³ CO ₂ is 97.8%. The mass fraction of NaH ¹³ CO ₃ in the isolated product, determined by the weight loss of the sample upon calcination at a temperature of 280-300 ° C, is 99.9%. The isotopic purity of NaH ¹³ CO ₃ , determined by the number of HCl equivalents required for titration of 100 g of analyte, referred to the theoretical equivalent value for sodium bicarbonate containing ¹³ C carbon isotope, is 99.3%.

The infrared spectrum of the obtained NaH ¹³ CO ₃ recorded on a Nicolet 6700 FT-IR spectrophotometer in KBr pellets was consistent with the spectrum of a NaH ¹³ CO ₃ sample manufactured by Cambridge Isotope Laboratories, Inc. (USA) recorded under the same conditions. The main absorption bands of the isolated NaH ¹³ CO ₂ , cm ^-1 : 808, 1385, 1584, 1631. The main absorption bands of the reference sample, cm ^-1 : 807, 1382, 1582, 1623.

Example 2

The reaction is carried out as in example 1, but at room temperature. In addition, the product is dried at 80 ° C. The yield of bicarbonate per ¹³ CO ₂ is 79%. Mass fraction of bicarbonate in the selected product is 90.6%.

Example 3

The reaction is carried out in the same way as in example 1, but at a temperature of 40 ° C, and the product is dried at 80 ° C. The yield of bicarbonate per ¹³ CO ₂ is 92.6%. Mass fraction of bicarbonate in the selected product is 91%.

Example 4

The reaction is carried out in the same way as in example 1, but at a temperature of 80 ° C, and the product is dried on a rotary evaporator at 40 ° C. The yield of bicarbonate per ¹³ CO ₂ is 76.3%. Mass fraction of bicarbonate in the selected product is 86.4%.

Example 5

The reaction is carried out as in example 1, but at a temperature of 80 ° C. The yield of bicarbonate per ¹³ CO ₂ is 94.3%. Mass fraction of bicarbonate in the selected product is 99.6%. The isotopic purity of NaH ¹³ CO ₃ is 99.1%.

Example 6

The reaction is carried out as in example 1, but 5.68 g (142 mmol) of sodium hydroxide and 50 ml of distilled water are charged into the reactor. Overpressure ¹³ CO ₂ support not more than 0.5 ATM. The yield of NaH ¹³ CO ₃ based on CO ₂ is 93%. Mass fraction of NaH ¹³ CO ₃ in the selected product is 99.7%. The isotopic purity of NaH ¹³ CO ₂ is 99.3%.

Thus, the developed process is effective, because allows you to increase the product yield up to 97.8% (according to the prototype - 78%), more technological, because from start to finish, the synthesis is carried out in an aqueous medium, and more economical, because provides minimal loss of costly ¹³ CO ₂ . In this case, the isotopic purity of the target product of at least 98% is achieved.

Claims (1)

A method of producing sodium bicarbonate containing a stable ¹³ C isotope by reacting sodium hydroxide with ¹³ CO ₂ in a solution by heating under excessive pressure, characterized in that the process is carried out from beginning to end in an aqueous medium under a pressure of not more than 1 atm at a temperature of 70- 80 ° C.