The Application Of Organic Amine Solvents In The Separation Of Carbon Isotope By Chemical Exchange Method

The carbon-13 urea breath test is widely used in the detection of Helicobacter pylori,and the demand increases year by year.However,13C-urea detection is relatively expensive,and the raw materials of this reagent are all imported from abroad,and there are no reports of carbon-13 isotope industrialization in our country.Therefore,it is of great significance to choose appropriate and effective methods to achieve the separation of carbon-13 isotope.Chemical exchange method is one of the most promising technologies for separating carbon-13 isotope.This method used di-n-butylamine as the separating agent and n-octane as the dilution solvent of the separation system to separate the carbon-13 isotopes in carbon dioxide.However,the disadvantages,especially long equilibrium time and crystal precipitation when multiple stages operation,limits the further industrialization.The separation systems of long carbon chain organic amine,cyclic organic amine and long carbon chain organic alcohol amine were selected in this paper.Single-stage separation factors of all these organic amine were measured by stable isotope mass spectrometry,and diethanolamine-ethanol system showed the best separation performance.The operating conditions,such as dilution solvent types,organic amine concentration,desorption temperatures,reaction temperatures and reaction time,were optimized.When the concentration of organic amine was 1 mol/L,and the reaction time was 12 h,as well was the reaction temperature was 25?,and the desorption temperature was 90?,the best single-stage separation factor of CO2-diethanolamine-ethanol system could reached 1.011.Density functional calculation method was used to optimize the geometric configuration and calculate the vibration frequency of the chemical exchange system through Gaussian 09 software.The single-stage separation factor of chemical exchange reaction in ideal environment was 1.0120,and the deviation between calculated and experimental value was 0.0989%.After that,the solvation effect during the chemical exchange process was explored,and the single-stage separation factor was 1.0114 when the dilution solvent was ethanol.In addition,the differences of structural parameters of diethanolamine isotope molecular carbamic acid in ideal environment,water and ethanol were also explored.The influence of dilution solvents was investigated with bond bond length and bond angle.Finally,the zero-order vibration energy of all organic amine systems.It was found that the difference of the zero-order vibration energy of diethanolamine system was the largest,and the corresponding single-stage separation factor was the highest.