METHOD OF DETERMINING MOLECULAR-WEIGHT DISTRIBUTION OF PARAFFINS IN MIXTURE OF HYDROCARBONS VIA NUCLEAR MAGNETIC RESONANCE

摘要

FIELD: chemistry.;SUBSTANCE: heated mixture of hydrocarbons is slowly cooled and the value of the fraction of the solid-state component of the nuclear magnetic resonance signal is detected in the range of -150 to +150°C. The mixture is then slowly heated and the value of the fraction of the solid-state component of the nuclear magnetic resonance signal for the analysed mixture of hydrocarbons is then detected in a temperature range which includes the melting point range of paraffins. Further, a graph of the fraction of the solid-state component versus temperature is then plotted, after which the obtained temperature curve is then approximated with a function of a given type. Further, using the obtained function, the component arising from phase transitions of paraffins is then selected in the temperature curve of the fraction of the solid-state component. Paraffins are identified on the temperature curve of the fraction of the solid-state component based on presence of thermal lag. The derivative of component of the obtained function arising from phase transitions of paraffins is calculated. Temperature shift of the first-order phase transition of paraffins in the mixture of hydrocarbons is considered in comparison with the same for paraffins in pure form. Further, using the relationship between the melting point of paraffins and the number of carbon atoms in a molecule, the obtained derivative function is plotted depending on the number of carbon atoms in the molecule of n-paraffin, after which the by normalising the obtained relationship to a complete integral under the curve, a function is obtained, which characterises the molecular weight distribution of paraffins in the analysed mixture.;EFFECT: high accuracy of determining molecular weight distribution of paraffins in a mixture of hydrocarbons.;1 tbl, 5 dwg