A study of diffusional behavior of n-paraffin in urea/ n-paraffin adduct by high field-gradient 1H NMR spectroscopy

Abstract

The self-diffusion coefficients ( D) of n-C 21H 44 in long channels of deuterated urea-d 4/ n-C 21H 44 adduct have been successfully measured over a wide range of temperatures from 0 to 75 °C by means of high field-gradient spin-echo 1H NMR method, in order to clarify diffusional behavior of the n-paraffin. From these experimental results, it is found that n-C 21H 44 molecules are diffusing in long urea channels of urea adduct and has two diffusion components such as the fast diffusion component ( D≈10 −10 m 2 /s) and the slow diffusion component ( D≈10 −12 m 2 /s), and that n-C 21H 44 molecules at the two external regions near the ends of the channel and the inner region in one of long channels of urea adduct contribute to the fast diffusion component and the slow diffusion component, respectively.