화학공학소재연구정보센터
Petroleum Chemistry, Vol.45, No.5, 338-344, 2005
An NMR study on the structural-dynamic parameters and dispersion characteristics of water-bitumen emulsion
The temperature dependence of proton magnetic relaxation times in water-bitumen emulsion was studied by a pulse NMR technique using equipment designed earlier. The temperature range in which the emulsion was examined could be divided into three intervals of Delta 10(3)/(T, K)) with second-order phase transition points and different values of activation energy of molecular motion. It was found that processes of structural-dynamic ordering at the water/bitumen interface took place in the form of correlated or group diffusion of water molecules under the confined conditions of droplet space, as this diffusion mode was suggested by an abnormal slope of the temperature dependence of relaxation times. A modification of classical expressions for the relaxation times with allowance for a correlation factor f in diffusion and a radial distribution function was proposed. Experimentally, it was found that the relaxation times T-2B and T-2C corresponding to molecules at the water/bitumen interface become equal to the relaxation times T-2D and T-2E of bitumen phases at the initial boiling point of the water-bitumen emulsion. The structural-dynamic surface characteristics of water were calculated to fit to experimental data. The dispersive distribution of water molecules in emulsion was analyzed with the use of a method combining the pulse Fourier transform and pulsed-field-gradient NMR techniques.