12.パルス^1H-NMRによる石炭の溶媒膨潤に伴う相分離構造変化の評価

抄録

Blind Canyon coal was swollen by deuterate pyridine and was subjected to ^1H NMR relaxation measurements. The effect of solvent-to-coal mass ratio (S/C) on the relaxation characteristics was examined. The fractional amount of mobile hydrogen yielding the exponential decay,f_<MH>, was increased up to 0.5 with increase in S/C. However, f_<MH> kept almost constant value above S/C=2.24, indicating that there exist the solvent impenetrable regions in the swollen coal even at S/C=4.72. Although there exist at least two distinct structural regions in the swollen coals based on the transverse relaxation characteristics, the measured longitudinal relaxation was best characterized by a single component as spin diffusion is rapid in the swollen coals. The dynamics of spin diffusion were revealed using a partially modified Goldman-Shen pulse sequence and analyzed by a simple mathematical model of a two phase system. The interdomain spacing, d, was estimated based on the diffusive path length for each spatial dimension. The d value evaluated under one-dimension was 15nm and agreed with d determined by small angle neutron scattering, suggesting that the domain shape is sheet.