โ Scribed by Mary J. Wornat; Richard Sakurovs
No coin nor oath required. For personal study only.
Four versions of a Yallourn brown coal, each distinguished by the form of its carboxyl groups (acidic or cation-exchanged with Na, Ca or Ba), were subjected to proton magnetic resonance thermal analysis from 25 to 575ยฐC. Analysis of the profiles of two second-moment parameters, calculated from the transverse relaxation signals of each coal, indicates the following: (1) Upon heating, cation-exchanged coals attain a lower extent of fusion (i.e. they are more rigid structures) than the acid-form coal--the two divalent cations Ba and Ca having a greater effect on fusion reduction than the monovalent cation Na. (2) The matrix densities of the coals follow the order: acid-form < Na-form < Ba-form = Ca-form. The results provide insight into earlier experimental observations of the cation-induced hindrance of solvent penetration into coals and of the suppression of plastic behaviour and tar production during rapid pyrolysis.
๐ SIMILAR VOLUMES
Proton nuclear magnetic resonance ('H n.m.r.) has been used to measure changes in the water-binding capacity of bed-moist brown coal lithotypes subjected to heat treatment. A rapid reduction in the coalwater interaction was found to occur at treatment temperatures > 420K. A Pale lithotype was found