The concept of a mobile or molecular phase within the macromolecular network of coals: A debate

Study on the relation of solvent extractable material and resistivity of pyrolysed coal

“…The heterogenous structure of bituminous coal has not been fully cleared up yet [1,2]. It was thought to consist of macromolecular substances and compounds of low molecular weights filling gaps formed by the macromolecular network [3][4][5].…”

Catalysis in Direct Coal Liquefaction

“…Whereas cellulose and hemicelluloses are easily degradable by enzymatic hydrolysis of the glycosidic bonds, lignin is much more resistant towards (bio)chemical degradation. Based on this and the observation of slow and rapid relaxation rates in 1 H NMR experiments, a molecular/macromolecular (two-''phase'') model was proposed for the general structure of coal: A covalently cross-linked three-dimensional macromolecular network forms an immobile ''phase'' which is the ''host'' for a multitude of relatively small embedded ''guest'' molecules of varying structures which form a mobile ''phase'' [41,42]. In view of the structure of lignin, it appears that coal for a major part has a macromolecular network structure too and support for this has been deduced from the mechanical/viscoelastic properties and swelling behavior [36][37][38][39][40].…”

Effects of low-temperature catalytic pretreatments on coal structure and reactivity in liquefaction. Technical progress report, October 1991--December 1991

“…This finding is, however, in distinct contrast to those of other liquefaction (Larsen t al., 1980;Chamberlin and Schobert, 1991) and pyrolysis (O'Brien et al, 1987) studies where prior removal of chloroform-extractable materials significantly reduced conversions. These treatments are apparently associated with modification in either physical structure (by solvent swelling or extraction) or some change in chemical composition which is caused by the removal (via extraction) of the so-called mobile phase (Given et al, 1986). The information from above-mentioned chemical and physical pretreatments, though indirectly, could also be useful in examining the effects of catalytic and thermal pretreatments.…”