Nature of hydrogen bonding in coal-derived asphaltenes

Abstract

Near-infrared (n.i.r.) and proton magnetic resonance (p.m.r.) studies are reported of hydrogen bonding between the hydroxyl group of o-phenylphenol (OPP) and two coal-derived asphaltenes, and their acid and base components. The asphaltenes were isolated from two centrifuged liquid product (CLP) samples prepared from West Virginia, Ireland Mine bituminous coal under the same reaction conditions, except that CLP FB44–56 was prepared with the reactor charged with a CoMo catalyst, while CLP FB50-17 was prepared with glass pellets in place of the catalyst. The base asphaltene components from both FB44–56 and FB50-17 cause a decrease in the OPPOH absorbance at 1.44 μm in CS 2 and a downfield shift of the OPPOH p.m.r. resonance in CS 2, while these changes are not observed for the original asphaltenes or their acid components. Furthermore, the base asphaltene component from CLP 44–56 is more effective in decreasing the OPPOH absorbance when compared with the base asphaltene component from CLP FB50-17. Also, the absorbance of a pentane-soluble fraction of the acid asphaltene component at 1.42 μm in CS 2 from CLP FB50-17 is decreased upon addition of the corresponding base asphaltene component. Our results lead to the conclusion that the use of a CoMo catalyst leads to a base asphaltene component of lower molecular weight and higher hydrogen-bond acceptor strength.