CHEMICAL-STRUCTURE OF BITUMEN-DERIVED ASPHALTENES BY NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY AND X-RAY-DIFFRACTOMETRY

Asphaltene samples obtained from bitumen processed at three Indian ref ineries were characterized for chemical composition and structure by n uclear magnetic resonance (n.m.r.) spectroscopy and X-ray diffractomet ry (XRD). The average structural parameters were obtained by combined H-1, C-13 and DEPT spectral editing techniques. New equations were use d for the estimation of n.m.r. average structure parameters. The macro structure and crystalline parameters of these samples were obtained by XRD. A combined n.m.r. and XRD procedure was used to estimate the siz e of the average aromatic structural unit. Asphaltenes from one of the bitumens (ASP-D) was found to have different structural parameters fr om those of the asphaltenes from the other two bitumens. The number of aromatic rings per unit sheet in ASP-D was eight, compared with 13 fo r both ASP-M and ASP-H. XRD data indicated that the aromatic sheets ar e randomly oriented in ASP-D. The structural parameters allowed a mode l structure of the asphaltenes to be constructed. (C) 1996 Elsevier Sc ience Ltd.