Elucidating the chemical structures of petroleum resin using solid-state 13C NMR

Abstract

In this study, a new method to perform the solid-state 13C NMR analysis of oil resin has been proposed and the 3D molecular model of oil resin has been established for the first time. This method is not only suitable for petroleum resin, but also can be used in the structural detection of all colloidal component of fossil fuel. In this research, both liquid- and solid-state 13C NMR based on CP-TOSS/MAS method have been carried out to detect the chemical structural of petroleum resin. Solid-state 13C NMR showed less influence from solvent peaks and achieved a more accurate identification of aromatic carbon and oxygen-containing functional groups than liquid-state 13C NMR, and the FT-IR was used to verify this; thus, it is more suitable for resin structure detection. Based on the results of the two types of NMR, the petroleum resin structure was found to consist of aromatic clusters at the core, with short aliphatic chains and cycloalkanes connected in the periphery. In addition, two new parameters were established to evaluate the length of aliphatic chains (CnR) and oxygen-containing in resins (OINMR: NMR oxygen index of resin). Combined with elemental analysis, the average 3D resin molecular model was established in this research. In general, this study underscored a suitable method for detecting chemical structures in the field of fossil fuel and energy engineering, and successfully introduced solid-state 13C NMR for the analysis of colloidal component of fuel. At the same time, the most stable structural model of petroleum resin in three-dimensional space was established; this provides a basic model for the molecular simulation research of the constituents of petroleum. Considering the important influence of resin on the properties of petroleum, this research has a great significance to migration and exploitation of heavy oil.