Syntheses of Alkylated Aromatic Model Compounds To Facilitate Mass Spectral Characterization of Heavy Oils, Resids, and Bitumens

Abstract

This study summarizes the synthesis of model compounds. Long-chain alkyl multi-ring heteroaromatics are the synthetic targets. These compounds are considered analogues of similar compounds that are present at abundant levels in petroleum crude oils, resids, heavy oils, deasphalted oils, asphaltenes, and bitumens, and they are responsible for coke formation and other processing problems. Model compounds are not readily available. Some models have been synthesized to approximate the physical and chemical behavior of real asphaltenes, but the structures are not completely consistent with the current structural understanding. The composition of petroleum crudes, resids, heavy oils, and bitumens has been a subject of intense research for years. The structure of these coke-forming molecules is generally thought to be an aromatic core of critical molecular weight and number of fused aromatic rings. This critical ring number is around 4–5 fused aromatic rings, which bear alkyl side chains and heteroatoms. This general structural view is still being improved. During coking, these side chains thermally cleave off of the aromatic core and leave the coker as volatile liquids and gas. The aromatic cores are thermally stable, and they are not volatile. They remain in the coker until they condense and form low-value coke. The purpose of this research was to synthesize model compounds representing the molecular structure of the coke-forming molecules. These compounds will be used to model the behavior of resids, heavy oils, and bitumens to understand their processing chemistry and their physical and chemical properties. Model compounds that reasonably represent the structural data with boiling point ranges that map directly onto the boiling point ranges of real heavy oils, resids, and bitumens have been successfully synthesized. Important structural features are emphasized in these models, such as high molecular weight [∼1000 atomic mass units (amu)] with multi-ring aromatic cores, long alkyl side chains, and the inclusion of sulfur and nitrogen. These model compounds can be used to calibrate analytical methods to provide response factors for quantitative characterization of alkylated aromatics in real petroleum fractions and to better understand thermal chemistry kinetics.