Article pubs.acs.org/EF
Deriving the Molecular Composition of Vacuum Distillates by Integrating Statistical Modeling and Detailed Hydrocarbon Characterization Anton Alvarez-Majmutov, Rafal Gieleciak, and Jinwen Chen* Natural Resources Canada, CanmetENERGY-Devon, One Oil Patch Drive, Devon, Alberta T9G 1A8, Canada ABSTRACT: Characterization of the chemical composition of petroleum vacuum distillate fractions is essential to advance the understanding of the fundamental chemistry of refining processes, such as fluid catalytic cracking and hydrocracking. This is a challenging task, primarily as a result of the limitations of current analytical techniques to deal with heavy hydrocarbon samples. A different path toward this goal is through the use of hydrocarbon composition modeling techniques to derive the molecular make up of petroleum fractions with limited analytical data. The purpose of this study is to demonstrate this approach for simulating the molecular composition of vacuum distillates. The method consists of generating a computational mixture of representative hydrocarbon molecules that mimics the properties of an actual oil sample. Molecules are built according to the specific chemistry of vacuum distillates with a Monte Carlo algorithm, and the abundance of each molecule is optimized by entropy maximization. The model was applied to simulate two vacuum gas oil samples differing substantially in chemical composition and geographic origin. The samples were experimentally characterized in detail to obtain the necessary model inputs. Simulations revealed that the model adequately predicts the analytical properties and carbon number distributions of the two samples, proving its capability to capture a wide range of distinct vacuum distillate chemistries.
1. INTRODUCTION Vacuum gas oil fractions are heavy hydrocarbon mixtures produced by crude distillation and heavy oil/residue upgrading. Because of their high boiling range (343−524 °C), vacuum distillates are further processed in fluid catalytic cracking and/ or hydrocracking units to produce lighter liquid products, such as naphtha and middle distillates. The gradual tendency for the average quality of crude oil stocks to deteriorate indicates that heavy fractions will be produced in larger amounts, and consequently, they will constitute a primary source of transportation fuels.1 For this reason, there is a strong need to decipher the chemical nature of these petroleum fractions to fully understand their processing behavior. While significant progress has been achieved in the detailed characterization of light and middle petroleum fractions (
