Molecular-Level Kinetic Modeling of Resid Pyrolysis

A Molecular-level kinetic model of heavy ii pyrolysis was developed for a Venezuelan vacuum residue. Model development proceeded in three major steps: creation of a molecular description of the feedstoCk, generation of a reaction network, and model solution and parameter tuning. The feedstock composition, as described in previous work [Zhang et al. Energy Fuels 2014, 28, 1736-1749]) was modeled in terms of probability density functions (PDFs) Of three finite attribute groups (385 cores, 2 intercore linkages, and 194 side chains) and a PDF for each of a cluster-size and binding site distribution. These attributes, or molecule building blocks, represent more than OA M molecules An attribute reaction network was developed using the fundamental reaction chemistry for resid pyrolysis including 6274 reactions that fall into one of 11 reaction families. To make solution time tractable, we used attribute reaction modeling (ARM) which constrained-the number Of material balances to the number of attributes and irreducible molecules in the system or 2841 total equations. Therefore, reactor output was a Set of reaction-altered attribute PDFs and molar amounts of irreducible molecule. The quantitative, molecular composition of the reactor outlet was obtained through the juxtaposition of the final attribute PDFs. The properties of both the sampled molecules and the char fraction were obtained using quantitative structure property relationships (QSPRs). The kinetic model was tuned using a least-squares objective function comparing the model predictions to measurements from the-molecular to bulk-property level for all teleyant boiling point fractions. The tuned model showed reasonably good, agreement with the experimental measurements.