Oxygen Chemistry in Polymer Fouling: Insights from Multiphase Detailed Kinetic Modeling

Abstract

Polymer fouling is a pervasive challenge in the downstream processes of steam cracking. Molecular oxygen is likely to present and is known to strongly affect various polymerization processes, yet the role of oxygen in distillation column fouling remains poorly understood. Building upon the foundations laid in our preceding study [Pang et al., Ind. Eng. Chem. Res. 2023, 62, 36, 14266−14285], this work presents a detailed kinetic modeling approach to investigate the impact of oxygen on polymer fouling in a typical debutanizer. The fouling model incorporates molecular oxygen as a primary source of contamination in the feedstock and encompasses a comprehensive network of chemical reactions, phase equilibria, and interphase transport phenomena. Critical model parameters are derived from quantum chemistry calculations to ensure accuracy. The sensitivity of fouling rates to varying levels of dissolved oxygen is examined. We find that even small traces (ppm level) of the molecular oxygen contaminant in the feedstock can significantly accelerate fouling growth in the colder section. Furthermore, the dominant pathways of fouling are observed to shift over time due to diffusion limitations. This study showcases the power and adaptability of predictive detailed kinetic modeling in deciphering the mechanistic fundamentals of polymer fouling.

Subgraph Isomorphic Decision Tree to Predict Radical Thermochemistry with Bounded Uncertainty Estimation

“…Thermochemical data for 2210 radical molecules excluding duplicates were collected from past publications of detailed kinetic models. ,− , For duplicate calculations, the one with a lower energy was kept. Among them, 1978 radicals were collected from Dong et al, , Pio et al, and Liang et al, 187 were collected from Pang et al, , and 45 were collected from Johnson et al The distribution of collected radical thermochemical parameters can be found in Figure S1 in the Supporting Information.…”

“…Key molecular features of radicals collected from past publications − ,− , after data augmentation with equivalent resonance radicals: (a) atom types in radicals and of radical centers, (b) number of rings, (c) number of heavy atoms, and (d) number of rotatable bonds.…”

“…Detailed chemical kinetic models are valuable tools for many industrial applications, including investigating the fundamentals of polymer fouling, , fuel pyrolysis and oxidation, − and active pharmaceutical ingredient oxidative degradation. , Radicals are vital to the chemical kinetic models in all the above-mentioned and many other applications. During the process of automatic mechanism generation, hundreds of thousands of potential molecules (including radicals) are generated and assessed for their importance under given reacting conditions .…”

“…It is straightforward to extend and (re)­train, does not necessitate GPU access, features a hierarchical structure that facilitates interpretation, enables uncertainty estimation, allows for the easy integration of expert knowledge, and gives reasonable results despite smaller data set sizes. We collect thermochemical parameters derived from quantum chemistry calculations from past publications of detailed kinetic models. − ,− , We consider equivalent resonance structures of each radical from the collected data and derive the HBI corrections. We develop a SIDT model to predict the HBI corrections, implement an uncertainty estimation from a bounded weighted standard deviation, and implement and evaluate prepruning methods.…”