arXiv subjects

Mohammad Adib

Publications and source records attributed to Mohammad Adib.

2 recordsLinked to original sources

arXiv2026

Carbon black and hydrogen production from methane pyrolysis: measured and modeled insights from integrated gas and particle diagnostics in shock tubes

Methane (CH4) pyrolysis is a promising route to co-produce hydrogen (H2) and carbon black (CB) while avoiding emissions associated with steam-methane reforming and furnace black processes. Model development of pyrolytic CB synthesis requires experimental observations of concurrent gas chemistry, particulate formation, and morphology. This work presents a combined experimental and modeling study of CH4 pyrolysis behind reflected shock waves in 5% CH4/Argon mixtures at post-reflected shock temperatures (T5) of 1850-2450 K and P5 around 4.5 atm. Laser absorption diagnostics quantified CH4, C2H4, and C2H2 mole fractions, while multiwavelength extinction (633 and 1064 nm) resolved time-dependent particle formation and the temperature-dependent evolution of optical maturity. Simulations reproduce small-molecule speciation well, but large variations in predicted polycyclic aromatic hydrocarbons (PAHs) persist among models. Coupled gas-particle simulations capture accurate volume fraction (fv) trends and the influence of gas dynamics but underpredict induction times at high T5. Samples collected at the shock tube endwall were analyzed by transmission electron microscopy (TEM) to quantify primary particle size distributions and nanostructure arrangement. Image segmentation and manual measurements showed reduced primary particle size growth (dp) with increasing T5, while graphitic nanostructure generally increased. This study provides an integrated benchmark for improving models of CB and H2 production from CH4 pyrolysis by constraining gas-phase kinetics, PAH-driven inception, particle dynamics, and particle maturity. The results highlight that accurate partitioning of mass between particle number and particle size is an important constraint for further model development.

physics.chem-ph↗

arXiv2025

Omnisoot: an object-oriented process design package for gas-phase synthesis of carbonaceous nanoparticles

A computational tool, Omnisoot, was developed utilizing the chemical kinetics capabilities of Cantera to model the formation of carbonaceous nanoparticles, such as soot and Carbon Black (CB), from the reactions of gaseous hydrocarbons. Omnisoot integrates constant volume, constant pressure, perfectly stirred, and plug flow reactor models with four inception models from the literature, as well as two population balance models: a monodisperse model and a sectional model. This package serves as an integrated process design tool to predict soot mass, morphology, and composition under varying process conditions. The modeling approach accounts for soot inception, surface growth, and oxidation, coupled with detailed gas-phase chemistry, to close the mass and energy balances of the gas-particle system; subsequently, soot and gas-phase chemistry are linked to the particle dynamics models that consider the evolving fractal-like structure of soot agglomerates. The developed tool was employed to highlight the similarities and differences among the implemented inception models in predicting soot mass, morphology, and size distribution for three use-cases: methane pyrolysis in a shock tube, ethylene pyrolysis in a flow reactor, and ethylene combustion in a perfectly stirred reactor. The simulations of 5% $\mathrm{CH_4}$ pyrolysis in shock-tube with short residence times ($\approx1.5$ ms) demonstrated that multiple combinations of inception and surface growth rates minimized the prediction error for carbon yield but led to markedly different morphologies, emphasizing the need for measured data on soot morphology to constrain inception and surface growth rates. The comparison of simulation results in a pyrolysis flow reactor at three different flow rates suggested that only irreversible models can predict bimodality in particle size distribution.

physics.comp-ph↗