High temperature pyrolysis (HTP) is a commercial process to convert methane to acetylene. The HTP process consists of two reaction zones, followed by a quenching zone. In this work, a pilot scale HTP process was modeled to assess the effect of the amount of fuel burned and the cracking gas composition on acetylene and polycyclic aromatic hydrocarbon (PAH) production. The HTP process is simulated using a chemical reactor network, which consists of a series of ideal reactors. The composition of cracking gas in the second reaction zone varied from methane to hexane. The propensity of the feed to form acetylene vs PAH at a given process condition was determined using a detailed chemical kinetic mechanism. The chemical kinetic mechanism was developed using an automated mechanism generation software package, the Reaction Mechanism Generator (RMG). Compared to existing pyrolysis mechanisms that can only be used to model the cracking of a finite number of species, RMG can be used to model the cracking of any arbitrary species consisting of carbon, hydrogen, and oxygen. The modeling results showed that the C-2 yield is largely independent of either overall phi or cracking gas carbon number. In contrast, the lumped aromatic yield appears to have a positive correlation with both overall phi and cracking gas carbon number. Sensitivity and rate of production analyses were performed to identify the important pathways that lead to the formation of aromatics for various feed compositions.