Thermodynamic Analysis of Light Olefins Production via Cracking of n-Hexane Using Gibbs Energy Minimization Approach and Analysis of Overall Reactions

Thermodynamic analysis of the cracking of hexane has been conducted by the Gibbs free energy minimization method and second law analysis of overall reactions. By-products have been divided into three groups of methane, alkynes and aromatics and their possible production paths have been discussed. Effect of operating conditions such as temperature and steam-to-hexane ratio on the cracking performance has been investigated. The principal set of compounds considered in the modelling is hydrogen, water, ethane, ethylene, acetylene, propane, propylene, methyl acetylene, butane, butylene and hexane. Hexane conversion increased with increase of temperature and steam content. As temperature increases, the equilibrium olefin yield shows a volcano-shaped trend. In presence of methane, the maximum olefin yield declined and shifted to lower temperatures. When aromatics were considered in the product list, the light olefins yield is negligible. Equilibrium predicts that adding steam to the feed stream led to decrease of coke deposition through suppressing of aromatization reaction.