A modified group contribution method for estimating thermodynamic parameters of methanol-to-olefins over a SAPO-34 catalyst.

Group contribution (GC) methods, a semi-empirical approach based on the additivity of guest molecular properties, are widely applied to obtain the thermodynamic properties of complex reaction networks. In molecular sieve catalyzed processes, however, the interaction between guest molecules and host active sites also affects thermodynamic properties. In this study, therefore, we propose a modified group contribution (mGC) method by considering the interaction between the groups of guest molecules and independent active site functional groups (IASFGs) in molecular sieves. The mGC method has been used to estimate the thermodynamic properties of guest molecules as well as elementary reactions for the initial stage of methanol to olefins (MTO) reaction over SAPO-34 molecular sieves. It shows that mGC is more accurate than the conventional GC (cGC) methods when compared with the reference data calculated by density functional theory (DFT), indicating that mGC provides an effective way for batch calculation of thermodynamic properties in molecular sieve catalyzed processes.