Comparison between a Homo- and a Heterosegmented Group Contribution Approach Based on the Perturbed-Chain Polar Statistical Associating Fluid Theory Equation of State

Abstract

Depending on the molecular model, group contribution (GC) approaches based on the statistical associating fluid theory (SAFT) can be classified in homosegmented and heterosegmented GC approaches. In homosegmented GC approaches, molecules are modeled as chains composed of identical segments. Heterosegmented GC approaches, on the other hand, consider molecular chains composed of different segment types and thus maintain a more detailed picture of real molecules. Therefore, heterosegmented GC approaches are arguably more physically realistic and ought to give more accurate descriptions of thermodynamic properties. In this work, we evaluate the performance of a homosegmented and a heterosegmented GC approach based on the perturbed-chain polar SAFT (PCP-SAFT) equation of state (EoS). To ensure a meaningful comparison between both GC approaches, a dipole term for the heterosegmented GC approach is formulated. Group parameters of 22 functional groups were adjusted to pure component property data. The comparison between both GC approaches shows that the heterosegmented GC approach leads to significantly better agreement with experimental data for various chemical families.

The A in SAFT: developing the contribution of association to the Helmholtz free energy within a Wertheim TPT1 treatment of generic Mie fluids

“…The Wertheim TPT1 treatment therefore provides a route to the separate contributions to the EOS for both reversible association (e.g., resulting from intermolecular HB) and for molecules formed from bonded segments. A consideration of mixtures of associating monomers can also be employed to provide a reliable description of the thermodynamic properties of heteronuclear dimers [59,60], trimers [61,62], and generic molecules formed from segments of different type [55,[62][63][64][65][66][67][68][69][70][71]; such a formalism has been invaluable in the recent development of group-contribution approaches for heteronuclear molecules based on the SAFT EOS, allowing for the separate chemical moieties to be considered explicitly [72][73][74][75][76][77][78].…”

Computer-aided molecular design in the continuous-molecular targeting framework using group-contribution PC-SAFT

“…The molecular search space is limited to components consisting of the functional groups presented in the work of Sauer et al (2014). Their study was concerned with the comparison of homo-and hetero-segmented group contribution methods, rather than setting up the GC-method for a large amount of groups.…”

“…Thus, a single GCmethod is sufficient in the proposed method independently from any specific application. The employed GC method is the homosegmented approach from (Sauer et al, 2014), called here GPC-SAFT. The GC-method was fitted to VLE (vapor-liquid equilibrium) data and densities from a database for a range of fluids.…”

“…The GCmethod calculates the PC-SAFT pure component parameters from the molecular structure of the fluid. In GPC-SAFT, the mixing rules of Vijande et al (2004) are used and m, m 3 , m(ε/k) and are calculated for a defined number of segments n i of type i (Sauer et al, 2014), as…”

“…This CAMD method is based on a GC-approach for PC-SAFT (GPC-SAFT), where the pure component parameters of a fluid are calculated from the molecular structure (Sauer et al, 2014). We demonstrate the general applicability of the proposed approach in two important areas of fluid design: the design of solvents for pre-combustion carbon capture and the design of working fluids for ORCs.…”