Thermodynamic study of hydrocarbon synthesis from carbon dioxide and hydrogen

Abstract

Abstract The thermodynamics of jet fuel range alkane synthesis from carbon dioxide and hydrogen has been investigated. The hydrocarbon synthesis process is divided into three elementary steps, including light olefins formation (C 2 ‐C 6 ) from hydrogenation of CO 2 , α‐olefins (C 7 ‐C 16 ) synthesis from oligomerization of light olefins, and hydrogenation of α‐olefins (C 8 ‐C 16 ) to straight‐chain paraffin (C 8 ‐C 16 ). The enthalpy changes and Gibbs free energy changes of the relevant reactions were calculated, and the equilibrium products distribution was computed based on the Gibbs free energy minimization method. The calculation results show that lower temperature (below 673.15 K), higher pressure (3 MPa), higher molar ratio of H 2 to CO 2 (3:1‐4:1), and introducing a small amount of N 2 in the reactants are favorable for the hydrogenation of CO 2 ; lower temperature (below 500 K), higher pressure (2‐3 MPa), addition of N 2 is favorable for the oligomerization of light olefins; and lower temperature (below 700 K), higher pressure (2‐3 MPa), and addition of N 2 is favorable for the hydrogenation of α‐olefins. The overall positive effect of introducing N 2 results from its heat dilution of the process. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.