Study of Different Feed Mixtures for the Sorption-Enhanced Methanation (SEM) Process on a Lab-Scale TRL-3 Fixed-Bed Reactor

This work presents an exhaustive analysis of different variables that affect the sorption-enhanced methanation (SEM) process for synthetic natural gas (SNG) production. The effect of temperature and inlet gas composition including the presence of other compounds (CH4, C2H4, and higher hydrocarbons) was carefully investigated for a feed gas based on H2/CO2 or H2/CO2/CO mixtures. All of these variables were experimentally evaluated using two commercial materials in the bed, namely, a Ni-based catalyst and a zeolite 4A, in a lab-scale TRL-3 fixed-bed reactor. The reactor operated at 10 bar, temperatures ranging between 200 and 230 °C, and gas space velocities ranging from 0.8 to 1.4 kgC/kgcat·h. These experiments demonstrated that pure CH4 production was exclusively achieved when using H2/CO2/CO mixtures as feed gas. When the reactor was fed with synthetic syngas, H2 contents above the stoichiometric value were necessary for converting all of the hydrocarbons present in the mixture. Pure CH4 streams were obtained for approximately 16 min under operating conditions more realistic (200 °C, 10 bar, and 1.4 kgC/kgcat·h) in the SEM stage with synthetic syngas. By comprehending and optimizing the effect of these variables, it is possible to enhance the efficiency and reproducibility of large-scale SNG production, thus facilitating its implementation in various technological applications.