CO2 methanation enhanced with a cyclic SERP process using a commercial Ni-based catalyst mixed with 3A zeolite as adsorbent

Valorization of greenhouse gas CO2 is needed to mitigate and reduce climate change impact. The sustainable production of methane to obtain synthetic natural gas (SNG) is one of the most attractive solutions, given current needs. The methanation reaction, known as the Sabatier reaction, is limited by the formation of CO as an in-termediate at high temperatures and the formation of H2O as a by-product. For this reason, recent research has focused on the use of catalysts/adsorbents mixtures capable of retaining the water produced as well as being methane-selective at low temperatures. In this work, the kinetic model of a commercial Ni/SiAl catalyst in an experimental reaction bed was obtained. Moreover, the water adsorption capacity of the catalyst has been studied in the typical reaction temperature range (473-623 K), and the adsorption equilibrium and diffusional parameters were determined. With the data obtained from these experiments, the methane production in a cyclic Sorption Enhanced Reaction Process (SERP) has been simulated, adding zeolite 3A as a water selective adsorbent. The process consists of three consecutive stages: an adsorption/reaction stage and two other stages, rinse and purge, to desorb the adsorbed water and remove it by condensation. A sensitivity analysis has been carried out to determine the effect of the operational variables on the process performance to obtain methane suitable for domestic natural gas consumption. A CO2 conversion of 99.7 %, methane selectivity of 99.9 %, molar purity of CH4 of 98.2 % as product, and compression energy consumption (6.97 kJ/mol CH4) 99 times lower than methane combustion energy has been obtained, proposing, therefore, a new process of methanation.

Automated summary

Valorization of CO2 is necessary for climate change mitigation. Sustainable methane production for synthetic natural gas (SNG) is an attractive solution. Recent research focuses on catalyst/adsorbent mixtures capable of retaining water and producing methane at low temperatures. This study obtained a kinetic model for a Ni/SiAl catalyst and examined its water adsorption capacity. The results were used to simulate methane production in a Sorption Enhanced Reaction Process (SERP) using zeolite 3A. The proposed method achieved high CO2 conversion, methane selectivity, molar purity, and low compression energy consumption, presenting a new methanation process.