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

Abstract

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 intermediate 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.