Sorption enhanced CO2 methanation via two-step reaction-regeneration process at atmospheric pressure using Ni-based catalysts and zeolite 3A

Abstract

Methane synthesis via the Sabatier reaction is one of the most widely used CO 2 recovery methods. However, one of the main limitations of this reaction is that it is constrained by the equilibrium at high temperatures and limitated by the kinetics at low temperatures. Process intensification, such as Sorption Enhanced Reaction Process technology, can help to overcome these limitations. In this study, two nickel catalysts were experimentally compared for methane production at atmospheric pressure. One was a commercial catalyst, and the other was a catalyst synthesised in the research group. Two CO 2 Gas Hourly Space Velocities (GHSV) of 110 and 2750 Nml CO 2 / gcat · h were experimentally investigated, demonstrating the potential applicability of the proposed process at low reaction temperatures (150–250 °C). Furthermore, in terms of process improvement, Zeolite 3A was chosen as a water-selective adsorbent due to its exceptional capacity and its well-known rapid adsorption/desorption kinetics. In this way, complete conversion was reached at 225 and 250 °C, overcoming the thermodynamic equilibrium for both temperatures. Subsequently, two-stage cycles were applied concerning a reaction/adsorption stage followed by a purge stage, where a mixture of hydrogen and helium was fed to the bed to desorb the water retained, under the same conditions of pressure and reaction temperature. Three purge times were studied at 225 °C, obtaining a five times increase of the gas mass fed to the reactor until zeolite 3A saturation by increasing 30 min the purge stage time after five cycles (0.014 to 0.072 g gas fed/g zeolite 3A ). In this way, a Sorption Enhanced Reaction Process CO 2 methanation process with a regeneration step was successfully applied with no temperature or pressure variation.

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