Effect of CeO2 Promotion on Ni Catalyst for Sorption-Enhanced Methanation

Series of nickel catalysts, supported on γ-alumina and promoted with different Ce loading (1–5%), have been studied in conventional and sorption-enhanced CO2 methanation reaction. In addition, a detailed kinetic water adsorption study has been performed on commercial zeolite (13X, 4 A, 3 A). The decrease in adsorption capacity is observed for all zeolites with increasing temperature. The highest water adsorption capacity is observed for the 13X zeolite for all investigated temperatures (100–350 °C). However, the 13X zeolite showed loss of 50% of its capacity after 100 adsorption/desorption cycles while the 4 A and 3 A zeolites are almost unchanged. The catalyst characterization results indicate that upon addition of a small amount of ceria, dispersion of the Ni catalyst is improved as well as CO2 conversion in conventional methanation. The catalyst that showed best performance was further tested for sorption-enhanced methanation, where water sorbents (13X, 4 A, 3 A) are mixed with catalysts. All the tests performed in presence of zeolites showed an increase in CO2 conversion compared to those carried out in their absence. In addition, a 34% increase in CO2 conversion was observed when increasing the H2/CO2 ratio to 8 for the system with 13X zeolite. This indicates the enhancement effect when water is removed from the reaction.