Nickel-doped sodium zirconate catalysts for carbon dioxide storage and hydrogen production through dry methane reforming process

Abstract

NiO-doped sodium zirconate ceramics with different amounts of NiO (between 0 and 10wt%) were synthetized and characterized by powder XRD, SEM-EDS and N2 physisorption. Structural and microstructural characteristics of a Na2ZrO3 based-ceramic were maintained in all NiO-containing samples. These materials were tested for CO2 capture (TGA), desorption processes (TPD) and dry CH4 reforming (DMR, catalytic tests). Initially, samples were dynamically tested for CO2 chemisorption; these tests showed a slight inhibition for CO2 capture due to the presence of NiO, which partially blocked Na2ZrO3 surface sites where CO2 can be chemisorbed. Then, NiO-doped samples were carbonated and exposed to a CH4 flow in order to perform DMR reaction, using carbonate samples as CO2 source. In all cases, NiO addition resulted in greater production of H2 than that of pure Na2ZrO3. Additionally, a drastic reduction in the reaction temperature was observed, especially for NiO-doped Na2ZrO3 containing 10wt% of NiO. Additionally, regeneration and cyclic behavior showed that it is possible to accomplish consecutive cycles of CO2 capture-DMR with considerable Na2ZrO3 regeneration. On the other hand, cyclability was affected due to a partial NiO reduction after DMR steps. However, if a pre-oxidation step was performed, the catalytic activity and H2 production were recovered. Hence, it was established that NiO-doped Na2ZrO3 materials can be used as bifunctional materials as (i) CO2 captors and then as (ii) catalytic materials during DMR reaction.