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

摘要

NiO-doped sodium zirconate ceramics with different amounts of NiO (between 0 and 10 wt%) were synthetized and characterized by powder XRD, SEM-EDS and N-2 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 H-2 than that of pure Na2ZrO3. Additionally, a drastic reduction in the reaction temperature was observed, especially for NiO-doped Na2ZrO3 containing 10 wt% 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 H-2 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.