Alkaline zirconates as effective materials for hydrogen production through consecutive carbon dioxide capture and conversion in methane dry reforming

Abstract

In this work, H2 production was evaluated using different carbonation conditions and two alkaline zirconates. For this purpose, Li2ZrO3 and Na2ZrO3 were synthesized, characterized and tested on a consecutive process composed of initial CO2 capture, followed by methane dry reforming (MDR). Thermogravimetric results showed that under the four gas mixtures tested (diluted and saturated CO2, CO and CO-O2), both ceramics are able to chemisorb CO2, with Na2ZrO3 having the highest capture with saturated CO2. In catalytic tests, ceramics carbonated with saturated CO2 or CO-O2 gas flows were able to act as sorbents and catalysts, producing H2 at T > 750 °C through the partial oxidation of methane. This reaction was produced because CO2 desorption did not occur, thus avoiding the MDR process. On the other hand, carbonated ceramics under a CO-O2 gas mixture presented an outstanding catalytic performance. Between 450 and 750 °C, H2 was formed through the MDR process promoted by CO2 desorption from both ceramics. This result is in line with CO2 desorption results, where a weaker CO2–solid interaction was observed in comparison with saturated CO2. Afterward, both ceramics presented a similar catalytic behavior, good regeneration and cyclability after the double process proposed (CO2 capture-MDR reaction). Lithium zirconate also presented high thermal stability during cycle tests; meanwhile, sodium zirconate showed an important H2 production increase as a function of cycles. Finally, both materials are feasible options for producing a clean energy source in a moderate temperature range through the catalytic conversion of two greenhouse gases (CO2 and CH4).