CO2 sorption properties of Li4SiO4 with a Li2ZrO3 coating

The application of a CO2 sorbent which releases CO2 at a lower temperature than calcium oxide is of interest in view of reducing the operating temperature or increasing the operating pressure of the super-dry reforming process. To this end, three different CO2 sorbents based on lithium orthosilicate (Li4SiO4) were prepared and characterized: (i) Li4SiO4 as such; (ii) zirconia coated Li4SiO4, denoted Li4SiO4@ZrO2; (iii) Li4SiO4, coated with lithium metazirconate and denoted as Li4SiO4@Li2ZrO3. While the carbonation properties of Li4SiO4 were found satisfactory, its decarbonation was incomplete. Li4SiO4@ZrO2 on the other hand, was found to contain Li2SiO3 and Li2ZrO3 rather than the anticipated Li4SiO4 and showed fast carbonation and decarbonation of Li2ZrO3. The best performing material in terms of CO2 sorption capacity, stability and rate of carbonation-decarbonation was Li4SiO4@Li2ZrO3. Its superior performance is ensured by the core-shell structure saturated with Li, allowing for easy restructuring during carbonation and fast regeneration upon decarbonation.