Alkali-Doped Lithium Orthosilicate Sorbents for Carbon Dioxide Capture

New alkali-doped (Na2CO3 and K2CO3) Li4SiO4 sorbents with excellent performance at low CO2 concentrations were synthesized. We speculate that alkali doping breaks the orderly arrangement of the Li4SiO4 crystals, hence increasing its specific surface area and the number of pores. It was shown that 10wt% Na2CO3 and 5wt% K2CO3 are the optimal additive ratios for doped sorbents to attain the highest conversions. Moreover, under 15vol% CO2, the doped sorbents present clearly faster absorption rates and exhibit stable cyclic durability with impressive conversions of about 90%, at least 20% higher than that of non-doped Li4SiO4. The attained conversions are also 10% higher than the reported highest conversion of 80% on doped Li4SiO4. The performance of Li4SiO4 is believed to be enhanced by the eutectic melt, and it is the first time that the existence of eutectic Li/Na or Li/K carbonate on doped sorbents when absorbing CO2 at high temperature is confirmed; this was done using systematical analysis combining differential scanning calorimetry with insitu powder X-ray diffraction.