Dolomite-derived catalyst-free dual function materials pellets for integrating calcium-looping and reverse–water–gas–shift reaction

Integrated CO 2 capture and utilization via reverse water–gas shift reaction (ICCU-RWGS) for syngas production is a promising step contributing to carbon neutrality . Naturally occurring Ca-rich ores are potential candidates of dual function materials (DFMs) for ICCU-RWGS, while the practical circulating operation in twin fluidized-bed reactors necessitates DFMs pellets with high reactivity and good mechanical properties, to overcome powder elutriation and to withstand particle attrition . Dolomite (DM)-derived catalyst-free DFMs pellets are synthesized via the extrusion-spheronization (ES) and graphite-casting (GC) methods. Pelletization will result in pore structure blockage while the decline in textural properties has been remedied to some extent, due to the decomposition of CaMg(CO 3 ) 2 . The hydration activation of Ca species in molding has benefited the DFMs pellets with uniform dispersion of CaO with smaller grain size. The dolomite-derived DFMs pellets outperform the pristine dolomite and the calcined dolomite DFMs regarding the ICCU-RWGS performance. Promoters such as Al 2 O 3 , ZrO 2 or aluminate cement (AC) are incorporated to enhance the mechanical strength of the DM-GC pellets. The formed Ca 3 Al 2 O 6 , CaAl 2 O 4 , CaZrO 3 , and Ca 2 Al 2 SiO 7 due to the interaction between CaO and the promoter, act as supporting skeleton for reinforced mechanical strength and physical barrier for retarding crystal sintering and particle agglomeration . Upon doping 10 wt% ZrO 2 , the compressive strength of the DM-GC pellets increases remarkably from 0.13 to 1.35 MPa. The desired DM-GC-Zr5 DFMs pellets exhibit excellent ICCU-RWGS performance with high and stabilized CO 2 capture capacity (6.01 mmol CO 2 /g) and CO yield (5.01 mmol CO/g) within 10 cycles, demonstrating as a good DFMs candidate for cost-effective CO 2 capture and conversion.