Chemical looping gasification of biomass based on the oxygen carrier derived from the layered double hydroxide (LDH) precursor

Layered double hydroxide (LDH) precursors with different metal elements were prepared by co-precipitation method at constant pH value; highly dispersed Cu/Al/Zn, Cu/Al/Ni and Cu/Al/Ni/Zn mixed metal oxygen carriers were obtained by calculation of the corresponding precursors. These oxygen carriers were characterized by XRD, XRF, H₂-TPR, SEM and nitrogen adsorption and their activity in the chemical looping gasification (CLG) of biomass was investigated in a fixed bed reactor. The results indicated that typical hydrotalcite structure appears in the three precursors with stable layer board. The interlayer spacing of Cu/Al/Zn precursor is 0.2642nm, larger than that of the Cu/Al/Ni precursor. The oxygen carriers derived from the corresponding precursors display similar elements contents as the preparation reagents. Due to the synergy among various metals, the Cu/Al/Ni/Zn oxygen carrier shows the highest reaction activity and anti-sintering ability. The addition of Ni and Zn has a positive effect on the activity of CuO and reduce its reduction temperature; Zn shows a better synergistic effect than Ni with Cu. The carbon conversion reaches 82.03% for the CLG of biomass with Cu/Al/Ni/Zn as oxygen carrier; the surface area of Cu/Al/Ni/Zn remanis 5.995m²/g after the CLG reaction, suggesting that it could be an ideal candidate for the CLG of biomass.