Sorption-enhanced biogas steam reforming over the Pb-modified Ni-CaO bifunctional catalysts

Sorption-enhanced biogas steam reforming (SESRB) can efficiently produce high-purity "green hydrogen" from biogas with the adaptability to high and variable CO2 content of biogas. The key challenge faced by SESRB is the rapid, sintering-induced decline of sorption capacity. Herein, a Pb-modified Ni-CaO bifunctional catalyst is prepared based on the adsorption of Pb2+ by CaCO3, in which the replacement of CaCO3 by PbCO3 is achieved on the surface of CaCO3. After thermal treatment, CaPbO3 was generated on the surface of CaO particles in the bifunctional catalyst, by which CaO particles are separated effectively, and thus the sintering of Ca species is weakened. 5Ni-8PbO-CaO as the optimum catalyst with only 7.9 wt% PbO maintains 57.6 % of the initial sorption capacity after 20 cycles, higher than that of 5Ni-CaO (40.5 %). Due to the excellent stability of the 5Ni-8PbO-CaO catalyst, high-purity hydrogen (94.1 vol%) with 95.0 % CH4 conversion is continuously obtained from biogas for 20 consecutive SESRB-decarbonation cycles.