Production of high-purity hydrogen from paper recycling black liquor via sorption enhanced steam reforming

Environmentally friendly and energy saving treatment of black liquor (BL), a massively produced waste in Kraft papermaking process, still remains a big challenge. Here, by adopting a NiCaOCa₁₂Al₁₄O₃₃ bifunctional catalyst derived from hydrotalcite-like materials, we demonstrate the feasibility of producing high-purity H₂ (∼96%) with 0.9 mol H₂ mol^-1 C yield via the sorption enhanced steam reforming (SESR) of BL. The SESRBL performance in terms of H₂ production maintained stable for 5 cycles, but declined from the 6th cycle. XRD, Raman spectroscopy, elemental analysis and energy dispersive techniques were employed to rationalize the deactivation of the catalyst. It was revealed that gradual sintering and agglomeration of Ni and CaO and associated coking played important roles in catalyst deactivation and performance degradation of SESRBL, while deposition of Na and K from the BL might also be responsible for the declined performance. On the other hand, it was demonstrated that the SESRBL process could effectively reduce the emission of sulfur species by storing it as CaSO₃. Our results highlight a promising alternative for BL treatment and H₂ production, thereby being beneficial for pollution control and environment governance in the context of mitigation of climate change.