Sustainable Production of High-Purity Hydrogen by Sorption Enhanced Steam Reforming of Glycerol over CeO2-Promoted Ca9Al6O18–CaO/NiO Bifunctional Material

The present work investigates the sustainable production of high-purity hydrogen through sorption enhanced steam reforming of glycerol (SESRG) over Ca 9 Al 6 O 18 –CaO/ x NiO ( x = 15, 20, and 25 wt %) and Ca 9 Al 6 O 18 –CaO/20NiO– y CeO 2 ( y = 5, 10, and 15 wt %) bifunctional catalyst-sorbent materials. A wet mixing method involving limestone acidification coupled with two-step calcination was employed to prepare the bifunctional materials. Cyclic carbonation/calcination tests revealed that the bifunctional materials promoted with 10 and 15 wt % of CeO 2 possessed an excellent CaO conversion (97% in both cases) and a remarkable cyclic stability (up to 15 cycles). This was mainly attributed to the thin shell-connected structure formed by the addition of CeO 2 and the oxygen mobility characteristic of CeO 2 . The use of Ca 9 Al 6 O 18 –CaO/ x NiO materials in five consecutive SESRG/regeneration cycles revealed that they suffered from fast deactivation mainly due to CaO sintering and coke deposition. Despite the high H 2 purity obtained (∼98%), the prebreakthrough time and hydrogen yield decreased significantly over five cycles. Interestingly, the addition of CeO 2 to the most efficient catalyst (Ca 9 Al 6 O 18 –CaO/20NiO) resulted in a significant improvement in material stability during cyclic operation. The performance of CeO 2 -promoted materials was shown to depend strongly on the CeO 2 content which controlled the number of adjacent Ni active sites, the amount of coke deposition, and the degree of CaO sintering. The bifunctional material promoted with 10 wt % of CeO 2 showed the best performance over five consecutive SESRG/regeneration cycles, with a stable H 2 purity of ∼98%, H 2 yield of ∼91%, and prebreakthrough time of 48 min. The long-term cyclic stability test of Ca 9 Al 6 O 18 –CaO/20NiO–10CeO 2 over 20 cycles exhibited a very stable performance with a H 2 yield of 91% and H 2 purity of 98% within 20 cycles, confirming the high potential of this material for SESRG process.