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

Abstract

The present work investigates the sustainable production of high-purity hydrogen through sorption enhanced steam reforming of glycerol (SESRG) over Ca9Al6O18–CaO/xNiO (x = 15, 20, and 25 wt %) and Ca9Al6O18–CaO/20NiO–yCeO2 (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 CeO2 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 CeO2 and the oxygen mobility characteristic of CeO2. The use of Ca9Al6O18–CaO/xNiO 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 H2 purity obtained (∼98%), the prebreakthrough time and hydrogen yield decreased significantly over five cycles. Interestingly, the addition of CeO2 to the most efficient catalyst (Ca9Al6O18–CaO/20NiO) resulted in a significant improvement in material stability during cyclic operation. The performance of CeO2-promoted materials was shown to depend strongly on the CeO2 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 CeO2 showed the best performance over five consecutive SESRG/regeneration cycles, with a stable H2 purity of ∼98%, H2 yield of ∼91%, and prebreakthrough time of 48 min. The long-term cyclic stability test of Ca9Al6O18–CaO/20NiO–10CeO2 over 20 cycles exhibited a very stable performance with a H2 yield of 91% and H2 purity of 98% within 20 cycles, confirming the high potential of this material for SESRG process.

Synthesis of lanthanide series (La, Ce, Pr, Eu & Gd) promoted Ni/γ-Al2O3 catalysts for methanation of CO2 at low temperature under atmospheric pressure

“…Los menores tamaños de partícula obtenidos a través de la incorporación del promotor de CeO2, se atribuye a una mayor interacción metalsoporte, de los sistemas Ni-MgAl y Ni-CaAl, como resultado del efecto de confinamiento electrónico que ejerce el promotor sobre el sólido [65,165], dificultando el crecimiento de las partículas metálicas de Ni 0 durante la activación que dan como resultado una disminución de la sinterización de las partículas de Ni 0 e incrementa la dispersión de la fase activa, además, de posiblemente favorecer la actividad catalítica e impedir la formación de depósitos de coque sobre la superficie del catalizador [166][167][168].…”

Dual functional catalytic materials of Ni over Ce-modified CaO sorbents for integrated CO2 capture and conversion

“…However, the major challenge for the CaO-based sorbents and the Ni-based catalysts is the fast decay of CO2 capture performance and the deactivation of catalytic performance with the number of cycles, respectively [35]. CeO2, with a Tammann temperature of 1064 ˚C [36,37], also has a possibility to be incorporated into CaO as a good inert material. Wang et al synthesized a series of Ce-doped sorbents by a simple sol-gel method, and the sample (Ca/Ce = 15:1) showed a favourable capture capacity and cyclic stability, maintaining a CO2 uptake capacity of 13.4 mmol g -1 after 18 cycles [36].…”

Development of an effective bi-functional Ni–CaO catalyst-sorbent for the sorption-enhanced water gas shift reaction through structural optimization and the controlled deposition of a stabilizer by atomic layer deposition

“…Besides the capture of CO 2 , CaO-based sorbents have the potential to be integrated in processes that combine CO 2 capture with a catalytic reaction, e.g., steam reforming [46][47][48][49][50] and/ or the water-gas shi reaction [51][52][53][54] to yield high-purity H 2 . For example, a typical composition of the effluent gas of an industrial water-gas shi unit is approximately 76% H 2 , 17% CO 2 , 3% CO, and 4% CH 4 .…”