Chemical-Looping Steam Methane Reforming over a CeO₂–Fe₂O₃ Oxygen Carrier: Evolution of Its Structure and Reducibility

Abstract

Chemical-looping steam methane reforming (CL-SMR) is a promising method for the co-generation of pure hydrogen and syngas on the basis of redox cycles via a gas−solid reaction using an oxygen carrier. The performance and life of the oxygen carrier play pivotal roles in determining the feasibility and economy of the CL-SMR process. The present research was focused on the evolution of the structure and reducibility of a CeO 2 −Fe 2 O 3 oxygen carrier during the CL-SMR redox process to further understand the sustainability of the oxygen carrier. The investigated CeO 2 −Fe 2 O 3 complex oxide exhibited satisfactory performance in the CL-SMR process because of the chemical interaction between Ce and Fe species. A Ce−Fe−O phase equilibrium based on a stable composition of CeO 2 , Fe 3 O 4 , and CeFeO 3 formed in the recycled samples. Surface oxygen was removed, which was accompanied by an increase in the concentration of oxygen vacancies and a decrease in the surface area of the recycled samples; these effects resulted in an increase in the high-temperature reducibility and syngas selectivity of the samples. Oxygen mobility was intensified by the Ce−Fe chemical interaction via the formation of CeFeO 3 and a micromorphological transformation. These properties counteracted the sintering of the materials and guaranteed the stability of the oxygen carrier in the CL-SMR process.

Reduction kinetics of lanthanum ferrite perovskite for the production of synthesis gas by chemical-looping methane reforming

“…However, iron oxide based redox catalysts are not particularly active for methane oxidation (Cabello et al, 2014a;Shafiefarhood et al, 2014), and tend to have low selectivity toward methane partial oxidation. Notably, the reactivity and selectivity in CLMR process can be improved by combining different materials to bring synergetic effect or form solid solution (spinel, perovskite, et al) (Cabello et al, 2014a;Neal et al, 2014Neal et al, , 2015Bhavsar and Veser, 2013;Zhu et al, 2014;Chen et al, 2014). As mentioned above, although many work to increase the reactivity and syngas selectivity have been carried out for a long time, the reduction kinetics of oxygen carriers using methane as fuel at representative conditions of CLMR system has been seldom investigated (Dueso et al, 2012;Rashidi et al, 2013aRashidi et al, , 2013b).…”

Progress in oxygen carrier development of methane-based chemical-looping reforming: A review

“…A novel two-step SRM configuration on the basis of CLC concept (CL-SRM) has been proposed and is shown in Fig. 4 [38][39][40][41][42].…”

“…Among these materials, Fe-based OCs were proved to be ideal for WSR. However, being thermodynamically constrained, H 2 evolution via WSR requires Fe phase to be as fully reduced as possible, while it is difficult for Fe phase to be completely oxidized beyond Fe 3 O 4 by using steam [40].…”

Synthesis and Application of Cerium-Incorporated SBA-16 Supported Ni-Based Oxygen Carrier in Cyclic Chemical Looping Steam Methane Reforming

“…Since combustion of fossil fuels releases different greenhouse gases, such as CO 2 , NO x , SO x , and CH 4 that causes global warming effect. Hydrogen can replace these fuels [5][6][7][8].…”