Synthesis Gas Generation by Chemical-Looping Reforming Using Ce-Based Oxygen Carriers Modified with Fe, Cu, and Mn Oxides

Abstract

Chemical-looping reforming (CLR) is a technology that can be used for partial oxidation and steam reforming of hydrocarbon fuels. It involves the use of a metal oxide as an oxygen carrier, which transfers oxygen from combustion air to the fuel. Composite oxygen carriers of cerium oxide added with Fe, Cu, and Mn oxides were prepared by co-precipitation and investigated in a thermogravimetric analyzer and a fixed-bed reactor using methane as fuel and air as oxidizing gas. It was revealed that the addition of transition-metal oxides into cerium oxide can improve the reactivity of the Ce-based oxygen carrier. The three kinds of mixed oxides showed high CO and H2 selectivity at above 800 °C. As for the Ce−Fe−O oxygen carrier, methane was converted to synthesis gas at a H2/CO molar ratio close to 2:1 at a temperature of 800−900 °C; however, the methane thermolysis reaction was found on Ce−Cu−O and Ce−Mn−O oxygen carriers at 850−900 °C. Among the three kinds of oxygen carriers, Ce−Fe−O presented the best performance for methane CLR. On Ce−Fe−O oxygen carriers, the CO and H2 selectivity decreased as the Fe content increased in the carrier particles. An optimal range of the Ce/Fe molar ratio is Ce/Fe > 1 for Ce−Fe−O oxygen carriers. Scanning electron microscopy (SEM) analysis revealed that the microstructure of the Ce−Fe−O oxides was not dramatically changed before and after 20 cyclic reactions. A small amount of Fe3C was found in the reacted Ce−Fe−O oxides by X-ray diffraction (XRD) analysis.

Steam gasification of safflower seed cake and catalytic tar decomposition over ceria modified iron oxide catalysts

“…He and co-workers [25], have investigated the methane conversion and reported that the composite oxygen carriers (Ce-Fe-O) have better reactivity than the pure CeO 2 .…”

“…Because of this, the addition of CeO 2 to Fe 2 O 3 increased tar conversion activity of the catalyst at low temperatures. In addition to the redox property of CeO 2 , the addition of CeO 2 to Fe 2 O 3 may improve the basic nature of iron oxide [25]. Ashok and Kawi [29] have also reported that the addition of CeO 2 to Ca-Al support increased the basic strength of the catalyst which enhances the reaction between steam and carbon and also suppresses the coke formation via neutralization of the support acidity.…”

“…The redox features of ceria could be greatly enhanced by the addition of transition metals as well as noble metals, and the improvement in catalytic performance was often attributed to the strong metal-ceria interaction and the generation of metal-ceria solid solutions. CeO 2 has also been reported to prohibit coke deposition on catalysts [6,24,25]. In literature, ceria supported catalyst has been used mainly in the gasification of bio-oil derived from biomass pyrolysis and bio-oil model compounds.…”

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].…”

Chemical‐Looping Reforming of Methane Using Iron Based Oxygen Carrier Modified with Low Content Nickel

“…At present, steam or CO 2 reforming of natural gas was reacted in reactor tubes packed with catalyst and it has been developed into a large-scale production. The chemical reactions of the above-mentioned routes are shown as follows: [1] Steam reforming: CH 4 ＋H 2 O＝CO＋3H 2 (∆H 298 K ＝206 kJ/mol) (1) CO 2 reforming: [2] CH 4 ＋CO 2 ＝2CO＋2H 2 (∆H 298 K ＝260.5 kJ/mol) (2) These two reactions, which are highly endothermic reactions, consume a large amount of energy, and the H 2 /CO ratio is unsuitable for the Fischer-Tropsch and methanol syntheses in which the desired H 2 /CO ratio is 2. In contrast to the two methods above mentioned, another methane reforming approach, i.e.…”