Syngas Generation from Methane Using a Chemical‐Looping Concept: A Review of Oxygen Carriers

Abstract

Conversion of methane to syngas using a chemical-looping concept is a novel method for syngas generation. This process is based on the transfer of gaseous oxygen source to fuel (e.g., methane) by means of a cycling process using solid oxides as oxygen carriers to avoid direct contact between fuel and gaseous oxygen. Syngas is produced through the gas-solid reaction between methane and solid oxides (oxygen carriers), and then the reduced oxygen carriers can be regenerated by a gaseous oxidant, such as air or water. The oxygen carrier is recycled between the two steps, and the syngas with a ratio of H2/CO = 2.0 can be obtained successively. Air is used instead of pure oxygen allowing considerable cost savings, and the separation of fuel from the gaseous oxidant avoids the risk of explosion and the dilution of product gas with nitrogen. The design and elaboration of suitable oxygen carriers is a key issue to optimize this method. As one of the most interesting oxygen storage materials, ceria-based and perovskite oxides were paid much attention for this process. This paper briefly introduced the recent research progresses on the oxygen carriers used in the chemical-looping selective oxidation of methane (CLSOM) to syngas.

Endogenous Nanoparticles Strain Perovskite Host Lattice Providing Oxygen Capacity and Driving Oxygen Exchange and CH4 Conversion to Syngas

“…To illustrate the applicability of our concept, we employ it towards the challenging process of CH4 activation and conversion [25,26] via chemical looping partial oxidation (CLPO). In this process, the oxygen carrier material which reacts cyclically with a reducing and an oxidizing stream also needs to fulfil the catalytic role of CH4 activation [27][28][29][30] . We exemplify this by using a titanate perovskite oxide (La0.8Ce0.1Ni0.4Ti0.6O3), which is traditionally not ideal for such applications due to low surface area and low oxygen exchange capability [31] .…”

Chemical looping beyond combustion: production of synthesis gas via chemical looping partial oxidation of methane

“…Among the very limited number of investigations into alternative, cheaper, and non-toxic carriers, a few studies on Fe-Ce mixed oxide carriers and LaFeO 3 and La x Sr 1Àx FeO 3 perovskites have reported promising results, albeit all of these carriers suffer from low reactivity. 19,[21][22][23][24][25][26] Building on this previous work, in the present contribution, we aim to demonstrate a viable process for syngas generation via chemical looping by systematically optimizing both the oxygen carrier and the operation of the periodic redox process to tune the C/O ratio in the fuel reactor. Towards this goal, we synthesized mixed oxides of iron and nickel with the aim of combining the high reactivity of nickel with the selective oxidation properties of iron.…”

Chemical Looping Conversion of Gaseous and Liquid Fuels for Chemical Production: A Review

“…Although the Ce−Zr mixed oxides show similar activity to Ce−Fe mixed oxides for chemical looping partial oxidation of methane, they are significantly less favorable for syngas generation compared to Ce−Fe mixed oxides. 52 The Ce−Zr mixed oxides with 10 mol % CuO addition produce higher yields of syngas and retain better thermal stability after 20 cycles, all of which are attributed to the abundant oxygen vacancies on the surface. 132 Ce−Cu−O, Ce−Mn−O, Ce−Ni−O, Ce−Nb−O, and Ce− Sm−O are investigated as OCs for the CL-POM process.…”

“…132 Ce−Cu−O, Ce−Mn−O, Ce−Ni−O, Ce−Nb−O, and Ce− Sm−O are investigated as OCs for the CL-POM process. 30,52,93,135,141,148,150 He et al 93 and Li et al 128,148 exhibit high CO and H 2 selectivity above 800 °C, but the thermolysis reaction of methane takes place when the temperature is higher than 850 °C. 93 For the Ce−Ni−O system, a moderate Ni loading (no more than 20%) is essential to prevent the decomposition of methane.…”