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Significantly enhanced oxygen transfer capacity by the oxygen delivery channels formed in the inverse spinel Cu x Mg 2‐ x Mn y Ti 1‐ y O 4.0 particle
Author(s) -
Son Namgyu,
Do Jeong Yeon,
Park NoKuk,
Ryu Si Ok,
Kwak Byeong Sub,
Baek JeomIn,
Kim Ui Sik,
Ryu HoJung,
Lee Doyeon,
Kang Misook
Publication year - 2018
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.4133
Subject(s) - spinel , ilmenite , oxygen , chemistry , sintering , adsorption , redox , chemical looping combustion , non blocking i/o , inorganic chemistry , materials science , analytical chemistry (journal) , mineralogy , metallurgy , catalysis , organic chemistry , biochemistry , chromatography
Summary Particles containing Cu and Mn as oxygen transfer species in the development of alternative oxygen carriers for commercialized NiO‐based particles used in CH 4 chemical looping combustion were investigated in this study. To maximize their oxygen transfer capacity, divalent Cu and tetravalent Mn were maintained in their respective oxidation states, which resulted in their reduction capacities not being canceled by each other. To prevent abrasion and sintering caused by collision and aggregation between 2 metals at high temperatures, they were stably fixed in an Mg 1.0 Ti 1.0 O 3.0 ilmenite support. As the result, the Cu‐substituted particle transferred to a pseudobrookite Mg 1.0 Ti 2.0 O 5.0 structure, and the particles with Cu 2+ and Mn 4+ substituting Mg 2+ and Ti 4+ , respectively, changed to an inverse spinel Mg 2.0 Ti 1.0 O 4.0 structure, and not an ilmenite structure. In the hydrogen temperature‐programmed reduction test, the reduction temperatures of the Cu and Mn ions in Cu x Mg 2‐ x Mn y Ti 1‐ y O 4.0 particles were significantly lower by 200°C or higher than those in the particles containing only Cu or Mn. Furthermore, adsorption curves of CH 4 and CO were shifted to low temperatures, and the adsorption concentrations were greatly increased for Cu x Mg 2‐ x Mn y Ti 1‐ y O 4.0 . For the cycling test for the CH 4 ‐CO 2 /air redox system, the oxygen transfer capacities in particles containing only Cu or Mn were 3.4% or 3.1%, respectively, but this increased to 9.4% in Cu 1.5 Mg 0.5 Mn 0.5 Ti 0.5 O 4.0 . In Cu x Mg 2‐ x Mn y Ti 1‐ y O 4.0 , the Mn species was present in the tetravalent state, and it participated in the CH 4 combustion reaction with the Cu ion, resulting in improved oxygen transfer ability. Finally, this study demonstrated an important mechanism, in which the Cu 2+ and Mn 4+ ions were reduced while combusting CH 4 , and the Mg 2+ and Ti 4+ transfer oxygen to the reduced Cu and Mn through the inverse spinel lattice of Cu x Mg 2‐ x Mn y Ti 1‐ y O 4.0 . All metal species were reduced to like a dominos in the reduction system, creating a regular oxygen delivery channel in the crystal during the CH 4 ‐CO 2 /air redox reaction, and resulting in improved oxygen transfer capacity.