scholarly journals Study on the unsteady state oxidative coupling of methane: effects of oxygen species from O2, surface lattice oxygen, and CO2 on the C2+ selectivity

RSC Advances ◽  
2020 ◽  
Vol 10 (59) ◽  
pp. 35889-35897
Author(s):  
Suji Yoon ◽  
Seoyeon Lim ◽  
Jae-Wook Choi ◽  
Dong Jin Suh ◽  
Kwang Ho Song ◽  
...  
Keyword(s):  
Oxidative Coupling ◽  
Oxidative Coupling Of Methane ◽  
Lattice Oxygen ◽  
Oxygen Species ◽  
Unsteady State ◽  
Surface Lattice

This study examined the effects of oxygen species on the unsteady-state oxidative coupling of methane (OCM) using a lengthy catalyst bed of Na2WO4/Mn/SiO2.

scholarly journals Alkali-Added Catalysts Based on LaAlO3 Perovskite for the Oxidative Coupling of Methane

2021 ◽  
Vol 5 (1) ◽  
pp. 14
Author(s):  
Suna An ◽  
JeongHyun Cho ◽  
Dahye Kwon ◽  
Ji Chul Jung
Keyword(s):  
Catalytic Activity ◽  
Oxidative Coupling ◽  
Oxidative Coupling Of Methane ◽  
Lattice Oxygen ◽  
Oxygen Species ◽  
Methyl Radicals ◽  
Ethylene Selectivity ◽  
Perovskite Catalysts ◽  
C2 Hydrocarbons ◽  
Selective Formation

In this study, we aimed to enhance the catalytic activity of perovskite catalysts and elucidate their catalytic behavior in the oxidative coupling of methane (OCM), using alkali-added LaAlO3 perovskite catalysts. We prepared LaAlO3_XY (X = Li, Na, K, Y = mol %) catalysts and applied them to the OCM reaction. The results showed that the alkali-added catalysts’ activities were promoted compared to the LaAlO3 catalyst. In this reaction, ethane was first synthesized through the dimerization of methyl radicals, which were produced from the reaction of methane and oxygen vacancy in the perovskite catalysts. The high ethylene selectivity of the alkali-added catalysts originated from their abundance of electrophilic lattice oxygen species, facilitating the selective formation of C2 hydrocarbons from ethane. The high COx (carbon monoxide and carbon dioxide) selectivity of the LaAlO3 catalyst originated from its abundance of nucleophilic lattice oxygen species, favoring the selective production of COx from ethane. We concluded that electrophilic lattice oxygen species play a significant role in producing ethylene. We obtained that alkali-adding could be an effective method for improving the catalytic activity of perovskite catalysts in the OCM reaction.

scholarly journals Nanosheet-Like Ho2O3 and Sr-Ho2O3 Catalysts for Oxidative Coupling of Methane

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 388
Author(s):  
Yuqiao Fan ◽  
Changxi Miao ◽  
Yinghong Yue ◽  
Weiming Hua ◽  
Zi Gao
Keyword(s):  
Oxidative Coupling ◽  
Temperature Programmed Desorption ◽  
Oxidative Coupling Of Methane ◽  
Molar Ratio ◽  
Impregnation Method ◽  
Oxygen Species ◽  
N2 Adsorption ◽  
Basic Sites ◽  
Chemisorbed Oxygen ◽  
Temperature Programmed

In this work, Ho2O3 nanosheets were synthesized by a hydrothermal method. A series of Sr-modified Ho2O3 nanosheets (Sr-Ho2O3-NS) with a Sr/Ho molar ratio between 0.02 and 0.06 were prepared via an impregnation method. These catalysts were characterized by several techniques such as XRD, N2 adsorption, SEM, TEM, XPS, O2-TPD (temperature-programmed desorption), and CO2-TPD, and they were studied with respect to their performances in the oxidative coupling of methane (OCM). In contrast to Ho2O3 nanoparticles, Ho2O3 nanosheets display greater CH4 conversion and C2-C3 selectivity, which could be related to the preferentially exposed (222) facet on the surface of the latter catalyst. The incorporation of small amounts of Sr into Ho2O3 nanosheets leads to a higher ratio of (O− + O2−)/O2− as well as an enhanced amount of chemisorbed oxygen species and moderate basic sites, which in turn improves the OCM performance. The optimal catalytic behavior is achievable on the 0.04Sr-Ho2O3-NS catalyst with a Sr/Ho molar ratio of 0.04, which gives a 24.0% conversion of CH4 with 56.7% selectivity to C2-C3 at 650 °C. The C2-C3 yield is well correlated with the amount of moderate basic sites present on the catalysts.

Oxidative coupling of methane with participation of oxide catalyst lattice oxygen

1990 ◽  
Vol 6 (4) ◽  
pp. 543-549 ◽  
Author(s):  
M.Yu. Sinev ◽  
V.Yu. Bychkov ◽  
V.N. Korchak ◽  
O.V. Krylov
Keyword(s):  
Oxidative Coupling ◽  
Oxide Catalyst ◽  
Oxidative Coupling Of Methane ◽  
Lattice Oxygen
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