Online Kinetics Study of Oxidative Coupling of Methane over La2O3 for Methane Activation: What Is Behind the Distinguished Light-off Temperatures?

ACS Catalysis ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 11761-11772 ◽  
Author(s):  
Zebang Liu ◽  
Jerry Pui Ho Li ◽  
Evgeny Vovk ◽  
Yan Zhu ◽  
Shenggang Li ◽  
...  
Keyword(s):  
Oxidative Coupling ◽  
Oxidative Coupling Of Methane ◽  
Methane Activation ◽  
Kinetics Study

scholarly journals “Soft” oxidative coupling of methane to ethylene: Mechanistic insights from combined experiment and theory

2021 ◽  
Vol 118 (23) ◽  
pp. e2012666118
Author(s):  
Shanfu Liu ◽  
Sagar Udyavara ◽  
Chi Zhang ◽  
Matthias Peter ◽  
Tracy L. Lohr ◽  
...  
Keyword(s):  
Oxidative Coupling ◽  
Methane Conversion ◽  
Density Functional ◽  
Activation Barrier ◽  
Oxidative Coupling Of Methane ◽  
Methane Activation ◽  
Kinetic Isotope ◽  
Mechanistic Analysis ◽  
Adsorbed Sulfur ◽  
Product Forms

The oxidative coupling of methane to ethylene using gaseous disulfur (2CH4 + S2 → C2H4 + 2H2S) as an oxidant (SOCM) proceeds with promising selectivity. Here, we report detailed experimental and theoretical studies that examine the mechanism for the conversion of CH4 to C2H4 over an Fe3O4-derived FeS2 catalyst achieving a promising ethylene selectivity of 33%. We compare and contrast these results with those for the highly exothermic oxidative coupling of methane (OCM) using O2 (2CH4 + O2 → C2H4 + 2H2O). SOCM kinetic/mechanistic analysis, along with density functional theory results, indicate that ethylene is produced as a primary product of methane activation, proceeding predominantly via CH2 coupling over dimeric S–S moieties that bridge Fe surface sites, and to a lesser degree, on heavily sulfided mononuclear sites. In contrast to and unlike OCM, the overoxidized CS2 by-product forms predominantly via CH4 oxidation, rather than from C2 products, through a series of C–H activation and S-addition steps at adsorbed sulfur sites on the FeS2 surface. The experimental rates for methane conversion are first order in both CH4 and S2, consistent with the involvement of two S sites in the rate-determining methane C–H activation step, with a CD4/CH4 kinetic isotope effect of 1.78. The experimental apparent activation energy for methane conversion is 66 ± 8 kJ/mol, significantly lower than for CH4 oxidative coupling with O2. The computed methane activation barrier, rate orders, and kinetic isotope values are consistent with experiment. All evidence indicates that SOCM proceeds via a very different pathway than that of OCM.

A kinetics study for the oxidative coupling of methane on a Mn/Na2WO4/SiO2 catalyst

2012 ◽  
Vol 433-434 ◽  
pp. 96-108 ◽  
Author(s):  
T.P. Tiemersma ◽  
M.J. Tuinier ◽  
F. Gallucci ◽  
J.A.M. Kuipers ◽  
M. van Sint Annaland
Keyword(s):  
Oxidative Coupling ◽  
Oxidative Coupling Of Methane ◽  
Kinetics Study

scholarly journals Identification of the structure of the Bi promoted Pt non-oxidative coupling of methane catalyst: a nanoscale Pt3Bi intermetallic alloy

2019 ◽  
Vol 9 (6) ◽  
pp. 1349-1356 ◽  
Author(s):  
Johnny Zhu Chen ◽  
Zhenwei Wu ◽  
Xiaoben Zhang ◽  
Slgi Choi ◽  
Yang Xiao ◽  
...  
Keyword(s):  
Oxidative Coupling ◽  
Oxidative Coupling Of Methane ◽  
Intermetallic Alloy ◽  
Alloy Catalyst

Identification of a Pt3Bi nanoscale, surface intermetallic alloy catalyst for non-oxidative coupling of methane (NOCM).

Catalytic performance of Na-Mn2O3-based catalysts towards oxidative coupling of methane

2021 ◽  
Author(s):  
P. Saychu ◽  
M. Thanasiriruk ◽  
C. Khajonvittayakul ◽  
R. Viratikul ◽  
V. Tongnan ◽  
...  
Keyword(s):  
Oxidative Coupling ◽  
Catalytic Performance ◽  
Oxidative Coupling Of Methane

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.

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