Oxidative Methane Conversion to Ethane on Highly Oxidized Pd/CeO₂ Catalysts Below 400 °C

Abstract

Methane upgrading into more valuable chemicals has received much attention. Herein, we report oxidative methane conversion to ethane using gaseous O2 at low temperatures (<400 °C) and atmospheric pressure in a continuous reactor. A highly oxidized Pd deposited on ceria could produce ethane with a productivity as high as 0.84 mmol gcat−1 h−1. The Pd−O−Pd sites, not Pd−O−Ce, were the active sites for the selective ethane production at low temperatures. Density functional theory calculations confirmed that the Pd−O−Pd site is energetically more advantageous for C−C coupling, whereas Pd−O−Ce promotes CH4 dehydrogenation. The ceria helped Pd maintain a highly oxidic state despite reductive CH4 flow. This work can provide new insight for methane upgrading into C2 species.

Mechanochemical Route for Preparation of MFI-Type Zeolites Containing Highly Dispersed and Small Ce Species and Catalytic Application to Low-Temperature Oxidative Coupling of Methane

“…The 3 wt % Pd/Ce/SiO 2 catalyst exhibited catalytic performance to some extent, but the maximum ethane yield was less than half of those achieved by 3 wt % Pd/Ce-MFI MC and 3 wt % Pd/Ce-MFI HT . In stark contrast to these three catalysts, neither 3 wt % Pd/Ce/silicalite-1 nor 3 wt % Pd/CeO 2 , the latter of which was similar to a previously reported catalyst that exhibited some catalytic activity at reaction temperatures below 400 °C, provided ethane in comparable yields (i.e., at most 0.04% C at 250 °C on 3 wt % Pd/CeO 2 ). The bulk CeO 2 support itself was also inactive for this reaction under the same conditions.…”

“…Although a further detailed mechanistic study involving isotope tracer analysis and operando spectroscopy is necessary, this agreement suggested that the supported Pd species helped the completion of the redox cycle of Ce species activating methane in the reaction. As reported elsewhere, 22,54 methane coupling induced by oxygen species activated over the Pd surface, to which CeO 2−x supplies its lattice oxygen, is another possibility that cannot be ruled out from our current experimental data. The STEM-EDS images of 3 wt % Pd/Ce-MFI MC in Figure S10 demonstrated that the Pd species were located near the Ce species.…”

Single Atom Catalysts for Selective Methane Oxidation to Oxygenates

“…The self-coupling of methane to ethane and other higher hydrocarbons has been reported at a higher temperature. 270,271 Direct conversion of methane to acetic acid has attracted significant attention due to the wide use of CH 3 COOH as commodity chemicals such as vinyl acetate, acetate esters (ethylene-vinyl acetate, ethyl acetate, etc.). 272 Global CH 3 COOH production was 9.07 million tons in 2020 and is expected to increase up to 11.85 million tons by 2026.…”

Ultra‐Small Noble Metal Ceria‐Based Catalytic Materials: From Synthesis to Application

“…For example, Kwon et al utilized Pd/ CeO 2 to catalyze methane conversion to ethane with the temperature below 400°C. [7] Li et al reported the synthesis of Ir/CeO 2 with the size of Ir from 1.0 to 2.5 nm for CO 2 hydrogenation. The selectivity of CO 2 hydrogenation could be tuned by the Ir loading.…”

“…For example, Kwon et al. utilized Pd/CeO 2 to catalyze methane conversion to ethane with the temperature below 400 °C [7] . Li et al.…”